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Sample records for subglacial hydrothermal alteration

  1. Subglacial hydrothermal alteration minerals in Jökulhlaup deposits of Southern Iceland, with implications for detecting past or present habitable environments on Mars.

    Science.gov (United States)

    Warner, Nicholas H; Farmer, Jack D

    2010-06-01

    Jökulhlaups are terrestrial catastrophic outfloods, often triggered by subglacial volcanic eruptions. Similar volcano-ice interactions were likely important on Mars where magma/lava may have interacted with the planet's cryosphere to produce catastrophic floods. As a potential analogue to sediments deposited during martian floods, the Holocene sandurs of Iceland are dominated by basaltic clasts derived from the subglacial environment and deposited during jökulhlaups. Palagonite tuffs and breccias, present within the deposits, represent the primary alteration lithology. The surface abundance of palagonite on the sandurs is 1-20%. X-ray diffraction (XRD) analysis of palagonite breccias confirms a mineral assemblage of zeolites, smectites, low-quartz, and kaolinite. Oriented powder X-ray diffractograms (habitable environments for microbial life may be found.

  2. Reconstruction of Ancestral Hydrothermal Systems on Mount Rainier Using Hydrothermally Altered Rocks in Holocene Debris Flows and Tephras

    Science.gov (United States)

    John, D. A.; Breit, G. N.; Sisson, T. W.; Vallance, J. W.; Rye, R. O.

    2005-12-01

    Mount Rainier is the result of episodic stages of edifice growth during periods of high eruptive activity and edifice destruction during periods of relative magmatic quiescence over the past 500 kyr. Edifice destruction occurred both by slow erosion and by catastrophic collapses, some of which were strongly influenced by hydrothermal alteration. Several large-volume Holocene debris-flow deposits contain abundant clasts of hydrothermally altered rocks, most notably the 4-km3 clay-rich Osceola Mudflow which formed by collapse of the northeast side and upper 1000+ m of the edifice about 5600 ya and flowed >120 km downstream into Puget Sound. Mineral assemblages and stable isotope data of hydrothermal alteration products in Holocene debris-flow deposits indicate formation in distinct hydrothermal environments, including magmatic-hydrothermal, steam-heated (including a large fumarolic component), magmatic steam (including a possible fumarolic component), and supergene. The Osceola Mudflow and phreatic components of coeval tephras contain the highest-temperature and inferred most deeply formed alteration minerals; assemblages include magmatic-hydrothermal quartz-alunite, quartz-topaz, quartz-pyrophyllite and quartz-illite (all +pyrite), in addition to steam-heated opal-alunite-kaolinite and abundant smectite-pyrite. In contrast, the Paradise lahar, which formed by a collapse of the surficial upper south side of the edifice, contains only steam-heated assemblages including those formed largely above the water table from condensation of fumarolic vapor (opal-alunite-jarosite). Younger debris-flow deposits on the west side of the volcano (Round Pass lahar and Electron Mudflow) contain only smectite-pyrite alteration, whereas an early 20th century rock avalanche on Tahoma Glacier also contains magmatic-hydrothermal alteration that is exposed in the avalanche headwall of Sunset Amphitheater. Mineralogy and isotopic composition of the alteration phases, geologic and

  3. Hydrothermal alteration in oceanic ridge volcanics: A detailed study at the Galapagos Fossil Hydrothermal Field

    Science.gov (United States)

    Ridley, W.I.; Perfit, M.R.; Josnasson, I.R.; Smith, M.F.

    1994-01-01

    The Galapagos Fossil Hydrothermal Field is composed of altered oceanic crust and extinct hydrothermal vents within the eastern Galapagos Rift between 85??49???W and 85??55???W. The discharge zone of the hydrothermal system is revealed along scarps, thus providing an opportunity to examine the uppermost mineralized, and highly altered interior parts of the crust. Altered rocks collected in situ by the submersible ALVIN show complex concentric alteration zones. Microsamples of individual zones have been analysed for major/minor, trace elements, and strontium isotopes in order to describe the complex compositional details of the hydrothermal alteration. Interlayered chlorite-smectite and chlorite with disequilibrium compositions dominate the secondary mineralogy as replacement phases of primary glass and acicular pyroxene. Phenocrysts and matrix grains of plagioclase are unaffected during alteration. Using a modification of the Gresens' equation we demonstrate that the trivalent rare earth elements (REEs) are relatively immobile, and calculate degrees of enrichment and depletion in other elements. Strontium isotopic ratios increase as Sr concentrations decrease from least-altered cores to most-altered rims and cross-cutting veins in individual samples, and can be modeled by open system behaviour under low fluid-rock ratio (< 10) conditions following a period of lower-temperature weathering of volcanics within the rift zone. The complex patterns of element enrichment and depletion and strontium isotope variations indicate mixing between pristine seawater and ascending hot fluids to produce a compositional spectrum of fluids. The precipitation of base-metal sulfides beneath the seafloor is probably a result of fluid mixing and cooling. If, as suggested here, the discharge zone alteration occurred under relatively low fluid-rock ratios, then this shallow region must play an important role in determining the exit composition of vent fluids in marine hydrothermal systems

  4. rights reserved Geophysical Identification of Hydrothermally Altered ...

    African Journals Online (AJOL)

    ADOWIE PERE

    the pole to the magnetic data aided in mapping of various hydrothermally altered structures that may favour gold mineralisation. The interpretation of the aero data set has enhanced a lot of ... water serves as a concentrating, transporting and depositing agent through faults (structures) to the earth's surface. Hydrothermal ...

  5. Hydrothermal Alteration of the Mt Unzen Conduit (Shimabara/Japan)

    Science.gov (United States)

    Yilmaz, T. I.; Mayer, K.; Hess, K. U.; Janots, E.; Gilg, H. A.; Dingwell, D. B.

    2016-12-01

    Investigations were carried out on hydrothermally altered coherent dacitic dykes samples from (USDP-4) drill core at Mt Unzen stratovolcano (Shimabara/Japan). XRF, XRD, EMPA, and C-O-isotope analysis led to insights concerning chemistry, mineralogy, and intensity of alteration as well as the origin of carbonate-precipitating fluids. Additionally a textural characterization of the occurring replacement features in the magma conduit zone was performed. The occurrence of the main secondary phases such as chlorite, pyrite, carbonates, and R1 (Reichweite parameter) illite-smectite indicate a weak to moderate propylitic to phyllic hydrothermal alteration. The dacitic samples of the dykes show different hydrothermal alteration features: (i) carbonate pseudomorphs after hornblende as well as core and zonal textures due to replacement of plagioclase by R1 illite-smectite, (ii) colloform banded fracture fillings and fillings in dissolution vugs, and (iii) chlorite and R1 illite-smectite in the groundmass. Carbonates in fractures comprise iron-rich dolomite solid solutions ("ankerite") and calcite. Isotopic values of d13Cvpdb = -4.59 ± 0.6‰ and d18Ovpdb = -21.73 ± 0.5‰ indicate a hydrothermal-magmatic origin for the carbonate formation. The chlorite-carbonate-pyrite index (CCPI) and the Ishikawa alteration index (AI), applied to the investigated samples show significant differences (CCPI=52.7-57.8; AI=36.1-40.6) indicating their different degree of alteration. According to Nakada et al., 2005, the C13 to C16 dykes represent the feeder dyke from the latest eruption (1991-1995) whereas C8 represents an earlier dyke feeder dyke from an older eruption. Weakest conduit alteration, which was obtained in samples C16-1-5 and C13-2-5, correlates with the alteration degree of the pristine dome rocks. Highest CCPI value was determined for sample C14-1-5 and the highest AI value was determined for sample C15-2-6. The degrees of alteration do not indicate highest alteration of the

  6. Hydrothermal alteration in Dumoga Barat, Bolaang Mongondow area North Sulawesi

    International Nuclear Information System (INIS)

    Agus Harjanto' Sutanto; Sutarto; Achmad Subandrio; I Made Suasta; Juanito Salamat; Giri Hartono; Putu Suputra; I Gde Basten; Muhammad Fauzi; Rosdiana

    2016-01-01

    Bolaang Mongondow is located in central north Sulawesi arm, which is composed of Neogen magmatic arc and potentially contain economic minerals. This condition is behind the research purpose to study the mineral resources potencies. Research aim is to study alteration caused by hydrothermal process and its relation with gold (Au) deposit based on field study and laboratory analysis. Methodologies used for the research are literature study, geological survey, rocks sampling, laboratory analysis, and data processing. Research area is a multiply diorite intrusion complex. Andesite, volcaniclastic rocks, and dacite, the older rocks, were intruded by this complex. Later, dacitic tuff, volcanic sandstone, and alluvium deposited above them. There are three measured and mapped major faults heading NE-SW crossed by E-W fault and NW-SE fault lately crossed all the older faults. Early stage hydrothermal alteration related to the existence of young quartz diorite, showing alteration stage from the potassic center to distal prophylatic. Final stage hydrothermal alteration consist of argilic, advanced argilic, and silica-clay mineral±magnetite±chlorite alteration overlapping the earlier alteration. Mineralization of Cu-Au±Ag in central part of research area or Tayap-Kinomaligan area is mostly associated with potassic altered young quartz diorite and crossed by parallel and stock worked quartz-magnetite-chalcopyrite±bornite vein. (author)

  7. rights reserved Geophysical Identification of Hydrothermally Altered

    African Journals Online (AJOL)

    ADOWIE PERE

    Geophysical Identification of Hydrothermally Altered Structures That Favour .... aircraft. Total line kilometers of 36,500 were covered in the survey. Magnetic ... tie lines occur at about 2000 metres interval in the ... visual inspection of the map.

  8. Chemistry, mineralogy and alteration intensity of hydrothermal altered Mt Unzen conduit rocks (Shimabara/Japan)

    Science.gov (United States)

    Hess, Kai-Uwe; Yilmaz, Tim; Gilg, H. Albert; Janots, Emilie; Mayer, Klaus; Nakada, Setsuya; Dingwell, Donald

    2017-04-01

    Investigations were carried out on hydrothermally altered coherent dacitic dykes samples from (USDP-4) drill core at Mt Unzen stratovolcano (Shimabara/Japan). XRF, XRD, EMPA, C-O-isotope, hot-cathode CL and SEM analysis led to insights concerning chemistry, mineralogy, and intensity and type of alteration as well as the origin of carbonate-precipitating fluids. Additionally a textural characterization of the occurring replacement features in the volcanic conduit rocks was performed. The occurrence of the main secondary phases such as chlorite, pyrite, carbonates, and R1 (Reichweite parameter) illite-smectite and kaolinite group minerals indicate a weak to moderate propylitic to phyllic hydrothermal alteration. The dacitic samples of the dykes show different hydrothermal alteration features: (i) carbonate and chlorite pseudomorphs after hornblende as well as core and zonal textures due to replacement of plagioclase by R1 illite-smectite as well as kaolinite group minerals, (ii) colloform banded fracture fillings and fillings in dissolution vugs, and (iii) chlorite, R1 illite-smectite as well as kaolinite group minerals in the groundmass. Late chlorite veins crosscut precipitates of R1 illite-smectite as well as kaolinite group minerals. Carbonates in fractures and in pseudomorphs after hornblende comprise iron-rich dolomite solid solutions ("ankerite") and calcite. Isotopic values indicate a hydrothermal-magmatic origin for the carbonate formation. The chlorite-carbonate-pyrite index (CCPI) and the Ishikawa alteration index (AI), applied to the investigated samples show significant differences (CCPI=52.7-57.8; AI=36.1-40.6) indicating their different degree of alteration. According to Nakada et al., 2005, the C13 to C16 dykes represent the feeder dyke from the latest eruption (1991-1995) whereas C8 represents an earlier dyke feeder dyke from an older eruption. Weakest alteration, which was obtained in samples C16-1-5 and C13-2-5, correlates with the alteration

  9. Stable isotopic and mineralogical studies of hydrothermal alteration at Arima Spa, Southwest Japan

    International Nuclear Information System (INIS)

    Masuda, Harue; Osaka City Univ.; Sakai, Hitoshi; Chiba, Hitoshi; Matsuhisa, Yukihiro; Nakamura, Takeshi

    1986-01-01

    The waters of Arima Spa, Southwest Japan, have high salinity (Cl = 54 g/kg) and high isotopic ratios (deltaD = -32, and delta 18 O = +10 per mille), and issue from shallow wells drilled into altered rhyolitic pyroclastic rocks of Cretaceous age. Alteration of the host rocks occurred in two stages. The earlier regional alteration stage is characterized by the presence of 2M- and 1M-type muscovite, albite, chlorite, calcite and epidote, whereas muscovite and Fe-chlorite formation at the expense of partly albitized plagioclase and altered biotite or hornblende occurred in the following hydrothermal stage. Pyrite, sphalerite, galena and siderite are present in the central part of the hydrothermal alteration zone. Oxygen and hydrogen isotopic ratios of secondary muscovite show that regional alteration proceeded under the meteoric circulation, and that the hydrothermal fluid for the second stage had chemical and stable isotopic characteristics of non-meteoric origin similar to the present-day Arima brine. The oxygen and to a lesser extent the hydrogen isotopic ratios of the muscovite rapidly decrease with increasing distance from the central zone of hydrothermal alteration. The isotopic variation is best interpreted as reflecting rapidly decreasing fluid/rock ratios with increasing distance of fluid penetration from the narrow hydrothermal alteration zone into the surrounding area. The results are discussed. (author)

  10. Mineralization and hydrothermal alteration of the Tajroud vein system, south of Neyshabour

    Directory of Open Access Journals (Sweden)

    Mohsen Alikhani Banghani

    2013-10-01

    Full Text Available The Tajroud vein system is located 190 km southwest of Mashhad, and in the southern part of the Sabzevar zone. The vein host rocks consist of Eocene intermediate to silicic volcanic rocks. The mineralization occurs as open space filling, taking place as veins, veinlets and hydrothermal breccias. Based on field geology and textural evidence, three main stages of mineralization were identified. Stage I mainly contains quartz, pyrite, chalcopyrite and magnetite. Stage II, which has the same mineral assemblage as stage I, is the most important stage in terms of volume. Finally, stage III is characterized by repetitive quartz and calcite banding with negligible amounts of sulfide minerals. Hydrothermal alteration is developed around the veins and tends to be more intense in the vicinity of the veins. The plot of the Ishikawa alteration index (AI versus chlorite-carbonate-pyrite index (CCPI, known as alteration box plot, displays three main alteration trends. The hydrothermal alteration assemblage of quartz, adularia, chlorite, illite, calcite, and epidote that envelops the Tajroud vein system formed from the upwelling of near-neutral to weakly alkaline hydrothermal solutions. The mineralogic, alteration and geochemical characteristics of the studied area and comparison with epithermal ore deposits indicate that the Tajroud vein system represents an epithermal system of low-sulfidation type.

  11. ALTERATION RELATED TO HYDROTHERMAL ACTIVITY OF THE NEVADO DEL RUIZ VOLCANO (NRV), COLOMBIA

    OpenAIRE

    Forero, Jhon; Zuluaga, Carlos; Mojica, Jaime

    2011-01-01

    The hydrothermal activity in the NRV generates alteration characterized by mineral associations depending on a number of physic-chemical factors of the hydrothermal system. Petrography of unaltered rocks was used to establish the mineral assemblage prior to rock-fluid interaction. XRD was used in altered rocks, where it was not possible to recognize the alteration products. The observed mineral assemblages indicate advanced and intermediate argillic alterations, this and the observation of ve...

  12. Pore Pressure Distribution and Flank Instability in Hydrothermally Altered Stratovolcanoes

    Science.gov (United States)

    Ball, J. L.; Taron, J.; Hurwitz, S.; Reid, M. E.

    2015-12-01

    Field and geophysical investigations of stratovolcanoes with long-lived hydrothermal systems commonly reveal that initially permeable regions (such as brecciated layers of pyroclastic material) can become both altered and water-bearing. Hydrothermal alteration in these regions, including clay formation, can turn them into low-permeability barriers to fluid flow, which could increase pore fluid pressures resulting in flank slope instability. We examined elevated pore pressure conditions using numerical models of hydrothermal flow in stratovolcanoes, informed by geophysical data about internal structures and deposits. Idealized radially symmetric meshes were developed based on cross-sectional profiles and alteration/permeability structures of Cascade Range stratovolcanoes. We used the OpenGeoSys model to simulate variably saturated conditions in volcanoes heated only by regional heat fluxes, as well as 650°C intrusions at two km depth below the surface. Meteoric recharge was estimated from precipitation rates in the Cascade Range. Preliminary results indicate zones of elevated pore pressures form: 1) where slopes are underlain by continuous low-permeability altered layers, or 2) when the edifice has an altered core with saturated, less permeable limbs. The first scenario might control shallow collapses on the slopes above the altered layers. The second could promote deeper flank collapses that are initially limited to the summit and upper slopes, but could progress to the core of an edifice. In both scenarios, pore pressures can be further elevated by shallow intrusions, or evolve over longer time scales under forcing from regional heat flux. Geometries without confining low-permeability layers do not show these pressure effects. Our initial scenarios use radially symmetric models, but we are also simulating hydrothermal flow under real 3D geometries with asymmetric subsurface structures (Mount Adams). Simulation results will be used to inform 3D slope

  13. Mapping hydrothermal altered mineral deposits using Landsat 7 ...

    Indian Academy of Sciences (India)

    the colour composite, band ratio, principal component analysis, least square ... to hydrothermal alteration mapping using multi- ..... ing of the two images is also achieved by PCA; .... remote sensing perspective; 2nd edn, Prentice Hall Series.

  14. Effect of Hydrothermal Alteration on Rock Properties in Active Geothermal Setting

    Science.gov (United States)

    Mikisek, P.; Bignall, G.; Sepulveda, F.; Sass, I.

    2012-04-01

    Hydrothermal alteration records the physical-chemical changes of rock and mineral phases caused by the interaction of hot fluids and wall rock, which can impact effective permeability, porosity, thermal parameters, rock strength and other rock properties. In this project, an experimental approach has been used to investigate the effects of hydrothermal alteration on rock properties. A rock property database of contrastingly altered rock types and intensities has been established. The database details horizontal and vertical permeability, porosity, density, thermal conductivity and thermal heat capacity for ~300 drill core samples from wells THM12, THM13, THM14, THM17, THM18, THM22 and TH18 in the Wairakei-Tauhara geothermal system (New Zealand), which has been compared with observed hydrothermal alteration type, rank and intensity obtained from XRD analysis and optical microscopy. Samples were selected from clay-altered tuff and intercalated siltstones of the Huka Falls Formation, which acts as a cap rock at Wairakei-Tauhara, and tuffaceous sandstones of the Waiora Formation, which is a primary reservoir-hosting unit for lateral and vertical fluid flows in the geothermal system. The Huka Falls Formation exhibits argillic-type alteration of varying intensity, while underlying Waiora Formations exhibits argillic- and propylithic-type alteration. We plan to use a tempered triaxial test cell at hydrothermal temperatures (up to 200°C) and pressures typical of geothermal conditions, to simulate hot (thermal) fluid percolation through the rock matrix of an inferred "reservoir". Compressibility data will be obtained under a range of operating (simulation reservoir) conditions, in a series of multiple week to month-long experiments that will monitor change in permeability and rock strength accompanying advancing hydrothermal alteration intensity caused by the hot brine interacting with the rock matrix. We suggest, our work will provide new baseline information concerning

  15. The partitioning of uranium and neptunium onto hydrothermally altered concrete

    International Nuclear Information System (INIS)

    Zhao, P.; Allen, P.G.; Sylwester, E.R.; Viani, B.E.

    2000-01-01

    Partition coefficients (K d ) of U(VI) and Np(V) on untreated and hydrothermally altered concrete were measured in 0.01 M NaCl and 0.01 M NaHCO 3 solutions as functions of concentration of the radionuclides, pH, and time. The partition coefficients for both U(VI) and Np(V) on hydrothermally altered concrete are significantly lower than those on untreated concrete. The partition of both U(VI) and Np(V) are pH dependent, although the pH dependence does not appear to reflect precipitation of U and Np-bearing phases. Both sorption and precipitation are likely processes controlling partitioning of U to concrete; sorption is the most likely process controlling the partitioning of Np to concrete. The presence of 0.01 M carbonate species in solution decreases K d of U(VI) for both hydrothermally altered and untreated concrete from ≥ 10 4 mL/g to ∝ 400 to 1000 mL/g indicating a significant impact on U(VI) sorption. In contrast, the presence of carbonate only reduced the K d of Np(V) by one order of magnitude or less. X-ray absorption spectroscopy analysis of U/concrete mixtures at different pHs and times indicate that uranyl ions are partitioned as monomeric species on untreated concrete, but oligomeric species on hydrothermally altered concrete. Similar analysis of Np/concrete mixtures shows that about half of the partitioned Np(V) is reduced to Np(IV) over a period of 6 months. (orig.)

  16. Subglacial drainage patterns of Devon Island, Canada: detailed comparison of rivers and subglacial meltwater channels

    Science.gov (United States)

    Grau Galofre, Anna; Jellinek, A. Mark; Osinski, Gordon R.; Zanetti, Michael; Kukko, Antero

    2018-04-01

    Subglacial meltwater channels (N-channels) are attributed to erosion by meltwater in subglacial conduits. They exert a major control on meltwater accumulation at the base of ice sheets, serving as drainage pathways and modifying ice flow rates. The study of exposed relict subglacial channels offers a unique opportunity to characterize the geomorphologic fingerprint of subglacial erosion as well as study the structure and characteristics of ice sheet drainage systems. In this study we present detailed field and remote sensing observations of exposed subglacial meltwater channels in excellent preservation state on Devon Island (Canadian Arctic Archipelago). We characterize channel cross section, longitudinal profiles, and network morphologies and establish the spatial extent and distinctive characteristics of subglacial drainage systems. We use field-based GPS measurements of subglacial channel longitudinal profiles, along with stereo imagery-derived digital surface models (DSMs), and novel kinematic portable lidar data to establish a detailed characterization of subglacial channels in our field study area, including their distinction from rivers and other meltwater drainage systems. Subglacial channels typically cluster in groups of ˜ 10 channels and are oriented perpendicular to active or former ice margins. Although their overall direction generally follows topographic gradients, channels can be oblique to topographic gradients and have undulating longitudinal profiles. We also observe that the width of first-order tributaries is 1 to 2 orders of magnitude larger than in Devon Island river systems and approximately constant. Furthermore, our findings are consistent with theoretical expectations drawn from analyses of flow driven by gradients in effective water pressure related to variations in ice thickness. Our field and remote sensing observations represent the first high-resolution study of the subglacial geomorphology of the high Arctic, and provide

  17. Hydrothermal alteration at Roosevelt Hot Springs KGRA: DDH 1976-1

    Energy Technology Data Exchange (ETDEWEB)

    Bryant, N.L.; Parry, W.T.

    1977-09-01

    Hot waters of the Roosevelt Thermal Area, Utah, have altered granitic rocks and detritus of the Mineral Range pluton, Utah. Alteration and mineral deposition recognized in a 200' drill core from DDH 1-76 is most intense in the upper 100 feet which consists of altered alluvium and opal deposits; the lower 100 feet is weakly altered quartz monzonite. Petrographic, x-ray, and chemical methods were used to characterize systematic changes in chemistry and mineralogy. Comparison of the alteration mineral assemblages with known water chemistry and equilibrium activity diagrams suggests that a simple solution equilibrium model cannot account for the alteration. A model is proposed in which upward moving thermal water supersaturated with respect to quartz and a downward moving cool water undersaturated with respect to quartz produces the observed alteration. An estimate of the heat flow contributions from hydrothermal alteration was made by calculating reaction enthalpies for alteration reactions at each depth. The estimated heat flow varied from .02 HFU (for 200' depth, 400,000 yr duration, and no sulfur oxidation) to 67 HFU (for 5,000' depth, 1,000 yr duration, and all sulfur oxidized from sulfide). Heat flow contributions from hydrothermal alteration are comparable with those from a cooling granitic magma.

  18. Hydrothermal alteration of deep fractured granite: Effects of dissolution and precipitation

    Science.gov (United States)

    Nishimoto, Shoji; Yoshida, Hidekazu

    2010-03-01

    This paper investigates the mineralogical effects of hydrothermal alteration at depth in fractures in granite. A fracture accompanied by an alteration halo and filled with clay was found at a depth of 200 m in a drill core through Toki granite, Gifu, central Japan. Microscopic observation, XRD, XRF, EPMA and SXAM investigations revealed that the microcrystalline clays consist of illite, quartz and pyrite and that the halo round the fracture can be subdivided into a phyllic zone adjacent to the fracture, surrounded by a propylitic zone in which Fe-phyllosilicates are present, and a distinctive outer alteration front characterized by plagioclase breakdown. The processes that result in these changes took place in three successive stages: 1) partial dissolution of plagioclase with partial chloritization of biotite; 2) biotite dissolution and precipitation of Fe-phyllosilicate in the dissolution pores; 3) dissolution of K-feldspar and Fe-phyllosilicate, and illite precipitation associated with development of microcracks. These hydrothermal alterations of the granite proceed mainly by a dissolution-precipitation process resulting from the infiltration of hydrothermal fluid along microcracks. Such infiltration causes locally high mobility of Al and increases the ratio of fluid to rock in the alteration halo. These results contribute to an understanding of how granitic rock becomes altered in orogenic fields such as the Japanese island arc.

  19. Hydrothermal Alteration in an Acid-Sulphate Geothermal Field: Sulphur Springs, Saint Lucia

    Science.gov (United States)

    Joseph, E. P.; Barrett, T. J.

    2017-12-01

    Sulphur Springs is a vigorous geothermal field associated with the Soufrière Volcanic Centre in southern Saint Lucia. Bubbling hydrothermal pools are rich in sodium-calcium sulphate, with pHs of 3-7 and temperatures of 41-97ºC. Fumaroles have temperatures up to, and at times above, 100°C. Gases from bubbling pools and fumaroles have high contents of CO2 (601-993 mmol/mol) and H2S (3-190 mmol/mol). To investigate the nature and extent of hydrothermal alteration, detailed chemical analysis was carried out on 25 altered rocks, 10 sediments from pools and creeks in the main discharge area, and 15 little-altered rocks up to 2 km away from geothermal field. Eight altered samples were also analysed for stable isotope compositions, with mineralogy determined by X-ray diffraction and mineral liberation analysis. Least-altered host rocks comprise calc-alkaline feldspar-quartz-porphyritic dacites of near-uniform composition that form massive domes and volcaniclastic units. These rocks were emplaced 10-30 Ka ago (Lindsay et al. 2013). Within the geothermal field, the dacites have been highly altered to kaolinite, quartz, cristobalite, alunite, natroalunite, smectite, native sulphur, jarosite, gypsum and amorphous compounds. Muds from grey to blackish hydrothermal pools additionally contain iron sulphides, mainly pyrite. Despite intense alteration of the original dacites, Zr and Ti have remained essentially immobile, allowing the calculation of mass changes. Major depletions of Fe, Mg, Ca, Na and commonly Si occur over an area of at least 200 x 400 m. The most altered rocks also show losses of Al, light REE and Y, implying leaching by highly acidic waters. A few altered rocks have, however, gained Al together with Si and P. Also present are m-scale zones of silica + native sulphur, wherein the silica appears to represent a residue from the leaching of dacite, rather than a hydrothermal addition. Delta-34S values of samples containing mixtures of sulphates, native sulphur and

  20. Paris vs. Murchison: Impact of hydrothermal alteration on organic matter in CM chondrites

    Science.gov (United States)

    Vinogradoff, V.; Le Guillou, C.; Bernard, S.; Binet, L.; Cartigny, P.; Brearley, A. J.; Remusat, L.

    2017-09-01

    Unravelling the origin of organic compounds that were accreted into asteroids requires better constraining the impact of asteroidal hydrothermal alteration on their isotopic signatures, molecular structures, and spatial distribution. Here, we conducted a multi-scale/multi-technique comparative study of the organic matter (OM) from two CM chondrites (that originate from the same parent body or from identical parent bodies that accreted the same mixture of precursors) and underwent a different degree of hydrothermal alteration: Paris (a weakly altered CM chondrite - CM 2.8) and Murchison (a more altered one - CM 2.5). The Paris insoluble organic matter (IOM) shows a higher aliphatic/aromatic carbon ratio, a higher radical abundance and a lower oxygen content than the Murchison IOM. Analysis of the OM in situ shows that two texturally distinct populations of organic compounds are present within the Paris matrix: sub-micrometric individual OM particles and diffuse OM finely distributed within phyllosilicates and amorphous silicates. These results indicate that hydrothermal alteration on the CM parent body induced aromatization and oxidation of the IOM, as well as a decrease in radical and nitrogen contents. Some of these observations were also reported by studies of variably altered fragment of Tagish Lake (C2), although the hydrothermal alteration of the OM in Tagish Lake was apparently much more severe. Finally, comparison with data available in the literature suggests that the parent bodies of other chondrite petrologic groups could have accreted a mixture of organic precursors different from that accreted by the parent body of CMs.

  1. Hydrothermal alterations as natural analogues of radionuclide migration in granitic rocks

    International Nuclear Information System (INIS)

    Piantone, P.

    1989-01-01

    The document is the final report of the project Hydrothermal alteration systems as analogues of nuclear waste repositories in granitic rocks which was the subject of contract n 0 F1 1 W/0072-F (CD) performed at shared cost between the Bureau de Recherches Geologiques et Minieres (BRGM), the Commissariat a l'Energie Atomique and the Commission of the European Communities as part of the MIRAGE programme. This study is the continuation of a preliminary study made by BRGM in 1986 and which concerned the same programme. The data given in this report were obtained from the study of the infilling and hydrothermalized walls of a mineralized vein located at Fombillou, Lot Department, in the French Massif Central. A satisfactory model of the processes generated by hydrothermal alteration then by climatic weathering such as formation of new minerals, flow of elements and variations in volume, was thus built. The mobility of elements displaying physical and chemical properties similar to those of radionuclides present in high-level radioactive waste was studied. A preliminary thermodynamic simulation of mineral transformations and transfers of matter during hydrothermal alteration was performed using the calculation code CEQCSY (Chemical EQuilibrium in Complex SYstem). This simulation is based on the values of the main physical and chemical parameters deduced from the analysis of the natural system. On the basis of the results obtained from Fombillou, an appraisal was made of the response of the granitic environment which has been disturbed by a hydrothermal system produced by heat emitted by the storage of high-level radio-active waste as well as its potential capacities of retention in case of possible leakage

  2. Hydrothermal alteration styles in ancient and modern orogenic gold deposits, New Zealand

    International Nuclear Information System (INIS)

    Craw, D.; Upton, P.; MacKenzie, D.J.

    2009-01-01

    Orogenic hydrothermal systems in the South Island of New Zealand were active during Mesozoic and late Cenozoic collisional deformation and metamorphism of greywacke/schist terranes. Observations on the currently active mountain-building environment yield insights on processes occurring in the upper 5-15 km of the crust, and observations on an adjacent lithologically identical exhumed ancient mountain belt provide information on processes at 10-20 km in the crust. Hydrothermal fluids were mainly derived from metamorphic dehydration reactions and/or circulating topographically driven meteoric water in these mountain belts. Three geochemically and mineralogically different types of hydrothermal alteration and vein mineralisation occurred in these orogenic belts, and gold enrichment (locally economic) occurred in some examples of each of these three types. The first type of alteration involved fluids that were in or near chemical equilibrium with their greenschist facies host rocks. Fluid flow was controlled by discontinuous fractures, and by microshears and grain boundaries in host rocks, in zones from metres to hundreds of metres thick. Vein and alteration mineralogy was similar to that of the host rocks, and included calcite and chlorite. The second type of alteration occurred where the fluids were in distinct disequilibrium with the host rocks. Fracture permeability was important for fluid flow, but abundant host rock alteration occurred as well. The alteration zones were characterised by decomposition of chlorite and replacement by ankeritic carbonate in zones up to tens of metres thick. The mineralising fluid was deep-sourced and initially rock-equilibrated, with some meteoric input. The third type of mineralisation was controlled almost exclusively by fracture permeability, and host rock alteration was minor (centimetre scale). This mineralisation type commonly involved calcite and chlorite as vein and alteration minerals, and mineralisation fluids had a major

  3. International Planning for Subglacial Lake Exploration

    Science.gov (United States)

    Kennicutt, M.; Priscu, J.

    2003-04-01

    As one of the last unexplored frontiers on our planet, subglacial lakes offer a unique and exciting venue for exploration and research. Over the past several years, subglacial lakes have captured the imagination of the scientific community and public, evoking images of potential exotic life forms surviving under some of the most extreme conditions on earth. Various planning activities have recognized that due to the remote and harsh conditions, that a successful subglacial lake exploration program will entail a concerted effort for a number of years. It will also require an international commitment of major financial and human resources. To begin a detailed planning process, the Scientific Committee on Antarctic Research (SCAR) convened the Subglacial Antarctic Lake Exploration Group of Specialists (SALEGOS) in Tokyo in 2000. The group was asked to build on previous workshops and meetings to develop a plan to explore subglacial lake environments. Its mandate adopted the guiding principles as agreed in Cambridge in 1999 that the program would be interdisciplinary in scope, be designed for minimum contamination and disturbance of the subglacial lake environment, have as a goal lake entry and sample retrieval, and that the ultimate target of the program should be Lake Vostok exploration. Since its formation SALEGOS has met three times and addressed some of the more intractable issues related to subglacial lake exploration. Topics under discussion include current state-of-the-knowledge of subglacial environments, technological needs, international management and organizational strategies, a portfolio of scientific projects, "clean" requirements, and logistical considerations. In this presentation the actvities of SALEGOS will be summarized and recommendations for an international subglacial lake exploration program discussed.

  4. The hydrothermal alteration in the context of geologic evolution from Pocos de Caldas Alkaline Massif, MG-SP

    International Nuclear Information System (INIS)

    Garda, G.M.

    1990-01-01

    The Pocos de Caldas Alkaline Massif covers 800 km 2 , a quarter of which is hydrothermally altered. Such proportion is uncommon, when compared to the know alkaline massifs of the world. The hydrothermal alteration is associated with Zr, U and Mo mineralizations which are predominantly located in the central-southern portion of the massif, in the central-eastern circular structure. The colour of the altered rock (and its soil) in that area is typically whitish beige to yellowish white and is regionally called potassic rock. The Osamu Utsumi Mine, also referred to as the uranium ore of Campo do Cercado, is located 25 Km to the south of Pocos de Caldas City and was explored, from 1977 to 1989, through the open pit method. A sequence of alteration minerals adapted to lowering temperatures should be expected; however, only illite and alkaline feldspar are observed in the hydrothermally altered portions of the massif, and their formation must have been controlled mainly by kinetic, other than thermal factors. The irrestrict circulation of relatively hotter hydrothermal fluids must have happened at the beginning of the process, diminishing immediately after the cooling of the brecciated areas (and the subjacent magmatic body), leading the system to kinetics levels that made subsequent hydrothermal alteration impossible. (author)

  5. Genesis of hydrothermal alterations using stable isotope geochemistry in Takestan area (Tarom zone

    Directory of Open Access Journals (Sweden)

    Batool Taghipou

    2015-12-01

    Full Text Available Hydrothermal alteration processes are extensively took place on volcanic and pyroclstics of Takestan area. Existence of abundant, deep fracturing and subvolcanic intrusions are enhanced extend hydrothermal alteration zones. The following alteration zones are determined: propylitic, argillic, advanced argillic and sillicic. There are outcropped and widespread in different size and limit. Formation of siliceous sinter, silicified tuffs with preserved primary sedimentary layering including pure mineralized alunite patches are most outstanding. Quartz, sussoritic plagioclase, chlorite, sericite and alunite are main mineral constituents in the volcanics. On the basis of geochemical data volcanic rocks are rhyolite, dacite, andesite, andesitic-basalt and basalt in composition. Acid-sulfate zone is the type of alteration in Tarom area and alunite is an index mineral of this zone. Results of 18O, D and 34S stable isotope geochemistry on altered minerals (muscovite, kaolinite and alunite, revealed that alteration fluids are magmatic in origin.

  6. Hydrothermal alteration of a rhyolitic hyaloclastite from Ponza Island, Italy

    Science.gov (United States)

    Ylagan, Robert F.; Altaner, Stephen P.; Pozzuoli, Antonio

    1996-12-01

    A rhyolitic hyaloclastite from Ponza island, Italy, has been hydrothermally altered producing four distinct alteration zones based on XRD and field textures: (1) non-pervasive argillic zone; (2) propylitic zone; (3) silicic zone; and (4) sericitic zone. The unaltered hyaloclastite is a volcanic breccia with clasts of vesiculated obsidian in a matrix of predominantly pumice lapilli. Incomplete alteration of the hyaloclastite resulted in the non pervasive argillic zone, characterized by smectite and disordered opal-CT. Obsidian clasts, some pumice lapilli, and pyrogenic plagioclase and biotite are unaltered. Smectite has an irregular flakey morphology, although euhedral particles are occasionally observed. The propylitic zone is characterized by mixed-layer illite/smectite (I/S) with 10 to 85% illite (I), mordenite, opal-C and authigenic K-feldspar (akspar). The matrix of the hyaloclastite is completely altered and obsidian clasts are silicified; however, plagioclase and biotite phenocrysts remain unaltered. Flakey I/S replaces pumice, and mordenite, akspar and silica line and fill pores. I/S particles are composed predominantly of subequant plates and euhedral laths. The silicic zone is characterized by highly illitic I/S with ≥ 90% I, quartz, akspar and occasional albite. In this zone the matrix and clasts are completely altered, and pyrogenic plagioclase shows significant alteration. Illitic I/S has a euhedral lath-like morphology. In the sericitic zone the hyaloclastite altered primarily to illitic I/S with ≥ 66% I, quartz, and minor akspar and pyrite. Clay minerals completely replace pyrogenic feldspars and little evidence remains of the original hyaloclastite texture. Unlike other zones, illitic I/S is fibrous and pure illite samples are composed of euhedral laths and hexagonal plates. The temperatures of hydrothermal alteration likely ranged from 30 to 90 °C for the argillic zone, from 110 to 160 °C for the propylitic zone, from 160 to 270 °C for the

  7. Rare earth element behaviour and hydrothermal alteration, Lihir Island, Papua New Guinea

    International Nuclear Information System (INIS)

    Lottermoser, B.G.

    1990-01-01

    This contribution documents extreme rare earth elements (REE) mobility associated with a currently active subaerial hydrothermal system on Lihir Island, Papua New Guinea, which is host to a large epithermal gold deposit. Instrumental thermal activation analysis for selected REE and for other trace elements has been performed at the Lucas Heights Research Laboratories in Sydney. Samples and standards were irradiated with thermal neutrons and subsequently counted on coaxial and planar detectors after several decay periods. The gamma-ray spectra were processed using FORTRAN data reduction program. The wide range of (La/Lu) c n, (La/Sm) c n and (Tb/Lu) c n ratios reflects a pronounced mobilisation and fractionation of REE during the hydrothermal process. It is estimated that the increasing fractionation of REE, and especially of 'light rare earth' (La to Sm), up the alteration sequence is the result of decreasing pH, temperature and alkalinity of the hydrothermal fluids with increasing alteration intensity. 15 refs., 2 figs

  8. Alteration related to hydrothermal activity of the Nevado del Ruiz volcano (NRV), Colombia

    International Nuclear Information System (INIS)

    Forero, Jhon; Zuluaga, Carlos; Mojica, Jaime

    2011-01-01

    The hydrothermal activity in the NRV generates alteration characterized by mineral associations depending one number of physic-chemical factors of the hydrothermal system. Petrography of unaltered rocks was used to establish the mineral assemblage prior to rock-fluid interaction. XRD was used in altered rocks, where it was not possible to recognize the alteration products. the observed mineral assemblages indicate advanced and intermediate argillic alterations, this and the observation of very low modal proportion of sulphates, sulphides and native sulphur in some areas could point to a low sulphidation zone. However, the proximity to the volcano and the presence of acid thermal waters and steam pose an apparent contradiction with an expected high sulphidation zone which is explained by climatic conditions, where excess water has dissolved and leached sulfides, sulphur and sulphates close to the volcano. fault zones serve as conducts for fluid transport and have acid-sulphate mineral associations produced by atmospheric oxidation at the water table in a steam-heated environment of H 2 S released by deeper, boiling fluids or by the disproportionation of magmatic SO 2 to H 2 S and H 2 SO 4 during condensation of magmatic vapor plume at intermedia depths in magmatic hydrothermal environment in andesitic volcanic terrain characteristic of high sulphidation zones.

  9. A Paleomagnetic and Diagenetic Study of the Woodford Shale, Oklahoma, U.S.A.: The Timing of Hydrothermal Alteration

    Science.gov (United States)

    Roberts, J.; Elmore, R. D.

    2017-12-01

    An oriented Woodford Shale core from the Ardmore Basin near the Ouachita thrust zone (Core B) was sampled to identify diagenetic events and interpret their origin, and to test if a magnetization was present that can be used to date the altering event(s). The shale is extensively altered, exhibiting a complex paragenesis with multiple fractures and brecciated intervals. Multiple hydrothermal minerals, including biotite, magnesite, norsethite, witherite, gorceixite, potassium feldspar, sphalerite, chalcopyrite, and saddle dolomite, are present in and around fractures and in the matrix. Vitrinite and bitumen reflectance measurements indicate VRo values of 1.82% ( 230°C). Two other Woodford Shale cores (A and C) from the Anadarko Basin also contain hydrothermal minerals. Vitrinite and bitumen reflectance data reveal trends between thermal maturity and the level of hydrothermal alteration, with Core A (0.80% VRo ( 125°C) displaying the lowest alteration, and Core C ( 1.5% VRo ( 210°C) displaying intermediate alteration compared to core B. Paleomagnetic analysis of Core B reveals the presence of a characteristic remanent magnetization (ChRM) with south-southeasterly declinations and shallow inclinations that is unblocked by 450°C and is interpreted to reside in magnetite. This ChRM is interpreted to be either a chemical remanent magnetization (CRM) or a thermochemical remanent magnetization (TCRM) acquired during the Late Permian based on the pole position. The presence of specimens with the CRM/TCRM in altered rock and high thermal maturities suggests that this CRM/TCRM originated from alteration by hydrothermal fluids. These results suggest that the Woodford Shale evolved into an open diagenetic system. In addition to causing heightened thermal maturities, these hydrothermal fluids both increased porosity through dissolution and decreased porosity through precipitation of minerals. The Late Permian timing agrees with the dating of hydrothermal alteration found

  10. Effects of chemical alteration on fracture mechanical properties in hydrothermal systems

    Science.gov (United States)

    Callahan, O. A.; Eichhubl, P.; Olson, J. E.

    2015-12-01

    Fault and fracture networks often control the distribution of fluids and heat in hydrothermal and epithermal systems, and in related geothermal and mineral resources. Additional chemical influences on conduit evolution are well documented, with dissolution and precipitation of mineral species potentially changing the permeability of fault-facture networks. Less well understood are the impacts of chemical alteration on the mechanical properties governing fracture growth and fracture network geometry. We use double-torsion (DT) load relaxation tests under ambient air conditions to measure the mode-I fracture toughness (KIC) and subcritical fracture growth index (SCI) of variably altered rock samples obtained from outcrop in Dixie Valley, NV. Samples from southern Dixie Valley include 1) weakly altered granite, characterized by minor sericite in plagioclase, albitization and vacuolization of feldspars, and incomplete replacement of biotite with chlorite, and 2) granite from an area of locally intense propylitic alteration with chlorite-calcite-hematite-epidote assemblages. We also evaluated samples of completely silicified gabbro obtained from the Dixie Comstock epithermal gold deposit. In the weakly altered granite KIC and SCI are 1.3 ±0.2 MPam1/2 (n=8) and 59 ±25 (n=29), respectively. In the propylitic assemblage KIC is reduced to 0.6 ±0.1 MPam1/2 (n=11), and the SCI increased to 75 ±36 (n = 33). In both cases, the altered materials have lower fracture toughness and higher SCI than is reported for common geomechanical standards such as Westerly Granite (KIC ~1.7 MPam1/2; SCI ~48). Preliminary analysis of the silicified gabbro shows a significant increase in fracture toughness, 3.6 ±0.4 MPam1/2 (n=2), and SCI, 102 ±45 (n=19), compared to published values for gabbro (2.9 MPam1/2 and SCI = 32). These results suggest that mineralogical and textural changes associated with different alteration assemblages may result in spatially variable rates of fracture

  11. Understanding and Observing Subglacial Friction Using Seismology

    Science.gov (United States)

    Tsai, V. C.

    2017-12-01

    Glaciology began with a focus on understanding basic mechanical processes and producing physical models that could explain the principal observations. Recently, however, more attention has been paid to the wealth of recent observations, with many modeling efforts relying on data assimilation and empirical scalings, rather than being based on first-principles physics. Notably, ice sheet models commonly assume that subglacial friction is characterized by a "slipperiness" coefficient that is determined by inverting surface velocity observations. Predictions are usually then made by assuming these slipperiness coefficients are spatially and temporally fixed. However, this is only valid if slipperiness is an unchanging material property of the bed and, despite decades of work on subglacial friction, it has remained unclear how to best account for such subglacial physics in ice sheet models. Here, we describe how basic seismological concepts and observations can be used to improve our understanding and determination of subglacial friction. First, we discuss how standard models of granular friction can and should be used in basal friction laws for marine ice sheets, where very low effective pressures exist. We show that under realistic West Antarctic Ice Sheet conditions, standard Coulomb friction should apply in a relatively narrow zone near the grounding line and that this should transition abruptly as one moves inland to a different, perhaps Weertman-style, dependence of subglacial stress on velocity. We show that this subglacial friction law predicts significantly different ice sheet behavior even as compared with other friction laws that include effective pressure. Secondly, we explain how seismological observations of water flow noise and basal icequakes constrain subglacial physics in important ways. Seismically observed water flow noise can provide constraints on water pressures and channel sizes and geometry, leading to important data on subglacial friction

  12. Iron isotope fractionation during hydrothermal ore deposition and alteration

    Science.gov (United States)

    Markl, Gregor; von Blanckenburg, Friedhelm; Wagner, Thomas

    2006-06-01

    Iron isotopes fractionate during hydrothermal processes. Therefore, the Fe isotope composition of ore-forming minerals characterizes either iron sources or fluid histories. The former potentially serves to distinguish between sedimentary, magmatic or metamorphic iron sources, and the latter allows the reconstruction of precipitation and redox processes. These processes take place during ore formation or alteration. The aim of this contribution is to investigate the suitability of this new isotope method as a probe of ore-related processes. For this purpose 51 samples of iron ores and iron mineral separates from the Schwarzwald region, southwest Germany, were analyzed for their iron isotope composition using multicollector ICP-MS. Further, the ore-forming and ore-altering processes were quantitatively modeled using reaction path calculations. The Schwarzwald mining district hosts mineralizations that formed discontinuously over almost 300 Ma of hydrothermal activity. Primary hematite, siderite and sulfides formed from mixing of meteoric fluids with deeper crustal brines. Later, these minerals were partly dissolved and oxidized, and secondary hematite, goethite and iron arsenates were precipitated. Two types of alteration products formed: (1) primary and high-temperature secondary Fe minerals formed between 120 and 300 °C, and (2) low-temperature secondary Fe minerals formed under supergene conditions (illustrates the potential of the new technique in deciphering ore formation and alteration processes. Isotope ratios are strongly dependent on and highly characteristic of fluid and precipitation histories. Therefore, they are less suitable to provide information on Fe sources. However, it will be possible to unravel the physico-chemical processes leading to the formation, dissolution and redeposition of ores in great detail.

  13. Lithological and Hydrothermal Alteration Mapping of Epithermal, Porphyry and Tourmaline Breccia Districts in the Argentine Andes Using ASTER Imagery

    Directory of Open Access Journals (Sweden)

    Francisco J. Testa

    2018-01-01

    Full Text Available The area of interest is located on the eastern flank of the Andean Cordillera, San Juan province, Argentina. The 3600 km2 area is characterized by Siluro-Devonian to Neogene sedimentary and igneous rocks and unconsolidated Quaternary sediments. Epithermal, porphyry-related, and magmatic-hydrothermal breccia-hosted ore deposits, common in this part of the Frontal Cordillera, are associated with various types of hydrothermal alteration assemblages. Kaolinite – alunite-rich argillic, quartz – illite-rich phyllic, epidote – chlorite – calcite-rich propylitic and silicic are the most common hydrothermal alteration assemblages in the study area. VNIR, SWIR and TIR ASTER data were used to characterize geological features on a portion of the Frontal Cordillera. Red-green-blue band combinations, band ratios, logical operations, mineral indices and principal component analysis were applied to successfully identify rock types and hydrothermal alteration zones in the study area. These techniques were used to enhance geological features to contrast different lithologies and zones with high concentrations of argillic, phyllic, propylitic alteration mineral assemblages and silicic altered rocks. Alteration minerals detected with portable short-wave infrared spectrometry in hand specimens confirmed the capability of ASTER to identify hydrothermal alteration assemblages. The results from field control areas confirmed the presence of those minerals in the areas classified by ASTER processing techniques and allowed mapping the same mineralogy where pixels had similar information. The current study proved ASTER processing techniques to be valuable mapping tools for geological reconnaissance of a large area of the Argentinean Frontal Cordillera, providing preliminary lithologic and hydrothermal alteration maps that are accurate as well as cost and time effective.

  14. Geothermometry, geochronology, and mass transfer associated with hydrothermal alteration of a rhyolitic hyaloclastite from Ponza Island, Italy

    Science.gov (United States)

    Altaner, S.P.; Ylagan, R.F.; Savin, S.M.; Aronson, J.L.; Belkin, H.E.; Pozzuoli, A.

    2003-01-01

    A rhyolitic hyaloclastite from Ponza Island, Italy, was hydrothermally altered, producing four distinct alteration zones based on X-ray diffraction mineralogy and field textures: (1) nonpervasive argillic zone; (2) propylitic zone; (3) silicic zone; and (4) sericitic zone. The unaltered hyaloclastite is volcanic breccia with clasts of vesiculated obsidian in a matrix of predominantly pumice lapilli. Incomplete alteration of the hyaloclastite resulted in the nonpervasive argillic zone, characterized by smectite and disordered opal-CT. The other three zones exhibit more complete alteration of the hyaloclastite. The propylitic zone is characterized by mixed-layer illite-smectite (I-S) with 10 to 85% I, mordenite, opal-C, and authigenic K-feldspar (akspar). The silicic zone is characterized by I-S with ???90% I, pure illite, quartz, akspar, and occasional albite. The sericitic zone consists primarily of I-S with ???66% I, pure illite, quartz, and minor akspar and pyrite. K/Ar dates of I-S indicate hydrothermal alteration occurred at 3.38 ?? 0.08 Ma. Oxygen isotope compositions of I-S systematically decrease from zones 1 to 4. In the argillic zone, smectite has ??18 O values of 21.7 to 22.0??? and I-S from the propylitic, silicic, and sericitic zones ranges from 14.5 to 16.3???, 12.5 to 14.0???, and 8.6 to 11.9???, respectively. ??18 O values for quartz from the silicic and sericitic zones range from 12.6 to 15.9???. By use of isotope fractionation equations and data from authigenic quartz-hosted primary fluid inclusions, alteration temperatures ranged from 50 to 65 ??C for the argillic zone, 85 to 125 ??C for the propylitic zone, 110 to 210 ??C for the silicic zone, and 145 to 225 ??C for the sericitic zone. Fluid inclusion data and calculated ??18 O water values indicate that hydrothermal fluids were seawater dominated. Mass-transfer calculations indicate that hydrothermal alteration proceeded in a relatively open chemical system and alteration in the sericitic zone

  15. Investigating palaeo-subglacial lakes in the central Barents Sea

    Science.gov (United States)

    Esteves, M.; Shackleton, C.; Winsborrow, M.; Andreassen, K.; Bjarnadóttir, L. R.

    2017-12-01

    In the past decade hundreds of subglacial lakes have been detected beneath the Antarctic Ice Sheet, and several more beneath the Greenland Ice Sheet. These are important components of the subglacial hydrological system and can influence basal shear stress, with implications for ice sheet dynamics and mass balance, potentially on rapid timescales. Improvements in our understanding of subglacial hydrological systems are therefore important, but challenging due to the inaccessibility of contemporary subglacial environments. Whilst the beds of palaeo-ice sheets are easier to access, few palaeo-subglacial lakes have been identified due to uncertainties in the sedimentological and geomorphological diagnostic criteria. In this study we address these uncertainties, using a suite of sedimentological, geomorphological and modelling approaches to investigate sites of potential palaeo-subglacial lakes in the central Barents Sea. Geomorphological signatures of hydraulic activity in the area include large meltwater channels, tunnel valleys, and several interlinked basins. Modelling efforts indicate the potential for subglacial hydraulic sinks within the area during the early stages of ice retreat since the Last Glacial Maximum. In support of this, sedimentological observations indicate the presence of a dynamic glaciolacustrine depositional environment. Using the combined results of the modelling, geomorphology, and sedimentological analyses, we conclude that palaeo-subglacial lakes are likely to have formed on the northwestern banks of Thor Iversenbanken, central Barents Sea, and suggest that numerous other subglacial lakes may have been present beneath the Barents Sea Ice Sheet. Furthermore, we investigate and refine the existing diagnostic criteria for the identification of palaeo-subglacial lakes.

  16. Mechanical and physical properties of hydrothermally altered rocks, Taupo Volcanic Zone, New Zealand

    Science.gov (United States)

    Wyering, L. D.; Villeneuve, M. C.; Wallis, I. C.; Siratovich, P. A.; Kennedy, B. M.; Gravley, D. M.; Cant, J. L.

    2014-11-01

    Mechanical characterization of hydrothermally altered rocks from geothermal reservoirs will lead to an improved understanding of rock mechanics in a geothermal environment. To characterize rock properties of the selected formations, we prepared samples from intact core for non-destructive (porosity, density and ultrasonic wave velocities) and destructive laboratory testing (uniaxial compressive strength). We characterised the hydrothermal alteration assemblage using optical mineralogy and existing petrography reports and showed that lithologies had a spread of secondary mineralisation that occurred across the smectite, argillic and propylitic alteration zones. The results from the three geothermal fields show a wide variety of physical rock properties. The testing results for the non-destructive testing shows that samples that originated from the shallow and low temperature section of the geothermal field had higher porosity (15 - 56%), lower density (1222 - 2114 kg/m3) and slower ultrasonic waves (1925 - 3512 m/s (vp) and 818 - 1980 m/s (vs)), than the samples from a deeper and higher temperature section of the field (1.5 - 20%, 2072 - 2837 kg/m3, 2639 - 4593 m/s (vp) and 1476 - 2752 m/s (vs), respectively). The shallow lithologies had uniaxial compressive strengths of 2 - 75 MPa, and the deep lithologies had strengths of 16 - 211 MPa. Typically samples of the same lithologies that originate from multiple wells across a field have variable rock properties because of the different alteration zones from which each sample originates. However, in addition to the alteration zones, the primary rock properties and burial depth of the samples also have an impact on the physical and mechanical properties of the rock. Where this data spread exists, we have been able to derive trends for this specific dataset and subsequently have gained an improved understanding of how hydrothermal alteration affects physical and mechanical properties.

  17. Laboratory simulated hydrothermal alteration of sedimentary organic matter from Guaymas Basin, Gulf of California. Ph.D. Thesis

    Science.gov (United States)

    Leif, Roald N.

    1993-01-01

    High temperature alteration of sedimentary organic matter associated with marine hydrothermal systems involves complex physical and chemical processes that are not easily measured in most natural systems. Many of these processes can be evaluated indirectly by examining the geochemistry of the hydrothermal system in the laboratory. In this investigation, an experimental organic geochemical approach to studying pyrolysis of sedimentary organic matter is applied to the hydrothermal system in the Guaymas Basin, Gulf of California. A general survey of hydrothermal oils and extractable organic matter (bitumen) in hydrothermally altered sediments identified several homologous series of alkanones associated with a high temperature hydrothermal origin. The alkanones range in carbon number from C11 to C30 with no carbon number preference. Alkan-2-ones are in highest concentrations, with lower amounts of 3-, 4-, 5- (and higher) homologs. The alkanones appear to be pyrolysis products synthesized under extreme hydrothermal conditions. Hydrous pyrolysis and confinement pyrolysis experiments were performed to simulate thermally enhanced diagenetic and catagenetic changes in the immature sedimentary organic matter. The extent of alteration was measured by monitoring the n-alkanes, acyclic isoprenoids, steroid and triterpenoid biomarkers, polycyclic aromatic hydrocarbons and alkanones. The results were compared to bitumen extracts from sediments which have been naturally altered by a sill intrusion and accompanied hydrothermal fluid flow. These pyrolysis experiments duplicated many of the organic matter transformations observed in the natural system. Full hopane and sterane maturation occurred after 48 hr in experiments at 330 deg C with low water/rock mass ratios (0.29). A variety of radical and ionic reactions are responsible for the organic compound conversions which occur under extreme hydrothermal conditions. Short duration pyrolysis experiments revealed that a portion of the

  18. Hydrothermal alteration and mass exchange in the hornblende latite porphyry, Rico, Colorado

    Science.gov (United States)

    Larson, P.B.; Cunningham, C.G.; Naeser, C.W.

    1994-01-01

    The Rico paleothermal anomaly, southwestern Colorado, records the effects of a large hydrothermal system that was active at 4 Ma. This hydrothermal system produced the deep Silver Creek stockwork Mo deposit, which formed above the anomaly's heat source, and shallower base and precious-metal vein and replacement deposits. A 65 Ma hornblende latite porphyry is present as widespread sills throughout the area and provided a homogenous material that recorded the effects of the hydrothermal system up to 8 km from the center. Hydrothermal alteration in the latite can be divided into a proximal facies which consists of two assemblages, quartz-illite-calcite and chlorite-epidote, and a distal facies which consists of a distinct propylitic assemblage. Temperatures were gradational vertically and laterally in the anomaly, and decreased away from the centra heat source. A convective hydrothermal plume, 3 km wide and at least 2 km high, was present above the stock-work molybdenum deposit and consisted of upwelling, high-temperature fluids that produced the proximal alteration facies. Distal facies alteration was produced by shallower cooler fluids. The most important shallow base and precious-metal vein deposits in the Rico district are at or close to the boundary of the thermal plume. Latite within the plume had a large loss of Na2O, large addition of CaO, and variable SiO2 exchante. Distal propylitized latite samples lost small amounts of Na2O and CaO and exchanged minor variable amounts of SiO2. The edge of the plume is marked by steep Na2O exchange gradients. Na2O exchange throughout the paleothermal anomaly was controlled by the reaction of the albite components in primary plagioclase and alkali feldspars. Initial feldspar alteration in the distal facies was dominated by reaction of the plagioclase, and the initial molar ratio of reactants (alkali feldspar albite component to plagioclase albite component) was 0.35. This ratio of the moles of plagioclase to alkali feldspar

  19. Hydrothermal alteration at Roosevelt Hot Springs KGRA - DDH 1976-1

    Energy Technology Data Exchange (ETDEWEB)

    Bryant, N.L.; Parry, W.T.

    1977-09-01

    Hot waters of the Roosevelt Thermal Area, Utah, have altered granitic rocks and detritus of the Mineral Range pluton, Utah. Petrographic, x-ray, and chemical methods were used to characterize systematic changes in chemistry and mineralogy. Major alteration zones include: 1) an advanced argillic zone in the upper 30 feet of altered detritus containing alunite, opal, vermiculite, and relic quartz; 2) an argillic zone from 30 feet to 105 feet containing kaolinite, muscovite, and minor alunite; and 3) a propylitic zone from 105 to 200 feet containing muscovite, pyrite, marcasite, montmorillonite, and chlorite in weakly altered quartz monzonite. Comparison of the alternation mineral assemblages with known water chemistry and equilibrium activity diagrams suggests that a simple solution equilibrium model cannot account for the alteration. A model is proposed in which upward moving thermal water supersaturated with respect to quartz and a downward moving cool water undersaturated with respect to quartz produces the observed alteration. An estimate of the heat flow contributions from hydrothermal alteration was made by calculating reaction enthalpies for alteration reactions at each depth.

  20. Crystallization process of zircon and fergusonite during hydrothermal alteration in Nechalacho REE deposit, Thor Lake, Canada

    Science.gov (United States)

    Hoshino, M.; Watanabe, Y.; Murakami, H.; Kon, Y.; Tsunematsu, M.

    2012-04-01

    The core samples of two drill holes, which penetrate sub-horizontal mineralized horizons at Nechalacho REE deposit in the Proterozoic Thor Lake syenite, Canada, were studied in order to clarify magmatic and hydrothermal processes that enriched HFSE (e.g. Zr, Nb, Y and REE). Zircon is the most common REE minerals in Nechalacho REE deposit. The zircon is divided into five types as follows: Type-1 zircon occurs as single grain in phlogopite and the chondrite-normalized REE pattern is characterized by a steeply-rising slope from the LREE to the HREE with a positive Ce-anomaly and negative Eu-anomaly. This chemical characteristic is similar to that of igneous zircon. Type-2 zircon consists of HREE-rich magmatic porous core and LREE-Nb-F-rich hydrothermal rim. This type zircon is mostly included in phlogopite and fluorite, and occasionally in microcline. Type-3 zircon is characterized by euhedral to anhedral crystal, occurring in a complex intergrowth with REE fluorocarbonates. Type-3 zircons have high contents of REE, Nb and fluorine. Type-4 zircon consists of porous-core and -rim zones, but their chemical compositions are similar to each other. This type zircon is a subhedral crystal rimmed by fergusonite. Type-5 zircon is characterized by smaller, porous and subhedral to anhedral crystals. The interstices between small zircons are filled by fergusonite. Type-4 and -5 zircons show low REE and Nb contents. Occurrences of these five types of zircon are different according to the depth and degree of the alteration by hydrothermal solutions rich in F- and CO3 of the two drill holes, which permit a model for evolution of the zircon crystallization in Nechalacho REE deposit as follows: (1) type-1 (single magmatic zircon) is formed in miaskitic syenite. (2) LREE-Nb-F-rich hydrothermal zircon formed around HREE-rich magmatic zircon (type-2 zircon); (3) type-3 zircon crystallized thorough F and CO3-rich hydrothermal alteration of type-2 zircon which formed the complex

  1. A varied subglacial landscape under Thwaites Glacier, West Antarctica

    Science.gov (United States)

    Christianson, K. A.; Holschuh, N.; Paden, J. D.; Sprick, J.; Peters, L. E.; Anandakrishnan, S.; Alley, R. B.

    2017-12-01

    Deglaciated landscapes, whether subaerial or submarine, are often host to a rich panoply of subglacial landforms, such as drumlims, crags, megascale glacial lineations, grounding-line wedges, deep meltwater channels, and more. These landforms are formed and shaped by interactions between the ice and underlying substrate, and thus have implications for the flow of the overlying ice. Robust interpretations of the relationship between the ice and its substrate based on subglacial landforms that remain after deglaciation have been inhibited by a dearth of high-resolution observations of currently glaciated subglacial landscapes, where ice flow speed is known and where subglacial conditions can be ascertained using geophysical methods. Past direct observations of landforms under currently fast-flowing ice have been limited to a few ice streams, where relatively homogeneous, thick dilatant till layers may favor formation of specific subglacial features, i.e., megascale glacial lineations and grounding-zone wedges. Here we present two detailed gridded subglacial topographies, obtained from ice-penetrating radar measurements, from Thwaites Glacier, West Antarctica, where ice flows over a highly variable bed (in both topography and model-inferred basal shear stress). One grid is located ˜170 km downstream from the ice divide where ice is moving ˜100 m/yr. Here the ice advects over a broad basin and then flows into a subglacial ridge (of several hundred meters amplitude) oriented orthogonally to flow. A deep canyon ( 400 m) that cuts through this ridge in roughly the ice-flow direction and relatively soft sediments on the downstream side of the basin (immediately upstream of the canyon) suggest that a large subglacial lake may have formed in this location and drained catastrophically, as has been hypothesized as the formation mechanism for the deep canyons observed on the Amundsen Sea continental shelf. Numerous multiscale glacial lineations are also observed in the

  2. OPAQUE MINERAL CONTENT OF DUTLUCA VOLCANICS (BURHANİYE - BALIKESİR: THE EFFECT OF HYDROTHERMAL ALTERATION ON THESE MINERALS

    Directory of Open Access Journals (Sweden)

    Şükrü KOÇ

    2016-12-01

    Full Text Available Dutluca volcanics, which are known as Hallaçlar Formation in regional scale in the study area (Kurshens- ky, 1976, are composed of hydrothermally altered andesite and basaltic andesite. In these rocks, sulfidic minerals such as pyrite, enargite and chalcosine, and oxide and hydroxide minerals such as magnetite, hematite and goethite were detected as opaque minerals. The presence of enargite in opaque mineral para- genesis, and the changes observed in structures and textures of opaque and silicate minerals indicate that examined volcanics have been altered by highly sulfidic hydrothermal solutions. During the hydrothermal alteration process, which indicates at least in two phases, a diffuse pyritization rich in H S in reducing conditions and enargite mineral, which is known as pathfinder minerals in such processes, formed in the first phase. Later on; the extensive martitization developed in oxidizing conditions.

  3. Characteristics, extent and origin of hydrothermal alteration at Mount Rainier Volcano, Cascades Arc, USA: Implications for debris-flow hazards and mineral deposits

    Science.gov (United States)

    John, D.A.; Sisson, T.W.; Breit, G.N.; Rye, R.O.; Vallance, J.W.

    2008-01-01

    Hydrothermal alteration at Mount Rainier waxed and waned over the 500,000-year episodic growth of the edifice. Hydrothermal minerals and their stable-isotope compositions in samples collected from outcrop and as clasts from Holocene debris-flow deposits identify three distinct hypogene argillic/advanced argillic hydrothermal environments: magmatic-hydrothermal, steam-heated, and magmatic steam (fumarolic), with minor superimposed supergene alteration. The 3.8??km3 Osceola Mudflow (5600??y BP) and coeval phreatomagmatic F tephra contain the highest temperature and most deeply formed hydrothermal minerals. Relatively deeply formed magmatic-hydrothermal alteration minerals and associations in clasts include quartz (residual silica), quartz-alunite, quartz-topaz, quartz-pyrophyllite, quartz-dickite/kaolinite, and quartz-illite (all with pyrite). Clasts of smectite-pyrite and steam-heated opal-alunite-kaolinite are also common in the Osceola Mudflow. In contrast, the Paradise lahar, formed by collapse of the summit or near-summit of the edifice at about the same time, contains only smectite-pyrite and near-surface steam-heated and fumarolic alteration minerals. Younger debris-flow deposits on the west side of the volcano (Round Pass and distal Electron Mudflows) contain only low-temperature smectite-pyrite assemblages, whereas the proximal Electron Mudflow and a formed at higher temperatures. The pre-Osceola Mudflow alteration geometry is inferred to have consisted of a narrow feeder zone of intense magmatic-hydrothermal alteration limited to near the conduit of the volcano, which graded outward to more widely distributed, but weak, smectite-pyrite alteration within 1??km of the edifice axis, developed chiefly in porous breccias. The edifice was capped by a steam-heated alteration zone, most of which resulted from condensation of fumarolic vapor and oxidation of H2S in the unsaturated zone above the water table. Weakly developed smectite-pyrite alteration extended into

  4. Hydrothermal alteration in the Aluto-Langano geothermal field, Ethopia

    Energy Technology Data Exchange (ETDEWEB)

    Teklemariam, M. [Ethiopian Institute of Geological Surveys, Addis Adaba (Ethiopia). Geothermal Exploration Project; Battaglia, S.; Gianelli, G.; Ruggieri, G. [Consiglio Nazionale delle Ricerche, Pisa (Italy). Ist. Internazionale per le Ricerche Geotermiche

    1996-12-01

    The hydrothermal mineral assemblages found in eight wells (with a depth range of 1320-2500 m) of the active geothermal field of Aluto-Langano (Ethiopia) indicate a complex evolution of water-rock interaction processes. The zone of upflow is characterized by high temperatures (up to 335{sup o}C) and the presence of a propylitic alteration (epidote, calcite, quartz and chlorite, as major phases) coexisting with calcite and clay minerals. The zone of lateral outflow is characterized by mixing of deep and shallow waters and the occurrence of a calcite-clay alteration that overprints a previous propylitic assemblage. Clay minerals have a mushroom-shaped zonal distribution consistent with the present thermal structure of the field. Microprobe analyses have been carried out on chlorite and illite in order to apply several geothermometers. (author)

  5. Extraction of hydrothermal alterations from ASTER SWIR data from east Zanjan, northern Iran

    Science.gov (United States)

    Azizi, H.; Tarverdi, M. A.; Akbarpour, A.

    2010-07-01

    The use of satellite images for mineral exploration has been very successful in pointing out the presence of minerals such as smectite and kaolinite which are important in the identification of hydrothermal alterations. Shortwave infrared (SWIR) bands from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) with the wavelength of ASTER SWIR bands between 1.65 and 2.43 μm has a good potential for mapping a hydrothermal alteration minerals such as alunite, pyrophyllite, kaolinite, illite-muscovite-sericite, and carbonate. In this range, hydroxide minerals which have been produced by hydrothermal alteration exhibit good absorption compared to shorter or longer wavelengths. In this research which aims to remove atmospheric and topographic effects from ASTER SWIR data, the authors used the log-residual method (LRM) with the minimum noise fraction (MNF) transformation to create a pixel purity index (PPI) which was used to extract the most spectrally pure pixels from multispectral images. Spectral analyses of the clay mineralogy of the study area (east Zanjan, in northern Iran) were obtained by matching the unknown spectra of the purest pixels to the U.S. Geological Survey (USGS) mineral library. Three methods, spectral feature fitting (SFF), spectral angle mapping (SAM), and binary encoding (BE) were used to generate a score between 0 and 1, where a value of 1 indicates a perfect match showing the exact mineral type. In this way, it was possible to identify certain mineral classes, including chlorite, carbonate, calcite-dolomite-magnesite, kaolinite-smectite, alunite, and illite. In this research, two main propylitic and phyllic-argillic zones could be separated using their compositions of these minerals. These two alteration zones are important for porphyry copper deposits and gold mineralization in this part of Iran.

  6. Pukala intrusion, its age and connection to hydrothermal alteration in Orivesi, southwestern Finland

    Directory of Open Access Journals (Sweden)

    Matti Talikka

    2005-01-01

    Full Text Available The Pukala intrusion is situated in the Paleoproterozoic Svecofennian domain of the Fennoscandian Shield in the contact region between the Central Finland Granitoid Complex and the Tampere Belt. The acid subvolcanic intrusion, which is in contact or close to severalaltered domains, mainly consists of porphyritic granodiorite and trondhjemite. The Pukala intrusion was emplaced into volcanic sequence in an island-arc or fore-arc setting before or during the early stages of the main regional deformation phase of the Svecofennian orogeny. On the basis of the geochemical data, the Pukala intrusion is a peraluminous volcanic-arc granitoid. After crystallisation at 1896±3 Ma, multiphase deformation and metamorphismcaused alteration, recrystallisation, and orientation of the minerals, and tilted the intrusion steeply towards south. The 1851±5 Ma U-Pb age for titanite is connected to the late stages of the Svecofennian tectonometamorphic evolution of the region. Several hydrothermally altered domains are located in the felsic and intermediate metavolcanic rocks of the Tampere Belt within less than one kilometre south of the Pukala intrusion. Alteration is divided into three basic types: partial silica alteration, chlorite-sericite±silica alteration, and sericite alteration in shear zones. The first two types probably formed during the emplacement and crystallisation of the Pukala intrusion, and the third is linked to late shearing. Intense sericitisation and comb quartz bands in the contact of theintrusion and the altered domain at Kutemajärvi suggest that the hydrothermal system was driven by the Pukala intrusion.

  7. Hydrothermal Alteration Products as Key to Formation of Duricrust and Rock Coatings on Mars

    Science.gov (United States)

    Bishop, J. L.

    1999-03-01

    A model is presented for the formation of duricrust and rock coatings on Mars. Hydrothermal alteration of volcanic tephra may produce a corrosive agent that attacks rock surfaces and binds dust particles to form duricrust.

  8. Characteristics, extent and origin of hydrothermal alteration at Mount Rainier Volcano, Cascades Arc, USA: Implications for debris-flow hazards and mineral deposits

    Science.gov (United States)

    John, David A.; Sisson, Thomas W.; Breit, George N.; Rye, Robert O.; Vallance, James W.

    2008-08-01

    Hydrothermal alteration at Mount Rainier waxed and waned over the 500,000-year episodic growth of the edifice. Hydrothermal minerals and their stable-isotope compositions in samples collected from outcrop and as clasts from Holocene debris-flow deposits identify three distinct hypogene argillic/advanced argillic hydrothermal environments: magmatic-hydrothermal, steam-heated, and magmatic steam (fumarolic), with minor superimposed supergene alteration. The 3.8 km 3 Osceola Mudflow (5600 y BP) and coeval phreatomagmatic F tephra contain the highest temperature and most deeply formed hydrothermal minerals. Relatively deeply formed magmatic-hydrothermal alteration minerals and associations in clasts include quartz (residual silica), quartz-alunite, quartz-topaz, quartz-pyrophyllite, quartz-dickite/kaolinite, and quartz-illite (all with pyrite). Clasts of smectite-pyrite and steam-heated opal-alunite-kaolinite are also common in the Osceola Mudflow. In contrast, the Paradise lahar, formed by collapse of the summit or near-summit of the edifice at about the same time, contains only smectite-pyrite and near-surface steam-heated and fumarolic alteration minerals. Younger debris-flow deposits on the west side of the volcano (Round Pass and distal Electron Mudflows) contain only low-temperature smectite-pyrite assemblages, whereas the proximal Electron Mudflow and a < 100 y BP rock avalanche on Tahoma Glacier also contain magmatic-hydrothermal alteration minerals that are exposed in the avalanche headwall of Sunset Amphitheater, reflecting progressive incision into deeper near-conduit alteration products that formed at higher temperatures. The pre-Osceola Mudflow alteration geometry is inferred to have consisted of a narrow feeder zone of intense magmatic-hydrothermal alteration limited to near the conduit of the volcano, which graded outward to more widely distributed, but weak, smectite-pyrite alteration within 1 km of the edifice axis, developed chiefly in porous breccias

  9. Hydrothermal alteration maps of the central and southern Basin and Range province of the United States compiled from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data

    Science.gov (United States)

    Mars, John L.

    2013-01-01

    Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and Interactive Data Language (IDL) logical operator algorithms were used to map hydrothermally altered rocks in the central and southern parts of the Basin and Range province of the United States. The hydrothermally altered rocks mapped in this study include (1) hydrothermal silica-rich rocks (hydrous quartz, chalcedony, opal, and amorphous silica), (2) propylitic rocks (calcite-dolomite and epidote-chlorite mapped as separate mineral groups), (3) argillic rocks (alunite-pyrophyllite-kaolinite), and (4) phyllic rocks (sericite-muscovite). A series of hydrothermal alteration maps, which identify the potential locations of hydrothermal silica-rich, propylitic, argillic, and phyllic rocks on Landsat Thematic Mapper (TM) band 7 orthorectified images, and geographic information systems shape files of hydrothermal alteration units are provided in this study.

  10. Hydrothermal alteration in the Matok Igneous Complex, Southern Marginal Zone of the Limpopo Belt, South Africa

    International Nuclear Information System (INIS)

    Sieber, T.; Van Reenen, D.D.; Barton, J.M.

    1991-01-01

    Ductile shear zones associated with the 2700 to 2650 Ma Limpopo Orogeny locally contained gold mineralization. Some of these shear zones were reactivated under brittle conditions and contain zones of hydrothermal alteration that are of potential economic significance. Within the approximately 2670 Ma Matok Complex, two examples of this shear zone controlled alteration are exposed, the Dwars River and Sand River alteration zones. The granitic rocks of this Complex experienced early selective sericitization of plagioclase and the subsequent development of perthitic porphyroblasts. This early regional alteration was overprinted along brittle shear zones by pervasive propylitization and vein controlled quartz-albite alteration. The setting, composition, and the age of the Matok Complex make it a possible source for Archaean gold mineralization. The Dwars River and Sand River alteration zones are characterized by the absence of significant gold mineralization. The pattern of wall-rock alteration indicates that the hydrothermal processes were different from typical Archaean lode gold deposits. P-T conditions during the shear-zone controlled alteration were less than 400 degrees C and 1,9 - 2,8 kb. The shear zone hosted alteration could have taken place anytime between emplacement of the Matok Complex and about 1315 Ma ago. 35 refs., 10 figs., 4 tabs

  11. Subglacial discharge at tidewater glaciers revealed by seismic tremor

    Science.gov (United States)

    Bartholomaus, Timothy C.; Amundson, Jason M.; Walter, Jacob I.; O'Neel, Shad; West, Michael E.; Larsen, Christopher F.

    2015-01-01

    Subglacial discharge influences glacier basal motion and erodes and redeposits sediment. At tidewater glacier termini, discharge drives submarine terminus melting, affects fjord circulation, and is a central component of proglacial marine ecosystems. However, our present inability to track subglacial discharge and its variability significantly hinders our understanding of these processes. Here we report observations of hourly to seasonal variations in 1.5–10 Hz seismic tremor that strongly correlate with subglacial discharge but not with basal motion, weather, or discrete icequakes. Our data demonstrate that vigorous discharge occurs from tidewater glaciers during summer, in spite of fast basal motion that could limit the formation of subglacial conduits, and then abates during winter. Furthermore, tremor observations and a melt model demonstrate that drainage efficiency of tidewater glaciers evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured glacierized environments.

  12. Hydraulic characterization of hydrothermally altered Nopal tuff

    Energy Technology Data Exchange (ETDEWEB)

    Green, R.T.; Meyer-James, K.A. [Southwest Research Institute, San Antonio, TX (United States); Rice, G. [George Rice and Associates, San Antonio, TX (United States)

    1995-07-01

    Understanding the mechanics of variably saturated flow in fractured-porous media is of fundamental importance to evaluating the isolation performance of the proposed high-level radioactive waste repository for the Yucca Mountain site. Developing that understanding must be founded on the analysis and interpretation of laboratory and field data. This report presents an analysis of the unsaturated hydraulic properties of tuff cores from the Pena Blanca natural analog site in Mexico. The basic intent of the analysis was to examine possible trends and relationships between the hydraulic properties and the degree of hydrothermal alteration exhibited by the tuff samples. These data were used in flow simulations to evaluate the significance of a particular conceptual (composite) model and of distinct hydraulic properties on the rate and nature of water flow.

  13. Hydraulic characterization of hydrothermally altered Nopal tuff

    International Nuclear Information System (INIS)

    Green, R.T.; Meyer-James, K.A.; Rice, G.

    1995-07-01

    Understanding the mechanics of variably saturated flow in fractured-porous media is of fundamental importance to evaluating the isolation performance of the proposed high-level radioactive waste repository for the Yucca Mountain site. Developing that understanding must be founded on the analysis and interpretation of laboratory and field data. This report presents an analysis of the unsaturated hydraulic properties of tuff cores from the Pena Blanca natural analog site in Mexico. The basic intent of the analysis was to examine possible trends and relationships between the hydraulic properties and the degree of hydrothermal alteration exhibited by the tuff samples. These data were used in flow simulations to evaluate the significance of a particular conceptual (composite) model and of distinct hydraulic properties on the rate and nature of water flow

  14. Characteristics of hydrothermal alteration mineralogy and geochemistry of igneous rocks from the epithermal Co-O mine and district, Eastern Mindanao (Philippines)

    Science.gov (United States)

    Sonntag, Iris; Hagemann, Steffen

    2010-05-01

    Detailed petrographic as well as hyperspectral analyses using PIMA (Portable Infrared Mineral Analyser) and geochemical (major, trace and rare earth elements) studies were conducted on samples of the epithermal, low sulfidation Co-O mine (47,869 ounces gold produced in 2009 with an average grade of 13.3 g/t gold) and district in Eastern Mindanao (Philippines). The aims of the study were to unravel the petrogenetic origin of the various volcanic (host rocks) and intrusive rocks (potential fluid driver) as well as their relationship and influence on the hydrothermal alteration zoning and fluid chemistry. The auriferous veins at the Co-O mine were formed during two hydrothermal stages associated with the district wide D1 and D2 deformation events. Gold in stage 1 quartz veins is in equilibrium with galena and sphalerite, whereas in stage 2 it is associated with pyrite. Auriferous quartz veins of stage 1 reflect temperatures below 250° C or strong variations in pH and fO2 at higher temperatures, due to potential involvement of acidic gas or meteoric water. Cathodoluminescense studies revealed strong zonation of quartz associated with Au, presumably related to changes in the Al content, which is influenced by the pH. Plumose textures indicate times of rapid deposition, whereas saccharoidal quartz grains are related to potential calcite replacement. The geology of the Co-O mine and district is dominated by Miocene volcanic rocks (basic to intermediate flows and pyroclastics units), which are partly covered by Pliocene volcanic rocks and late Oligocene to Miocene limestones. The Miocene units are intruded by diorite (presumably Miocene in age). The epithermal mineralization event may be related to diorite intrusions. The geochemistry of all igneous rocks in the district is defined by a sub-alkaline affinity and is low to medium K in composition. Most units are related to a Miocene subduction zone with westward subduction, whereas the younger Pliocene rocks are related to

  15. Hydrothermal alteration of Hercynian granites, its significance to the evolution of geothermal systems in granitic rocks

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Jose M.; Matias, Maria J.; Basto, Maria J.; Aires-Barros, Luis A. [Instituto Superior Tecnico, Centro de Petrologia e Geoquimica, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Carreira, Paula M. [Instituto Tecnologico e Nuclear, Estrada Nacional n 10, 2686 - 953 Sacavem (Portugal); Goff, Fraser E. [Earth and Planetary Sciences Department, Univ. of New Mexico, Albuquerque, NM 87131 (United States)

    2010-06-15

    We discuss geochemical and isotopic ({sup 18}O/{sup 16}O, {sup 2}H/{sup 1}H and {sup 87}Sr/{sup 86}Sr) data recording the hydrothermal alteration of northern Portuguese Hercynian granites by Na-HCO{sub 3}-CO{sub 2}-rich mineral waters. Whole-rock samples from drill cores of Vilarelho da Raia granite have {delta}{sup 18}O values in the +11.47 to +10.10 permille range. The lower values correspond to highly fractured granite samples displaying vein and pervasive alteration. In the pervasive alteration stage, which probably results from a convective hydrothermal system set up by the intrusion of the granites, the metamorphic waters are in equilibrium with hydrous minerals. In contrast, the vein alteration of these granitic rocks was caused by water of meteoric origin. The oxygen ratios between water (W) and rock (R), the so-called W/R ratios, obtained for the open system (where the heated water is lost from the system by escape to the surface) range between 0.05 and 0.11, suggesting that the recrystallization of the veins was influenced by a small flux of meteoric water. Stable isotope analyses performed on the cores show that the vein alteration stage relates to post-emplacement tectonic stresses acting on the granite, probably of late Hercynian age. Our results are consistent with the existence of two separate alteration events (pervasive and vein) caused by hydrothermal waters of different isotopic characteristics. The studies presented in this paper should be viewed as a natural analogue that uses the alteration features observed in a fossil geothermal system at Vilarelho da Raia to assess possible water-rock reactions presently occurring at depth in granitic rocks of the nearby Chaves area. (author)

  16. Modeling Antarctic Subglacial Lake Filling and Drainage Cycles

    Science.gov (United States)

    Dow, Christine F.; Werder, Mauro A.; Nowicki, Sophie; Walker, Ryan T.

    2016-01-01

    The growth and drainage of active subglacial lakes in Antarctica has previously been inferred from analysis of ice surface altimetry data. We use a subglacial hydrology model applied to a synthetic Antarctic ice stream to examine internal controls on the filling and drainage of subglacial lakes. Our model outputs suggest that the highly constricted subglacial environment of our idealized ice stream, combined with relatively high rates of water flow funneled from a large catchment, can combine to create a system exhibiting slow-moving pressure waves. Over a period of years, the accumulation of water in the ice stream onset region results in a buildup of pressure creating temporary channels, which then evacuate the excess water. This increased flux of water beneath the ice stream drives lake growth. As the water body builds up, it steepens the hydraulic gradient out of the overdeepened lake basin and allows greater flux. Eventually this flux is large enough to melt channels that cause the lake to drain. Lake drainage also depends on the internal hydrological development in the wider system and therefore does not directly correspond to a particular water volume or depth. This creates a highly temporally and spatially variable system, which is of interest for assessing the importance of subglacial lakes in ice stream hydrology and dynamics.

  17. Mechanisms of hydrothermal alteration in a granitic rock. Consequences for high-level radioactive waste disposal

    International Nuclear Information System (INIS)

    Parneix, J.C.

    1987-06-01

    The study of hydrothermal alteration in the Auriat granitic rock (France, Massif-Central) has evidenced three main events: - a pervasive chloritisation of biotites in some parts of the drill-core, - an alteration localized around subvertical cracks and superimposed on previously chloritized or unaltered granite, - an alteration localized around subhorizontal cracks cross-cutting the preceding ones. The second type of alteration, produced by a geothermal system, gives the most interesting results to be applied to the nuclear radwaste disposal problem. Among primary minerals of granite, only biotite (or chlorite) and oligoclase are intensively altered. Therefore, the chemical composition of these minerals induces the nature of secondary parageneses. These, associated to the subvertical cracks network, indicate a thermal gradient of 150 C/Km. The geochemical code has allowed to corroborate that the thermal gradient was responsible for the occurrence of different parageneses with depth. Moreover, it was shown that the variable mineralogy around cracks was due to a thermal profile established at equilibrium between the rock and the fluid. Therefore, the extent of the alteration was proportional to the thermal power of the fluid. A dissolution and next a precipitation phase of new minerals characterize hydrothermal alteration, which is due to the thermal power emitted by radioactive waste and linked with the evolution of temperature during time. This alteration provokes two favourable events to storage: decrease of rock porosity and increase of sorption capacity [fr

  18. Properties of the subglacial till inferred from supraglacial lake drainage

    Science.gov (United States)

    Neufeld, J. A.; Hewitt, D.

    2017-12-01

    The buildup and drainage of supraglacial lakes along the margins of the Greenland ice sheet has been previously observed using detailed GPS campaigns which show that rapid drainage events are often preceded by localised, transient uplift followed by rapid, and much broader scale, uplift and flexure associated with the main drainage event [1,2]. Previous models of these events have focused on fracturing during rapid lake drainage from an impermeable bedrock [3] or a thin subglacial film [4]. We present a new model of supraglacial drainage that couples the water flux from rapid lake drainage events to a simplified model of the pore-pressure in a porous, subglacial till along with a simplified model of the flexure of glacial ice. Using a hybrid mathematical model we explore the internal transitions between turbulent and laminar flow throughout the evolving subglacial cavity and porous till. The model predicts that an initially small water flux may locally increase pore-pressure in the till leading to uplift and a local divergence in the ice velocity that may ultimately be responsible for large hydro-fracturing and full-scale drainage events. Furthermore, we find that during rapid drainage while the presence of a porous, subglacial till is crucial for propagation, the manner of spreading is remarkably insensitive to the properties of the subglacial till. This is in stark contrast to the post-drainage relaxation of the pore pressure, and hence sliding velocity, which is highly sensitive to the permeability, compressibility and thickness of subglacial till. We use our model, and the inferred sensitivity to the properties of the subglacial till after the main drainage event, to infer the properties of the subglacial till. The results suggest that a detailed interpretation of supraglacial lake drainage may provide important insights into the hydrology of the subglacial till along the margins of the Greenland ice sheet, and the coupling of pore pressure in subglacial till

  19. Mass changes during hydrothermal alteration/mineralization in the gold-bearing Astaneh granitoid, western Iran

    Science.gov (United States)

    Zahra Afshooni, Seyedeh; Esmaeily, Dariush

    2010-05-01

    The Astaneh granitoid massif, located in western Iran, is a part of Sanandaj-Sirjan structural Zone. This body, mainly consist of granodioritic rocks, is widely affected under hydrothermal alteration and four alteration zones including phyllic (sericitic), chloritic, propylitic and argillic zones could be identified in this area. Four main mineralization- related alteration episodes have been studied in terms of mass transfer and element mobility during the hydrothermal evolution of Astaneh deposit. In order to illustrate these changes quantitatively, isocon plots have been applied. Isocon plots illustrate that Al, Ti, Ga and Tm was relatively immobile during alteration and that mass were essentially conserved during alteration. Phyllic alteration was accompanied by the depletion of Na and Fe and the enrichment of Si and Cu. The loss of Na and Fe reflects the sericitization of alkali feldspar and the destruction of ferromagnesian minerals. The addition of Si is consistent with widespread silicification wich is a major feature of phyllic alteration. All of the HFSE (except in Y), were enriched but all REEs were depleted in this zone. The overall obtained results show that major oxides such as SiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O, P2O5 and TiO2 and also LOI show dissimilar behaviors in the different zones. All of the LFSE, HFSE and FTSM (except in Cu and Mo) were depleted in argillic alteration but show dissimilar behaviors in the other alteration zones. The results shown strong depletion in REE, in particular LREE, in all of the alteration facies (except in chloritic zone), equivalent fresh rocks. In chloritic zone, compared with HREE, the LREE represent more enrichment.

  20. Landscape evolution by subglacial quarrying

    DEFF Research Database (Denmark)

    Ugelvig, Sofie Vej; Egholm, D.L.; Iverson, Neal R.

    In glacial landscape evolution models, subglacial erosion rates are often related to basal sliding or ice discharge by a power-law. This relation can be justified for bedrock abrasion because rock debris transported in the basal ice drives the erosion. However, a simple relation between rates of ...... evolution models. Geology, v. 40, no. 8, 679-682 (2012). Schoof, C. The effect of cavitation on glacier sliding. Proc. R. Soc. A , 461, 609-627 (2005). Jaeger, J.C., and Cook, N.G.W. Fundamentals of rock mechanics: New York, Chapman and Hall, 593 p. (1979)......In glacial landscape evolution models, subglacial erosion rates are often related to basal sliding or ice discharge by a power-law. This relation can be justified for bedrock abrasion because rock debris transported in the basal ice drives the erosion. However, a simple relation between rates...... of sliding and erosion is not well supported when considering models for quarrying of rock blocks from the bed. Iverson (2012) introduced a new subglacial quarrying model that operates from the theory of adhesive wear. The model is based on the fact that cavities, with a high level of bedrock differential...

  1. Timing of Secondary Hydrothermal Alteration of the Luobusa Chromitites Constrained by Ar/Ar Dating of Chrome Chlorites

    Directory of Open Access Journals (Sweden)

    Wei Guo

    2018-05-01

    Full Text Available Chrome chlorites are usually found as secondary phases formed by hydrothermal alteration of chromite deposits and associated mafic/ultramafic rocks. Here, we report the 40Ar/39Ar age of chrome chlorites separated from the Luobusa massive chromitites which have undergone secondary alteration by CO2-rich hydrothermal fluids. The dating results reveal that the intermediate heating steps (from 4 to 10 of sample L7 generate an age plateau of 29.88 ± 0.42 Ma (MSWD = 0.12, plateau 39Ar = 74.6%, and the plateau data points define a concordant inverse isochron age of 30.15 ± 1.05 Ma (MSWD = 0.08, initial 40Ar/36Ar = 295.8 ± 9.7. The Ar release pattern shows no evidence of later degassing or inherited radiogenic component indicated by an atmospheric intercept, thus representing the age of the hydrothermal activity. Based on the agreement of this hydrothermal age with the ~30 Ma adakitic plutons exposed in nearby regions (the Zedong area, tens of kilometers west Luobusa and the extensive late Oligocene plutonism distributed along the southeastern Gangdese magmatic belt, it is suggested that the hydrothermal fluids are likely related to the ~30 Ma magmatism. The hydrothermal fluid circulation could be launched either by remote plutons (such as the Sangri granodiorite, the nearest ~30 Ma pluton west Luobusa or by a similar coeval pluton in the local Luobusa area (inferred, not found or reported so far. Our results provide important clues for when the listwanites in Luobusa were formed.

  2. Magma-Hydrothermal Transition: Basalt Alteration at Supercritical Conditions in Drill Core from Reykjanes, Iceland, Iceland Deep Drilling Project.

    Science.gov (United States)

    Zierenberg, R. A.; Fowler, A. P.; Schiffman, P.; Fridleifsson, G. Ó.; Elders, W. A.

    2017-12-01

    The Iceland Deep Drilling Project well IDDP-2, drilled to 4,659 m in the Reykjanes geothermal system, the on-land extension of the Mid Atlantic Ridge, SW Iceland. Drill core was recovered, for the first time, from a seawater-recharged, basalt-hosted hydrothermal system at supercritical conditions. The well has not yet been allowed to heat to in situ conditions, but temperature and pressure of 426º C and 340 bar was measured at 4500 m depth prior to the final coring runs. Spot drill cores were recovered between drilling depths of 3648.00 m and 4657.58 m. Analysis of the core is on-going, but we present the following initial observations. The cored material comes from a basaltic sheeted dike complex in the brittle-ductile transition zone. Felsic (plagiogranite) segregation veins are present in minor amounts in dikes recovered below 4300 m. Most core is pervasively altered to hornblende + plagioclase, but shows only minor changes in major and minor element composition. The deepest samples record the transition from the magmatic regime to the presently active hydrothermal system. Diabase near dike margins has been locally recrystallized to granoblastic-textured orthopyroxene-clinopyroxe-plagioclase hornfels. High temperature hydrothermal alteration includes calcic plagioclase (up to An100) and aluminous hornblende (up to 11 Wt. % Al2O3) locally intergrown with hydrothermal biotite, clinopyroxene, orthopyroxene and/or olivine. Hydrothermal olivine is iron-rich (Mg # 59-64) compared to expected values for igneous olivine. Biotite phenocrysts in felsic segregation veins have higher Cl and Fe compared to hydrothermal biotites. Orthopyroxene-clinopyroxene pairs in partially altered quench dike margins give temperature of 955° to 1067° C. Orthopyroxene-clinopyroxene pairs from hornfels and hydrothermal veins and replacements give temperature ranging from 774° to 888° C. Downhole fluid sampling is planned following thermal equilibration of the drill hole. Previous work

  3. An assessment of hydrothermal alteration in the Santiaguito lava dome complex, Guatemala: implications for dome collapse hazards

    Science.gov (United States)

    Ball, Jessica L.; Calder, Eliza S.; Hubbard, Bernard E.; Bernstein, Marc L.

    2013-01-01

    A combination of field mapping, geochemistry, and remote sensing methods has been employed to determine the extent of hydrothermal alteration and assess the potential for failure at the Santiaguito lava dome complex, Guatemala. The 90-year-old complex of four lava domes has only experienced relatively small and infrequent dome collapses in the past, which were associated with lava extrusion. However, existing evidence of an active hydrothermal system coupled with intense seasonal precipitation also presents ideal conditions for instability related to weakened clay-rich edifice rocks. Mapping of the Santiaguito dome complex identified structural features related to dome growth dynamics, potential areas of weakness related to erosion, and locations of fumarole fields. X-ray diffraction and backscattered electron images taken with scanning electron microscopy of dacite and ash samples collected from around fumaroles revealed only minor clay films, and little evidence of alteration. Mineral mapping using ASTER and Hyperion satellite images, however, suggest low-temperature (<150 °C) silicic alteration on erosional surfaces of the domes, but not the type of pervasive acid-sulfate alteration implicated in collapses of other altered edifices. To evaluate the possibility of internal alteration, we re-examined existing aqueous geochemical data from dome-fed hot springs. The data indicate significant water–rock interaction, but the Na–Mg–K geoindicator suggests only a short water residence time, and δ18O/δD ratios show only minor shifts from the meteoric water line with little precipitation of secondary (alteration) minerals. Based on available data, hydrothermal alteration on the dome complex appears to be restricted to surficial deposits of hydrous silica, but the study has highlighted, importantly, that the 1902 eruption crater headwall of Santa María does show more advanced argillic alteration. We also cannot rule out the possibility of advanced alteration

  4. Geochemical behavior of rare earth elements of the hydrothermal alterations within the Tepeoba porphyry Cu-Mo-Au deposits at Balikesir, NW Turkey

    Science.gov (United States)

    Doner, Zeynep; Abdelnasser, Amr; Kiran Yildirim, Demet; Kumral, Mustafa

    2016-04-01

    This work reports the geochemical characteristics and behavior of the rare earth elements (REE) of the hydrothermal alteration of the Tepeoba porphyry Cu-Mo-Au deposit located in the Anatolian tectonic belt at Biga peninsula (Locally Balikesir province), NW Turkey. The Cu-Mo-Au mineralization at this deposit hosted in the hornfels rocks and related to the silicic to intermediate intrusion of Eybek pluton. It locally formed with brecciated zones and quartz vein stockworks, as well as the brittle fracture zones associated with intense hydrothermal alteration. Three main alteration zones with gradual boundaries formed in the mine area in the hornfels rock that represents the host rock, along that contact the Eybek pluton; potassic, propylitic and phyllic alteration zones. The potassic alteration zone that formed at the center having high amount of Cu-sulfide minerals contains biotite, muscovite, and sericite with less amount of K-feldspar and associated with tourmalinization alteration. The propylitic alteration surrounds the potassic alteration having high amount of Mo and Au and contains chlorite, albite, epidote, calcite and pyrite. The phyllic alteration zone also surrounds the potassic alteration containing quartz, sericite and pyrite minerals. Based on the REE characteristics and content and when we correlate the Alteration index (AI) with the light REEs and heavy REEs of each alteration zone, it concluded that the light REEs decrease and heavy REEs increase during the alteration processes. The relationships between K2O index with Eu/Eu* and Sr/Sr* reveals a positive correlation in the potassic and phyllic alteration zones and a negative correlation in the propylitic alteration zone. This refers to the hydrothermal solution which is responsible for the studied porphyry deposits and associated potassic and phyllic alterations has a positive Eu and Sr anomaly as well as these elements were added to the altered rock from the hydrothermal solution. Keywords: Rare

  5. Hydrothermal alteration of sediments associated with surface emissions from the Cerro Prieto geothermal field

    Energy Technology Data Exchange (ETDEWEB)

    Valette-Silver, J.N.; Esquer P., I.; Elders, W.A.; Collier, P.C.; Hoagland, J.R.

    1981-01-01

    A study of the mineralogical changes associated with these hydrothermal vents was initiated with the aim of developing possible exploration tools for geothermal resources. The Cerro Prieto reservoir has already been explored by extensive deep drilling so that relationships between surface manifestations and deeper hydrothermal processes could be established directly. Approximately 120 samples of surface sediments were collected both inside and outside of the vents. The mineralogy of the altered sediments studied appears to be controlled by the type of emission. A comparison between the changes in mineralogy due to low temperature hydrothermal activity in the reservoir, seen in samples from boreholes, and mineralogical changes in the surface emission samples shows similar general trends below 180 C: increase of quartz, feldspar and illite, with subsequent disappearance of kaolinite, montmorillonite, calcite and dolomite. These mineral assemblages seem to be characteristic products of the discharge from high intensity geothermal fields.

  6. Mineralogical and structural transformations related to alterations in hydrothermal and climatological conditions of basic vulcanic rocks from northern Parana (Ribeirao Preto region, SP, Brazil)

    International Nuclear Information System (INIS)

    Goncalves, N.M.M.

    1987-01-01

    Detailed studies of the basic vulcanic rocks of northern Parana basin (Region of Ribeirao Preto, SP) reveled that these rocks were affected by pre-meteoric activity (hydrothermal alteration) before being exposed to the supergene system of alteration linked to the lithosphere/atmosphere interface. Mineralogical and structural transformation are studied. The appearance of sequential crystalline-chemical paragenesis in zones suggest that the hydrothermal activity occurred during two successives processes of alteration: the expulsion of the water from the rock during the later stages of magma cooling and the continous process of dissolution of the rock wall and the ionic diffusion involving the rock sistem of structural voids. The hydro-thermal action was followed by weathering action developing a thin 'front' of superficial alteration. This alteration system, can lead to the formation of three major levels of alteration horizons and superficial accumulations: alterites, glebular and suil surface materials. (C.D.G.) [pt

  7. Mineral types of hydrothermal alteration zones in the Dukat ore field and their relationships to leucogranite and epithermal gold-silver ore, northeastern Russia

    Science.gov (United States)

    Filimonova, L. G.; Trubkin, N. V.; Chugaev, A. V.

    2014-05-01

    The paper considers the localization of potassic and propylitic hydrothermal alteration zones in the domal volcanic-plutonic structure controlling the position of the Dukat ore field with the eponymous unique epithermal Au-Ag deposit. Comprehensive mineralogical and geochemical data on rocks and minerals in hydrothermal alteration zones and associated intrusions have shown that quartz-jarosite-sericite, quartz-pyrite-sericite, and quartz-adularia-chlorite alterations were formed with the participation of fluid flows related to a fingerlike projection of a high-K leucogranite porphyry intrusion with large phenocrysts. These hydrothermal alterations developed in the rifted graben under conditions of divergent plate boundaries, whereas quartz-clinozoisite-calcite, epidote-chlorite, and garnet-calcite-chlorite alterations were linked to K-Na leucogranite intrusive bodies and developed under conditions of convergent plate boundaries reactivated as a result of formation of the marginal Okhotsk-Chukotka volcanic belt. Phase separation and coagulation of specific portions of ascending fluids resulted in the formation and stabilization of small-sized particles of native silver and other ore components, which enabled involvement in flows of secondary geothermal solutions and ore-forming fluids. The Sr, Nd, and Pb isotopic compositions of rocks and minerals from the hydrothermal alteration zones, associated intrusions, and economic orebodies at the Dukat deposit indicate that their components have been derived from the juvenile continental crust, which was altered in pre-Cretaceous periods of endogenic activity. The components of gangue minerals of potassic and propylitic hydrothertmal alterations and associated intrusions have been taken from deep sources differing in 87Sr/86Sr and 143Nd/144Nd at similar U/Pb and Th/Pb ratios. Chalcophile lead in products of hydrothermal activity and melanocratic inclusions in leucogranite has been taken from regions with elevated U/Pb and

  8. A study of the hydrothermal alteration in Paleoproterozoic volcanic centers, São Félix do Xingu region, Amazonian Craton, Brazil, using short-wave infrared spectroscopy

    Science.gov (United States)

    da Cruz, Raquel Souza; Fernandes, Carlos Marcello Dias; Villas, Raimundo Netuno Nobre; Juliani, Caetano; Monteiro, Lena Virgínia Soares; de Almeida, Teodoro Isnard Ribeiro; Lagler, Bruno; de Carvalho Carneiro, Cleyton; Misas, Carlos Mario Echeverri

    2015-10-01

    Hypogene hydrothermal minerals have been identified by short-wave infrared spectroscopy in hydrothermally altered rocks from the Sobreiro and Santa Rosa formations, which belong to a Paleoproterozoic volcano-plutonic system in Amazonian craton. Three clay minerals are spectrally recognized: montmorillonite, kaolinite, and illite. The integration of these data with those available in the literature, including gold occurrences, suggests that those rocks are hydrothermal products of both volcanic thermal sources and later crustal intrusions, as evidenced by variable styles of propylitic, sericitic, potassic, and intermediate argillic alteration. The influence of meteoric fluids is emphasized. This low cost exploratory technique, which can be applied to hand samples, seems to be promising in the separation of hydrothermally altered volcano-plutonic centers in regions submitted to severe weathering conditions, in addition to aid elaborating models for prospecting mineral deposits.

  9. Investigation of Mineral Alteration in Andesite and Dacite from Three Different Volcano Hydrothermal Systems on Dominica, Lesser Antilles

    Science.gov (United States)

    Smith, C. I. V.; Frey, H. M.; Joseph, E. P.; Manon, M. R. F.

    2017-12-01

    The thermal discharges of Dominica are classified as steam-heated acidic-sulphate waters, produced by the mixing of shallow ground waters heated by sulphur bearing gases coming from magmatic sources. This study investigates the mineral alteration associated with three hydrothermal areas in Dominica that exhibit different temperature, pH, water composition and surface water abundance. Hydrothermal features (fumaroles, pools, springs) from Sulphur Springs ranged in temperature from 41 - 97 °C and pH from 1-3 in a predominantly gaseous environment, whereas the Valley of Desolation (69-98 °C and pH 1- 4) and the Cold Soufriere (18-32 °C and pH 1-4) have significant inputs of surface water. At each location, the host andesite-dacite rock was enveloped by a thin rind (up 2 cm) of precipitates, but the degree of alteration and rind thickness/composition varied with location. Cobbles from Sulphur Springs (SS) are grayish white in color with a thin outer rind (3-13 mm), and seemingly unaltered cores. Valley of Desolation (VoD) samples have a variety of patterns of alteration, with some clasts a uniform white-orange color, whereas others have variable thicknesses of an altered rind (1-20 mm), with relatively unaltered cores. Multiple hydrothermal minerals precipitated in the outer rinds display distinctive colors, suggestive of sulphides (dark gray), sulphates (orange and yellow), and iron oxides(?) (pink and purple). Cold Soufriere (CS) samples appear to be the most altered, often crumbling at touch. Others had rinds (2-10 mm) and pinkish gray cores that suggest more alteration compared to VoD and SS samples. Preliminary mineral identification of rind compositions was determined by XRD. Scans indicate the presence of silica polymorphs cristobalite and tridymite, as well as pyrite and sulphur. Elemental maps created using a SEM to identify any gradation caused by the elemental leaching and/or precipitation show that the boundaries between the weathering rind and the host

  10. Ecology of Subglacial Lake Vostok (Antarctica, Based on Metagenomic/Metatranscriptomic Analyses of Accretion Ice

    Directory of Open Access Journals (Sweden)

    Tom D'Elia

    2013-03-01

    Full Text Available Lake Vostok is the largest of the nearly 400 subglacial Antarctic lakes and has been continuously buried by glacial ice for 15 million years. Extreme cold, heat (from possible hydrothermal activity, pressure (from the overriding glacier and dissolved oxygen (delivered by melting meteoric ice, in addition to limited nutrients and complete darkness, combine to produce one of the most extreme environments on Earth. Metagenomic/metatranscriptomic analyses of ice that accreted over a shallow embayment and over the southern main lake basin indicate the presence of thousands of species of organisms (94% Bacteria, 6% Eukarya, and two Archaea. The predominant bacterial sequences were closest to those from species of Firmicutes, Proteobacteria and Actinobacteria, while the predominant eukaryotic sequences were most similar to those from species of ascomycetous and basidiomycetous Fungi. Based on the sequence data, the lake appears to contain a mixture of autotrophs and heterotrophs capable of performing nitrogen fixation, nitrogen cycling, carbon fixation and nutrient recycling. Sequences closest to those of psychrophiles and thermophiles indicate a cold lake with possible hydrothermal activity. Sequences most similar to those from marine and aquatic species suggest the presence of marine and freshwater regions.

  11. Direct observations of evolving subglacial drainage beneath the Greenland Ice Sheet.

    Science.gov (United States)

    Andrews, Lauren C; Catania, Ginny A; Hoffman, Matthew J; Gulley, Jason D; Lüthi, Martin P; Ryser, Claudia; Hawley, Robert L; Neumann, Thomas A

    2014-10-02

    Seasonal acceleration of the Greenland Ice Sheet is influenced by the dynamic response of the subglacial hydrologic system to variability in meltwater delivery to the bed via crevasses and moulins (vertical conduits connecting supraglacial water to the bed of the ice sheet). As the melt season progresses, the subglacial hydrologic system drains supraglacial meltwater more efficiently, decreasing basal water pressure and moderating the ice velocity response to surface melting. However, limited direct observations of subglacial water pressure mean that the spatiotemporal evolution of the subglacial hydrologic system remains poorly understood. Here we show that ice velocity is well correlated with moulin hydraulic head but is out of phase with that of nearby (0.3-2 kilometres away) boreholes, indicating that moulins connect to an efficient, channelized component of the subglacial hydrologic system, which exerts the primary control on diurnal and multi-day changes in ice velocity. Our simultaneous measurements of moulin and borehole hydraulic head and ice velocity in the Paakitsoq region of western Greenland show that decreasing trends in ice velocity during the latter part of the melt season cannot be explained by changes in the ability of moulin-connected channels to convey supraglacial melt. Instead, these observations suggest that decreasing late-season ice velocity may be caused by changes in connectivity in unchannelized regions of the subglacial hydrologic system. Understanding this spatiotemporal variability in subglacial pressures is increasingly important because melt-season dynamics affect ice velocity beyond the conclusion of the melt season.

  12. ANOMALY DETECTION AND COMPARATIVE ANALYSIS OF HYDROTHERMAL ALTERATION MATERIALS TROUGH HYPERSPECTRAL MULTISENSOR DATA IN THE TURRIALBA VOLCANO

    Directory of Open Access Journals (Sweden)

    J. G. Rejas

    2012-07-01

    Full Text Available The aim of this work is the comparative study of the presence of hydrothermal alteration materials in the Turrialba volcano (Costa Rica in relation with computed spectral anomalies from multitemporal and multisensor data adquired in spectral ranges of the visible (VIS, short wave infrared (SWIR and thermal infrared (TIR. We used for this purposes hyperspectral and multispectral images from the HyMAP and MASTER airborne sensors, and ASTER and Hyperion scenes in a period between 2002 and 2010. Field radiometry was applied in order to remove the atmospheric contribution in an empirical line method. HyMAP and MASTER images were georeferenced directly thanks to positioning and orientation data that were measured at the same time in the acquisition campaign from an inertial system based on GPS/IMU. These two important steps were allowed the identification of spectral diagnostic bands of hydrothermal alteration minerals and the accuracy spatial correlation. Enviromental impact of the volcano activity has been studied through different vegetation indexes and soil patterns. Have been mapped hydrothermal materials in the crater of the volcano, in fact currently active, and their surrounding carrying out a principal components analysis differentiated for a high and low absorption bands to characterize accumulations of kaolinite, illite, alunite and kaolinite+smectite, delimitating zones with the presence of these minerals. Spectral anomalies have been calculated on a comparative study of methods pixel and subpixel focused in thermal bands fused with high-resolution images. Results are presented as an approach based on expert whose main interest lies in the automated identification of patterns of hydrothermal altered materials without prior knowledge or poor information on the area.

  13. Anomaly Detection and Comparative Analysis of Hydrothermal Alteration Materials Trough Hyperspectral Multisensor Data in the Turrialba Volcano

    Science.gov (United States)

    Rejas, J. G.; Martínez-Frías, J.; Bonatti, J.; Martínez, R.; Marchamalo, M.

    2012-07-01

    The aim of this work is the comparative study of the presence of hydrothermal alteration materials in the Turrialba volcano (Costa Rica) in relation with computed spectral anomalies from multitemporal and multisensor data adquired in spectral ranges of the visible (VIS), short wave infrared (SWIR) and thermal infrared (TIR). We used for this purposes hyperspectral and multispectral images from the HyMAP and MASTER airborne sensors, and ASTER and Hyperion scenes in a period between 2002 and 2010. Field radiometry was applied in order to remove the atmospheric contribution in an empirical line method. HyMAP and MASTER images were georeferenced directly thanks to positioning and orientation data that were measured at the same time in the acquisition campaign from an inertial system based on GPS/IMU. These two important steps were allowed the identification of spectral diagnostic bands of hydrothermal alteration minerals and the accuracy spatial correlation. Enviromental impact of the volcano activity has been studied through different vegetation indexes and soil patterns. Have been mapped hydrothermal materials in the crater of the volcano, in fact currently active, and their surrounding carrying out a principal components analysis differentiated for a high and low absorption bands to characterize accumulations of kaolinite, illite, alunite and kaolinite+smectite, delimitating zones with the presence of these minerals. Spectral anomalies have been calculated on a comparative study of methods pixel and subpixel focused in thermal bands fused with high-resolution images. Results are presented as an approach based on expert whose main interest lies in the automated identification of patterns of hydrothermal altered materials without prior knowledge or poor information on the area.

  14. Spatio-temporal evolution of efficient subglacial water discharge at Lemon Creek Glacier, Alaska

    Science.gov (United States)

    Bartholomaus, T. C.; Labedz, C. R.; Amundson, J. M.; Gimbert, F.; Tsai, V. C.; Vore, M. E.; Karplus, M. S.

    2017-12-01

    The impact of subglacial hydrology on glacier motion, glacier erosion and sediment transport, and submarine melt is well established. However, despite its importance, critical gaps in our understanding of subglacial hydrology and its seasonal evolution remain, in large part due to the challenge of making observations of glacier beds. Thus far, no spatially extensive, temporally continuous observations of subglacial water discharge exist. Seismic signals produced by subglacial water flow, and which correlate with subglacial water discharge, can meet this need. Here, we present the first observations from a 2017 summer seismic, geodetic, and hydrologic experiment. Our experiment seeks to better understand the evolution of efficient subglacial drainage and water storage through data collection and analysis at Lemon Creek Glacier, a 5.7 km-long glacier with a gauged outlet in Southeast Alaska. Data with nested spatial resolutions create an unparalleled perspective of subglacial discharge and its seasonal evolution. Six broadband seismometers and two GPS receivers installed for 80 days provide a long-term view of subglacial discharge and its impact on glacier dynamics. More than 100 nodes, installed approximately every 250 m over the glacier surface ( 13 nodes per 1 km^2) and deployed for up to 25 days, reveal the detailed spatial pattern of glaciohydraulic tremor amplitudes. These nodes enable us to more precisely infer the locations of subglacial discharge and its change, as well as better interpret long-term patterns of glaciohydraulic tremor observed by the broadband seismometers. We infer the subglacial response to hydraulic transients over the duration of the deployment through examination of intermittent melt and rain events, and the abrupt drainage of a glacier-dammed lake. These observations demonstrate the promise of seismology to significantly advance our understanding of glacier hydrology and associated glaciological processes.

  15. Geochemistry of Hydrothermal Alteration Associated with Cenozoic Intrusion-Hosted Cu-Pb-Zn Mineralization at Tavşanlı Area, Kütahya, NW Turkey

    Directory of Open Access Journals (Sweden)

    Mustafa Kumral

    2016-02-01

    Full Text Available The Miocene magmatic intrusion in the Tavşanlı zone of the Kütahya-Bolkardağ Belt (KBB in the northwestern region of Turkey is represented by the Eğrigöz granitoids. This paper studies the petrology and geochemistry of hydrothermal alterations associated with the vein-type Cu-Pb-Zn mineralization hosted by this pluton, focusing on the determination of the mass gains and losses of chemical components, which reflect the chemical exchanges between the host rocks and hydrothermal fluids. Vein-type Cu-Pb-Zn mineralization is closely associated with intense hydrothermal alterations within the brecciation, quartz stockwork veining, and brittle fracture zones that are controlled by NW-SE trending faults cutting through the Eğrigöz granitoids. Paragenetic relationships reveal three stages of mineralization: pre-ore, ore, and supergene. The ore mineralogy typically includes hypogene chalcopyrite, sphalerite, galena, and pyrite, with locally supergene covellite, malachite, and azurite. Wall-rock hypogene hydrothermal alterations include pervasive silicification, sulfidation, sericitization, and selective carbonatization and albitization. These are distributed in three main alteration zones (zone 1: silicified/iron carbonatized alterations ± albite, zone 2: argillic-silicic alterations, and zone 3: phyllic alterations. Based on the gains and losses of mass and volume (calculated by the GEOISO-Windows™ program, zone 1 has a higher mass and volume gain than zones 2 and 3. Non-systematic zonal distributions of alterations are observed in which the silicic-carbonate alterations +/− albitization appeared in zone 1 in the center and the phyllic-argillic alterations appeared in zones 2 and 3, with an increase in base metals (Cu-Pb-Zn in the zone from Cu, Cu-Pb, to Cu-Pb-Zn moving outwards.

  16. Incorporating modelled subglacial hydrology into inversions for basal drag

    Directory of Open Access Journals (Sweden)

    C. P. Koziol

    2017-12-01

    Full Text Available A key challenge in modelling coupled ice-flow–subglacial hydrology is initializing the state and parameters of the system. We address this problem by presenting a workflow for initializing these values at the start of a summer melt season. The workflow depends on running a subglacial hydrology model for the winter season, when the system is not forced by meltwater inputs, and ice velocities can be assumed constant. Key parameters of the winter run of the subglacial hydrology model are determined from an initial inversion for basal drag using a linear sliding law. The state of the subglacial hydrology model at the end of winter is incorporated into an inversion of basal drag using a non-linear sliding law which is a function of water pressure. We demonstrate this procedure in the Russell Glacier area and compare the output of the linear sliding law with two non-linear sliding laws. Additionally, we compare the modelled winter hydrological state to radar observations and find that it is in line with summer rather than winter observations.

  17. Obsidian: alteration study under hydrothermal-like conditions for its assessment as a nuclear waste glass

    Energy Technology Data Exchange (ETDEWEB)

    Rania, Nishi; Shrivastava, J.P. [Department of Geology, University of Delhi, Delhi - 110007 (India); Bajpai, R.K. [BETDD, Nuclear Recycle Group, BARC, Mumbai - 400008 (India)

    2013-07-01

    Alteration experiments of obsidian (from Osham Hill, Gujarat, India) were performed under hydrothermal-like conditions. Neo-formed minerals were compared with naturally altered minerals to assess its performance. Altered specimens show partial to complete leaching of glass, where ionic release is of the order of Na>Si>K>Ca>Al = Mg>Mn>Ti. SEM-BSE images show distinct microstructures and mineral paragenesis of smectite, chlorite, nontronite, and illite inside and outside of the secondary layers - show retention of Si, Al, and Mg ions, fixation in the alteration products after their meager release to the solution. Secondary minerals-palagonite, chlorite, calcite, zeolite and white colored clays - formed after experiments largely correspond to altered obsidian in the natural environment since ∼ 65 Ma. (authors)

  18. Obsidian: alteration study under hydrothermal-like conditions for its assessment as a nuclear waste glass

    International Nuclear Information System (INIS)

    Rania, Nishi; Shrivastava, J.P.; Bajpai, R.K.

    2013-01-01

    Alteration experiments of obsidian (from Osham Hill, Gujarat, India) were performed under hydrothermal-like conditions. Neo-formed minerals were compared with naturally altered minerals to assess its performance. Altered specimens show partial to complete leaching of glass, where ionic release is of the order of Na>Si>K>Ca>Al = Mg>Mn>Ti. SEM-BSE images show distinct microstructures and mineral paragenesis of smectite, chlorite, nontronite, and illite inside and outside of the secondary layers - show retention of Si, Al, and Mg ions, fixation in the alteration products after their meager release to the solution. Secondary minerals-palagonite, chlorite, calcite, zeolite and white colored clays - formed after experiments largely correspond to altered obsidian in the natural environment since ∼ 65 Ma. (authors)

  19. Raman and X-ray absorption spectroscopic studies of hydrothermally altered alkali-borosilicate nuclear waste glass

    Energy Technology Data Exchange (ETDEWEB)

    McKeown, David A., E-mail: davidm@vsl.cua.ed [Vitreous State Laboratory, Catholic University of America, 620 Michigan Ave., N.E., Washington, DC 20064 (United States); Buechele, Andrew C.; Viragh, Carol; Pegg, Ian L. [Vitreous State Laboratory, Catholic University of America, 620 Michigan Ave., N.E., Washington, DC 20064 (United States)

    2010-04-01

    Raman spectroscopy and X-ray absorption spectroscopy (XAS) are used to characterize structural changes that took place in hydrothermally altered (Na,K)-alumina-borosilicate glasses with different Na/K ratios, formulated as part of a durability study to investigate the behavior of glasses for nuclear waste storage. The hydrothermal experiments, or vapor hydration tests (VHT), were performed on each glass for 3 and 20 days at 200 deg. C to accelerate and approximate long-term alteration processes that may occur in a nuclear waste repository. Results found for both glasses and their VHT altered counterparts show little, if any, structural influence from the different starting Na/K ratios. X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and Raman spectroscopy indicate that the altered samples are mostly amorphous with small amounts of analcime-like and leucite-like crystals within 200 mum of the sample surface and contain up to 9.7 wt.% water or OH. The Raman data are nearly identical for the amorphous portions of all altered VHT samples investigated, and indicate that two glass structural changes took place during alteration: one, partial depolymerization of the alumina-borosilicate network, and two, introduction of water or OH. Al and Si XAS data indicate tetrahedral AlO{sub 4} and SiO{sub 4} environments in the original glasses as well as in the altered samples. Small energy shifts of the Si K-edge also show that the altered VHT samples have less polymerized networks than the original glass. Na XAS data indicate expanded Na environments in the VHT samples with longer Na-O distances and more nearest-neighbor oxygen atoms, compared with the original glasses, which may be due to hydrous species introduced into the expanding Na-sites.

  20. Evidence for intense hydrothermal alteration associated with flood basalt volcanism during the birth of the Azores Plateau

    Science.gov (United States)

    Bach, W.; Busch, A.; Genske, F. S.; Beier, C.; Krumm, S.

    2017-12-01

    A stratigraphic section comprising >1000 m of upper crust in the Princess Alice Bank (PAB) of the western Azores Plateau was sampled during RV Meteor cruise M128 in July of 2016, using the ROV MARUM Quest 4000m. Twenty-two samples were recovered between 2484 and 1439 m water depth from the southfacing footwall of the Master fault bounding a prominent NW-SE striking rift zone within the PAB. Our geochemical and petrographic results show that virtually all samples are pervasively altered. The deeper part of the section (up to 1750 m water depth) was altered under greenschist-facies conditions to assemblages that include epidote, chlorite, albite, titanite, and actinolite. These rocks show 87Sr/86Sr values between 0.7036 and 0.7050. The topmost section was altered under lower metamorphic grades to chlorite/smectite-quartz-anatase. These rocks show severe losses of Ca and Sr, and gains in Mg, Li, and B, with 87Sr/86Sr ratios as high as 0.708. These geochemical signatures indicate an intensity of hydrothermal exchange between seawater and crust that is unmatched by any in situ section of upper ocean crust sampled by ocean drilling to date. Oxygen isotope data for epidote-calcite veins indicate temperatures of 250-300°C. Later quartz gives about 200°C. The implications of the intense hydrothermal alteration for crust-seawater exchange budgets can be evaluated in the light of the geological evolution of the PAB. Based on immobile element ratios of whole rocks and REE characteristics of relict clinopyroxene in the only incompletely altered sample, an E-type MORB primary composition of the basalts can be reconstructed. Our data suggest that the degrees of mantle melting were much higher than during extrusion of the <4 Ma old alkali-basalts recovered from the top of PAB (Beier et al., 2015, doi:10.1130/2015.2511(02)), and even higher than modern MORB at the adjacent mid-Atlantic Ridge. These results lead us to suggest that the deeper sections of the PAB formed during the

  1. Hydrothermal alteration, fumarolic deposits and fluids from Lastarria Volcanic Complex: A multidisciplinary study

    OpenAIRE

    Aguilera, Felipe; Layana, Susana; Rodríguez-Díaz, Augusto; González, Cristóbal; Cortés, Julio; Inostroza, Manuel

    2016-01-01

    A multidisciplinary study that includes processing of Landsat ETM+ satellite images, chemistry of gas condensed, mineralogy and chemistry of fumarolic deposits, and fluid inclusion data from native sulphur deposits, has been carried out in the Lastarria Volcanic Complex (LVC) with the objective to determine the distribution and characteristics of hydrothermal alteration zones and to establish the relations between gas chemistry and fumarolic deposits. Satellite image processing shows the pres...

  2. Radiogeochemical features of hydrothermal metasomatic formations

    International Nuclear Information System (INIS)

    Plyushchev, E.V.; Ryabova, L.A.; Shatov, V.V.

    1978-01-01

    Considered are the most general peculiarities of uranium and thorium distributions in hydrothermal-metasomatic formations of three levels of substance formation: 1) in hydrothermal minerals; 2) in natural associations of these minerals (in the altered rocks, metasomatites, ores, etc.); 3) ordened series of zonally and in stage conjugated hydrothermal-metasomatic formations. Statistically stable recurrence of natural combinations of hydrothermal-metasomatic formations points out conjugation of their formation in the directed evolution in the general hydrothermal process. Series of metasomatic formations, the initial members of which are potassium metasomatites, mostly result in accumulation up to industrial concentrations of radioactive elements in final members of these formations. Development of midlow-temperature propylitic alterations in highly radiative rocks causes the same accumulation

  3. Automatic detection of subglacial lakes in radar sounder data acquired in Antarctica

    Science.gov (United States)

    Ilisei, Ana-Maria; Khodadadzadeh, Mahdi; Dalsasso, Emanuele; Bruzzone, Lorenzo

    2017-10-01

    Subglacial lakes decouple the ice sheet from the underlying bedrock, thus facilitating the sliding of the ice masses towards the borders of the continents, consequently raising the sea level. This motivated increasing attention in the detection of subglacial lakes. So far, about 70% of the total number of subglacial lakes in Antarctica have been detected by analysing radargrams acquired by radar sounder (RS) instruments. Although the amount of radargrams is expected to drastically increase, from both airborne and possible future Earth observation RS missions, currently the main approach to the detection of subglacial lakes in radargrams is by visual interpretation. This approach is subjective and extremely time consuming, thus difficult to apply to a large amount of radargrams. In order to address the limitations of the visual interpretation and to assist glaciologists in better understanding the relationship between the subglacial environment and the climate system, in this paper, we propose a technique for the automatic detection of subglacial lakes. The main contribution of the proposed technique is the extraction of features for discriminating between lake and non-lake basal interfaces. In particular, we propose the extraction of features that locally capture the topography of the basal interface, the shape and the correlation of the basal waveforms. Then, the extracted features are given as input to a supervised binary classifier based on Support Vector Machine to perform the automatic subglacial lake detection. The effectiveness of the proposed method is proven both quantitatively and qualitatively by applying it to a large dataset acquired in East Antarctica by the MultiChannel Coherent Radar Depth Sounder.

  4. Effect of Topography on Subglacial Discharge and Submarine Melting During Tidewater Glacier Retreat

    Science.gov (United States)

    Amundson, J. M.; Carroll, D.

    2018-01-01

    To first order, subglacial discharge depends on climate, which determines precipitation fluxes and glacier mass balance, and the rate of glacier volume change. For tidewater glaciers, large and rapid changes in glacier volume can occur independent of climate change due to strong glacier dynamic feedbacks. Using an idealized tidewater glacier model, we show that these feedbacks produce secular variations in subglacial discharge that are influenced by subglacial topography. Retreat along retrograde bed slopes (into deep water) results in rapid surface lowering and coincident increases in subglacial discharge. Consequently, submarine melting of glacier termini, which depends on subglacial discharge and ocean thermal forcing, also increases during retreat into deep water. Both subglacial discharge and submarine melting subsequently decrease as glacier termini retreat out of deep water and approach new steady state equilibria. In our simulations, subglacial discharge reached peaks that were 6-17% higher than preretreat values, with the highest values occurring during retreat from narrow sills, and submarine melting increased by 14% for unstratified fjords and 51% for highly stratified fjords. Our results therefore indicate that submarine melting acts in concert with iceberg calving to cause tidewater glacier termini to be unstable on retrograde beds. The full impact of submarine melting on tidewater glacier stability remains uncertain, however, due to poor understanding of the coupling between submarine melting and iceberg calving.

  5. Hydrothermal processes above the Yellowstone magma chamber: Large hydrothermal systems and large hydrothermal explosions

    Science.gov (United States)

    Morgan, L.A.; Shanks, W.C. Pat; Pierce, K.L.

    2009-01-01

    Hydrothermal explosions are violent and dramatic events resulting in the rapid ejection of boiling water, steam, mud, and rock fragments from source craters that range from a few meters up to more than 2 km in diameter; associated breccia can be emplaced as much as 3 to 4 km from the largest craters. Hydrothermal explosions occur where shallow interconnected reservoirs of steam- and liquid-saturated fluids with temperatures at or near the boiling curve underlie thermal fields. Sudden reduction in confi ning pressure causes fluids to fl ash to steam, resulting in signifi cant expansion, rock fragmentation, and debris ejection. In Yellowstone, hydrothermal explosions are a potentially signifi cant hazard for visitors and facilities and can damage or even destroy thermal features. The breccia deposits and associated craters formed from hydrothermal explosions are mapped as mostly Holocene (the Mary Bay deposit is older) units throughout Yellowstone National Park (YNP) and are spatially related to within the 0.64-Ma Yellowstone caldera and along the active Norris-Mammoth tectonic corridor. In Yellowstone, at least 20 large (>100 m in diameter) hydrothermal explosion craters have been identifi ed; the scale of the individual associated events dwarfs similar features in geothermal areas elsewhere in the world. Large hydrothermal explosions in Yellowstone have occurred over the past 16 ka averaging ??1 every 700 yr; similar events are likely in the future. Our studies of large hydrothermal explosion events indicate: (1) none are directly associated with eruptive volcanic or shallow intrusive events; (2) several historical explosions have been triggered by seismic events; (3) lithic clasts and comingled matrix material that form hydrothermal explosion deposits are extensively altered, indicating that explosions occur in areas subjected to intense hydrothermal processes; (4) many lithic clasts contained in explosion breccia deposits preserve evidence of repeated fracturing

  6. Discrimination of hydrothermal alteration mineral assemblages at Virginia City, Nevada, using the airborne imaging spectrometer

    Science.gov (United States)

    Hutsinpiller, Amy

    1988-01-01

    The purpose of this study is to use airborne imaging spectrometer data to discriminate hydrothermal alteration mineral assemblages associated with silver and gold mineralization at Virginia City, NV. The data is corrected for vertical striping and sample gradients, and converted to flat-field logarithmic residuals. Log residual spectra from areas known to be altered are compared to field spectra for kaolinitic, illitic, sericitic, and propylitic alteration types. The areal distributions of these alteration types are estimated using a spectral matching technique. Both visual examination of spectra and the matching techniques are effective in distinguishing kaolinitic, illitic, and propylitic alteration types from each other. However, illitic and sericitic alteration cannot be separated using these techniques because the spectra of illite and sericite are very similar. A principal components analysis of 14 channels in the 2.14-2.38 micron wavelength region is also successful in discriminating and mapping illitic, kaolinitic, and propylitic alteration types.

  7. Blood Falls: A novel management approach for a subglacial feature of outstanding scientific importance

    Science.gov (United States)

    Carr, J. R.; Penhale, P. A.; Dahood, A.; Biletnikoff, N.; Harris, C. M.

    2012-04-01

    Blood Falls is a subglacial feature located in the ablation zone of the Taylor Glacier, Taylor Valley, McMurdo Dry Valleys, Antarctica. Blood Falls has a unique physical configuration, microbial ecology and geochemistry and consists of a subglacial brine reservoir and an iron-rich, saline surface discharge at the Taylor Glacier terminus. The feature provides a rare opportunity to sample properties of a subglacial reservoir and its ecosystem without the need for direct contact and is a key site for exobiological studies. The Blood Falls subglacial feature is globally unique and of outstanding scientific importance. As such, it warrants special protection from potential damage by drilling and/or surface activities. Moreover, currently subglacial environments are not represented in the Antarctic protected area network. To address these points, the United States National Science Foundation is working with the scientific community to develop at Blood Falls the first subglacial protected area in Antarctica. The protected area aims to maintain the integrity of the Blood Falls system, whilst allowing continued access for scientific and management purposes. Novel management approaches are being designed to protect the values of the site in three dimensions. Specific guidelines on activities conducted within the area, most notably drilling and coring, are being defined in a management plan. This new approach incorporates uncertainties in the location of the Blood Falls brine reservoir and the connectivity of the subglacial hydrological system of the Taylor Glacier. The management approaches employed at Blood Falls draw on the experience of the subglacial research community and potentially offer an effective framework for the protection of other subglacial environments.

  8. Mass change calculations of hydrothermal alterations within the volcanogenic metasediments hosted Cu-Pb (-Zn) mineralization at Halilar area, NW Turkey

    Science.gov (United States)

    Kiran Yildirim, Demet; Abdelnasser, Amr; Doner, Zeynep; Kumral, Mustafa

    2016-04-01

    The Halilar Cu-Pb (-Zn) mineralization that is formed in the volcanogenic metasediments of Bagcagiz Formation at Balikesir province, NW Turkey, represents locally vein-type deposit as well as restricted to fault gouge zone directed NE-SW along with the lower boundary of Bagcagiz Formation and Duztarla granitic intrusion in the study area. Furthermore, This granite is traversed by numerous mineralized sheeted vein systems, which locally transgress into the surrounding metasediments. Therefore, this mineralization closely associated with intense hydrothermal alteration within brecciation, and quartz stockwork veining. The ore mineral assemblage includes chalcopyrite, galena, and some sphalerite with covellite and goethite formed during three phases of mineralization (pre-ore, main ore, and supergene) within an abundant gangue of quartz and calcite. The geologic and field relationships, petrographic and mineralogical studies reveal two alteration zones occurred with the Cu-Pb (-Zn) mineralization along the contact between the Bagcagiz Formation and Duztarla granite; pervasive phyllic alteration (quartz, sericite, and pyrite), and selective propylitic alteration (albite, calcite, epidote, sericite and/or chlorite). This work, by using the mass balance calculations, reports the mass/volume changes (gain and loss) of the chemical components of the hydrothermal alteration zones associated with Halilar Cu-Pb (-Zn) mineralization at Balikesir area (Turkey). It revealed that the phyllic alteration has enrichments of Si, Fe, K, Ba, and LOI with depletion of Mg, Ca, and Na reflect sericitization of alkali feldspar and destruction of ferromagnesian minerals. This zone has high Cu and Pb with Zn contents represents the main mineralized zone. On the other hand, the propylitic zone is characterized by addition of Ca, Na, K, Ti, P, and Ba with LOI and Cu (lower content) referring to the replacement of plagioclase and ferromagnesian minerals by albite, calcite, epidote, and sericite

  9. Chemical reaction path modeling of hydrothermal processes on Mars: Preliminary results

    Science.gov (United States)

    Plumlee, Geoffrey S.; Ridley, W. Ian

    1992-01-01

    Hydrothermal processes are thought to have had significant roles in the development of surficial mineralogies and morphological features on Mars. For example, a significant proportion of the Martian soil could consist of the erosional products of hydrothermally altered impact melt sheets. In this model, impact-driven, vapor-dominated hydrothermal systems hydrothermally altered the surrounding rocks and transported volatiles such as S and Cl to the surface. Further support for impact-driven hydrothermal alteration on Mars was provided by studies of the Ries crater, Germany, where suevite deposits were extensively altered to montmorillonite clays by inferred low-temperature (100-130 C) hydrothermal fluids. It was also suggested that surface outflow from both impact-driven and volcano-driven hydrothermal systems could generate the valley networks, thereby eliminating the need for an early warm wet climate. We use computer-driven chemical reaction path calculation to model chemical processes which were likely associated with postulated Martian hydrothermal systems.

  10. Targeting Hydrothermal Alterations Utilizing LANDSAT-8 Andaster Data in Shahr-E Iran

    Science.gov (United States)

    Safari, M.; Pour, A. B.; Maghsoudi, A.; Hashim, M.

    2017-10-01

    Shahr-e-Babak tract of the Kerman metalogenic belt is one of the most potential segments of Urumieh-Dokhtar (Sahand-Bazman) magmatic arc. This area encompasses several porphyry copper deposits in exploration, development and exploitation hierarchy. The aim of this study is to map hydrothermal alterations caused by early Cenozoic magmatic intrusions in Shahr-e-Babak area. To this purpose, mineral mapping methods including band combinations, ratios and multiplications as well as PCA and MNF data space transforms in SWIR and VNIR for both ASTER and OLI sensors. Alteration zones according to spectral signatures of each type of alteration mineral assemblages such as argillic, phyllic and propylitic are successfully mapped. For enhancing the target areas false color composites and HSI-RGB color space transform are performed on developed band combinations. Previous studies have proven the robust application of ASTER in geology and mineral exploration; nonetheless, the results of this investigation prove applicability of OLI sensor from landsat-8 for alteration mapping. According to the results, evidently OLI sensor data can accurately map alteration zones. Additionally, the 12-bit quantization of OLI data is its privilege over 8-bit data of ASTER in VNIR and SWIR, thus OLI high quality results, which makes it easy to distinguish targets with enhanced color contrast between the altered and unaltered rocks.

  11. Oxygen and Hydrogen Isotope Values for Unaltered and Hydrothermally Altered Samples from the Cretaceous Linga Plutonic Complex of the Peruvian Coastal Batholith near Ica.

    Science.gov (United States)

    Gonzalez, L. U.; Holk, G. J.; Clausen, B. L.; Poma Porras, O. A.

    2015-12-01

    A portion of the Peruvian Coastal Batholith near Ica, Peru is being studied using stable isotopes to determine the source of hydrothermal fluids that caused propylitic, phyllic, and potassic alteration in the mineralized Linga plutonic complex. Sources of hydrothermal fluids and water/rock ratios are estimated to understand the role of such fluids in alteration during cooling. A set of 64 mineral analysis from 18 igneous samples, 7 unaltered and 11 altered, were analyzed for D/H and 18O/16O isotopes. The δ18O values for whole rocks with no apparent alteration vary from +6.8‰ to +7.9‰, with sets of δ18O mineral values indicating isotopic equilibrium at closure temperatures from 571°C to 651°C, and no interaction with meteoric water. This conclusion is bolstered by hornblende (-87‰ to -64‰) and biotite (-81‰ to -74‰) δD values Most δ18O values for samples with hydrothermal alteration suggest that alteration results from magmatic fluids; however, several analyses indicate interaction with other fluids. The high δ18O values for plagioclase (+9.3‰) and hornblende (+6.3‰) from a metamorphic aureole in volcanic host rock near a plutonic intrusion may be due to interaction with metamorphic or low temperature magmatic fluids. Plagioclase (+2.6‰) and biotite (+0.1‰) δ18O values in a sample from the Jurassic volcanic envelope indicate a significant effect from meteoric-hydrothermal fluids. An altered monzonite yielded δ18O values for quartz (+5.5‰), K-spar (+5.6‰), and magnetite (+0.4‰), also suggesting interaction with meteoric fluids. A diorite from an area with strong epidotization produced an epidote δD value of -25.8‰ and a monzonite from a highly veined area has an epidote δD value of -36.1‰ suggesting interaction with sea water. This new data indicate that the Linga complex was primarily influenced by magmatic hydrothermal fluids, but metamorphic, meteoric, and sea water may have had some influence in producing alteration

  12. Subglacial sediment mechanics investigated by computer simulation of granular material

    DEFF Research Database (Denmark)

    Damsgaard, Anders; Egholm, David Lundbek; Tulaczyk, Slawek

    The mechanical properties of subglacial sediments are known to directly influence the stability of ice streams and fast-moving glaciers, but existing models of granular sediment deformation are poorly constrained. In addition, upscaling to generalized mathematical models is difficult due to the m......The mechanical properties of subglacial sediments are known to directly influence the stability of ice streams and fast-moving glaciers, but existing models of granular sediment deformation are poorly constrained. In addition, upscaling to generalized mathematical models is difficult due....... The numerical method is applied to better understand the mechanical properties of the subglacial sediment and its interaction with meltwater. The computational approach allows full experimental control and offers insights into the internal kinematics, stress distribution, and mechanical stability. During...

  13. Hydrothermal alteration and diagenesis of terrestrial lacustrine pillow basalts: Coordination of hyperspectral imaging with laboratory measurements

    Science.gov (United States)

    Greenberger, Rebecca N.; Mustard, John F.; Cloutis, Edward A.; Mann, Paul; Wilson, Janette H.; Flemming, Roberta L.; Robertson, Kevin M.; Salvatore, Mark R.; Edwards, Christopher S.

    2015-12-01

    We investigate an outcrop of ∼187 Ma lacustrine pillow basalts of the Talcott Formation exposed in Meriden, Connecticut, USA, focusing on coordinated analyses of one pillow lava to characterize the aqueous history of these basalts in the Hartford Basin. This work uses a suite of multidisciplinary measurements, including hyperspectral imaging, other spectroscopic techniques, and chemical and mineralogical analyses, from the microscopic scale up to the scale of an outcrop. The phases identified in the sample are albite, large iron oxides, and titanite throughout; calcite in vesicles; calcic clinopyroxene, aegirine, and Fe/Mg-bearing clay in the rind; and fine-grained hematite and pyroxenes in the interior. Using imaging spectroscopy, the chemistry and mineralogy results extend to the hand sample and larger outcrop. From all of the analyses, we suggest that the pillow basalts were altered initially after emplacement, either by heated lake water or magmatic fluids, at temperatures of at least 400-600 °C, and the calcic clinopyroxenes and aegirine identified in the rind are a preserved record of that alteration. As the hydrothermal system cooled to slightly lower temperatures, clays formed in the rind, and, during this alteration, the sample oxidized to form hematite in the matrix of the interior and Fe3+ in the pyroxenes in the rind. During the waning stages of the hydrothermal system, calcite precipitated in vesicles within the rind. Later, diagenetic processes albitized the sample, with albite replacing plagioclase, lining vesicles, and accreting onto the exterior of the sample. This albitization or Na-metasomatism occurred when the lake within the Hartford Basin evaporated during a drier past climatic era, resulting in Na-rich brines. As Ca-rich plagioclase altered to albite, Ca was released into solution, eventually precipitating as calcite in previously-unfilled vesicles, dominantly in the interior of the pillow. Coordinated analyses of this sample permit

  14. The carbonaceous matter in the uraniferous dequartzified and albitized leucogranite of Saraya (Senegal): an example of superimposed hydrothermal alterations

    International Nuclear Information System (INIS)

    Mouthier, B.

    1988-01-01

    Two superimposed early hydrothermal alterations have been recognized in the Proterozoic Saraya leucogranite. Successively are described a major dequartzification leading to an episyenite infilled with carbonaceous matter and sulfate during an interruption of the system, succeeded by a mobilization of U and other elements during an albitization. A dolomite filling up followed by a silicopotassic feed-back alteration, close down the system [fr

  15. Isotope geochemistry of hydrothermal alteration in East of Esfahan, Central Iran

    Science.gov (United States)

    Taghipour, Sedigheh; Taghipour, Batoul

    2010-05-01

    In the Cenozoic magmatic belt of Central Iran, the Eocene volcanics and pyroclastics from the East of Esfahan underwent extensive hydrothermal alteration. The Eocene volcanics composed mostly of andesite lava and tuffs have been altered. The survey area is laterally zoned from an inner quartz-sericite alteration zone to an outer propylitic zone. Quartz-sericite alteration is predominant (>95%), but smaller zones of alunite-jarosite and silicified zones are present and superimposed onto a quartz-sericite alteration. In the quartz-sericite zone all altered rocks are light grayish to whitish in color and porphyritic with aphanitic groundmass. Concentrations of alunite and jarosite veinlets and stockworks are dispersed irregularly in this zone. Alunite and jarosite occur also as coatings on fractured rocks. All types of alunite occurrences are brick-red, cream, white and buff in colors, while jarosite is brown to rusty in colors. To verify, chemical composition of alunite and jarosite were identified by X-ray diffraction in mineral assemblages. Major alteration zones show inclusions of propylite, quartz sericite, advanced argillic and silicified zones. These alunites are mainly porcelaneous and their compositions show a solid solution between alunite and jarosite. In alteration zones, the mineral assemblage is characterized by alunite-jarosite + quartz + sericite + alkali feldspars + chlorite ± turquoise ± barite ± iron oxides. There are numerous alunite and jarosite occurrences, mainly as veinlets, in parts of the advanced argillic zone. Alunite δ18O and δ D values range from -1.76 to 8.81‰ and from -52.86 to -129.26‰ respectively. Field observations, mineralogical evidence and results from light element stable isotope data (δ18O, δ D and δ34S); indicate that in this area alunitization is supergene in origin.

  16. Penicillium mycobiota in Arctic subglacial ice

    DEFF Research Database (Denmark)

    Sonjak, S.; Frisvad, Jens Christian; Gunde-Cimerman, N.

    2006-01-01

    , representing on the average half of all isolated strains from all three glaciers. The other most frequently isolated species were P. bialowiezense, P. chrysogenum, P. thomii, P. solitum, P. palitans, P. echinulatum, P. polonicum, P. commune, P. discolor, P. expansum, and new Penicillium species (sp. 1). Twelve...... to be inhabited exclusively by heterotrophic bacteria. In this study we report on the very high occurrence (up to 9000 CFU L-1) and diversity of filamentous Penicillium spp. in the sediment-rich subglacial ice of three different polythermal Arctic glaciers (Svalbard, Norway). The dominant species was P. crustosum...... more Penicillium species were occasionally isolated. The fungi isolated produced consistent profiles of secondary metabolites, not different from the same Penicillium species from other habitats. This is the first report on the presence of large populations of Penicillium spp. in subglacial sediment...

  17. Field Trip Guide to Serpentinite, Silica-Carbonate Alteration, and Related Hydrothermal Activity in the Clear Lake Region, California

    Energy Technology Data Exchange (ETDEWEB)

    Fraser Goff; George Guthrie

    1999-06-01

    This guide is designed to familiarize scientists with the geology, structure, alteration, and fluids typical of California serpentinites for purposes of carbon dioxide sequestration (Lackner et al., 1995). Goff et al. (1997) and Goff and Lackner (1998) describe the geology and geochemistry of some of the serpentinites from this area. Mechanisms of silica-carbonate alteration were outlined by Barnes et al. (1973). Donnelly-Nolan et al. (1993) most recently reviewed relations between regional hydrothermal alteration and Quarternary volcanic activity. Stanley et al. (1998) summarized geophysical characteristics of the region.

  18. Greenland Subglacial Drainage Evolution Regulated by Weakly Connected Regions of the Bed

    Science.gov (United States)

    Hoffman, Matthew J.; Andrews, Lauren C.; Price, Stephen F.; Catania, Ginny A.; Neumann, Thomas A.; Luthi, Martin P.; Gulley, Jason; Ryser, Claudia; Hawley, Robert L.; Morriss, Blaine

    2016-01-01

    Penetration of surface meltwater to the bed of the Greenland Ice Sheet each summer causes an initial increase in ice speed due to elevated basal water pressure, followed by slowdown in late summer that continues into fall and winter. While this seasonal pattern is commonly explained by an evolution of the subglacial drainage system from an inefficient distributed to efficient channelized configuration, mounting evidence indicates that subglacial channels are unable to explain important aspects of hydrodynamic coupling in late summer and fall. Here we use numerical models of subglacial drainage and ice flow to show that limited, gradual leakage of water and lowering of water pressure in weakly connected regions of the bed can explain the dominant features in late and post melt season ice dynamics. These results suggest that a third weakly connected drainage component should be included in the conceptual model of subglacial hydrology.

  19. Precursors predicted by artificial neural networks for mass balance calculations: Quantifying hydrothermal alteration in volcanic rocks

    Science.gov (United States)

    Trépanier, Sylvain; Mathieu, Lucie; Daigneault, Réal; Faure, Stéphane

    2016-04-01

    This study proposes an artificial neural networks-based method for predicting the unaltered (precursor) chemical compositions of hydrothermally altered volcanic rock. The method aims at predicting precursor's major components contents (SiO2, FeOT, MgO, CaO, Na2O, and K2O). The prediction is based on ratios of elements generally immobile during alteration processes; i.e. Zr, TiO2, Al2O3, Y, Nb, Th, and Cr, which are provided as inputs to the neural networks. Multi-layer perceptron neural networks were trained on a large dataset of least-altered volcanic rock samples that document a wide range of volcanic rock types, tectonic settings and ages. The precursors thus predicted are then used to perform mass balance calculations. Various statistics were calculated to validate the predictions of precursors' major components, which indicate that, overall, the predictions are precise and accurate. For example, rank-based correlation coefficients were calculated to compare predicted and analysed values from a least-altered test dataset that had not been used to train the networks. Coefficients over 0.87 were obtained for all components, except for Na2O (0.77), indicating that predictions for alkali might be less performant. Also, predictions are performant for most volcanic rock compositions, except for ultra-K rocks. The proposed method provides an easy and rapid solution to the often difficult task of determining appropriate volcanic precursor compositions to rocks modified by hydrothermal alteration. It is intended for large volcanic rock databases and is most useful, for example, to mineral exploration performed in complex or poorly known volcanic settings. The method is implemented as a simple C++ console program.

  20. Geophysical Investigations of Hypersaline Subglacial Water Systems in the Canadian Arctic: A Planetary Analog

    Science.gov (United States)

    Rutishauser, A.; Sharp, M. J.; Blankenship, D. D.; Skidmore, M. L.; Grima, C.; Schroeder, D. M.; Greenbaum, J. S.; Dowdeswell, J. A.; Young, D. A.

    2017-12-01

    Robotic exploration and remote sensing of the solar system have identified the presence of liquid water beneath ice on several planetary bodies, with evidence for elevated salinity in certain cases. Subglacial water systems beneath Earth's glaciers and ice sheets may provide terrestrial analogs for microbial habitats in such extreme environments, especially those with higher salinity. Geological data suggest that several ice caps and glaciers in the eastern Canadian High Arctic are partially underlain by evaporite-rich sedimentary rocks, and subglacial weathering of these rocks is potentially conducive to the formation of hypersaline subglacial waters. Here, we combine airborne geophysical data with geological constraints to identify and characterize hypersaline subglacial water systems beneath ice caps in Canada's Queen Elizabeth Islands. High relative bedrock reflectivity and specularity anomalies that are apparent in radio-echo sounding data indicate multiple locations where subglacial water is present in areas where modeled ice temperatures at the glacier bed are well below the pressure melting point. This suggests that these water systems are hypersaline, with solute concentrations that significantly depress the freezing point of water. From combined interpretations of geological and airborne-magnetic data, we define the geological context within which these systems have developed, and identify possible solute-sources for the inferred brine-rich water systems. We also derive subglacial hydraulic potential gradients using airborne laser altimetry and ice thickness data, and apply water routing models to derive subglacial drainage pathways. These allow us to identify marine-terminating glaciers where outflow of the brine-rich waters may be anticipated. These hypersaline subglacial water systems beneath Canadian Arctic ice caps and glaciers may represent robust microbial habitats, and potential analogs for brines that may exist beneath ice masses on planetary

  1. Clean subglacial access: prospects for future deep hot-water drilling

    Science.gov (United States)

    Pearce, David; Hodgson, Dominic A.; Smith, Andrew M.; Rose, Mike; Ross, Neil; Mowlem, Matt; Parnell, John

    2016-01-01

    Accessing and sampling subglacial environments deep beneath the Antarctic Ice Sheet presents several challenges to existing drilling technologies. With over half of the ice sheet believed to be resting on a wet bed, drilling down to this environment must conform to international agreements on environmental stewardship and protection, making clean hot-water drilling the most viable option. Such a drill, and its water recovery system, must be capable of accessing significantly greater ice depths than previous hot-water drills, and remain fully operational after connecting with the basal hydrological system. The Subglacial Lake Ellsworth (SLE) project developed a comprehensive plan for deep (greater than 3000 m) subglacial lake research, involving the design and development of a clean deep-ice hot-water drill. However, during fieldwork in December 2012 drilling was halted after a succession of equipment issues culminated in a failure to link with a subsurface cavity and abandonment of the access holes. The lessons learned from this experience are presented here. Combining knowledge gained from these lessons with experience from other hot-water drilling programmes, and recent field testing, we describe the most viable technical options and operational procedures for future clean entry into SLE and other deep subglacial access targets. PMID:26667913

  2. Hydrothermal Alteration in Submarine Basaltic Rocks from the Reykjanes Geothermal Field, Iceland. (Invited)

    Science.gov (United States)

    Zierenberg, R. A.; Schiffman, P.; Fowler, A. P.; Marks, N.; Fridleifsson, G.; Elders, W. A.

    2013-12-01

    The Iceland Deep Drilling Project (IDDP) is preparing to drill to 4-5 km in the Reykjanes Geothermal Field to sample geothermal fluids at supercritical temperature and pressure for power generation. The Reykjanes geothermal field is the on-land extension of the Reykjanes Ridge spreading center. The upper 1-2 kilometers drilled at Reykjanes are submarine basalts and basaltic sediments, hyalloclastites, and breccias, with an increasing proportion of basaltic intrusive rocks below 2 km depth. Geothermal fluids are evolved seawater with a composition similar to mid-ocean ridge hydrothermal systems. Zn- and Cu-rich sulfide scale, locally enriched in Au and Ag, are deposited in production pipes. The sulfide deposits are compositionally and isotopically similar to seafloor massive sulfides. In anticipation of deeper drilling, we have investigated the mineralogy and geochemistry of drill cuttings from a 3 km deep well (RN-17). The depth zoning of alteration minerals is similar to that described from other Icelandic geothermal fields, and is comparable to observed seafloor metamorphic gradients in ODP drill holes and ophiolites. Chlorite-epidote alteration occurs at depths >400 m and passes downhole through epidote-actinolite alteration and into amphibole facies (hornblende-calcic plagioclase) alteration below 2.5 km. Local zones of high temperature (>800°C), granoblastic-textured, pyroxene hornfels, are interpreted to form by contact metamorphism during dike/sill emplacement. Similar granoblasically altered basalts were recovered from the base of the sheeted dikes in IODP Hole 1256D. Downhole compositional variations of drill cuttings, collected every 50 m, suggest that rocks below ~ 2 km are little altered. Whole-rock oxygen isotope profiles are consistent with low water/rock ratios, but suggest that early stages of hydrothermal alteration included meteoric water-derived fluids. Strontium isotope profiles indicate more extensive exchange with seawater-derived fluids

  3. Indication Of Hydrothermal Alteration Activities Based On Petrography Of Volcanic Rocks In Abang Komba Submarine Volcano, East Flores Sea

    OpenAIRE

    Sarmili, Lili; Hutabarat, Johanes

    2014-01-01

    The presence of mineral alteration or secondary processes to rocks on submarine volcano of Abang Komba was caused by an introduction of hydrothermal solutions. Those are indicated by the presence of a resembly of minerals alteration seen in their petrographic analyses. They are characterized by replacement partially surrounding of plagioclase phenocrysts, partially replacing plagioclase by sericite, carbonate and clay minerals. The replacement of pyroxene partly by chlorite, and the presence ...

  4. TARGETING HYDROTHERMAL ALTERATIONS UTILIZING LANDSAT-8 ANDASTER DATA IN SHAHR-E-BABAK, IRAN

    Directory of Open Access Journals (Sweden)

    M. Safari

    2017-10-01

    Full Text Available Shahr-e-Babak tract of the Kerman metalogenic belt is one of the most potential segments of Urumieh–Dokhtar (Sahand-Bazman magmatic arc. This area encompasses several porphyry copper deposits in exploration, development and exploitation hierarchy. The aim of this study is to map hydrothermal alterations caused by early Cenozoic magmatic intrusions in Shahr-e-Babak area. To this purpose, mineral mapping methods including band combinations, ratios and multiplications as well as PCA and MNF data space transforms in SWIR and VNIR for both ASTER and OLI sensors. Alteration zones according to spectral signatures of each type of alteration mineral assemblages such as argillic, phyllic and propylitic are successfully mapped. For enhancing the target areas false color composites and HSI-RGB color space transform are performed on developed band combinations. Previous studies have proven the robust application of ASTER in geology and mineral exploration; nonetheless, the results of this investigation prove applicability of OLI sensor from landsat-8 for alteration mapping. According to the results, evidently OLI sensor data can accurately map alteration zones. Additionally, the 12-bit quantization of OLI data is its privilege over 8-bit data of ASTER in VNIR and SWIR, thus OLI high quality results, which makes it easy to distinguish targets with enhanced color contrast between the altered and unaltered rocks.

  5. Viable cold-tolerant iron-reducing microorganisms in geographically diverse subglacial environments

    Science.gov (United States)

    Nixon, Sophie L.; Telling, Jon P.; Wadham, Jemma L.; Cockell, Charles S.

    2017-03-01

    Subglacial environments are known to harbour metabolically diverse microbial communities. These microbial communities drive chemical weathering of underlying bedrock and influence the geochemistry of glacial meltwater. Despite its importance in weathering reactions, the microbial cycling of iron in subglacial environments, in particular the role of microbial iron reduction, is poorly understood. In this study we address the prevalence of viable iron-reducing microorganisms in subglacial sediments from five geographically isolated glaciers. Iron-reducing enrichment cultures were established with sediment from beneath Engabreen (Norway), Finsterwalderbreen (Svalbard), Leverett and Russell glaciers (Greenland), and Lower Wright Glacier (Antarctica). Rates of iron reduction were higher at 4 °C compared with 15 °C in all but one duplicated second-generation enrichment culture, indicative of cold-tolerant and perhaps cold-adapted iron reducers. Analysis of bacterial 16S rRNA genes indicates Desulfosporosinus were the dominant iron-reducing microorganisms in low-temperature Engabreen, Finsterwalderbreen and Lower Wright Glacier enrichments, and Geobacter dominated in Russell and Leverett enrichments. Results from this study suggest microbial iron reduction is widespread in subglacial environments and may have important implications for global biogeochemical iron cycling and export to marine ecosystems.

  6. Can Subglacial Meltwater Films Carve Into the till Beneath? Insights from a Coupled Till-Water Model

    Science.gov (United States)

    Kasmalkar, I.; Mantelli, E.; Suckale, J.

    2017-12-01

    Networks of water channels are known to exist beneath regions of the continental ice sheets such as Antarctica and Greenland. These channels are fed by meltwater and form along the interface between the ice and the underlying till layer. Their presence localizes basal strength by reducing pore pressure and hence alters the resistance to ice slip provided by the till. Subglacial channels thus play a major role in determining the rate of ice flow for glaciers and ice streams. It is unclear whether subglacial meltwater can evolve from a thin film into a network of distributed channels by erosion of the sediment bed. Models that involve hard-rock beds can only account for water channels that carve into the ice and not the till. Alternative approaches that include erodible sediment mostly assume viscous behavior in the till layer, which is not well supported by laboratory experiments of till failure. To better understand the physical processes that govern channelization, we couple water flow in a thin film with sediment transport to capture the dynamic interactions between water and till. We present a two-dimensional model which consists of a thin subglacial water film that is in the laminar regime and an erodible till layer that obeys the Shield's criterion. We use analytic techniques to study the long-term behavior of perturbations of the water-till interface. We discuss the stability of the system under such perturbations in the context of channel formation.

  7. Controls on thallium uptake during hydrothermal alteration of the upper ocean crust

    Science.gov (United States)

    Coggon, Rosalind M.; Rehkämper, Mark; Atteck, Charlotte; Teagle, Damon A. H.; Alt, Jeffrey C.; Cooper, Matthew J.

    2014-11-01

    Hydrothermal circulation is a fundamental component of global biogeochemical cycles. However, the magnitude of the high temperature axial hydrothermal fluid flux remains disputed, and the lower temperature ridge flank fluid flux is difficult to quantify. Thallium (Tl) isotopes behave differently in axial compared to ridge flank systems, with Tl near-quantitatively stripped from the intrusive crust by high temperature hydrothermal reactions, but added to the lavas during low temperature reaction with seawater. This contrasting behavior provides a unique approach to determine the fluid fluxes associated with axial and ridge flank environments. Unfortunately, our understanding of the Tl isotopic mass balance is hindered by poor knowledge of the mineralogical, physical and chemical controls on Tl-uptake by the ocean crust. Here we use analyses of basaltic volcanic upper crust from Integrated Ocean Drilling Program Hole U1301B on the Juan de Fuca Ridge flank, combined with published analyses of dredged seafloor basalts and upper crustal basalts from Holes 504B and 896A, to investigate the controls on Tl-uptake by mid-ocean ridge basalts and evaluate when in the evolution of the ridge flank hydrothermal system Tl-uptake occurs. Seafloor basalts indicate an association between basaltic uptake of Tl from cold seawater and uptake of Cs and Rb, which are known to partition into K-rich phases. Although there is no clear relationship between Tl and K contents of seafloor basalts, the data do not rule out the incorporation of at least some Tl into the same minerals as the alkali elements. In contrast, we find no relationship between the Tl content and either the abundance of secondary phyllosilicate minerals, or the K, Cs or Rb contents in upper crustal basalts. We conclude that the uptake of Tl and alkali elements during hydrothermal alteration of the upper crust involves different processes and/or mineral phases compared to those that govern seafloor weathering. Furthermore

  8. Unveiling the Antarctic subglacial landscape.

    Science.gov (United States)

    Warner, Roland; Roberts, Jason

    2010-05-01

    Better knowledge of the subglacial landscape of Antarctica is vital to reducing uncertainties regarding prediction of the evolution of the ice sheet. These uncertainties are associated with bedrock geometry for ice sheet dynamics, including possible marine ice sheet instabilities and subglacial hydrological pathways (e.g. Wright et al., 2008). Major collaborative aerogeophysics surveys motivated by the International Polar Year (e.g. ICECAP and AGAP), and continuing large scale radar echo sounding campaigns (ICECAP and NASA Ice Bridge) are significantly improving the coverage. However, the vast size of Antarctica and logistic difficulties mean that data gaps persist, and ice thickness data remains spatially inhomogeneous. The physics governing large scale ice sheet flow enables ice thickness, and hence bedrock topography, to be inferred from knowledge of ice sheet surface topography and considerations of ice sheet mass balance, even in areas with sparse ice thickness measurements (Warner and Budd, 2000). We have developed a robust physically motivated interpolation scheme, based on these methods, and used it to generate a comprehensive map of Antarctic bedrock topography, using along-track ice thickness data assembled for the BEDMAP project (Lythe et al., 2001). This approach reduces ice thickness biases, compared to traditional inverse distance interpolation schemes which ignore the information available from considerations of ice sheet flow. In addition, the use of improved balance fluxes, calculated using a Lagrangian scheme, eliminates the grid orientation biases in ice fluxes associated with finite difference methods (Budd and Warner, 1996, Le Brocq et al., 2006). The present map was generated using a recent surface DEM (Bamber et al., 2009, Griggs and Bamber, 2009) and accumulation distribution (van de Berg et al., 2006). Comparing our results with recent high resolution regional surveys gives confidence that all major subglacial topographic features are

  9. Stable Isotope Geochemistry of Extremely Well-Preserved 2.45-Billion-Year-Old Hydrothermal Systems in the Vetreny Belt, Baltic Shield: Insights into Paleohydrosphere

    Science.gov (United States)

    Zakharov, D. O.; Bindeman, I. N.

    2015-12-01

    The early Paleoproterozoic was an eventful period in the Earth's history. The first portions of free oxygen emerged in the atmosphere, Snowball Earth glaciations happened several times and the first supercontinent broke up due to extensive rifting. These events should have affected the stable isotopic composition of the hydrosphere. In this study, we use rocks that were altered in underwater hydrothermal systems to investigate the stable isotopic composition of the hydrosphere 2.39-2.45 billion years ago (hereinafter, Ga). Extremely low-δ18O (down to -27.5‰ SMOW) rocks from 2.39 Ga metamorphosed subglacial hydrothermal systems of the Belomorian belt, Baltic Shield formed at near-equatorial latitudes suggesting a Snowball (or Slushball) Earth glaciation. These results motivated us to look at temporally and geographically close hydrothermal systems from the unmetamorhposed 2.45 Ga Vetreny Belt rift. The length of the rift is 250 km and it is composed of high-Mg basalts, mafic-ultramafic intrusions and sedimentary successions. We examined several localities of high-Mg basalt flows that include astonishingly fresh pillow lavas, often with preserved volcanic glass, eruptive breccias, and hydrothermal alteration zones. Collected samples serve a great textural evidence of water-rock interaction that occurred in situ while basalts were cooling. The preliminary results from coexisting quartz and epidote (T, D18O=311°C), and from coexisting calcite and quartz (T, D18O=190°C) yield values of δ18O of involved water between -1.6 and -0.9 ‰. The values of δ13C in calcites vary between -4.0 and -2.3 ‰. It is likely that hydrothermal fluids operated in the Vetreny Belt rift were derived from seawater that is no different from modern oceanic water in terms of δ18O. Apparently, the rift was a Paleoproterozoic analog of the modern Red Sea, filled with oceanic water. The result is important because the Vetreny Belt rift predates the onset of Snowball Earth glaciation at 2

  10. Subglacial hydrology and the formation of ice streams.

    Science.gov (United States)

    Kyrke-Smith, T M; Katz, R F; Fowler, A C

    2014-01-08

    Antarctic ice streams are associated with pressurized subglacial meltwater but the role this water plays in the dynamics of the streams is not known. To address this, we present a model of subglacial water flow below ice sheets, and particularly below ice streams. The base-level flow is fed by subglacial melting and is presumed to take the form of a rough-bedded film, in which the ice is supported by larger clasts, but there is a millimetric water film which submerges the smaller particles. A model for the film is given by two coupled partial differential equations, representing mass conservation of water and ice closure. We assume that there is no sediment transport and solve for water film depth and effective pressure. This is coupled to a vertically integrated, higher order model for ice-sheet dynamics. If there is a sufficiently small amount of meltwater produced (e.g. if ice flux is low), the distributed film and ice sheet are stable, whereas for larger amounts of melt the ice-water system can become unstable, and ice streams form spontaneously as a consequence. We show that this can be explained in terms of a multi-valued sliding law, which arises from a simplified, one-dimensional analysis of the coupled model.

  11. Sup(210)Pb, sup(230)Th, and sup(10)Be in Central Indian Basin seamount sediments: Signatures of degassing and hydrothermal alteration of recent origin

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.; Borole, D.V.; Aldahan, A.; Patil, S.K.; Mascarenhas-Pereira, M.B.L.; Possnert, G.; Ericsson, T.; Ramaswamy, V.; Gupta, S.M.

    ) the presence of altered minerals such as smectite and zeolites, and 4) distinctly different magnetic properties in the altered sediments. A predominant influence of neutral chloride type hydrothermal fluids is interpreted. This is the first report of recently...

  12. The mass balance calculation of hydrothermal alteration in Sarcheshmeh porphyry copper deposit

    Directory of Open Access Journals (Sweden)

    Mohammad Maanijou

    2013-10-01

    Full Text Available Sarcheshmeh porphyry copper deposit is located 65 km southwest of Rafsanjan in Kerman province. The Sarcheshmeh deposit belongs to the southeastern part of Urumieh-Dokhtar magmatic assemblage (i.e., Dehaj-Sarduyeh zone. Intrusion of Sarcheshmeh granodiorite stock in faulted and thrusted early-Tertiary volcano-sedimentary deposits, led to mineralization in Miocene. In this research, the mass changes and element mobilities during hydrothermal process of potassic alteration were studied relative to fresh rock from the deeper parts of the plutonic body, phyllic relative to potassic, argillic relative to phyllic and propylitic alteration relative to fresh andesites surrounding the deposit. In the potassic zone, enrichment in Fe2O3 and K2O is so clear, because of increasing Fe coming from biotite alteration and presence of K-feldspar, respectively. Copper and molybdenum enrichments resulted from presence of chalcopyrite, bornite and molybdenite mineralization in this zone. Enrichment of SiO2 and depletion of CaO, MgO, Na2O and K2O in the phyllic zone resulted from leaching of sodium, calcium and magnesium from the aluminosilicate rocks and alteration of K-feldspar to sericite and quartz. In the argillic zone, Al2O3, CaO, MgO, Na2O and MnO have also been enriched in which increasing Al2O3 may be from kaolinite and illite formation. Also, enrichment in SiO2, Al2O3 and CaO in propylitic alteration zone can be attributed to the formation of chlorite, epidote and calcite as indicative minerals of this zone.

  13. Hydrothermal alteration and permeability changes in granitic intrusions related to Sn-W deposits : case study of Panasqueira (Portugal)

    Science.gov (United States)

    Launay, Gaetan; Sizaret, Stanislas; Guillou-Frottier, Laurent; Gloaguen, Eric; Melleton, Jérémie; Pichavant, Michel; Champallier, Rémi; Pinto, Filipe

    2017-04-01

    The Panasqueira Sn-W deposit occurs as a dense network of flat wolframite and cassiterite-bearing quartz veins concentrated in the vicinity of a hidden greisen cupola, and to a lesser extent as disseminated cassiterites in the greisen. Previous studies (Thadeu 1951; 1979) have suggested that the Panasqueira deposit is genetically related to magmatic activity for which the most part is unexposed, and being only represented by the greisen cupola. Hydrothermal fluid circulation during the final stages of granite crystallisation has probably led to the greisenisation of the cupola followed by the deposition of the mineralization in the veins system. Mineral replacement reactions that occurred during the greisenisation could affect rock properties (porosity, density and permeability) which control fluid circulation in the granite. This study aims to investigate effects of greisenisation reactions on the dynamic (time varying) permeability that ultimately leads to fluid circulation in the greisen cupola. To do so, petrological study and experimental determinations of hydrodynamic features (porosity and permeability) for different granite alteration levels and petrographic types (unaltered granite to greisen) are combined and then integrated in coupled numerical models of fluid circulation around the granitic intrusion. Greisen occurs in the apical part of the granitic body and results in the pervasive alteration of the granite along the granite-schist contact. This greisen consists mainly of quartz and muscovite formed by the replacement of feldspars and bleaching of biotites of the initial granite. Otherwise, greisen is generally vuggy which suggests a porosity increase of the granite during hydrothermal alteration processes. This porosity increase has a positive effect on the permeability of the granitic system. Indeed, experimental measurements of permeability with the Paterson press indicate that the initial granite is impermeable (10-20 m2) whereas the greisen is

  14. Lasting Effects of Glacial Lake Outburst Floods on Subglacial Drainage Networks

    Science.gov (United States)

    Robbins, M.; Hendy, I. L.; Bassis, J. N.; Aciego, S.; Stevenson, E. I.

    2017-12-01

    Supraglacial lakes forming in the ablation zone around the Greenland Ice Sheet will likely migrate toward higher elevations as polar temperatures rise through the 21st century. Present understanding of lake drainage shows it can temporarily enhance ice sheet motion, but other possible effects and interactions - especially with older pre-existing subglacial reservoirs - remain unexamined. Here we investigate possible enduring effects of the record high 2012 melt year on the en/subglacial hydrologic network, how this network responds to immediate high fluxes of water from floods, and how these phenomena might connect to previously isolated subglacial pools. Lake Hullet is a large ice dammed lake situated in south Greenland 22km up-ice from where Kiattuut Sermiat (KS) branches from a larger outlet glacier. Lake Hullet rests on bedrock and is contained by a bedrock ridge. It drains roughly annually through Lake Hullet's hydrologic network in a glacial lake outburst flood (GLOF) when water level rises such that it can flow over the obstructive ridge. Subglacial water samples collected from the toe of KS in July 2013 pre-flood were dated using U isotopes with 222Rn concentrations as well as noble gas ratios. These two independent methods reveal an exceedingly old water age of > 1000 years, indicating existence of isolated enduring subglacial meltwater pool(s). A comparison field study at the KS toe in August and September 2015 re-examined glacial hydrochemistry in a time series. 2015 222Rn concentrations are lower than 2013 values, suggesting less water-rock interaction, a reduction in residence time, and a proximal meltwater source. Increased water volume from the record high 2012 melt year may have enlarged the existing en/subglacial drainage network further into the ice sheet releasing meltwater with longer residence times beneath the ice, with effects lasting into subsequent melt seasons due to the stability of channels maintained from recurrent floods. These

  15. Impact-generated Hydrothermal Activity at the Chicxulub Crater

    Science.gov (United States)

    Kring, D. A.; Zurcher, L.; Abramov, O.

    2007-05-01

    Borehole samples recovered from PEMEX exploration boreholes and an ICDP scientific borehole indicate the Chicxulub impact event generated hydrothermal alteration throughout a large volume of the Maya Block beneath the crater floor and extending across the bulk of the ~180 km diameter crater. The first indications of hydrothermal alteration were observed in the crater discovery samples from the Yucatan-6 borehole and manifest itself in the form of anhydrite and quartz veins. Continuous core from the Yaxcopoil-1 borehole reveal a more complex and temporally extensive alteration sequence: following a brief period at high temperatures, impact- melt-bearing polymict breccias and a thin, underlying unit of impact melt were subjected to metasomatism, producing alkali feldspar, sphene, apatite, and magnetite. As the system continued to cool, smectite-series phyllosilicates appeared. A saline solution was involved. Stable isotopes suggest the fluid was dominated by a basinal brine created mostly from existing groundwater of the Yucatan Peninsula, although contributions from down-welling water also occurred in some parts of the system. Numerical modeling of the hydrothermal system suggests circulation occurred for 1.5 to 2.3 Myr, depending on the permeability of the system. Our understanding of the hydrothermal system, however, is still crude. Additional core recovery projects, particularly into the central melt sheet, are needed to better evaluate the extent and duration of hydrothermal alteration.

  16. Paleomagnetic and stable isotope study of the pluton at Rio Hondo near Questa, New Mexico: Implications for CRM related to hydrothermal alteration

    Energy Technology Data Exchange (ETDEWEB)

    Hagstrum, J T; Johnson, C M

    1986-06-01

    Paleomagnetic and rock magnetic data combined with stable isotope data from the middle Tertiary pluton along the Rio Hondo in northern New Mexico suggest that its magnetic remanence has both thermal (TRM) and high-temperature chemical (CRM) components. Oxygen isotope temperatures indicate that magnetite associated with the more rapidly cooled higher levels of the pluton, and with mafic inclusions and cogenetic rhyolitic dikes sampled at lower levels of exposure, ceased subsolidus recrystallization and isotopic exchange above its Curie temperature (580/sup 0/C) in the presence of a magmatic fluid. Continued cooling imparted a TRM to these portions of the pluton. The more slowly cooled granodiorite at lower levels has quartz-magnetite isotopic temperatures that are below the Curie temperature of magnetite implying that its magnetization is high-temperature CRM. Sub-Curie isotopic temperatures for other granitic plutons in the western U.S.A. suggest that CRM may be commonly derived from subsolidus interactions between magnetite and magmatic fluids in plutonic rocks. A meteoric-hydrothermal system generated by the cooling Rio Hondo pluton, and not by younger adjacent intrusions, resulted in limited alteration along zones of high permeability near the southern margin of the Rio Hondo pluton, and in more prevasive alteration of the pluton to the north. The meteoric-hydrothermal alteration occurred at relatively high temperatures (>350/sup 0/C) and, with the exception of local chloritization, caused little visible alteration of the rocks. The isotopic ratios indicate that little of the magnetite could have grown from or exchanged with a meteoric-hydrothermal fluid.

  17. Characterization of terrestrial hydrothermal alteration products with Mars analog instrumentation: Implications for current and future rover investigations

    Science.gov (United States)

    Black, Sarah R.; Hynek, Brian M.

    2018-06-01

    Interpretation of Martian geology relies heavily on our understanding of terrestrial analog deposits and our ability to obtain comprehensive and accurate mineralogical compositions. Many previous studies of terrestrial hydrothermal deposits relied on limited datasets and/or did not use instruments analogous to those deployed on Mars. We analyzed 100 hydrothermally altered basalts from Costa Rica, Nicaragua, and Iceland with Mars analog Visible to Short Wave Infrared (VSWIR) spectroscopy, X-ray Diffraction (XRD), and Raman laser spectrometry. Alteration mineralogy consisted of amorphous and crystalline SiO2 (cristobalite, tridymite, quartz), Ca/Al/Fe/Mg-sulfates (gypsum, anhydrite, alunite, jarosite, hexahydrite, alunogen), Fe-, Ti-, and Mg-oxides/hydroxides (hematite, goethite, anatase/brookite, brucite), elemental sulfur, and phyllosilicates (montmorillonite, kaolinite). Results indicate VSWIR is best suited for identification of X-ray amorphous materials such as hydrated SiO2 and phyllosilicates, while XRD is best utilized for highly ordered crystalline materials such as sulfates, crystalline SiO2 polymorphs, elemental sulfur, and Mg-hydroxides identification. Surprisingly, XRD had the lowest identification rates for Fe-oxides/hydroxides (42% compared to 61% and 75% for VNIR and Raman, respectively), and nearly equal identification rates as VSWIR for kaolinite (76% for VSWIR, 71% for XRD). Identification of phyllosilicates in XRD, while possible, is not as effective as VSWIR without extensive sample preparation. Our observed identification rates may be attributed to the relative abundance of materials-Fe-oxides/hydroxides being present as surface coatings, the presence of large amounts of kaolinite in some samples, and an increased particle size for kaolinite relative to other clays. Elemental sulfur and Fe- and Ti-oxides/hydroxides were more readily identified with Raman. With NASA's current focus on habitability, hydrothermally altered areas-which we know to

  18. Hydrothermal Alteration and Seawater Exchange at Surtsey Volcano, Iceland: New results from 1979 Surtsey Drill Core.

    Science.gov (United States)

    Rhodes, M.; Bryce, J. G.; Jercinovic, M. J.; Fahnestock, M. F.; Jackson, M. D.

    2017-12-01

    The archetypal volcano Surtsey erupted spectacularly out of the North Atlantic Ocean from November 1963 to June 1967, on the southern submarine extension of the E. Icelandic Rift Zone. Twelve years later, in 1979, the eastern cone (Surtur I) was drilled to a depth of 181 m to document the growth of the volcano and the interaction of basaltic tephra with seawater [1]. The present study is a pilot project for the International Continental Drilling Project on Surtsey, SUSTAIN, starting in August, 2017. The overall intent is to document the nature, extent and rates of hydrothermal and seawater reaction with tephra over the past 50 years. This work builds on the 1979 drilling studies through new electron microprobe and laser ablation (LA- ICPMS) analyses to document varying degrees of palagonitic alteration of volcanic glass and primary phases to form authigenic minerals (smectite, zeolites, Al-tobermorite, anhydrite) in the intervening 12 years since the eruption. Combined with modal data and inferred phase densities, the data documents the mass balance of major and trace elements among the phases and the relationship of these changes to core depth, temperature and porosity. Although hydrothermal alteration is extensive, especially in the hotter submarine intervals from 60 to 120 m, detailed whole-rock major, trace and isotopic data (Sr, Nd, Pb), show that, apart from hydration and oxidation, there is only modest exchange of elements between tephra and seawater, or hydrothermal fluids, in the upper 140 m of the core prior to 1979. Below 140 m, in a cooler zone of coarse, more porous tephra, extensive exchange of elements, involving hydrothermal introduction of sulfur and growth of anhydrite, is associated with the loss of Ca, K, Rb, Sr and addition of MgO and Na and seawater isotopic signatures. It is surely no coincidence that this zone of elemental and isotopic exchange supports active microbial colonies [2]. Our results serve as an important baseline for the 2017

  19. Geology, mineralization, and hydrothermal alteration and relationships to acidic and metal-bearing surface waters in the Palmetto Gulch area, southwestern Colorado

    Science.gov (United States)

    Bove, Dana J.; Kurtz, Jeffrey P.; Wright, Winfield G.

    2002-01-01

    The Palmetto Gulch area is affected by low pH and metal-bearing drainage from abandoned mines, and perhaps, from natural weathering around vein zones. To investigate these anthropogenic and potential natural sources of acidity and metals, we mapped the geology, veins, and hydrothermally altered areas; conducted mine dump leachate studies; and collected reconnaissance water quality data. Several small abandoned mines are present in the Palmetto Gulch area that produced small amounts of relatively high-grade silver ore from fault-controlled polymetallic vein deposits. These veins are hosted in lavas, breccias, and related volcaniclastic sediments that ponded within the 28 Ma San Juan-Uncompahgre caldera complex. These rock units generally have conformable contacts and have shallow dips to the northwest. Lava flows of pyroxene andesite, which host the Roy-Pray mine, are massive near their base and typically grade upward into tightly jointed rock with 2-15 cm joint spacing. In general, most hydrothermally altered rock within the Palmetto Gulch area is restricted to envelopes surrounding the mineralized veins and faults. Composite zones of vein-related alteration vary from about 50 to 80 m wide along the high ridgelines and narrow to less than 10 to 15 m beneath an elevation of about 5,462 m. Where unaffected by surficial oxidation, these altered zones contain as much as 7 to 10 volume percent finely-disseminated pyrite. The majority of rocks in the area were affected by regional and vein-related propylitic alteration. These greenish-colored rocks have alteration products consisting of chlorite, illite, and calcite; and feldspars are typically weakly altered. Most of these rocks have detectable amounts of calcite, while as much as 11 percent by weight was detected in samples collected during this study. The Palmetto Gulch area is affected by low pH and metal-bearing drainage from abandoned mines, and perhaps, from natural weathering around vein zones. To investigate

  20. Temporal evolution of the giant Salobo IOCG deposit, Carajás Province (Brazil): constraints from paragenesis of hydrothermal alteration and U-Pb geochronology

    Science.gov (United States)

    deMelo, Gustavo H. C.; Monteiro, Lena V. S.; Xavier, Roberto P.; Moreto, Carolina P. N.; Santiago, Erika S. B.; Dufrane, S. Andrew; Aires, Benevides; Santos, Antonio F. F.

    2017-06-01

    The giant Salobo copper-gold deposit is located in the Carajás Province, Amazon Craton. Detailed drill core description, petrographical studies, and U-Pb SHRIMP IIe and LA-ICP-MS geochronology unravel its evolution regarding the host rocks, hydrothermal alteration and mineralization. Within the Cinzento Shear Zone, the deposit is hosted by orthogneisses of the Mesoarchean Xingu Complex (2950 ± 25 and 2857 ± 6.7 Ma) and of the Neoarchean Igarapé Gelado suite (2763 ± 4.4 Ma), which are crosscut by the Old Salobo granite. Remnants of the Igarapé Salobo metavolcanic-sedimentary sequence are represented by a quartz mylonite with detrital zircon populations (ca. 3.1-3.0, 2.95, 2.86, and 2.74 Ga). High-temperature calcic-sodic hydrothermal alteration (hastingsite-actinolite) was followed by silicification, iron-enrichment (almandine-grunerite-magnetite), tourmaline formation, potassic alteration with biotite, copper-gold ore formation, and later Fe-rich hydrated silicate alteration. Myrmekitic bornite-chalcocite and magnetite comprise the bulk of copper-gold ore. All these alteration assemblages have been overprinted by post-ore hematite-bearing potassic and propylitic alteration, which is also recognized in the Old Salobo granite. In the central zone of the deposit the mylonitized Igarapé Gelado suite rocks yield an age of 2701 ± 30 Ma. Zircon ages of 2547 ± 5.3 and 2535 ± 8.4 Ma were obtained for the Old Salobo granite and for the high-grade copper ore, respectively. A U-Pb LA-ICP-MS monazite age (2452 ± 14 Ma) from the copper-gold ore indicates hydrothermal activity and overprinting in the Siderian. Therefore, a protracted tectono-thermal event due to the reactivation of the Cinzento Shear Zone is proposed for the evolution of the Salobo deposit.

  1. Petrography and Mineral Chemistry of Magmatic and Hydrothermal Biotite in Porphyry Copper-Gold Deposits: A Tool for Understanding Mineralizing Fluid Compositional Changes During Alteration Processes

    Directory of Open Access Journals (Sweden)

    Arifudin Idrus

    2018-01-01

    Full Text Available DOI: 10.17014/ijog.5.1.47-64This study aims to understand the petrography and chemistry of both magmatic and hydrothermal biotites in porphyry copper-gold deposits, and to evaluate the fluid compositional changes during alteration processes. A total of 206 biotite grains from selected rock samples taken from the Batu Hijau porphyry Cu-Au deposit was analyzed. Detailed petrography and biotite chemistry analysis were performed on thin sections and polished thin sections, respectively, representing various rocks and alteration types. A JEOL JXA-8900R electron microprobe analyzer (EMPA was used for the chemistry analysis. The biotite is texturally divided into magmatic and hydrothermal types. Ti, Fe, and F contents can be used to distinguish the two biotite types chemically. Some oxide and halogen contents of biotite from various rocks and alteration types demonstrate a systematic variation in chemical composition. Biotite halogen chemistry shows a systematic increase in log (XCl/XOH and decrease in log (XF/XOH values from biotite (potassic through chlorite-sericite (intermediate argillic to actinolite (inner propylitic zones. The y-intercepts on the log (XCl/XOH vs. XMg and log (XF/XOH vs. XFe plotted for biotite from potassic and intermediate argillic zones are similar or slightly different. In contrast, the y-intercepts on the log (XCl/XOH vs. XMg and log (XF/XOH vs. XFe plotted for biotite from inner propylitic zone display different values in comparison to the two alteration zones. Halogen (F,Cl fugacity ratios in biotite show a similar pattern: in the potassic and intermediate argillic zones they show little variation, whereas in the inner propylitic zone they are distinctly different. These features suggest the hydrothermal fluid composition remained fairly constant in the inner part of the deposit during the potassic and intermediate argillic alteration events, but changed significantly towards the outer part affected by inner propylitic

  2. Distribution of hydrothermally altered rocks in the Reko Diq, Pakistan mineralized area based on spectral analysis of ASTER data

    Science.gov (United States)

    Rowan, L.C.; Schmidt, R.G.; Mars, J.C.

    2006-01-01

    The Reko Diq, Pakistan mineralized study area, approximately 10??km in diameter, is underlain by a central zone of hydrothermally altered rocks associated with Cu-Au mineralization. The surrounding country rocks are a variable mixture of unaltered volcanic rocks, fluvial deposits, and eolian quartz sand. Analysis of 15-band Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data of the study area, aided by laboratory spectral reflectance and spectral emittance measurements of field samples, shows that phyllically altered rocks are laterally extensive, and contain localized areas of argillically altered rocks. In the visible through shortwave-infrared (VNIR + SWIR) phyllically altered rocks are characterized by Al-OH absorption in ASTER band 6 because of molecular vibrations in muscovite, whereas argillically altered rocks have an absorption feature in band 5 resulting from alunite. Propylitically altered rocks form a peripheral zone and are present in scattered exposures within the main altered area. Chlorite and muscovite cause distinctive absorption features at 2.33 and 2.20????m, respectively, although less intense 2.33????m absorption is also present in image spectra of country rocks. Important complementary lithologic information was derived by analysis of the spectral emittance data in the 5 thermal-infrared (TIR) bands. Silicified rocks were not distinguished in the 9 VNIR + SWIR bands because of the lack of diagnostic spectral absorption features in quartz in this wavelength region. Quartz-bearing surficial deposits, as well as hydrothermally silicified rocks, were mapped in the TIR bands by using a band 13/band 12 ratio image, which is sensitive to the intensity of the quartz reststrahlen feature. Improved distinction between the quartzose surficial deposits and silicified bedrock was achieved by using matched-filter processing with TIR image spectra for reference. ?? 2006 Elsevier Inc. All rights reserved.

  3. Hydrothermal Upflow, Serpentinization and Talc Alteration Associated with a High Angle Normal Fault Cutting an Oceanic Detachment, Northern Apennines, Italy

    Science.gov (United States)

    Alt, J.; Crispini, L.; Gaggero, L.; Shanks, W. C., III; Gulbransen, C.; Lavagnino, G.

    2017-12-01

    Normal faults cutting oceanic core complexes are observed at the seafloor and through geophysics, and may act as flow pathways for hydrothermal fluids, but we know little about such faults in the subsurface. We present bulk rock geochemistry and stable isotope data for a fault that acted as a hydrothermal upflow zone in a seafloor ultramafic-hosted hydrothermal system in the northern Apennines, Italy. Peridotites were exposed on the seafloor by detachment faulting, intruded by MORB gabbros, and are overlain by MORB lavas and pelagic sediments. North of the village of Reppia are fault shear zones in serpentinite, oriented at a high angle to the detachment surface and extending 300 m below the paleo-seafloor. The paleo-seafloor strikes roughly east-west, dipping 30˚ to the north. At depth the fault zone occurs as an anticlinal form plunging 40˚ to the west. A second fault strikes approximately north-south, with a near vertical dip. The fault rock outcrops as reddish weathered talc + sulfide in 0.1-2 m wide anastomosing bands, with numerous splays. Talc replaces serpentinite in the fault rocks, and the talc rocks are enriched in Si, metals (Fe, Cu, Pb), Light Rare Earth Elements (LREE), have variable Eu anomalies, and have low Mg, Cr and Ni contents. In some cases gabbro dikes are associated with talc-alteration and may have enhanced fluid flow. Sulfide from a fault rock has d34S=5.7‰. The mineralogy and chemistry of the fault rocks indicate that the fault acted as the upflow pathway for high-T black-smoker type fluids. Traverses away from the fault (up to 1 km) and with depth below the seafloor (up to 500 m) reveal variable influences of hydrothermal fluids, but there are no consistent trends with distance. Background serpentinites 500 m beneath the paleoseafloor have LREE depleted trends. Other serpentinites exhibit correlations of LREE with HFSE as the result of melt percolation, but there is significant scatter, and hydrothermal effects include LREE enrichment

  4. Constraining local subglacial bedrock erosion rates with cosmogenic nuclides

    Science.gov (United States)

    Wirsig, Christian; Ivy-Ochs, Susan; Christl, Marcus; Reitner, Jürgen; Reindl, Martin; Bichler, Mathias; Vockenhuber, Christof; Akcar, Naki; Schlüchter, Christian

    2014-05-01

    The constant buildup of cosmogenic nuclides, most prominently 10Be, in exposed rock surfaces is routinely employed for dating various landforms such as landslides or glacial moraines. One fundamental assumption is that no cosmogenic nuclides were initially present in the rock, before the event to be dated. In the context of glacially formed landscapes it is commonly assumed that subglacial erosion of at least a few meters of bedrock during the period of ice coverage is sufficient to remove any previously accumulated nuclides, since the production of 10Be ceases at a depth of 2-3 m. Insufficient subglacial erosion leads to overestimation of surface exposure ages. If the time since the retreat of the glacier is known, however, a discordant concentration of cosmogenic nuclides delivers information about the depth of subglacial erosion. Here we present data from proglacial bedrock at two sites in the Alps. Goldbergkees in the Hohe Tauern National Park in Austria and Gruebengletscher in the Grimsel Pass area in Switzerland. Samples were taken inside as well as outside of the glaciers' Little Ice Age extent. Measured nuclide concentrations are analyzed with the help of a MATLAB model simulating periods of exposure or glacial cover of user-definable length and erosion rates.

  5. Hydrothermal reequilibration of igneous magnetite in altered granitic plutons and its implications for magnetite classification schemes: Insights from the Handan-Xingtai iron district, North China Craton

    Science.gov (United States)

    Wen, Guang; Li, Jian-Wei; Hofstra, Albert H.; Koenig, Alan E.; Lowers, Heather A.; Adams, David

    2017-09-01

    Magnetite is a common mineral in igneous rocks and has been used as an important petrogenetic indicator as its compositions and textures reflect changing physiochemical parameters such as temperature, oxygen fugacity and melt compositions. In upper crustal settings, igneous rocks are often altered by hydrothermal fluids such that the original textures and compositions of igneous magnetite may be partly or completely obliterated, posing interpretive problems in petrological and geochemical studies. In this paper, we present textural and compositional data of magnetite from variably albitized granitoid rocks in the Handan-Xingtai district, North China Craton to characterize the hydrothermal reequilibration of igneous magnetite. Four types of magnetite have been identified in the samples studied: pristine igneous magnetite (type 1), reequilibrated porous magnetite (type 2), reequilibrated nonporous magnetite (type 3), and hydrothermal magnetite (type 4). Pristine igneous magnetite contains abundant well-developed ilmenite exsolution lamellae that are largely replaced by titanite during subsequent hydrothermal alteration. The titanite has a larger molar volume than its precursor ilmenite and thus causes micro-fractures in the host magnetite grains, facilitating dissolution and reprecipitation of magnetite. During sodic alteration, the igneous magnetite is extensively replaced by type 2 and type 3 magnetite via fluid-induced dissolution and reprecipitation. Porous type 2 magnetite is the initial replacement product of igneous magnetite and is subsequently replaced by the nonoporous type 3 variety as its surface area is reduced and compositional equilibrium with the altering fluid is achieved. Hydrothermal type 4 magnetite is generally euhedral and lacks exsolution lamellae and porosity, and is interpreted to precipitate directly from the ore-forming fluids. Hydrothermal reequilibration of igneous magnetite has led to progressive chemical purification, during which trace

  6. Long-term subglacial sliding patterns based on a sliding law with cavitation

    DEFF Research Database (Denmark)

    Ugelvig, Sofie Vej; Egholm, D.L.

    In ice-sheet models and glacial landscape evolution models, subglacial sliding rates are often related to basal shear stress by a power-law. However, the power-law relationship implies that the subglacial bed can provide unlimited levels of basal drag as sliding rates increases, which is recognized...... as an inadequate assumption, particularly when the effects of subglacial cavities are considered (Schoof 2005). We have implemented a glacial sliding law suggested by Schoof (2005) in a depth-integrated higher-order ice-sheet model (Egholm et al. 2011) and coupled this to a model for glacial hydrology. The sliding...... law includes an upper bound to the basal drag and depends on the effects of longitudinal and transverse stress components for obtaining force balance along the glacier bed. Computational experiments indicate that high annually averaged sliding rates concentrate along valley sides when basal melt...

  7. A paleomagnetic and stable isotope study of the pluton at Rio Hondo near Questa, New Mexico: Implications for CRM related to hydrothermal alteration

    International Nuclear Information System (INIS)

    Hagstrum, J.T.; Johnson, C.M.

    1986-01-01

    Paleomagnetic and rock magnetic data combined with stable isotope data from the middle Tertiary pluton along the Rio Hondo in northern New Mexico suggest that its magnetic remanence has both thermal (TRM) and high-temperature chemical (CRM) components. Oxygen isotope temperatures indicate that magnetite associated with the more rapidly cooled higher levels of the pluton, and with mafic inclusions and cogenetic rhyolitic dikes sampled at lower levels of exposure, ceased subsolidus recrystallization and isotopic exchange above its Curie temperature (580 0 C) in the presence of a magmatic fluid. Continued cooling imparted a TRM to these portions of the pluton. The more slowly cooled granodiorite at lower levels has quartz-magnetite isotopic temperatures that are below the Curie temperature of magnetite implying that its magnetization is high-temperature CRM. Sub-Curie isotopic temperatures for other granitic plutons in the western U.S.A. suggest that CRM may be commonly derived from subsolidus interactions between magnetite and magmatic fluids in plutonic rocks. A meteoric-hydrothermal system generated by the cooling Rio Hondo pluton, and not by younger adjacent intrusions, resulted in limited alteration along zones of high permeability near the southern margin of the Rio Hondo pluton, and in more prevasive alteration of the pluton to the north. The meteoric-hydrothermal alteration occurred at relatively high temperatures (>350 0 C) and, with the exception of local chloritization, caused little visible alteration of the rocks. The isotopic ratios indicate that little of the magnetite could have grown from or exchanged with a meteoric-hydrothermal fluid. (orig.)

  8. Seismic observations of subglacial water discharge from glacier-dammed lake drainage at Lemon Creek Glacier, Alaska

    Science.gov (United States)

    Labedz, C. R.; Bartholomaus, T. C.; Gimbert, F.; Amundson, J. M.; Vore, M. E.; Karplus, M. S.; Tsai, V. C.

    2017-12-01

    Subglacial water flow affects the dynamics of glaciers, influencing basal sliding, sediment transport, fracturing, and terminus dynamics. However, the difficulty of directly observing glacial hydrologic systems creates significant challenges in understanding such glacier behavior. Recently-developed descriptions of ground motion generated by subglacial water flow provide a promising basis for new and unique characterization of glacial hydrologic systems. Particularly, high-frequency ( 1.5-20 Hz) seismic tremor observed near glaciers has been shown to correlate with subglacial runoff. In addition, specific properties of subglacial water flow like water pressure, conduit size, sediment flux, and grain size can be inferred by examining hysteretic behavior over time between different parts of these signals. In this study, we observe the seismic signals generated by subglacial water flow using a high-density array of more than 100 nodes deployed for 10-25 days, and six broadband seismometers deployed for 80 days at Lemon Creek Glacier, Alaska. Specifically, we examine the 36-hour drainage of a glacier-dammed lake into subglacial conduits, comparing hydrologic metrics such as lake level, precipitation, and outlet stream flow rate to the power of seismic signals. Our node array captures this annually-significant hydraulic transient with sensors spaced approximately every 250 m over the majority of the 5.7 km long glacier. This and other lake drainage events provide natural experiments for exploring glaciohydraulic tremor, because the increased water flux through the glacier increases the power of the tremor and hosts the hysteretic behaviors described previously. Analysis of the tremor from events such as this can be extended to further understand subglacial runoff at Lemon Creek glacier and for glacier hydrology in general.

  9. Physiological ecology of microorganisms in Subglacial Lake Whillans

    Directory of Open Access Journals (Sweden)

    Trista J Vick-Majors

    2016-10-01

    Full Text Available Subglacial microbial habitats are widespread in glaciated regions of our planet. Some of these environments have been isolated from the atmosphere and from sunlight for many thousands of years. Consequently, ecosystem processes must rely on energy gained from the oxidation of inorganic substrates or detrital organic matter. Subglacial Lake Whillans (SLW is one of more than 400 subglacial lakes known to exist under the Antarctic ice sheet; however, little is known about microbial physiology and energetics in these systems. When it was sampled through its 800 m thick ice cover in 2013, the SLW water column was shallow (~2 m deep, oxygenated, and possessed sufficient concentrations of C, N, and P substrates to support microbial growth. Here, we use a combination of physiological assays and models to assess the energetics of microbial life in SLW. In general, SLW microorganisms grew slowly in this energy-limited environment. Heterotrophic cellular carbon turnover times, calculated from 3H-thymidine and 3H-leucine incorporation rates, were long (60 to 500 days while cellular doubling times averaged 196 days. Inferred growth rates (average ~0.006 d-1 obtained from the same incubations were at least an order of magnitude lower than those measured in Antarctic surface lakes and oligotrophic areas of the ocean. Low growth efficiency (8% indicated that heterotrophic populations in SLW partition a majority of their carbon demand to cellular maintenance rather than growth. Chemoautotrophic CO2-fixation exceeded heterotrophic organic C-demand by a factor of ~1.5. Aerobic respiratory activity associated with heterotrophic and chemoautotrophic metabolism surpassed the estimated supply of oxygen to SLW, implying that microbial activity could deplete the oxygenated waters, resulting in anoxia. We used thermodynamic calculations to examine the biogeochemical and energetic consequences of environmentally imposed switching between aerobic and anaerobic metabolisms

  10. Landscape evolution by subglacial quarrying

    Science.gov (United States)

    Ugelvig, Sofie V.; Egholm, David L.; Iverson, Neal R.

    2014-05-01

    In glacial landscape evolution models, subglacial erosion rates are often related to basal sliding or ice discharge by a power-law. This relation can be justified for bedrock abrasion because rock debris transported in the basal ice drives the erosion. However, a simple relation between rates of sliding and erosion is not well supported when considering models for quarrying of rock blocks from the bed. Iverson (2012) introduced a new subglacial quarrying model that operates from the theory of adhesive wear. The model is based on the fact that cavities, with a high level of bedrock differential stress, form along the lee side of bed obstacles when the sliding velocity is to high to allow for the ice to creep around the obstacles. The erosion rate is quantified by considering the likelihood of rock fracturing on topographic bumps. The model includes a statistical treatment of the bedrock weakness: larger rock bodies have lower strengths since they have greater possibility of containing a large flaw [Jaeger and Cook, 1979]. Inclusion of this effect strongly influences the erosion rates and questions the dominant role of sliding rate in standard models for subglacial erosion. Effective pressure, average bedslope, and bedrock fracture density are primary factors that, in addition to sliding rate, influence the erosion rate of this new quarrying model [Iverson, 2012]. We have implemented the quarrying model in a depth-integrated higher-order ice-sheet model [Egholm et al. 2011], coupled to a model for glacial hydrology. In order to also include the effects of cavitation on the subglacial sliding rate, we use a sliding law proposed by Schoof (2005), which includes an upper limit for the stress that can be supported at the bed. Computational experiments show that the combined influence of pressure, sliding rate and bed slope leads to realistically looking landforms such as U-shaped valleys, cirques, hanging valleys and overdeepenings. Compared to model results using a

  11. Thermal Expansivity Between 150 and 800°C of Hydrothermally Altered Conduit Dyke Samples from USDP-4 Drill Core (Mt Unzen, Shimabara, Japan)

    Science.gov (United States)

    Yilmaz, T. I.; Hess, K. U.; Vasseur, J.; Wadsworth, F. B.; Gilg, H. A.; Nakada, S.; Dingwell, D. B.

    2017-12-01

    When hot magma intrudes the crust, the surrounding rocks expand. Similarly, the cooling magma contracts. The expansion and contraction of these multiphase materials is not simple and often requires empirical constraint. Therefore, we constrained the thermal expansivity of Unzen dome and conduit samples using a NETZSCH® DIL 402C. Following experiments, those samples were scanned using a Phoenix v|tome|x m to observe the cracks that may have developed during the heating and cooling. The dome samples do not show petrological or chemical signs of alteration. However, the alteration of the conduit dykes is represented by the occurrence of the main secondary phases such as chlorite, sulfides, carbonates, R1 (Reichweite parameter) illite-smectite, and kaolinite. These alteration products indicate an (I) early weak to moderate argillic magmatic alteration, and a (II) second stage weak to moderate propylitic hydrothermal alteration. The linear thermal expansion coefficient aL of the dome material is K-1 between 150° and 800°C and shows a sharp peak of up to K-1 around the alpha-beta-quartz-transition ( 573°C). In contrast, aL of the hydrothermally altered conduit samples starts to increase around 180° and reaches K-1 at 400°C. We interpret this effect as being due to the water content of the kaolinite and the R1 illite-smectite, which induces larger expansions per degree temperature change. Furthermore, the altered conduit samples show a more pronounced increases of aL between 500 and 650°C of up to peaks at K-1, which is generated by the breakdown of chlorite, iron-rich dolomite solid solutions, calcite, and pyrite. We use a 1D conductive model of heat transfer to explore how the country rock around the Unzen conduit zone would heat up after intrusion. In turn, we convert these temperature profiles to thermal stress profiles, assuming the edifice is largely undeformable. We show that these high linear thermal expansion coefficients of the hydrothermally altered

  12. Effects Of Hydrothermal Alteration On Magnetic Properties And Magnetic Signatures - Implications For Predictive Magnetic Exploration Models

    Science.gov (United States)

    Clark, D.

    2012-12-01

    Magnetics is the most widely used geophysical method in hard rock exploration and magnetic surveys are an integral part of exploration programs for many types of mineral deposit, including porphyry Cu, intrusive-related gold, volcanic-hosted epithermal Au, IOCG, VMS, and Ni sulfide deposits. However, the magnetic signatures of ore deposits and their associated mineralized systems are extremely variable and exploration that is based simply on searching for signatures that resemble those of known deposits and systems is rarely successful. Predictive magnetic exploration models are based upon well-established geological models, combined with magnetic property measurements and geological information from well-studied deposits, and guided by magnetic petrological understanding of the processes that create, destroy and modify magnetic minerals in rocks. These models are designed to guide exploration by predicting magnetic signatures that are appropriate to specific geological settings, taking into account factors such as tectonic province; protolith composition; post-formation tilting/faulting/ burial/ exhumation and partial erosion; and metamorphism. Patterns of zoned hydrothermal alteration are important indicators of potentially mineralized systems and, if properly interpreted, can provided vectors to ore. Magnetic signatures associated with these patterns at a range of scales can provide valuable information on prospectivity and can guide drilling, provided they are correctly interpreted in geological terms. This presentation reviews effects of the important types of hydrothermal alteration on magnetic properties within mineralized systems, with particular reference to porphyry copper and IOCG deposits. For example, an unmodified gold-rich porphyry copper system, emplaced into mafic-intermediate volcanic host rocks (such as Bajo de la Alumbrera, Argentina) exhibits an inner potassic zone that is strongly mineralized and magnetite-rich, which is surrounded by an outer

  13. Characteristics of a Low-Sulfidation Epithermal Deposit in the River Reef Zone and the Watuputih Hill, the Poboya Gold Prospect, Central Sulawesi, Indonesia: Host Rocks and Hydrothermal Alteration

    Directory of Open Access Journals (Sweden)

    Syafrizal

    2017-07-01

    Full Text Available Systematic exploration has delineated significant gold mineralization in the River Reef Zone and the presence of a siliceous body at Watuputih Hill, which is a Poboya gold prospect in Central Sulawesi, Indonesia. The mineralization is hosted within the Palu Metamorphic Complex. The host rocks consist of granite, biotite gneiss, and biotite schist, which is intercalated by feldspar porphyroblastic biotite schist and amphibolitic schist. The X-ray fluorescence (XRF analysis of the granite and biotite gneiss suggests that the granitic rocks can be characterized as magnesian arc calc-alkaline rocks, with a weakly peraluminous composition. Alteration minerals were analyzed by a combination of petrographic and X-ray diffraction (XRD. In the River Reef Zone, the hydrothermal alteration zones can be sorted by their proximity to the primary fluid conduit and divided into inner, high-T, and low-T propylitic zones. In Watuputih Hill, the hydrothermal alteration can be divided into advanced argillic and argillic zones. The hydrothermal alteration assemblages indicated that the fluid was at a near-neutral pH in the River Reef Zone, whereas the fluid was acidic within Watuputih Hill. Because the hill is relatively distant from the River Reef Zone, the presence of these zones at Watuputih Hill may be indicative of another mineralization system beneath the hill.

  14. A balanced water layer concept for subglacial hydrology in large-scale ice sheet models

    Directory of Open Access Journals (Sweden)

    S. Goeller

    2013-07-01

    Full Text Available There is currently no doubt about the existence of a widespread hydrological network under the Antarctic Ice Sheet, which lubricates the ice base and thus leads to increased ice velocities. Consequently, ice models should incorporate basal hydrology to obtain meaningful results for future ice dynamics and their contribution to global sea level rise. Here, we introduce the balanced water layer concept, covering two prominent subglacial hydrological features for ice sheet modeling on a continental scale: the evolution of subglacial lakes and balance water fluxes. We couple it to the thermomechanical ice-flow model RIMBAY and apply it to a synthetic model domain. In our experiments we demonstrate the dynamic generation of subglacial lakes and their impact on the velocity field of the overlaying ice sheet, resulting in a negative ice mass balance. Furthermore, we introduce an elementary parametrization of the water flux–basal sliding coupling and reveal the predominance of the ice loss through the resulting ice streams against the stabilizing influence of less hydrologically active areas. We point out that established balance flux schemes quantify these effects only partially as their ability to store subglacial water is lacking.

  15. A balanced water layer concept for subglacial hydrology in large scale ice sheet models

    Science.gov (United States)

    Goeller, S.; Thoma, M.; Grosfeld, K.; Miller, H.

    2012-12-01

    There is currently no doubt about the existence of a wide-spread hydrological network under the Antarctic ice sheet, which lubricates the ice base and thus leads to increased ice velocities. Consequently, ice models should incorporate basal hydrology to obtain meaningful results for future ice dynamics and their contribution to global sea level rise. Here, we introduce the balanced water layer concept, covering two prominent subglacial hydrological features for ice sheet modeling on a continental scale: the evolution of subglacial lakes and balance water fluxes. We couple it to the thermomechanical ice-flow model RIMBAY and apply it to a synthetic model domain inspired by the Gamburtsev Mountains, Antarctica. In our experiments we demonstrate the dynamic generation of subglacial lakes and their impact on the velocity field of the overlaying ice sheet, resulting in a negative ice mass balance. Furthermore, we introduce an elementary parametrization of the water flux-basal sliding coupling and reveal the predominance of the ice loss through the resulting ice streams against the stabilizing influence of less hydrologically active areas. We point out, that established balance flux schemes quantify these effects only partially as their ability to store subglacial water is lacking.

  16. Ice-Shelf Tidal Flexure and Subglacial Pressure Variations

    Science.gov (United States)

    Walker, Ryan T.; Parizek, Byron R.; Alley, Richard B.; Anandakrishnan, Sridhar; Riverman, Kiya L.; Christianson, Knut

    2013-01-01

    We develop a model of an ice shelf-ice stream system as a viscoelastic beam partially supported by an elastic foundation. When bed rock near the grounding line acts as a fulcrum, leverage from the ice shelf dropping at low tide can cause significant (approx 1 cm) uplift in the first few kilometers of grounded ice.This uplift and the corresponding depression at high tide lead to basal pressure variations of sufficient magnitude to influence subglacial hydrology.Tidal flexure may thus affect basal lubrication, sediment flow, and till strength, all of which are significant factors in ice-stream dynamics and grounding-line stability. Under certain circumstances, our results suggest the possibility of seawater being drawn into the subglacial water system. The presence of sea water beneath grounded ice would significantly change the radar reflectivity of the grounding zone and complicate the interpretation of grounded versus floating ice based on ice-penetrating radar observations.

  17. Comparison of hydrothermal alteration patterns associated with porphyry Cu deposits hosted by granitoids and intermediate-mafic volcanic rocks, Kerman Magmatic Arc, Iran: Application of geological, mineralogical and remote sensing data

    Science.gov (United States)

    Yousefi, Seyyed Jabber; Ranjbar, Hojjatollah; Alirezaei, Saeed; Dargahi, Sara; Lentz, David R.

    2018-06-01

    The southern section of the Cenozoic Urumieh-Dokhtar Magmatic Arc (UDMA) of Iran, known as Kerman Magmatic Arc (KMA) or Kerman copper belt, is a major host to porphyry Cu ± Mo ± Au deposits, collectively known as PCDs. In this study, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and spectral angle mapper (SAM) method, combined with field data, mineralogical studies, and spectral analysis are used to determine hydrothermal alteration patterns related to PCDs in the KMA. Gossans developed over some of these porphyry type deposits were mapped using Landsat 8 data. In the NKMA gossans are more developed than in the SKMA due to comparatively lower rate of erosion. The hydrothermal alteration pattern mapped by ASTER data were evaluated using mineralogical and spectral data. ASTER data proved to be useful for mapping the hydrothermal alteration in this semi-arid type of climate. Also Landsat 8 was useful for mapping the iron oxide minerals in the gossans that are associated with the porphyry copper deposits. Our multidisciplinary approach indicates that unlike the PCDs in the northern KMA that are associated with distinct and widespread propylitic alteration, those in the granitoid country rocks lack propylitic alteration or the alteration is only weakly and irregularly developed. The porphyry systems in southern KMA are further distinguished by development of quartz-rich phyllic alteration zones in the outer parts of the PCDs that could be mapped using remote sensing data. Consideration of variations in alteration patterns and specific alteration assemblages are critical in regional exploration for PCDs.

  18. Elemental Mass Balance of the Hydrothermal Alteration Associated with the Baturappe Epithermal Silver-Base Metal Prospect, South Sulawesi, Indonesia

    OpenAIRE

    Nur, Irzal; Idrus, Arifudin; Pramumijoyo, Subagyo; Harijoko, Agung; Watanabe, Koichiro; Imai, Akira; Jaya, Asri; Irfan, Ulva Ria; Sufriadin

    2012-01-01

    Abstract The Baturappe prospect situated in southernmost part of Sulawesi island, Indonesia, is a hydrothermal mineralization district which is characterized by occurrences of epithermal silver-base metal mineralizations. The mineralizations hosted in basaltic-andesitic volcanic rocks of the late Middle-Miocene Baturappe Volcanics. This paper discusses a recent study of relationships between alteration mineralogy and whole-rock geochemistry, which focused on elemental mass balance calculat...

  19. ENVIRONMENT PROTECTION AND ENVIRONMENT MONITORING ISSUES IN THE PROJECTS OF SUBGLACIAL LAKES STUDIES IN ANTARCTICA

    Directory of Open Access Journals (Sweden)

    I. A. Alekhina

    2012-01-01

    Full Text Available Antarctic subglacial lakes can represent extreme natural habitats for microorganisms from the position of their evolution and adaptation, as well as they can contain the information on Antarctic ice sheet history and climatic changes in their sediments. Now only direct measurements and sampling from these habitats can answer on many fundamental questions. Special precaution should be complied at penetration into these unique relic environments without unfavorable impacts and contamination. A number of recommendations were developed on levels of cleanliness and sterility during direct exploration and research of subglacial environments. Documents considered in the article are the first and necessary steps for appropriate and long-term ecological management of subglacial Antarctic environments. Today there are three projects of subglacial aquatic environment research which are in preparation and realization – the Russian project of Lake Vostok, the similar British project of Lake Ellsworth and the American project on Whillans Ice Stream. The programs of ecological stewardship for direct exploration of these lakes are discussed. All these subglacial aquatic objects of further exploration and research are so various on their structure, age and regime, that only results of all programs as a whole can help to draw us a uniform picture of a subglacial ecological system. Ecological stewardship of these should provide the minimal ecological impact with maximal scientific results. On the basis of existing documents and recommendations the general approaches and the program of ecological stewardship for Lake Vostok research are discussed. Study of drilling fluid, drilling chips, Vostok ice core and the fresh frozen water will allow to make an assessment of biological and chemical contamination as a result of the first penetration and to modify the further stewardship program for the second penetration and direct exploration of lake water.

  20. Geochemistry of hydrothermal alteration at the Roosevelt Hot Springs thermal area, Utah

    Energy Technology Data Exchange (ETDEWEB)

    Parry, W T; Ballantyne, J M; Bryant, N L; Dedolph, R E

    1980-01-01

    Hot spring deposits in the Roosevelt thermal area consist of opaline sinter and sinter-cemented alluvium. Alluvium, plutonic rocks, and amphibolite-facies gneiss have been altered by acid-sulfate water to alunite and opal at the surface, and alunite, kaolinite, montmorillonite, and muscovite to a depth of 70 m. Marcasite, pyrite, chlorite, and calcite occur below the water table at about 30 m. The thermal water is dilute (ionic strength 0.1 to 0.2) sodium-chloride brine. The spring water now contains 10 times as much Ca, 100 times as much Mg, and up to 2.5 times as much SO/sub 4/ as the deep water. Although the present day spring temperature is 25/sup 0/C, the temperature was 85/sup 0/C in 1950. A model for development of the observed alteration is supported by observation and irreversible mass transfer calculations. Hydrothermal fluid convectively rises along major fractures. Water cools by conduction and steam separation, and the pH rises due to carbon dioxide escape. At the surface, hydrogen and sulfate ions are produced by oxidation of H/sub 2/S. The low pH water percolates downward and reacts with feldspar in the rocks to produce alunite, kaolinite, montmorillonite, and muscovite as hydrogen ion is consumed. 4 figures, 4 tables.

  1. Representing Glaciations and Subglacial Processes in Hydrogeological Models: A Numerical Investigation

    Directory of Open Access Journals (Sweden)

    Arnaud Sterckx

    2017-01-01

    Full Text Available The specific impact of glacial processes on groundwater flow and solute transport under ice-sheets was determined by means of numerical simulations. Groundwater flow and the transport of δ18O, TDS, and groundwater age were simulated in a generic sedimentary basin during a single glacial event followed by a postglacial period. Results show that simulating subglacial recharge with a fixed flux boundary condition is relevant only for small fluxes, which could be the case under partially wet-based ice-sheets. Glacial loading decreases overpressures, which appear only in thick and low hydraulic diffusivity layers. If subglacial recharge is low, glacial loading can lead to underpressures after the retreat of the ice-sheet. Isostasy reduces considerably the infiltration of meltwater and the groundwater flow rates. Below permafrost, groundwater flow is reduced under the ice-sheet but is enhanced beyond the ice-sheet front. Accounting for salinity-dependent density reduces the infiltration of meltwater at depth. This study shows that each glacial process is potentially relevant in models of subglacial groundwater flow and solute transport. It provides a good basis for building and interpreting such models in the future.

  2. Hydrothermal Alteration Promotes Humic Acid Formation in Sediments: A Case Study of the Central Indian Ocean Basin

    Science.gov (United States)

    Sarma, Nittala S.; Kiran, Rayaprolu; Rama Reddy, M.; Iyer, Sridhar D.; Peketi, A.; Borole, D. V.; Krishna, M. S.

    2018-01-01

    Anomalously high concentrations of humic-rich dissolved organic matter (DOM) in extant submarine hydrothermal vent plumes traveled far from source are increasingly being reported. This DOM, able to mobilize trace metals (e.g., Fe2+) has been hypothesized as originating from organic matter produced by thermogenic bacteria. To eliminate a possible abiogenic origin of this DOM, study is required of well-preserved organic compounds that can be attributed to thermogenic bacteria. The Central Indian Ocean Basin (CIOB) is part of a diffuse plate boundary and an intraplate deformation zone. Coarse fraction (>63 µ) characteristics, mineralogy, magnetic susceptibility, and geochemistry were examined in sediments of a core raised close to a north-south fracture zone near the Equator. Two horizons of distinctly brown-colored sediments were shown as hydrothermally altered from their charred fragments and geochemistry (CaCO3, Corg, Ti/Al, Al/(Al + Fe + Mn), Sr/Ba, Mg/Li, Mn micronodules, Fe/Mn). We examined whether humic substances were preserved in these sediments, and if so whether their carbon isotope distribution would support their hydrothermal origin. Alkali extraction of sediments afforded humic acids (HA) in yields up to 1.2% in the brown sediments. The remaining portions of the core had nil or low concentrations of HA. The carbon of hydrothermal HA is isotopically heavier (average δ13C, ˜ -16.3‰) compared to nonhydrothermal HA (-18.1‰), suggesting that they were probably formed from organic matter that remained after elimination of lighter carbon enriched functional groups during diagenesis. The results provide compelling evidence of HA formation from lipids originating from thermogenic bacteria.

  3. Antarctic Active Subglacial Lake Inventory from ICESat Altimetry, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains lake boundaries, volume changes, and gridded elevations for 124 active subglacial lakes beneath the Antarctic ice sheet. Lakes were identified...

  4. The hydrothermal evolution of the Kawerau geothermal system, New Zealand

    Science.gov (United States)

    Milicich, S. D.; Chambefort, I.; Wilson, C. J. N.; Charlier, B. L. A.; Tepley, F. J.

    2018-03-01

    Hydrothermal alteration zoning and processes provide insights into the evolution of heat source(s) and fluid compositions associated with geothermal systems. Traditional petrological techniques, combined with hydrothermal alteration studies, stable isotope analyses and geochronology can resolve the nature of the fluids involved in hydrothermal processes and their changes through time. We report here new findings along with previous unpublished works on alteration patterns, fluid inclusion measurements and stable isotope data to provide insights into the thermal and chemical evolution of the Kawerau geothermal system, New Zealand. These data indicate the presence of two hydrothermal events that can be coupled with chronological data. The earlier period of hydrothermal activity was initiated at 400 ka, with the heat driving the hydrothermal system inferred to be from the magmatic system that gave rise to rhyolite lavas and sills of the Caxton Formation. Isotopic data fingerprint fluids attributed to this event as meteoric, indicating that the magma primarily served as a heat source driving fluid circulation, and was not releasing magmatic fluids in sufficient quantity to affect the rock mineralogy and thus inferred fluid compositions. The modern Kawerau system was initiated at 16 ka with hydrothermal eruptions linked to shallow intrusion of magma at the onset of activity that gave rise to the Putauaki andesite cone. Likely associated with this later event was a pulse of magmatic CO2, resulting in large-scale deposition of hydrothermal calcite enriched in 18O. Meteoric water-dominated fluids subsequently overwhelmed the magmatic fluids associated with this 18O-rich signature, and both the fluid inclusion microthermometry and stable isotope data reflect a change to the present-day fluid chemistry of low salinity, meteoric-dominated waters.

  5. The study of the mineralogy and rare earth elements behavior in the hydrothermal alteration zones of the Astaneh granitoid massif (SW Arak, Markazi province, Iran)

    International Nuclear Information System (INIS)

    Esmaeily, D.; Afshooni, S. Z.; Valizadeh, M. V.

    2009-01-01

    The Astaneh granitoid massif is located about 40 km to Arak city, central Iran, is a part of Sanandaj-Sirjan structural zone. These intrusive rocks which are mainly composed of gronodioritic rocks, widely affected under hydrothermal alteration. The alteration zones, on the basis of field studies and mineralogy as well as the study of the REE behavior, are investigated in this paper. Eight alteration zones including phyllic (sericitic) with quartz, sericite and pyrite; chloritic with quartz, sericite and chlorite; propylitic with chlorite, epidot, calcite and albite; argillic with clay minerals (chlorite and illite); silicic with abundant quartz; albitic with albite, chlorite and quartz; hematitisation with hematite, Fe-carbonates (ankerite and siderite) and tourmalinisation with tourmaline (dravite) are identified. The results demonstrate notable differences in the REE behavior in the different alteration zones. Accordingly, comparison with the fresh rocks, in the phyllic (sericitic) alteration, LREE are enriched, but HREE, except Yb which enriched, unchanged. Also in chloritic alteration zone, LREEs are depleted, but HREEs represent different behaviors. In the argillic and propylitic alteration zones, all REE are depleted, but compared with HREE, the LREE represent more depletion. In the silicic and hematitisation alteration zones, compared with HREE, the LREE are enriched. Finally, in the albitic and tourmalinisation alteration zones all REE are depleted. These features indicate that the behavior of REE in the hydrothermal alteration zones of the Astaneh granitoid rocks is mainly controlled by p H, availability of complexing ions in the fluid as well as the presence of secondary phases as host REE minerals

  6. Mineralogical, IR-spectral and geochemical monitoring of hydrothermal alteration in a deformed and metamorphosed Jurassic VMS deposit at Arroyo Rojo, Tierra del Fuego, Argentina

    Science.gov (United States)

    Biel, C.; Subías, I.; Acevedo, R. D.; Yusta, I.; Velasco, F.

    2012-04-01

    The Arroyo Rojo Zn-Pb-Cu volcanogenic massive sulfide deposit is the main deposit of the Fin del Mundo District in the Fuegian Andes, Argentina. This deposit is hosted by a Middle Jurassic volcanic and volcanoclastic sequence forming the Lemaire Formation. The latter consists, from the base up, of the following: rhyolitic and dacitic porphyritic rocks, ignimbrite, tuff, and flow. It is underlain by a pre-Jurassic basement and overlain by the hyaloclastic andesites of the Yahgán Formation. The Arroyo Rojo consists of stacked lenticular lenses that are associated with disseminated mineralization in both the footwall and the hanging wall. The internal structure of the ore lenses is marked by the occurrence of massive, semi-massive and banded facies, along with stringer and brecciated zones and minor ore disseminations. The mineral assemblage comprises mainly pyrite and sphalerite, with minor amounts of galena and chalcopyrite and rare pyrrhotite, arsenopyrite, tetrahedrite and bournonite. The ores and the volcanic host rocks have metamorphosed to greenschist facies and were overprinted by a penetrative tectonic foliation, which led to the development of mylonitic, and cataclastic textures, recrystallization and remobilization. Primary depositional characteristics and regional and hydrothermal alteration patterns were preserved despite deformation and metamorphism. Therefore, primary banding was preserved between facies boundaries. In addition, some remnants of magmatic origin are recognizable in preserved phenocrysts and volcaniclastic phenoclasts. Most of the volcanic and volcaniclastic rocks of the host sequence show a rhyolitic to rhyo-dacitic composition. Regional seafloor alteration, characterized by the presence of clinozoisite, Fe-chlorite and titanite, along with quartz and albite, is partially obliterated by hydrothermal alteration. The hydrothermal alteration is stratabound with the following assemblages, which developed from the base to top: (1) Quartz

  7. Meltwater drainage beneath ice sheets: What can we learn from uniting observations of paleo- and contemporary subglacial hydrology?

    Science.gov (United States)

    Simkins, L. M.; Carter, S. P.; Greenwood, S. L.; Schroeder, D. M.

    2017-12-01

    Understanding meltwater at the base of ice sheets is critical for predicting ice flow and subglacial sediment deformation. Whereas much progress has been made with observing contemporary systems, these efforts have been limited by the short temporal scales of remote sensing data, the restricted spatial coverage of radar sounding data, and the logistical challenges of direct access. Geophysical and sedimentological data from deglaciated continental shelves reveal broad spatial and temporal perspectives of subglacial hydrology, that complement observations of contemporary systems. Massive bedrock channels, such as those on the sediment-scoured inner continental shelf of the Amundsen Sea and the western Antarctic Peninsula, are up to hundreds of meters deep, which indicate either catastrophic drainage events or slower channel incision over numerous glaciations or sub-bank full drainage events. The presence of these deep channels has implications for further ice loss as they may provide conduits today for warm water incursion into sub-ice shelf cavities. Sediment-based subglacial channels, widespread in the northern hemisphere terrestrial domain and increasingly detected on both Arctic and Antarctic marine margins, help characterize more ephemeral drainage systems active during ice sheet retreat. Importantly, some observed sediment-based channels are connected to upstream subglacial lakes and terminate at paleo-grounding lines. From these records of paleo-subglacial hydrology, we extract the relative timing of meltwater drainage, estimate water fluxes, and contemplate the sources and ultimate fate of basal meltwater, refining predictive models for modern systems. These insights provided by geological data fill a gap in knowledge regarding spatial and temporal dynamics of subglacial hydrology and offer hindsight into meltwater drainage influence/association with ice flow and retreat behavior. The union of information gathered from paleo- and contemporary subglacial

  8. Dissolution of calcite in glacial water; evidence of inhibition and consequences for subglacial speleogenesis.

    Science.gov (United States)

    Lauritzen, S.-E.

    2012-04-01

    Subglacial speleogenesis (i.e. formation of caves by ice-contact underneath or along glaciers) is an important speleogenetic modus that have taken place in many previously glaciated areas. It is however controversial how efficient this process is when compared to speleogenesis under non-glacial conditions: Can caves be formed from 'scratch' - from a pristine, microscopic fracture (speleogenesis sensu stricto) - or is this process more intensive under non-glacial conditions, so that ice-contact water can only widen pre-existing conduits (speleogenesis sensu lato)? Subglacial waters are low in CO2 and close to zero degrees. A critical parameter for transforming a fracture into a cave is the breakthrough time, tB, which is the time from commencement of flow until undersaturated water can flow freely through the full length of the flowpath. The breathrough effect (i.e. when radial widening accelerates) is dependent on the switching concentration, Cs, which drops dramatically with low CO2 in the system. Apart from the initial aperture and length of the percolation paths through the rock mass, two additional factors are important for tB: 1) the concentration of glacial rock flour and 2) its ability to interfer with the carbonate chemistry. A series of thermostated dissolution experiments using marble and various additions of authentic glacier silt and crushed metamorphic rocks demonstrate and support theoretical considerations that subglacial speleogenesis in low CO2 waters is slower than first anticipated. The sensu stricto mechanism is also severely hampered by the clogging effect of glacial silt, whilst the sensu lato mechanism is sluggish because corrosion of the large specific area of silt particles consumes aggressiveness thus slowing first-order rates when the water comes in contact with the karst surface. Also, for the same reason, Cs may be exceeded before the water enters karst, so that breakthrough may be totally suppressed. Interglacial waters seem > 50 times

  9. Evolution of interstellar organic compounds under asteroidal hydrothermal conditions

    Science.gov (United States)

    Vinogradoff, V.; Bernard, S.; Le Guillou, C.; Remusat, L.

    2018-05-01

    Carbonaceous chondrites (CC) contain a diversity of organic compounds. No definitive evidence for a genetic relationship between these complex organic molecules and the simple organic molecules detected in the interstellar medium (ISM) has yet been reported. One of the many difficulties arises from the transformations of organic compounds during accretion and hydrothermal alteration on asteroids. Here, we report results of hydrothermal alteration experiments conducted on a common constituent of interstellar ice analogs, Hexamethylenetetramine (HMT - C6H12N4). We submitted HMT to asteroidal hydrothermal conditions at 150 °C, for various durations (up to 31 days) and under alkaline pH. Organic products were characterized by gas chromatography mass spectrometry, infrared spectroscopy and synchrotron-based X-ray absorption near edge structure spectroscopy. Results show that, within a few days, HMT has evolved into (1) a very diverse suite of soluble compounds dominated by N-bearing aromatic compounds (> 150 species after 31 days), including for instance formamide, pyridine, pyrrole and their polymers (2) an aromatic and N-rich insoluble material that forms after only 7 days of experiment and then remains stable through time. The reaction pathways leading to the soluble compounds likely include HMT dissociation, formose and Maillard-type reactions, e.g. reactions of sugar derivatives with amines. The present study demonstrates that, if interstellar organic compounds such as HMT had been accreted by chondrite parent bodies, they would have undergone chemical transformations during hydrothermal alteration, potentially leading to the formation of high molecular weight insoluble organic molecules. Some of the diversity of soluble and insoluble organic compounds found in CC may thus result from asteroidal hydrothermal alteration.

  10. Metabasalts from the Mid-Atlantic Ridge: new insights into hydrothermal systems in slow-spreading crust

    Science.gov (United States)

    Gillis, Kathryn M.; Thompson, Geoffrey

    1993-12-01

    An extensive suite of hydrothermally altered rocks were recovered by Alvin and dredging along the MARK [Mid-Atlantic Ridge, south of the Kane Fracture Zone (23 24°N)] where detachment faulting has provided a window into the crustal component of hydrothermal systems. Rocks of basaltic composition are altered to two assemblages with these characteristics: (i) type I: albitic plagioclase (An02 10)+mixed-layer smectite/chlorite or chlorite±actinolite±quartz±sphene, 20% of the clinopyroxene is altered, and Cu and Zn are leached. The geochemical signature of these alteration types reflects the relative proportion and composition of secondary minerals, and the degree of alteration of primary phases, and does not show simple predictive relationships. Element mobilities indicate that both alteration types formed at low water/rock ratios. The MARK assemblages are typical of the greenschist and transition to the amphibolite facies, and represent two distinct, albeit overlapping, temperature regimes: type I-180 to 300°C and type II-250 to 450°C. By analogy with DSDP/ODP Hole 504B and many ophiolites, the MARK metabasalts were altered within the downwelling limb of a hydrothermal cell and type I and II samples formed in the upper and lower portions of the sheeted like complex, respectively. Episodic magmatic and hydrothermal events at slow-spreading ridges suggest that these observed mineral assemblages represent the cumulative effects of more than one hydrothermal event. Groundmass and vein assemblages in the MARK metabasalts indicate either that alteration conditions did not change during successive hydrothermal events or that these assemblages record only the highest temperature event. Lack of retrograde reactions or overprinting of lower temperature assemblages (e.g., zeolites) suggests that there is a continuum in alteration conditions while crustal segments remain in the ridge axis environment. The type II samples may be representative of the reaction zone where

  11. Integrated 3D Geological Modeling to Gain Insight in the Effects of Hydrothermal Alteration on Post-Ore Deformation Style and Strain Localization in the Flin Flon Volcanogenic Massive Sulfide Ore System

    Directory of Open Access Journals (Sweden)

    Ernst Schetselaar

    2017-12-01

    Full Text Available 3D geological modeling of lithogeochemical and geological data provides insight into the role of the sulfide ore horizon and associated footwall hydrothermal alteration in localizing shear strain in the Flin Flon volcanogenic massive sulfide deposits, Canada, as deformation evolved from brittle-ductile to ductile regimes during collisional stages of the 1.9–1.8 Ga Trans-Hudson orogeny. 3D spatial characterization of hydrothermal alteration based on the Ishikawa index (AI and normative corundum percentages outline sericite + chlorite-rich high strain zones, consisting of Al-enriched and Na-depleted felsic and mafic volcanic rocks in the footwall of the sulfide ore horizon. The hydrothermal vent complex, from which these sheared alteration zones originated, was stacked together with the ore horizon by W-vergent thrust faults during an early collisional deformation regime, imbricating molasse-type clastic sediments with the ore-hosting volcanic and volcaniclastic rocks of the Flin Flon arc assemblage. Chlorite-rich planar zones marked by high values of the Carbonate–chlorite–pyrite index (CCPI are laterally more extensive and outline a later system of ductile shear zones, in which phyllosilicates, quartz and chalcopyrite in stringer zones localized shear strain and enhanced transposition of the hydrothermal vent stockwork. The contrasting deformation styles of these two thrusting events and their localization within the ore horizon and hydrothermal vent stockwork have important implications for vectoring towards undiscovered ore in this mature mining camp that are possibly also relevant to other strongly deformed VMS ore systems.

  12. Crushing of Subglacial Lake Sediment as a Source of Bio-utilisable Gases.

    Science.gov (United States)

    Gill Olivas, B.; Telling, J.; Michaud, A. B.; Skidmore, M. L.; Priscu, J. C.; Tranter, M.

    2017-12-01

    Recent research has shown microbial ecosystems exist under glaciers and ice sheets. The sources of energy to support these ecosystems are still not fully understood, particularly beneath the Antarctic Ice Sheet, where direct access to the atmosphere and in-washed organic matter and oxidising agents does not occur. Hence, sub-ice sheet energy sources are restricted to those in subglacial environments, except for ice-margin environments. This study focuses on sediments from Subglacial Lake Whillans (SLW), the first subglacial lake to be directly and cleanly sampled. Sediment from three depths in a shallow core extracted from SLW were used to assess the possible energy contributions from mechanochemical reactions to this subglacial ecosystem. To do this, the samples were crushed under an anoxic atmosphere using a ball mill. The sediments were then transferred into serum bottles under anoxic conditions. They were wetted and the headspace gas was subsequently sampled and analysed during a 40 day incubation. Results show the release of substantial amounts of hydrogen, which could potentially serve as an abiotic source of energy to microbes, in particular, methanogenic archaea. Significant amounts of short chain hydrocarbons (including methane and ethylene), possibly from the reactivation of ancient organic carbon, were also observed. Crushed samples showed a significant concentration of hydrogen peroxide produced on contact with water, as well as significant amounts of Si radicals, showing comminution of these sediments unlocks the potential for a wide range of redox conditions and reactions to develop within glacially eroded sediment under ice. This in turn provides a previously overlooked source of nutrients and energy for microbes to utilise.

  13. Non-traditional Stable Isotope Systematics of Seafloor Hydrothermal Systems

    Science.gov (United States)

    Rouxel, O. J.

    2009-05-01

    Seafloor hydrothermal activity at mid-ocean ridges is one of the fundamental processes controlling the chemistry of the oceans and the altered oceanic crust. Past studies have demonstrated the complexity and diversity of seafloor hydrothermal systems and have highlighted the importance of subsurface environments in controlling the composition of hydrothermal fluids and mineralization types. Traditionally, the behavior of metals in seafloor hydrothermal systems have been investigated by integrating results from laboratory studies, theoretical models, mineralogy and fluid and mineral chemistry. Isotope ratios of various metals and metalloids, such as Fe, Cu, Zn, Se, Cd and Sb have recently provided new approaches for the study of seafloor hydrothermal systems. Despite these initial investigations, the cause of the isotopic variability of these elements remains poorly constrained. We have little understanding of the isotope variations between vent types (black or white smokers) as well as the influence of source rock composition (basalt, felsic or ultrabasic rocks) and alteration types. Here, I will review and present new results of metal isotope systematics of seafloor hydrothermal systems, in particular: (1) determination of empirical isotope fractionation factors for Zn, Fe and Cu-isotopes through isotopic analysis of mono-mineralic sulfide grains lining the internal chimney wall in contact with hydrothermal fluid; (2) comparison of Fe- and Cu-isotope signatures of vent fluids from mid- oceanic and back-arc hydrothermal fields, spanning wide ranges of pH, temperature, metal concentrations and contributions of magmatic fluids enriched in SO2. Ultimately, the use of complementary non-traditional stable isotope systems may help identify and constrain the complex interactions between fluids,minerals, and organisms in seafloor hydrothermal systems.

  14. Porosity evolution in Icelandic hydrothermal systems

    Science.gov (United States)

    Thien, B.; Kosakowski, G.; Kulik, D. A.

    2014-12-01

    Mineralogical alteration of reservoir rocks, driven by fluid circulation in natural or enhanced hydrothermal systems, is likely to influence the long-term performance of geothermal power generation. A key factor is the change of porosity due to dissolution of primary minerals and precipitation of secondary phases. Porosity changes will affect fluid circulation and solute transport, which, in turn, influence mineralogical alteration. This study is part of the Sinergia COTHERM project (COmbined hydrological, geochemical and geophysical modeling of geotTHERMal systems, grant number CRSII2_141843/1) that is an integrative research project aimed at improving our understanding of the sub-surface processes in magmatically-driven natural geothermal systems. These are typically high enthalphy systems where a magmatic pluton is located at a few kilometers depth. These shallow plutons increase the geothermal gradient and trigger the circulation of hydrothermal waters with a steam cap forming at shallow depth. Field observations suggest that active and fossil Icelandic hydrothermal systems are built from a superposition of completely altered and completely unaltered layers. With help of 1D and 2D reactive transport models (OpenGeoSys-GEM code), we investigate the reasons for this finding, by studying the mineralogical evolution of protoliths with different initial porosities at different temperatures and pressures, different leaching water composition and gas content, and different porosity geometries (i.e. porous medium versus fractured medium). From this study, we believe that the initial porosity of protoliths and volume changes due to their transformation into secondary minerals are key factors to explain the different alteration extents observed in field studies. We also discuss how precipitation and dissolution kinetics can influence the alteration time scales.

  15. The study of hydrothermal alteration zones in Kahang exploration area (north eastern of Isfahan, central of Iran) using microscopy studies and TM and Aster satellite data

    Science.gov (United States)

    Zahra Afshooni, Seyedeh; Esmaeily, Dariush

    2010-05-01

    Kahang ore deposit located in 73 km to the northeast of Isfahan city and 10 km to the east of Zefreh town, covering an area about 18.6 km2. This ore deposit is a part of Uromieh-Dokhtar volcanopolotonic belt. The rocks of the area included Andesite, Porphyritic Andesite, Dacite, Porphyritic, Rhyodacite, Diorite, Quartz Monzonite and Porphyry Micro Granite. In plutons, there is a trend from basic to acid features along with decreasing of age from margin to center of massive. Kahang region is an alteration and breccia zone. The occurrence of alteration zones and iron oxides were confirmed by satellite images processing. Generally, more than 90% of rocks of this region have been affected by hydrothermal fluids. Remote sensing refers to detection and measurement from a distance. For the first time, this exploration area was studied using satellite images processing (TM) and primary results showed that is suitable place for resources of Copper (Cu) and Molybdenum (Mo). Hydrothermal alteration commonly occurs in geothermal areas in association with ore deposits producing alteration assemblages typically dominated by silicates, sulfides, sulfates and carbonates. In the alteration zones studies the subject discussed is the study of existing minerals in such zones and study of chemical specifications of altering fluids. Four alteration zones Based on observations derived from the study of thin sections, XRD analysis and deep remote sensing using TM and Aster satellite images studies could be identified in this area: propylitic alteration zone with chlorite, epidot, calcite; argillic alteration zone with clay minerals; phyllic (qartz-sericite) alteration zone with quartz, sericite and pyrite and silicic alteration zone with abundant quartz.

  16. Oxygen 18 isotopic analysis of sub-glacial concentrations of the Laurentide Ice Sheet

    Energy Technology Data Exchange (ETDEWEB)

    Hillaire-Marcel, C [Quebec Univ., Montreal (Canada); Cailleux, A [Observatoire de Paris, Section de Meudon, 92 (France); Soucy, J

    1979-07-01

    Calcareous concretions occuring on Grenvillian gneiss have been discovered north of Hull, Quebec. Their structure and isotopic composition (delta/sub PDB//sup 18/O approximately equal to -26%; delta/sub PDB//sup 13/C approximately equal to 0%; /sup 14/C age > 35,000 BP) indicate subglacial conditions of precipitation. It is concluded that they were deposited at the base of the Laurentide ice sheet. Assuming equilibrium conditions with the subglacial film of water during precipitation of calcite, it is possible to define a -27.5 to -31.8% (vs. 'standard mean ocean water' (SMOW)) range for the oxygen-18 content of ice.

  17. Modeling the response of subglacial drainage at Paakitsoq, west Greenland, to 21st century climate change

    Science.gov (United States)

    Mayaud, Jerome R.; Banwell, Alison F.; Arnold, Neil S.; Willis, Ian C.

    2014-12-01

    Although the Greenland Ice Sheet (GrIS) is losing mass at an accelerating rate, much uncertainty remains about how surface runoff interacts with the subglacial drainage system and affects water pressures and ice velocities, both currently, and into the future. Here, we apply a physically based, subglacial hydrological model to the Paakitsoq region, west Greenland, and run it into the future to calculate patterns of daily subglacial water pressure fluctuations in response to climatic warming. The model is driven with moulin input hydrographs calculated by a surface routing model, forced with distributed runoff. Surface runoff and routing are simulated for a baseline year (2000), before the model is forced with future climate scenarios for the years 2025, 2050, and 2095, based on the IPCC's Representative Concentration Pathways (RCPs). Our results show that as runoff increases throughout the 21st century, and/or as RCP scenarios become more extreme, the subglacial drainage system makes an earlier transition from a less efficient network operating at high water pressures, to a more efficient network with lower pressures. This will likely cause an overall decrease in ice velocities for marginal areas of the GrIS. However, short-term variations in runoff, and therefore subglacial pressure, can still cause localized speedups, even after the system has become more efficient. If these short-term pressure fluctuations become more pronounced as future runoff increases, the associated late-season speedups may help to compensate for the drop in overall summer velocities, associated with earlier transitioning from a high to a low pressure system.

  18. Evolution of Morphology and Crystallinity of Silica Minerals Under Hydrothermal Conditions

    Science.gov (United States)

    Isobe, H.

    2011-12-01

    Silica minerals are quite common mineral species in surface environment of the terrestrial planets. They are good indicator of terrestrial processes including hydrothermal alteration, diagenesis and soil formation. Hydrothermal quartz, metastable low temperature cristobalite and amorphous silica show characteristic morphology and crystallinity depending on their formation processes and kinetics under wide range of temperature, pressure, acidity and thermal history. In this study, silica minerals produced by acidic hydrothermal alteration related to volcanic activities and hydrothermal crystallization experiments from diatom sediment are examined with crystallographic analysis and morphologic observations. Low temperature form of cistobalite is a metastable phase and a common alteration product occured in highly acidic hydrothermal environment around fumaroles in geothermal / volcanic areas. XRD analysis revealed that the alteration degree of whole rock is represented by abundance of cristobalite. Detailed powder XRD analysis show that the primary diffraction peak of cristobalite composed with two or three phases with different d-spacing and FWHM by peak profile fitting analysis. Shorter d-spacing and narrower FWHM cristobalite crystallize from precursor materials with less-crystallized, longer d-spacing and wider FWHM cristobalite. Textures of hydrothermal cristobalite in altered rock shows remnant of porphylitic texture of the host rock, pyroxene-amphibole andesite. Diatom has amorphous silica shell and makes diatomite sediment. Diatomite found in less diagenetic Quarternary formation keeps amorphous silica diatom shells. Hydrothermal alteration experiments of amorphous silica diatomite sediment are carried out from 300 °C to 550 °C. Mineral composition of run products shows crystallization of cristobalite and quartz progress depending on temperature and run durations. Initial crystallization product, cristobalite grains occur as characteristic lepispheres and

  19. Ion-adsorption REEs in regolith of the Liberty Hill pluton, South Carolina, USA: An effect of hydrothermal alteration

    Science.gov (United States)

    Bern, Carleton R.; Yesavage, Tiffany; Foley, Nora K.

    2017-01-01

    Ion-adsorbed rare earth element (REE) deposits supply the majority of world heavy REE production and substantial light REE production, but relatively little is known of their occurrence outside Southeast Asia. We examined the distribution and forms of REEs on a North American pluton located in the highly weathered and slowly eroding South Carolina Piedmont. The Hercynian Liberty Hill pluton experiences a modern climate that includes ~ 1500 mm annual rainfall and a mean annual temperature of 17 °C. The pluton is medium- to coarse-grained biotite-amphibole granite with minor biotite granite facies. REE-bearing phases are diverse and include monazite, zircon, titanite, allanite, apatite and bastnäsite. Weathered profiles were sampled up to 7 m-deep across the ~ 400 km2 pluton. In one profile, ion-adsorbed REEs plus yttrium (REE + Y) ranged up to 581 mg/kg and accounted for up to 77% of total REE + Y in saprolite. In other profiles, ion-adsorbed REE + Y ranged 12–194 mg/kg and only accounted for 3–37% of totals. The profile most enriched in ion-adsorbed REEs was located along the mapped boundary of two granite facies and contained trioctahedral smectite in the saprolite, evidence suggestive of hydrothermal alteration of biotite at that location. Post-emplacement deuteric alteration can generate easily weathered REE phases, particularly fluorocarbonates. In the case of Liberty Hill, hydrothermal alteration may have converted less soluble to more soluble REE minerals. Additionally, regolith P content was inversely correlated with the fraction ion-adsorbed REEs, and weathering related secondary REE-phosphates were found in some regolith profiles. Both patterns illustrate how low P content aids in the accumulation of ion-adsorbed REEs. The localized occurrence at Liberty Hill sheds light on conditions and processes that generate ion-adsorbed REEs.

  20. An assessment of AVIRIS data for hydrothermal alteration mapping in the Goldfield Mining District, Nevada

    Science.gov (United States)

    Carrere, Veronique; Abrams, Michael J.

    1988-01-01

    Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) data were acquired over the Goldfield Mining District, Nevada, in September 1987. Goldfield is one of the group of large epithermal precious metal deposits in Tertiary volcanic rocks, associated with silicic volcanism and caldera formation. Hydrothermal alteration consists of silicification along fractures, advanced agrillic and argillic zones further away from veins and more widespread propylitic zones. An evaluation of AVIRIS data quality was performed. Faults in the data, related to engineering problems and a different behavior of the instrument while on-board the U2, were encountered. Consequently, a decision was made to use raw data and correct them only for dark current variations and detector read-out-delays. New software was written to that effect. Atmospheric correction was performed using the flat field correction technique. Analysis of the data was then performed to extract spectral information, mainly concentrating on the 2 to 2.45 micron window, as the alteration minerals of interest have their distinctive spectral reflectance features in this region. Principally kaolinite and alunite spectra were clearly obtained. Mapping of the different minerals and alteration zones was attempted using ratios and clustering techniques. Poor signal-to-noise performance of the instrument and the lack of appropriate software prevented the production of an alteration map of the area. Spectra extracted locally from the AVIRIS data were checked in the field by collecting representative samples of the outcrops.

  1. The effect of prior hydrothermal alteration on the melting behaviour during rhyolite formation in Yellowstone, and its importance in the generation of low-δ18O magmas

    Science.gov (United States)

    Troch, Juliana; Ellis, Ben S.; Harris, Chris; Ulmer, Peter; Bachmann, Olivier

    2018-01-01

    Constraining the contribution of crustal lithologies to silicic magmas has important implications for understanding the dynamics of these potentially highly explosive systems. Low-δ18O rhyolite lavas erupted after caldera-forming events in Yellowstone have been interpreted as the products of bulk crustal melting of previously deposited and hydrothermally altered rhyolitic material in the down-dropped caldera roof. For lack of compositional data, the "self-cannibalisation bulk melting"-theory relies on the assumption that hydrothermally altered materials are near-cotectic and hydrous (>3 wt% H2O) and will therefore readily melt at temperatures below 850 °C. In this study, we examine the drillcores Y2, Y9 and Y13 from a USGS drilling campaign in Yellowstone in order to characterise the hydrothermally altered material in terms of major and trace elements, oxygen isotopes and water contents. Rhyolite δ18O values can decrease from "normal" (+5.8 to +6.1‰) on the surface to as low as -5‰ at depths of 100-160 m and probably lower as a function of increasing temperature with depth. While material in the drillcores is variably altered and silicified, oxygen isotope exchange in these samples is not accompanied by systematic changes in major and trace element composition and is independent of uptake of water. More than 75% of the drillcore samples have 1100 °C. Therefore, large-scale bulk melting is unrealistic and low-δ18O rhyolite magmas more likely result from assimilation of <30% partially melted altered crust with low δ18O into a normal-δ18O rhyolite magma from the main reservoir. This mechanism is supported by isotopic mass-balance models as well as thermal and volumetric constraints, and may be similarly applicable to other low-δ18O settings worldwide.

  2. Modeling subglacial sediment discharge in 1-dimension: comparison with measurments and implications for glacial retreat

    Science.gov (United States)

    Delaney, I. A.; Werder, M.; Farinotti, D.

    2017-12-01

    In recent decades increased sedimentation rates have been observed in reservoirs downstream of some retreating glaciers. This material either originates from slopes recently exposed by glacier retreat and no longer stabilized by ice, or subglacially, where pressurized melt water transports sediments from the glacier bed. Some evidence suggests that recently exposed periglacial areas can stablize relatively quickly and in some catchments provides a smaller precentage of the total sediment compared to the subglacial environment. As a result, in order predict and forecast sediment yield from glaciated catchments as glaciers thin and thier hydrology evolves, a subglacial sediment transport model must be implemented. Here a simple 1-dimensional glacio-hydraulic model uses the Darcy-Weissbach relationship to determine shear-stress of presurized water on the glacier bed. This is coupled with a sediment transport relationship to determine quantity of discharged material from the glacier snout. Several tuning factors allow calibration and the model to reproduces processes known to occur subglacially, including seasonal evolution of sediment expulsion and deposition of sediment on adverse slopes of overdeepenings. To asses the model's application to real glaciers, sediment flux data has been collected from Gornergletscher, Aletschgletscher and Griesgletscher in the Swiss Alps over time-scales of up to decades. By calibrating to these data, the skill of the model in recreating sediment trends and volumes is assesed. The outputs capture annual erosion quanities relatively well, however, challenges exist in capturing inter-annual variations in sediment discharge. Many of the model's short comings relate to caputuring the spatial distribution of sediment throughout the glacier bed, which is particularing difficult in 1-dimension. However, this work suggests that a simple models can be used to predict subglacial sediment transport with reasonable ability. Additionally, further

  3. Quantification of diagenetic overprint processes deduced from fossil carbonate shells and laboratory-based hydrothermal alteration experiments

    Science.gov (United States)

    Griesshaber, Erika; Casella, Laura; Mavromatis, Vasileios; Dietzel, Martin; Immenhauser, Adrian; Schmahl, Wolfgang

    2016-04-01

    Benthic and nektonic marine biogenic carbonate archives represent the foundation of numerous studies aiming at reconstructions of past climate dynamics and environmental change. However, living organisms are not in thermodynamic equilibrium and create local chemical environments where physiologic processes such as biomineralization takes place. After the death of the organism the former physiologic disequilibrium conditions are not sustained any more and all biological tissues are altered by equilibration according to the surrounding environment: diagenesis. With increasing diagenetic alteration, the biogenic structure and fingerprint fades away and is replaced by inorganic features. Thus, recrystallization of organism-specific microstructure is a clear indicator for diagenetic overprint. Microstructural data, which mirror recrystallization, are of great value for interpreting geochemical proxies for paleo-environment reconstruction. Despite more than a century of research dealing with carbonate diagenesis, many of the controlling processes and factors are only understood in a qualitative manner. One of the main issues is that diagenetically altered carbonates are usually present as the product of a complex preceding diagenetic pathway with an unknown number of intermediate steps. In this contribution we present and discuss laboratory based alteration experiments with the aim to investigate time-series data sets in a controlled manner. We conducted hydrothermal alteration experiments with modern Arctica islandica (bivalvia) and Notosaria nigricans (brachiopoda) in order to mimic diagenetic overprint. We explore first the potential of electron backscattered diffraction (EBSD) measurements together with statistical data evaluation as a tool to quantify diagenetic alteration of carbonate skeletons. Subsequently, we compare microstructural patterns obtained from experimentally altered shell material with those of fossil specimens that have undergone variable degrees of

  4. Feedbacks between subglacial dynamics and long-term glacial landscape evolution

    DEFF Research Database (Denmark)

    Brædstrup, Christian; Egholm, D.L.; Ugelvig, Sofie Vej

    focus this presentation on feedbacks between the evolving bed topography and the subglacial erosion patterns. We have performed our experiments with different sliding and erosion laws, including highly non-linear rules representing coulomb-type slip at the bed (Schoof, 2010) and a quarrying model...

  5. Fractal Dimension Change Point Model for Hydrothermal Alteration Anomalies in Silk Road Economic Belt, the Beishan Area, Gansu, China

    Science.gov (United States)

    Han, H. H.; Wang, Y. L.; Ren, G. L.; LI, J. Q.; Gao, T.; Yang, M.; Yang, J. L.

    2016-11-01

    Remote sensing plays an important role in mineral exploration of “One Belt One Road” plan. One of its applications is extracting and locating hydrothermal alteration zones that are related to mines. At present, the extracting method for alteration anomalies from principal component image mainly relies on the data's normal distribution, without considering the nonlinear characteristics of geological anomaly. In this study, a Fractal Dimension Change Point Model (FDCPM), calculated by the self-similarity and mutability of alteration anomalies, is employed to quantitatively acquire the critical threshold of alteration anomalies. The realization theory and access mechanism of the model are elaborated by an experiment with ASTER data in Beishan mineralization belt, also the results are compared with traditional method (De-Interfered Anomalous Principal Component Thresholding Technique, DIAPCTT). The results show that the findings produced by FDCPM are agree with well with a mounting body of evidence from different perspectives, with the extracting accuracy over 80%, indicating that FDCPM is an effective extracting method for remote sensing alteration anomalies, and could be used as an useful tool for mineral exploration in similar areas in Silk Road Economic Belt.

  6. High-grade iron ore at Windarling, Yilgarn Craton: a product of syn-orogenic deformation, hypogene hydrothermal alteration and supergene modification in an Archean BIF-basalt lithostratigraphy

    Science.gov (United States)

    Angerer, Thomas; Hagemann, Steffen G.; Danyushevsky, Leonid

    2013-08-01

    Banded iron formation (BIF)-hosted iron ore deposits in the Windarling Range are located in the lower greenstone succession of the Marda-Diemals greenstone belt, Southern Cross domain, Yilgarn Craton and constitute a total hematite-martite-goethite ore resource of minimum 52 Mt at 60 wt.% Fe (0.07 P). Banded iron formation is interlayered with high-Mg basalts at Windarling and precipitated during episodes of volcanic quiescence. Trace element content and the rare earth element (REE) ratios Y/Ho (42 to 45), Sm/Yb (1.5), together with positive La and Gd anomalies in `least-altered' hematite-magnetite-metachert-BIF indicate the precipitation from Archean seawater that was fertilised by hydrothermal vent fluids with a basaltic HREE-Y signature. Hypogene iron ore in sub-greenschist facies metamorphosed BIF formed during three distinct stages: ore stage 1 was a syn- to post-metamorphic, syn-D1, Fe-Ca-Mg-Ni-Co-P-REE metasomatism that produced local Ni-REE-rich Fe-dolomite-magnetite alteration in BIF. Hydrothermal alteration was induced by hot fluid flow controlled by brittle-ductile reactivation of BIF-basalt margins and crosscutting D1 faults. The Ni-Co-rich content of dolomite and a shift in REE ratios in carbonate-altered BIF towards Archean mafic rock signature (Y/Ho to 31 to 40, Sm/Yb to 1 to 2 and Gd/Gd* to 1.2 to 1.4) suggest that high-Mg basalts in the Windarling Range were the primary source of introduced metals. During ore stage 2, a syn-deformational and likely acidic and oxidised fluid flow along BIF-basalt margins and within D1 faults leached carbonate and precipitated lepidoblastic and anhedral/granoblastic hematite. High-grade magnetite-hematite ore is formed during this stage. Ore stage 3 hydrothermal specular hematite (spcH)-Fe-dolomite-quartz alteration was controlled by a late-orogenic, brittle, compressional/transpressional stage (D4; the regional-scale shear-zone-related D3 is not preserved in Windarling). This minor event remobilised iron oxides

  7. Prospects of obtaining samples of bottom sediments from subglacial lake Vostok

    Directory of Open Access Journals (Sweden)

    Н. И. Васильев

    2017-04-01

    Full Text Available The paper proves the timeliness of obtaining and examining bottom sediments from subglacial Lake Vostok. Predictive geological section of Lake Vostok and information value of bottom sediments have been examined. Severe requirements towards environmental security of lake examinations and sampling of bottom sediments rule out the use of conventional drilling technologies, as they would pollute the lake with injection liquid from the borehole. In order to carry out sampling of bottom sediments from the subglacial lake, it is proposed to use a dynamically balanced tool string, which enables rotary drilling without any external support on borehole walls to transmit counter torque.     A theoretical analysis has been carried out to assess the operation of the tool string, which is a two-mass oscillatory electromechanical system of reciprocating and rotating motion (RRM with two degrees of freedom.

  8. Mapping hydrothermally altered rocks at Cuprite, Nevada, using the advanced spaceborne thermal emission and reflection radiometer (Aster), a new satellite-imaging system

    Science.gov (United States)

    Rowan, L.C.; Hook, S.J.; Abrams, M.J.; Mars, J.C.

    2003-01-01

    The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a 14-band multispectral instrument on board the Earth Observing System (EOS), TERRA. The three bands between 0.52 and 0.86 ??m and the six bands from 1.60 and 2.43 ??m, which have 15- and 30-m spatial resolution, respectively, were selected primarily for making remote mineralogical determinations. The Cuprite, Nevada, mining district comprises two hydrothermal alteration centers where Tertiary volcanic rocks have been hydrothermally altered mainly to bleached silicified rocks and opalized rocks, with a marginal zone of limonitic argilized rocks. Country rocks are mainly Cambrian phyllitic siltstone and limestone. Evaluation of an ASTER image of the Cuprite district shows that spectral reflectance differences in the nine bands in the 0.52 to 2.43 ??m region provide a basis for identifying and mapping mineralogical components which characterize the main hydrothermal alteration zones: opal is the spectrally dominant mineral in the silicified zone; whereas, alunite and kaolinite are dominant in the opalized zone. In addition, the distribution of unaltered country rocks was mapped because of the presence of spectrally dominant muscovite in the siltstone and calcite in limestone, and the tuffaceous rocks and playa deposits were distinguishable due to their relatively flat spectra and weak absorption features at 2.33 and 2.20 ??m, respectively. An Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) image of the study area was processed using a similar methodology used with the ASTER data. Comparison of the ASTER and AVIRIS results shows that the results are generally similar, but the higher spectral resolution of AVIRIS (224 bands) permits identification of more individual minerals, including certain polymorphs. However, ASTER has recorded images of more than 90 percent of the Earth's land surface with less than 20 percent cloud cover, and these data are available at nominal or no cost

  9. Hydrothermal alteration of deep sea sediments from the Izu-Bonin fore arc basin, leg 126, ODp. Izuter dot Ogasawara ko no shinkaitei taisekibutsu ni okeru netsusui henshitsu sayo

    Energy Technology Data Exchange (ETDEWEB)

    Tazaki, K. (Shimane Univ., Shimane (Japan). Faculty of Science)

    1991-08-25

    The deep sea drilling according to ODP has been performed in the Izu-Bonin arc during a period of April 22 to June 19 in 1989, and the drilling across the forearc, island arc and backarc was successful in the Leg 126 of it. The drill length of 1682 m at Site 793 was achieved and it is the deepest world record including the drilling of basement. In this report, the various measurements and observations were performed focussing the hydrothermal effects accompanied with the volcanic activities, on the Site 793 achieved the longest drilling in the forearc basin and the Site 792 in the same forearc. As a result, there are many dehydration veins, clastic dikes and small faults in the volcanic sediments, and the gypsum, smectite, zeolite and prehnite etc. are filled in these parts as a zonal distribution, suggesting the thermal gradient and thermal history at that time. The volcanic glass and feldspar etc. are changed partly to the smectite and zeolite etc. by the hydrothermal alteration. The effective keys as mentioned above were obtained about the temperature condition of hydrothermal alteration and the paleo-environment. 31 refs., 15figs.

  10. Behavior of nuclear waste elements during hydrothermal alteration of glassy rhyolite in an active geothermal system: Yellowstone National Park, Wyoming

    International Nuclear Information System (INIS)

    Sturchio, N.C.; Seitz, M.G.

    1984-01-01

    The behavior of a group of nuclear waste elements (U, Th, Sr, Zr, Sb, Cs, Ba, and Sm) during hydrothermal alteration of glassy rhyolite is investigated through detailed geochemical analyses of whole rocks, glass and mineral separates, and thermal waters. Significant mobility of U, Sr, Sb, Cs, and Ba is found, and the role of sorption processes in their observed behavior is identified. Th, Zr, and Sm are relatively immobile, except on a microscopic scale. 9 references, 2 figures, 2 tables

  11. Dissolution of subglacial volcanic glasses from Iceland: laboratory study and modelling

    International Nuclear Information System (INIS)

    Crovisier, J.-L.; Honnorez, J.; Fritz, B.; Petit, J.-C.

    1992-01-01

    Subglacial hyaloclastites from Iceland with ages ranging from 2 ka to 2.2 Ma have been studied from a mineralogical and geochemical standpoint. The chemical composition of palagonite (alteration crust formed on the surface of the glass) is almost identical with that of the clayey material filling the intergranular spaces of the rock. The clayey material is made up of two particle populations: the first is Si-, Mg-and Ca-rich with a smectite structure, while the second is amorphous, Fe-, Ti- and Al-rich, and has a smectite-like morphology. It is suggested that these two types of particles can be formed simultaneously, in the same solution, such that it is not necessary to explain their existence by local or temporary equilibria. The mineralogical sequences observed in natural samples were reproduced using the geochemical computer code DISSOL. The geochemical mass balances calculated with DISSOL also fit quite well with those calculated from Icelandic samples, illustrating the predictive capability of such a calculation code and give us confidence in applying a similar approach to nuclear waste-form glass problems. (author)

  12. Investigations into the Regional and Local Timescale Variations of Subglacial Drainage Networks

    Science.gov (United States)

    Hiester, Justin

    Subglacial water plays an important role in the regulation of an ice sheet's mass balance. It may be the dominant control on the velocities of ice streams and outlet glaciers on scales of months to millennia. Recent satellite observations of ice surface elevation changes have given researchers new insights into how subglacial water is stored and transported. Localized uplift and settling of the ice surface implies that lakes exist beneath the ice sheet that are being filled and drained on relatively short time scales. At the base of an ice sheet water can be transported through a variety of drainage networks or stored in subglacial lakes. Here, a numerical investigation of the mechanisms of transport and storage of subglacial water and the associated time scales is presented. Experiments are carried out using a finite element model of coupled ice and water flow. The first experiment seeks to understand the relationship between the depth of a basal depression and the area over which the feature affects basal water flow. It is found that as the perturbation to a topographic depression's depth is increased, water is rerouted in response to the perturbation. Additionally it is found that the relationship between perturbation depth and the extent upstream to which its effects reach is nonlinear. The second experiment examines how the aspect ratio of bed features (prolate, oblate, or equidimensional) influences basal water flow. It is found that the systems that develop and their interactions are mediated by both the topography and the feedbacks taken into account by the coupling of the systems in the model. Features oriented parallel to ice and water flow are associated with distributed fan systems that develop branches which migrate laterally across the domain and interact with one another on monthly and yearly timescales. Laterally oriented features develop laterally extensive ponds. As the ratio of longitudinal to lateral dimension of the topography is increased, a

  13. Detection of subglacial lakes in airborne radar sounding data from East Antarctica.

    Science.gov (United States)

    Carter, S. P.; Blankenship, D. D.; Peters, M. E.; Morse, D. L.

    2004-12-01

    Airborne ice penetrating radar is an essential tool for the identification of subglacial lakes. With it, we can measure the ice thickness, the amplitude of the reflected signal from the base of the ice, the depth to isochronous surfaces and, with high quality GPS, the elevation of the ice surface. These four measurements allow us to calculate the reflection coefficient from the base of the ice, the hydrostatic head, the surface slope and basal temperature. A subglacial lake will be characterized by: a consistently high reflection coefficient from the base of the ice, a nearly flat hydraulic gradient at a relative minimum in the hydraulic potential, an exceptionally smooth ice surface, and an estimated basal temperature that is at or near the pressure melting point of ice. We have developed a computerized algorithm to identify concurrences of the above-mentioned criteria in the radar data sets for East Antarctica collected by the University of Texas (UT). This algorithm is henceforth referred to as the "lake detector". Regions which meet three or more of the above mentioned criteria are identified as subglacial lakes, contingent upon a visual inspection by the human operator. This lake detector has added over 40 lakes to the most recent inventory of subglacial lakes for Antarctica. In locations where the UT flight lines approach or intersect flight lines from other airborne radar surveys, there is generally good agreement between the "lake detector" lakes and lakes identified in these data sets. In locations where the "lake detector" fails to identify a lake which is present in another survey, the most common failing is the estimated basal temperature. However, in some regions where a bright, smooth basal reflector is shown to exist, the lake detector may be failing due to a persistent slope in the hydraulic gradient. The nature of these "frozen" and "sloping" lakes is an additional focus of this presentation.

  14. Investigating the hydrological origins of Blood Falls - geomicrobiological insights into a briny subglacial Antarctic aquifer

    Science.gov (United States)

    Mikucki, J.; Tulaczyk, S. M.; Purcell, A. M.; Dachwald, B.; Lyons, W. B.; Welch, K. A.; Auken, E.; Dugan, H. A.; Walter, J. I.; Pettit, E. C.; Doran, P. T.; Virginia, R. A.; Schamper, C.; Foley, N.; Feldmann, M.; Espe, C.; Ghosh, D.; Francke, G.

    2015-12-01

    Subglacial waters tend to accumulate solutes from extensive rock-water interactions, which, when released to the surface, can provide nutrients to surface ecosystems providing a 'hot spot' for microbial communities. Blood Falls, an iron-rich, saline feature at the terminus of Taylor Glacier in the McMurdo Dry Valleys, Antarctica is a well-studied subglacial discharge. Here we present an overview of geophysical surveys, thermomechanical drilling exploration and geomicrobiological analyses of the Blood Falls system. A helicopter-borne transient electromagnetic system (SkyTEM) flown over the Taylor Glacier revealed a surprisingly extensive subglacial aquifer and indicates that Blood Falls may be the only surface manifestation of this extensive briny groundwater. Ground-based temperature sensing and GPR data combined with the helicopter-borne TEM data enabled targeted drilling into the englacial conduit that delivers brine to the surface. During the 2014-15 austral summer field season, we used a novel ice-melting drill (the IceMole) to collect englacial brine for geomicrobiological analyses. Results from previously collected outflow and more recent samples indicate that the brine harbors a metabolically active microbial community that persists, despite cold, dark isolation. Isotope geochemistry and molecular analysis of functional genes from BF suggested that a catalytic or 'cryptic' sulfur cycle was linked to iron reduction. Recent metagenomic analysis confirms the presence of numerous genes involved in oxidative and reductive sulfur transformations. Metagenomic and metabolic activity data also indicate that subglacial dark CO2 fixation occurs via various pathways. Genes encoding key steps in CO2 fixation pathways including the Calvin Benson Basham and Wood Ljungdahl pathway were present and brine samples showed measureable uptake of 14C-labeled bicarbonate. These results support the notion that, like the deep subsurface, subglacial environments are chemosynthetic

  15. Seawater bicarbonate removal during hydrothermal circulation

    Science.gov (United States)

    Proskurowski, G. K.; Seewald, J.; Sylva, S. P.; Reeves, E.; Lilley, M. D.

    2013-12-01

    High temperature fluids sampled at hydrothermal vents represent a complex alteration product of water-rock reactions on a multi-component mixture of source fluids. Sources to high-temperature hydrothermal samples include the 'original' seawater present in the recharge limb of circulation, magmatically influenced fluids added at depth as well as any seawater entrained during sampling. High-temperature hydrothermal fluids are typically enriched in magmatic volatiles, with CO2 the dominant species, characterized by concentrations of 10's-100's of mmol/kg (1, 2). Typically, the high concentration of CO2 relative to background seawater bicarbonate concentrations (~2.3 mmol/kg) obscures a full analysis of the fate of seawater bicarbonate during high-temperature hydrothermal circulation. Here we present data from a suite of samples collected over the past 15 years from high-temperature hydrothermal vents at 9N, Endeavour, Lau Basin, and the MAR that have endmember CO2 concentrations less than 10 mmol/kg. Using stable and radiocarbon isotope measurements these samples provide a unique opportunity to examine the balance between 'original' seawater bicarbonate and CO2 added from magmatic sources. Multiple lines of evidence from multiple hydrothermal settings consistently points to the removal of ~80% of the 'original' 2.3 mmol/kg seawater bicarbonate. Assuming that this removal occurs in the low-temperature, 'recharge' limb of hydrothermal circulation, this removal process is widely occurring and has important contributions to the global carbon cycle over geologic time. 1. Lilley MD, Butterfield DA, Lupton JE, & Olson EJ (2003) Magmatic events can produce rapid changes in hydrothermal vent chemistry. Nature 422(6934):878-881. 2. Seewald J, Cruse A, & Saccocia P (2003) Aqueous volatiles in hydrothermal fluids from the Main Endeavour Field, northern Juan de Fuca Ridge: temporal variability following earthquake activity. Earth and Planetary Science Letters 216(4):575-590.

  16. Paleoproterozoic volcanic centers of the São Félix do Xingu region, Amazonian craton, Brazil: Hydrothermal alteration and metallogenetic potential

    Science.gov (United States)

    da Cruz, Raquel Souza; Fernandes, Carlos Marcello Dias; Villas, Raimundo Netuno Nobre; Juliani, Caetano; Monteiro, Lena Virgínia Soares; Lagler, Bruno; Misas, Carlos Mario Echeverri

    2016-06-01

    Geological, petrographic, scanning electron microscopy, and X-ray diffraction studies revealed hydrothermalized lithotypes evidenced by overprinted zones of potassic, propylitic, sericitic, and intermediate argillic alterations types, with pervasive and fracture-controlled styles, in Paleoproterozoic volcano-plutonic units of the São Félix do Xingu region, Amazonian craton, northern Brazil. The Sobreiro Formation presents propylitic (epidote + chlorite + carbonate + clinozoisite + sericite + quartz ± albite ± hematite ± pyrite), sericitic (sericite + quartz + carbonate), and potassic (potassic feldspar + hematite) alterations. The prehnite-pumpellyite pair that is common in geothermal fields also occurs in this unit. The Santa Rosa Formation shows mainly potassic (biotite + microcline ± magnetite), sericitic (sericite + quartz + carbonate ± chlorite ± gold), and intermediate argillic (montmorillonite + kaolinite/halloysite + illite) alterations. These findings strongly suggest the involvement of magma-sourced and meteoric fluids and draw attention to the metallogenetic potential of these volcanic units for Paleoproterozoic epithermal and rare and base metal porphyry-type mineralizations, similar to those already identified in other portions of the Amazonian craton.

  17. Tracking seasonal subglacial drainage evolution of alpine glaciers using radiogenic Nd and Sr isotope systematics: Lemon Creek Glacier, Alaska

    Science.gov (United States)

    Clinger, A. E.; Aciego, S.; Stevenson, E. I.; Arendt, C. A.

    2014-12-01

    The transport pathways of water beneath a glacier are subject to change as melt seasons progress due to variability in the balance between basal water pressure and water flux. Subglacial hydrology has been well studied, but the understanding of spatial distribution is less well constrained. Whereas radiogenic isotopic tracers have been traditionally used as proxies to track spatial variability and weathering rates in fluvial and riverine systems, these techniques have yet to be applied extensively to the subglacial environment and may help resolve ambiguity in subglacial hydrology. Research has shown the 143Nd/144Nd values can reflect variation in source provenance processes due to variations in the age of the continental crust. Correlating the 143Nd/144Nd with other radiogenic isotope systematics such as strontium (87Sr/86Sr) provides important constraints on the role of congruent and incongruent weathering processes. Our study presents the application of Nd and Sr systematics using isotopic ratios to the suspended load of subglacial meltwater collected over a single melt season at Lemon Creek Glacier, USA (LCG). The time-series data show an average ɛNd ~ -6.83, indicating a young bedrock (~60 MYA). Isotopic variation helps track the seasonal expansion of the subglacial meltwater channels and subsequent return to early season conditions due to the parabolic trend towards less radiogenic Nd in June and towards more radiogenic Nd beginning in mid-August. However, the high variability in July and early August may reflect a mixture of source as the channels diverge and derive sediment from differently aged lithologies. We find a poor correlation between 143Nd/144Nd and 87Sr/86Sr (R2= 0.38) along with a slight trend towards more radiogenic 87Sr/86Sr values with time ((R2= 0.49). This may indicate that, even as the residence time decreases over the melt season, the LCG subglacial system is relatively stable and that the bedrock is congruently weathered. Our study

  18. Distribution of hydrothermal fluid around the ore body in the subseafloor of the Izena hydrothermal field

    Science.gov (United States)

    Toki, T.; Otake, T.; Ishibashi, J. I.; Matsui, Y.; Kawagucci, S.; Kato, H.; Fuchida, S.; Miyahara, R.; Tsutsumi, A.; Kawakita, R.; Uza, H.; Uehara, R.; Shinjo, R.; Nozaki, T.; Kumagai, H.; Maeda, L.

    2017-12-01

    would be distributed in the upper and lower layers of the ore body. The hydrothermally altered sediment layers above the ore body contain relatively unstable minerals that dissociate immediately in a room temperature, which could play a role as a boundary between hydrothermal fluids and intruded seawater in in-situ environments.

  19. Alteration, slope-classified alteration, and potential lahar inundation maps of volcanoes for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Volcano Archive

    Science.gov (United States)

    Mars, John C.; Hubbard, Bernard E.; Pieri, David; Linick, Justin

    2015-01-01

    This study identifies areas prone to lahars from hydrothermally altered volcanic edifices on a global scale, using visible and near infrared (VNIR) and short wavelength infrared (SWIR) reflectance data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and digital elevation data from the ASTER Global Digital Elevation Model (GDEM) dataset. This is the first study to create a global database of hydrothermally altered volcanoes showing quantitatively compiled alteration maps and potentially affected drainages, as well as drainage-specific maps illustrating modeled lahars and their potential inundation zones. We (1) identified and prioritized 720 volcanoes based on population density surrounding the volcanoes using the Smithsonian Institution Global Volcanism Program database (GVP) and LandScan™ digital population dataset; (2) validated ASTER hydrothermal alteration mapping techniques using Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) and ASTER data for Mount Shasta, California, and Pico de Orizaba (Citlaltépetl), Mexico; (3) mapped and slope-classified hydrothermal alteration using ASTER VNIR-SWIR reflectance data on 100 of the most densely populated volcanoes; (4) delineated drainages using ASTER GDEM data that show potential flow paths of possible lahars for the 100 mapped volcanoes; (5) produced potential alteration-related lahar inundation maps using the LAHARZ GIS code for Iztaccíhuatl, Mexico, and Mount Hood and Mount Shasta in the United States that illustrate areas likely to be affected based on DEM-derived volume estimates of hydrothermally altered rocks and the ~2x uncertainty factor inherent within a statistically-based lahar model; and (6) saved all image and vector data for 3D and 2D display in Google Earth™, ArcGIS® and other graphics display programs. In addition, these data are available from the ASTER Volcano Archive (AVA) for distribution (available at http://ava.jpl.nasa.gov/recent_alteration_zones.php).

  20. Characterization of subglacial Lake Vostok as seen from physical and isotope properties of accreted ice.

    Science.gov (United States)

    Lipenkov, Vladimir Ya; Ekaykin, Alexey A; Polyakova, Ekaterina V; Raynaud, Dominique

    2016-01-28

    Deep drilling at the Vostok Station has reached the surface of subglacial Lake Vostok (LV) twice-in February 2012 and January 2015. As a result, three replicate cores from boreholes 5G-1, 5G-2 and 5G-3 became available for detailed and revalidation analyses of the 230 m thickness of the accreted ice, down to its contact with water at 3769 m below the surface. The study reveals that the concentration of gases in the lake water beneath Vostok is unexpectedly low. A clear signature of the melt water in the surface layer of the lake, which is subject to refreezing on the icy ceiling of LV, has been discerned in the three different properties of the accreted ice: the ice texture, the isotopic and the gas content of the ice. These sets of data indicate in concert that poor mixing of the melt (and hydrothermal) water with the resident lake water and pronounced spatial and/or temporal variability of local hydrological conditions are likely to be the characteristics of the southern end of the lake. The latter implies that the surface water may be not representative enough to study LV's behaviour, and that direct sampling of the lake at different depths is needed in order to move ahead with our understanding of the lake's hydrological regime. © 2015 The Author(s).

  1. Absolute Magnetization Distribution on Back-arc Spreading Axis Hosting Hydrothermal Vents; Insight from Shinkai 6500 Magnetic Survey

    Science.gov (United States)

    Fujii, M.; Okino, K.; Honsho, C.; Mochizuki, N.; Szitkar, F.; Dyment, J.

    2013-12-01

    Near-bottom magnetic profiling using submersible, deep-tow, Remotely Operated Vehicle (ROV) and Autonomous Underwater Vehicle (AUV) make possible to conduct high-resolution surveys and depict detailed magnetic features reflecting, for instance, the presence of fresh lavas or hydrothermal alteration, or geomagnetic paleo-intensity variations. We conducted near-bottom three component magnetic measurements onboard submersible Shinkai 6500 in the Southern Mariana Trough, where five active hydrothermal vent fields (Snail, Yamanaka, Archean, Pica, and Urashima sites) have been found in both on- and off-axis areas of the active back-arc spreading center, to detect signals from hydrothermally altered rock and to distinguish old and new submarine lava flows. Fourteen dives were carried out at an altitude of 1-40 m during the R/V Yokosuka YK10-10 and YK10-11 cruises in 2010. We carefully corrected the effect of the induced and permanent magnetizations of the submersible by applying the correction method for the shipboard three-component magnetometer measurement modified for deep-sea measurement, and subtracted the IGRF values from the corrected data to obtain geomagnetic vector anomalies along the dive tracks. We then calculated the synthetic magnetic vector field produced by seafloor, assumed to be uniformly magnetized, using three dimensional forward modeling. Finally, values of the absolute magnetizations were estimated by using a linear transfer function in the Fourier domain from the observed and synthetic magnetic anomalies. The distribution of estimated absolute magnetization generally shows low values around the five hydrothermal vent sites. This result is consistent with the equivalent magnetization distribution obtained from previous AUV survey data. The areas of low magnetization are also consistent with hydrothermal deposits identified in video records. These results suggest that low magnetic signals are due to hydrothermal alteration zones where host rocks are

  2. Mapping Of The Hydrothermal Alteration Zones At Haimur Gold Mine Area, South Eastern Desert, Egypt, Using Remote Sensing Techniques

    International Nuclear Information System (INIS)

    Madani, A.A.; Abdel Rahman, E.M.; FA WZY, Kh.M.; EMAM, A.

    2003-01-01

    The utilization of the Landsat-7 ETM+ imagery and scanned aerial photograph for mapping hydrothermal alteration zones at the Haimur gold mine area, south Eastern Desert, Egypt and the production of large scale geologic image map, scale 1 :20 000, using fusion technique are the main tasks of this article. The study area lies at the conjunction of two shear zones, namely the Allaqi shear zone (NW-SE) and the Haimur shear zone (NE-SW). The basement rocks covering Haimur gold mine area include ophiolitic blocks and sheets that were tectonically thrusted over and mixed within a matrix of island arc rocks. Principal Component Analysis, band ratios and data fusion are the main remote sensing techniques applied in the present work. The eigenvalue of the first principal component (PCl) includes 95.9% of the information content of the image whereas PC2 and PC5 mark 3.03% and 0.10%, respectively. The PC5 image was found to represent the highly altered rocks in the study area (serpentinites and carbonates), which display dark image signatures. The metagabbros and metapyroclastics can be easily discriminated on the PC1:R, PC2:G and PC5:B false color composite image in which they have dark red and blue image signatures, respectively. The talc carbonates and the serpentinites have bright image signatures on 5/7 band ratio image whereas metapyroxenites have dark image signatures. The talc carbonates are composed mainly of talc, magnesite and calcite with subordinate amounts of fibrous antigorite. These minerals have absorption features near 2.35 m which lead to increase 5/7 band ratio value. The false color composite ratio image 5/7:R, 4/5:G and 3/1:B was merged with scanned high spatial resolution aerial photograph using IHS transformation method. The resultant fused image was then used to delineate the hydrothermal alteration zones as well as listwaenite ridges exposed at the Haimur gold mine area

  3. Comparative assessment of five potential sites for hydrothermal magma systems: geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    White, A.F.

    1980-08-01

    A brief discussion is given of the geochemical objectives and questions that must be addressed in such an evaluation. A summary of the currently published literature that is pertinent in answering these questions is presented for each of the five areas: The Geysers-Clear Lake region, Long Valley, Rio Grand Rift, Roosevelt Hot Springs, and the Salton Trough. The major geochemical processes associated with proposed hydrothermal sites are categorized into three groups for presentation: geochemistry of magma and associated volcanic rocks, geochemistry of hydrothermal solutions, and geochemistry of hydrothermal alteration. (MHR)

  4. Geochemistry and hydrothermal alteration at selected Utah hot springs. Final report: Volume 3 (revised)

    Energy Technology Data Exchange (ETDEWEB)

    Parry, W.T.; Benson, N.L.; Miller, C.D.

    1976-07-01

    Application of Na-K-Ca geothermometry to warm springs in Utah indicates several areas with sufficiently high apparent temperatures to be of interest as geothermal exploration targets. A zone of warm springs in the Bonneville Basin show Na-K-Ca temperatures from 150/sup 0/C to 233/sup 0/C. Examination of Great Salt Lake, Bonneville sediment pore water, and Jordan Valley well-water chemistry indicates that mixing a small percent of these fluids with warm spring water can cause substantial errors in Na-K-Ca temperature estimates. Other saline deposits which may influence Na-K-Ca temperature estimates are the Paradox formation in southeastern Utah, the Muddy Creek formation in southwestern Utah, the Arapien shale in central Utah, the Preuss formation in northeastern Utah, and Playa salts in much of western Utah. The Roosevelt KGRA is the most attractive target identified by Na-K-Ca geothermometry. Hydrothermal alteration, heavy metal distribution, and water chemistry provide additional characterization of the Roosevelt system. Chemistry of a cool water seep (25/sup 0/C) shows Na-K-Ca temperature of 241/sup 0/C and SiO/sub 2/ temperature of 125/sup 0/C. A Phillips well flowing from below 1500' (457m) shows Na-K-Ca temperature of 262/sup 0/C, SiO/sub 2/ temperature of 262/sup 0/C, and K of 1.5 times the surface spring value. The near surface alteration assemblage is best explained in terms of a decrease in pH of near surface fluids as sulfide oxidizes. Increasing potassium and pH with depth indicates that a K-feldspar stable zone may be intersected with deeper drilling. Geology and alteration were mapped in the Monroe KGRA. (JGB)

  5. Mapping advanced argillic alteration at Cuprite, Nevada, using imaging spectroscopy

    Science.gov (United States)

    Swayze, Gregg A.; Clark, Roger N.; Goetz, Alexander F.H.; Livo, K. Eric; Breit, George N.; Kruse, Fred A.; Sutley, Stephen J.; Snee, Lawrence W.; Lowers, Heather A.; Post, James L.; Stoffregen, Roger E.; Ashley, Roger P.

    2014-01-01

    Mineral maps based on Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data were used to study late Miocene advanced argillic alteration at Cuprite, Nevada. Distributions of Fe-bearing minerals, clays, micas, sulfates, and carbonates were mapped using the Tetracorder spectral-shape matching system. The Al content of white micas increases toward altered areas and near intrusive rocks. Alunite composition varies from pure K to intimate mixtures of Na-K endmembers with subpixel occurrences of huangite, the Ca analogue of alunite. Intimately mixed Na-K alunite marks areas of relatively lower alteration temperature, whereas co-occurring Na-alunite and dickite may delineate relict hydrothermal conduits. The presence of dickite, halloysite, and well-ordered kaolinite, but absence of disordered kaolinite, is consistent with acidic conditions during hydrothermal alteration. Partial lichen cover on opal spectrally mimics chalcedony, limiting its detection to lichen-free areas. Pods of buddingtonite are remnants of initial quartz-adularia-smectite alteration. Thus, spectral maps provide a synoptic view of the surface mineralogy, and define a previously unrecognized early steam-heated hydrothermal event.Faulting and episodes of hydrothermal alteration at Cuprite were intimately linked to upper plate movements above the Silver Peak-Lone Mountain detachment and growth, collapse, and resurgence of the nearby Stonewall Mountain volcanic complex between 8 and 5 Ma. Isotopic dating indicates that hydrothermal activity started at least by 7.61 Ma and ended by about 6.2 Ma. Spectral and stable isotope data suggest that Cuprite is a late Miocene low-sulfidation adularia-sericite type hot spring deposit overprinted by late-stage, steam-heated advanced argillic alteration formed along the margin of the Stonewall Mountain caldera.

  6. A linked lake system beneath Thwaites Glacier, West Antarctica reveals an efficient mechanism for subglacial water flow.

    Science.gov (United States)

    Smith, B. E.; Gourmelen, N.; Huth, A.; Joughin, I. R.

    2016-12-01

    In this presentation we show the results of a multi-sensor survey of a system of subglacial lakes beneath Thwaites Glacier, West Antarctica. This is the first substantial active (meaning draining or filling on annual time scales) lake system detected under the fast-flowing glaciers of the Amundsen Coast. Altimetry data show that over the 2013 calendar year, four subglacial lakes drained, essentially simultaneously, with the bulk of the drainage taking place over the course the first three months of the year. The largest of the lakes appears to have drained around 3.7 km3 of water, with the others each draining less than 1 km3. The high-resolution radar surveys conducted in this area by NASA's IceBridge program allow detailed analysis of the subglacial hydrologic potential, which shows that the potential map in this area is characterized by small closed basins that should not, under the common assumption that water flow is directed down the gradient of the hydropotential, allow long-range water transport. The lakes' discharge demonstrates that, at least in some cases, water can flow out of apparently closed hydropotential basins. Combining a basal-flow routing map with a map of basal melt production suggests that the largest drainage event could recur as often as every 22 years, provided that overflow or leakage of mapped hydropotential basins allows melt water transport to refill the lake. An analysis of ice-surface speed records both around the lakes and at the Thwaites grounding line shows small changes in ice speed, but none clearly associated with the drainage event, suggesting that, at least in this area where subglacial melt is abundant, the addition of further water to the subglacial hydrologic system need not have any significant effect on ice flow. It is likely that the main impact of the lake system on the glacier is that as an efficient mechanism to remove meltwater from the system, it drains water that would otherwise flow through less efficient

  7. Multifractal magnetic susceptibility distribution models of hydrothermally altered rocks in the Needle Creek Igneous Center of the Absaroka Mountains, Wyoming

    Directory of Open Access Journals (Sweden)

    M. E. Gettings

    2005-01-01

    Full Text Available Magnetic susceptibility was measured for 700 samples of drill core from thirteen drill holes in the porphyry copper-molybdenum deposit of the Stinkingwater mining district in the Absaroka Mountains, Wyoming. The magnetic susceptibility measurements, chemical analyses, and alteration class provided a database for study of magnetic susceptibility in these altered rocks. The distribution of the magnetic susceptibilities for all samples is multi-modal, with overlapping peaked distributions for samples in the propylitic and phyllic alteration class, a tail of higher susceptibilities for potassic alteration, and an approximately uniform distribution over a narrow range at the highest susceptibilities for unaltered rocks. Samples from all alteration and mineralization classes show susceptibilities across a wide range of values. Samples with secondary (supergene alteration due to oxidation or enrichment show lower susceptibilities than primary (hypogene alteration rock. Observed magnetic susceptibility variations and the monolithological character of the host rock suggest that the variations are due to varying degrees of alteration of blocks of rock between fractures that conducted hydrothermal fluids. Alteration of rock from the fractures inward progressively reduces the bulk magnetic susceptibility of the rock. The model introduced in this paper consists of a simulation of the fracture pattern and a simulation of the alteration of the rock between fractures. A multifractal model generated from multiplicative cascades with unequal ratios produces distributions statistically similar to the observed distributions. The reduction in susceptibility in the altered rocks was modelled as a diffusion process operating on the fracture distribution support. The average magnetic susceptibility was then computed for each block. For the purpose of comparing the model results with observation, the simulated magnetic susceptibilities were then averaged over the same

  8. Multifractal magnetic susceptibility distribution models of hydrothermally altered rocks in the Needle Creek Igneous Center of the Absaroka Mountains, Wyoming

    Science.gov (United States)

    Gettings, M.E.

    2005-01-01

    Magnetic susceptibility was measured for 700 samples of drill core from thirteen drill holes in the porphyry copper-molybdenum deposit of the Stinkingwater mining district in the Absaroka Mountains, Wyoming. The magnetic susceptibility measurements, chemical analyses, and alteration class provided a database for study of magnetic susceptibility in these altered rocks. The distribution of the magnetic susceptibilities for all samples is multi-modal, with overlapping peaked distributions for samples in the propylitic and phyllic alteration class, a tail of higher susceptibilities for potassic alteration, and an approximately uniform distribution over a narrow range at the highest susceptibilities for unaltered rocks. Samples from all alteration and mineralization classes show susceptibilities across a wide range of values. Samples with secondary (supergene) alteration due to oxidation or enrichment show lower susceptibilities than primary (hypogene) alteration rock. Observed magnetic susceptibility variations and the monolithological character of the host rock suggest that the variations are due to varying degrees of alteration of blocks of rock between fractures that conducted hydrothermal fluids. Alteration of rock from the fractures inward progressively reduces the bulk magnetic susceptibility of the rock. The model introduced in this paper consists of a simulation of the fracture pattern and a simulation of the alteration of the rock between fractures. A multifractal model generated from multiplicative cascades with unequal ratios produces distributions statistically similar to the observed distributions. The reduction in susceptibility in the altered rocks was modelled as a diffusion process operating on the fracture distribution support. The average magnetic susceptibility was then computed for each block. For the purpose of comparing the model results with observation, the simulated magnetic susceptibilities were then averaged over the same interval as the

  9. Surface-discharging hydrothermal systems at Yucca Mountain: Examining the evidence

    International Nuclear Information System (INIS)

    Levy, S.S.

    1992-01-01

    This paper discusses exposures of altered rock that have been thought to form by recent discharge of water from depth. They were examined to address a concern that hydrothermal processes could compromise the isolation capability of a potential high-level nuclear waste repository at Yucca Mountain. Suspected hot-spring and hydrothermal-vent deposits are more likely the products of infiltration of meteoric water into newly deposited and still-hot pyroclastic flows >12 Myr ago

  10. Chemical environments of submarine hydrothermal systems

    Science.gov (United States)

    Shock, Everett L.

    1992-01-01

    determinations rely on studies of pieces of deep oceanic crust uplifted by tectonic forces such as along the Southwest Indian Ridge, or more complete sections of oceanic crust called ophiolite sequences which are presently exposed on continents owing to tectonic emplacement. Much of what is thought to happen in submarine hydrothermal systems is inferred from studies of ophiolite sequences, and especially from the better-exposed ophiolites in Oman, Cyprus and North America. The focus of much that follows is on a few general features: pressure, temperature, oxidation states, fluid composition and mineral alteration, because these features will control whether organic synthesis can occur in hydrothermal systems.

  11. A new approach for hydrothermal alteration mapping by selecting and interpreting principal components in Landsat ETM+ images

    Directory of Open Access Journals (Sweden)

    Mohammad Kashkoei Jahroomi

    2016-07-01

    Full Text Available Introduction In remote sensing studies, especially those in which multi-spectral image data are used, (i.e., Landsat-7 Enhanced Thematic Mapper, various statistical methods are often applied for image enhancement and feature extraction (Reddy, 2008. Principal component analysis is a multivariate statistical technique which is frequently used in multidimensional data analysis. This method attempts to extract and place the spectral information into a smaller set of new components that are more interpretable. However, the results obtained from this method are not so straightforward and require somewhat sophisticated techniques to interpret (Drury, 2001. In this paper we present a new approach for mapping of hydrothermal alteration by analyzing and selecting the principal components extracted through processing of Landsat ETM+ images. The study area is located in a mountainous region of southern Kerman. Geologically, it lies in the volcanic belt of central Iran adjacent to the Gogher-Baft ophiolite zone. The region is highly altered with sericitic, propyliticand argillic alterationwell developed, and argillic alteration is limited (Jafari, 2009; Masumi and Ranjbar, 2011. Multispectral data of Landsat ETM+ was acquired (path 181, row 34 in this study. In these images the color composites of Band 7, Band 4 and Band 1 in RGB indicate the lithology outcropping in the study area. The principal component analysis (PCA ofimage data is often implemented computationally using three steps: (1 Calculation of the variance, covariance matrix or correlation matrix of the satellite sensor data. (2 Computation of the eigenvalues and eigenvectors of the variance-covariance matrix or correlation matrix, and (3 Linear transformation of the image data using the coefficients of the eigenvector matrix. Results By applying PCA to the spectral data, according to the eigenvectors obtained, 6 principal components were extracted from the data set. In the PCA matrix, theeigen

  12. Geochemical results of a hydrothermally altered area at Baker Creek, Blaine County, Idaho

    Science.gov (United States)

    Erdman, James A.; Moye, Falma J.; Theobald, Paul K.; McCafferty, Anne E.; Larsen, Richard K.

    2001-01-01

    fault-controlled silicified breccia that is most likely the source of anomalous silver and molybdenum levels identified in the soils; silver, molybdenum, and manganese in stream sediments; thallium in Douglas-fir; bismuth and silver in concentrates; and gold, silver, arsenic, antimony, and molybdenum and lead in aquatic mosses. An interpretation of regional aeromagnetic data delineated the subsurface extent of shallow, steeply dipping magnetic sources inferred to be shallower parts of an Eocene batholith thought to underlie much of the Baker Creek area. The Eocene intrusive event(s) may have served as the heat source(s) that caused the hydrothermal alteration. Examination of core from a 1,530-ft-deep (466 m) hole drilled in 1982 confirmed a bedrock source for the anomalous silver and base-metal suite at the quartz stockwork location, and indicated subeconomic levels of molybdenum.

  13. A Model for Generation of Martian Surface Dust, Soil and Rock Coatings: Physical vs. Chemical Interactions, and Palagonitic Plus Hydrothermal Alteration

    Science.gov (United States)

    Bishop, J. L.; Murchie, S.; Pieters, C.; Zent, A.

    1999-01-01

    This model is one of many possible scenarios to explain the generation of the current surface material on Mars using chemical, magnetic and spectroscopic data from Mars and geologic analogs from terrestrial sites. One basic premise is that there are physical and chemical interactions of the atmospheric dust particles and that these two processes create distinctly different results. Physical processes distribute dust particles on rocks, forming physical rock coatings, and on the surface between rocks forming soil units; these are reversible processes. Chemical reactions of the dust/soil particles create alteration rinds on rock surfaces or duricrust surface units, both of which are relatively permanent materials. According to this model the mineral components of the dust/soil particles are derived from a combination of "typical" palagonitic weathering of volcanic ash and hydrothermally altered components, primarily from steam vents or fumeroles. Both of these altered materials are composed of tiny particles, about 1 micron or smaller, that are aggregates of silicates and iron oxide/oxyhydroxide/sulfate phases. Additional information is contained in the original extended abstract.

  14. Numerical Modeling of Subglacial Sediment Deformation

    DEFF Research Database (Denmark)

    Damsgaard, Anders

    2015-01-01

    may cause mass loss in the near future to exceed current best estimates. Ice flow in larger ice sheets focuses in fast-moving streams due to mechanical non-linearity of ice. These ice streams often move at velocities several magnitudes larger than surrounding ice and consequentially constitute...... glaciers move by deforming their sedimentary beds. Several modern ice streams, in particular, move as plug flows due to basal sediment deformation. An intense and long-winded discussion about the appropriate description for subglacial sediment mechanics followed this discovery, with good reason...... incompatible with commonly accepted till rheology models. Variation in pore-water pressure proves to cause reorganization in the internal stress network and leads to slow creeping deformation. The rate of creep is non-linearly dependent on the applied stresses. Granular creep can explain slow glacial...

  15. Geochemical element mobility during the hydrothermal alteration in the Tepeoba porphyry Cu-Mo-Au deposits at Balikesir, NW Turkey

    Science.gov (United States)

    Abdelnasser, Amr; Kiran Yildirim, Demet; Doner, Zeynep; Kumral, Mustafa

    2016-04-01

    The Tepeoba porphyry Cu-Mo-Au deposit represents one of the important copper source and mineral deposits in the Anatolian tectonic belt at Balikesir province, NW Turkey. It considered as a vein-type deposit locally associated with intense hydrothermal alteration within the brecciation, quartz stockwork veining, and brittle fracture zones in the main host rock that represented by hornfels, as well as generally related to the shallow intermediate to silicic intrusive Eybek pluton. Based on the field and geologic relationships and types of ore mineral assemblages and the accompanied alteration types, there are two mineralization zones; hypogene (primary) and oxidation/supergene zones are observed associated with three alteration zones; potassic, phyllic, and propylitic zones related to this porphyry deposit. The phyllic and propylitic alterations locally surrounded the potassic alteration. The ore minerals related to the hypogene zone represented by mostly chalcopyrite, Molybdenite, and pyrite with subordinate amount of marcasite, enargite, and gold. On the other hand they include mainly cuprite with chalcopyrite, pyrite and gold as well as hematite and goethite at the oxidation/supergene zone. This study deals with the quantitative calculations of the mass/volume changes (gains and losses) of the major and trace elements during the different episodes of alteration in this porphyry deposit. These mass balance data reveal that the potassic alteration zone that the main Cu- and Mo-enriched zone, has enrichment of K, Si, Fe, and Mg, and depletion of Na referring to replacement of plagioclase and amphibole by K-feldspar, sericite and biotite. While the propylitic alteration that is the main Mo- and Au-enriched zone is accompanied with K and Na depletion with enrichment of Si, Fe, Mg, and Ca forming chlorite, epidote, carbonate and pyrite. On the other hand the phyllic alteration that occurred in the outer part around the potassic alteration, characterized by less amount

  16. 210Pb, 230Th, and 10Be in Central Indian Basin seamount sediments: Signatures of degassing and hydrothermal alteration of recent origin

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.; Borole, D.V.; Aldahan, A.; Patil, S; Mascarenhas-Pereira, M.B.L.; Possnert, G.; Ericsson, T.; Ramaswamy, V.; Gupta, S

    , 230 Th, and 10 Be in Central Indian Basin seamount sediments: Signatures of degassing and hydrothermal alteration of recent origin B. N. Nath, 1 D. V. Borole, 1 A. Aldahan, 2 S. K. Patil, 3 M. B. L. Mascarenhas-Pereira, 1 G. Possnert, 4 T. Ericsson, 2... V. Ramaswamy, 1 and S. M. Gupta 1 Received 4 March 2008; revised 17 March 2008; accepted 8 April 2008; published 14 May 2008. [1] Isotopic ( 210 Pb, 238 U- 230 Th, 10 Be), major and trace elements, and micromorphological and microchemical data, were...

  17. Physical, chemical and mineralogical evolution of the Tolhuaca geothermal system, southern Andes, Chile: Insights into the interplay between hydrothermal alteration and brittle deformation

    Science.gov (United States)

    Sanchez-Alfaro, Pablo; Reich, Martin; Arancibia, Gloria; Pérez-Flores, Pamela; Cembrano, José; Driesner, Thomas; Lizama, Martin; Rowland, Julie; Morata, Diego; Heinrich, Christoph A.; Tardani, Daniele; Campos, Eduardo

    2016-09-01

    In this study, we unravel the physical, chemical and mineralogical evolution of the active Tolhuaca geothermal system in the Andes of southern Chile. We used temperature measurements in the deep wells and geochemical analyses of borehole fluid samples to constrain present-day fluid conditions. In addition, we reconstructed the paleo-fluid temperatures and chemistry from microthermometry and LA-ICP-MS analysis of fluid inclusions taken from well-constrained parageneses in vein samples retrieved from a 1000 m borehole core. Based on core logging, mineralogical observations and fluid inclusions data we identify four stages (S1-S4) of progressive hydrothermal alteration. An early heating event (S1) was followed by the formation of a clay-rich cap in the upper zone (propylitic alteration assemblage at greater depth (S2). Boiling, flashing and brecciation occurred later (S3), followed by a final phase of fluid mixing and boiling (S4). The evolution of hydrothermal alteration at Tolhuaca has produced a mineralogical, hydrological and structural vertical segmentation of the system through the development of a low-permeability, low-cohesion clay-rich cap at shallow depth. The quantitative chemical analyses of fluid inclusions and borehole fluids reveal a significant change in chemical conditions during the evolution of Tolhuaca. Whereas borehole (present-day) fluids are rich in Au, B and As, but Cu-poor (B/Na 100.5, As/Na 10- 1.1, Cu/Na 10- 4.2), the paleofluids trapped in fluid inclusions are Cu-rich but poor in B and As (B/Na 10- 1, As/Na 10- 2.5, Cu/Na 10- 2.5 in average). We interpret the fluctuations in fluid chemistry at Tolhuaca as the result of transient supply of metal-rich, magmatically derived fluids where As, Au and Cu are geochemically decoupled. Since these fluctuating physical and chemical conditions at the reservoir produced a mineralogical vertical segmentation of the system that affects the mechanical and hydrological properties of host rock, we explored

  18. Alteration of MX-80 by hydrothermal treatment under high salt content conditions

    Energy Technology Data Exchange (ETDEWEB)

    Pusch, R. [Geodevelopment AB, Lund (Sweden); Kasbohm, J. [Greifswald Univ. (Germany). Geological Dep.

    2002-02-01

    If brammalit, i.e. sodium illite, is formed from smectite in Na-rich salt water at high temperature such conversion can also take place in the buffer clay that surrounds the canisters in a KBS-3 repository. The present study comprised two laboratory test series with MX-80 clay, one with compacted clay powder with a dry density of 1200 to 1300 kg/m{sup 3} and saturation with 10% and 20% NaCl solutions followed by heating to 110 deg C under closed conditions for 30 days. In the second series air-dry compacted clay powder in a cell was heated at 110 deg C for the same period of time and connected to vessels with 10% and 20% NaCl solutions. The first series represents the conditions in the buffer clay after saturation with Na-rich salt water while the second one corresponds to the conditions in the course of saturation with such water. All laboratory tests were made after short-term percolation with distilled water for making sure that the hydro-thermally treated samples were fully fluid-saturated. The results from the physical testing showed that the hydraulic conductivity and swelling pressure of the hydrothermally treated clay samples were on the same order of magnitude as for untreated clay. Comparison with illitic clays shows that the latter are at least a hundred times more permeable than the hydrothermally treated salt clays in the present study, which hence indicates that conversion to illite was insignificant. This is obvious also from the fact that while illitic clays have very low swelling pressures the hydrothermally treated clays exhibited swelling pressures on the same order of magnitude as untreated MX-80. XRD analysis showed a clear difference in mineral constitution between the two test series. Thus, while no significant change from the typical mineralogy of untreated MX-80 was found for hydrothermal treatment of clay saturated with 10 and 20% NaCl solution, except for some very slight neoformation of illite-smectite mixed layers or irreversible

  19. Hydrothermal alteration at the Roosevelt Hot Springs thermal area, Utah: Petrographic characterization of the alteration to 2 kilometers depth

    Energy Technology Data Exchange (ETDEWEB)

    Ballantyne, J.M.; Parry, W.T.

    1978-04-01

    Hydrothermal alteration in drill cuttings from Thermal Power drillhole 14-2, Roosevelt Hot Springs Thermal area, has been studied petrographically. The hole is sited in alluvium approximately 1.6 km southeast of the old Resort and was rotary drilled to a depth of 1866.0 m. The exact hole location is 2310 FNL, 350 FWL, Sec. 2, Twp 27S, Rge 9W, elevation 1908.5 m. Core was extracted from 792.5 to 795.5 m. Thin sections were made from samples at 15.2 m intervals of drill cuttings collected at 1.5 or 3.0 m intervals during drilling. Thin sections were made of 1.5 or 3.0 m intervals from 274.3 to 304.8 m, 487.9 to 581.2 m, and 868.7 to 899.2 m. These intervals were chosen for close spaced sampling on the basis of increases in temperature, porosity, conductivity and acoustic velocity shown in geophysical logs. A total of 153 thin sections of cuttings were made, and an additional 9 sections were made from the core. Depths of thin section samples are listed in the appendix. A visual estimate of the percentage of each rock type was made for each thin section.

  20. Volcano-ice interaction as a microbial habitat on Earth and Mars.

    Science.gov (United States)

    Cousins, Claire R; Crawford, Ian A

    2011-09-01

    Volcano-ice interaction has been a widespread geological process on Earth that continues to occur to the present day. The interaction between volcanic activity and ice can generate substantial quantities of liquid water, together with steep thermal and geochemical gradients typical of hydrothermal systems. Environments available for microbial colonization within glaciovolcanic systems are wide-ranging and include the basaltic lava edifice, subglacial caldera meltwater lakes, glacier caves, and subsurface hydrothermal systems. There is widespread evidence of putative volcano-ice interaction on Mars throughout its history and at a range of latitudes. Therefore, it is possible that life on Mars may have exploited these habitats, much in the same way as has been observed on Earth. The sedimentary and mineralogical deposits resulting from volcano-ice interaction have the potential to preserve evidence of any indigenous microbial populations. These include jökulhlaup (subglacial outflow) sedimentary deposits, hydrothermal mineral deposits, basaltic lava flows, and subglacial lacustrine deposits. Here, we briefly review the evidence for volcano-ice interactions on Mars and discuss the geomicrobiology of volcano-ice habitats on Earth. In addition, we explore the potential for the detection of these environments on Mars and any biosignatures these deposits may contain.

  1. A new methodology to simulate subglacial deformation of water saturated granular material

    DEFF Research Database (Denmark)

    Damsgaard, Anders; Egholm, David Lundbek; Piotrowski, Jan A.

    2015-01-01

    The dynamics of glaciers are to a large degree governed by processes operating at the ice-bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglac......The dynamics of glaciers are to a large degree governed by processes operating at the ice-bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response...... or weakening components, depending on the rate of deformation, the material state, clay mineral content, and the hydrological properties of the material. The influence of the fluid phase is negligible when relatively permeable sediment is deformed. However, by reducing the local permeability, fast deformation...... can cause variations in the pore-fluid pressure. The pressure variations weaken or strengthen the granular phase, and in turn influence the distribution of shear strain with depth. In permeable sediments the strain distribution is governed by the grain-size distribution and effective normal stress...

  2. Subglacial hydrology of the lake district ice lobe during the Younger Dryas (ca. 12 500 - 11 600 years ago) in the Kylaeniemi area, SE Finland

    Energy Technology Data Exchange (ETDEWEB)

    Lunkka, J. P.; Moisio, K.; Vainio, A. [Univ. of Oulu (Finland)

    2013-07-15

    It is essential to gain knowledge on the subglacial hydrological conditions at the glacier bed / bedrock interface when assessing how bedrock fracture zones affect subglacial melt water flow and in which subglacial zones pressurized and oxygen-rich melt water penetrates into the bedrock fracture systems. In the warm-based glacier zones, a part of subglacial melt water will penetrate deep into the fracture systems although the major part of melt water is drained to and beyond the ice margin via subglacial tunnel networks especially in the areas where ice is flowing on the crystalline bedrock. During the last deglaciation phase of the former Scandinavian Ice Sheet, glaciofluvial accumulations were deposited and these sediment accumulations are highly important when picturing the subglacial hydrology of different ice streams during deglaciation in the crystalline bedrock area. The aim of the present work was to map the bedrock fracture zones in the Kylaeniemi area and to shed light on the subglacial hydrology of the Scandinavian Ice Sheet's Lake District Ice Stream that occupied the Kylaeniemi area during the Younger Dryas between ca. 12 500 - 11 600 years ago. The special emphasis within this general aim was to study the relationship between bedrock fracture zones and the routes of subglacial drainage paths. The methods used to map and study bedrock fracture zones and subglacial drainage paths included remotes sensing methods, field observations, ground penetrating radar (GPR) investigations and GIS-based reconstructions. Conventional geological field methods aided by the GPR-method were also used to map bedrock exposures and their structures and to define the type of glaciofluvial sediments and glaciofluvial landform associations. Two main fracture zone sets occur in the study area. The most prominent bedrock fracture zone set trends NW-SE while the other, less prominent fracture zone set is aligned in NE-SW direction. The majority of the minor joint sets in

  3. Subglacial hydrology of the lake district ice lobe during the Younger Dryas (ca. 12 500 - 11 600 years ago) in the Kylaeniemi area, SE Finland

    International Nuclear Information System (INIS)

    Lunkka, J. P.; Moisio, K.; Vainio, A.

    2013-07-01

    It is essential to gain knowledge on the subglacial hydrological conditions at the glacier bed / bedrock interface when assessing how bedrock fracture zones affect subglacial melt water flow and in which subglacial zones pressurized and oxygen-rich melt water penetrates into the bedrock fracture systems. In the warm-based glacier zones, a part of subglacial melt water will penetrate deep into the fracture systems although the major part of melt water is drained to and beyond the ice margin via subglacial tunnel networks especially in the areas where ice is flowing on the crystalline bedrock. During the last deglaciation phase of the former Scandinavian Ice Sheet, glaciofluvial accumulations were deposited and these sediment accumulations are highly important when picturing the subglacial hydrology of different ice streams during deglaciation in the crystalline bedrock area. The aim of the present work was to map the bedrock fracture zones in the Kylaeniemi area and to shed light on the subglacial hydrology of the Scandinavian Ice Sheet's Lake District Ice Stream that occupied the Kylaeniemi area during the Younger Dryas between ca. 12 500 - 11 600 years ago. The special emphasis within this general aim was to study the relationship between bedrock fracture zones and the routes of subglacial drainage paths. The methods used to map and study bedrock fracture zones and subglacial drainage paths included remotes sensing methods, field observations, ground penetrating radar (GPR) investigations and GIS-based reconstructions. Conventional geological field methods aided by the GPR-method were also used to map bedrock exposures and their structures and to define the type of glaciofluvial sediments and glaciofluvial landform associations. Two main fracture zone sets occur in the study area. The most prominent bedrock fracture zone set trends NW-SE while the other, less prominent fracture zone set is aligned in NE-SW direction. The majority of the minor joint sets in

  4. High-resolution insights into episodes of crystallization, hydrothermal alteration and remelting in the Skaergaard intrusive complex

    DEFF Research Database (Denmark)

    Wotzlaw, Joern-Frederik; Bindeman, Ilya N.; Schaltegger, Urs

    2012-01-01

    of the most incompatible trace element rich horizon, similar to 100 m above SH. As the Skaergaard intrusion is also the most classic example of a shallow meteoric hydrothermal system, this work documents the alternating processes in a life of an intrusion with periods of hydrothermal cooling, heating by new...

  5. Mapping Hydrothermal Alteration Zones at a Sediment-Hosted Gold Deposit - Goldstrike Mining District, Utah, Using Ground-Based Hyperspectral Imaging

    Science.gov (United States)

    Krupnik, D.; Khan, S.; Crockett, M.

    2017-12-01

    Understanding the origin, genesis, as well as depositional and structural mechanisms of gold mineralization as well as detailed mapping of gold-bearing mineral phases at centimeter scale can be useful for exploration. This work was conducted in the Goldstrike mining district near St. George, UT, a structurally complex region which contains Carlin-style disseminated gold deposits in permeable sedimentary layers near high-angle fault zones. These fault zones are likely a conduit for gold-bearing hydrothermal fluids, are silicified, and are frequently gold-bearing. Alteration patterns are complex, difficult to distinguish visually, composed of several phases, and vary significantly over centimeter to meter scale distances. This makes identifying and quantifying the extent of the target zones costly, time consuming, and discontinuous with traditional geochemical methods. A ground-based hyperspectral scanning system with sensors collecting data in the Visible Near Infrared (VNIR) and Short-Wave Infrared (SWIR) portions of the electromagnetic spectrum are utilized for close-range outcrop scanning. Scans were taken of vertical exposures of both gold-bearing and barren silicified rocks (jasperoids), with the intent to produce images which delineate and quantify the extent of each phase of alteration, in combination with discrete geochemical data. This ongoing study produces mineralogical maps of surface minerals at centimeter scale, with the intent of mapping original and alteration minerals. This efficient method of outcrop characterization increases our understanding of fluid flow and alteration of economic deposits.

  6. Modeling of subglacial hydrological development following rapid supraglacial lake drainage

    OpenAIRE

    Dow, C F; Kulessa, B; Rutt, I C; Tsai, V C; Pimentel, S; Doyle, S H; van As, D; Lindb?ck, K; Pettersson, R; Jones, G A; Hubbard, A

    2015-01-01

    The rapid drainage of supraglacial lakes injects substantial volumes of water to the bed of the Greenland ice sheet over short timescales. The effect of these water pulses on the development of basal hydrological systems is largely unknown. To address this, we develop a lake drainage model incorporating both (1) a subglacial radial flux element driven by elastic hydraulic jacking and (2) downstream drainage through a linked channelized and distributed system. Here we present the model and exa...

  7. Recent massive sulfide deposits of the Semenov ore district, Mid-Atlantic Ridge, 13°31' N: Associated rocks of the oceanic core complex and their hydrothermal alteration

    Science.gov (United States)

    Pertsev, A. N.; Bortnikov, N. S.; Vlasov, E. A.; Beltenev, V. E.; Dobretsova, I. G.; Ageeva, O. A.

    2012-09-01

    The oceanic core complexes and large-offset detachment faults characteristic of the slow-spreading Mid-Atlantic Ridge are crucial for the structural control of large hydrothermal systems, including those forming sub-seafloor polymetallic sulfide mineralization. The structural-geological, petrographic, and mineralogical data are considered for the oceanic core complex enclosing the Semenov-1, -2, -3, -4, and -5 inactive hydrothermal sulfide fields recently discovered on the Mid-Oceanic Ridge at 13°31' N. The oceanic core complex is composed of serpentinized and talc-replaced peridotites and sporadic gabbroic rocks, however, all hydrothermal fields reveal compositional indications of basaltic substrate. The volcanic structures superposed on the oceanic core complex are marked by outcrops of pillow lavas with fresh quenched glass. Dolerites regarded as volcanic conduits seem to represent separate dike swarms. The superposed volcanic structures develop largely along the near-latitudinal high-angle tectonic zone controlling the Semenov-1, -2, -5, and -3 hydrothermal sulfide fields. The manifestations of hydrothermal metasomatic alteration are diverse. The widespread talcose rocks with pyrrhotite-pyrite mineralization after serpentinite, as well as finding of talc-chlorite metabasalt are interpreted as products of hydrothermal activity in the permeable zone of detachment fault. Chloritization and brecciation of basalts with superposed quartz or opal, barite, and pyrite or chalcopyrite mineralization directly related to the sub-seafloor sulfide deposition. The native copper mineralization in almost unaltered basalts at the Semenov-4 field is suggested to precipitate from ore-forming fluids before they reach the level of sub-seafloor sulfide deposition. Amphibolites with plagiogranite veinlets are interpreted as tectonic fragments of the highest-temperature portions of hydrothermal systems, where partial melting of basic rocks in the presence of aqueous fluid with

  8. Development and Antarctic Testing of a Maneuverable Probe for Clean In-Situ Analysis and Sampling of Subsurface Ice and Subglacial Aquatic Ecosystems

    Science.gov (United States)

    Francke, G.; Dachwald, B.; Kowalski, J.; Digel, I.; Tulaczyk, S. M.; Mikucki, J.; Feldmann, M.; Espe, C.; Schöngarth, S.; Hiecker, S.; Blandfort, D.; Schüller, K.; Plescher, E.

    2016-12-01

    There is significant interest in sampling subglacial environments for geochemical and microbiological studies, but those environments are difficult to access. Such environments exist not only on Earth but are also expected beneath the icy crusts of some outer solar system bodies, like the Jovian moon Europa and the Saturnian moon Enceladus. Existing ice drilling technologies make it cumbersome to maintain microbiologically clean access for sample acquisition and environmental stewardship of potentially fragile subglacial aquatic ecosystems. The "IceMole" is a maneuverable subsurface ice probe for clean in-situ analysis and sampling of glacial ice and subglacial materials. The design is based on combining melting and mechanical propulsion, using an ice screw at the tip of the melting head to maintain firm contact between the melting head and the ice. It can change melting direction by differential heating of the melting head and optional side wall heaters. The first two prototypes were successfully tested between 2010 and 2012 on glaciers in Switzerland and Iceland, where they demonstrated downward, horizontal and upward melting, as well as curve driving and dirt layer penetration. Hence, the IceMole allows maneuvers which may be necessary for obstacle avoidance or target selection. Maneuverability, however, necessitates a sophisticated on-board navigation system capable of autonomous operations. Therefore, between 2012 and 2014, a more advanced probe was developed as part of the "Enceladus Explorer" (EnEx) project. The EnEx-IceMole offers systems for relative positioning based on in-ice attitude determination, acoustic positioning, ultrasonic obstacle and target detection, which is all integrated through a high-level sensor fusion. In December 2014, it was used for clean access into a unique subglacial aquatic environment at Blood Falls, Antarctica, where a subglacial brine sample was successfully obtained after about 17 meters of oblique melting. Particular

  9. The transport of oxygen isotopes in hydrothermal systems

    International Nuclear Information System (INIS)

    McKibbin, R.; Absar, A.; Blattner, P.

    1986-01-01

    As groundwater passes through porous rocks, exchange of oxygen between the fluid and the solid matrix causes a change in the oxygen isotope concentrations in both water and rock. If the rate at which the exchange takes place can be estimated (as a function of the isotope concentrations and temperature) then the time taken for a rock/water system to come to equilibrium with respect to isotope concentration might be calculated. In this paper, the equation for isotope transport is derived using conservation laws, and a simple equation to describe the rate of isotope exchange is proposed. These are combined with the equations for fluid flow in a porous medium, to produce a general set of equations describing isotope transport in a hydrothermal system. These equations are solved numerically, using typical parameters, for the one-dimensional case. Oxygen isotope data from the basement rocks underlying Kawerau geothermal field are modelled. The results indicate that the time taken for exchange of 18 O to present-day values is less than the postulated age of hydrothermal alteration in that field. This suggests that, although controlled by similar parameters, oxygen isotope exchange, in felsic rocks at least, is much faster than hydrothermal alteration. This conclusion is consistent with the petrographic observations from the Kawerau system as well as other geothermal fields

  10. Geochronology, geochemical and Sr-Nd-Hf-Pb isotopic compositions of the granitoids in the Yemaquan orefield, East Kunlun orogenic belt, northern Qinghai-Tibet Plateau: Implications for magmatic fractional crystallization and sub-solidus hydrothermal alteration

    Science.gov (United States)

    Yin, Shuo; Ma, Changqian; Xu, Jiannan

    2017-12-01

    A general consensus has emerged that high field strength elements (HFSE) can mobile to some extent in a hydrothermal fluid. However, there are hot debates on whether sub-solidus hydrothermal alteration can lower the Nb/Ta ratio in evolved melts. In this study, we present petrography, geochronology and geochemistry of the barren and mineralized rocks in the Yemaquan skarn iron deposit, northern Qinghai-Tibet Plateau, to probe magmatic-hydrothermal transition. The barren rocks consist of diorites, granodiorites, granites and syenogranites, whereas the porphyritic granodiorites are associated with mineralization for an excellent consistency between the magmatic zircon U-Pb age (225 ± 2 Ma) and the hydrothermal phlogopite 40Ar-39Ar age (225 ± 1.5 Ma). The Sr-Nd-Hf-Pb isotopic data demonstrate that the Yemaquan granitoids are originated from a relatively homogenous enriched mantle with different degrees of crust contamination (assimilation fractional crystallization, AFC). Trace elements signatures indicate that the porphyritic granodiorites related to mineralization display amphibole crystallization for high water contents, whereas the barren granites have gone through biotite crystallization due to potassium enrichment by continuous upper crust contamination, both of which are responsible for their Nb/Ta ratios, respectively. Modeling results suggest that a basaltic melt with Nb/Ta ratio of 15.3 can reach a minimum Nb/Ta ratio of 12 in the producing granodioritic melt by amphibole fractional crystallization based on partition coefficients of Nb and Ta between amphibole and melts from previous experiments. This may explain the average Nb/Ta ratio (13.7) of the barren granodiorites, while it cannot account for the average Nb/Ta ratio (8.4) of the mineralized porphyritic granodiorites, and it is even lower than that of the granites (10.3) with biotite fractional crystallization. Exsolution of a magmatic-hydrothermal fluid is inevitable when a water saturated magma

  11. Reconstructing Magmatic-Hydrothermal Systems via Geologic Mapping of the Tilted, Cross-sectional Exposures of the Yerington District, Nevada

    Science.gov (United States)

    Dilles, J. H.; Proffett, J. M.

    2011-12-01

    The Jurassic Yerington batholith was cut by Miocene to recent normal faults and tilted ~90° west (Proffett, 1977). Exposures range from the volcanic environment to ~6 km depth in the batholith. Magmatic-hydrothermal fluids derived from the Luhr Hill granite and associated porphyry dikes produced characteristic porphyry copper mineralization and rock alteration (K-silicate, sericitic, and advanced argillic) in near-vertical columnar zones above cupolas on the deep granite. In addition, saline brines derived from the early Mesozoic volcanic and sedimentary section intruded by the batholith were heated and circulated through the batholith producing voluminous sodic-calcic and propylitic alteration. The magnetite-copper ore body at Pumpkin Hollow is hosted in early Mesozoic sedimentary rocks in the contact aureole of the batholith, and appears to be an IOCG type deposit produced where the sedimentary brines exited the batholith. Although many advances in understanding of Yerington have been made by lab-based geochronology and geochemistry studies, the first order igneous and hydrothermal features were recognized first in the 1960s and 1970s and are best documented by geological mapping at a variety of scales ranging from 1:500 to 1:24,000. The Anaconda technique of mapping mine benches, trenches, and drill cores was perfected here (Einaudi, 1997), and other techniques were used for surface exposures. The geologic and hydrothermal alteration maps establish that hydrothermal alteration accompanied each of several porphyry dike intrusions, and affected more than 100 km3 of rock. Both zonation in alteration mineralogy and vein orientations allow reconstruction of source areas and >5 km-long flow-paths of hydrothermal fluids through the batholith and contact aureole.

  12. Sediment Microbial Communities Influenced by Cool Hydrothermal Fluid Migration

    Directory of Open Access Journals (Sweden)

    Laura A. Zinke

    2018-06-01

    Full Text Available Cool hydrothermal systems (CHSs are prevalent across the seafloor and discharge fluid volumes that rival oceanic input from rivers, yet the microbial ecology of these systems are poorly constrained. The Dorado Outcrop on the ridge flank of the Cocos Plate in the northeastern tropical Pacific Ocean is the first confirmed CHS, discharging minimally altered <15°C fluid from the shallow lithosphere through diffuse venting and seepage. In this paper, we characterize the resident sediment microbial communities influenced by cool hydrothermal advection, which is evident from nitrate and oxygen concentrations. 16S rRNA gene sequencing revealed that Thaumarchaea, Proteobacteria, and Planctomycetes were the most abundant phyla in all sediments across the system regardless of influence from seepage. Members of the Thaumarchaeota (Marine Group I, Alphaproteobacteria (Rhodospirillales, Nitrospirae, Nitrospina, Acidobacteria, and Gemmatimonadetes were enriched in the sediments influenced by CHS advection. Of the various geochemical parameters investigated, nitrate concentrations correlated best with microbial community structure, indicating structuring based on seepage of nitrate-rich fluids. A comparison of microbial communities from hydrothermal sediments, seafloor basalts, and local seawater at Dorado Outcrop showed differences that highlight the distinct niche space in CHS. Sediment microbial communities from Dorado Outcrop differ from those at previously characterized, warmer CHS sediment, but are similar to deep-sea sediment habitats with surficial ferromanganese nodules, such as the Clarion Clipperton Zone. We conclude that cool hydrothermal venting at seafloor outcrops can alter the local sedimentary oxidation–reduction pathways, which in turn influences the microbial communities within the fluid discharge affected sediment.

  13. Petrography and Mineral Chemistry of Magmatic and Hydrothermal Biotite in Porphyry Copper-Gold Deposits: A Tool for Understanding Mineralizing Fluid Compositional Changes During Alteration Processes

    OpenAIRE

    Arifudin Idrus

    2018-01-01

    DOI: 10.17014/ijog.5.1.47-64This study aims to understand the petrography and chemistry of both magmatic and hydrothermal biotites in porphyry copper-gold deposits, and to evaluate the fluid compositional changes during alteration processes. A total of 206 biotite grains from selected rock samples taken from the Batu Hijau porphyry Cu-Au deposit was analyzed. Detailed petrography and biotite chemistry analysis were performed on thin sections and polished thin sections, respectively, represent...

  14. Hydrothermal effects on montmorillonite

    International Nuclear Information System (INIS)

    Pusch, R.; Karnland, O.

    1988-06-01

    Hydrothermal effects on montmorillonite clay are usually taken to have the form of conversion of this clay mineral to other species, such as illite, disregarding microstructural alteration and cementation caused by precipitation of silica and other compounds. The report is focussed on identification of the primary processes that are involved in such alteration, the release of silica and the microstructural changes associated with heating being of major interest. In the first test phase, Na montmorillonite in distilled water was investigated by XRD, rheology tests and electron microscopy after heating to 60-225 0 C for 0.01 to 1 year. The preliminary conclusions are that heating produces contraction of the particle network to form dense 'branches', the effect being most obvious at the highest temperature but of significance even at 60-100 0 C. Release of substantial amounts of silica gas been documented for temperatures exceeding 150 0 and precipitation of silica was observed on cooling after the hydrothermal testing under the closed conditions that prevailed throughout the tests. The precipitates, which appeared to be amorphous and probably consisted of hydrous silica gels, were concluded to have increased the mechanical strength and caused some brittleness, particularly of the dense clays. The nature of the silica release, which is assumed to be associated with beidellitization, may be closely related to an unstable state of a certain fraction of tetrahedral silica at heat-inducted transfer between two different crystal modes of montmorillonite. (orig.)

  15. Some genetic aspects of hydrothermal uranium deposits in the Bakulja granitoide (Serbia)

    International Nuclear Information System (INIS)

    Jelenkovic, Rade

    1998-01-01

    This paper discusses the influence of temperature and the way of hydrothermal fluids flow in function of both the degree of tectonized granitoid and the origin of solutions, and partly the processes accompanying mineralization expressed through physico-chemical, mineralogical and mechanical alterations of the mother rock. It has been concluded that heat energy exchange is in function of: 1) petrochemical characteristic of a rock the hydrothermal fluids flow through; 2) degree of tectonization of the surrounding mineralized rocks; 3) volume and morphology of the fissured-porous space; 4) form of uranium bonding in mineral carriers; 5) degree of uranium leaching in hydrothermal solutions; 6) the way of hydrothermal fluids flow, and 7) coefficient of heat exchange expressed by distribution of heat energy within a fluid-rock system. It has also been established that contraction of granite volume results from physico-chemical processes that take place within a granitoid-hydrothermal fluid system and its quantification has been carried out. (Author)

  16. Hydrothermal Processes

    Science.gov (United States)

    German, C. R.; von Damm, K. L.

    2003-12-01

    (after C. A. Stein and S. Stein, 1994). The first geochemical evidence for the existence of hydrothermal vents on the ocean floor came in the mid-1960s when investigations in the Red Sea revealed deep basins filled with hot, salty water (40-60 °C) and underlain by thick layers of metal-rich sediment (Degens and Ross, 1969). Because the Red Sea represents a young, rifting, ocean basin it was speculated that the phenomena observed there might also prevail along other young MOR spreading centers. An analysis of core-top sediments from throughout the world's oceans ( Figure 2) revealed that such metalliferous sediments did, indeed, appear to be concentrated along the newly recognized global ridge crest (Boström et al., 1969). Another early indication of hydrothermal activity came from the detection of plumes of excess 3He in the Pacific Ocean Basin (Clarke et al., 1969) - notably the >2,000 km wide section in the South Pacific ( Lupton and Craig, 1981) - because 3He present in the deep ocean could only be sourced through some form of active degassing of the Earth's interior, at the seafloor. (62K)Figure 2. Global map of the (Al+Fe+Mn):Al ratio for surficial marine sediments. Highest ratios mimic the trend of the global MOR axis (after Boström et al., 1969). One area where early heat-flow studies suggested hydrothermal activity was likely to occur was along the Galapagos Spreading Center in the eastern equatorial Pacific Ocean (Anderson and Hobart, 1976). In 1977, scientists diving at this location found hydrothermal fluids discharging chemically altered seawater from young volcanic seafloor at elevated temperatures up to 17 °C ( Edmond et al., 1979). Two years later, the first high-temperature (380±30 °C) vent fluids were found at 21° N on the East Pacific Rise (EPR) (Spiess et al., 1980) - with fluid compositions remarkably close to those predicted from the lower-temperature Galapagos findings ( Edmond et al., 1979). Since that time, hydrothermal activity has been

  17. Rare-earth elements and uranium in high-temperature solutions from East Pacific Rise hydrothermal vent field (130N)

    International Nuclear Information System (INIS)

    Michard, A.; Albarede, F.; Michard, G.; Minster, J.F.; Charlou, J.L.

    1983-01-01

    The mobility of rare-earth elements (REE) and U during hydrothermal alteration of the basalts at spreading centres has long been a matter of concern because of its bearing on the evolution and recycling of the oceanic crust. Previous approaches to this problem have been indirect, through studies on altered dredged basalts or ophiolites. Sampling of hydrothermal vent waters from the East Pacific Rise (EPR) at 13 0 N is reported. It provides the first direct evidence of REE-enriched solutions which, however, leave the budget of these elements in the crust and the ocean rather unmodified. In constrast, uranium, like magnesium, is quantitatively taken up from the seawater during the hydrothermal process. (author)

  18. Genesis of the hydrothermal gold deposits in the Canan area, Lepaguare District, Honduras

    Science.gov (United States)

    Mattioli, Michele; Menichetti, Marco; Renzulli, Alberto; Toscani, Lorenzo; Salvioli-Mariani, Emma; Suarez, Pedro; Murroni, Alessandro

    2014-04-01

    The Canan area (Honduras) is characterized by a gold-bearing ore deposit that is associated with quartz-veined shear zones. Gold mineralization occurs in low-to medium-grade metamorphic host-rocks (graphitic and sericitic schists). Hydrothermal fluids, which are associated with the emplacement of Cretaceous-Tertiary granodioritic intrusions, are responsible for the formation of quartz veins and the hydrothermal alteration of wall-rocks. Three main altered zones have been detected in the wall-rocks as far as 150 cm from the quartz veins. The distal zone (up to 50-cm thick) contains quartz, chlorite and illite. The intermediate zone is the thickest (up to 80 cm) and is marked by quartz, muscovite, sulphides, kaolinite and native elements such as Au and Ag. The proximal zone, which is close to the quartz veins, is rather thin (up to 25 cm) and contains clay minerals, Al-oxides-hydroxides and sulphides. The transition from the distal to the proximal zone is accompanied by the enrichment of SiO2 and the depletion of all other major elements, except for Fe2O3(tot). Precious metals occur in the highest concentrations in the intermediate zone (Au up to 7.6 ppm and Ag up to 11 ppm). We suggest that gold was transported as a reduced sulphur complex and was precipitated from the hydrothermal solution by the reaction of the sulphur complexes with Fe2+ from the alteration of the mafic minerals of the host-rock. Fluid-wall-rock interactions seem to be the main cause of gold mineralization. Genetic relationships with a strike-slip fault system, hydrothermal alteration zones within the metamorphic wall-rocks, and an entire set of geochemical anomalies are consistent with orogenic-type gold deposits of the epizonal class.

  19. Hydrothermal Alteration Mineral Mapping Using Sentinel-2A MSI and ASTER Data in the Duolong Ore Concentrating Area,Tibetau Plateau,China

    Science.gov (United States)

    Hu, B.; Wan, B.

    2017-12-01

    The porphyry copper deposits are characterized by alteration zones. Hydrothermal alteration minerals have diagnostic spectral absorption properties in the visible and near-infrared (VNIR) through the shortwave infrared (SWIR) regions. In order to identify the alteration zones in the study area, the Sentinel-2A Multi-Spectral Instrument(MSI) * Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and field inspection were combined. The Sentinel-2A MSI has ten bands in the visible and near-infrared (VNIR) regions, which has advantages of detecting ferric iron alteration minerals. Six ASTER bands in the shortwave infrared(SWIR) regions have been demonstrated to be effective in the mapping of Al-OH * Mg-OH group minerals. Integrating ASTER and Sentinel-2A MSI (AM) for mineral mapping can compensate each other's defect. The methods of minimum noise fraction(MNF) * band combination * matched filtering were applied to get Al-OH and Mg-OH group minerals information from AM data. The anomaly-overlaying selection method was used to process three temporal Sentinel-2A MSI data for extracting iron oxides minerals. The ground inspection has confirmed the validity of AM and Sentinel-2A MSI data in mineral mapping. The methodology proved effective in an arid area of Duolong ore concentrating area,Tibet and hereby suggested for application in similar geological settings.

  20. Halogen Chemistry of Hydrothermal Micas: a Possible Geochemical Tool in Vectoring to Ore for Porphyry Copper-Gold Deposit

    OpenAIRE

    Arifudin Idrus

    2018-01-01

    Porphyry copper-gold deposit commonly exhibits an extensive alteration zone of hydrothermal micas particularly biotite and sericite. This study is aimed to analyze and utilize the chemistry of halogen fluorine and chlorine of biotite and sericite to be a possible tool in vectoring to ore for copper porphyry deposits. To achieve the objectives, several selected altered rock samples were taken crossing the Batu Hijau copper-gold mine from inner to outer of the deposit, and hydrothermal micas co...

  1. Stress Redistribution Explains Anti-correlated Subglacial Pressure Variations

    Directory of Open Access Journals (Sweden)

    Pierre-Marie Lefeuvre

    2018-01-01

    Full Text Available We used a finite element model to interpret anti-correlated pressure variations at the base of a glacier to demonstrate the importance of stress redistribution in the basal ice. We first investigated two pairs of load cells installed 20 m apart at the base of the 210 m thick Engabreen glacier in Northern Norway. The load cell data for July 2003 showed that pressurisation of a subglacial channel located over one load cell pair led to anti-correlation in pressure between the two pairs. To investigate the cause of this anti-correlation, we used a full Stokes 3D model of a 210 m thick and 25–200 m wide glacier with a pressurised subglacial channel represented as a pressure boundary condition. The model reproduced the anti-correlated pressure response at the glacier bed and variations in pressure of the same order of magnitude as the load cell observations. The anti-correlation pattern was shown to depend on the bed/surface slope. On a flat bed with laterally constrained cross-section, the resulting bridging effect diverted some of the normal forces acting on the bed to the sides. The anti-correlated pressure variations were then reproduced at a distance >10–20 m from the channel. In contrast, when the bed was inclined, the channel support of the overlying ice was vertical only, causing a reduction of the normal stress on the bed. With a bed slope of 5 degrees, the anti-correlation occurred within 10 m of the channel. The model thus showed that the effect of stress redistribution can lead to an opposite response in pressure at the same distance from the channel and that anti-correlation in pressure is reproduced without invoking cavity expansion caused by sliding.

  2. A deep hydrothermal fault zone in the lower oceanic crust, Samail ophiolite Oman

    Science.gov (United States)

    Zihlmann, B.; Mueller, S.; Koepke, J.; Teagle, D. A. H.

    2017-12-01

    Hydrothermal circulation is a key process for the exchange of chemical elements between the oceans and the solid Earth and for the extraction of heat from newly accreted crust at mid-ocean ridges. However, due to a dearth of samples from intact oceanic crust, or continuous samples from ophiolites, there remain major short comings in our understanding of hydrothermal circulation in the oceanic crust, especially in the deeper parts. In particular, it is unknown whether fluid recharge and discharge occurs pervasively or if it is mainly channeled within discrete zones such as faults. Here, we present a description of a hydrothermal fault zone that crops out in Wadi Gideah in the layered gabbro section of the Samail ophiolite of Oman. Field observations reveal a one meter thick chlorite-epidote normal fault with disseminated pyrite and chalcopyrite and heavily altered gabbro clasts at its core. In both, the hanging and the footwall the gabbro is altered and abundantly veined with amphibole, epidote, prehnite and zeolite. Whole rock mass balance calculations show enrichments in Fe, Mn, Sc, V, Co, Cu, Rb, Zr, Nb, Th and U and depletions of Si, Ca, Na, Cr, Zn, Sr, Ba and Pb concentrations in the fault rock compared to fresh layered gabbros. Gabbro clasts within the fault zone as well as altered rock from the hanging wall show enrichments in Na, Sc, V, Co, Rb, Zr, Nb and depletion of Cr, Ni, Cu, Zn, Sr and Pb. Strontium isotope whole rock data of the fault rock yield 87Sr/86Sr ratios of 0.7046, which is considerably more radiogenic than fresh layered gabbro from this locality (87Sr/86Sr = 0.7030 - 0.7034), and similar to black smoker hydrothermal signatures based on epidote, measured elsewhere in the ophiolite. Altered gabbro clasts within the fault zone show similar values with 87Sr/86Sr ratios of 0.7045 - 0.7050, whereas hanging wall and foot wall display values only slightly more radiogenic than fresh layered gabbro.The secondary mineral assemblages and strontium isotope

  3. Plumbing the depths of Yellowstone's hydrothermal system from helicopter magnetic and electromagnetic data

    Science.gov (United States)

    Finn, C.; Bedrosian, P.; Holbrook, W. S.; Auken, E.; Lowenstern, J. B.; Hurwitz, S.; Sims, K. W. W.; Carr, B.; Dickey, K.

    2017-12-01

    Although Yellowstone's iconic hydrothermal systems and lava flows are well mapped at the surface, their groundwater flow systems and thickness are almost completely unknown. In order to track the geophysical signatures of geysers, hot springs, mud pots, steam vents, hydrothermal explosion craters and lava flows at depths to hundreds of meters, we collected helicopter electromagnetic and magnetic (HEM) data. The data cover significant portions of the caldera including a majority of the known thermal areas. HEM data constrain electrical resistivity which is sensitive to groundwater salinity and temperature, phase distribution (liquid-vapor), and clay formed during chemical alteration of rocks. The magnetic data are sensitive to variations in the magnetization of lava flows, faults and hydrothermal alteration. The combination of electromagnetic and magnetic data is ideal for mapping zones of cold fresh water, hot saline water, steam, clay, and altered and unaltered rock. Preliminary inversion of the HEM data indicates very low resistivity directly beneath the northern part of Yellowstone Lake, intersecting with the lake bottom in close correspondence with mapped vents, fractures and hydrothermal explosion craters and are also associated with magnetic lows. Coincident resistivity and magnetic lows unassociated with mapped alteration occur, for example, along the southeast edge of the Mallard Lake dome and along the northeastern edge of Sour Creek Dome, suggesting the presence of buried alteration. Low resistivities unassociated with magnetic lows may relate to hot and/or saline groundwater or thin (<50 m) layers of early lake sediments to which the magnetic data are insensitive. Resistivity and magnetic lows follow interpreted caldera boundaries in places, yet deviate in others. In the Norris-Mammoth Corridor, NNE-SSW trending linear resistivity and magnetic lows align with mapped faults. This pattern of coincident resistivity and magnetic lows may reflect fractures

  4. Anhydrite precipitation in seafloor hydrothermal systems

    Science.gov (United States)

    Theissen-Krah, Sonja; Rüpke, Lars H.

    2016-04-01

    The composition and metal concentration of hydrothermal fluids venting at the seafloor is strongly temperature-dependent and fluids above 300°C are required to transport metals to the seafloor (Hannington et al. 2010). Ore-forming hydrothermal systems and high temperature vents in general are often associated with faults and fracture zones, i.e. zones of enhanced permeabilities that act as channels for the uprising hydrothermal fluid (Heinrich & Candela, 2014). Previous numerical models (Jupp and Schultz, 2000; Andersen et al. 2015) however have shown that high permeabilities tend to decrease fluid flow temperatures due to mixing with cold seawater and the resulting high fluid fluxes that lead to short residence times of the fluid near the heat source. A possible mechanism to reduce the permeability and thereby to focus high temperature fluid flow are mineral precipitation reactions that clog the pore space. Anhydrite for example precipitates from seawater if it is heated to temperatures above ~150°C or due to mixing of seawater with hydrothermal fluids that usually have high Calcium concentrations. We have implemented anhydrite reactions (precipitation and dissolution) in our finite element numerical models of hydrothermal circulation. The initial results show that the precipitation of anhydrite efficiently alters the permeability field, which affects the hydrothermal flow field as well as the resulting vent temperatures. C. Andersen et al. (2015), Fault geometry and permeability contrast control vent temperatures at the Logatchev 1 hydrothermal field, Mid-Atlantic Ridge, Geology, 43(1), 51-54. M. D. Hannington et al. (2010), Modern Sea-Floor Massive Sulfides and Base Metal Resources: Toward an Estimate of Global Sea-Floor Massive Sulfide Potential, in The Challenge of Finding New Mineral Resources: Global Metallogeny, Innovative Exploration, and New Discoveries, edited by R. J. Goldfarb, E. E. Marsh and T. Monecke, pp. 317-338, Society of Economic Geologists

  5. Physico-chemistry and geochemistry of Balengou clay deposit (West Cameroon) with inference to an argillic hydrothermal alteration

    Science.gov (United States)

    Tassongwa, Bernard; Eba, François; Njoya, Dayirou; Tchakounté, Jacqueline Numbem; Jeudong, Narcisse; Nkoumbou, Charles; Njopwouo, Daniel

    2017-09-01

    Field description and sampling along two pits, granulometry, Atterberg limits, mineralogical (XRD, FTIR, DSC & TGA) and geochemical analyses of the Balengou clays help to determine their characteristics and the genesis of the deposit. The mineralogical composition is comprised of halloysite-kaolinite, quartz, montmorillonite, hematite, anatase, feldspar, zircon, chromite, and apatite. Gibbsite and illite occur at the shallow and deep depth, respectively. Dikes of sand-poor clays contain also cristobalite and tridymite. Pairs of elements Rb-Ba, Rb-Sr, Nb-Ta, Ta-Zr, TiO2-Zr display good positive correlations (R2 > 0.85). REE patterns are highly fractionated (LaN up to 3312, LaN/YbN: 19-10) and are marked by deep Ce and Eu negative anomalies. Immobile element canonical ratios indicate that the protoliths were commendite/pantelerite, rhyolite and dacite, or their plutonic equivalents. Mineralogical and geochemical features lead to the suggestion that the clays derived from an advanced argillic hydrothermal alteration.

  6. PROSPECTS FOR LIFE IN THE SUBGLACIAL LAKE VOSTOK, EAST ANTARCTICA

    Directory of Open Access Journals (Sweden)

    S. A. Bulat

    2012-01-01

    Full Text Available The objective was to estimate the genuine microbial content of ice samples from refrozen water (accretion ice from the subglacialLakeVostok(Antarctica buried beneath the 4-km thick East Antarctic ice sheet as well as surface snow nearby Vostok station. The lake ice samples were extracted by heavy deep ice drilling from3764 mbelow the surface reaching the depth3769.3 mby February 2011 (lake entering. High pressure, an ultra low carbon and chemical content, isolation, complete darkness and the probable excess of oxygen in water for millions of years characterize this extreme environment. A decontamination protocol was first applied to samples selected for the absence of cracks to remove the outer part contaminated by handling and drilling fluid. Preliminary indications showed the accretion ice samples to be almost gas free with the very low impurity content. Flow cytometry showed the very low unevenly distributed biomass in both accretion (0–19 cells per ml and glacier (0–24 cells per ml ice and surface snow (0–0.02 cells per ml as well while repeated microscopic observations were unsuccessful meaning that the whole Central East Antarctic ice sheet seems to be microbial cell-free.We used strategies of Ancient DNA research that include establishing contaminant databases and criteria to validate the amplification results. To date, positive results that passed the artifacts and contaminant databases have been obtained for a few bacterial phylotypes only in accretion ice samples featured by some bedrock sediments. Amongst them are the chemolithoautotrophic thermophile Hydrogenophilus thermoluteolus of beta-Proteobacteria, the actinobacterium rather related (95% to Ilumatobacter luminis and one unclassified phylotype distantly related (92% to soil-inhabiting uncultured bacteria. Combined with geochemical and geophysical considerations, our results suggest the presence of a deep biosphere, possibly thriving within some active faults of the bedrock

  7. Hydrothermally-induced changes in mineralogy and magnetic properties of oxidized A-type granites

    Science.gov (United States)

    Nédélec, Anne; Trindade, Ricardo; Peschler, Anne; Archanjo, Carlos; Macouin, Mélina; Poitrasson, Franck; Bouchez, Jean-Luc

    2015-01-01

    The changes in magnetic mineralogy due to the hydrothermal alteration of A-type granitic rocks have been thoroughly investigated in samples from the granite of Tana (Corsica, France), and compared with other A-type granites: Meruoca (NE Brazil), Bushveld (South Africa), Mount Scott (Wichita Mountains, Oklahoma, USA) and the stratoid hypersolvus granites of Madagascar. The altered red-colored samples and their non-altered equivalents were magnetically characterized by means of magnetic susceptibility measurements, hysteresis loops, remanent coercivity spectra, and Lowrie test. It is shown that hydrothermalization in magnetite-bearing granites is related to the formation of fine-grained magnetite and hematite, and to coeval depletion in the content of primary low-coercive coarse-grained magnetite. These mineralogical changes give typical rock magnetic signatures, namely lower susceptibility magnitudes and anisotropy degrees, prolate AMS (anisotropy of magnetic susceptibility) fabrics and increased coercivities. Optical microscopy and SEM (scanning electronic microscopy) images suggest that the orientation of the secondary magnetic minerals is related to fluid-pathways and micro-fractures formed during the hydrothermal event and therefore may be unrelated to magma emplacement and crystallization fabrics. Changes in magnetic mineralogy and grain-size distribution have also to be considered for any paleomagnetic and iron isotope studies in granites.

  8. Hydrothermal activity in the Tulancingo-Acoculco Caldera Complex, central Mexico. Exploratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Hernandez, Aida [Gerencia de Proyectos Geotermoelectricos, CFE, Alejandro Volta 655, 58290 Morelia, Michoacan (Mexico); Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro., 76230 (Mexico); Garcia-Estrada, Gerardo; Palma-Guzman, Hugo; Quijano-Leon, Jose L. [Gerencia de Proyectos Geotermoelectricos, CFE, Alejandro Volta 655, 58290 Morelia, Michoacan (Mexico); Aguirre-Diaz, Gerardo; Gonzalez-Partida, Eduardo [Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro., 76230 (Mexico)

    2009-09-15

    Mineral alteration and fluid inclusion studies of drill cuttings and core samples indicate that the sedimentary basement rocks and the volcanic rocks associated with Tulancingo-Acoculco Caldera Complex have been the site of two distinct and major hydrothermal events. The complex, located in the eastern portion of the Trans-Mexican Volcanic Belt, is formed by the Pliocene Tulancingo Caldera and the younger (Pleistocene) Acoculco Caldera, which developed within the older depression. The volcanic rocks are underlain by Cretaceous sedimentary rocks of the Sierra Madre Oriental. The earliest important hydrothermal event occurred during the emplacement of Mid-Tertiary granitic intrusions that metamorphosed the sedimentary rocks; these intrusives are not exposed at the surface. However, granitic rocks were encountered at the bottom of exploratory borehole EAC-1, drilled within the Caldera Complex. The second main event occurred during the formation of the Tulancingo and Acoculco Calderas. Both episodes lead to secondary mineralization that reduced the permeability of the reservoir rocks. A possible third hydrothermal event may be associated with the recent magmatic activity within the Acoculco Caldera.Thermal logs from well EAC-1 display a conductive thermal gradient with maximum temperatures exceeding 300 C at 2000 m depth. Although there are no active thermal springs in the area, there is extensive fossil surface hydrothermal alteration and cold gas discharges with high He{sup 3}/He{sup 4} ratios. (author)

  9. Representing glaciations and subglacial processes in hydrogeological models : a numerical investigation

    OpenAIRE

    Sterckx, Arnaud; Lemieux, Jean-Michel; Vaikmäe, Rein

    2017-01-01

    The specific impact of glacial processes on groundwater flow and solute transport under ice-sheets was determined by means of numerical simulations. Groundwater flow and the transport of δ18O, TDS, and groundwater age were simulated in a generic sedimentary basin during a single glacial event followed by a postglacial period. Results show that simulating subglacial recharge with a fixed flux boundary condition is relevant only for small fluxes, which could be the case under partially wet-base...

  10. Hydrogen and oxygen isotope constraints on hydrothermal alteration of the Trinity peridotite, Klamath Mountains, California

    Science.gov (United States)

    Liakhovitch, V.; Quick, J.E.; Gregory, R.T.

    2005-01-01

    The Trinity peridotite represents a rare opportunity to examine a relatively fertile plagioclase peridotite that was exhumed and later subjected to intrusive events in a seafloor environment, followed by its emplacement and incorporation into a continent. Over 250 stable isotopic determinations on whole rocks and minerals elucidate the hydrothermal evolution of the Trinity complex. All three serpentine polymorphs are present in the Trinity peridotite; these separate on the basis of their ??D values: antigorite, -46 serpentinization, or overprinting of earlier low-temperature seafloor serpentinization. Regionally, contours of ??D values exhibit bull's-eye patterns associated with the gabbroic plutons, with ??D maxima coinciding with the blackwall alteration at the margins on the plutons. In contrast to the hydrogen isotope behavior, oxygen isotope values of the three polymorphs are indistinguishable, spanning the range 5.3 history: (1) lithospheric emplacement and cooling of the peridotite in an oceanic environment ??? 472 Ma; (2) intrusion of gabbroic plutons into cold peridotite in an arc environment between 435 and 404 Ma; and finally (3) intrusion of felsic plutons between 171 and 127 Ma, long after the peridotite was incorporated into the continental crust. Copyright ?? 2005 by V. H. Winston & Son, Inc. All rights reserved.

  11. Marine Subsurface Microbial Communities Across a Hydrothermal Gradient in Okinawa Trough Sediments

    Science.gov (United States)

    Brandt, L. D.; Hser Wah Saw, J.; Ettema, T.; House, C. H.

    2015-12-01

    IODP Expedition 331 to the Okinawa backarc basin provided an opportunity to study the microbial stratigraphy within the sediments surrounding a hydrothermal vent. The Okinawa backarc basin is a sedimented region of the seafloor located on a continental margin, and also hosts a hydrothermal network within the subsurface. Site C0014 within the Iheya North hydrothermal field is located 450 m east of the active vent and has a surface temperature of 5°C with no evidence of hydrothermal alteration within the top 10 meters below sea floor (mbsf). Temperature increases with depth at an estimated rate of 3°C/m and transitions from non-hydrothermal margin sediments to a hydrothermally altered regime below 10 mbsf. In this study, we utilized deep 16S rRNA sequencing of DNA from IODP Expedition 331 Site C0014 sediment horizons in order to assess diversity throughout the sediment column as well as determine the potential limits of the biosphere. Analysis of the amplicon data shows a shift over 15 mbsf from a heterogeneous community of cosmopolitan marine subsurface taxa toward an archaeal-dominated community in the deepest horizons of the predicted biosphere. Notably, the phylum Chloroflexi represents a substantial taxon through most horizons, where it appears to be replaced below 10 mbsf by punctuations of thermophilic and methanotrophic Archaea and Miscellaneous Crenarchaeotic Group abundances. DNA from the aforementioned transition horizons was further analyzed using metagenomic sequencing. Preliminary taxonomic analysis of the metagenomic data agrees well with amplicon data in capturing the shift in relative abundance of Archaea increasing with depth. Additionally, reverse gyrase, a gene found exclusively in hyperthermophilic microorganisms, was recovered only in the metagenome of the deepest horizon. A BLAST search of this protein sequence against the GenBank non-redudnant protein database produced top hits with reverse gyrase from Thermococcus and Pyrococcus, which are

  12. Recent technical developments at the IMAU: A new generation of AWS and wireless subglacial measurements

    NARCIS (Netherlands)

    Smeets, C.J.P.P.; Boot, W.; van den Broeke, M.R.; van de Wal, R.S.W.

    2011-01-01

    Two technical developments are presented: a new generation of AWS and a wireless subglacial measurement system. Both systems build on the experience of the IMAU in developing GPS systems (Den Ouden et al., 2010). Combining methods to minimize energy consumption and wireless communication form the

  13. Hydrovolcanic and Hydrothermal Biomediated Mineral Growth in Basaltic Tuff, Surtsey Volcano, Iceland

    Science.gov (United States)

    Jackson, M. D.; Couper, S.; Ivarsson, M.; Stan, C. V.; Tamura, N.; Miyagi, L. M.; Moore, J. G.

    2017-12-01

    Fine-scale analyses of hydroclasts in 1979 Surtsey basaltic tuff drill core provide new methods for examining hydrovolcanic and hydrothermal magma-rock influences on biomediated alteration in palagonitized submarine tephra. Synchrotron source X-ray microdiffraction and microfluorescence studies from Advanced Light Source beamline 12.3.2, epifluorescent UVA illumination microscopy, S/TEM EDX compositional analyses, and Raman spectroscopy define diverse nanocrystalline clay mineral structures at 137.9 m depth (93.8 °C (1980)) and 102.6 m depth (141.3 °C (1980)). At 137.9 m, olivine contains endolithic microborings; vermicular microstructures in altered glass contain nontronite exhibiting crystallographic preferred orientation; and 75-150 µm sub-circular microstructures in altered glass contain Al-tobermorite, a calcium-silicate-hydrate with 11.3 Å interlayer spacing, zeolite, and epifluorescent, thread-like structures. At 102.6 m depth, concentrically-layered microstructures occur in altered glass and altered olivine. These have nontronite crystallographic preferred orientations that rotate around a longitudinal axis commonly occupied by a 10-80 µm long, epifluorescent thread-like structure. Pronounced carbon concentrations detected by S/TEM EDX trace layer boundaries. First-order Raman bands at 1370 cm-1 (disorder-related) and at 1580 cm-1 (order-related), and second-order bands at 2500-3300 cm-1 (overtone scattering) detect degraded organic carbonaceous matter, a strong indication of biological origin. Sub-circular nanostructures in altered glass at 137.9 m depth show similar spectra. Borehole fluid temperatures at 102.6 m, 141.3 °C in 1980, exceeded 130 °C, the assumed limit for growth of microorganisms, however. Previous analyses suggest an early low temperature episode in submarine deposits, prior to development of a hydrothermal system driven by 1964-1967 magmatic intrusions. The abundant traces of biomediated nanocrystalline clay mineral growth validate

  14. Argentine hydrothermal panorama

    Energy Technology Data Exchange (ETDEWEB)

    1976-12-01

    An attempt is made to give a realistic review of Argentine thermal waters. The topics discussed are the characteristics of the hydrothermal resources, classification according to their mineral content, hydrothermal flora and fauna, uses of hydrothermal resources, hydrothermal regions of Argentina, and meteorology and climate. A tabulation is presented of the principal thermal waters. (JSR)

  15. Fluid Evolution of the Magmatic Hydrothermal Porphyry Copper Deposit Based on Fluid Inclusion and Stable Isotope Studies at Darrehzar, Iran

    OpenAIRE

    Alizadeh Sevari, B.; Hezarkhani, A.

    2014-01-01

    The Darrehzar porphyry Cu-Mo deposit is located in southwestern Iran (~70 km southwest of Kerman City). The porphyries occur as Tertiary quartz-monzonite stocks and dikes, ranging in composition from microdiorite to diorite and granodiorite. Hydrothermal alteration and mineralization at Darrehzar are centered on the stock and were broadly synchronous with its emplacement. Early hydrothermal alteration was dominantly potassic and propylitic and was followed by later phyllic and argillic altera...

  16. Quantitative impact of hydrothermal alteration on electrical resistivity in geothermal systems from a joint analysis of laboratory measurements and borehole data in Krafla area, N-E Iceland

    Science.gov (United States)

    Lévy, Léa; Páll Hersir, Gylfi; Flóvenz, Ólafur; Gibert, Benoit; Pézard, Philippe; Sigmundsson, Freysteinn; Briole, Pierre

    2016-04-01

    Rock permeability and fluid temperature are the two most decisive factors for a successful geothermal drilling. While those parameters are only measured from drilling, they might be estimated on the basis of their impact on electrical resistivity that might be imaged from surface soundings, for example through TEM (Transient Electro Magnetic) down to one km depth. The electrical conductivity of reservoir rocks is the sum of a volume term depending on fluid parameters and a surface term related to rock alteration. Understanding the link between electrical resistivity and geothermal key parameters requires the knowledge of hydrothermal alteration and its petrophysical signature with the Cation Exchange Capacity (CEC). Fluid-rock interactions related to hydrothermal circulation trigger the precipitation of alteration minerals, which are both witnesses of the temperature at the time of reaction and new paths for the electrical current. Alteration minerals include zeolites, smectites, chlorites, epidotes and amphiboles among which low temperatures parageneses are often the most conductive. The CEC of these mineral phases contributes to account for surface conductivity occuring at the water-rock interface. In cooling geothermal systems, these minerals constitute in petrophysical terms and from surface electrical conduction a memory of the equilibrium phase revealed from electrical probing at all scales. The qualitative impact of alteration minerals on resistivity structure has been studied over the years in the Icelandic geothermal context. In this work, the CEC impact on pore surfaces electrical conductivity is studied quantitatively at the borehole scale, where several types of volcanic rocks are mixed together, with various degrees of alteration and porosity. Five boreholes located within a few km at the Krafla volcano, Northeast Iceland, constitute the basis for this study. The deepest and reference hole, KJ-18, provides cuttings of rock and logging data down to 2215

  17. Hydrothermal reactions of nuclear waste solids . A preliminary study

    International Nuclear Information System (INIS)

    Westsik, J.H. Jr.; Turcotte, R.P.

    1978-09-01

    A simulated high-level waste glass, Supercalcine, and some common ceramic and metallic solids were exposed to hydrothermal conditions at 250 and 350 0 C for time periods ranging from three days to three weeks. Most of the experiments were done in salt brine, but the glass study did include deionized water tests so that the influence of salt could be better understood. Under the extreme hydrothermal conditions of these tests, all of the materials examined underwent measurable changes. The glass is converted to a mixture of crystalline phases, depending upon conditions, giving NaFeSi 2 O 6 as the primary alteration product. The rate of alteration is higher in deionized water than in salt brine; however, under equivalent test conditions, 66% of the Cs originally in the glass is released to the salt brine, while only 6% is released to deionized water. Rb and Mo are the only other fission product elements significantly leached from the glass. Evidence is presented which shows that sintered Supercalcine undergoes chemical changes in salt brine that are qualitatively similar to those experienced by glass samples. High concentrations of Cs enter the aqueous phase, and Sn and Mo are mobilized. Scouting tests were made with a variety of materials including commercial glasses, granite, UO 2 , Al 2 O 3 , steel, and waste glasses. Weight losses under hydrothermal conditions are in a relatively narrow band, with glass and ceramic materials showing 3 to 20 times greater weight losses than 304L stainless steel in the 250 0 C test used. The conclusion from these studies is that virtually all solid materials show hydrothermal reactivity at temperatures between 250 and 350 0 C, and that these extreme conditions are not desirable

  18. Coastal submarine hydrothermal activity off northern Baja California

    International Nuclear Information System (INIS)

    Vidal, V.M.V.; Vidal, F.V.; Isaacs, J.D.; Young, D.R.

    1978-01-01

    In situ observations of submarine hydrothermal activity have been conducted in Punta Banda. Baja Califronia, Mexico, approximately 400 m from the coast and at a seawater depth of 30 m. The hydrothermal activity occurs within the Agua Blanca Fault, a major transverse structure of Northern Baja California. Hot springwater samples have been collected and analyzed. Marked differences exist between the submarine hot springwater, local land hot springwaters, groundwater, and local seawater. SiO 2 , HCO 3 , Ca, K, Li, B, Ba, Rb, Fe, Mn, As, and Zn are enriched in the submarine hot springwater, while Cl, Na, So 4 2 , Mg, Cu, Ni, Cd, Cr, and perhaps Pb are depleted in relation to average and local seawater values. Very high temperatures, at the hydrothermal vents, have been recorded (102 0 C at 4-atm pressure). Visible gaseous emanations rich in CH 4 and N 2 coexist with the hydrothermal solutions. Metalliferous deposits, pyrite, have been encountered with high concentrations of Fe, S, Si, Al, Mn, Ca, and the volatile elements As, Hg, Sb, and Tl, X ray dispersive spectrometry (1500-ppm detection limit). X ray diffraction, and scanning electron microscopy of the isolated metalliferous precipitates indicate that the principal products of precipitation are pyrite and gypsum accompanied by minor amounts of amorphous material containing Si and Al. Chemical analyses and XRD of the reference control rocks of the locality (volcanics) versus the hydrothermally altered rocks indicate that high-temperature and high-pressure water-rock interactions can in part explain the water chemistry characteristics of the submarine hydrothermal waters. Their long residence time, the occurrence of an extensive marine sedimentary formation, their association with CH 4 and their similarities with connate waters of oil and gas fields suggest that another component of their genesis could be in cation exchange reactions within deeply buried sediments of marine origin

  19. Geologic evolution of the Lost City Hydrothermal Field

    Science.gov (United States)

    Denny, Alden R.; Kelley, Deborah S.; Früh-Green, Gretchen L.

    2016-02-01

    The Lost City Hydrothermal Field (LCHF) is a novel serpentinite-hosted vent field located on the Atlantis Massif southern wall. Results of 2 m resolution bathymetry, side scan, and video and still imagery, integrated with direct submersible observations provide the first high-resolution geologic map of the LCHF. These data form the foundation for an evolutionary model for the vent system over the past >120,000 years. The field is located on a down-dropped bench 70 m below the summit of the massif. The bench is capped by breccia and pelagic carbonate deposits underlain by variably deformed and altered serpentinite and gabbroic rocks. Hydrothermal activity is focused at the 60 m tall, 100 m across, massive carbonate edifice "Poseidon," which is venting 91°C fluid. Hydrothermal activity declines south and west of the Poseidon complex and dies off completely at distances greater than 200 m. East of Poseidon, the most recent stage of hydrothermal flow is characterized by egress of diffuse fluids from narrow fissures within a low-angle, anastomosing mylonite zone. South of the area of current hydrothermal activity, there is evidence of two discrete previously unrecognized relict fields. Active venting sites defined by carbonate-filled fissures that cut the carbonate cap rock at the summit of the massif mark the present-day northernmost extent of venting. These spatial relationships reflect multiple stages of field development, the northward migration of venting over time, and the likely development of a nascent field at the massif summit.

  20. Duration of hydrothermal treatment and peeling of 'Murcott' tangor

    Directory of Open Access Journals (Sweden)

    Ana Luiza Pinheiro

    2011-12-01

    Full Text Available Hydrothermal treatment facilitates the peeling of 'Pera' sweet orange fruit and does not alter its quality. The aim of this work was to adapt the technology of peeling for the use of hydrothermal treatment in 'Murcott' tangor and to evaluate its influence in the CO2 production and the physicochemical, microbiologic and sensorial characteristics of fruits. The peeling time, the yield of marketable fruits and the internal temperature of fruits during the treatment were also evaluated. The hydrothermal treatment consisted of placing the fruits in a water-bath at 50 ºC for 5, 10, 15, 20, 25 and 30 min. Fruits were peeled by first opening a gap in the peduncle region with a knife and then manually removing the flavedo and albedo. Fruits were stored at 5 ºC for six days. Hydrothermal treatment caused changes in the fruits' CO2 production for only the first few hours after processing. Internal fruit temperature after 30 min of treatment reached 35 ºC. There were no changes in the physicochemical and microbiologic characteristics of the fruits. The treatment did not change the flavor, improved the fruits' appearance, decreased the peeling time of the treated fruits by 57 % and increased the yield of marketable fruits. In conclusion, the hydrothermal treatment accomplished from 5 to 30 min at 50 ºC can be used as part of the peeling process for 'Murcott' tangor.

  1. Hydrothermal chimneys and Sulphide mineralised breccias from the Kolbeinsey and the Mohns Ridge

    Science.gov (United States)

    Nygård, T. E.; Bjerkgård, T.; Kelly, D.; Thorseth, I.; Pedersen, R. B.

    2003-04-01

    An inactive hydrothermal ventsite was discovered at the Kolbeinsey Ridge, (68^o56'N,17^o12'W) during the SUBMAR-99 cruise. The field is located in the neovolcanic sone at the flat top of a circular volcano at 900 m water depth. Two major fields contain about 30 chimneys. The top of one chimney was collected for further research. The mineralogy of the chimney is dominated by sphalerite, silica and barite, with minor amounts of galena and pyrrhotite, an assemblage which suggest a formation temperature white smokers [1]. The outer part of the chimney is enriched in LREE and shows a large positive Eu-anomaly compared to the inner parts of the chimney. Variation in Ce-anomaly reflects varying degrees of seawater infiltration during mineral precipitation. The first formed minerals in the lower part, and the outer part of the chimney appears to contain the most seawater-affected minerals. The Ag content of sphalerite may be as high as 1 wt%, but is restricted to small domains especially around fluid channels. A zonation in the Fe/Zn ratio of sphalerite is observed across fluid channels, suggesting variations in the fluid composition with time. The Pb-content of the chimney is extremely high, with up to 10 wt% in some sphalerite grains, and the bulk values are as high as 10 000 ppm. These high values suggest that sediments may have been present in the reaction zone of this hydrothermal system. Sulphide mineralised breccias were recovered by dredging the northern fault wall of the Mohns Ridge at 72^o39,33'N, 02^o40,87'E, during the SUBMAR-2000 cruise. The breccias exhibit several progressive stages of hydrothermal alteration: 1) the least altered parts are composed of partly altered basalt clasts and some chlorite, 2) more strongly altered samples mainly consist of quarts in a chlorite matrix, 3) and the most heavily mineralised parts contain secondary quarts and chalcopyrite. The final hydrothermal stage recorded by the breccias involved oxidation of chalcopyrite and

  2. The Influence Of Hydrothermal Alteration And Weathering On Rock Magnetic Properties Of Granites From The Eps-1 Drilling (soultz-sous-forÊts / France)

    Science.gov (United States)

    Just, J.; Schleicher, A.; Kontny, A.; de Wall, H.

    The EPS-1 drilling in Soultz-sous-Forêts (Rhinegraben, France) recovered a core pro- file of Tertiary to Permo-Mesozoic sediments deposited on a Variscan granitic base- ment. Magnetic susceptibility (k) measurements on the core material revealed a con- tinous increase from the basement/cover boundary (kmean 0.4 x 10-3 SI) into the magnetite-bearing granite (kmean 13 x 10-3 SI) over a depth range of 1417 U 1555 m. Rock magnetic and mineralogic studies were performed for the fresh granite, the hydrothermally altered granite near a fault zone and the altered granite from the fossil land surface near the basement/cover boundary. The decrease in susceptibility can be correlated with a gradual decomposition of magnetite to hematite and an alteration of the matrix minerals feldspars, biotite and hornblende to clay minerals and carbon- ates. Along with this transition, characteristic rock magnetic signatures can be dis- criminated for different degrees of alteration. While temperature-dependent magnetic susceptibility k(T)-curves in fresh granites indicate a typical multidomain magnetite course with good reversibility, different types of irreversible courses are observed for the altered granite. However, hematite could not be identified in the k(T)-curves. Al- tered granite shows relatively weak magnetic behaviour in AF-demagnetisation exper- iments, untypical for hematite. The alteration of the fresh granite also causes a change in magnetic fabric parameter, especially of the anisotropy factor. The magnetic min- eralogy from the altered granite in respect to the changes in rock magnetic properties will be discussed.

  3. Tracking Hydrothermal Fluid Pathways from Surface Alteration Mineralogy: The Case of Licancura Geothermal Field, Northern Chile

    Science.gov (United States)

    Camus, E.; Elizalde, J. D.; Morata, D.; Wechsler, C.

    2017-12-01

    In geothermal systems alteration minerals are evidence of hot fluid flow, being present even in absence of other surface manifestations. Because these minerals result from the interaction between geothermal fluids and surrounding host rocks, they will provide information about features of thermal fluids as temperature, composition and pH, allowing tracking their changes and evolution. In this work, we study the Licancura Geothermal field located in the Andean Cordillera in Northern Chile. The combination of Principal Components Analysis on ASTER-L1T imagery and X Ray Diffraction (XRD) allow us to interpret fluid conditions and the areas where fluid flow took place. Results from red, green, blue color composite imagery show the presence of three types of secondary paragenesis. The first one corresponds to hematite and goethite, mainly at the east of the area, in the zone of eroded Pliocene volcanic edifices. The second one, mainly at the center of the area, highlighting propylitic alteration, includes minerals such as chlorite, illite, calcite, zeolites, and epidote. The third paragenesis, spatially related to the intersection between faults, represents advanced argillic alteration, includes minerals as alunite, kaolinite, and jarosite. XRD analysis support results from remote sensing techniques. These results suggest an acid pH hydrothermal fluid reaching temperatures at surface up to 80-100°C, which used faults as a conduit, originating advanced argillic minerals. The same fluid was, probably, responsible for propylitic paragenesis. However, iron oxides paragenesis identified in the area of eroded volcanoes probably corresponds to other processes associated with weathering rather than geothermal activity. In this work, we propose the applicability of remote sensing techniques as a first level exploration tool useful for high-altitude geothermal fields. Detailed clay mineral studies (XRD and SEM) would allow us to a better characterization of the geothermal fluid

  4. 87Sr/86Sr ratios in hydrothermal waters and deposits from the east pacific rise at 210N

    International Nuclear Information System (INIS)

    Albarede, F.; Michard, A.; Minster, J.F.; Michard, G.

    1981-01-01

    87 Sr/ 86 Sr ratios of three hydrothermal waters collected on the East Pacific Rise at 21 0 N define a mixing line between seawater and a hydrothermal end-member at 0.7030 which is derived by seawater-basalt interaction at ca. 350 0 C and water/rock ratio of about 1.5. Sr concentrations are not affected in the process while Mg uptake from seawater is almost complete. Up to 2/3 of this hydrothermal component is involved in anhydrite precipitation while the Sr isotopic ratio in sulfides (chalcopyrite + sphalerite) cannot be distinguished from that of sulfate. It is estimated that ca. 1 x 10 10 moles of strontium are yearly cycled in the hydrothermal systems of mid-oceanic ridges, thereby affecting the 87 Sr/ 86 Sr budget of seawater. Mass balance between river runoff, limestone precipitation and ridge basalt alteration suggests that the 87 Sr/ 86 Sr ratios of the river runoff are in the range 0.7097-0.7113, and are largely dominated by limestone alteration. (orig.)

  5. Alteration zone Mapping in the Meiduk and Sar Cheshmeh Porphyry Copper Mining Districts of Iran using Advanced Land Imager (ALI Satellite Data

    Directory of Open Access Journals (Sweden)

    A. Beiranvand Pour

    2015-10-01

    Full Text Available This study evaluates the capability of Earth Observing-1 (EO1 Advanced Land Imager (ALI data for hydrothermal alteration mapping in the Meiduk and Sar Cheshmeh porphyry copper mining districts, SE Iran. Feature-oriented principal components selection, 4/2, 8/9, 5/4 band ratioing were applied to ALI data for enhancing the hydrothermally altered rocks associated with porphyry copper mineralization, lithological units and vegetation. Mixture-tuned matched-filtering (MTMF was tested to discriminate the hydrothermal alteration areas of porphyry copper mineralization from surrounding environment using the shortwave infrared bands of ALI. Results indicate that the tested methods are able to yield spectral information for identifying vegetation, iron oxide/hydroxide and clay minerals, lithological units and the discrimination of hydrothermally altered rocks from unaltered rocks using ALI data.

  6. Development of a mixed seawater-hydrothermal fluid geochemical signature during alteration of volcanic rocks in the Archean (∼2.7 Ga) Abitibi Greenstone Belt, Canada

    Science.gov (United States)

    Brengman, Latisha A.; Fedo, Christopher M.

    2018-04-01

    We investigated a group of silicified volcanic rocks from the ∼2.72 Ga Hunter Mine Group (HMG), Abitibi Greenstone Belt, Canada, in order to document progressive compositional change associated with alteration in a subaqueous caldera system. Rocks of the HMG divide into three groups based on mineralogy and texture for petrographic and geochemical analyses. Volcanic features (phenocrysts, pseudomorphs after primary glass shards, lapilli, volcanic clasts) are preserved in all groups, despite changing mineralogy from primarily quartz, feldspar, chlorite (Groups 1 and 2), to quartz, hematite and carbonate (Groups 2 and 3). Compositionally, Group 1 rocks resemble volcanic rocks in the region, while Group 2 and 3 rocks show a change in mineralogy to iron, silica, and carbonate minerals, which is associated with depletion of many major and trace elements associated with volcanic rocks (Al2O3, Na2O, K2O, Zr). In addition, rare earth elements display a clear progression from volcanic signatures in Group 1 (PrSN/YbSN = 1.7-2.96, EuSN/EuSN∗ = 0.84-1.72, Y/Ho = 25.20-27.41, LaSN/LaSN∗ = 0.97-1.29, and Zr/Hf = 38.38-42.09) to transitional mixed volcanic, hydrothermal, and seawater signatures in Group 2 (PrSN/YbSN 1.33-2.89, EuSN/EuSN∗ 1.33-2.5, Y/Ho = 23.94-30, LaSN/LaSN∗ 0.93-1.34, and Zr/Hf = 40-70), to mixed hydrothermal and seawater signatures in Group 3 (PrSN/YbSN 0.62-2.88, EuSN/EuSN∗ 1.30-7.15, LaSN/LaSN∗ 1.02-1.86, Y/Ho = 25.56-55, and Zr/Hf = 35-50). We interpret that silicification of volcanic rocks (Group 1) produced transitional altered volcanic rocks (Group 2), and siliceous and jaspilitic rocks (Group 3), based on preservation of delicate volcanic features. Building on this explanation, we interpret that major, trace- and rare-earth element mobility occurred during the process of silicification, during which siliceous and jaspilitic rocks (Group 3) acquired aspects of the rare-earth element geochemical signatures of marine chemical precipitates. We

  7. Hydrothermal surface alteration in the Copahue Geothermal Field (Argentina)

    Energy Technology Data Exchange (ETDEWEB)

    Mas, Graciela R.; Mas, Luis C.; Bengochea, Leandro

    1996-01-24

    In the area of the Copahue Geothermal Field, there are five active geothermal manifestations, which mainly consist of fumaroles, hot springs and mud pots. Four of these manifestations are located in Argentina: Las Máquinas, Termas de Copahue, Las Maquinitas and El Anfiteatro, and the fifth on the Chilean side: Chancho Co. All of them present a strong acid sulfate country rock alteration, characterized by the assemblage alunite + kaolinite + quartz + cristobalite + pyrite + sulfur + jarosite, as the result of the base leaching by fluids concentrated in H2SO4 by atmospheric oxidation at the water table in a steam heated environment of H2S released by deeper boiling fluids. Another alteration zone in this area, called COP-2, is a fossil geothermal manifestation which shows characteristics of neutral to alkaline alteration represented mainly by the siliceous sinter superimposed over the acid alteration. The mineralogy and zoning of these alteration zones, and their relation with the hidrothermal solutions and the major structures of the area are analized.

  8. Hydrothermal behaviors and long-term stability of bentonitic buffer material

    International Nuclear Information System (INIS)

    Lee, Jae Owan; Cho, Won Jin

    2007-01-01

    In hydrothermal reaction tests, smectite-to-illite conversion was identified using a domestic bentonite which is favorably considered as a buffer material, and its dependency on various hydrothermal conditions was investigated. The analysis results of the XRD and Si concentration indicated that the smectite-to- illite conversion was a major process of bentonite alteration under the hydrothermal conditions. The temperature, potassium concentration in solution, and pH were observed to significantly affect the smectite-to illite conversion. A model of conversion reaction rate was suggested evaluate the long-term stability of smectite composing a major constituent of bentonitic buffer. It was expected from the evaluation results that the smectite would keep its integrity for very long disposal time under a normal condition, while as it might be converted to illite by 50 percent after over 5 x 10 4 year of disposal time under a conservative condition and consequently lose its swelling capacity as a buffer material of a repository

  9. Three-dimensional geophysical mapping of shallow water saturated altered rocks at Mount Baker, Washington: Implications for slope stability

    Science.gov (United States)

    Finn, Carol A.; Deszcz-Pan, Maryla; Ball, Jessica L.; Bloss, Benjamin J.; Minsley, Burke J.

    2018-05-01

    Water-saturated hydrothermal alteration reduces the strength of volcanic edifices, increasing the potential for catastrophic sector collapses that can lead to far traveled and destructive debris flows. Intense hydrothermal alteration significantly lowers the resistivity and magnetization of volcanic rock and therefore hydrothermally altered rocks can be identified with helicopter electromagnetic and magnetic measurements. Geophysical models constrained by rock properties and geologic mapping show that intensely altered rock is restricted to two small (500 m diameter), >150 m thick regions around Sherman Crater and Dorr Fumarole Field at Mount Baker, Washington. This distribution of alteration contrasts with much thicker and widespread alteration encompassing the summits of Mounts Adams and Rainier prior to the 5600 year old Osceola collapse, which is most likely due to extreme erosion and the limited duration of summit magmatism at Mount Baker. In addition, the models suggest that the upper 300 m of rock contains water which could help to lubricate potential debris flows. Slope stability modeling incorporating the geophysically modeled distribution of alteration and water indicates that the most likely and largest ( 0.1 km3) collapses are from the east side of Sherman Crater. Alteration at Dorr Fumarole Field raises the collapse hazard there, but not significantly because of its lower slope angles. Geochemistry and analogs from other volcanoes suggest a model for the edifice hydrothermal system.

  10. Three-dimensional geophysical mapping of shallow water saturated altered rocks at Mount Baker, Washington: Implications for slope stability

    Science.gov (United States)

    Finn, Carol A.; Deszcz-Pan, Maria; Ball, Jessica L.; Bloss, Benjamin J.; Minsley, Burke J.

    2018-01-01

    Water-saturated hydrothermal alteration reduces the strength of volcanic edifices, increasing the potential for catastrophic sector collapses that can lead to far traveled and destructive debris flows. Intense hydrothermal alteration significantly lowers the resistivity and magnetization of volcanic rock and therefore hydrothermally altered rocks can be identified with helicopter electromagnetic and magnetic measurements. Geophysical models constrained by rock properties and geologic mapping show that intensely altered rock is restricted to two small (500 m diameter), >150 m thick regions around Sherman Crater and Dorr Fumarole Field at Mount Baker, Washington. This distribution of alteration contrasts with much thicker and widespread alteration encompassing the summits of Mounts Adams and Rainier prior to the 5600 year old Osceola collapse, which is most likely due to extreme erosion and the limited duration of summit magmatism at Mount Baker. In addition, the models suggest that the upper ~300 m of rock contains water which could help to lubricate potential debris flows. Slope stability modeling incorporating the geophysically modeled distribution of alteration and water indicates that the most likely and largest (~0.1 km3) collapses are from the east side of Sherman Crater. Alteration at Dorr Fumarole Field raises the collapse hazard there, but not significantly because of its lower slope angles. Geochemistry and analogs from other volcanoes suggest a model for the edifice hydrothermal system.

  11. Hydrothermal plumes over spreading-center axes: Global distributions and geological inferences

    Science.gov (United States)

    Baker, Edward T.; German, Christopher R.; Elderfield, Henry

    Seafloor hydrothermal circulation is the principal agent of energy and mass exchange between the ocean and the earth's crust. Discharging fluids cool hot rock, construct mineral deposits, nurture biological communities, alter deep-sea mixing and circulation patterns, and profoundly influence ocean chemistry and biology. Although the active discharge orifices themselves cover only a minuscule percentage of the ridge-axis seafloor, the investigation and quantification of their effects is enhanced as a consequence of the mixing process that forms hydrothermal plumes. Hydrothermal fluids discharged from vents are rapidly diluted with ambient seawater by factors of 104-105 [Lupton et al., 1985]. During dilution, the mixture rises tens to hundreds of meters to a level of neutral buoyancy, eventually spreading laterally as a distinct hydrographic and chemical layer with a spatial scale of tens to thousands of kilometers [e.g., Lupton and Craig, 1981; Baker and Massoth, 1987; Speer and Rona, 1989].

  12. Investigations of alteration zones based on fluid inclusion microthermometry at Sungun porphyry copper deposit, Iran

    Directory of Open Access Journals (Sweden)

    Omid ASGHARI

    2010-06-01

    Full Text Available The Sungun porphyry copper deposit is located in East Azerbaijan, NW of Iran. The porphyries occur as stocks and dikes ranging in composition from quartz monzodiorite to quartz monzonite. Four types of hypogene alteration are developed; potassic, phyllic, propylitic and argillic. Three types of fluid inclusions are typically observed at Sungun; (1 vapor-rich, (2 liquid-rich and (3 multi-phase. Halite is the principal solid phase in the latter. The primary multiphase inclusions within the quartz crystals were chosen for micro-thermometric analyses and considered to calculate the geological pressure and hydrothermal fluid density. In potassic zone, the average of homogenization temperature is 413.6 °C while in phyllic alteration, 375.9 °C. As expected in potassic alteration, the temperature of hydrothermal solutions is higher than that in the phyllic zone. The salinity of the hydrothermal fluids has a high coherency with homogenization temperature, so the average of salinity in potassic samples is 46.3 (wt% NaCl which is higher than phyllic samples. Based on the location of potassic alteration, as expected, the lithostatic pressure is much more than the phyllic one. Finally, the average density of hydrothermal fluids in the potassically altered samples is 1.124 (gr/cm3 which is higher than the ones in phyllic zone (1.083 gr/cm3 .

  13. Report on static hydrothermal alteration studies of Topopah Spring tuff waters in J-13 water at 150{sup 0}C

    Energy Technology Data Exchange (ETDEWEB)

    Knauss, K.G.; Beiriger, W.B.

    1984-08-31

    This report presents the results of preliminary experimental work done to define the package environment in a potential nuclear waste repository in the Topopah Spring Member of the Paintbrush Tuff. The work is supported by the Nevada Nuclear Waste Storage Investigations (NNWSI) Project as a part of the Waste Package task to design a package suitable for waste storage within volcanic units at the Nevada Test Site. Static hydrothermal alteration experiments were run for 4 months using polished wafers either fully submerged in an appropriate natural ground water or exposed to water-saturated air with enough excess water to allow refluxing. The aqueous results agreed favorably with similar experiments run using crushed tuff, and the use of solid polished wafers allowed us to directly evaluate the effects of reaction on the tuff. The results are preliminary in the sense that these experiments were run in Teflon-lined, static autoclaves, whereas subsequent experiments have been run in Dickson-type gold-cell rocking autoclaves. The results predict relatively minor changes in water chemistry, very minor alteration of the host rock, and the production of slight amounts of secondary minerals, when liquid water could return to the rock pores following the temperature maximum during the thermal period. 7 references, 16 figures, 10 tables.

  14. The chemistry of hydrothermal magnetite: a review

    Science.gov (United States)

    Nadoll, Patrick; Angerer, Thomas; Mauk, Jeffrey L.; French, David; Walshe, John

    2014-01-01

    Magnetite (Fe3O4) is a well-recognized petrogenetic indicator and is a common accessory mineral in many ore deposits and their host rocks. Recent years have seen an increased interest in the use of hydrothermal magnetite for provenance studies and as a pathfinder for mineral exploration. A number of studies have investigated how specific formation conditions are reflected in the composition of the respective magnetite. Two fundamental questions underlie these efforts — (i) How can the composition of igneous and, more importantly, hydrothermal magnetite be used to discriminate mineralized areas from barren host rocks, and (ii) how can this assist exploration geologists to target ore deposits at greater and greater distances from the main mineralization? Similar to igneous magnetite, the most important factors that govern compositional variations in hydrothermal magnetite are (A) temperature, (B) fluid composition — element availability, (C) oxygen and sulfur fugacity, (D) silicate and sulfide activity, (E) host rock buffering, (F) re-equilibration processes, and (G) intrinsic crystallographic controls such as ionic radius and charge balance. We discuss how specific formation conditions are reflected in the composition of magnetite and review studies that investigate the chemistry of hydrothermal and igneous magnetite from various mineral deposits and their host rocks. Furthermore, we discuss the redox-related alteration of magnetite (martitization and mushketovitization) and mineral inclusions in magnetite and their effect on chemical analyses. Our database includes published and previously unpublished magnetite minor and trace element data for magnetite from (1) banded iron formations (BIF) and related high-grade iron ore deposits in Western Australia, India, and Brazil, (2) Ag–Pb–Zn veins of the Coeur d'Alene district, United States, (3) porphyry Cu–(Au)–(Mo) deposits and associated (4) calcic and magnesian skarn deposits in the southwestern United

  15. Subglacial drainage effects on surface motion on a small surge type alpine glacier on the St. Elias range, Yukon Territory, Canada.

    Science.gov (United States)

    Rada, C.; Schoof, C.; King, M. A.; Flowers, G. E.; Haber, E.

    2017-12-01

    Subglacial drainage is known to play an important role in glacier dynamics trough its influence on basal sliding. However, drainage is also one of the most poorly understood process in glacier flow due to the difficulties of observing, identifying and modeling the physics involved. In an effort to improve understanding of subglacial processes, we have monitored a small, approximately 100 m thick surge-type alpine glacier for nine years. Over 300 boreholes were instrumented with pressure transducers over a 0.5 km² in its upper ablation area, in addition to a weather station and a permanent GPS array consisting on 16 dual-frequency receivers within the study area. We study the influence of the subglacial drainage system on the glacier surface velocity. However, pressure variations in the drainage system during the melt season are dominated by diurnal oscillations.Therefore, GPS solutions have to be computed at sub-diurnal time intervals in order to explore the effects of transient diurnal pressure variations. Due to the small displacements of the surface of the glacier over those periods (4-10 cm/day), sub-diurnal solutions are dominated by errors, making it impossible to observe the diurnal variations in glacier motion. We have found that the main source of error is GPS multipath. This error source does largely cancel out when solutions are computed over 24 hour periods (or more precisely, over a sidereal day), but solution precisions decrease quickly when computed over shorter periods of time. Here we present an inverse problem approach to remove GPS multipath errors on glaciers, and use the reconstructed glacier motion to explore how the subglacial drainage morphology and effective pressure influence glacier dynamics at multiple time scales.

  16. Subglacial bed conditions during Late Pleistocene glaciations and their impact on ice dynamics in the southern North Sea

    NARCIS (Netherlands)

    Passchier, S.; Laban, C.; Mesdag, C.S.; Rijsdijk, K.F.

    2010-01-01

    Changes in subglacial bed conditions through multiple glaciations and their effect on ice dynamics are addressed through an analysis of glacigenic sequences in the Upper Pleistocene stratigraphy of the southern North Sea basin. During Elsterian (MIS 12) ice growth, till deposition was subdued when

  17. Oxygen isotope mapping and evaluation of paleo-hydrothermal systems associated with synvolcanic intrusion and VMS deposits

    International Nuclear Information System (INIS)

    Taylor, B.E

    2001-01-01

    Whole-rock oxygen isotope mapping provides a useful method for the delineation and quantitative evaluation of paleo-hydrothermal systems associated with syn-volcanic intrusions and volcanic-associated massive sulfide (VMS) deposits. During the course of a four-year study of regional alteration systems associated with VMS Deposits, four syn-volcanic intrusive complexes in Canada were mapped using stable isotope techniques. The complexes included Noranda, Quebec; Clifford-Ben Nevis, Ontario; Snow Lake, Manitoba, and Sturgeon Lake, Ontario. This study was regional in extent, involving large areas and large numbers of whole-rock samples: Noranda (625 km 2 ;≥600 samples, plus others (total = 1198); Sturgeon Lake (525 km 2 ; 452 samples); Clifford-Ben Nevis (160 km 2 ; 251 samples); and Snow Lake (84 km 2 ; 575 samples). Isotopic data on whole-rock carbonates and hydrous minerals were also collected. The regional isotopic studies were carried out in concert with other studies on mineral assemblages and mineral composition, and on associated intrusive and extrusive rocks. The Clifford-Ben Nevis area was selected as a control area, in as much as it contains no known VMS deposits; all other areas are well-known, productive VMS districts. Oxygen isotope maps are, in a sense, thermal maps, illustrating the paleo-distribution of heat and fluids, and offering a potential aid to exploration. The isotopic data may be contoured to reveal zones of 18 O depletion and enrichment, relative to unaltered rocks. Zones of δ 18 O≤60% comprise rocks that have reacted with seawater at high (e.g., 300+ o C) temperatures. The volume of foot-wall rocks isotopically-depleted by water/rock interaction during the life of one or more episodes of submarine hydrothermal activity is proportional to the amount of heat available from the syn-volcanic intrusive center. These altered rocks comprise the reaction zone often inferred to have supplied metals and other constituents for the VMS deposits

  18. Disseminated sulphides in basalts from the northern central Indian ridge: Implications on late-stage hydrothermal activity

    Digital Repository Service at National Institute of Oceanography (India)

    Banerjee, R.; Ray, D.

    interplay between oceanic crust fractur- ing due to tectonically active megamullions and subsequent hydrothermal alteration, accounting for the formation of dis- seminated sulphides at the NCIR. In a novel attempt, this study examines the mineralogy... of samples. Instead, the dark greyish coloured altered basalts, frequently fractured and often with a greenish tint, dominate the assemblage. Specks of sulphides are un- evenly distributed in these altered basalts as disseminated grains or fine stringers...

  19. Thin-layer effects in glaciological seismic amplitude-versus-angle (AVA analysis: implications for characterising a subglacial till unit, Russell Glacier, West Greenland

    Directory of Open Access Journals (Sweden)

    A. D. Booth

    2012-08-01

    Full Text Available Seismic amplitude-versus-angle (AVA methods are a powerful means of quantifying the physical properties of subglacial material, but serious interpretative errors can arise when AVA is measured over a thinly-layered substrate. A substrate layer with a thickness less than 1/4 of the seismic wavelength, λ, is considered "thin", and reflections from its bounding interfaces superpose and appear in seismic data as a single reflection event. AVA interpretation of subglacial till can be vulnerable to such thin-layer effects, since a lodged (non-deforming till can be overlain by a thin (metre-scale cap of dilatant (deforming till. We assess the potential for misinterpretation by simulating seismic data for a stratified subglacial till unit, with an upper dilatant layer between 0.1–5.0 m thick (λ / 120 to > λ / 4, with λ = 12 m. For dilatant layers less than λ / 6 thick, conventional AVA analysis yields acoustic impedance and Poisson's ratio that indicate contradictory water saturation. A thin-layer interpretation strategy is proposed, that accurately characterises the model properties of the till unit. The method is applied to example seismic AVA data from Russell Glacier, West Greenland, in which characteristics of thin-layer responses are evident. A subglacial till deposit is interpreted, having lodged till (acoustic impedance = 4.26±0.59 × 106 kg m−2 s−1 underlying a water-saturated dilatant till layer (thickness < 2 m, Poisson's ratio ~ 0.5. Since thin-layer considerations offer a greater degree of complexity in an AVA interpretation, and potentially avoid misinterpretations, they are a valuable aspect of quantitative seismic analysis, particularly for characterising till units.

  20. Uranium metallogenesis of the peraluminous leucogranite from the Pontivy-Rostrenen magmatic complex (French Armorican Variscan belt): the result of long-term oxidized hydrothermal alteration during strike-slip deformation

    Science.gov (United States)

    Ballouard, C.; Poujol, M.; Mercadier, J.; Deloule, E.; Boulvais, P.; Baele, J. M.; Cuney, M.; Cathelineau, M.

    2018-06-01

    In the French Armorican Variscan belt, most of the economically significant hydrothermal U deposits are spatially associated with peraluminous leucogranites emplaced along the south Armorican shear zone (SASZ), a dextral lithospheric scale wrench fault that recorded ductile deformation from ca. 315 to 300 Ma. In the Pontivy-Rostrenen complex, a composite intrusion, the U mineralization is spatially associated with brittle structures related to deformation along the SASZ. In contrast to monzogranite and quartz monzodiorite (3 3), the leucogranite samples are characterized by highly variable U contents ( 3 to 27 ppm) and Th/U ratios ( 0.1 to 5) suggesting that the crystallization of magmatic uranium oxide in the more evolved facies was followed by uranium oxide leaching during hydrothermal alteration and/or surface weathering. U-Pb dating of uranium oxides from the deposits reveals that they mostly formed between ca. 300 and 270 Ma. In monzogranite and quartz monzodiorite, apatite grains display magmatic textures and provide U-Pb ages of ca. 315 Ma reflecting the time of emplacement of the intrusions. In contrast, apatite grains from the leucogranite display textural, geochemical, and geochronological evidences for interaction with U-rich oxidized hydrothermal fluids contemporaneously with U mineralizing events. From 300 to 270 Ma, infiltration of surface-derived oxidized fluids leached magmatic uranium oxide from fertile leucogranite and formed U deposits. This phenomenon was sustained by brittle deformation and by the persistence of thermal anomalies associated with U-rich granitic bodies.

  1. Experimental hydrothermal alteration of crystalline and radiation-damaged pyrochlore

    International Nuclear Information System (INIS)

    Geisler, T.; Seydoux-Guillaume, A.-M.; Poeml, P.; Golla-Schindler, U.; Berndt, J.; Wirth, R.; Pollok, K.; Janssen, A.; Putnis, A.

    2005-01-01

    We have performed hydrothermal experiments with a crystalline microlite and a heavily self-irradiation-damaged (i.e., X-ray amorphous) betafite in a solution containing 1 mol/l HCl and 1 mol/l CaCl 2 at 175 deg. C for 14 days. The well-crystalline microlite grains were partly (∼5-10 μm rim) replaced by a Ca and Na-poorer, defect pyrochlore phase with a larger unit-cell and a sharp chemical gradient at the interface (on a nm scale) to the unreacted core. The amorphous betafite grains (up to ∼2 mm in diameter), on the other hand, were completely transformed into an intergrowth of different crystalline phases (polycrystalline anatase and rutile, a yet unidentified Nb-Ta oxide, and a Y-REE phase), showing complex non-equilibrium structures. Our experimental observations bear a remarkable resemblance to those made on natural samples. They indicate that the processes of the fluid-pyrochlore interaction are influenced by self-irradiation structural damage and that thermodynamic equilibrium models can hardly be applied to adequately describe such systems

  2. Redistribution of strontium and cesium during alteration of smectite to illite

    International Nuclear Information System (INIS)

    Ohnuki, Toshihiko; Murakami, Takashi; Sato, Tsutomu; Isobe, Hiroshi

    1994-01-01

    The redistribution of strontium and cesium during the alteration of smectite to illite has been studied under hydrothermal conditions at 200 C using solutions of 1x10 -4 M Sr and Cs. Two different sorption conditions were applied for the hydrothermal experiments. One was the condition in which strontium and cesium were sorbed by smectite before the hydrothermal experiments (dynamic condition). The other was the condition in which strontium and cesium were sorbed by the alteration products, illite/smectite (I/S) interstratified minerals after the hydrothermal experiments (static condition). The sorption characteristics of strontium and cesium by smectite, I/S interstratified minerals were examined by a sequential extraction method. Most of the strontium was desorbed from smectite and the I/S interstratified minerals with a 1 M KCl solution under both the dynamic and static conditions. Less than 1% of cesium was desorbed from the I/S interstratified minerals with any solution of a 1 M KCl, a 1 M HCl and a 6 M HCl under the dynamic condition, while most of cesium was desorbed with either solution of a 1 M KCl and 1 M HCl from smectite and from the I/S interstratified minerals under the static condition. These suggest that cesium sorbed by smectite changes its sorption characteristic during the alteration process, but strontium does not. Possible sites for more strongly bounded cesium to the I/S interstratified minerals may be at the 'ditrigonal cavity' of adjacent tetrahedral layers. (orig.)

  3. Exploration of Gamburtsev Subglacial Mountains, East Antarctica: Background and Plans for the Near Future

    Science.gov (United States)

    Talalay, Pavel; Sun, Youhong; Zhao, Yue; Li, Yuansheng; Cao, Pinlu; Xu, Huiwen; Zheng, Zhichuan; Wang, Rusheng; Zhang, Nan; Markov, Alexey; Yu, Dahui; Fan, Xiaopeng; Hu, Zhengyi; Yang, Cheng; Gong, Da; Hong, Jialing; Liu, Chunpeng; Han, Junjie; Yu, Chengfeng; Wang, Lili

    2014-05-01

    The Gamburtsev Subglacial Mountains (GSM), located in the central part of East Antarctica, were discovered by the Soviet team of the 3rd Complex Antarctic Expedition in 1958-1959. The GSM has highly dissected Alpine topography reaching maximum elevations of 3000 m and are completely covered by over 600 m of ice and snow. The mechanism driving uplift of the young-shaped GSM in the middle of the old East Antarctic Shield is unknown. With only limited constraints available on the topography, geology, and lithospheric structure, the origin of the GSM has been a matter of considerable speculation. The latest interpretation suggested that the GSM were formed during Permian and Cretaceous (roughly 250-100 Ma ago) due to the combination of rift-flank uplift, root buoyancy and the isostatic response. Later on, the Antarctic Ice Sheet covered the range and protected it from erosion. However, this theory cannot explain lack of erosion process during many millions years in between uplifting and beginning of glaciation. The next step of the GSM exploration focuses on the direct observation of ice sheet bed by drilling. In order to penetrate into subglacial bedrock in the GSM region the development activity already has been started in China. Drilling operations in Antarctica are complicated by extremely low temperature at the surface and within ice sheet, by ice flow, the absence of roads and infrastructures, storms, winds, snowfalls, etc. All that are the reasons that up to the present moment bedrock cores were never obtained at inland of Antarctica. It is proposed to use cable-suspended drilling technology in which an armored cable with a winch is used instead of a pipe-string to provide power to the down-hole motor system and to retrieve the down-hole unit. It is assumed to choose the drill site with the ice thickness at most of 1000 m and to pierce into the mountain slope to a depth of few meters. Proposed borehole construction includes five following steps: (1) dry core

  4. Integrating Data of ASTER and Landsat-8 OLI (AO for Hydrothermal Alteration Mineral Mapping in Duolong Porphyry Cu-Au Deposit, Tibetan Plateau, China

    Directory of Open Access Journals (Sweden)

    Tingbin Zhang

    2016-10-01

    Full Text Available One of the most important characteristics of porphyry copper deposits (PCDs is the type and distribution pattern of alteration zones which can be used for screening and recognizing these deposits. Hydrothermal alteration minerals with diagnostic spectral absorption properties in the visible and near-infrared (VNIR through the shortwave infrared (SWIR regions can be identified by multispectral and hyperspectral remote sensing data. Six Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER bands in SWIR have been shown to be effective in the mapping of Al-OH, Fe-OH, Mg-OH group minerals. The five VNIR bands of Landsat-8 (L8 Operational Land Imager (OLI are useful for discriminating ferric iron alteration minerals. In the absence of complete hyperspectral coverage area, an opportunity, however, exists to integrate ASTER and L8-OLI (AO to compensate each other’s shortcomings in covering area for mineral mapping. This study examines the potential of AO data in mineral mapping in an arid area of the Duolong porphyry Cu-Au deposit(Tibetan Plateau in China by using spectral analysis techniques. Results show the following conclusions: (1 Combination of ASTER and L8-OLI data (AO has more mineral information content than either alone; (2 The Duolong PCD alteration zones of phyllic, argillic and propylitic zones are mapped using ASTER SWIR bands and the iron-bearing mineral information is best mapped using AO VNIR bands; (3 The multispectral integration data of AO can provide a compensatory data of ASTER VNIR bands for iron-bearing mineral mapping in the arid and semi-arid areas.

  5. Subglacial Lake Vostok (Antarctica accretion ice contains a diverse set of sequences from aquatic, marine and sediment-inhabiting bacteria and eukarya.

    Directory of Open Access Journals (Sweden)

    Yury M Shtarkman

    Full Text Available Lake Vostok, the 7(th largest (by volume and 4(th deepest lake on Earth, is covered by more than 3,700 m of ice, making it the largest subglacial lake known. The combination of cold, heat (from possible hydrothermal activity, pressure (from the overriding glacier, limited nutrients and complete darkness presents extreme challenges to life. Here, we report metagenomic/metatranscriptomic sequence analyses from four accretion ice sections from the Vostok 5G ice core. Two sections accreted in the vicinity of an embayment on the southwestern end of the lake, and the other two represented part of the southern main basin. We obtained 3,507 unique gene sequences from concentrates of 500 ml of 0.22 µm-filtered accretion ice meltwater. Taxonomic classifications (to genus and/or species were possible for 1,623 of the sequences. Species determinations in combination with mRNA gene sequence results allowed deduction of the metabolic pathways represented in the accretion ice and, by extension, in the lake. Approximately 94% of the sequences were from Bacteria and 6% were from Eukarya. Only two sequences were from Archaea. In general, the taxa were similar to organisms previously described from lakes, brackish water, marine environments, soil, glaciers, ice, lake sediments, deep-sea sediments, deep-sea thermal vents, animals and plants. Sequences from aerobic, anaerobic, psychrophilic, thermophilic, halophilic, alkaliphilic, acidophilic, desiccation-resistant, autotrophic and heterotrophic organisms were present, including a number from multicellular eukaryotes.

  6. Effects of glacial/post-glacial weathering compared with hydrothermal alteration - implications for matrix diffusion. Results from drillcore studies in porphyritic quartz monzodiorite from Aespoe SE Sweden

    International Nuclear Information System (INIS)

    Landstroem, Ove; Tullborg, Eva-Lena

    2001-08-01

    The effects of hydrothermal + subsequent low temperature alteration and glacial/post-glacial weathering have been studied in two cores of quartz monzodiorite. One core (YA 1192) was drilled into the hydrothermally altered wall rock of a water-conducting fracture exposed at 170 m depth in the access tunnel to the Aespoe Hard Rock Laboratory. The other one (Bas 1) was drilled from an outcrop with a glacially polished surface, 1 km north of the YA 1192 site. Both drill cores were sectioned into mm-thick slices perpendicular to the core axis. The fracture filling of the YA 1192 core, the weathered surface of the BAS 1 core and the different slices were analysed for major and trace elements and isotopes of U and Th. The altered zone of the YA 1192 core extends to approx. 2.5 cm from the fracture surface. The alteration (mainly plagioclase → albite + sericite + epidote) has resulted in a higher porosity and formation of sorbing secondary minerals (e.g. sericite), favouring matrix diffusion. Increased Br concentrations in the altered zone are indicative of saline water in pores and micro fractures i.e. the presence of a diffusion medium. 234U/238U activity ratios > 1 and increased Cs in the altered zone are then interpreted as diffusion of U and Cs from fracture groundwater and subsequent sorption. The U migration is geologically recent (< 1 Ma). The 2.5 cm altered zone (corresponding to the zone of active matrix diffusion) significantly exceeds the visible red staining zone (0.5 cm) caused by hematite/FeOOH micrograins, emphasizing the need of microscopy to identify zones of alteration. The conspicuous weathering at the BAS 1 site is confined to a narrow rim of the bedrock surface (approx. 0.2-0.5 cm thick). Mass balance calculations for this rim (based on immobility of K) indicate that mechanical erosion has dominated over chemical dissolution processes (is roughly 10 times greater). The chemical weathering has affected mainly plagioclase and chlorite resulting in

  7. Sensitivity analysis for the coupling of a subglacial hydrology model with a 3D ice-sheet model.

    Science.gov (United States)

    Bertagna, L.; Perego, M.; Gunzburger, M.; Hoffman, M. J.; Price, S. F.

    2017-12-01

    When studying the movement of ice sheets, one of the most important factors that influence the velocity of the ice is the amount of friction against the bedrock. Usually, this is modeled by a friction coefficient that may depend on the bed geometry and other quantities, such as the temperature and/or water pressure at the ice-bedrock interface. These quantities are often assumed to be known (either by indirect measurements or by means of parameter estimation) and constant in time. Here, we present a 3D computational model for the simulation of the ice dynamics which incorporates a 2D model proposed by Hewitt (2011) for the subglacial water pressure. The hydrology model is fully coupled with the Blatter-Pattyn model for the ice sheet flow, as the subglacial water pressure appears in the expression for the ice friction coefficient, and the ice velocity appears as a source term in the hydrology model. We will present results on real geometries, and perform a sensitivity analysis with respect to the hydrology model parameters.

  8. Weathering of post-impact hydrothermal deposits from the Haughton impact structure: implications for microbial colonization and biosignature preservation.

    Science.gov (United States)

    Izawa, M R M; Banerjee, Neil R; Osinski, G R; Flemming, R L; Parnell, J; Cockell, C S

    2011-01-01

    Meteorite impacts are among the very few processes common to all planetary bodies with solid surfaces. Among the effects of impact on water-bearing targets is the formation of post-impact hydrothermal systems and associated mineral deposits. The Haughton impact structure (Devon Island, Nunavut, Canada, 75.2 °N, 89.5 °W) hosts a variety of hydrothermal mineral deposits that preserve assemblages of primary hydrothermal minerals commonly associated with secondary oxidative/hydrous weathering products. Hydrothermal mineral deposits at Haughton include intra-breccia calcite-marcasite vugs, small intra-breccia calcite or quartz vugs, intra-breccia gypsum megacryst vugs, hydrothermal pipe structures and associated surface "gossans," banded Fe-oxyhydroxide deposits, and calcite and quartz veins and coatings in shattered target rocks. Of particular importance are sulfide-rich deposits and their associated assemblage of weathering products. Hydrothermal mineral assemblages were characterized structurally, texturally, and geochemically with X-ray diffraction, micro X-ray diffraction, optical and electron microscopy, and inductively coupled plasma atomic emission spectroscopy. Primary sulfides (marcasite and pyrite) are commonly associated with alteration minerals, including jarosite (K,Na,H(3)O)Fe(3)(SO(4))(2)(OH)(6), rozenite FeSO(4)·4(H(2)O), copiapite (Fe,Mg)Fe(4)(SO(4))(6)(OH)(2)·20(H(2)O), fibroferrite Fe(SO(4))(OH)·5(H(2)O), melanterite FeSO(4)·7(H(2)O), szomolnokite FeSO(4)·H(2)O, goethite α-FeO(OH), lepidocrocite γ-FeO(OH) and ferrihydrite Fe(2)O(3)·0.5(H(2)O). These alteration assemblages are consistent with geochemical conditions that were locally very different from the predominantly circumneutral, carbonate-buffered environment at Haughton. Mineral assemblages associated with primary hydrothermal activity, and the weathering products of such deposits, provide constraints on possible microbial activity in the post-impact environment. The initial period of

  9. Hydrothermal evolution of repository groundwaters in basalt

    International Nuclear Information System (INIS)

    Apps, J.A.

    1984-01-01

    Groundwaters in the near field of a radioactive waste repository in basalt will change their chemical composition in response to reactions with the basalt. These reactions will be promoted by the heat generated by the decaying waste. It is important to predict both the rate and the extent of these reactions, and the secondary minerals produced, because the alteration process controls the chemical environment affecting the corrosion of the canister, the solubility and complexation of migrating radionuclides, the reactivity of the alteration products to radionuclides sorption, and the porosity and permeability of the host rock. A comprehensive review of the literature leads to the preliminary finding that hydrothermally altering basalts in geothermal regions such as Iceland lead to a secondary mineralogy and groundwater composition similar to that expected to surround a repository. Furthermore, laboratory experiments replicating the alteration conditions approximate those observed in the field and expected in a repository. Preliminary estimates were made of the rate of hydration and devitrification of basaltic glass and the zero-order dissolution rate of basaltic materials. The rates were compared with those for rhyolitic glasses and silicate minerals. Preliminary calculations made of mixed process alteration kinetics, involving pore diffusion and surface reaction suggest that at temperatures greater than 150 0 C, alteration proceeds so rapidly as to become pervasive in normally fractured basalt exposed to higher temperatures in the field. 70 references

  10. Evolution of the Bucium Rodu and Frasin magmatic-hydrothermal system, Metaliferi Mountains, Romania

    Science.gov (United States)

    Iatan, Elena Luisa; Berbeleac, Ion; Visan, Madalina; Minut, Adrian; Nadasan, Laurentiu

    2013-04-01

    The Miocene Bucium Rodu and Frasin maar-diatreme structures and related Au-Ag epithermal low sulfidation with passing to mesothermal mineralizations are located in the Bucium-Rosia Montana-Baia de Aries metallogenetic district, within so called the "Golden Quatrilaterum", in the northeastern part of the Metaliferi Mountains. These structures are situated at about 5 km southeast from Rosia Montana, the largest European Au-Ag deposit. The total reserves for Bucium Rodu-Frasin are estimated at 43.3 Mt with average contents of 1.3 g/t Au and 3 g/t Ag. The Miocene geological evolution of Bucium Rodu and Frasin magmatic-hydrothermal system took place in closely relationships with tectonic, magmatic and metallogenetic activity from Bucium-Rosia Montana-Baia de Aries district in general, and adjacent areas, in special. The hydrothermal alteration is pervasive; adularia followed by phyllic, carbonatization and silicification alterations, usually show a close relationship with the mineralizations. Propylitic alteration occurs dominantly towards the depth; argillic alteration shows a local character. The mineralization occurs in veins, breccias, stockworks and disseminations and is hosted within two volcanic structures emplaced into a sequence of Cretaceous sediments in closely genetically relations with the Miocene phreatomagmatic fracturing and brecciation events. Within Rodu maar-diatreme structure the mineralizations follow especially the contact between the diatreme and Cretaceous flysch. The vein sets with low, moderately and near vertical dippings, cover 400x400m with N-S trend. The most important mineralization style is represented by veins, accompanied by hydrothermal breccias and disseminations. The veins spatial distribution relives as "en echelon" tension veins. They carry gold, minor base metal sulphides (pyrite, chalcopyrite, sphalerite, galena, tetrahedrite, arsenopyrite). Gangue is represented by carbonates (calcite, dolomite, ankerite, siderite, rhodochrosite

  11. U-Pb zircon and 40Ar/39Ar geochronology of sericite from hydrothermal alteration zones: new constraints for the timing of Ediacaran gold mineralization in the Sukhaybarat area, western Afif terrane, Saudi Arabia

    Science.gov (United States)

    Harbi, Hesham M.; Ali, Kamal A.; McNaughton, Neal J.; Andresen, Arild

    2018-04-01

    The Sukhaybarat East and Red Hill deposits, in the northeastern part of the Arabian Shield, are mesothermal vein-type gold deposits hosted by late Cryogenian-Ediacaran intrusive rocks of the Idah suites (diorite, tonalite, granodiorite) and, at Sukhaybarat East, also by Ediacaran metasedimentary rocks. Gold mineralization comprises quartz-arsenopyrite veins (Sukhaybarat East), quartz-carbonate-pyrite veins (Red Hill), and subordinate gold-base metal sulfide veins. In the Red Hill deposit, alteration is complicated due to multiple overprinting hydrothermal events and is characteristically affected by pervasive, pink quartz-K-feldspar-hematite alteration which is overprinted by potassic alteration characterized by a quartz-biotite-carbonate-muscovite/sericite-rutile-apatite assemblage. This assemblage is associated with molybdenite veins which appear to form late in the paragenetic sequence and may represent either evolution of the ore fluid composition, or a later, unrelated mineralized fluids. Hydrothermal alteration at the Sukhaybarat East deposit is dominated by quartz-carbonate-sericite-arsenopyrite assemblages. Zircon from ore-hosting tonalite at Sukhaybarat East yields a U-Pb age of 629 ± 6 Ma, and biotite from the same rock gives an 40Ar/39Ar age of 622 ± 23 Ma. The 40Ar/39Ar age is within the uncertainty range for the U-Pb age of the host intrusion and is interpreted as a minimally disturbed cooling age for the tonalite. In the Red Hill area, granodiorite was emplaced at 615 ± 5 Ma, whereas muscovite/sericite separated from a mineralized sample of a quartz-carbonate-pyrite vein, that was overprinted by molybdenite-bearing veinlets, yields an 40Ar/39Ar age of 597 ± 8 Ma. We interpreted this age to represent the maximum age of the molybdenite mineralization and the probable minimum age of gold mineralization in the Red Hill deposit.

  12. Transmission Electron Microscope Observations of Phyllosilicate Development During Experimental Aqueous Alteration of Allende

    Science.gov (United States)

    Jones, C. L.; Brearley, A. J.

    2000-01-01

    Samples of Allende have been altered hydrothermally under oxidizing conditions at 200 C. TEM studies show that within 30 days evidence of replacement of matrix olivines by fine-grained serpentine is present and by 90 days complete alteration of many grains has occurred.

  13. The interplay of evolved seawater and magmatic-hydrothermal fluids in the 3.24 Ga panorama volcanic-hosted massive sulfide hydrothermal system, North Pilbara Craton, Western Australia

    Science.gov (United States)

    Drieberg, Susan L.; Hagemann, Steffen G.; Huston, David L.; Landis, Gary; Ryan, Chris G.; Van Achterbergh, Esmé; Vennemann, Torsten

    2013-01-01

    The ~3240 Ma Panorama volcanic-hosted massive sulfide (VHMS) district is unusual for its high degree of exposure and low degree of postdepositional modification. In addition to typical seafloor VHMS deposits, this district contains greisen- and vein-hosted Mo-Cu-Zn-Sn mineral occurrences that are contemporaneous with VHMS orebodies and are hosted by the Strelley granite complex, which also drove VHMS circulation. Hence the Panorama district is a natural laboratory to investigate the role of magmatic-hydrothermal fluids in VHMS hydrothermal systems. Regional and proximal high-temperature alteration zones in volcanic rocks underlying the VHMS deposits are dominated by chlorite-quartz ± albite assemblages, with lesser low-temperature sericite-quartz ± K-feldspar assemblages. These assemblages are typical of VHMS hydrothermal systems. In contrast, the alteration assemblages associated with granite-hosted greisens and veins include quartz-topaz-muscovite-fluorite and quartz-muscovite (sericite)-chlorite-ankerite. These vein systems generally do not extend into the overlying volcanic pile. Fluid inclusion and stable isotope studies suggest that the greisens were produced by high-temperature (~590°C), high-salinity (38–56 wt % NaCl equiv) fluids with high densities (>1.3 g/cm3) and high δ18O (9.3 ± 0.6‰). These fluids are compatible with the measured characteristics of magmatic fluids evolved from the Strelley granite complex. In contrast, fluids in the volcanic pile (including the VHMS ore-forming fluids) were of lower temperature (90°–270°C), lower salinity (5.0–11.2 wt % NaCl equiv), with lower densities (0.88–1.01 g/cm3) and lower δ18O (−0.8 ± 2.6‰). These fluids are compatible with evolved Paleoarchean seawater. Fluids that formed the quartz-chalcopyrite-sphalerite-cassiterite veins, which are present within the granite complex near the contact with the volcanic pile, were intermediate in temperature and isotopic composition between the greisen

  14. Implications for carbon processing beneath the Greenland Ice Sheet from dissolved CO2 and CH4 concentrations of subglacial discharge

    Science.gov (United States)

    Pain, A.; Martin, J.; Martin, E. E.

    2017-12-01

    Subglacial carbon processes are of increasing interest as warming induces ice melting and increases fluxes of glacial meltwater into proglacial rivers and the coastal ocean. Meltwater may serve as an atmospheric source or sink of carbon dioxide (CO2) or methane (CH4), depending on the magnitudes of subglacial organic carbon (OC) remineralization, which produces CO2 and CH4, and mineral weathering reactions, which consume CO2 but not CH4. We report wide variability in dissolved CO2 and CH4 concentrations at the beginning of the melt season (May-June 2017) between three sites draining land-terminating glaciers of the Greenland Ice Sheet. Two sites, located along the Watson River in western Greenland, drain the Isunnguata and Russell Glaciers and contained 1060 and 400 ppm CO2, respectively. In-situ CO2 flux measurements indicated that the Isunnguata was a source of atmospheric CO2, while the Russell was a sink. Both sites had elevated CH4 concentrations, at 325 and 25 ppm CH4, respectively, suggesting active anaerobic OC remineralization beneath the ice sheet. Dissolved CO2 and CH4 reached atmospheric equilibrium within 2.6 and 8.6 km downstream of Isunnguata and Russell discharge sites, respectively. These changes reflect rapid gas exchange with the atmosphere and/or CO2 consumption via instream mineral weathering. The third site, draining the Kiagtut Sermiat in southern Greenland, had about half atmospheric CO2 concentrations (250 ppm), but approximately atmospheric CH4 concentrations (2.1 ppm). Downstream CO2 flux measurements indicated ingassing of CO2 over the entire 10-km length of the proglacial river. CO2 undersaturation may be due to more readily weathered lithologies underlying the Kiagtut Sermiat compared to Watson River sites, but low CH4 concentrations also suggest limited contributions of CO2 and CH4 from OC remineralization. These results suggest that carbon processing beneath the Greenland Ice Sheet may be more variable than previously recognized

  15. Hyperspectral Alteration Information from Drill Cores and Deep Uranium Exploration in the Baiyanghe Uranium Deposit in the Xuemisitan Area, Xinjiang, China

    Directory of Open Access Journals (Sweden)

    Qing-Jun Xu

    2017-05-01

    Full Text Available The Baiyanghe uranium deposit is a currently important medium-sized deposit in the Xuemisitan area, Xinjiang. The hydrothermal alteration in this deposit is closely related to the uranium mineralization of the deposit. In this study, hyperspectral data are collected from drill cores in the Baiyanghe uranium deposit using a FieldSpec4 visible-shortwave infrared spectrometer to study the hydrothermal alteration. The results reveal that the altered mineral assemblages have obvious zonation characteristics: (1 the upper section comprises long-wavelength illite and minor hematite and montmorillonite; (2 the middle section contains three types of illite (long-, medium- and short-wavelength illite and hematite; and (3 the lower section includes short-wavelength illite, chlorite and carbonate. Additionally, the variety in the characteristic absorption-peak wavelength of illite at 2200 nm gradually shifts to shorter wavelength and ranges between 2195 nm and 2220 nm with increasing depth, while the SWIR-IC (short-wavelength infrared illite crystallinity, a dimensionless quantity of the drill holes gradually increases from 0.2 to 2.1. These patterns reflect the hydrothermal fluid activity in the deposit, which features relatively high-temperature, high-pressure hydrothermal fluid in the deeper section and low-temperature, low-pressure hydrothermal fluid in the shallower section. Additionally, the uranium mineralization is located near the fracture zone, which represents the center of hydrothermal fluid activity or mineralization. This area has abundant alteration minerals, and the minerals illite (short- and medium-wavelength, hematite and fluorite can be used as uranium-prospecting indicators for uranium exploration in the deeper sections of the Baiyanghe uranium deposit.

  16. Lithium isotope as a proxy for water/rock interaction between hydrothermal fluids and oceanic crust at Milos, Greece

    Science.gov (United States)

    Lou, U.-Lat; You, Chen-Feng; Wu, Shein-Fu; Chung, Chuan-Hsiung

    2014-05-01

    Hydrothermal activity at Milos in the Aegean island (Greece) is mainly located at rather shallow depth (about 5 m). It is interesting to compare these chemical compositions and the evolution processes of the hydrothermal fluids at deep sea hydrothermal vents in Mid-ocean Ridge (MOR). Lithium (Li) is a highly mobile element and its isotopic composition varies at different geological settings. Therefore, Li and its isotope could be used as an indicator for many geochemical processes. Since 6Li preferential retained in the mineral phase where 7Li is leached into fluid phase during basalt alteration, the Li isotopic fractionation between the rocks and the fluids reflect sensitively the degree of water-rock interaction. In this study, Bio-Rad AG-50W X8 cation exchange resin was used for purifying the hydrothermal fluids to separate Li from other matrix elements. The Li isotopic composition (δ7Li) was determined by Multi-collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS) with precision better than 0.2‰ (2σ, n=20). The Li concentration in the hydrothermal fluids falls between 0.02 to 10.31 mM. The δ7Li values vary from +1.9 to +29.7‰, indicating significant seawater contamination have occurred. These hydrothermal fluids fit well with seawater and brine two end-member binary mixing model. During phase separation, lithium, boron, chlorine, iodine, bromine, sodium and potassium were enriched in the brine phase. On the other hand, aluminum, sulphur and iron were enriched in the vapor phase. There is no significant isotope fractionation between the two phases. The water/rock ratio (W/R) calculated is low (about 1.5 to 1.8) for the Milos fluids, restricted seawater recharge into the oceanic crust. Moreover, the oceanic crust in the region becomes less altered since the W/R is low. The δ7Li value of the hydrothermal fluids can be used as a sensitive tool for studying water-rock interaction.

  17. Behaviour of elements in soils developed from nephelinites at Mount Etinde (Cameroon): Impact of hydrothermal versus weathering processes

    Science.gov (United States)

    Etame, J.; Gerard, M.; Bilong, P.; Suh, C. E.

    2009-05-01

    The progressive weathering of 0.65 Ma nephelinites from Mount Etinde (South Western Cameroon) in a humid tropical setting has resulted in the formation of a 150 cm thick weathering crust. The soil profiles consist of three horizons: Ah/Bw/C. A major differentiation of the chemical and mineralogical parameters is related to the complexity of the saprolites, some of which were hydrothermally altered. Bulk geochemical and microgeochemical analyses were performed on selected minerals from the different horizons of two reference profiles, of which one (E 4) was developed from unaltered nephelinite (nephelinite U) while the other (BO 1) formed from hydrothermally altered nephelinite (nephelinite H). The results show that the primary minerals (clinopyroxene, nepheline, leucite, haüyne, titanomagnetite, perovskite, apatite and sphene) experienced differential weathering rates with primary minerals rich in rare earth elements (titanomagnetite, perovskite, apatite and sphene) surviving in the saprolite and the Bw horizons. The weathering of the primary minerals is reflected in the leaching of alkaline and alkaline-earth elements, except for Ba and Rb in the hydrothermalised nephelinite soil. The order of mobility is influenced by hydrothermal processes: Na > K > Rb > Ca > Cs > Sr in nephelinite U soil , Na > K > Sr > Ca > Mg in nephelinite H soil; Rb/Sr and Sr/Mg can be used as indicators of the kinetic of the weathering on nephelinite U and on nephelinite H. Barium enrichment is related to variable concentrations in the nephelinites, to the formation of crandallites and the leaching of surface horizons. The content of metallic elements is higher in nephelinite H soil than in the nephelinite U soil. Results show that hydrothermal alteration leads to an enrichment of light (La, Ce, Nd) and intermediate (Sm, Eu, Dy) rare earth elements. The enrichment in Cr and Pb in the surface horizons is discussed in relation to organic matter activity, the dissolution of magnetites, and

  18. Alteration zone mapping for detecting potential mineralized areas in Kaladawan of north altyn tagh using ASTER data

    International Nuclear Information System (INIS)

    Yong-gui, Zhou; Bai-lin, Chen; Xing-tong, Chen; Zheng-le, Chen

    2014-01-01

    The Kaladawan area has been found developing intense hydrothermal altered rocks associated with mineralized area such as Kaladaban Pb-Zn deposit, A-bei Ag-Pb depositduring earlier geological investigations.Yet the sparse vegetation cover and excellent bedrock exposure make it a suitable place for the use of remote sensing methods for lithological mapping. ASTER data has been used in this study to identify alteration zones, and then to detect potential mineralized areas. Band ratio and PCA procedures were applied based on the analysis of spectral properties of typical alteration minerals. Band 4/2 and mineralogic indices proposed by Ninomiya were designed to map the distribution of Fe-oxides and alteration zones. Selected bands combinations were transformed in a PCA procedure to map the Al-OH, Mg-OH, CO 3 2− and Fe-oxides altered minerals. The analysis focused on the spatial distribution of hydrothermal altered minerals. Band ratio result images including both Fe-oxides and mineralogic indices show high-level similarity with the PCA transform procedure. They both show intense hydrothermal alteration zone in Kaladaban,west Kaladawan and A-bei area. Hence, these areas are considered to have potential for further mineralogic exploration. The results were validated by field work in the Kaladaban and west Kaladawan area,indicating that this method can be a useful tool for detecting potential mineralization area in Kaladawan and similar areas elsewhere

  19. Identification and analysis of low molecular weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography

    Science.gov (United States)

    Lawson, E. C.; Wadham, J. L.; Lis, G. P.; Tranter, M.; Pickard, A. E.; Stibal, M.; Dewsbury, P.; Fitzsimons, S.

    2015-08-01

    Glacial runoff is an important source of dissolved organic carbon (DOC) for downstream heterotrophic activity, despite the low overall DOC concentrations. This is because of the abundance of bioavailable, low molecular weight (LMW) DOC species. However, the provenance and character of LMW-DOC is not fully understood. We investigated the abundance and composition of DOC in subglacial environments via a molecular level DOC analysis of basal ice, which forms by water/sediment freeze-on to the glacier sole. Spectrofluorometry and a novel ion chromatographic method, which has been little utilised in glacial science for LMW-DOC determinations, were employed to identify and quantify the major LMW fractions (free amino acids, carbohydrates and carboxylic acids) in basal ice from four glaciers, each with a different basal debris type. Basal ice from Joyce Glacier (Antarctica) was unique in that 98 % of the LMW-DOC was derived from the extremely diverse FAA pool, comprising 14 FAAs. LMW-DOC concentrations in basal ice were dependent on the bioavailability of the overridden organic carbon (OC), which in turn, was influenced by the type of overridden material. Mean LMW-DOC concentrations in basal ice from Russell Glacier (Greenland), Finsterwalderbreen (Svalbard) and Engabreen (Norway) were low (0-417 nM C), attributed to the relatively refractory nature of the OC in the overridden paleosols and bedrock. In contrast, mean LMW-DOC concentrations were an order of magnitude higher (4430 nM C) in basal ice from Joyce Glacier, a reflection of the high bioavailability of the overridden lacustrine material (>17 % of the sediment OC comprised extractable carbohydrates, a proxy for bioavailable OC). We find that the overridden material may act as a direct (via abiotic leaching) and indirect (via microbial cycling) source of DOC to the subglacial environment and provides a range of LMW-DOC compounds that may stimulate microbial activity in wet sediments in current subglacial

  20. Hydrothermal temperature effect on crystal structures, optical properties and electrical conductivity of ZnO nanostructures

    Science.gov (United States)

    Dhafina, Wan Almaz; Salleh, Hasiah; Daud, Mohd Zalani; Ghazali, Mohd Sabri Mohd; Ghazali, Salmah Mohd

    2017-09-01

    ZnO is an wide direct band gap semiconductor and possess rich family of nanostructures which turned to be a key role in the nanotechnology field of applications. Hydrothermal method was proven to be simple, robust and low cost among the reported methods to synthesize ZnO nanostructures. In this work, the properties of ZnO nanostructures were altered by varying temperatures of hydrothermal process. The changes in term of morphological, crystal structures, optical properties and electrical conductivity were investigated. A drastic change of ZnO nanostructures morphology and decreases of 002 diffraction peak were observed as the hydrothermal temperature increased. The band gap of samples decreased as the size of ZnO nanostructure increased, whereas the electrical conductivity had no influence on the band gap value but more on the morphology of ZnO nanostructures instead.

  1. Hydrothermal processes in the Edmond deposits, slow- to intermediate-spreading Central Indian Ridge

    Science.gov (United States)

    Cao, Hong; Sun, Zhilei; Zhai, Shikui; Cao, Zhimin; Jiang, Xuejun; Huang, Wei; Wang, Libo; Zhang, Xilin; He, Yongjun

    2018-04-01

    The Edmond hydrothermal field, located on the Central Indian Ridge (CIR), has a distinct mineralization history owing to its unique magmatic, tectonic, and alteration processes. Here, we report the detailed mineralogical and geochemical characteristics of hydrothermal metal sulfides recovered from this area. Based on the mineralogical investigations, the Edmond hydrothermal deposits comprise of high-temperature Fe-rich massive sulfides, medium-temperature Zn-rich sulfide chimney and low-temperature Ca-rich sulfate mineral assemblages. According to these compositions, three distinctive mineralization stages have been identified: (1) low-temperature consisting largely of anhydrite and pyrite/marcasite; (2) medium-high temperature distinguished by the mineral assemblage of pyrite, sphalerite and chalcopyrite; and (3) low-temperature stage characterized by the mineral assemblage of colloidal pyrite/marcasite, barite, quartz, anglesite. Several lines of evidence suggest that the sulfides were influenced by pervasive low-temperature diffuse flows in this area. The hydrothermal deposits are relatively enriched in Fe (5.99-18.93 wt%), Zn (2.10-10.00 wt%) and Ca (0.02-19.15 wt%), but display low Cu (0.28-0.81 wt%). The mineralogical varieties and low metal content of sulfides in the Edmond hydrothermal field both indicate that extensive water circulation is prevalent below the Edmond hydrothermal field. With regard to trace elements, the contents of Pb, Ba, Sr, As, Au, Ag, and Cd are significantly higher than those in other sediment-starved mid-ocean ridges, which is indicative of contribution from felsic rock sources. Furthermore, the multiphase hydrothermal activity and the pervasive water circulation underneath are speculated to play important roles in element remobilization and enrichment. Our findings deepen our understanding about the complex mineralization process in slow- to intermediate-spreading ridges globally.

  2. Hydrothermal behaviour of sedimentary saponitic clays from Madrid Basin

    International Nuclear Information System (INIS)

    Cuevas Rodriguez, J.

    1993-01-01

    The hydrothermal behavior of sedimentary saponitic clays from Madrid Basin has been investigated to assess their potential use as a buffer material in high level radioactive waste repositories. This paper deals with a review of several aspects that has been studied: the adsorption and irreversible fixation of K'+, the alteration in absence of potassium and the effects of heat and steam on textural properties of the smectitic clay. Experiments have covered temperatures up to 175 degree centigree with an excess of liquid water except on the last subject. Chemical and XRD analyses of final clay products and solutions indicates minor alteration of the saponite in the hydrothermal experiments either in the presence or absence of potassium. No illitization or chloritization processes seems to affect the smectite. Sepiolite was found to be largely dissolved at 175 degree centigree, a process that inhibited recrystallization or formation of illite observed when illite was present in significant amounts in starting materials. Accessory minerals (illite and sepiolite) accompanying as traces the saponitic material underwent and intense degradation at 175 degree centigree in absence of potassium. On the other hand, clay steamed at 200 degree centigree showed significant textural changes forming highly stable silt size aggregates which hindered the swelling abilities of the saponitic material, a fact that was previously observed in montmorillonites. (Author) 25 refs

  3. Complexing and hydrothermal ore deposition

    CERN Document Server

    Helgeson, Harold C

    1964-01-01

    Complexing and Hydrothermal Ore Deposition provides a synthesis of fact, theory, and interpretative speculation on hydrothermal ore-forming solutions. This book summarizes information and theory of the internal chemistry of aqueous electrolyte solutions accumulated in previous years. The scope of the discussion is limited to those aspects of particular interest to the geologist working on the problem of hydrothermal ore genesis. Wherever feasible, fundamental principles are reviewed. Portions of this text are devoted to calculations of specific hydrothermal equilibriums in multicompone

  4. Lytological characterization and hydrothermal alteration Infiernillo porphyry, provincia Mendoza, Argentina

    International Nuclear Information System (INIS)

    Gomez, A.; Rubinstein, N.; Kleiman, L.. E.mail: kleiman@cae.cnea.gov.ar

    2007-01-01

    El Infiernillo porphyry copper and Mo deposit, in southern Mendoza, Argentina is hosted by ignimbrites of the Cochico Group (lower Permian). The alteration zone consists of a small central quartz neck with appreciable hematite surrounded by an intense quartz-injected zone with local pervasive potassic alteration. Outwards, there is a well-developed phyllic halo with intense bleaching which consists of pervasive and vein-type silicification, sericitization and pyritization. In the outer part of the alteration zone, small polymetallic veins with pyrite, arsenopyrite, galena and minor, chalcopyrite, sphalerite and electrum in quartz gangue crop out. New field, petro-mineralogic and geochemical data confirmed that the host rocks are equivalent to the dacitic and rhyodacitic ignimbrites of the Toba Vieja Gorda Member (Yacimiento Los Reyunos Formation, Cochico Group)

  5. Hydrothermal Phase Relations Among Uranyl Minerals at the Nopal I Analog Site

    International Nuclear Information System (INIS)

    Murphy, William M.

    2007-01-01

    Uranyl mineral paragenesis at Nopal I is an analog of spent fuel alteration at Yucca Mountain. Petrographic studies suggest a variety of possible hydrothermal conditions for uranium mineralization at Nopal I. Calculated equilibrium phase relations among uranyl minerals show uranophane stability over a broad range of realistic conditions and indicate that uranyl mineral variety reflects persistent chemical potential heterogeneity. (author)

  6. Clastic dykes in over-consolidated tills: evidence for subglacial hydrofracturing at Killiney Bay, eastern Ireland

    Science.gov (United States)

    Rijsdijk, Kenneth F.; Owen, Geraint; Warren, William P.; McCarroll, Danny; van der Meer, Jaap J. M.

    1999-11-01

    A swarm of vertical gravel-filled dykes up to 6 m high and several decimetres wide, cut through an over-consolidated till at Killiney Bay. The dykes are rooted in a gravel layer and many display plumes of clastic debris ejected into the overlying sediments — `burst-out structures'. Such features have not previously been described. These clastic dykes are interpreted as the infillings of hydrofractures which formed when water pressures in the basal gravel layer exceeded the overburden pressure and tensile shear strength of the capping till. The burst-out structures extend up to 7 m from the tops of the dykes and provide strong evidence for forceful upward flow. Evidence suggests that the hydrofractures formed subglacially, probably during a minor re-advance. Their presence in Late Devensian (26-13 ka BP) tills with an Irish Sea provenance (`Irish Sea till') may have important implications for the subglacial hydrology of the last Irish Sea ice sheet. These hydrofractures cannot form in unconsolidated glacimarine sediment and their presence precludes a glacimarine origin for these deposits. They greatly affect the geotechnical properties of Irish Sea tills, in particular providing very permeable routes through otherwise impermeable layers, with important consequences in situations elsewhere in the Irish Sea basin, where they have been used as aquicludes in landfill and low-level nuclear waste disposal sites.

  7. Halogen Chemistry of Hydrothermal Micas: a Possible Geochemical Tool in Vectoring to Ore for Porphyry Copper-Gold Deposit

    Directory of Open Access Journals (Sweden)

    Arifudin Idrus

    2018-03-01

    Full Text Available Porphyry copper-gold deposit commonly exhibits an extensive alteration zone of hydrothermal micas particularly biotite and sericite. This study is aimed to analyze and utilize the chemistry of halogen fluorine and chlorine of biotite and sericite to be a possible tool in vectoring to ore for copper porphyry deposits. To achieve the objectives, several selected altered rock samples were taken crossing the Batu Hijau copper-gold mine from inner to outer of the deposit, and hydrothermal micas contained by the rocks were analyzed petrographically and chemically. Mineral chemistry was detected by electron microprobe analyzer, whilst biotite is petrographically classified as either magmatic or hydrothermal types. Sericite replacing plagioclase occurred as fine-grained mineral and predominantly associated with argillic-related alteration types. Biotites in the Batu Hijau deposit are classified as phlogopite with a relatively low mole fraction magnesium (XMg (~0.75 compared to the “typical” copper porphyry deposit (~0.82. The relationship between the XMg and halogen contents are generally consistent with “Fe-F and Mg-Cl avoidance rules”.  F content in biotite and sericite decrease systematically from inner part of the deposit which is represented by early biotite (potassic zone where the main copper-gold hosted, to the outer part of the deposit. However, chlorine in both biotite and sericite from each of the alteration zones shows a relative similar concentration, which suggests that it is not suitable to be used in identification of the alteration zones associated with strong copper-gold mineralization. H2O content of the biotite and sericite also exhibits a systematic increase outward which may also provide a possible geochemical vector to ore for the copper porphyry deposits. This is well correlated with fluorine content of biotite in rocks and bulk concentration of copper from the corresponding rocks.

  8. The fossil hydrothermal system from Volta Grande, Lavras do Sul, RS. Part 2: Geochemical of chlorites

    International Nuclear Information System (INIS)

    Mexias, A.S.; Formoso, M.L.L.; Mattos, I.C.; Gomes, M.E.B.; Meunier, A.; Beaufort, D.

    1990-01-01

    Chlorites related to propylitic phyllic processes in Fossil Hydrothermal System of Volta Grande/RS, quite similar to porphyry copper type deposit, were studied. Electron probe analysis in chlorites and chemical total rock analysis made the study of macro and micro system possible. The geochemical study of the micro system enable to characterize the inactive and active flow regimes of hydrothermal process in propylitic and phyllic, respectively. Geo-thermometric data, at least qualitatively, indicate that the phyllic alteration is the same or slightly higher than propylitic alteration. The detailed study of the composition of chlorites in micro system permitted to know the diadochic replacement of elements, especially in chloritization of biotite, in which the mobility of Al 3+ (at least in mineral scale) is possible under constant volume and Ti 4+ . The rocks were analysed by absorption spectroscopy, X-ray fluorescence analysis and gravimetry. (author)

  9. Hydrothermal liquefaction of biomass

    DEFF Research Database (Denmark)

    Toor, Saqib; Rosendahl, Lasse; Rudolf, Andreas

    2011-01-01

    This article reviews the hydrothermal liquefaction of biomass with the aim of describing the current status of the technology. Hydrothermal liquefaction is a medium-temperature, high-pressure thermochemical process, which produces a liquid product, often called bio-oil or bi-crude. During...... the hydrothermal liquefaction process, the macromolecules of the biomass are first hydrolyzed and/or degraded into smaller molecules. Many of the produced molecules are unstable and reactive and can recombine into larger ones. During this process, a substantial part of the oxygen in the biomass is removed...... by dehydration or decarboxylation. The chemical properties of bio-oil are highly dependent of the biomass substrate composition. Biomass constitutes of various components such as protein; carbohydrates, lignin and fat, and each of them produce distinct spectra of compounds during hydrothermal liquefaction...

  10. Gold-bearing hydrothermal veins in Chukotka

    Energy Technology Data Exchange (ETDEWEB)

    Davidenko, N.M.

    1980-01-01

    Indicators such as the correlation of mineralization to plutonic and vulcanic formations and various facies of metamorphism, the character of the structural-tectonic control of mineralization, characteristics of silica redistribution as well that of calcium, water, and other components in altering ore zones, the specificity of sygenetic fluid inclusions in minerals, morphology, the internal structure and other typomorphic indicators of native gold and its accessories are utilized in the working out of a genetic classification for compiling a complex of diagnostic indicators of post-magmatic mineralization on Chukotka at various depths. Those indicators, in addition to earlier known hydrothermal gold ore formations, can be used to identify still other types of mineralization, particularly pyrite group minerals.

  11. Hyperspectral image analysis for the determination of alteration minerals in geothermal fields: Çürüksu (Denizli) Graben, Turkey

    Science.gov (United States)

    Uygur, Merve; Karaman, Muhittin; Kumral, Mustafa

    2016-04-01

    Çürüksu (Denizli) Graben hosts various geothermal fields such as Kızıldere, Yenice, Gerali, Karahayıt, and Tekkehamam. Neotectonic activities, which are caused by extensional tectonism, and deep circulation in sub-volcanic intrusions are heat sources of hydrothermal solutions. The temperature of hydrothermal solutions is between 53 and 260 degree Celsius. Phyllic, argillic, silicic, and carbonatization alterations and various hydrothermal minerals have been identified in various research studies of these areas. Surfaced hydrothermal alteration minerals are one set of potential indicators of geothermal resources. Developing the exploration tools to define the surface indicators of geothermal fields can assist in the recognition of geothermal resources. Thermal and hyperspectral imaging and analysis can be used for defining the surface indicators of geothermal fields. This study tests the hypothesis that hyperspectral image analysis based on EO-1 Hyperion images can be used for the delineation and definition of surfaced hydrothermal alteration in geothermal fields. Hyperspectral image analyses were applied to images covering the geothermal fields whose alteration characteristic are known. To reduce data dimensionality and identify spectral endmembers, Kruse's multi-step process was applied to atmospherically and geometrically-corrected hyperspectral images. Minimum Noise Fraction was used to reduce the spectral dimensions and isolate noise in the images. Extreme pixels were identified from high order MNF bands using the Pixel Purity Index. n-Dimensional Visualization was utilized for unique pixel identification. Spectral similarities between pixel spectral signatures and known endmember spectrum (USGS Spectral Library) were compared with Spectral Angle Mapper Classification. EO-1 Hyperion hyperspectral images and hyperspectral analysis are sensitive to hydrothermal alteration minerals, as their diagnostic spectral signatures span the visible and shortwave

  12. Deformation associated with the denudation of mantle-derived rocks at the Mid-Atlantic Ridge 13°-15°N: The role of magmatic injections and hydrothermal alteration

    Science.gov (United States)

    Picazo, Suzanne; Cannat, Mathilde; Delacour, AdéLie; EscartíN, Javier; RouméJon, StéPhane; Silantyev, Sergei

    2012-09-01

    Outcrops of deeply derived ultramafic rocks and gabbros are widespread along slow spreading ridges where they are exposed in the footwall of detachment faults. We report on the microstructural and petrological characteristics of a large number of samples from ultramafic exposures in the walls of the Mid-Atlantic Ridge (MAR) axial valley at three distinct locations at lat. 13°N and 14°45'N. One of these locations corresponds to the footwall beneath a corrugated paleo-fault surface. Bearing in mind that dredging and ROV sampling may not preserve the most fragile lithologies (fault gouges), this study allows us to document a sequence of deformation, and the magmatic and hydrothermal history recorded in the footwall within a few hundred meters of the axial detachment fault. At the three sampled locations, we find that tremolitic amphiboles have localized deformation in the ultramafic rocks prior to the onset of serpentinization. We interpret these tremolites as hydrothermal alteration products after evolved gabbroic rocks intruded into the peridotites. We also document two types of brittle deformation in the ultramafic rocks, which we infer could produce the sustained low magnitude seismicity recorded at ridge axis detachment faults. The first type of brittle deformation affects fresh peridotite and is associated with the injection of the evolved gabbroic melts, and the second type affects serpentinized peridotites and is associated with the injection of Si-rich hydrothermal fluids that promote talc crystallization, leading to strain localization in thin talc shear zones. We also observed chlorite + serpentine shear zones but did not identify samples with serpentine-only shear zones. Although the proportion of magmatic injections in the ultramafic rocks is variable, these characteristics are found at each investigated location and are therefore proposed as fundamental components of the deformation in the footwall of the detachment faults associated with denudation of

  13. Geological investigation of hydrothermal alteration haloes in Toyoha geothermal field, Hakkaido

    Energy Technology Data Exchange (ETDEWEB)

    Igarashi, T; Furukawa, Y; Sugawara, K; Nishimura, S; Okabe, K

    1978-01-01

    In Toyoha geothermal field, the altered haloes are located along a tectonic line extending on a NW-SE direction along the Yunosawa River, east of the Toyoha Mine, a well known Neogene epithermal ore deposit. The investigation was carried out to clarify the stage of alteration, based on the altered haloes geologic structure, composition, and size. The Quaternary distribution at the eastern foot of Mt. Yotei was also studied. The field is covered by various kinds of Miocene sediments but the altered haloes are found only in an area covered by the Takinosawa formation and its older formations. Among the Yunosawa, Koyanagizawa and Takinosawa alteration haloes, the Yunosawa is the most important. It is composed of blocky silicified rock extending along a river and surrounding argillaceous rock. The silicified rock is composed primarily of quartz and subordinate alunite and opal, while the argillaceous rock consists chiefly of kaloin and is characterized by the occasional presence of sericite and montmorillinite. Fission-track and /sup 14/C methods were employed to determine the stage of alteration, but the results were unsatisfactory. The sublimation sulfur ore deposits in the Yunosawa and Koyanagizawa areas were comparatively small, but their original depositional features remain intact, indicating that geothermal activity continued until recently. Yunosawa is the most promising area as it is closely related to the tectonic line and also it has extraordinarily high ground temperature determined by a recent heat flow survey. Twenty-three references are provided.

  14. A Conspicuous Clay Ovoid in Nakhla: Evidence for Subsurface Hydrothermal Alteration on Mars with Implications for Astrobiology

    Science.gov (United States)

    Haigh, Sarah; Lyon, Ian

    2014-01-01

    Abstract A conspicuous biomorphic ovoid structure has been discovered in the Nakhla martian meteorite, made of nanocrystalline iron-rich saponitic clay and amorphous material. The ovoid is indigenous to Nakhla and occurs within a late-formed amorphous mesostasis region of rhyolitic composition that is interstitial to two clinopyroxene grains with Al-rich rims, and contains acicular apatite crystals, olivine, sulfides, Ti-rich magnetite, and a new mineral of the rhoenite group. To infer the origin of the ovoid, a large set of analytical tools was employed, including scanning electron microscopy and backscattered electron imaging, wavelength-dispersive X-ray analysis, X-ray mapping, Raman spectroscopy, time-of-flight secondary ion mass spectrometry analysis, high-resolution transmission electron microscope imaging, and atomic force microscope topographic mapping. The concentric wall of the ovoid surrounds an originally hollow volume and exhibits internal layering of contrasting nanotextures but uniform chemical composition, and likely inherited its overall shape from a preexisting vesicle in the mesostasis glass. A final fibrous layer of Fe-rich phases blankets the interior surfaces of the ovoid wall structure. There is evidence that the parent rock of Nakhla has undergone a shock event from a nearby bolide impact that melted the rims of pyroxene and the interstitial matter and initiated an igneous hydrothermal system of rapidly cooling fluids, which were progressively mixed with fluids from the melted permafrost. Sharp temperature gradients were responsible for the crystallization of Al-rich clinopyroxene rims, rhoenite, acicular apatites, and the quenching of the mesostasis glass and the vesicle. During the formation of the ovoid structure, episodic fluid infiltration events resulted in the precipitation of saponite rinds around the vesicle walls, altered pyrrhotite to marcasite, and then isolated the ovoid wall structure from the rest of the system by depositing a

  15. Comparison between the chemistry of igneous and hydrothermal biotite in the igneous rocks of Sakhtehesar mountain

    Directory of Open Access Journals (Sweden)

    Farima Ayati

    2015-12-01

    Full Text Available Sakhtehesar mountain is located in Urumieh-Dokhtar magmatic belt and is composed of volcanic and subvolcanic rocks (Pliocene andesite to dacite which intruded the volcanics and pyroclastics of Paleocene age. Three alteration zones including potassic, phyllic and propylitic are recognized in the area. In this paper, the mineral chemistry of magmatic and primary biotite and the mineral chemistry of biotite in potassic and phyllic alteration zones have been studied. Investigations show that primary and secondary biotites are different from each other and hydrothermal fluids associated with the potassic alteration are distinctively different from the fluids associated with the phyllic alteration zone in the area.

  16. Hydrothermal Growth of Polyscale Crystals

    Science.gov (United States)

    Byrappa, Kullaiah

    In this chapter, the importance of the hydrothermal technique for growth of polyscale crystals is discussed with reference to its efficiency in synthesizing high-quality crystals of various sizes for modern technological applications. The historical development of the hydrothermal technique is briefly discussed, to show its evolution over time. Also some of the important types of apparatus used in routine hydrothermal research, including the continuous production of nanosize crystals, are discussed. The latest trends in the hydrothermal growth of crystals, such as thermodynamic modeling and understanding of the solution chemistry, are elucidated with appropriate examples. The growth of some selected bulk, fine, and nanosized crystals of current technological significance, such as quartz, aluminum and gallium berlinites, calcite, gemstones, rare-earth vanadates, electroceramic titanates, and carbon polymorphs, is discussed in detail. Future trends in the hydrothermal technique, required to meet the challenges of fast-growing demand for materials in various technological fields, are described. At the end of this chapter, an Appendix 18.A containing a more or less complete list of the characteristic families of crystals synthesized by the hydrothermal technique is given with the solvent and pressure-temperature (PT) conditions used in their synthesis.

  17. Hydrothermal phenomena in Risovaca cave and within Vencac massif Shumadies, Serbia

    Directory of Open Access Journals (Sweden)

    Wrzak-Tomić Janina

    2004-01-01

    Full Text Available In the Risovaca cave are found, for the karst, atypical alteration in the limestones structure. Also, morphogenesis of the object can not be logically interpret. Those differences are result of hydrothermal process in initial phase of karstic cycle. And then activity of hot water and hot emanations brought up to the metasomatism and destruction of rock, enormous excrete of ornaments and later, ceiling collapse and fill up of cave room.

  18. Evolution evidence of a basic fluid to an acid based in the analysis of hydrothermal alteration of the geothermic field of the Azufres, Michoacan; Evidencias de evolucion de un fluido basico a acido a partir del analisis de la alteracion hidrotermal del campo geotermico de los Azufres, Michoacan

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez Partida, Eduardo [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)

    2000-07-01

    Hydrothermal alteration at the Los Azufres geothermal field is mostly composed of calc-silicate minerals that define a propylitic alteration zone, which shows progressive dehydration with depth and temperature increase. A generalized zoning of the calc-silicate zone can be observed, with zeolites in the upper part and epidote-clinozoisite at the deepest levels. An argillic alteration zone overlies the calc-silicate zone and is the dominant surface manifestation of the hydrothermal alteration. In some parts, there is a mineral assemblage composed of kaolinite-alunite-native sulfur-quartz (advanced argillic zone) formed by the interaction of vapor and shallow groundwater. The proto-fluid at the Los Azufres geothermal system is related to a neutral sodium chlorine brine, which favors deep propyllitic alteration (productive zone). This zone is characterized by secondary permeability due to fracturing. At depth the geothermal field is dominated by a pressurized liquid, yielding to vapor at more shallow zone. The gradual change from a liquid to a vapor phase occurs through boiling at depths between 1,200 and 1,500 m, and is accompanied by changes in the hydrothermal alteration mineralogy. The type of alteration passes from proylitic to argillic by means of an oxidation-acidification process, which includes the participation of a gas, particularly CO{sub 2}. Considering the physicochemical characteristic of the brine and the evolution of the paragenetic sequence, the Los Azufres geothermal field could de considered a model for hydrothermal behavior at ore deposits which develop by boiling and oxidation of low sulfidation fossil hydrothermal fluids. [Spanish] En el campo geotermico de Los Azufres la zona de alteracion hidrotermal esta formada en su mayor parte por calcosilicatos (que definen una zona paragenetica del tipo propilitico), los cuales muestran una deshidratacion progresiva conforme se va profundizando e incrementandose la temperatura. Se puede generalizar un

  19. Mars analogue glaciovolcanic hydrothermal environments in Iceland : detection and implications for astrobiology

    OpenAIRE

    Cousins, Claire Rachel; Crawford, Ian; Carrivick, Jonathan; Gunn, Matthew; Harris, Jennifer; Kee, Terence; Karlsson, Magnus; Carmody, Laura; Cockell, Charles; Herschy, Barry; Joy, Katherine

    2013-01-01

    This work was funded by the Leverhulme Trust, and the Science and Technology Facility Council. Volcanism has been a dominant process on Mars, along with a pervasive global cryosphere. Therefore, the interaction between these two is considered likely. Terrestrial glaciovolcanism produces distinctive lithologies and alteration terrains, as well as hydrothermal environments that can be inhabited by microorganisms. Here, we provide a framework for identifying evidence of such glaciovolcanic en...

  20. Geology, alteration, mineralization, petrogenesis, geochronology, geochemistry and airborne geophysics of Kuh Shah prospecting area, SW Birjand

    Directory of Open Access Journals (Sweden)

    Maryam Abdi

    2012-04-01

    Full Text Available The Kuh Shah prospecting area is located in Tertiary volcano-plutonic belt of the Lut Block. More than seventeen subvolcanic intermediate to acidic intrusive rocks, diorite to syenite in composition, were identified in the study area. The intrusions are related to hydrothermal alteration zones and contain argillic, propylitic, advanced argillic, silicified, quartz-sericite-pyrite, gossan and hydrothermal breccia which overprinted to each other and are accompanied by weathering which made it complicated to distinguish zoning. Mineralization is observed as sulfide (pyrite and rare chalcopyrite, disseminated Fe-oxides and quartz-Fe-oxide stockwork veinlets. Intrusive rocks are metaluminous, calc-alkaline with shoshonitic affinity with high values of magnetic susceptibility. The Kuh Shah intrusive rocks are classified as magnetite-series of oxidant I-type granitoids. Based on zircon U–Pb age dating, the age of these granitoid rocks is 39.7± 0.7 Ma (Middle Eocene. The radioisotope data (initial 87Sr/86Sr and 143Nd/144Nd ratios as well as εNd and geochemical data suggest that the Kuh Shah granitoid rocks formed from depleted mantle in a subduction-related magmatic arc setting. Geochemical anomalies of elements such as Cu, Au, Fe, Pb, Zn, As, Sb, Mo, Bi, Hg and also Mn, Ba, Te and Se, correlated with quartz-sericite-pyrite, gossan-stockwork-hydrothermal breccias, irregular silicified bodies and advanced argillic hydrothermal alteration zones. Geophysical anomalies correlated with hydrothermal alteration and mineralization zones. The interpretation of the results represents complex patterns of sub-circular to ellipsoid shape with north-east to south-west direction. These evidences are similar to the other for known Cu-Au porphyry and Au-epithermal systems in Iran and worldwide.

  1. Effect of solution chemistry on the characteristics of hydrothermally grown WO_3 for electroactive applications

    International Nuclear Information System (INIS)

    Christou, K.; Louloudakis, D.; Vernardou, D.; Savvakis, C.; Katsarakis, N.; Koudoumas, E.; Kiriakidis, G.

    2015-01-01

    Hydrothermally grown tungsten trioxide coatings were prepared at 95 °C using different metal sulfates. Morphology of the oxides was altered from grains to flower- and urchin-like structures using potassium sulfate, sodium sulfate and lithium sulfate, respectively. The flower-like structures presented the highest deintercalated charge, 35 mC cm"−"2 with time response of 96 s. In addition, they indicated a charge transfer resistance across the tungsten trioxide–electrolyte interface of 752 Ω. These outcomes imply that they are promising candidates for electroactive applications. - Highlights: • Hydrothermally grown WO_3 coatings with controlled properties. • The choice of metal sulfate is important in determining their properties. • Flower-like hexagonal WO_3 structures for electroactive applications.

  2. Asymmetrical structure, hydrothermal system and edifice stability: The case of Ubinas volcano, Peru, revealed by geophysical surveys

    Science.gov (United States)

    Gonzales, Katherine; Finizola, Anthony; Lénat, Jean-François; Macedo, Orlando; Ramos, Domingo; Thouret, Jean-Claude; Fournier, Nicolas; Cruz, Vicentina; Pistre, Karine

    2014-04-01

    Ubinas volcano, the historically most active volcano in Peru straddles a low-relief high plateau and the flank of a steep valley. A multidisciplinary geophysical study has been performed to investigate the internal structure and the fluids flow within the edifice. We conducted 10 self-potential (SP) radial (from summit to base) profiles, 15 audio magnetotelluric (AMT) soundings on the west flank and a detailed survey of SP and soil temperature measurements on the summit caldera floor. The typical “V” shape of the SP radial profiles has been interpreted as the result of a hydrothermal zone superimposed on a hydrogeological zone in the upper parts of the edifice, and depicts a sub-circular SP positive anomaly, about 6 km in diameter. The latter is centred on the summit, and is characterised by a larger extension on the western flank located on the low-relief high plateau. The AMT resistivity model shows the presence of a conductive body beneath the summit at a depth comparable to that of the bottom of the inner south crater in the present-day caldera, where intense hydrothermal manifestations occur. The lack of SP and temperature anomalies on the present caldera floor suggests a self-sealed hydrothermal system, where the inner south crater acts as a pressure release valve. Although no resistivity data exists on the eastern flank, we presume, based on the asymmetry of the basement topography, and the amplitude of SP anomalies on the east flank, which are approximately five fold that on the west flank, that gravitational flow of hydrothermal fluids may occur towards the deep valley of Ubinas. This hypothesis, supported by the presence of hot springs and faults on the eastern foot of the edifice, reinforces the idea that a large part of the southeast flank of the Ubinas volcano may be altered by hydrothermal activity and will tend to be less stable. One of the major findings that stems from this study is that the slope of the basement on which a volcano has grown

  3. Growth and alteration of uranium-rich microlite

    International Nuclear Information System (INIS)

    Giere, R.; Swope, R. J.; Buck, E. C.; Guggenheim, R.; Mathys, D.; Reusser, E.

    2000-01-01

    Uranium-rich microlite, a pyrochlore-group mineral, occurs in 440 Ma old lithium pegmatites of the Mozambique Belt in East Africa. Microlite exhibits a pronounced growth zoning, with a U-free core surrounded by a U-rich rim (UO 2 up to 17 wt.%). The core exhibits conjugate sets of straight cracks (cleavage planes) which provided pathways for a late-stage U-enriched pegmatitic fluid which interacted with the U-free microlite to produce a distinct U enrichment along the cracks and led to the formation of the U-rich rim. Following the stage of U incorporation into microlite, a second generation of hydrothermal fluids deposited mica along the cleavage planes. Subsequent to these two hydrothermal stages, the host rock was uplifted and subjected to intense low-temperature alteration during which Na, Ca and F were leached from the microlite crystals. This alteration also led to a hydration of microlite, but there is no evidence of U loss. These low-temperature alteration effects were only observed in the U-rich rim which is characterized by a large number of irregular cracks which are most probably the result of metamictization, as indicated by electron diffraction images and powder X-ray patterns. The pyrochlore-group minerals provide excellent natural analogues for pyrochlore-based nuclear waste forms, because samples of variable age and with high actinide contents are available

  4. Petrophysical characterization of the hydrothermal root zone in the sheeted dike complex from IODP Hole 1256D.

    Science.gov (United States)

    Violay, M.; Pezard, P. A.; Ildefonse, B.; Belghoul, A.; Mainprice, D.

    2009-04-01

    IODP (Integrated Ocean Drilling Program.) Site 1256 is located on the Cocos Plate in the Eastern Equatorial Pacific Ocean. It samples 15 Ma-old oceanic lithosphere that was formed at the EPR during a period of superfast spreading rate (> 200mm/yr). Drilling operations at Site 1256 were conducted during three ODP and IODP expeditions, and reached for the first time gabbros below the sheeted dike complex in Hole 1256D. This offers a unique opportunity to study in situ the fossil root zone of the sheeted dike complex in present-day oceanic crust. This zone is a boundary layer between the magmatic system of the melt lens (around 1100 °C), and the overlying high temperature hydrothermal system (≤ 450 °C). This boundary layer during crustal accretion is critical to our understanding of crustal processes along mid-ocean ridges. This work focuses on the petrophysical characterization of the root zone. Physical properties were determined from downhole geophysical profiles and images, and from laboratory petrophysical measurements from 21 minicores. Dikes, granoblastic dikes and gabbros testify to an important hydrothermal circulation in the vicinity of the magmatic lens. Porosity is primarily controlled by sample initial texture, hydrothermal alteration, and recrystallization processes. Green schist facies alteration of basalts is associated to relatively higher porosity values (≈ 2%) and a very variable organization of the pore space, as revealed by electrical properties. The electrical formation factor in diabase is high and variable (920 to 6087). Granoblastic dikes are characterized by locally recrystallized texture with Cpx and Opx (granulite facies) and little alteration at low temperature. The recrystallization induces abrupt decrease in porosity (fairly constant porosity, which likely consist mostly in microcracks. Crack density increases linearly with depth from 0.02 in diabase to 0.08 in gabbros. It is consistent with a fissural porosity (crack aspect ratio

  5. Deposition of talc - kerolite-smectite - smectite at seafloor hydrothermal vent fields: Evidence from mineralogical, geochemical and oxygen isotope studies

    Science.gov (United States)

    Dekov, V.M.; Cuadros, J.; Shanks, Wayne C.; Koski, R.A.

    2008-01-01

    Talc, kerolite-smectite, smectite, chlorite-smectite and chlorite samples from sediments, chimneys and massive sulfides from six seafloor hydrothermal areas have been analyzed for mineralogy, chemistry and oxygen isotopes. Samples are from both peridotite- and basalt-hosted hydrothermal systems, and basaltic systems include sediment-free and sediment-covered sites. Mg-phyllosilicates at seafloor hydrothermal sites have previously been described as talc, stevensite or saponite. In contrast, new data show tri-octahedral Mg-phyllosilicates ranging from pure talc and Fe-rich talc, through kerolite-rich kerolite-smectite to smectite-rich kerolite-smectite and tri-octahedral smectite. The most common occurrence is mixed-layer kerolite-smectite, which shows an almost complete interstratification series with 5 to 85% smectitic layers. The smectite interstratified with kerolite is mostly tri-octahedral. The degree of crystal perfection of the clay sequence decreases generally from talc to kerolite-smectite with lower crystalline perfection as the proportion of smectite layers in kerolite-smectite increases. Our studies do not support any dependence of the precipitated minerals on the type/subtype of hydrothermal system. Oxygen isotope geothermometry demonstrates that talc and kerolite-smectite precipitated in chimneys, massive sulfide mounds, at the sediment surface and in open cracks in the sediment near seafloor are high-temperature (> 250????C) phases that are most probably the result of focused fluid discharge. The other end-member of this tri-octahedral Mg-phyllosilicate sequence, smectite, is a moderate-temperature (200-250????C) phase forming deep within the sediment (??? 0.8??m). Chlorite and chlorite-smectite, which constitute the alteration sediment matrix around the hydrothermal mounds, are lower-temperature (150-200????C) phases produced by diffuse fluid discharge through the sediment around the hydrothermal conduits. In addition to temperature, other two

  6. Evidence for Subglacial Deformation and Deposition during a Complete Advance-Stagnation Cycle of Kötlujökull, Iceland – A Case Study

    DEFF Research Database (Denmark)

    Klint, K E S; Richardt, N; Krüger, Johannes

    2010-01-01

    A geological section, 70 m long and 3–4 m high, cut into dead-ice moraine in front of Kötlujökull, has been described. Five-sediment associations were recognized representing (1) proglacial glacio-fluvial sedimentation, (2) deposition and deformation in ice-marginal environment, (3) subglacial...

  7. Hydrothermal synthetic strategies of inorganic semiconducting nanostructures.

    Science.gov (United States)

    Shi, Weidong; Song, Shuyan; Zhang, Hongjie

    2013-07-07

    Because of their unique chemical and physical properties, inorganic semiconducting nanostructures have gradually played a pivotal role in a variety of research fields, including electronics, chemical reactivity, energy conversion, and optics. A major feature of these nanostructures is the quantum confinement effect, which strongly depends on their size, shape, crystal structure and polydispersity. Among all developed synthetic methods, the hydrothermal method based on a water system has attracted more and more attention because of its outstanding advantages, such as high yield, simple manipulation, easy control, uniform products, lower air pollution, low energy consumption and so on. Precise control over the hydrothermal synthetic conditions is a key to the success of the preparation of high-quality inorganic semiconducting nanostructures. In this review, only the representative hydrothermal synthetic strategies of inorganic semiconducting nanostructures are selected and discussed. We will introduce the four types of strategies based on exterior reaction system adjustment, namely organic additive- and template-free hydrothermal synthesis, organic additive-assisted hydrothermal synthesis, template-assisted hydrothermal synthesis and substrate-assisted hydrothermal synthesis. In addition, the two strategies based on exterior reaction environment adjustment, including microwave-assisted and magnetic field-assisted hydrothermal synthesis, will be also described. Finally, we conclude and give the future prospects of this research area.

  8. Evolution of Pine Island Glacier subglacial conditions in response to 18 years of ice flow acceleration

    Science.gov (United States)

    Brisbourne, A.; Bougamont, M. H.; Christoffersen, P.; Cornford, S. L.; Nias, I.; Vaughan, D.; Smith, A.

    2017-12-01

    Antarctica's main contribution to sea-level rise originates from the Amundsen Coast, when warm ocean water intrudes onto the continental shelf. As a result, strong melting beneath the ice shelves induces thinning near the grounding line of glaciers, which is ensued by large ice flow speed up diffusing rapidly inland. In particular, ice loss from Pine Island Glacier (PIG) accounts for 20% of the total ice loss in West Antarctica, amounting to 0.12 mm yr-1 of global sea-level rise. Forecasting the future flow of Amundsen Coast glaciers is however hindered by large uncertainties regarding how the thinning initiated at the grounding line is transmitted upstream, and how the grounded flow will ultimately respond. This work aims at elucidating the role of subglacial processes beneath PIG tributaries in modulating the ice flow response to frontal perturbations. We used the Community Ice Sheet Model (CISM 2.0) to perform numerical inversions of PIG surface velocity as observed in 1996 and 2014. Over that time period, ice flow acceleration has been widespread over PIG's basin, and the inversions provide insights into the related evolution of the basal thermal and stress conditions. We assume the latter to be directly related to changes in the properties of a soft sediment (till) layer known to exist beneath PIG. We find that the overall bed strength has weakened by 18% in the region of enhanced flow, and that the annual melt production for PIG catchment increased by 25% between 1996 and 2014. Specifically, regions of high melt production are located in the southern tributaries, where the overall stronger bed allows for more frictional melting. However, we find no significant and widespread change in the basal strength of that region, and we infer that the water produced is transported away in a concentrated hydrological system, without much interaction with the till layer. In contrast, we find that relatively less basal melting occurs elsewhere in the catchment, where the

  9. Remote Sensing Analysis of Mineralized Alteration in the Ramand Area (Qazvin Province

    Directory of Open Access Journals (Sweden)

    Seyed Abolfazl Ezzati

    2016-07-01

    Full Text Available Introduction The Ramand area, southwest of Buin- Zahra, about 60 kilometers from Qazvin, lies in the igneous belt of the Urmieh-Dokhtar region, the main structural zone of north-central Iran. Rhyodacite and rhyolite lava flows are the principal host rocks of mineralization and alteration of the area, most of which occurs in faulted and brecciated zones alongmaj or northwest-trending fault systems (such as Kour-Cheshmeh, Hassan Abad and their branches. Clay minerals determined from satellite images indicated principally argillic hydrothermal alteration before laboratory mineralogical analysis. According to instrumental analyses, mineralized alteration with greater amounts of argillic halos and lesser amounts of sericitic-propylitic minerals contains quartz veinlets in the vertical and lateral sections. Initially, alteration in the Ramand area was revealed in ETM images by using the SPCA technique of Crosta and Moore, 1990 (Selective Principle Component Analysis. Compared with other techniques, SPCA results have reliable spectral signatures for identifying argillic minerals and Fe-oxides as the main mineralogical association in hydrothermal environments. Subsequently, multispectral images (ASTER were analyzed using band ratios.The results indicated silicification alteration along the faulted regions in the Ramand area. Later, areas of silicification alteration were prospected for precious and base metal mineralization.Sampling results suggested that the altered areas have some potential for epithermal mineralization, according to instrumental analyses and micrographic evidence. Materials and methods 1- Collecting satellite images, geological evidence and related documents 2- Image processing to reveal and identify the mineralized alteration. 3- Sampling of the mineralized zones indicated by the remote sensing. 4- Thin- and polished section microscopic studies. 5- X-ray diffraction analysis (XRD (19 samples, inductively coupled plasma mass

  10. First Survey For Submarine Hydrothermal Vents In NE Sulawesi, Indonesia

    Science.gov (United States)

    McConachy, T.; Binns, R.; Permana, H.

    2001-12-01

    parasitic to Awu volcano. It has a summit crater or small caldera, about 800 m across and breached to the northwest. A dredge hauled within the caldera returned numerous un-abraded fragments of fresh pumiceous dacite glass with prominent phenocrysts of plagioclase, orthopyroxene and clinopyroxene, plus small angular fragments of a similar but less vesicular lithology. Coatings of soft ferruginous deposit on some fragments suggest that the caldera is hydrothermally active. A highlight of the expedition was a visit to Banua Wuhu, classed as an active volcano (eruption in 1919) whose summit is just exposed at low tide. Gas bubbling, subsurface sonic activity, and venting of hydrothermal fluids with temperatures around 50ºC are known to occur on the summit at around 10 m depth, and ferruginous oxide deposits several mm thick are common. A multibeam bathymetric chart to 1000 m was prepared and deeper narrow-beam echo sounding show that Banua Wuhu is a parasitic feature on the north-western side of adjacent Mahenetang Island, also a volcanic construction, the combined edifice exceeding 3000 m in height. We recovered thoroughly altered porphyritc andesite containing disseminated pyrite and a carbonate-chlorite-clay mineral assemblage. In summary, while the IASSHA cruise located only a single but potentially significant example of modern seafloor hydrothermal activity, we collected much valuable new geological and oceanographic data on two contrasted areas in northeastern Sulawesi that with on going post-cruise processing will greatly expand our knowledge of these regions. Binns and Permana Co-Chief Scientists

  11. Overview of hydrothermal testing of waste-package barrier materials at the Basalt Waste Isolation Project

    International Nuclear Information System (INIS)

    1982-01-01

    The current Waste Package Department (WPD) hydrothermal testing program for the Basalt Waste Isolation Project (BWIP) has followed a systematic approach for the testing of waste-barrier-basalt interactions based on sequential penetration of barriers by intruding groundwaters. Present test activities in the WPD program have focused on determining radionuclide solubility limits (or steady-state conditions) of simulated waste forms and the long-term stability of waste package barriers under site-specific hydrothermal conditions. The resulting data on solution compositions and solid alteration products have been used to evaluate waste form degradation under conditions specific to a nuclear waste repository located in basalt (NWRB). Isothermal, time-invariant compositional data on sampled solutions have been coupled with realistic hydrologic flow data for near-field and far-field modeling for the calculation of meaningful radionuclide release rates. Radionuclides that are not strongly sorbed or precipitated from solution and that, therefore, may require special attention to ensure their isolation within the waste package have been identified. Taken together, these hydrothermal test data have been used to establish design requirements for waste packages located in basalt

  12. Potential Activity of Subglacial Microbiota Transported to Anoxic River Delta Sediments

    DEFF Research Database (Denmark)

    Cameron, Karen A.; Stibal, Marek; Olsen, Nikoline S.

    2017-01-01

    -related organisms. Later, a reduction in methane was observed to be paired with the depletion of sulphate, and we hypothesise that sulphate reduction out competed hydrogenotrophic methanogenesis. The structure and diversity of the original CO2/H2-amended incubation communities changed dramatically with a major......The Watson River drains a portion of the SW Greenland ice sheet, transporting microbial communities from subglacial environments to a delta at the head of Søndre Strømfjord. This study investigates the potential activity and community shifts of glacial microbiota deposited and buried under layers...... of sediments within the river delta. A long-term (12-month) incubation experiment was established using Watson River delta sediment under anaerobic conditions, with and without CO2/H2 enrichment. Within CO2/H2-amended incubations, sulphate depletion and a shift in the microbial community to a 52% predominance...

  13. Dynamics of the Yellowstone hydrothermal system

    Science.gov (United States)

    Hurwitz, Shaul; Lowenstern, Jacob B.

    2014-01-01

    The Yellowstone Plateau Volcanic Field is characterized by extensive seismicity, episodes of uplift and subsidence, and a hydrothermal system that comprises more than 10,000 thermal features, including geysers, fumaroles, mud pots, thermal springs, and hydrothermal explosion craters. The diverse chemical and isotopic compositions of waters and gases derive from mantle, crustal, and meteoric sources and extensive water-gas-rock interaction at variable pressures and temperatures. The thermal features are host to all domains of life that utilize diverse inorganic sources of energy for metabolism. The unique and exceptional features of the hydrothermal system have attracted numerous researchers to Yellowstone beginning with the Washburn and Hayden expeditions in the 1870s. Since a seminal review published a quarter of a century ago, research in many fields has greatly advanced our understanding of the many coupled processes operating in and on the hydrothermal system. Specific advances include more refined geophysical images of the magmatic system, better constraints on the time scale of magmatic processes, characterization of fluid sources and water-rock interactions, quantitative estimates of heat and magmatic volatile fluxes, discovering and quantifying the role of thermophile microorganisms in the geochemical cycle, defining the chronology of hydrothermal explosions and their relation to glacial cycles, defining possible links between hydrothermal activity, deformation, and seismicity; quantifying geyser dynamics; and the discovery of extensive hydrothermal activity in Yellowstone Lake. Discussion of these many advances forms the basis of this review.

  14. The aeromagnetic method as a tool to identify Cenozoic magmatism in the West Antarctic Rift System beneath the West Antarctic Ice Sheet: a review; Thiel subglacial volcano as possible source of the ash layer in the WAISCOR

    Science.gov (United States)

    Behrendt, John C.

    2013-01-01

    The West Antarctic Ice Sheet (WAIS) flows through the volcanically active West Antarctic Rift System (WARS). The aeromagnetic method has been the most useful geophysical tool for identification of subglacial volcanic rocks, since 1959–64 surveys, particularly combined with 1978 radar ice-sounding. The unique 1991–97 Central West Antarctica (CWA) aerogeophysical survey covering 354,000 km2 over the WAIS, (5-km line-spaced, orthogonal lines of aeromagnetic, radar ice-sounding, and aerogravity measurements), still provides invaluable information on subglacial volcanic rocks, particularly combined with the older aeromagnetic profiles. These data indicate numerous 100–>1000 nT, 5–50-km width, shallow-source, magnetic anomalies over an area greater than 1.2 × 106 km2, mostly from subglacial volcanic sources. I interpreted the CWA anomalies as defining about 1000 “volcanic centers” requiring high remanent normal magnetizations in the present field direction. About 400 anomaly sources correlate with bed topography. At least 80% of these sources have less than 200 m relief at the WAIS bed. They appear modified by moving ice, requiring a younger age than the WAIS (about 25 Ma). Exposed volcanoes in the WARS are The present rapid changes resulting from global warming, could be accelerated by subglacial volcanism.

  15. Geochemical constraints on sources of metabolic energy for chemolithoautotrophy in ultramafic-hosted deep-sea hydrothermal systems.

    Science.gov (United States)

    McCollom, Thomas M

    2007-12-01

    Numerical models are employed to investigate sources of chemical energy for autotrophic microbial metabolism that develop during mixing of oxidized seawater with strongly reduced fluids discharged from ultramafic-hosted hydrothermal systems on the seafloor. Hydrothermal fluids in these systems are highly enriched in H(2) and CH(4) as a result of alteration of ultramafic rocks (serpentinization) in the subsurface. Based on the availability of chemical energy sources, inferences are made about the likely metabolic diversity, relative abundance, and spatial distribution of microorganisms within ultramafic-hosted systems. Metabolic reactions involving H(2) and CH(4), particularly hydrogen oxidation, methanotrophy, sulfate reduction, and methanogenesis, represent the predominant sources of chemical energy during fluid mixing. Owing to chemical gradients that develop from fluid mixing, aerobic metabolisms are likely to predominate in low-temperature environments (energy per kilogram of hydrothermal fluid, while anaerobic metabolic reactions can supply about 1 kJ, which is sufficient to support a maximum of approximately 120 mg (dry weight) of primary biomass production by aerobic organisms and approximately 20-30 mg biomass by anaerobes. The results indicate that ultramafic-hosted systems are capable of supplying about twice as much chemical energy as analogous deep-sea hydrothermal systems hosted in basaltic rocks.

  16. Subglacial groundwater flow at Aespoe as governed by basal melting and ice tunnels

    International Nuclear Information System (INIS)

    Svensson, Urban

    1999-02-01

    A high resolution three dimensional numerical model of subglacial groundwater flow is described. The model uses conductivity data from the Aespoe region and is thus site specific. It is assumed that the groundwater flow is governed by the basal melting and ice tunnels; ice surface melting is not considered. Results are presented for the meltwater transport time (to the ice margin) and maximum penetration depth. Conditions at repository depth, i.e. about 500 metres, are also analysed. The general conclusion from the study is that the model presented gives plausible results, considering the basic conceptual assumptions made. It is however questioned if the hydraulics of the ice tunnels is well enough understood; this is a topic that is suggested for further studies

  17. Alteration of basaltic glass in Iceland as a natural analogue for nuclear waste glasses

    International Nuclear Information System (INIS)

    Crovisier, J.L.; Advocat, T.; Fritz, B.; Petit, J.C.

    1989-01-01

    The authors describe the longer term geochemical consequences of basaltic glass dissolution in fresh water at 0 0 C calculated with the computer code DISSOL. The clay minerals were represented by an ideal solid solution model (CISSFIT) able to describe variations in chemical composition of a clay phase in response to variations of the solution chemistry. The predicted mineral phases were iron hydroxides followed by kaolinite, TOT clays, chabazite and clinoptilolite. These results are in reasonably good agreement with experimental results and observations of altered subglacial hyaloclastites from Iceland. The formation of secondary products are mainly controlled by thermodynamic constraints. Kinetic effects, such as diffusion in the near glass surface are not important

  18. A thermoelectric cap for seafloor hydrothermal vents

    International Nuclear Information System (INIS)

    Xie, Yu; Wu, Shi-jun; Yang, Can-jun

    2016-01-01

    Highlights: • We developed a thermoelectric cap (TC) to harvest hydrothermal energy. • The TC was deployed at a hydrothermal vent site near Kueishantao islet, Taiwan. • The TC monitored the temperature of the hydrothermal fluids during the field test. • The TC could make the thermal energy of hydrothermal fluids a viable power source. - Abstract: Long-term in situ monitoring is crucial to seafloor scientific investigations. One of the challenges of operating sensors in seabed is the lifespan of the sensors. Such sensors are commonly powered by batteries when other alternatives, such as tidal or solar energy, are unavailable. However, the batteries have a limited lifespan and must be recharged or replaced periodically, which is costly and impractical. A thermoelectric cap, which harvests the thermal energy of hydrothermal fluids through a conduction pipe and converts the heat to electrical energy by using thermoelectric generators, was developed to avoid these inconveniences. The thermoelectric cap was combined with a power and temperature measurement system that enables the thermoelectric cap to power a light-emitting diode lamp, an electronic load (60 Ω), and 16 thermocouples continuously. The thermoelectric cap was field tested at a shallow hydrothermal vent site near Kueishantao islet, which is located offshore of northeastern Taiwan. By using the thermal gradient between hydrothermal fluids and seawater, the thermoelectric cap obtained a sustained power of 0.2–0.5 W during the field test. The thermoelectric cap successfully powered the 16 thermocouples and recorded the temperature of the hydrothermal fluids during the entire field test. Our results show that the thermal energy of hydrothermal fluids can be an alternative renewable power source for oceanographic research.

  19. The Guaymas Basin hiking guide to hydrothermal mounds, chimneys and microbial mats: complex seafloor expressions of subsurface hydrothermal circulation

    Directory of Open Access Journals (Sweden)

    Andreas eTeske

    2016-02-01

    Full Text Available The hydrothermal mats, mounds and chimneys of the southern Guaymas Basin are the surface expression of complex subsurface hydrothermal circulation patterns. In this overview we document the most frequently visited features of this hydrothermal area with photographs, temperature measurements, and selected geochemical data; many of these distinct habitats await characterization of their microbial communities and activities. Microprofiler deployments on microbial mats and hydrothermal sediments show their steep geochemical and thermal gradients at millimeter-scale vertical resolution. Mapping these hydrothermal features and sampling locations within the southern Guaymas Basin suggest linkages to underlying shallow sills and heatflow gradients. Recognizing the inherent spatial limitations of much current Guaymas Basin sampling calls for a wider survey of the entire spreading region.

  20. Trace elements mobility in soils from the hydrothermal area of Nisyros (Greece

    Directory of Open Access Journals (Sweden)

    Kyriaki Daskalopoulou

    2015-03-01

    Full Text Available Nisyros Island, Greece, is a stratovolcano known for its intense hydrothermal activity. On June 2013, during a multidisciplinary field campaign, soil samples were collected in the caldera area to determinate the main mineralogical assemblages and to investigate the distribution of trace element concentrations and the possible relationship to the contribution of fluids of deep origin. Soil samples were analysed with XRD and for the chemical composition of their leachable (deionized water and pseudo total (microwave digestion fraction both for major and trace elements. The results allow to divide the samples in 2 groups: Lakki Plain and Stefanos Crater. The latter, where a fumarolic area is located, shows a mineralogical assemblage dominated by phases typical of hydrothermal alteration. Their very low pH values (1.9 – 3.4 show the strong impact of fumarolic gases which are probably also the cause of strong enrichments in these soils of highly volatile elements like S, As, Se, Bi, Sb, Tl and Te. 

  1. Insights From Magnesium Isotopic Compositions on the Oceanic Hydrothermal Circulation: Is Seamount Weathering the Solution?

    Science.gov (United States)

    Galy, A.; Carder, E.; Elderfield, H.

    2006-12-01

    It has been long recognised that the input of Mg in the ocean by river is removed by precipitation of Mg-rich bearing phases, either directly from the ocean such as dolomite or through hydrothermal circulation in the oceanic crust. The sampling of hydrothermal fluids demonstrated the efficiency of Mg consumption by the alteration of the oceanic crust, even at temperatures as low as 15°. For high-temperature fluids vented through black or white smokers in the vicinity of the ridge, the Mg concentration is up to 50 time lower than in seawater, and the close relationship between chlorine and Mg led to the idea that seawater was feeding the hydrothermal system and that Mg is quantitatively removed from it during high-T° alteration, the so called zero Mg hypothesis. Despite some hint for a non zero Mg hydrothermal end-member for a handful sites, the low concentration of Mg in oceanic hydrothermal fluids (around 1 mmol/l) has been mainly attributed to contamination by seawater during the sampling. Here we present Mg isotopic composition of 14 seawater samples from the Atlantic, Pacific and Indian Oceans and the Mediterranean and Red Seas and covering a range of depth of almost 5km and 26 hydrothermal fluids from 7 sites in the Atlantic and Pacific Oceans with temperature from 15° to 380°C. We find the magnesium isotope composition of seawater to be constant, with a δ^{26}Mg = -0.82±0.10 ‰ relative to the DSM3 standard. This value is consistent with a long residence time for Mg in seawater. In addition, out of the 26 hydrothermal fluids studied, more than 58% differ from seawater for their Mg isotopic composition by more than 2σ. This number rises up to 88% at 2σmean level and the shift is systematic with the fluids being either indistinguishable from seawater or enriched in light isotopes by up to 2.4‰ in δ^{26}Mg. This clearly demonstrates that fluids having low Mg concentrations are not solely bearing Mg added by contamination during sampling. The isotopic

  2. Hydrothermal oxidation in the Biwabik Iron Formation, MN, USA

    Science.gov (United States)

    Losh, Steven; Rague, Ryan

    2018-02-01

    Precambrian iron formations throughout the world, notably in Australia, Brazil, and South Africa, show evidence of hypogene (≥ 110 °C, mostly > 250 °C) oxidation, alteration, and silica dissolution as a result of tectonic or magmatic activity. Although hydrothermal oxidation has been proposed for the prototype Lake Superior-type iron formation, the Biwabik Iron Formation in Minnesota (USA), it has not been documented there. By examining oxidized and unoxidized Biwabik Iron Formation in three mines, including material from high-angle faults that are associated with oxidation, we document an early hypogene oxidation event ( 175 °C) involving medium-salinity aqueous fluids (8.4 ± 4.9 wt% NaCl equiv) that infiltrated iron formation along high-angle faults. At the Hibbing Taconite Mine, hydrothermal fluids oxidized iron carbonates and silicates near faults, producing goethite ± quartz. In contrast with much of the oxidized iron ores on the Mesabi Range, silica was not removed but rather recrystallized during this event, perhaps lying in a rock-dominated system at low cumulative fluid flux. During the hydrothermal oxidation event in the Hibbing Taconite deposit, quartz-filled microfractures and irregular inclusions commonly formed in coarse variably oxidized magnetite, currently the ore mineral: these inclusions degrade the ore by introducing excess silica in magnetic concentrate. Hydrothermal oxidation at Hibbing Taconite Mine is overprinted by later, relatively minor supergene oxidation both along faults and near the surface, which locally dissolved quartz. At the Fayal Reserve Mine, widespread silicate and carbonate gangue dissolution and iron oxidation was followed by precipitation of pyrite, Mn-siderite, apatite, and other minerals in void spaces, which prevented post-oxidation compaction and significant volume loss in the sampled rocks. Although definitive temperature data for this assemblage are needed, the weight of evidence indicates that this

  3. Joint Geodetic and Seismic Analysis of the effects of Englacial and Subglacial Hydraulics on Surface Crevassing near a Seasonal, Glacier-Dammed Lake on Gornergletscher, Switzerland

    Science.gov (United States)

    Garcia, L.; Luttrell, K. M.; Kilb, D. L.; Walter, F.

    2017-12-01

    Glacial outburst floods are difficult to predict and threaten human life and property near glaciated regions. These events are characterized by rapid draining of glacier-dammed lakes via the sub/englacial hydraulic network to the proglacial stream. The glacier-dammed lake on Gornergletscher in Switzerland, which fills and drains each summer, provides an opportunity to study this hazard. For three drainages (2004, 2006, and 2007), we track icequakes (IQ) and on-ice GPS movement. Our seasonal seismic networks had 8 - 24 three component stations and apertures of about 300 - 400 m on the glacier surface. The seasonal GPS arrays contained 4 - 8 GPS antennae on the glacier surface. Using Rayleigh wave coherence surface IQ location, we located 2924, 7822 and 3782 IQs, in 2004, 2006 and 2007, respectively. The GPS data were smoothed using a nonparametric protocol, with average station velocities of 10 - 90 mm/day. In 2006, strains were calculated using five stations within 500 m of the lake, co-located with the seismic network. IQ productivity increased substantially during lake drainage only in 2004, which was the only year when the lake drainage was rapid ( 6 days) and primarily subglacial. In 2006, there was no obvious increase in GPS speeds with slow ( 21 days), supraglacial lake drainage. However, when drainage was subglacial as in 2004 and 2007 (sub/englacial over 11 days), GPS speed increased up to 160%. This speed increase is evidence for basal sliding induced by subglacial drainage. In general, we find that when the strain increase on the principle extension axis aligns with the crevasse opening direction, IQ are more prolific. We also observe a diurnal signal in both IQ occurrence and surface strain, with peak strain occurring in the mid- to late-afternoon (15:00 - 19:00 local) across the study area in 2006. We interpret this time-shift in strain and spatiotemporal dependence of IQs to be caused by diurnal variations in melt-induced sliding. Our analysis sheds

  4. Effect of hydrothermal treatment temperature on the properties of sewage sludge derived solid fuel

    Directory of Open Access Journals (Sweden)

    Mi Yan

    2015-10-01

    Full Text Available High moisture content along with poor dewaterability are the main challenges for sewage sludge treatment and utilization. In this study, the effect of hydrothermal treatment at various temperature (120-200 ˚C on the properties of sewage sludge derived solid fuel was investigated in the terms of mechanical dewatering character, drying character, calorific value and heavy metal distribution. Hydrothermal treatment (HT followed by dewatering process significantly reduced moisture content and improved calorific value of sewage sludge with the optimum condition obtained at 140˚C. No significant alteration of drying characteristic was produced by HT. Heavy metal enrichment in solid particle was found after HT that highlighted the importance of further study regarding heavy metal behavior during combustion. However, it also implied the potential application of HT on sewage sludge for heavy metal removal from wastewater.

  5. Modelling of hydrothermal characteristics of centrifugal nozzles

    International Nuclear Information System (INIS)

    Yarkho, A.A.; Omelchenko, M.P.; Borshchev, V.A.

    1990-01-01

    Presented for the first time is a method of recalculating the hydrothermal characteristics of centrifugal nozzles obtained in laboratory conditions for full-scale nozzles. From the experimental hydrothermal characteristics of nozzles observed in the laboratory it is allowed to calculate the hydrothermal characteristics of any other centrifugal nozzle whose diameter and dimensionless geometric characteristic are known

  6. Unrest at Bárdarbunga: Preparations for possible flooding due to subglacial volcanism

    Science.gov (United States)

    Hardardottir, Jorunn; Roberts, Matthew; Pagneux, Emmanuel; Einarsson, Bergur; Thorarinsdottir, Tinna; Johannesson, Tomas; Sigurdsson, Oddur; Egilson, David; Sigurdsson, Gunnar; Imo hydrological-monitoring-team

    2015-04-01

    Located partly beneath northwest Vatnajökull, Iceland, the Bárdarbunga volcanic system comprises an ice-capped central volcano and a fissure swarm extending beyond the ice margin. During the last 1100 years the volcano has erupted on at least 26 occasions. Outburst floods (jökulhlaups) on a scale of >100,000 m3 s-1 are known to have occurred during major explosive eruptions. Repeated jökulhlaups from Bárdarbunga have inundated the Jökulsá á Fjöllum River, which drains over 200 km northwards from the Dyngjujökull outlet glacier to the north coast of Iceland. Depending on the location of the eruption within the 80 km2 caldera, jökulhlaups could also flow northwards along Skjálfandafljót River and towards west and southwest into present-day tributaries of the extensively hydropower-harnessed Thjórsá River. On 16 August 2014, an intense earthquake swarm began within the Bárdarbunga caldera. Seismicity propagated from the caldera, extending ~10 km northwards of the ice margin where a fissure eruption developed in late August and remains ongoing in early January 2015. In connection with the lateral migration of magma from the caldera, the ice surface of Bárdarbunga has lowered by over 60 m; also associated with increased geothermal heat on the caldera rim, as manifested by the development of ice-surface depressions. In preparation for a subglacial eruption in the Bárdarbunga volcanic system, the Icelandic Meteorological Office (IMO) has made several assessments of likely hydrological hazards. Assessments were undertaken on Jökulsá á Fjöllum and Skjálfandafljót at key locations where preliminary evacuation plans for populated areas were made in cooperation with the local police. Floodwater extent was estimated for key infrastructures, such as bridges, telecommunication and power lines for maximum discharge levels ranging from 3,000 to 20,000 m3 s-1. The estimations were made using either simple Manning's calculations or HEC-RAS modelling

  7. Study on the hydrothermal treatment of Shenhua coal

    Energy Technology Data Exchange (ETDEWEB)

    Zhicai Wang; Hengfu Shui; Zhanning Pei; Jinsheng Gao [Anhui University of Technology, Ma' anshan (China). School of Chemistry and Chemical Engineering

    2008-04-15

    In this paper, the hydrothermal treatment of Shenhua coal was carried out under 0.1 MPa (initial pressure) nitrogen and different temperature. Effects of hydrothermal treatment on the structure and the hydro-liquefaction activity of Shenhua coal were investigated by the ultimate and proximate analyses, the FTIR measurements and TG analyses of hydrothermally treated coals, and the characterizations of extraction and swelling properties, and the batch hydro-liquefaction of treated coal were also carried out. The results indicate that hydrothermal treatment above 200{sup o}C can increase the hydrogen content of treated coal and decrease the yield of volatiles and the content of ash, especially a large amount of CO and CH{sub 4} are found in gas products obtained by the hydrothermal treatment above 250{sup o}C. Hydrothermal treatment disrupts the weak covalent bond such as ether, ester and side-chain substituent by hydrolysis and pyrolysis, and changes the distribution of H-bond in coal. The swelling ratio and the Soxhlet extraction yield of treated coal decrease with the increase of hydrothermal treatment temperature. The conversion of liquefaction and the yield of CS{sub 2}/NMP mixed solvent extraction at ambient temperature are enhanced by hydrothermal treatment at 300{sup o}C. Therefore hydrogen donation reactions and the rupture of non-covalent bond and weak covalent bonds present in the process of hydrothermal treatment resulting in the changes of structure and reactivity of Shenhua coal. The results show that the hydro-liquefaction activity of Shenhua coal can be improved by hydrothermal pretreatment between 250{sup o}C and 300{sup o}C. 15 refs., 5 figs., 4 tabs.

  8. High-pressure hydrogen respiration in hydrothermal vent samples from the deep biosphere

    Science.gov (United States)

    Morgan-Smith, D.; Schrenk, M. O.

    2013-12-01

    Cultivation of organisms from the deep biosphere has met with many challenges, chief among them the ability to replicate this extreme environment in a laboratory setting. The maintenance of in situ pressure levels, carbon sources, and gas concentrations are important, intertwined factors which may all affect the growth of subsurface microorganisms. Hydrogen in particular is of great importance in hydrothermal systems, but in situ hydrogen concentrations are largely disregarded in attempts to culture from these sites. Using modified Hungate-type culture tubes (Bowles et al. 2011) within pressure-retaining vessels, which allow for the dissolution of higher concentrations of gas than is possible with other culturing methods, we have incubated hydrothermal chimney and hydrothermally-altered rock samples from the Lost City and Mid-Cayman Rise hydrothermal vent fields. Hydrogen concentrations up to 15 mmol/kg have been reported from Lost City (Kelley et al. 2005), but data are not yet available from the recently-discovered Mid-Cayman site, and the elevated concentration of 30 mmol/kg is being used in all incubations. We are using a variety of media types to enrich for various metabolic pathways including iron and sulfur reduction under anoxic or microaerophilic conditions. Incubations are being carried out at atmospheric (0.1 MPa), in situ (9, 23, or 50 MPa, depending on site), and elevated (50 MPa) pressure levels. Microbial cell concentrations, taxonomic diversity, and metabolic activities are being monitored during the course of these experiments. These experiments will provide insight into the relationships between microbial activities, pressure, and gas concentrations typical of deep biosphere environments. Results will inform further culturing studies from both fresh and archived samples. References cited: Bowles, M.W., Samarkin, V.A., Joye, S.B. 2011. Improved measurement of microbial activity in deep-sea sediments at in situ pressure and methane concentration

  9. The Significance of Acid Alteration in the Los Humeros High-Temperature Geothermal Field, Puebla, Mexico.

    Science.gov (United States)

    Elders, W. A.; Izquierdo, G.

    2014-12-01

    The Los Humeros geothermal field is a high-enthalpy hydrothermal system with more than 40 drilled deep wells, mostly producing high steam fractions at > 300oC. However, although it has a large resource potential, low permeability and corrosive acid fluids have hampered development so that it currently has an installed electrical generating capacity of only 40 MWe. The widespread production of low pH fluids from the reservoir is inconsistent with the marked absence in the reservoir rocks of hydrothermal minerals typical of acid alteration. Instead the hydrothermal alteration observed is typical of that due to neutral to alkaline pH waters reacting with the volcanic rocks of the production zones. Thus it appears that since the reservoir has recently suffered a marked drop in fluid pressure and is in process of transitioning from being water-dominated to being vapor-dominated. However sparse examples of acid leaching are observed locally at depths of about 2 km in the form of bleached, intensely silicified zones, in low permeability and very hot (>350oC) parts of reservoir. Although these leached rocks retain their primary volcanic and pyroclastic textures, they are altered almost entirely to microcrystalline quartz, with some relict pseudomorphs of plagioclase phenocrysts and traces of earlier-formed hydrothermal chlorite and pyrite. These acid-altered zones are usually only some tens of meters thick and deeper rocks lack such silicification. The acid fluids responsible for their formation could either be magmatic volatiles, or could be formed during production (e.g. reaction of water and salts forming hydrogen chloride by hydrolysis at high temperatures). The very high boron content of the fluids produced by the Los Humeros wells suggests that their ultimate source is most likely magmatic gases. However, these acid gases did not react widely with the rocks. We suggest that the silicified zones are forming locally where colder descending waters are encountering

  10. Origin of convex tetrads in rare earth element patterns of hydrothermally altered siliceous igneous rocks from the Zinnwald Sn W deposit, Germany

    Science.gov (United States)

    Monecke, T.; Dulski, P.; Kempe, U.

    2007-01-01

    The chondrite-normalized rare earth element (REE) patterns of whole rock samples from evolved granitic systems hosting rare metal deposits sometimes show a split into four consecutive curved segments, referred to as tetrads. In the present contribution, a rigorous statistical method is proposed that can be used to test whether geological significance should be attributed to tetrads that are only of limited size. The method involves a detailed evaluation of element and sample specific random and systematic errors that are constrained on the basis of independent repeated preparations and analyses of sample and reference materials. Application of the proposed method to samples from the granite-hosted Zinnwald Sn-W deposit, Germany, revealed that at least two tetrads in normalized whole rock REE patterns have to be analytically significant to rule out that fractional crystallization led to the unusual behavior of the REEs. Based on the analysis of altered albite granite and greisen samples from the endocontact of the Zinnwald granite massif, it is demonstrated that the lanthanide tetrad effect is responsible for the formation of the convex tetrads. Geological and petrological evidence suggests that the tetrads in the samples developed prior to greisenization and related cassiterite precipitation. In contrast to the endocontact samples, the rhyolitic wall rocks are typified by normalized REE patterns having tetrads that are variable in size and frequently close to the limit of analytical significance. The sizes of the tetrads apparently correlate with the intensity of albitization, but show no relation to subsequent alteration processes including greisenization and low-temperature argillization. This observation proves that curved segments in normalized whole rock REE patterns can be introduced during hydrothermal fluid-rock interaction.

  11. Alteration of submarine volcanic rocks in oxygenated Archean oceans

    Science.gov (United States)

    Ohmoto, H.; Bevacqua, D.; Watanabe, Y.

    2009-12-01

    Most submarine volcanic rocks, including basalts in diverging plate boundaries and andesites/dacites in converging plate boundaries, have been altered by low-temperature seawater and/or hydrothermal fluids (up to ~400°C) under deep oceans; the hydrothermal fluids evolved from shallow/deep circulations of seawater through the underlying hot igneous rocks. Volcanogenic massive sulfide deposits (VMSDs) and banded iron formations (BIFs) were formed by mixing of submarine hydrothermal fluids with local seawater. Therefore, the behaviors of various elements, especially of redox-sensitive elements, in altered submarine volcanic rocks, VMSDs and BIFs can be used to decipher the chemical evolution of the oceans and atmosphere. We have investigated the mineralogy and geochemistry of >500 samples of basalts from a 260m-long drill core section of Hole #1 of the Archean Biosphere Drilling Project (ABDP #1) in the Pilbara Craton, Western Australia. The core section is comprised of ~160 m thick Marble Bar Chert/Jasper Unit (3.46 Ga) and underlying, inter-bedded, and overlying submarine basalts. Losses/gains of 65 elements were quantitatively evaluated on the basis of their concentration ratios against the least mobile elements (Ti, Zr and Nb). We have recognized that mineralogical and geochemical characteristics of many of these samples are essentially the same as those of hydrothermally-altered modern submarine basalts and also those of altered volcanic rocks that underlie Phanerozoic VMSDs. The similarities include, but are not restricted to: (1) the alteration mineralogy (chlorite ± sericite ± pyrophyllite ± carbonates ± hematite ± pyrite ± rutile); (2) the characteristics of whole-rock δ18O and δ34S values; (3) the ranges of depletion and enrichment of Si, Al, Mg, Ca, K, Na, Fe, Mn, and P; (4) the enrichment of Ba (as sulfate); (5) the increases in Fe3+/Fe2+ ratios; (6) the enrichment of U; (7) the depletion of Cr; and (8) the negative Ce anomalies. Literature data

  12. Palaeomagnetism in the Sines massif (SW Iberia) revisited: evidences for Late Cretaceous hydrothermal alteration and associated partial remagnetization

    Science.gov (United States)

    Ribeiro, P.; Silva, P. F.; Moita, P.; Kratinová, Z.; Marques, F. O.; Henry, B.

    2013-10-01

    This study revisits the palaeomagnetism of the Sines massif (˜76 Ma) in the southwestern Iberian Margin (Portugal). The palaeomagnetic analysis was complemented by a comprehensive study of the magnetic mineralogy by means of rock magnetic measurements and petrographic observations. The overall dispersion of palaeomagnetic directions (declination ranging between ˜N0° and ˜N50°) and their migration observed during stepwise demagnetizations have revealed the superposition of remanence components. We interpret this complex palaeomagnetic behaviour as related to the regional hydrothermalism associated with the last stages of Late Cretaceous magmatic activity. This environment favoured mineralogical alteration and a partial chemical remagnetization, giving in most samples a composite magnetization, which has been erroneously interpreted as the primary one in a previous study, then leading to a questionable model for Cretaceous Iberia rotation. Nonetheless, for some samples a single component has been isolated. Interesting rock magnetic properties and microscopic observations point to a well-preserved magnetic mineralogy for these samples, with magnetite clearly of primary origin. The associated ChRM mean direction (D/I = 3.9°/46.5°, α95 = 1.7°, N = 31 samples) then represents the true primary magnetization of the Sines massif. This new palaeomagnetic direction and the corresponding palaeomagnetic pole (long = 332.0°, lat = -79.5°, A95 = 1.7°) agrees with those from the other palaeomagnetic works for the same period and region (e.g. the Sintra and Monchique massifs), yielding a lack of significant rotation of Iberia relative to stable Europe since the uppermost Late Cretaceous (Campanian-Maastrichtian).

  13. Limited Impact of Subglacial Supercooling Freeze-on for Greenland Ice Sheet Stratigraphy

    Science.gov (United States)

    Dow, Christine F.; Karlsson, Nanna B.; Werder, Mauro A.

    2018-02-01

    Large units of disrupted radiostratigraphy (UDR) are visible in many radio-echo sounding data sets from the Greenland Ice Sheet. This study investigates whether supercooling freeze-on rates at the bed can cause the observed UDR. We use a subglacial hydrology model to calculate both freezing and melting rates at the base of the ice sheet in a distributed sheet and within basal channels. We find that while supercooling freeze-on is a phenomenon that occurs in many areas of the ice sheet, there is no discernible correlation with the occurrence of UDR. The supercooling freeze-on rates are so low that it would require tens of thousands of years with minimal downstream ice motion to form the hundreds of meters of disrupted radiostratigraphy. Overall, the melt rates at the base of the ice sheet greatly overwhelm the freeze-on rates, which has implications for mass balance calculations of Greenland ice.

  14. Application of Hydrothermal and Non-Hydrothermal TiO2 Nanoporous Materials as New Adsorbents for Removal of Heavy Metal Ions from Aqueous System

    Directory of Open Access Journals (Sweden)

    Mansoor Anbia

    2016-06-01

    Full Text Available Hydrothermal and non-hydrothermal spherical TiO2 nanoporous with crystalline framework were prepared by sol-gel method. The Crystalline structures, morphologies and surface texturing of materials were determined by X-ray diffraction (XRD, scanning electron microscopy (SEM and N2 adsorption-desorption isotherms. The Hydrothermal spherical TiO2 nanoporous was found to have a narrow and strong pore size distribution peaks with average of 37.8 Å and pore volume of 0.41 cm3/g and the (Brunauer–Emmett–TellerBET specific surface area of 365 m2/g. Hydrothermal and non-hydrothermal spherical TiO2 nanoporous have been used as adsorbent to study of the adsorption behavior of Pb(II, Co(II and Ni(II ions from aqueous system in a batch system. Effect of equilibrium time on adsorption Pb(II, Co(II and Ni(II ions on these adsorbent was studied The results show that the shaking time 0.5 to 10h has no serious effect on the percentage of ions removal, and the adsorption is fast in all cases. The maximum uptake capacities of Hydrothermal and non-hydrothermal spherical TiO2 nanoporous was calculated. Both hydrothermal and non-hydrothermal TiO2 nanoporous materials were found to have very good potential as new adsorbents in removal of these ions. In batch systems the maximum uptake capacities of Pb(II, Ni(II and Co(II on the hydrothermal and non-hydrothermal TiO2 nanoporous materials was Co(II > Pb(II > Ni(II and Co(II > Ni(II > Pb(II, respectively.

  15. Volcanic and Hydrothermal Activity of the North Su Volcano: New Insights from Repeated Bathymetric Surveys and ROV Observations

    Science.gov (United States)

    Thal, J.; Bach, W.; Tivey, M.; Yoerger, D.

    2013-12-01

    Bathymetric data from cruises in 2002, 2006, and 2011 were combined and compared to determine the evolution of volcanic activity, seafloor structures, erosional features and to identify and document the distribution of hydrothermal vents on North Su volcano, SuSu Knolls, eastern Manus Basin (Papua New Guinea). Geologic mapping based on ROV observations from 2006 (WHOI Jason-2) and 2011 (MARUM Quest-4000) combined with repeated bathymetric surveys from 2002 and 2011 are used to identify morphologic features on the slopes of North Su and to track temporal changes. ROV MARUM Quest-4000 bathymetry was used to develop a 10 m grid of the top of North Su to precisely depict recent changes. In 2006, the south slope of North Su was steeply sloped and featured numerous white smoker vents discharging acid sulfate waters. These vents were covered by several tens of meters of sand- to gravel-sized volcanic material in 2011. The growth of this new cone changed the bathymetry of the south flank of North Su up to ~50 m and emplaced ~0.014 km3 of clastic volcanic material. This material is primarily comprised of fractured altered dacite and massive fresh dacite as well as crystals of opx, cpx, olivine and plagioclase. There is no evidence for pyroclastic fragmentation, so we hypothesize that the fragmentation is likely related to hydrothermal explosions. Hydrothermal activity varies over a short (~50 m) lateral distance from 'flashing' black smokers to acidic white smoker vents. Within 2 weeks of observation time in 2011, the white smoker vents varied markedly in activity suggesting a highly episodic hydrothermal system. Based on ROV video recordings, we identified steeply sloping (up to 30°) slopes exposing pillars and walls of hydrothermal cemented volcaniclastic material representing former fluid upflow zones. These features show that hydrothermal activity has increased slope stability as hydrothermal cementation has prevented slope collapse. Additionally, in some places

  16. Ideas and perspectives: hydrothermally driven redistribution and sequestration of early Archaean biomass - the "hydrothermal pump hypothesis"

    Science.gov (United States)

    Duda, Jan-Peter; Thiel, Volker; Bauersachs, Thorsten; Mißbach, Helge; Reinhardt, Manuel; Schäfer, Nadine; Van Kranendonk, Martin J.; Reitner, Joachim

    2018-03-01

    Archaean hydrothermal chert veins commonly contain abundant organic carbon of uncertain origin (abiotic vs. biotic). In this study, we analysed kerogen contained in a hydrothermal chert vein from the ca. 3.5 Ga Dresser Formation (Pilbara Craton, Western Australia). Catalytic hydropyrolysis (HyPy) of this kerogen yielded n-alkanes up to n-C22, with a sharp decrease in abundance beyond n-C18. This distribution ( ≤ n-C18) is very similar to that observed in HyPy products of recent bacterial biomass, which was used as reference material, whereas it differs markedly from the unimodal distribution of abiotic compounds experimentally formed via Fischer-Tropsch-type synthesis. We therefore propose that the organic matter in the Archaean chert veins has a primarily microbial origin. The microbially derived organic matter accumulated in anoxic aquatic (surface and/or subsurface) environments and was then assimilated, redistributed and sequestered by the hydrothermal fluids (hydrothermal pump hypothesis).

  17. Hydrothermal alteration mapping using ASTER data in Baogutu porphyry deposit, China

    International Nuclear Information System (INIS)

    Li, Q; Zhang, B; Lu, L; Lin, Q

    2014-01-01

    Remote sensing plays an important role in mineral exploration. One of its proven applications is extracting host-rock lithology and alteration zones that are related to porphyry copper deposits. An Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) was used to map the Baogutu porphyry deposit alteration area. A circular alteration mineral zoning pattern was clearly observed in the classification result of potassic, phyllic, argillic, propylitic zones. The potassic is characterized by biotite and anhydrite with an absorption feature centered at 1.94 and 2.1um. The phyllic zone is characterized by illite and sericite that indicates an intense Al-OH absorption feature centered at 2.20um. The narrower argillic zone including kaolinite and alunite displays a secondary Al-OH absorption feature at 2.17 um. The mineral assemblages of the outer propylitic zone are epidote, chlorite and calcite that exhibit absorption features at 2.335um.The performance of Principal Component Analysis(PCA), Minimum Noise Fraction (MNF), band ratio(BR) and Constrained Energy Minimization(CEM) has been evaluated. These techniques identified new prospects of porphyry copper mineralization in the study areas. These results indicate that ASTER is a powerful tool in the initial steps of mineral exploration

  18. Hydrothermal alteration mapping using ASTER data in Baogutu porphyry deposit, China

    Science.gov (United States)

    Li, Q.; Zhang, B.; Lu, L.; Lin, Q.

    2014-03-01

    Remote sensing plays an important role in mineral exploration. One of its proven applications is extracting host-rock lithology and alteration zones that are related to porphyry copper deposits. An Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) was used to map the Baogutu porphyry deposit alteration area. A circular alteration mineral zoning pattern was clearly observed in the classification result of potassic, phyllic, argillic, propylitic zones. The potassic is characterized by biotite and anhydrite with an absorption feature centered at 1.94 and 2.1um. The phyllic zone is characterized by illite and sericite that indicates an intense Al-OH absorption feature centered at 2.20um. The narrower argillic zone including kaolinite and alunite displays a secondary Al-OH absorption feature at 2.17 um. The mineral assemblages of the outer propylitic zone are epidote, chlorite and calcite that exhibit absorption features at 2.335um.The performance of Principal Component Analysis(PCA), Minimum Noise Fraction (MNF), band ratio(BR) and Constrained Energy Minimization(CEM) has been evaluated. These techniques identified new prospects of porphyry copper mineralization in the study areas. These results indicate that ASTER is a powerful tool in the initial steps of mineral exploration.

  19. Looking Through the Ice: Searching for Past and Present Habitable Zones in the Martian North Polar Region Using MOLA DEMs

    Science.gov (United States)

    Payne, M. C.; Farmer, J. D.

    2002-12-01

    Hydrothermal systems have been acknowledged as important gateways to accessing a potential subsurface biology (extant or extinct) on Mars. Groundwater circulation, sustained for up to one billion years by large plutonic bodies (as modeled by previous authors), might well be capable of tapping into a deep subsurface biosphere and subsequently carrying members of microbial communities to the surface. Hence, future robotic missions with near surface drilling capabilities may be able to unearth cryopreserved biosignatures, or perhaps extant organisms, in the midst of the hydrothermal system itself. Digital Elevation Models (DEMs) constructed from Mars Orbiter Laser Altimeter (MOLA) data have proved to be a valuable tool in the search for potential habitable zones for extant and extinct life, and the detection of possible hydrothermal systems on Mars. When formatted for use in a Geographical Information Systems (GIS) software package such as ESRI's ArcView, MOLA data can be used to compose DEMs. Those DEMs can, in turn, be used to create contour maps, to allow profiling through features of interest, and to generate hillshaded views, which provide an image-like perspective of a selected area. Furthermore, DEMs eliminate many problems associated with photographic images such as over-/underexposure, poor focus, and albedo values too high or low for optimal observations. During this study, DEMs were used in the analysis of several regions north of 70° N latitude, in the Martian north polar cap and polar cap margin. The regions were selected during a Viking image survey that concentrated on the location of surface expressions of potential magma-ice interactions, and hence past or present hydrothermal activity. Specific features sought included individual volcanoes and volcanic fields, as well as pseudocrater fields, subglacial volcanic constructs (such as tuyas and tindar ridges), fluvial channels and outwash plains (indicative of j”kulhlaup flooding events), possible

  20. Combining ammonium mapping and short-wave infrared (SWIR) reflectance spectroscopy to constrain a model of hydrothermal alteration for the Acoculco geothermal zone, Eastern Mexico

    OpenAIRE

    Canet Miquel, Carles; Hernández-Cruz, B; Jiménez Franco, Abigail; Pi, Teresa; Peláez, B; Villanueva Estrada, Ruth Esther; Alfonso Abella, María Pura; González Partida, Eduardo; Salinas, S.

    2015-01-01

    The Acoculco geothermal system is hosted by a caldera complex located at the eastern portion of the Trans-Mexican Volcanic Belt. Surface manifestations are scarce and consist of low temperature, bubbling, acid–sulfate springs that are concentrated in two zones separated from each other by ~1750 m. In the northernmost one, there are conspicuous features suggesting recent, explosive, hydrothermal activity. Most of the rocks that crop out are tuffs and breccias that show pervasive hydrothermal a...

  1. The Role of Siliceous Hydrothermal Breccias in the Genesis of Volcanic Massive Sulphide Deposits - Ancient and Recent Systems

    Science.gov (United States)

    Costa, I. A.; Barriga, F. J.; Fouquet, Y.

    2014-12-01

    Siliceous hydrothermal breccias were sampled in two Mid-Atlantic Ridge active sites: Lucky Strike and Menez Gwen. These hydrothermal fields are located in the border of the Azorean plateau, southwest of the Azores islands where the alteration processes affecting basaltic rocks are prominent (Costa et al., 2003). The hydrothermal breccias are genetically related with the circulation of low temperature hydrothermal fluids in diffuse vents. The groundmass of these breccias precipitates from the fluid and consolidates the clastic fragments mostly composed of basalt. The main sources are the surrounding volcanic hills. Breccias are found near hydrothermal vents and may play an important role in the protection of subseafloor hydrothermal deposits forming an impermeable cap due to the high content in siliceous material. The amorphous silica tends to precipitate when the fluid is conductively cooled as proposed by Fouquet et al. (1998) after Fournier (1983). The process evolves gradually from an initial stage where we have just the fragments and circulating seawater. The ascending hydrothermal fluid mixes with seawater, which favours the precipitation of the sulphide components. Sealing of the initially loose fragments begins, the temperature rises below this crust, and the processes of mixing fluid circulation and conductive cooling are simultaneous. At this stage the fluid becomes oversaturated with respect to amorphous silica. This form of silica can precipitate in the open spaces of the porous sulphides and seal the system. Normally this can happen at low temperatures. At this stage the hydrothermal breccia is formed creating a progressively less permeable, eventually impermeable cap rock at the surface. Once the fluid is trapped under this impermeable layer, conductive cooling is enhanced and mixing with seawater is restricted, making the precipitation of amorphous silica more efficient. Since the first discovery and description of recent mineralized submarine

  2. Hydrothermal activity and subsoil complexity: implication for degassing processes at Solfatara crater, Campi Flegrei caldera

    Science.gov (United States)

    Montanaro, Cristian; Mayer, Klaus; Isaia, Roberto; Gresse, Marceau; Scheu, Bettina; Yilmaz, Tim I.; Vandemeulebrouck, Jean; Ricci, Tullio; Dingwell, Donald B.

    2017-12-01

    The Solfatara area and its fumaroles are the main surface expression of the vigorous hydrothermal activity within the active Campi Flegrei caldera system. At depth, a range of volcanic and structural processes dictate the actual state of the hydrothermal system below the crater. The presence of a large variety of volcanic products at shallow depth (including pyroclastic fallout ash beds, pyroclastic density current deposits, breccias, and lavas), and the existence of a maar-related fault system appears to exert major controls on the degassing and alteration behavior. Adding further to the complexity of this environment, variations in permeability and porosity, due to subsoil lithology and alteration effects, may further influence fluid flow towards the surface. Here, we report results from a field campaign conducted in July 2015 that was designed to characterize the in situ physical (temperature, humidity) and mechanical (permeability, strength, stiffness) properties of the Solfatara crater subsoil. The survey also included a mapping of the surficial hydrothermal features and their distributions. Finally, laboratory measurements (porosity, granulometry) of selected samples were performed. Our results enable the discrimination of four main subsoils around the crater: (1) the Fangaia domain located in a topographic low in the southwestern sector, (2) the silica flat domain on the western altered side, (3) the new crust domain in the central area, and (4) the crusted hummocks domain that dominates the north, east, and south parts. These domains are surrounded by encrusted areas, reworked material, and vegetated soil. The distribution of these heterogeneous subsoils suggests that their formation is mostly related to (i) the presence of the Fangaia domain within the crater and (ii) a system of ring faults bordering it. The subsoils show an alternation between very high and very low permeabilities, a fact which seems to affect both the temperature distribution and

  3. Hydrothermal treatment followed by enzymatic hydrolysis and hydrothermal carbonization as means to valorise agro- and forest-based biomass residues.

    Science.gov (United States)

    Wikberg, Hanne; Grönqvist, Stina; Niemi, Piritta; Mikkelson, Atte; Siika-Aho, Matti; Kanerva, Heimo; Käsper, Andres; Tamminen, Tarja

    2017-07-01

    The suitability of several abundant but underutilized agro and forest based biomass residues for hydrothermal treatment followed by enzymatic hydrolysis as well as for hydrothermal carbonization was studied. The selected approaches represent simple biotechnical and thermochemical treatment routes suitable for wet biomass. Based on the results, the hydrothermal pre-treatment followed by enzymatic hydrolysis seemed to be most suitable for processing of carbohydrate rich corn leaves, corn stover, wheat straw and willow. High content of thermally stable components (i.e. lignin) and low content of ash in the biomass were advantageous for hydrothermal carbonization of grape pomace, coffee cake, Scots pine bark and willow. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. The origin and history of alteration and carbonatization of the Yucca Mountain ignimbrites. Volume I

    International Nuclear Information System (INIS)

    Szymanski, J.S.

    1992-04-01

    This document contains Volume I of the report entitled The Origin and History of Alteration and Carbonatization of the Yucca Mountain Ignimbrites by Jerry S. Szymanski and a related correspondence with comments by Donald E. Livingston. In the Great Basin, the flow of terrestrial heat through the crust is affected in part by the flow of fluids. At Yucca Mountain, the role of fluids in crustal heat transport is manifested at the surface by youthful calcretes, sinters, bedrock veins, hydrothermal eruption breccias and hydrothermal alteration. This report discusses evidence for recent metasomatism high in the stratigraphic section at Yucca Mountain. Over the last several hundred years, episodes of calcite emplacement contemporaneous with local mafic volcanism have occurred at intervals that are not long in comparison with the isolation time required for a High-Level Radioactive Waste repository

  5. PREDICTED SEDIMENTARY SECTION OF SUBGLACIAL LAKE VOSTOK

    Directory of Open Access Journals (Sweden)

    G. I. Leychenkov

    2012-01-01

    Full Text Available In early February 2012, the drill hole at the Vostok Station encountered theLakeVostokwater. This step is important to study the lake composition including possible microbial life and to model subglacial environments however, the next ambitious target of the Vostok Drilling Project is sampling of bottom sediments, which contain the unique record of ice sheet evolution and environmental changes in centralAntarcticafor millions of years. In this connection, the forecast of sedimentary succession based on existing geophysical data, study of mineral inclusions in the accretion ice cores and tectonic models is important task. Interpretation of Airborne geophysical data suggests thatLakeVostokis the part of spacious rift system, which exists at least from Cretaceous. Reflection and refraction seismic experiments conducted in the southern part ofLakeVostokshow very thin (200–300 m stratified sedimentary cover overlying crystalline basement with velocity of 6.0–6.2 km/s. At present, deposition in southernLakeVostokis absent and similar conditions occurred likely at least last3 m.y. when ice sheet aboveLakeVostokchanged insignificantly. It can be also inferred that from the Late Miocene the rate of deposition inLakeVostokwas extremely low and so the most of sedimentary section is older being possibly of Oligocene to early to middle Miocene age when ice sheet oscillated and deposition was more vigorous. If so, the sampling of upper few meters of this condensed section is very informative in terms of history of Antarctic glaciation. Small thickness of sedimentary cover raises a question about existence of lake (rift depression during preglacial and early glacial times.

  6. Phenol compounds in the borehole 5G, Vostok station, after the unlocking of the subglacial lake

    Directory of Open Access Journals (Sweden)

    I. A. Alekhina

    2017-01-01

    Full Text Available The main results after the first unlocking into the subglacial Lake Vostok were as follows: the Lake had been opened and not polluted; the water pressure within the lake was not balanced by a column of the drilling liquid that resulted in unplanned rise of water in the borehole up to 340 m. The main problem during the drilling in the lake ice was to prevent a pollution of water by the drilling fluid, which filled the borehole, and thus, to avoid a compression of the fluid which could be the main source of chemical and biological pollution of not only the Lake itself, but also the Lake water samples and ice cores. The article presents results of analysis of causes for the occurrence of phenolic compounds in the central channel in the core of secondary ice, being formed by the lake water that rose into the well after the first penetration (the range of depths was 3426–3450 m. It was found that the process, running within the borehole during the drilling, can be described as the fractionation of phenolic compounds, being contained in the filling liquid, to the water phase with its subsequent freezing. We have developed methods for the determination of concentrations of phenolic compounds in the original aviation kerosene and Freon HCFC-141b: 6. mg·l−1 and 0.032 mg·l−1, respectively. To analyze the composition of phenolic compounds in the extract of real filling liquid, located at the bottom of the borehole, the method of gas chromatography-mass spectrometry (GC-MS was used. The corresponding peaks were quite well resolved and identified as phenol and its derivatives. The main components of the extract were phenol (20%, 2.5-dimethyl phenol (23,8%, 2,4,6-trimethylphenol, and other congeners of phenol. In our case, the Lake Vostok was not polluted during both, the first and second penetrations, however, the problem of human impact on these pristine and unique subglacial reservoirs remains extremely relevant. This impact includes not only

  7. Whole Algae Hydrothermal Liquefaction Technology Pathway

    Energy Technology Data Exchange (ETDEWEB)

    Biddy, M.; Davis, R.; Jones, S.

    2013-03-01

    This technology pathway case investigates the feasibility of using whole wet microalgae as a feedstock for conversion via hydrothermal liquefaction. Technical barriers and key research needs have been assessed in order for the hydrothermal liquefaction of microalgae to be competitive with petroleum-derived gasoline-, diesel-, and jet-range hydrocarbon blendstocks.

  8. Episodic intrusion, internal differentiation, and hydrothermal alteration of the miocene tatoosh intrusive suite south of Mount Rainier, Washington

    Science.gov (United States)

    du Bray, E.A.; Bacon, C.R.; John, D.A.; Wooden, J.L.; Mazdab, F.K.

    2011-01-01

    The Miocene Tatoosh intrusive suite south of Mount Rainier is composed of three broadly granodioritic plutons that are manifestations of ancestral Cascades arc magmatism. Tatoosh intrusive suite plutons have individually diagnostic characteristics, including texture, mineralogy, and geochemistry, and apparently lack internal contacts. New ion-microprobe U-Pb zircon ages indicate crystallization of the Stevens pluton ca. 19.2 Ma, Reflection-Pyramid pluton ca. 18.5 Ma, and Nisqually pluton ca. 17.5 Ma. The Stevens pluton includes rare, statistically distinct ca. 20.1 Ma zircon antecrysts. Wide-ranging zircon rare earth element (REE), Hf, U, and Th concentrations suggest late crystallization from variably evolved residual liquids. Zircon Eu/Eu*-Hf covariation is distinct for each of the Reflection-Pyramid, Nisqually, and Stevens plutons. Although most Tatoosh intrusive suite rocks have been affected by weak hydrothermal alteration, and sparse mineralized veins cut some of these rocks, significant base or precious metal mineralization is absent. At the time of shallow emplacement, each of these magma bodies was largely homogeneous in bulk composition and petrographic features, but, prior to final solidification, each of the Tatoosh intrusive suite plutons developed internal compositional variation. Geochemical and petrographic trends within each pluton are most consistent with differential loss of residual melt, possibly represented by late aplite dikes or erupted as rhyolite, from crystal-rich magma. Crystal-rich magma that formed each pluton evidently accumulated in reservoirs below the present level of exposure and then intruded to a shallow depth. Assembled by episodic intrusion, the Tatoosh intrusive suite may be representative of midsized composite plutonic complexes beneath arc volcanoes. ?? 2011 Geological Society of America.

  9. Post-drilling changes in seabed landscape and megabenthos in a deep-sea hydrothermal system, the Iheya North field, Okinawa Trough.

    Science.gov (United States)

    Nakajima, Ryota; Yamamoto, Hiroyuki; Kawagucci, Shinsuke; Takaya, Yutaro; Nozaki, Tatsuo; Chen, Chong; Fujikura, Katsunori; Miwa, Tetsuya; Takai, Ken

    2015-01-01

    There has been an increasing interest in seafloor exploitation such as mineral mining in deep-sea hydrothermal fields, but the environmental impact of anthropogenic disturbance to the seafloor is poorly known. In this study, the effect of such anthropogenic disturbance by scientific drilling operations (IODP Expedition 331) on seabed landscape and megafaunal habitation was surveyed for over 3 years using remotely operated vehicle video observation in a deep-sea hydrothermal field, the Iheya North field, in the Okinawa Trough. We focused on observations from a particular drilling site (Site C0014) where the most dynamic change of landscape and megafaunal habitation was observed among the drilling sites of IODP Exp. 331. No visible hydrothermal fluid discharge had been observed at the sedimentary seafloor at Site C0014, where Calyptogena clam colonies were known for more than 10 years, before the drilling event. After drilling commenced, the original Calyptogena colonies were completely buried by the drilling deposits. Several months after the drilling, diffusing high-temperature hydrothermal fluid began to discharge from the sedimentary subseafloor in the area of over 20 m from the drill holes, 'artificially' creating a new hydrothermal vent habitat. Widespread microbial mats developed on the seafloor with the diffusing hydrothermal fluids and the galatheid crab Shinkaia crosnieri endemic to vents dominated the new vent community. The previously soft, sedimentary seafloor was hardened probably due to barite/gypsum mineralization or silicification, becoming rough and undulated with many fissures after the drilling operation. Although the effects of the drilling operation on seabed landscape and megafaunal composition are probably confined to an area of maximally 30 m from the drill holes, the newly established hydrothermal vent ecosystem has already lasted 2 years and is like to continue to exist until the fluid discharge ceases and thus the ecosystem in the area has

  10. Geochemical features of sulfides from the Deyin-1 hydrothermal field at the southern Mid-Atlantic Ridge near 15°S

    Science.gov (United States)

    Wang, Shujie; Li, Huaiming; Zhai, Shikui; Yu, Zenghui; Cai, Zongwei

    2017-12-01

    mainly attributed to precipitating directly from the hydrothermal fluid, while those collected from the extinct hydrothermal chimney might have already been altered by the seawater. Generally, ore-forming elements in the sulfides can be divided into three groups: Fe-based element group, Cu-based element group and Zn-based element group. The first group includes Fe, Mn, Cr, Mo, Sn, Rb and bio-enriching elements, such as P and Si, reflecting the similar characteristics to Fe in the study area. And the second group contains Cu, W, Co, Se, Te and Bi, suggesting the similar behavior with Cu. Moreover, the third group includes Zn, Hf, Hg, Cd, Ta, Ga, Pb, As, Ag, Ni and Sb, which indicates the geochemical characteristics of most dispersed trace elements controlled by Zn-bearing minerals to some extent.

  11. Hydrothermal circulation, serpentinization, and degassing at a rift valley-fracture zone intersection: Mid-Atlantic Ridge near 15[degree]N, 45[degree]W

    Energy Technology Data Exchange (ETDEWEB)

    Rona, P.A.; Nelson, T.A. (National Oceanic and Atmospheric Administration, Miami, FL (United States)); Bougault, H.; Charlou, J.L.; Needham, H.D. (Inst. Francais de Recherche pour I' Exploitation de la Mer, Centre de Brest (France)); Appriou, P. (Univ. of Western Brittany, Brest (France)); Trefry, J.H. (Florida Inst. of Technology, Melbourne (United States)); Eberhart, G.L.; Barone, A. (Lamont-Doherty Geological Observatory, Palisades, NY (United States))

    1992-09-01

    A hydrothermal system characterized by high ratios of methane to both manganese and suspended particulate matter was detected in seawater sampled at the eastern intersection of the rift valley of the Mid-Atlantic Ridge with the Fifteen-Twenty Fracture Zone. This finding contrasts with low ratios in black smoker-type hydrothermal systems that occur within spreading segments. Near-bottom water sampling coordinated with SeaBeam bathymetry and camera-temperature tows detected the highest concentrations of methane at fault zones in rocks with the appearance of altered ultramafic units in a large dome that forms part of the inside corner high at the intersection. The distinct chemical signatures of the two types of hydrothermal systems are inferred to be controlled by different circulation pathways related to reaction of seawater primarily with ultramafic rocks at intersections of spreading segments with fracture zones but with mafic rocks within spreading segments.

  12. HYDROTHEMAL ALTERATION MAPPING USING FEATURE-ORIENTED PRINCIPAL COMPONENT SELECTION (FPCS METHOD TO ASTER DATA:WIKKI AND MAWULGO THERMAL SPRINGS, YANKARI PARK, NIGERIA

    Directory of Open Access Journals (Sweden)

    A. J. Abubakar

    2017-10-01

    Full Text Available Geothermal systems are essentially associated with hydrothermal alteration mineral assemblages such as iron oxide/hydroxide, clay, sulfate, carbonate and silicate groups. Blind and fossilized geothermal systems are not characterized by obvious surface manifestations like hot springs, geysers and fumaroles, therefore, they could not be easily identifiable using conventional techniques. In this investigation, the applicability of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER were evaluated in discriminating hydrothermal alteration minerals associated with geothermal systems as a proxy in identifying subtle Geothermal systems at Yankari Park in northeastern Nigeria. The area is characterized by a number of thermal springs such as Wikki and Mawulgo. Feature-oriented Principal Component selection (FPCS was applied to ASTER data based on spectral characteristics of hydrothermal alteration minerals for a systematic and selective extraction of the information of interest. Application of FPCS analysis to bands 5, 6 and 8 and bands 1, 2, 3 and 4 datasets of ASTER was used for mapping clay and iron oxide/hydroxide minerals in the zones of Wikki and Mawulgo thermal springs in Yankari Park area. Field survey using GPS and laboratory analysis, including X-ray Diffractometer (XRD and Analytical Spectral Devices (ASD were carried out to verify the image processing results. The results indicate that ASTER dataset reliably and complementarily be used for reconnaissance stage of targeting subtle alteration mineral assemblages associated with geothermal systems.

  13. Hydrothermal and alkaline hydrothermal pretreatments plus anaerobic digestion of sewage sludge for dewatering and biogas production: Bench-scale research and pilot-scale verification.

    Science.gov (United States)

    Li, Chunxing; Wang, Xingdong; Zhang, Guangyi; Yu, Guangwei; Lin, Jingjiang; Wang, Yin

    2017-06-15

    To test the feasibility and practicability of the process combing hydrothermal pretreatment for dewatering with biogas production for full utilization of sewage sludge, hydrothermal/alkaline hydrothermal pretreatments and in turn anaerobic digestion of the filtrates obtained after dewatering the pretreated sludge were performed at bench- and pilot-scales. The hydrothermal temperature fell within the range of 140 °C-220 °C and the pretreatment time varied from 30 min to 120 min. For the alkaline hydrothermal pretreatment the pH value of the sludge was adjusted to 9.0-11.0 by adding Ca(OH) 2 . The results showed that the dewaterability of the sewage sludge was improved with increasing pretreatment temperature but the impact of the pretreatment time was not significant. The addition of Ca(OH) 2 gave better performance on the subsequent mechanical dewatering of the pretreated sludge compared to pure hydrothermal pretreatment, and the higher the pH value was, the better the dewaterability of the pretreated sludge was. The conditions of 180 °C/30 min and 160 °C/60 min/pH = 10.0 (for hydrothermal and alkaline hydrothermal pretreatments, respectively) resulted in relatively good results in the theoretical energy balance, which were verified in the pilot-scale tests. Based on the data from the pilot tests, the alkaline hydrothermal process realized self-sufficiency in energy at the cost of a proper amount of CaO. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Hydrothermal alterations and O, H, C isotopic characterization of fluids and minerals in uraniferous massif of Saint Sylvestre (France). Extension to other French intragranitic uranium deposits

    International Nuclear Information System (INIS)

    Turpin, L.

    1984-05-01

    Petrographical, mineralogical, geochemical and stable isotope ( 18 O/ 16 O, D/H, 13 C/ 12 C) studies have been performed on the leucogranitic massif of St Sylvestre (Limousin, Massif Central francais), particularly on the different hydrothermal alterations. The oxygen isotope geochemistry of granites confirms the unicity of the different facies and their sialic origin (delta 18 O whole rocks = +11.0 +- 0.5 per mill), with a major contribution of detritic sediments rich in organic matter and poor in carbonate (delta 13 C magm. CO 2 = -10.6 per mill). Late lamprophyres have a deep-seated origin (delta 18 O = + 6 per mill). The pervasive chloritization of granitic biotites occurs during the convective circulation of a fluid of meteoric origin, at temperatures around 350-450 0 C. The chemical composition of chlorite which is buffered by that of biotite and the large 18 O-shift of fluid towards high delta values indicate that water-rock ratio was not very high. Chloritization takes place in high permeability zones. In regions where porosity is generally low, fluids are ''canalised'' in localised micro-fissured zones. Very high water/rock ratios lead to the dissolution of quartz, and the formation of the ''feldspathic episyenite'' alteration facies. The isotopic features of this fluid (delta 18 O approximately - 8 per mill, deltaD approximately - 50 per mill) indicate an elevated altitude. An isotopically similar fluid is responsible for the later ''micaceous episyenite'' alteration facies, found in fractured zones. Mixing of this fluid with a sedimentary fluid (delta 18 O approximately + 10 per mill, deltaD approximately - 30 per mill, delta 13 C approximately - 18 per mill) yielded the conditions necessary for the deposit of primary economic ore. Such fluids, sedimentary or metamorphic in origin, have been recognized in most hercynian intragranitic U and Sn-W deposits [fr

  15. Combined hydrothermal liquefaction and catalytic hydrothermal gasification system and process for conversion of biomass feedstocks

    Science.gov (United States)

    Elliott, Douglas C.; Neuenschwander, Gary G.; Hart, Todd R.

    2017-09-12

    A combined hydrothermal liquefaction (HTL) and catalytic hydrothermal gasification (CHG) system and process are described that convert various biomass-containing sources into separable bio-oils and aqueous effluents that contain residual organics. Bio-oils may be converted to useful bio-based fuels and other chemical feedstocks. Residual organics in HTL aqueous effluents may be gasified and converted into medium-BTU product gases and directly used for process heating or to provide energy.

  16. The Timber Mountain magmato-thermal event: An intense widespread culmination of magmatic and hydrothermal activity at the southwestern Nevada volcanic field

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, Jr., Mac Roy [Univ. of Nevada, Reno, NV (United States)

    1988-05-01

    Eruption of the Rainier Mesa and Ammonia Tanks Members Timber Mountain Tuff at about 11.5 and 11.3 Ma, respectively, resulted in formation of the timber Mountain (TM) caldera; new K-Ar ages show that volcanism within and around the TM caldera continued for about 1 m.y. after collapse. Some TM age magmatic activity took place west and southeast of the TM caldera in the Beatty -- Bullfrog Hills and Shoshone Mountain areas, suggesting that volcanic activity at the TM caldera was an intense expression of an areally extensive magmatic system active from about 11.5 to 10Ma. Epithermal Au-Ag, Hg and fluorite mineralization and hydrothermal alteration are found in both within and surrounding the Timber Mountain -- Oasis Valley caldera complex. New K-Ar ages date this hydrothermal activity between about 13 and 10 Ma, largely between about 11.5 and 10 Ma, suggesting a genetic relation of hydrothermal activity to the TM magmatic system.

  17. The Timber Mountain magmato-thermal event: An intense widespread culmination of magmatic and hydrothermal activity at the southwestern Nevada volcanic field

    International Nuclear Information System (INIS)

    Jackson, M.R. Jr.

    1988-05-01

    Eruption of the Rainier Mesa and Ammonia Tanks Members Timber Mountain Tuff at about 11.5 and 11.3 Ma, respectively, resulted in formation of the timber Mountain (TM) caldera; new K-Ar ages show that volcanism within and around the TM caldera continued for about 1 m.y. after collapse. Some TM age magmatic activity took place west and southeast of the TM caldera in the Beatty -- Bullfrog Hills and Shoshone Mountain areas, suggesting that volcanic activity at the TM caldera was an intense expression of an areally extensive magmatic system active from about 11.5 to 10Ma. Epithermal Au-Ag, Hg and fluorite mineralization and hydrothermal alteration are found in both within and surrounding the Timber Mountain -- Oasis Valley caldera complex. New K-Ar ages date this hydrothermal activity between about 13 and 10 Ma, largely between about 11.5 and 10 Ma, suggesting a genetic relation of hydrothermal activity to the TM magmatic system

  18. Hydrothermal system of the Papandayan Volcano from temperature, self-potential (SP) and geochemical measurements

    Science.gov (United States)

    Byrdina, Svetlana; Revil, André; Gunawan, Hendra; Saing, Ugan B.; Grandis, Hendra

    2017-07-01

    Papandayan volcano in West Java, Indonesia, is characterized by intense hydrothermal activities manifested by numerous fumaroles at three craters or kawah, i.e. Mas, Manuk and Baru. The latter was created after November 2002 phreatic eruption. Since 2011, numerous volcano-tectonic B events are encountered and the volcano was set on alert status on several occasions. The purpose of the present study is to delineate the structure of the summital hydrothermal system from Self-Potential (SP), soil temperature and gas concentrations in the soil (CO2, SO2 and H2S) data. This combination of geophysical and geochemical methods allows identification of the weak permeable zones serving as preferential pathways for hydrothermal circulation and potential candidates to future landslides or flank collapses. This study is an on-going collaborative research project and we plan to conduct electrical resistivity tomography (ERT) and also Induced-Polarization (IP) surveys. Additional data would allow the 3D imaging of the studied area. The IP parameters will be used to characterise and to quantify the degree of alteration of the volcanic rocks as has been shown very recently in the laboratory studies. There are also rocks and soil samples that will undergo laboratory analyses at ISTerre for IP and complex resistivity parameters at the sample scale that will help to interpret the survey results.

  19. Al-doped SnO2 nanocrystals from hydrothermal systems

    International Nuclear Information System (INIS)

    Jin Haiying; Xu Yaohua; Pang Guangsheng; Dong Wenjun; Wan Qiang; Sun Yan; Feng Shouhua

    2004-01-01

    Nanoparticles of Al-doped SnO 2 have been hydrothermally synthesized. The influences of the hydrothermal reaction time, the molar ratio of Sn/Al as well as the pH value of the solution have been studied. During the hydrothermal synthesis, the particle's core is rich in Sn and the surface is rich in Al. The Al-rich surface prevents the particles from further growing up either in the hydrothermal condition or during the calcination at 600 deg. C for a short period of time. The optimal hydrothermal synthesis condition of the nanoparticles is pH 5, Sn/Al=4:1 and 12 h at 160 deg. C. The products have been studied by XRD, TEM and 27 Al solid-state NMR

  20. Petrography, alteration and genesis of iron mineralization in Roshtkhar

    Directory of Open Access Journals (Sweden)

    Habib Biabangard

    2017-07-01

    Full Text Available Introduction Iron mineralization in Roshtkhar is located in 48 Km east of the city of Roshtkhar and south of the Khorasan Razavi province. It is geologically located in the north east of the Lut block and the Khaf-Bardeskan volcano-plutonic belt. The Khaf-Bardeskan belt is an important metallogenic province since it is a host of valuable ore deposits such as the Kuh-e-Zar Au-Spicularite, the Tanourcheh and the Khaf Iron ore deposits (Karimpour and Malekzadeh Shafaroudi, 2007. Iron and Copper mineralization in this belt are known as the hydrothermal, skarn and IOCG types (Karimpour and Malekzadeh Shafaroudi, 2007. IOCG deposits are a new type of magmatic to hydrothermal mineralization in the continental crust (Hitzman et al., 1992. Precambrian marble, Lower Paleozoic schist and metavolcanics are the oldest rocks of the area. The younger units are Oligocene conglomerate, shale and sandstone, Miocene marl and Quaternary deposits. Iron oxides and Cu sulfides are associated with igneous rocks. Fe and Cu mineralization in Roshtkhar has been subject of a few studies such as Yousefi Surani (2006. This study describes the petrography of the host rocks, ore paragenesis, alteration types, geochemistry, genesis and other features of the Fe and Cu mineralization in the Roshtkhar iron. Methods After detailed field studies and sampling, 30 thin sections and 20 polished sections that were prepared from host rocks and ores were studied by conventional petrographic and mineraloghraphic methods in the geology department of the University of Sistan and Baluchestan. 5 samples from the alteration zones were examined by XRD in the Yamagata University in Japan, and 8 samples from the less altered ones were analyzed by XRF and ICP-OES in the Kharazmi University and the Iranian mineral processing research center (IMPRC in Karaj, respectively. The XRF and ICP-OES data are presented in Table 1. Result and discussion The host rocks of the Roshtkhar Iron deposit are diorite

  1. Hydrothermal systems and volcano geochemistry

    Science.gov (United States)

    Fournier, R.O.

    2007-01-01

    The upward intrusion of magma from deeper to shallower levels beneath volcanoes obviously plays an important role in their surface deformation. This chapter will examine less obvious roles that hydrothermal processes might play in volcanic deformation. Emphasis will be placed on the effect that the transition from brittle to plastic behavior of rocks is likely to have on magma degassing and hydrothermal processes, and on the likely chemical variations in brine and gas compositions that occur as a result of movement of aqueous-rich fluids from plastic into brittle rock at different depths. To a great extent, the model of hydrothermal processes in sub-volcanic systems that is presented here is inferential, based in part on information obtained from deep drilling for geothermal resources, and in part on the study of ore deposits that are thought to have formed in volcanic and shallow plutonic environments.

  2. Ideas and perspectives: hydrothermally driven redistribution and sequestration of early Archaean biomass – the “hydrothermal pump hypothesis”

    Directory of Open Access Journals (Sweden)

    J.-P. Duda

    2018-03-01

    Full Text Available Archaean hydrothermal chert veins commonly contain abundant organic carbon of uncertain origin (abiotic vs. biotic. In this study, we analysed kerogen contained in a hydrothermal chert vein from the ca. 3.5 Ga Dresser Formation (Pilbara Craton, Western Australia. Catalytic hydropyrolysis (HyPy of this kerogen yielded n-alkanes up to n-C22, with a sharp decrease in abundance beyond n-C18. This distribution ( ≤  n-C18 is very similar to that observed in HyPy products of recent bacterial biomass, which was used as reference material, whereas it differs markedly from the unimodal distribution of abiotic compounds experimentally formed via Fischer–Tropsch-type synthesis. We therefore propose that the organic matter in the Archaean chert veins has a primarily microbial origin. The microbially derived organic matter accumulated in anoxic aquatic (surface and/or subsurface environments and was then assimilated, redistributed and sequestered by the hydrothermal fluids (hydrothermal pump hypothesis.

  3. Modeling of the fault-controlled hydrothermal ore-forming systems

    International Nuclear Information System (INIS)

    Pek, A.A.; Malkovsky, V.I.

    1993-07-01

    A necessary precondition for the formation of hydrothermal ore deposits is a strong focusing of hydrothermal flow as fluids move from the fluid source to the site of ore deposition. The spatial distribution of hydrothermal deposits favors the concept that such fluid flow focusing is controlled, for the most part, by regional faults which provide a low resistance path for hydrothermal solutions. Results of electric analog simulations, analytical solutions, and computer simulations of the fluid flow, in a fault-controlled single-pass advective system, confirm this concept. The influence of the fluid flow focusing on the heat and mass transfer in a single-pass advective system was investigated for a simplified version of the metamorphic model for the genesis of greenstone-hosted gold deposits. The spatial distribution of ore mineralization, predicted by computer simulation, is in reasonable agreement with geological observations. Computer simulations of the fault-controlled thermoconvective system revealed a complex pattern of mixing hydrothermal solutions in the model, which also simulates the development of the modern hydrothermal systems on the ocean floor. The specific feature of the model considered, is the development under certain conditions of an intra-fault convective cell that operates essentially independently of the large scale circulation. These and other results obtained during the study indicate that modeling of natural fault-controlled hydrothermal systems is instructive for the analysis of transport processes in man-made hydrothermal systems that could develop in geologic high-level nuclear waste repositories

  4. An estimate of hydrothermal fluid residence times and vent chimney growth rates based on 210Pb/Pb ratios and mineralogic studies of sulfides dredged from the Juan de Fuca Ridge

    International Nuclear Information System (INIS)

    Kadko, D.; Tatsumoto, Mitsunobu

    1985-01-01

    The 210 Pb/Pb ratios across two sulfide samples dredged from the Juan de Fuca Ridge are used to estimate the growth rate of the sulfide material and the residence time of the hydrothermal fluid within the oceanic crust from the onset of basalt alteration. 210 Pb is added to the hydrothermal fluid by two processes: 1) high-temperature alteration of basalt and 2) if the residence time of the fluid is on the order of the 22.3-year half-life of 210 Pb, by in-situ growth from 222 Rn (Krishnaswami and Turekian, 1982). Stable lead is derived only from the alteration of basalt. The 210 Pb/Pb ratio across one sample was proportional 0.5 dpm/10 -6 g Pb, and across the other is was proportional 0.4 dpm/10 -6 g Pb. These values are quite close to the 238 U/Pb ratios of basalts from the area, suggesting that the residence time of the hydrothermal fluid from the onset of basalt alteration is appreciably less than the mean life of 210 Pb, i.e., the time required for ingrowth from the radon. An apparent growth rate of 1.2 cm/yr is derived from the slope of the 210 Pb/Pb curve for one of the samples. This is consistent with its mineralogy and texture which suggest an accretionary pattern of development. There is no obvious sequential growth pattern, and virtually no gradient in 210 Pb/Pb across the second sample. This is consistent with alteration of the original 210 Pb/Pb distribution by extensive remobilization reactions which are inferred from the mineralogic and textural relationships of the sample. (orig.)

  5. The nature of hydrothermal fluids in the Kahang porphyry copper deposit (Northeast of Isfahan based on mineralography, fluid inclusion and stable isotopic data

    Directory of Open Access Journals (Sweden)

    Salimeh Sadat Komeili

    2017-02-01

    Full Text Available Introduction The Kahang Cu- Mo deposit is situated approximately 73 Km northeast of Isfahan. Asadi (2007 identified a geological reserve of 40 Mt (proven reserve grading at 0.53 Cu, 0.02 Mo and estimated reserve of 120 Mt. All the rock types in the region have been subjected to hydrothermal solutions which gave rise to three different alteration facies. The dacite and rhyodacite volcanic rocks and granitic- granodioritic stocks have experienced phyllic alteration. Disseminated and stockwork siliceous veins are the major styles of mineralization in this zone. Intermediate argillitic alteration developed on a part of dacitic and rhyodacitic rocks whereas andesite and basaltic-andesite plus related pyroclastic rocks have been subjected to propyllitic alteration. This paper presents the results of geological and mineralogical studies carried out in the Kahang area. This preliminary information is integrated with additional data on ore mineralogy, fluid inclusions and stable isotopes in view of understanding the genesis of the Cu- Mo deposit and the nature of the fluids involved in ore formation. Materials and Methods A total of 18 polished thin sections were prepared at the University of Isfahan for optical study. Fluid inclusions study was carried out on 8 double polished quartz thin sections (stockworks containing ore mineralization from phyllic zone. H – O stable isotope analysis was performed on 4 quartz samples from siliceous stockworks (from phyllic altered zone and one vein epidote sample (from propyllitic zone. All isotopic analyses were performed at the University of Oregan, Oregan, USA. Discussion In the investigated mineralization area, the hypogene zone is characterized by the presence of pyrite, chalcopyrite, bornite and magnetite. Hematite, goethite, jarosite, malachite and azurite are the predominant minerals of supergene zone. The major textures of the primary sulfides are disseminated, vein and veinlet. Pyrite is the most common

  6. Stable isotope fractionation at a glacial hydrothermal field: implications for biogeochemistry and biosignatures on Mars

    Science.gov (United States)

    Cousins, C.; Bowden, R.; Fogel, M.; Cockell, C.; Crawford, I.; Gunn, M.; Karlsson, M. T.; Thorsteinsson, T.

    2012-12-01

    Hydrothermal environments that arise through the interaction between volcanogenic heat and glacial ice are ideal sites for understanding microbial biogeochemical processes on Earth, and also potentially on Mars where similar volcano-cryosphere interactions are thought to have occurred in the past. The Kverkfjöll subglacial basaltic volcano in central Iceland is geographically isolated, with little influence from flora, fauna, and human activity. Major environmental inputs include geothermal heat, meltwater from ice and snow, and outgassing of CO2, H2S, and SO2. Large physiochemical gradients exist, from steaming fumaroles and boiling hydrothermal pools, to frozen geothermal ground and glacial ice. Stable isotope measurements of total organic carbon, total sulphur, and total nitrogen were coupled with metagenomic analysis of the residing microbial communities, with the aim to identify biogeochemical relationships and processes operating within the Kverkfjöll geothermal environment, and also to identify any isotopic biosignatures that could be preserved within geothermal sediments. This study focused on a variety of samples taken along a hot spring stream that fed into a large ice-confined geothermal lake. Samples analysed range from unconsolidated hot spring sediments, well-developed microbial mats, and dissolved sulphate from hot spring fluids. From the anoxic spring source, the stream water increases in dissolved oxygen, decreases in temperature, yet maintains a pH of ~4. The spring environment is dominated by dissolved sulphate (~2.3 mM), with lower levels of nitrate (~50 μM), phosphorus (~5μM), and ammonium (~1.5 μM). Stable S isotope analysis reveals a fractionation of ~3.2 ‰ between sediment sulphide (as pyrite; δ34S ~0‰), and dissolved water sulphate (δ34S ~3.2 ‰) consistently along the hot spring stream, indicating the presence of an active sulphur cycle, although not one dominated by sulphate reduction (e.g. very negative sulphide δ34S). This

  7. The BGU/CERN solar hydrothermal reactor

    CERN Document Server

    Bertolucci, Sergio; Caspers, Fritz; Garb, Yaakov; Gross, Amit; Pauletta, Stefano

    2014-01-01

    We describe a novel solar hydrothermal reactor (SHR) under development by Ben Gurion University (BGU) and the European Organization for Nuclear Research CERN. We describe in broad terms the several novel aspects of the device and, by extension, of the niche it occupies: in particular, enabling direct off-grid conversion of a range of organic feedstocks to sterile useable (solid, liquid) fuels, nutrients, products using only solar energy and water. We then provide a brief description of the high temperature high efficiency panels that provide process heat to the hydrothermal reactor, and review the basics of hydrothermal processes and conversion taking place in this. We conclude with a description of a simulation of the pilot system that will begin operation later this year.

  8. Hydrothermal uranium deposits containing molybdenum and fluorite in the Marysvale volcanic field, west-central Utah

    Science.gov (United States)

    Cunningham, C.G.; Rasmussen, J.D.; Steven, T.A.; Rye, R.O.; Rowley, P.D.; Romberger, S.B.; Selverstone, J.

    1998-01-01

    Uranium deposits containing molybdenum and fluorite occur in the Central Mining Area, near Marysvale, Utah, and formed in an epithermal vein system that is part of a volcanic/hypabyssal complex. They represent a known, but uncommon, type of deposit; relative to other commonly described volcanic-related uranium deposits, they are young, well-exposed and well-documented. Hydrothermal uranium-bearing quartz and fluorite veins are exposed over a 300 m vertical range in the mines. Molybdenum, as jordisite (amorphous MoS2, together with fluorite and pyrite, increase with depth, and uranium decreases with depth. The veins cut 23-Ma quartz monzonite, 20-Ma granite, and 19-Ma rhyolite ash-flow tuff. The veins formed at 19-18 Ma in a 1 km2 area, above a cupola of a composite, recurrent, magma chamber at least 24 ?? 5 km across that fed a sequence of 21- to 14-Ma hypabyssal granitic stocks, rhyolite lava flows, ash-flow tuffs, and volcanic domes. Formation of the Central Mining Area began when the intrusion of a rhyolite stock, and related molybdenite-bearing, uranium-rich, glassy rhyolite dikes, lifted the fractured roof above the stock. A breccia pipe formed and relieved magmatic pressures, and as blocks of the fractured roof began to settle back in place, flat-lying, concave-downward, 'pull-apart' fractures were formed. Uranium-bearing, quartz and fluorite veins were deposited by a shallow hydrothermal system in the disarticulated carapace. The veins, which filled open spaces along the high-angle fault zones and flat-lying fractures, were deposited within 115 m of the ground surface above the concealed rhyolite stock. Hydrothermal fluids with temperatures near 200??C, ??18OH2O ~ -1.5, ?? -1.5, ??DH2O ~ -130, log fO2 about -47 to -50, and pH about 6 to 7, permeated the fractured rocks; these fluids were rich in fluorine, molybdenum, potassium, and hydrogen sulfide, and contained uranium as fluoride complexes. The hydrothermal fluids reacted with the wallrock resulting in

  9. Base hydrolysis and hydrothermal processing of PBX-9404

    International Nuclear Information System (INIS)

    Flesner, R.L.; Spontarelli, T.; Dell'Orco, P.C.; Sanchez, J.A.

    1994-01-01

    Base hydrolysis in combination with hydrothermal processing has been proposed as an environmentally acceptable alternative to open burning/open detonation for degradation and destruction of high explosives. In this report, the authors examine gaseous and aqueous products of base hydrolysis of the HMX-based plastic bonded explosive, PBX-9404. They also examined products from the subsequent hydrothermal treatment of the base hydrolysate. The gases produced from hydrolysis of PBX-9404 are ammonia, nitrous oxide, and nitrogen. Major aqueous products are sodium formate, acetate, nitrate, and nitrite, but not all carbon products have been identified. Hydrothermal processing of base hydrolysate destroyed up to 98% of the organic carbon in solution, and higher destruction efficiencies are possible. Major gas products detected from hydrothermal processing were nitrogen and nitrous oxide

  10. Bacterial Diets of Primary Consumers at Hydrothermal Vents

    Science.gov (United States)

    Govenar, B.; Shank, T. M.

    2008-12-01

    Chemical energy produced by mixing hydrothermal fluids and seawater supports dense biological communities on mid-ocean ridges. The base of the food web at deep-sea hydrothermal vents is formed by chemolithoautotrophic bacteria that use the energy from the oxidation of reduced chemicals to fix inorganic carbon into simple sugars. With the exception of a few species that have chemolithoautotropic bacterial symbionts, most of the vent-endemic macrofauna are heterotrophs that feed on free-living bacteria, protists, and other invertebrates. The most abundant and diverse group of primary consumers in hydrothermal vent communities belong to the Gastropoda, particularly the patellomorph limpets. Gastropod densities can be as high as 2000 individuals m-2, and there can be as many as 13 species of gastropods in a single aggregation of the siboglinid tubeworm Riftia pachyptila and more than 40 species along the East Pacific Rise. Some gastropods are ubiquitous and others are found in specific microhabitats, stages of succession, or associated with different foundation species. To determine the mechanisms of species coexistence (e.g. resource partitioning or competition) among hydrothermal vent primary consumers and to track the flow of energy in hydrothermal vent communities, we employed molecular genetic techniques to identify the gut contents of four species of co-occurring hydrothermal vent gastropods, Eulepetopsis vitrea, Lepetodrilus elevatus, Lepetodrilus ovalis and Lepetodrilus pustulosus, collected from a single diffuse-flow hydrothermal vent site on the East Pacific Rise. Unique haplotypes of the 16S gene that fell among the epsilon-proteobacteria were found in the guts of every species, and two species had gut contents that were similar only to epsilon-proteobacteria. Two species had gut contents that also included haplotypes that clustered with delta-proteobacteria, and one species had gut contents that clustered with alpha- proteobacteria. Differences in the diets

  11. Dissolution and alteration of uraninite under reducing conditions

    International Nuclear Information System (INIS)

    Janeczek, J.; Ewing, R.C.

    1992-01-01

    The behavior of uraninite under hydrothermal, reducung conditions is discussed on the basis of data in the literature and the authors' investigation of samples from two natural analogue sites: Oklo, Gabon and Cigar Lake, Canada. Uraninite under reducing conditions, in the presence of saline hydrothermal solutions may be altered through dissolution, preferential loss of lead and/or Y + HREE, and coffinitization. Textural features indicative of dissolution or uraninite include embayed grain boundaries, corroded relicts of uraninite embedded in a clay matrix, and replacement of uraninite by clays and sulfides. The alteration textures and phase chemistries at Oklo and Cigar Lake are remarkably similar. Dissolution of uraninite at Cigar Lake and Oklo was associated with the precipitation or illite and was probably caused by saline, uraninite moderately acidic solutions at approximately 200deg C. Increased oxygen fugacity may have occured locally due to release of excess oxygen from uraninite during dissolution or by α-radiolysis of the solution. The formation of Pb-rich (up to 18 wt% Pb, uraninite-I) and Pb-depleted (approximately 7-8 wt% Pb, uraninite-II) uraninites at both Oklo and Cigar Lake resulted from the loss of Pb due to predominantly episodic volume diffusion related to regional geologic events. Lead loss was not associated with U mobilization. In addition to uraninite dissolution, coffinitization resulted in U, Pb and REE release. (orig.)

  12. Organic sulfur metabolisms in hydrothermal environments.

    Science.gov (United States)

    Rogers, Karyn L; Schulte, Mitchell D

    2012-07-01

    Sulfur is central to the metabolisms of many organisms that inhabit extreme environments. While biotic and abiotic cycling of organic sulfur compounds has been well documented in low-temperature anaerobic environments, cycling of organic sulfur in hydrothermal environments has received less attention. Recently published thermodynamic data have been used to estimate aqueous alkyl thiol and sulfide activities in deep-sea hydrothermal systems. Here we use geochemical mixing models to predict fluid compositions that result from mixing end-member hydrothermal fluid from the East Pacific Rise with bottom seawater. These fluid compositions are combined with estimates of methanethiol and dimethylsulfide activities to evaluate energy yields for potential organic sulfur-based metabolisms under hydrothermal conditions. Aerobic respiration has the highest energy yields (over -240 kJ/mol e⁻) at lower temperature; however, oxygen is unlikely to persist at high temperatures, restricting aerobic respiration to mesophilic communities. Nitrite reduction to N₂ has the highest energy yields at higher temperatures (greater than ∼40 °C). Nitrate and nitrite reduction to ammonium also yield significant energy (up to -70 kJ/mol e⁻). Much lower, but still feasible energy yields are calculated for sulfate reduction, disproportionation, and reduction with H₂. Organic compound family and the activity of methanethiol and dimethylsulfide were less important than metabolic strategy in determining overall energy yields. All metabolic strategies considered were exergonic within some portion of the mixing regime suggesting that organic sulfur-based metabolisms may be prevalent within deep-sea hydrothermal vent microbial communities. © 2012 Blackwell Publishing Ltd.

  13. Voltammetric Investigation Of Hydrothermal Iron Speciation

    Directory of Open Access Journals (Sweden)

    Charlotte eKleint

    2016-05-01

    Full Text Available Hydrothermal vent fluids are highly enriched in iron (Fe compared to ambient seawater, and organic ligands may play a role in facilitating the transport of some hydrothermal Fe into the open ocean. This is important since Fe is a limiting micronutrient for primary production in large parts of the world`s surface ocean. We have investigated the concentration and speciation of Fe in several vent fluid and plume samples from the Nifonea vent field, Coriolis Troughs, New Hebrides Island Arc, South Pacific Ocean using competitive ligand exchange - adsorptive cathodic stripping voltammetry (CLE - AdCSV with salicylaldoxime (SA as the artificial ligand. Our results for total dissolved Fe (dFe in the buoyant hydrothermal plume samples showed concentrations up to 3.86 µM dFe with only a small fraction between 1.1% and 11.8% being chemically labile. Iron binding ligand concentrations ([L] were found in µM level with strong conditional stability constants up to log K[L],Fe3+ of 22.9. Within the non-buoyant hydrothermal plume above the Nifonea vent field, up to 84.7% of the available Fe is chemically labile and [L] concentrations up to 97 nM were measured. [L] was consistently in excess of Felab, indicating that all available Fe is being complexed, which in combination with high Felab values in the non-buoyant plume, signifies that a high fraction of hydrothermal dFe is potentially being transported away from the plume into the surrounding waters, contributing to the global oceanic Fe budget.

  14. Detailed magnetic and gravity surveys around the hydrothermal area off Kumejima Island in the Mid-Okinawa Trough, southwestern Japan

    Science.gov (United States)

    Kitada, K.; Kasaya, T.; Iwamoto, H.; Nogi, Y.

    2017-12-01

    The Okinawa Trough is an active back-arc basin formed by the rifting associated with extension of the continental margin behind the Ryukyu trench. New hydrothermal sites were recently discovered off Kumejima Island in the Mid-Okinawa Trough and the hydrothermal mineral deposits were identified by seafloor surveys and rock samplings by ROV (e.g., JOGMEC, 2015). In order to characterize the sub-seafloor structures and the spatial distribution of the magmatic activity around the sites, we conducted the dense magnetic, gravity and bathymetric surveys with a line spacing of 0.5 nmi aboard the R/Vs Yokosuka and Kairei, operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in 2016. The geophysical data collected during the previous cruises in the area by JAMSTEC were additionally used for this study. Magnetic anomaly was calculated by subtracting the IGRF model and the magnetization intensity was estimated by the method of Parker and Huestis (1974). Free-air gravity anomaly was calculated with subtracting the normal gravity field and with corrections of the drift and of the Eötvös effect. Bouguer gravity anomaly was calculated based on the method of Parker (1972). The magnetization intensity and the Bouguer gravity anomaly reveal three characteristics of the hydrothermal area off Kumejima Island: 1) The distribution of magnetization around the hydrothermal sites shows two different types of sub-seafloor magnetic features. One is corresponded to the submarine knolls with a relatively high magnetization of 4 A/M. The other is an ENE-WSW trending magnetization distribution with relatively high and low intensities, which is consistent with the trend of the bathymetric lineament. These features are considered to be formed by magmatism associated with submarine volcanoes and back-arc rifting. 2) The reduced magnetization zone corresponding to the hydrothermal area probably attributes to hydrothermal alteration of the host rock. 3) The hydrothermal

  15. Biosphere in 3.5 Ga submarine hydrothermal system

    Energy Technology Data Exchange (ETDEWEB)

    Ueno, Yuichiro [Tokyo Univ. (Japan). Dept. of Earth Science and Astronomy

    2003-04-01

    Abundant organic matter (kerogen) was identified in {approx}3.5 Ga hydrothermal silica dikes from the North Pole area in the Pilbara craton, Western Australia. The silica dikes developed in the uppermost 1000 m of the ancient oceanic crust. Thus, they would have been deposited in the 3.5 Ga sub-seafloor hydrothermal system. The carbon and nitrogen isotopic compositions of the kerogen were analyzed in this study. Their highly {sup 13}C-depleted isotopic compositions ({delta}{sup 13}C = -38 to -33 per mille) strongly suggest that they are originally derived from biologically produced organic matter. The remarkable similarity of the {delta}{sup 13}C values between the kerogen and modern hydrothermal vent organisms may suggest that the kerogen was derived from chemoautotrophic organisms. This idea is also consistent with their nitrogen isotopic compositions ({delta}{sup 15}N = -4 to +4 per mille). The silica dikes consist mainly of fine-grained silica with minor pyrite and sphalerite. These mineral assemblages indicate that the silica dike was deposited from relatively low-temperature (probably less than 150degC) reducing hydrothermal fluid. Thus, anaerobic thermophilic/hyperthermophilic organisms could have survived in the hydrothermal fluid, which formed the silica dikes. Therefore, it is plausible that a chemoautotrophic-based biosphere (possibly methanogenesis) probably existed in the Early Archean sub-seafloor hydrothermal system. (author)

  16. Impact of hydrothermalism on the ocean iron cycle.

    Science.gov (United States)

    Tagliabue, Alessandro; Resing, Joseph

    2016-11-28

    As the iron supplied from hydrothermalism is ultimately ventilated in the iron-limited Southern Ocean, it plays an important role in the ocean biological carbon pump. We deploy a set of focused sensitivity experiments with a state of the art global model of the ocean to examine the processes that regulate the lifetime of hydrothermal iron and the role of different ridge systems in governing the hydrothermal impact on the Southern Ocean biological carbon pump. Using GEOTRACES section data, we find that stabilization of hydrothermal iron is important in some, but not all regions. The impact on the Southern Ocean biological carbon pump is dominated by poorly explored southern ridge systems, highlighting the need for future exploration in this region. We find inter-basin differences in the isopycnal layer onto which hydrothermal Fe is supplied between the Atlantic and Pacific basins, which when combined with the inter-basin contrasts in oxidation kinetics suggests a muted influence of Atlantic ridges on the Southern Ocean biological carbon pump. Ultimately, we present a range of processes, operating at distinct scales, that must be better constrained to improve our understanding of how hydrothermalism affects the ocean cycling of iron and carbon.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

  17. Comparison of microbial communities associated with three Atlantic ultramafic hydrothermal systems.

    Science.gov (United States)

    Roussel, Erwan G; Konn, Cécile; Charlou, Jean-Luc; Donval, Jean-Pierre; Fouquet, Yves; Querellou, Joël; Prieur, Daniel; Bonavita, Marie-Anne Cambon

    2011-09-01

    The distribution of Archaea and methanogenic, methanotrophic and sulfate-reducing communities in three Atlantic ultramafic-hosted hydrothermal systems (Rainbow, Ashadze, Lost City) was compared using 16S rRNA gene and functional gene (mcrA, pmoA and dsrA) clone libraries. The overall archaeal community was diverse and heterogeneously distributed between the hydrothermal sites and the types of samples analyzed (seawater, hydrothermal fluid, chimney and sediment). The Lost City hydrothermal field, characterized by high alkaline warm fluids (pH>11; Tphylum and Methanopyrales order were also retrieved from the Rainbow and Ashadze hydrothermal fluids. However, the methanogenic Methanococcales was the most widely distributed hyper/thermophilic archaeal group among the hot and acidic ultramafic-hosted hydrothermal system environments. Most of the lineages detected are linked to methane and hydrogen cycling, suggesting that in ultramafic-hosted hydrothermal systems, large methanogenic and methanotrophic communities could be fuelled by hydrothermal fluids highly enriched in methane and hydrogen. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

  18. Community Structure of Lithotrophically-Driven Hydrothermal Microbial Mats from the Mariana Arc and Back-Arc

    Directory of Open Access Journals (Sweden)

    Kevin W. Hager

    2017-08-01

    Full Text Available The Mariana region exhibits a rich array of hydrothermal venting conditions in a complex geological setting, which provides a natural laboratory to study the influence of local environmental conditions on microbial community structure as well as large-scale patterns in microbial biogeography. We used high-throughput amplicon sequencing of the bacterial small subunit (SSU rRNA gene from 22 microbial mats collected from four hydrothermally active locations along the Mariana Arc and back-arc to explore the structure of lithotrophically-based microbial mat communities. The vent effluent was classified as iron- or sulfur-rich corresponding with two distinct community types, dominated by either Zetaproteobacteria or Epsilonproteobacteria, respectively. The Zetaproteobacterial-based communities had the highest richness and diversity, which supports the hypothesis that Zetaproteobacteria function as ecosystem engineers creating a physical habitat within a chemical environment promoting enhanced microbial diversity. Gammaproteobacteria were also high in abundance within the iron-dominated mats and some likely contribute to primary production. In addition, we also compare sampling scale, showing that bulk sampling of microbial mats yields higher diversity than micro-scale sampling. We present a comprehensive analysis and offer new insights into the community structure and diversity of lithotrophically-driven microbial mats from a hydrothermal region associated with high microbial biodiversity. Our study indicates an important functional role of for the Zetaproteobacteria altering the mat habitat and enhancing community interactions and complexity.

  19. Hydrothermal processing of actinide contaminated organic wastes

    International Nuclear Information System (INIS)

    Worl, A.; Buelow, S.J.; Le, L.A.; Padilla, D.D.; Roberts, J.H.

    1997-01-01

    Hydrothermal oxidation is an innovative process for the destruction of organic wastes, that occurs above the critical temperature and pressure of water. The process provides high destruction and removal efficiencies for a wide variety of organic and hazardous substances. For aqueous/organic mixtures, organic materials, and pure organic liquids hydrothermal processing removes most of the organic and nitrate components (>99.999%) and facilitates the collection and separation of the actinides. We have designed, built and tested a hydrothermal processing unit for the removal of the organic and hazardous substances from actinide contaminated liquids and solids. Here we present results for the organic generated at the Los Alamos National Laboratory Plutonium Facility

  20. Experimental Rock-on-Rock Abrasive Wear Under Aqueous Conditions: its Role in Subglacial Abrasion

    Science.gov (United States)

    Rutter, E. H.; Lee, A. G.

    2003-12-01

    We have determined experimentally the rate of abrasive wear of rock on rock for a range of rock types as a function of normal stress and shear displacement. Unlike abrasive wear in fault zones, where wear products accumulate as a thickening gouge zone, in our experiments wear particles were removed by flowing water. The experiments are thus directly pertinent to one of the most important processes in subglacial erosion, and to some extent in river incision. Wear was produced between rotating discs machined from rock samples and measured from the progressive approach of the disc axes towards each other under various levels of normal load. Shear displacements of several km were produced. Optical and scanning electron microscopy were used to study the worn rock surfaces, and particle size distributions in wear products were characterized using a laser particle size analyzer. Rock types studied were sandstones of various porosities and cement characteristics, schists and a granite. In all cases abrasion rate decreased logarithmically with displacement by up to 2 orders of magnitude until a steady state was approached, but only after at least 1 km displacement. The more porous, less-well cemented rocks wore fastest. Amount of abrasion could be characterized quantitatively using an exponentially decaying plus a steady-state term. Wear rate increased non-linearly with normal contact stress, apparently to an asymptote defined by the unconfined compressive strength. Microstructural study showed that the well-cemented and/or lowest porosity rocks wore by progressive abrasion of grains without plucking, whereas whole grains were plucked out of weakly-cemented and/or more porous rocks. This difference in behavior was reflected in wear-product particle size distributions. Where whole-grain plucking was possible, wear products were dominated by particles of the original grain size rather than finer rock flour. Comparison of our results to glacier basal abrasive wear estimated

  1. Hydrothermal processing of inorganic components of Hanford tank sludge

    International Nuclear Information System (INIS)

    Oldenborg, R.; Buelow, S.J.; Dyer, R.B.; Anderson, G.; Dell'Orco, P.C.; Funk, K.; Wilmanns, E.; Knutsen, K.

    1994-09-01

    Hydrothermal Processing (HTP) is an attractive approach for the treatment of Hanford tank sludge. Hydrothermal Processing refers to a waste treatment technique in which an aqueous waste stream is fed through a chemical reactor at elevated temperatures and pressures to effect desired chemical transformations and separations. Transformations such as organic and nitrate destruction and sludge reformulation have been demonstrated at pilot scale using simulants of Hanford tank wastes. At sufficiently high temperatures and pressures organics and nitrates are destroyed in seconds, producing primarily simple products such as CO 3 2- , H 2 O, N 2 , N 2 O and OH - , and sludges are reduced in volume and reformulated as rapid settling oxides amenable to downstream separation, or in some cases reformulated as soluble products. This report describes the hydrothermal dissolution of chromium and chromium oxide; the hydrothermal oxidation of chromium with nitrate; hydrothermal dissolution of aluminum-bearing sludges; the solubility of aluminum compounds in caustic hydrothermal media; experimental techniques for the study of solubility and phase behavior; optical cell studies of basic aluminate solution solubilities; and high temperature, low density salt solubility in the packed-bed flow apparatus

  2. Hydrothermal influence on nearshore sediments of Kos Island, Aegean Sea

    Science.gov (United States)

    Megalovasilis, Pavlos; Godelitsas, Athanasios

    2015-04-01

    The Kos-Nisyros volcanic centre is a long-active, Plio-Pleistocene magmatic system in the subduction zone along the easternmost edge of the active Hellenic volcanic arc in the Aegean Sea. Although today there are signs of relative quiescence in volcanic activity, active onshore fumaroles and shallow-sea hydrothermal vents persist on, amongst others, the island of Kos. The present study explores the large-scale imprint of hydrothermally sourced heavy metals and nutrients on the island's coastal marine environment, based on geochemical data collected in September 2007 from hydrothermal waters and surficial nearshore sediments (Kos is severely influenced by ongoing submarine hydrothermal activity, and confirm that shallow-water sediment Fe, Mn, Zn and Pb levels are substantially higher than those of other islands along the Hellenic volcanic arc, and even exceed those of some deep-water hydrothermal vents in other world regions. Evidently, there may be significant metallic sulphide deposits of hydrothermal origin at depth beneath Kos.

  3. Spontaneous and Widespread Electricity Generation in Natural Deep-Sea Hydrothermal Fields.

    Science.gov (United States)

    Yamamoto, Masahiro; Nakamura, Ryuhei; Kasaya, Takafumi; Kumagai, Hidenori; Suzuki, Katsuhiko; Takai, Ken

    2017-05-15

    Deep-sea hydrothermal vents discharge abundant reductive energy into oxidative seawater. Herein, we demonstrated that in situ measurements of redox potentials on the surfaces of active hydrothermal mineral deposits were more negative than the surrounding seawater potential, driving electrical current generation. We also demonstrated that negative potentials in the surface of minerals were widespread in the hydrothermal fields, regardless of the proximity to hydrothermal fluid discharges. Lab experiments verified that the negative potential of the mineral surface was induced by a distant electron transfer from the hydrothermal fluid through the metallic and catalytic properties of minerals. These results indicate that electric current is spontaneously and widely generated in natural mineral deposits in deep-sea hydrothermal fields. Our discovery provides important insights into the microbial communities that are supported by extracellular electron transfer and the prebiotic chemical and metabolic evolution of the ocean hydrothermal systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Hydrothermal systems in small ocean planets.

    Science.gov (United States)

    Vance, Steve; Harnmeijer, Jelte; Kimura, Jun; Hussmann, Hauke; Demartin, Brian; Brown, J Michael

    2007-12-01

    We examine means for driving hydrothermal activity in extraterrestrial oceans on planets and satellites of less than one Earth mass, with implications for sustaining a low level of biological activity over geological timescales. Assuming ocean planets have olivine-dominated lithospheres, a model for cooling-induced thermal cracking shows how variation in planet size and internal thermal energy may drive variation in the dominant type of hydrothermal system-for example, high or low temperature system or chemically driven system. As radiogenic heating diminishes over time, progressive exposure of new rock continues to the current epoch. Where fluid-rock interactions propagate slowly into a deep brittle layer, thermal energy from serpentinization may be the primary cause of hydrothermal activity in small ocean planets. We show that the time-varying hydrostatic head of a tidally forced ice shell may drive hydrothermal fluid flow through the seafloor, which can generate moderate but potentially important heat through viscous interaction with the matrix of porous seafloor rock. Considering all presently known potential ocean planets-Mars, a number of icy satellites, Pluto, and other trans-neptunian objects-and applying Earth-like material properties and cooling rates, we find depths of circulation are more than an order of magnitude greater than in Earth. In Europa and Enceladus, tidal flexing may drive hydrothermal circulation and, in Europa, may generate heat on the same order as present-day radiogenic heat flux at Earth's surface. In all objects, progressive serpentinization generates heat on a globally averaged basis at a fraction of a percent of present-day radiogenic heating and hydrogen is produced at rates between 10(9) and 10(10) molecules cm(2) s(1).

  5. Coupling hydrothermal liquefaction and anaerobic digestion for energy valorization from model biomass feedstocks.

    Science.gov (United States)

    Posmanik, Roy; Labatut, Rodrigo A; Kim, Andrew H; Usack, Joseph G; Tester, Jefferson W; Angenent, Largus T

    2017-06-01

    Hydrothermal liquefaction converts food waste into oil and a carbon-rich hydrothermal aqueous phase. The hydrothermal aqueous phase may be converted to biomethane via anaerobic digestion. Here, the feasibility of coupling hydrothermal liquefaction and anaerobic digestion for the conversion of food waste into energy products was examined. A mixture of polysaccharides, proteins, and lipids, representing food waste, underwent hydrothermal processing at temperatures ranging from 200 to 350°C. The anaerobic biodegradability of the hydrothermal aqueous phase was examined through conducting biochemical methane potential assays. The results demonstrate that the anaerobic biodegradability of the hydrothermal aqueous phase was lower when the temperature of hydrothermal processing increased. The chemical composition of the hydrothermal aqueous phase affected the anaerobic biodegradability. However, no inhibition of biodegradation was observed for most samples. Combining hydrothermal and anaerobic digestion may, therefore, yield a higher energetic return by converting the feedstock into oil and biomethane. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Hydrothermal processing of radioactive combustible waste

    International Nuclear Information System (INIS)

    Worl, L.A.; Buelow, S.J.; Harradine, D.; Le, L.; Padilla, D.D.; Roberts, J.H.

    1998-01-01

    Hydrothermal processing has been demonstrated for the treatment of radioactive combustible materials for the US Department of Energy. A hydrothermal processing system was designed, built and tested for operation in a plutonium glovebox. Presented here are results from the study of the hydrothermal oxidation of plutonium and americium contaminated organic wastes. Experiments show the destruction of the organic component to CO 2 and H 2 O, with 30 wt.% H 2 O 2 as an oxidant, at 540 C and 46.2 MPa. The majority of the actinide component forms insoluble products that are easily separated by filtration. A titanium liner in the reactor and heat exchanger provide corrosion resistance for the oxidation of chlorinated organics. The treatment of solid material is accomplished by particle size reduction and the addition of a viscosity enhancing agent to generate a homogeneous pumpable mixture

  7. Hydrothermal Liquefaction of Biomass

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, Douglas C.

    2010-12-10

    Hydrothermal liquefaction technology is describes in its relationship to fast pyrolysis of biomass. The scope of work at PNNL is discussed and some intial results are presented. HydroThermal Liquefaction (HTL), called high-pressure liquefaction in earlier years, is an alternative process for conversion of biomass into liquid products. Some experts consider it to be pyrolysis in solvent phase. It is typically performed at about 350 C and 200 atm pressure such that the water carrier for biomass slurry is maintained in a liquid phase, i.e. below super-critical conditions. In some applications catalysts and/or reducing gases have been added to the system with the expectation of producing higher yields of higher quality products. Slurry agents ('carriers') evaluated have included water, various hydrocarbon oils and recycled bio-oil. High-pressure pumping of biomass slurry has been a major limitation in the process development. Process research in this field faded away in the 1990s except for the HydroThermal Upgrading (HTU) effort in the Netherlands, but has new resurgence with other renewable fuels in light of the increased oil prices and climate change concerns. Research restarted at Pacific Northwest National Laboratory (PNNL) in 2007 with a project, 'HydroThermal Liquefaction of Agricultural and Biorefinery Residues' with partners Archer-Daniels-Midland Company and ConocoPhillips. Through bench-scale experimentation in a continuous-flow system this project investigated the bio-oil yield and quality that could be achieved from a range of biomass feedstocks and derivatives. The project was completed earlier this year with the issuance of the final report. HydroThermal Liquefaction research continues within the National Advanced Biofuels Consortium with the effort focused at PNNL. The bench-scale reactor is being used for conversion of lignocellulosic biomass including pine forest residue and corn stover. A complementary project is an international

  8. Oxygen and U-Th isotopes and the timescales of hydrothermal exchange and melting in granitoid wall rocks at Mount Mazama, Crater Lake, Oregon

    Science.gov (United States)

    Ankney, Meagan E.; Bacon, Charles R.; Valley, John W.; Beard, Brian L.; Johnson, Clark M.

    2017-01-01

    highest U excess (≥5.8%) also has the most 18O isotope depletion (average δ18Oplag = −4.0‰). The granitoids are a probable assimilant and source of U excess in volcanic rocks from Mt. Mazama. Two granitoids have Th excess and low δ18O values, interpreted to record leaching of U during hydrothermal alteration. A U-Th isochron based on the U excess array of the granitoids and volcanic rocks indicates that hydrothermal circulation initiated ∼40–75 kyrs before the climactic eruption, potentially marking the initiation of a persistent upper-crustal magma chamber. The U-Th ages are consistent with the maximum timescales inferred for hydrothermal alteration based on oxygen isotope zoning in quartz.

  9. Determining the Extent of Hydrothermal Interaction on the Southern Costa Rica Rift Ridge Flank During the Past 8 Ma from Joint Inversion of Geophysical Data

    Science.gov (United States)

    Wilson, D. J.; Moorkamp, M.; Hobbs, R. W.; Peirce, C.; Harris, R. N.; Morgan, J. V.

    2017-12-01

    Advective hydrothermal systems preferentially develop in zones of high porosity and permeability, driven by a local heat source. Associated chemical reactions lead to changes in the bulk physical properties, so variations in velocity and density, and the relationship connecting them, may provide a record of alteration by hydrothermal fluids. Oceanic crust accreted at intermediate rate ridges displays a range of characteristics between those typical for fast and slow spreading rates so changes in crustal porosity and permeability are sensitive to the interplay between tectonic stretching, magmatic supply and plate motions. Hence, changes in spreading style and sediment cover will influence the extent of the hydrothermal interaction that occurs and the mode of heat loss as evidenced by heat flow measurements. Using a variety of geophysical data we determine where hydrothermal circulation has been active in young oceanic crust that was accreted at an intermediate spreading rate. Results from traveltime tomography along a 300 km profile across the southern flank of the Costa Rica Rift reveal several variations in the P-wave velocity structure of the upper crust (layer 2). Following an initial increase in P-wave velocity near the ridge axis there is a section of the model 80 km in length that has lower P-wave velocity (up to 0.5 km s-1) compared to adjacent crust. This section has shallower bathymetry, by up to 500 m, than predicted by the subsidence curve and the top basement surface is rougher with a greater amount of faulting and larger throws. This zone is preceded by crust with significantly faster P-wave velocities (up to 1.0 km s-1) that was sampled by DSDP/ODP 504B. We characterise these changes in the shallow crustal structure by jointly inverting travel-time data and gravity data with deeper control from coincident magnetotelluric data. Using a cross-gradient approach allows us to search for models with a structural match, thus determining the relationship

  10. Treatment of urban sludge by hydrothermal carbonization.

    Science.gov (United States)

    Xu, Xiwei; Jiang, Enchen

    2017-08-01

    Urban sludge was treated by Hydrothermal carbonization (HTC). The effect of hydrothermal carbonization temperature, mixing with or without catalysts on solid products yield, heavy metal contents, turbidity and COD value was evaluated. The result showed solid products yield decreased from 92.04% to 52.65% when the temperature increased from 180 to 300°C. And the Cu, Zn, and Pb contents under exchangeable states decreased and reached discharge standard. Addition of FeCl 3 or Al(OH) 3 resulted in a significant increase in the exchangeable states of Zn, Pb, Cr, and Cd and decrease in their residual states. The turbidity and COD value of hydrothermal liquid decreased from 450° to 175°, and 13 to 6.8g/L, with increasing hydrothermal temperature. Comparison with HTC, solid productivity from low-temperature pyrolysis is higher. The exchangeable states of Cu, Zn, and Cr exceeded the limiting values. Our results show HTC can facilitate transforming urban sludge into no-pollution and energy-rich products. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Water column imaging on hydrothermal vent in Central Indian Ridge

    Science.gov (United States)

    Koh, J.; Park, Y.

    2017-12-01

    Water column imaging with Multibeam echosounder systems (MBES) is recently becoming of increasing interest for oceanographic studies. Especially gas bubbles and hot water exposed from hydrothermal vents make acoustic impedance anomalies in cold seawater, water column imaging is very useful for the researchers who want to detect some kinds of hydrothermal activity. We conducted a hydrothermal exploration program, called "INVENT17", using the MBES system, KONGBERG EM122 (12kHz, 1°×1°), mounted on R/V ISABU and we deployed other equipments including video guided hydraulic grab, tow-yo CTD and general CTD with MAPR (Miniature Autonomous Plume Recorder) in 2017. First, to evaluate its capabilities of detection of hydrothermal vent, the surveys using the MBES were conducted at the Solitaire Field, previously identified hydrothermal area of the Central Indian Ridge. The bathymetric data obtained from MBES provided information about detailed morphology of seafloor, but we were not able to achieve the information from the water column imaging data. But the clue of existence of active hydrothermal vent was detected through the values of ΔNTU, dEh/dt, and OPR gained from MAPR, the data means that the hydrothermal activity affects 100m from the seafloor. It could be the reason that we can't find the hydrothermal activity because the range resolution of water column imaging is pretty rough so that the size of 100m-scaled activity has low possibility to distinguish from seafloor. The other reason is there are no sufficient objects to cause strong scattering like as CO2 bubbles or droplets unlike in the mid-Okinawa Trough. And this suggests that can be a important standard to identify properties of hydrothermal vent sites depending on the presence of scattering objects in water mass. To justify this, we should perform more chemical analysis of hot water emanating from hydrothermal vent and collected several bottles of water sample to do that.

  12. Hydrothermal Carbonization of Seaweed For Advanced Biochar Production

    Directory of Open Access Journals (Sweden)

    Prakoso Tirto

    2018-01-01

    Full Text Available Seaweed such as Eucheuma Cottonii is a potential source of biomaterialIts high moisture content makes it suitable for hydrothermal conversion process since it doesn’t need to utilize dry feedstock. The aim of this study is to convert the biomass of red seaweed Eucheuma Cottonii into alternative fuels and high value biomaterials using hydrothermal process. The hydrothermal process seaweed Eucheuma Cottonii produce two types of products, liquid product and char (solid. This research focus on the char product. The char from hydrothermal process was then activated using the tubular furnace. The yield for activated char is 7.5 % and results of SEM analysis of activated char showed the formation of allotropes carbon include carbon micro spheres, carbon micro fibres and graphene. These structures have encountered application in a wide range of technological fields, such as adsorption, catalysis, hydrogen storage or electronics.

  13. Solidification of glass powder by a hydrothermal hot-pressing technique

    International Nuclear Information System (INIS)

    Nishioka, Mamoru; Yanagisawa, Kazumichi; Yamasaki, Nakamichi

    1986-01-01

    A borosilicate glass powder was solidified with a NaOH solution or distilled water by the hydrothermal hot-pressing technique. The effect of hydrothermal conditions on the compressive strength was investigated, and the densification mechanism of the glass powder during the hydrothermal hot-pressing was discussed in terms of isothermal shrinkage. The glass powder was successfully solidified by hydrothermal hot-pressing at a reaction temperature lower than that of an ordinary pressure sintering. The solidified body obtained in the presence of distilled water (10 wt%) at 280 deg C had a high compressive strength of about 2300 kg/cm 2 . The analysis of initial densification process of the glass powder in hydrothermal hot-pressing with Murray's rate equation revealed that the densification proceeds both by viscous flow and by rearrangement process. Analysis of the shrinkage rates with a rate equation of hydrothermal reaction suggested that the dissolution of particles into solution controlled the initial densification of the glass powder, and that the alkaline metal acted as a catalyst. (author)

  14. Effect of hydrothermal treatment of coal on its associative structure

    Energy Technology Data Exchange (ETDEWEB)

    Shui Heng-fu; Wang Zhi-cai; Wang Gao-qiang; Niu Min-feng [Anhui University of Technology, Maanshan (China). School of Chemistry & Chemical Engineering

    2006-10-15

    4 bituminous coals with different ranks were thermally and hydrothermally treated under different conditions, and the raw and treated coals were extracted with carbon disulfide/N-2-pyrrolidinone (CS{sub 2}/NMP) mixed solvent (1:1 by volume). It is found that the extraction yields of the thermal or hydrothermal treated coals at proper conditions increase in different extent. The increments of extraction yields for hydrothermal treated coals are higher than those of thermal treated coals. FT-IR shows that the adsorption peaks at 3410 cm{sup -1} attributed to OH group for the hydrothermal treated coals decrease, suggesting the dissociation of the coal aggregation structure due to the breakage of hydrogen bonds, resulting in the increase of extraction yields for the treated coals. For higher rank coal, the removal of minerals and the dissociation of {pi}-cation association after hydrothermal treatment of coal may be responsible for the increase of extraction yield. In addition, the mechanism of hydrothermal treatment of coal was discussed. 15 refs., 2 figs., 5 tabs.

  15. Synthesis of stable TiO2 nanotubes: effect of hydrothermal treatment, acid washing and annealing temperature.

    Science.gov (United States)

    López Zavala, Miguel Ángel; Lozano Morales, Samuel Alejandro; Ávila-Santos, Manuel

    2017-11-01

    Effect of hydrothermal treatment, acid washing and annealing temperature on the structure and morphology of TiO 2 nanotubes during the formation process was assessed. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy analysis were conducted to describe the formation and characterization of the structure and morphology of nanotubes. Hydrothermal treatment of TiO 2 precursor nanoparticles and acid washing are fundamental to form and define the nanotubes structure. Hydrothermal treatment causes a change in the crystallinity of the precursor nanoparticles from anatase phase to a monoclinic phase, which characterizes the TiO 2 nanosheets structure. The acid washing promotes the formation of high purity nanotubes due to Na + is exchanged from the titanate structure to the hydrochloric acid (HCl) solution. The annealing temperature affects the dimensions, structure and the morphology of the nanotubes. Annealing temperatures in the range of 400 °C and 600 °C are optimum to maintain a highly stable tubular morphology of nanotubes. Additionally, nanotubes conserve the physicochemical properties of the precursor Degussa P25 nanoparticles. Temperatures greater than 600 °C alter the morphology of nanotubes from tubular to an irregular structure of nanoparticles, which are bigger than those of the precursor material, i.e., the crystallinity turn from anatase phase to rutile phase inducing the collapse of the nanotubes.

  16. Hydrothermal industrialization: direct heat development. Final report

    Energy Technology Data Exchange (ETDEWEB)

    1982-05-01

    A description of hydrothermal resources suitable for direct applications, their associated temperatures, geographic distribution and developable capacity are given. An overview of the hydrothermal direct-heat development infrastructure is presented. Development activity is highlighted by examining known and planned geothermal direct-use applications. Underlying assumptions and results for three studies conducted to determine direct-use market penetration of geothermal energy are discussed.

  17. EFFECTS OF HEAT-FLOW AND HYDROTHERMAL FLUIDS FROM ...

    African Journals Online (AJOL)

    Volcanic intrusions and hydrothermal activity have modified the diagenetic minerals. In the Ulster Basin, UK, most of the authigenic mineralization in the Permo-Triassic sandstones pre-dated tertiary volcanic intrusions. The hydrothermal fluids and heat-flow from the volcanic intrusions did not affect quartz and feldspar ...

  18. Geology and environments of subglacial Lake Vostok.

    Science.gov (United States)

    Leitchenkov, German L; Antonov, Anton V; Luneov, Pavel I; Lipenkov, Vladimir Ya

    2016-01-28

    The reconstruction of the geological (tectonic) structure and environments of subglacial Lake Vostok is based on geophysical surveys and the study of mineral particles found in cores of accreted ice and frozen lake water (sampled after the lake was unsealed). Seismic reflection and refraction investigations conducted in the southern part of Lake Vostok show very thin (200-300 m) sedimentary cover overlying a crystalline basement. Most of this thin veneer is thought to have been deposited during temperate-glacial conditions in Oligocene to Middle Miocene time (ca 34-14 Ma). The composition of the lake-bottom sediments can be deduced from mineral inclusions found in cores of accreted ice. Inclusions are represented by soft aggregates consisting mainly of clay-mica minerals and micrometre-sized quartz grains. Some of these inclusions contain subangular to semi-rounded rock clasts (siltstones and sandstones) ranging from 0.3 to 8 mm in size. In total, 31 zircon grains have been identified in two rock clasts and dated using SHRIMP-II. The ages of the studied zircons range from 0.6 to 2.0 Ga with two distinct clusters between 0.8 and 1.15 Ga and between 1.6 and 1.8 Ga. Rock clasts obviously came from the western lake shore, which is thus composed of terrigenous strata with an age of not older than 600 Ma. The sedimentary nature of the western lake shore is also confirmed by seismic refraction data showing seismic velocities there of 5.4-5.5 km s(-1) at the bedrock surface. After Lake Vostok was unsealed, its water (frozen and sampled next season) was also studied with scanning electron microscopy and X-ray microprobe analysis. This study showed the existence of calcium carbonate and silica microparticles (10-20 μm across) in frozen water. © 2015 The Author(s).

  19. Uranium-lead dating of hydrothermal zircon and monazite from the Sin Quyen Fe-Cu-REE-Au-(U) deposit, northwestern Vietnam

    Science.gov (United States)

    Li, Xiao-Chun; Zhou, Mei-Fu; Chen, Wei Terry; Zhao, Xin-Fu; Tran, MyDung

    2018-03-01

    The Sin Quyen deposit in northwestern Vietnam contains economic concentrations of Cu, Au and LREE, and sub-economic concentration of U. In this deposit, massive and banded replacement ores are hosted in Neoproterozoic metapelite. The paragenetic sequence includes sodic alteration (stage I), calcic-potassic alteration and associated Fe-REE-(U) mineralization (stage II), Cu-Au mineralization (stage III), and sulfide-(quartz-carbonate) veins (stage IV). The Sin Quyen deposit experienced an extensive post-ore metamorphic overprint, which makes it difficult to precisely determine the mineralization age. In this study, zircon and monazite U-Pb geochronometers and the Rb-Sr isochron method are used to constrain the timing of mineralization. Zircon grains in the ore are closely intergrown or texturally associated with hydrothermal minerals of stage II (e.g., garnet, allanite, and hedenbergite). They may contain primary fluid inclusions and display irregular zoning in cathodoluminescence (CL) images. Zircon grains are rich in U (688 to 2902 ppm) and poor in Th (0.2 to 2.9 ppm). Their δ18OV-SMOW values range from 11.9 to 14.0‰, higher than those of typical magmatic zircon. These textural and compositional features imply that zircon precipitated from 18O- and U-rich hydrothermal fluids, coeval with the minerals of stage II. Monazite occurs in close association with stage II magnetite and allanite and has low contents of Th (<2700 ppm), indicative of a hydrothermal origin. Hydrothermal zircon and monazite have indistinguishable U-Pb ages of 841 ± 12 and 836 ± 18 Ma, respectively, representing the timing of Fe-REE mineralization. There is no direct isotopic constraint on the timing of the Cu-Au mineralization, but geological observations suggest that the Cu-Au and Fe-REE ores most likely formed within a single evolved hydrothermal process. In the plot of 87Rb/86Sr vs. 87Sr/86Sr, the composition of bulk-ore and biotite separates from ore lie along a reference line for 30 Ma

  20. Mineralogy and geological significance of hydrothermal deposits from the Okinawa Trough

    Science.gov (United States)

    Zhang, Xia; Zhai, Shikui; Yu, Zenghui; Wang, Shujie; Cai, Zongwei

    2018-04-01

    The study of hydrothermal deposits in the Okinawa Trough can help us to uncover the hydrothermal mineralization characteristics in the back-arc basin during the early expanding stage. Mineralogy and geological significance of hydrothermal deposits from both the middle and southern trough are studied in this paper. First of all, using optical microscope to confirm the mineral compositions, characteristics of crystal shape, paragenetic relationship and minerals crystallization order. Then the minerals chemical composition were analyzed in virtue of electron microprobe. On these basis, the paragenetic sequence and the mineralization characteristics of the hydrothermal deposits were discussed. The results show that the hydrothermal deposit from the mid-Okinawa Trough belongs to Zn-Cu-rich type, consisting dominantly of sulfide minerals such as sphalerite, chalcopyrite, pyrite, etc. The minerals crystallization order is first generation pyrite(PyI)-sphalerite-chalcopyrite-galena-second generation pyrite(PyII)-amorphous silica. While the deposit from the southern Okinawa Trough is Ba-Zn-Pb-rich type mainly composing of barite, sphalerite, galena, etc. The minerals crystallization order is barite-pyrite-sphalerite-tetrahedrite-galena-chalcopyrite-amorphous silica. Hydrothermal fluid temperature in the mid-Okinawa Trough undergoes a process from high to low, which is high up to 350 °C in the early stage, but decreasing gradually with the evolution of hydrothermal fluid. On the contrary, the hydrothermal activity in the southern Okinawa Trough is low temperature dominated, but the mineralization environment is unstable and the fluid temperature changes drastically during the period of hydrothermal activity.

  1. A Sr-isotopic comparison between thermal waters, rocks, and hydrothermal calcites, Long Valley caldera, California

    Science.gov (United States)

    Goff, F.; Wollenberg, H.A.; Brookins, D.C.; Kistler, R.W.

    1991-01-01

    The 87Sr/86Sr values of thermal waters and hydrothermal calcites of the Long Valley caldera geothermal system are more radiogenic than those of young intracaldera volcanic rocks. Five thermal waters display 87Sr/86Sr of 0.7081-0.7078 but show systematically lighter values from west to east in the direction of lateral flow. We believe the decrease in ratio from west to east signifies increased interaction of deeply circulating thermal water with relatively fresh volcanic rocks filling the caldera depression. All types of pre-, syn-, and post-caldera volcanic rocks in the west and central caldera have (87Sr/86Sr)m between about 0.7060 and 0.7072 and values for Sierra Nevada granodiorites adjacent to the caldera are similar. Sierran pre-intrusive metavolcanic and metasedimentary rocks can have considerably higher Sr-isotope ratios (0.7061-0.7246 and 0.7090-0.7250, respectively). Hydrothermally altered volcanic rocks inside the caldera have (87Sr/86Sr)m slightly heavier than their fresh volcanic equivalents and hydrothermal calcites (0.7068-0.7105) occupy a midrange of values between the volcanic/plutonic rocks and the Sierran metamorphic rocks. These data indicate that the Long Valley geothermal reservoir is first equilibrated in a basement complex that contains at least some metasedimentary rocks. Reequilibration of Sr-isotope ratios to lower values occurs in thermal waters as convecting geothermal fluids flow through the isotopically lighter volcanic rocks of the caldera fill. ?? 1991.

  2. Hydrothermal liquefaction of biomass

    DEFF Research Database (Denmark)

    Toor, Saqib; Rosendahl, Lasse; Hoffmann, Jessica

    2014-01-01

    Biomass is one of the most abundant sources of renewable energy, and will be an important part of a more sustainable future energy system. In addition to direct combustion, there is growing attention on conversion of biomass into liquid en-ergy carriers. These conversion methods are divided...... into biochemical/biotechnical methods and thermochemical methods; such as direct combustion, pyrolysis, gasification, liquefaction etc. This chapter will focus on hydrothermal liquefaction, where high pressures and intermediate temperatures together with the presence of water are used to convert biomass...... into liquid biofuels, with the aim of describing the current status and development challenges of the technology. During the hydrothermal liquefaction process, the biomass macromolecules are first hydrolyzed and/or degraded into smaller molecules. Many of the produced molecules are unstable and reactive...

  3. Chemical variation in hydrothermal minerals of the Los Humeros geothermal system, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Serrano, R.G. [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico). Insituto de Geofisica

    2002-10-01

    The Los Humeros geothermal system is composed of more than 2200 m of Quaternary altered volcanic rocks and an underlying Cretaceous sedimentary sequence. The low salinity of the fluids discharged at present (Na{sup +} and Cl{sup -} concentrations <500 ppm), and the excess steam, indicate that the reservoir contains a mixture of steam and dilute groundwater. Water-rock equilibrium is not attained. Hydrothermal minerals are present in veinlets, vugs, and replacing primary minerals. Three mineral zones are recognized: 1) a shallow argillic zone (<400 m depth), 2) a propylitic zone (ranging between 500 and 1800 m) and 3) a skarn zone (>1800 m). Petrographic examination of cuttings from five wells and temperature data indicate at least two stages of hydrothermal activity. Temperature is the main factor that affects the chemical composition of chlorite, epidote and biotite. Fe{sup 2+} and Al{sup IV} increase in chlorite with temperature [from 1.4 formula position unit (fpu) to 2.8, and from 0.7 to 2.4 fpu, respectively]. The pistacite content of epidote varies from 18 to 33 mol% in high-temperature regions (>270 {sup o}C) and from 13 to 26 mol% in low-temperature regions (<250 {sup 0}C). Biotite displays a slight increase in Al{sup IV} contents (1.55-2.8) and octahedral occupancy (5.93-6.0 fpu) with temperature. Whole rock composition and variations in oxygen fugacity condition are factors that also affect the concentrations of Fe, Al and Mg in the octahedral sites of chlorite, epidote, biotite and amphiboles. Chemical variations observed in alteration minerals at different depths in the Colapso Central-Xalapazco region could be used as indicator of relict physico-chemical conditions in the reservoir, before the present economic exploitation. (author)

  4. Can Life Begin on Enceladus? A Perspective from Hydrothermal Chemistry.

    Science.gov (United States)

    Deamer, David; Damer, Bruce

    2017-09-01

    Enceladus is a target of future missions designed to search for existing life or its precursors. Recent flybys of Enceladus by the Cassini probe have confirmed the existence of a long-lived global ocean laced with organic compounds and biologically available nitrogen. This immediately suggests the possibility that life could have begun and may still exist on Enceladus. Here we will compare the properties of two proposed sites for the origin of life on Earth-hydrothermal vents on the ocean floor and hydrothermal volcanic fields at the surface-and ask whether similar conditions could have fostered the origin of life on Enceladus. The answer depends on which of the two sites would be more conducive for the chemical evolution leading to life's origin. A hydrothermal vent origin would allow life to begin in the Enceladus ocean, but if the origin of life requires freshwater hydrothermal pools undergoing wet-dry cycles, the Enceladus ocean could be habitable but lifeless. These arguments also apply directly to Europa and indirectly to early Mars. Key Words: Enceladus-Hydrothermal vents-Hydrothermal fields-Origin of life. Astrobiology 17, 834-839.

  5. Hydrothermal carbonization and torrefaction of grape pomace: a comparative evaluation.

    Science.gov (United States)

    Pala, Mehmet; Kantarli, Ismail Cem; Buyukisik, Hasan Baha; Yanik, Jale

    2014-06-01

    Grape pomace was treated by hydrothermal carbonization (sub-critical water, 175-275°C) and torrefaction (nitrogen atmosphere, 250 and 300°C), with mass yield of solid product (char) ranging between 47% and 78%, and energy densification ratio to 1.42-1.15 of the original feedstock. The chars were characterised with respect to their fuel properties, morphological and structural properties and combustion characteristics. The hydrothermal carbonization produced the char with greater energy density than torrefaction. The chars from torrefaction were found to be more aromatic in nature than that from hydrothermal carbonization. Hydrothermal carbonization process produced the char having high combustion reactivity. Most interesting was the finding that aqueous phase from hydrothermal carbonization had antioxidant activity. The results obtained in this study showed that HTC appears to be promising process for a winery waste having high moisture content. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. A model for Nb-Zr-REE-Ga enrichment in Lopingian altered alkaline volcanic ashes: Key evidence of H-O isotopes

    Science.gov (United States)

    Dai, Shifeng; Nechaev, Victor P.; Chekryzhov, Igor Yu.; Zhao, Lixin; Vysotskiy, Sergei V.; Graham, Ian; Ward, Colin R.; Ignatiev, Alexander V.; Velivetskaya, Tatyana A.; Zhao, Lei; French, David; Hower, James C.

    2018-03-01

    Clay-altered volcanic ash with highly-elevated concentrations of Nb(Ta), Zr(Hf), rare earth elements (REE), and Ga, is a new type of critical metal deposit with high commercial prospects that has been discovered in Yunnan Province, southwest China. Previous studies showed that the volcanic ashes had been subjected to hydrothermal fluids, the nature of which, however, is not clear. Here we show that the volcanic ashes were originated from alkaline magmatism, followed by a continuous hydrothermal-weathering process. Heated meteoric waters, which were sourced from acidic rains and mixed with CO2 from degassing of the Emeishan plume, have caused partial, but widespread, acidic leaching of Nb, Ta, Zr, Hf, REE, and Ga into ground water and residual enrichment of these elements, along with Al and Ti, in the deeply altered rocks. Subsequent alteration occurring under cooler, neutral or alkaline conditions, caused by water-rock interaction, resulted in precipitation of the leached critical metals in the deposit. Polymetallic mineralization of similar origin may be found in other continental regions subjected to explosive alkaline volcanism associated with deep weathering in humid conditions.

  7. Cuprous oxide thin films grown by hydrothermal electrochemical deposition technique

    International Nuclear Information System (INIS)

    Majumder, M.; Biswas, I.; Pujaru, S.; Chakraborty, A.K.

    2015-01-01

    Semiconducting cuprous oxide films were grown by a hydrothermal electro-deposition technique on metal (Cu) and glass (ITO) substrates between 60 °C and 100 °C. X-ray diffraction studies reveal the formation of cubic cuprous oxide films in different preferred orientations depending upon the deposition technique used. Film growth, uniformity, grain size, optical band gap and photoelectrochemical response were found to improve in the hydrothermal electrochemical deposition technique. - Highlights: • Cu 2 O thin films were grown on Cu and glass substrates. • Conventional and hydrothermal electrochemical deposition techniques were used. • Hydrothermal electrochemical growth showed improved morphology, thickness and optical band gap

  8. Products of an Artificially Induced Hydrothermal System at Yucca Mountain

    International Nuclear Information System (INIS)

    Levy, S.

    2000-01-01

    Studies of mineral deposition in the recent geologic past at Yucca Mountain, Nevada, address competing hypotheses of hydrothermal alteration and deposition from percolating groundwater. The secondary minerals being studied are calcite-opal deposits in fractures and lithophysal cavities of ash-flow tuffs exposed in the Exploratory Studies Facility (ESF), a 7.7-km tunnel excavated by the Yucca Mountain Site Characterization Project within Yucca Mountain. An underground field test in the ESF provided information about the minerals deposited by a short-lived artificial hydrothermal system and an opportunity for comparison of test products with the natural secondary minerals. The heating phase lasted nine months, followed by a nine-month cooling period. Natural pore fluids were the only source of water during the thermal test. Condensation and reflux of water driven away from the heater produced fluid flow in certain fractures and intersecting boreholes. The mineralogic products of the thermal test are calcite-gypsum aggregates of less than 4-micrometer crystals and amorphous silica as glassy scale less than 0.2 mm thick and as mounds of tubules with diameters less than 0.7 micrometers. The minute crystal sizes of calcite and gypsum from the field test are very different from the predominantly coarser calcite crystals (up to cm scale) in natural secondary-mineral deposits at the site. The complex micrometer-scale textures of the amorphous silica differ from the simple forms of opal spherules and coatings in the natural deposits, even though some natural spherules are as small as 1 micrometer. These differences suggest that the natural minerals, especially if they were of hydrothermal origin, may have developed coarser or simpler forms during subsequent episodes of dissolution and redeposition. The presence of gypsum among the test products and its absence from the natural secondary-mineral assemblage may indicate a higher degree of evaporation during the test than

  9. Influence of fluorine substitution on the morphology and structure of hydroxyapatite nanocrystals prepared by hydrothermal method

    International Nuclear Information System (INIS)

    Joseph Nathanael, A.; Mangalaraj, D.; Hong, S.I.; Masuda, Y.; Rhee, Y.H.; Kim, H.W.

    2013-01-01

    Hydroxyapatite (HAp) nanocrystals with different levels of fluorine substitution (P/F = 0, 6, 4 and 2) on the OH sites were produced via hydrothermal method. The fluorine substitution was found to alter the morphology of crystals appreciably. The aspect ratio and the crystallinity of HAp crystals increased with increasing fluorine substitution. The presence of broad ring and hallow ring patterns in electron diffraction suggests the low-crystalline nature of HAp crystals. With increasing fluorine substitution, the diffraction patterns exhibited discrete rings and numerous diffraction spots, implying the increased crystallinity. Raman spectra from the HAp nanoparticles also support the less-crystalline nature of the pristine HAp and the enhanced crystallization by fluorine substitution. In HAp crystals processed with no fluorine substitution, surface energy and planar Ca 2+ density are less sensitive to the crystallographic orientation because of its low-crystalline nature, favoring equi-axed or slightly elongated particles. The addition of fluorine apparently increased the crystallinity, enhancing the orientation dependent growth and accordingly the aspect ratio. Osteoblast proliferation was observed to be enhanced by fluorine substitution in HAp. In vitro biological data support that the excellent osteoblastic cell viability and functional activity of the fluoridated apatite. -- Highlights: ► Fluorapatite nanorods were produced hydrothermally with different fluorine content. ► Fluorine substitution was found to alter the morphology of crystals appreciably. ► It enhances the crystallinity, orientation dependent growth and hence aspect ratio. ► In vitro cellular analysis shows excellent cell viability of the fluorapatite.

  10. Hydrothermal dolomite reservoir facies in the Sinian Dengying Fm, central Sichuan Basin

    Directory of Open Access Journals (Sweden)

    Yuqiang Jiang

    2017-07-01

    Full Text Available The Upper Sinian Dengying Fm is the focus of natural gas exploration in the central part of the Sichuan Basin (central Sichuan Basin in recent years. Especially, epigenic karstification and its resulted reservoir-seepage spaces have always been the focal points in researches. Based on the petrographic characteristics of drilling cuttings and core samples, and through experimental analysis by using trace elements, isotopes, and cathodoluminescence, the Dengying Fm dolomite was demonstrated to have matrix recrystallized dolomite (MRD, filled saddle dolomite (FSD (the mean homogenization temperature of inclusion: 178.5 °C, high concentrations of Fe & Mn, slightly positive 87Sr/86Sr value and hydrothermal minerals combination (including sphalerite, galena, pyrite, and quartz, etc.. Thus, it was proposed that hydrothermal dolomite reservoir facies (HDRF exist in the Dengying Fm dolomite, in other words, the dolomite reservoir is composed of hydrothermal dissolved pores, intercrystalline pores of hydrothermal origin, hydrothermal caverns and expanded fractures, and was formed due to the reworking of hydrothermal fluid on tight matrix dolomite. Identification marks are presented in terms of petrography and geochemistry so that hydrothermal dolomite reservoir facies can be effectively recognized and identified. It is concluded that the development of hydrothermal dolomite reservoir facies in this area are preliminary controlled by deep and large basement faults and the strength of hydrothermal fluids.

  11. Cu-As Decoupling in Hydrothermal Systems: A Link Between Pyrite Chemistry and Fluid Composition

    Science.gov (United States)

    Reich, M.; Tardani, D.; Deditius, A.; Chryssoulis, S.; Wrage, J.; Sanchez-Alfaro, P.; Andrea, H.; Cinthia, J.

    2016-12-01

    Chemical zonations in pyrite have been recognized in most hydrothermal ore deposit types, showing in some cases marked oscillatory alternation of metals and metalloids in pyrite growth zones (e.g., of Cu-rich, As-(Au)-depleted zones and As-(Au)-rich, Cu-depleted zones). This decoupled geochemical behavior of Cu and As has been interpreted as a result of chemical changes in ore-forming fluids, although direct evidence connecting fluctuations in hydrothermal fluid composition with metal partitioning into pyrite growth zones is still lacking. Here we report a comprehensive trace element database of pyrite from an active hydrothermal system, the Tolhuaca Geothermal System (TGS) in southern Chile. We combined high-spatial resolution and X-ray mapping capabilities of electron microprobe analysis (EMPA) with low detection limits and depth-profiling capabilities of secondary-ion mass spectrometry (SIMS) in a suite of pyrite samples retrieved from a 1 km drill hole that crosses the argillic and propylitic alteration zones of the geothermal system. We show that the concentrations of precious metals (e.g., Au, Ag), metalloids (e.g., As, Sb, Se, Te), and base and heavy metals (e.g., Cu, Co, Ni, Pb) in pyrite at the TGS are significant. Among the elements analyzed, arsenic, Cu and Co are the most abundant with concentrations that vary from sub-ppm levels to a few wt. %. Pyrites from the deeper propylitic zone do not show significant zonation and high Cu-(Co)-As concentrations correlate with each other. In contrast, well-developed zonations were detected in pyrite from the shallow argillic alteration zone, where Cu(Co)-rich, As-depleted cores alternate with Cu(Co)-depleted, As-rich rims. These microanalytical data were contrasted with chemical data of fluid inclusion in quartz veins (high Cu/Na and low As/Na) and borehole fluids (low Cu/Na and high As/Na) reported at the TGS, showing a clear correspondence between Cu and As concentrations in pyrite-forming fluids and chemical

  12. Hydrothermal contamination of public supply wells in Napa and Sonoma Valleys, California

    International Nuclear Information System (INIS)

    Forrest, M.J.; Kulongoski, J.T.; Edwards, M.S.; Farrar, C.D.; Belitz, K.; Norris, R.D.

    2013-01-01

    Highlights: ► We analyzed the geochemistry of 44 public supply wells in Napa and Sonoma Valleys. ► We investigated mixing of groundwater with hydrothermal fluids. ► We used multivariate statistical analyses and modeling to characterize wells. ► We found that nine public supply wells contained 14–30% hydrothermal fluids. ► Some contaminated wells contain potentially harmful concentrations of As, F and B. - Abstract: Groundwater chemistry and isotope data from 44 public supply wells in the Napa and Sonoma Valleys, California were determined to investigate mixing of relatively shallow groundwater with deeper hydrothermal fluids. Multivariate analyses including Cluster Analyses, Multidimensional Scaling (MDS), Principal Components Analyses (PCA), Analysis of Similarities (ANOSIM), and Similarity Percentage Analyses (SIMPER) were used to elucidate constituent distribution patterns, determine which constituents are significantly associated with these hydrothermal systems, and investigate hydrothermal contamination of local groundwater used for drinking water. Multivariate statistical analyses were essential to this study because traditional methods, such as mixing tests involving single species (e.g. Cl or SiO 2 ) were incapable of quantifying component proportions due to mixing of multiple water types. Based on these analyses, water samples collected from the wells were broadly classified as fresh groundwater, saline waters, hydrothermal fluids, or mixed hydrothermal fluids/meteoric water wells. The Multivariate Mixing and Mass-balance (M3) model was applied in order to determine the proportion of hydrothermal fluids, saline water, and fresh groundwater in each sample. Major ions, isotopes, and physical parameters of the waters were used to characterize the hydrothermal fluids as Na–Cl type, with significant enrichment in the trace elements As, B, F and Li. Five of the wells from this study were classified as hydrothermal, 28 as fresh groundwater, two as

  13. Hydrothermal activity at slow-spreading ridges: variability and importance of magmatic controls

    Science.gov (United States)

    Escartin, Javier

    2016-04-01

    Hydrothermal activity along mid-ocean ridge axes is ubiquitous, associated with mass, chemical, and heat exchanges between the deep lithosphere and the overlying envelopes, and sustaining chemiosynthetic ecosystems at the seafloor. Compared with hydrothermal fields at fast-spreading ridges, those at slow spreading ones show a large variability as their location and nature is controlled or influenced by several parameters that are inter-related: a) tectonic setting, ranging from 'volcanic systems' (along the rift valley floor, volcanic ridges, seamounts), to 'tectonic' ones (rift-bounding faults, oceanic detachment faults); b) the nature of the host rock, owing to compositional heterogeneity of slow-spreading lithosphere (basalt, gabbro, peridotite); c) the type of heat source (magmatic bodies at depth, hot lithosphere, serpentinization reactions); d) and the associated temperature of outflow fluids (high- vs.- low temperature venting and their relative proportion). A systematic review of the distribution and characteristics of hydrothermal fields along the slow-spreading Mid-Atlantic Ridge suggests that long-lived hydrothermal activity is concentrated either at oceanic detachment faults, or along volcanic segments with evidence of robust magma supply to the axis. A detailed study of the magmatically robust Lucky Strike segment suggests that all present and past hydrothermal activity is found at the center of the segment. The association of these fields to central volcanos, and the absence of indicators of hydrothermal activity along the remaining of the ridge segment, suggests that long-lived hydrothermal activity in these volcanic systems is maintained by the enhanced melt supply and the associated magma chamber(s) required to build these volcanic edifices. In this setting, hydrothermal outflow zones at the seafloor are systematically controlled by faults, indicating that hydrothermal fluids in the shallow crust exploit permeable fault zones to circulate. While

  14. Hydrothermal uranium vein deposits in Marysvale volcanic field, Utah

    International Nuclear Information System (INIS)

    Rasmussen, J.D.; Cunningham, C.G.; Steven, T.A.; Rye, R.O.; Romberger, S.B.

    1984-01-01

    Hydrothermal uranium veins are exposed over a 300 m (980 ft) vertical range in mines of the Central Mining area, near Marysvale, Utah. They cut 23 Ma quartz monzonite, 21 Ma granite, and 19 Ma rhyolite ash-flow tuff. The veins formed 18-19 Ma, in an area 1 km (0.6 mi) across, above the center of a composite magma chamber at least 12 x 6 km across that fed a sequence of 21-14 Ma hypabyssal granitic stocks, and rhyolitic lava flows, ash-flow tuffs, and volcanic domes. Intrusive pressure uplifted and fractured the roof; molybdenite-bearing, uranium-rich glassy dikes were intruded; and a breccia pipe and uranium-bearing veins were formed. The veins appear to have been deposited near the surface above a concealed rhyolite stock, where they filled high-angle fault zones and flat-lying to concave-downward pull-apart fractures. Low pH and fO 2 hydrothermal fluids at temperatures near 200 0 C (392 0 F) permeated the fractured rocks; these fluids were rich in fluorine and potassium, and contained uranium as uranous-fluoride complexes. Fluid-wall rock interaction increased fluid pH, causing precipitation of uranium minerals. At the deepest exposed levels, wall rocks were altered to kaolinite and sericite, and uraninite, coffinite, jordisite, fluorite, molybdenite, quartz, and pyrite (with delta 34 S near zero per mil) were deposited. The fluids were progressively oxidized higher in the system; iron in the wall rocks was oxidized to hematite, and sooty uraninite and umohoite were deposited

  15. Chronology of magmatism and mineralization in the Kassandra mining area, Greece: The potentials and limitations of dating hydrothermal illites

    Science.gov (United States)

    Gilg, H. Albert; Frei, Robert

    1994-05-01

    Various geochronological methods ( U/Pb, Rb/Sr, and K/Ar) have been applied to constrain the timing of magmatism and polymetallic mineralization in the Kassandra mining district, northern Greece. These data provide the first geochronological evidence that porphyry copper mineralization, proximal copper skarns, and distal high-temperature carbonate-hosted Pb-Zn-Ag-Au replacement ores formed contemporaneously and probably within less than 2 million years. Polymetallic mineralization is temporally related to the emplacement of granodioritic to quartz dioritic porphyries (24-25 Ma) that postdate the largest post-tectonic intrusion of the area, the Stratoni granodiorite (27.9 ± 1.2 Ma). Andesite porphyry dikes, which crosscut the Pb-Zn-Ag-Au ores and associated alterations, represent the last magmatic phase in the area (19.1 ± 0.6 Ma) and did not contribute to metal concentration. The combination of K/Ar, Rb/Sr, and oxygen isotope studies of hydrothermal illite-rich clays and careful granulometric analysis constrains the reliability of these geochronological methods and emphasizes the importance of characterizing the post-formational history of the sample. We identify various processes which partly disturbed the K/Ar and Rb/Sr system of some clays, such as retrograde alteration by heated meteoric waters, superimposed supergene illitization, and resetting of both isotopic systems due to a hydrothermal overprint related to the intrusion of the andesite porphyry. Our data, however, suggest that diffusive Ar loss from the finest clay fractions ( 200°C), therefore, do not give reliable formation ages. The loss of Ar may be used to model the cooling history of the hydrothermal system applying the concept of closure temperatures ( DODSON, 1973). 40K- 40Ar rad isochrons of natural, coarser grained (> 0.6 μm) size fractions of illites from single samples, even when slightly contaminated with feldspars, may yield meaningful ages either of the formation or of a reheating event

  16. Effects of iron-containing minerals on hydrothermal reactions of ketones

    Science.gov (United States)

    Yang, Ziming; Gould, Ian R.; Williams, Lynda B.; Hartnett, Hilairy E.; Shock, Everett L.

    2018-02-01

    Hydrothermal organic transformations occurring in geochemical processes are influenced by the surrounding environments including rocks and minerals. This work is focused on the effects of five common minerals on reactions of a model ketone substrate, dibenzylketone (DBK), in an experimental hydrothermal system. Ketones play a central role in many hydrothermal organic functional group transformations, such as those converting hydrocarbons to oxygenated compounds; however, how these minerals control the hydrothermal chemistry of ketones is poorly understood. Under the hydrothermal conditions of 300 °C and 70 MPa for up to 168 h, we observed that, while quartz (SiO2) and corundum (Al2O3) had no detectable effect on the hydrothermal reactions of DBK, iron-containing minerals, such as hematite (Fe2O3), magnetite (Fe3O4), and troilite (synthetic FeS), accelerated the reaction of DBK by up to an order of magnitude. We observed that fragmentation products, such as toluene and bibenzyl, dominated in the presence of hematite or magnetite, while use of troilite gave primarily the reduction products, e.g., 1, 3-diphenyl-propane and 1, 3-diphenyl-2-propanol. The roles of the three iron minerals in these transformations were further explored by (1) control experiments with various mineral surface areas, (2) measuring H2 in hydrothermal solutions, and (3) determining hydrogen balance among the organic products. These results suggest the reactions catalyzed by iron oxides (hematite and magnetite) are promoted mainly by the mineral surfaces, whereas the sulfide mineral (troilite) facilitated the reduction of ketone in the reaction solution. Therefore, this work not only provides a useful chemical approach to study and uncover complicated hydrothermal organic-mineral interactions, but also fosters a mechanistic understanding of ketone reactions in the deep carbon cycle.

  17. Preliminary Mineralogic and Stable Isotope Studies of Altered Summit and Flank Rocks and Osceola Mudflow Deposits on Mount Rainier, Washington

    Science.gov (United States)

    Rye, Robert O.; Breit, George N.; Zimbelman, David R.

    2003-01-01

    About 5600 years ago part of Mount Rainier?s edifice collapsed with the resultant Osceola Mudflow traveling more than 120 km and covering an area of at least 505 km2. Mineralogic and stable isotope studies were conducted on altered rocks from outcrops near the summit and east flank of the volcano and samples of clasts and matrix from the Osceola Mudflow. Results of these analyses are used to constrain processes responsible for pre-collapse alteration and provide insight into the role of alteration in edifice instability prior to the Osceola collapse event. Jarosite, pyrite, alunite, and kaolinite occur in hydrothermally altered rock exposed in summit scarps formed by edifice collapse events and in altered rock within the east-west structural zone (EWSZ) of the volcano?s east flank. Deposits of the Osceola Mudflow contain clasts of variably altered and unaltered andesite within a clay-rich matrix. Minerals detected in samples from the edifice are also present in many of the clasts. The matrix includes abundant smectite, kaolinite and variably abundant jarosite. Hydrothermal fluid compositions calculated from hydrogen and oxygen isotope data of alunite, and smectite on Mount Rainier reflect mixing of magmatic and meteoric waters. The range in the dD values of modern meteoric water on the volcano (-85 to 155?) reflect the influence of elevation on the dD of precipitation. The d34S and d18OSO4 values of alunite, gypsum and jarosite are distinct but together range from 1.7 to 17.6? and -12.3 to 15.0?, respectively; both parameters increase from jarosite to gypsum to alunite. The variations in sulfur isotope composition are attributed to the varying contributions of disproportionation of magmatic SO2, the supergene oxidation of hydrothermal pyrite and possible oxidation of H2S to the parent aqueous sulfate. The 18OSO4 values of jarosite are the lowest recorded for the mineral, consistent with a supergene origin. The mineralogy and isotope composition of alteration

  18. Quantification of porosity evolution from unaltered to propylitic-altered granites: the 14C-PMMA method applied on the hydrothermal system of Lavras do Sul, Brazil

    Directory of Open Access Journals (Sweden)

    Everton M. Bongiolo

    2007-09-01

    Full Text Available This work is an application of the 14C-Polymethylmethacrylate method to compare the porosity evolution between unaltered and propylitic-altered granites, using samples from Lavras do Sul region, Brazil. This method, when coupled with optical and electronic petrography has the advantage over other methods to provide the quantification and identification of total and local porosity of rocks. From petrographic observations, different kinds of porous zones were identified and quantified (microfractures, grain boundaries, alteration of minerals, etc. Results show that unaltered granites have 0.5 to 0.6% porosity and propylitic-altered ones have 1.7 to 1.8% porosity, even between samples with different textures. Porosity of altered rocks increases mainly due to higher porosity of neoformed chlorite, calcite, sericite and microfractures. Field observations show that later phyllic alteration halos are wider in equigranular than in porphyritic granites, which could not be explained by different original porosity between those rocks. The observed differences of phyllic halos diffusion were controlled by structural and fluid/rock ratio variations between the equigranular and porphyritic granitic facies during the later hydrothermal stage.Este trabalho é uma aplicação do método 14C-polimetilmetacrilato na comparação da evolução da porosidade entre granitos não alterados e propilitizados, utilizando amostras da região de Lavras do Sul, Brasil. Este método, quando associado a análises por petrografia ótica, eletrônica e processamento digital de imagens tem a vantagem de fornecer, além da porosidade total, a quantificação e identificação da porosidade em locais específicos das rochas. A partir da petrografia foi possível identificar e quantificar os diferentes tipos de poros presentes nas rochas (microfraturas, limites de grãos, alteração de minerais, etc. Os resultados mostram que granitos não alterados têm porosidade de 0,5 a 0,6% e

  19. A conspicuous clay ovoid in Nakhla: evidence for subsurface hydrothermal alteration on Mars with implications for astrobiology.

    Science.gov (United States)

    Chatzitheodoridis, Elias; Haigh, Sarah; Lyon, Ian

    2014-08-01

    Abstract A conspicuous biomorphic ovoid structure has been discovered in the Nakhla martian meteorite, made of nanocrystalline iron-rich saponitic clay and amorphous material. The ovoid is indigenous to Nakhla and occurs within a late-formed amorphous mesostasis region of rhyolitic composition that is interstitial to two clinopyroxene grains with Al-rich rims, and contains acicular apatite crystals, olivine, sulfides, Ti-rich magnetite, and a new mineral of the rhoenite group. To infer the origin of the ovoid, a large set of analytical tools was employed, including scanning electron microscopy and backscattered electron imaging, wavelength-dispersive X-ray analysis, X-ray mapping, Raman spectroscopy, time-of-flight secondary ion mass spectrometry analysis, high-resolution transmission electron microscope imaging, and atomic force microscope topographic mapping. The concentric wall of the ovoid surrounds an originally hollow volume and exhibits internal layering of contrasting nanotextures but uniform chemical composition, and likely inherited its overall shape from a preexisting vesicle in the mesostasis glass. A final fibrous layer of Fe-rich phases blankets the interior surfaces of the ovoid wall structure. There is evidence that the parent rock of Nakhla has undergone a shock event from a nearby bolide impact that melted the rims of pyroxene and the interstitial matter and initiated an igneous hydrothermal system of rapidly cooling fluids, which were progressively mixed with fluids from the melted permafrost. Sharp temperature gradients were responsible for the crystallization of Al-rich clinopyroxene rims, rhoenite, acicular apatites, and the quenching of the mesostasis glass and the vesicle. During the formation of the ovoid structure, episodic fluid infiltration events resulted in the precipitation of saponite rinds around the vesicle walls, altered pyrrhotite to marcasite, and then isolated the ovoid wall structure from the rest of the system by depositing a

  20. Influence of hydrothermal processing on functional properties and grain morphology of finger millet.

    Science.gov (United States)

    Dharmaraj, Usha; Meera, M S; Reddy, S Yella; Malleshi, Nagappa G

    2015-03-01

    Finger millet was hydrothermally processed followed by decortication. Changes in color, diameter, density, sphericity, thermal and textural characteristics and also some of the functional properties of the millet along with the grain morphology of the kernels after hydrothermal processing and decortication were studied. It was observed that, the millet turned dark after hydrothermal processing and color improved over native millet after decortication. A slight decrease in grain diameter was observed but sphericity of the grains increased on decortication. The soft and fragile endosperm turned into a hard texture and grain hardness increased by about 6 fold. Hydrothermal processing increased solubility and swelling power of the millet at ambient temperature. Pasting profile indicated that, peak viscosity decreased significantly on hydrothermal processing and both hydrothermally processed and decorticated millet exhibited zero breakdown viscosity. Enthalpy was negative for hydrothermally processed millet and positive for decorticated grains. Microscopic studies revealed that the orderly structure of endosperm changed to a coherent mass after hydrothermal processing and the different layers of seed coat get fused with the endosperm.

  1. Effect of hydrothermal process for inorganic alumina sol on crystal structure of alumina gel

    Directory of Open Access Journals (Sweden)

    K. Yamamura

    2016-09-01

    Full Text Available This paper reports the effect of a hydrothermal process for alumina sol on the crystal structure of alumina gel derived from hydrothermally treated alumina sol to help push forward the development of low temperature synthesis of α-Al2O3. White precipitate of aluminum hydroxide was prepared with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution. The obtained aluminum hydroxide precipitate was peptized by using acetic acid at room temperature, which resulted in the production of a transparent alumina sol. The alumina sol was treated with a hydrothermal process and transformed into an alumina gel film by drying at room temperature. Crystallization of the alumina gel to α-Al2O3 with 900 °C annealing was dominant for a hydrothermal temperature of 100 °C and a hydrothermal time of 60 min, as production of diaspore-like species was promoted with the hydrothermal temperature and time. Excess treatments with hydrothermal processes at higher hydrothermal temperature for longer hydrothermal time prevented the alumina gel from being crystallized to α-Al2O3 because the excess hydrothermal treatments promoted production of boehmite.

  2. Hydrothermal treatment of coprecipitated YSZ powders

    International Nuclear Information System (INIS)

    Arakaki, Alexander Rodrigo; Yoshito, Walter Kenji; Ussui, Valter; Lazar, Dolores Ribeiro Ricci

    2009-01-01

    Zirconia stabilized with 8.5 mol% yttria (YSZ) were synthesized by coprecipitation and resulting gels were hydrothermally treated at 200°C and 220 PSI for 4, 8 and 16 hours. Products were oven dried at 70°C for 24 hours, uniaxially pressed as pellets and sintered at 1500 °C for 1 hour. Powders were characterized for surface area with N 2 gas adsorption, X-ray diffraction, laser diffraction granulometric analysis and scanning and transmission electronic microscopy. Density of ceramics was measured by an immersion method based on the Archimedes principle. Results showed that powders dried at 70°C are amorphous and after treatment has tetragonal/cubic symmetry. Surface area of powders presented a significant reduction after hydrothermal treatment. Ceramics prepared from hydrothermally treated powders have higher green density but sintered pellets are less dense when compared to that made with powders calcined at 800°C for 1 hour due to the agglomerate state of powders. Solvothermal treatment is a promising procedure to enhance density. (author)

  3. Radionuclides in hydrothermal systems as indicators of repository conditions

    International Nuclear Information System (INIS)

    Wollenberg, H.A.; Flexser, S.; Smith, A.R.

    1990-11-01

    Hydrothermal systems in tuffaceous and older sedimentary rocks contain evidence of the interaction of radionuclides in fluids with rock matrix minerals and with materials lining fractures, in settings somewhat analogous to the candidate repository site at Yucca Mountain, NV. Earlier studies encompassed the occurrences of U and Th in a ''fossil'' hydrothermal system in tuffaceous rock of the San Juan Mountains volcanic field, CO. More recent and ongoing studies examine active hydrothermal systems in calderas at Long Valley, CA and Valles, NM. At the Nevada Test Site, occurrences of U and Th in fractured and unfractured rhyolitic tuff that was heated to simulate the introduction of radioactive waste are also under investigation. Observations to date suggest that U is mobile in hydrothermal systems, but that localized reducing environments provided by Fe-rich minerals and/or carbonaceous material concentrate U and thus attenuate its migration. 11 refs., 6 figs., 1 tab

  4. Geochemistry and genesis of APS minerals in advanced argillic alteration zone, northwest of Shir-Kuh, Yazd

    Directory of Open Access Journals (Sweden)

    Batool Taghipour

    2010-11-01

    Full Text Available Northwest of Shir-Kuh batholith, a number of leucocratic granitic and granodioritic plutons have intruded sedimentary hosts including shale-sandstone (Triassic-Jurassic and sandstone-conglomerate (Lower Cretaceous. Contact metamorphism and hydrothermal alterations are widespread. Late alteration assemblage mainly occurs in arkosic sandstones of Sangestan Formation and includes propylitic, quartz-sericitic, advanced argillic and silicific zones. Quartz-sericite zone is the most widespread. Advanced argillic alteration is characterized by the following assemblage: jarosite, alunite, turquoise, from the Al-Phosphate-Sulfate group (APS. Considering this mineral assemblage and probable interactions taking place between the minerals, a geochemical environment with high fO2 and low pH is thought to be prevailing at the time of alteration and formation of alunite, jarosite and turquoise.

  5. Geochemical constraints on chemolithoautotrophic reactions in hydrothermal systems

    Science.gov (United States)

    Shock, Everett L.; McCollom, Thomas; Schulte, Mitchell D.

    1995-06-01

    Thermodynamic calculations provide the means to quantify the chemical disequilibrium inherent in the mixing of redeuced hydrothermal fluids with seawater. The chemical energy available for metabolic processes in these environments can be evaluated by taking into account the pressure and temperature dependence of the apparent standard Gibbs free energies of reactions in the S-H2-H2O system together with geochemical constraints on pH, activities of aqueous sulfur species and fugacities of H2 and/or O2. Using present-day mixing of hydrothermal fluids and seawater as a starting point, it is shown that each mole of H2S entering seawater from hydrothermal fluids represents about 200,000 calories of chemical energy for metabolic systems able to catalyze H2S oxidation. Extrapolating to the early Earth, which was likely to have had an atmosphere more reduced than at present, shows that this chemical energy may have been a factor of two or so less. Nevertheless, mixing of hydrothermal fluids with seawater would have been an abundant source of chemical energy, and an inevitable consequence of the presence of an ocean on an initially hot Earth. The amount of energy available was more than enough for organic synthesis from CO2 or CO, and/or polymer formation, indicating that the vicinity of hydrothermal systems at the sea floor was an ideal location for the emergence of the first chemolithoautotrophic metabolic systems.

  6. Mineralogical Characterization of The Alteration Facies at Gabal El-Missikat Area, Central Eastern Desert, Egypt

    International Nuclear Information System (INIS)

    El-Sherif, A.M.

    2013-01-01

    The present study deals with the petrographical, mineralogical and geochemical characteristics of the alteration facies zones recognized around the shear zone at Gabal El-Missikat area, Central Eastern Desert, Egypt. Petrographically, the fresh granitic samples are composed mainly of quartz, K-feldspars (microcline and microcline perthite), plagioclase, biotite. The secondary minerals are sericite, kaolinite, muscovite, chlorite and epidote as well as zircon, apatite, fluorite, titanite and iron oxides as accessory minerals. Two alteration facies zones are recognized and namely as propylitic and advanced argillic. The propylitic facies zone is composed mainly of sericite with minor kaolinite, muscovite, quartz, relics of plagioclases, chlorite and rare epidote as well as zircon, hematite, goethite, magnetite, ilmenite, ilmenorutile, rutile, titanite, apatite, columbite and fluorite and secondary uranium minerals, the advanced argillic facies zone is composed mainly of kaolinite with minor sericite, quartz, muscovite, chlorite and rare epidote as well as zircon, hematite, goethite, magnetite, ilmenite, ilmenorutile, rutile, titanite, apatite and garnet of spessartine type as accessory minerals. The identified minerals in the studied two alteration facies zones can be grouped into three mineral groups which are: the primary minerals (pyrite, magnetite, galena, columbite and gold), the secondary minerals (uranophane, kasolite and wulfenite) and the gangue minerals (anhydrite, barite, celestine, hematite, goethite and fluorite). The identified mineral assemblage of the studied propylitic alteration facies zone may be attributed to strongly alkaline hydrothermal solutions at ph value of more than 7 with temperature varying between 350 and 450°C, while the advanced argillic alteration facies zone is essentially associated with strongly acidic hydrothermal solutions at ph value less than 7 with temperature varying between 150 and 400°C

  7. Direct catalytic hydrothermal liquefaction of spirulina to biofuels with hydrogen

    Science.gov (United States)

    Zeng, Qin; Liao, Hansheng; Zhou, Shiqin; Li, Qiuping; Wang, Lu; Yu, Zhihao; Jing, Li

    2018-01-01

    We report herein on acquiring biofuels from direct catalytic hydrothermal liquefaction of spirulina. The component of bio-oil from direct catalytic hydrothermal liquefaction was similar to that from two independent processes (including liquefaction and upgrading of biocrude). However, one step process has higher carbon recovery, due to the less loss of carbons. It was demonstrated that the yield and HHV of bio-oil from direct catalytic algae with hydrothermal condition is higher than that from two independent processes.

  8. Genetic diversity of archaea in deep-sea hydrothermal vent environments.

    Science.gov (United States)

    Takai, K; Horikoshi, K

    1999-08-01

    Molecular phylogenetic analysis of naturally occurring archaeal communities in deep-sea hydrothermal vent environments was carried out by PCR-mediated small subunit rRNA gene (SSU rDNA) sequencing. As determined through partial sequencing of rDNA clones amplified with archaea-specific primers, the archaeal populations in deep-sea hydrothermal vent environments showed a great genetic diversity, and most members of these populations appeared to be uncultivated and unidentified organisms. In the phylogenetic analysis, a number of rDNA sequences obtained from deep-sea hydrothermal vents were placed in deep lineages of the crenarchaeotic phylum prior to the divergence of cultivated thermophilic members of the crenarchaeota or between thermophilic members of the euryarchaeota and members of the methanogen-halophile clade. Whole cell in situ hybridization analysis suggested that some microorganisms of novel phylotypes predicted by molecular phylogenetic analysis were likely present in deep-sea hydrothermal vent environments. These findings expand our view of the genetic diversity of archaea in deep-sea hydrothermal vent environments and of the phylogenetic organization of archaea.

  9. Hydrothermal mobilization of pegmatite-hosted REE and Zr at Strange Lake, Canada: A reaction path model

    Science.gov (United States)

    Gysi, Alexander P.; Williams-Jones, Anthony E.

    2013-12-01

    Petrological and geochemical observations of pegmatites in the Strange Lake pluton, Canada, have been combined with numerical simulations to improve our understanding of fluid-rock interaction in peralkaline granitic systems. In particular, they have made it possible to evaluate reaction paths responsible for hydrothermal mobilization and mineralization of rare earth elements (REE) and Zr. The focus of the study was the B-Zone in the northwest of the pluton, which contains a pegmatite swarm and is the target of exploration for an economically exploitable REE deposit. Many of the pegmatites are mineralogically zoned into a border consisting of variably altered primary K-feldspar, arfvedsonite, quartz, and zirconosilicates, and a core rich in quartz, fluorite and exotic REE minerals. Textural relationships indicate that the primary silicate minerals in the pegmatites were leached and/or replaced during acidic alteration by K-, Fe- and Al-phyllosilicates, aegirine, hematite, fluorite and/or quartz, and that primary zirconosilicates (e.g., elpidite) were replaced by gittinsite and/or zircon. Reaction textures recording coupled dissolution of silicate minerals and crystallization of secondary REE-silicates indicate hydrothermal mobilization of the REE. The mobility of the light (L)REE was limited by the stability of REE-F-(CO2)-minerals (basnäsite-(Ce) and fluocerite-(Ce)), whereas zirconosilicates and secondary gadolinite-group minerals controlled the mobility of Zr and the heavy (H)REE. Hydrothermal fluorite and fluorite-fluocerite-(Ce) solid solutions are interpreted to indicate the former presence of F-bearing saline fluids in the pegmatites. Numerical simulations show that the mobilization of REE and Zr in saline HCl-HF-bearing fluids is controlled by pH, ligand activity and temperature. Mobilization of Zr is significant in both saline HF- and HCl-HF-bearing fluids at low temperature (250 °C). In contrast, the REE are mobilized by saline HCl-bearing fluids

  10. Fractionation of boron isotopes in Icelandic hydrothermal systems

    International Nuclear Information System (INIS)

    Aggarwal, J.K.

    1995-01-01

    Boron isotope ratios have been determined in a variety of different geothermal waters from hydrothermal systems across Iceland. Isotope ratios from the high temperature meteoric water recharged systems reflect the isotope ratio of the host rocks without any apparent fractionation. Seawater recharged geothermal systems exhibit more positive δ 1 1B values than the meteoric water recharged geothermal systems. Water/rock ratios can be assessed from boron isotope ratios in the saline hydrothermal systems. Low temperature hydrothermal systems also exhibit more positive δ 1 1B than the high temperature systems, indicating fractionation of boron due to absorption of the lighter isotope onto secondary minerals. Fractionation of boron in carbonate deposits may indicate the level of equilibrium attained within the systems. (author). 14 refs., 2 figs

  11. Versatile hydrothermal synthesis of one-dimensional composite structures

    Science.gov (United States)

    Luo, Yonglan

    2008-12-01

    In this paper we report on a versatile hydrothermal approach developed to fabricate one-dimensional (1D) composite structures. Sulfur and selenium formed liquid and adsorbed onto microrods as droplets and subsequently reacted with metallic ion in solution to produce nanoparticles-decorated composite microrods. 1D composites including ZnO/CdS, ZnO/MnS, ZnO/CuS, ZnO/CdSe, and FeOOH/CdS were successfully made using this hydrothermal strategy and the growth mechanism was also discussed. This hydrothermal strategy is simple and green, and can be extended to the synthesis of various 1D composite structures. Moreover, the interaction between the shell nanoparticles and the one-dimensional nanomaterials were confirmed by photoluminescence investigation of ZnO/CdS.

  12. Hydrogen is an energy source for hydrothermal vent symbioses.

    Science.gov (United States)

    Petersen, Jillian M; Zielinski, Frank U; Pape, Thomas; Seifert, Richard; Moraru, Cristina; Amann, Rudolf; Hourdez, Stephane; Girguis, Peter R; Wankel, Scott D; Barbe, Valerie; Pelletier, Eric; Fink, Dennis; Borowski, Christian; Bach, Wolfgang; Dubilier, Nicole

    2011-08-10

    The discovery of deep-sea hydrothermal vents in 1977 revolutionized our understanding of the energy sources that fuel primary productivity on Earth. Hydrothermal vent ecosystems are dominated by animals that live in symbiosis with chemosynthetic bacteria. So far, only two energy sources have been shown to power chemosynthetic symbioses: reduced sulphur compounds and methane. Using metagenome sequencing, single-gene fluorescence in situ hybridization, immunohistochemistry, shipboard incubations and in situ mass spectrometry, we show here that the symbionts of the hydrothermal vent mussel Bathymodiolus from the Mid-Atlantic Ridge use hydrogen to power primary production. In addition, we show that the symbionts of Bathymodiolus mussels from Pacific vents have hupL, the key gene for hydrogen oxidation. Furthermore, the symbionts of other vent animals such as the tubeworm Riftia pachyptila and the shrimp Rimicaris exoculata also have hupL. We propose that the ability to use hydrogen as an energy source is widespread in hydrothermal vent symbioses, particularly at sites where hydrogen is abundant.

  13. Hydrothermal conversion of biomass

    NARCIS (Netherlands)

    Knezevic, D.

    2009-01-01

    This thesis presents research of hydrothermal conversion of biomass (HTC). In this process, hot compressed water (subcritical water) is used as the reaction medium. Therefore this technique is suitable for conversion of wet biomass/ waste streams. By working at high pressures, the evaporation of

  14. Hydrothermal decomposition of liquid crystal in subcritical water

    International Nuclear Information System (INIS)

    Zhuang, Xuning; He, Wenzhi; Li, Guangming; Huang, Juwen; Lu, Shangming; Hou, Lianjiao

    2014-01-01

    Highlights: • Hydrothermal technology can effectively decompose the liquid crystal of 4-octoxy-4'-cyanobiphenyl. • The decomposition rate reached 97.6% under the optimized condition. • Octoxy-4'-cyanobiphenyl was mainly decomposed into simple and innocuous products. • The mechanism analysis reveals the decomposition reaction process. - Abstract: Treatment of liquid crystal has important significance for the environment protection and human health. This study proposed a hydrothermal process to decompose the liquid crystal of 4-octoxy-4′-cyanobiphenyl. Experiments were conducted with a 5.7 mL stainless tube reactor and heated by a salt-bath. Factors affecting the decomposition rate of 4-octoxy-4′-cyanobiphenyl were evaluated with HPLC. The decomposed liquid products were characterized by GC-MS. Under optimized conditions i.e., 0.2 mL H 2 O 2 supply, pH value 6, temperature 275 °C and reaction time 5 min, 97.6% of 4-octoxy-4′-cyanobiphenyl was decomposed into simple and environment-friendly products. Based on the mechanism analysis and products characterization, a possible hydrothermal decomposition pathway was proposed. The results indicate that hydrothermal technology is a promising choice for liquid crystal treatment

  15. Hydrothermal stability of microporous silica and niobia-silica membranes

    NARCIS (Netherlands)

    Boffa, V.; Blank, David H.A.; ten Elshof, Johan E.

    2008-01-01

    The hydrothermal stability of microporous niobia–silica membranes was investigated and compared with silica membranes. The membranes were exposed to hydrothermal conditions at 150 and 200 °C for 70 h. The change of pore structure before and after exposure to steam was probed by single-gas permeation

  16. Influence of fluorine substitution on the morphology and structure of hydroxyapatite nanocrystals prepared by hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Joseph Nathanael, A., E-mail: ajosephnc@yahoo.com [Department of Nanomaterials Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Thin Film and Nanomaterials Laboratory, Department of Physics, Bharathiar University, Coimbatore 641 046 (India); Mangalaraj, D., E-mail: dmraj800@yahoo.com [Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641 046 (India); Hong, S.I., E-mail: sihong@cnu.ac.kr [Thin Film and Nanomaterials Laboratory, Department of Physics, Bharathiar University, Coimbatore 641 046 (India); Masuda, Y. [National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Shimoshidami, Moriyama-ku, Nagoya 463-8560 (Japan); Rhee, Y.H.; Kim, H.W. [Department of Microbiology, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

    2013-01-15

    Hydroxyapatite (HAp) nanocrystals with different levels of fluorine substitution (P/F = 0, 6, 4 and 2) on the OH sites were produced via hydrothermal method. The fluorine substitution was found to alter the morphology of crystals appreciably. The aspect ratio and the crystallinity of HAp crystals increased with increasing fluorine substitution. The presence of broad ring and hallow ring patterns in electron diffraction suggests the low-crystalline nature of HAp crystals. With increasing fluorine substitution, the diffraction patterns exhibited discrete rings and numerous diffraction spots, implying the increased crystallinity. Raman spectra from the HAp nanoparticles also support the less-crystalline nature of the pristine HAp and the enhanced crystallization by fluorine substitution. In HAp crystals processed with no fluorine substitution, surface energy and planar Ca{sup 2+} density are less sensitive to the crystallographic orientation because of its low-crystalline nature, favoring equi-axed or slightly elongated particles. The addition of fluorine apparently increased the crystallinity, enhancing the orientation dependent growth and accordingly the aspect ratio. Osteoblast proliferation was observed to be enhanced by fluorine substitution in HAp. In vitro biological data support that the excellent osteoblastic cell viability and functional activity of the fluoridated apatite. -- Highlights: Black-Right-Pointing-Pointer Fluorapatite nanorods were produced hydrothermally with different fluorine content. Black-Right-Pointing-Pointer Fluorine substitution was found to alter the morphology of crystals appreciably. Black-Right-Pointing-Pointer It enhances the crystallinity, orientation dependent growth and hence aspect ratio. Black-Right-Pointing-Pointer In vitro cellular analysis shows excellent cell viability of the fluorapatite.

  17. Distal transport of dissolved hydrothermal iron in the deep South Pacific Ocean.

    Science.gov (United States)

    Fitzsimmons, Jessica N; Boyle, Edward A; Jenkins, William J

    2014-11-25

    Until recently, hydrothermal vents were not considered to be an important source to the marine dissolved Fe (dFe) inventory because hydrothermal Fe was believed to precipitate quantitatively near the vent site. Based on recent abyssal dFe enrichments near hydrothermal vents, however, the leaky vent hypothesis [Toner BM, et al. (2012) Oceanography 25(1):209-212] argues that some hydrothermal Fe persists in the dissolved phase and contributes a significant flux of dFe to the global ocean. We show here the first, to our knowledge, dFe (Pacific Ocean, where dFe of 1.0-1.5 nmol/kg near 2,000 m depth (0.4-0.9 nmol/kg above typical deep-sea dFe concentrations) was determined to be hydrothermally derived based on its correlation with primordial (3)He and dissolved Mn (dFe:(3)He of 0.9-2.7 × 10(6)). Given the known sites of hydrothermal venting in these regions, this dFe must have been transported thousands of kilometers away from its vent site to reach our sampling stations. Additionally, changes in the size partitioning of the hydrothermal dFe between soluble (Pacific Rise only leaks 0.02-1% of total Fe vented into the abyssal Pacific, this dFe persists thousands of kilometers away from the vent source with sufficient magnitude that hydrothermal vents can have far-field effects on global dFe distributions and inventories (≥3% of global aerosol dFe input).

  18. Hydrothermal systems on Mars: an assessment of present evidence

    Science.gov (United States)

    Farmer, J. D.

    1996-01-01

    Hydrothermal processes have been suggested to explain a number of observations for Mars, including D/H ratios of water extracted from Martian meteorites, as a means for removing CO2 from the Martian atmosphere and sequestering it in the crust as carbonates, and as a possible origin for iron oxide-rich spectral units on the floors of some rifted basins (chasmata). There are numerous examples of Martian channels formed by discharges of subsurface water near potential magmatic heat sources, and hydrothermal processes have also been proposed as a mechanism for aquifer recharge needed to sustain long term erosion of sapping channels. The following geological settings have been identified as targets for ancient hydrothermal systems on Mars: channels located along the margins of impact crater melt sheets and on the slopes of ancient volcanoes; chaotic and fretted terranes where shallow subsurface heat sources are thought to have interacted with ground ice; and the floors of calderas and rifted basins (e.g. chasmata). On Earth, such geological environments are often a locus for hydrothermal mineralization. But we presently lack the mineralogical information needed for a definitive evaluation of hypotheses. A preferred tool for identifying minerals by remote sensing methods on Earth is high spatial resolution, hyperspectral, near-infrared spectroscopy, a technique that has been extensively developed by mineral explorationists. Future efforts to explore Mars for ancient hydrothermal systems would benefit from the application of methods developed by the mining industry to look for similar deposits on Earth. But Earth-based exploration models must be adapted to account for the large differences in the climatic and geological history of Mars. For example, it is likely that the early surface environment of Mars was cool, perhaps consistently below freezing, with the shallow portions of hydrothermal systems being dominated by magma-cryosphere interactions. Given the smaller

  19. Extreme hydrothermal conditions at an active plate-bounding fault

    Science.gov (United States)

    Sutherland, Rupert; Townend, John; Toy, Virginia; Upton, Phaedra; Coussens, Jamie; Allen, Michael; Baratin, Laura-May; Barth, Nicolas; Becroft, Leeza; Boese, Carolin; Boles, Austin; Boulton, Carolyn; Broderick, Neil G. R.; Janku-Capova, Lucie; Carpenter, Brett M.; Célérier, Bernard; Chamberlain, Calum; Cooper, Alan; Coutts, Ashley; Cox, Simon; Craw, Lisa; Doan, Mai-Linh; Eccles, Jennifer; Faulkner, Dan; Grieve, Jason; Grochowski, Julia; Gulley, Anton; Hartog, Arthur; Howarth, Jamie; Jacobs, Katrina; Jeppson, Tamara; Kato, Naoki; Keys, Steven; Kirilova, Martina; Kometani, Yusuke; Langridge, Rob; Lin, Weiren; Little, Timothy; Lukacs, Adrienn; Mallyon, Deirdre; Mariani, Elisabetta; Massiot, Cécile; Mathewson, Loren; Melosh, Ben; Menzies, Catriona; Moore, Jo; Morales, Luiz; Morgan, Chance; Mori, Hiroshi; Niemeijer, Andre; Nishikawa, Osamu; Prior, David; Sauer, Katrina; Savage, Martha; Schleicher, Anja; Schmitt, Douglas R.; Shigematsu, Norio; Taylor-Offord, Sam; Teagle, Damon; Tobin, Harold; Valdez, Robert; Weaver, Konrad; Wiersberg, Thomas; Williams, Jack; Woodman, Nick; Zimmer, Martin

    2017-06-01

    Temperature and fluid pressure conditions control rock deformation and mineralization on geological faults, and hence the distribution of earthquakes. Typical intraplate continental crust has hydrostatic fluid pressure and a near-surface thermal gradient of 31 ± 15 degrees Celsius per kilometre. At temperatures above 300-450 degrees Celsius, usually found at depths greater than 10-15 kilometres, the intra-crystalline plasticity of quartz and feldspar relieves stress by aseismic creep and earthquakes are infrequent. Hydrothermal conditions control the stability of mineral phases and hence frictional-mechanical processes associated with earthquake rupture cycles, but there are few temperature and fluid pressure data from active plate-bounding faults. Here we report results from a borehole drilled into the upper part of the Alpine Fault, which is late in its cycle of stress accumulation and expected to rupture in a magnitude 8 earthquake in the coming decades. The borehole (depth 893 metres) revealed a pore fluid pressure gradient exceeding 9 ± 1 per cent above hydrostatic levels and an average geothermal gradient of 125 ± 55 degrees Celsius per kilometre within the hanging wall of the fault. These extreme hydrothermal conditions result from rapid fault movement, which transports rock and heat from depth, and topographically driven fluid movement that concentrates heat into valleys. Shear heating may occur within the fault but is not required to explain our observations. Our data and models show that highly anomalous fluid pressure and temperature gradients in the upper part of the seismogenic zone can be created by positive feedbacks between processes of fault slip, rock fracturing and alteration, and landscape development at plate-bounding faults.

  20. Extreme hydrothermal conditions at an active plate-bounding fault.

    Science.gov (United States)

    Sutherland, Rupert; Townend, John; Toy, Virginia; Upton, Phaedra; Coussens, Jamie; Allen, Michael; Baratin, Laura-May; Barth, Nicolas; Becroft, Leeza; Boese, Carolin; Boles, Austin; Boulton, Carolyn; Broderick, Neil G R; Janku-Capova, Lucie; Carpenter, Brett M; Célérier, Bernard; Chamberlain, Calum; Cooper, Alan; Coutts, Ashley; Cox, Simon; Craw, Lisa; Doan, Mai-Linh; Eccles, Jennifer; Faulkner, Dan; Grieve, Jason; Grochowski, Julia; Gulley, Anton; Hartog, Arthur; Howarth, Jamie; Jacobs, Katrina; Jeppson, Tamara; Kato, Naoki; Keys, Steven; Kirilova, Martina; Kometani, Yusuke; Langridge, Rob; Lin, Weiren; Little, Timothy; Lukacs, Adrienn; Mallyon, Deirdre; Mariani, Elisabetta; Massiot, Cécile; Mathewson, Loren; Melosh, Ben; Menzies, Catriona; Moore, Jo; Morales, Luiz; Morgan, Chance; Mori, Hiroshi; Niemeijer, Andre; Nishikawa, Osamu; Prior, David; Sauer, Katrina; Savage, Martha; Schleicher, Anja; Schmitt, Douglas R; Shigematsu, Norio; Taylor-Offord, Sam; Teagle, Damon; Tobin, Harold; Valdez, Robert; Weaver, Konrad; Wiersberg, Thomas; Williams, Jack; Woodman, Nick; Zimmer, Martin

    2017-06-01

    Temperature and fluid pressure conditions control rock deformation and mineralization on geological faults, and hence the distribution of earthquakes. Typical intraplate continental crust has hydrostatic fluid pressure and a near-surface thermal gradient of 31 ± 15 degrees Celsius per kilometre. At temperatures above 300-450 degrees Celsius, usually found at depths greater than 10-15 kilometres, the intra-crystalline plasticity of quartz and feldspar relieves stress by aseismic creep and earthquakes are infrequent. Hydrothermal conditions control the stability of mineral phases and hence frictional-mechanical processes associated with earthquake rupture cycles, but there are few temperature and fluid pressure data from active plate-bounding faults. Here we report results from a borehole drilled into the upper part of the Alpine Fault, which is late in its cycle of stress accumulation and expected to rupture in a magnitude 8 earthquake in the coming decades. The borehole (depth 893 metres) revealed a pore fluid pressure gradient exceeding 9 ± 1 per cent above hydrostatic levels and an average geothermal gradient of 125 ± 55 degrees Celsius per kilometre within the hanging wall of the fault. These extreme hydrothermal conditions result from rapid fault movement, which transports rock and heat from depth, and topographically driven fluid movement that concentrates heat into valleys. Shear heating may occur within the fault but is not required to explain our observations. Our data and models show that highly anomalous fluid pressure and temperature gradients in the upper part of the seismogenic zone can be created by positive feedbacks between processes of fault slip, rock fracturing and alteration, and landscape development at plate-bounding faults.

  1. Analysis on deep metallogenic trace and simulation experiment in xiangshan large-scale volcanic hydrothermal type uranium deposit

    International Nuclear Information System (INIS)

    Liu Zhengyi; Liu Zhangyue; Wen Zhijian; Du Letian

    2010-01-01

    Based on series experiments on field geologic analysis, and associated with deep metallogenic trace experiment model transformed from establishment of field deep metallogenic trace model, this paper come to the conclusion that distribution coefficients of U and Th first domestic from the magmatic experiment, and then discuss the geochemical behaviors of U, Th, K during magmatic evolution stage. The experiment shows that close relationship between U and Na during the hydrothermal alteration stage; and relationship between U and K during metallogenic stage, which prove that U and K are incompatible and regularity of variation between K and Na. The conclusion of uranium dissolving ability increased accompany with pressure increasing in basement metamorphic rocks and host rocks, is obtained from this experiment, which indicate a good deep metallogenic prospect. Furthermore, Pb, Sr, Nd, He isotopes show that the volcanic rocks and basement rocks are ore source beds; due to the combined functions of volcanic hydrothermal and mantle ichor, uranium undergo multi-migration and enrichment and finally concentrated to large rich deposit. (authors)

  2. Porosity, Fracturing and Alteration of Young Oceanic Crust: New Seismic Analyses at Borehole 504B

    Science.gov (United States)

    Gregory, E. P. M.; Hobbs, R. W.; Peirce, C.; Wilson, D. J.

    2017-12-01

    DSDP/ODP borehole 504B, drilled 2111 m into 6.9 Ma oceanic crust, provides in-situ core and logging measurements of the lithology, fracturing and porosity of crust originally formed at the Costa Rica Rift and its subsequent alteration by hydrothermal fluids. A recent active seismic survey over the borehole and surrounding area reveals wider spatial variations in velocity that can be related to this porosity and fracturing. Over 10,000 airgun shots were fired in a 30 x 30 km grid over the borehole region, using both high-frequency and low-frequency airgun arrays. The shots were recorded on a 4.5 km-long streamer and 24 ocean-bottom seismographs, each equipped with a three-component geophone and an hydrophone. A vertical hydrophone array recorded the downgoing source wavelet, and underway gravity, magnetic field and multibeam bathymetry data were also recorded. This combined dataset enables the most comprehensive geophysical analysis of this area of crust to date, while the ground-truthing provided by 504B enables us to address the questions of what do the seismic oceanic crustal layers represent and what controls their characteristics as the crust ages? Wide-angle seismic modelling with a Monte Carlo based uncertainty analysis reveals new 2D and 3D Vp and Vs models of the area, which show relatively homogeneous crust around borehole 504B, and place the seismic layer 2B/2C, and seismic layer 2/3 boundaries coincident with fracturing and alteration fronts rather than the lithological boundaries between lavas and dykes, and dykes and gabbros, respectively. Analysis of Poisson's ratio, seismic anisotropy and particle motions reveal patterns in fracturing and porosity across the survey area, and locate possible fossilised hydrothermal circulation cells. These cells appear to have influenced the porosity of the crust through alteration and mineralisation processes, with faults inherited from initial crustal accretion influencing basement topographic highs and providing

  3. Hydrothermal modification of host rock geochemistry within Mo-Cu porphyry deposits in the Galway Granite, western Ireland

    Science.gov (United States)

    Tolometti, Gavin; McCarthy, Will

    2016-04-01

    Hydrothermal alteration of host rock is a process inherent to the formation of porphyry deposits and the required geochemical modification of these rocks is regularly used to indicate proximity to an economic target. The study involves examining the changes in major, minor and trace elements to understand how the quartz vein structures have influenced the chemistry within the Murvey Granite that forms part of the 380-425Ma Galway Granite Complex in western Ireland. Molybdenite mineralisation within the Galway Granite Complex occurred in close association with protracted magmatism at 423Ma, 410Ma, 407Ma, 397Ma and 383Ma and this continues to be of interest to active exploration. The aim of the project is to characterize hydrothermal alteration associated with Mo-Cu mineralisation and identify geochemical indicators that can guide future exploration work. The Murvey Granite intrudes metagabbros and gneiss that form part of the Connemara Metamorphic complex. The intrusion is composed of albite-rich pink granite, garnetiferous granite and phenocrytic orthoclase granite. Minor doleritic dykes post-date the Murvey Granite, found commonly along its margins. Field mapping shows that the granite is truncated to the east by a regional NW-SE fault and that several small subparallel structures host Mo-Cu bearing quartz veins. Petrographic observations show heavily sericitized feldspars and plagioclase and biotite which have undergone kaolinization and chloritisation. Chalcopyrite minerals are fine grained, heavily fractured found crystallized along the margins of the feldspars and 2mm pyrite crystals. Molybdenite are also seen along the margins of the feldspars, crystallized whilst the Murvey Granite cooled. Field and petrographic observations indicate that mineralisation is structurally controlled by NW-SE faults from the selected mineralization zones and conjugate NE-SW cross cutting the Murvey Granite. Both fault orientations exhibit quartz and disseminated molybdenite

  4. Additive effects of acetic acid upon hydrothermal reaction of amylopectin

    International Nuclear Information System (INIS)

    Sugano, Motoyuki; Katoh, Harumi; Komatsu, Akihiro; Kobayashi, Hiroshi; Okado, Kohta; Kakuta, Yusuke; Hirano, Katsumi

    2012-01-01

    It is well known that over 0.8 kg kg −1 of starch is consisted of amylopectin (AP). In this study, production of glucose for raw material of ethanol by hydrothermal reaction of AP as one of the model compound of food is discussed. Further, additive effects of acetic acid upon hydrothermal reactions of AP are also investigated. During hydrothermal reaction of AP, production of glucose occurred above 453 K, and the glucose yield increased to 0.48 kg kg −1 at 473 K. Upon hydrothermal reaction of AP at 473 K, prolongation of the holding time was not effective for the increase of the glucose yield. Upon hydrothermal reaction of AP at 473 K for 0 s, the glucose yield increased significantly by addition between 0.26 mol L −1 and 0.52 mol L −1 of acetic acid. However, the glucose yield decreased and the yield of the other constituents increased with the increases of concentration of acetic acid from 0.65 mol L −1 to 3.33 mol L −1 . It was considered that hydrolysis of AP to yield glucose was enhanced due to the increase of the amount of proton derived from acetic acid during hydrothermal reaction with 0.52 mol L −1 of acetic acid. -- Highlights: ► Glucose production by hydrothermal reaction of amylopectin (AP) at 473 K. ► Glucose yield increased to 0.48 kg kg -1 at 473 K. ► Prolongation of holding time was not effective for glucose yield. ► Glucose yield increased significantly by acetic acid (0.26–0.52 mol L-1) addition. ► Hydrolysis of AP to glucose was enhanced due to increase of proton from acetic acid.

  5. Hydrothermal processing of transuranic contaminated combustible waste

    International Nuclear Information System (INIS)

    Buelow, S.J.; Worl, L.; Harradine, D.; Padilla, D.; McInroy, R.

    2001-01-01

    Experiments at Los Alamos National Laboratory have demonstrated the usefulness of hydrothermal processing for the disposal of a wide variety of transuranic contaminated combustible wastes. This paper provides an overview of the implementation and performance of hydrothermal treatment for concentrated salt solutions, explosives, propellants, organic solvents, halogenated solvents, and laboratory trash, such as paper and plastics. Reaction conditions vary from near ambient temperatures and pressure to over 1000degC and 100 MPa pressure. Studies involving both radioactive and non-radioactive waste simulants are discussed. (author)

  6. Rapid Access Ice Drill: A New Tool for Exploration of the Deep Antarctic Ice Sheets and Subglacial Geology

    Science.gov (United States)

    Goodge, J. W.; Severinghaus, J. P.

    2014-12-01

    The Rapid Access Ice Drill (RAID) will penetrate the Antarctic ice sheets in order to core through deep ice, the glacial bed, and into bedrock below. This new technology will provide a critical first look at the interface between major ice caps and their subglacial geology. Currently in construction, RAID is a mobile drilling system capable of making several long boreholes in a single field season in Antarctica. RAID is interdisciplinary and will allow access to polar paleoclimate records in ice >1 Ma, direct observation at the base of the ice sheets, and recovery of rock cores from the ice-covered East Antarctic craton. RAID uses a diamond rock-coring system as in mineral exploration. Threaded drill-pipe with hardened metal bits will cut through ice using reverse circulation of Estisol for pressure-compensation, maintenance of temperature, and removal of ice cuttings. Near the bottom of the ice sheet, a wireline bottom-hole assembly will enable diamond coring of ice, the glacial bed, and bedrock below. Once complete, boreholes will be kept open with fluid, capped, and made available for future down-hole measurement of thermal gradient, heat flow, ice chronology, and ice deformation. RAID will also sample for extremophile microorganisms. RAID is designed to penetrate up to 3,300 meters of ice and take sample cores in less than 200 hours. This rapid performance will allow completion of a borehole in about 10 days before moving to the next drilling site. RAID is unique because it can provide fast borehole access through thick ice; take short ice cores for paleoclimate study; sample the glacial bed to determine ice-flow conditions; take cores of subglacial bedrock for age dating and crustal history; and create boreholes for use as an observatory in the ice sheets. Together, the rapid drilling capability and mobility of the drilling system, along with ice-penetrating imaging methods, will provide a unique 3D picture of the interior Antarctic ice sheets.

  7. Simulating Electrochemistry of Hydrothermal Vents on Enceladus and Other Ocean Worlds

    Science.gov (United States)

    Barge, L. M.; Krause, F. C.; Jones, J. P.; Billings, K.; Sobron, P.

    2017-12-01

    Gradients generated in hydrothermal systems provide a significant source of free energy for chemosynthetic life, and may play a role in present-day habitability on ocean worlds such as Enceladus that are thought to host hydrothermal activity. Hydrothermal vents are similar in some ways to typical fuel cell devices: redox/pH gradients between seawater and hydrothermal fluid are analogous to the oxidant and fuel reservoirs; conductive natural mineral deposits are analogous to electrodes; and, in hydrothermal chimneys, the porous chimney wall can function as a separator or ion-exchange membrane. Electrochemistry, founded on quantitative study of redox and other chemical disequilibria as well as the chemistry of interfaces, is uniquely suited to studying these systems. We have performed electrochemical studies to better understand the catalytic potential of seafloor minerals and vent chimneys, using samples from a black smoker vent chimney as an initial demonstration. Fuel cell experiments with electrodes made from black smoker chimney material accurately simulated the redox reactions that occur in a geological setting with this particular catalyst. Similar methods with other geo-catalysts (natural or synthetic) could be utilized to test which redox reactions or metabolisms could be driven in other hydrothermal systems, including putative vent systems on other worlds.

  8. Elemental geochemical records of seafloor hydrothermal activities in the sediments from the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    ZHAI Shikui; YU Zenghui; DU Tongjun

    2007-01-01

    The major and minor element contents in the sediment core H9 from the hydrothermal fields of the Okinawa Trough show a sharp change at the depth of 80 cm. The elements enriched in the upper 80 cm core are those enriched in the hydrothermal deposits and in the surface sediments recovered from the hydrothermal fields in the trough, which indicates the input of hydrothermal materials. Comparing with other hydrothermal sediments from Mid-ocean Ridges or the Lau Basin, the degree of the enrichment of elements iron, copper, cobalt, and nickel is relatively low. However, the enrichment of elements manganese, lead, arsenic, antimony and mercury is remarkable. The average contents of these elements in the upper 80 cm core sediments are three to six times those in the lower section, and 3 ~ 12 times those in the surface sediments which are not influenced by hydrothermal activities. Hydrothermal activities have contributed significant manganese, lead, arsenic, antimony and mercury to the sediments, and these elements are distinct indicators for the hydrothermal activity in the Okinawa Trough. The significant enrichment of these elements in Core H9 upward from the depth 80 cm indicates the start or the significant enhancing of the hydrothermal activity in this area at about 5 740 aB. P. The average accumulation rate of manganese during this period is about 40 461 μg/( cm2 · ka), which is similar to the hydrothermal sediments in the Lau Basin or the East Pacific Rise.

  9. Comparative study on microwave and conventional hydrothermal pretreatment of bamboo sawdust: Hydrochar properties and its pyrolysis behaviors

    International Nuclear Information System (INIS)

    Dai, Leilei; He, Chao; Wang, Yunpu; Liu, Yuhuan; Yu, Zhenting; Zhou, Yue; Fan, Liangliang; Duan, Dengle

    2017-01-01

    Highlights: • Two pretreatments affect differently the hydrochar properties and its pyrolysis behaviors. • Hydrochar by conventional hydrothermal pretreatment shows higher thermal stability. • Microwave hydrothermal pretreatment removes more acetyl. • Hydrochar by microwave hydrothermal pretreatment produces more glucopyranose and less acids. - Abstract: Comparative study on microwave and conventional hydrothermal pretreatment of bamboo sawdust was carried out in this study. Microwave and conventional hydrothermal pretreatment both improved the hydrochar properties and its pyrolysis behaviors. Proximate and elemental analyses show that the properties of hydrochar from microwave hydrothermal pretreatment are better than conventional hydrothermal pretreatment in terms of calorific value and oxygen content except for 150 °C. Microwave hydrothermal pretreatment removes more acetyl groups in hemicellulose compared to conventional hydrothermal pretreatment, which may be attributed to the hot spot effect of microwave irradiation. The peaks of thermogravimetric and derivative thermogravimetric curves of pretreated samples always shifted to higher temperature region. Also, the conventional hydrothermal pretreated samples are more thermally stable than those by microwave heating. In addition, the glucopyranose content in pyrolysis vapors of microwave hydrothermal pretreated bamboo sawdust (190 °C) was 9.82% higher than that from conventional hydrothermal pretreated bamboo sawdust. However, the acids content from microwave hydrothermal pretreated bamboo sawdust (150 °C) was 4.12% lower. In this regard, microwave hydrothermal pretreatment is more suitable for upgrading the pyrolysis oil quality than conventional hydrothermal pretreatment.

  10. Au-bearing magnetite mineralizaion in Kashmar (alteration, mineralization, geochemistry, geochemistry and fluid inclusions;

    Directory of Open Access Journals (Sweden)

    Alireza Almasi

    2017-02-01

    fractures of rocks are filled with tourmaline (Dumortierite type and iron oxides. Kashmar surface mineralization is described in the ore-bearing quartz veins. Principal mineralization textures are layered, comb and Brecciation. The most important types of veins are those containing Chalcopyrite - Quartz veins, Specularite-rich veins – Quartz-Galena veins accompany with hydrothermal Breccias. Barren barite veins also exist in the region. The Chalcopyrite - Quartz veins occur on the main fracture zone and next to the Argillic alterations and silica cap in three regions (Bahariyeh, Uch Palang and Sarsefidal. Hydrothermal Breccias, Spicularite- rich veins, Quartz - Galena and barite veins occurred within Hematite- Carbonate-Chlorite-Silicification alterations in the Kamarmard area. Geochemistry of veins indicates anomalies of gold, copper, lead and zinc in them. Most enrichments of gold are accompanied with copper, lead and zinc and they occurs in hydrothermal Breccias and then specularite- rich veins. Gold values up to about 15 ppm and Cu, Pb and Zn each to > 1%. Temperature – salinity studies of fluid inclusions of ore-bearing Quartz veins in Kashmar show the fluid temperature and salinity values in all veins are close together. Temperatures are moderate to relatively high and between 245° C and 530 ° C and salinities are relatively low to moderate and between 14 to 18 (wt% NaCl. Maximum and minimum of temperatures and salinities are related to fluid inclusions of hydrothermal Breccias and Quartz-Galena vein. Co-existence between two-phase liquid-vapor rich fluids and single-phase gas fluids in the veins indicate that conditions were close to boiling, and maybe a little boiling occurred, which strengthened with brecciaing of rock and view rare CO2-bearing fluid inclusion in veins on the Kamarmard peak. Non-existence of vuggy Quartz in silica caps in the region shows this issue. The frequency of oxide minerals (Specularite, Barite, H2O-NaCl-CaCl2 system, and the low

  11. Hydrothermal Synthesis of Analcime from Kutingkeng Formation Mudstone

    Science.gov (United States)

    Hsiao, Yin-Hsiu; Chen, Kuan-Ting; Ray, Dah-Tong

    2015-04-01

    In southwest of Taiwan, the foothill located in Tainan-Kaohsiung city is the exposed area of Pliocene strata to early Pleistocene strata. The strata are about a depth of five thousand, named as Kutigkeng Formation. The outcrop of Kutigkeng Formation is typical badlands, specifically called 'Moon World.' It is commonly known as no important economic applications of agricultural land. The mineral compositions of Kutingkeng Formation are quartz, clay minerals and feldspar. The clay minerals consist of illite, clinochlore and swelling clays. To study how the phase and morphology of analcime formed by hydrothermal synthesis were affected, analcime was synthesized from the mudstone of Kutinkeng Formation with microwave hydrothermal reaction was investigated. The parameters of the experiment were the reaction temperature, the concentration of mineralizer, solids/liquid ratio and time. The sodium silicate (Na2SiO3) were used as mineralizer. The results showed that the analcime could be synthesized by hydrothermal reaction above 180° from Kutinkeng Formation mudstone samples. At the highest temperature (240°) of this study, the high purity analcime could be produced. When the concentration of Na2SiO3=3~6M, analcime could be synthesized at 240°. The best solids/liquid ratio was approximate 1 to 5. The hydrothermal reaction almost was completed after 4 hours.

  12. Effects of hydrothermal post-treatment on microstructures and morphology of titanate nanoribbons

    International Nuclear Information System (INIS)

    Yu Huogen; Yu Jiaguo; Cheng Bei; Zhou Minghua

    2006-01-01

    Titanate nanoribbons were prepared via a hydrothermal treatment of rutile-type TiO 2 powders in a 10 M NaOH solution at 200 deg. C for 48 h. The as-prepared titanate nanoribbons were then hydrothermally post-treated at 150 deg. C for 12-36 h. The titanate nanoribbons before and after hydrothermal post-treatment were characterized with FESEM, XRD, TEM, UV-VIS and nitrogen adsorption-desorption isotherms. The results showed that the hydrothermal post-treatment not only promoted the phase transformation from titanate to anatase TiO 2 , but also was beneficial to the removal of Na + ions remained in the titanate nanoribbons. After hydrothermal post-treatment, the TiO 2 samples retained the one-dimensional structure feature of the titanate nanoribbons and showed an obvious increase in the specific surface area and the pore volume

  13. Hydrothermal Processes in the Archean - New Insights from Imaging Spectroscopy

    NARCIS (Netherlands)

    Ruitenbeek, F.J.A. van

    2007-01-01

    The aim of this research was to gain new insights in fossil hydrothermal systems using airborne imaging spectroscopy. Fossil submarine hydrothermal systems in Archean greenstone belts and other geologic terranes are important because of their relationship with volcanic massive sulfide (VMS) mineral

  14. Vein networks in hydrothermal systems provide constraints for the monitoring of active volcanoes.

    Science.gov (United States)

    Cucci, Luigi; Di Luccio, Francesca; Esposito, Alessandra; Ventura, Guido

    2017-03-10

    Vein networks affect the hydrothermal systems of many volcanoes, and variations in their arrangement may precede hydrothermal and volcanic eruptions. However, the long-term evolution of vein networks is often unknown because data are lacking. We analyze two gypsum-filled vein networks affecting the hydrothermal field of the active Lipari volcanic Island (Italy) to reconstruct the dynamics of the hydrothermal processes. The older network (E1) consists of sub-vertical, N-S striking veins; the younger network (E2) consists of veins without a preferred strike and dip. E2 veins have larger aperture/length, fracture density, dilatancy, and finite extension than E1. The fluid overpressure of E2 is larger than that of E1 veins, whereas the hydraulic conductance is lower. The larger number of fracture intersections in E2 slows down the fluid movement, and favors fluid interference effects and pressurization. Depths of the E1 and E2 hydrothermal sources are 0.8 km and 4.6 km, respectively. The decrease in the fluid flux, depth of the hydrothermal source, and the pressurization increase in E2 are likely associated to a magma reservoir. The decrease of fluid discharge in hydrothermal fields may reflect pressurization at depth potentially preceding hydrothermal explosions. This has significant implications for the long-term monitoring strategy of volcanoes.

  15. Chemistry of a serpentinization-controlled hydrothermal system at the Lost City hydrothermal vent field

    Science.gov (United States)

    Ludwig, K. A.; Kelley, D. S.; Butterfield, D. A.; Nelson, B. K.; Karson, J. A.

    2003-12-01

    The Lost City Hydrothermal Field (LCHF), at 30° N near the Mid-Atlantic Ridge, is an off-axis, low temperature, high-pH, ultramafic-hosted vent system. Within the field, carbonate chimneys tower up to 60 m above the seafloor, making them the tallest vent structures known. The chemistry of the vent structures and fluids at the LCHF is controlled by reactions between seawater and ultramafic rocks beneath the Atlantis massif. Mixing of warm alkaline vent fluids with seawater causes precipitation of calcium carbonate and growth of the edifaces, which range from tall, graceful pinnacles to fragile flanges and colloform deposits. Geochemical and petrological analyses of the carbonate rocks reveal distinct differences between the active and extinct structures. Actively venting chimneys and flanges are extremely porous, friable formations composed predominantly of aragonite and brucite. These structures provide important niches for well-developed microbial communities that thrive on and within the chimney walls. Some of the active chimneys may also contain the mineral ikaite, an unstable, hydrated form of calcium carbonate. TIMS and ICP-MS analyses of the carbonate chimneys show that the most active chimneys have low Sr isotope values and that they are low in trace metals (e.g., Mn, Ti, Pb). Active structures emit high-pH, low-Mg fluids at 40-90° C. The fluids also have low Sr values, indicating circulation of hydrothermal solutions through the serpentinite bedrock beneath the field. In contrast to the active structures, extinct chimneys are less porous, are well lithified, and they are composed predominantly of calcite that yields Sr isotopes near seawater values. Prolonged lower temperature seawater-hydrothermal fluid interaction within the chimneys results in the conversion of aragonite to calcite and in the enrichment of some trace metals (e.g., Mn, Ti, Co, Zn). It also promotes the incorporation of foraminifera within the outer, cemented walls of the carbonate

  16. Timing of multiple hydrothermal events in the iron oxide-copper-gold deposits of the Southern Copper Belt, Carajás Province, Brazil

    Science.gov (United States)

    Moreto, Carolina P. N.; Monteiro, Lena V. S.; Xavier, Roberto P.; Creaser, Robert A.; DuFrane, S. Andrew; Melo, Gustavo H. C.; Delinardo da Silva, Marco A.; Tassinari, Colombo C. G.; Sato, Kei

    2015-06-01

    The Southern Copper Belt, Carajás Province, Brazil, hosts several iron oxide-copper-gold (IOCG) deposits, including Sossego, Cristalino, Alvo 118, Bacuri, Bacaba, Castanha, and Visconde. Mapping and U-Pb sensitive high-resolution ion microprobe (SHRIMP) IIe zircon geochronology allowed the characterization of the host rocks, situated within regional WNW-ESE shear zones. They encompass Mesoarchean (3.08-2.85 Ga) TTG orthogneiss, granites, and remains of greenstone belts, Neoarchean (ca. 2.74 Ga) granite, shallow-emplaced porphyries, and granophyric granite coeval with gabbro, and Paleoproterozoic (1.88 Ga) porphyry dykes. Extensive hydrothermal zones include albite-scapolite, biotite-scapolite-tourmaline-magnetite alteration, and proximal potassium feldspar, chlorite-epidote and chalcopyrite formation. U-Pb laser ablation multicollector inductively coupled mass spectrometry (LA-MC-ICP-MS) analysis of ore-related monazite and Re-Os NTIMS analysis of molybdenite suggest multiple Neoarchean (2.76 and 2.72-2.68 Ga) and Paleoproterozoic (2.06 Ga) hydrothermal events at the Bacaba and Bacuri deposits. These results, combined with available geochronological data from the literature, indicate recurrence of hydrothermal systems in the Southern Copper Belt, including 1.90-1.88-Ga ore formation in the Sossego-Curral ore bodies and the Alvo 118 deposit. Although early hydrothermal evolution at 2.76 Ga points to fluid migration coeval with the Carajás Basin formation, the main episode of IOCG genesis (2.72-2.68 Ga) is related to basin inversion coupled with Neoarchean (ca. 2.7 Ga) felsic magmatism. The data suggest that the IOCG deposits in the Southern Copper Belt and those in the Northern Copper Belt (2.57-Ga Salobo and Igarapé Bahia-Alemão deposits) do not share a common metallogenic evolution. Therefore, the association of all IOCG deposits of the Carajás Province with a single extensive hydrothermal system is precluded.

  17. Spatial Distribution of Viruses Associated with Planktonic and Attached Microbial Communities in Hydrothermal Environments

    Science.gov (United States)

    Nunoura, Takuro; Kazama, Hiromi; Noguchi, Takuroh; Inoue, Kazuhiro; Akashi, Hironori; Yamanaka, Toshiro; Toki, Tomohiro; Yamamoto, Masahiro; Furushima, Yasuo; Ueno, Yuichiro; Yamamoto, Hiroyuki; Takai, Ken

    2012-01-01

    Viruses play important roles in marine surface ecosystems, but little is known about viral ecology and virus-mediated processes in deep-sea hydrothermal microbial communities. In this study, we examined virus-like particle (VLP) abundances in planktonic and attached microbial communities, which occur in physical and chemical gradients in both deep and shallow submarine hydrothermal environments (mixing waters between hydrothermal fluids and ambient seawater and dense microbial communities attached to chimney surface areas or macrofaunal bodies and colonies). We found that viruses were widely distributed in a variety of hydrothermal microbial habitats, with the exception of the interior parts of hydrothermal chimney structures. The VLP abundance and VLP-to-prokaryote ratio (VPR) in the planktonic habitats increased as the ratio of hydrothermal fluid to mixing water increased. On the other hand, the VLP abundance in attached microbial communities was significantly and positively correlated with the whole prokaryotic abundance; however, the VPRs were always much lower than those for the surrounding hydrothermal waters. This is the first report to show VLP abundance in the attached microbial communities of submarine hydrothermal environments, which presented VPR values significantly lower than those in planktonic microbial communities reported before. These results suggested that viral lifestyles (e.g., lysogenic prevalence) and virus interactions with prokaryotes are significantly different among the planktonic and attached microbial communities that are developing in the submarine hydrothermal environments. PMID:22210205

  18. Kinetics of the hydrothermal treatment of tannin for producing carbonaceous microspheres.

    Science.gov (United States)

    Braghiroli, F L; Fierro, V; Izquierdo, M T; Parmentier, J; Pizzi, A; Celzard, A

    2014-01-01

    Aqueous solutions of condensed tannins were submitted to hydrothermal carbonization (HTC) in a stainless steel autoclave, and the kinetics of hydrothermal carbon formation was investigated by changing several parameters: amount of tannin (0.5; 1.0; 1.5; 2.0 g in 16 mL of water), HTC temperature (130, 160, 180 and 200°C) and reaction times (from 1 to 720 h). The morphology and the structure of the tannin-based hydrothermal carbons were studied by TEM, krypton adsorption at -196°C and helium pycnometry. These materials presented agglomerated spherical particles, having surface areas ranging from 0.6 to 10.0 m(2) g(-1). The chemical composition of the hydrothermal carbons was found to be constant and independent of reaction time. HTC kinetics of tannin were determined and shown to correspond to first-order reaction. Temperature-dependent measurements led to an activation energy of 91 kJ mol(-1) for hydrothermal conversion of tannin into carbonaceous microspheres separable by centrifugation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Levulinic acid from orange peel waste by hydrothermal carbonization (HTC)

    NARCIS (Netherlands)

    Puccini, Monica; Licursi, Domenico; Stefanelli, Eleonora; Vitolo, Sandra; Galletti, Anna Maria Raspolli; Heeres, Hero Jan

    2016-01-01

    With the awareness of the need for optimal and sustainable use of natural resources, hydrothermal treatment of biomass and biomass waste for energy and resource recovery has received increasing attention. The hydrothermal carbonization (HTC) of a biomass is achieved using water as the reaction

  20. Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

    Directory of Open Access Journals (Sweden)

    Zhigang Zeng

    2018-01-01

    Full Text Available Studies of the major components of hydrothermal plumes in seafloor hydrothermal fields are critical for an improved understanding of biogeochemical cycles and the large-scale distribution of elements in the submarine environment. The composition of major components in hydrothermal plume water column samples from 25 stations has been investigated in the middle and southern Okinawa Trough. The physical and chemical properties of hydrothermal plume water in the Okinawa Trough have been affected by input of the Kuroshio current, and its influence on hydrothermal plume water from the southern Okinawa Trough to the middle Okinawa Trough is reduced. The anomalous layers of seawater in the hydrothermal plume water columns have higher K+, Ca2+, Mn2+, B3+, Ca2+/SO42-, and Mn2+/Mg2+ ratios and higher optical anomalies than other layers. The Mg2+, SO42-, Mg2+/Ca2+, and SO42-/Mn2+ ratios of the anomalous layers are lower than other layers in the hydrothermal plume water columns and are consistent with concentrations in hydrothermal vent fluids in the Okinawa Trough. This suggests that the chemical variations of hydrothermal plumes in the Tangyin hydrothermal field, like other hydrothermal fields, result in the discharge of high K+, Ca2+, and B3+ and low Mg2+ and SO42- fluid. Furthermore, element ratios (e.g., Sr2+/Ca2+, Ca2+/Cl− in hydrothermal plume water columns were found to be similar to those in average seawater, indicating that Sr2+/Ca2+ and Ca2+/Cl− ratios of hydrothermal plumes might be useful proxies for chemical properties of seawater. The hydrothermal K+, Ca2+, Mn2+, and B3+ flux to seawater in the Okinawa Trough is about 2.62–873, 1.04–326, 1.30–76.4, and 0.293–34.7 × 106 kg per year, respectively. The heat flux is about 0.159–1,973 × 105 W, which means that roughly 0.0006% of ocean heat is supplied by seafloor hydrothermal plumes in the Okinawa Trough.

  1. Basin-scale transport of hydrothermal dissolved metals across the South Pacific Ocean.

    Science.gov (United States)

    Resing, Joseph A; Sedwick, Peter N; German, Christopher R; Jenkins, William J; Moffett, James W; Sohst, Bettina M; Tagliabue, Alessandro

    2015-07-09

    Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean. Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle. It has been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources and is thus of limited importance for ocean biogeochemistry. This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal dissolved iron may facilitate its long-range oceanic transport. Such transport has been subsequently inferred from spatially limited oceanographic observations. Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. Dissolved iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed. Based on our observations, we estimate a global hydrothermal dissolved iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates. Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal dissolved iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export production.

  2. SiC-dopped MCM-41 materials with enhanced thermal and hydrothermal stabilities

    International Nuclear Information System (INIS)

    Wang, Yingyong; Jin, Guoqiang; Tong, Xili; Guo, Xiangyun

    2011-01-01

    Graphical abstract: Novel SiC-dopped MCM-41 materials were synthesized by adding silicon carbide suspension in the molecular sieve precursor solvent followed by in situ hydrothermal synthesis. The dopped materials have a wormhole-like mesoporous structure and exhibit enhanced thermal and hydrothermal stabilities. Highlights: → SiC-dopped MCM-41 was synthesized by in situ hydrothermal synthesis of molecular sieve precursor combined with SiC. → The dopped MCM-41 materials show a wormhole-like mesoporous structure. → The thermal stability of the dopped materials have an increment of almost 100 o C compared with the pure MCM-41. → The hydrothermal stability of the dopped materials is also better than that of the pure MCM-41. -- Abstract: SiC-dopped MCM-41 mesoporous materials were synthesized by the in situ hydrothermal synthesis, in which a small amount of SiC was added in the precursor solvent of molecular sieve before the hydrothermal treatment. The materials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N 2 physical adsorption and thermogravimetric analysis, respectively. The results show that the thermal and hydrothermal stabilities of MCM-41 materials can be improved obviously by incorporating a small amount of SiC. The structure collapse temperature of SiC-dopped MCM-41 materials is 100 o C higher than that of pure MCM-41 according to the differential scanning calorimetry analysis. Hydrothermal treatment experiments also show that the pure MCM-41 will losses it's ordered mesoporous structure in boiling water for 24 h while the SiC-dopped MCM-41 materials still keep partial porous structure.

  3. Preservation of iron(II) by carbon-rich matrices in a hydrothermal plume

    Energy Technology Data Exchange (ETDEWEB)

    Toner, Brandy M.; Fakra, Sirine C.; Manganini, Steven J.; Santelli, Cara M.; Marcus, Matthew A.; Moffett, James W.; Rouxel, Olivier; German, Christopher R.; Edwards, Katrina J.

    2008-09-20

    Hydrothermal venting associated with mid-ocean ridge volcanism is globally widespread. This venting is responsible for a dissolved iron flux to the ocean that is approximately equal to that associated with continental riverine runoff. For hydrothermal fluxes, it has long been assumed that most of the iron entering the oceans is precipitated in inorganic forms. However, the possibility of globally significant fluxes of iron escaping these mass precipitation events and entering open-ocean cycles is now being debated, and two recent studies suggest that dissolved organic ligands might influence the fate of hydrothermally vented metals. Here we present spectromicroscopic measurements of iron and carbon in hydrothermal plume particles at the East Pacific Rise mid-ocean ridge. We show that organic carbon-rich matrices, containing evenly dispersed iron(II)-rich materials, are pervasive in hydrothermal plume particles. The absence of discrete iron(II) particles suggests that the carbon and iron associate through sorption or complexation. We suggest that these carbon matrices stabilize iron(II) released from hydrothermal vents in the region, preventing its oxidation and/or precipitation as insoluble minerals. Our findings have implications for deep-sea biogeochemical cycling of iron, a widely recognized limiting nutrient in the oceans.

  4. Effects of hydrothermal treatment of sewage sludge on pyrolysis and steam gasification

    International Nuclear Information System (INIS)

    Moon, Jihong; Mun, Tae-Young; Yang, Won; Lee, Uendo; Hwang, Jungho; Jang, Ensuk; Choi, Changsik

    2015-01-01

    Highlights: • Hydrothermal treatment (HT) is energy efficient and increases fuel energy density. • Pyrolysis and steam gasification were performed with sewage sludge before/after HT. • Product gases resembled those from wood chips, particularly at high temperature. • HT increases sludge lignin content, possibly enhancing methane yield of product gas. • HT can improve sewage sludge for use as an alternative to biomass and fossil fuels. - Abstract: Hydrothermal treatment is a promising option for pretreatment drying of organic waste, due to its low energy consumption and contribution to increasing fuel energy density. In this study, the characteristics of hydrothermally treated sewage sludge were investigated, and pyrolysis and steam gasification were performed with the sludge before and after hydrothermal treatment. The overall composition of product gases from treated sludge was similar to that obtained from steam gasification of wood chips, particularly under high-temperature conditions. In addition, the increase in lignin content of sewage sludge following hydrothermal treatment could help enhance methane yield in product gas during pyrolysis and steam gasification. The findings suggest that hydrothermal treatment is an appropriate method for improving sewage sludge for use as an alternative to biomass and fossil fuels

  5. Guidelines to Avoid Biocontamination of Antarctic Subglacial Aquatic Environments: Forward Contamination Concerns, Environmental Management and Scientific Stewardship of Icy analogue environments

    Science.gov (United States)

    Race, M. S.; Hobbie, J.; et al.

    2007-12-01

    For more than a decade, scientists and space mission planners have recognized the importance of collaborative information exchange with the Antarctic research community to address their many shared exploration challenges, from drilling methods, remote sample collection, and data interpretation, to concerns about cross contamination that could adversely impact both the environment and interpretation of scientific data. Another shared concern exists in the regulatory realm; both the Antarctic and outer space environments are subject to separate international treaties that impose regulatory controls and oversight with serious implications for exploration planning. In recent years, both communities have faced the need to adjust their regulatory controls in light of fast-paced advances in scientific understanding of extreme environments, particularly related to potential microbial life. Both communities have sought and received advice from the National Research Council (NRC) through studies that suggested ways to update their respective oversight and regulatory systems while allowing for continued scientific exploration. A recently completed NRC study "Exploration of Antarctic Subglacial Aquatic Environments: Environmental and Scientific Stewardship" provided a suite of recommendations to address1) 'cleanliness' levels necessary for equipment and devices used in exploration of subglacial aquatic environments, as well as 2) the scientific basis for contamination standards, and 3) the steps for defining an overall exploration strategy conducive to sound environmental management and scientific stewardship. This talk will present the findings of the recent multinational NRC study, which is likely to translate into useful information for analogue studies that proceed to test techniques and capabilities for exploring an Europan ocean, other icy celestial locations, and related science targets on Earth. As the science and exploration of subglacial environments grows beyond its

  6. Effects of headspace fraction and aqueous alkalinity on subcritical hydrothermal gasification of cellulose

    Energy Technology Data Exchange (ETDEWEB)

    Dolan, Ryan; Yin, Sudong; Tan, Zhongchao [Department of Mechanical and Manufacturing Engineering, Centre for Environmental Engineering Research and Education, Schulich School of Engineering, University of Calgary, 2500 University Dr. N.W. Calgary, AB (Canada)

    2010-07-15

    In order to better understand the pathways of hydrothermal gasification of cellulose, the effect of headspace fraction and alkalinity on the hydrothermal gasification of cellulose has been studied at 315 C in the presence of Pt/Al{sub 2}O{sub 3} as catalyst. It was found that regardless of alkalinity the headspace fraction had a large impact on gasification yield, with larger headspace fractions resulting in considerably more gas product. Without the addition of sodium carbonate, the effect of headspace fraction became more pronounced, with gas increasing by approximately a factor of forty from the lowest to highest headspace fraction. On the other hand, for the same residence time the addition of sodium carbonate co-catalyst dampened the magnitude of the effect, to a factor of 2.5 and 1.5, for 50 and 100 mM sodium carbonate solutions, respectively. These results indicated that the headspace fraction affected the phase behaviour, and that this altered the pathway of the cellulose decomposition. While furfural alcohol was the major product obtained with a 49% headspace fraction, it was effectively suppressed by using 78% or greater headspace fractions. Based on the effects of phase behaviour and previous literature, the reduced effect occurring upon the addition of sodium carbonate may relate to catalysis of the Lobry de-bruyn Van Eckenstein transform to produce lactic acid rather than intermediates proceeding through glycolaldehyde. (author)

  7. Hydrothermal response to a volcano-tectonic earthquake swarm, Lassen, California

    Science.gov (United States)

    Ingebritsen, Steven E.; Shelly, David R.; Hsieh, Paul A.; Clor, Laura; P.H. Seward,; Evans, William C.

    2015-01-01

    The increasing capability of seismic, geodetic, and hydrothermal observation networks allows recognition of volcanic unrest that could previously have gone undetected, creating an imperative to diagnose and interpret unrest episodes. A November 2014 earthquake swarm near Lassen Volcanic National Park, California, which included the largest earthquake in the area in more than 60 years, was accompanied by a rarely observed outburst of hydrothermal fluids. Although the earthquake swarm likely reflects upward migration of endogenous H2O-CO2 fluids in the source region, there is no evidence that such fluids emerged at the surface. Instead, shaking from the modest sized (moment magnitude 3.85) but proximal earthquake caused near-vent permeability increases that triggered increased outflow of hydrothermal fluids already present and equilibrated in a local hydrothermal aquifer. Long-term, multiparametric monitoring at Lassen and other well-instrumented volcanoes enhances interpretation of unrest and can provide a basis for detailed physical modeling.

  8. Subcritical hydrothermal conversion of organic wastes and biomass. Reaction pathways

    Directory of Open Access Journals (Sweden)

    Alejandro Amadeus Castro Vega

    2007-01-01

    Full Text Available Hydrothermal conversion is a procedure which emulates organic matter’s natural conversion into bio-crude having physical and chemical properties analogous to petroleum. The artificial transformation of biomass requi- res previous knowledge of the main reaction routes and product availability. The main component of biomass (depolymerisation by hydrolysis is presented in hydrothermal cellulose conversion, producing oligosaccharides which exhibit dehydration and retro-aldol condensation reactions for transforming into furfurals and carboxylic acids. Other biomass components (such as lignin, proteins, and fat esters present both hydrolysis and pyrolysis reaction routes. As long as biomass mainly contains carbohydrates, subcritical hydrothermal conversion products and their wastes will be fundamentally analogous to those displaying cellulose. These substances have added- value by far surpassing raw material’s acquisition cost. When the main hydrothermal conversion products’ O/C, H/C molar ratios as reported in literature are plotted, an evolutionary tralectory for conversion products appears to be closely or even overlapped with fossil fuels’ geological evolution.

  9. Dynamic behavior of Kilauea Volcano and its relation to hydrothermal systems and geothermal energy

    Science.gov (United States)

    Kauhikaua, Jim; Moore, R.B.; ,

    1993-01-01

    Exploitation of hydrothermal systems on active basaltic volcanoes poses some unique questions about the role of volcanism and hydrothermal system evolution. Volcanic activity creates and maintains hydrothermal systems while earthquakes create permeable fractures that, at least temporarily, enhance circulation. Magma and water, possibly hydrothermal water, can interact violently to produce explosive eruptions. Finally, we speculate on whether volcanic behavior can be affected by high rates of heat extraction.

  10. Hydrothermal alteration of plagioclase and growth of secondary feldspar in the Hengill Volcanic Centre, SW Iceland

    Science.gov (United States)

    Larsson, D.; Grönvold, K.; Oskarsson, N.; Gunnlaugsson, E.

    2002-05-01

    Dissolution of igneous feldspar and the formation and occurrence of secondary feldspar in tholeiitic basalts from the Hengill volcanic centre, in SW Iceland was studied by microprobe analysis of cuttings from two ca. 2000 m deep geothermal wells. Well NG-7 in Nesjavellir represents a geothermal system in a rift zone where the intensity of young, insignificantly altered intrusions increases with depth. Well KhG-1 in Kolviðarhóll represents the margin of a rift zone where the intensity of intrusives is lower and the intensity of alteration higher. This marginal well represents altered basaltic crust in an early retrograde state. The secondary plagioclase in both wells is mainly oligoclase, occurring in association with K-feldspar and chlorite±actinolite. The texture of this assemblage depends on the lithology and intensity of alteration. In Nesjavellir (NG-7) the composition of secondary albite-oligoclase is correlated with the host-rock composition. This connection is not apparent in more intensely altered samples from Kolviðarhóll (KhG-1). The influence of temperature on composition of secondary Na-feldspar is unclear in both wells although Ca is expected to increase with temperature. Any temperature dependence may be suppressed by the influence of rock composition in Nesjavellir and by retrograde conditions at Kolviðarhóll. The absence of clear compositional gradients between igneous plagioclase and secondary feldspar and between Na-feldspar and K-feldspar suggests that secondary feldspars formed by dissolution precipitation reactions.

  11. Hydrothermal metallurgy for recycling of slag and glass

    International Nuclear Information System (INIS)

    Tanaka, Toshihiro; Yoshikawa, Takeshi; Hirai, Nobumitsu; Katsuyama, Shigeru

    2009-01-01

    The authors have applied hydrothermal reactions to develop recycling processing of slag or glass. As an example, under hydrothermal conditions such as 200 300 deg. C and 30 40MPa with H 2 O, powders made of glass can be sintered to become solidified glass materials containing about 10mass% H 2 O. When the glass containing H 2 O is heated again under normal pressure, the glass expands releasing H 2 O to make porous microstructure. H 2 O starts to emit just above the glass transition temperature. Therefore, when we have a glass with low glass transition temperature, we can make low temperature foaming glass. The SiO 2 -Na 2 O-B 2 O 3 glass is a candidate to be such a foaming glass. In this paper, we describe our recent trial on the fabrication of the low temperature foaming glass by using hydrothermal reaction.

  12. Effect of hydrothermal treatment on some properties of Shenhua coal

    Energy Technology Data Exchange (ETDEWEB)

    Wang Zhi-cai; Shui Heng-fu; Zhang De-xiang; Gao Jin-sheng [East China University of Science and Technology, Shanghai (China). College of Resource and Environmental Engineering

    2006-10-15

    Effects of hydrothermal treatment on swelling, extraction and liquefaction behavior of Shenhua coal were studied through analyses of element content, ash content, volatile content and IR spectrum of treated coal. The results indicate that hydrogenation of coal is distinctly carried out in the process of hydrothermal pre-treatment and the hydrogen content of treated coal is more than that of raw coal. The contents of ash and volatile matters of treated coal are lower than those of raw coal. With the increase of treatment temperature the volatile content of the hydrothermal treated coal decreases and the ash content of treated coal increases. CO{sub 2} is main gas product and unvaries with the temperature changing, whereas CO and CH{sub 4} are formed when the temperature is above 250{sup o}C and increase with the temperature during hydrothermal treatment. Hydrothermal treatment is not in favor of coal swelling and the swelling ratio of treated coal decreases with the increase of treatment temperature. The swelling ratio of extraction residue by CS{sub 2}/NMP mixed solvent in NMP solvent is lower than that of the corresponding raw coal. The CS{sub 2}/NMP mixed solvent extraction yields of coal treated at appropriate temperature are higher than that of raw coal, but the extraction yields of treated coal obtained by n-hexane, toluene and THF successive Soxhelt extraction are lower. Hydrothermal treatment at 250-300{sup o}C can increase the conversion of treated coal in direct hydro-liquefaction. The gas + oil yield of treated coal is lower than that of raw coal and the preasphaltene yield of treated coal is much higher. IR spectra of treated coals show that the forms of non-covalent bonds are changed by hydrothermal treatment, and the hydrolysis of ester and ether bonds and the pyrolysis of aromatic side chains also maybe occur at high treatment temperature. 21 refs., 3 figs., 4 tabs.

  13. Hydrothermal synthesis, characterization and luminescent ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 4. Hydrothermal synthesis, characterization and luminescent properties of lanthanide-doped NaLaF 4 nanoparticles. JIGMET LADOL HEENA KHAJURIA SONIKA KHAJURIA ... Keywords. Citric acid; X-ray diffraction; down-conversion emission; energy transfer.

  14. Hydrothermal Alteration of Open Fractures in Prospective Geothermal Drill Cores, Akutan Island, Alaska

    Science.gov (United States)

    Kent, T.

    2011-12-01

    The goal of this study is to constrain the most recent thermal alteration of two drill cores (HSB2/HSB4) from the Island of Akutan in the Aleutian Islands of Alaska. These cores are characterized by identifying mineralogy using x-ray diffraction spectra, energy dispersive spectroscopy with a scanning electron microscope and optical mineralogy. This is then compared with the coincident thermal data gathered on site in order to help constrain the most recent thermal activity of this dynamic resource. Using multiple temperature diagnostic minerals and their paragenesis, a relative thermal history is produced of expansive propylitic alteration. When combined with the wireline temperature gradients of the cores a model of downward migration emerges. Shallow occurrences of high temperature minerals that lie above the boiling point to depth curve indicate higher hydrostatic pressures in the past which can be attributed to a combination of glacial effects, including a significant amount of glacial erosion that is recognized due to a lack of significant clay cap to the geothermal resource.

  15. Glacial removal of late Cenozoic subglacially emplaced volcanic edifices by the West Antarctic ice sheet

    Science.gov (United States)

    Behrendt, John C.; Blankenship, D.D.; Damaske, D.; Cooper, A. K.

    1995-01-01

    Local maxima of the horizontal gradient of pseudogravity from closely spaced aeromagnetic surveys over the Ross Sea, northwestern Ross Ice Shelf, and the West Antarctic ice sheet, reveal a linear magnetic rift fabric and numerous subcircular, high-amplitude anomalies. Geophysical data indicate two or three youthful volcanic edifices at widely separated areas beneath the sea and ice cover in the West Antarctic rift system. In contrast, we suggest glacial removal of edifices of volcanic sources of many more anomalies. Magnetic models, controlled by marine seismic reflection and radar ice-sounding data, allow us to infer that glacial removal of the associated late Cenozoic volcanic edifices (probably debris, comprising pillow breccias, and hyaloclastites) has occurred essentially concomitantly with their subglacial eruption. "Removal' of unconsolidated volcanic debris erupted beneath the ice is probably a more appropriate term than "erosion', given its fragmented, ice-contact origin. The exposed volcanoes may have been protected from erosion by the surrounding ice sheet because of more competent rock or high elevation above the ice sheet. -from Authors

  16. Synthesis of non-aggregated nicotinic acid coated magnetite nanorods via hydrothermal technique

    Energy Technology Data Exchange (ETDEWEB)

    Attallah, Olivia A., E-mail: olivia.adly@hu.edu.eg [Center of Nanotechnology, Nile University, 12677 Giza (Egypt); Pharmaceutical Chemistry Department, Heliopolis University, 11777 El Salam, Cairo (Egypt); Girgis, E. [Solid State Physics Department, National Research Center, 12622 Dokki, Giza (Egypt); Advanced Materials and Nanotechnology Lab, CEAS, National Research Center, 12622 Dokki, Giza (Egypt); Abdel-Mottaleb, Mohamed M.S.A. [Center of Nanotechnology, Nile University, 12677 Giza (Egypt)

    2016-02-01

    Non-aggregated magnetite nanorods with average diameters of 20–30 nm and lengths of up to 350 nm were synthesized via in situ, template free hydrothermal technique. These nanorods capped with different concentrations (1, 1.5, 2 and 2.5 g) of nicotinic acid (vitamin B3); possessed good magnetic properties and easy dispersion in aqueous solutions. Our new synthesis technique maintained the uniform shape of the nanorods even with increasing the coating material concentration. The effect of nicotinic acid on the shape, particle size, chemical structure and magnetic properties of the prepared nanorods was evaluated using different characterization methods. The length of nanorods increased from 270 nm to 350 nm in nicotinic acid coated nanorods. Goethite and magnetite phases with different ratios were the dominant phases in the coated samples while a pure magnetite phase was observed in the uncoated one. Nicotinic acid coated magnetic nanorods showed a significant decrease in saturation magnetization than uncoated samples (55 emu/g) reaching 4 emu/g in 2.5 g nicotinic acid coated sample. The novel synthesis technique proved its potentiality to prepare coated metal oxides with one dimensional nanostructure which can function effectively in different biological applications. - Highlights: • We synthesize nicotinic acid coated magnetite nanorods via hydrothermal technique • Effect of nicotinic acid concentration on the nanorods properties was significant • Nanorods maintained uniform shape with increased concentration of nicotinic acid • Alterations occurred in particle size, mineral phases and magnetics of coated samples.

  17. Synthesis of non-aggregated nicotinic acid coated magnetite nanorods via hydrothermal technique

    International Nuclear Information System (INIS)

    Attallah, Olivia A.; Girgis, E.; Abdel-Mottaleb, Mohamed M.S.A.

    2016-01-01

    Non-aggregated magnetite nanorods with average diameters of 20–30 nm and lengths of up to 350 nm were synthesized via in situ, template free hydrothermal technique. These nanorods capped with different concentrations (1, 1.5, 2 and 2.5 g) of nicotinic acid (vitamin B3); possessed good magnetic properties and easy dispersion in aqueous solutions. Our new synthesis technique maintained the uniform shape of the nanorods even with increasing the coating material concentration. The effect of nicotinic acid on the shape, particle size, chemical structure and magnetic properties of the prepared nanorods was evaluated using different characterization methods. The length of nanorods increased from 270 nm to 350 nm in nicotinic acid coated nanorods. Goethite and magnetite phases with different ratios were the dominant phases in the coated samples while a pure magnetite phase was observed in the uncoated one. Nicotinic acid coated magnetic nanorods showed a significant decrease in saturation magnetization than uncoated samples (55 emu/g) reaching 4 emu/g in 2.5 g nicotinic acid coated sample. The novel synthesis technique proved its potentiality to prepare coated metal oxides with one dimensional nanostructure which can function effectively in different biological applications. - Highlights: • We synthesize nicotinic acid coated magnetite nanorods via hydrothermal technique • Effect of nicotinic acid concentration on the nanorods properties was significant • Nanorods maintained uniform shape with increased concentration of nicotinic acid • Alterations occurred in particle size, mineral phases and magnetics of coated samples.

  18. Synthesis of ZrO2 nanoparticles by hydrothermal treatment

    International Nuclear Information System (INIS)

    Machmudah, Siti; Widiyastuti, W.; Prastuti, Okky Putri; Nurtono, Tantular; Winardi, Sugeng; Wahyudiono,; Kanda, Hideki; Goto, Motonobu

    2014-01-01

    Zirconium oxide (zirconia, ZrO 2 ) is the most common material used for electrolyte of solid oxide fuel cells (SOFCs). Zirconia has attracted attention for applications in optical coatings, buffer layers for growing superconductors, thermal-shield, corrosion resistant coatings, ionic conductors, and oxygen sensors, and for potential applications including transparent optical devices and electrochemical capacitor electrodes, fuel cells, catalysts, and advanced ceramics. In this work, zirconia particles were synthesized from ZrCl 4 precursor with hydrothermal treatment in a batch reactor. Hydrothermal treatment may allow obtaining nanoparticles and sintered materials with controlled chemical and structural characteristics. Hydrothermal treatment was carried out at temperatures of 150 – 200°C with precursor concentration of 0.1 – 0.5 M. Zirconia particles obtained from this treatment were analyzed by using SEM, PSD and XRD to characterize the morphology, particle size distribution, and crystallinity, respectively. Based on the analysis, the size of zirconia particles were around 200 nm and it became smaller with decreasing precursor concentration. The increasing temperature caused the particles formed having uniform size. Zirconia particles formed by hydrothermal treatment were monoclinic, tetragonal and cubic crystal

  19. Production of lightweight refractory material by hydrothermal process

    International Nuclear Information System (INIS)

    Sulejmani, Ramiz B.

    2002-01-01

    Many different processes of production of lightweight refractories are well known over the World. Traditional production of lightweight refractories is by addition of combustibles or by a special frothing process. This work is concerned with hydrothermal of lightweight refractories from rice husk ash. The rice husk ash, used in present investigations were from Kocani region, R. Macedonia. The chemical analysis of the rice husk ash shows that it contains 91,8 - 93,7% SiO 2 and some alkaline and alkaline earth oxides. Microscopic and X - ray diffraction examinations of the rice husk ash have shown that it is composed of cristobalite, tridimite and amorphous silica. The composition of the mixture for lightweight refractory brick production is 93,4% rice husk ash and 6,6% Ca(OH) 2 . The mixtures were well mixed, moistened and pressed at 5 - 10 MPa. The hydrothermal reactions between calcium hydroxide and rice husk ash over the temperature range 80 - 160 o C were investigated. The period of autoclave treatment was from 2 to 72 h. After the hydrothermal treatment of the samples, the mineralogical composition, bulk density, density, cold crushing strength, porosity, refractoriness and thermal expansion were examined. Analysing the properties of the obtained samples it can be concluded that from rice husk ash and calcium hydroxide under hydrothermal condition it is possible to obtain lightweight acid refractory material with high quality.(Author)

  20. Heat flux from magmatic hydrothermal systems related to availability of fluid recharge

    Science.gov (United States)

    Harvey, M. C.; Rowland, J.V.; Chiodini, G.; Rissmann, C.F.; Bloomberg, S.; Hernandez, P.A.; Mazot, A.; Viveiros, F.; Werner, Cynthia A.

    2015-01-01

    Magmatic hydrothermal systems are of increasing interest as a renewable energy source. Surface heat flux indicates system resource potential, and can be inferred from soil CO2 flux measurements and fumarole gas chemistry. Here we compile and reanalyze results from previous CO2 flux surveys worldwide to compare heat flux from a variety of magma-hydrothermal areas. We infer that availability of water to recharge magmatic hydrothermal systems is correlated with heat flux. Recharge availability is in turn governed by permeability, structure, lithology, rainfall, topography, and perhaps unsurprisingly, proximity to a large supply of water such as the ocean. The relationship between recharge and heat flux interpreted by this study is consistent with recent numerical modeling that relates hydrothermal system heat output to rainfall catchment area. This result highlights the importance of recharge as a consideration when evaluating hydrothermal systems for electricity generation, and the utility of CO2 flux as a resource evaluation tool.

  1. Hydrothermal plume anomalies over the southwest Indian ridge: magmatic control

    Science.gov (United States)

    Yue, X.; Li, H.; Tao, C.; Ren, J.; Zhou, J.; Chen, J.; Chen, S.; Wang, Y.

    2017-12-01

    Here we firstly reported the extensive survey results of the hydrothermal activity along the ultra-slow spreading southwest Indian ridge (SWIR). The study area is located at segment 27, between the Indomed and Gallieni transform faults, SWIR. The seismic crustal thickness reaches 9.5km in this segment (Li et al., 2015), which is much thicker than normal crustal. The anomaly thickened crust could be affected by the Crozet hotspot or highly focused melt delivery from the mantle. The Duanqiao hydrothermal field was reported at the ridge valley of the segment by Tao et al (2009). The Deep-towed Hydrothermal Detection System (DHDS) was used to collect information related with hydrothermal activity, like temperature, turbidity, oxidation-reduction potential (ORP) and seabed types. There are 15 survey lines at the interval of 2 to 3 km which are occupied about 1300 km2 in segment 27. After processing the raw data, including wiping out random noise points, 5-points moving average processing and subtracting the ambient, we got anomalous Nephelometric Turbidity Units values (ΔNTU). And dE/dt was used to identify the ORP anomalous as the raw data is easily influenced by electrode potentials drifting (Baker et al., 2016). According to the results of water column turbidity and ORP distributions, we confirmed three hydrothermal anomaly fields named A1, A2 and A3. The three fields are all located in the western part of the segment. The A1 field lies on the ridge valley, west side of Duanqiao field. The A2 and A3 field lie on the northern and southern of the ridge valley, respectively. We propose that recent magmatic activity probably focus on the western part of segment 27.And the extensive distribution of hydrothermal plume in the segment is the result of the discrete magma intrusion. References Baker E T, et al. How many vent fields? New estimates of vent field populations on ocean ridges from precise mapping of hydrothermal discharge locations. EPSL, 2016, 449:186-196. Li J

  2. Free-living nematode species (Nematoda) dwelling in hydrothermal sites of the North Mid-Atlantic Ridge

    Science.gov (United States)

    Tchesunov, Alexei V.

    2015-12-01

    Morphological descriptions of seven free-living nematode species from hydrothermal sites of the Mid-Atlantic Ridge are presented. Four of them are new for science: Paracanthonchus olgae sp. n. (Chromadorida, Cyatholaimidae), Prochromadora helenae sp. n. (Chromadorida, Chromadoridae), Prochaetosoma ventriverruca sp. n. (Desmodorida, Draconematidae) and Leptolaimus hydrothermalis sp. n. (Plectida, Leptolaimidae). Two species have been previously recorded in hydrothermal habitats, and one species is recorded for the first time in such an environment. Oncholaimus scanicus (Enoplida, Oncholaimidae) was formerly known from only the type locality in non-hydrothermal shallow milieu of the Norway Sea. O. scanicus is a very abundant species in Menez Gwen, Lucky Strike and Lost City hydrothermal sites, and population of the last locality differs from other two in some morphometric characteristics. Desmodora marci (Desmodorida, Desmodoridae) was previously known from other remote deep-sea hydrothermal localities in south-western and north-eastern Pacific. Halomonhystera vandoverae (Monhysterida, Monhysteridae) was described and repeatedly found in mass in Snake Pit hydrothermal site. The whole hydrothermal nematode assemblages are featured by low diversity in comparison with either shelf or deep-sea non-hydrothermal communities. The nematode species list of the Atlantic hydrothermal vents consists of representatives of common shallow-water genera; the new species are also related to some shelf species. On the average, the hydrothermal species differ from those of slope and abyssal plains of comparable depths by larger sizes, diversity of buccal structures, presence of food content in the gut and ripe eggs in uteri.

  3. Heavy metals from Kueishantao shallow-sea hydrothermal vents, offshore northeast Taiwan

    Science.gov (United States)

    Chen, Xue-Gang; Lyu, Shuang-Shuang; Garbe-Schönberg, Dieter; Lebrato, Mario; Li, Xiaohu; Zhang, Hai-Yan; Zhang, Ping-Ping; Chen, Chen-Tung Arthur; Ye, Ying

    2018-04-01

    Shallow water hydrothermal vents are a source of heavy metals leading to their accumulation in marine organisms that manage to live under extreme environmental conditions. This is the case at Kueishantao (KST) shallow-sea vents system offshore northeast Taiwan, where the heavy metal distribution in vent fluids and ambient seawater is poorly understood. This shallow vent is an excellent natural laboratory to understand how heavy and volatile metals behave in the nearby water column and ecosystem. Here, we investigated the submarine venting of heavy metals from KST field and its impact on ambient surface seawater. The total heavy metal concentrations in the vent fluids and vertical plumes were 1-3 orders of magnitude higher than the overlying seawater values. When compared with deep-sea hydrothermal systems, the estimated KST end-member fluids exhibited much lower concentrations of transition metals (e.g., Fe and Mn) but comparable concentrations of toxic metals such as Pb and As. This may be attributed to the lower temperature of the KST reaction zone and transporting fluids. Most of the heavy metals (Fe, Mn, As, Y, and Ba) in the plumes and seawater mainly originated from hydrothermal venting, while Cd and Pb were largely contributed by external sources such as contaminated waters (anthropogenic origin). The spatial distribution of heavy metals in the surface seawater indicated that seafloor venting impacts ambient seawater. The measurable influence of KST hydrothermal activity, however, was quite localized and limited to an area of heavy metals emanating from the yellow KST hydrothermal vent were: 430-2600 kg Fe, 24-145 kg Mn, 5-32 kg Ba, 10-60 kg As, 0.3-1.9 kg Cd, and 2-10 kg Pb. This study provides important data on heavy metals from a shallow-sea hydrothermal field, and it helps to better understand the environmental impact of submarine shallow hydrothermal venting.

  4. Conversion of sewage sludge to clean solid fuel using hydrothermal carbonization: Hydrochar fuel characteristics and combustion behavior

    International Nuclear Information System (INIS)

    He, Chao; Giannis, Apostolos; Wang, Jing-Yuan

    2013-01-01

    Highlights: • The hydrothermal carbonization of sewage sludge process is developed. • Hydrochars are solid fuels with less nitrogen and sulfur contents. • The first order combustion reaction of hydrochars is derived. • Main combustion decomposition of hydrochars is easier and more stable. • Formation pathways of hydrochars during hydrothermal carbonization are proposed. - Abstract: Conventional thermochemical treatment of sewage sludge (SS) is energy-intensive due to its high moisture content. To overcome this drawback, the hydrothermal carbonization (HTC) process was used to convert SS into clean solid fuel without prior drying. Different carbonization times were applied in order to produce hydrochars possessing better fuel properties. After the carbonization process, fuel characteristics and combustion behaviors of hydrochars were evaluated. Elemental analysis showed that 88% of carbon was recovered while 60% of nitrogen and sulfur was removed. Due to dehydration and decarboxylation reactions, hydrogen/carbon and oxygen/carbon atomic ratios reduced to 1.53 and 0.39, respectively. It was found that the fuel ratio increased to 0.18 by prolonging the carbonization process. Besides, longer carbonization time seemed to decrease oxygen containing functional groups while carbon aromaticity structure increased, thereby rendering hydrochars highly hydrophobic. The thermogravimetric analysis showed that the combustion decomposition was altered from a single stage for raw sludge to two stages for hydrochars. The combustion reaction was best fitted to the first order for both raw sludge and hydrochars. The combustion of hydrochars is expected to be easier and more stable than raw sludge because of lower activation energy and pre-exponential factor

  5. Exploration Method Development for hydrothermal plume hunting by XCTD

    Science.gov (United States)

    Kitagawa, Y.; Ikeda, M.; Kadoshima, K.; Koizumi, Y.; Nakano, J.; Asakawa, E.; Sumi, T.

    2017-12-01

    J-MARES (Research and Development Partnership for Next Generation Technology of Marine Resources Survey, JAPAN) has been designing a low-cost and high-efficiency exploration system for seafloor hydrothermal massive sulfide deposits in "Cross-ministerial Strategic Innovation Promotion Program (SIP)" granted by the Cabinet Office, Government of Japan since 2014. We proposed hydrothermal plume hunting by XCTD (eXpendables Conductivity, Temperature and Depth). We applied this method to an area of interest more than 100km x 100km over Okinawa Trough, including some known seafloor massive sulfide deposits. Generally, hydrothermal plume exploration has been by ship mounted with MBES (Multi Beam Echo Sounder) or AUV with sound anomaly observation. However, these methods have to charter the sophisticated ship costly. On the other hand, throw-in type water quality meters (eg. XCTD and XBT) can be low-cost and easily operable. Moreover, that can make a quick look at seawater temperature and conductivity even in rough waters.Firstly, we confirmed XCTD probes position on the seafloor by ROV mounted deep-sea high vision camera. As a result of the test, probes swept downstream about 40 m in horizontal distance from throwing positions with about 1,600m in water depth. Following the previous test results, we had performed to the next test that confirmed detection range of hydrothermal plume at the chimney of North Mound in Izena Cauldron, so we had caught anomaly of seawater temperature and conductivity successfully which could be possibly derived from hydrothermal activities. Although averaged seawater temperature at a depth of 1500 m or more was about 3.95 degrees C, near the chimney was about 4.93 degrees C. The temperature anomalies originated from the hydrothermal plumes could be distributed at most 30m in horizontal distance and became smaller away from the chimney. Moreover, temperature anomaly mass of sea water tended to move upward in depth with distance away from the

  6. Enhanced bioactivity and biocompatibility of nanostructured hydroxyapatite coating by hydrothermal annealing

    International Nuclear Information System (INIS)

    Hahn, Byung-Dong; Lee, Jeong-Min; Park, Dong-Soo; Choi, Jong-Jin; Ryu, Jungho; Yoon, Woon-Ha; Choi, Joon-Hwan; Lee, Byoung-Kuk; Kim, Jong-Woo; Kim, Hyoun-Ee; Kim, Seong-Gon

    2011-01-01

    The crystallinity of hydroxyapatite (HA) coatings prepared by aerosol deposition may be increased by heating in air or low-temperature hydrothermal processing. From the X-ray diffraction and Fourier transform infrared spectroscopy results, it was revealed that the crystallinity of the HA coatings significantly increased after the post-annealing. Transmission electron microscopy showed that the conventional furnace heating induced the substantial growth of the HA crystallites, whereas the hydrothermal treatment did not bring about any remarkable change in the HA crystallite size, which remained below 20 nm. The bioactivity of the HA coatings was estimated by the acellular simulated body fluid immersion test. After immersion for 7 days, newly-precipitated apatite crystals were only observed on the surfaces of the samples hydrothermally treated at 170 and 190 deg. C. In addition, the alkaline phosphatase activity of MC3T3-E1 preosteoblast cells cultured on the hydrothermally treated samples was significantly higher than those on the as-deposited coating and conventional furnace heated samples. The enhanced bioactivity and excellent biological in vitro cellular response of the hydrothermally treated samples were attributed to their nanostructured nature and high degree of crystallinity.

  7. Genome-resolved metagenomics reveals that sulfur metabolism dominates the microbial ecology of rising hydrothermal plumes

    Science.gov (United States)

    Anantharaman, K.; Breier, J. A., Jr.; Jain, S.; Reed, D. C.; Dick, G.

    2015-12-01

    Deep-sea hydrothermal plumes occur when hot fluids from hydrothermal vents replete with chemically reduced elements and compounds like sulfide, methane, hydrogen, ammonia, iron and manganese mix with cold, oxic seawater. Chemosynthetic microbes use these reduced chemicals to power primary production and are pervasive throughout the deep sea, even at sites far removed from hydrothermal vents. Although neutrally-buoyant hydrothermal plumes have been well-studied, rising hydrothermal plumes have received little attention even though they represent an important interface in the deep-sea where microbial metabolism and particle formation processes control the transformation of important elements and impact global biogeochemical cycles. In this study, we used genome-resolved metagenomic analyses and thermodynamic-bioenergetic modeling to study the microbial ecology of rising hydrothermal plumes at five different hydrothermal vents spanning a range of geochemical gradients at the Eastern Lau Spreading Center (ELSC) in the Western Pacific Ocean. Our analyses show that differences in the geochemistry of hydrothermal vents do not manifest in microbial diversity and community composition, both of which display only minor variance across ELSC hydrothermal plumes. Microbial metabolism is dominated by oxidation of reduced sulfur species and supports a diversity of bacteria, archaea and viruses that provide intriguing insights into metabolic plasticity and virus-mediated horizontal gene transfer in the microbial community. The manifestation of sulfur oxidation genes in hydrogen and methane oxidizing organisms hints at metabolic opportunism in deep-sea microbes that would enable them to respond to varying redox conditions in hydrothermal plumes. Finally, we infer that the abundance, diversity and metabolic versatility of microbes associated with sulfur oxidation impart functional redundancy that could allow it to persist in the dynamic settings of hydrothermal plumes.

  8. Sulfur metabolizing microbes dominate microbial communities in Andesite-hosted shallow-sea hydrothermal systems.

    Directory of Open Access Journals (Sweden)

    Yao Zhang

    Full Text Available To determine microbial community composition, community spatial structure and possible key microbial processes in the shallow-sea hydrothermal vent systems off NE Taiwan's coast, we examined the bacterial and archaeal communities of four samples collected from the water column extending over a redoxocline gradient of a yellow and four from a white hydrothermal vent. Ribosomal tag pyrosequencing based on DNA and RNA showed statistically significant differences between the bacterial and archaeal communities of the different hydrothermal plumes. The bacterial and archaeal communities from the white hydrothermal plume were dominated by sulfur-reducing Nautilia and Thermococcus, whereas the yellow hydrothermal plume and the surface water were dominated by sulfide-oxidizing Thiomicrospira and Euryarchaeota Marine Group II, respectively. Canonical correspondence analyses indicate that methane (CH(4 concentration was the only statistically significant variable that explains all community cluster patterns. However, the results of pyrosequencing showed an essential absence of methanogens and methanotrophs at the two vent fields, suggesting that CH(4 was less tied to microbial processes in this shallow-sea hydrothermal system. We speculated that mixing between hydrothermal fluids and the sea or meteoric water leads to distinctly different CH(4 concentrations and redox niches between the yellow and white vents, consequently influencing the distribution patterns of the free-living Bacteria and Archaea. We concluded that sulfur-reducing and sulfide-oxidizing chemolithoautotrophs accounted for most of the primary biomass synthesis and that microbial sulfur metabolism fueled microbial energy flow and element cycling in the shallow hydrothermal systems off the coast of NE Taiwan.

  9. Sulfur metabolizing microbes dominate microbial communities in Andesite-hosted shallow-sea hydrothermal systems.

    Science.gov (United States)

    Zhang, Yao; Zhao, Zihao; Chen, Chen-Tung Arthur; Tang, Kai; Su, Jianqiang; Jiao, Nianzhi

    2012-01-01

    To determine microbial community composition, community spatial structure and possible key microbial processes in the shallow-sea hydrothermal vent systems off NE Taiwan's coast, we examined the bacterial and archaeal communities of four samples collected from the water column extending over a redoxocline gradient of a yellow and four from a white hydrothermal vent. Ribosomal tag pyrosequencing based on DNA and RNA showed statistically significant differences between the bacterial and archaeal communities of the different hydrothermal plumes. The bacterial and archaeal communities from the white hydrothermal plume were dominated by sulfur-reducing Nautilia and Thermococcus, whereas the yellow hydrothermal plume and the surface water were dominated by sulfide-oxidizing Thiomicrospira and Euryarchaeota Marine Group II, respectively. Canonical correspondence analyses indicate that methane (CH(4)) concentration was the only statistically significant variable that explains all community cluster patterns. However, the results of pyrosequencing showed an essential absence of methanogens and methanotrophs at the two vent fields, suggesting that CH(4) was less tied to microbial processes in this shallow-sea hydrothermal system. We speculated that mixing between hydrothermal fluids and the sea or meteoric water leads to distinctly different CH(4) concentrations and redox niches between the yellow and white vents, consequently influencing the distribution patterns of the free-living Bacteria and Archaea. We concluded that sulfur-reducing and sulfide-oxidizing chemolithoautotrophs accounted for most of the primary biomass synthesis and that microbial sulfur metabolism fueled microbial energy flow and element cycling in the shallow hydrothermal systems off the coast of NE Taiwan.

  10. Selective oxidation of propylene to acrolein by hydrothermally synthesized bismuth molybdates

    DEFF Research Database (Denmark)

    Schuh, Kirsten; Kleist, Wolfgang; Høj, Martin

    2014-01-01

    Hydrothermal synthesis has been used as a soft chemical method to prepare bismuth molybdate catalysts for the selective oxidation of propylene to acrolein. All obtained samples displayed a plate-like morphology, but their individual aspect ratios varied with the hydrothermal synthesis conditions...... of nitric acid during hydrothermal synthesis enhanced both propylene conversion and acrolein yield, possibly due to a change in morphology. Formation of β-Bi2Mo2O9 was not observed under the applied conditions. In general, the catalytic performance of all samples decreased notably after calcination at 550...

  11. Hydrothermal Disintegration and Extraction of Different Microalgae Species

    Directory of Open Access Journals (Sweden)

    Michael Kröger

    2018-02-01

    Full Text Available For the disintegration and extraction of microalgae to produce lipids and biofuels, a novel processing technology was investigated. The utilization of a hydrothermal treatment was tested on four different microalgae species (Scenedesmus rubescens, Chlorella vulgaris, Nannochloropsis oculata and Arthorspira platensis (Spirulina to determine whether it has an advantage in comparison to other disintegration methods for lipid extraction. It was shown, that hydrothermal treatment is a reasonable opportunity to utilize microalgae without drying and increase the lipid yield of an algae extraction process. For three of the four microalgae species, the extraction yield with a prior hydrothermal treatment elevated the lipid yield up to six times in comparison to direct extraction. Only Scenedesmus rubescens showed a different behaviour. Reason can be found in the different cell wall of the species. The investigation of the differences in cell wall composition of the used species indicate that the existence of algaenan as a cell wall compound plays a major role in stability.

  12. Characteristics of Biochar Obtained by Hydrothermal Carbonization of Cellulose for Renewable Energy

    OpenAIRE

    Daegi Kim; Kunio Yoshikawa; Ki Young Park

    2015-01-01

    The effect of hydrothermal carbonization on the properties of cellulose present in lignocellulosic biomass was investigated for converting it into a renewable energy resource with high energy recovery efficiency. The biochar obtained from cellulose subjected to hydrothermal carbonization showed a significant increase in its carbon content and a calorific value. 13C NMR spectroscopy showed that when raw cellulose was subjected to hydrothermal carbonization above 220 °C, the resulting biochar h...

  13. Barium isotope composition of altered oceanic crust from the IODP Site 1256 at the East Pacific Rise

    Science.gov (United States)

    Nan, X.; Yu, H.; Gao, Y.

    2017-12-01

    To understand the behavior of Ba isotopes in the oceanic crust during seawater alteration, we analyzed Ba isotopes for altered oceanic crust (AOC) from the IODP Site 1256 at the East Pacific Rise (EPR). The samples include 33 basalts, 5 gabbros, and 1 gabbronorite. This drill profile has four sections from top to bottom, including the volcanic section, transition zone, sheeted dyke complex, and plutonic complex. They display various degrees of alteration with obviously variable temperatures and water/rock ratios (Gao et al., 2012). The volcanic section is slightly to moderately altered by seawater at 100 to 250°; the transition zone is a mixing zone between upwelling hydrothermal fluids and downwelling seawater; and the sheeted dyke complex and plutonic complex are highly altered by hydrothermal fluids (˜250°). Ba isotopes were analyzed on a Neptune Plus MC-ICP-MS at the University of Science and Technology of China. The long-term precision of δ137/134Ba is better than 0.04‰ (2SD). The δ137/134Ba of the volcanic section and the top of the transition zone range between -0.01 and 0.30‰, higher than the δ137/134Ba of fresh MORB and upper mantle (0.020 ± 0.021‰, 2SE, Huang et al., 2015). Similarly, the δ137/134Ba of the sheeted dyke complex ranges from 0.05 to 0.28‰. The plutonic section has δ137/134Ba from -0.17 to -0.05‰, which is lower than the upper mantle, with one exception that has δ137/134Ba of 0.19‰. No correlation exists between Ba contents and δ137/134Ba. The weighted average δ137/134Ba of the AOC samples is 0.13±0.04‰ (2SE), significantly higher than that of the upper mantle. In all, our AOC data reveal obvious Ba isotopic fractionation, reflecting alteration of the AOC by hydrothermal fluids and seawater. The obvious difference of Ba isotope composition between the AOC and the upper mantle further indicates that recycling of the AOC could result in Ba isotope heterogeneity of the mantle. References: Gao Y, Vils F, Cooper K M, et

  14. Hydrothermal germination models: Improving experimental efficiency by limiting data collection to the relevant hydrothermal range

    Science.gov (United States)

    Hydrothermal models used to predict germination response in the field are usually parameterized with data from laboratory experiments that examine the full range of germination response to temperature and water potential. Inclusion of low water potential and high and low-temperature treatments, how...

  15. Geochemical behaviour of rare earth elements on metasomatic alteration of volcanic rocks

    International Nuclear Information System (INIS)

    Jordanov, J.A.; Kunov, A.J.

    1987-01-01

    Investigations are carried out on metasomatically altered Paleogene latites in order to follow up the rare earth elements (REE) geochemical behavour. Representative samples of the initial rocks (latites), from propylitized latites and quartz-sericite rocks, as well as from dickite, alumite, diaspore and monoquartzites, are analysed. The results show that REE have a behaviour of moderately mobile elements. They undergo redistribution both in quantity and in the composition of the group. The different concentrations and changes in the ΣREE compared to the initial rocks are observed and direct relationships to the degree of endogenic leaching are made. The REE mobility and redistribution during the metasomatic alterations in the region investigated are controlled by the physical-chemical conditions which play a significant role both in determining the composition of the mineral paragenese and in the fixing of REE. The distribution patterns indicate that REE redistribution in the case of metasomatic alterations is almost isochemical without any supply from hydrothermal solutions

  16. Comparison of anti-corrosive properties between hot alkaline nitrate blackening and hydrothermal blackening routes

    Energy Technology Data Exchange (ETDEWEB)

    Fattah-alhosseini, A. [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Yazdani Khan, H., E-mail: hamid.yazdanikhan@gmail.com [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Heidarpour, A. [Department of Metallurgy and Materials Engineering, Hamedan University of Technology, Hamedan, 65155-579 (Iran, Islamic Republic of)

    2016-08-15

    In this study, the oxide films were formed on carbon steel by using hot alkaline nitrate and hydrothermal treatments. A dense and protective oxide film was obtained by hydrothermal method due to application of high pressure and by increasing solution temperature from boiling temperature (155 °C) to 250 °C. Oxide films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and electrochemical tests including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). These analyses showed that the magnetite film which was formed on carbon steel surface by hydrothermal treatment offers the best resistance in 3.5 wt.% NaCl solution. Although thicker oxide film could be obtained via hot alkaline nitrate black oxidizing, corrosion resistance was lower as a result of being highly porous and the presence of hematite. - Highlights: • Oxide films have been formed on steel by using of hot alkaline nitrate and hydrothermal treatments. • A dense and protective oxide film was obtained by hydrothermal treatment. • SEM micrographs showed that a dense and protective oxide film was obtained by hydrothermal treatment. • Film formed by hydrothermal treatment could have the best resistance in 3.5 wt.% NaCl solution.

  17. Hydrothermal Testing of K Basin Sludge and N Reactor Fuel at Sludge Treatment Project Operating Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Delegard, Calvin H.; Schmidt, Andrew J.; Thornton, Brenda M.

    2007-03-30

    The Sludge Treatment Project (STP), managed for the U. S. DOE by Fluor Hanford (FH), was created to design and operate a process to eliminate uranium metal from K Basin sludge prior to packaging for Waste Isolation Pilot Plant (WIPP). The STP process uses high temperature liquid water to accelerate the reaction, produce uranium dioxide from the uranium metal, and safely discharge the hydrogen. Under nominal process conditions, the sludge will be heated in pressurized water at 185°C for as long as 72 hours to assure the complete reaction (corrosion) of up to 0.25-inch diameter uranium metal pieces. Under contract to FH, the Pacific Northwest National Laboratory (PNNL) conducted bench-scale testing of the STP hydrothermal process in November and December 2006. Five tests (~50 ml each) were conducted in sealed, un-agitated reaction vessels under the hydrothermal conditions (e.g., 7 to 72 h at 185°C) of the STP corrosion process using radioactive sludge samples collected from the K East Basin and particles/coupons of N Reactor fuel also taken from the K Basins. The tests were designed to evaluate and understand the chemical changes that may be occurring and the effects that any changes would have on sludge rheological properties. The tests were not designed to evaluate engineering aspects of the process. The hydrothermal treatment affected the chemical and physical properties of the sludge. In each test, significant uranium compound phase changes were identified, resulting from dehydration and chemical reduction reactions. Physical properties of the sludge were significantly altered from their initial, as-settled sludge values, including, shear strength, settled density, weight percent water, and gas retention.

  18. Xenopumice erupted on 15 October 2011 offshore of El Hierro (Canary Islands): a subvolcanic snapshot of magmatic, hydrothermal and pyrometamorphic processes

    Science.gov (United States)

    Del Moro, S.; Di Roberto, A.; Meletlidis, S.; Pompilio, M.; Bertagnini, A.; Agostini, S.; Ridolfi, F.; Renzulli, A.

    2015-06-01

    On 15 October 2011, a submarine eruption offshore of El Hierro Island gave rise to floating volcanic products, known as xenopumices, i.e., pumiceous xenoliths partly mingled and coated with the juvenile basanitic magma. Over the last few years, no consensus in the scientific community in explaining the origin of these products has been reached. In order to better understand the formation of xenopumice, we present a textural, mineralogical, and geochemical study of the possible magmatic, hydrothermal, and pyrometamorphic processes, which usually operate in the plumbing systems of active volcanoes. We carried out a comprehensive SEM investigation and Sr-Nd-Pb isotope analyses on some samples representative of three different xenopumice facies. All the data were compared with previous studies, new data for El Hierro extrusives and a literature dataset of Canary Islands igneous and sedimentary rocks. In the investigated xenopumices, we emphasize the presence of restitic magmatic phases as well as crystallization of minerals (mainly olivine + pyroxene + magnetite aggregates) as pseudomorphs after pre-existing mafic phenocrysts, providing evidence of pyrometamorphism induced by the high-T juvenile basanitic magma. In addition, we identify veins consisting of zircon + REE-oxides + mullite associated with Si-rich glass and hydrothermal quartz, which indicate the fundamental role played by hydrothermal fluid circulation in the xenopumice protolith. The petrological data agree with a pre-syneruptive formation of the xenopumice, when El Hierro basanite magma intruded hydrothermally altered trachyandesite to trachyte rocks and triggered local partial melting. Therefore, the El Hierro xenopumice represents a snapshot of the transient processes at the magma-wall rock interface, which normally occurs in the feeding system of active volcanoes.

  19. Comparison of hydrothermal activity between the Adriatic and the Red Sea rift margins

    Science.gov (United States)

    Ball, Philip; Incerpi, Nicolò; Birkle, Peter; Lacsamana, Elizabeth; Manatschal, Gianreto; Agar, Susan; Zhang, Shuo; Borsato, Ron

    2017-04-01

    Detailed field studies, and access to high-quality seismic reflection and refraction data have led to an improved understanding of the architecture and evolution of magma poor and magma rich margins. Associated with the spatial-temporal evolution of the rift, it is evident that there are evolving, extensive, fluid-rock interactions due to the infiltration of fluids within the sediment, basement and lithospheric mantle. Key questions therefore arise: What are the different fluid-rock reactions that can be typed to different geodynamic stages of the rift evolution? What are their compositions and how do they interact with their environment (basement, sediments, evaporites, hydrosphere, and magmatism)? What are the implications for the evolution of the margin rheology, thermal structure, depositional environments/organic matter maturity, and reservoir quality? The Adriatic paleo-rifted margin is preserved in both SE Switzerland and northern Italy. The field exposures provide a unique opportunity to study the fluid flow history of a hyperextended magma poor extensional margin. Analysis of breccias, cement veins and replacement minerals reveal that the margin records a complex, long-lasting history of dolomitization, calcification and silicification during the Jurassic rifting. The Red Sea by contrast is a young rifted margin. It differs from the paleo-Adriatic margin by several characteristics: volcanism is more evident, and syn-tectonic sediments, including evaporites (halite and anhydrite) are thicker. Several core and fluid samples are available from both onshore and offshore wells, which reveal rift-related hydrothermal alteration. In addition, we find evidence for the presence of an extreme dynamic hydraulic system with infiltration of surface water into sub-salt units during Late Pleistocene. In this study we present results from petrographic and geochemical analysis of basement and sedimentary rocks from Adriatic field-derived samples and core/subsurface fluid

  20. Metallogenic hydrothermal solution system of post volcanic magma in Xiangshan ore field

    International Nuclear Information System (INIS)

    Xu Hengli; Shao Fei; Zou Maoqin

    2009-01-01

    This paper has systematically described uranium metallogenic characteristics of Xiangshan ore field.Sources of metallogenic materials are discussed in different temporal and spatial scale. Combining with background analysis of metallogenic tectonic-magmatic-geodynamics, formation and evolution of metallogenic hydrothermal solution system in Xiangshan volcanic basin are studied. Metallogenic hydrothermal solution system in Xiangshan ore field is considered as the objective product of systematic evolution of hydrothermal solution in post volcanic magma constrained by regional tectonic environment. In time scale, metallogenic hydrothermal solution system developed for about 50 Ma, but its active spaces varied in different time domains. So temporal and spatial distribution of uranium mineralization is constrained. Further exploration for the ore field is also suggested in this paper. (authors)