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Sample records for hydrothermally altered crustal

  1. 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 ...

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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)

  9. 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

  10. 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

    meteoric water component. The three mineralisation types can be traced spatially and/or temporally from one to another with some overlap. The first type is characteristic of the deeper parts of an orogenic hydrothermal system, and this type gave way to the second type formed at shallower crustal levels, locally near to the surface. The third type of alteration is typically a late-stage, shallow-level phenomenon. (author). 58 refs., 9 figs., 3 tabs

  11. 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.

  12. 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

  13. 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.)

  14. 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

  15. 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

  16. 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

  17. 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)

  18. 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

  19. 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...

  20. Did a whole-crustal hydrothermal system generate the Irish Zn-Pb orefield?

    Science.gov (United States)

    Daly, J. Stephen; Badenszki, Eszter; Chew, David; Kronz, Andreas; O'Rourke, Helen; Whitehouse, Martin; Menuge, Julian; van den Berg, Riana

    2016-04-01

    Current models[1] for the genesis of the giant Irish Carboniferous-hosted Zn-Pb orefield propose shallow (700°C) metamorphism and melting during the Acadian orogeny at ~390Ma and during separate episodes of extension at ~ 381-373Ma and ~362Ma. Sm-Nd garnet dating shows that the lower crust remained hot or was re-heated to ~600°C at ~341Ma during Lower Carboniferous volcanism, also associated with extension and, in part, coincident with the mineralization[1]. Isotopic data from the xenoliths correspond closely to Sr and Nd isotopic analyses of gangue calcite[8] and galena Pb[9] isotopic data from the major ore deposits. While Zn contents of the xenoliths permit them to be metal sources, their mineralogy and texture provide an enriched template and a plausible extraction mechanism. In situ analyses of modally-abundant biotite and garnet show significant enrichment in Zn (and other relevant metals) as well as order of magnitude depletion of Zn during retrograde alteration, providing a metal-release mechanism and pointing to a hydrothermal fluid system operating at least to depths of ~ 25km. References [1] Wilkinson, J.J. & Hitzman, M.W. 2015. The Irish Pb-Zn orefield: The view from 2014. In: Archibald, S.M. and Piercey, S.J. (eds) Current Perspectives on Zinc deposits. Irish Association for Economic Geology, pp. 59-72.; [2] Davidheiser-Kroll, B., Stuart, F.M. & Boyce, A.J. 2014. Mineralium Deposita, 49, 547-553; [3] Elliott, H. 2015. Unpublished PhD thesis, University of Southampton; [4] Hnatyshin, D., Creaser, R.A., Wilkinson, J.J. & Gleeson, S.A. 2015. Geology, 43, 143-146; [5] McCusker, J. & Reed, C. 2013. Mineralium Deposita, 48, 687-695; [6] Van den Berg, R., Daly, J.S. & Salisbury, M.H. 2005. Tectonophysics, 407(1-2), 81-99; [7] Hauser, F., O'Reilly, B.M., Readman, P.W., Daly, J. S. & Van den Berg, R. 2008. Geophysical Journal International 175, 1254-1272; [8] Walshaw, R.D., Menuge, J.F. & Tyrrell, S. 2006. Mineralium Deposita, 41, 803-819; [9] Everett, C

  1. 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.

  2. 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)

  3. 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.

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

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    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.

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

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    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.

  6. 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

  7. 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

  8. Fluid transfer and vein thickness distribution in high and low temperature hydrothermal systems at shallow crustal level in southern Tuscany (Italy

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    Francesco Mazzarini

    2014-06-01

    Full Text Available Geometric analysis of vein systems hosted in upper crustal rocks and developed in high and low temperature hydrothermal systems is presented. The high temperature hydrothermal system consists of tourmaline-rich veins hosted within the contact aureole of the upper Miocene Porto Azzurro pluton in the eastern Elba Island. The low temperature hydrothermal system consists of calcite-rich veins hosted within the Oligocene sandstones of the Tuscan Nappe, exposed along the coast in southern Tuscany. Vein thickness distribution is here used as proxy for inferring some hydraulic properties (transmissivity of the fluid circulation at the time of veins’ formation. We derive estimations of average thickness of veins by using the observed distributions. In the case of power law thickness distributions, the lower the scaling exponent of the distribution the higher the overall transmissivity. Indeed, power law distributions characterised by high scaling exponents have transmissivity three order of magnitude lower than negative exponential thickness distribution. Simple observations of vein thickness may thus provides some clues on the transmissivity in hydrothermal systems.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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)

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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)

  5. 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...

  6. 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)

  7. 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)

  8. Re-Os, Sm-Nd, U-Pb, and stepwise lead leaching isotope systematics in shear-zone hosted gold mineralization: genetic tracing and age constraints of crustal hydrothermal activity

    Science.gov (United States)

    Frei, R.; Nägler, Th. F.; Schönberg, R.; Kramers, J. D.

    1998-06-01

    A combined Re-Os, Sm-Nd, U-Pb, and stepwise Pb leaching (PbSL) isotope study of hydrothermal (Mo-W)-bearing minerals and base metal sulfides from two adjacent shear zone hosted gold deposits (RAN, Kimberley) in the Harare-Shamva greenstone belt (Zimbabwe) constrain the timing of the mineralizing events to two periods. During an initial Late Archean event (2.60 Ga) a first molybdenite-scheelite bearing paragenesis was deposited in both shear zone systems, followed by a local reactivation of the shear systems during an Early Proterozoic (1.96 Ga) tectono-thermal overprint, during which base metal sulfides and most of the gold was (re-)deposited. While PbSL has revealed an open-system behavior of the U-Pb systematics in molybdenite and wolframite from the RAN mine, initial Archean Re-Os ages are still preserved implying that this system in these minerals was more resistant to the overprint. A similar retentivity could be shown for the Sm-Nd system in scheelite and powellite associated with the above ore minerals. Re-Os isotopic data from the Proterozoic mineralization in the Kimberley mine point to a recent gain of Re, most pronouncedly affecting Fe-rich sulfides such as pyrrhotite. A significant Re-loss in powellitic scheelite (an alteration phase of molybdenite-bearing scheelite), coupled with a marked loss of U in W-Mo ore minerals, complements the observation of a major Re uptake in Fe-sulfides during oxidizing conditions in a weathering environment. Pyrrhotite under these conditions behaves as an efficient Re-sink. Lead isotope signatures from PbSL residues of molybdenite, powellite, and quartz indicate a continental crustal source and/or contamination for the mineralizing fluid by interaction of the fluids with older sedimentary material as represented by the direct host country rocks. Our investigation reveals the potential of the Re-Os isotopic system applied to crustal hydrothermal ore minerals for genetic tracing and dating purposes. The simplified chemical

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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

  15. 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)

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. Investigating Crustal Scale Fault Systems Controlling Volcanic and Hydrothermal Fluid Processes in the South-Central Andes, First Results from a Magnetotelluric Survey

    Science.gov (United States)

    Pearce, R.; Mitchell, T. M.; Moorkamp, M.; Araya, J.; Cembrano, J. M.; Yanez, G. A.; Hammond, J. O. S.

    2017-12-01

    At convergent plate boundaries, volcanic orogeny is largely controlled by major thrust fault systems that act as magmatic and hydrothermal fluid conduits through the crust. In the south-central Andes, the volcanically and seismically active Tinguiririca and Planchon-Peteroa volcanoes are considered to be tectonically related to the major El Fierro thrust fault system. These large scale reverse faults are characterized by 500 - 1000m wide hydrothermally altered fault cores, which possess a distinct conductive signature relative to surrounding lithology. In order to establish the subsurface architecture of these fault systems, such conductivity contrasts can be detected using the magnetotelluric method. In this study, LEMI fluxgate-magnetometer long-period and Metronix broadband MT data were collected at 21 sites in a 40km2 survey grid that surrounds this fault system and associated volcanic complexes. Multi-remote referencing techniques is used together with robust processing to obtain reliable impedance estimates between 100 Hz and 1,000s. Our preliminary inversion results provide evidence of structures within the 10 - 20 km depth range that are attributed to this fault system. Further inversions will be conducted to determine the approximate depth extent of these features, and ultimately provide constraints for future geophysical studies aimed to deduce the role of these faults in volcanic orogeny and hydrothermal fluid migration processes in this region of the Andes.

  8. 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.

  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 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

  11. 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

  12. 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...

  13. 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

  14. 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.

  15. 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 ...

  16. Crustal layering, simplicity, and the oil industry: The alteration of an epistemic paradigm by a commercial environment

    Science.gov (United States)

    Anduaga, Aitor

    This paper proposes that the gradual alteration of the predominant epistemic paradigm in crustal seismology in the interwar period-namely, simplicity-came about because of the strong influence of a particular commercial environment, i.e. the oil industry. I begin by demonstrating the interwar predominance of Jeffreys' 'simplicity postulate' and his probabilistic epistemology, highlighting the espousal by several seismologists (Bullen, Stoneley, Byerly), whose crustal models drew on mathematical idealisations. Next, I demonstrate that the renunciation of simplicity in the 1930s came about too quickly, and, above all, too heterodoxically to have been the result of new geological evidence. Rather, I argue, the paradigm shift among seismologists was a result of the significant rise in seismic exploration generated by the oil industry. Driven by market demands, American petroleum companies pioneered new technologies, organised research initiatives, and trained young geophysicists who, through the fusion of experimentalism and field experience, brought about fundamental progress in earthquake seismology. Remarkably, historians of science have almost entirely failed to recognise the interwar primacy of the simplicity paradigm as well as its subsequent renunciation. More importantly, they have failed to acknowledge the role the oil industry played in contributing to this renunciation and to the development of new paradigms in seismology.

  17. 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.

  18. 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.

  19. 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.

  20. 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)

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Deep magmatism alters and erodes lithosphere and facilitates decoupling of Rwenzori crustal block

    Science.gov (United States)

    Wallner, Herbert; Schmeling, Harro

    2013-04-01

    The title is the answer to the initiating question "Why are the Rwenzori Mountains so high?" posed at the EGU 2008. Our motivation origins in the extreme topography of the Rwenzori Mountains. The strong, cold proterozoic crustal horst is situated between rift segments of the western branch of the East African Rift System. Ideas of rift induced delamination (RID) and melt induced weakening (MIW) have been tested with one- and two-phase flow physics. Numerical model parameter variations and new observations lead to a favoured model with simple and plausible definitions. Results coincide in the scope of their comparability with different observations or vice versa reduce ambiguity and uncertainties in model input. Principle laws of the thermo-mechanical physics are the equations of conservation of mass, momentum, energy and composition for a two-phase (matrix-melt) system with nonlinear rheology. A simple solid solution model determines melting and solidification under consideration of depletion and enrichment. The Finite Difference Method with markers is applied to visco-plastic flow using the streamfunction in an Eulerian formulation in 2D. The Compaction Boussinesq and the high Prandtl number Approximation are employed. Lateral kinematic boundary conditions provide long-wavelength asthenospheric upwelling and extensional stress conditions. Partial melts are generated in the asthenosphere, extracted above a critical fraction, and emplaced into a given intrusion level. Temperature anomalies positioned beneath the future rifts, the sole specialization to the Rwenzori situation, localize melts which are very effective in weakening the lithosphere. Convection patterns tend to generate dripping instabilities at the lithospheric base; multiple slabs detach and distort uprising asthenosphere; plumes migrate, join and split. In spite of appearing chaotic flow behaviour a characteristic recurrence time of high velocity events (drips, plumes) emerges. Chimneys of increased

  7. 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...

  8. 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

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. Crustal structure and mantle transition zone thickness beneath a hydrothermal vent at the ultra-slow spreading Southwest Indian Ridge (49°39'E): a supplementary study based on passive seismic receiver functions

    Science.gov (United States)

    Ruan, Aiguo; Hu, Hao; Li, Jiabiao; Niu, Xiongwei; Wei, Xiaodong; Zhang, Jie; Wang, Aoxing

    2017-06-01

    As a supplementary study, we used passive seismic data recorded by one ocean bottom seismometer (OBS) station (49°41.8'E) close to a hydrothermal vent (49°39'E) at the Southwest Indian Ridge to invert the crustal structure and mantle transition zone (MTZ) thickness by P-to-S receiver functions to investigate previous active seismic tomographic crustal models and determine the influence of the deep mantle thermal anomaly on seafloor hydrothermal venting at an ultra-slow spreading ridge. The new passive seismic S-wave model shows that the crust has a low velocity layer (2.6 km/s) from 4.0 to 6.0 km below the sea floor, which is interpreted as partial melting. We suggest that the Moho discontinuity at 9.0 km is the bottom of a layer (2-3 km thick); the Moho (at depth of 6-7 km), defined by active seismic P-wave models, is interpreted as a serpentinized front. The velocity spectrum stacking plot made from passive seismic data shows that the 410 discontinuity is depressed by 15 km, the 660 discontinuity is elevated by 18 km, and a positive thermal anomaly between 182 and 237 K is inferred.

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. 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

  1. 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

  2. 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

  3. 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

  4. 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.

  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. 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

  7. 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

  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, 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

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. Hydrothermal alteration studies of gabbros from northern central Indian ridge and their geodynamic implications

    Digital Repository Service at National Institute of Oceanography (India)

    Ray, Dwijesh; Mevel, C.; Banerjee, R.

    , IPGP, 4 Place Jussieu, F-75252 Paris Cedex 5, France. 3 National Institute of Oceanography, Goa 403 004, India. ∗ e-mail: dwijesh@rediffmail.com Mylonitic gabbro and altered gabbro were recovered from off-axis high and corner high loca- tions at ridge... microprobe analyzer at the CAMPARIS service of the IPG-Paris (University of Paris 6, France). Analytical conditions used were 15 kV accelerating voltage, 20 nA beam current and 20–40 s count- ing times. All analyses were performed in a point mode. A 2–3 µm...

  4. 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.

  5. 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

  6. 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.

  7. 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...

  8. 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

  9. 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

  10. 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.

  11. 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...

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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).

  17. 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

  18. 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.)

  19. 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.

  20. 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

  1. 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

  2. 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

  3. 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

  4. Massive Hydrothermal Flows of Fluids and Heat: Earth Constraints and Ocean World Considerations

    Science.gov (United States)

    Fisher, A. T.

    2018-05-01

    This presentation reviews the hydrogeologic nature of Earth's ocean crust and evidence for massive flows of low-temperature (≤70°C), seafloor hydrothermal circulation through ridge flanks, including the influence of crustal relief and crustal faults.

  5. 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

  6. 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...

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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

  13. Crustal permeability

    Science.gov (United States)

    Gleeson, Tom; Ingebritsen, Steven E.

    2016-01-01

    Permeability is the primary control on fluid flow in the Earth’s crust and is key to a surprisingly wide range of geological processes, because it controls the advection of heat and solutes and the generation of anomalous pore pressures.  The practical importance of permeability – and the potential for large, dynamic changes in permeability – is highlighted by ongoing issues associated with hydraulic fracturing for hydrocarbon production (“fracking”), enhanced geothermal systems, and geologic carbon sequestration.  Although there are thousands of research papers on crustal permeability, this is the first book-length treatment.  This book bridges the historical dichotomy between the hydrogeologic perspective of permeability as a static material property and the perspective of other Earth scientists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. 

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. Recent crustal movements

    Science.gov (United States)

    Maelzer, H.

    Calculation of temporal height changes for the determination of recent vertical crustal movements in northern, western, and southern Germany is described. Precise geodetic measurements and their analysis for the determination of recent crustal movements in north-eastern Iceland, western Venezuela, and central Peru are described. Determination of recent vertical crustal movements by leveling and gravity data; geodetic modeling of deformations and recent crustal movements; geodetic modeling of plate motions; and instrumental developments in geodetic measuring are discussed.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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...

  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. 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

  11. The Yatela gold deposit in Mali, West Africa: The final product of a long-lived history of hydrothermal alteration and weathering

    Science.gov (United States)

    Masurel, Quentin; Miller, John; Hein, Kim A. A.; Hanssen, Eric; Thébaud, Nicolas; Ulrich, Stanislav; Kaisin, Jean; Tessougue, Samuel

    2016-01-01

    The Yatela gold deposit is located in the Kédougou-Kénieba inlier (KKI), a window of ca. 2200-2050 Ma rocks that are exposed in eastern Senegal and western Mali. The geology of the KKI differs from other Paleoproterozoic granite-greenstone belts and sedimentary basins by the abundance of carbonate rocks. The Yatela deposit occurs within 8 km of the regional-scale Senegal-Mali Shear Zone. Country rocks in the Yatela region have been subjected to polycyclic deformation and regional greenschist-facies metamorphism. A syn-kinematic diorite stock has intruded the metasedimentary sequences in the open pit and is associated with a hornblende-hornfels contact aureole. Field relationships and micro-textural data indicate that the primary gold mineralisation is shear-hosted. The similar relative timing and structural setting between the Yatela primary gold mineralisation and other world-class deposits in the region (e.g., Loulo, Lawrence et al., 2013a; Massawa, Treloar et al., 2014; Sadiola Hill, Masurel et al., in press) suggest that regional orogenic gold mineralisation occurred during a period of transcurrent tectonics, after the cessation of regional compressional deformation. The primary gold mineralisation at Yatela, however, is low-grade and sub-economic. It is hosted by marbles and, to a lesser extent, diorite. The primary ore is pyrite-rich, with abundant chalcopyrite, minor arsenopyrite and accessory Zn-Pb-Sb-Fe-Ag-Co-Ni-bearing mineral species. Post-Birimian surficial dissolution of hydrothermally altered and mineralised host marbles resulted in the creation of troughs, which were draped and infilled with a ferruginous dissolution residue enriched in gold. This auriferous residuum formed the economic resource mined at Yatela until decommissioning in 2013. The Yatela gold deposit is unique with respect to mineralisation types encountered in West Africa because an auriferous residuum of economic interest (>1 Moz) derives from an underlying sub-economic Birimian

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Thermal and petrologic constraints on lower crustal melt accumulation under the Salton Sea Geothermal Field

    Science.gov (United States)

    Karakas, Ozge; Dufek, Josef; Mangan, Margaret T.; Wright, Heather M.; Bachmann, Olivier

    2017-06-01

    In the Salton Sea region of southern California (USA), concurrent magmatism, extension, subsidence, and sedimentation over the past 0.5 to 1.0 Ma have led to the creation of the Salton Sea Geothermal Field (SSGF)-the second largest and hottest geothermal system in the continental United States-and the small-volume rhyolite eruptions that created the Salton Buttes. In this study, we determine the flux of mantle-derived basaltic magma that would be required to produce the elevated average heat flow and sustain the magmatic roots of rhyolite volcanism observed at the surface of the Salton Sea region. We use a 2D thermal model to show that a lower-crustal, partially molten mush containing Salton Trough, and are consistent with seismic observations. Our results indicate limited melting and assimilation of pre-existing rocks in the lower crust. Instead, we find that basalt fractionation in the lower crust produces derivative melts of andesitic to dacitic composition. Such melts are then expected to ascend and accumulate in the upper crust, where they further evolve to give rise to small-volume rhyolite eruptions (Salton Buttes) and fuel local spikes in surface heat flux as currently seen in the SSGF. Such upper crustal magma evolution, with limited assimilation of hydrothermally altered material, is required to explain the slight decrease in δ18 O values of zircons (and melts) that have been measured in these rhyolites.

  17. 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

  18. 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

  19. 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

  20. Along-Axis Structure and Crustal Construction Processes of Spreading Segments in Iceland: Implications for Magmatic Rifts

    Science.gov (United States)

    Siler, D. L.; Karson, J. A.

    2017-10-01

    Magmatic rift systems are composed of discrete spreading segments defined by morphologic, structural, and volcanic features that vary systematically along strike. In Iceland, structural features mapped in the glaciated and exhumed Miocene age upper crust correlate with analogous features in the seismically and volcanically active neovolcanic zone. Integrating information from both the active rift zones and ancient crust provides a three-dimensional perspective of crustal structure and the volcanic and tectonic processes that construct crust along spreading segments. Crustal exposures in the Skagi region of northern Iceland reveal significant along-strike variations in geologic structure. The upper crust at exhumed magmatic centers (segment centers) is characterized by a variety of intrusive rocks, high-temperature hydrothermal alteration, and geologic evidence for kilometer-scale subsidence. In contrast, the upper crust along segment limbs, which extend along strike from magmatic centers, is characterized by thick sections of gently dipping lava flows, cut by varying proportions of subvertical dikes. This structure implies relatively minor upper crustal subsidence and lateral dike intrusion. The differing modes of subsidence beneath segment centers and segment limbs require along-axis mass redistribution in the underlying upper, middle, and lower crust during crustal construction. This along-axis material transport is accomplished through lateral dike intrusion in the upper crust and by along-axis flow of magmatic to high-temperature solid-state gabbroic material in the middle and lower crust. These processes, inferred from outcrop evidence in Skagi, are consistent with processes inferred to be important during active rifting in Iceland and at analogous magmatic oceanic and continental rifts.

  1. 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.)

  2. 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

  3. 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)

  4. Application of fractal modeling and PCA method for hydrothermal alteration mapping in the Saveh area (Central Iran based on ASTER multispectral data

    Directory of Open Access Journals (Sweden)

    Mirko Ahmadfaraj

    2016-06-01

    Full Text Available The aim of this study is determination and separation of alteration zones using Concentration-Area (C-A fractal model based on remote sensing data which has been extracted from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER images. The studied area is on the SW part of Saveh, 1:250,000 geological map, which is located in Urumieh-Dokhtar magmatic belt, Central Iran. The pixel values were computed by Principal Component Analysis (PCA method used to determine phyllic, argillic, and propylitic alteration zones. The C-A fractal model is utilized for separation of different parts of alteration zones due to their intensity. The log-log C-A plots reveal multifractal nature for phyllic, argillic, and propylitic alteration zones. The obtained results based on fractal model show that the main trend of the alteration zones is in NW-SE direction. Compared to the geological map of the study area and copper mineralizations, the alteration zones have been detected properly and correlate with the mineral occurrences, intrusive rock, and faults.

  5. Oxygen isotope exchange kinetics of mineral pairs in closed and open systems: Applications to problems of hydrothermal alteration of igneous rocks and Precambrian iron formations

    Science.gov (United States)

    Gregory, R.T.; Criss, R.E.; Taylor, H.P.

    1989-01-01

    The systematics of stable-isotope exchange between minerals and fluids are examined in the context of modal mineralogical variations and mass-balance considerations, both in closed and in open systems. On mineral-pair ??18O plots, samples from terranes that have exchanged with large amounts of fluid typically map out steep positively-sloped non-equilibrium arrays. Analytical models are derived to explain these effects; these models allow for different exchange rates between the various minerals and the external fluids, as well as different fluid fluxes. The steep arrays are adequately modelled by calculated isochron lines that involve the whole family of possible exchange trajectories. These isochrons have initially-steep near-vertical positive slopes that rotate toward a 45?? equilibrium slope as the exchange process proceeds to completion. The actual data-point array is thus analogous to the hand of an "isotopic clock" that measures the duration of the hydrothermal episode. The dimensionless ratio of the volumetric fluid flux to the kinetic rate parameter ( u k) determines the shape of each individual exchange trajectory. In a fluid-buffered system ( u k ??? 1), the solutions to the equations: (1) are independent of the mole fractions of the solid phases; (2) correspond to Taylor's open-system water/rock equation; and (3) yield straight-line isochrons that have slopes that approach 1 f, where f is the fraction reacted of the more sluggishly exchanging mineral. The isochrons for this simple exchange model are closely congruent with the isochrons calculated for all of the more complex models, thereby simplifying the application of theory to actual hydrothermal systems in nature. In all of the models an order of magnitude of time (in units of kt) separates steep non-equilibrium arrays (e.g., slope ??? 10) from arrays approaching an equilibrium slope of unity on a ??-?? diagram. Because we know the approximate lifetimes of many hydrothermal systems from geologic and

  6. Three-Dimensional Seismic Structure of the Mid-Atlantic Ridge: An Investigation of Tectonic, Magmatic, and Hydrothermal Processes in the Rainbow Area

    Science.gov (United States)

    Dunn, Robert A.; Arai, Ryuta; Eason, Deborah E.; Canales, J. Pablo; Sohn, Robert A.

    2017-12-01

    To test models of tectonic, magmatic, and hydrothermal processes along slow-spreading mid-ocean ridges, we analyzed seismic refraction data from the Mid-Atlantic Ridge INtegrated Experiments at Rainbow (MARINER) seismic and geophysical mapping experiment. Centered at the Rainbow area of the Mid-Atlantic Ridge (36°14'N), this study examines a section of ridge with volcanically active segments and a relatively amagmatic ridge offset that hosts the ultramafic Rainbow massif and its high-temperature hydrothermal vent field. Tomographic images of the crust and upper mantle show segment-scale variations in crustal structure, thickness, and the crust-mantle transition, which forms a vertical gradient rather than a sharp boundary. There is little definitive evidence for large regions of sustained high temperatures and melt in the lower crust or upper mantle along the ridge axes, suggesting that melts rising from the mantle intrude as small intermittent magma bodies at crustal and subcrustal levels. The images reveal large rotated crustal blocks, which extend to mantle depths in some places, corresponding to off-axis normal fault locations. Low velocities cap the Rainbow massif, suggesting an extensive near-surface alteration zone due to low-temperature fluid-rock reactions. Within the interior of the massif, seismic images suggest a mixture of peridotite and gabbroic intrusions, with little serpentinization. Here diffuse microearthquake activity indicates a brittle deformation regime supporting a broad network of cracks. Beneath the Rainbow hydrothermal vent field, fluid circulation is largely driven by the heat of small cooling melt bodies intruded into the base of the massif and channeled by the crack network and shallow faults.

  7. 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.

  8. A low-δ18O intrusive breccia from Koegel Fontein, South Africa: Remobilisation of basement that was hydrothermally altered during global glaciation?

    Science.gov (United States)

    Olianti, Camille A. E.; Harris, Chris

    2018-02-01

    The Cretaceous Koegel Fontein igneous complex is situated on the west coast of South Africa, and has a high proportion of rocks with abnormally low δ18O values. The rocks with the lowest δ18O values (- 5.2‰) belong to intrusive matrix-supported breccia pipes and dykes, containing a variety of clast types. The breccia rocks range in SiO2 from 44 to 68 wt% and their whole-rock δ18O values vary between - 5.2‰ and + 1.8‰. The major and trace element composition of the breccia rocks is consistent with them containing variable proportions of clasts of Cretaceous intrusive rocks and basement gneiss and the matrix being fluidized material derived from the same source as the clasts. Based on the nature of the clasts contained in the breccia, it was emplaced just prior to intrusion of the main Rietpoort Granite at 134 Ma. All components of the breccia have low δ18O value and, at least in the case of the gneiss clasts, this predates incorporation in the fluidized material. Although the early Cretaceous appears to have been a period of cold climate, it is unlikely that the δ18O values of ambient precipitation ( - 10‰) would have been low enough to have generated the required 18O-depletion. The basement gneiss was probably 2-3 km below the Cretaceous surface, minimizing the possibility of interaction with isotopically unmodified meteoric water, and there is no evidence for foundered blocks of cover rocks in the breccia. There is, therefore, no evidence for downwards movement of material. We favour a model where basement gneiss interacted with extremely 18O-depleted fluid during crustal reworking at 547 Ma, a time of global glaciation. Low-δ18O metamorphic fluids produced by dehydration melting of 18O-depleted gneiss became trapped and, as the fluid pressure increased, failure of the seal resulted in explosive upwards movement of fluidized breccia. Migration was along pre-existing dykes, incorporating fragments of these dykes, as well as the country rock gneiss.

  9. Quantification of porosity evolution from unaltered to propylitic-altered granites: the 14C-PMMA method applied on the hydrothermal system of Lavras do Sul, Brazil

    OpenAIRE

    Bongiolo, Everton M.; Bongiolo, Daniela E.; Sardini, Paul; Mexias, André S.; Siitari-Kauppi, Marja; Gomes, Márcia E.B.; Formoso, Milton L.L.

    2007-01-01

    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 (microfra...

  10. Application of fractal modeling and PCA method for hydrothermal alteration mapping in the Saveh area (Central Iran) based on ASTER multispectral data

    OpenAIRE

    Mirko Ahmadfaraj; Mirsaleh Mirmohammadi; Peyman Afzal

    2016-01-01

    The aim of this study is determination and separation of alteration zones using Concentration-Area (C-A) fractal model based on remote sensing data which has been extracted from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images. The studied area is on the SW part of Saveh, 1:250,000 geological map, which is located in Urumieh-Dokhtar magmatic belt, Central Iran. The pixel values were computed by Principal Component Analysis (PCA) method used to determine phyllic, a...

  11. 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

  12. Hydrothermal minerals

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.

    flux. Circulation of seawater through the oceanic crust and upper mantle gives rise to a complex series of physical and chemical reactions that lead to the 1) formation of seafloor mineral deposits; 2) alteration of oceanic crust; 3) control... temperature in the high-temperature reaction zone near the heat source. Important parameters in determining the high- temperature fluid composition are • pressure, • temperature, • water/rock ratio, • rock composition, • recharge fluid...

  13. 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

  14. Crustal deformation and volcanism at active plate boundaries

    Science.gov (United States)

    Geirsson, Halldor

    geometry and secular rates across the plate boundary segments, reveals a deep magma chamber under Hekla and gives a geodetic estimate of the current location of the North-America Eurasian plate boundary in south Iceland. Different geometries were tested for Hekla's magma chamber: spherical, horizontally elongated ellipsoidal, and pipe-like magma chambers. The data could not reliably distinguish the actual geometry; however, all three models indicate magma accumulation near the Moho (˜20-25 km) under Hekla. The February -- March 2000 eruption of Hekla gave another opportunity to image the magmatic system. In Chapter 5, I used co-eruptive GPS and InSAR displacements, borehole strain, and tilt measurements to jointly invert for co-eruptive deformation associated with the 2000 eruption and found a depth of approximately 20 km for the magma chamber, in accordance with my previous results. Telica is a highly seismically active volcano in Nicaragua. The seismicity is mostly of shallow (earthquake per minute averaged over 24 hours, but overall trends in seismic activity, as observed since 1993, do not have an obvious correlation with eruptive activity. This variability causes difficulties for hazard monitoring of Telica. Telica erupted in a small (VEI 2) explosive eruption in 2011. Eruptions of this style and size seem to occur on decadal time scales at Telica. In Chapter 3, I used an extensive multidisciplinary data set consisting of seismic and GPS data, multivariate ash analysis, SO2 measurements, fumarole temperatures, and visual observations, to show that the eruption was essentially an amagmatic eruption of hydrothermally altered materials from the conduit, and that short-term sealing of hydrothermal pathways led to temporary pressure build-up, resulting in the explosions. No significant crustal deformation was detected before or during the eruption, in accordance with low (earthquake offshore El Salvador was the largest event to rupture this segment of the subduction

  15. Experimental study of the hydrothermal alteration of a chemical analogue of the French nuclear glass in a thermal gradient: characterization of newly formed phases and of matter transfers

    International Nuclear Information System (INIS)

    Poinssot, Christophe

    1994-01-01

    As the most dangerous radioactive wastes are to be stored in deep geological layers after having been packaged in barrels made of borosilicate glasses, this research report addresses the study of the alteration of such glasses through the study of a chemical analogue. In order to experimentally model phenomena involved within a storage, the studied glass has been submitted to different thermal gradients between 320 and 150 C and during 3 to 5 months. These gradients comply with those met about the parcels, and allows the spatial evolution of the waste parcel at a given moment, as well as the evolution in time (progressive cooling of wastes) to be simultaneously simulated. The different phases formed within the gradient have been studied and characterized by scanning electronic microscopy, semi-quantitative microanalysis, and X-ray micro-diffraction [fr

  16. 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.

  17. Crustal Magnetic Field Anomalies and Global Tectonics

    Science.gov (United States)

    Storetvedt, Karsten

    2014-05-01

    A wide variety of evidence suggests that the ruling isochron (geomagnetic polarity versus age) hypothesis of marine magnetic lineations has no merit - undermining therefore one of the central tenets of plate tectonics. Instead, variable induction by the ambient geomagnetic field is likely to be the principal agent for mega-scale crustal magnetic features - in both oceanic and continental settings. This revitalizes the fault-controlled susceptibility-contrast model of marine magnetic lineations, originally proposed in the late 1960s. Thus, the marine magnetic 'striping' may be ascribed to tectonic shearing and related, but variable, disintegration of the original iron-oxide mineralogy, having developed primarily along one of the two pan-global sets of orthogonal fractures and faults. In this way, fault zones (having the more advanced mineral alteration) would be characterized by relatively low susceptibility, while more moderately affected crustal sections (located between principal fault zones) would be likely to have less altered oxide mineralogy and therefore higher magnetic susceptibility. On this basis, induction by the present geomagnetic field is likely to produce oscillating magnetic field anomalies with axis along the principal shear grain. The modus operandi of the alternative magneto-tectonic interpretation is inertia-driven wrenching of the global Alpine age palaeo-lithosphere - triggered by changes in Earth's rotation. Increasing sub-crustal loss to the upper mantle during the Upper Mesozoic had left the ensuing Alpine Earth in a tectonically unstable state. Thus, sub-crustal eclogitization and associated gravity-driven delamination to the upper mantle led to a certain degree of planetary acceleration which in turn gave rise to latitude-dependent, westward inertial wrenching of the global palaeo-lithosphere. During this process, 1) the thin and mechanically fragile oceanic crust were deformed into a new type of broad fold belts, and 2) the continents

  18. 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.

  19. Crustal response to lithosphere evolution

    DEFF Research Database (Denmark)

    Artemieva, Irina; Thybo, Hans; Cherepanova, Yulia

    2012-01-01

    We present a new model for the structure of the crust in an area which stretches from the North Atlantic region in the west to the Verkhoyansk Ridge in the east and encompasses Greenland, Iceland, most of Europe, West Siberian basin, and the Siberian cratons. The model is based on critically asse......, thicknesses of different crustal layers, and Pn seismic velocities....... assessed results from various seismic studies, including reflection and refraction profiles and receiver function studies. The region includes a nearly continuous age record for crustal evolution over ca. 3.6-3.8 billion years. We present an analysis of the crustal structure heterogeneity in relation...

  20. Crustal thickness controlled by plate tectonics

    DEFF Research Database (Denmark)

    Artemieva, Irina M.; Meissner, Rolf

    2012-01-01

    /gabbro–eclogite phase transition in crustal evolution and the links between lithosphere recycling, mafic magmatism, and crustal underplating. We advocate that plate tectonics processes, togetherwith basalt/gabbro–eclogite transition, limit crustal thickness worldwide by providing effective mechanisms of crustal...

  1. Characterization and modelling of fluid flows in fissured and fractured media. relation with hydrothermal alterations and paleo-stress quantification; Caracterisation et modelisation des ecoulements fluides en milieu fissure. relation avec les alterations hydrothermales et quantification des paleocontraintes

    Energy Technology Data Exchange (ETDEWEB)

    Sausse, J.

    1998-10-15

    In all materials (rocks, concretes, ceramics,...), the presence of fractures at different scales implies high permeability and often oriented fluid flows. These fluid circulations in fractures induce more or less intense fluid-rock interactions with mineral crystallisation and/or dissolution. These phenomena directly depend on the nature of the fluids and the rocks, the physical and chemical properties of the media and the rate of fluid renewal (permeabilities). Usually, the development of such alterations leads to a massive sealing of the fractures (vein alterations) and of the fissures (fluid inclusion planes and microcracks, pervasive alteration). Therefore, their study brings us precious indications for the understanding of the mechanisms of fluid migrations in fossil systems. A geometrical study of the fracture systems at micro or macroscopic scales, based on the spatial distribution of sealing minerals, is applied to two different granites: the Soultz-sous-Foret granite (Bas-Rhin, France) and the Brezouard granite (Vosges, France). At the macroscopic scale, a new graphical method is proposed in order to study drilling data (Soultz granite). It allows to identify the presence of three independent mineral associations (quartz - illite, calcite-chlorite and hematite) in independent fracture systems characterised by a specific 3D geometry and hydraulic properties. These three types of vein alteration correspond to distinct and non contemporaneous fluid percolations. At the microscopic scale, the reconstitution of crack opening - fluid percolation - crack sealing stages is delicate. However, the study of their geometrical characteristics (orientations, radius, volume densities) and thereby the quantification of their porosities, exchange surfaces and permeabilities, allow to identify their respective roles in the fluid propagation. These microstructures, which are very numerous in granites, imply high but variable matrix permeabilities. This has been confirmed by

  2. 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.

  3. Hydrothermal alterations of Bentonites in Almeria (Spain)

    International Nuclear Information System (INIS)

    Linares Gonzalez, J.; Barahona Fernandez, E.; Huertas Garcia, F.; Caballero Mesa, E.; Cuadros Ojeda, J.

    1996-01-01

    The use of bentonite as backfilling and sealing material in the high level radioactive waste disposals has been treated in previous studies accomplished by different authors. However, the use of this clayey barrier needs the resolution of different problems so that its efficiency will be enhanced. between those could be cited the study of the actual capacity of sealing the space around the canister and the accommodation to the pressure of the rocky environment; the possible variations in plasticity; the diffusion and reaction processes that can be produced through the barrier by groundwater, the capacity of radionuclides adsorption, etc. These studies, show that the bentonites with high content in smectite fulfill satisfactorily with the physical and chemical conditions to be used as sealing material, but it is known that the smectite can be unstable in diagenetic conditions similar to those are given in a deep repository of radioactive wastes, being transformed into illite. A conclusion of immediate interest is deduced from this last study. The bentonites used as sealing material in radioactive waste repositories must no contain Na as interlayer cation since it is very easily exchangeable by K. It is better to select those smectites with Ca and Mg that detain the entry of K in the interlayer and as a consequence the transformation process of smectite into illite is made more difficult. (Author)

  4. A numerical model for dynamic crustal-scale fluid flow

    Science.gov (United States)

    Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel

    2015-04-01

    Fluid flow in the crust is often envisaged and modeled as continuous, yet minimal flow, which occurs over large geological times. This is a suitable approximation for flow as long as it is solely controlled by the matrix permeability of rocks, which in turn is controlled by viscous compaction of the pore space. However, strong evidence (hydrothermal veins and ore deposits) exists that a significant part of fluid flow in the crust occurs strongly localized in both space and time, controlled by the opening and sealing of hydrofractures. We developed, tested and applied a novel computer code, which considers this dynamic behavior and couples it with steady, Darcian flow controlled by the matrix permeability. In this dual-porosity model, fractures open depending on the fluid pressure relative to the solid pressure. Fractures form when matrix permeability is insufficient to accommodate fluid flow resulting from compaction, decompression (Staude et al. 2009) or metamorphic dehydration reactions (Weisheit et al. 2013). Open fractures can close when the contained fluid either seeps into the matrix or escapes by fracture propagation: mobile hydrofractures (Bons, 2001). In the model, closing and sealing of fractures is controlled by a time-dependent viscous law, which is based on the effective stress and on either Newtonian or non-Newtonian viscosity. Our simulations indicate that the bulk of crustal fluid flow in the middle to lower upper crust is intermittent, highly self-organized, and occurs as mobile hydrofractures. This is due to the low matrix porosity and permeability, combined with a low matrix viscosity and, hence, fast sealing of fractures. Stable fracture networks, generated by fluid overpressure, are restricted to the uppermost crust. Semi-stable fracture networks can develop in an intermediate zone, if a critical overpressure is reached. Flow rates in mobile hydrofractures exceed those in the matrix porosity and fracture networks by orders of magnitude

  5. Crustal Ages of the Ocean Floor - Poster

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Crustal Ages of the Ocean Floor Poster was created at NGDC using the Crustal Ages of the Ocean Floor database draped digitally over a relief of the ocean floor...

  6. 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...

  7. Archaeal Viruses Contribute to the Novel Viral Assemblage Inhabiting Oceanic, Basalt-Hosted Deep Subsurface Crustal Fluids

    Science.gov (United States)

    Nigro, O. D.; Rappe, M. S.; Jungbluth, S.; Lin, H. T.; Steward, G.

    2015-12-01

    Fluids contained in the basalt-hosted deep subsurface of the world's oceans represent one of the most inaccessible and understudied biospheres on earth. Recent improvements in sampling infrastructure have allowed us to collect large volumes of crustal fluids (~104 L) from Circulation Obviation Retrofit Kits (CORKs) placed in boreholes located on the eastern flank of the Juan de Fuca Ridge (JdFR). We detected viruses within these fluids by TEM and epifluorescence microscopy in samples collected from 2010 to 2014. Viral abundance, determined by epifluorescence counts, indicated that concentrations of viruses in subsurface basement fluids (~105 ml-1) are lower than the overlying seawater, but are higher in abundance than microbial cells in the same samples. Analysis of TEM images revealed distinct viral morphologies (rod and spindle-shaped) that resemble the morphologies of viral families infecting archaea. There are very few, if any, direct observations of these viral morphologies in marine samples, although they have been observed in enrichment cultures and their signature genes detected in metagenomic studies from hydrothermal vents and marine sediments. Analysis of metagenomes from the JdFR crustal fluids revealed sequences with homology to archaeal viruses from the rudiviridae, bicaudaviridae and fuselloviridae. Prokaryotic communities in fluids percolating through the basaltic basement rock of the JdFR flank are distinct from those inhabiting the overlying sediments and seawater. Similarly, our data support the idea that the viral assemblage in these fluids is distinct from viral assemblages in other marine and terrestrial aquatic environments. Our data also suggest that viruses contribute to the mortality of deep subsurface prokaryotes through cell lysis, and viruses may alter the genetic potential of their hosts through the processes of lysogenic conversion and horizontal gene transfer.

  8. The crustal thickness of Australia

    Science.gov (United States)

    Clitheroe, G.; Gudmundsson, O.; Kennett, B.L.N.

    2000-01-01

    We investigate the crustal structure of the Australian continent using the temporary broadband stations of the Skippy and Kimba projects and permanent broadband stations. We isolate near-receiver information, in the form of crustal P-to-S conversions, using the receiver function technique. Stacked receiver functions are inverted for S velocity structure using a Genetic Algorithm approach to Receiver Function Inversion (GARFI). From the resulting velocity models we are able to determine the Moho depth and to classify the width of the crust-mantle transition for 65 broadband stations. Using these results and 51 independent estimates of crustal thickness from refraction and reflection profiles, we present a new, improved, map of Moho depth for the Australian continent. The thinnest crust (25 km) occurs in the Archean Yilgarn Craton in Western Australia; the thickest crust (61 km) occurs in Proterozoic central Australia. The average crustal thickness is 38.8 km (standard deviation 6.2 km). Interpolation error estimates are made using kriging and fall into the range 2.5-7.0 km. We find generally good agreement between the depth to the seismologically defined Moho and xenolith-derived estimates of crustal thickness beneath northeastern Australia. However, beneath the Lachlan Fold Belt the estimates are not in agreement, and it is possible that the two techniques are mapping differing parts of a broad Moho transition zone. The Archean cratons of Western Australia appear to have remained largely stable since cratonization, reflected in only slight variation of Moho depth. The largely Proterozoic center of Australia shows relatively thicker crust overall as well as major Moho offsets. We see evidence of the margin of the contact between the Precambrian craton and the Tasman Orogen, referred to as the Tasman Line. Copyright 2000 by the American Geophysical Union.

  9. 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

  10. 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

  11. 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.

  12. Hydrothermal treatment favors peeling of 'Pera' sweet orange fruit and does not alter quality Tratamento hidrotérmico facilita o descascamento de laranja 'Pera' e não afeta sua qualidade

    Directory of Open Access Journals (Sweden)

    Maria Cecília de Arruda

    2008-04-01

    Full Text Available Consumer demand for ready-to-eat-products has stimulated the development of new processing techniques to prepare fresh-cut fruit and vegetables. The aim of this study was to propose a peeling method for 'Pera' oranges (Citrus sinensis [L.] Osb. by using a hydrothermal treatment and to determine its influence on the respiratory activity, physicochemical and sensorial characteristics, as well as on the peeling time. Cooled oranges (6ºC were immersed in heated water (50ºC for eight minutes and then, peeled and stored at 6ºC. The internal fruit temperatures taken at 1 and 3 cm depths (from fruit surface were 15ºC and 10ºC, respectively, at the end of the hydrothermal treatment. Non-hydrothermally-treated peeled oranges were used as control. The peeling time for treated oranges was 3.2 times as short as the time used for the control. The yield of marketable oranges was 95% for hydrothermally-treated oranges versus 60% for control. The respiratory activity of hydrothermally-treated oranges was greater than that of control oranges only during the first hour after peeling. The hydrothermal treatment influenced neither the physicochemical quality (given by soluble solids, titratable acidity and ascorbic acid content nor fruit flavor. Oranges peeled with the aid of the hydrothermal treatment had better appearance. The hydrothermal treatment makes the peeling of oranges easier and does not affect their respiratory activity or their physicochemical and sensorial qualities.A demanda dos consumidores por produtos 'prontos para o consumo' tem estimulado o desenvolvimento de técnicas de processamento para preparar frutas e hortaliças minimamente processadas. O objetivo deste trabalho foi propor um método de descascamento para laranja 'Pera' (Citrus sinensis [L.] Osb. pelo uso do tratamento hidrotérmico e determinar sua influência na atividade respiratória, características físico-químicas e sensoriais e no tempo de descascamento de laranja 'Pera

  13. Crustal Seismic Anisotropy: Implications for Understanding Crustal Dynamics

    Science.gov (United States)

    Meltzer, A.; Christensen, N.; Okaya, D.

    2003-12-01

    The Nanga Parbat - Haramosh massif, in the core of the western syntaxis of the Himalaya, represents a unique exposure of mid-lower continental crust from beneath a collisional orogen. The exhumed core of the massif forms a large scale antiformal structure with axial orientation of N10E and associated lineation directed north-south with near-vertical dips. Laboratory measurements of seismic velocity on a suite of quartzofeldspathic gneisses from the massif show a relatively strong degree of anisotropy, up to 12.5% for compressional waves and up to 21% for shear waves. The degree of velocity anisotropy is primarily a function of mica content and rock fabric strength. The strong anisotropy measured in these rocks should be observable in recorded seismic field data and provides a means of mapping rock fabric at depth provided the rock fabric is coherent over appropriate length scales. An IRIS/PASSCAL deployment of 50 short period instruments recorded local and regional earthquakes to characterize seismicity and determine crustal structure beneath the massif as part of a multidisciplinary NSF Continental Dynamics study investigating the active tectonic processes responsible for exhumation and crustal reworking at Nanga Parbat. Microseismicity at Nanga Parbat is distributed along strike beneath the massif but exhibits a sharp drop-off laterally into adjacent terranes and with depth. This data set is ideal for studying crustal seismic anisotropy because the raypaths are restricted to the crust, sharp onsets in P and S allow for clear identification of arrivals, and source-receiver geometries sample a range of azimuths with respect to structure. Preliminary analysis indicates that the majority of local events exhibit some degree of splitting and that splitting patterns, while complicated, are coherent. While splitting delay normally increases with distance traveled through anisotropic material, the range of delay times can be due to heterogeneity in composition, lateral

  14. Crustal Structure of Active Deformation Zones in Africa: Implications for Global Crustal Processes

    Science.gov (United States)

    Ebinger, C. J.; Keir, D.; Bastow, I. D.; Whaler, K.; Hammond, J. O. S.; Ayele, A.; Miller, M. S.; Tiberi, C.; Hautot, S.

    2017-12-01

    The Cenozoic East African rift (EAR), Cameroon Volcanic Line (CVL), and Atlas Mountains formed on the slow-moving African continent, which last experienced orogeny during the Pan-African. We synthesize primarily geophysical data to evaluate the role of magmatism in shaping Africa's crust. In young magmatic rift zones, melt and volatiles migrate from the asthenosphere to gas-rich magma reservoirs at the Moho, altering crustal composition and reducing strength. Within the southernmost Eastern rift, the crust comprises 20% new magmatic material ponded in the lower crust and intruded as sills and dikes at shallower depths. In the Main Ethiopian Rift, intrusions comprise 30% of the crust below axial zones of dike-dominated extension. In the incipient rupture zones of the Afar rift, magma intrusions fed from crustal magma chambers beneath segment centers create new columns of mafic crust, as along slow-spreading ridges. Our comparisons suggest that transitional crust, including seaward dipping sequences, is created as progressively smaller screens of continental crust are heated and weakened by magma intrusion into 15-20 km thick crust. In the 30 Ma Recent CVL, which lacks a hot spot age progression, extensional forces are small, inhibiting the creation and rise of magma into the crust. In the Atlas orogen, localized magmatism follows the strike of the Atlas Mountains from the Canary Islands hot spot toward the Alboran Sea. CVL and Atlas magmatism has had minimal impact on crustal structure. Our syntheses show that magma and volatiles are migrating from the asthenosphere through the plates, modifying rheology, and contributing significantly to global carbon and water fluxes.

  15. 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.

  16. Crustal Structure of the Tengchong Intra-plate Volcanic Area

    Science.gov (United States)

    Qian, Rongyi; Tong, Vincent C. H.

    2015-09-01

    We here provide an overview of our current understanding of the crustal structure of Tengchong in southwest China, a key intra-plate volcanic area along the Himalayan geothermal belt. Given that there is hitherto a lack of information about the near-surface structure of intra-plate volcanic areas, we present the first seismic reflection and velocity constraints on the shallow crust between intra-plate volcanoes. Our near-surface seismic images reveal the existence of dome-shaped seismic reflectors (DSRs) in the shallow crust between intra-plate volcanic clusters in Tengchong. The two DSRs are both ~2 km wide, and the shallowest parts of the DSRs are found at the depth of 200-300 m. The velocity model shows that the shallow low-velocity layer (<4 km/s) is anomalously thick (~1 km) in the region where the DSRs are observed. The presence of DSRs indicates significant levels of intra-plate magmatism beneath the along-axis gap separating two volcano clusters. Along-axis gaps between volcano clusters are therefore not necessarily an indicator of lower levels of magmatism. The seismic images obtained in this technically challenging area for controlled-source seismology allow us to conclude that shallow crustal structures are crucial for understanding the along-axis variations of magmatism and hydrothermal activities in intra-plate volcanic areas.

  17. 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.

  18. 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

  19. 3D upper crustal seismic structure across Santorini volcanic field: Constraints on magmatic and tectonic interactions

    Science.gov (United States)

    Heath, B.; Hooft, E. E. E.; Toomey, D. R.; Papazachos, C. V.; Walls, K.; Paulatto, M.; Morgan, J. V.; Nomikou, P.; Warner, M.

    2017-12-01

    To investigate magmatic-tectonic interactions at an arc volcano, we collected a dense, active-source, seismic dataset across the Santorini Volcano, Greece, with 90 ocean bottom seismometers, 65 land seismometers, and 14,300 marine sound sources. We use over 140,000 travel-time picks to obtain a P-wave tomography model of the upper crustal structure of the Santorini volcano and surrounding tectonically extended region. Regionally, the shallow (Bouguer gravity anomalies and preliminary shallow attenuation results (using waveform amplitudes and t* values). We find regional Pliocene and younger faults bounding basement grabens and horsts to be predominately oriented in a NE-SW direction with Santorini itself located in a graben bounded by faults striking in this direction. In contrast, volcanic vents and dikes expressed at the surface seem to strike about 20° clockwise relative to these regional faults. In the northern caldera of Santorini, a 4-km wide region of anomalously low velocities and high attenuation directly overlies an inferred source of 2011-2012 inflation (4-4.5 km depth), however it is located at shallower depths ( 1-2km). The imaged low-velocity anomaly may correspond to hydrothermal activity (due to increased porosity and alteration) and/or brecciation from a prior episode of caldera collapse. It is bounded by anomalously fast velocities (at 1-2 km depth) that parallel the regional fault orientation and are correspondingly rotated 20° to surface dikes. At 4-5 km depth beneath the northern caldera basin, low-velocity anomalies and attenuated seismic arrivals provide preliminary evidence for a magma body; the low-velocity anomaly is elongated in the same direction as regional volcanic vents. The difference in strike of volcanic and tectonic features indicates oblique extension and potential time-variation in the minimum stress direction.

  20. 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.

  1. Linking fault permeability, fluid flow, and earthquake triggering in a hydrothermally active tectonic setting: Numerical Simulations of the hydrodynamics in the Tjörnes Fracture Zone, Iceland.

    Science.gov (United States)

    Lupi, M.; Geiger, S.; Graham, C.; Claesson, L.; Richter, B.

    2007-12-01

    A good insight into the transient fluid flow evolution within a hydrothermal system is of primary importance for the understanding of several geologic processes, for example the hydrodynamic triggering of earthquakes or the formation of mineral deposits. The strong permeability contrast between different crustal layers as well as the high geothermal gradient of these areas are elements that strongly affect the flow behaviour. In addition, the sudden and transient occurrence of joints, faults and magmatic intrusions are likely to change the hydrothermal flow paths in very short time. The Tjörnes Fracture Zone (TFZ) north of Iceland, is such a hydrothermal area where a high geothermal gradient, magmatic bodies, faults, and the strong contrast between sediments and fractured lava layers govern the large-scale fluid flow. The TFZ offsets the Kolbeinsey Ridge and the Northern Rift Zone. It is characterized by km-scale faults that link sub-seafloor sediments and lava layers with deeper crystalline rocks. These structures focus fluid flow and allow for the mixing between cold seawater and deep hydrothermal fluids. A strong seismic activity is present in the TFZ: earthquakes up to magnitude 7 have been recorded over the past years. Hydrogeochemical changes before, during and after a magnitude 5.8 earthquake suggest that the evolving stress state before the earthquake leads to (remote) permeability variations, which alter the fluid flow paths. This is in agreement with recent numerical fluid flow simulations which demonstrate that fluid flow in magmatic- hydrothermal systems is often convective and very sensitive to small variations in permeability. In order to understand the transient fluid flow behaviour in this complex geological environment, we have conducted numerical simulations of heat and mass transport in two geologically realistic cross-sectional models of the TFZ. The geologic models are discretised using finite element and finite volume methods. They hence have

  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. 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.

  4. 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

  5. Crustal structure of Central Sicily

    Science.gov (United States)

    Giustiniani, Michela; Tinivella, Umberta; Nicolich, Rinaldo

    2018-01-01

    We processed crustal seismic profile SIRIPRO, acquired across Central Sicily. To improve the seismic image we utilized the wave equation datuming technique, a process of upward or downward continuation of the wave-field between two arbitrarily shaped surfaces. Wave equation datuming was applied to move shots and receivers to a given datum plane, removing time shifts related to topography and to near-surface velocity variations. The datuming procedure largely contributed to attenuate ground roll, enhance higher frequencies, increase resolution and improve the signal/noise ratio. Processed data allow recognizing geometries of crust structures differentiating seismic facies and offering a direct image of ongoing tectonic setting within variable lithologies characterizing the crust of Central Sicily. Migrated sections underline distinctive features of Hyblean Plateau foreland and above all a crustal thinning towards the Caltanissetta trough, to the contact with a likely deep Permo-Triassic rifted basin or rather a zone of a continent to oceanic transition. Inhomogeneity and fragmentation of Sicily crust, with a distinct separation of Central Sicily basin from western and eastern blocks, appear to have guided the tectonic transport inside the Caltanissetta crustal scale syncline and the accumulation of allochthonous terrains with south and north-verging thrusts. Major tectonic stack operated on the construction of a wide anticline of the Maghrebian chain in northern Sicily. Sequential south-verging imbrications of deep elements forming the anticline core denote a crust wedge indenting foreland structures. Deformation processes involved multiple detachment planes down to decoupling levels located near crust/mantle transition, supporting a presence of high-density lenses beneath the chain, interrelated to a southwards push of Tyrrhenian mantle and asthenosphere.

  6. 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

  7. 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

  8. 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...

  9. Geothermic analysis of high temperature hydrothermal activities area in Western plateau of Sichuan province, China

    Science.gov (United States)

    Zhang, J.

    2016-12-01

    There is a high temperature hydrothermal activity area in the western plateau of Sichuan. More than 200 hot springs points have been found in the region, including 11 hot spring water temperature above local boiling point. Most of these distribute along Jinshajjiang fracture, Dege-Xiangcheng fracture, Ganzi-Litang fracture as well as Xianshuihe fracture, and form three high-temperature hydrothermal activity strips in the NW-SE direction. Using gravity, magnetic, seismic and helium isotope data, this paper analyzed the crust-mantle heat flow structure, crustal heat source distribution and water heating system. The results show that the geothermal activity mainly controlled by the "hot" crust. The ratio of crustal heat flow and surface heat flow is higher than 60%. In the high temperature hydrothermal activities area, there is lower S wave velocity zone with VsGeothermal water mainly reserve in the Triassic strata of the containing water good carbonate rocks, and in the intrusive granite which is along the fault zone. The thermal energy of Surface heat thermal activities mainly comes from the high-temperature hot source which is located in the middle and lower crust. Being in the deep crustal fracture, the groundwater infiltrated to the deep crust and absorbed heat, then, quickly got back to the surface and formed high hot springs.

  10. Magnetotelluric Investigations of the Yellowstone Caldera: Understanding the Emplacement of Crustal Magma Bodies

    Science.gov (United States)

    Gurrola, R. M.; Neal, B. A.; Bennington, N. L.; Cronin, R.; Fry, B.; Hart, L.; Imamura, N.; Kelbert, A.; Bowles-martinez, E.; Miller, D. J.; Scholz, K. J.; Schultz, A.

    2017-12-01

    Wideband magnetotellurics (MT) presents an ideal method for imaging conductive shallow magma bodies associated with contemporary Yellowstone-Snake River Plain (YSRP) magmatism. Particularly, how do these magma bodies accumulate in the mid to upper crust underlying the Yellowstone Caldera, and furthermore, what role do hydrothermal fluids play in their ascent? During the summer 2017 field season, two field teams from Oregon State University and the University of Wisconsin-Madison installed forty-four wideband MT stations within and around the caldera, and using data slated for joint 3-D inversion with existing seismic data, two 2-D vertical conductivity sections of the crust and upper mantle were constructed. These models, in turn, provide preliminary insight into the emplacement of crustal magma bodies and hydrothermal processes in the YSRP region.

  11. New constraints on the crustal structure beneath northern Tyrrhenian Sea

    Science.gov (United States)

    Levin, V. L.; Park, J. J.

    2009-12-01

    We present new seismological data on the seismic structure beneath the Tyrrhenian Sea between Corsica and the coast of Italy. Teleseismic receiver functions from two Tyrrhenian islands (Elba and Gorgona) identify clear P-to-S mode-converted waves from two distinct interfaces, at ~20 and ~45 km depth. Both interfaces are characterized by an increase of seismic wavespeed with depth. Using a summation of direct and multiply-reflected body waves within the P wave coda we estimate the mean ratio of compressional and shear wave speeds above the 45 km interface to be 1.75-1.80. Using reflectivity computations in 1D layered models we develop a model of seismic wavespeed distribution that yields synthetic seismograms very similar to those observed. We apply a Ps-multiple summation procedure to the synthetic waveforms to further verify the match between observed and predicted wavefields. The lower layer of our model, between 20 and 45 km, has Vp ~ 7.5 km/sec, a value that can be ascribed to either very fast crustal rocks or very slow upper mantle rocks. The Vp/Vs ratio is ~1.8 in this intermediate layer. On the basis of a well-constrained downward increase in seismic wave speed beneath this second layer, we interpret it as the magmatically reworked lower crust, a lithology that has been proposed to explain high-Vp layers in the crustal roots of island-arc terranes and volcanically altered continental margins, as well as lower-crustal high-Vp features sometimes seen beneath continental rifts. The presence of a thick layer of high-Vp, but crustal, lithology beneath the Tyrrhenian Sea differs considerably from previous estimates that interpreted the interface at ~20 km as the Moho. Our new interpretation obviates a need for a crustal thickness change of over 20 km at the crest of the Apennines orogen. We propose an alteration in the properties of the lower crust instead. We argue that ongoing convergent subduction of the Adriatic lithospehre is not required beneath northern

  12. Investigating Microbial Biofilm Formations on Crustal Rock Substrates

    Science.gov (United States)

    Weiser, M.; D'Angelo, T.; Carr, S. A.; Orcutt, B.

    2017-12-01

    Ocean crust hosts microbial life that, in some cases, alter the component rocks as a means of obtaining energy. Variations in crust lithology, included trace metal and mineral content, as well as the chemistry of the fluids circulating through them, provide substrates for some microbes to metabolize, leading to formation of biofilm community structures. Microbes have different parameters for the situations in which they will form biofilms, but they must have some source of energy in excess at the site of biofilm formation for them to become stationary and form the carbohydrate-rich structures connecting the cells to one another and the substrate. Generally, the requirements for microbes to form biofilms on crustal minerals are unclear. We designed two experiments to test (1) mineral preference and biofilm formation rates by natural seawater microbial communities, and (2) biofilm development as a function of phosphate availability for an organism isolated from subseafloor ocean crust. In Experiment 1, we observed that phyric basalt groundmass is preferentially colonized over aphyric basalt or metal sulfides in a shallow water and oxic seawater environment. In experiment 2, tests of the anaerobic heterotroph Thalassospira bacteria isolated from oceanic crustal fluids showed that they preferentially form biofilms, lose motility, and increase exponentially in number over time in higher-PO4 treatments (50 micromolar), including with phosphate-doped basalts, than in treatments with low phosphate concentrations (0.5 micromolar) often found in crustal fluids. These observations suggest phosphate as a main driver of biofilm formation in subsurface crust. Overall, these data suggest that the drivers of microbial biofilm formation on crustal substrates are selective to the substrate conditions, which has important implications for estimating the global biomass of life harbored in oceanic crust.

  13. The origin of methanethiol in midocean ridge hydrothermal fluids.

    Science.gov (United States)

    Reeves, Eoghan P; McDermott, Jill M; Seewald, Jeffrey S

    2014-04-15

    Simple alkyl thiols such as methanethiol (CH3SH) are widely speculated to form in seafloor hot spring fluids. Putative CH3SH synthesis by abiotic (nonbiological) reduction of inorganic carbon (CO2 or CO) has been invoked as an initiation reaction for the emergence of protometabolism and microbial life in primordial hydrothermal settings. Thiols are also presumptive ligands for hydrothermal trace metals and potential fuels for associated microbial communities. In an effort to constrain sources and sinks of CH3SH in seafloor hydrothermal systems, we determined for the first time its abundance in diverse hydrothermal fluids emanating from ultramafic, mafic, and sediment-covered midocean ridge settings. Our data demonstrate that the distribution of CH3SH is inconsistent with metastable equilibrium with inorganic carbon, indicating that production by abiotic carbon reduction is more limited than previously proposed. CH3SH concentrations are uniformly low (∼10(-8) M) in high-temperature fluids (>200 °C) from all unsedimented systems and, in many cases, suggestive of metastable equilibrium with CH4 instead. Associated low-temperature fluids (<200 °C) formed by admixing of seawater, however, are invariably enriched in CH3SH (up to ∼10(-6) M) along with NH4(+) and low-molecular-weight hydrocarbons relative to high-temperature source fluids, resembling our observations from a sediment-hosted system. This strongly implicates thermogenic interactions between upwelling fluids and microbial biomass or associated dissolved organic matter during subsurface mixing in crustal aquifers. Widespread thermal degradation of subsurface organic matter may be an important source of organic production in unsedimented hydrothermal systems and may influence microbial metabolic strategies in cooler near-seafloor and plume habitats.

  14. 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.

  15. Spatial and temporal zoning of hydrothermal alteration and mineralization in the Sossego iron oxide-copper-gold deposit, Carajás Mineral Province, Brazil: Paragenesis and stable isotope constraints

    Science.gov (United States)

    Monteiro, Lena V.S.; Xavier, R.P.; Carvalho, E.R.; Hitzman, M.W.; Johnson, C.A.; Souza, Filho C.R.; Torresi, I.

    2008-01-01

    The Sossego iron oxide–copper–gold deposit (245 Mt @ 1.1% Cu, 0.28 g/t Au) in the Carajás Mineral Province of Brazil consists of two major groups of orebodies (Pista–Sequeirinho–Baiano and Sossego–Curral) with distinct alteration assemblages that are separated from each other by a major high angle fault. The deposit is located along a regional WNW–ESE-striking shear zone that defines the contact between metavolcano–sedimentary units of the ∼2.76 Ga Itacaiúnas Supergroup and tonalitic to trondhjemitic gneisses and migmatites of the ∼2.8 Ga Xingu Complex. The deposit is hosted by granite, granophyric granite, gabbro, and felsic metavolcanic rocks. The Pista–Sequeirinho–Baiano orebodies have undergone regional sodic (albite–hematite) alteration and later sodic–calcic (actinolite-rich) alteration associated with the formation of massive magnetite–(apatite) bodies. Both these alteration assemblages display ductile to ductile–brittle fabrics. They are cut by spatially restricted zones of potassic (biotite and potassium feldspar) alteration that grades outward to chlorite-rich assemblages. The Sossego–Curral orebodies contain weakly developed early albitic alteration and very poorly developed subsequent calcic–sodic alteration. These orebodies contain well-developed potassic alteration assemblages that were formed during brittle deformation that resulted in the formation of breccia bodies. Breccia matrix commonly displays coarse mineral infill suggestive of growth into open space. Sulfides in both groups of deposits were precipitated first with potassic alteration and more importantly with a later assemblage of calcite–quartz–epidote–chlorite. In the Sequeirinho orebodies, sulfides range from undeformed to deformed; sulfides in the Sossego–Curral orebodies are undeformed. Very late, weakly mineralized hydrolytic alteration is present in the Sossego/Currral orebodies. The sulfide assemblage is dominated by chalcopyrite with

  16. 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

  17. NASA plan for international crustal dynamics studies

    Science.gov (United States)

    1979-01-01

    The international activities being planned as part of the NASA geodynamics program are described. Methods of studying the Earth's crustal movements and deformation characteristics are discussed. The significance of the eventual formalations of earthquake predictions methods is also discussed.

  18. 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

  19. Hydrothermally grown zeolite crystals

    International Nuclear Information System (INIS)

    Durrani, S.K.; Qureshi, A.H.; Hussain, M.A.; Qazi, N.K.

    2009-01-01

    The aluminium-deficient and ferrosilicate zeolite-type materials were synthesized by hydrothermal process at 150-170 degree C for various periods of time from the mixtures containing colloidal reactive silica, sodium aluminate, sodium hydroxide, iron nitrate and organic templates. Organic polycation templates were used as zeolite crystal shape modifiers to enhance relative growth rates. The template was almost completely removed from the zeolite specimens by calcination at 550 degree C for 8h in air. Simultaneous thermogravimetric (TG) and differential thermal analysis (DTA) was performed to study the removal of water molecules and the amount of organic template cations occluded inside the crystal pore of zeolite framework. The 12-13% weight loss in the range of (140-560 degree C) was associated with removal of the (C/sub 3/H/sub 7/)/sub 4/ N+ cation and water molecules. X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) techniques were employed to study the structure, morphology and surface features of hydrothermally grown aluminium-deficient and ferrosilicate zeolite-type crystals. In order to elucidate the mode of zeolite crystallization the crystallinity and unit cell parameters of the materials were determined by XRD, which are the function of Al and Fe contents of zeolites. (author)

  20. Crustal balance and crustal flux from shortening estimates in the Central Andes

    Science.gov (United States)

    Hindle, David; Kley, Jonas; Oncken, Onno; Sobolev, Stephan

    2005-01-01

    The Central Andes of South America form the second largest high elevation plateau on earth. Extreme elevations have formed on a noncollisional margin with abundant associated arc magmatism. It has long been thought that the crustal thickness necessary to support Andean topography was not accounted for by known crustal shortening alone. We show that this may in part be due to a two-dimensional treatment of the problem. A three-dimensional analysis of crustal shortening and crustal thickness shows that displacement of material towards the axis of the bend in the Central Andes has added a significant volume of crust not accounted for in previous comparisons. We find that present-day crustal thickness between 12°S and 25°S is accounted for (∼-10% to ∼+3%)with the same shortening estimates, and the same assumed initial crustal thickness as had previously led to the conclusion of a ∼25-35% deficit in shortening relative to volume of crustal material. We suggest that the present-day measured crustal thickness distribution may not match that predicted due to shortening, and substantial redistribution of crust may have occurred by both erosion and deposition at the surface and lower crustal flow in regions of the thermally weakened middle and lower crust.

  1. 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.

  2. Nanogeochemistry of hydrothermal magnetite

    Science.gov (United States)

    Deditius, Artur P.; Reich, Martin; Simon, Adam C.; Suvorova, Alexandra; Knipping, Jaayke; Roberts, Malcolm P.; Rubanov, Sergey; Dodd, Aaron; Saunders, Martin

    2018-06-01

    Magnetite from hydrothermal ore deposits can contain up to tens of thousands of parts per million (ppm) of elements such as Ti, Si, V, Al, Ca, Mg, Na, which tend to either structurally incorporate into growth and sector zones or form mineral micro- to nano-sized particles. Here, we report micro- to nano-structural and chemical data of hydrothermal magnetite from the Los Colorados iron oxide-apatite deposit in Chile, where magnetite displays both types of trace element incorporation. Three generations of magnetites (X-Z) were identified with concentrations of minor and trace elements that vary significantly: SiO2, from below detection limit (bdl) to 3.1 wt%; Al2O3, 0.3-2.3 wt%; CaO, bdl-0.9 wt%; MgO, 0.02-2.5 wt%; TiO2, 0.1-0.4 wt%; MnO, 0.04-0.2 wt%; Na2O, bdl-0.4 wt%; and K2O, bdl-0.4 wt%. An exception is V2O3, which is remarkably constant, ranging from 0.3 to 0.4 wt%. Six types of crystalline nanoparticles (NPs) were identified by means of transmission electron microscopy in the trace element-rich zones, which are each a few micrometres wide: (1) diopside, (2) clinoenstatite; (3) amphibole, (4) mica, (5) ulvöspinel, and (6) Ti-rich magnetite. In addition, Al-rich nanodomains, which contain 2-3 wt% of Al, occur within a single crystal of magnetite. The accumulation of NPs in the trace element-rich zones suggest that they form owing to supersaturation from a hydrothermal fluid, followed by entrapment during continuous growth of the magnetite surface. It is also concluded that mineral NPs promote exsolution of new phases from the mineral host, otherwise preserved as structurally bound trace elements. The presence of abundant mineral NPs in magnetite points to a complex incorporation of trace elements during growth, and provides a cautionary note on the interpretation of micron-scale chemical data of magnetite.

  3. 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.

  4. 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.

  5. 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.

  6. 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)

  7. 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

  8. 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...

  9. 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...

  10. 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

  11. Hydrothermal pretreatment of coal

    Energy Technology Data Exchange (ETDEWEB)

    Ross, D.S.

    1989-12-21

    We have examined changes in Argonne Premium samples of Wyodak coal following 30 min treatment in liquid water at autogenous pressures at 150{degrees}, 250{degrees}, and 350{degrees}C. In most runs the coal was initially dried at 60{degrees}C/1 torr/20 hr. The changes were monitored by pyrolysis field ionization mass spectrometry (py-FIMS) operating at 2.5{degrees}C/min from ambient to 500{degrees}C. We recorded the volatility patterns of the coal tars evolved over that temperature range, and in all cases the tar yields were 25%--30% of the starting coal on mass basis. There was essentially no change after the 150{degrees}C treatment. Small increases in volatility were seen following the 250{degrees}C treatment, but major effects were seen in the 350{degrees} work. The tar quantity remained unchanged; however, the volatility increased so the temperature of half volatility for the as-received coal of 400{degrees}C was reduced to 340{degrees}C. Control runs with no water showed some thermal effect, but the net effect from the presence of liquid water was clearly evident. The composition was unchanged after the 150{degrees} and 250{degrees}C treatments, but the 350{degrees} treatment brought about a 30% loss of oxygen. The change corresponded to loss of the elements of water, although loss of OH'' seemed to fit the analysis data somewhat better. The water loss takes place both in the presence and in the absence of added water, but it is noteworthy that the loss in the hydrothermal runs occurs at p(H{sub 2}O) = 160 atm. We conclude that the process must involve the dehydration solely of chemically bound elements of water, the dehydration of catechol is a specific, likely candidate.

  12. Nd isotopes and crustal growth rate

    International Nuclear Information System (INIS)

    Albarede, F.

    1988-01-01

    Sm/Nd isotopic constraints on crustal growth is discussed. In order to constrain Sm/Nd fractionation between continental crust and depleted mantle, an extensive data base of isotopic measurements (assumed to be adequately representative of continental crust) was compiled. The results imply that the evolution of depleted mantles was roughly linear, with no major discontinuities over the course of geologic time. This is different from other determinations of depleting mantle evolution, which show nonlinear behavior. The Sm/Nd evolution lines for continental crust and depleted mantle intersect between 3.8 to 4.0 Ga, which may indicate that the onset of continental growth was later than 4.5 Ga. A mathematical model is described, the results of which imply that time integrated crustal additions from the mantle are about 1.8 to 2.5 cu km/a, whereas crustal subtractions by sediment recycling are about 0.6 to 1.5 cu km/a. This results in a net time integrated crustal growth rate of about 1 cu km/a, which is similar to present day rates determined, for example, by Reymer and Schubert

  13. Crustal structure of the Khartoum Basin, Sudan

    CSIR Research Space (South Africa)

    El Tahir, N

    2013-05-01

    Full Text Available Basin ranges between 33 and 37 km, with an average of 35 km, and that the crustal Vp/Vs ratio ranges from 1.74 to 1.81, with an average of 1.78. From the joint inversion of receiver functions and Rayleigh wave group velocities,we obtained similar results...

  14. Estimating the Crustal Power Spectrum From Vector Magsat Data: Crustal Power Spectrum

    Science.gov (United States)

    Lowe, David A. J.; Parker, Robert L.; Purucker, Michael E.; Constable, Catherine G.

    2000-01-01

    The Earth's magnetic field can be subdivided into core and crustal components and we seek to characterize the crustal part through its spatial power spectrum (R(sub l)). We process vector Magsat data to isolate the crustal field and then invert power spectral densities of flight-local components along-track for R(sub l) following O'Brien et al. [1999]. Our model (LPPC) is accurate up to approximately degree 45 (lambda=900 km) - this is the resolution limit of our data and suggests that global crustal anomaly maps constructed from vector Magsat data should not contain features with wavelengths less than 900 km. We find continental power spectra to be greater than oceanic ones and attribute this to the relative thicknesses of continental and oceanic crust.

  15. Cool seafloor hydrothermal springs reveal global geochemical fluxes

    Science.gov (United States)

    Wheat, C. Geoffrey; Fisher, Andrew T.; McManus, James; Hulme, Samuel M.; Orcutt, Beth N.

    2017-10-01

    We present geochemical data from the first samples of spring fluids from Dorado Outcrop, a basaltic edifice on 23 M.y. old seafloor of the Cocos Plate, eastern Pacific Ocean. These samples were collected from the discharge of a cool hydrothermal system (CHS) on a ridge flank, where typical reaction temperatures in the volcanic crust are low (2-20 °C) and fluid residence times are short. Ridge-flank hydrothermal systems extract 25% of Earth's lithospheric heat, with a global discharge rate equivalent to that of Earth's river discharge to the ocean; CHSs comprise a significant fraction of this global flow. Upper crustal temperatures around Dorado Outcrop are ∼15 °C, the calculated residence time is V, U, Mg, phosphate, Si and Li are different. Applying these observed differences to calculated global CHS fluxes results in chemical fluxes for these ions that are ≥15% of riverine fluxes. Fluxes of K and B also may be significant, but better analytical resolution is required to confirm this result. Spring fluids also have ∼50% less dissolved oxygen (DO) than bottom seawater. Calculations of an analytical model suggest that the loss of DO occurs primarily (>80%) within the upper basaltic crust by biotic and/or abiotic consumption. This calculation demonstrates that permeable pathways within the upper crust can support oxic water-rock interactions for millions of years.

  16. Crustal-scale shear zones recording 400 m.y. of tectonic activity in the North Caribou greenstone belt, western Superior Province of Canada

    Science.gov (United States)

    Kalbfleisch, Netasha

    A series of crustal-scale shear zones demarcates the northern and eastern margins of the North Caribou greenstone belt (NCGB), proximal to a Mesoarchean terrane boundary in the core of the western Superior Province of Canada. The dominant deformation produced a pervasive steeply dipping fabric that trends broadly parallel to the doubly arcuate shape of the belt and was responsible for tight folding the banded iron formation host to Goldcorp's prolific gold deposit at Musselwhite mine. The shear zones in the North Caribou greenstone belt are of particular interest because of their ability to channel hydrothermal fluids with the potential to bear ore and cause alteration of the middle to shallow crust. Shear zones are commonly reactivated during subsequent tectonism, but exhibit a consistent and dominant dextral shear sense across the belt; fabric-forming micas and chlorite are generally Mg-rich. Although garnets samples from within the shear zones are dominantly almandine, they possess variable geochemical trends (HREEs of >2 orders of magnitude) and can be syn-, intra-, or post-tectonic in origin. In situ geochronological analysis of zircon (U-Pb) and monazite (total-Pb) in high strain rocks in and around the NCGB, interpreted in light of in situ geochemical analysis of garnet and fabric-forming micas and chlorite, reveals four relatively discrete events that span 400 million years. Metamorphism of the mid-crust was coeval with magmatism during docking of the Island Lake domain at c. 2.86 Ga and subsequent terrane accretion at the north and south margins of the North Caribou Superterrane from c. 2.75 to 2.71 Ga. Transpressive shear at c. 2.60 to 2.56 Ga and late re-activation of shear zones at c. 2.44 Ga produced a steeply-dipping pervasive fabric, and channeled fluids for late crystallization of garnet and monazite recorded in the Markop Lake deformation zone. These observations implicate a horizontal tectonic model similar to the modern eastern Pacific plate

  17. Constraints on the formation of the Martian crustal dichotomy from remnant crustal magnetism

    Science.gov (United States)

    Citron, Robert I.; Zhong, Shijie

    2012-12-01

    The Martian crustal dichotomy characterizing the topographic difference between the northern and southern hemispheres is one of the most important features on Mars. However, the formation mechanism for the dichotomy remains controversial with two competing proposals: exogenic (e.g., a giant impact) and endogenic (e.g., degree-1 mantle convection) mechanisms. Another important observation is the Martian crustal remnant magnetism, which shows a much stronger field in the southern hemisphere than in the northern hemisphere and also magnetic lineations. In this study, we examine how exogenic and endogenic mechanisms for the crustal dichotomy are constrained by the crustal remnant magnetism. Assuming that the dichotomy is caused by a giant impact in the northern hemisphere, we estimate that the average thickness of ejecta in the southern hemisphere is 20-25 km. While such a giant impact may cause crustal demagnetization in the northern hemisphere, we suggest that the impact could also demagnetize the southern hemisphere via ejecta thermal blanketing, impact demagnetization, and heat transfer from the hot layer of ejecta, thus posing a challenge for the giant impact model. We explore how the pattern of magnetic lineations relates to endogenic theories of dichotomy formation, specifically crustal production via degree-1 mantle convection. We observe that the pattern of lineations roughly corresponds to concentric circles about a single pole, and determine the pole for the concentric circles at 76.5° E and 84.5° S, which nearly overlaps with the centroid of the thickened crust in the southern hemisphere. We suggest that the crustal magnetization pattern, magnetic lineations, and crustal dichotomy (i.e., thickened crust in the highlands) can be explained by a simple endogenic process; one-plume convection causes melting and crustal production above the plume in the southern hemisphere, and strong crustal magnetization and magnetic lineations are formed in the southern

  18. 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.

  19. Crustal parameters in the Iberian Peninsula

    Science.gov (United States)

    Banda, E.

    1988-06-01

    The structure of the crust in the Iberian Peninsula has been investigated for the last 15 years by Spanish and Portuguese groups in close collaboration with other European institutions. The first experiments were carried out in Portugal (Mueller et al., 1973) with the aim of investigating the crustal structure of the Hercynian belt in the southwest corner of the Iberian peninsula. Other experiments have been subsequently realized to study different aspects of the crust in various regions of Portugal. In Spain the main effort has been focused in Alpine areas, with the first experiments in the Alboran Sea and the Betic Cordilleras (Working Group for Deep Seismic Sounding in Spain, 1974-1975, 1977; Working Group for Deep Seismic Sounding in the Alboran Sea, 1974-1975, 1978). Follow-up experiments until 1981 completed the work in the Betic Cordillera. Extensive experiments were carried out in the Pyrenees in 1978. Further surveys covered the Balearic Islands in 1976, the Valencia Trough in 1976 and 1983, and the Celtiberian Chain (or Iberic system) in 1981. The Hercynian belt has only been studied in detail in the northwest corner of Spain in 1982, with smaller studies in the central Iberian Massif in 1976 and 1986. Mostaanpour (1984) has compiled some crustal parameters (crustal thickness, average crustal velocity and Pn velocity) for western Europe. Meanwhile, more complete data are available for the Iberian Peninsula. The results presented here were derived from a large number of seismic refraction experiments which have been carried out mostly along or close to coastal areas of the Iberian Peninsula. Offshore explosions of various sizes were used as the energy source in most cases, in addition to some quarry blasts. Unfortunately this leaves most of the inner part of the Iberian Peninsula unsurveyed. Our purpose is to summarize some of the crustal parameters obtained so far and to detail the appropriate literature for the interested reader.

  20. Crustal processes of the Mid-Ocean Ridge

    Science.gov (United States)

    Ballard, Richard D.; Craig, H.; Edmond, J.; Einaudi, M.; Holcomb, R.; Holland, H.D.; Hopson, C.A.; Luyendyk, B.P.; Macdonald, K.; Morton, J.; Orcutt, J.; Sleep, N.

    1981-01-01

    Independent geological and geophysical investigations of the Mid-Ocean Ridge system have begun to focus on the nature of the magma chamber system underlying its central axis. Thermal models predict the existence of a steady-state chamber beneath a thin crustal lid ranging in thickness from 2 to 13 kilometers. The only aspect of the system that these models fail to account for is the extremely slow spreading rates. Seismological studies reveal the existence of a low-velocity zone beneath segments of the East Pacific Rise, which is thought to correspond to a chamber system having a half-width of approximately 5 to 10 kilometers. These estimates compare favorably with those derived separately through petrological investigations of deep-sea drilling results, various sampling programs, and field and laboratory studies of ophiolites. The chamber is thought to be wing-shaped and to remain continuously open; it is thought to be fed from the center while simultaneously solidifying at the sides as spreading carries the two halves apart. Progressive fractionation occurs by crystal settling coupled with repeated replenishment and magma mixing in an open steady-state system. Near-bottom studies reveal that the zone of extrusion above the chamber is narrow, but its eruptive history is cyclic in nature, in conflict with the predictions of a steady-state model. On-bottom gravity data at 21 ??N on the East Pacific Rise reveal a negative gravity anomaly that may be related to the uppermost part of the chamber. The anomaly is only 2 kilometers wide and 1 kilometer below the sea floor. This feature may be associated with a short-term upper magma reservoir. The cyclic volcanic activity is directly related to the active phase of hydrothermal circulation responsible for the observed negative thermal anomaly. The volume of water associated with this circulation is equal to the entire ocean volume passing through the accretion zone approximately every 8 million years. This is about 0

  1. Crustal processes of the mid-ocean ridge.

    Science.gov (United States)

    1981-07-03

    Independent geological and geophysical investigations of the Mid-Ocean Ridge system have begun to focus on the nature of the magma chamber system underlying its central axis. Thermal models predict the existence of a steady-state chamber beneath a thin crustal lid ranging in thickness from 2 to 13 kilometers. The only aspect of the system that these models fail to account for is the extremely slow spreading rates. Seismological studies reveal the existence of a low-velocity zone beneath segments of the East Pacific Rise, which is thought to correspond to a chamber system having a half-width of approximately 5 to 10 kilometers. These estimates compare favorably with those derived separately through petrological investigations of deep-sea drilling results, various sampling programs, and field and laboratory studies of ophiolites. The chamber is thought to be wing-shaped and to remain continuously open; it is thought to be fed from the center while simultaneously solidifying at the sides as spreading carries the two halves apart. Progressive fractionation occurs by crystal settling coupled with repeated replenishment and magma mixing in an open steady-state system. Near-bottom studies reveal that the zone of extrusion above the chamber is narrow, but its eruptive history is cyclic in nature, in conflict with the predictions of a steady-state model. On-bottom gravity data at 21 degrees N on the East Pacific Rise reveal a negative gravity anomaly that may be related to the uppermost part of the chamber. The anomaly is only 2 kilometers wide and 1 kilometer below the sea floor. This feature may be associated with a short-term upper magma reservoir. The cyclic volcanic activity is directly related to the active phase of hydrothermal circulation responsible for the observed negative thermal anomaly. The volume of water associated with this circulation is equal to the entire ocean volume passing through the accretion zone approximately every 8 million years. This is about 0

  2. 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.

  3. Hydrothermal Cold Sintering

    Science.gov (United States)

    Kang, Xiaoyu

    Solid state sintering transforms particle compact to a physically robust and dense polycrystalline monolith driven by reduction of surface energy and curvature. Since bulk diffusion is required for neck formation and pore elimination, sintering temperature about 2/3 of melting point is needed. It thus places limitations for materials synthesis and integration, and contributes to significant energy consumption in ceramic processing. Furthermore, since surface transport requires lower temperature than bulk processes, grain growth is often rapid and can be undesired for physical properties. For these reasons, several techniques have been developed including Liquid Phase Sintering (LPS), Hot Pressing (HP) and Field Assisted Sintering Technique (FAST), which introduce either viscous melt, external pressure or electric field to speed up densification rates at lower temperature. However, because of their inherent reliability on bulk diffusion, temperatures required are often too high for integrating polymers and non-noble metals. Reduction of sintering temperature below 400 °C would require a different densification mechanism that is based on surface transport with external forces to drive volume shrinkage. Densification method combining uniaxial pressure and solution under hydrothermal condition was first demonstrated by Kanahara's group at Kochi University in 1986 and was brought to our attention by the work of Kahari, etc, from University of Oulu on densification of Li2MoO 4 in 2015. This relatively new process showed promising ultra-low densification temperature below 300 °C, however little was known about its fundamental mechanism and scope of applications, which became the main focus of this dissertation. In this work, a uniaxial hydraulic press, a standard stainless steel 1/2 inch diameter die with heating band were utilized in densifying metal oxides. Applied pressure and sintering temperature were between 100 MPa and 700 MPa and from room temperature to 300

  4. 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

  5. A hydrogeological conceptual model of the Suio hydrothermal area (central Italy)

    Science.gov (United States)

    Saroli, Michele; Lancia, Michele; Albano, Matteo; Casale, Anna; Giovinco, Gaspare; Petitta, Marco; Zarlenga, Francesco; dell'Isola, Marco

    2017-09-01

    A hydrogeological conceptual model has been developed that describes the hydrothermal system of Suio Terme (central Italy). The studied area is located along the peri-Tyrrhenian zone of the central Apennines, between the Mesozoic and Cenozoic carbonate platform sequences of the Aurunci Mountains and the volcanic sequences of the Roccamonfina. A multi-disciplinary approach was followed, using new hydrogeological surveys, the interpretation of stratigraphic logs of boreholes and water wells, and geophysical data—seismic sections, shear-wave velocity (Vs) crustal model and gravimetric model. The collected information allowed for construction of a conceptual hydrogeological model and characterization of the hydrothermal system. The Suio hydrothermal system is strongly influenced by the Eastern Aurunci hydrostructure. Along the southeastern side, the top of the hydrostructure sinks to -1,000 m relative to sea level via a series of normal faults which give origin to the Garigliano graben. Geological and hydrogeological data strongly suggest the propagation and mixing of hot fluids, with cold waters coming from the shallow karst circuit. The aquitard distribution, the normal tectonic displacements and the fracturing of the karst hydrostructure strongly influence the hydrothermal basin. Carbon dioxide and other gasses play a key role in the whole circuit, facilitating the development of the hydrothermal system. The current level of knowledge suggests that the origin of the Suio hydrothermalism is the result of interaction between the carbonate reservoir of the Eastern Aurunci Mountains and the hot and deep crust of this peri-Tyrrhenian sector, where the Roccamonfina volcano represents the shallowest expression.

  6. Crustal-scale recycling in caldera complexes and rift zones along the Yellowstone hotspot track: O and Hf isotopic evidence in diverse zircons from voluminous rhyolites of the Picabo volcanic field, Idaho

    Science.gov (United States)

    Drew, Dana L.; Bindeman, Ilya N.; Watts, Kathryn E.; Schmitt, Axel K.; Fu, Bin; McCurry, Michael

    2013-01-01

    Rhyolites of the Picabo volcanic field (10.4–6.6 Ma) in eastern Idaho are preserved as thick ignimbrites and lavas along the margins of the Snake River Plain (SRP), and within a deep (>3 km) borehole near the central axis of the Yellowstone hotspot track. In this study we present new O and Hf isotope data and U–Pb geochronology for individual zircons, O isotope data for major phenocrysts (quartz, plagioclase, and pyroxene), whole rock Sr and Nd isotope ratios, and whole rock geochemistry for a suite of Picabo rhyolites. We synthesize our new datasets with published Ar–Ar geochronology to establish the eruptive framework of the Picabo volcanic field, and interpret its petrogenetic history in the context of other well-studied caldera complexes in the SRP. Caldera complex evolution at Picabo began with eruption of the 10.44±0.27 Ma (U–Pb) Tuff of Arbon Valley (TAV), a chemically zoned and normal-δ18O (δ18O magma=7.9‰) unit with high, zoned 87Sr/86Sri (0.71488–0.72520), and low-εNd(0) (−18) and εHf(0) (−28). The TAV and an associated post caldera lava flow possess the lowest εNd(0) (−23), indicating ∼40–60% derivation from the Archean upper crust. Normal-δ18O rhyolites were followed by a series of lower-δ18O eruptions with more typical (lower crustal) Sr–Nd–Hf isotope ratios and whole rock chemistry. The voluminous 8.25±0.26 Ma West Pocatello rhyolite has the lowest δ18O value (δ18Omelt=3.3‰), and we correlate it to a 1,000 m thick intracaldera tuff present in the INEL-1 borehole (with published zircon ages 8.04–8.35 Ma, and similarly low-δ18O zircon values). The significant (4–5‰) decrease in magmatic-δ18O values in Picabo rhyolites is accompanied by an increase in zircon δ18O heterogeneity from ∼1‰ variation in the TAV to >5‰ variation in the late-stage low-δ18O rhyolites, a trend similar to what is characteristic of Heise and Yellowstone, and which indicates remelting of variably hydrothermally altered tuffs

  7. MAGNETAR FIELD EVOLUTION AND CRUSTAL PLASTICITY

    International Nuclear Information System (INIS)

    Lander, S. K.

    2016-01-01

    The activity of magnetars is believed to be powered by colossal magnetic energy reservoirs. We sketch an evolutionary picture in which internal field evolution in magnetars generates a twisted corona, from which energy may be released suddenly in a single giant flare, or more gradually through smaller outbursts and persistent emission. Given the ages of magnetars and the energy of their giant flares, we suggest that their evolution is driven by a novel mechanism: magnetic flux transport/decay due to persistent plastic flow in the crust, which would invalidate the common assumption that the crustal lattice is static and evolves only under Hall drift and Ohmic decay. We estimate the field strength required to induce plastic flow as a function of crustal depth, and the viscosity of the plastic phase. The star’s superconducting core may also play a role in magnetar field evolution, depending on the star’s spindown history and how rotational vortices and magnetic fluxtubes interact.

  8. 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.

  9. Hydrothermal precipitation of artificial violarite

    DEFF Research Database (Denmark)

    Jørgensen, W. H.; Toftlund, H.; Warner, T. E.

    2012-01-01

    The nonstoichiometric nickel-ore mineral, violarite, (Ni,Fe)3S4 was prepared as a phase-pure fine powder by a comparatively quick hydrothermal method from an aqueous solution of iron(II) acetate, nickel(II) acetate and DL-penicillamine in an autoclave at 130 °C for 45 h. Powder-XRD showed that th...

  10. Crustal Structure beneath Alaska from Receiver Functions

    Science.gov (United States)

    Zhang, Y.; Li, A.

    2017-12-01

    The crustal structure in Alaska has not been well resolved due to the remote nature of much of the state. The USArray Transportable Array (TA), which is operating in Alaska and northwestern Canada, significantly increases the coverage of broadband seismic stations in the region and allows for a more comprehensive study of the crust. We have analyzed P-receiver functions from earthquake data recorded by 76 stations of the TA and AK networks. Both common conversion point (CCP) and H-K methods are used to estimate the mean crustal thickness. The results from the CCP stacking method show that the Denali fault marks a sharp transition from thick crust in the south to thin crust in the north. The thickest crust up to 52 km is located in the St. Elias Range, which has been formed by oblique collision between the Yakutat microplate and North America. A thick crust of 48 km is also observed beneath the eastern Alaska Range. These observations suggest that high topography in Alaska is largely compensated by the thick crust root. The Moho depth ranges from 28 km to 35 km beneath the northern lowlands and increases to 40-45 km under the Books Range. The preliminary crustal thickness from the H-K method generally agrees with that from the CCP stacking with thicker crust beneath high mountain ranges and thinner crust beneath lowlands and basins. However, the offshore part is not well constrained due to the limited coverage of stations. The mean Vp/Vs ratio is around 1.7 in the Yukon-Tanana terrane and central-northern Alaska. The ratio is about 1.9 in central and southern Alaska with higher values at the Alaska Range, Wrangell Mountains, and St. Elias Range. Further data analyses are needed for obtaining more details of the crustal structure in Alaska to decipher the origin and development of different tectonic terranes.

  11. Magmatic-hydrothermal fluid evolution of the Dalli porphyry Cu-Au deposit; using Amphibole and Plagioclas mineral chemistry

    Directory of Open Access Journals (Sweden)

    Houshang Pourkaseb

    2017-07-01

    -Tethys, during compression and crustal shortening favourable conditions were provided for mixing of mantle melts with crustal materials. The geothermobaromerty calculations using amphibole and plagioclase minerals indicate conditions of 777 - 850 oC and 1-4 Kbar, representing magmatic stage of Dalli intrusions. Also, amphibole minerals are characterized by Fetot/Fetot + Mg > 0.3 and AlIV > 0.7 which reveal the presence of primary oxidative magma in the Dalli porphyry Cu-Au deposit. Oxidative conditions seem to have prevailed during the onset of the hydrothermal stage of the Dalli porphyry deposit. This is because it has been confirmed by laser Raman spectroscopy analyses that the most primitive quartz veins in the potassic alteration of the Dalli deposit are characterized by the presence of anhydrite and hematite minerals (see Zarasvandi et al., 2015b. Also, microthermometry results on the most primitive barren quartz veins in potassic alteration represent temperatures as high as 620oC which indicate the beginning temperature of hydrothermal conditions. Acknowledgements Many thanks are due to the office of vice-chancellor of the Shahid Chamran University of Ahvaz for valuable information concerning the field work and sampling. References Ridolfi, F., Renzulli, A. and Puerini, M., 2010. Stability and chemical equilibrium of amphibole in calc-alkaline magmas: An overview, new thermobarometric formulations and application to subduction-related volcanoes. Contributions to Mineralogy and Petrology, 160(1: 45–66. Sillitoe, R.H., 2010. Porphyry Copper Systems. Economic Geology, 105(1: 3-41. Titley, S.R. and Beane, R.E., 1981. Porphyry copper deposits. Part 1. Geologic Setting, Petrology, and Tectogenesis. In: J.W. Hedenquist, J.F.H. Thompson, R.J. Goldfarb and J.P. Richards (Editors, Economic Geologists, 75th Anniversary Volume. Society of Economic Geologists, U.S.A, pp. 214-234. Wang, R., Richards, J.P., Hou, Z.Q., Yang, Z.M., Gou, Z.B. and DuFrane, A., 2014. Increasing Magmatic

  12. 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

  13. Chemical cycles and health risks of some crustal nuclides

    International Nuclear Information System (INIS)

    McKone, T.E.

    1981-01-01

    This dissertation describes and utilizes an approach for assessing long term health risks due to dispersion of naturally occurring radionuclide series and chemical toxins by normal and altered landscape chemical cycles. In particular, the health risks resulting from geochemical mobilizations of arsenic, lead, uranium and radium are considered. Based on a review of toxic waste hazard-measures and risk assessment studies, a general expression is developed for quantifying health risks imposed by the introduction of toxic materials to components of the total environment. This general measure deals with long term interactions within and between the internal human environment and the external biogeochemical environment. Health hazards are expressed as dose factors which convert environmental concentrations into a corresponding dose field (organ doses in rad for radionuclides; daily intake for toxic elements). The dose field is translated into population health risk expressed as lifetime cancer risk for carcinogens and average blood levels for other toxins. The landscape cell (or prism) is presented as a tool for visualizing and mapping toxic material cycles near the crustal surface. The overall process is incorporated in the GEOTOX code which is a geochemical systems model for describing the dynamics of crustal toxins within a landscape and the resulting health risks. GEOTOX is used to investigate the response of regional landscapes to increased soil and rock inventories of 238 U, 226 Ra, arsenic and lead. It is found that each decay series of element imposes a hazard by its behavior in the total environment that can not be quantified by a similar measure of toxicity

  14. Origin of sulfur and crustal recycling of copper in polymetallic (Cu-Au-Co-Bi-U ± Ag) iron-oxide-dominated systems of the Great Bear Magmatic Zone, NWT, Canada

    Science.gov (United States)

    Acosta-Góngora, P.; Gleeson, S. A.; Samson, I. M.; Corriveau, L.; Ootes, L.; Jackson, S. E.; Taylor, B. E.; Girard, I.

    2018-03-01

    The Great Bear Magmatic Zone, in northwest Canada, contains numerous polymetallic mineral occurrences, prospects, and deposits of the iron oxide copper-gold deposit (IOCG) family. The mineralization is hosted by the Treasure Lake Group and igneous rocks of the Great Bear arc and was deposited concomitantly with the arc magmatism (ca. 1.88 to 1.87 Ga). In situ δ 34S ( n = 48) and δ 65Cu ( n = 79) analyses were carried out on ore-related sulfides from a number of these systems. The δ 34S values mainly vary between 0 and +5‰, consistent with derivation of sulfur from the mantle. Lower δ 34S values (-7.7 to +1.4‰) from the Sue-Dianne breccia may indicate SO2 disproportionation of a magmatic hydrothermal fluid. The δ 65Cu values vary between -1.2 and -0.3‰, and are lower than the igneous δ 65Cu range of values (0.0 ± 0.27‰). The S and Cu isotopic data are decoupled, which suggests that Cu (and possibly some S) was dissolved and remobilized from supracrustal rocks during early stages of alteration (e.g., sodic alteration) and then precipitated by lower temperature, more oxidizing fluids (e.g., Ca-Fe-K alteration). A limited fluid inclusion dataset and δ 13C and δ 18O values are also presented. The δ 18Ofluid values are consistent with a magmatic origin or a host-rock equilibrated meteoric water source, whereas the δ 13Cfluid values support a marine carbonate source. Combined, the S and Cu isotopic data indicate that while the emplacement of the Great Bear magmatic bodies may have driven fluid convection and may be the source of fluids and sulfur, metals such as Cu could have been recycled from crustal sources.

  15. Crustal basement controls granitoid magmatism, and implications for generation of continental crust in subduction zones: A Sr-Nd-Hf-O isotopic study from the Paleozoic Tongbai orogen, central China

    Science.gov (United States)

    Wang, Hao; Wu, Yuan-Bao; Yang, Jin-Hui; Qin, Zheng-Wei; Duan, Rui-Chun; Zhou, Lian; Yang, Sai-Hong

    2017-06-01

    Ascertaining the petrogenesis of granitoid rocks in subduction zones holds the key for understanding the processes of how continental crust is produced. The synchronous Taoyuan and Huanggang plutons occur in two different geological units of the Paleozoic Tongbai orogen of central China. They provide an optimal opportunity for a study to address the role of the crustal basement in generating voluminous granitoid magmatism in subduction zones. The Taoyuan and Huanggang plutons have identical U-Pb zircon crystallization ages of 440-444 Ma, which are temporally related to northward subduction of the Paleotethyan Ocean. The Taoyuan samples show high SiO2 (73.36-79.16%) and low Al2O3 (12.00-13.45%) contents, Mg numbers (20.6-38.2), and Sr/Y (2.04-10.1) and (La/Yb)N (2.34-7.32) ratios with negative Eu anomalies (Eu/Eu* = 0.33-0.93). They yielded positive εNd(t) (+ 3.0 to + 6.7) and εHf(t) (+ 11.8 to + 13.2) values, elevated initial Sr isotopic ratios (0.7040-0.7057) and relatively low zircon δ18O values of 4.62-5.39‰. These suggest that they were produced through partial melting of hydrothermally altered lower crust of the accreted Erlangping oceanic arc. In contrast, the Huanggang samples exhibit variable whole-rock geochemical and isotopic compositions with SiO2 contents of 57.01-64.42 wt.%, initial Sr isotopic ratios of 0.7065-0.7078, and εNd(t) values of - 5.7 to - 9.4. Additionally, they have high zircon δ18O values of 7.57-8.45‰ and strongly negative zircon εHf(t) values of - 14.4 to - 10.5. They were suggested to have been mainly derived from ancient continental crust of the Kuanping crustal unit with the addition of 20-40% juvenile, mantle-derived material. Accordingly, the granitoids in both oceanic and continental arcs are likely to be mainly derived from intracrustal melting of their crustal basement. It is revealed by the Huanggang pluton that little net continental crust growth occurs in continental arcs, and addition of new volume of continental

  16. 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.

  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. Hydrothermal synthesis of nanostructured titania

    International Nuclear Information System (INIS)

    Yoshito, Walter Kenji; Ferreira, Nildemar A.M.; Rumbao, Ana Carolina S. Coutinho; Lazar, Dolores R.R.; Ussui, Valter

    2009-01-01

    Titania ceramics have many applications due to its surface properties and, recently, its nanostructured compounds, prepared by hydrothermal treatments, have been described to improve these properties. In this work, commercial titanium dioxide was treated with 10% sodium hydroxide solution in a pressurized reactor at 150°C for 24 hours under vigorous stirring and then washed following two different procedures. The first one consisted of washing with water and ethanol and the second with water and hydrochloric acid solution (1%). Resulting powders were characterized by X-ray diffraction, N 2 gas adsorption and field emission gun scanning and transmission electronic microscopy. Results showed that from an original starting material with mainly rutile phase, both anatase and H 2 Ti 3 O 7 phase could be identified after the hydrothermal treatment. Surface area of powders presented a notable increase of one order of magnitude and micrographs showed a rearrangement on the microstructure of powders. (author)

  19. Zinc stannate nanostructures: hydrothermal synthesis

    International Nuclear Information System (INIS)

    Baruah, Sunandan; Dutta, Joydeep

    2011-01-01

    Nanostructured binary semiconducting metal oxides have received much attention in the last decade owing to their unique properties rendering them suitable for a wide range of applications. In the quest to further improve the physical and chemical properties, an interest in ternary complex oxides has become noticeable in recent times. Zinc stannate or zinc tin oxide (ZTO) is a class of ternary oxides that are known for their stable properties under extreme conditions, higher electron mobility compared to its binary counterparts and other interesting optical properties. The material is thus ideal for applications from solar cells and sensors to photocatalysts. Among the different methods of synthesizing ZTO nanostructures, the hydrothermal method is an attractive green process that is carried out at low temperatures. In this review, we summarize the conditions leading to the growth of different ZTO nanostructures using the hydrothermal method and delve into a few of its applications reported in the literature. (topical review)

  20. Hydrothermal synthesis of nanostructured titania

    International Nuclear Information System (INIS)

    Yoshito, W.K.; Ferreira, N.A.M.; Lazar, D.R.R.; Ussui, V.; Rumbao, A.C.S.

    2011-01-01

    Titania ceramics have many applications due to its surface properties and, recently, its nanostructured compounds, prepared by hydrothermal treatments, have been described to improve these properties. In this work, commercial titanium dioxide was treated with 10% sodium hydroxide solution in a pressurized reactor at 150 deg C for 24 hours under vigorous stirring and then washed following two different procedures. The first one consisted of washing with water and ethanol and the second with water and hydrochloric acid solution (1%). Resulting powders were characterized by X-ray diffraction, N 2 gas adsorption and field emission gun scanning and transmission electronic microscopy. Results showed that from an original starting material with mainly rutile phase, both anatase and H 2 Ti 3 O 7 phase could be identified after the hydrothermal treatment. Surface area of powders presented a notable increase of one order of magnitude and micrographs showed a rearrangement on the microstructure of powders. (author)

  1. Modes of continental extension in a crustal wedge

    KAUST Repository

    Wu, Guangliang

    2015-07-01

    © 2015 Elsevier B.V. We ran numerical experiments of the extension of a crustal wedge as an approximation to extension in an orogenic belt or a continental margin. We study the effects of the strength of the lower crust and of a weak mid-crustal shear zone on the resulting extension styles. A weak mid-crustal shear zone effectively decouples upper crustal extension from lower crustal flow. Without the mid-crustal shear zone, the degree of coupling between the upper and the lower crust increases and extension of the whole crust tends to focus on the thickest part of the wedge. We identify three distinct modes of extension determined by the strength of the lower crust, which are characterized by 1) localized, asymmetric crustal exhumation in a single massif when the lower crust is weak, 2) the formation of rolling-hinge normal faults and the exhumation of lower crust in multiple core complexes with an intermediate strength lower crust, and 3) distributed domino faulting over the weak mid-crustal shear zone when the lower crust is strong. A frictionally stronger mid-crustal shear zone does not change the overall model behaviors but extension occurred over multiple rolling-hinges. The 3 modes of extension share characteristics similar to geological models proposed to explain the formation of metamorphic core complexes: 1) the crustal flow model for the weak lower crust, 2) the rolling-hinge and crustal flow models when the lower crust is intermediate and 3) the flexural uplift model when the lower crust is strong. Finally we show that the intensity of decoupling between the far field extension and lower crustal flow driven by the regional pressure gradient in the wedge control the overall style of extension in the models.

  2. Modes of continental extension in a crustal wedge

    KAUST Repository

    Wu, Guangliang; Lavier, Luc L.; Choi, Eunseo

    2015-01-01

    © 2015 Elsevier B.V. We ran numerical experiments of the extension of a crustal wedge as an approximation to extension in an orogenic belt or a continental margin. We study the effects of the strength of the lower crust and of a weak mid-crustal shear zone on the resulting extension styles. A weak mid-crustal shear zone effectively decouples upper crustal extension from lower crustal flow. Without the mid-crustal shear zone, the degree of coupling between the upper and the lower crust increases and extension of the whole crust tends to focus on the thickest part of the wedge. We identify three distinct modes of extension determined by the strength of the lower crust, which are characterized by 1) localized, asymmetric crustal exhumation in a single massif when the lower crust is weak, 2) the formation of rolling-hinge normal faults and the exhumation of lower crust in multiple core complexes with an intermediate strength lower crust, and 3) distributed domino faulting over the weak mid-crustal shear zone when the lower crust is strong. A frictionally stronger mid-crustal shear zone does not change the overall model behaviors but extension occurred over multiple rolling-hinges. The 3 modes of extension share characteristics similar to geological models proposed to explain the formation of metamorphic core complexes: 1) the crustal flow model for the weak lower crust, 2) the rolling-hinge and crustal flow models when the lower crust is intermediate and 3) the flexural uplift model when the lower crust is strong. Finally we show that the intensity of decoupling between the far field extension and lower crustal flow driven by the regional pressure gradient in the wedge control the overall style of extension in the models.

  3. Vision in hydrothermal vent shrimp.

    OpenAIRE

    Chamberlain, S C

    2000-01-01

    Bresiliid shrimp from hydrothermal vents on the Mid-Atlantic Ridge have non-imaging eyes adapted for photodetection in light environments of very low intensity. Comparison of retinal structures between both vent shrimp and surface-dwelling shrimp with imaging eyes, and between juvenile and adult vent shrimp, suggests that vent shrimp have evolved from ancestors that lived in a light environment with bright cyclic lighting. Whether the vent shrimp live in swarms and have large dorsal eyes or l...

  4. Hydrothermal alteration zones and present reservoir conditions: an approach to define production zones at the eastern portion of the Cerro Prieto geothermal field, BC; Zonas de alteracion hidrotermal y condiciones actuales del yacimiento: un enfoque para determinar zonas productoras al oriente del campo geotermico de Cerro Prieto, BC

    Energy Technology Data Exchange (ETDEWEB)

    Camacho Hernandez, Juan Manuel [Comision Federal de Electricidad, Residencia General de Cerro Prieto, Mexicali, Baja California (Mexico)]. E-mail: juan.camacho02@cfe.gob.mx

    2009-07-15

    Geological factors are as essential for locating new wells as they are for defining the production zones of these wells. At the Cerro Prieto geothermal field (CGCP), one of the most important geological factors is identification of the hydrothermal alteration zones (ZAH). These are divided into silica and epidote mineralogical zones (ZMSE), without CaCO{sub 3}, and silica and epidote mineralogical transition zones (ZTMSE), with CaCO{sub 3}. It has been observed that the continuous variation of reservoir thermodynamic conditions (temperature, pressure and enthalpy) is due mainly to the exploitation of geothermal resources. The presence of new thermodynamic conditions recorded at the reservoir has led to the re-location of production wells originally located during the drilling campaign of 2004 to 2006. At the geological sections on the eastern part of the CGCP, adjustments made to the well completions lie on the limits between the ZMSE and ZTMSE zones. In turn, this is related to the current, superior, thermodynamic reservoir conditions. Based on this, a new geologic approach is proposed to define possible production zones for new wells, relating the ZAH zones to current thermodynamic reservoir conditions. [Spanish] Los factores geologicos son determinantes, tanto para establecer nuevos sitios de perforacion como para determinar el intervalo productor de un pozo nuevo. En el campo geotermico de Cerro Prieto (CGCP) una de los factores mas importantes es la determinacion de las zonas de alteracion hidrotermal (ZAH) que se dividen en dos: zona mineralogica de silice y epidota (ZMSE), sin presencia de CaCO{sub 3}, y zona de transicion mineralogica de silice y epidota (ZTMSE), con presencia de CaCO{sub 3}. Por otra parte, tambien se ha constatado que la continua variacion de las condiciones termodinamicas del yacimiento (temperatura, presion y entalpia) es originada en buena medida por la explotacion del recurso geotermico. La ocurrencia de nuevas condiciones

  5. 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

  6. 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

  7. Crustal Growth: In Defense of the Dogma

    Science.gov (United States)

    Albarede, F.; Blichert-Toft, J.; Guitreau, M.

    2012-12-01

    Plate tectonics was not even in its teens when Armstrong suggested that mantle and crust have interacted at steady-state over Earth's history. With the help of new geochemical tools and large-scale compilations, the concept of steady-state crust (as opposed to continuous crustal growth) is being revived with the implications that the equivalent of several volumes of present-day crust (PDCV) may have been subducted through geological times. Here we argue --or recall-- that four different lines of evidence invalidate this model. (i) The subduction filter must be particularly efficient for argon, even more so than for LILE and most other volatile elements. Atmosphere collects 40Ar degassed from both the extant crust and the crust dragged down at subduction zones over geological time. Regardless of the residence time of the crust at the surface, the amount of atmospheric 40Ar limits subduction of continental crust into the mantle to < 30% of the PDCV [1]. (ii) EM II, the only component that undoubtedly represents subducted continental crust in oceanic basalts, is extremely uncommon. (iii) Crustal age histograms are irrepressibly episodic. It has been argued that erosion selectively removes the crust with the elusive ages [2]. Ages of detrital zircons, which in the selective erosion conjecture should fill the voids, do not support this view [3]. Episodicity is difficult to reconcile with a continental protolith isolated by the common geological processes working either at mid-ocean ridges or subduction zones. A role may be recognized for Wilson cycles, if they can be shown to have prevailed for the entire history of the Earth. Geochemistry demonstrates that superplume material makes up the crustal protolith of all the major juvenile provinces. (iv) The residence time in the mantle of the elements distinctive of the crust is similar to the age of the Earth or even longer [4]. Continental crust finds its source in the instabilities of the lower mantle and the irreversible

  8. 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)

  9. Crustal permeability: Introduction to the special issue

    Science.gov (United States)

    Ingebritsen, Steven E.; Gleeson, Tom

    2015-01-01

    The topic of crustal permeability is of broad interest in light of the controlling effect of permeability on diverse geologic processes and also timely in light of the practical challenges associated with emerging technologies such as hydraulic fracturing for oil and gas production (‘fracking’), enhanced geothermal systems, and geologic carbon sequestration. This special issue of Geofluids is also motivated by the historical dichotomy between the hydrogeologic concept of permeability as a static material property that exerts control on fluid flow and the perspective of economic geologists, geophysicists, and crustal petrologists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. Issues associated with fracking, enhanced geothermal systems, and geologic carbon sequestration have already begun to promote a constructive dialog between the static and dynamic views of permeability, and here we have made a conscious effort to include both viewpoints. This special issue also focuses on the quantification of permeability, encompassing both direct measurement of permeability in the uppermost crust and inferential permeability estimates, mainly for the deeper crust.

  10. Controls on Magmatic and Hydrothermal Processes at Yellowstone Supervolcano: The Wideband Magnetotelluric Component of an Integrated MT/Seismic Investigation

    Science.gov (United States)

    Schultz, A.; Bennington, N. L.; Bowles-martinez, E.; Imamura, N.; Cronin, R. A.; Miller, D. J.; Hart, L.; Gurrola, R. M.; Neal, B. A.; Scholz, K.; Fry, B.; Carbonari, R.

    2017-12-01

    Previous seismic and magnetotelluric (MT) studies beneath Yellowstone (YS) have provided insight into the origin and migration of magmatic fluids within the volcanic system. However, important questions remain concerning the generation of magmatism at YS, the migration and storage of these magmatic fluids, as well as their relationships to hydrothermal expressions. Analysis of regional-scale EarthScope MT data collected previously suggests a relative absence of continuity in crustal partial melt accumulations directly beneath YS. This is in contrast to some seismic interpretations, although such long-period MT data have limited resolving power in the upper-to-mid crustal section. A wideband MT experiment was designed as a component of an integrated MT/seismic project to examine: the origin and location of magmatic fluids at upper mantle/lower crustal depths, the preferred path of migration for these magmatic fluids into the mid- to upper-crust, the resulting distribution of the magma reservoir, the composition of the magma reservoir, and implications for future volcanism at YS. A high-resolution wideband MT survey was carried out in the YS region in the summer of 2017, with more than forty-five wideband stations installed within and immediately surrounding the YS National Park boundary. These data provided nearly six decades of bandwidth ( 10-3 Hz -to- 103 Hz). Extraordinary permitting restrictions prevented us from using conventional installation methods at many of our sites, and an innovative "no-dig" subaerial method of wideband MT was developed and used successfully. Using these new data along with existing MT datasets, we are inverting for the 3D resistivity structure at upper crustal through upper mantle scales at YS. Complementary to this MT work, a joint inversion for the 3D crustal velocity structure is being carried out using both ambient noise and earthquake travel time data. Taken together, these data should better constrain the crustal velocity

  11. The Interplay Between Saline Fluid Flow and Dynamic Permeability in Magmatic-Hydrothermal Systems

    Science.gov (United States)

    Weis, P.

    2014-12-01

    Magmatic-hydrothermal ore deposits document the interplay between saline fluid flow and rock permeability. Numerical simulations of multi-phase flow of variably miscible, compressible H20-NaCl fluids in concert with a dynamic permeability model can reproduce characteristics of porphyry copper and epithermal gold systems. This dynamic permeability model incorporates depth-dependent permeability profiles characteristic for tectonically active crust as well as pressure- and temperature-dependent relationships describing hydraulic fracturing and the transition from brittle to ductile rock behavior. In response to focused expulsion of magmatic fluids from a crystallizing upper crustal magma chamber, the hydrothermal system self-organizes into a hydrological divide, separating an inner part dominated by ascending magmatic fluids under near-lithostatic pressures from a surrounding outer part dominated by convection of colder meteoric fluids under near-hydrostatic pressures. This hydrological divide also provides a mechanism to transport magmatic salt through the crust, and prevents the hydrothermal system to become "clogged" by precipitation of solid halite due to depressurization of saline, high-temperature magmatic fluids. The same physical processes at similar permeability ranges, crustal depths and flow rates are relevant for a number of active systems, including geothermal resources and excess degassing at volcanos. The simulations further suggest that the described mechanism can separate the base of free convection in high-enthalpy geothermal systems from the magma chamber as a driving heat source by several kilometers in the vertical direction in tectonic settings with hydrous magmatism. This hydrology would be in contrast to settings with anhydrous magmatism, where the base of the geothermal systems may be closer to the magma chamber.

  12. Seismically constrained two-dimentional crustal thermal structure of ...

    Indian Academy of Sciences (India)

    Cambay basin; P-wave velocity; heat flow; heat generation; 2-D modelling; crustal thermal structure; Mohodepth; Curie isotherm. ... This work deals with the two-dimensional thermal modelling to delineate the crustal thermal structure along a 230 km long Deep Seismic Sounding (DSS) profile in the north Cambay basin.

  13. 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.

  14. Hydrothermal performance of catalyst supports

    Energy Technology Data Exchange (ETDEWEB)

    Elam, Jeffrey W.; Marshall, Christopher L.; Libera, Joseph A.; Dumesic, James A.; Pagan-Torres, Yomaira J.

    2018-04-10

    A high surface area catalyst with a mesoporous support structure and a thin conformal coating over the surface of the support structure. The high surface area catalyst support is adapted for carrying out a reaction in a reaction environment where the thin conformal coating protects the support structure within the reaction environment. In various embodiments, the support structure is a mesoporous silica catalytic support and the thin conformal coating comprises a layer of metal oxide resistant to the reaction environment which may be a hydrothermal environment.

  15. Hydrothermal diamond-anvil cell: Application to studies of geologic fluids

    Science.gov (United States)

    Chou, I.-Ming

    2003-01-01

    The hydrothermal diamond-anvil cell (HDAC) was designed to simulate the geologic conditions of crustal processes in the presence of water or other fluids. The HDAC has been used to apply external pressure to both synthetic and natural fluid inclusions in quartz to minimize problems caused by stretching or decrepitation of inclusions during microthermometric analysis. When the HDAC is loaded with a fluid sample, it can be considered as a large synthetic fluid inclusion and therefore, can be used to study the PVTX properties as well as phase relations of the sample fluid. Because the HDAC has a wide measurement pressure-temperature range and also allows in-situ optical observations, it has been used to study critical phenomena of various chemical systems, such as the geologically important hydrous silicate melts. It is possible, when the HDAC is combined with synchrotron X-ray sources, to obtain basic information on speciation and structure of metal including rare-earth elements (REE) complexes in hydrothermal solutions as revealed by X-ray absorption fine structure (XAFS) spectra. Recent modifications of the HDAC minimize the loss of intensity of X-rays due to scattering and absorption by the diamonds. These modifications are especially important for studying elements with absorption edges below 10 keV and therefore particularly valuable for our understanding of transport and deposition of first-row transition elements and REE in hydrothermal environments.

  16. Basin scale permeability and thermal evolution of a magmatic hydrothermal system

    Science.gov (United States)

    Taron, J.; Hickman, S. H.; Ingebritsen, S.; Williams, C.

    2013-12-01

    Large-scale hydrothermal systems are potentially valuable energy resources and are of general scientific interest due to extreme conditions of stress, temperature, and reactive chemistry that can act to modify crustal rheology and composition. With many proposed sites for Enhanced Geothermal Systems (EGS) located on the margins of large-scale hydrothermal systems, understanding the temporal evolution of these systems contributes to site selection, characterization and design of EGS. This understanding is also needed to address the long-term sustainability of EGS once they are created. Many important insights into heat and mass transfer within natural hydrothermal systems can be obtained through hydrothermal modeling assuming that stress and permeability structure do not evolve over time. However, this is not fully representative of natural systems, where the effects of thermo-elastic stress changes, chemical fluid-rock interactions, and rock failure on fluid flow and thermal evolution can be significant. The quantitative importance of an evolving permeability field within the overall behavior of a large-scale hydrothermal system is somewhat untested, and providing such a parametric understanding is one of the goals of this study. We explore the thermal evolution of a sedimentary basin hydrothermal system following the emplacement of a magma body. The Salton Sea geothermal field and its associated magmatic system in southern California is utilized as a general backdrop to define the initial state. Working within the general framework of the open-source scientific computing initiative OpenGeoSys (www.opengeosys.org), we introduce full treatment of thermodynamic properties at the extreme conditions following magma emplacement. This treatment utilizes a combination of standard Galerkin and control-volume finite elements to balance fluid mass, mechanical deformation, and thermal energy with consideration of local thermal non-equilibrium (LTNE) between fluids and solids

  17. 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.

  18. 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.

  19. Crustal evolution inferred from apollo magnetic measurements

    International Nuclear Information System (INIS)

    Dyal, P.; Daily, W.D.; Vanyan, L.L.

    1978-09-01

    Magnetic field and solar wind plasma density measurements were analyzed to determine the scale size characteristics of remanent fields at the Apollo 12, 15, and 16 landing sites. Theoretical model calculations of the field-plasma interaction, involving diffusion of the remanent field into the solar plasma, were compared to the data. The information provided by all these experiments shows that remanent fields over most of the lunar surface are characterized by spatial variations as small as a few kilometers. Large regions (50 to 100 km) of the lunar crust were probably uniformly magnetized during early crustal evolution. Bombardment and subsequent gardening of the upper layers of these magnetized regions left randomly oriented, smaller scale (5 to 10 km) magnetic sources close to the surface. The larger scale size fields of magnitude approximately 0.1 gammas are measured by the orbiting subsatellite experiments and the small scale sized remanent fields of magnitude approximately 100 gammas are measured by the surface experiments

  20. Glacial rebound and crustal stress in Finland

    International Nuclear Information System (INIS)

    Lambeck, K.; Purcell, A.

    2003-11-01

    The last ice age of Fennoscandinavia continues to have geological repercussions across Finland despite the last ice having retreated almost 10,000 years ago: land uplift, shoreline retreat, and the stress state of the crust continues to evolve. This report focusses on the glacial rebound signals for Finland and the Gulf of Bothnia and explores the consequences of the ongoing deformation. The rebound signals include the geological evidence as well as instrumental observations: the tide gauge and lake-level measurements of the past century, the changes in geodetic levels recorded in the repeat levelling surveys of the region and the direct measurement of crustal deformation (radial and horizontal) using high-precision space-geodesy measurements. These signals provide constraints on the Earth's rheology, its elasticity and viscosity, and the glacial history of the region. Once observationally constrained, the rebound models are used to predict both the ongoing evolution of shorelines and the changing state of stress within the crust. This report covers: (i) A review of glacial rebound modelling for Scandinavia (Sections 2 and 3). (ii) Review of observational evidence relating to sea-level change and crustal rebound (Section 4). (iii) New earth and ice-sheet model results from the inversion of the geological evidence for sea-level change, including models of shoreline evolution (Sections 5 and 6). (iv) Earth-model results from the inversion of the geodetic evidence for sea-level change (Section 7). (v) Development of crustal stress models for past and present stress states (Section 8). (vi) Conclusions and recommendations (Section 9). Specific conclusions reached pertain to: (i) Thickness of ice cover over Scandinavia since the Last Glacial Maximum, particularly for the Lateglacial period. (ii) Sea-level change and shoreline evolution for the Baltic area since the time the region became ice-free for the last time. (iii) The predicted rates of present-day crustal

  1. GPS-derived crustal deformation in Azerbaijan

    Science.gov (United States)

    Safarov, Rafig; Mammadov, Samir; Kadirov, Fakhraddin

    2017-04-01

    Crustal deformations of the Earth's crust in Azerbaijan were studied based on GPS measurements. The GPS velocity vectors for Azerbaijan, Iran, Georgia, and Armenia were used in order to estimate the deformation rates. It is found that compression is observable along the Greater Caucasus, in Gobustan, the Kura depression, Nakhchyvan Autonomous Republic, and adjacent areas of Iran. The axes of compression/contraction of the crust in the Greater Caucasus region are oriented in the S-NE direction. The maximum strain rate is observed in the zone of mud volcanism at the SHIK site (Shykhlar), which is marked by a sharp change in the direction of the compression axes (SW-NE). It is revealed that the deformation field also includes the zones where strain rates are very low. These zones include the Caspian-Guba and northern Gobustan areas, characterized by extensive development of mud volcanism. The extension zones are confined to the Lesser Caucasus and are revealed in the Gyadabei (GEDA) and Shusha (SHOU) areas. The analysis of GPS data for the territory of Azerbaijan and neighboring countries reveals the heterogeneous patterns of strain field in the region. This fact suggests that the block model is most adequate for describing the structure of the studied region. The increase in the number of GPS stations would promote increasing the degree of detail in the reconstructions of the deformation field and identifying the microplate boundaries.It is concluded that the predominant factor responsible for the eruption of mud volcanoes is the intensity of gasgeneration processes in the earth's interior, while deformation processes play the role of a trigger. The zone of the epicenters of strong earthquakes is correlated to the gradient zone in the crustal strain rates.

  2. Fractal behavior in continental crustal heat production

    Directory of Open Access Journals (Sweden)

    N. Vedanti

    2011-02-01

    Full Text Available The distribution of crustal heat production, which is the most important component in the elucidation of continental thermal structure, still remains a theoretical assumption. In general the heat production values must decrease with depth, but the form of decrease of heat production in the crust is not well understood. The commonly used heat production models are: "block model", in which heat production is constant from the surface to a given depth and the "exponential model", in which heat production diminishes as an exponential function of depth. The exponential model is more widely used wherein sources of the errors are heterogeneity of rock and long wavelength changes due to changes in lithology and tectonic elements, and as such exponential distribution does not work satisfactorily for the entire crust. In the present study, we analyze for the first time, deep crustal heat production data of six global areas namely Dharwar craton (India, Kaapvaal craton (South Africa, Baltic shield (Kola, Russia, Hidaka metamorphic belt (Japan, Nissho pluton (Japan and Continental Deep Drilling site (KTB, Germany. The power spectrum of all the studied data sets exhibits power law behaviour. This would mean slower decay of heat production with depth, which conforms to the known geologic composition of the crust. Minimum value of the scaling exponent has been found for the KTB borehole, which is apparently related to higher heat production of gneisses, however for other study areas, scaling exponent is almost similar. We also found that the lower values of scaling exponents are related to higher heat production in the crust as is the case in KTB. Present finding has a direct relevance in computation of temperature-depth profiles in continental regions.

  3. Fractal behavior in continental crustal heat production

    Science.gov (United States)

    Vedanti, N.; Srivastava, R. P.; Pandey, O. P.; Dimri, V. P.

    2011-02-01

    The distribution of crustal heat production, which is the most important component in the elucidation of continental thermal structure, still remains a theoretical assumption. In general the heat production values must decrease with depth, but the form of decrease of heat production in the crust is not well understood. The commonly used heat production models are: "block model", in which heat production is constant from the surface to a given depth and the "exponential model", in which heat production diminishes as an exponential function of depth. The exponential model is more widely used wherein sources of the errors are heterogeneity of rock and long wavelength changes due to changes in lithology and tectonic elements, and as such exponential distribution does not work satisfactorily for the entire crust. In the present study, we analyze for the first time, deep crustal heat production data of six global areas namely Dharwar craton (India), Kaapvaal craton (South Africa), Baltic shield (Kola, Russia), Hidaka metamorphic belt (Japan), Nissho pluton (Japan) and Continental Deep Drilling site (KTB, Germany). The power spectrum of all the studied data sets exhibits power law behaviour. This would mean slower decay of heat production with depth, which conforms to the known geologic composition of the crust. Minimum value of the scaling exponent has been found for the KTB borehole, which is apparently related to higher heat production of gneisses, however for other study areas, scaling exponent is almost similar. We also found that the lower values of scaling exponents are related to higher heat production in the crust as is the case in KTB. Present finding has a direct relevance in computation of temperature-depth profiles in continental regions.

  4. The Glacial BuzzSaw, Isostasy, and Global Crustal Models

    Science.gov (United States)

    Levander, A.; Oncken, O.; Niu, F.

    2015-12-01

    The glacial buzzsaw hypothesis predicts that maximum elevations in orogens at high latitudes are depressed relative to temperate latitudes, as maximum elevation and hypsography of glaciated orogens are functions of the glacial equilibrium line altitude (ELA) and the modern and last glacial maximum (LGM) snowlines. As a consequence crustal thickness, density, or both must change with increasing latitude to maintain isostatic balance. For Airy compensation crustal thickness should decrease toward polar latitudes, whereas for Pratt compensation crustal densities should increase. For similar convergence rates, higher latitude orogens should have higher grade, and presumably higher density rocks in the crustal column due to more efficient glacial erosion. We have examined a number of global and regional crustal models to see if these predictions appear in the models. Crustal thickness is straightforward to examine, crustal density less so. The different crustal models generally agree with one another, but do show some major differences. We used a standard tectonic classification scheme of the crust for data selection. The globally averaged orogens show crustal thicknesses that decrease toward high latitudes, almost reflecting topography, in both the individual crustal models and the models averaged together. The most convincing is the western hemisphere cordillera, where elevations and crustal thicknesses decrease toward the poles, and also toward lower latitudes (the equatorial minimum is at ~12oN). The elevation differences and Airy prediction of crustal thickness changes are in reasonable agreement in the North American Cordillera, but in South America the observed crustal thickness change is larger than the Airy prediction. The Alpine-Himalayan chain shows similar trends, however the strike of the chain makes interpretation ambiguous. We also examined cratons with ice sheets during the last glacial period to see if continental glaciation also thins the crust toward

  5. 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...

  6. Quantitative tectonic reconstructions of Zealandia based on crustal thickness estimates

    Science.gov (United States)

    Grobys, Jan W. G.; Gohl, Karsten; Eagles, Graeme

    2008-01-01

    Zealandia is a key piece in the plate reconstruction of Gondwana. The positions of its submarine plateaus are major constraints on the best fit and breakup involving New Zealand, Australia, Antarctica, and associated microplates. As the submarine plateaus surrounding New Zealand consist of extended and highly extended continental crust, classic plate tectonic reconstructions assuming rigid plates and narrow plate boundaries fail to reconstruct these areas correctly. However, if the early breakup history shall be reconstructed, it is crucial to consider crustal stretching in a plate-tectonic reconstruction. We present a reconstruction of the basins around New Zealand (Great South Basin, Bounty Trough, and New Caledonia Basin) based on crustal balancing, an approach that takes into account the rifting and thinning processes affecting continental crust. In a first step, we computed a crustal thickness map of Zealandia using seismic, seismological, and gravity data. The crustal thickness map shows the submarine plateaus to have a uniform crustal thickness of 20-24 km and the basins to have a thickness of 12-16 km. We assumed that a reconstruction of Zealandia should close the basins and lead to a most uniform crustal thickness. We used the standard deviation of the reconstructed crustal thickness as a measure of uniformity. The reconstruction of the Campbell Plateau area shows that the amount of extension in the Bounty Trough and the Great South Basin is far smaller than previously thought. Our results indicate that the extension of the Bounty Trough and Great South Basin occurred simultaneously.

  7. Global variations in gravity-derived oceanic crustal thickness: Implications on oceanic crustal accretion and hotspot-lithosphere interactions

    Science.gov (United States)

    Lin, J.; Zhu, J.

    2012-12-01

    We present a new global model of oceanic crustal thickness based on inversion of global oceanic gravity anomaly with constrains from seismic crustal thickness profiles. We first removed from the observed marine free-air gravity anomaly all gravitational effects that can be estimated and removed using independent constraints, including the effects of seafloor topography, marine sediment thickness, and the age-dependent thermal structure of the oceanic lithosphere. We then calculated models of gravity-derived crustal thickness through inversion of the residual mantle Bouguer anomaly using best-fitting gravity-modeling parameters obtained from comparison with seismically determined crustal thickness profiles. Modeling results show that about 5% of the global crustal volume (or 9% of the global oceanic surface area) is associated with model crustal thickness 8.6 km and is interpreted to have been affected by excess magmatism. The percentage of oceanic crustal volume that is associated with thick crustal thickness (>8.6 km) varies greatly among tectonic plates: Pacific (33%), Africa (50%), Antarctic (33%), Australia (30%), South America (34%), Nazca (23%), North America (47%), India (74%), Eurasia (68%), Cocos (20%), Philippine (26%), Scotia (41%), Caribbean (89%), Arabian (82%), and Juan de Fuca (21%). We also found that distribution of thickened oceanic crust (>8.6 km) seems to depend on spreading rate and lithospheric age: (1) On ocean basins younger than 5 Ma, regions of thickened crust are predominantly associated with slow and ultraslow spreading ridges. The relatively strong lithospheric plate at slow and ultraslow ridges might facilitate the loading of large magmatic emplacements on the plate. (2) In contrast, crustal thickness near fast and intermediately fast spreading ridges typically does not exceed 7-8 km. The relatively weak lithosphere at fast and intermediately fast ridges might make it harder for excess magmatism to accrete. We further speculate that

  8. 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

  9. Satellite measurements of the earth's crustal magnetic field

    Science.gov (United States)

    Schnetzler, C. C.

    1989-01-01

    The literature associated with the Magsat mission has evaluated the capabilities and limitations of satellite measurements of the earth's crustal magnetic field, and demonstrated that there exists a 300-3000 km magnetic field, related to major features in the earth's crust, which is primarily caused by induction. Due to its scale and sensitivity, satellite data have been useful in the development of models for such large crustal features as subduction zones, submarine platforms, continental accretion boundaries, and rifts. Attention is presently given to the lack of agreement between laboratory and satellite estimates of lower crustal magnetization.

  10. 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].

  11. 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.

  12. 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

  13. The precambrian crustal evolution and mineralization cycle of uranium in the northeast of norern China platform

    International Nuclear Information System (INIS)

    Guo Zhitian.

    1986-01-01

    According to the evolution history of the crust the region is divided into three Precambrian structural structural units: (1) Archaean craton; (2) Early Proterozoic zone of fold; (3) Middle-late Proterozoic depression zone. The Archaean-craton mainly consists of granite complex and metasediments. They form the first generation of uranium sources. Proterozoic is characterized by the obvious cycle of sedimentation which consists of the second generation of uranium source. There were multiplestage and congenetic nature in the formation of uranium deposit. The mineralization of uranium coincides with geotectonicdeveloping stage -- igneous activity -- metamorphism in their time. The formation of uranium deposits generally underwent the weathering and erosion of original uraniferous bodies-the migration, redeposition and reformed concentration by metamorphism and metamorphosed hydrothermal solution, and the mineralization was not only of intermittence, but also of inheritance. The evolutional process of forming uranium deposits undergoing various geological function of a structural cycle in the uranium geochemical anomalous area is called uranium mineralizational cycle. The Northeast of Northern China Platform had undergone multiple times structural movements causing migration and concentration of uranium and having mutiple cycle mineralizational character. Corresponding to the three main developing stages of the crustal evolution the Precambrian uranium mineralization in the Northeast of northern China platform area may be divided into three cycles: Late Archaeozoic mineralizational cycle, Early Proterozoic mineralizational cycle, and Middle Proterozoic mineralizational cycle. It is possible to search for potential uranium metallogenetic provinces to study the crustal evolution and the multiple cycle characters of uranium minerogenetic process in the Northern China platform

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. Coupling Flow & Transport Modeling with Electromagnetic Geophysics to Better Understand Crustal Permeability

    Science.gov (United States)

    Pepin, J.; Folsom, M.; Person, M. A.; Kelley, S.; Gomez-Velez, J. D.; Peacock, J.

    2016-12-01

    Over the last 30 years, considerable effort has focused on understanding the distribution of permeability within the earth's crust and its implications for flow and transport. The scarcity of direct observations makes the description of permeabilities beyond depths of about 3 km particularly challenging. Numerous studies have defined depth-decay relationships for basement permeability, while others note that it is too complex to be characterized by a general relationship. Hydrothermal modeling studies focusing on two geothermal systems within the tectonically active Rio Grande rift of New Mexico suggest that there may be laterally extensive regions of highly permeable (10-14 to 10-12 m2) basement rocks at depths ranging between 4 and 8 km. The NaCl groundwater signature, elevated fracture density, and secondary mineralization of fractured basement outcrops associated with these geothermal systems indicate that there may indeed be significant groundwater flow within the basement rocks of the rift. We hypothesize that there are extensive regions of highly permeable crystalline basement rocks at depths greater than 3 km within the Rio Grande rift. These fractured zones serve as large conduits for geothermal fluids before they ascend to shallow depths through gaps in overlying confining sediments or along faults. To test these hypotheses, we use a combination of geophysical observations and flow and transport modeling. We used electromagnetic geophysics (TEM & MT) to image resistivity in one of the hypothesized deep circulation geothermal systems near Truth or Consequences, NM. The resistivity dataset, in tandem with geochemical and thermal observations, is then used to calibrate a hydrothermal model of the system. This new calibration methodology has the potential to change the way researchers study crustal fluid flow and geothermal systems; thereby providing a tool to explore depths greater than 3 km where minimal data is available. In addition, it has the advantage

  19. 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)

  20. Early Neoarchaean A-type granitic magmatism by crustal reworking ...

    Indian Academy of Sciences (India)

    29

    marginal part of the Singhbhum craton whose origin and role in crustal evolution are poorly ...... Lu-Hf and Sm-Nd isotope systematics of Archean komatiites; Earth Planet. ..... Association Commission on New Minerals and Mineral Names; Can.

  1. Early Neoarchaean A-type granitic magmatism by crustal reworking ...

    Indian Academy of Sciences (India)

    29

    understand their petrogenesis and tectonic setting. .... crystallize from magmas with temperatures significantly higher than those of other intracrustal ...... blanketing by greenstone belt volcanic rocks, crustal thickening and hot subduction or a. 1.

  2. Crustal structure and tectonic model of the Arctic region

    DEFF Research Database (Denmark)

    Petrov, Oleg; Morozov, Andrey; Shokalsky, Sergey

    2016-01-01

    We present a new model of the crustal and tectonic structure of the Arctic region north of 60° N latitude, constrained as a part of the international Atlas of Geological Maps of the Circumpolar Arctic under the aegis of the Commission for the Geological Map of the World. The region is largely...... formed by (i) Archean-Paleoproterozoic shields and platforms, (ii) orogenic belts of the Neoproterozoic to the Late Mesozoic ages overlain by platform and basin sediments, (iii) Cenozoic rift structures formed in part as a consequence of seafloor spreading in the North East Atlantic Ocean...... and thickness of the sedimentary cover and presents tectonic regionalization based on 18 major crustal types (oceanic, transitional, and continental) recognized in the Arctic. A 7600. km-long crustal geotransect across the region illustrates the details of its crustal and tectonic structure. We discuss...

  3. Continental crustal formation and recycling: Evidence from oceanic basalts

    Science.gov (United States)

    Saunders, A. D.; Tarney, J.; Norry, M. J.

    1988-01-01

    Despite the wealth of geochemical data for subduction-related magma types, and the clear importance of such magmas in the creation of continental crust, there is still no concensus about the relative magnitudes of crustal creation versus crustal destruction (i.e., recycling of crust into the mantle). The role of subducted sediment in the formation of the arc magmas is now well documented; but what proportion of sediment is taken into the deeper mantle? Integrated isotopic and trace element studies of magmas erupted far from presently active subduction zones, in particular basaltic rocks erupted in the ocean basins, are providing important information about the role of crustal recycling. By identifying potential chemical tracers, it is impossible to monitor the effects of crustal recycling, and produce models predicting the mass of material recycled into the mantle throughout long periods of geological time.

  4. Ionospheric precursors for crustal earthquakes in Italy

    Directory of Open Access Journals (Sweden)

    L. Perrone

    2010-04-01

    Full Text Available Crustal earthquakes with magnitude 6.0>M≥5.5 observed in Italy for the period 1979–2009 including the last one at L'Aquila on 6 April 2009 were considered to check if the earlier obtained relationships for ionospheric precursors for strong Japanese earthquakes are valid for the Italian moderate earthquakes. The ionospheric precursors are based on the observed variations of the sporadic E-layer parameters (h'Es, fbEs and foF2 at the ionospheric station Rome. Empirical dependencies for the seismo-ionospheric disturbances relating the earthquake magnitude and the epicenter distance are obtained and they have been shown to be similar to those obtained earlier for Japanese earthquakes. The dependences indicate the process of spreading the disturbance from the epicenter towards periphery during the earthquake preparation process. Large lead times for the precursor occurrence (up to 34 days for M=5.8–5.9 tells about a prolong preparation period. A possibility of using the obtained relationships for the earthquakes prediction is discussed.

  5. The crustal dynamics intelligent user interface anthology

    Science.gov (United States)

    Short, Nicholas M., Jr.; Campbell, William J.; Roelofs, Larry H.; Wattawa, Scott L.

    1987-01-01

    The National Space Science Data Center (NSSDC) has initiated an Intelligent Data Management (IDM) research effort which has, as one of its components, the development of an Intelligent User Interface (IUI). The intent of the IUI is to develop a friendly and intelligent user interface service based on expert systems and natural language processing technologies. The purpose of such a service is to support the large number of potential scientific and engineering users that have need of space and land-related research and technical data, but have little or no experience in query languages or understanding of the information content or architecture of the databases of interest. This document presents the design concepts, development approach and evaluation of the performance of a prototype IUI system for the Crustal Dynamics Project Database, which was developed using a microcomputer-based expert system tool (M. 1), the natural language query processor THEMIS, and the graphics software system GSS. The IUI design is based on a multiple view representation of a database from both the user and database perspective, with intelligent processes to translate between the views.

  6. Alumino-silicate speciation in aqueous fluids at deep crustal conditions

    Science.gov (United States)

    Mookherjee, M.; Keppler, H.; Manning, C. E.

    2014-12-01

    Alumina and silica are major oxides in most crustal rocks. While SiO2 is quite soluble in aqueous fluids at metamorphic conditions, behavior of Al2O3 in crustal metamorphic fluids has been poorly understood. It is known that alumina is dramatically less soluble in aqueous fluids and hence it is difficult to explain the common occurrence of quartz with aluminous minerals in metamorphic veins. In order to understand this complex behavior of alumina, we investigated aluminum speciation in aqueous fluids in equilibrium with corundum using in situ Raman spectroscopy in hydrothermal diamond anvil cells to 20 kbar and 1000 oC. In order to better understand the spectral features of the aqueous fluids, we used first principles simulations based on density functional theory to calculate and predict the energetics and vibrational spectra for various aluminum species that are likely to be present in aqueous solutions. The Raman spectra of pure water in equilibrium with Al2O3 are devoid of any characteristic spectral features. In contrast, aqueous fluids with KOH solution in equilibrium with Al2O3 show a sharp band at ~620 cm-1 which could be attributed to the [Al(OH)4]1- species. The band grows in intensity with temperature along an isochore. In the limited pressure, temperature and density explored in the present study, we do not find any evidence for the polymerization of the [Al(OH)4]1- species to dimers [(OH)2-Al-O2-Al(OH)2]2- or [(OH)3-Al-O-Al(OH)3]2-. This is likely due to the relatively low concentration of Al in the solutions and does not rule out significant polymerization at higher pressures and temperatures. We are also investigating the effect of SiO2 on the solubility of Al2O3 and the relative energetics of formation of pure alumina dimer [(OH)3-Al-O-Al(OH)3]2- vs. the aluminosilicate dimers, [(OH)3-Al-O-Si(OH)3]2- at deep crustal conditions. Acknowledgement- MM is supported by the US National Science Foundation grant (EAR-1250477).

  7. Ge/Si Ratios as a Tracer of Hydrothermal Activity in the Nepal Himalaya

    Science.gov (United States)

    Evans, M. J.; Derry, L. A.

    2001-12-01

    Advection of deep-seated crustal rocks, high internal heat production, and rapid erosion of the thrust wedge result in steep thermal gradients in the crystalline rocks of the Himalayan front. Meteoric water circulation within these rocks produces geothermal activity in the deeply-incised river valleys near the Main Central Thrust shear zone. The springs have measured temperatures up to 70° C and TDS up to 8000 mg/L and drive significant anomalies in river chemistry. We have carried out a detailed study of the role of hot springs in the Narayani River basin of central Nepal (area 35,000 km2), the major drainage of the central Nepal Himalaya and a major tributary to the Ganges. In order to quantify the fluxes of heat and solutes from geothermal systems in the Narayani basin, the hydrothermal fluid flux must be estimated. As part of an ongoing effort to investigate the use of germanium-silicon systematics, we measured Ge/Si ratios in main stem, tributary and hot spring waters of the Narayani basin. While Ge/Si ratios in tributaries are similar to non-polluted world rivers (Iceland (9 to 150 μ mol/mol). The high Ge/Si ratios in the hot springs may reflect Rayleigh fractionation as low Ge/Si quartz is precipitated. The wide disparity in stream vs. hydrothermal values makes Ge/Si a valuable tool for quantifying hydrothermal fluid flux by mass balance. We can use a hydrothermal fluid flux estimate derived from the chemical mass balance to estimate convective heat loss in the Narayani basin. Preliminary estimates in the Marsyandi River yield a thermal power output rate of 200 MW, comparable with geothermal fields in the Taupo Volcanic Zone and when distributed over the spring affected area, yield a hydrothermal heat flow (160 mW/m2) comparable to continental heat flow and hydrothermal heat loss in the geothermal belt across Tibet. Fluxes of solutes and heat carried by Himalayan hot springs appear to be significant for Himalayan river chemistry and for thermal models of

  8. Cooperative research in space geodesy and crustal dynamics

    Science.gov (United States)

    1994-01-01

    This research grant, which covered the period of July 1991 to August 1994, was concerned with a variety of topics within the geodesy and crustal dynamics fields. The specific topics of this grant included satellite tracking and gravity field determinations and crustal dynamics (this concentrated of space geodetic site stability for VLBI sites). Summaries of the specific research projects are included along with a list of publications and presentations supported by this research grant.

  9. Lower crustal earthquakes in the North China Basin and implications for crustal rheology

    Science.gov (United States)

    Yuen, D. A.; Dong, Y.; Ni, S.; LI, Z.

    2017-12-01

    The North China Basin is a Mesozoic-Cenozoic continental rift basin on the eastern North China Craton. It is the central region of craton destruction, also a very seismically active area suffering severely from devastating earthquakes, such as the 1966 Xingtai M7.2 earthquake, the 1967 Hejian M6.3 earthquake, and the 1976 Tangshan M7.8 earthquake. We found remarkable discrepancies of depth distribution among the three earthquakes, for instance, the Xingtai and Tangshan earthquakes are both upper-crustal earthquakes occurring between 9 and 15 km on depth, but the depth of the Hejian earthquake was reported of about 30 72 km, ranging from lowermost crust to upper mantle. In order to investigate the focal depth of earthquakes near Hejian area, we developed a method to resolve focal depth for local earthquakes occurring beneath sedimentary regions by P and S converted waves. With this method, we obtained well-resolved depths of 44 local events with magnitudes between M1.0 and M3.0 during 2008 to 2016 at the Hejian seismic zone, with a mean depth uncertainty of about 2 km. The depth distribution shows abundant earthquakes at depth of 20 km, with some events in the lower crust, but absence of seismicity deeper than 25 km. In particular, we aimed at deducing some constraints on the local crustal rheology from depth-frequency distribution. Therefore, we performed a comparison between the depth-frequency distribution and the crustal strength envelop, and found a good fit between the depth profile in the Hejian seismic zone and the yield strength envelop in the Baikal Rift Systems. As a conclusion, we infer that the seismogenic thickness is 25 km and the main deformation mechanism is brittle fracture in the North China Basin . And we made two hypotheses: (1) the rheological layering of dominant rheology in the North China Basin is similar to that of the Baikal Rift Systems, which can be explained with a quartz rheology at 0 10 km depth and a diabase rheology at 10 35 km

  10. 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

  11. CRUSTAL THICKNESS VARIATIONS AND SEISMICITY OF NORTHWESTERN SOUTH AMERICA

    Directory of Open Access Journals (Sweden)

    Woo Kim Jeong

    2007-06-01

    Full Text Available Any uncompensated mass of the northern Andes Mountains is presumably under pressure to adjust within the Earth to its ideal state of isostatic equilibrium. Isostasy is the ideal state that any
    uncompensated mass seeks to achieve in time. These pressures interact with the relative motions between adjacent plates that give rise to earthquakes along the plate boundaries. By combining the
    gravity MOHO estimates and crustal discontinuities with historical and instrumental seismological catalogs the correlation between isostatically disturbed terrains and seismicity has been established.
    The thinner and thicker crustal regions were mapped from the zero horizontal curvature of the crustal thickness estimates. These boundaries or edges of crustal thickness variations were compared to
    crustal discontinuities inferred from gravity and magnetic anomalies and the patterns of seismicity that have been catalogued for the last 363 years. The seismicity is very intense along the Nazca-North
    Andes, Caribbean-North American and North Andes-South American collision zones and associated with regional tectonic compressional stresses that have locally increased and/or diminished by
    compressional and tensional stress, respectively, due to crustal thickness variations. High seismicity is also associated with the Nazca-Cocos diverging plate boundary whereas low seismicity is associated with the Panama-Nazca Transform Fault and the South American Plate.

  12. Hydrothermal pretreatments of macroalgal biomass for biorefineries

    DEFF Research Database (Denmark)

    Ruiz, Héctor A.; Rodríguez-Jasso, Rosa M.; Aguedo, Mario

    2015-01-01

    in accordance with the integrated biorefineries. Furthermore, biorefinery concept requires processes that allow efficient utilization of all components of the biomass. The pretreatment step in a biorefinery is often based on hydrothermal principles of high temperatures in aqueous solution. Therefore...

  13. 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)

  14. 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.

  15. 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

  16. 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)

  17. 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

  18. Costa Rica Rift Revisited: Constraints on Shallow and Deep Hydrothermal Circulation in Oceanic Crust

    Science.gov (United States)

    Davis, E. E.; Becker, K.; He, J.

    2002-12-01

    New heat-flow observations made along two seismic reflection profiles on 6 Ma crust of the Costa Rica Rift flank show an inverse correlation between heat flow and sediment thickness similar to that observed on other sedimented ridges and young ridge flanks. Extrapolation of the seafloor heat-flow values to the top of the igneous crust - justified by comparing seafloor and borehole determinations where observations are colocated - show the surface of the igneous crust to be of uniform temperature despite large local sediment thickness variations. This is consistent with observations made at DSDP/ODP Holes 504B and 896A where basement temperatures are observed to be nearly identical, also despite contrasting sediment thicknesses. Efficient lateral heat exchange via vigorous crustal hydrothermal circulation is required to create the degree of uniformity inferred and observed. Permeability measurements at the two drill sites show that this vigorous circulation may be restricted to as little as the uppermost tens of m of the crust. Permeability determined deeper in Hole 504B is too low to permit thermally significant flow, although temperature logs suggest that thermally significant flow extends throughout the 2 km section penetrated at Site 504, presumably via pathways not intersected by the borehole. The laterally uniform temperatures in the uppermost igneous crust here and elsewhere are remarkable given the small apparent depth-extent of the circulation that so efficiently distributes heat. While certainly not as vigorous, the circulation at depth suggested by the temperature logs at Site 504 is also noteworthy; unfortunately the observation cannot be generalized because of the lack of other deep crustal holes that could permit direct observations, and the lack of a method for inferring deep hydrothermal structure.

  19. Geochemistry of hydrothermal fluids from the PACMANUS, Northeast Pual and Vienna Woods hydrothermal fields, Manus Basin, Papua New Guinea

    Science.gov (United States)

    Reeves, Eoghan P.; Seewald, Jeffrey S.; Saccocia, Peter; Bach, Wolfgang; Craddock, Paul R.; Shanks, Wayne C.; Sylva, Sean P.; Walsh, Emily; Pichler, Thomas; Rosner, Martin

    2011-01-01

    Processes controlling the composition of seafloor hydrothermal fluids in silicic back-arc or near-arc crustal settings remain poorly constrained despite growing evidence for extensive magmatic-hydrothermal activity in such environments. We conducted a survey of vent fluid compositions from two contrasting sites in the Manus back-arc basin, Papua New Guinea, to examine the influence of variations in host rock composition and magmatic inputs (both a function of arc proximity) on hydrothermal fluid chemistry. Fluid samples were collected from felsic-hosted hydrothermal vent fields located on Pual Ridge (PACMANUS and Northeast (NE) Pual) near the active New Britain Arc and a basalt-hosted vent field (Vienna Woods) located farther from the arc on the Manus Spreading Center. Vienna Woods fluids were characterized by relatively uniform endmember temperatures (273-285 degrees C) and major element compositions, low dissolved CO2 concentrations (4.4 mmol/kg) and high measured pH (4.2-4.9 at 25 degrees C). Temperatures and compositions were highly variable at PACMANUS/NE Pual and a large, newly discovered vent area (Fenway) was observed to be vigorously venting boiling (358 degrees C) fluid. All PACMANUS fluids are characterized by negative delta DH2O values, in contrast to positive values at Vienna Woods, suggesting substantial magmatic water input to circulating fluids at Pual Ridge. Low measured pH (25 degrees C) values (~2.6-2.7), high endmember CO2 (up to 274 mmol/kg) and negative delta 34SH2S values (down to -2.7 permille) in some vent fluids are also consistent with degassing of acid-volatile species from evolved magma. Dissolved CO2 at PACMANUS is more enriched in 13C (-4.1 permille to -2.3 permille) than Vienna Woods (-5.2 permille to -5.7 permille), suggesting a contribution of slab-derived carbon. The mobile elements (e.g. Li, K, Rb, Cs and B) are also greatly enriched in PACMANUS fluids reflecting increased abundances in the crust there relative to the Manus

  20. Effective stress, friction and deep crustal faulting

    Science.gov (United States)

    Beeler, N.M.; Hirth, Greg; Thomas, Amanda M.; Burgmann, Roland

    2016-01-01

    Studies of crustal faulting and rock friction invariably assume the effective normal stress that determines fault shear resistance during frictional sliding is the applied normal stress minus the pore pressure. Here we propose an expression for the effective stress coefficient αf at temperatures and stresses near the brittle-ductile transition (BDT) that depends on the percentage of solid-solid contact area across the fault. αf varies with depth and is only near 1 when the yield strength of asperity contacts greatly exceeds the applied normal stress. For a vertical strike-slip quartz fault zone at hydrostatic pore pressure and assuming 1 mm and 1 km shear zone widths for friction and ductile shear, respectively, the BDT is at ~13 km. αf near 1 is restricted to depths where the shear zone is narrow. Below the BDT αf = 0 is due to a dramatically decreased strain rate. Under these circumstances friction cannot be reactivated below the BDT by increasing the pore pressure alone and requires localization. If pore pressure increases and the fault localizes back to 1 mm, then brittle behavior can occur to a depth of around 35 km. The interdependencies among effective stress, contact-scale strain rate, and pore pressure allow estimates of the conditions necessary for deep low-frequency seismicity seen on the San Andreas near Parkfield and in some subduction zones. Among the implications are that shear in the region separating shallow earthquakes and deep low-frequency seismicity is distributed and that the deeper zone involves both elevated pore fluid pressure and localization.

  1. Intensity attenuation for active crustal regions

    Science.gov (United States)

    Allen, Trevor I.; Wald, David J.; Worden, C. Bruce

    2012-07-01

    We develop globally applicable macroseismic intensity prediction equations (IPEs) for earthquakes of moment magnitude M W 5.0-7.9 and intensities of degree II and greater for distances less than 300 km for active crustal regions. The IPEs are developed for two distance metrics: closest distance to rupture ( R rup) and hypocentral distance ( R hyp). The key objective for developing the model based on hypocentral distance—in addition to more rigorous and standard measure R rup—is to provide an IPE which can be used in near real-time earthquake response systems for earthquakes anywhere in the world, where information regarding the rupture dimensions of a fault may not be known in the immediate aftermath of the event. We observe that our models, particularly the model for the R rup distance metric, generally have low median residuals with magnitude and distance. In particular, we address whether the direct use of IPEs leads to a reduction in overall uncertainties when compared with methods which use a combination of ground-motion prediction equations and ground motion to intensity conversion equations. Finally, using topographic gradient as a proxy and median model predictions, we derive intensity-based site amplification factors. These factors lead to a small reduction of residuals at shallow gradients at strong shaking levels. However, the overall effect on total median residuals is relatively small. This is in part due to the observation that the median site condition for intensity observations used to develop these IPEs is approximately near the National Earthquake Hazard Reduction Program CD site-class boundary.

  2. 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

  3. Hydrothermal synthesis of cathode materials

    Science.gov (United States)

    Chen, Jiajun; Wang, Shijun; Whittingham, M. Stanley

    A number of cathodes are being considered for the next generation of lithium ion batteries to replace the expensive LiCoO 2 presently used. Besides the layered oxides, such as LiNi yMn yCo 1-2 yO 2, a leading candidate is lithium iron phosphate with the olivine structure. Although this material is inherently low cost, a manufacturing process that produces electrochemically active LiFePO 4 at a low cost is also required. Hydrothermal reactions are one such possibility. A number of pure phosphates have been prepared using this technique, including LiFePO 4, LiMnPO 4 and LiCoPO 4; this method has also successfully produced mixed metal phosphates, such as LiFe 0.33Mn 0.33Co 0.33PO 4. Ascorbic acid was found to be better than hydrazine or sugar at preventing the formation of ferric ions in aqueous media. When conductive carbons are added to the reaction medium excellent electrochemical behavior is observed.

  4. 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)

  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. 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.

  7. 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.

  8. 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...

  9. The geochemical evolution of syncollisional magmatism and the implications for significant magmatic-hydrothermal lead-zinc mineralization (Gangdese, Tibet)

    Science.gov (United States)

    Zhou, Jinsheng; Yang, Zhusen; Hou, Zengqian; Liu, Yingchao; Zhao, Xiaoyan; Zhang, Xiong; Zhao, Miao; Ma, Wang

    2017-09-01

    In addition to well-known subduction processes, the collision of two continents also generates abundant ore deposits, as in the case of the Tibetan Plateau, which is the youngest and most spectacular collisional belt on Earth. During the building history of the Gangdese magmatic belt, several magmatic flare-up events developed, however, significant magmatic-hydrothermal lead-zinc mineralization dominantly accompanied the magmatism during the syncollisional period ( 65-41 Ma). Based on integrated geochemical and isotopic data, we provide insights into the genesis and evolution of syncollisional magmas, and their implications for significant magmatic-hydrothermal lead-zinc mineralization. The Sr-Nd isotopic compositions of most syncollisional igneous rocks (87Sr/86Sr = 0.7034-0.7123; εNd(t) = - 9.0 to + 1.8) indicate a mixing origin between mantle-derived basaltic magmas and ancient crustal melts, and fractional crystallization is a fundamental mechanism by which syncollisional magmas evolve towards intermediate to silicic compositions. Most lead-zinc mineralization-related plutons are high silica (76.14% wt.% SiO2 on average), high oxygen fugacity (average ΔFMQ + 2.5) granites with highly evolved chemical signatures [average Eun/Eun* = 0.33, high Rb/Sr (average = 3.9)], and they represent the final products from primary magmas. Due to the contribution of ancient crustal melts to the genesis of mineralization-related parent magmas, the spatial distribution of Pb-Zn deposits within the northern Gangdese magmatic belt is controlled by the lithospheric architecture. In compressional environments, magmas have low evacuation efficiency and long magma chamber lifespan, which is favorable for basaltic parents evolved to high silica granites through sufficient fractional crystallization. This scenario contributes to our understanding of the significant magmatic-hydrothermal lead-zinc mineralization that occurred in the syncollisional period.

  10. New Crustal Thickness for Djibouti, Afar, Using Seismic Techniques

    Science.gov (United States)

    Dugda, Mulugeta; Bililign, Solomon

    2008-10-01

    Crustal thickness and Poisson's ratio for the seismic station ATD in Djibouti, Afar, has been investigated using two seismic techniques (H-κ stacking of receiver functions and a joint inversion of receiver functions and surface wave group velocities). Both techniques give consistent results of crustal thickness 23±1.5 km and Poisson's ratio 0.31±0.02. We also determined a mean P-wave velocity (Vp) of ˜6.2 km/s but ˜6.9-7.0 km/s below a 2 - 5 km thick low velocity layer at the surface. Previous studies of crustal structure for Djibouti reported that the crust is 6 to 11 km thick while our study shows that the crust beneath Djibouti is between 20 and 25 km. This study argues that the crustal thickness values reported for Djibouti for the last 3 decades were not consistent with the reports for the other neighboring region in central and eastern Afar. Our results for ATD in Djibouti, however, are consistent with the reports of crustal thickness in many other parts of central and eastern Afar. We attribute this difference to how the Moho (the crust-mantle discontinuity) is defined (an increase of Vp to 7.4 km/s in this study vs. 6.9 km/s in previous studies).

  11. 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

  12. 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

  13. 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.

  14. Origin of fumarolic fluids from Tupungatito Volcano (Central Chile): interplay between magmatic, hydrothermal, and shallow meteoric sources

    Science.gov (United States)

    Benavente, Oscar; Tassi, Franco; Gutiérrez, Francisco; Vaselli, Orlando; Aguilera, Felipe; Reich, Martin

    2013-08-01

    Tupungatito is a poorly known volcano located about 100 km eastward of Santiago (Chile) in the northernmost sector of the South Volcanic Zone. This 5,682 m high volcano shows intense fumarolic activity. It hosts three crater lakes within the northwestern portion of the summit area. Chemical compositions of fumarolic gases and isotopic signatures of noble gases (3He/4He and 40Ar/36Ar are up to 6.09 Ra and 461, respectively), and steam (δ18O and δD) suggest that they are produced by mixing of fluids from a magmatic source rich in acidic gas compounds (SO2, HCl, and HF), and meteoric water. The magmatic-hydrothermal fluids are affected by steam condensation that controls the outlet fumarolic temperatures (contamination from the subducting slab, (2) the sedimentary basement, and (3) limited contribution from crustal sediments. Gas geothermometry based on the kinetically rapid H2-CO equilibria indicates equilibrium temperatures 200 °C and redox conditions are consistent with those inferred by the presence of the SO2-H2S redox pair, typical of fluids that have attained equilibrium in magmatic environment. A comprehensive conceptual geochemical model describing the circulation pattern of the Tupungatito hydrothermal-magmatic fluids is proposed. It includes fluid source regions and re-equilibration processes affecting the different gas species due to changing chemical-physical conditions as the magmatic-hydrothermal fluids rise up toward the surface.

  15. 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.

  16. Heat Source for Active Venting at the Lost City Hydrothermal Field

    Science.gov (United States)

    Smith, J. E.; Germanovich, L. N.; Lowell, R. P.

    2014-12-01

    Located at the inside corner high of the Mid-Atlantic Ridge (MAR), 30°N and the Atlantis Transform Fault (ATF), the Atlantis Massif has been uplifted over the past ~2 my. The Southern Ridge of this massif hosts the Lost City Hydrothermal Field (LCHF), an off-axis hydrothermal vent field with carbonate chimney ages surpassing 120,000 yrs. The fluids discharging at LCHF carry geochemical signals that show a direct interaction with serpentinites. However, mineralogical evidence suggests that peridotite hydration began early in the formation of oceanic core complexes and previous modeling results indicate that serpentinization is unlikely to generate the heat necessary to maintain current levels of discharge at LCHF. This work develops a model for the LCHF venting based on the evidence of tectonic strain, detachment faulting, serpentinization, and convective fluid flow. We constrain fluid flow at the LCHF by vent geochemistry, vent temperature, seismically inferred faulting, and expected geothermal gradient ≈100°C/km. Present understanding of tectonic processes at the intersection of MAR and ATF suggests that unroofing of the footwall and crustal flexing of the massif induced normal faults, which run parallel to the MAR, throughout the Southern Ridge. In the absence of the evidence of magmatism, we test the feasibility of the geothermal gradient to cause fluid circulation in the high-permeability, sub-vertical fault zone. Fluid circulation in the fault zone is complemented by the bulk porous flow driven through the Southern Ridge by the lateral temperature gradient between the cold water on the steep face along the ATF side and the hot interior of the massif. In this scenario, the high pH hydrothermal fluids pass through the serpentinized zone before discharging as both high-temperature focused flow (40°-91°C) and low-temperature (≈15°C) diffuse flow at the LCHF.

  17. The geophysical character of southern Alaska - Implications for crustal evolution

    Science.gov (United States)

    Saltus, R.W.; Hudson, T.L.; Wilson, Frederic H.

    2007-01-01

    The southern Alaska continental margin has undergone a long and complicated history of plate convergence, subduction, accretion, and margin-parallel displacements. The crustal character of this continental margin is discernible through combined analysis of aeromagnetic and gravity data with key constraints from previous seismic interpretation. Regional magnetic data are particularly useful in defining broad geophysical domains. One of these domains, the south Alaska magnetic high, is the focus of this study. It is an intense and continuous magnetic high up to 200 km wide and ∼1500 km long extending from the Canadian border in the Wrangell Mountains west and southwest through Cook Inlet to the Bering Sea shelf. Crustal thickness beneath the south Alaska magnetic high is commonly 40–50 km. Gravity analysis indicates that the south Alaska magnetic high crust is dense. The south Alaska magnetic high spatially coincides with the Peninsular and Wrangellia terranes. The thick, dense, and magnetic character of this domain requires significant amounts of mafic rocks at intermediate to deep crustal levels. In Wrangellia these mafic rocks are likely to have been emplaced during Middle and (or) Late Triassic Nikolai Greenstone volcanism. In the Peninsular terrane, the most extensive period of mafic magmatism now known was associated with the Early Jurassic Talkeetna Formation volcanic arc. Thus the thick, dense, and magnetic character of the south Alaska magnetic high crust apparently developed as the response to mafic magmatism in both extensional (Wrangellia) and subduction-related arc (Peninsular terrane) settings. The south Alaska magnetic high is therefore a composite crustal feature. At least in Wrangellia, the crust was probably of average thickness (30 km) or greater prior to Triassic mafic magmatism. Up to 20 km (40%) of its present thickness may be due to the addition of Triassic mafic magmas. Throughout the south Alaska magnetic high, significant crustal growth

  18. Crustal Viscosity Structure Estimated from Multi-Phase Mixing Theory

    Science.gov (United States)

    Shinevar, W. J.; Behn, M. D.; Hirth, G.

    2014-12-01

    Estimates of lower crustal viscosity are typically constrained by analyses of isostatic rebound, post seismic creep, and laboratory-derived flow laws for crustal rocks and minerals. Here we follow a new approach for calculating the viscosity structure of the lower continental crust. We use Perple_X to calculate mineral assemblages for different crustal compositions. Effective viscosity is then calculated using the rheologic mixing model of Huet et al. (2014) incorporating flow laws for each mineral phase. Calculations are performed along geotherms appropriate for the Basin and Range, Tibetan Plateau, Colorado Plateau, and the San Andreas Fault. To assess the role of crustal composition on viscosity, we examined two compositional gradients extending from an upper crust with ~67 wt% SiO2 to a lower crust that is either: (i) basaltic with ~53 wt% SiO2 (Rudnick and Gao, 2003), or (ii) andesitic with ~64% SiO2 (Hacker et al., 2011). In all cases, the middle continental crust has a viscosity that is 2-3 orders of magnitude greater than that inferred for wet quartz, a common proxy for mid-crustal viscosities. An andesitic lower crust results in viscosities of 1020-1021 Pa-s and 1021-1022 Pa-s for hotter and colder crustal geotherms, respectively. A mafic lower crust predicts viscosities that are an order of magnitude higher for the same geotherm. In all cases, the viscosity calculated from the mixing model decreases less with depth compared to single-phase estimates. Lastly, for anhydrous conditions in which alpha quartz is stable, we find that there is a strong correlation between Vp/Vs and bulk viscosity; in contrast, little to no correlation exists for hydrous conditions.

  19. Along-axis crustal structure of the Porcupine Basin from seismic refraction data modelling

    Science.gov (United States)

    Prada, Manel; Watremez, Louise; Chen, Chen; O'Reilly, Brian; Minshull, Tim; Reston, Tim; Wagner, Gerlind; Gaws, Viola; Klaschen, Dirk; Shannon, Patrick

    2016-04-01

    values of the mantle are lower than those expected for a non-altered mantle (i.e. ~8 km/s) supporting mantle serpentinization. The outcome of this study reveals the complexity of the crustal structure of the Porcupine Basin and demonstrates the importance and value of this type of analysis in understanding rift systems. This project is funded by the Irish Shelf Petroleum Studies Group (ISPSG) of the Irish Petroleum Infrastructure Programme Group 4.

  20. 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

  1. 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.

  2. 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

  3. Crustal fraction of moment of inertia in pulsars

    International Nuclear Information System (INIS)

    Atta, Debasis; Mukhopadhyay, Somnath; Basu, D.N.

    2015-01-01

    In the present work, stability of the β-equilibrated dense nuclear matter is analyzed with respect to the thermodynamic stability conditions. Based on the density dependent M3Y (DDM3Y) effective nucleon-nucleon (NN) interaction, the location of the inner edge of neutron star crusts and core-crust transition density and pressure are calculated and crustal fraction of moment of inertia is determined. These results for pressure and density at core-crust transition together with the observed minimum crustal fraction of the total moment of inertia provide a new limit for the radius of the Vela pulsar

  4. Crustal structure and active tectonics in the Eastern Alps

    DEFF Research Database (Denmark)

    Brückl, E.; Behm, M.; Decker, K.

    2010-01-01

    fragment (PA), was interpreted and a triple junction was inferred. The goal of this study has been to relate these deep crustal structures to active tectonics. We used elastic plate modeling to reconsider the Moho fragmentation. We interpret subduction of EU below AD and PA from north to south......During the last decade, a series of controlled source seismic experiments brought new insight into the crustal and lithospheric structure of the Eastern Alps and their adjacent tectonic provinces. A fragmentation of the lithosphere into three blocks, Europe (EU), Adria (AD), and the new Pannonian...

  5. Insights on the Origin of Volatiles from the Geochemical Investigation of Hydrothermal Gas Discharges from Dominica, Lesser Antilles.

    Science.gov (United States)

    Buskop, J.; Joseph, E. P.; Inguaggiato, S.; Varekamp, J. C.; Ku, T.

    2017-12-01

    The major goals of volcano hydrothermal monitoring are to obtain information on temperature, origin, and changes in chemical composition of volcanic fluids. This data contributes to the baseline geochemical monitoring of volcanic activity and informs on potential volcanic hazards to which the public may be exposed. The origins of hydrothermal fluids are diverse and can be magmatic, crustal and atmospheric. Studies of isotopes, inert gases, and thermodynamic calculations help elucidate the origin in each case and determine provenance of volatiles and a re-evaluation of reservoir temperatures. Sulphur isotope ratio (δ34S) for H2S leached from rock is 0 ‰. Low δ15N (-7.3 ‰) is indicative of low sediment addition to source magmas, while high δ15N (+2.1 ‰) indicates greater sediment contribution in magma formation. Baseline monitoring of hydrothermal gases of Dominica for the period 2000 - 2006 show compositions typical of those found in arc-type settings, with N2 excess and low amounts of He and Ar. The dry gas is dominated by CO2 (ranging from 492 to 993 mmol/mol), and has a hydrothermal signature with hydrogen sulphide as the main sulphurous gas. Over the past decade, Dominica has experienced volcanic and tectonic seismicity and a sudden draining episode at the Boiling Lake in November 2016. This study evaluates data obtained in 2017 on gas composition from five (5) hydrothermal areas across the island (Valley of Desolation, Sulphur Spring, Watten Waven, Galion and Penville cold Soufriere) to determine temporal and spatial deviations from baseline geochemical conditions. This study also presents new data, obtained in 2017, on sulphur and nitrogen isotopes to evaluate contributions from various source components. Preliminary results show high CH4/CO2 ratios for gases from Sulphur Springs and Galion, indicative of a significant hydrothermal contribution to these fluids. However, high helium isotope compositions of 7.02 R/Ra signify a clear magmatic origin

  6. 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)

  7. Crustal Gravitational Potential Energy Change and Subduction Earthquakes

    Science.gov (United States)

    Zhu, P. P.

    2017-05-01

    Crustal gravitational potential energy (GPE) change induced by earthquakes is an important subject in geophysics and seismology. For the past forty years the research on this subject stayed in the stage of qualitative estimate. In recent few years the 3D dynamic faulting theory provided a quantitative solution of this subject. The theory deduced a quantitative calculating formula for the crustal GPE change using the mathematic method of tensor analysis under the principal stresses system. This formula contains only the vertical principal stress, rupture area, slip, dip, and rake; it does not include the horizontal principal stresses. It is just involved in simple mathematical operations and does not hold complicated surface or volume integrals. Moreover, the hanging wall vertical moving (up or down) height has a very simple expression containing only slip, dip, and rake. The above results are significant to investigate crustal GPE change. Commonly, the vertical principal stress is related to the gravitational field, substituting the relationship between the vertical principal stress and gravitational force into the above formula yields an alternative formula of crustal GPE change. The alternative formula indicates that even with lack of in situ borehole measured stress data, scientists can still quantitatively calculate crustal GPE change. The 3D dynamic faulting theory can be used for research on continental fault earthquakes; it also can be applied to investigate subduction earthquakes between oceanic and continental plates. Subduction earthquakes hold three types: (a) crust only on the vertical up side of the rupture area; (b) crust and seawater both on the vertical up side of the rupture area; (c) crust only on the vertical up side of the partial rupture area, and crust and seawater both on the vertical up side of the remaining rupture area. For each type we provide its quantitative formula of the crustal GPE change. We also establish a simplified model (called

  8. 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

  9. 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).

  10. Upper mantle and crustal structure of the East Greenland Caledonides

    DEFF Research Database (Denmark)

    Schiffer, Christian; Balling, N.; Jacobsen, B. H.

    The East Greenland and Scandinavian Caledonides once formed a major coherent mountain range, as a consequence of the collision of the continents of Laurentia and Baltica. The crustal and upper mantle structure was furthermore influenced by several geodynamic processes leading to the formation of ...

  11. Mars - Crustal structure inferred from Bouguer gravity anomalies.

    Science.gov (United States)

    Phillips, R. J.; Saunders, R. S.; Conel, J. E.

    1973-01-01

    Bouguer gravity has been computed for the equatorial region of Mars by differencing free air gravity and the gravity predicted from topographic variations. The free air gravity was generated from an eighth-order set of spherical harmonic coefficients. The gravity from topographic variations was generated by integrating a two-dimensional Green's function over each contour level. The Bouguer gravity indicates crustal inhomogeneities on Mars that are postulated to be variations in crustal thickness. The Tharsis ridge is a region of thick continental type crust. The gravity data, structural patterns, topography, and surface geology of this region lead to the interpretation of the Tharsis topographic high as a broad crustal upwarp possibly associated with local formation of lower-density crustal material and subsequent rise of a thicker crust. The Amazonis region is one of several basins of relatively thin crust, analogous to terrestrial ocean basins. The Libya and Hellas basins, which are probable impact features, are also underlain by thin crust and are possible regions of mantle upwelling.

  12. Seismically constrained two-dimensional crustal thermal structure of ...

    Indian Academy of Sciences (India)

    The temperature field within the crust is closely related to tectonic history as well as many other geological processes inside the earth. Therefore, knowledge of the crustal thermal structure of a region is of great importance for its tectonophysical studies. This work deals with the two-dimensional thermal modelling to ...

  13. Deep Crustal Melting and the Survival of Continental Crust

    Science.gov (United States)

    Whitney, D.; Teyssier, C. P.; Rey, P. F.; Korchinski, M.

    2017-12-01

    Plate convergence involving continental lithosphere leads to crustal melting, which ultimately stabilizes the crust because it drives rapid upward flow of hot deep crust, followed by rapid cooling at shallow levels. Collision drives partial melting during crustal thickening (at 40-75 km) and/or continental subduction (at 75-100 km). These depths are not typically exceeded by crustal rocks that are exhumed in each setting because partial melting significantly decreases viscosity, facilitating upward flow of deep crust. Results from numerical models and nature indicate that deep crust moves laterally and then vertically, crystallizing at depths as shallow as 2 km. Deep crust flows en masse, without significant segregation of melt into magmatic bodies, over 10s of kms of vertical transport. This is a major mechanism by which deep crust is exhumed and is therefore a significant process of heat and mass transfer in continental evolution. The result of vertical flow of deep, partially molten crust is a migmatite dome. When lithosphere is under extension or transtension, the deep crust is solicited by faulting of the brittle upper crust, and the flow of deep crust in migmatite domes traverses nearly the entire thickness of orogenic crust in Recognition of the importance of migmatite (gneiss) domes as archives of orogenic deep crust is applicable to determining the chemical and physical properties of continental crust, as well as mechanisms and timescales of crustal differentiation.

  14. An Approach to the Crustal Thickness Inversion Problem

    Science.gov (United States)

    De Marchi, F.; Di Achille, G.

    2017-12-01

    We describe a method to estimate the crustal thickness of a planet and we apply it to Venus. As in the method of (Parker, 1972), modified by (Wieczorek & Phillips, 1998), the gravity field anomalies of a planet are assumed to be due to the combined effect of topography and relief on the crust-mantle interface. No assumptions on isostasy are necessary. In our case, rather than using the expansion of the powers of the relief in Taylor series, we model the gravitational field of topography/relief by means of a large number of prism-shaped masses covering the whole surface of the planet. Under the hypothesis that crustal and mantle densities are the same everywhere, we solve for the relief depths on the crust-mantle interface by imposing that observed and modeled gravity field at a certain reference spherical surface (external to the planet) must be equal. This method can be extended to the case of non-uniform densities. Finally, we calculate a map of the crustal thickness of Venus and compare our results with those predicted by previous work and with the global distribution of main geological features (e.g. rift zones, tesserae, coronae). We discuss the agremeent between our results and the main geodynamical and crustal models put forth to explain the origin of such features and the applicability of this method in the context of the mission VOX (Venus Origins Explore), proposed for NASA's NF4 call.

  15. 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.

  16. Hydrothermal Liquefaction of the Microalgae Phaeodactylum tricornutum

    DEFF Research Database (Denmark)

    Sigaard Christensen, Per; Peng, Gaël; Vogel, Frédéric

    2014-01-01

    The microalgae Phaeodactylum tricornutum was processed by hydrothermal liquefaction in order to assess the influence of reaction temperature and reaction time on the product and elemental distribution. The experiments were carried out at different reaction times (5 and 15 min) and over a wide range...

  17. Hydrothermal synthesis, structure and characterization of new ...

    Indian Academy of Sciences (India)

    Unknown

    Keywords. Hydrothermal; crystal structure; solid electrolyte; iron (III) pyrophosphate. 1. Introduction ... tion, structure and electrical conductivity and the higher values of ..... type cavity structure. Acknowledgements. The authors would like to express their thanks to DST,. New Delhi, for financial assistance under the projects.

  18. Hydrothermal synthesis of a new ethylenediammonium intercalated ...

    Indian Academy of Sciences (India)

    Unknown

    Vanadyl phosphate; hydrothermal synthesis; intercalation; single crystal ... presence of 'en'.7–15 In all these solids en molecules occur in suitable ... all the cases, the mixture was transferred to a 45 ml Teflon lined Parr acid digestion .... position cannot be fully occupied at the same time as it will lead to a P-P distance of.

  19. Valorization of Furfural Residue by Hydrothermal Carbonization

    DEFF Research Database (Denmark)

    Yue, Fen; Zhang, Jia; Pedersen, Christian Marcus

    2017-01-01

    Furfural residue (FR) is a low-cost by-product generated in the furfural production from corncobs, which is mainly composed of cellulose and lignin. In this report, hydrothermal carbonization (HTC) of deashed FR was conducted at various reaction temperatures (200, 220 and 240 °C) and reaction times...

  20. Phase Transformation of Hydrothermally Synthesized Nanoparticle ...

    African Journals Online (AJOL)

    Mild hydrothermal hydrolysis of TiCl4 produces nanorods of the rutile phase of titanium dioxide in high yield, while in the presence of organic acids (citric, acetic, D-tartaric and benzoic acids) anatase is the only product. The effect of these organic acids on the products of the hydrolysis reaction as well as the reaction kinetics ...

  1. 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.

  2. 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.

  3. 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.

  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. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. The Crustal Structure and Seismicity of Eastern Venezuela

    Science.gov (United States)

    Schmitz, M.; Martins, A.; Sobiesiak, M.; Alvarado, L.; Vasquez, R.

    2001-12-01

    Eastern Venezuela is characterized by a moderate to high seismicity, evidenced recently by the 1997 Cariaco earthquake located on the El Pilar Fault, a right lateral strike slip fault which marks the plate boundary between the Caribbean and South-American plates in this region. Recently, the seismic activity seems to migrate towards the zone of subduction of the Lesser Antilles in the northeast, where a mb 6.0 earthquake occurred in October 2000 at 120 km of depth. Periodical changes in the seismic activity are related to the interaction of the stress fields of the strike-slip and the subduction regimes. The seismic activity decreases rapidly towards to the south with some disperse events on the northern edge of the Guayana Shield, related to the Guri fault system. The crustal models used in the region are derived from the information generated by the national seismological network since 1982 and by microseismicity studies in northeastern Venezuela, coinciding in a crustal thickness of about 35 km in depth. Results of seismic refraction measurements for the region were obtained during field campains in 1998 (ECOGUAY) for the Guayana Shield and the Cariaco sedimentary basin and in 2001 (ECCO) for the Oriental Basin. The total crustal thickness decreases from about 45 km on the northern edge of the Guayana Shield to some 36 km close to El Tigre in the center of the Oriental Basin. The average crustal velocity decreases in the same sense from 6.5 to 5.8 km/s. In the Cariaco sedimentary basin a young sedimentary cover of 1 km thickness with a seismic velocity of 2 km/s was derived. Towards the northern limit of the South-American plate, no deep seismic refraction data are available up to now. The improvement of the crustal models used in that region would constitute a step forward in the analysis of the seismic hazard. Seismic refraction studies funded by CONICIT S1-97002996 and S1-2000000685 projects and PDVSA (additional drilling and blasting), recording equipment

  12. 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

  13. 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.)

  14. Whole Algae Hydrothermal Liquefaction Technology Pathway

    Energy Technology Data Exchange (ETDEWEB)

    Biddy, Mary J.; Davis, Ryan; Jones, Susanne B.; Zhu, Yunhua

    2013-03-31

    In support of the Bioenergy Technologies Office, the National Renewable Energy Laboratory (NREL) and the Pacific Northwest National Laboratory (PNNL) are undertaking studies of biomass conversion technologies to hydrocarbon fuels to identify barriers and target research toward reducing conversion costs. Process designs and preliminary economic estimates for each of these pathway cases were developed using rigorous modeling tools (Aspen Plus and Chemcad). These analyses incorporated the best information available at the time of development, including data from recent pilot and bench-scale demonstrations, collaborative industrial and academic partners, and published literature and patents. This 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 blendstocks.

  15. Compositional stratigraphy of crustal material from near-infrared spectra

    International Nuclear Information System (INIS)

    Pieters, C.M.

    1987-01-01

    An Earth-based telescopic program to acquire near-infrared spectra of freshly exposed lunar material now contains data for 17 large impact craters with central peaks. Noritic, gabbroic, anorthositic and troctolitic rock types can be distinguished for areas within these large craters from characteristic absorptions in individual spectra of their walls and central peaks. Norites dominate the upper lunar crust while the deeper crustal zones also contain significant amounts of gabbros and anorthosites. Data for material associated with large craters indicate that not only is the lunar crust highly heterogeneous across the nearside, but that the compositional stratigraphy of the lunar crust is nonuniform. Crustal complexity should be expected for other planetary bodies, which should be studied using high spatial and spectral resolution data in and around large impact craters

  16. Compositional stratigraphy of crustal material from near-infrared spectra

    Science.gov (United States)

    Pieters, Carle M.

    1987-01-01

    An Earth-based telescopic program to acquire near-infrared spectra of freshly exposed lunar material now contains data for 17 large impact craters with central peaks. Noritic, gabbroic, anorthositic and troctolitic rock types can be distinguished for areas within these large craters from characteristic absorptions in individual spectra of their walls and central peaks. Norites dominate the upper lunar crust while the deeper crustal zones also contain significant amounts of gabbros and anorthosites. Data for material associated with large craters indicate that not only is the lunar crust highly heterogeneous across the nearside, but that the compositional stratigraphy of the lunar crust is nonuniform. Crustal complexity should be expected for other planetary bodies, which should be studied using high spatial and spectral resolution data in and around large impact craters.

  17. A new model of crustal structure of Siberia

    DEFF Research Database (Denmark)

    Cherepanova, Yulia; Artemieva, Irina; Thybo, Hans

    2010-01-01

    to the Verkoyansk Ridge/Lena river in the east, and from the Arctic shelf in the north to the Tien Shan and Altay-Sayans mountains in the south. The new crustal model is based on our new ("from scratch") compilation of all available reliable seismic data and includes the results of seismic reflection, refraction...... orientation. Low surface heat flow (on average around 20-22 microW/m3) and the absence of the high-velocity (Vp>7.2 km/s) lowercrustal layer in the block with the thick crust suggest that eclogitization in the crustal root was subdued, thus allowing preservation of the ultra thick, seismically distinguishable...

  18. Hydrothermal optimal power flow using continuation method

    International Nuclear Information System (INIS)

    Raoofat, M.; Seifi, H.

    2001-01-01

    The problem of optimal economic operation of hydrothermal electric power systems is solved using powerful continuation method. While in conventional approach, fixed generation voltages are used to avoid convergence problems, in the algorithm, they are treated as variables so that better solutions can be obtained. The algorithm is tested for a typical 5-bus and 17-bus New Zealand networks. Its capabilities and promising results are assessed

  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. The nature of crustal reflectivity at the southwest Iberian margin

    Science.gov (United States)

    Buffett, G. G.; Torne, M.; Carbonell, R.; Melchiorre, M.; Vergés, J.; Fernàndez, M.

    2017-11-01

    Reprocessing of multi-channel seismic reflection data acquired over the northern margin of the Gulf of Cádiz (SW Iberian margin) places new constraints on the upper crustal structure of the Guadalquivir-Portimão Bank. The data presented have been processed with optimized stacking and interval velocity models, a better approach to multiple attenuation, preserved amplitude information to derive the nature of seismic reflectivity, and accurate time-to-depth conversion after migration. The reprocessed data reveal a bright upper crustal reflector just underneath the Paleozoic basement that spatially coincides with the local positive free-air gravity high called the Gulf of Cádiz Gravity High. To investigate the nature of this reflector and to decipher whether it could be associated with pieces of mantle material emplaced at upper crustal levels, we calculated its reflection coefficient and compared it to a buried high-density ultramafic body (serpentinized peridotite) at the Gorringe Bank. Its reflection coefficient ratio with respect to the sea floor differs by only 4.6% with that calculated for the high-density ultramafic body of the Gorringe Bank, while it differs by 35.8% compared to a drilled Miocene limestone unconformity. This means that the Gulf of Cádiz reflector has a velocity and/or density contrast similar to the peridotite at the Gorringe Bank. However, considering the depth at which it is found (between 2.0 and 4.0 km) and the available geological information, it seems unlikely that the estimated shortening from the Oligocene to present is sufficient to emplace pieces of mantle material at these shallow levels. Therefore, and despite the similarity in its reflection coefficient with the peridotites of the Gorringe Bank, our preferred interpretation is that the upper crustal Gulf of Cádiz reflector represents the seismic response of high-density intracrustal magmatic intrusions that may partially contribute to the Gulf of Cádiz Gravity High.

  1. Parallel Fast Multipole Boundary Element Method for crustal dynamics

    International Nuclear Information System (INIS)

    Quevedo, Leonardo; Morra, Gabriele; Mueller, R Dietmar

    2010-01-01

    Crustal faults and sharp material transitions in the crust are usually represented as triangulated surfaces in structural geological models. The complex range of volumes separating such surfaces is typically three-dimensionally meshed in order to solve equations that describe crustal deformation with the finite-difference (FD) or finite-element (FEM) methods. We show here how the Boundary Element Method, combined with the Multipole approach, can revolutionise the calculation of stress and strain, solving the problem of computational scalability from reservoir to basin scales. The Fast Multipole Boundary Element Method (Fast BEM) tackles the difficulty of handling the intricate volume meshes and high resolution of crustal data that has put classical Finite 3D approaches in a performance crisis. The two main performance enhancements of this method: the reduction of required mesh elements from cubic to quadratic with linear size and linear-logarithmic runtime; achieve a reduction of memory and runtime requirements allowing the treatment of a new scale of geodynamic models. This approach was recently tested and applied in a series of papers by [1, 2, 3] for regional and global geodynamics, using KD trees for fast identification of near and far-field interacting elements, and MPI parallelised code on distributed memory architectures, and is now in active development for crustal dynamics. As the method is based on a free-surface, it allows easy data transfer to geological visualisation tools where only changes in boundaries and material properties are required as input parameters. In addition, easy volume mesh sampling of physical quantities enables direct integration with existing FD/FEM code.

  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. Crustal thickness of Antarctica estimated using data from gravimetric satellites

    Science.gov (United States)

    Llubes, Muriel; Seoane, Lucia; Bruinsma, Sean; Rémy, Frédérique

    2018-04-01

    Computing a better crustal thickness model is still a necessary improvement in Antarctica. In this remote continent where almost all the bedrock is covered by the ice sheet, seismic investigations do not reach a sufficient spatial resolution for geological and geophysical purposes. Here, we present a global map of Antarctic crustal thickness computed from space gravity observations. The DIR5 gravity field model, built from GOCE and GRACE gravimetric data, is inverted with the Parker-Oldenburg iterative algorithm. The BEDMAP products are used to estimate the gravity effect of the ice and the rocky surface. Our result is compared to crustal thickness calculated from seismological studies and the CRUST1.0 and AN1 models. Although the CRUST1.0 model shows a very good agreement with ours, its spatial resolution is larger than the one we obtain with gravimetric data. Finally, we compute a model in which the crust-mantle density contrast is adjusted to fit the Moho depth from the CRUST1.0 model. In East Antarctica, the resulting density contrast clearly shows higher values than in West Antarctica.

  4. Crustal thickness of Antarctica estimated using data from gravimetric satellites

    Directory of Open Access Journals (Sweden)

    M. Llubes

    2018-04-01

    Full Text Available Computing a better crustal thickness model is still a necessary improvement in Antarctica. In this remote continent where almost all the bedrock is covered by the ice sheet, seismic investigations do not reach a sufficient spatial resolution for geological and geophysical purposes. Here, we present a global map of Antarctic crustal thickness computed from space gravity observations. The DIR5 gravity field model, built from GOCE and GRACE gravimetric data, is inverted with the Parker–Oldenburg iterative algorithm. The BEDMAP products are used to estimate the gravity effect of the ice and the rocky surface. Our result is compared to crustal thickness calculated from seismological studies and the CRUST1.0 and AN1 models. Although the CRUST1.0 model shows a very good agreement with ours, its spatial resolution is larger than the one we obtain with gravimetric data. Finally, we compute a model in which the crust–mantle density contrast is adjusted to fit the Moho depth from the CRUST1.0 model. In East Antarctica, the resulting density contrast clearly shows higher values than in West Antarctica.

  5. Boron isotope fractionation in magma via crustal carbonate dissolution.

    Science.gov (United States)

    Deegan, Frances M; Troll, Valentin R; Whitehouse, Martin J; Jolis, Ester M; Freda, Carmela

    2016-08-04

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ(11)B values down to -41.5‰, reflecting preferential partitioning of (10)B into the assimilating melt. Loss of (11)B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports (11)B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ(11)B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  6. Precambrian crustal history of the Nimrod Group, central Transantarctic Mountains

    International Nuclear Information System (INIS)

    Goodge, J.W.; Fanning, C.M.

    2002-01-01

    High-grade metamorphic and igneous rocks of the Nimrod Group represent crystalline basement to the central Transantarctic Mountains. Despite metamorphism and penetrative deformation during the Ross Orogeny, they preserve a deep record of Precambrian geologic history in this sector of the East Antarctic shield. A review of available U-Pb geochronometric data reveals multiple geologic events spanning 2.5 b.y. of Archean to Early Paleozoic time, including: (1) juvenile Archean crust production by magmatism between 3150 and 3000 Ma; (2) crustal stabilisation and metamorphism between 2955 and 2900 Ma; (3) ultra-metamorphism or anatexis at c. 2500 Ma; (4) deep-crustal metamorphism and magmatism between 1720 and 1730 Ma, redefining the Nimrod Orogeny; (5) post-1700 Ma sedimentation; and (6) basement reactivation involving high-grade metamorphism, magmatism, and penetrative deformation during the Ross Orogeny between 540 and 515 Ma. A strong regional metamorphic and deformational Ross overprint, dated by U-Pb and Ar thermochronology, had pronounced thermomechanical effects on the basement assemblage, yet rocks of the Nimrod Group retain robust evidence of their Precambrian ancestry. The zircon U-Pb record therefore demonstrates that primary crustal lithosphere of the East Antarctic shield extends to the central Transantarctic Mountains, and that it has undergone multiple episodes of reactivation culminating in the Ross Orogeny. (author). 48 refs., 2 figs., 1 tab

  7. Boron isotope fractionation in magma via crustal carbonate dissolution

    Science.gov (United States)

    Deegan, Frances M.; Troll, Valentin R.; Whitehouse, Martin J.; Jolis, Ester M.; Freda, Carmela

    2016-08-01

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ11B values down to -41.5‰, reflecting preferential partitioning of 10B into the assimilating melt. Loss of 11B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports 11B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ11B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  8. 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.

  9. 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

  10. Magnetic Mineralogy of a Complete Oceanic Crustal Section (IODP hole 1256D)

    Science.gov (United States)

    Krasa, D.; Herrero-Bervera, E.; Acton, G.; Rodriguez Durand, S.

    2008-12-01

    lower part of the sheeted dykes witnesses the onset of hydrothermal alteration. In the gabbroic part of the section, grain sizes of TMs reach values of up to several mm. These findings lead to the conclusion that the different parts of the section had acquired their remanent magnetisation by different mechanisms: The extrusive part carries a TRM, the intensity of which was later influenced by LT oxidation and inversion. The sheeted dyke part is likely to carry a CRM acquired during hydrothermal alteration, and the underlying gabbro acquired a TCRM at a time significantly after emplacement due to slow cooling at this depth.

  11. "Storms of crustal stress" and AE earthquake precursors

    Directory of Open Access Journals (Sweden)

    G. P. Gregori

    2010-02-01

    Full Text Available Acoustic emission (AE displays violent paroxysms preceding strong earthquakes, observed within some large area (several hundred kilometres wide around the epicentre. We call them "storms of crustal stress" or, briefly "crustal storms". A few case histories are discussed, all dealing with the Italian peninsula, and with the different behaviour shown by the AE records in the Cephalonia island (Greece, which is characterized by a different tectonic setting.

    AE is an effective tool for diagnosing the state of some wide slab of the Earth's crust, and for monitoring its evolution, by means of AE of different frequencies. The same effect ought to be detected being time-delayed, when referring to progressively lower frequencies. This results to be an effective check for validating the physical interpretation.

    Unlike a seismic event, which involves a much limited focal volume and therefore affects a restricted area on the Earth's surface, a "crustal storm" typically involves some large slab of lithosphere and crust. In general, it cannot be easily reckoned to any specific seismic event. An earthquake responds to strictly local rheological features of the crust, which are eventually activated, and become crucial, on the occasion of a "crustal storm". A "crustal storm" lasts typically few years, eventually involving several destructive earthquakes that hit at different times, at different sites, within that given lithospheric slab.

    Concerning the case histories that are here discussed, the lithospheric slab is identified with the Italian peninsula. During 1996–1997 a "crustal storm" was on, maybe elapsing until 2002 (we lack information for the period 1998–2001. Then, a quiet period occurred from 2002 until 26 May 2008, when a new "crustal storm" started, and by the end of 2009 it is still on. During the 1996–1997 "storm" two strong earthquakes occurred (Potenza and

  12. 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.

  13. Geometry and subsidence history of the Dead Sea basin: A case for fluid-induced mid-crustal shear zone?

    Science.gov (United States)

    ten Brink, Uri S.; Flores, C.H.

    2012-01-01

    Pull-apart basins are narrow zones of crustal extension bounded by strike-slip faults that can serve as analogs to the early stages of crustal rifting. We use seismic tomography, 2-D ray tracing, gravity modeling, and subsidence analysis to study crustal extension of the Dead Sea basin (DSB), a large and long-lived pull-apart basin along the Dead Sea transform (DST). The basin gradually shallows southward for 50 km from the only significant transverse normal fault. Stratigraphic relationships there indicate basin elongation with time. The basin is deepest (8-8.5 km) and widest (???15 km) under the Lisan about 40 km north of the transverse fault. Farther north, basin depth is ambiguous, but is 3 km deep immediately north of the lake. The underlying pre-basin sedimentary layer thickens gradually from 2 to 3 km under the southern edge of the DSB to 3-4 km under the northern end of the lake and 5-6 km farther north. Crystalline basement is ???11 km deep under the deepest part of the basin. The upper crust under the basin has lower P wave velocity than in the surrounding regions, which is interpreted to reflect elevated pore fluids there. Within data resolution, the lower crust below ???18 km and the Moho are not affected by basin development. The subsidence rate was several hundreds of m/m.y. since the development of the DST ???17 Ma, similar to other basins along the DST, but subsidence rate has accelerated by an order of magnitude during the Pleistocene, which allowed the accumulation of 4 km of sediment. We propose that the rapid subsidence and perhaps elongation of the DSB are due to the development of inter-connected mid-crustal ductile shear zones caused by alteration of feldspar to muscovite in the presence of pore fluids. This alteration resulted in a significant strength decrease and viscous creep. We propose a similar cause to the enigmatic rapid subsidence of the North Sea at the onset the North Atlantic mantle plume. Thus, we propose that aqueous fluid flux

  14. Smectite alteration

    International Nuclear Information System (INIS)

    Anderson, D.M.

    1984-11-01

    This report contains the proceedings of a second workshop in Washington DC December 8-9, 1983 on the alteration of smectites intended for use as buffer materials in the long-term containment of nuclear wastes. It includes extended summaries of all presentations and a transcript of the detailed scientific discussion. The discussions centered on three main questions: What is the prerequisite for and what is the precise mechanism by which smectite clays may be altered to illite. What are likly sources of potassium with respect to the KBS project. Is it likely that the conversion of smectite to illite will be of importance in the 10 5 to the 10 6 year time frame. The workshop was convened to review considerations and conclusions in connection to these questions and also to broaden the discussion to consider the use of smectite clays as buffer materials for similar applications in different geographical and geological settings. SKBF/KBS technical report 83-03 contains the proceedings from the first workshop on these matters that was held at the State University of New York, Buffalo May 26-27, 1982. (Author)

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. 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

  1. 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...

  2. Hydrothermal synthesis of hexagonal magnesium hydroxide nanoflakes

    International Nuclear Information System (INIS)

    Wang, Qiang; Li, Chunhong; Guo, Ming; Sun, Lingna; Hu, Changwen

    2014-01-01

    Graphical abstract: Hexagonal Mg(OH) 2 nanoflakes were synthesized via hydrothermal method in the presence of PEG-20,000. Results show that PEG-20,000 plays an important role in the formation of this kind of nanostructure. The SAED patterns taken from the different positions on a single hexagonal Mg(OH) 2 nanoflake yielded different crystalline structures. The structure of the nanoflakes are polycrystalline and the probable formation mechanism of Mg(OH) 2 nanoflakes is discussed. - Highlights: • Hexagonal Mg(OH) 2 nanoflakes were synthesized via hydrothermal method. • PEG-20,000 plays an important role in the formation of hexagonal nanostructure. • Mg(OH) 2 nanoflakes show different crystalline structures at different positions. • The probable formation mechanism of hexagonal Mg(OH) 2 nanoflakes was reported. - Abstract: Hexagonal magnesium hydroxide (Mg(OH) 2 ) nanoflakes were successfully synthesized via hydrothermal method in the presence of the surfactant polyethylene glycol 20,000 (PEG-20,000). Results show that PEG-20,000 plays an important role in the formation of this kind of nanostructure. The composition, morphologies and structure of the Mg(OH) 2 nanoflakes were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). The SAED patterns taken from the different positions on a single hexagonal Mg(OH) 2 nanoflake show different crystalline structures. The structure of the nanoflakes are polycrystalline and the probable formation mechanism of Mg(OH) 2 nanoflakes is discussed. Brunauer–Emmett–Teller (BET) analysis were performed to investigate the porous structure and surface area of the as-obtained nanoflakes

  3. Borehole plugging by hydrothermal transport. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Roy, D.M.; White, W.B.

    1976-02-28

    Calcium silicate--and aluminosilicate--compositions based on mixtures of fine grained quartz with various cements or calcium silicate compounds have been investigated under hydrothermal conditions in the temperature range 110-250/sup 0/C and pressure range 1,000-10,000 psi, pressures which are always in excess of that required to maintain liquid H/sub 2/O, and approximate the confining pressures which might be anticipated in deep boreholes. All silicate cement combinations investigated produce materials having adequate strength after reaction times of 1 day or longer. The calcium aluminate cement was also adequate with respect to strength but would need to be investigated more extensively for overall properties because of its highly reactive chemistry. The mini-rock cylinder-cement plug hydrothermal experiments in both limestone and sandstone resulted in reasonable magnitudes of bonding strength. The typical shear strength of a hydrothermally treated cement-sandstone plug is 1030 psi, and the compressive strength of the extruded cement plug is 9550 psi. Reactions having a potential for producing calcium carbonate plugs in holes drilled in carbonate rocks were studied. It should be noted that most cements are calcium silicate systems and are chemically compatible with the CaCO/sub 3/ and CaMg(CO/sub 3/)/sub 2/ in the rock walls of the hole. A side benefit from this research is some insight into the suitability of massive carbonate rocks as disposal sites. Carbonate rocks by themselves are highly impermeable, have low exchange capacity, and a low water content--all properties that are desirable in the storage medium. A major drawback is the presence of secondary permeability in the form of solutionally modified joints, fractures, and bedding planes.

  4. Borehole plugging by hydrothermal transport. Final report

    International Nuclear Information System (INIS)

    Roy, D.M.; White, W.B.

    1976-01-01

    Calcium silicate--and aluminosilicate--compositions based on mixtures of fine grained quartz with various cements or calcium silicate compounds have been investigated under hydrothermal conditions in the temperature range 110-250 0 C and pressure range 1,000-10,000 psi, pressures which are always in excess of that required to maintain liquid H 2 O, and approximate the confining pressures which might be anticipated in deep boreholes. All silicate cement combinations investigated produce materials having adequate strength after reaction times of 1 day or longer. The calcium aluminate cement was also adequate with respect to strength but would need to be investigated more extensively for overall properties because of its highly reactive chemistry. The mini-rock cylinder-cement plug hydrothermal experiments in both limestone and sandstone resulted in reasonable magnitudes of bonding strength. The typical shear strength of a hydrothermally treated cement-sandstone plug is 1030 psi, and the compressive strength of the extruded cement plug is 9550 psi. Reactions having a potential for producing calcium carbonate plugs in holes drilled in carbonate rocks were studied. It should be noted that most cements are calcium silicate systems and are chemically compatible with the CaCO 3 and CaMg(CO 3 ) 2 in the rock walls of the hole. A side benefit from this research is some insight into the suitability of massive carbonate rocks as disposal sites. Carbonate rocks by themselves are highly impermeable, have low exchange capacity, and a low water content--all properties that are desirable in the storage medium. A major drawback is the presence of secondary permeability in the form of solutionally modified joints, fractures, and bedding planes

  5. Hydrothermal Liquefaction Treatment Preliminary Hazard Analysis Report

    Energy Technology Data Exchange (ETDEWEB)

    Lowry, Peter P.; Wagner, Katie A.

    2015-08-31

    A preliminary hazard assessment was completed during February 2015 to evaluate the conceptual design of the modular hydrothermal liquefaction treatment system. The hazard assessment was performed in 2 stages. An initial assessment utilizing Hazard Identification and Preliminary Hazards Analysis (PHA) techniques identified areas with significant or unique hazards (process safety-related hazards) that fall outside of the normal operating envelope of PNNL and warranted additional analysis. The subsequent assessment was based on a qualitative What-If analysis. This analysis was augmented, as necessary, by additional quantitative analysis for scenarios involving a release of hazardous material or energy with the potential for affecting the public.

  6. Vertical Cable Seismic Survey for Hydrothermal Deposit

    Science.gov (United States)

    Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

    2012-04-01

    The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have, however, also confirmed that the uncertainty in the locations of the source and of the hydrophones could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures a accurate positioning and a deployment techniques

  7. Crustal heterogeneity and seismotectonics of the region around Beijing, China

    Science.gov (United States)

    Huang, Jinli; Zhao, Dapeng

    2004-07-01

    A detailed three-dimensional (3-D) P-wave velocity model of the crust and uppermost mantle under the Chinese capital (Beijing) region is determined with a spatial resolution of 25 km in the horizontal direction and 4-17 km in depth. We used 48,750 precise P-wave arrival times from 2973 events of local crustal earthquakes, controlled seismic explosions and quarry blasts. These events were recorded by a new digital seismic network consisting of 101 seismic stations equipped with high-sensitivity seismometers. The data are analyzed by using a 3-D seismic tomography method. Our tomographic model provides new insights into the geological structure and tectonics of the region, such as the lithological variations and large fault zones across the major geological terranes like the North China Basin, the Taihangshan and the Yanshan mountainous areas. The velocity images of the upper crust reflect well the surface geological and topographic features. In the North China Basin, the depression and uplift areas are imaged as slow and fast velocities, respectively. The Taihangshan and Yanshan mountainous regions are generally imaged as broad high-velocity zones, while the Quaternary intermountain basins show up as small low-velocity anomalies. Velocity changes are visible across some of the large fault zones. Large crustal earthquakes, such as the 1976 Tangshan earthquake ( M=7.8) and the 1679 Sanhe earthquake ( M=8.0), generally occurred in high-velocity areas in the upper to middle crust. In the lower crust to the uppermost mantle under the source zones of the large earthquakes, however, low-velocity and high-conductivity anomalies exist, which are considered to be associated with fluids. The fluids in the lower crust may cause the weakening of the seismogenic layer in the upper and middle crust and thus contribute to the initiation of the large crustal earthquakes.

  8. Effect of Crustal Density Structures on GOCE Gravity Gradient Observables

    Directory of Open Access Journals (Sweden)

    Robert Tenzer Pavel Novák

    2013-01-01

    Full Text Available We investigate the gravity gradient components corrected for major known anomalous density structures within the Earth¡¦s crust. Heterogeneous mantle density structures are disregarded. The gravimetric forward modeling technique is utilized to compute the gravity gradients based on methods for a spherical harmonic analysis and synthesis of a gravity field. The Earth¡¦s gravity gradient components are generated using the global geopotential model GOCO-03s. The topographic and stripping gravity corrections due to the density contrasts of the ocean and ice are computed from the global topographic/bathymetric model DTM2006.0 (which also includes the ice-thickness dataset. The discrete data of sediments and crust layers taken from the CRUST2.0 global crustal model are then used to apply the additional stripping corrections for sediments and remaining anomalous crustal density structures. All computations are realized globally on a one arc-deg geographical grid at a mean satellite elevation of 255 km. The global map of the consolidated crust-stripped gravity gradients reveals distinctive features which are attributed to global tectonics, lithospheric plate configuration, lithosphere structure and mantle dynamics (e.g., glacial isostatic adjustment, mantle convection. The Moho signature, which is the most pronounced signal in these refined gravity gradients, is superimposed over a weaker gravity signal of the lithospheric mantle. An interpretational quality of the computed (refined gravity gradient components is mainly limited by a low accuracy and resolution of the CRUST2.0 sediment and crustal layer data and unmodeled mantle structures.

  9. Evidence for Cyclical Fractional Crystallization, Recharge, and Assimilation in Basalts of the Kimama Core, Central Snake River Plain, Idaho: A 5.5-million-year Highlight Reel of Petrogenetic processes in a Mid-Crustal Sill Complex

    Science.gov (United States)

    Potter, Katherine E.; Shervais, John W.; Christiansen, Eric H.; Vetter, Scott K.

    2018-02-01

    Basalts erupted in the Snake River Plain of central Idaho and sampled in the Kimama drill core link eruptive processes to the construction of mafic intrusions over 5.5 Ma. Cyclic variations in basalt composition reveal temporal chemical heterogeneity related to fractional crystallization and the assimilation of previously-intruded mafic sills. A range of compositional types are identified within 1912 m of continuous drill core: Snake River olivine tholeiite (SROT), low K SROT, high Fe-Ti, and evolved and high K-Fe lavas similar to those erupted at Craters of the Moon National Monument. Detailed lithologic and geophysical logs document 432 flow units comprising 183 distinct lava flows and 78 flow groups. Each lava flow represents a single eruptive episode, while flow groups document chemically and temporally related flows that formed over extended periods of time. Temporal chemical variation demonstrates the importance of source heterogeneity and magma processing in basalt petrogenesis. Low-K SROT and high Fe-Ti basalts are genetically related to SROT as, respectively, hydrothermally-altered and fractionated daughters. Cyclic variations in the chemical composition of Kimama flow groups are apparent as 21 upward fractionation cycles, six recharge cycles, eight recharge-fractionation cycles, and five fractionation-recharge cycles. We propose that most Kimama basalt flows represent typical fractionation and recharge patterns, consistent with the repeated influx of primitive SROT parental magmas and extensive fractional crystallization coupled with varying degrees of assimilation of gabbroic to ferrodioritic sills at shallow to intermediate depths over short durations. Trace element models show that parental SROT basalts were generated by 5-10% partial melting of enriched mantle at shallow depths above the garnet-spinel lherzolite transition. The distinctive evolved and high K-Fe lavas are rare. Found at four depths, 319 m, 1045 m, 1078 m, and 1189 m, evolved and high K

  10. Improved H-κ Method by Harmonic Analysis on Ps and Crustal Multiples in Receiver Functions with respect to Dipping Moho and Crustal Anisotropy

    Science.gov (United States)

    Li, J.; Song, X.; Wang, P.; Zhu, L.

    2017-12-01

    The H-κ method (Zhu and Kanamori, 2000) has been widely used to estimate the crustal thickness and Vp/Vs ratio with receiver functions. However, in regions where the crustal structure is complicated, the method may produce uncertain or even unrealistic results, arising particularly from dipping Moho and/or crustal anisotropy. Here, we propose an improved H-κ method, which corrects for these effects first before stacking. The effect of dipping Moho and crustal anisotropy on Ps receiver function has been well studied, but not as much on crustal multiples (PpPs and PpSs+PsPs). Synthetic tests show that the effect of crustal anisotropy on the multiples are similar to Ps, while the effect of dipping Moho on the multiples is 5 times that on Ps (same cosine trend but 5 times in time shift). A Harmonic Analysis (HA) method for dipping/anisotropy was developed by Wang et al. (2017) for crustal Ps receiver functions to extract parameters of dipping Moho and crustal azimuthal anisotropy. In real data, the crustal multiples are much more complicated than the Ps. Therefore, we use the HA method (Wang et al., 2017), but apply separately to Ps and the multiples. It shows that although complicated, the trend of multiples can still be reasonably well represented by the HA. We then perform separate azimuthal corrections for Ps and the multiples and stack to obtain a combined receiver function. Lastly, the traditional H-κ procedure is applied to the stacked receiver function. We apply the improved H-κ method on 40 CNDSN (Chinese National Digital Seismic Network) stations distributed in a variety of geological setting across the Chinese continent. The results show apparent improvement compared to the traditional H-κ method, with clearer traces of multiples and stronger stacking energy in the grid search, as well as more reliable H-κ values.

  11. Volcanism and hydrothermalism on a hotspot-influenced ridge: Comparing Reykjanes Peninsula and Reykjanes Ridge, Iceland

    Science.gov (United States)

    Pałgan, Dominik; Devey, Colin W.; Yeo, Isobel A.

    2017-12-01

    Current estimates indicate that the number of high-temperature vents (one of the primary pathways for the heat extraction from the Earth's mantle) - at least 1 per 100 km of axial length - scales with spreading rate and should scale with crustal thickness. But up to present, shallow ridge axes underlain by thick crust show anomalously low incidences of high-temperature activity. Here we compare the Reykjanes Ridge, an abnormally shallow ridge with thick crust and only one high-temperature vent known over 900 km axial length, to the adjacent subaerial Reykjanes Peninsula (RP), which is characterized by high-temperature geothermal sites confined to four volcanic systems transected by fissure swarms with young (Holocene) volcanic activity, multiple faults, cracks and fissures, and continuous seismic activity. New high-resolution bathymetry (gridded at 60 m) of the Reykjanes Ridge between 62°30‧N and 63°30‧N shows seven Axial Volcanic Ridges (AVR) that, based on their morphology, geometry and tectonic regime, are analogues for the volcanic systems and fissure swarms on land. We investigate in detail the volcano-tectonic features of all mapped AVRs and show that they do not fit with the previously suggested 4-stage evolution model for AVR construction. Instead, we suggest that AVR morphology reflects the robust or weak melt supply to the system and two (or more) eruption mechanisms may co-exist on one AVR (in contrast to 4-stage evolution model). Our interpretations indicate that, unlike on the Reykjanes Peninsula, faults on and around AVRs do not cluster in orientation domains but all are subparallel to the overall strike of AVRs (orthogonal to spreading direction). High abundance of seamounts shows that the region centered at 62°47‧N and 25°04‧W (between AVR-5 and -6) is volcanically robust while the highest fault density implies that AVR-1 and southern part of AVR-6 rather undergo period of melt starvation. Based on our observations and interpretations we

  12. Testing Predictions of Continental Insulation using Oceanic Crustal Thicknesses

    Science.gov (United States)

    Hoggard, Mark; Shorttle, Oliver; White, Nicky

    2016-04-01

    The thermal blanketing effect of continental crust has been predicted to lead to elevated temperatures within the upper mantle beneath supercontinents. Initial break-up is associated with increased magmatism and the generation of flood basalts. Continued rifting and sea-floor spreading lead to a steady reduction of this thermal anomaly. Recently, evidence in support of this behaviour has come from the major element geochemistry of mid-ocean ridge basalts, which suggest excess rifting temperatures of ˜ 150 °C that decay over ˜ 100 Ma. We have collated a global inventory of ˜ 1000 seismic reflection profiles and ˜ 500 wide-angle refraction experiments from the oceanic realm. Data are predominantly located along passive margins, but there are also multiple surveys in the centres of the major oceanic basins. Oceanic crustal thickness has been mapped, taking care to avoid areas of secondary magmatic thickening near seamounts or later thinning such as across transform faults. These crustal thicknesses are a proxy for mantle potential temperature at the time of melt formation beneath a mid-ocean ridge system, allowing us to quantify the amplitude and duration of thermal anomalies generated beneath supercontinents. The Jurassic break-up of the Central Atlantic and the Cretaceous rifting that formed the South Atlantic Ocean are both associated with excess temperatures of ˜ 50 °C that have e-folding times of ˜ 50 Ma. In addition to this background trend, excess temperatures reach > 150 °C around the region of the Rio Grande Rise, associated with the present-day Tristan hotspot. The e-folding time of this more local event is ˜ 10 Ma, which mirrors results obtained for the North Atlantic Ocean south of Iceland. In contrast, crustal thicknesses from the Pacific Ocean reveal approximately constant potential temperature through time. This observation is in agreement with predictions, as the western Pacific was formed by rifting of an oceanic plate. In summary

  13. Lower crustal intrusions beneath the southern Baikal Rift Zone

    DEFF Research Database (Denmark)

    Nielsen, Christoffer; Thybo, Hans

    2009-01-01

    centre. The BEST (Baikal Explosion Seismic Transect) project acquired a 360-km long, deep seismic, refraction/wide-angle reflection profile in 2002 across southern Lake Baikal. The data from this project is used for identification of large-scale crustal structures and modelling of the seismic velocities....../s and 7.9 km/s. We interpret this feature as resulting from mafic to ultra-mafic intrusions in the form of sills. Petrological interpretation of the velocity values suggests that the intrusions are sorted by fractional crystallization into plagioclase-rich low-velocity layers and pyroxene- and olivine...

  14. 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.

  15. 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.

  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. 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

  18. 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

  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. 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 ...

  1. 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

  2. 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.

  3. Hydrothermal carbonization. Investigation of process parameters

    Energy Technology Data Exchange (ETDEWEB)

    Steinbrueck, J.; Rossbach, M.; Reichert, D.; Bockhorn, H. [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. of Technical Chemistry and Polymerchemistry; Walz, L. [Energie Baden-Wuerttemberg AG, Karlsruhe (Germany); Eyler, D. [European Institute