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 ...

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

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

2013-01-01

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

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

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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)

Radon surveys and monitoring at active volcanoes: an open window on deep hydrothermal systems and their dynamics

Science.gov (United States)

Cigolini, Corrado; Laiolo, Marco; Coppola, Diego

2017-04-01

The behavior of fluids in hydrothermal systems is critical in volcano monitoring and geothermal prospecting. Analyzing the time series of radon emissions on active volcanoes is strategic for detecting and interpreting precursory signals of changes in volcanic activity, eventually leading to eruptions. Radon is a radioactive gas generated from the decay of U bearing rocks, soils and magmas. Although radon has been regarded as a potential precursor of earthquakes, radon anomalies appear to be better suited to forecast volcanic eruptions since we know where paroxysms may occur and we can follow the evolution of volcanic activity. Radon mapping at active volcanoes is also a reliable tool to assess diffuse and concentrated degassing as well as efficiently detecting earthquake-volcano interactions. Systematic radon monitoring has been shown to be a key factor for evaluating the rise of volcanic and hydrothermal fluids. In fact, the decay properties of radon, the duration of radon anomalies together with sampling rates may be cross-checked with the chemistry of hydrothermal fluids (and their transport properties) to constrain fluids ascent rates and to infer the permeability and porosity of rocks in sectors surrounding the active conduits. We hereby further discuss the data of radon surveys and monitoring at Somma-Vesuvius, Stromboli and La Soufrière (Guadeloupe, Lesser Antilles). The integrated analysis of seismic and geochemical data, including radon emissions, may be successfully used in testing temperature distributions and variations of porosity and permeability in volcanic hydrothermal systems and can be used as a proxy to analyze geothermal reservoirs.

Geochemical and visual indicators of hydrothermal fluid flow through a sediment-hosted volcanic ridge in the Central Bransfield Basin (Antarctica.

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Alfred Aquilina

Full Text Available In the austral summer of 2011 we undertook an investigation of three volcanic highs in the Central Bransfield Basin, Antarctica, in search of hydrothermal activity and associated fauna to assess changes since previous surveys and to evaluate the extent of hydrothermalism in this basin. At Hook Ridge, a submarine volcanic edifice at the eastern end of the basin, anomalies in water column redox potential (E(h were detected close to the seafloor, unaccompanied by temperature or turbidity anomalies, indicating low-temperature hydrothermal discharge. Seepage was manifested as shimmering water emanating from the sediment and from mineralised structures on the seafloor; recognisable vent endemic fauna were not observed. Pore fluids extracted from Hook Ridge sediment were depleted in chloride, sulfate and magnesium by up to 8% relative to seawater, enriched in lithium, boron and calcium, and had a distinct strontium isotope composition ((87Sr/(86Sr = 0.708776 at core base compared with modern seawater ((87Sr/(86Sr ≈ 0.70918, indicating advection of hydrothermal fluid through sediment at this site. Biogeochemical zonation of redox active species implies significant moderation of the hydrothermal fluid with in situ diagenetic processes. At Middle Sister, the central ridge of the Three Sisters complex located about 100 km southwest of Hook Ridge, small water column E(h anomalies were detected but visual observations of the seafloor and pore fluid profiles provided no evidence of active hydrothermal circulation. At The Axe, located about 50 km southwest of Three Sisters, no water column anomalies in E(h, temperature or turbidity were detected. These observations demonstrate that the temperature anomalies observed in previous surveys are episodic features, and suggest that hydrothermal circulation in the Bransfield Strait is ephemeral in nature and therefore may not support vent biota.

Dynamic behavior of Kilauea Volcano and its relation to hydrothermal systems and geothermal energy

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Kauhikaua, Jim; Moore, R.B.; ,

1993-01-01

Exploitation of hydrothermal systems on active basaltic volcanoes poses some unique questions about the role of volcanism and hydrothermal system evolution. Volcanic activity creates and maintains hydrothermal systems while earthquakes create permeable fractures that, at least temporarily, enhance circulation. Magma and water, possibly hydrothermal water, can interact violently to produce explosive eruptions. Finally, we speculate on whether volcanic behavior can be affected by high rates of heat extraction.

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

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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.

Vein networks in hydrothermal systems provide constraints for the monitoring of active volcanoes.

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Cucci, Luigi; Di Luccio, Francesca; Esposito, Alessandra; Ventura, Guido

2017-03-10

Vein networks affect the hydrothermal systems of many volcanoes, and variations in their arrangement may precede hydrothermal and volcanic eruptions. However, the long-term evolution of vein networks is often unknown because data are lacking. We analyze two gypsum-filled vein networks affecting the hydrothermal field of the active Lipari volcanic Island (Italy) to reconstruct the dynamics of the hydrothermal processes. The older network (E1) consists of sub-vertical, N-S striking veins; the younger network (E2) consists of veins without a preferred strike and dip. E2 veins have larger aperture/length, fracture density, dilatancy, and finite extension than E1. The fluid overpressure of E2 is larger than that of E1 veins, whereas the hydraulic conductance is lower. The larger number of fracture intersections in E2 slows down the fluid movement, and favors fluid interference effects and pressurization. Depths of the E1 and E2 hydrothermal sources are 0.8 km and 4.6 km, respectively. The decrease in the fluid flux, depth of the hydrothermal source, and the pressurization increase in E2 are likely associated to a magma reservoir. The decrease of fluid discharge in hydrothermal fields may reflect pressurization at depth potentially preceding hydrothermal explosions. This has significant implications for the long-term monitoring strategy of volcanoes.

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

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

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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.

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

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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

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

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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.

Submarine Hydrothermal Activity and Gold-Rich Mineralization at Brothers Volcano, Southern Kermadec Arc, New Zealand

Science.gov (United States)

de Ronde, C. E.; Massoth, G. J.; Christenson, B. W.; Butterfield, D. A.; Ishibashi, J.; Hannington, M. D.; Ditchburn, B. G.; Embley, R. W.; Lupton, J. E.; Kamenetsky, D.; Reyes, A. G.; Lahr, J.; Takai, K.

2006-12-01

Brothers volcano is one of several hydrothermally active volcanoes that occur along the Kermadec active arc front, NE of New Zealand. It forms an elongate edifice 13 km long by 8 km across that strikes NW-SE. The volcano has a caldera with a basal diameter of ~3 km and a floor at 1,850 m below sea level, surrounded by 290 to 530 m high walls. A volcanic cone of dacite rises 350 m from the caldera floor and partially coalesces with the southern caldera wall. Three hydrothermal sites have been located; on the NW caldera wall, on the SE caldera wall, and on the dacite cone. The NW caldera vent site is a long-term hydrothermal system that is today dominated by evolved seawater but has had episodic injections of magmatic fluid. The SE caldera site represents the main upflow of a relatively well-established magmatic-hydrothermal system on the seafloor where sulfide-rich chimneys are extant. The cone site is a nascent magmatic-hydrothermal system where crack zones localize upwelling acidic waters. Each of these different vent sites represent diverse parts of an evolving hydrothermal system, any one of which may be typical of submarine volcanic arcs. Hydrothermal venting is today occurring at the NW caldera and cone sites. The former is characterized by high-temperature (up to 302°C) venting with pH down to 2.8, low Mg and SO4 values, Cl between 510 and 760 mM, elevated Si and increasing Fe and Mn values with increasing Cl concentrations, consistent with a mostly Cl-enriched endmember. By contrast, vent fluids from the cone site are gas-rich (up to 220 mM total gas), have temperatures 30 ppm) zones in some chimneys formed over a short period of time, coincident with pulses of magmatic fluid into the hydrothermal system.

Hydrothermal Petroleum in Active Continental Rift: Lake Chapala, Western Mexico, Initial Results.

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Zarate-del Valle, P. F.; Simoneit, B. R.; Ramirez-Sanchez, H. U.

2003-12-01

Lake Chapala in western Mexico is located partially in the Citala Rift, which belongs to the well-known neotectonic Jalisco continental triple junction. The region is characterized by active volcanism (Ceboruco, Volcan de Fuego), tectonic (1995 earthquake, M=8, 40-50 mm to SW) and hydrothermal (San Juan Cosala & Villa Corona spas and La Calera sinter deposit) activities. Hydrothermal petroleum has been described in active continental rift (East African Rift) and marine spreading zones (Guaymas Basin, Gulf of California). In 1868 the Mexican local press reported that manifestations of bitumen were appearing in front of the Columba Cap on the mid south shore of Lake Chapala. This bitumen is linked to the lake bottom and when the water level decreases sufficiently it is possible to access these tar bodies as islands. Because of these manifestations the Mexican oil company (PEMEX) drilled an exploration well (2,348m) at Tizapan El Alto without success. Hydrothermal activity is evident in the tar island zone as three in-shore thermal springs (26.8 m depth, 48.5° C, pH 7.8 and oriented N-S). The preliminary analyses by GC-MS of the tar from these islands indicate hydrothermal petroleum derived from lake sedimentary organic matter, generated at low temperatures (150° -200° C). The tars contain no n-alkanes, no PAH or other aromatics, but a major UCM of branched and cyclic hydrocarbons and mature biomarkers derived from lacustrine biota. The biomarkers consist of mainly 17α (H),21β (H)-hopanes ranging from C27 to C34 (no C28), gammacerane, tricyclic terpanes (C20-C26), carotane and its cracking products, and drimanes (C14-C16). The biomarker composition indicates an organic matter source from bacteria and algae, typical of lacustrine ecosystems. 14C dating of samples from two tar islands yielded ages exceeding 40 kyrs, i.e., old carbon from hydrothermal/tectonic remobilization of bitumen from deeper horizons to the surface. The occurrence of hydrothermal petroleum in

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

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...

Chemistry of ash-leachates to monitor volcanic activity: An application to Popocatepetl volcano, central Mexico

Energy Technology Data Exchange (ETDEWEB)

Armienta, M.A., E-mail: victoria@geofisica.unam.mx [Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, Circuito Exterior, C.U., Mexico 04510 D.F. (Mexico); De la Cruz-Reyna, S. [Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, Circuito Exterior, C.U., Mexico 04510 D.F. (Mexico); Soler, A. [Grup de Mineralogia Aplicada i Medi Ambient, Dep. Cristal.lografia, Mineralogia i Diposits Minerals, Fac. Geologia, Universidad de Barcelona (Spain); Cruz, O.; Ceniceros, N.; Aguayo, A. [Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, Circuito Exterior, C.U., Mexico 04510 D.F. (Mexico)

2010-08-15

Monitoring volcanic activity and assessing volcanic risk in an on-going eruption is a problem that requires the maximum possible independent data to reduce uncertainty. A quick, relatively simple and inexpensive method to follow the development of an eruption and to complement other monitoring parameters is the chemical analysis of ash leachates, particularly in the case of eruptions related to dome emplacement. Here, the systematic analysis of SO{sub 4}{sup 2-}, Cl{sup -} and F{sup -} concentrations in ash leachates is proposed as a valuable tool for volcanic activity monitoring. However, some results must be carefully assessed, as is the case for S/Cl ratios, since eruption of hydrothermally altered material may be confused with degassing of incoming magma. Sulfur isotopes help to identify SO{sub 4} produced by hydrothermal processes from magmatic SO{sub 2}. Lower S isotopic values correlated with higher F{sup -} percentages represent a better indicator of fresh magmatic influence that may lead to stronger eruptions and emplacement of new lava domes. Additionally, multivariate statistical analysis helps to identify different eruption characteristics, provided that the analyses are made over a long enough time to sample different stages of an eruption.

Chemistry of ash-leachates to monitor volcanic activity: An application to Popocatepetl volcano, central Mexico

International Nuclear Information System (INIS)

Armienta, M.A.; De la Cruz-Reyna, S.; Soler, A.; Cruz, O.; Ceniceros, N.; Aguayo, A.

2010-01-01

Monitoring volcanic activity and assessing volcanic risk in an on-going eruption is a problem that requires the maximum possible independent data to reduce uncertainty. A quick, relatively simple and inexpensive method to follow the development of an eruption and to complement other monitoring parameters is the chemical analysis of ash leachates, particularly in the case of eruptions related to dome emplacement. Here, the systematic analysis of SO 4 2- , Cl - and F - concentrations in ash leachates is proposed as a valuable tool for volcanic activity monitoring. However, some results must be carefully assessed, as is the case for S/Cl ratios, since eruption of hydrothermally altered material may be confused with degassing of incoming magma. Sulfur isotopes help to identify SO 4 produced by hydrothermal processes from magmatic SO 2 . Lower S isotopic values correlated with higher F - percentages represent a better indicator of fresh magmatic influence that may lead to stronger eruptions and emplacement of new lava domes. Additionally, multivariate statistical analysis helps to identify different eruption characteristics, provided that the analyses are made over a long enough time to sample different stages of an eruption.

Hydrothermal and magmatic components in the Ruapehu, Pinatubo, Lonquimay and Yasur volcanic ashes

International Nuclear Information System (INIS)

Reyes, A.G.; Trompetter, W.J.

2005-01-01

Fresh ash from explosive volcanic eruptions of Ruapehu in New Zealand (1995-1996), Pinatubo in the Philippines (1991), Lonquimay in Chile (1989) and Ysur in Vanuatu (1988) were leached in distilled water in a boiling water bath. The leachates were analysed by ion chromatography and ICP-MS and the chemical composition of leached ash measured by IBA, NAA and XRF. Water-soluble minerals adhering on ash surfaces were examined under SEM-EDX and thin sections of the ash were mineralogically analysed under petrographic microscope. The leachates contain mainly adsorbed material from the volcanic plume and the leached ash insoluble plume precipitates or primary volcanic mineral. At Yasur and Lonquimay, where the erupted material is entirely magmatic, the F/S and F/Cl ratios are 100x to 1000x higher and the S/B ratio 10x lower than in Pinatubo where an extensive hydrothermal system had been extant prior to eruption. In Ruhapehu, the adsorbed material contains a significant component of evaporated Crater Lake water. (author). 9 refs., 1 fig

The role of magmas in the formation of hydrothermal ore deposits

Science.gov (United States)

Hedenquist, Jeffrey W.; Lowenstern, Jacob B.

1994-01-01

Magmatic fluids, both vapour and hypersaline liquid, are a primary source of many components in hydrothermal ore deposits formed in volcanic arcs. These components, including metals and their ligands, become concentrated in magmas in various ways from various sources, including subducted oceanic crust. Leaching of rocks also contributes components to the hydrothermal fluid—a process enhanced where acid magmatic vapours are absorbed by deeply circulating meteoric waters. Advances in understanding the hydrothermal systems that formed these ore deposits have come from the study of their active equivalents, represented at the surface by hot springs and volcanic fumaroles.

Japan-U. S. seminar on magmatic contributions to hydrothermal systems

Energy Technology Data Exchange (ETDEWEB)

Muffler, L. (U. S. Geological Survey, CA (United States)); Hedenquist, J. (Geological Survey of Japan, Tsukuba (Japan)); Kesler, S. (University of Michigan, MI (United States)); Izawa, E. (Kyushu University, Fukuoka (Japan). Faculty of Engineering)

1992-08-31

A multidisciplinary Seminar on Magmatic Contributions to Hydrothermal Systems'' was held at Ebino and Kagoshima at Kyushu, November, 1991. The principal purpose of the Ebino/Kagoshima Seminar was to bring together a small group of individuals which have been conducting active research on magmatic contributions to hydrothermal systems. The Seminar focussed on the porphyry and epithermal ore environments because of the potential to relate these environments to active volcanic and geothermal systems. Disciplines included valcanology, volcanic gas geochemistry, water geochemistry, isotope geochemistry, geochemical modeling, experimental geochemistry, igneous petrology, geothermal geology, economic geology, fluid-inclusion study, geophysics, and physical modeling. This paper summarizes the outline and significance of the Seminar. It was pointed out that understanding magmatic contributions to hydrothermal systems would require augmented experimental investigations, numerical modeling, field studies, and drilling.

Carbon dioxide diffuse emission and thermal energy release from hydrothermal systems at Copahue-Caviahue Volcanic Complex (Argentina)

Science.gov (United States)

Chiodini, Giovanni; Cardellini, Carlo; Lamberti, María Clara; Agusto, Mariano; Caselli, Alberto; Liccioli, Caterina; Tamburello, Giancarlo; Tassi, Franco; Vaselli, Orlando; Caliro, Stefano

2015-10-01

The north-western sector of Caviahue caldera (Argentina), close to the active volcanic system of Copahue, is characterized by the presence of several hydrothermal sites that host numerous fumarolic emissions, anomalous soil diffuse degassing of CO2 and hot soils. In March 2014, measurements of soil CO2 fluxes in 5 of these sites (namely, Las Máquinas, Las Maquinitas I, Las Maquinitas II, Anfiteatro, and Termas de Copahue) allowed an estimation that 165 t of deeply derived CO2 is daily released. The gas source is likely related to a relatively shallow geothermal reservoir containing a single vapor phase as also suggested by both the geochemical data from the 3 deep wells drilled in the 1980s and gas geoindicators applied to the fumarolic discharges. Gas equilibria within the H-C-O gas system indicate the presence of a large, probably unique, single phase vapor zone at 200-210 °C feeding the hydrothermal manifestations of Las Máquinas, Las Maquinitas I and II and Termas de Copahue. A natural thermal release of 107 MW was computed by using CO2 as a tracer of the original vapor phase. The magmatic signature of the incondensable fumarolic gases, the wide expanse of the hydrothermal areas and the remarkable high amount of gas and heat released by fluid expulsion seem to be compatible with an active magmatic intrusion beneath this portion of the Caviahue caldera.

Analysis on deep metallogenic trace and simulation experiment in xiangshan large-scale volcanic hydrothermal type uranium deposit

International Nuclear Information System (INIS)

Liu Zhengyi; Liu Zhangyue; Wen Zhijian; Du Letian

2010-01-01

Based on series experiments on field geologic analysis, and associated with deep metallogenic trace experiment model transformed from establishment of field deep metallogenic trace model, this paper come to the conclusion that distribution coefficients of U and Th first domestic from the magmatic experiment, and then discuss the geochemical behaviors of U, Th, K during magmatic evolution stage. The experiment shows that close relationship between U and Na during the hydrothermal alteration stage; and relationship between U and K during metallogenic stage, which prove that U and K are incompatible and regularity of variation between K and Na. The conclusion of uranium dissolving ability increased accompany with pressure increasing in basement metamorphic rocks and host rocks, is obtained from this experiment, which indicate a good deep metallogenic prospect. Furthermore, Pb, Sr, Nd, He isotopes show that the volcanic rocks and basement rocks are ore source beds; due to the combined functions of volcanic hydrothermal and mantle ichor, uranium undergo multi-migration and enrichment and finally concentrated to large rich deposit. (authors)

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

A large hydrothermal reservoir beneath Taal Volcano (Philippines) revealed by magnetotelluric observations and its implications to the volcanic activity.

Science.gov (United States)

Alanis, Paul K B; Yamaya, Yusuke; Takeuchi, Akihiro; Sasai, Yoichi; Okada, Yoshihiro; Nagao, Toshiyasu

2013-01-01

Taal Volcano is one of the most active volcanoes in the Philippines. The magnetotelluric 3D forward analyses indicate the existence of a large high resistivity anomaly (∼100 Ω·m) with a volume of at least 3 km×3 km×3 km, which is capped by a conductive layer (∼10 Ω·m), beneath the Main Crater. This high resistivity anomaly is hypothesized to be a large hydrothermal reservoir, consisting of the aggregate of interconnected cracks in rigid and dense host rocks, which are filled with hydrothermal fluids coming from a magma batch below the reservoir. The hydrothermal fluids are considered partly in gas phase and liquid phase. The presence of such a large hydrothermal reservoir and the stagnant magma below may have influences on the volcano's activity. Two possibilities are presented. First, the 30 January 1911 explosion event was a magmatic hydrothermal eruption rather than a base-surge associated with a phreato-magmatic eruption. Second, the earlier proposed four eruption series may be better interpreted by two cycles, each consisting of series of summit and flank eruptions.

Geophysical expression of caldera related volcanism, structures and mineralization in the McDermitt volcanic field

Science.gov (United States)

Rytuba, J. J.; Blakely, R. J.; Moring, B.; Miller, R.

2013-12-01

30 km trend that then arcs NE into the caldera. These anomalies reflect near surface rhyolite intrusions that underlie the caldera-fill sediments that have been altered to K-feldpar and clay minerals. K gamma ray anomalies also delineate this zone of alteration. The last phase of volcanism occurs in the central part of the caldera and is associated with a broad aeromagnetic high with individual high-amplitude aeromagnetic highs coincident with three large volcanic vents. No hydrothermal alteration is associated with this last phase of volcanism. On the SW side of the McDermitt volcanic field a 10 km wide, 60 km long, NNW-trending zone of late Miocene normal faults developed after cessation of volcanism and prior to Basin and Range faulting. We propose that this extensional fault zone is the eastern continuation of the NW trending Brothers Fault Zone, but changes to a NNW trend where it is deflected by the plutons that underlies the McDermitt volcanic field. Plutons that underlie all three of these Mid Miocene volcanic fields have minimized post-caldera extensional faulting. Thus only caldera ring fracture faults were available for the development of hydrothermal systems in areas where post caldera intrusive activity was localized.

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

Mercury Anomaly in the Okinawa Trough Sediments—An Indicator of Modern Seafloor Hydrothermal Activity

Institute of Scientific and Technical Information of China (English)

赵一阳; 鄢明才

1995-01-01

The Okinawa Trough is located between the shelf-sea area of the East China Sea and the deep-sea area of western Pacific Ocean.More than 60 chemical elements in the sediments from the shelf area of the East China Sea,the Okinawa Trough and western Pacific Ocean were determined by advanced techniques including neutron acti-vation analysis,X-ray fluorescence spectrometry,atomic fluorescence spectrometry and atomic absorption spectrometry.Quantitative comparisons of the element abundances of the sediments were made in terms of the enrichment coefficients(K) of the elements.K>1.5 indicates enrichment (K=1.5-2, weak enrichment;K=2-4,strong enrichment) and K>4,anomalous enrichment.The results show that the Okinawa Trough sediments are characterized by Hg anomaly and the enrichment of such elements as Au,Ag,Se,Te,Sb,Cd,Mn,Mo,etc.Detailed studies show that the excess Hg comes from hydrothermal solutions rather than from the continent,sea water ,marine organisms,cosmic dust or vol-canic rocks.Attributed to modern hydrothermal activities on the sea floor ,Hg anomaly can be used as a geochemical indicator of modern seafloor hydrothermal activity.

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.

Towards understanding the puzzling lack of acid geothermal springs in Tibet (China): Insight from a comparison with Yellowstone (USA) and some active volcanic hydrothermal systems

Science.gov (United States)

Guo, Qinghai; Kirk Nordstrom, D.; Blaine McCleskey, R.

2014-11-01

Explanations for the lack of acid geothermal springs in Tibet are inferred from a comprehensive hydrochemical comparison of Tibetan geothermal waters with those discharged from Yellowstone (USA) and two active volcanic areas, Nevado del Ruiz (Colombia) and Miravalles (Costa Rica) where acid springs are widely distributed and diversified in terms of geochemical characteristic and origin. For the hydrothermal areas investigated in this study, there appears to be a relationship between the depths of magma chambers and the occurrence of acid, chloride-rich springs formed via direct magmatic fluid absorption. Nevado del Ruiz and Miravalles with magma at or very close to the surface (less than 1-2 km) exhibit very acidic waters containing HCl and H2SO4. In contrast, the Tibetan hydrothermal systems, represented by Yangbajain, usually have fairly deep-seated magma chambers so that the released acid fluids are much more likely to be fully neutralized during transport to the surface. The absence of steam-heated acid waters in Tibet, however, may be primarily due to the lack of a confining layer (like young impermeable lavas at Yellowstone) to separate geothermal steam from underlying neutral chloride waters and the possible scenario that the deep geothermal fluids below Tibet carry less H2S than those below Yellowstone.

Towards understanding the puzzling lack of acid geothermal springs in Tibet (China): Insight from a comparison with Yellowstone (USA) and some active volcanic hydrothermal systems

Science.gov (United States)

Nordstrom, D. Kirk; Guo, Qinghai; McCleskey, R. Blaine

2014-01-01

Explanations for the lack of acid geothermal springs in Tibet are inferred from a comprehensive hydrochemical comparison of Tibetan geothermal waters with those discharged from Yellowstone (USA) and two active volcanic areas, Nevado del Ruiz (Colombia) and Miravalles (Costa Rica) where acid springs are widely distributed and diversified in terms of geochemical characteristic and origin. For the hydrothermal areas investigated in this study, there appears to be a relationship between the depths of magma chambers and the occurrence of acid, chloride-rich springs formed via direct magmatic fluid absorption. Nevado del Ruiz and Miravalles with magma at or very close to the surface (less than 1–2 km) exhibit very acidic waters containing HCl and H2SO4. In contrast, the Tibetan hydrothermal systems, represented by Yangbajain, usually have fairly deep-seated magma chambers so that the released acid fluids are much more likely to be fully neutralized during transport to the surface. The absence of steam-heated acid waters in Tibet, however, may be primarily due to the lack of a confining layer (like young impermeable lavas at Yellowstone) to separate geothermal steam from underlying neutral chloride waters and the possible scenario that the deep geothermal fluids below Tibet carry less H2S than those below Yellowstone.

Monitoring diffuse volcanic degassing during volcanic unrests: the case of Campi Flegrei (Italy).

Science.gov (United States)

Cardellini, C; Chiodini, G; Frondini, F; Avino, R; Bagnato, E; Caliro, S; Lelli, M; Rosiello, A

2017-07-28

In volcanoes with active hydrothermal systems, diffuse CO 2 degassing may constitute the primary mode of volcanic degassing. The monitoring of CO 2 emissions can provide important clues in understanding the evolution of volcanic activity especially at calderas where the interpretation of unrest signals is often complex. Here, we report eighteen years of CO 2 fluxes from the soil at Solfatara of Pozzuoli, located in the restless Campi Flegrei caldera. The entire dataset, one of the largest of diffuse CO 2 degassing ever produced, is made available for the scientific community. We show that, from 2003 to 2016, the area releasing deep-sourced CO 2 tripled its extent. This expansion was accompanied by an increase of the background CO 2 flux, over most of the surveyed area (1.4 km 2 ), with increased contributions from non-biogenic source. Concurrently, the amount of diffusively released CO 2 increased up to values typical of persistently degassing active volcanoes (up to 3000 t d -1 ). These variations are consistent with the increase in the flux of magmatic fluids injected into the hydrothermal system, which cause pressure increase and, in turn, condensation within the vapor plume feeding the Solfatara emission.

Amazonian volcanism inside Valles Marineris on Mars

Czech Academy of Sciences Publication Activity Database

Brož, Petr; Hauber, E.; Wray, J. J.; Michael, G.

2017-01-01

Roč. 473, September (2017), s. 122-130 ISSN 0012-821X Institutional support: RVO:67985530 Keywords : Mars * Valles Marineris * volcanism * scoria cone * hydrothermal activity Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology Impact factor: 4.409, year: 2016

Hydrothermal uranium deposits containing molybdenum and fluorite in the Marysvale volcanic field, west-central Utah

Science.gov (United States)

Cunningham, C.G.; Rasmussen, J.D.; Steven, T.A.; Rye, R.O.; Rowley, P.D.; Romberger, S.B.; Selverstone, J.

1998-01-01

Uranium deposits containing molybdenum and fluorite occur in the Central Mining Area, near Marysvale, Utah, and formed in an epithermal vein system that is part of a volcanic/hypabyssal complex. They represent a known, but uncommon, type of deposit; relative to other commonly described volcanic-related uranium deposits, they are young, well-exposed and well-documented. Hydrothermal uranium-bearing quartz and fluorite veins are exposed over a 300 m vertical range in the mines. Molybdenum, as jordisite (amorphous MoS2, together with fluorite and pyrite, increase with depth, and uranium decreases with depth. The veins cut 23-Ma quartz monzonite, 20-Ma granite, and 19-Ma rhyolite ash-flow tuff. The veins formed at 19-18 Ma in a 1 km2 area, above a cupola of a composite, recurrent, magma chamber at least 24 ?? 5 km across that fed a sequence of 21- to 14-Ma hypabyssal granitic stocks, rhyolite lava flows, ash-flow tuffs, and volcanic domes. Formation of the Central Mining Area began when the intrusion of a rhyolite stock, and related molybdenite-bearing, uranium-rich, glassy rhyolite dikes, lifted the fractured roof above the stock. A breccia pipe formed and relieved magmatic pressures, and as blocks of the fractured roof began to settle back in place, flat-lying, concave-downward, 'pull-apart' fractures were formed. Uranium-bearing, quartz and fluorite veins were deposited by a shallow hydrothermal system in the disarticulated carapace. The veins, which filled open spaces along the high-angle fault zones and flat-lying fractures, were deposited within 115 m of the ground surface above the concealed rhyolite stock. Hydrothermal fluids with temperatures near 200??C, ??18OH2O ~ -1.5, ?? -1.5, ??DH2O ~ -130, log fO2 about -47 to -50, and pH about 6 to 7, permeated the fractured rocks; these fluids were rich in fluorine, molybdenum, potassium, and hydrogen sulfide, and contained uranium as fluoride complexes. The hydrothermal fluids reacted with the wallrock resulting in

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

On stages of hydrothermal mineralization of molybdenum-uranium ore manifestation in volcanic edifice

International Nuclear Information System (INIS)

Yakovlev, P.D.; Mamotin, S.A.

1976-01-01

Volcanogenic-intrusive complex of the ore manifestation region is represented by various facies of liparite and granitoid formation rocks. Numerous dislocations with breaks in continuity and the corresponding feathering fissures relate to 3 stages of hydrothermal mineralization of rocks. Quartz-sericite-kaolin metasomatites were formed at the earlier (volcanic) stage. Tourmalinization was associated with the middle stage which accompanied the granitoid intrusive formation. The later mineralization stage was accompanied by formation of beresites and molibdenum-uranium ores. Identification was controlled by the dislocation, ore bodies had the shape of lens, vein or small nest. 7 stages separated by shores were identified at the ore stage: quartz-sericite pyritic; quartz-pyrite-arsenopyritic; sulfide-pitchblendic; chalcedonic; ankeritic; quartz-calcitic and pyrite-ankeritic

Constraining Silicate Weathering Processes in an Active Volcanic Complex: Implications for the Long-term Carbon Cycle

Science.gov (United States)

Washington, K.; West, A. J.; Hartmann, J.; Amann, T.; Hosono, T.; Ide, K.

2017-12-01

While analyzing geochemical archives and carbon cycle modelling can further our understanding of the role of silicate weathering as a sink in the long-term carbon cycle, it is necessary to study modern weathering processes to inform these efforts. A recent compilation of data from rivers draining basaltic catchments estimates that rock weathering in active volcanic fields (AVFs) consumes atmospheric CO2 approximately three times faster than in inactive volcanic fields (IVFs), suggesting that the eruption and subsequent weathering of large igneous provinces likely played a major role in the carbon cycle in the geologic past [1]. The study demonstrates a significant correlation between catchment mean annual temperature (MAT) and atmospheric CO2 consumption rate for IVFs. However CO2 consumption due to weathering of AVFs is not correlated with MAT as the relationship is complicated by variability in hydrothermal fluxes, reactive surface area, and groundwater flow paths. To investigate the controls on weathering processes in AVFs, we present data for dissolved and solid weathering products from Mount Aso Caldera, Japan. Aso Caldera is an ideal site for studying the how the chemistry of rivers draining an AVF is impacted by high-temperature water/rock interactions, volcanic ash weathering, and varied groundwater flow paths and residence times. Samples were collected over five field seasons from two rivers and their tributaries, cold groundwater springs, and thermal springs. These samples capture the region's temperature and precipitation seasonality. Solid samples of unaltered volcanic rocks, hydrothermally-altered materials, volcanic ash, a soil profile, and suspended and bedload river sediments were also collected. The hydrochemistry of dissolved phases were analyzed at the University of Hamburg, while the mineralogy and geochemical compositions of solid phases were analyzed at the Natural History Museum of Los Angeles. This work will be discussed in the context of

Monitoring the Sumatra volcanic arc with InSAR

Science.gov (United States)

Chaussard, E.; Hong, S.; Amelung, F.

2009-12-01

The Sumatra volcanic arc is the result of the subduction of the Indo-Australian plate under the Sunda plate. The arc consists of 35 known volcanic centers, subaerials on the west coast of the Sumatra and Andaman Islands and submarines between these islands. Six active centers are known in the Sumatra volcanic arc. Surface deformation in volcanic areas usually indicates movement of magma or hydrothermal fluids at depth. Here we present a satellite-based Interferometric synthetic aperture radar (InSAR) survey of the Sumatra volcanic arc using ALOS data. Spanning the years 2007 to beginning of 2009, our survey reveals the background level of activity of the 35 volcanoes. We processed data from 40 tracks (24 in descending orbit and 16 in ascending orbit) to cover the whole Sumatra arc. In the first results five of these six known active centers show no sign of activity: Dempo, Kaba, Marapi, Talang and Peuet. The remaining active volcano, Mount Kerinci, has an ambiguous signal. We used pair-wise logic and InSAR time series of the available ALOS data to determine if the observed InSAR signal is caused by ground deformation or by atmospheric delays.

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.

Extensive hydrothermal activity revealed by multi-tracer survey in the Wallis and Futuna region (SW Pacific)

OpenAIRE

Konn, Cecile; Fourre, E.; Jean-baptiste, P.; Donval, Jean-pierre; Guyader, Vivien; Birot, Dominique; Alix, Anne-sophie; Gaillot, Arnaud; Perez, Florian; Dapoigny, A.; Pelleter, Ewan; Resing, J. A.; Charlou, Jean-luc; Fouquet, Yves

2016-01-01

The study area is close to the Wallis and Futuna Islands in the French EEZ. It exists on the western boundary of the fastest tectonic area in the world at the junction of the Lau and North-Fiji basins. At this place, the unstable back-arc accommodates the plate motion in three ways: (i) the north Fiji transform fault, (ii) numerous unstable spreading ridges, and (iii) large areas of recent volcanic activity. This instability creates bountiful opportunity for hydrothermal discharge to occur. B...

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.

Gas geochemistry of the magmatic-hydrothermal fluid reservoir in the Copahue-Caviahue Volcanic Complex (Argentina)

Science.gov (United States)

Agusto, M.; Tassi, F.; Caselli, A. T.; Vaselli, O.; Rouwet, D.; Capaccioni, B.; Caliro, S.; Chiodini, G.; Darrah, T.

2013-05-01

Copahue volcano is part of the Caviahue-Copahue Volcanic Complex (CCVC), which is located in the southwestern sector of the Caviahue volcano-tectonic depression (Argentina-Chile). This depression is a pull-apart basin accommodating stresses between the southern Liquiñe-Ofqui strike slip and the northern Copahue-Antiñir compressive fault systems, in a back-arc setting with respect to the Southern Andean Volcanic Zone. In this study, we present chemical (inorganic and organic) and isotope compositions (δ13C-CO2, δ15N, 3He/4He, 40Ar/36Ar, δ13C-CH4, δD-CH4, and δD-H2O and δ18O-H2O) of fumaroles and bubbling gases of thermal springs located at the foot of Copahue volcano sampled in 2006, 2007 and 2012. Helium isotope ratios, the highest observed for a Southern American volcano (R/Ra up to 7.94), indicate a non-classic arc-like setting, but rather an extensional regime subdued to asthenospheric thinning. δ13C-CO2 values (from - 8.8‰ to - 6.8‰ vs. V-PDB), δ15N values (+ 5.3‰ to + 5.5‰ vs. Air) and CO2/3He ratios (from 1.4 to 8.8 × 109) suggest that the magmatic source is significantly affected by contamination of subducted sediments. Gases discharged from the northern sector of the CCVC show contribution of 3He-poor fluids likely permeating through local fault systems. Despite the clear mantle isotope signature in the CCVC gases, the acidic gas species have suffered scrubbing processes by a hydrothermal system mainly recharged by meteoric water. Gas geothermometry in the H2O-CO2-CH4-CO-H2 system suggests that CO and H2 re-equilibrate in a separated vapor phase at 200°-220 °C. On the contrary, rock-fluid interactions controlling CO2, CH4 production from Sabatier reaction and C3H8 dehydrogenation seem to occur within the hydrothermal reservoir at temperatures ranging from 250° to 300 °C. Fumarole gases sampled in 2006-2007 show relatively low N2/He and N2/Ar ratios and high R/Ra values with respect to those measured in 2012. Such compositional and

Metal concentration and structural changes in Corallina elongata (Corallinales, Rhodophyta) from hydrothermal vents

International Nuclear Information System (INIS)

Couto, Ruben P.; Neto, Ana I.; Rodrigues, Armindo S.

2010-01-01

Shallow-water hydrothermal activity is widely present at Azores archipelago. Organisms in such environments present great potential as sentinels of the effects derived from chronically exposure to increased temperature, metal concentrations and reduced pH. This study aimed to evaluate metal concentration in Corallina elongata collected at locations exposed and not exposed to shallow-water hydrothermal activity and evaluate changes in its calcareous structure. Elemental concentration was determined and morphometric analysis was performed by scanning electron microscopy. Thicker cell walls and a bleached appearance were observed on C. elongata specimens from the hydrothermally active location, as well as increased concentrations of elements associated to volcanic activity. This study reports on metal accumulation and morphometric changes in the calcareous structure of C. elongata from a hydrothermally active location, adding new data for further research on such habitats and communities, providing an insight on how coralline algae might be affected by ocean acidification.

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.

The Sierra Pena Blanca (Mexico) and the Meseta Los Frailes (Bolivia): the uranium concentration mechanisms in volcanic environment during hydrothermal processes

International Nuclear Information System (INIS)

Leroy, J.L.; Aniel, B.; Poty, B.

1987-01-01

Tertiary felsic volcanics of the Sierra Pena Blanca in Mexico host potentially economic uranium deposits, and of Meseta Los Frailes in Bolivia contain interesting U anomalies but no significant deposits. A comparative study of the two uranium districts reveals differences that may explain the different degrees of U concentration. The host ignimbrite in Mexico, namely the Nopal Formation dated at 44 Myr. ago, is potassic alkaline rhyolite which is poorly compacted and contains phenocrysts of quartz, orthoclase, ilmenite and magnetite, totalling 30% of the rock. Vapour phase crystallization is well developed in the Mexican tuff, and has led to a primary concentration of labile U not tied up in refractory accessory minerals, as shown by fission-track studies. The Bolivian tuffs lack such vapour phase primary concentration of U. Subsequent hydrothermal alteration, in particular kaolinization is intense in the Mexican district, but is relatively less intense in the Bolivian one. It is postulated that an intense hydrothermal activity, probably of prolonged duration, in rocks displaying primary enrichment of labile U, is essential to form volcanogenic U deposits of the type found in Mexico. 26 refs.; 13 figs.; 3 plates; 3 tabs

Seismic activity and thermal regime of low temperature fumaroles at Mt. Vesuvius in 2004-2011: distinguishing among seismic, volcanic and hydrological signals

Directory of Open Access Journals (Sweden)

Paola Cusano

2013-11-01

Full Text Available Seismological, soil temperature and hydrological data from Mt. Vesuvius are collected to characterize the present-day activity of the volcanic/hydrothermal system and to detect possible unrest-related phenomena. We present patterns of seismicity and soil temperature in the crater area during the period February 2004-December 2011. The temporal distribution of number and depth of Volcano-Tectonic earthquakes and the energy release are considered. Hourly data of soil temperature have been acquired since January 2004 in different locations along the rim and within the crater. The observed changes of temperature are studied to establish a temporal-based correlation with the volcanic activity and/or with external forcing, as variations of the regional and local stress field acting on the volcano or meteorological phenomena. The comparison between seismic activity and temperature data highlights significant variations possibly related to changes in fluid circulation in the hydrothermal system of the volcano. The common continuous observations start just before a very shallow earthquake occurred in August 2005, which was preceded by a thermal anomaly. This coincidence has been interpreted as related to fluid-driven rock fracturing, as observed in other volcanoes. For the successive temporal patterns, the seismicity rate and energy release are characterized by slight variations accompanied by changes in temperature. This evidence of reactivity of the fumarole thermal field to seismic strain can be used to discriminate between tectonic and volcanic signals at Mt. Vesuvius.

Metal concentration and structural changes in Corallina elongata (Corallinales, Rhodophyta) from hydrothermal vents.

Science.gov (United States)

Couto, Ruben P; Neto, Ana I; Rodrigues, Armindo S

2010-04-01

Shallow-water hydrothermal activity is widely present at Azores archipelago. Organisms in such environments present great potential as sentinels of the effects derived from chronically exposure to increased temperature, metal concentrations and reduced pH. This study aimed to evaluate metal concentration in Corallina elongata collected at locations exposed and not exposed to shallow-water hydrothermal activity and evaluate changes in its calcareous structure. Elemental concentration was determined and morphometric analysis was performed by scanning electron microscopy. Thicker cell walls and a bleached appearance were observed on C. elongata specimens from the hydrothermally active location, as well as increased concentrations of elements associated to volcanic activity. This study reports on metal accumulation and morphometric changes in the calcareous structure of C. elongata from a hydrothermally active location, adding new data for further research on such habitats and communities, providing an insight on how coralline algae might be affected by ocean acidification. (c) 2009 Elsevier Ltd. All rights reserved.

The Online GVP/USGS Weekly Volcanic Activity Report: Providing Timely Information About Worldwide Volcanism

Science.gov (United States)

Mayberry, G. C.; Guffanti, M. C.; Luhr, J. F.; Venzke, E. A.; Wunderman, R. L.

2001-12-01

The awesome power and intricate inner workings of volcanoes have made them a popular subject with scientists and the general public alike. About 1500 known volcanoes have been active on Earth during the Holocene, approximately 50 of which erupt per year. With so much activity occurring around the world, often in remote locations, it can be difficult to find up-to-date information about current volcanism from a reliable source. To satisfy the desire for timely volcano-related information the Smithsonian Institution and US Geological Survey combined their strengths to create the Weekly Volcanic Activity Report. The Smithsonian's Global Volcanism Program (GVP) has developed a network of correspondents while reporting worldwide volcanism for over 30 years in their monthly Bulletin of the Global Volcanism Network. The US Geological Survey's Volcano Hazards Program studies and monitors volcanoes in the United States and responds (upon invitation) to selected volcanic crises in other countries. The Weekly Volcanic Activity Report is one of the most popular sites on both organization's websites. The core of the Weekly Volcanic Activity Report is the brief summaries of current volcanic activity around the world. In addition to discussing various types of volcanism, the summaries also describe precursory activity (e.g. volcanic seismicity, deformation, and gas emissions), secondary activity (e.g. debris flows, mass wasting, and rockfalls), volcanic ash hazards to aviation, and preventative measures. The summaries are supplemented by links to definitions of technical terms found in the USGS photoglossary of volcano terms, links to information sources, and background information about reported volcanoes. The site also includes maps that highlight the location of reported volcanoes, an archive of weekly reports sorted by volcano and date, and links to commonly used acronyms. Since the Weekly Volcanic Activity Report's inception in November 2000, activity has been reported at

Screening criteria of volcanic hazards aspect in the NPP site evaluation

International Nuclear Information System (INIS)

Nur Siwhan

2013-01-01

Studies have been conducted on the completeness of regulation in Indonesia particularly on volcanic hazards aspects in the evaluation of nuclear power plant site. Volcanic hazard aspect needed to identify potential external hazards that may endanger the safety of the operation of nuclear power plants. There are four stages for evaluating volcanic hazards, which are initial assessment, characterization sources of volcanic activity in the future, screening volcanic hazards and assessment of capable volcanic hazards. This paper discuss the third stage of the general evaluation which is the screening procedure of volcanic hazards. BAPETEN Chairman Regulation No. 2 Year of 2008 has only one screening criteria for missile volcanic phenomena, so it required screening criteria for other hazard phenomena that are pyroclastic flow density; lava flows; avalanche debris materials; lava; opening hole new eruptions, volcano missile; tsunamis; ground deformation; and hydrothermal system and ground water anomaly. (author)

Integrated Geoscience Studies in the Greater Yellowstone Area - Volcanic, Tectonic, and Hydrothermal Processes in the Yellowstone Geoecosystem

Science.gov (United States)

Morgan, Lisa A.

2007-01-01

Yellowstone National Park, rimmed by a crescent of older mountainous terrain, has at its core the Quaternary Yellowstone Plateau, an undulating landscape shaped by forces of volcanism, tectonism, and later glaciation. Its spectacular hydrothermal systems cap this landscape. From 1997 through 2003, the United States Geological Survey Mineral Resources Program conducted a multidisciplinary project of Yellowstone National Park entitled Integrated Geoscience Studies of the Greater Yellowstone Area, building on a 130-year foundation of extensive field studies (including the Hayden survey of 1871, the Hague surveys of the 1880s through 1896, the studies of Iddings, Allen, and Day during the 1920s, and NASA-supported studies starting in the 1970s - now summarized in USGS Professional Paper 729 A through G) in this geologically dynamic terrain. The project applied a broad range of scientific disciplines and state-of-the-art technologies targeted to improve stewardship of the unique natural resources of Yellowstone and enable the National Park Service to effectively manage resources, protect park visitors from geologic hazards, and better educate the public on geologic processes and resources. This project combined a variety of data sets in characterizing the surficial and subsurface chemistry, mineralogy, geology, geophysics, and hydrothermal systems in various parts of the park. The sixteen chapters presented herein in USGS Professional Paper 1717, Integrated Geoscience Studies in the Greater Yellowstone Area - Volcanic, Tectonic, and Hydrothermal Processes in the Yellowstone Geoecosystem, can be divided into four major topical areas: (1) geologic studies, (2) Yellowstone Lake studies, (3) geochemical studies, and (4) geophysical studies. The geologic studies include a paper by Ken Pierce and others on the influence of the Yellowstone hotspot on landscape formation, the ecological effects of the hotspot, and the human experience and human geography of the greater

The structural architecture of the Los Humeros volcanic complex and geothermal field, Trans-Mexican Volcanic Belt, Central Mexico

Science.gov (United States)

Norini, Gianluca; Groppelli, Gianluca; Sulpizio, Roberto; Carrasco Núñez, Gerardo; Davila Harris, Pablo

2014-05-01

The development of geothermal energy in Mexico is a very important goal, given the presence of a large heat anomaly, associated with the Trans-Mexican Volcanic Belt, the renewability of the resource and the low environmental impact. The Quaternary Los Humeros volcanic complex is an important geothermal target, whose evolution involved at least two caldera events, that alternated with other explosive and effusive activity. The first caldera forming event was the 460 ka eruption that produced the Xaltipan ignimbrite and formed a 15-20 km wide caldera. The second collapse event occurred 100 ka with the formation of the Zaragoza ignimbrite and a nested 8-10 km wide caldera. The whole volcano structure, the style of the collapses and the exact location of the calderas scarps and ring faults are still a matter of debate. The Los Humeros volcano hosts the productive Los Humeros Geothermal Field, with an installed capacity of 40 MW and additional 75 MW power plants under construction. Recent models of the geothermal reservoir predict the existence of at least two reservoirs in the geothermal system, separated by impermeable rock units. Hydraulic connectivity and hydrothermal fluids circulation occurs through faults and fractures, allowing deep steam to ascend while condensate flows descend. As a consequence, the plans for the exploration and exploitation of the geothermal reservoir have been based on the identification of the main channels for the circulation of hydrothermal fluids, constituted by faults, so that the full comprehension of the structural architecture of the caldera is crucial to improve the efficiency and minimize the costs of the geothermal field operation. In this study, we present an analysis of the Los Humeros volcanic complex focused on the Quaternary tectonic and volcanotectonics features, like fault scarps and aligned/elongated monogenetic volcanic centres. Morphostructural analysis and field mapping reveal the geometry, kinematics and dynamics of

Crustal deformation and volcanism at active plate boundaries

Science.gov (United States)

Geirsson, Halldor

Most of Earth's volcanoes are located near active tectonic plate boundaries, where the tectonic plates move relative to each other resulting in deformation. Likewise, subsurface magma movement and pressure changes in magmatic systems can cause measurable deformation of the Earth's surface. The study of the shape of Earth and therefore studies of surface deformation is called geodesy. Modern geodetic techniques allow precise measurements (˜1 mm accuracy) of deformation of tectonic and magmatic systems. Because of the spatial correlation between tectonic boundaries and volcanism, the tectonic and volcanic deformation signals can become intertwined. Thus it is often important to study both tectonic and volcanic deformation processes simultaneously, when one is trying to study one of the systems individually. In this thesis, I present research on crustal deformation and magmatic processes at active plate boundaries. The study areas cover divergent and transform plate boundaries in south Iceland and convergent and transform plate boundaries in Central America, specifically Nicaragua and El Salvador. The study is composed of four main chapters: two of the chapters focus on the magma plumbing system of Hekla volcano, Iceland and the plate boundary in south Iceland; one chapter focuses on shallow controls of explosive volcanism at Telica volcano, Nicaragua; and the fourth chapter focuses on co- and post-seismic deformation from a Mw = 7.3 earthquake which occurred offshore El Salvador in 2012. Hekla volcano is located at the intersection of a transform zone and a rift zone in Iceland and thus is affected by a combination of shear and extensional strains, in addition to co-seismic and co-rifting deformation. The inter-eruptive deformation signal from Hekla is subtle, as observed by a decade (2000-2010) of GPS data in south Iceland. A simultaneous inversion of this data for parameters describing the geometry and source characteristics of the magma chamber at Hekla, and

Radionuclides in hydrothermal systems as indicators of repository conditions

International Nuclear Information System (INIS)

Wollenberg, H.A.; Flexser, S.; Smith, A.R.

1990-11-01

Hydrothermal systems in tuffaceous and older sedimentary rocks contain evidence of the interaction of radionuclides in fluids with rock matrix minerals and with materials lining fractures, in settings somewhat analogous to the candidate repository site at Yucca Mountain, NV. Earlier studies encompassed the occurrences of U and Th in a ''fossil'' hydrothermal system in tuffaceous rock of the San Juan Mountains volcanic field, CO. More recent and ongoing studies examine active hydrothermal systems in calderas at Long Valley, CA and Valles, NM. At the Nevada Test Site, occurrences of U and Th in fractured and unfractured rhyolitic tuff that was heated to simulate the introduction of radioactive waste are also under investigation. Observations to date suggest that U is mobile in hydrothermal systems, but that localized reducing environments provided by Fe-rich minerals and/or carbonaceous material concentrate U and thus attenuate its migration. 11 refs., 6 figs., 1 tab

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

Mercury and Iodine systematics of volcanic arc fluids

Science.gov (United States)

Varekamp, J. C.; Kading, T.; Fehn, U.; Lu, Z.

2008-12-01

The mantle has low Mercury and Iodine concentrations, but these elements occur in volcanic gases and hydrothermal fluids at ppb (Hg) and ppm (Iodine) levels. Possibly, the Hg and Iodine concentrations in volcanic fluids reflect subducted sediment sources in arc magmas. Iodine is a biophilic element, and I129/I values indicate that subducted sediment (especially organic matter) is an important Iodine source for arc magmas. It is uncertain if this is true for Hg as well, although in the surface environment Hg is commonly associated with organic matter. We present 60 new analyses of Hg and I in fluids from volcanoes in Central America, New Zealand, Japan, and the Cascades. A first assessment suggests that Iodine is released to some degree in the early stage of subduction in the forearc, whereas Hg may be released largely below the main volcanic arc. Isotope and trace element signatures of volcanic rocks of the investigated volcanoes show no simple correlation with Hg or Iodine abundances. The acid hot spring fluids of Copahue volcano (Argentina) carried ~ 200 ppt Hg in January 1999, ~80 ppt Hg in March 2008, and 90 ppt Hg in the crater lake in March 1997. The dissolved Hg fluxes from the Copahue hydrothermal system are ~300 gr Hg/year in 1999 and ~130 gr Hg/year in 2008. The bulk hydrothermal Hg flux (particle bound+dissolved) in 2008 was ~ 350 gr Hg/year. The potential Mercury evasion from these hydrothermal spring fluids into the air has not yet been incorporated in these estimates.

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.

Modelling ground deformation patterns associated with volcanic processes at the Okataina Volcanic Centre

Science.gov (United States)

Holden, L.; Cas, R.; Fournier, N.; Ailleres, L.

2017-09-01

The Okataina Volcanic Centre (OVC) is one of two large active rhyolite centres in the modern Taupo Volcanic Zone (TVZ) in the North Island of New Zealand. It is located in a complex section of the Taupo rift, a tectonically active section of the TVZ. The most recent volcanic unrest at the OVC includes the 1315 CE Kaharoa and 1886 Tarawera eruptions. Current monitoring activity at the OVC includes the use of continuous GPS receivers (cGPS), lake levelling and seismographs. The ground deformation patterns preceding volcanic activity the OVC are poorly constrained and restricted to predictions from basic modelling and comparison to other volcanoes worldwide. A better understanding of the deformation patterns preceding renewed volcanic activity is essential to determine if observed deformation is related to volcanic, tectonic or hydrothermal processes. Such an understanding also means that the ability of the present day cGPS network to detect these deformation patterns can also be assessed. The research presented here uses the finite element (FE) modelling technique to investigate ground deformation patterns associated with magma accumulation and diking processes at the OVC in greater detail. A number of FE models are produced and tested using Pylith software and incorporate characteristics of the 1315 CE Kaharoa and 1886 Tarawera eruptions, summarised from the existing body of research literature. The influence of a simple ring fault structure at the OVC on the modelled deformation is evaluated. The ability of the present-day continuous GPS (cGPS) GeoNet monitoring network to detect or observe the modelled deformation is also considered. The results show the modelled horizontal and vertical displacement fields have a number of key features, which include prominent lobe based regions extending northwest and southeast of the OVC. The results also show that the ring fault structure increases the magnitude of the displacements inside the caldera, in particular in the

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

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

Thermal monitoring of hydrothermal activity by permanent infrared automatic stations: Results obtained at Solfatara di Pozzuoli, Campi Flegrei (Italy)

Science.gov (United States)

Chiodini, G.; Vilardo, G.; Augusti, V.; Granieri, D.; Caliro, S.; Minopoli, C.; Terranova, C.

2007-12-01

A permanent automatic infrared (IR) station was installed at Solfatara crater, the most active zone of Campi Flegrei caldera. After a positive in situ calibration of the IR camera, we analyze 2175 thermal IR images of the same scene from 2004 to 2007. The scene includes a portion of the steam heated hot soils of Solfatara. The experiment was initiated to detect and quantify temperature changes of the shallow thermal structure of a quiescent volcano such as Solfatara over long periods. Ambient temperature is the main parameter affecting IR temperatures, while air humidity and rain control image quality. A geometric correction of the images was necessary to remove the effects of slow movement of the camera. After a suitable correction the images give a reliable and detailed picture of the temperature changes, over the period October 2004 to January 2007, which suggests that origin of the changes were linked to anthropogenic activity, vegetation growth, and the increase of the flux of hydrothermal fluids in the area of the hottest fumaroles. Two positive temperature anomalies were registered after the occurrence of two seismic swarms which affected the hydrothermal system of Solfatara in October 2005 and October 2006. It is worth noting that these signs were detected in a system characterized by a low level of activity with respect to systems affected by real volcanic crisis where more spectacular results will be expected. Results of the experiment show that this kind of monitoring system can be a suitable tool for volcanic surveillance.

The Marsili Volcanic Seamount (Southern Tyrrhenian Sea: A Potential Offshore Geothermal Resource

Directory of Open Access Journals (Sweden)

Francesco Italiano

2014-06-01

Full Text Available Italy has a strong geothermal potential for power generation, although, at present, the only two geothermal fields being exploited are Larderello-Travale/Radicondoli and Mt. Amiata in the Tyrrhenian pre-Apennine volcanic district of Southern Tuscany. A new target for geothermal exploration and exploitation in Italy is represented by the Southern Tyrrhenian submarine volcanic district, a geologically young basin (Upper Pliocene-Pleistocene characterised by tectonic extension where many seamounts have developed. Heat-flow data from that area show significant anomalies comparable to those of onshore geothermal fields. Fractured basaltic rocks facilitate seawater infiltration and circulation of hot water chemically altered by rock/water interactions, as shown by the widespread presence of hydrothermal deposits. The persistence of active hydrothermal activity is consistently shown by many different sources of evidence, including: heat-flow data, gravity and magnetic anomalies, widespread presence of hydrothermal-derived gases (CO2, CO, CH4, 3He/4He isotopic ratios, as well as broadband OBS/H seismological information, which demonstrates persistence of volcano-tectonic events and High Frequency Tremor (HFT. The Marsili and Tyrrhenian seamounts are thus an important—and likely long-lasting-renewable energy resource. This raises the possibility of future development of the world’s first offshore geothermal power plant.

Hydrothermal Fe-Si-Mn oxide deposits from the Central and South Valu Fa Ridge, Lau Basin

International Nuclear Information System (INIS)

Sun Zhilei; Zhou Huaiyang; Yang Qunhui; Sun Zhixue; Bao Shenxu; Yao Huiqiang

2011-01-01

Highlights: → The Fe-Mn crust in the HHF has seawater contribution, whereas the Fe-Si oxide in the MHF is dominated by hydrothermal fluid → The Nd isotope of diffuse flow Fe-Si-Mn deposits indicates the obvious hydrothermal origin. → The Mn/Fe ratio in hydrothermal deposit may be a good indicator of propagating activities of the Valu Fa Ridge. - Abstract: A series of samples from the Hine Hina hydrothermal field (HHF) and the Mariner hydrothermal field (MHF) in the Central and Southern Valu Fa Ridge (VFR), Lau Basin were examined to explain the source origin and formation of the hydrothermal Fe-Si-Mn oxide deposits. The mineralogy was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Moessbauer spectroscopy, and energy-dispersive spectroscopy (EDS). For the Fe-Mn oxide crusts in the HHF, varying amounts of volcanic fragments and some seawater contributions were recognized, along with higher concentrations of Mn, Al, Co, Ni, Zn, Sr, Mo, elevated ΣREE and negative Ce anomalies. In contrast, the Si-rich oxide samples of the MHF were enriched in Cu, Pb and Ba, indicative of proximity to a hydrothermal jet. Moreover, conductive cooling of hydrothermal fluid evoked the Si-rich deposit formation in the MHF. The Sr, Nd and Pb isotope data provided further constraints regarding the source and formation of the Fe-Si-Mn deposits in the VFR by showing that the samples of the HHF are a mixture of three components, namely, hydrothermal fluid, seawater and volcanic materials, whereas the samples of the MHF were dominated by hydrothermal fluids. The seawater had a minor influence on the Nd isotope data, and the Pb isotope data exhibited a close association with the substrate rock and preformed volcaniclastic layers in this area. The occurrence of relatively high Mn/Fe ratios in the hydrothermal deposits of this area may be a good indicator of the propagating activities of the VFR over geological time.

Hydrothermal activity and subsoil complexity: implication for degassing processes at Solfatara crater, Campi Flegrei caldera

Science.gov (United States)

Montanaro, Cristian; Mayer, Klaus; Isaia, Roberto; Gresse, Marceau; Scheu, Bettina; Yilmaz, Tim I.; Vandemeulebrouck, Jean; Ricci, Tullio; Dingwell, Donald B.

2017-12-01

The Solfatara area and its fumaroles are the main surface expression of the vigorous hydrothermal activity within the active Campi Flegrei caldera system. At depth, a range of volcanic and structural processes dictate the actual state of the hydrothermal system below the crater. The presence of a large variety of volcanic products at shallow depth (including pyroclastic fallout ash beds, pyroclastic density current deposits, breccias, and lavas), and the existence of a maar-related fault system appears to exert major controls on the degassing and alteration behavior. Adding further to the complexity of this environment, variations in permeability and porosity, due to subsoil lithology and alteration effects, may further influence fluid flow towards the surface. Here, we report results from a field campaign conducted in July 2015 that was designed to characterize the in situ physical (temperature, humidity) and mechanical (permeability, strength, stiffness) properties of the Solfatara crater subsoil. The survey also included a mapping of the surficial hydrothermal features and their distributions. Finally, laboratory measurements (porosity, granulometry) of selected samples were performed. Our results enable the discrimination of four main subsoils around the crater: (1) the Fangaia domain located in a topographic low in the southwestern sector, (2) the silica flat domain on the western altered side, (3) the new crust domain in the central area, and (4) the crusted hummocks domain that dominates the north, east, and south parts. These domains are surrounded by encrusted areas, reworked material, and vegetated soil. The distribution of these heterogeneous subsoils suggests that their formation is mostly related to (i) the presence of the Fangaia domain within the crater and (ii) a system of ring faults bordering it. The subsoils show an alternation between very high and very low permeabilities, a fact which seems to affect both the temperature distribution and

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

Using Volcanic Lightning Measurements to Discern Variations in Explosive Volcanic Activity

Science.gov (United States)

Behnke, S. A.; Thomas, R. J.; McNutt, S. R.; Edens, H. E.; Krehbiel, P. R.; Rison, W.

2013-12-01

VHF observations of volcanic lightning have been made during the recent eruptions of Augustine Volcano (2006, Alaska, USA), Redoubt Volcano (2009, Alaska, USA), and Eyjafjallajökull (2010, Iceland). These show that electrical activity occurs both on small scales at the vent of the volcano, concurrent with an eruptive event and on large scales throughout the eruption column during and subsequent to an eruptive event. The small-scale discharges at the vent of the volcano are often referred to as 'vent discharges' and are on the order of 10-100 meters in length and occur at rates on the order of 1000 per second. The high rate of vent discharges produces a distinct VHF signature that is sometimes referred to as 'continuous RF' radiation. VHF radiation from vent discharges has been observed at sensors placed as far as 100 km from the volcano. VHF and infrasound measurements have shown that vent discharges occur simultaneously with the onset of eruption, making their detection an unambiguous indicator of explosive volcanic activity. The fact that vent discharges are observed concurrent with explosive volcanic activity indicates that volcanic ejecta are charged upon eruption. VHF observations have shown that the intensity of vent discharges varies between eruptive events, suggesting that fluctuations in eruptive processes affect the electrification processes giving rise to vent discharges. These fluctuations may be variations in eruptive vigor or variations in the type of eruption; however, the data obtained so far do not show a clear relationship between eruption parameters and the intensity or occurrence of vent discharges. Further study is needed to clarify the link between vent discharges and eruptive behavior, such as more detailed lightning observations concurrent with tephra measurements and other measures of eruptive strength. Observations of vent discharges, and volcanic lightning observations in general, are a valuable tool for volcano monitoring, providing a

Melt zones beneath five volcanic complexes in California: an assessment of shallow magma occurrences

Energy Technology Data Exchange (ETDEWEB)

Goldstein, N.E.; Flexser, S.

1984-12-01

Recent geological and geophysical data for five magma-hydrothermal systems were studied for the purpose of developing estimates for the depth, volume and location of magma beneath each area. The areas studied were: (1) Salton Trough, (2) The Geysers-Clear Lake, (3) Long Valley caldera, (4) Coso volcanic field, and (5) Medicine Lake volcano, all located in California and all selected on the basis of recent volcanic activity and published indications of crustal melt zones. 23 figs.

Hydrothermal response to a volcano-tectonic earthquake swarm, Lassen, California

Science.gov (United States)

Ingebritsen, Steven E.; Shelly, David R.; Hsieh, Paul A.; Clor, Laura; P.H. Seward,; Evans, William C.

2015-01-01

The increasing capability of seismic, geodetic, and hydrothermal observation networks allows recognition of volcanic unrest that could previously have gone undetected, creating an imperative to diagnose and interpret unrest episodes. A November 2014 earthquake swarm near Lassen Volcanic National Park, California, which included the largest earthquake in the area in more than 60 years, was accompanied by a rarely observed outburst of hydrothermal fluids. Although the earthquake swarm likely reflects upward migration of endogenous H2O-CO2 fluids in the source region, there is no evidence that such fluids emerged at the surface. Instead, shaking from the modest sized (moment magnitude 3.85) but proximal earthquake caused near-vent permeability increases that triggered increased outflow of hydrothermal fluids already present and equilibrated in a local hydrothermal aquifer. Long-term, multiparametric monitoring at Lassen and other well-instrumented volcanoes enhances interpretation of unrest and can provide a basis for detailed physical modeling.

Fluid circulation and structural system of Cerritos Colorados geothermal field in La Primavera volcanic caldera (Mexico) inferred from geophysical surveys

Science.gov (United States)

Bolós, X.; Cifuentes-Nava, G.; Macias, J. L.; Sosa-Ceballos, G.; García-Tenorio, F.; Albor, M., III; Juarez, M.; Gamez, V.

2017-12-01

Hydrothermal activity in volcanic calderas is the consequence of energy transfer between deep magmatic chambers and subsurface layers saturated in water. This hydrothermal system is generated by convection of the groundwater supplied by meteoric water recharged and the ascent of hot volcanic gasses exsolved from deep magma reservoirs. Calderas are heterogeneous geological structures that due to their formation and evolution produced a complex stratigraphy. All of these heterogeneities can be affected by deformation and also by the presence of fractures and faults which constitute the main pathways whereby hydrothermal fluids can move easily through the surface as spring discharges and fumarolic activity. Geophysical methods have been used in the last decades to investigate the relationship between structural geology and hydrothermal systems in different volcanic areas around the world. In this work, we have focused on the role of subsurface structures to understand and localize the pathways of fluids related to the hydrothermal system of the Cerritos Colorados geothermal field. We focused in the central area of the caldera (P12 well and Cerritos Colorados graben), where active hydrothermal activity is evidenced by fumaroles, thermal anomalies, CO2 diffuse emission, and sulfur precipitation. We have applied a self-potential method (SP) that combined with temperature measurements that allowed to identify the main infiltration and ascending fluid zones in the area, and their specific surface temperature coinciding with fumarolic activity. From this data we an applied Electrical Resistivity Tomography (ERT) survey in two selected places. One ERT profile (1.2 km in length) was located in the P12 well area. A 3D resistivity model used with the equatorial method was carried out on the Cerritos Colorados graben area. Combining the results of the SP, TºC, and ERT data with a detailed structural map we identified the main degassing zones (i.e. fumaroles) that correspond to

Volcanic deformation in the Andes

Science.gov (United States)

Riddick, S.; Fournier, T.; Pritchard, M.

2009-05-01

We present the results from an InSAR survey of volcanic activity in South America. We use data from the Japanese Space Agency's ALOS L-band radar satellite from 2006-2009. The L-band instrument provides better coherence in densely vegetated regions, compared to the shorter wave length C-band data. The survey reveals volcano related deformation in regions, north, central and southern, of the Andes volcanic arc. Since observations are limited to the austral summer, comprehensive coverage of all volcanoes is not possible. Yet, our combined observations reveal volcanic/hydrothermal deformation at Lonquimay, Llaima, Laguna del Maule, and Chaitén volcanoes, extend deformation measurements at Copahue, and illustrate temporal complexity to the previously described deformation at Cerro Hudson and Cordón Caulle. No precursory deformation is apparent before the large Chaitén eruption (VEI_5) of 2 May 2008, (at least before 16 April) suggesting rapid magma movement from depth at this long dormant volcano. Subsidence at Ticsani Volcano occurred coincident with an earthquake swarm in the same region.

Ferrous iron- and ammonium-rich diffuse vents support habitat-specific communities in a shallow hydrothermal field off the Basiluzzo Islet (Aeolian Volcanic Archipelago).

Science.gov (United States)

Bortoluzzi, G; Romeo, T; La Cono, V; La Spada, G; Smedile, F; Esposito, V; Sabatino, G; Di Bella, M; Canese, S; Scotti, G; Bo, M; Giuliano, L; Jones, D; Golyshin, P N; Yakimov, M M; Andaloro, F

2017-09-01

Ammonium- and Fe(II)-rich fluid flows, known from deep-sea hydrothermal systems, have been extensively studied in the last decades and are considered as sites with high microbial diversity and activity. Their shallow-submarine counterparts, despite their easier accessibility, have so far been under-investigated, and as a consequence, much less is known about microbial communities inhabiting these ecosystems. A field of shallow expulsion of hydrothermal fluids has been discovered at depths of 170-400 meters off the base of the Basiluzzo Islet (Aeolian Volcanic Archipelago, Southern Tyrrhenian Sea). This area consists predominantly of both actively diffusing and inactive 1-3 meters-high structures in the form of vertical pinnacles, steeples and mounds covered by a thick orange to brown crust deposits hosting rich benthic fauna. Integrated morphological, mineralogical, and geochemical analyses revealed that, above all, these crusts are formed by ferrihydrite-type Fe 3+ oxyhydroxides. Two cruises in 2013 allowed us to monitor and sampled this novel ecosystem, certainly interesting in terms of shallow-water iron-rich site. The main objective of this work was to characterize the composition of extant communities of iron microbial mats in relation to the environmental setting and the observed patterns of macrofaunal colonization. We demonstrated that iron-rich deposits contain complex and stratified microbial communities with a high proportion of prokaryotes akin to ammonium- and iron-oxidizing chemoautotrophs, belonging to Thaumarchaeota, Nitrospira, and Zetaproteobacteria. Colonizers of iron-rich mounds, while composed of the common macrobenthic grazers, predators, filter-feeders, and tube-dwellers with no representatives of vent endemic fauna, differed from the surrounding populations. Thus, it is very likely that reduced electron donors (Fe 2+ and NH 4 + ) are important energy sources in supporting primary production in microbial mats, which form a habitat

First Survey For Submarine Hydrothermal Vents In NE Sulawesi, Indonesia

Science.gov (United States)

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

2001-12-01

The IASSHA-2001 cruise (Indonesia-Australia Survey for Submarine Hydrothermal Activity) was successfully conducted from June 1 to June 29 on board Baruna Jaya VIII. Preliminary results are reported of the first expedition to locate and study submarine hydrothermal activity in north east Sulawesi. Leg A focussed on Tomini Bay, a virtually unexplored Neogene sedimentary basin. Its objective was to test whether modern sediment-hosted hydrothermal activity occurred on the sea floor. The results of new bathymetric mapping, sediment coring and CTD/transmissometer hydrocasts negate the likely presence in central Tomini Bay of large-scale modern analogues of hydrothermal massive sulfide environments involving hydrothermal venting of basinal or magma-derived fluids into reduced sediments. It is possible that the "heat engine" required to drive circulation of basinal and hydrothermal fluids is today too weak. Surveys around Colo volcano indicate that it may be in its final stage of evolution. Leg B studied the arc and behind-arc sectors of the Sangihe volcanic island chain extending northwards from Quaternary volcanoes on the northeastern tip of Sulawesi's North Arm, near Manado. West of the main active chain and extending northwards from Manado there is a subparallel ridge surmounted by a number of high (>2000 m) seamounts of uncertain age. Fifteen relatively high-standing submarine edifices were crossed during this leg, of which nine were tested for hydrothermal activity by hydrocast and dredging. Eight sites were known from previous bathymetric surveys, and seven are new discoveries made by narrow-beam or multibeam echo sounding. Two submarine edifices at least 1000 m high were discovered in the strait immediately north of Awu volcano on Sangihe Island. One, with crest at 206 m, is surrounded by a circular platform 300m deep which we infer to be a foundered fringing reef to a formerly emergent island. The other, lacking such a platform, appears relatively young and may be

Hydrothermal activity on the summit of Loihi Seamount, Hawaii

Energy Technology Data Exchange (ETDEWEB)

Sakai, H; Tsubota, H; Nakai, T; Ishibashi, J; Akagi, T; Gamo, T; Tilbrook, B; Igarashi, G; Kodera, M; Shitashima, K

1987-01-01

Loihi Seamount is located about 30km southeast of the Island of Hawaii; it rises from the sea floor at a depth of 4000m and reaches a maximum elevation of 1000m blow sea level. Oceanographic studies including CTD survey of warm sites and bottom photography confirmed several hydrothermal fields on the summit of the seamount. The summit is covered with hydrothermal plumes which are extremely rich in methane, helium, carbon dioxide, iron and manganese; the maximum concentration of helium is 91.8 n1/1, the highest so far reported for open-ocean water. The /sup 3/He//sup 4/He ratio of helium injected into seawater is 14 times the atmospheric level. The 3He/heat and CO/sub 2//heat ratios in the plumes are one to two orders of magnitude greater than those at oceanic spreading centers, implying a more primitive source region for hotspot volcanism. The plumes also show negative pH anomalies up to half a pH unit from ambient owing to the high injection rate of CO/sub 2/. (4 figs, 3 photos, 1 tab, 31 refs)

The importance of shallow hydrothermal island arc systems in ocean biogeochemistry

NARCIS (Netherlands)

Hawkes, J.A.; Connelly, D.P.; Rijkenberg, M.J.A.; Achterberg, E.P.

2014-01-01

Hydrothermal venting often occurs at submarine volcanic calderas on island arc chains, typically at shallower depths than mid-ocean ridges. The effect of these systems on ocean biogeochemistry has been under-investigated to date. Here we show that hydrothermal effluent from an island arc caldera was

Estimates of fluid pressure and tectonic stress in hydrothermal/volcanic areas:a methodological approach

Directory of Open Access Journals (Sweden)

G. Vilardo

2005-06-01

Full Text Available An analytical approach to estimate the relative contribution of the fluid pressure and tectonic stress in hydrothermal/ volcanic areas is proposed assuming a Coulomb criterion of failure. The analytical procedure requires the coefficient of internal friction, cohesion, rock density, and thickness of overburden to be known from geological data. In addition, the orientation of the principal stress axes and the stress ratio must be determined from the inversion of fault-slip or seismic data (focal mechanisms. At first, the stress magnitude is calculated assuming that faulting occurs in 'dry' conditions (fluid pressure=0. In a second step, the fluid pressure is introduced performing a grid search over the orientation of 1 fault planes that slip by shear failure or 2 cracks that open under different values of fluid pressure and calculating the consistency with the observed fault planes (i.e. strike and dip of faults, cracks, nodal planes from focal mechanisms. The analytical method is applied using fault-slip data from the Solfatara volcano (Campi Flegrei, Italy and seismic data (focal mechanisms from the Vesuvius volcano (Italy. In these areas, the fluid pressure required to activate faults (shear fractures and cracks (open fractures is calculated. At Solfatara, the ratio between the fluid pressure and the vertical stress ?is very low for faults ( ?=0.16 and relatively high for cracks ( ?=0.5. At Vesuvius, ?=0.6. Limits and uncertainties of the method are also discussed.

ORP and pH measurements to detect redox and acid-base anomalies from hydrothermal activity

Science.gov (United States)

Santana-Casiano, J. M.; González-Dávila, M.; Fraile-Nuez, E.

2017-12-01

The Tagoro submarine volcano is located 1.8 km south of the Island of El Hierro at 350 m depth and rises up to 88 m below sea level. It was erupting melting material for five months, from October 2011 to March 2012, changing drastically the physical-chemical properties of the water column in the area. After this eruption, the system evolved to a hydrothermal system. The character of both reduced and acid of the hydrothermal emissions in the Tagoro submarine volcano allowed us to detect anomalies related with changes in the chemical potential and the proton concentration using ORP and pH sensors, respectively. Tow-yos using a CTD-rosette with these two sensors provided the locations of the emissions plotting δ(ORP)/δt and ΔpH versus the latitude or longitude. The ORP sensor responds very quickly to the presence of reduced chemicals in the water column. Changes in potential are proportional to the amount of reduced chemical species present in the water. The magnitude of these changes are examined by the time derivative of ORP, δ(ORP)/δt. To detect changes in the pH, the mean pH for each depth at a reference station in an area not affected by the vent emission is subtracted from each point measured near the volcanic edifice, defining in this way ΔpH. Detailed surveys of the volcanic edifice were carried out between 2014 and 2016 using several CTD-pH-ORP tow-yo studies, localizing the ORP and pH changes, which were used to obtain surface maps of anomalies. Moreover, meridional tow-yos were used to calculate the amount of volcanic CO2 added to the water column. The inputs of CO2 along multiple sections combined with measurements of oceanic currents produced an estimated volcanic CO2 flux = 6.0 105 ± 1.1 105 kg d-1 which increases the acidity above the volcano by 20%. Sites like the Tagoro submarine volcano, in its degasification stage, provide an excellent opportunity to study the carbonate system in a high CO2 world, the volcanic contribution to the global

Characterising hydrothermal fluid pathways beneath Aluto volcano, Main Ethiopian Rift, using shear wave splitting

Science.gov (United States)

Nowacki, Andy; Wilks, Matthew; Kendall, J.-Michael; Biggs, Juliet; Ayele, Atalay

2018-05-01

Geothermal resources are frequently associated with silicic calderas which show evidence of geologically-recent activity. Hence development of geothermal sites requires both an understanding of the hydrothermal system of these volcanoes, as well as the deeper magmatic processes which drive them. Here we use shear wave splitting to investigate the hydrothermal system at the silicic peralkaline volcano Aluto in the Main Ethiopian Rift, which has experienced repeated uplift and subsidence since at least 2004. We make over 370 robust observations of splitting, showing that anisotropy is confined mainly to the top ∼3 km of the volcanic edifice. We find up to 10% shear wave anisotropy (SWA) is present with a maximum centred at the geothermal reservoir. Fast shear wave orientations away from the reservoir align NNE-SSW, parallel to the present-day minimum compressive stress. Orientations on the edifice, however, are rotated NE-SW in a manner we predict from field observations of faults at the surface, providing fluid pressures are sufficient to hold two fracture sets open. These fracture sets may be due to the repeated deformation experienced at Aluto and initiated in caldera formation. We therefore attribute the observed anisotropy to aligned cracks held open by over-pressurised gas-rich fluids within and above the reservoir. This study demonstrates that shear wave splitting can be used to map the extent and style of fracturing in volcanic hydrothermal systems. It also lends support to the hypothesis that deformation at Aluto arises from variations of fluid pressures in the hydrothermal system. These constraints will be crucial for future characterisation of other volcanic and geothermal systems, in rift systems and elsewhere.

Multiple sources of selenium in ancient seafloor hydrothermal systems: Compositional and Se, S, and Pb isotopic evidence from volcanic-hosted and volcanic-sediment-hosted massive sulfide deposits of the Finlayson Lake District, Yukon, Canada

Science.gov (United States)

Layton-Matthews, Daniel; Leybourne, Matthew I.; Peter, Jan M.; Scott, Steven D.; Cousens, Brian; Eglington, Bruce M.

2013-09-01

Volcanic-hosted massive sulfide (VHMS) and volcanic-sediment-hosted massive sulfide (VSHMS; i.e., hosted by both volcanic and sedimentary rocks) deposits in the Finlayson Lake District, Yukon, Canada, provide a unique opportunity to study the influence of seafloor and sub-seafloor hydrothermal processes on the formation of Se-poor (GP4F VHMS deposit; 7 ppm Se average), intermediate (Kudz Ze Kayah—KZK VHMS deposit; 200 ppm Se average), and Se-enriched (Wolverine VSHMS deposit; 1100 ppm Se average) mineralization. All three deposits are hosted by mid-Paleozoic (˜360-346 Ma) felsic volcanic rocks, but only the Wolverine deposit has voluminous coeval carbonaceous argillites (black shales) in the host rock package. Here we report the first application of Se isotope analyses to ancient seafloor mineralization and use these data, in conjunction with Pb and S isotope analyses, to better understand the source(s) and depositional process(es) of Se within VHMS and VSHMS systems. The wide range of δ82Se (-10.2‰ to 1.3‰, relative to NIST 3149), δ34S (+2.0‰ to +12.8‰ CDT), and elevated Se contents (up to 5865 ppm) within the Wolverine deposit contrast with the narrower range of δ82Se (-3.8‰ to -0.5‰), δ34S (9.8‰ to 13.0‰), and lower Se contents (200 ppm average) of the KZK deposit. The Wolverine and KZK deposits have similar sulfide depositional histories (i.e., deposition at the seafloor, with concomitant zone refining). The Se in the KZK deposit is magmatic (leaching or degassing) in origin, whereas the Wolverine deposit requires an additional large isotopically negative Se source (i.e. ˜-15‰ δ82Se). The negative δ82Se values for the Wolverine deposit are at the extreme light end for measured terrestrial samples, and the lightest observed for hypogene sulfide minerals, but are within calculated equilibrium values of δ82Se relative to NIST 3149 (˜30‰ at 25 °C between SeO4 and Se2-). We propose that the most negative Se isotope values at the

Reservoir Space Evolution of Volcanic Rocks in Deep Songliao Basin, China

Science.gov (United States)

Zheng, M.; Wu, X.; Zheng, M.; HU, J.; Wang, S.

2015-12-01

Recent years, large amount of natural gas has been discovered in volcanic rock of Lower Crataceous of Songliao basin. Volcanic reservoirs have become one of the important target reservoir types of eastern basin of China. In order to study the volcanic reservoirs, we need to know the main factors controlling the reservoir space. By careful obsercation on volcanic drilling core, casting thin sections and statistical analysis of petrophysical properties of volcanic reservoir in Songliao basin, it can be suggested that the igneous rock reservoir in Yingcheng formation of Lower Crataceous is composed of different rock types, such ad rohylite, rohylitic crystal tuff, autoclastic brecciation lava and so on. There are different reservoirs storage space in in various lithological igneous rocks, but they are mainly composed of primary stoma, secondary solution pores and fractures.The evolution of storage space can be divided into 3 stage: the pramary reservoir space,exogenic leaching process and burial diagenesis.During the evolution process, the reservoir space is effected by secondary minerals, tectonic movement and volcanic hydrothermal solution. The pore of volcanic reservoirs can be partially filled by secondary minerals, but also may be dissoluted by other chemical volcanic hydrothermal solution. Therefore, the favorable places for better-quality volcanic reservoirs are the near-crater facies of vocanic apparatus and dissolution zones on the high position of paleo-structures.

Transition from phreatic to phreatomagmatic explosive activity of Zhupanovsky volcano (Kamchatka) in 2013-2016 due to volcanic cone collapse

Science.gov (United States)

Gorbach, Natalia; Plechova, Anastasiya; Portnyagin, Maxim

2017-04-01

Zhupanovsky volcano, situated 70 km north from Petropavlovsk-Kamchatsky city, resumed its activity in October 2013 [3]. In 2014 and in the first half of 2015, episodic explosions with ash plumes rising up to 6-8 km above sea level occurred on Priemish cone - one of four cones on the Zhupanovsky volcanic edifice [1]. In July 2015 after a series of seismic and explosive events, the southern sector of the active cone collapsed. The landslide and lahar deposits resulted from the collapse formed a large field on the volcano slopes [2]. In November 2015 and January-March 2016, a series of powerful explosions took place sending ash up to 8-10 km above sea level. No pure magmatic, effusive or extrusive, activity has been observed on Zhupanovsky in 2013-2016. We have studied the composition, morphology and textural features of ash particles produced by the largest explosive events of Zhupanovsky in the period from October 2013 to March 2016. The main components of the ash were found to be hydrothermally altered particles and lithics, likely originated by the defragmentation of rocks composing the volcanic edifice. Juvenile glass fragments occur in very subordinate quantities. The maximum amount of glass particles (up to 7%) was found in the ash erupted in January-March 2016, after the cone collapse. We suggest that the phreatic to phreatomagmatic explosive activity of Zhupanovsky volcano in 2013-2016 was initially caused by the intrusion of a new magma batch under the volcano. The intrusion and associated degassing of magma led to heating, overpressure and instability in the hydrothermal system of the volcano, causing episodic, predominantly phreatic explosions. Decompression of the shallow magmatic and hydrothermal system of the volcano due to the cone collapse in July 2015 facilitated a larger involvement of the magmatic component in the eruption and more powerful explosions. [1] Girina O.A. et al., 2016 Geophysical Research Abstracts Vol. 18, EGU2016-2101, doi: 10

Active hydrothermal and non-active massive sulfide mound investigation using a new multiparameter chemical sensor

Science.gov (United States)

Han, C.; Wu, G.; Qin, H.; Wang, Z.

2012-12-01

Investigation of active hydrothermal mound as well as non-active massive sulfide mound are studied recently. However, there is still lack of in-situ detection method for the non-active massive sulfide mound. Even though Transient ElectroMagnetic (TEM) and Electric Self-potential (SP) methods are good, they both are labour, time and money cost work. We proposed a new multiparameter chemical sensor method to study the seafloor active hydrothermal mound as well as non-active massive sulfide mound. This sensor integrates Eh, S2- ions concentration and pH electrochemical electrodes together, and could found chemical change caused by the active hydrothermal vent, even weak chemical abnormalities by non-active massive sulfide hydrothermal mound which MARP and CTD sometimes cannot detect. In 2012, the 1st Leg of the Chinese 26th cruise, the multiparameter chemical sensor was carried out with the deepsea camera system over the Carlsberg Ridge in Indian Ocean by R/V DAYANGYIHAO. It was shown small Eh and S2- ions concentration abnormal around a site at Northwest Indian ridge. This site was also evidenced by the TV grab. In the 2nd Leg of the same cruise in June, this chemical sensor was carried out with TEM and SP survey system. The chemical abnormalities are matched very well with both TEM and SP survey results. The results show that the multiparameter chemical sensor method not only can detect active hydrothermal mound, but also can find the non-active massive sulfide hydrothermal mound.

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.

Groundwater flow processes and mixing in active volcanic systems: the case of Guadalajara (Mexico)

Science.gov (United States)

Hernández-Antonio, A.; Mahlknecht, J.; Tamez-Meléndez, C.; Ramos-Leal, J.; Ramírez-Orozco, A.; Parra, R.; Ornelas-Soto, N.; Eastoe, C. J.

2015-09-01

other active volcanic systems on Earth.

Calderas and mineralization: volcanic geology and mineralization in the Chianti caldera complex, Trans-Pecos Texas

Energy Technology Data Exchange (ETDEWEB)

Duex, T.W.; Henry, C.D.

1981-01-01

This report describes preliminary results of an ongoing study of the volcanic stratigraphy, caldera activity, and known and potential mineralization of the Chinati Mountains area of Trans-Pecos Texas. Many ore deposits are spatially associated with calderas and other volcanic centers. A genetic relationship between calderas and base and precious metal mineralization has been proposed by some and denied by others. Steven and others have demonstrated that calderas provide an important setting for mineralization in the San Juan volcanic field of Colorado. Mineralization is not found in all calderas but is apparently restricted to calderas that had complex, postsubsidence igneous activity. A comparison of volcanic setting, volcanic history, caldera evolution, and evidence of mineralization in Trans-Pecos to those of the San Juan volcanic field, a major mineral producer, indicates that Trans-Pecos Texas also could be an important mineralized region. The Chianti caldera complex in Trans-Pecos Texas contains at least two calderas that have had considerable postsubsidence activity and that display large areas of hydrothermal alteration and mineralization. Abundant prospects in Trans-Pecos and numerous producing mines immediately south of the Trans-Pecos volcanic field in Mexico are additional evidence that ore-grade deposits could occur in Texas.

40Ar/39Ar chronology of the McMurdo Volcanic Group at The Pleiades, Northern Victoria Land, Antarctica

International Nuclear Information System (INIS)

Esser, R.P.; Kyle, P.R.

2002-01-01

Fifteen samples from The Pleiades volcanic centre in northern Victoria Land, Antarctica, were dated using the 40 Ar/ 39 Ar furnace step-heating method. Ages range from 847 to 6 ka. Eight samples are <100 ka, showing that The Pleiades are very young. Three trachyte samples suggest eruptive activity started at c. 830 ka. An apparent increase in volcanic activity began at c. 100 ka, and at c. 65 ka a significant phase of cone building occurred at Mt Atlas, the largest volcanic cone at The Pleiades. At c. 45 ka, lava flows were erupted on the western flank of Mt Pleiones adjacent to Mt Atlas and near the summit of Alcyone Cone. The youngest activity (6 ± 6 ka) occurred at Taygete Cone, an endogenous dome of trachyte. The near-zero age for Taygete Cone is consistent with evidence of recent volcanism, including fresh hydrothermal activity and compositionally similar pumice lapilli scattered over parts of The Pleiades. (author). 6 refs., 3 figs., 1 tab

Asymmetrical hydrothermal system below Merapi volcano imaged by geophysical data.

Science.gov (United States)

Byrdina, Svetlana; Friedel, Sven; Budi-Santoso, Agus; Suryanto, Wiwit; Suhari, Aldjarishy; Vandemeulebrouck, Jean; Rizal, Mohhamed H.; Grandis, Hendra

2017-04-01

, while the liquid water flows down to the base of the volcanic dome. Our ERT results suggest the existence of a peripheral hydrothermal system below the south and west flanks in agreement with previous electromagnetic studies. In contrast, no evidence of hydrothermal system is found below the north flank, where the resistivity values are too high to be assigned to a hydrothermal system, at least to the ERT investigation depth. A probable cause of this asymmetry could be a non-axial location of the magmatic heat source. Such non-axial location of the magmatic source relative to the edifice is suggested by the shift of the volcanic activity to the south as proposed in the geological model by Camus et al, (2000). In addition, the hypocenters of seismic events located by Budi-Santoso et al, (2013) seem to be distributed to the SW from the active crater suggesting that the magma conduits and likely, the magmatic source, are shifted to the SW with respect to the actual crater.

Structural analysis and thermal remote sensing of the Los Humeros Volcanic Complex: Implications for volcano structure and geothermal exploration

Science.gov (United States)

Norini, G.; Groppelli, G.; Sulpizio, R.; Carrasco-Núñez, G.; Dávila-Harris, P.; Pellicioli, C.; Zucca, F.; De Franco, R.

2015-08-01

The Los Humeros Volcanic Complex (LHVC) is an important geothermal target in the Trans-Mexican Volcanic Belt. Understanding the structure of the LHVC and its influence on the occurrence of thermal anomalies and hydrothermal fluids is important to get insights into the interplay between the volcano-tectonic setting and the characteristics of the geothermal resources in the area. In this study, we present a structural analysis of the LHVC, focused on Quaternary tectonic and volcano-tectonic features, including the areal distribution of monogenetic volcanic centers. Morphostructural analysis and structural field mapping revealed the geometry, kinematics and dynamics of the structural features in the study area. Also, thermal infrared remote sensing analysis has been applied to the LHVC for the first time, to map the main endogenous thermal anomalies. These data are integrated with newly proposed Unconformity Bounded Stratigraphic Units, to evaluate the implications for the structural behavior of the caldera complex and geothermal field. The LHVC is characterized by a multistage formation, with at least two major episodes of caldera collapse: Los Humeros Caldera (460 ka) and Los Potreros Caldera (100 ka). The study suggests that the geometry of the first collapse recalls a trap-door structure and impinges on a thick volcanic succession (10.5-1.55 Ma), now hosting the geothermal reservoir. The main ring-faults of the two calderas are buried and sealed by the widespread post-calderas volcanic products, and for this reason they probably do not have enough permeability to be the main conveyers of the hydrothermal fluid circulation. An active, previously unrecognized fault system of volcano-tectonic origin has been identified inside the Los Potreros Caldera. This fault system is the main geothermal target, probably originated by active resurgence of the caldera floor. The active fault system defines three distinct structural sectors in the caldera floor, where the

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

International Nuclear Information System (INIS)

Taylor, B.E

2001-01-01

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

Diffuse CO_{2} degassing monitoring of the oceanic active volcanic island of El Hierro, Canary Islands, Spain

Science.gov (United States)

Hernández, Pedro A.; Norrie, Janice; Withoos, Yannick; García-Merino, Marta; Melián, Gladys; Padrón, Eleazar; Barrancos, José; Padilla, Germán; Rodríguez, Fátima; Pérez, Nemesio M.

2017-04-01

Even during repose periods, volcanoes release large amounts of gases from both visible (fumaroles, solfataras, plumes) and non-visible emanations (diffuse degassing). In the last 20 years, there has been considerable interest in the study of diffuse degassing as a powerful tool in volcano monitoring programs, particularly in those volcanic areas where there are no visible volcanic-hydrothermal gas emissions. Historically, soil gas and diffuse degassing surveys in volcanic environments have focused mainly on CO2 because it is, after water vapor, the most abundant gas dissolved in magma. As CO2 travels upward by advective-diffusive transport mechanisms and manifests itself at the surface, changes in its flux pattern over time provide important information for monitoring volcanic and seismic activity. Since 1998, diffuse CO2 emission has been monitored at El Hierro Island, the smallest and south westernmost island of the Canarian archipelago with an area of 278 km2. As no visible emanations occur at the surface environment of El Hierro, diffuse degassing studies have become the most useful geochemical tool to monitor the volcanic activity in this volcanic island. The island experienced a volcano-seismic unrest that began in July 2011, characterized by the location of a large number of relatively small earthquakes (MHierro at depths between 8 and 15 km. On October 12, 2011, a submarine eruption was confirmed during the afternoon of October 12, 2011 by visual observations off the coast of El Hierro, about 2 km south of the small village of La Restinga in the southernmost part of the island. During the pre-eruptive and eruptive periods, the time series of the diffuse CO2 emission released by the whole island experienced two significant increases. The first started almost 2 weeks before the onset of the submarine eruption, reflecting a clear geochemical anomaly in CO2 emission, most likely due to increasing release of deep seated magmatic gases to the surface. The second

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)

Elemental geochemical records of seafloor hydrothermal activities in the sediments from the Okinawa Trough

Institute of Scientific and Technical Information of China (English)

ZHAI Shikui; YU Zenghui; DU Tongjun

2007-01-01

The major and minor element contents in the sediment core H9 from the hydrothermal fields of the Okinawa Trough show a sharp change at the depth of 80 cm. The elements enriched in the upper 80 cm core are those enriched in the hydrothermal deposits and in the surface sediments recovered from the hydrothermal fields in the trough, which indicates the input of hydrothermal materials. Comparing with other hydrothermal sediments from Mid-ocean Ridges or the Lau Basin, the degree of the enrichment of elements iron, copper, cobalt, and nickel is relatively low. However, the enrichment of elements manganese, lead, arsenic, antimony and mercury is remarkable. The average contents of these elements in the upper 80 cm core sediments are three to six times those in the lower section, and 3 ~ 12 times those in the surface sediments which are not influenced by hydrothermal activities. Hydrothermal activities have contributed significant manganese, lead, arsenic, antimony and mercury to the sediments, and these elements are distinct indicators for the hydrothermal activity in the Okinawa Trough. The significant enrichment of these elements in Core H9 upward from the depth 80 cm indicates the start or the significant enhancing of the hydrothermal activity in this area at about 5 740 aB. P. The average accumulation rate of manganese during this period is about 40 461 μg/( cm2 · ka), which is similar to the hydrothermal sediments in the Lau Basin or the East Pacific Rise.

Seismo-volcanic monitoring at Furnas Volcano (Azores): radon (222Rn) concentration in groundwater

Science.gov (United States)

Silva, Catarina; Virgílio Cruz, José; Ferreira, Teresa; Viveiros, Fátima; Freire, Pedro; Allard, Patrick

2017-04-01

The Azores archipelago, located in the middle of the North Atlantic Ocean, is composed of nine volcanic islands that formed at the triple junction of the North American, Eurasian and African (Nubian) tectonic plates. These volcanic islands were the sites of several eruptions and destructive earthquakes since human settlement in the 15th century. S. Miguel Island, the largest and most densely populated island of the Azores, hosts three active strato-volcanoes with calderas. Furnas Volcano is one of these. Its eruptive activity has been essentially explosive, involving magmas with trachytic (s.l.) composition. In the last 5000 years at least 10 explosive eruptions occurred inside the caldera of Furnas. The last one occurred in 1630 and was subplinian in character. Since then an intense hydrothermal activity has persisted, involving four main fumarolic fields, thermal springs, CO2-rich springs, several soil diffuse degassing areas (CO2 and 222Rn), as well as occasional hydrothermal explosions. In the past decade we have developed a radon survey of Furnas hydrothermal manifestations. Here we report on the radon survey of twelve water springs, located inside the caldera, and representative of the different water types encountered at the volcano (orthothermal, thermal and CO2-rich springs). Bimonthly sampling and determination of radon activity and water temperature was performed in the selected springs between years 2007 and 2011. At each sampling point two water samples were collected for radon dosing in laboratory with the RAD7 equipment. A decay correction was applied to each sample. The average radon activities were found to vary between 1.15 Bq/L and 29.77 Bq/L, while water temperatures ranged between 16.5 °C and 76.2 °C. As a whole radon activities inversely correlate with water temperature, with orthothermal springs showing higher radon activity than thermal springs. Temporal variations in both parameters appear to be mainly determined by seasonal variations of

Petrogeochemistry of Mesozoic basaltic volcanics in Daqingshan area

International Nuclear Information System (INIS)

Li Xiaoguang; Li Ziying; Wei Sanyuan; Qi Da'neng

2009-01-01

Through the discussion on petrogeochemistry of Later Mesozoic basaltic volcanics in Daqingshan Basin in Manzhouli area, combined with field observation and the predecessors' study, its magma evolution,genesis and diagenetic structural environment are discussed, and some suggestion are provided for the further work. Basaltic magma in this area is believed to be derived from mantle with incompatible elements which were later participated by some crustal materials. It is a partially melting product of mantle by early metasomatized fluid under lithosphere extension. Through petrogeochemical analysis of the volcanics and the contrast to the adjacent uranium-producing volcanics, it is concluded that this region has structural environment to form magma evolution series which are more favorable for volcanic hydrothermal-type uranium and polymetallic mineralization. (authors)

The volcanic rocks construction of the late paleozoic era and uranium mineralization in Beishan area of Gansu province

International Nuclear Information System (INIS)

An Zhengchang; Luo Xiaoqiang

2010-01-01

Late Paleozoic volcanic rocks in Beishan area are the favorable constructions of hydrothermal type and volcanic type deposit. From the distribution of volcanic rocks, the volcanic compositions, the volcanic facies, volcanic eruption method and rhythm, chemical and trace elements compositions, and so on, it discusses the characteristics of the Late Devonian volcanic construction in this area and its relationship with uranium mineralization, analyzes the role of volcanic ore-control mechanism, and summarizes uranium ore forming regularity of volcanic construction in Late Paleozoic. (authors)

Astrobiology, Mars Exploration and Lassen Volcanic National Park

Science.gov (United States)

Des Marais, David J.

2015-01-01

The search for evidence of life beyond Earth illustrates how the charters of NASA and the National Park Service share common ground. The mission of NPS is to preserve unimpaired the natural and cultural resources of the National Park System for the enjoyment, education and inspiration of this and future generations. NASA's Astrobiology program seeks to understand the origins, evolution and distribution of life in the universe, and it abides by the principles of planetary stewardship, public outreach, and education. We cannot subject planetary exploration destinations to Earthly biological contamination both for ethical reasons and to preserve their scientific value for astrobiology. We respond to the public's interest in the mysteries of life and the cosmos by honoring their desire to participate in the process of discovery. We involve youth in order to motivate career choices in science and technology and to perpetuate space exploration. The search for evidence of past life on Mars illustrates how the missions of NASA and NPS can become synergistic. Volcanic activity occurs on all rocky planets in our Solar System and beyond, and it frequently interacts with water to create hydrothermal systems. On Earth these systems are oases for microbial life. The Mars Exploration Rover Spirit has found evidence of extinct hydrothermal system in Gusev crater, Mars. Lassen Volcanic National Park provides a pristine laboratory for investigating how microorganisms can both thrive and leave evidence of their former presence in hydrothermal systems. NASA scientists, NPS interpretation personnel and teachers can collaborate on field-oriented programs that enhance Mars mission planning, engage students and the public in science and technology, and emphasize the ethics of responsible exploration.

Mainshock-Aftershocks Clustering Detection in Volcanic Regions

Science.gov (United States)

Garza Giron, R.; Brodsky, E. E.; Prejean, S. G.

2017-12-01

Crustal earthquakes tend to break their general Poissonean process behavior by gathering into two main kinds of seismic bursts: swarms and mainshock-aftershocks sequences. The former is commonly related to volcanic or geothermal processes whereas the latter is a characteristic feature of tectonically driven seismicity. We explore the mainshock-aftershock clustering behavior of different active volcanic regions in Japan and its comparison to non-volcanic regions. We find that aftershock production in volcanoes shows mainshock-aftershocks clustering similar to what is observed in non-volcanic areas. The ratio of volanic areas that cluster in mainshock-aftershocks sequences vs the areas that do not is comparable to the ratio of non-volcanic regions that show clustering vs the ones that do not. Furthermore, the level of production of aftershocks for most volcanic areas where clustering is present seems to be of the same order of magnitude, or slightly higher, as the median of the non-volcanic regions. An interesting example of highly aftershock-productive volcanoes emerges from the 2000 Miyakejima dike intrusion. A big seismic cluster started to build up rapidly in the south-west flank of Miyakejima to later propagate to the north-west towards the Kozushima and Niijima volcanoes. In Miyakejima the seismicity showed a swarm-like signature with a constant earthquake rate, whereas Kozushima and Niijima both had expressions of highly productive mainshock-aftershocks sequences. These findings are surprising given the alternative mechanisms available in volcanic systems for releasing deviatoric strain. We speculate that aftershock behavior might hold a relationship with the rheological properties of the rocks of each system and with the capacity of a system to accumulate or release the internal pressures caused by magmatic or hydrothermal systems.

Tellurium in active volcanic environments: Preliminary results

Science.gov (United States)

Milazzo, Silvia; Calabrese, Sergio; D'Alessandro, Walter; Brusca, Lorenzo; Bellomo, Sergio; Parello, Francesco

2014-05-01

Tellurium is a toxic metalloid and, according to the Goldschmidt classification, a chalcophile element. In the last years its commercial importance has considerably increased because of its wide use in solar cells, thermoelectric and electronic devices of the last generation. Despite such large use, scientific knowledge about volcanogenic tellurium is very poor. Few previous authors report result of tellurium concentrations in volcanic plume, among with other trace metals. They recognize this element as volatile, concluding that volcanic gases and sulfur deposits are usually enriched with tellurium. Here, we present some results on tellurium concentrations in volcanic emissions (plume, fumaroles, ash leachates) and in environmental matrices (soils and plants) affected by volcanic emissions and/or deposition. Samples were collected at Etna and Vulcano (Italy), Turrialba (Costa Rica), Miyakejima, Aso, Asama (Japan), Mutnovsky (Kamchatka) at the crater rims by using common filtration techniques for aerosols (polytetrafluoroethylene filters). Filters were both eluted with Millipore water and acid microwave digested, and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Volcanic ashes emitted during explosive events on Etna and Copahue (Argentina) were analyzed for tellurium bulk composition and after leaching experiments to evaluate the soluble fraction of tellurium. Soils and leaves of vegetation were also sampled close to active volcanic vents (Etna, Vulcano, Nisyros, Nyiragongo, Turrialba, Gorely and Masaya) and investigated for tellurium contents. Preliminary results showed very high enrichments of tellurium in volcanic emissions comparing with other volatile elements like mercury, arsenic, thallium and bismuth. This suggests a primary transport in the volatile phase, probably in gaseous form (as also suggested by recent studies) and/or as soluble salts (halides and/or sulfates) adsorbed on the surface of particulate particles and ashes. First

Diffuse flow hydrothermal manganese mineralization along the active Mariana and southern Izu-Bonin arc system, western Pacific

Science.gov (United States)

Hein, James R.; Schulz, Marjorie S.; Dunham, Rachel E.; Stern, Robert J.; Bloomer, Sherman H.

2008-08-01

Abundant ferromanganese oxides were collected along 1200 km of the active Izu-Bonin-Mariana arc system. Chemical compositions and mineralogy show that samples were collected from two deposit types: Fe-Mn crusts of mixed hydrogenetic/hydrothermal origin and hydrothermal Mn oxide deposits; this paper addresses only the second type. Mn oxides cement volcaniclastic and biogenic sandstone and breccia layers (Mn sandstone) and form discrete dense stratabound layers along bedding planes and within beds (stratabound Mn). The Mn oxide was deposited within coarse-grained sediments from diffuse flow systems where precipitation occurred below the seafloor. Deposits were exposed at the seabed by faulting, mass wasting, and erosion. Scanning electron microscopy and microprobe analyses indicate the presence of both amorphous and crystalline 10 Å and 7 Å manganate minerals, the fundamental chemical difference being high water contents in the amorphous Mn oxides. Alternation of amorphous and crystalline laminae occurs in many samples, which likely resulted from initial rapid precipitation of amorphous Mn oxides from waxing pulses of hydrothermal fluids followed by precipitation of slow forming crystallites during waning stages. The chemical composition is characteristic of a hydrothermal origin including strong fractionation between Fe (mean 0.9 wt %) and Mn (mean 48 wt %) for the stratabound Mn, generally low trace metal contents, and very low rare earth element and platinum group element contents. However, Mo, Cd, Zn, Cu, Ni, and Co occur in high concentrations in some samples and may be good indicator elements for proximity to the heat source or to massive sulfide deposits. For the Mn sandstones, Fe (mean 8.4%) and Mn (12.4%) are not significantly fractionated because of high Fe contents in the volcaniclastic material. However, the proportion of hydrothermal Fe (nondetrital Fe) to total Fe is remarkably constant (49-58%) for all the sample groups, regardless of the degree of

Diffuse flow hydrothermal manganese mineralization along the active Mariana and southern Izu-Bonin arc system, western Pacific

Science.gov (United States)

Hein, J.R.; Schulz, M.S.; Dunham, R.E.; Stern, R.J.; Bloomer, S.H.

2008-01-01

Abundant ferromanganese oxides were collected along 1200 km of the active Izu-Bonin-Mariana arc system. Chemical compositions and mineralogy show that samples were collected from two deposit types: Fe-Mn crusts of mixed hydrogenetic/hydrothermal origin and hydrothermal Mn oxide deposits; this paper addresses only the second type. Mn oxides cement volcaniclastic and biogenic sandstone and breccia layers (Mn sandstone) and form discrete dense stratabound layers along bedding planes and within beds (stratabound Mn). The Mn oxide was deposited within coarse-grained sediments from diffuse flow systems where precipitation occurred below the seafloor. Deposits were exposed at the seabed by faulting, mass wasting, and erosion. Scanning electron microscopy and microprobe analyses indicate the presence of both amorphous and crystalline 10 ?? and 7 ?? manganate minerals, the fundamental chemical difference being high water contents in the amorphous Mn oxides. Alternation of amorphous and crystalline laminae occurs in many samples, which likely resulted from initial rapid precipitation of amorphous Mn oxides from waxing pulses of hydrothermal fluids followed by precipitation of slow forming crystallites during waning stages. The chemical composition is characteristic of a hydrothermal origin including strong fractionation between Fe (mean 0.9 wt %) and Mn (mean 48 wt %) for the stratabound Mn, generally low trace metal contents, and very low rare earth element and platinum group element contents. However, Mo, Cd, Zn, Cu, Ni, and Co occur in high concentrations in some samples and may be good indicator elements for proximity to the heat source or to massive sulfide deposits. For the Mn sandstones, Fe (mean-8.4%) and Mn (12.4%) are not significantly fractionated because of high Fe contents in the volcaniclastic material. However, the proportion of hydrothermal Fe (nondetrital Fe) to total Fe is remarkably constant (49-58%) for all the sample groups, regardless of the degree of

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

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

Directory of Open Access Journals (Sweden)

Batool Taghipou

2015-12-01

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

Geochemical characterisation of Taal volcano-hydrothermal system and temporal evolution during continued phases of unrest (1991-2017)

Science.gov (United States)

Maussen, Katharine; Villacorte, Edgardo; Rebadulla, Ryan R.; Maximo, Raymond Patrick; Debaille, Vinciane; Bornas, Ma. Antonia; Bernard, Alain

2018-02-01

Taal volcano (Luzon Island, Philippines) has last erupted in 1977 but has known some periods of increased activity, characterised by seismic swarms, ground deformation, increased carbon dioxide flux and in some cases temperature anomalies and the opening of fissures. We studied major, trace element and sulphur and strontium isotopic composition of Taal lake waters and hot springs over a period of 25 years to investigate the geochemical evolution of Taal volcano's hydrothermal system and its response to volcanic unrest. Long-term evolution of Main Crater Lake (MCL) composition shows a slow but consistent decrease of acidity, SO4, Mg, Fe and Al concentrations and a trend from light to heavy sulphate, consistent with a general decrease of volcanic gases dissolving in the hydrothermal system. Na, K and Cl concentrations remain constant indicating a non-volcanic origin for these elements. Sulphate and strontium isotopic data suggest this neutral chloride-rich component represents input of geothermal water into Taal hydrothermal system. A significant deviation from the long-term baseline can be seen in two samples from 1995. That year, pH dropped from 2.6 to 2.2, F, Si and Fe concentrations increased and Na, K and Cl concentrations decreased. Sulphate was depleted in 34S and temperature was 4 °C above baseline level at the time of sampling. We attribute these changes to the shallow intrusion of a degassing magma body during the unrest in 1991-1994. More recent unrest periods have not caused significant changes in the geochemistry of Taal hydrothermal waters and are therefore unlikely to have been triggered by shallow magma intrusion. A more likely cause for these events is thus pressurisation of the hydrothermal reservoir by increasing degassing from a stagnant magma reservoir. Our study indicates that new magmatic intrusions that might lead to the next eruption of Taal volcano are expected to change the geochemistry of MCL in the same way as in 1994-1995, with the most

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...

Assessing volcanic hazard at the most populated caldera in the world: Campi Flegrei, Southern Italy

Science.gov (United States)

Somma, R.; de Natale, G.; Troise, C.; Kilburn, C.; Moretti, R.

2017-12-01

Naples and its hinterland in Southern Italy are one of the most urbanized areas in the world under threat from volcanic activity. The region lies within range of three active volcanic centers: Vesuvius, Campi Flegrei, and Ischia. The Campi Flegrei caldera, in particular, has been in unrest for six decades. The unrest followed four centuries of quiescence and has heightened concern about an increased potential for eruption. Innovative geochemical and geophysical analysis, combined with scientific drilling, are being used to investigate Campi Flegrei. Results highlight key directions for better understanding the mechanisms of caldera formation and the respective roles of magma intrusion and hydrothermal activity in determining the volcano's behavior. They also provide a framework for evaluating and mitigating the risk from this caldera and other large ones worldwide.

Active Volcanism on Io as Seen by Galileo SSI

Science.gov (United States)

McEwen, A.S.; Keszthelyi, L.; Geissler, P.; Simonelli, D.P.; Carr, M.H.; Johnson, T.V.; Klaasen, K.P.; Breneman, H.H.; Jones, T.J.; Kaufman, J.M.; Magee, K.P.; Senske, D.A.; Belton, M.J.S.; Schubert, G.

1998-01-01

Active volcanism on Io has been monitored during the nominal Galileo satellite tour from mid 1996 through late 1997. The Solid State Imaging (SSI) experiment was able to observe many manifestations of this active volcanism, including (1) changes in the color and albedo of the surface, (2) active airborne plumes, and (3) glowing vents seen in eclipse. About 30 large-scale (tens of kilometers) surface changes are obvious from comparison of the SSI images to those acquired by Voyager in 1979. These include new pyroclastic deposits of several colors, bright and dark flows, and caldera-floor materials. There have also been significant surface changes on Io during the Galileo mission itself, such as a new 400-km-diameter dark pyroclastic deposit around Pillan Patera. While these surface changes are impressive, the number of large-scale changes observed in the four months between the Voyager 1 and Voyager 2 flybys in 1979 suggested that over 17 years the cumulative changes would have been much more impressive. There are two reasons why this was not actually the case. First, it appears that the most widespread plume deposits are ephemeral and seem to disappear within a few years. Second, it appears that a large fraction of the volcanic activity is confined to repeated resurfacing of dark calderas and flow fields that cover only a few percent of Io's surface. The plume monitoring has revealed 10 active plumes, comparable to the 9 plumes observed by Voyager. One of these plumes was visible only in the first orbit and three became active in the later orbits. Only the Prometheus plume has been consistently active and easy to detect. Observations of the Pele plume have been particularly intriguing since it was detected only once by SSI, despite repeated attempts, but has been detected several times by the Hubble Space Telescope at 255 nm. Pele's plume is much taller (460 km) than during Voyager 1 (300 km) and much fainter at visible wavelengths. Prometheus-type plumes (50

Changes in heat released by hydrothermal circulation monitored during an eruptive cycle at Mt. Etna (Italy)

Science.gov (United States)

Diliberto, I. S.; Gagliano Candela, E.; Morici, S.; Pecoraino, G.; Bellomo, S.; Bitetto, M.; Longo, M.

2018-04-01

The shallow vertical temperature profile has been measured in the proximity of an eruptive fissure far about 4 km north-northeast from Mt. Etna central craters. The monitoring site was a steam-heated soil lying between a group of flank fractures on the upper northeast flank of Mt. Etna (Italy), i.e., on the northeast rift. We chose this area because it was close to an eruptive fissure, that opened in 2002 and extended from about 2500 to about 1500 m a.s.l., with our aim being to determine a connection between this fracture system and the ongoing volcanic activity. Heat flux anomalies from the ground from September 2009 to September 2012 were evaluated. Changes in the hydrothermal release—which can be related to variations in volcanic activity—are discussed and compared to the published geophysical data. The heat flux ranges varied during the pre-eruptive (from about 7 to 38 W × m-2), syn-eruptive (from about 3 to 49 W × m-2), and post-eruptive phases, with the heat released being lowest at the latter phase (from about 1 to 20 W × m-2). Moreover, the heat flux time variation was strongly correlated with the eruption rate from the new southeast crater between January 2011 and April 2012. The migration of magma through active conduits acts as a changing heating source for steam-heated soils located above the active fractures. Our findings suggest that tracking the heat flux above active fractures constitutes a useful investigation field for low-cost thermal monitoring of volcanic activity. Time variations in their emissions could highlight the relationship between a hydrothermal circuit and the local network of fractures, possibly indicating variation in the structural weakness of a volcanic edifice. Continuous monitoring of heat flux, combined with a realistic model, would contribute to multidisciplinary investigations aimed at evaluating changes in volcano dynamics.

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.

Multiteide Project: Multiparametric characterization of the activity of Teide-Pico Viejo volcanic system

Science.gov (United States)

Domínguez Cerdeña, Itahiza; Villasante-Marcos, Victor; Meletlidis, Stavros; Sainz-Maza, Sergio; Abella, Rafael; Torres, Pedro A.; Sánchez, Nieves; Luengo-Oroz, Natividad; José Blanco, María; García-Cañada, Laura; Pereda de Pablo, Jorge; Lamolda, Héctor; Moure, David; Del Fresno, Carmen; Finizola, Anthony; Felepto, Alicia

2017-04-01

addition, they will allow identifying the response of all the analyzed parameters to specific events that are traditionally studied with a single technique, such as short episodes of tremor (sporadically registered in Teide-Pico Viejo surroundings) or changes in activity of the hydrothermal system of the volcanic complex. We present here the first multiparametric results obtained from the project, including locations with the seismic array, CO2 and temperature maps of Teide fumaroles zones and magnetometric measurements.

Division of volcanic activity cycles in the late mesozoic in South Jiangxi and North Guangdong

International Nuclear Information System (INIS)

Li Qinglong; Wu Jianhua

1999-01-01

Based on stratigraphical unconformity, rock association, fossil assemblage, isotope age and tectonic features, the volcanic activity in late Mesozoic in south Jiangxi and north Guandong can be divided into four cycles: Yutian volcanic activity cycle, Lianhuazhai volcanic activity cycle. Banshi volcanic activity cycle and Nanxiong volcanic activity cycle. Yutian volcanic cycle which occurs in middle Jurassic epoch is the bimodal rock association composed of rhyolite and basalt. Lianhuazhai volcanic cycle which occurs in late Jurassic epoch is unimodal rock association composed of rhyolite. Banshi volcanic cycle occurs from the late stage of early Cretaceous to the early stage of late Cretaceous epoch. There are two types of rock associations related to this cycle: unimodal rock association composed of rhyolite or basalt and bimodal rock association composed of rhyolite and basalt. Nanxiong volcanic activity cycle which occurred in late stage of late Cretaceous epoch is the unimodal rock association composed of basalt which is the interlayer of the red sedimentary series

Volcanic gas composition changes during the gradual decrease of the gigantic degassing activity of Miyakejima volcano, Japan, 2000-2015

Science.gov (United States)

Shinohara, Hiroshi; Geshi, Nobuo; Matsushima, Nobuo; Saito, Genji; Kazahaya, Ryunosuke

2017-02-01

The composition of volcanic gases discharged from Miyakejima volcano has been monitored during the intensive degassing activity that began after the eruption in 2000. During the 15 years from 2000 to 2015, Miyakejima volcano discharged 25.5 Mt of SO2, which required degassing of 3 km3 of basaltic magma. The SO2 emission rate peaked at 50 kt/day at the end of 2000 and quickly decreased to 5 kt/day by 2003. During the early degassing period, the volcanic gas composition was constant with the CO2/SO2 = 0.8 (mol ratio), H2O/SO2 = 35, HCl/SO2 = 0.08, and SO2/H2S = 15. The SO2 emission rate decreased gradually to 0.5 kt/day by 2012, and the gas composition also changed gradually to CO2/SO2 = 1.5, H2O/SO2 = 150, HCl/SO2 = 0.15, and SO2/H2S = 6. The compositional changes are not likely caused by changes in degassing pressure or volatile heterogeneity of a magma chamber but are likely attributed to an increase of hydrothermal scrubbing caused by large decrease of the volcanic gas emission rate, suggesting a supply of gases with constant composition during the 15 years. The intensive degassing was modeled based on degassing of a convecting magma conduit. The gradual SO2 emission rate that decrease without changes in volcanic gas composition is attributed to a reduction of diameter of the convecting magma conduit.

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

Topographic stress and catastrophic collapse of volcanic islands

Science.gov (United States)

Moon, S.; Perron, J. T.; Martel, S. J.

2017-12-01

Flank collapse of volcanic islands can devastate coastal environments and potentially induce tsunamis. Previous studies have suggested that factors such as volcanic eruption events, gravitational spreading, the reduction of material strength due to hydrothermal alteration, steep coastal cliffs, or sea level change may contribute to slope instability and induce catastrophic collapse of volcanic flanks. In this study, we examine the potential influence of three-dimensional topographic stress perturbations on flank collapses of volcanic islands. Using a three-dimensional boundary element model, we calculate subsurface stress fields for the Canary and Hawaiian islands to compare the effects of stratovolcano and shield volcano shapes on topographic stresses. Our model accounts for gravitational stresses from the actual shapes of volcanic islands, ambient stress in the underlying plate, and the influence of pore water pressure. We quantify the potential for slope failure of volcanic flanks using a combined model of three-dimensional topographic stress and slope stability. The results of our analysis show that subsurface stress fields vary substantially depending on the shapes of volcanoes, and can influence the size and spatial distribution of flank failures.

Volcanic ash in ancient Maya ceramics of the limestone lowlands: implications for prehistoric volcanic activity in the Guatemala highlands

Science.gov (United States)

Ford, Anabel; Rose, William I.

1995-07-01

In the spirit of collaborative research, Glicken and Ford embarked on the problem of identifying the source of volcanic ash used as temper in prehistoric Maya ceramics. Verification of the presence of glass shards and associated volcanic mineralogy in thin sections of Maya ceramics was straightforward and pointed to the Guatemala Highland volcanic chain. Considering seasonal wind rose patterns, target volcanoes include those from the area west of and including Guatemala City. Joint field research conducted in 1983 by Glicken and Ford in the limestone lowlands of Belize and neighboring Guatemala, 300 km north of the volcanic zone and 150 km from the nearest identified ash deposits, was unsuccessful in discovering local volcanic ash deposits. The abundance of the ash in common Maya ceramic vessels coupled with the difficulties of long-distance procurement without draft animals lead Glicken to suggest that ashfall into the lowlands would most parsimoniously explain prehistoric procurement; it literally dropped into their hands. A major archaeological problem with this explanation is that the use of volcanic ash occurring over several centuries of the Late Classic Period (ca. 600-900 AD). To accept the ashfall hypothesis for ancient Maya volcanic ash procurement, one would have to demonstrate a long span of consistent volcanic activity in the Guatemala Highlands for the last half of the first millennium AD. Should this be documented through careful petrographic, microprobe and tephrachronological studies, a number of related archaeological phenomena would be explained. In addition, the proposed model of volcanic activity has implications for understanding volcanism and potential volcanic hazards in Central America over a significantly longer time span than the historic period. These avenues are explored and a call for further collaborative research of this interdisciplinary problem is extended in this paper.

Volcanic Gases and Hot Spring Water to Evaluate the Volcanic Activity of the Mt. Baekdusan

Science.gov (United States)

Yun, S. H.; Lee, S.; Chang, C.

2017-12-01

This study performed the analysis on the volcanic gases and hot spring waters from the Julong hot spring at Mt. Baekdu, also known as Changbaishan on the North Korea(DPRK)-China border, during the period from July 2015 to August 2016. Also, we confirmed the errors that HCO3- concentrations of hot spring waters in the previous study (Lee et al. 2014) and tried to improve the problem. Dissolved CO2 in hot spring waters was analyzed using gas chromatograph in Lee et al.(2014). Improving this, from 2015, we used TOC-IC to analysis dissolved CO2. Also, we analyzed the Na2CO3 standard solutions of different concentrations using GC, and confirmed the correlation between the analytical concentrations and the real concentrations. However, because the analytical results of the Julong hot spring water were in discord with the estimated values based on this correlation, we can't estimate the HCO3-concentrations of 2014 samples. During the period of study, CO2/CH4 ratios in volcanic gases are gradually decreased, and this can be interpreted in two different ways. The first interpretation is that the conditions inside the volcanic edifice are changing into more reduction condition, and carbon in volcanic gases become more favorable to distribute into CH4 or CO than CO2. The second interpretation is that the interaction between volcanic gases and water becomes greater than past, and the concentrations of CO2which have much higher solubility in water decreased, relatively. In general, the effect of scrubbing of volcanic gas is strengthened during the quiet periods of volcanic activity rather than active periods. Meanwhile, the analysis of hot spring waters was done on the anion of acidic gases species, the major cations, and some trace elements (As, Cd, Re).This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMIPA 2015-3060.

The bulk isotopic composition of hydrocarbons in subaerial volcanic-hydrothermal emissions from different tectonic settings

Science.gov (United States)

Fiebig, J.; Tassi, F.; Vaselli, O.; Viveiros, M. F.; Silva, C.; Lopez, T. M.; D'Alessandro, W.; Stefansson, A.

2015-12-01

Assuming that methane and its higher chain homologues derive from a common source, carbon isotope patterns have been applied as a criterion to identify occurrences of abiogenic hydrocarbons. Based on these, it has been postulated that abiogenic hydrocarbon production occurs within several (ultra)mafic environments. More evolved volcanic-hydrothermal systems may also provide all the prerequisites necessary for abiogenic hydrocarbon production, such as availability of inorganic CO2, hydrogen and heat. We have investigated the chemical and isotopic composition of n-alkanes contained within subaerial hydrothermal discharges emitted from a range of hot spot, subduction and rift-related volcanoes to determine the origin of hydrocarbons in these systems. Amongst these are Nisyros (Greece), Vesuvio, Campi Flegrei, Ischia, Pantelleria and Vulcano (all Italy), Mt. Mageik and Trident (USA), Copahue (Argentina), Teide (Spain), Furnas and Fogo (Portugal). The carbon isotopic composition of methane emitted from these sites varies from -65 to -8‰ , whereas δ13C of ethane and propane exhibit a much narrower variation from -17‰ to -31‰. Methane that occurs most enriched in 13C is also characterized by relatively positive δD values ranging up to -80‰. Carbon isotope reversals between methane and ethane are only observed for locations exhibiting δ13C-CH4 values > -20‰, such as Teide, Pantelleria, Trident and Furnas. At Furnas, δ13C-CH4 varies by 50‰ within a relatively short distance of <50m between two vents, whereas δ13C-C2H6 varies by less than 2‰ only. For some of the investigated locations apparent carbon isotopic temperatures between methane and CO2 are in agreement with those derived from gas concentration geothermometers. At these locations methane, however seems to be in disequilibrium with ethane and propane. These findings imply that methane on the one hand and the C2+ hydrocarbons on the other hand often might derive from distinct sources.

The Role of Volcanic Activity in Climate and Global Change

KAUST Repository

Stenchikov, Georgiy L.

2015-09-23

Explosive volcanic eruptions are magnificent events that in many ways affect the Earth\\'s natural processes and climate. They cause sporadic perturbations of the planet\\'s energy balance, activating complex climate feedbacks and providing unique opportunities to better quantify those processes. We know that explosive eruptions cause cooling in the atmosphere for a few years, but we have just recently realized that volcanic signals can be seen in the subsurface ocean for decades. The volcanic forcing of the previous two centuries offsets the ocean heat uptake and diminishes global warming by about 30%. The explosive volcanism of the twenty-first century is unlikely to either cause any significant climate signal or to delay the pace of global warming. The recent interest in dynamic, microphysical, chemical, and climate impacts of volcanic eruptions is also excited by the fact that these impacts provide a natural analogue for climate geoengineering schemes involving deliberate development of an artificial aerosol layer in the lower stratosphere to counteract global warming. In this chapter we aim to discuss these recently discovered volcanic effects and specifically pay attention to how we can learn about the hidden Earth-system mechanisms activated by explosive volcanic eruptions. To demonstrate these effects we use our own model results when possible along with available observations, as well as review closely related recent publications.

The Geothermal Systems along the Watukosek fault system (East Java, Indonesia):The Arjuno-Welirang Volcanic Complex and the Lusi Mud-Eruption

Science.gov (United States)

Inguaggiato, Salvatore; Mazzini, Adriano; Vita, Fabio; Sciarra, Alessandra

2016-04-01

The Java Island is characterized by an intense volcanic activity with more then 100 active volcanoes. Moreover, this island is also known by the presence of many mud volcanoes and hydrothermal springs. In particular, in the 2006 several sudden hot mud eruptions, with fluids around 100° C, occurred in the NE side of the island resulting in a prominent eruption named Lusi (contraction of Lumpur Sidoarjo) located along the major Watukosek strike-slip fault zone. The Watukosek fault system, strikes from the Arjuno-Welirang volcanic complex, intersects Lusi and extends towards the NE of the Java island. Conversely of the normal mud eruptions (cold fluids emitted in a short time period of few days), the Lusi eruption was characterized by a persistent effusive hot fluids emissions for a long-time period of, so far, nearly a decade. Moreover, the isotopic composition of emitted gases like Helium showed a clear magmatic origin. For this reasons we decided to investigate the near Arjuno-Welirang complex located on the same strike-slip fault. Arjuno-Welirang is a twin strato-volcano system located in the East of Java along the Watukosek fault, at about 25 km SW respect to the Lusi volcano system. It features two main peaks: Arjuno (3339 masl) and Welirang (3156 masl). The last recorded eruptive activity took place in August 1950 from the flanks of Kawah Plupuh and in October 1950 from the NW part of the Gunung Welirang. This strato-volcano is characterized by a S-rich area, with high T-vent fumarole at least up to 220° C (and likely higher), located mainly in the Welirang crater. In addition, several hot springs vent from the flanks of the volcano, indicate the presence of a large hydrothermal system. During July 2015, in the framework of the Lusi Lab project (ERC grant n° 308126), we carried out a geochemical field campaign on the Arjuno-Welirang volcano hydrothermal system area, sampling water and dissolved gases from the thermal and cold springs located on the flanks of

Rapid response of a hydrologic system to volcanic activity: Masaya volcano, Nicaragua

Science.gov (United States)

Pearson, S.C.P.; Connor, C.B.; Sanford, W.E.

2008-01-01

Hydrologic systems change in response to volcanic activity, and in turn may be sensitive indicators of volcanic activity. Here we investigate the coupled nature of magmatic and hydrologic systems using continuous multichannel time series of soil temperature collected on the flanks of Masaya volcano, Nicaragua, one of the most active volcanoes in Central America. The soil temperatures were measured in a low-temperature fumarole field located 3.5 km down the flanks of the volcano. Analysis of these time series reveals that they respond extremely rapidly, on a time scale of minutes, to changes in volcanic activity also manifested at the summit vent. These rapid temperature changes are caused by increased flow of water vapor through flank fumaroles during volcanism. The soil temperature response, ~5 °C, is repetitive and complex, with as many as 13 pulses during a single volcanic episode. Analysis of the frequency spectrum of these temperature time series shows that these anomalies are characterized by broad frequency content during volcanic activity. They are thus easily distinguished from seasonal trends, diurnal variations, or individual rainfall events, which triggered rapid transient increases in temperature during 5% of events. We suggest that the mechanism responsible for the distinctive temperature signals is rapid change in pore pressure in response to magmatism, a response that can be enhanced by meteoric water infiltration. Monitoring of distal fumaroles can therefore provide insight into coupled volcanic-hydrologic-meteorologic systems, and has potential as an inexpensive monitoring tool.

A seismic network to investigate the sedimentary hosted hydrothermal Lusi system

Science.gov (United States)

Javad Fallahi, Mohammad; Mazzini, Adriano; Lupi, Matteo; Obermann, Anne; Karyono, Karyono

2016-04-01

The 29th of May 2006 marked the beginning of the sedimentary hosted hydrothermal Lusi system. During the last 10 years we witnessed numerous alterations of the Lusi system behavior that coincide with the frequent seismic and volcanic activity occurring in the region. In order to monitor the effect that the seismicity and the activity of the volcanic arc have on Lusi, we deployed a ad hoc seismic network. This temporary network consist of 10 broadband and 21 short period stations and is currently operating around the Arjuno-Welirang volcanic complex, along the Watukosek fault system and around Lusi, in the East Java basin since January 2015. We exploit this dataset to investigate surface wave and shear wave velocity structure of the upper-crust beneath the Arjuno-Welirang-Lusi complex in the framework of the Lusi Lab project (ERC grant n° 308126). Rayleigh and Love waves travelling between each station-pair are extracted by cross-correlating long time series of ambient noise data recorded at the stations. Group and phase velocity dispersion curves are obtained by time-frequency analysis of cross-correlation functions, and are tomographically inverted to provide 2D velocity maps corresponding to different sampling depths. 3D shear wave velocity structure is then acquired by inverting the group velocity maps.

Sedimentary response to volcanic activity in the Okinawa Trough since the last deglaciation

Institute of Scientific and Technical Information of China (English)

蒋富清; 李安春; 李铁刚

2010-01-01

To investigate the relationship between volcanic activity and sediment record on regional and temporal scales,158 surface sediment samples were collected from the East China Sea Shelf to the northern Okinawa Trough (OT),and two cores recovered in the northern and southern OT,respectively.Mineralogy,grain-size,and geochemical analyses of those samples show that:1) volcanic glass,volcanic-type pyroxene,hypersthenes,and magnetite increase in sediment influenced by volcanic activity;2) sediment grain sizes (and...

Deformation in volcanic areas: a numerical approach for their prediction in Teide volcano (Tenerife, Canary Islands); Deformaciones en areas volcanicas: una aproximacin numerica para su prediccion en el volcan Teide (Tenerife, Islas Canarias)

Energy Technology Data Exchange (ETDEWEB)

Charco, M.; Galan del Sastre, P.

2011-07-01

Active volcanic areas study comprises both, observation of physical changes in the natural media and the interpretation of such changes. Nowadays, the application of spatial geodetic techniques, such as GPS (Global Positioning System) or InSAR (Interferometry with Synthetic Aperture Radar), for deformation understanding in volcanic areas, revolutionizes our view of this geodetic signals. Deformation of the Earth's surface reflects tectonic, magmatic and hydrothermal processes at depth. In this way, the prediction of volcanic deformation through physical modelling provides a link between the observation and depth interior processes that could be crucial for volcanic hazards assessment. In this work, we develop a numerical model for elastic deformation study. The Finite Element Method (FEM) is used for the implementation of the numerical model. FEM allows to take into account different morphology, structural characteristics and the mechanical heterogeneities of the medium. Numerical simulations of deformation in Tenerife (Canary Islands) taking into account different medium hypothesis allow us to conclude that the accuracy of the predictions depends on how well the natural system is described. (Author) 22 refs.

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.

Constraints on the source of Cu in a submarine magmatic-hydrothermal system, Brothers volcano, Kermadec island arc

Science.gov (United States)

Keith, Manuel; Haase, Karsten M.; Klemd, Reiner; Smith, Daniel J.; Schwarz-Schampera, Ulrich; Bach, Wolfgang

2018-05-01

Most magmatic-hydrothermal Cu deposits are genetically linked to arc magmas. However, most continental or oceanic arc magmas are barren, and hence new methods have to be developed to distinguish between barren and mineralised arc systems. Source composition, melting conditions, the timing of S saturation and an initial chalcophile element-enrichment represent important parameters that control the potential of a subduction setting to host an economically valuable deposit. Brothers volcano in the Kermadec island arc is one of the best-studied examples of arc-related submarine magmatic-hydrothermal activity. This study, for the first time, compares the chemical and mineralogical composition of the Brothers seafloor massive sulphides and the associated dacitic to rhyolitic lavas that host the hydrothermal system. Incompatible trace element ratios, such as La/Sm and Ce/Pb, indicate that the basaltic melts from L'Esperance volcano may represent a parental analogue to the more evolved Brothers lavas. Copper-rich magmatic sulphides (Cu > 2 wt%) identified in fresh volcanic glass and phenocryst phases, such as clinopyroxene, plagioclase and Fe-Ti oxide suggest that the surrounding lavas that host the Brothers hydrothermal system represent a potential Cu source for the sulphide ores at the seafloor. Thermodynamic calculations reveal that the Brothers melts reached volatile saturation during their evolution. Melt inclusion data and the occurrence of sulphides along vesicle margins indicate that an exsolving volatile phase extracted Cu from the silicate melt and probably contributed it to the overlying hydrothermal system. Hence, the formation of the Cu-rich seafloor massive sulphides (up to 35.6 wt%) is probably due to the contribution of Cu from a bimodal source including wall rock leaching and magmatic degassing, in a mineralisation style that is hybrid between Cyprus-type volcanic-hosted massive sulphide and subaerial epithermal-porphyry deposits.

An Overview of Thermal Measurements (IR) at the Summit of Piton de la Fournaise Active Volcano and Inferences on the Structure and Dynamics of its Hydrothermal System

Science.gov (United States)

Fontaine, F.; Peltier, A.; Kowalski, P.; Di Muro, A.; Villeneuve, N.; Ferrazzini, V.; Staudacher, T.

2017-12-01

Piton de la Fournaise, located on La Réunion Island in the South East Indian Ocean, is one of the most active basaltic volcanoes (hotspot) of the world with a mean eruption frequency 100×106 m3) on the island, led to the formation of a 400-m-deep, 1000-m-large, funnel-shaped summit caldera. Since then, the floor and inner flanks of this summit depression hosting hot grounds and active fumaroles, are monitored using an infra-red camera device permanently installed on the caldera rim.This thermal dataset constitutes the first opportunity to understand the structure and dynamics of the hydrothermal system and its ability to relay deep-seated heat and mass perturbations. We present in this communication an overview of this thermal datasets focusing on ground/fumaroles temperature evolution during volcanic crisis and rest periods and analyzing correlations with the other permanently acquired data such as the temporal evolution of gas geochemistry (CO2, SO2, H2S), ground deformation and micro-seismic activity. We finally propose a conceptual model of fluid flow architecture within the edifice which paves the way for future quantitative models of hydrothermal heat and mass transfers.

Can Life Begin on Enceladus? A Perspective from Hydrothermal Chemistry.

Science.gov (United States)

Deamer, David; Damer, Bruce

2017-09-01

Enceladus is a target of future missions designed to search for existing life or its precursors. Recent flybys of Enceladus by the Cassini probe have confirmed the existence of a long-lived global ocean laced with organic compounds and biologically available nitrogen. This immediately suggests the possibility that life could have begun and may still exist on Enceladus. Here we will compare the properties of two proposed sites for the origin of life on Earth-hydrothermal vents on the ocean floor and hydrothermal volcanic fields at the surface-and ask whether similar conditions could have fostered the origin of life on Enceladus. The answer depends on which of the two sites would be more conducive for the chemical evolution leading to life's origin. A hydrothermal vent origin would allow life to begin in the Enceladus ocean, but if the origin of life requires freshwater hydrothermal pools undergoing wet-dry cycles, the Enceladus ocean could be habitable but lifeless. These arguments also apply directly to Europa and indirectly to early Mars. Key Words: Enceladus-Hydrothermal vents-Hydrothermal fields-Origin of life. Astrobiology 17, 834-839.

Diffuse H_{2} emission: a useful geochemical tool to monitor the volcanic activity at El Hierro volcano system

Science.gov (United States)

Pérez, Nemesio M.; Melián, Gladys; González-Santana, Judit; Barrancos, José; Padilla, Germán; Rodríguez, Fátima; Padrón, Eleazar; Hernández, Pedro A.

2016-04-01

The occurrence of interfering processes affecting reactive gases as CO2 during its ascent from magmatic bodies or hydrothermal systems toward the surface environment hinders the interpretation of their enrichments in the soil atmosphere and fluxes for volcano monitoring purposes (Marini and Gambardella, 2005). These processes include gas scrubbing by ground-waters and interaction with rocks, decarbonatation processes, biogenic production, etc. Within the rest of the soil gases, particularly interest has been addressed to light and highly mobile gases. They offer important advantages for the detection of vertical permeability structures, because their interaction with the surrounding rocks or fluids during the ascent toward the surface is minimum. H2 is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the hydrothermal reservoir gas (Giggenbach, 1987). Although H2 can be produced in soils by N2-fixing and fertilizing bacteria, soils are considered nowadays as sinks of molecular hydrogen (Smith-Downey et al., 2006). Because of its chemical and physical characteristics, H2 generated within the crust moves rapidly and escapes to the atmosphere. These characteristics make H2 one of the best geochemical indicators of magmatic and geothermal activity at depth. El Hierro is the youngest and the SW-most of the Canary Islands and the scenario of the last volcanic eruption of the archipelago, a submarine eruption that took place 2 km off the southern coast of the island from October 2011 to March 2012. Since at El Hierro Island there are not any surface geothermal manifestations (fumaroles, etc), we have focused our studies on soil degassing surveys. Here we show the results of soil H2 emission surveys that have been carried out regularly since mid-2012. Soil gas samples were collected in ˜600 sites selected based on their accessibility and geological criteria. Soil gases were sampled at ˜40

Synthesis of morphotectonics and volcanics of the Central Indian Ocean Basin

Digital Repository Service at National Institute of Oceanography (India)

Mukherjee, A.D.; Iyer, S.D.

to the hydrothermal effect on the pre-existing subalkaline basalts. Besides these rocks, there is a wide occurrence of pumice of probably in situ origin. A distinct relation occurs between the morpho-tectonic forms and the volcanics. For example, in and around...

Magma injection beneath the urban area of Naples: a new mechanism for the 2012-2013 volcanic unrest at Campi Flegrei caldera.

Science.gov (United States)

D'Auria, Luca; Pepe, Susi; Castaldo, Raffaele; Giudicepietro, Flora; Macedonio, Giovanni; Ricciolino, Patrizia; Tizzani, Pietro; Casu, Francesco; Lanari, Riccardo; Manzo, Mariarosaria; Martini, Marcello; Sansosti, Eugenio; Zinno, Ivana

2015-08-17

We found the first evidence, in the last 30 years, of a renewed magmatic activity at Campi Flegrei caldera from January 2012 to June 2013. The ground deformation, observed through satellite interferometry and GPS measurements, have been interpreted as the effect of the intrusion at shallow depth (3090 ± 138 m) of 0.0042 ± 0.0002 km(3) of magma within a sill. This interrupts about 28 years of dominant hydrothermal activity and occurs in the context of an unrest phase which began in 2005 and within a more general ground uplift that goes on since 1950. This discovery has implications on the evaluation of the volcanic risk and in the volcanic surveillance of this densely populated area.

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

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.

Radon in active volcanic areas of Southern Italy

International Nuclear Information System (INIS)

Avino, R.; Capaldi, G.; Pece, R.

1999-01-01

The paper presents the preliminary data dealing with the variations in time of the radiogenic gas radon in soils and waters of many active volcanic areas of Southern Italy. The greatest differences in Rn content of the investigated volcanic areas are: Ischia and Campi Flegrei, which have more Rn than Vesuvio and Volcano, both in soils and in waters. The thermalized waters of Ischia are enriched in Rn 15 times with respect to soils, while in the other areas soils and underground waters have comparable Rn contents

K-Ar chronological study of the quaternary volcanic activity in Shin-etsu Highland

International Nuclear Information System (INIS)

Kaneko, Takayuki; Shimizu, Satoshi; Itaya, Tetsumaru.

1989-01-01

In order to clarify the temporal and spatial patterns in arc volcanism, 55 K-Ar ages of volcanic rocks from 17 volcanoes in Shin-etsu Highland, central Japan were determined. In addition, life spans, volume of erupted materials and eruption rates of each volcano were estimated. Graphical analysis demonstrates that volume of ejecta varies proportionately with both life span and eruption rate, and that there is no significant correlation between eruption rate and distance from the volcanic front. The life span of each volcano in this Highland is less than 0.6 m.y. In the central Shiga and southern Asama area, the volcanism started at 1 Ma and is still active. However the former had a peak in the activity at around 0.5 Ma, while the latter is apparently most intense at present. Northern Kenashi area has the volcanism without peak in 1.7 - 0.2 Ma, though the activity within a volcanic cluster or chain in central Japan lasts generally for 1 m.y. or less with a peak. (author)

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.

Volcanic ash activates the NLRP3 inflammasome in murine and human macrophages

Science.gov (United States)

Damby, David; Horwell, Claire J.; Baxter, Peter J.; Kueppers, Ulrich; Schnurr, Max; Dingwell, Donald B.; Duewell, Peter

2018-01-01

Volcanic ash is a heterogeneous mineral dust that is typically composed of a mixture of amorphous (glass) and crystalline (mineral) fragments. It commonly contains an abundance of the crystalline silica (SiO2) polymorph cristobalite. Inhalation of crystalline silica can induce inflammation by stimulating the NLRP3 inflammasome, a cytosolic receptor complex that plays a critical role in driving inflammatory immune responses. Ingested material results in the assembly of NLRP3, ASC, and caspase-1 with subsequent secretion of the interleukin-1 family cytokine IL-1β. Previous toxicology work suggests that cristobalite-bearing volcanic ash is minimally reactive, calling into question the reactivity of volcanically derived crystalline silica, in general. In this study, we target the NLRP3 inflammasome as a crystalline silica responsive element to clarify volcanic cristobalite reactivity. We expose immortalized bone marrow-derived macrophages of genetically engineered mice and primary human peripheral blood mononuclear cells (PBMCs) to ash from the Soufrière Hills volcano as well as representative, pure-phase samples of its primary componentry (volcanic glass, feldspar, cristobalite) and measure NLRP3 inflammasome activation. We demonstrate that respirable Soufrière Hills volcanic ash induces the activation of caspase-1 with subsequent release of mature IL-1β in a NLRP3 inflammasome-dependent manner. Macrophages deficient in NLRP3 inflammasome components are incapable of secreting IL-1β in response to volcanic ash ingestion. Cellular uptake induces lysosomal destabilization involving cysteine proteases. Furthermore, the response involves activation of mitochondrial stress pathways leading to the generation of reactive oxygen species. Considering ash componentry, cristobalite is the most reactive pure-phase with other components inducing only low-level IL-1β secretion. Inflammasome activation mediated by inhaled ash and its potential relevance in chronic pulmonary

Volcanism on Io

Science.gov (United States)

Davies, Ashley Gerard

2014-03-01

Preface; Introduction; Part I. Io, 1610 to 1995: Galileo to Galileo: 1. Io, 1610-1979; 2. Between Voyager and Galileo: 1979-95; 3. Galileo at Io; Part II. Planetary Volcanism: Evolution and Composition: 4. Io and Earth: formation, evolution, and interior structure; 5. Magmas and volatiles; Part III. Observing and Modeling Volcanic Activity: 6. Observations: thermal remote sensing of volcanic activity; 7. Models of effusive eruption processes; 8. Thermal evolution of volcanic eruptions; Part IV. Galileo at Io: the Volcanic Bestiary: 9. The view from Galileo; 10. The lava lake at Pele; 11. Pillan and Tvashtar: lava fountains and flows; 12. Prometheus and Amirani: Effusive activity and insulated flows; 13. Loki Patera: Io's powerhouse; 14. Other volcanoes and eruptions; Part V. Volcanism on Io: The Global View: 15. Geomorphology: paterae, shields, flows and mountains; 16. Volcanic plumes; 17. Hot spots; Part VI. Io after Galileo: 18. Volcanism on Io: a post-Galileo view; 19. The future of Io observations; Appendix 1; Appendix 2; References; Index.

Ejection age of volcano rocks and trend of volcanic activity

Energy Technology Data Exchange (ETDEWEB)

Sakaguchi, Keiichi

1987-10-01

This report is II-7 of an interim report on research and development of the Sunshine Project for 1986. This report considers on the trend of volcanic activities in the South of Kyushu area. K-Ar age measurement was newly made and reported. Age values obtained were 1.09 plus minus 0.21 Ma for Nagaoyama andesite, 1.33 plus minus 0.18 Ma for Nozato andesite, and 0.3 plus minus 0.1 Ma for Imuta volcanos. Including these age values, from the age values and their distribution of the volcanic rocks in the South Kyushu district, the following three districts were selected to represent the volcanic activities since the Pliocene Epoch. As these districts are mutually overwrapped, verification at these overwrapped districts are necessary. (4 figs, 1 tab, 12 refs)

Stability and activity of doped transition metal zeolites in the hydrothermal processing

Directory of Open Access Journals (Sweden)

Thomas François Robin

2015-12-01

Full Text Available This study investigates the stability and activity of HZSM-5 doped with metals such as molybdenum, nickel, copper and iron in under hydrothermal conditions used for the direct liquefaction of microalgae. Catalysts have been prepared by ion exchange techniques, and MoZSM-5 was also prepared by wet incipient impregnation for comparison. Hydrothermal liquefaction is considered as a potential route to convert microalgae into a sustainable fuel. One of the drawbacks of this process is that the bio-crude produced contains significant levels of nitrogen and oxygen compounds which have an impact on the physical and chemical propriety of the fuel. Heterogeneous catalysts have been shown to improve the quality of the bio-crude by reducing nitrogen and oxygen contents. Zeolites, such as HZSM-5, are strong candidates due to their low cost compared to noble metal catalysts but their stability and activity under hydrothermal conditions is not well understood. The stability of the catalysts has been determined under hydrothermal conditions at 350 °C. Catalysts have been characterised before and after treatment using XRD, BET physisorption and STEM microscopy. Metal leaching was determined by analysis of the water phase following hydrothermal treatment. The inserted cation following ion-exchange can influence the physical properties of HZSM-5 for example molybdenum improves the crystallinity of the zeolite. In general, metal doped zeolites were relatively stable under subcritical water. Activity of the catalysts for processing lipids, protein and microalgae has been assessed. Four feedstocks were selected: sunflower oil, soya proteins, Chlorella and P. ellipsoidea. The catalysts exhibited greater activity towards converting lipids for example MoZSM-5 enhanced the formation of aromatic compounds. NiZSM-5 and CuZSM-5 were observed to be more efficient for deoxygenation.

Stability and Activity of Doped Transition Metal Zeolites in the Hydrothermal Processing

International Nuclear Information System (INIS)

Robin, Thomas François; Ross, Andrew B.; Lea-Langton, Amanda R.; Jones, Jenny M.

2015-01-01

This study investigates the stability and activity of HZSM-5 doped with metals such as molybdenum, nickel, copper, and iron under hydrothermal conditions used for the direct liquefaction of microalgae. Catalysts have been prepared by ion-exchange techniques, and MoZSM-5 was also prepared by wet incipient impregnation for comparison. Hydrothermal liquefaction is considered a potential route to convert microalgae into a sustainable fuel. One of the drawbacks of this process is that the bio-crude produced contains significant levels of nitrogen and oxygen compounds that have an impact on the physical and chemical properties of the fuel. Heterogeneous catalysts have been shown to improve the quality of the bio-crude by reducing nitrogen and oxygen contents. Zeolites, such as HZSM-5, are strong candidates due to their low cost compared to noble metal catalysts, but their stability and activity under hydrothermal conditions are not well understood. The stability of the catalysts has been determined under hydrothermal conditions at 350°C. Catalysts have been characterized before and after treatment using X-ray diffraction, BET physisorption, and scanning transmission electronic microscopy. Metal leaching was determined by the analysis of the water phase following the hydrothermal treatment. The inserted cation following ion-exchange can influence the physical properties of HZSM-5, for example, molybdenum improves the crystallinity of the zeolite. In general, metal-doped zeolites were relatively stable in subcritical water. The activity of the catalysts for processing lipids, protein, and microalgae has been assessed. Four feedstocks were selected: sunflower oil, soya proteins, Chlorella, and Pseudochoricystis ellipsoidea. The catalysts exhibited greater activity toward converting lipids, for example, MoZSM-5 enhanced the formation of aromatic compounds. NiZSM-5 and CuZSM-5 were observed to be more efficient for deoxygenation.

Stability and Activity of Doped Transition Metal Zeolites in the Hydrothermal Processing

Energy Technology Data Exchange (ETDEWEB)

Robin, Thomas François, E-mail: thomas.cognac@gmail.com; Ross, Andrew B.; Lea-Langton, Amanda R.; Jones, Jenny M. [School of Chemical and Process Engineering, University of Leeds, Leeds (United Kingdom)

2015-12-14

This study investigates the stability and activity of HZSM-5 doped with metals such as molybdenum, nickel, copper, and iron under hydrothermal conditions used for the direct liquefaction of microalgae. Catalysts have been prepared by ion-exchange techniques, and MoZSM-5 was also prepared by wet incipient impregnation for comparison. Hydrothermal liquefaction is considered a potential route to convert microalgae into a sustainable fuel. One of the drawbacks of this process is that the bio-crude produced contains significant levels of nitrogen and oxygen compounds that have an impact on the physical and chemical properties of the fuel. Heterogeneous catalysts have been shown to improve the quality of the bio-crude by reducing nitrogen and oxygen contents. Zeolites, such as HZSM-5, are strong candidates due to their low cost compared to noble metal catalysts, but their stability and activity under hydrothermal conditions are not well understood. The stability of the catalysts has been determined under hydrothermal conditions at 350°C. Catalysts have been characterized before and after treatment using X-ray diffraction, BET physisorption, and scanning transmission electronic microscopy. Metal leaching was determined by the analysis of the water phase following the hydrothermal treatment. The inserted cation following ion-exchange can influence the physical properties of HZSM-5, for example, molybdenum improves the crystallinity of the zeolite. In general, metal-doped zeolites were relatively stable in subcritical water. The activity of the catalysts for processing lipids, protein, and microalgae has been assessed. Four feedstocks were selected: sunflower oil, soya proteins, Chlorella, and Pseudochoricystis ellipsoidea. The catalysts exhibited greater activity toward converting lipids, for example, MoZSM-5 enhanced the formation of aromatic compounds. NiZSM-5 and CuZSM-5 were observed to be more efficient for deoxygenation.

Feasibility study on volcanic power generation system

Energy Technology Data Exchange (ETDEWEB)

None

1977-07-01

Investigations were carried out to determine the feasibility of volcanic power generation on Satsuma Io Island. Earthquakes were studied, as were the eruptions of subaerial and submarine hot springs. Hydrothermal rock alteration was studied and electrical surveys were made. General geophysical surveying was performed with thermocameras and radiation monitoring equipment. In particular, the Toyoba mine was studied, both with respect to its hot spring and its subsurface temperatures.

ESR dating of submarine hydrothermal activities using barite in sulfide deposition

Science.gov (United States)

Toyoda, S.; Fujiwara, T.; Ishibashi, J.; Isono, Y.; Uchida, A.; Takamasa, A.; Nakai, S.

2012-12-01

The temporal change of submarine hydrothermal activities has been an important issue in the aspect of the evolution of hydrothermal systems which is related with ore formation (Urabe, 1995) and biological systems sustained by the chemical species arising from hydrothermal activities (Macdonald et al., 1980). Determining the ages of the hydrothermal deposit will provide essential information on such studies. Dating methods using disequilibrium between radioisotopes such as U-Th method (e.g. You and Bickle, 1998), 226}Ra-{210Pb and 228}Ra-{228Th method (e.g. Noguchi et al., 2011) have been applied to date submarine hydrothermal deposits. ESR (electron spin resonance) dating method is commonly applied to fossil teeth, shells, and quartz of Quaternay period where the natural accumulated dose is obtained from the intensities of the ESR signals which are created by natural radiation. The natural dose is divided by the dose rate to the mineral/sample to deduce the age. Okumura et al., (2010) made the first practical application of ESR (electron spin resonance) dating technique to a sample of submarine hydrothermal barite (BaSO4) to obtain preliminary ages, where Kasuya et al. (1991) first pointed out that barite can be used for ESR dating. Knowing that ESR dating of barite is promising, in this paper, we will present how we have investigated each factor that contributes ESR dating of barite in submarine hydrothermal sulfide deposition. (1) The best ESR condition for measuring the SO3- signal in barite is with the microwave power of 1mW and modulation amplitude of 0.1mT. (2) As results of heating experiments, the signal was found to be stable for the dating age range of several thousands. (3) 226Ra replacing Ba in barite is the source of the radiation. The amount of radioactive elements in sulfide mineral surrounding barite is negligible. (4) The external radiation from the sea water is negligible even in the submarine hydrothermal area where the radiation level is much

Sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone terrane, western Dharwar Craton: Implications on pyroclastic volcanism and sedimentation in an active continental margin

Science.gov (United States)

Manikyamba, C.; Saha, Abhishek; Ganguly, Sohini; Santosh, M.; Lingadevaru, M.; Rajanikanta Singh, M.; Subba Rao, D. V.

2014-12-01

We report sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone belt of western Dharwar Craton which is associated with rhyolites, chlorite schists and pyroclastic rocks. The pyroclastic rocks of Yalavadahalli area of Shimoga greenstone belt host volcanogenic Pb-Cu-Zn mineralization. The sediment-infill volcanic breccia is clast-supported and comprises angular to sub-angular felsic volcanic clasts embedded in a dolomitic matrix that infilled the spaces in between the framework of volcanic clasts. The volcanic clasts are essentially composed of alkali feldspar and quartz with accessory biotite and opaques. These clasts have geochemical characteristics consistent with that of the associated potassic rhyolites from Daginkatte Formation. The rare earth elements (REE) and high field strength element (HFSE) compositions of the sediment-infill volcanic breccia and associated mafic and felsic volcanic rocks suggest an active continental margin setting for their generation. Origin, transport and deposition of these rhyolitic clasts and their aggregation with infiltrated carbonate sediments may be attributed to pyroclastic volcanism, short distance transportation of felsic volcanic clasts and their deposition in a shallow marine shelf in an active continental margin tectonic setting where the rhyolitic clasts were cemented by carbonate material. This unique rock type, marked by close association of pyroclastic volcanic rocks and shallow marine shelf sediments, suggest shorter distance between the ridge and shelf in the Neoarchean plate tectonic scenario.

The Lanzarote Geodynamic Laboratory: new capabilities for monitoring of volcanic activity at Canary Islands

Science.gov (United States)

Arnoso, J.; Vélez, E. J.; Soler, V.; Montesinos, F. G.; Benavent, M.

2012-04-01

The volcanic island of Lanzarote is located at the northeastern end of the Canary Islands. Together with Fuerteventura Island, Lanzarote constitutes the emergent part of the East Canary Ridge, which presents a NNE-SSW volcanic alignment. Last eruptive events took place in 1824 and during the period 1730-1736, which is the largest to occur in the archipelago and throw out about 1.3 km3 of volcanic materials. The Lanzarote Geodynamic Laboratory (LGL) was created in 1986 with the idea of making Lanzarote as a natural laboratory to carry out studies in order to acquire more knowledge about its origin, present status and evolution (Vieira et al., 1991; 2006). The LGL has a multidisciplinary scientific purpose and, among others, various objectives are devoted to investigate mass distribution in the Earth system and surface displacements associated to volcanic and/or seismic activity in the island. The influence of LGL is extended throughout the whole geographical area of Lanzarote, including small islands located at the north. The laboratory has 3 observing modules distributed along the island according to its infrastructure and scientific objectives, where more than 70 sensors are recording continuously gravity variations, ground deformations, sea level, seismic activity, meteorological parameters, etc. All these observations are supplemented by periodic measurement of geodetic and geophysical networks that allow us to make studies at local, insular and regional scales. The application of geodetic and geophysical techniques to identify geodynamic signals related to volcanic processes is then a permanent research activity of the laboratory. Nowadays, this fact becomes more interesting due to the ongoing volcanic eruption that is taking place in other island of the Canary Archipelago, El Hierro, since past July 2011. That is, the multidisciplinary research carry on up to now at the LGL allow us to apply multiparameter observations of different kinds of volcanic

Natural tracers for identifying the origin of the thermal fluids emerging along the Aegean Volcanic arc (Greece): Evidence of Arc-Type Magmatic Water (ATMW) participation

Science.gov (United States)

Dotsika, E.; Poutoukis, D.; Michelot, J. L.; Raco, B.

2009-01-01

The Aegean volcanic arc is the result of a lithosphere subduction process during the Quaternary time. Starting from the Soussaki area, from west to east, the arc proceeds through the islands of Egina, Methana, Milos, Santorini, the Columbus Bank, Kos and Nisyros. Volcano-tectonic activities are still pronounced at Santorini and Nisyros in form of seismic activity, craters of hydrothermal explosions, hot fumaroles and thermal springs. A significant number of cold water springs emerge in the vicinity of hot waters on these islands. Chemical and isotopic analyses were applied on water and fumaroles samples collected in different areas of the volcanic arc in order to attempt the assessment of these fluids. Stable isotopes of water and carbon have been used to evaluate the origin of cold and thermal water and CO 2. Chemical solute concentrations and isotopic contents of waters show that the fluids emerging in Egina, Soussaki, Methana and Kos areas represent geothermal systems in their waning stage, while the fluids from Milos, Santorini and Nisyros proceed from active geothermal systems. The δ 2H-δ 18O-Cl - relationships suggest that the parent hydrothermal liquids of Nisyros and Milos are produced through mixing of seawater and Arc-Type Magmatic Water (ATMW), with negligible to nil contribution of local ground waters and with very high participation of the magmatic component, which is close to 70% in both sites. A very high magmatic contribution to the deep geothermal system could occur at Santorini as well, perhaps with a percentage similar to Nisyros and Milos, but it cannot be calculated because of steam condensation heavily affecting the fumarolic fluids of Nea Kameni before the surface discharge. The parent hydrothermal liquid at Methana originates through mixing of local groundwaters, seawater and ATMW, with a magmatic participation close to 19%. All in all, the contribution of ATMW is higher in the central-eastern part of the Aegean volcanic arc than in the

Caldera unrest driven by CO2-induced drying of the deep hydrothermal system.

Science.gov (United States)

Moretti, R; Troise, C; Sarno, F; De Natale, G

2018-05-29

Interpreting volcanic unrest is a highly challenging and non-unique problem at calderas, since large hydrothermal systems may either hide or amplify the dynamics of buried magma(s). Here we use the exceptional ground displacement and geochemical datasets from the actively degassing Campi Flegrei caldera (Southern Italy) to show that ambiguities disappear when the thermal evolution of the deep hydrothermal system is accurately tracked. By using temperatures from the CO 2 -CH 4 exchange of 13 C and thermodynamic analysis of gas ascending in the crust, we demonstrate that after the last 1982-84 crisis the deep hydrothermal system evolved through supercritical conditions under the continuous isenthalpic inflow of hot CO 2 -rich gases released from the deep (~8 km) magma reservoir of regional size. This resulted in the drying of the base of the hot hydrothermal system, no more buffered along the liquid-vapour equilibrium, and excludes any shallow arrival of new magma, whose abundant steam degassing due to decompression would have restored liquid-vapour equilibrium. The consequent CO 2 -infiltration and progressive heating of the surrounding deforming rock volume cause the build-up of pore pressure in aquifers, and generate the striking temporal symmetry that characterizes the ongoing uplift and the post-1984 subsidence, both originated by the same but reversed deformation mechanism.

Hydrothermally Activated Graphene Fiber Fabrics for Textile Electrodes of Supercapacitors.

Science.gov (United States)

Li, Zheng; Huang, Tieqi; Gao, Weiwei; Xu, Zhen; Chang, Dan; Zhang, Chunxiao; Gao, Chao

2017-11-28

Carbon textiles are promising electrode materials for wearable energy storage devices owing to their conductive, flexible, and lightweight features. However, there still lacks a perfect choice for high-performance carbon textile electrodes with sufficient electrochemical activity. Graphene fiber fabrics (GFFs) are newly discovered carbon textiles, exhibiting various attractive properties, especially a large variability on the microstructure. Here we report the fabrication of hierarchical GFFs with significantly enlarged specific surface area using a hydrothermal activation strategy. By carefully optimize the activation process, the hydrothermally activated graphene fiber fabrics (HAGFFs) could achieve an areal capacitance of 1060 mF cm -2 in a very thin thickness (150 μm) and the capacitance is easily magnified by overlaying several layers of HAGFFs, even up to a record value of 7398 mF cm -2 . Meanwhile, a good rate capability and a long cycle life are also attained. As compared with other carbon textiles, including the commercial carbon fiber cloths, our HAGFFs present much better capacitive performance. Therefore, the mechanically stable, flexible, conductive, and highly active HAGFFs have provided an option for high-performance textile electrodes.

Relationship between Diffuse CO2 Degassing and Volcanic Activity. Case Study of the Poás, Irazú, and Turrialba Volcanoes, Costa Rica

Directory of Open Access Journals (Sweden)

Matthieu Epiard

2017-10-01

Full Text Available Active volcanoes exhibit diffuse gas emanations through the ground, the most abundant species of which is CO2. However, the relationship between diffuse degassing and volcanic activity is not often clear and some volcanoes may have low diffuse degassing levels despite having strong volcanic activity. The main goals of this study are to quantify diffuse CO2 degassing and determine whether patterns exist in relation to volcanic activity through the study of Turrialba, Poás, and Irazú, three active volcanoes in Costa Rica which are at different stages of activity. Structural controls of spatial distribution of diffuse degassing were also investigated. Measurement campaigns were conducted using the accumulation chamber method coupled with 10 cm depth ground temperature sampling with the aim of estimating the total diffuse CO2 degassing budget. The total amount of CO2 emitted diffusely by each volcano is ~113 ± 46 t/d over ~0.705 km2 for Turrialba, 0.9 ± 0.5 t/d for Poás over ~0.734 km2, 3.8 ± 0.9 t/d over ~0.049 km2 for Irazú's main crater, and 15 ± 12 t/d over 0.0059 km2 for Irazú's north flank. Turrialba and Poás volcano diffuse degassing budget represent about 10% of the whole gas output. Both volcanoes were in a transitional stage and the opening of new conduits may cause a loss in diffuse degassing and an increase of active degassing. Numerous diffuse degassing structures were also identified. At Turrialba, one of which was closely associated with the collapse of a crater wall in 2014 during the initiation of a new period of heightened eruptive activity. Similar structures were also observed on the outer slopes of the west crater, suggesting strong alteration and perhaps destabilization of the upper outer cone. Irazú's north flank is highly permeable and has experienced intense hydrothermal alteration.

Alteration of submarine volcanic rocks in oxygenated Archean oceans

Science.gov (United States)

Ohmoto, H.; Bevacqua, D.; Watanabe, Y.

2009-12-01

Most submarine volcanic rocks, including basalts in diverging plate boundaries and andesites/dacites in converging plate boundaries, have been altered by low-temperature seawater and/or hydrothermal fluids (up to ~400°C) under deep oceans; the hydrothermal fluids evolved from shallow/deep circulations of seawater through the underlying hot igneous rocks. Volcanogenic massive sulfide deposits (VMSDs) and banded iron formations (BIFs) were formed by mixing of submarine hydrothermal fluids with local seawater. Therefore, the behaviors of various elements, especially of redox-sensitive elements, in altered submarine volcanic rocks, VMSDs and BIFs can be used to decipher the chemical evolution of the oceans and atmosphere. We have investigated the mineralogy and geochemistry of >500 samples of basalts from a 260m-long drill core section of Hole #1 of the Archean Biosphere Drilling Project (ABDP #1) in the Pilbara Craton, Western Australia. The core section is comprised of ~160 m thick Marble Bar Chert/Jasper Unit (3.46 Ga) and underlying, inter-bedded, and overlying submarine basalts. Losses/gains of 65 elements were quantitatively evaluated on the basis of their concentration ratios against the least mobile elements (Ti, Zr and Nb). We have recognized that mineralogical and geochemical characteristics of many of these samples are essentially the same as those of hydrothermally-altered modern submarine basalts and also those of altered volcanic rocks that underlie Phanerozoic VMSDs. The similarities include, but are not restricted to: (1) the alteration mineralogy (chlorite ± sericite ± pyrophyllite ± carbonates ± hematite ± pyrite ± rutile); (2) the characteristics of whole-rock δ18O and δ34S values; (3) the ranges of depletion and enrichment of Si, Al, Mg, Ca, K, Na, Fe, Mn, and P; (4) the enrichment of Ba (as sulfate); (5) the increases in Fe3+/Fe2+ ratios; (6) the enrichment of U; (7) the depletion of Cr; and (8) the negative Ce anomalies. Literature data

Preservation of iron(II) by carbon-rich matrices in a hydrothermal plume

Energy Technology Data Exchange (ETDEWEB)

Toner, Brandy M.; Fakra, Sirine C.; Manganini, Steven J.; Santelli, Cara M.; Marcus, Matthew A.; Moffett, James W.; Rouxel, Olivier; German, Christopher R.; Edwards, Katrina J.

2008-09-20

Hydrothermal venting associated with mid-ocean ridge volcanism is globally widespread. This venting is responsible for a dissolved iron flux to the ocean that is approximately equal to that associated with continental riverine runoff. For hydrothermal fluxes, it has long been assumed that most of the iron entering the oceans is precipitated in inorganic forms. However, the possibility of globally significant fluxes of iron escaping these mass precipitation events and entering open-ocean cycles is now being debated, and two recent studies suggest that dissolved organic ligands might influence the fate of hydrothermally vented metals. Here we present spectromicroscopic measurements of iron and carbon in hydrothermal plume particles at the East Pacific Rise mid-ocean ridge. We show that organic carbon-rich matrices, containing evenly dispersed iron(II)-rich materials, are pervasive in hydrothermal plume particles. The absence of discrete iron(II) particles suggests that the carbon and iron associate through sorption or complexation. We suggest that these carbon matrices stabilize iron(II) released from hydrothermal vents in the region, preventing its oxidation and/or precipitation as insoluble minerals. Our findings have implications for deep-sea biogeochemical cycling of iron, a widely recognized limiting nutrient in the oceans.

Explosive Volcanic Activity at Extreme Depths: Evidence from the Charles Darwin Volcanic Field, Cape Verdes

Science.gov (United States)

Kwasnitschka, T.; Devey, C. W.; Hansteen, T. H.; Freundt, A.; Kutterolf, S.

2013-12-01

Volcanic eruptions on the deep sea floor have traditionally been assumed to be non-explosive as the high-pressure environment should greatly inhibit steam-driven explosions. Nevertheless, occasional evidence both from (generally slow-) spreading axes and intraplate seamounts has hinted at explosive activity at large water depths. Here we present evidence from a submarine field of volcanic cones and pit craters called Charles Darwin Volcanic Field located at about 3600 m depth on the lower southwestern slope of the Cape Verdean Island of Santo Antão. We examined two of these submarine volcanic edifices (Tambor and Kolá), each featuring a pit crater of 1 km diameter, using photogrammetric reconstructions derived from ROV-based imaging followed by 3D quantification using a novel remote sensing workflow, aided by sampling. The measured and calculated parameters of physical volcanology derived from the 3D model allow us, for the first time, to make quantitative statements about volcanic processes on the deep seafloor similar to those generated from land-based field observations. Tambor cone, which is 2500 m wide and 250 m high, consists of dense, probably monogenetic medium to coarse-grained volcaniclastic and pyroclastic rocks that are highly fragmented, probably as a result of thermal and viscous granulation upon contact with seawater during several consecutive cycles of activity. Tangential joints in the outcrops indicate subsidence of the crater floor after primary emplacement. Kolá crater, which is 1000 m wide and 160 m deep, appears to have been excavated in the surrounding seafloor and shows stepwise sagging features interpreted as ring fractures on the inner flanks. Lithologically, it is made up of a complicated succession of highly fragmented deposits, including spheroidal juvenile lapilli, likely formed by spray granulation. It resembles a maar-type deposit found on land. The eruption apparently entrained blocks of MORB-type gabbroic country rocks with

Magma injection beneath the urban area of Naples: a new mechanism for the 2012–2013 volcanic unrest at Campi Flegrei caldera

Science.gov (United States)

D’Auria, Luca; Pepe, Susi; Castaldo, Raffaele; Giudicepietro, Flora; Macedonio, Giovanni; Ricciolino, Patrizia; Tizzani, Pietro; Casu, Francesco; Lanari, Riccardo; Manzo, Mariarosaria; Martini, Marcello; Sansosti, Eugenio; Zinno, Ivana

2015-01-01

We found the first evidence, in the last 30 years, of a renewed magmatic activity at Campi Flegrei caldera from January 2012 to June 2013. The ground deformation, observed through satellite interferometry and GPS measurements, have been interpreted as the effect of the intrusion at shallow depth (3090 ± 138 m) of 0.0042 ± 0.0002 km3 of magma within a sill. This interrupts about 28 years of dominant hydrothermal activity and occurs in the context of an unrest phase which began in 2005 and within a more general ground uplift that goes on since 1950. This discovery has implications on the evaluation of the volcanic risk and in the volcanic surveillance of this densely populated area. PMID:26279090

Patterns of seismicity in a complex volcanic crisis at Brava, Cabo Verde

Science.gov (United States)

Faria, B. V. E.; Day, S. J.

2017-12-01

Brava is the smallest inhabited island of the Cape Verde archipelago, with an area of 62.5 km2 and a population of 6000. Geologically recent volcanism on Brava has produced lava (including carbonatite) flows, phonolite lava domes, pyroclastic density current deposits, and many phreatomagmatic craters in central Brava (where most of the population lives). Recent geological studies indicate that last eruptive period is about 1000 years old. Brava has experienced recurrent seismic swarms and felt earthquakes. The first permanent seismic station was installed in 1999, and a small network in 2011. From then until 2015 the seismic rate was near constant with sporadic peaks. Most seismic events were located offshore and associated with submarine volcanoes. However, the pattern of activity has been very different since 25th September 2015, when a M4 earthquake occurred in the submarine slopes of Brava. Subsequently, the seismicity became very complex with frequent volcano-tectonic (VT) earthquake swarms beneath Brava itself, with a few offshore events in some months. In addition, long-period, hybrid and hydrothermal events and likely very weak volcanic tremor episodes have been recorded. These non-VT events support the hypothesis that magma emplacement beneath Brava is at the origin of the abnormal seismic activity. The VT swarms indicate deformation around the magma body and possible dike intrusions, and there are indications of perturbation of a shallow hydrothermal system. The largest swarm occurred on the 1st and 2nd August 2016, with almost 1000 shallow events, including a M3.7 VT earthquake, medium-frequency events and weak volcanic tremor. An alert for a possible eruption was issued and a village (about 300 people) was evacuated as a precaution. Distributions of the cumulative number of events with depth in the main swarms suggest that the hypocenters are becoming shallower with time. Thus a possible eruption in the near future cannot be ruled out.

Experimental study on the effect of calcination on the volcanic ash activity of diatomite

Science.gov (United States)

Xiao, Liguang; Pang, Bo

2017-09-01

The volcanic ash activity of diatomite was studied under the conditions of aerobic calcination and vacuum calcination by the combined water rate method, it was characterized by XRD, BET and SEM. The results showed that the volcanic ash activity of diatomite under vacuum conditions was higher than that of aerobic calcination, 600°C vacuum calcination 2h, the combined water rate of diatomite-Ca(OH)2-H2O system was increased from 6.24% to 71.43%, the volcanic ash activity reached the maximum value, the specific surface

Poás volcano in Costa Rica as a hydrothermal analog for Mars

Science.gov (United States)

Elmaarry, M. R.; Hynek, B. M.

2017-12-01

Mars has experienced intensive volcanic and impact activity early in its history, coinciding with a similarly extensive hydrologic activity on a global scale. These activities constitute the main ingredients of hydrothermal activity. Data acquired from the study of Martian meteorites, remote sensing spectral observations, and robotic rovers has shown the surface of Mars to be mineralogically diverse including mineral assemblages that resemble those of analogous hydrothermal systems on Earth. In particular, evidence for extensive acid-sulfate weathering has been observed by the MERs at Gusev and Meridiani, as well as by MSL at Gale crater. Furthermore, there is growing evidence for silicic volcanism on Mars as indicated by the detection of silica-rich mudstone at Gale containing tridymite and cristobalite coupled with spectral observations indicative of felsic rocks in geographically disparate locations on Mars. For that, the Poás volcano in Costa Rica offers a geologic setting that can be analogous to similar environments on Mars. The Poás volcano is a basaltic andesite stratovolcano in central Costa Rica. Its caldera houses a highly acidic lake inside the caldera 130 m below the crater rim. The volcano has been active in recent historical times, and is currently displaying intensive activity since Apr 2017. Unaltered andesitic basalts collected from the 1953-1955 magmatic activity are mainly composed of plagioclase and minor amounts of orthopyroxene and olivine. We collected samples during our fieldwork in March 2017 (few weeks before its eruption) from fumaroles inside the caldera. The fumaroles were emitting gases at 92°C, and the acidic lake minor abundances of hematite, anatase, and amorphous silica. Most of these minerals have been observed on Mars under potentially similar settings. We plan to continue our investigation by carrying out additional analyses and compare to samples collected from earlier campaigns to gain a better understanding of how the

Volcanic eruptions and solar activity

Science.gov (United States)

Stothers, Richard B.

1989-01-01

The historical record of large volcanic eruptions from 1500 to 1980 is subjected to detailed time series analysis. In two weak but probably statistically significant periodicities of about 11 and 80 yr, the frequency of volcanic eruptions increases (decreases) slightly around the times of solar minimum (maximum). Time series analysis of the volcanogenic acidities in a deep ice core from Greenland reveals several very long periods ranging from about 80 to about 350 yr which are similar to the very slow solar cycles previously detected in auroral and C-14 records. Solar flares may cause changes in atmospheric circulation patterns that abruptly alter the earth's spin. The resulting jolt probably triggers small earthquakes which affect volcanism.

Deformation of a Volcanic Edifice by Pore Pressurization: An Analog Approach

Science.gov (United States)

Hyman, D.; Bursik, M. I.

2015-12-01

Volcanic flank destabilization, preceded by pressurization-induced surface deformation or weakening, presents a significant hazard at stratovolcanoes with ample supply of magmatic volatiles or preexisting hydrothermal systems as in Bezymianny- and Bandai-type eruptions, respectively. Deformation is also an important sign of the nature of unrest at large calderas such as Long Valley, USA. Previous studies of volcanic inflation have focused primarily on the role of ascending magma. Relatively few studies have centered on surface deformation caused by pressurization from other volcanic fluids, including exsolved volatiles and pressurized hydrothermal systems. Most investigations of pore-pressurization have focused on numerical modelling of pore pressure transients. In analog experiments presented here, pore-filling fluids are injected into the base of a damp sand medium without exceeding dike propagating pressures, simulating the pressurization and bulk-permeable flow of volatile fluids through volcanic systems. The experiments examine surface deformation from a range of source depths and pressures as well as edifice geometries. 3D imaging is possible through use of the Microsoft® Kinect™ sensor, which allows for the generation of high-resolution, high frame rate, lab-scale Digital Elevation Models (DEMs). After initial processing to increase signal-to-noise ratio, surface deformation is measured using the DEM time-series generated by the Kinect™. Analysis of preliminary experiments suggests that inflation is possible up to approx. 10 % of pressure source depth. We also show that the Kinect™ sensor is useful in analog volcanological studies, an environment to which it is well-suited.

Multiple edifice-collapse events in the Eastern Mexican Volcanic Belt: The role of sloping substrate and implications for hazard assessment

Science.gov (United States)

Carrasco-Nunez, Gerardo; Diaz-Castellon, Rodolfo; Siebert, L.; Hubbard, B.; Sheridan, M.F.; Rodriguez, Sergio R.

2006-01-01

The Citlalte??petl-Cofre de Perote volcanic chain forms an important physiographic barrier that separates the Central Altiplano (2500??masl) from the Gulf Coastal Plain (GCP) (1300??masl). The abrupt eastward drop in relief between these provinces gives rise to unstable conditions and consequent gravitational collapse of large volcanic edifices built at the edge of the Altiplano. Eastward sloping substrate, caused by the irregular configuration of the basement rocks, is the dominant factor that controls the direction of collapsing sectors in all major volcanoes in the region to be preferentially towards the GCP. These collapses produced voluminous debris avalanches and lahars that inundated the well-developed drainages and clastic aprons that characterize the Coastal Plain. Large catastrophic collapses from Citlalte??petl, Las Cumbres, and Cofre de Perote volcanoes are well documented in the geologic record. Some of the avalanches and transformed flows have exceptionally long runouts and reach the Gulf of Mexico traveling more than 120??km from their source. So far, no direct evidence has been found for magmatic activity associated with the initiation of these catastrophic flank-collapses. Apparently, instability of the volcanic edifices has been strongly favored by very intense hydrothermal alteration, abrupt topographic change, and intense fracturing. In addition to the eastward slope of the substrate, the reactivation of pre-volcanic basement structures during the Late Tertiary, and the E-W to ENE-SSW oriented regional stress regimes may have played an important role in the preferential movement direction of the avalanches and flows. In addition to magmatic-hydrothermal processes, high amounts of rainfall in the area is another factor that enhances alteration and eventually weakens the rocks. It is very likely that seismic activity may be the principal triggering mechanism that caused the flank collapse of large volcanic edifices in the Eastern Mexican Volcanic

Geologic evolution of the Jemez Mountains and their potential for future volcanic activity

International Nuclear Information System (INIS)

Burton, B.W.

1982-01-01

Geophysical and geochemical data and the geologic history of the Rio Grande rift and the vicinity of the Jemez Mountains are summarized to determine the probability of future volcanic activity in the Los Alamos, New Mexico area. The apparent cyclic nature of volcanism in the Jemez Mountains may be related to intermittent thermal inputs into the volcanic system beneath the region. The Jemez lineament, an alignment of late Cenozoic volcanic centers that crosses the rift near Los Alamos, has played an important role in the volcanic evolution of the Jemez Mountains. Geophysical data suggest that there is no active shallow magma body beneath the Valles caldera, though magma probably exists at about 15 km beneath this portion of the rift. The rate of volcanism in the Jemez Mountains during the last 10 million years has been 5 x 10 -9 /km 2 /y. Lava or ash flows overriding Laboratory radioactive waste disposal sites would have little potential to release radionuclides to the environment. The probability of a new volcano intruding close enough to a radioactive waste disposal site to effect radionuclide release is 2 x 10 -7 /y

Exploring the structural controls on helium, nitrogen and carbon isotope signatures in hydrothermal fluids along an intra-arc fault system

Science.gov (United States)

Tardani, Daniele; Reich, Martin; Roulleau, Emilie; Takahata, Naoto; Sano, Yuji; Pérez-Flores, Pamela; Sánchez-Alfaro, Pablo; Cembrano, José; Arancibia, Gloria

2016-07-01

There is a general agreement that fault-fracture meshes exert a primary control on fluid flow in both volcanic/magmatic and geothermal/hydrothermal systems. For example, in geothermal systems and epithermal gold deposits, optimally oriented faults and fractures play a key role in promoting fluid flow through high vertical permeability pathways. In the Southern Volcanic Zone (SVZ) of the Chilean Andes, both volcanism and hydrothermal activity are strongly controlled by the Liquiñe-Ofqui Fault System (LOFS), an intra-arc, strike-slip fault, and by the Arc-oblique Long-lived Basement Fault System (ALFS), a set of transpressive NW-striking faults. However, the role that principal and subsidiary fault systems exert on magma degassing, hydrothermal fluid flow and fluid compositions remains poorly constrained. In this study we report new helium, carbon and nitrogen isotope data (3He/4He, δ13C-CO2 and δ15N) of a suite of fumarole and hot spring gas samples from 23 volcanic/geothermal localities that are spatially associated with either the LOFS or the ALFS in the central part of the SVZ. The dataset is characterized by a wide range of 3He/4He ratios (3.39 Ra to 7.53 Ra, where Ra = (3He/4He)air), δ13C-CO2 values (-7.44‰ to -49.41‰) and δ15N values (0.02‰ to 4.93‰). The regional variations in 3He/4He, δ13C-CO2 and δ15N values are remarkably consistent with those reported for 87Sr/86Sr in lavas along the studied segment, which are strongly controlled by the regional spatial distribution of faults. Two fumaroles gas samples associated with the northern ;horsetail; transtensional termination of the LOFS are the only datapoints showing uncontaminated MORB-like 3He/4He signatures. In contrast, the dominant mechanism controlling helium isotope ratios of hydrothermal systems towards the south appears to be the mixing between mantle-derived helium and a radiogenic component derived from, e.g., magmatic assimilation of 4He-rich country rocks or contamination during the

A model for Nb-Zr-REE-Ga enrichment in Lopingian altered alkaline volcanic ashes: Key evidence of H-O isotopes

Science.gov (United States)

Dai, Shifeng; Nechaev, Victor P.; Chekryzhov, Igor Yu.; Zhao, Lixin; Vysotskiy, Sergei V.; Graham, Ian; Ward, Colin R.; Ignatiev, Alexander V.; Velivetskaya, Tatyana A.; Zhao, Lei; French, David; Hower, James C.

2018-03-01

Clay-altered volcanic ash with highly-elevated concentrations of Nb(Ta), Zr(Hf), rare earth elements (REE), and Ga, is a new type of critical metal deposit with high commercial prospects that has been discovered in Yunnan Province, southwest China. Previous studies showed that the volcanic ashes had been subjected to hydrothermal fluids, the nature of which, however, is not clear. Here we show that the volcanic ashes were originated from alkaline magmatism, followed by a continuous hydrothermal-weathering process. Heated meteoric waters, which were sourced from acidic rains and mixed with CO2 from degassing of the Emeishan plume, have caused partial, but widespread, acidic leaching of Nb, Ta, Zr, Hf, REE, and Ga into ground water and residual enrichment of these elements, along with Al and Ti, in the deeply altered rocks. Subsequent alteration occurring under cooler, neutral or alkaline conditions, caused by water-rock interaction, resulted in precipitation of the leached critical metals in the deposit. Polymetallic mineralization of similar origin may be found in other continental regions subjected to explosive alkaline volcanism associated with deep weathering in humid conditions.

The Importance of Differing Types of Io Volcanic Activity for the Jupiter Magnetosphere

Science.gov (United States)

Howell, R. R.

2016-12-01

The Jupiter magnetosphere is populated largely by sulfur and oxygen ultimately derived from the volcanoes on Io and correlations have been detected between changes in volcanic activity and the magnetosphere. However different types of volcanic activity on Io vary widely in the amount and composition of the gasses they release. For example while Loki is often the brightest volcanic hotspot in the infrared (and therefore most easily monitored from earth) it appears to release a comparatively small amount of gas compared to Prometheus type plumes and the giant plumes such as Pele. The dominant volatile released at most sites is sulfur dioxide but giant plumes such as Pele appear to contain significantly fractions of S2 gas. The amounts and type of dust produced may also differ. Finally, the way material is buffered in Io's surface and atmosphere before escaping to the magnetosphere is also uncertain. A better understanding of the connection between volcanic activity and the magnetosphere will require studying not just correlations between broad measures of activity but rather specific indices of different types of activity. Observations of possible storage buffers such as the atmosphere, as are now becoming possible with ALMA, will also be essential.

Geologic structure and volcanic history of the Yanaizu-Nishiyama (Okuaizu) geothermal field, Northeast Japan

Energy Technology Data Exchange (ETDEWEB)

Mizugaki, Keiko [Geological Survey of Japan, Geothermal Research Dept., Higashi Tsukuba (Japan)

2000-04-01

The Yanaizu-Nishiyama geothermal field, also known as Okuaizu, supports a 65 MWe geothermal power station. It is located in the western part of Fukushima Prefecture, northeast Japan. This field is characterised by rhyolitic volcanism of about 0.3-0.2 Ma that formed Sunagohara volcano. Drillcore geology indicates that volcanism began with a caldera-forming eruption in the center of this field, creating a 2-km-diameter funnel-shaped caldera. Subsequently, a fault-bounded block including this caldera subsided to form a 5-km-wide lake that accumulated lake sediments. Post-caldera volcanism formed lava domes and intrusions within the lake, and deposited ash-flow tuffs in and around the lake. The hydrothermal system of this field is strongly controlled by subvertical faults that have no relation to the volcanism. The principal production zone occurs at a depth of 1.0-2.6 km within fractured Neogene formations along two northwest-trending faults to the southeast of the caldera. These faults also formed fracture zones in the lake sediments, but there was no apparent offset of the sediments. Stratigraphic studies suggest that post-caldera activities of Sunagohara volcano have migrated southeastward to the present high-temperature zone. The source magma of Sunagohara volcano may contribute to the thermal potential of this field. (Author)

Late Cenozoic Samtskhe-Javakheti Volcanic Highland, Georgia:The Result of Mantle Plumes Activity

Science.gov (United States)

Okrostsvaridze, Avtandil

2017-04-01

Late Cenozoic Samtskhe-Javakheti continental volcanic highland (1500-2500 m a.s.l) is located in the SW part of the Lesser Caucasus. In Georgia the highland occupies more than 4500 km2, however its large part spreads towards the South over the territories of Turkey and Armenia. One can point out three stages of magmatic activity in this volcanic highland: 1. Early Pliocene activity (5.2-2.8 Ma; zircons U-Pb age) - when a large part of the highland was built up. It is formed from volcanic lava-breccias of andesite-dacitic composition, pyroclastic rocks and andesite-basalt lava flow. The evidences of this structure are: a large volume of volcanic material (>1500 km3); big thickness (700-1100 m in average), large-scale of lava flows (length 35 km, width 2.5-3.5 km, thickness 30-80 m), big thickness of volcanic ash horizons (300 cm at some places) and big size of volcanic breccias (diameter >1 m). Based on this data we assume that a source of this structure was a supervolcano (Okrostsvaridze et al., 2016); 2. Early Pleistocene activity (2.4 -1.6 Ma; zircons U-Pb age) - when continental flood basalts of 100-300 m thickness were formed. The flow is fully crystalline, coarse-grained, which mainly consist of olivine and basic labradorite. There 143Nd/144Nd parameter varies in the range of +0.41703 - +0.52304, and 87Sr/88Sr - from 0.7034 to 0.7039; 3. Late Pleistocene activity (0.35-0.021 Ma; zircons U-Pb age) - when intraplate Abul-Samsari linear volcanic ridge of andesite composition was formed stretching to the S-N direction for 40 km with the 8-12 km width and contains more than 20 volcanic edifices. To the South of the Abul-Samsari ridge the oldest (0.35-0.30 Ma; zircons U-Pb age) volcano Didi Abuli (3305 m a.s.l.) is located. To the North ages of volcano edifices gradually increase. Farther North the youngest volcano Tavkvetili (0.021-0. 030 Ma) is located (2583 m a.s.l.). One can see from this description that the Abul-Samsari ridge has all signs characterizing

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...

Debris Avalanches and Debris Flows Transformed from Collapses in the Trans-Mexican Volcanic Belt, México.

Science.gov (United States)

Capra, L.; Macias, J.; Scott, K.; Abrams, M.; Garduño, V.

2001-12-01

Volcanoes of the Trans-Mexican Volcanic Belt (TMVB) have yielded numerous sector and flank collapses during Pleistocene and Holocene time. Sector collapses associated with magmatic activity have yielded debris avalanches with generally limited runout extent (e.g. Popocatépetl, Jocotitlán, and Colima volcanoes). In contrast, flank collapses (smaller failures not involving the volcano summit), both associated and unassociated with magmatic activity and correlated with intense hydrothermal alteration in ice-capped volcanoes, commonly have yielded highly mobile cohesive debris flows (e.g. Pico de Orizaba and Nevado de Toluca volcanoes). Collapse orientation in the TMVB is preferentially to the south and north-east, probably reflecting the tectonic regime of active E-W and NNW faults. The different mobilities of the flows transformed from collapses have important implications for hazard assessment. Both sector and flank collapse can yield highly mobile debris flows, but this transformation is more common in the case of the smaller failures. High mobility is related to factors such as water and clay content of the failed material, the paleotopography, and the extent of entrainment of sediment during flow (bulking). Both debris-avalanches and debris-flows are volcanic hazards that occur from both active volcanoes, as well as those that are inactive or dormant volcanoes, and may by triggered by earthquakes, precipitation, or simple gravity. There will be no precursory warning in such non-volcanic cases.

Chemical composition of hydrothermal ores from Mid-Okinawa trough and Suiyo Seamount determined by neutron activation analysis

International Nuclear Information System (INIS)

Noguchi, Takuroh; Taira, Naoto; Oomori, Tamotsu; Taira, Hatsuo; Tanahara, Akira; Takada, Jitsuya

2007-01-01

Neutron activation analysis of 13 hydrothermal ore samples (70 subsamples) collected from the Mid-Okinawa Trough and Suiyo Seamount revealed higher contents of precious metal such as Au and Ag, and those of As, Sb, Ga, and Hg than those from mid-ocean ridge hydrothermal systems. In addition, the Mid-Okinawa Trough samples were richer in Ag and Sb than those from the Suiyo Seamount. The geochemical differences among these hydrothermal ore deposits are regarded as reflecting both differences in the chemical composition of the hosted magma of hydrothermal system and the abundance of sediments that is reacted with hydrothermal fluids. (author)

Structural controls on fluid circulation at the Caviahue-Copahue Volcanic Complex (CCVC) geothermal area (Chile-Argentina), revealed by soil CO2 and temperature, self-potential, and helium isotopes

Science.gov (United States)

Roulleau, Emilie; Bravo, Francisco; Pinti, Daniele L.; Barde-Cabusson, Stéphanie; Pizarro, Marcela; Tardani, Daniele; Muñoz, Carlos; Sanchez, Juan; Sano, Yuji; Takahata, Naoto; de la Cal, Federico; Esteban, Carlos; Morata, Diego

2017-07-01

Natural geothermal systems are limited areas characterized by anomalously high heat flow caused by recent tectonic or magmatic activity. The heat source at depth is the result of the emplacement of magma bodies, controlled by the regional volcano-tectonic setting. In contrast, at a local scale a well-developed fault-fracture network favors the development of hydrothermal cells, and promotes the vertical advection of fluids and heat. The Southern Volcanic Zone (SVZ), straddling Chile and Argentina, has an important, yet unexplored and undeveloped geothermal potential. Studies on the lithological and tectonic controls of the hydrothermal circulation are therefore important for a correct assessment of the geothermal potential of the region. Here, new and dense self-potential (SP), soil CO2 and temperature (T) measurements, and helium isotope data measured in fumaroles and thermal springs from the geothermal area located in the north-eastern flank of the Copahue volcanic edifice, within the Caviahue Caldera (the Caviahue-Copahue Volcanic Complex - CCVC) are presented. Our results allowed to the constraint of the structural origin of the active thermal areas and the understanding of the evolution of the geothermal system. NE-striking faults in the area, characterized by a combination of SP, CO2, and T maxima and high 3He/4He ratios (up to 8.16 ± 0.21Ra, whereas atmospheric Ra is 1.382 × 10- 6), promote the formation of vertical permeability preferential pathways for fluid circulation. WNW-striking faults represent low-permeability pathways for hydrothermal fluid ascent, but promote infiltration of meteoric water at shallow depths, which dilute the hydrothermal input. The region is scattered with SP, CO2, and T minima, representing self-sealed zones characterized by impermeable altered rocks at depth, which create local barriers for fluid ascent. The NE-striking faults seem to be associated with the upflowing zones of the geothermal system, where the boiling process

Multi-year high-frequency hydrothermal monitoring of selected high-threat Cascade Range volcanoes

Science.gov (United States)

Crankshaw, I. M.; Archfield, S. A.; Newman, A. C.; Bergfeld, D.; Clor, L. E.; Spicer, K. R.; Kelly, P. J.; Evans, W. C.; Ingebritsen, S. E.

2018-05-01

From 2009 to 2015 the U.S. Geological Survey (USGS) systematically monitored hydrothermal behavior at selected Cascade Range volcanoes in order to define baseline hydrothermal and geochemical conditions. Gas and water data were collected regularly at 25 sites on 10 of the highest-risk volcanoes in the Cascade Range. These sites include near-summit fumarole groups and springs/streams that show clear evidence of magmatic influence (high 3He/4He ratios and/or large fluxes of magmatic CO2 or heat). Site records consist mainly of hourly temperature and hydrothermal-flux data. Having established baseline conditions during a multiyear quiescent period, the USGS reduced monitoring frequency from 2015 to present. The archived monitoring data are housed at (doi:10.5066/F72N5088). These data (1) are suitable for retrospective comparison with other continuous geophysical monitoring data and (2) will provide context during future episodes of volcanic unrest, such that unrest-related variations at these thoroughly characterized sites will be more clearly recognizable. Relatively high-frequency year-round data are essential to achieve these objectives, because many of the time series reveal significant diurnal, seasonal, and inter-annual variability that would tend to mask unrest signals in the absence of baseline data. Here we characterize normal variability for each site, suggest strategies to detect future volcanic unrest, and explore deviations from background associated with recent unrest.

On the theory system of hydrothermal uranium metallization in China

International Nuclear Information System (INIS)

Du Letian

2011-01-01

Based on summarizing the mass of research outcome of the predecessors, the author attempts to make a brief generalization on the theory system of hydrothermal uranium mineralization in China. The system of uranium metallization is founded in the basic way of uranium source-migration-transportation-richment-reservation. The system mainly consists of the following frames: (1) mineralization type of silification zone; (2) age gap of mineralization to host rock; (3) alkli metasomatism; (4) metallogenic layer of crust; (5)integratation of 4 types mineralization (granite, volcanics, carbonaceous-siliceous-argilaceous rock and sandstone) in tectonic-hydrothermal process; (6) pre-enrichment process of metallization; (7) decouplement of granite magma evolution; (8) types of rich ore by high tempreture sericitization; (9)basalt event;(10) rock and ore formation by HARCON. (authors)

Volcano-hydrothermal system and activity of Sirung volcano (Pantar Island, Indonesia)

Science.gov (United States)

Caudron, Corentin; Bernard, Alain; Murphy, Sam; Inguaggiato, Salvatore; Gunawan, Hendra

2018-05-01

Sirung is a frequently active volcano located in the remote parts of Western Timor (Indonesia). Sirung has a crater with several hydrothermal features including a crater lake. We present a timeseries of satellite images of the lake and chemical and isotope data from the hyperacid hydrothermal system. The fluids sampled in the crater present the typical features of hyperacidic systems with high TDS, low pH and δ34SHSO4-δ34SS0 among the highest for such lakes. The cations concentrations are predominantly controlled by the precipitation of alunite, jarosite, silica phases, native sulfur and pyrite which dominate the shallow portions of the hydrothermal system. These minerals may control shallow sealing processes thought to trigger phreatic eruptions elsewhere. Sparse Mg/Cl and SO4/Cl ratios and lake parameters derived from satellite images suggest gradual increase in heat and gas flux, most likely SO2-rich, prior to the 2012 phreatic eruption. An acidic river was sampled 8 km far from the crater and is genetically linked with the fluids rising toward the active crater. This river would therefore be a relevant target for future remote monitoring purposes. Finally, several wells and springs largely exceeded the World Health Organization toxicity limits in total arsenic and fluoride.

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...

Unzen volcanic rocks as heat source of geothermal activity

Energy Technology Data Exchange (ETDEWEB)

Hayashi, Masao; Sugiyama, Hiromi

1987-03-25

Only a few radiometric ages have been reported so far for the Unzen volcanic rocks. In this connection, in order to clarify the relation between volcanism and geothermal activity, fission track ages of zircon seperated from the Unzen volcanic rocks in western Kyushu have been dated. Since all the rocks are thought to be young, the external surface re-etch method was adopted. The results are that the age and standard error of the basal volcaniclastic rocks of the Tatsuishi formation are 0.28 +- 0.05 Ma and 0.25 +- 0.05 Ma. The next oldest Takadake lavas range from 0.26 to 0.20 Ma. The Kusenbudake lavas fall in a narrow range from 0.19 to 0.17 Ma. The latest Fugendake lavas are younger than 0.07 Ma.In conclusion, the most promising site for geothermal power generation is the Unzen hot spring field because of its very high temperature. After that, comes the Obama hot spring field because of the considerable high temperature chemically estimated. In addition, the northwestern area of the Unzen volcanic region will be promising for electric power generation in spite of no geothermal manifestations, since its volcanos are younger than 0.2 Ma. (14 figs, 14 tabs, 22 refs)

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 ...

On the global distribution of hydrothermal vent fields: One decade later

Science.gov (United States)

Beaulieu, S. E.; Baker, E. T.; German, C. R.

2012-12-01

Since the last global compilation one decade ago, the known number of active submarine hydrothermal vent fields has almost doubled. At the end of 2009, a total of 518 active vent fields was catalogued, with about half (245) visually confirmed and others (273) inferred active at the seafloor. About half (52%) of these vent fields are at mid-ocean ridges (MORs), 25% at volcanic arcs, 21% at back-arc spreading centers (BASCs), and 2% at intra-plate volcanoes and other settings. One third are in high seas, and the nations with the most known active vent fields within EEZs are Tonga, USA, Japan, and New Zealand. The increase in known vent fields reflects a number of factors, including increased national and commercial interests in seafloor hydrothermal deposits as mineral resources. Here, we have comprehensively documented the percentage of strike length at MORs and BASCs that has been systematically explored for hydrothermal activity. As of the end of 2009, almost 30% of the ~60,000 km of MORs had been surveyed at least with spaced vertical profiles to detect hydrothermal plumes. A majority of the vents discovered at MORs in the past decade occurred at segments with vs. weighted-average full spreading rate (u_s), we predicted 676 vent fields remaining to be discovered at MORs. Even accounting for the lower F_s at slower spreading rates, almost half of the vents that are predicted remaining to be discovered at MORs are at ultra-slow to slow spreading rates (explored tend to be at high latitudes, such as the ultra-slow to slow spreading Arctic MORs (e.g., Kolbeinsey and Mohns Ridges), the ultra-slow American-Antarctic Ridge, and the intermediate spreading Pacific-Antarctic Ridge. Although a greater percentage of the ~11,000 km of BASCs has been surveyed for hydrothermal activity, the discoveries at BASCs in the past decade were mainly at segments with intermediate to fast spreading rates. Using the same equation for F_s vs. u_s, we predicted 71 vent fields remaining to

Template-free hydrothermal synthesis and high photocatalytic activity of ZnWO4 nanorods

International Nuclear Information System (INIS)

Gao, Bin; Fan, Huiqing; Zhang, Xiaojun; Song, Lixun

2012-01-01

Highlights: ► ZnWO 4 nanorods with uniform diameter are successfully prepared through a template-free hydrothermal method. ► The crystallinity of the products is influenced by the pH value of initial precursor suspension. ► Photocatalytic activity of the ZnWO 4 nanorods for degradation of methylene blue is evaluated. ► The ZnWO 4 nanorods exhibit good stability of photocatalytic activity. - Abstract: ZnWO 4 nanorods are successfully synthesized by a template-free hydrothermal method, and are characterized in detail by X-ray diffractometer (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The results show that the ZnWO 4 nanorods with wolframite structure are well-crystallized single crystallites. The crystallinity of the products is influenced by the pH value of initial precursor suspension. The width and length of the synthesized samples increase with hydrothermal reaction temperature. The photocatalytic efficiency of the ZnWO 4 nanorods for degradation of methylene blue (MB) in aqueous solution under UV light irradiation declines greatly with increasing crystallinity. The ZnWO 4 nanorods prepared at pH of 4 have the best activity in photo-degradation of MB. After six recycles, photocatalytic activity loss of the catalyst is not obvious.

Volcanic features of Io

International Nuclear Information System (INIS)

Carr, M.H.; Masursky, H.; Strom, R.G.; Terrile, R.J.

1979-01-01

The volcanic features of Io as detected during the Voyager mission are discussed. The volcanic activity is apparently higher than on any other body in the Solar System. Its volcanic landforms are compared with features on Earth to indicate the type of volcanism present on Io. (U.K.)

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

Characterization of the volcanic eruption emissions using neutron activation analysis

International Nuclear Information System (INIS)

Pla, Rita R.; Tafuri, Victoria V.

1997-01-01

Characterization of the volcanic particulate material has been performed by analyzing aerosols and ashes with instrumental neutron activation analysis. Crustal enrichment factors were calculated using the elemental concentration and clustering techniques, and multivariate analysis were done. The analytical and data treatment methodologies allowed the sample differentiation from their geographical origin viewpoint, based on their chemical composition patterns, which are related to the deposit formation processes, which consist of direct deposition from the volcanic cloud, and removal by wind action after the end of the eruption, and and finally the deposition. (author). 8 refs., 5 figs

Multi-Source Autonomous Response for Targeting and Monitoring of Volcanic Activity

Science.gov (United States)

Davies, Ashley G.; Doubleday, Joshua R.; Tran, Daniel Q.

2014-01-01

The study of volcanoes is important for both purely scientific and human survival reasons. From a scientific standpoint, volcanic gas and ash emissions contribute significantly to the terrestrial atmosphere. Ash depositions and lava flows can also greatly affect local environments. From a human survival standpoint, many people live within the reach of active volcanoes, and therefore can be endangered by both atmospheric (ash, debris) toxicity and lava flow. There are many potential information sources that can be used to determine how to best monitor volcanic activity worldwide. These are of varying temporal frequency, spatial regard, method of access, and reliability. The problem is how to incorporate all of these inputs in a general framework to assign/task/reconfigure assets to monitor events in a timely fashion. In situ sensing can provide a valuable range of complementary information such as seismographic, discharge, acoustic, and other data. However, many volcanoes are not instrumented with in situ sensors, and those that have sensor networks are restricted to a relatively small numbers of point sensors. Consequently, ideal volcanic study synergistically combines space and in situ measurements. This work demonstrates an effort to integrate spaceborne sensing from MODIS (Terra and Aqua), ALI (EO-1), Worldview-2, and in situ sensing in an automated scheme to improve global volcano monitoring. Specifically, it is a "sensor web" concept in which a number of volcano monitoring systems are linked together to monitor volcanic activity more accurately, and this activity measurement automatically tasks space assets to acquire further satellite imagery of ongoing volcanic activity. A general framework was developed for evidence combination that accounts for multiple information sources in a scientist-directed fashion to weigh inputs and allocate observations based on the confidence of an events occurrence, rarity of the event at that location, and other scientists

Isotope hydrology of some hydrothermal systems of the Kurilo-Kamchatskay volcanic region

International Nuclear Information System (INIS)

Esikov, A.D.

1990-01-01

The hydrogen and oxygen isotope composition of underground and surface (thermal and cold) waters, as well as local precipitation waters from the geothermal fields of the Uzon caldera, the Mutnovsky volcano (Kamchatka), and the Baransky volcano (island of Iturup) have been analysed. As has been demonstrated, hydrothermal solutions were formed due to hypogene circulation of water originating from local precipitation. Observed variations in the isotope composition of the water are easily explained by underground boiling of hydrothermal solutions and their exchange with bedrock, and also by the processes of non-steady evaporation of water under differing surface conditions and the widely-spread mutual intermixing of waters of different origin. Data on the isotope composition of 50 samples from the region studied are to be found in the paper. The method of constructing diagrams in coordinates of δD vs δ 18 O is discussed in detail, reflecting a single-step separation of the thermal fluid. Data obtained during the analysis of the thermal fields estimates the processes forming the isotope composition of the world's geothermal sub-aerial systems as being unique. (author)

2014 volcanic activity in Alaska: Summary of events and response of the Alaska Volcano Observatory

Science.gov (United States)

Cameron, Cheryl E.; Dixon, James P.; Neal, Christina A.; Waythomas, Christopher F.; Schaefer, Janet R.; McGimsey, Robert G.

2017-09-07

The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest or suspected unrest, and seismic events at 18 volcanic centers in Alaska during 2014. The most notable volcanic activity consisted of intermittent ash eruptions from long-active Cleveland and Shishaldin Volcanoes in the Aleutian Islands, and two eruptive episodes at Pavlof Volcano on the Alaska Peninsula. Semisopochnoi and Akutan volcanoes had seismic swarms, both likely the result of magmatic intrusion. The AVO also installed seismometers and infrasound instruments at Mount Cleveland during 2014.

Disruptive event analysis: volcanism and igneous intrusion

International Nuclear Information System (INIS)

Crowe, B.M.

1980-08-01

An evaluation is made of the disruptive effects of volcanic activity with respect to long term isolation of radioactive waste through deep geologic storage. Three major questions are considered. First, what is the range of disruption effects of a radioactive waste repository by volcanic activity. Second, is it possible, by selective siting of a repository, to reduce the risk of disruption by future volcanic activity. And third, can the probability of repository disruption by volcanic activity be quantified. The main variables involved in the evaluation of the consequences of repository disruption by volcanic activity are the geometry of the magma-repository intersection (partly controlled by depth of burial) and the nature of volcanism. Potential radionuclide dispersal by volcanic transport within the biosphere ranges in distance from several kilometers to global. Risk from the most catastrophic types of eruptions can be reduced by careful site selection to maximize lag time prior to the onset of activity. Certain areas or volcanic provinces within the western United States have been sites of significant volcanism and should be avoided as potential sites for a radioactive waste repository. Examples of projection of future sites of active volcanism are discussed for three areas of the western United States. Probability calculations require two types of data: a numerical rate or frequency of volcanic activity and a numerical evaluation of the areal extent of volcanic disruption for a designated region. The former is clearly beyond the current state of art in volcanology. The latter can be approximated with a reasonable degree of satisfaction. In this report, simplified probability calculations are attempted for areas of past volcanic activity

Geosphere-biosphere interactions in bio-activity volcanic lakes: evidences from Hule and Rìo Cuarto (Costa Rica.

Directory of Open Access Journals (Sweden)

Jacopo Cabassi

Full Text Available Hule and Río Cuarto are maar lakes located 11 and 18 km N of Poás volcano along a 27 km long fracture zone, in the Central Volcanic Range of Costa Rica. Both lakes are characterized by a stable thermic and chemical stratification and recently they were affected by fish killing events likely related to the uprising of deep anoxic waters to the surface caused by rollover phenomena. The vertical profiles of temperature, pH, redox potential, chemical and isotopic compositions of water and dissolved gases, as well as prokaryotic diversity estimated by DNA fingerprinting and massive 16S rRNA pyrosequencing along the water column of the two lakes, have highlighted that different bio-geochemical processes occur in these meromictic lakes. Although the two lakes host different bacterial and archaeal phylogenetic groups, water and gas chemistry in both lakes is controlled by the same prokaryotic functions, especially regarding the CO2-CH4 cycle. Addition of hydrothermal CO2 through the bottom of the lakes plays a fundamental priming role in developing a stable water stratification and fuelling anoxic bacterial and archaeal populations. Methanogens and methane oxidizers as well as autotrophic and heterotrophic aerobic bacteria responsible of organic carbon recycling resulted to be stratified with depth and strictly related to the chemical-physical conditions and availability of free oxygen, affecting both the CO2 and CH4 chemical concentrations and their isotopic compositions along the water column. Hule and Río Cuarto lakes were demonstrated to contain a CO2 (CH4, N2-rich gas reservoir mainly controlled by the interactions occurring between geosphere and biosphere. Thus, we introduced the term of bio-activity volcanic lakes to distinguish these lakes, which have analogues worldwide (e.g. Kivu: D.R.C.-Rwanda; Albano, Monticchio and Averno: Italy; Pavin: France from volcanic lakes only characterized by geogenic CO2 reservoir such as Nyos and Monoun

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

Geological development and uranium and thorium evolutions in volcanic basin No.460

International Nuclear Information System (INIS)

Zhou Dean.

1989-01-01

On the basis of summarizing the geological features and the developmental history of tectono-magmatic activity, the uranium and thorium evolutional rules of rocks in different times are studied. It is suggested that the uranium and thorium increments caused by potassic migmatization of late Archean basement rocks in this area is the material base which affected the subsequent evolution of the cover of volcanic rocks and uranium mineralization. The Upper Jurassic acid volcanic cover belonging to crustal remelting origin constituted the favorable stratigraphic background for uranium mineralization in this area due to its wide distribution, large thickness, various rock associations and lithological sequences, as well as high content of uranium and thorium. During the late Yanshanian stage acid subvolanic rocks or small intrusions with high uranium intruded along the regional fractures are the decisive factors for the emplacement of uranium mineralization in this area, which othen became the favorable wall rocks for preserving ores itself. During the late stage the hydrothermal uranium mineralization was the main geological process from which uranium and thorium in stratigraphy and terrain were finally separated

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.

Structure and evolution of an active resurgent dome evidenced by geophysical investigations: The Yenkahe dome-Yasur volcano system (Siwi caldera, Vanuatu)

Science.gov (United States)

Brothelande, E.; Lénat, J.-F.; Chaput, M.; Gailler, L.; Finizola, A.; Dumont, S.; Peltier, A.; Bachèlery, P.; Barde-Cabusson, S.; Byrdina, S.; Menny, P.; Colonge, J.; Douillet, G. A.; Letort, J.; Letourneur, L.; Merle, O.; Di Gangi, F.; Nakedau, D.; Garaebiti, E.

2016-08-01

In this contribution, we focus on one of the most active resurgences on Earth, that of the Yenkahe dome in the Siwi caldera (Tanna Island, Vanuatu), which is associated with the persistently active Yasur volcano. Gravity and magnetic surveys have been carried out over the past few years in the area, as well as electrical methods including electrical resistivity tomography (ERT), time domain electro-magnetics (TDEM) and self-potential (SP). These investigations were completed by thermometry, CO2 soil gas measurements, field observations and sampling. This multi-method approach allows geological structures within the caldera to be identified, as well as associated hydrothermal features. The global structure of the caldera is deduced from gravity data, which shows the caldera rim as a high density structure. Large lava fields, emplaced before and after the onset of resurgence, are evidenced by combined gravity, magnetic and resistivity signals. In the middle of the caldera, the Yenkahe dome apparently results from a combination of volcanic and tectonic events, showing that lava extrusion and resurgence have been operating simultaneously or alternately during the Siwi caldera post-collapse history. There is a clear distinction between the western and eastern parts of the dome. The western part is older and records the growth of an initial volcanic cone and the formation of a small caldera. This small caldera (paleo-Yasur caldera), partially filled with lava flows, is the present-day focus of volcanic activity and associated fluid circulation and alteration. The eastern part of the dome is presumably younger, and is characterized by intense, extensive hydrothermal alteration and activity. Its northern part is covered by lava flow piles and exhibits a shallow hydrothermal zone in ERT. The southern part has hydrothermal alteration and activity extending at least down to the base of the resurgent dome. This part of the dome is built up of low cohesion rock and is thus

Hydrothermal element fluxes from Copahue, Argentina: A "beehive" volcano in turmoil

Science.gov (United States)

Varekamp, J.C.; Ouimette, A.P.; Herman, S.W.; Bermudez, A.; Delpino, D.

2001-01-01

Copahue volcano erupted altered rock debris, siliceous dust, pyroclastic sulfur, and rare juvenile fragments between 1992 and 1995, and magmatic eruptions occurred in July-October 2000. Prior to 2000, the Copahue crater lake, acid hot springs, and rivers carried acid brines with compositions that reflected close to congruent rock dissolution. The ratio between rock-forming elements and chloride in the central zone of the volcano-hydrothermal system has diminished over the past few years, reflecting increased water/rock ratios as a result of progressive rock dissolution. Magmatic activity in 2000 provided fresh rocks for the acid fluids, resulting in higher ratios between rock-forming elements and chloride in the fluids and enhanced Mg fluxes. The higher Mg fluxes started several weeks prior to the eruption. Model data on the crater lake and river element flux determinations indicate that Copahue volcano was hollowed out at a rate of about 20 000-25 000 m3/yr, but that void space was filled with about equal amounts of silica and liquid elemental sulfur. The extensive rock dissolution has weakened the internal volcanic structure, making flank collapse a volcanic hazard at Copahue.

Contention between supply of hydrothermal fluid and conduit obstruction: inferences from numerical simulations

Science.gov (United States)

Tanaka, Ryo; Hashimoto, Takeshi; Matsushima, Nobuo; Ishido, Tsuneo

2018-05-01

We investigate a volcanic hydrothermal system using numerical simulations, focusing on change in crater temperature. Both increases and decreases in crater temperature have been observed before phreatic eruptions. We follow the system's response for up to a decade after hydrothermal fluid flux from the deep part of the system is increased and permeability is reduced at a certain depth in a conduit. Our numerical simulations demonstrate that: (1) changes in crater temperature are controlled by the magnitude of the increase in hydrothermal fluid flux and the degree of permeability reduction; (2) significant increases in hydrothermal flux with decreases in permeability induce substantial pressure changes in shallow depths in the edifice and decreases in crater temperature; (3) the location of maximum pressure change differs between the mechanisms. The results of this study imply that it is difficult to predict eruptions by crater temperature change alone. One should be as wary of large eruptions when crater temperature decreases as when crater temperature increases. It is possible to clarify the implications of changes in crater temperature with simultaneous observation of ground deformation.

Volcanic hazards to airports

Science.gov (United States)

Guffanti, M.; Mayberry, G.C.; Casadevall, T.J.; Wunderman, R.

2009-01-01

Volcanic activity has caused significant hazards to numerous airports worldwide, with local to far-ranging effects on travelers and commerce. Analysis of a new compilation of incidents of airports impacted by volcanic activity from 1944 through 2006 reveals that, at a minimum, 101 airports in 28 countries were affected on 171 occasions by eruptions at 46 volcanoes. Since 1980, five airports per year on average have been affected by volcanic activity, which indicates that volcanic hazards to airports are not rare on a worldwide basis. The main hazard to airports is ashfall, with accumulations of only a few millimeters sufficient to force temporary closures of some airports. A substantial portion of incidents has been caused by ash in airspace in the vicinity of airports, without accumulation of ash on the ground. On a few occasions, airports have been impacted by hazards other than ash (pyroclastic flow, lava flow, gas emission, and phreatic explosion). Several airports have been affected repeatedly by volcanic hazards. Four airports have been affected the most often and likely will continue to be among the most vulnerable owing to continued nearby volcanic activity: Fontanarossa International Airport in Catania, Italy; Ted Stevens Anchorage International Airport in Alaska, USA; Mariscal Sucre International Airport in Quito, Ecuador; and Tokua Airport in Kokopo, Papua New Guinea. The USA has the most airports affected by volcanic activity (17) on the most occasions (33) and hosts the second highest number of volcanoes that have caused the disruptions (5, after Indonesia with 7). One-fifth of the affected airports are within 30 km of the source volcanoes, approximately half are located within 150 km of the source volcanoes, and about three-quarters are within 300 km; nearly one-fifth are located more than 500 km away from the source volcanoes. The volcanoes that have caused the most impacts are Soufriere Hills on the island of Montserrat in the British West Indies

Study of Volcanic Activity at Different Time Scales Using Hypertemporal Land Surface Temperature Data

NARCIS (Netherlands)

Pavlidou, Efthymia; Hecker, Chris; van der Werff, Harald; van der Meijder, Mark

2017-01-01

We apply a method for detecting subtle spatiotemporal signal fluctuations to monitor volcanic activity. Whereas midwave infrared data are commonly used for volcanic hot spot detection, our approach utilizes hypertemporal longwave infrared-based land surface temperature (LST) data. Using LST data of

Iron-Oxidizing Bacteria Found at Slow-Spreading Ridge: a Case Study of Capelinhos Hydrothermal Vent (Lucky Strike, MAR 37°N)

Science.gov (United States)

Henri, P. A.; Rommevaux, C.; Lesongeur, F.; Emerson, D.; Leleu, T.; Chavagnac, V.

2015-12-01

Iron-oxidizing bacteria becomes increasingly described in different geological settings from volcanically active seamounts, coastal waters, to diffuse hydrothermal vents near seafloor spreading centers [Emerson et al., 2010]. They have been mostly identified and described in Pacific Ocean, and have been only recently found in hydrothermal systems associated to slow spreading center of the Mid-Atlantic Ridge (MAR) [Scott et al., 2015]. During the MoMARSAT'13 cruise at Lucky Strike hydrothermal field (MAR), a new hydrothermal site was discovered at about 1.5 km eastward from the lava lake and from the main hydrothermal vents. This active venting site, named Capelinhos, is therefore the most distant from the volcano, features many chimneys, both focused and diffuses. The hydrothermal end-member fluids from Capelinhos are different from those of the other sites of Lucky Strike, showing the highest content of iron (Fe/Mn≈3.96) and the lowest chlorinity (270 mmol/l) [Leleu et al., 2015]. Most of the chimneys exhibit rust-color surfaces and bacterial mats near diffuse flows. During the MoMARSAT'15 cruise, an active chimney, a small inactive one, and rust-color bacterial mat near diffuse flow were sampled at Capelinhos. Observations by SEM of the hydrothermal samples revealed the presence of iron oxides in an assemblage of tubular "sheaths", assembled "stalks", helical "stalks" and amorphous aggregates. These features are similar to those described from the Loihi iron-mats deposits and argue for the occurrence of iron-oxidizing bacteria. Cultures under micro-aerobic and neutral pH conditions allowed us to isolate strains from the small inactive chimney. Pyrosequencing of the 16S rRNA gene of the isolates and environmental samples will soon be performed, which should confirm the presence of iron-oxidizing bacteria and reveal the organization of bacterial communities in this original and newly discovered hydrothermal site of the slow spreading Mid-Atlantic Ridge. Emerson

MIGRATION OF SEISMIC AND VOLCANIC ACTIVITY AS DISPLAY OF WAVE GEODYNAMIC PROCESS

Directory of Open Access Journals (Sweden)

Alexander V. Vikulin

2012-01-01

Full Text Available Publications about the earthquake foci migration have been reviewed. An important result of such studies is establishment of wave nature of seismic activity migration that is manifested by two types of rotational waves; such waves are responsible for interaction between earthquakes foci and propagate with different velocities. Waves determining long-range interaction of earthquake foci are classified as Type 1; their limiting velocities range from 1 to 10 cm/s. Waves determining short-range interaction of foreshocks and aftershocks of individual earthquakes are classified as Type 2; their velocities range from 1 to 10 km/s. According to the classification described in [Bykov, 2005], these two types of migration waves correspond to slow and fast tectonic waves. The most complete data on earthquakes (for a period over 4.1 million of years and volcanic eruptions (for 12 thousand years of the planet are consolidated in a unified systematic format and analyzed by methods developed by the authors. For the Pacific margin, Alpine-Himalayan belt and the Mid-Atlantic Ridge, which are the three most active zones of the Earth, new patterns of spatial and temporal distribution of seismic and volcanic activity are revealed; they correspond to Type 1 of rotational waves. The wave nature of the migration of seismic and volcanic activity is confirmed. A new approach to solving problems of geodynamics is proposed with application of the data on migration of seismic and volcanic activity, which are consolidated in this study, in combination with data on velocities of movement of tectonic plate boundaries. This approach is based on the concept of integration of seismic, volcanic and tectonic processes that develop in the block geomedium and interact with each other through rotating waves with a symmetric stress tensor. The data obtained in this study give grounds to suggest that a geodynamic value, that is mechanically analogous to an impulse

Volcanic Alert System (VAS) developed during the (2011-2013) El Hierro (Canary Islands) volcanic process

Science.gov (United States)

Ortiz, Ramon; Berrocoso, Manuel; Marrero, Jose Manuel; Fernandez-Ros, Alberto; Prates, Gonçalo; De la Cruz-Reyna, Servando; Garcia, Alicia

2014-05-01

In volcanic areas with long repose periods (as El Hierro), recently installed monitoring networks offer no instrumental record of past eruptions nor experience in handling a volcanic crisis. Both conditions, uncertainty and inexperience, contribute to make the communication of hazard more difficult. In fact, in the initial phases of the unrest at El Hierro, the perception of volcanic risk was somewhat distorted, as even relatively low volcanic hazards caused a high political impact. The need of a Volcanic Alert System became then evident. In general, the Volcanic Alert System is comprised of the monitoring network, the software tools for the analysis of the observables, the management of the Volcanic Activity Level, and the assessment of the threat. The Volcanic Alert System presented here places special emphasis on phenomena associated to moderate eruptions, as well as on volcano-tectonic earthquakes and landslides, which in some cases, as in El Hierro, may be more destructive than an eruption itself. As part of the Volcanic Alert System, we introduce here the Volcanic Activity Level which continuously applies a routine analysis of monitoring data (particularly seismic and deformation data) to detect data trend changes or monitoring network failures. The data trend changes are quantified according to the Failure Forecast Method (FFM). When data changes and/or malfunctions are detected, by an automated watchdog, warnings are automatically issued to the Monitoring Scientific Team. Changes in the data patterns are then translated by the Monitoring Scientific Team into a simple Volcanic Activity Level, that is easy to use and understand by the scientists and technicians in charge for the technical management of the unrest. The main feature of the Volcanic Activity Level is its objectivity, as it does not depend on expert opinions, which are left to the Scientific Committee, and its capabilities for early detection of precursors. As a consequence of the El Hierro

Characterizing the dynamics of hydrothermal systems with muon tomography: the case of La Soufrière de Guadeloupe

Science.gov (United States)

Rosas-Carbajal, M.; Marteau, J.; Tramontini, M.; de Bremond d Ars, J.; Le Gonidec, Y.; Carlus, B.; Ianigro, J. C.; Deroussi, S.; Komorowski, J. C.; Gibert, D.

2017-12-01

Muon imaging has recently emerged as a powerful method to complement standard geophysical tools in the study of the Earth's subsurface. Muon measurements yield a radiography of the average density along the muon path, allowing to image large volumes of a geological body from a single observation point. Long-term measurements allow to infer density changes by tracking the associated variations in the muon flux. In the context of volcanic hydrothermal systems, this approach helps to characterize zones of steam formation, condensation, water infiltration and storage. We present results of imaging the La Soufrière de Guadeloupe dome and shallow active hydrothermal system with a network of muon telescopes viewing the dome from different positions around its base. First, we jointly invert the muon radiographies of the different telescopes with gravity data to obtain a three-dimensional density model of the lava dome. The model reveals an extended low density region where the hydrothermal system is most active. We then analyze the dynamics of the hydrothermal system from long-term measurements (more than 2 years of almost non-interrupted acquisition) with 5 simultaneous muon telescopes. We identify a periodicity of 1-2 months in the density increase/decrease in the most active zones below fumaroles and acid boiling ponds. Our simultaneous-muon telescope strategy provides constraints on the three-dimensional location of the density changes and an improved quantification of the associated mass flux changes. We compare the temporal trends acquired by the different muon telescopes to time-series of rainfall on the summit recharge area as well as to ground temperature profiles in the vicinity of thermal anomalies and high-discharge summit fumaroles.

Volcanic gas impacts on vegetation at Turrialba Volcano, Costa Rica

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Teasdale, R.; Jenkins, M.; Pushnik, J.; Houpis, J. L.; Brown, D. L.

2010-12-01

Turrialba volcano is an active composite stratovolcano that is located approximately 40 km east of San Jose, Costa Rica. Seismic activity and degassing have increased since 2005, and gas compositions reflect further increased activity since 2007 peaking in January 2010 with a phreatic eruption. Gas fumes dispersed by trade winds toward the west, northwest, and southwest flanks of Turrialba volcano have caused significant vegetation kill zones, in areas important to local agriculture, including dairy pastures and potato fields, wildlife and human populations. In addition to extensive vegetative degradation is the potential for soil and water contamination and soil erosion. Summit fumarole temperatures have been measured over 200 degrees C and gas emissions are dominated by SO2; gas and vapor plumes reach up to 2 km (fumaroles and gases are measured regularly by OVSICORI-UNA). A recent network of passive air sampling, monitoring of water temperatures of hydrothermal systems, and soil pH measurements coupled with measurement of the physiological status of surrounding plants using gas exchange and fluorescence measurements to: (1) identify physiological correlations between leaf-level gas exchange and chlorophyll fluorescence measurements of plants under long term stress induced by the volcanic gas emissions, and (2) use measurements in tandem with remotely sensed reflectance-derived fluorescence ratio indices to track natural photo inhibition caused by volcanic gas emissions, for use in monitoring plant stress and photosynthetic function. Results may prove helpful in developing potential land management strategies to maintain the biological health of the area.

Volcanic spreading forcing and feedback in geothermal reservoir development, Amiata Volcano, Italia

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Borgia, Andrea; Mazzoldi, Alberto; Brunori, Carlo Alberto; Allocca, Carmine; Delcroix, Carlo; Micheli, Luigi; Vercellino, Alberto; Grieco, Giovanni

2014-09-01

We made a stratigraphic, structural and morphologic study of the Amiata Volcano in Italy. We find that the edifice is dissected by intersecting grabens that accommodate the collapse of the higher sectors of the volcano. In turn, a number of compressive structures and diapirs exist around the margin of the volcano. These structures create an angular drainage pattern, with stream damming and captures, and a set of lakes within and around the volcano. We interpret these structures as the result of volcanic spreading of Amiata on its weak substratum, formed by the late Triassic evaporites (Burano Anhydrites) and the Middle-Jurassic to Early-Cretaceous clayey chaotic complexes (Ligurian Complex). Regional doming created a slope in the basement facilitating the outward flow and spreading of the ductile layers forced by the volcanic load. We model the dynamics of spreading with a scaled lubrication approximation of the Navier Stokes equations, and numerically study a set of solutions. In the model we include simple functions for volcanic deposition and surface erosion that change the topography over time. Scaling indicates that spreading at Amiata could still be active. The numerical solution shows that, as the central part of the edifice sinks into the weak basement, diapiric structures of the underlying formations form around the base of the volcano. Deposition of volcanic rocks within the volcano and surface erosion away from it both enhance spreading. In addition, a sloping basement may constitute a trigger for spreading and formation of trains of adjacent diapirs. As a feedback, the hot hydrothermal fluids decrease the shear strength of the anhydrites facilitating the spreading process. Finally, we observe that volcanic spreading has created ideal heat traps that constitute todays' exploited geothermal fields at Amiata. Normal faults generated by volcanic spreading, volcanic conduits, and direct contact between volcanic rocks (which host an extensive fresh

Evaluation of the Theoretical Geothermal Potential of Inferred Geothermal Reservoirs within the Vicano–Cimino and the Sabatini Volcanic Districts (Central Italy by the Application of the Volume Method

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Daniele Cinti

2018-01-01

Full Text Available The evaluation of the theoretical geothermal potential of identified unexploited hydrothermal reservoirs within the Vicano–Cimino and Sabatini volcanic districts (Latium region, Italy has been made on the basis of a revised version of the classical volume method. This method is based on the distribution of the partial pressure of CO2 (pCO2 in shallow and deep aquifers to delimit areas of geothermal interest, according to the hypothesis that zones of high CO2 flux, either from soil degassing and dissolved into aquifers, are spatially related to deep hydrothermal reservoirs. On the whole, 664 fluid discharges (cold waters, thermal waters, and bubbling pools have been collected from shallow and deep aquifers in the Vicano–Cimino Volcanic District and the Sabatini Volcanic District for chemical and isotopic composition, in an area of approximately 2800 km2. From this large hydro-geochemical dataset the pCO2 values have been computed and then processed to obtain a contour map of its spatial distribution by using geostatistical techniques (kriging. The map of pCO2 has been used to draw up the boundaries of potentially exploitable geothermal systems within the two volcanic districts, corresponding to the areas where endogenous CO2 raise up to the surface from the deep hydrothermal reservoirs. The overall estimated potential productivities and theoretical minimum and maximum thermal power of the two volcanic districts are of about 45 × 103 t/h and 3681–5594 MWt, respectively. This makes the Vicano–Cimino Volcanic District and the Sabatini Volcanic District very suitable for both direct and indirect exploitation of the geothermal resources, in view of the target to reduce electricity generation from conventional and poorly sustainable energy sources.

Preparation high photocatalytic activity of CdS/halloysite nanotubes (HNTs) nanocomposites with hydrothermal method

Energy Technology Data Exchange (ETDEWEB)

Xing Weinan [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Ni Liang, E-mail: xingweinan3@126.com [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Huo Pengwei; Lu Ziyang; Liu Xinlin; Luo Yingying; Yan Yongsheng [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China)

2012-10-15

Highlights: Black-Right-Pointing-Pointer CdS/halloysite nanotubes (HNTs) were synthesized by hydrothermal method. Black-Right-Pointing-Pointer The CdS/HNTs had better photocatalytic activity for degradation of tetracycline. Black-Right-Pointing-Pointer The presence of halloysite nanotubes both improved its photocatalytic activity and stability. - Abstract: A novel nanocatalyst CdS/halloysite nanotubes (HNTs) was synthesized by hydrothermal method with direct growth of CdS nanoparticles on the surface of HNTs. The as-prepared photocatalysts had been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis DRS), Fourier transform infrared (FT-IR) and the thermo gravimetric analysis (TGA). The photocatalytic activity of the sample was evaluated by the degradation of tetracycline (TC) under visible light irradiation. Benefit from the excellent properties of CdS and HNTs, the photocatalyst exhibited good photocatalytic activity and stability. In order to find out the optimum synthesis condition to obtain the best photocatalytic activity, a series of experiments were performed with different CdS loading capacity, different sources of sulfide and different hydrothermal temperatures, etc. The best photodegradation rate could reach 93% in 60 min under visible light irradiation. Therefore, the combination of CdS nanoparticles with HNTs endowed this material with a potential use in environmental treatments in industries.

Preparation high photocatalytic activity of CdS/halloysite nanotubes (HNTs) nanocomposites with hydrothermal method

International Nuclear Information System (INIS)

Xing Weinan; Ni Liang; Huo Pengwei; Lu Ziyang; Liu Xinlin; Luo Yingying; Yan Yongsheng

2012-01-01

Highlights: ► CdS/halloysite nanotubes (HNTs) were synthesized by hydrothermal method. ► The CdS/HNTs had better photocatalytic activity for degradation of tetracycline. ► The presence of halloysite nanotubes both improved its photocatalytic activity and stability. - Abstract: A novel nanocatalyst CdS/halloysite nanotubes (HNTs) was synthesized by hydrothermal method with direct growth of CdS nanoparticles on the surface of HNTs. The as-prepared photocatalysts had been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (UV–vis DRS), Fourier transform infrared (FT-IR) and the thermo gravimetric analysis (TGA). The photocatalytic activity of the sample was evaluated by the degradation of tetracycline (TC) under visible light irradiation. Benefit from the excellent properties of CdS and HNTs, the photocatalyst exhibited good photocatalytic activity and stability. In order to find out the optimum synthesis condition to obtain the best photocatalytic activity, a series of experiments were performed with different CdS loading capacity, different sources of sulfide and different hydrothermal temperatures, etc. The best photodegradation rate could reach 93% in 60 min under visible light irradiation. Therefore, the combination of CdS nanoparticles with HNTs endowed this material with a potential use in environmental treatments in industries.

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

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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.

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...

What governs the enrichment of Pb in the continental crust? An answer from the Mexican Volcanic Belt

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Goldstein, S. L.; Lagatta, A.; Langmuir, C. H.; Straub, S. M.; Martin-Del-Pozzo, A.

2009-12-01

One of Al Hofmann’s many important contributions to our understanding of geochemical cycling in the Earth is the observation that Pb behaves like the light rare earth elements Ce and Nd during melting to form oceanic basalts, but is enriched in the continental crust compared to the LREE by nearly an order of magnitude (Hofmann et al. 1986). This is unusual behavior, and has been called one of the Pb paradoxes, since in most cases, the ratios of elements are effectively the same in the continental crust and oceanic basalts if they show similar mantle melting behavior. One of several mechanisms suggested to mediate this special enrichment is hydrothermal circulation at ocean ridges, which preferentially transports Pb compared to the REE from the interior of the ocean crust to the surface. We confirm the importance of hydrothermal processes at the East Pacific to mediate Pb enrichment at the Trans-Mexican Volcanic Belt (TMVB, through comparison of Pb isotope and Ce/Pb ratios of TMVB lavas with sediments from DSDP Site 487 near the Middle America trench. The lavas of the Trans-Mexican Volcanic Belt include “high Nb” alkali basalts (HNAB), whose trace element patterns lack subduction signatures. The HNAB basalts and hydrothermally affected sediments from DSDP 487, form end-members that bound calcalkaline lavas from volcanoes Colima, Toluca, Popocatépetl, and Malinche in Ce/Pb versus Pb isotope space. The HNAB represent the high Ce/Pb and high Pb-isotope end-member. The hydrothermal sediments have Pb isotopes like Pacific MORB but Ce/Pb ratios typical of the arcs and the continental crust, and an order of magnitude lower than MORB. No analyzed calcalkaline lavas are have compositions outside of the bounds formed by the HNAB and the hydrothermal sediments. The Ce/Pb and Pb isotope ratios show that the calcalkaline lava compositions are inconsistent with contributions from HNAB and EPR MORB, rather the contributions are from HNAB upper mantle and subducted

Hydrothermal system of the Papandayan Volcano from temperature, self-potential (SP) and geochemical measurements

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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.

Field-based tests of geochemical modeling codes: New Zealand hydrothermal systems

International Nuclear Information System (INIS)

Bruton, C.J.; Glassley, W.E.; Bourcier, W.L.

1993-12-01

Hydrothermal systems in the Taupo Volcanic Zone, North Island, New Zealand are being used as field-based modeling exercises for the EQ3/6 geochemical modeling code package. Comparisons of the observed state and evolution of the hydrothermal systems with predictions of fluid-solid equilibria made using geochemical modeling codes will determine how the codes can be used to predict the chemical and mineralogical response of the environment to nuclear waste emplacement. Field-based exercises allow us to test the models on time scales unattainable in the laboratory. Preliminary predictions of mineral assemblages in equilibrium with fluids sampled from wells in the Wairakei and Kawerau geothermal field suggest that affinity-temperature diagrams must be used in conjunction with EQ6 to minimize the effect of uncertainties in thermodynamic and kinetic data on code predictions

Hydrothermal activity, functional diversity and chemoautotrophy are major drivers of seafloor carbon cycling.

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Bell, James B; Woulds, Clare; Oevelen, Dick van

2017-09-20

Hydrothermal vents are highly dynamic ecosystems and are unusually energy rich in the deep-sea. In situ hydrothermal-based productivity combined with sinking photosynthetic organic matter in a soft-sediment setting creates geochemically diverse environments, which remain poorly studied. Here, we use comprehensive set of new and existing field observations to develop a quantitative ecosystem model of a deep-sea chemosynthetic ecosystem from the most southerly hydrothermal vent system known. We find evidence of chemosynthetic production supplementing the metazoan food web both at vent sites and elsewhere in the Bransfield Strait. Endosymbiont-bearing fauna were very important in supporting the transfer of chemosynthetic carbon into the food web, particularly to higher trophic levels. Chemosynthetic production occurred at all sites to varying degrees but was generally only a small component of the total organic matter inputs to the food web, even in the most hydrothermally active areas, owing in part to a low and patchy density of vent-endemic fauna. Differences between relative abundance of faunal functional groups, resulting from environmental variability, were clear drivers of differences in biogeochemical cycling and resulted in substantially different carbon processing patterns between habitats.

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

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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.

Monitoring of fumarole discharge during the 1975-1982 rifting in Krafla volcanic center, North Iceland

Energy Technology Data Exchange (ETDEWEB)

Oskarsson, N.

1984-09-01

Fumarole discharge chemistry in the Krafla geothermal field changed regionally during the 1975-1982 rifting activity. The discharge chemistry previously encountered in the Krafla fumarole grounds was masked by a carbon dioxide-rich gas during the first weeks of rifting. The new discharge composition remained unchanged until 1983 when the first signs of recovery of the previous equilibrium composition appeared at the margins of the area. The outgassing carbon dioxide is released from the deep aquifers beneath the area by the interaction of magmatic gas with the hydrothermal system. In addition to juvenile magmatic carbon the outgassing contains carbon released from the hydrothermal system upon reaction with acid magmatic gases. Increased boiling of the hydrothermal fumaroles was induced by the lowering of the partial pressure of steam due to increased gas content in the fumarole conduits. At the center of rifting activity above the magma chamber the fumarole discharge was temporarily mixed with magmatic gases during local effusive activity. Hydrogen was the dominating magmatic gas in that discharge due to the preferred degassing of hydrogen from magma at shallow levels. These ''hydrogen pulses'' increased in magnitude and duration towards the end of rifting in 1982. The discharge chemistry correlates with the expansion of the magma reservoir of the volcano (regional change of long duration) and local volcanism (short-lived change, hydrogen pulses). The chemical monitoring of fumaroles in Krafla shows that the chemical surveillance of volcanos needs rapid methods for sampling and complete chemical analysis which can be interpreted in terms of reactions and magmatic processes.

Hydrothermal element fluxes from Copahue, Argentina: A “beehive” volcano in turmoil

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Varekamp, Johan C.; Ouimette, Andrew P.; Herman, Scott W.; Bermúdez, Adriana; Delpino, Daniel

2001-11-01

Copahue volcano erupted altered rock debris, siliceous dust, pyroclastic sulfur, and rare juvenile fragments between 1992 and 1995, and magmatic eruptions occurred in July October 2000. Prior to 2000, the Copahue crater lake, acid hot springs, and rivers carried acid brines with compositions that reflected close to congruent rock dissolution. The ratio between rock-forming elements and chloride in the central zone of the volcano-hydrothermal system has diminished over the past few years, reflecting increased water/rock ratios as a result of progressive rock dissolution. Magmatic activity in 2000 provided fresh rocks for the acid fluids, resulting in higher ratios between rock-forming elements and chloride in the fluids and enhanced Mg fluxes. The higher Mg fluxes started several weeks prior to the eruption. Model data on the crater lake and river element flux determinations indicate that Copahue volcano was hollowed out at a rate of about 20000 25000 m3/yr, but that void space was filled with about equal amounts of silica and liquid elemental sulfur. The extensive rock dissolution has weakened the internal volcanic structure, making flank collapse a volcanic hazard at Copahue.

Geochemical of trace elements in volcanics rocks Peninsula Fildes, Fildes Bay Rey Jorge island, south Shetland

International Nuclear Information System (INIS)

Masquelin, H.; Vaz Chavez, N.

1987-01-01

The authors present some geochemical data derived from the multielement analysis of three different types of volcanic rocks collected around Fildes Bay on King George Island, South Shetland. Volcanic rocks from Fildes Peninsula Group may be distinguished from those Marian Cove by their hydrothermal alteration. Apparently the correlation between NI ands Cr allows for the observation of the stratigraphic separation of samples of the same kind. Consequently, the correlation between Cu and As show a distinction between Marian Cove propylitised tuffites and both Brecciated Andesites and pyroclastic rock from Fildes Peninsula Group.

Geochemistry of the volcanic dome in the Municipality of Iza, Boyaca Department, geodynamic interpretation and comparison with Neogene volcanism of the Eastern Cordillera

International Nuclear Information System (INIS)

Vesga, Ana Maria; Jaramillo, Jose

2009-01-01

This work has as purpose to offer new analytic data, supplemented the available ones until the present regarding the volcanic rocks of the region of Iza, (Boyaca); in the same way, the development of a new approach, as for determining if exists a direct connection with other volcanic deposits geographically near to the study area, using descriptive statistical methods. It was realized a characterization geochemistry for 12 samples gathered in the area, where were analyzed big elements, smaller and traces and using diagrams of characterization for effusive rocks, it is corroborated that these possess an alkaline likeness of riolitic composition. Besides the use of normalized diagrams whose abundances of elements of strong electrostatic field (HFSE) as the Nb and Zr, and elements of big ionic radio (LILE) in this case the Rb, they allowed to this rocks characteristic of ambient coalitional. On the other hand, with the obtained results of the statistical analyses, the existent relationship settled down between two geographically places near, as are it volcanic bodies of Los Naranjos and those of Paipa. As for of Iza, it was found that relationship doesn't exist some with another volcanic body among the studied sectors, probably due the alteration hydrothermal that presents the dome of Iza.

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.

The Ignimbritic tertiary volcanism of the Andes (Peru, Bolivia, Argentina): its characteristics and uraniferous potentiality

International Nuclear Information System (INIS)

Leroy, J.L.; George-Aniel, B.

1988-01-01

The petrographic and geochemical characteristics of the volcanism and the primary U distribution at the magmatic stage: alkali-rich volcanic rocks (Peru) appear to be fertile source-rocks, whereas sub alkaline and calc-alkaline rocks (Bolivia and Argentina) are less favorable. Uranium can only be leached from the matrix, due to the stability of the accessory minerals during all the following events. The fertility of a volcanic rock is thus directly controlled by the volume proportion of the matrix and the U fractionation between glass and accessory minerals. The preconcentration and concentration stages: the existence of mineralizations in relation with a fertile rock will depend on other events which must occur successively at the same place: the cooling type and rate of the volcanic pile (pre-concentration stage), the intensity and the duration of the hydrothermal circulations, the presence of reducing agents and trapps. (author)

Monitoring eruption activity using temporal stress changes at Mount Ontake volcano.

Science.gov (United States)

Terakawa, Toshiko; Kato, Aitaro; Yamanaka, Yoshiko; Maeda, Yuta; Horikawa, Shinichiro; Matsuhiro, Kenjiro; Okuda, Takashi

2016-02-19

Volcanic activity is often accompanied by many small earthquakes. Earthquake focal mechanisms represent the fault orientation and slip direction, which are influenced by the stress field. Focal mechanisms of volcano-tectonic earthquakes provide information on the state of volcanoes via stresses. Here we demonstrate that quantitative evaluation of temporal stress changes beneath Mt. Ontake, Japan, using the misfit angles of focal mechanism solutions to the regional stress field, is effective for eruption monitoring. The moving average of misfit angles indicates that during the precursory period the local stress field beneath Mt. Ontake was deviated from the regional stress field, presumably by stress perturbations caused by the inflation of magmatic/hydrothermal fluids, which was removed immediately after the expulsion of volcanic ejecta. The deviation of the local stress field can be an indicator of increases in volcanic activity. The proposed method may contribute to the mitigation of volcanic hazards.

A Proposed Community Network For Monitoring Volcanic Emissions In Saint Lucia, Lesser Antilles

Science.gov (United States)

Joseph, E. P.; Beckles, D. M.; Robertson, R. E.; Latchman, J. L.; Edwards, S.

2013-12-01

Systematic geochemical monitoring of volcanic systems in the English-speaking islands of the Lesser Antilles was initiated by the UWI Seismic Research Centre (SRC) in 2000, as part of its volcanic surveillance programme for the English-speaking islands of the Lesser Antilles. This programme provided the first time-series observations used for the purpose of volcano monitoring in Dominica and Saint Lucia, permitted the characterization of the geothermal fluids associated with them, and established baseline studies for understanding of the hydrothermal systems during periods of quiescence (Joseph et al., 2011; Joseph et al., 2013). As part of efforts to improve and expand the capacity of SRC to provide volcanic surveillance through its geothermal monitoring programme, it is necessary to develop economically sustainable options for the monitoring of volcanic emissions/pollutants. Towards this effort we intend to work in collaboration with local authorities in Saint Lucia, to develop a monitoring network for quantifying the background exposure levels of ambient concentrations of volcanic pollutants, SO2 in air and As in waters (as health significant marker elements in the geothermal emissions) that would serve as a model for the emissions monitoring network for other volcanic islands. This programme would facilitate the building of local capacity and training to monitor the hazardous exposure, through the application and transfer of a regionally available low-cost and low-technology SO2 measurement/detection system in Saint Lucia. Existing monitoring technologies to inform evidence based health practices are too costly for small island Caribbean states, and no government policies or health services measures currently exist to address/mitigate these influences. Gases, aerosols and toxic elements from eruptive and non-eruptive volcanic activity are known to adversely affect human health and the environment (Baxter, 2000; Zhang et al., 2008). Investigations into the

Lithium, boron and chloride in volcanics and greywackes in Northland, Auckland and the Taupo Volcanic Zone

International Nuclear Information System (INIS)

Reyes, A.G.; Trompetter, W.J.

1998-01-01

During magmatic differentiation processes B preferentially partitions into the glassy mesostasis of rhyolite and andesite. The behaviour of Li, on the other hand, varies with the silica content of the rock. Lithium, B, Cl and water contents increase proportionally with the silica concentration of the volcanic rocks. Their relative proportions in andesites of the Taupo Volcanic Zone (TVZ) appear to reflect the nature of the underlying crust, the dip of the subducting slab and hence the depth and temperature of magma generation. The B/Li ratios of rhyolites associated with the northern Rotorua and Okataina eruptive centres yield lower B/Li ratios than those from Maroa and Taupo centres in the south, where the slab subducts at a shallower angle. Apparently, volcanics associated with a younger subduction event as in the TVZ, contain and retain more Cl, yielding lower Li/Cl ratios for the TVZ than Northland-Auckland basalts. The B/Li ratio of greywackes from the Torlesse terrane ( 1.4). In geothermal wells in Ngawha, hydrothermal alteration yields higher B/Li ratios of >2.8 for Waipapa terrane sedimentary rocks. The Li/Cl ratios for average South and North Island greywackes are similar and may reflect similar degrees of metamorphism. In general, the relative Li, B and Cl contents in greywackes are dictated by the composition of the detrital fragments, the clay fraction, the type of clays and the metamorphic grade. During hydrothermal alteration of rhyolite in the TVZ, Cl always partitions into solution while Li and B have an affinity for the rock. However, more Li remains in the rock than B at any given temperature. The distribution coefficients of Li and B between water and rock increase with increasing temperature. The partitioning of Li between rock and solution in TVZ hydrothermal systems is mainly dictated by temperature, whereas the mass distribution coefficient for B is related to the tectonic setting. An increase in relative Li of the rock is associated with the

The Evidence from Inclusions in Pumices for the Direct Degassing of Volatiles from the Magma to the Hydrothermal Fluids in the Okinawa Trough

Institute of Scientific and Technical Information of China (English)

YU Zenghui; ZHAI Shikui; ZHAO Guangtao

2002-01-01

This article presents the evidence in support of the direct magma degassing as the principal mechanism of volatilesreleasing into the hydrothermal fluids in the Okinawa Trough, as contrasted to the argument for the hydrothermal strippingof volatiles from the volcanic rocks.Laser Raman microprobe and stepped-heating techniques are employed to determine the compositions and contents of thevolatiles in pumices in the middle Okinawa Trough. The results show that the volatiles are similar to the gases in the hy-drothermal fluids and hydrothermal minerals in composition, the mean percent content of each component and variationtrend. This indicates the direct influence of magma degassing on the hydrothermal fluids. In addition, the contents ofvolatiles in pumices are rather low and do not support the hydrothermal stripping as the main mechanism to enrich the fluidswith gases. The results are consistent with the idea that the direct magma degassing is more important than hydrothermalstripping in supplying gases to the hydrothermal fluids in the Okinawa Trough.

Search for possible relationship between volcanic ash particles and thunderstorm lightning activity

Science.gov (United States)

Várai, A.; Vincze, M.; Lichtenberger, J.; Jánosi, I. M.

2011-12-01

Explosive volcanic eruptions that eject columns of ash from the crater often generate lightning discharges strong enough to be remotely located by very low frequency radio waves. A fraction of volcanic ash particles can stay and disperse long enough to have an effect on weather phenomena days later such as thunderstorms and lightnings. In this work we report on lightning activity analysis over Europe following two recent series of volcanic eruptions in order to identify possible correlations between ash release and subsequent thunderstorm flash frequency. Our attempts gave negative results which can be related to the fact that we have limited information on local atmospheric variables of high enough resolution, however lightning frequency is apparently determined by very local circumstances.

Search for possible relationship between volcanic ash particles and thunderstorm lightning activity

International Nuclear Information System (INIS)

Várai, A; Vincze, M; Jánosi, I M; Lichtenberger, J

2011-01-01

Explosive volcanic eruptions that eject columns of ash from the crater often generate lightning discharges strong enough to be remotely located by very low frequency radio waves. A fraction of volcanic ash particles can stay and disperse long enough to have an effect on weather phenomena days later such as thunderstorms and lightnings. In this work we report on lightning activity analysis over Europe following two recent series of volcanic eruptions in order to identify possible correlations between ash release and subsequent thunderstorm flash frequency. Our attempts gave negative results which can be related to the fact that we have limited information on local atmospheric variables of high enough resolution, however lightning frequency is apparently determined by very local circumstances.

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.

Mercury concentration, speciation and budget in volcanic aquifers: Italy and Guadeloupe (Lesser Antilles)

Science.gov (United States)

Bagnato, E.; Aiuppa, A.; Parello, F.; D'Alessandro, W.; Allard, P.; Calabrese, S.

2009-01-01

Quantifying the contribution of volcanism to global mercury (Hg) emissions is important to understand the pathways and the mechanisms of Hg cycling through the Earth's geochemical reservoirs and to assess its environmental impacts. While previous studies have suggested that degassing volcanoes might contribute importantly to the atmospheric budget of mercury, little is known about the amount and behaviour of Hg in volcanic aquifers. Here we report on detailed investigations of both the content and the speciation of mercury in aquifers of active volcanoes in Italy and Guadeloupe Island (Lesser Antilles). In the studied groundwaters, total Hg (THg) concentrations range from 10 to 500 ng/l and are lower than the 1000 ng/l threshold value for human health protection fixed by the World Health Organization [WHO (1993): WHO Guidelines for Drinking Water Quality- http://www.who.int/water_sanitation_health/GDWQ/index.htlm]. Positive co-variations of (THg) with sulphate indicate that Hg-SO 4-rich acid groundwaters receive a direct input of magmatic/hydrothermal gases carrying mercury as Hg 0(gas). Increasing THg in a volcanic aquifer could thus be a sensitive tracer of magmatic gas input prior to an eruption. Since the complex behaviour and toxicity of mercury in waters depend on its chemical speciation, we carefully determined the different aqueous forms of this element in our samples. We find that dissolved elemental Hg 0(aq) and particulate-bound Hg (Hg P) widely prevail in volcanic aquifers, in proportions that highlight the efficiency of Hg adsorption onto colloidal particles. Moreover, we observe that dissolved Hg 0aq and Hg(II) forms coexist in comparable amount in most of the waters, in stark contrast to the results of thermodynamic equilibrium modelling. Therefore, chemical equilibrium between dissolved mercury species in volcanic waters is either prevented by natural kinetic effects or not preserved in collected waters due to sampling/storage artefacts. Finally, we

The submarine hydrothermal system of Panarea (Southern Italy: biogeochemical processes at the thermal fluids - sea bottom interface

Directory of Open Access Journals (Sweden)

T. Maugeri

2006-06-01

Full Text Available Among the submarine hydrothermal systems located offshore the volcanic archipelago of the Aeolian Islands (Southern Italy, the most active is located off the coasts of Panarea island. Thermal waters, gases and sulfur deposits coexist at the sea bottom where hydrothermal fluids are released from both shallow and deep vents. The chemical and isotopic composition of the fluid phase shows the presence of a significant magmatic component and the physico-chemical conditions of the geothermal reservoir allow the release of reduced chemical species that are microbially mediated towards the production of organic carbon as a form of biochemical energy. Microorganisms inhabiting this environment possess nutritional requirements and overall metabolic pathways ideally suited to such ecosystem that represents a clear example of the close connection between geosphere and biosphere. Microscopic examination of the white mat attached to rock surfaces showed the presence of Thiothrix-like filamentous bacteria. Moderately thermophilic heterotrophic isolates were identified as strains of the genus Bacillus. Although the hydrothermal system of Panarea has to be considered a “shallow” system, it shows many characteristics that make it similar to the “deep” oceanic systems, giving a unique opportunity for improving our knowledge on such an unexplored world by working at this easily accessible site.

The Biological Deep Sea Hydrothermal Vent as a Model to Study Carbon Dioxide Capturing Enzymes

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Premila D. Thongbam

2011-04-01

Full Text Available Deep sea hydrothermal vents are located along the mid-ocean ridge system, near volcanically active areas, where tectonic plates are moving away from each other. Sea water penetrates the fissures of the volcanic bed and is heated by magma. This heated sea water rises to the surface dissolving large amounts of minerals which provide a source of energy and nutrients to chemoautotrophic organisms. Although this environment is characterized by extreme conditions (high temperature, high pressure, chemical toxicity, acidic pH and absence of photosynthesis a diversity of microorganisms and many animal species are specially adapted to this hostile environment. These organisms have developed a very efficient metabolism for the assimilation of inorganic CO2 from the external environment. In order to develop technology for the capture of carbon dioxide to reduce greenhouse gases in the atmosphere, enzymes involved in CO2 fixation and assimilation might be very useful. This review describes some current research concerning CO2 fixation and assimilation in the deep sea environment and possible biotechnological application of enzymes for carbon dioxide capture.

Geophysical characterization of an active hydrothermal shear zone in granitic rocks

Science.gov (United States)

Zahner, Tobias; Baron, Ludovic; Holliger, Klaus; Egli, Daniel

2016-04-01

Hydrothermally active faults and shear zones in the crystalline massifs of the central Alps are currently of particular interest because of their potential similarities and analogies with planned deep petrothermal reservoirs in the Alpine foreland. In order to better understand such hydrothermal systems, a near-vertical, hydrothermally active shear zone embedded in low-permeability granitic rocks has been drilled. This borehole is located on the Grimsel Pass in the central Swiss Alps, has an inclination of 24 degrees with regard to the vertical, and crosses the targeted shear zone between about 82 and 86 meters depth. The borehole has been fully cored and a comprehensive suite of geophysical logging data has been acquired. The latter comprises multi-frequency sonic, ground-penetrating radar, resistivity, self-potential, gamma-gamma, neutron-neutron, optical televiewer, and caliper log data. In addition to this, we have also performed a surface-to-borehole vertical seismic profiling experiment. The televiewer data and the retrieved core samples show a marked increase of the fracture density in the target region, which also finds its expression in rather pronounced and distinct signatures in all other log data. Preliminary results point towards a close correspondence between the ground-penetrating radar and the neutron-neutron log data, which opens the perspective of constraining the effective fracture porosity at vastly differing scales. There is also remarkably good agreement between the sonic log and the vertical seismic profiling data, which may allow for assessing the permeability of the probed fracture network by interpreting these data in a poroelastic context.

Miocene magmatism in the Bodie Hills volcanic field, California and Nevada: A long-lived eruptive center in the southern segment of the ancestral Cascades arc

Science.gov (United States)

John, David A.; du Bray, Edward A.; Blakely, Richard J.; Fleck, Robert J.; Vikre, Peter; Box, Stephen E.; Moring, Barry C.

2012-01-01

The Middle to Late Miocene Bodie Hills volcanic field is a >700 km2, long-lived (∼9 Ma) but episodic eruptive center in the southern segment of the ancestral Cascades arc north of Mono Lake (California, U.S.). It consists of ∼20 major eruptive units, including 4 trachyandesite stratovolcanoes emplaced along the margins of the field, and numerous, more centrally located silicic trachyandesite to rhyolite flow dome complexes. Bodie Hills volcanism was episodic with two peak periods of eruptive activity: an early period ca. 14.7–12.9 Ma that mostly formed trachyandesite stratovolcanoes and a later period between ca. 9.2 and 8.0 Ma dominated by large trachyandesite-dacite dome fields. A final period of small silicic dome emplacement occurred ca. 6 Ma. Aeromagnetic and gravity data suggest that many of the Miocene volcanoes have shallow plutonic roots that extend to depths ≥1–2 km below the surface, and much of the Bodie Hills may be underlain by low-density plutons presumably related to Miocene volcanism.Compositions of Bodie Hills volcanic rocks vary from ∼50 to 78 wt% SiO2, although rocks with Bodie Hills rocks are porphyritic, commonly containing 15–35 vol% phenocrysts of plagioclase, pyroxene, and hornblende ± biotite. The oldest eruptive units have the most mafic compositions, but volcanic rocks oscillated between mafic and intermediate to felsic compositions through time. Following a 2 Ma hiatus in volcanism, postsubduction rocks of the ca. 3.6–0.1 Ma, bimodal, high-K Aurora volcanic field erupted unconformably onto rocks of the Miocene Bodie Hills volcanic field.At the latitude of the Bodie Hills, subduction of the Farallon plate is inferred to have ended ca. 10 Ma, evolving to a transform plate margin. However, volcanism in the region continued until 8 Ma without an apparent change in rock composition or style of eruption. Equidimensional, polygenetic volcanoes and the absence of dike swarms suggest a low differential horizontal stress regime

Microgravity change as a precursor to volcanic activity

Science.gov (United States)

Rymer, Hazel

1994-07-01

In recent decades, systematic microgravity studies over some 20 active volcanoes in Central America, Iceland, Italy, Japan, Papua New Guinea and the USA have provided valuable data on sub-surface mass redistribution associated with volcanic activity. Concurrent data on ground deformation are essential to the unambiguous interpretation of gravity changes. In some instances, gravity and elevation vary along the free-air or Bouguer gradients, implying that there has been no sub-surface mass or density change, respectively. Where there are residual gravity changes after correction for elevation changes, magma movements in sub-surface chambers, feeder systems, vents and fissures (dykes) or water table variations are proposed. Although detailed interpretations depend on local circumstances and the calculations depend on source geometry, in general, the smallest residual gravity changes are associated with eruptions from volatile-poor basaltic vents and at extensional rift zones, whereas the highest residual values occur at explosive, subduction-related stratocones built from volatile-rich andesitic magma. The most intriguing, yet difficult, data to interpret derive from large-volume, infrequently erupting volcanic systems where caldera unrest is now becoming well documented and the ultimate hazards are most severe. Mass increases during inflation followed by limited mass loss during subsequent deflation typify these structures.

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

initial stages of flood basalt activity. The extreme hydrothermal alteration may hence be directly linked to the prolonged magmatic period during which excess melting produced a 13-km thick igneous crust. Our results indicate that marine plateau-forming events may cause transient highs in hydrothermal flux rates.

Water and gas geochemistry of the Calatrava Volcanic Province (CVP) hydrothermal system (Ciudad Real, central Spain)

Science.gov (United States)

Vaselli, Orlando; Nisi, Barbara; Tassi, Franco; Giannini, Luciano; Grandia, Fidel; Darrah, Tom; Capecchiacci, Francesco; del Villar, Pèrez

2013-04-01

An extensive geochemical and isotopic investigation was carried out in the water and gas discharges of the Late Miocene-Quaternary Calatrava Volcanic Province (CVP) (Ciudad Real, Spain) with the aim reconstruct the fluid circulation in the area. CVP consists of a series of scattered (monogenetic) vents from where alkaline lava flows and pyroclastic deposits formed in two different periods. The first stage (8.7-6.4 Ma) mainly included ultra-potassic mafic extrusives, whilst the second stage (4.7-1.75 Ma) prevalently originated alkaline and ultra-alkaline volcanics. Both stages were followed by a volcanic activity that extended up to 1.3 and 0.7 Ma, respectively. This area can likely be regarded as one of the most important emitting zones of CO2 in the whole Peninsular Spain along with that of Selva-Emporda in northeastern Spain (Cataluña) and it can be assumed as one of the best examples of natural analogues of CO2 leakages in Spain. This latter aspect is further evidenced by the relatively common water-gas blast events that characterize the CCVF. In the last few years the presence of a CO2-pressurized reservoir at a relatively shallow level as indeed caused several small-sized explosion particularly during the drilling of domestic wells. The fluid discharging sites are apparently aligned along well-defined directions: NW-SE and NNW-SSE and subordinately, ENE-WSW, indicating a clear relationship between the thermal discharges and the volcanic centers that also distribute along these lineaments. The CVP waters are mostly hypothermal (up to 33 °C) and are generally Mg(Ca)-HCO3 in composition and occasionally show relatively high concentrations of Fe and Mn, with pH and electrical conductivity down to 5.5 and up to 6.5 mS/cm, respectively. The oxygen and hydrogen isotopes suggest a meteoric origin for these waters. The mantle source of these volcanic products is apparently preserved in the many CO2-rich (up to 990,000 mmol/mol) gas discharges that characterize CVP

Acidic volcanic rock and its potential as an objective for uranium prospecting

International Nuclear Information System (INIS)

Rodriguez Torres, R.; Yza Dominguez, R.; Chavez Aguirre, R.; Constantino, H.E.S.E.

1976-01-01

The geographical distribution of recent Mexican volcanic rocks is continuous; the older formations are dispersed in isolated outcrops. Continental volcanic events, acidic and basal, took place in the Caenozoic, Mesozoic and Palaeozoic; basic submarine volcanism predominated in the Mesozoic, Palaeozoic and late Precambrian. Access to the Sierra Madre Occidental, a circum-Pacific mountain range covered by rhyolitic rocks, is limited, which restricts the sections studied. Calderas, sources of volcanic emission and preliminary litho-stratigraphic sections have been delimited on the eastern edge of the range. Subduction by the ocean magmatized the continent from the Permian onwards, extravasating and depositing cyclically various magmata through inverted and normal cortical throws. The Sierra Pena Blanca (Chihuahua) section consists of epiclastic and pyroclastic rocks. A calcareous conglomerate is overburdened by alternate basal tuffs and imbricates, forming five units. In the uraniferous district of the Sierra Pena Blanca the hydrothermal alteration argillitized both components of the ''Nopal'' formation. Primary minerals (pitchblende) are found together with silicification. Leaching favours secondary mineralization (uranium silicates) associated with opals. After extrapolation of the features, the following are considered worth-while objectives: the faces, offsets and prolongations of the Sierra Madre Occidental and the southern volcanic mesetas south of the Mexican Transcontinental Rift. Similar objectives of Mesozoic or Palaeozoic age exist in central and southern Mexico. Possible objectives for uranium are: the acidic volcanic rock of the southern and south-western United States of America, the circum-Pacific acidic volcanic rocks of North America and the acidic volcanic mesetas of Central America and in the Andes. (author)

Furthering the investigation of eruption styles through quantitative shape analyses of volcanic ash particles

Science.gov (United States)

Nurfiani, D.; Bouvet de Maisonneuve, C.

2018-04-01

Volcanic ash morphology has been quantitatively investigated for various aims such as studying the settling velocity of ash for modelling purposes and understanding the fragmentation processes at the origin of explosive eruptions. In an attempt to investigate the usefulness of ash morphometry for monitoring purposes, we analyzed the shape of volcanic ash particles through a combination of (1) traditional shape descriptors such as solidity, convexity, axial ratio and form factor and (2) fractal analysis using the Euclidean Distance transform (EDT) method. We compare ash samples from the hydrothermal eruptions of Iwodake (Japan) in 2013, Tangkuban Perahu (Indonesia) in 2013 and Marapi (Sumatra, Indonesia) in 2015, the dome explosions of Merapi (Java, Indonesia) in 2013, the Vulcanian eruptions of Merapi in 2010 and Tavurvur (Rabaul, Papaua New Guinea) in 2014, and the Plinian eruption of Kelud (Indonesia) in 2014. Particle size and shape measurements were acquired from a Particle Size Analyzer with a microscope camera attached to the instrument. Clear differences between dense/blocky particles from hydrothermal or dome explosions and vesicular particles produced by the fragmentation of gas-bearing molten magma are well highlighted by conventional shape descriptors and the fractal method. In addition, subtle differences between dense/blocky particles produced by hydrothermal explosions, dome explosions, or quench granulation during phreatomagmatic eruptions can be evidenced with the fractal method. The combination of shape descriptors and fractal analysis is therefore potentially able to distinguish between juvenile and non-juvenile magma, which is of importance for eruption monitoring.

Field-based tests of geochemical modeling codes usign New Zealand hydrothermal systems

International Nuclear Information System (INIS)

Bruton, C.J.; Glassley, W.E.; Bourcier, W.L.

1994-06-01

Hydrothermal systems in the Taupo Volcanic Zone, North Island, New Zealand are being used as field-based modeling exercises for the EQ3/6 geochemical modeling code package. Comparisons of the observed state and evolution of the hydrothermal systems with predictions of fluid-solid equilibria made using geochemical modeling codes will determine how the codes can be used to predict the chemical and mineralogical response of the environment to nuclear waste emplacement. Field-based exercises allow us to test the models on time scales unattainable in the laboratory. Preliminary predictions of mineral assemblages in equilibrium with fluids sampled from wells in the Wairakei and Kawerau geothermal field suggest that affinity-temperature diagrams must be used in conjunction with EQ6 to minimize the effect of uncertainties in thermodynamic and kinetic data on code predictions

Fluidal deep-sea volcanic ash as an indicator of explosive volcanism (Invited)

Science.gov (United States)

Clague, D. A.; Portner, R. A.; Paduan, J. B.; Dreyer, B. M.

2013-12-01

Fluidal glassy lava fragments are now known to be abundant at sites of submarine eruptions including the mid-ocean ridge system, near-ridge seamount chains, mid-plate volcanoes and the submarine rifts of ocean islands, deep-sea (4200m) alkalic lava fields, back-arc spreading centers, and arc volcanoes. Fluidal fragments at these diverse settings have compositions including basanite, tholeiite, boninite, andesite, dacite, and rhyolite. Fragments include straight, bent, curved, and coiled Pele's hair; flat, curved, twisted, folded, bent, or keeled ribbons; and flat, curved, or intensely folded limu o Pele. Most of these morphologies attach to blocky glass fragments. The fluidal fragments from different settings and depths are strikingly similar in morphology with variable vesicularity and particle thickness. They have been sampled flat and steep, rocky to sediment-covered substrates. Two different mechanisms are proposed to explain their origin: magmatic-volatile fragmentation during eruption and sea floor lava-water interactions. Volatiles in the melts and ambient water are present in all submarine volcanic settings, making it difficult to separate their role in forming the fragments. Submarine bubble-burst (strombolian) activity has been observed in situ at an active vent at -1200m on West Mata Volcano. However, lava-water interaction at elevated pressure has not been observed to make such fluidal fragments except in laboratory simulations. Lava-water interaction models suggest that pore water in sediment trapped beneath advancing lava flows migrates into the overlying flow where it expands to steam, and the expanding steam bubble escapes explosively through the flow top to form the fluidal fragments. This is different from the hollow (water-filled) pillars that form in inflating flows as trapped water escapes. Pillars grow upwards at contacts between flow lobes, thus the water exiting through pillars never enters (or exits) the molten lava flow interior. Another

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

Directory of Open Access Journals (Sweden)

Mohsen Alikhani Banghani

2013-10-01

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

Magmas near the critical degassing pressure drive volcanic unrest towards a critical state

Science.gov (United States)

Chiodini, Giovanni; Paonita, Antonio; Aiuppa, Alessandro; Costa, Antonio; Caliro, Stefano; De Martino, Prospero; Acocella, Valerio; Vandemeulebrouck, Jean

2016-01-01

During the reawaking of a volcano, magmas migrating through the shallow crust have to pass through hydrothermal fluids and rocks. The resulting magma–hydrothermal interactions are still poorly understood, which impairs the ability to interpret volcano monitoring signals and perform hazard assessments. Here we use the results of physical and volatile saturation models to demonstrate that magmatic volatiles released by decompressing magmas at a critical degassing pressure (CDP) can drive volcanic unrest towards a critical state. We show that, at the CDP, the abrupt and voluminous release of H2O-rich magmatic gases can heat hydrothermal fluids and rocks, triggering an accelerating deformation that can ultimately culminate in rock failure and eruption. We propose that magma could be approaching the CDP at Campi Flegrei, a volcano in the metropolitan area of Naples, one of the most densely inhabited areas in the world, and where accelerating deformation and heating are currently being observed. PMID:27996976

Soil radon concentration and volcanic activity of Mt. Etna before and after the 2002 eruption

International Nuclear Information System (INIS)

Imme, G.; La Delfa, S.; Lo Nigro, S.; Morelli, D.; Patane, G.

2006-01-01

Soil radon investigation, using a continuous measurement device, has been performed on Mt. Etna in order to observe possible anomalies due to seismic and/or volcanic activity. In October 2002 an eruptive event occurred. Measurements, performed on the NE flank, have shown a possible correlation between eruptive activity of the volcano and soil radon concentration anomaly. The study of the seismic activity recorded in the same flank has, also, allowed to characterize the volcano dynamics and to correlate it with the variations of radon. The obtained results seem to indicate a possible dependence on volcanic activity of the radon concentration

Disruptive event analysis: volcanism and igneous intrusion

International Nuclear Information System (INIS)

Crowe, B.M.

1979-01-01

Three basic topics are addressed for the disruptive event analysis: first, the range of disruptive consequences of a radioactive waste repository by volcanic activity; second, the possible reduction of the risk of disruption by volcanic activity through selective siting of a repository; and third, the quantification of the probability of repository disruption by volcanic activity

Hierarchical probabilistic regionalization of volcanism for Sengan region in Japan using multivariate statistical techniques and geostatistical interpolation techniques

International Nuclear Information System (INIS)

Park, Jinyong; Balasingham, P.; McKenna, Sean Andrew; Kulatilake, Pinnaduwa H. S. W.

2004-01-01

Sandia National Laboratories, under contract to Nuclear Waste Management Organization of Japan (NUMO), is performing research on regional classification of given sites in Japan with respect to potential volcanic disruption using multivariate statistics and geo-statistical interpolation techniques. This report provides results obtained for hierarchical probabilistic regionalization of volcanism for the Sengan region in Japan by applying multivariate statistical techniques and geostatistical interpolation techniques on the geologic data provided by NUMO. A workshop report produced in September 2003 by Sandia National Laboratories (Arnold et al., 2003) on volcanism lists a set of most important geologic variables as well as some secondary information related to volcanism. Geologic data extracted for the Sengan region in Japan from the data provided by NUMO revealed that data are not available at the same locations for all the important geologic variables. In other words, the geologic variable vectors were found to be incomplete spatially. However, it is necessary to have complete geologic variable vectors to perform multivariate statistical analyses. As a first step towards constructing complete geologic variable vectors, the Universal Transverse Mercator (UTM) zone 54 projected coordinate system and a 1 km square regular grid system were selected. The data available for each geologic variable on a geographic coordinate system were transferred to the aforementioned grid system. Also the recorded data on volcanic activity for Sengan region were produced on the same grid system. Each geologic variable map was compared with the recorded volcanic activity map to determine the geologic variables that are most important for volcanism. In the regionalized classification procedure, this step is known as the variable selection step. The following variables were determined as most important for volcanism: geothermal gradient, groundwater temperature, heat discharge, groundwater

Evidence for rapid epithermal mineralization and coeval bimodal volcanism, Bruner Au-Ag property, NV USA

Science.gov (United States)

Baldwin, Dylan

The character of Au-Ag mineralization and volcanic/hydrothermal relationships at the underexplored Miocene-age Bruner low-sulfidation epithermal Au-Ag deposit are elucidated using field and laboratory studies. Bruner is located in central Nevada within the Great Basin extensional province, near several major volcanic trends (Western Andesite, Northern Nevada Rift) associated with world-class Miocene-age epithermal Au-Ag provinces. Despite its proximity to several >1 Moz Au deposits, and newly discovered high-grade drill intercepts (to 117 ppm Au/1.5m), there is no published research on the deposit, the style of mineralization has not been systematically characterized, and vectors to mineralization remain elusive. By investigating the nature of mineralization and time-space relationships between volcanic/hydrothermal activity, the deposit has been integrated into a regional framework, and exploration targeting improved. Mineralization occurs within narrow quartz + adularia +/- pyrite veins that manifest as sheeted/stockwork zones, vein swarms, and rare 0.3-2 m wide veins hosted by two generations of Miocene high-K, high-silica rhyolite flow dome complexes overlying an andesite flow unit. The most prominent structural controls on veining are N­striking faults and syn-mineral basalt/rhyolite dikes. Productive veins have robust boiling indicators (high adularia content, bladed quartz after calcite, recrystallized colloform quartz bands), lack rhythmic banding, and contain only 1-2 stages; these veins overprint, or occur separately from another population of barren to weakly mineralized rhythmically banded quartz-only veins. Ore minerals consist of coarse Au0.5Ag 0.5 electrum, fine Au0.7Ag0.3 electrum, acanthite, uytenbogaardtite (Ag3AuS2) and minor embolite Ag(Br,Cl). Now deeply oxidized, veins typically contain Bruner appears to belong to a small subset of mid-Miocene epithermal deposits in Nevada with low base metal contents and low to no Se, related to calc

Dinasour extinction and volcanic activity

Science.gov (United States)

Gledhill, J. A.

There is at present some controversy about the reason for the mass extinction of dinosaurs and other forms of life at the end of the Cretaceous. A suggestion by Alvarez et al. [1980] that this was due to the collision of the earth with a meteorite 10 km or so in diameter has excited considerable interest [Silver and Schultz, 1982] and also some criticism [Stanley, 1984]. A recent publication [Wood, 1984] describing the catastrophic effects of a relatively minor lava flow in Iceland suggests that intense volcanic activity could have played a large part in the extinctions. In this letter it is pointed out that the Deccan lava flows in India took place in the appropriate time and may well have been of sufficient magnitude to be a major factor in the Cretaceous-Tertiary (C-T) boundary catastrophe.

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

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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.

Presence of radionuclides in clays of the hydrothermal system of the Volcano Turrialba, Costa Rica

International Nuclear Information System (INIS)

Garcia-Vindas, J.R.; Gazel, Esteban

2004-01-01

The first results obtained about the presence of radionuclides of terrigenous origin in the hydrothermal system of Turrialba Volcano are shown in this paper. Several samples were taken in the central and southwest craters, and analyzed by gamma-ray spectrometry, with Hyper pure Germanium detector. The values of the activities of the natural radioactive isotopes are shown in Bq/kg. A disequilibrium in the series of U-238 was found, which is explained by two different mechanisms: one convective and the other by Rn-222 enrichment. An increase of the activity of all isotopes is observed between September 2001 and May 2002. Because the low possibilities that this can be produced by the water runoff, it is proposed that such rise in the concentration of the elements can be explained by their presence in the water vapour and other volcanic gases. (Author) [es

Volcanic emissions from soils at the base of La Fossa volcano, Vulcano island, Italy

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Obenholzner, J. H.; Parks, J. L.

2006-12-01

A top-sealed plastic tube with a diameter of ca. 15 cm had been buried vertically at the base of La Fossa volcano, Volcano island, Italy, next to the front of the obsidian flow. The tube had been filled with quartz wool to condense vapors emanating from the soil. At ca. 75 cm below the surface the sample had been exposed to vapors from Sept. 2005 to April 2006. The leached sample had not been in touch with the ground. Another glass wool cushion (ca. 3 cm thick) had been underneath to minimize capillary effects. Leaching of the quartz wool and ICP-MS analysis documented positive values for: Mg, Al, Si, P, K, Ca, Cr, Mn, Ni, Cu, Zn, Cd, Sn, Pb. Leaching with nitric acid documented also V and Fe. Acid leaching produced higher values for all elements, except K and Sn, than leaching with deionized water. Negative values had been obtained for As, Se, Mo. Influence from soil breathing can be excluded as the active fumaroles contain As and Se. This experiment documents for the first time an unknown element transport by vapors/gases through a volcanic edifice interacting with hydrothermal and magmatic gases. It remains unknown if elements detected are entering the atmosphere or are getting adsorbed onto the volcanic ash soil particles derived from reworked surge beds. This question is very important as soils might be an unknown filter medium to filter volcanically polluted air in case of major volcanic crises. Data can be obtained from the authors.

2015 Volcanic activity in Alaska—Summary of events and response of the Alaska Volcano Observatory

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Dixon, James P.; Cameron, Cheryl E.; Iezzi, Alexandra M.; Wallace, Kristi

2017-09-28

The Alaska Volcano Observatory (AVO) responded to eruptions, volcanic unrest or suspected unrest, and seismic events at 14 volcanic centers in Alaska during 2015. The most notable volcanic activity consisted of continuing intermittent ash eruptions from Cleveland and Shishaldin volcanoes in the Aleutian Islands. Two eruptive episodes, at Veniaminof and Pavlof, on the Alaska Peninsula ended in 2015. During 2015, AVO re-established the seismograph network at Aniakchak, installed six new broadband seismometers throughout the Aleutian Islands, and added a Multiple component Gas Analyzer System (MultiGAS) station on Augustine.

A Serpentinite-Hosted Ecosystem: The Lost City Hydrothermal Field

Science.gov (United States)

Kelley, Deborah S.; Karson, Jeffrey A.; Früh-Green, Gretchen L.; Yoerger, Dana R.; Shank, Timothy M.; Butterfield, David A.; Hayes, John M.; Schrenk, Matthew O.; Olson, Eric J.; Proskurowski, Giora; Jakuba, Mike; Bradley, Al; Larson, Ben; Ludwig, Kristin; Glickson, Deborah; Buckman, Kate; Bradley, Alexander S.; Brazelton, William J.; Roe, Kevin; Elend, Mitch J.; Delacour, Adélie; Bernasconi, Stefano M.; Lilley, Marvin D.; Baross, John A.; Summons, Roger E.; Sylva, Sean P.

2005-03-01

The serpentinite-hosted Lost City hydrothermal field is a remarkable submarine ecosystem in which geological, chemical, and biological processes are intimately interlinked. Reactions between seawater and upper mantle peridotite produce methane- and hydrogen-rich fluids, with temperatures ranging from A low diversity of microorganisms related to methane-cycling Archaea thrive in the warm porous interiors of the edifices. Macrofaunal communities show a degree of species diversity at least as high as that of black smoker vent sites along the Mid-Atlantic Ridge, but they lack the high biomasses of chemosynthetic organisms that are typical of volcanically driven systems.

Evidence of volcanic and glacial activity in Chryse and Acidalia Planitiae, Mars

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Martinez-Alonso, Sara; Mellon, Michael T.; Banks, Maria E.; Keszthelyi, Laszlo P.; McEwen, Alfred S.

2011-01-01

Chryse and Acidalia Planitiae show numerous examples of enigmatic landforms previously interpreted to have been influenced by a water/ice-rich geologic history. These landforms include giant polygons bounded by kilometer-scale arcuate troughs, bright pitted mounds, and mesa-like features. To investigate the significance of the last we have analyzed in detail the region between 60°N, 290°E and 10°N, 360°E utilizing HiRISE (High Resolution Imaging Science Experiment) images as well as regional-scale data for context. The mesas may be analogous to terrestrial tuyas (emergent sub-ice volcanoes), although definitive proof has not been identified. We also report on a blocky unit and associated landforms (drumlins, eskers, inverted valleys, kettle holes) consistent with ice-emplaced volcanic or volcano-sedimentary flows. The spatial association between tuya-like mesas, ice-emplaced flows, and further possible evidence of volcanism (deflated flow fronts, volcanic vents, columnar jointing, rootless cones), and an extensive fluid-rich substratum (giant polygons, bright mounds, rampart craters), allows for the possibility of glaciovolcanic activity in the region.Landforms indicative of glacial activity on Chryse/Acidalia suggest a paleoclimatic environment remarkably different from today's. Climate changes on Mars (driven by orbital/obliquity changes) or giant outflow channel activity could have resulted in ice-sheet-related landforms far from the current polar caps.

Geology of the Mid-Miocene Rooster Comb Caldera and Lake Owyhee Volcanic Field, eastern Oregon: Silicic volcanism associated with Grande Ronde flood basalt

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Benson, Thomas R.; Mahood, Gail A.

2016-01-01

The Lake Owyhee Volcanic Field (LOVF) of eastern Oregon consists of rhyolitic caldera centers and lava fields contemporaneous with and spatially related to Mid-Miocene Columbia River flood basalt volcanism. Previous studies delineated two calderas in the southeastern part of LOVF near Owyhee Reservoir, the result of eruptions of two ignimbrites, the Tuff of Leslie Gulch and the Tuff of Spring Creek. Our new interpretation is that these two map units are differentially altered parts of a single ignimbrite produced in a major phreatomagmatic eruption at 15.8 Ma. Areas previously mapped as Tuff of Spring Creek are locations where the ignimbrite contains abundant clinoptilolite ± mordenite, which made it susceptible to erosion. The resistant intracaldera Tuff of Leslie Gulch has an alteration assemblage of albite ± quartz, indicative of low-temperature hydrothermal alteration. Our new mapping of caldera lake sediments and pre- and post-caldera rhyolitic lavas and intrusions that are chemically similar to intracaldera Tuff of Leslie Gulch point to a single 20 × 25 km caldera, which we name the Rooster Comb Caldera. Erosion of the resurgently uplifted southern half of the caldera created dramatic exposures of intracaldera Tuff of Leslie Gulch cut by post-caldera rhyolite dikes and intrusions that are the deeper-level equivalents of lava domes and flows that erupted into the caldera lake preserved in exposures to the northeast. The Rooster Comb Caldera has features in common with more southerly Mid-Miocene calderas of the McDermitt Volcanic Field and High Rock Caldera Complex, including formation in a basinal setting shortly after flood basalt eruptions ceased in the region, and forming on eruption of peralkaline ignimbrite. The volcanism at Rooster Comb Caldera postdates the main activity at McDermitt and High Rock, but, like it, begins 300 ky after flood basalt volcanism begins in the area, and while flood basalts don't erupt through the silicic focus, are

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)

Fluids in volcanic and geothermal systems

Science.gov (United States)

Sigvaldason, Gudmundur E.

-rift volcanism is accordingly not fed directly by mantle derived liquids. The model predicts that all volcanic fluids, with the exception of those which are associated with the most primitive olivine tholeiites, are partly or wholly recycled through all stages of hydrothermal and metamorphic reactions. In that sense associated volcanic and geothermal systems are a part of the same chemical fractionation column. It is concluded that the chemistry of fluids in volcanic and geothermal systems can be viewed in the perspective of predictable crustal fractionation processes before any conclusion need be drawn concerning more deep seated causes for chemical anomalies.

Photosynthesis within Mars' volcanic craters?: Insights from Cerro Negro Volcano, Nicaragua

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Rogers, K. L.; Hynek, B. M.; McCollom, T. M.

2011-12-01

Discrete locales of sulfate-rich bedrocks exist on Mars and in many cases represent the products of acid-sulfate alteration of martian basalt. In some places, the products have been attributed to hydrothermal processes from local volcanism. In order to evaluate the habitability of such an environment, we are investigating the geochemical and biological composition of active fumaroles at Cerro Negro Volcano, Nicaragua, where fresh basaltic cinders similar in composition to martian basalts are altered by acidic, sulfur-bearing gases. Temperatures at active fumaroles can reach as high as 400°C and the pH of the steam ranges from Cyanobacteria and Ktedonobacteria, however Actinobacteria, alpha-Proteobacteria and Acidobacteria were also identified. Many of the cyanobacterial sequences were similar to those of the eukaryotic Cyanidiales, red algae that inhabit acidic, geothermal environments. Many of sequences related to Ktedonobacteria and Actinobacteria have also been found in acid mine drainage environments. The Archaeal community was far less diverse, with sequences matching those of unclassified Desulfurococcales and unclassified Thermoprotei. These sequences were more distant from isolated species than the bacterial sequences. Similar bacterial and archaeal communities have been found in hot spring environments in Yellowstone National Park, Greenland, Iceland, New Zealand and Costa Rica. Some of Mars' volcanoes were active for billions of years and by analogy to Cerro Negro, may have hosted photosynthetic organisms that could have been preserved in alteration mineral assemblages. Even on a generally cold and dry Mars, volcanic craters likely provided long-lived warm and wet conditions and should be a key target for future exploration assessing habitability.

Conceptual model of volcanism and volcanic hazards of the region of Ararat valley, Armenia

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Meliksetian, Khachatur; Connor, Charles; Savov, Ivan; Connor, Laura; Navasardyan, Gevorg; Manucharyan, Davit; Ghukasyan, Yura; Gevorgyan, Hripsime

2015-04-01

Armenia and the adjacent volcanically active regions in Iran, Turkey and Georgia are located in the collision zone between the Arabian and Eurasian lithospheric plates. The majority of studies of regional collision related volcanism use the model proposed by Keskin, (2003) where volcanism is driven by Neo-Tethyan slab break-off. In Armenia, >500 Quaternary-Holocene volcanoes from the Gegham, Vardenis and Syunik volcanic fields are hosted within pull-apart structures formed by active faults and their segments (Karakhanyan et al., 2002), while tectonic position of the large in volume basalt-dacite Aragats volcano and periphery volcanic plateaus is different and its position away from major fault lines necessitates more complex volcano-tectonic setup. Our detailed volcanological, petrological and geochemical studies provide insight into the nature of such volcanic activity in the region of Ararat Valley. Most magmas, such as those erupted in Armenia are volatile-poor and erupt fairly hot. Here we report newly discovered tephra sequences in Ararat valley, that were erupted from historically active Ararat stratovolcano and provide evidence for explosive eruption of young, mid K2O calc-alkaline and volatile-rich (>4.6 wt% H2O; amph-bearing) magmas. Such young eruptions, in addition to the ignimbrite and lava flow hazards from Gegham and Aragats, present a threat to the >1.4 million people (~ ½ of the population of Armenia). We will report numerical simulations of potential volcanic hazards for the region of Ararat valley near Yerevan that will include including tephra fallout, lava flows and opening of new vents. Connor et al. (2012) J. Applied Volcanology 1:3, 1-19; Karakhanian et al. (2002), JVGR, 113, 319-344; Keskin, M. (2003) Geophys. Res. Lett. 30, 24, 8046.

Relationships between mineralization and silicic volcanism in the central Andes

Energy Technology Data Exchange (ETDEWEB)

Francis, P.W.; Halls, C.; Baker, M.C.W.

1983-10-01

Studies of late Tertiary silicic volcanic centers in the Western and Eastern Cordilleras of the Central Andes show that three volcanic environments are appropriate sites for mineralization: (1) ring-fracture extrusions post-dating large calderas; (2) similar extrusions within ignimbrite shields; and (3) isolated, small silicic volcanoes. Subvolcanic tin mineralization in the Eastern Cordillera is located in silicic stocks and associated breccias of Miocene age. The Cerro Rico stock, Potosi, Bolivia, contains tin and silver mineralization and has an intrusion age apparently millions of years younger than that of the associated Kari Kari caldera. Similar age relationships between mineralization and caldera formation have been described from the San Juan province, Colorado. The vein deposits of Chocaya, southern Bolivia, were emplaced in the lower part of an ignimbrite shield, a type of volcanic edifice as yet unrecognized in comparable areas of silicic volcanism. The El Salvador porphyry copper deposit, Chile, is related to silicic stocks which may have been intruded along a caldera ring fracture. Existing models for the genesis of porphyry copper deposits suggest that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. The dome of La Soufriere, Guadeloupe is proposed as a modern analog for the surface expression of subvolcanic mineralization processes, the phreatic eruptions there suggesting the formation of hydrothermal breccia bodies in depth.

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

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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

Nondestructive neutron activation analysis of volcanic samples: Hawaii

International Nuclear Information System (INIS)

Zoller, W.H.; Finnegan, D.L.; Crowe, B.

1986-01-01

Samples of volcanic emissions have been collected between and during eruptions of both Kilauea and Mauna Loa volcanoes during the last three years. Airborne particles have been collected on Teflon filters and acidic gases on base-impregnated cellulose filters. Chemically neutral gas-phase species are collected on charcoal-coated cellulose filters. The primary analytical technique used is nondestructive neutron activation analysis, which has been used to determine the quantities of up to 35 elements on the different filters. The use of neutron activation analysis makes it possible to analyze for a wide range of elements in the different matrices used for the collection and to learn about the distribution between particles and gas phases for each of the elements

Geologic Map of the Bodie Hills Volcanic Field, California and Nevada: Anatomy of Miocene Cascade Arc Magmatism in the Western Great Basin

Science.gov (United States)

John, D. A.; du Bray, E. A.; Blakely, R. J.; Box, S.; Fleck, R. J.; Vikre, P. G.; Rytuba, J. J.; Moring, B. C.

2011-12-01

primary volcanic morphologies indicate only minor post-volcanic extension of the Bodie Hills. Hydrothermal activity alternated with volcanism, forming both large epithermal Au-Ag vein deposits and large areas of strongly altered but weakly mineralized rock. Compared to AVF, BHVF had a higher average eruptive rate, includes more phenocryst-rich lavas, and formed diverse types of volcanoes inferred to be underlain by large plutons. Consequently, the 2 volcanic fields were probably associated with substantially different magmatic processes and formed in different stress regimes.

The research of modern He discharge in volcanic and tectonically active areas of China's continent

International Nuclear Information System (INIS)

Shangguan, Z.G.

1999-01-01

The realising features of modern helium in volcanic and tectonically active areas of China's continent are here discussed, presenting that the current escaped He in volcanic areas are mainly the mantle-derived He. The 3 He/ 4 He ratios of crustal gases in Eastern China are relatively higher than those gases in Middle-Western China. The author considers difficult to interpret this phenomenon by means of the differences of tectonic activity in those areas: it may be related to the variation of crustal thickness of China's continent from East to West

Water-rock interactions in discharge areas of Xiangshan Fossil hydrothermal system

International Nuclear Information System (INIS)

Zhou, Wenbin

1992-01-01

Xiangshan Fossil hydrothermal system is located within a volcanic basin of south-eastern China. The fact that most metal mineralizations were found in the discharge areas of the fossil hydrothermal system shows that the discharge areas were special geochemical fields. This paper discusses some important water-rock interactions in the discharge areas of Xiangshan fossil hydrothermal system. When the fluids circulating in the deep section of the hydrothermal system went upward to the discharge area, the physico-chemical conditions under which the fluids were saturated changed so considerably that the original physico-chemical equilibria were broken. Consequently, the fluids tended to move to new equilibrium by means of regulating their chemical compositions. Temperature and pressures of the fluids could be declined greatly in discharge area; the difference of temperature and pressure are determined to be 100--150 C and 1--2 x 10 7 Pa. As a result, a large amount of CO 2 in solution escaped from the fluids in the discharge area, and UO 2 (CO 3 ) n 2(1-n) , stable in CO 2 -rich solutions, could be decomposed into UUO 2 2+ , which could be easily reduced into pitchblende associated by calcite and hematite. The pH values for the fluids tended to increase with the CO 2 escaping, however, the interactions between the hydrothermal fluids and the wall rocks (dominantly aluminosilicate) served as the buffers for the pH, and regulated the pH value around neutral point. The buffer effect was of great importance to uranium mineralization. In addition, isotope exchangements between the fluids and rocks took place extensively

Integrating science and education during an international, multi-parametric investigation of volcanic activity at Santiaguito volcano, Guatemala

Science.gov (United States)

Lavallée, Yan; Johnson, Jeffrey; Andrews, Benjamin; Wolf, Rudiger; Rose, William; Chigna, Gustavo; Pineda, Armand

2016-04-01

In January 2016, we held the first scientific/educational Workshops on Volcanoes (WoV). The workshop took place at Santiaguito volcano - the most active volcano in Guatemala. 69 international scientists of all ages participated in this intensive, multi-parametric investigation of the volcanic activity, which included the deployment of seismometers, tiltmeters, infrasound microphones and mini-DOAS as well as optical, thermographic, UV and FTIR cameras around the active vent. These instruments recorded volcanic activity in concert over a period of 3 to 9 days. Here we review the research activities and present some of the spectacular observations made through this interdisciplinary efforts. Observations range from high-resolution drone and IR footage of explosions, monitoring of rock falls and quantification of the erupted mass of different gases and ash, as well as morphological changes in the dome caused by recurring explosions (amongst many other volcanic processes). We will discuss the success of such integrative ventures in furthering science frontiers and developing the next generation of geoscientists.

Volcanic sulfur dioxide index and volcanic explosivity index inferred from eruptive volume of volcanoes in Jeju Island, Korea: application to volcanic hazard mitigation

Science.gov (United States)

Ko, Bokyun; Yun, Sung-Hyo

2016-04-01

Jeju Island located in the southwestern part of Korea Peninsula is a volcanic island composed of lavaflows, pyroclasts, and around 450 monogenetic volcanoes. The volcanic activity of the island commenced with phreatomagmatic eruptions under subaqueous condition ca. 1.8-2.0 Ma and lasted until ca. 1,000 year BP. For evaluating volcanic activity of the most recently erupted volcanoes with reported age, volcanic explosivity index (VEI) and volcanic sulfur dioxide index (VSI) of three volcanoes (Ilchulbong tuff cone, Songaksan tuff ring, and Biyangdo scoria cone) are inferred from their eruptive volumes. The quantity of eruptive materials such as tuff, lavaflow, scoria, and so on, is calculated using a model developed in Auckland Volcanic Field which has similar volcanic setting to the island. The eruptive volumes of them are 11,911,534 m3, 24,987,557 m3, and 9,652,025 m3, which correspond to VEI of 3, 3, and 2, respectively. According to the correlation between VEI and VSI, the average quantity of SO2 emission during an eruption with VEI of 3 is 2-8 × 103 kiloton considering that the island was formed under intraplate tectonic setting. Jeju Island was regarded as an extinct volcano, however, several studies have recently reported some volcanic eruption ages within 10,000 year BP owing to the development in age dating technique. Thus, the island is a dormant volcano potentially implying high probability to erupt again in the future. The volcanoes might have explosive eruptions (vulcanian to plinian) with the possibility that SO2 emitted by the eruption reaches stratosphere causing climate change due to backscattering incoming solar radiation, increase in cloud reflectivity, etc. Consequently, recommencement of volcanic eruption in the island is able to result in serious volcanic hazard and this study provides fundamental and important data for volcanic hazard mitigation of East Asia as well as the island. ACKNOWLEDGMENTS: This research was supported by a grant [MPSS

Three-dimensional electrical resistivity model of the hydrothermal system in Long Valley Caldera, California, from magnetotellurics

Science.gov (United States)

Peacock, Jared R.; Mangan, Margaret T.; McPhee, Darcy K.; Wannamaker, Phil E.

2016-01-01

Though shallow flow of hydrothermal fluids in Long Valley Caldera, California, has been well studied, neither the hydrothermal source reservoir nor heat source has been well characterized. Here a grid of magnetotelluric data were collected around the Long Valley volcanic system and modeled in 3-D. The preferred electrical resistivity model suggests that the source reservoir is a narrow east-west elongated body 4 km below the west moat. The heat source could be a zone of 2–5% partial melt 8 km below Deer Mountain. Additionally, a collection of hypersaline fluids, not connected to the shallow hydrothermal system, is found 3 km below the medial graben, which could originate from a zone of 5–10% partial melt 8 km below the south moat. Below Mammoth Mountain is a 3 km thick isolated body containing fluids and gases originating from an 8 km deep zone of 5–10% basaltic partial melt.

Recent progress in volcanism studies: Site characterization activities for the Yucca Mountain site characterization project

International Nuclear Information System (INIS)

Crowe, B.M.; Valentine, G.; Morley, R.; Perry, F.V.

1992-01-01

Significant progress has been made on volcanism studies over the past calendar year. There are a number of major highlights from this work. Geochronology data have been obtained for the Lathrop Wells center using a range of isotopic, radiogenic, and age-calibrated methods. Initial work is encouraging but still insufficient to resolve the age of the center with confidence. Geologic mapping of the Sleeping Butte volcanic centers was completed and a report issued on the geology and chronology data. Twenty shallow trenches have been constructed in volcanic units of the Lathrop Wells volcanic center. Results of detailed studies of the trenches support a polycyclic eruptive history. New soil data from the trenches continue to support a late Pleistocene or Holocene age for many of the volcanic units at the center. Geochemical data (trace element and isotopic analysis) show that the volcanic units of the Lathrop Wells center cannot be related to one another by fractional crystallization of a single magma batch, supporting a polycyclic model of volcanism. Structural models using existing data are used to evaluate the probability of magmatic disruption of a potential repository. Several permissive models have been developed but none lead to significant differences in calculating the disruption ratio. Work was initiated on the eruptive and subsurface effects of magmatic activity on a repository. (author)

Late Miocene marine tephra beds : recorders of rhyolitic volcanism in North Island, New Zealand

International Nuclear Information System (INIS)

Shane, P.; Black, T.; Eggins, S.; Westgate, J.

1998-01-01

A deep-sea sequence of 72 rhyolitic tephra beds, now exposed at Mahia Peninsula in the Hawke's Bay region of the east coast, North Island, New Zealand, provides a record of Late Miocene volcanism of the Coromandel Volcanic Zone (CVZ): the precursor to large-scale explosive volcanism of the Quaternary Taupo Volcanic Zone (TVZ). The geochemical signature of the glasses in the Miocene tephra has been protected from hydrothermal alteration and prolonged subaerial exposure that have affected proximal CVZ deposits. The tephra beds are primarily eruption-driven sediment gravity flows that have been emplaced into a trench-slope basin, some 300 km from active volcanoes. Their occurrence is consistent with long-distance fluvial transport followed by a point-source discharge into the deep-sea environment, and has no implications for the paleogeographic location of the basins relative to the volcanic arc. The tephra beds are calc-alkaline rhyolites with SiO 2 contents in the range 72-78 wt% (recalculated on a volatile-free basis), and are broadly similar to glassy rocks of the CVZ. Their major oxide, trace element, and REE compositions are indistinguishable from glasses of TVZ rhyolites. The trace element and REE compositional variability in the Late Miocene tephra beds, which were erupted over an estimated duration of c. 0.5-2.4 m.y. is no greater than that of large silicic eruptives of the last 350 ka, and is suggestive of a long-lived source and/or similar magmatic processes. However, the individual tephra beds are products of discrete homogeneous magma batches. New fission track ages of the Miocene tephra beds suggest the main period of volcaniclastic deposition occurred in the interval c. 9-7 Ma. This corresponds well with the initiation of rhyolitic volcanism in the CVZ at c. 10 Ma, and a major period of caldera formation that took place to c. 7 Ma. The ages suggest a sediment accumulation rate of between 0.23 and 1.2 m/ka (av. 0.4 m/ka), and a frequency of eruption of

Hydrothermal Carbonization of Seaweed For Advanced Biochar Production

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Prakoso Tirto

2018-01-01

Full Text Available Seaweed such as Eucheuma Cottonii is a potential source of biomaterialIts high moisture content makes it suitable for hydrothermal conversion process since it doesn’t need to utilize dry feedstock. The aim of this study is to convert the biomass of red seaweed Eucheuma Cottonii into alternative fuels and high value biomaterials using hydrothermal process. The hydrothermal process seaweed Eucheuma Cottonii produce two types of products, liquid product and char (solid. This research focus on the char product. The char from hydrothermal process was then activated using the tubular furnace. The yield for activated char is 7.5 % and results of SEM analysis of activated char showed the formation of allotropes carbon include carbon micro spheres, carbon micro fibres and graphene. These structures have encountered application in a wide range of technological fields, such as adsorption, catalysis, hydrogen storage or electronics.

Study on the hydrothermal treatment of Shenhua coal

Energy Technology Data Exchange (ETDEWEB)

Zhicai Wang; Hengfu Shui; Zhanning Pei; Jinsheng Gao [Anhui University of Technology, Ma' anshan (China). School of Chemistry and Chemical Engineering

2008-04-15

In this paper, the hydrothermal treatment of Shenhua coal was carried out under 0.1 MPa (initial pressure) nitrogen and different temperature. Effects of hydrothermal treatment on the structure and the hydro-liquefaction activity of Shenhua coal were investigated by the ultimate and proximate analyses, the FTIR measurements and TG analyses of hydrothermally treated coals, and the characterizations of extraction and swelling properties, and the batch hydro-liquefaction of treated coal were also carried out. The results indicate that hydrothermal treatment above 200{sup o}C can increase the hydrogen content of treated coal and decrease the yield of volatiles and the content of ash, especially a large amount of CO and CH{sub 4} are found in gas products obtained by the hydrothermal treatment above 250{sup o}C. Hydrothermal treatment disrupts the weak covalent bond such as ether, ester and side-chain substituent by hydrolysis and pyrolysis, and changes the distribution of H-bond in coal. The swelling ratio and the Soxhlet extraction yield of treated coal decrease with the increase of hydrothermal treatment temperature. The conversion of liquefaction and the yield of CS{sub 2}/NMP mixed solvent extraction at ambient temperature are enhanced by hydrothermal treatment at 300{sup o}C. Therefore hydrogen donation reactions and the rupture of non-covalent bond and weak covalent bonds present in the process of hydrothermal treatment resulting in the changes of structure and reactivity of Shenhua coal. The results show that the hydro-liquefaction activity of Shenhua coal can be improved by hydrothermal pretreatment between 250{sup o}C and 300{sup o}C. 15 refs., 5 figs., 4 tabs.

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

Directory of Open Access Journals (Sweden)

Andreas eTeske

2016-02-01

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

Gold-silver mining districts, alteration zones, and paleolandforms in the Miocene Bodie Hills Volcanic Field, California and Nevada

Science.gov (United States)

Vikre, Peter G.; John, David A.; du Bray, Edward A.; Fleck, Robert J.

2015-09-25

The Bodie Hills is a ~40 by ~30 kilometer volcanic field that straddles the California-Nevada state boundary between Mono Lake and the East Walker River. Three precious metal mining districts and nine alteration zones are delineated in Tertiary-Quaternary volcanic and Mesozoic granitic and metamorphic rocks that comprise the volcanic field. Cumulative production from the mining districts, Bodie, Aurora, and Masonic, is 3.4 million ounces of gold and 28 million ounces of silver. Small amounts of mercury were produced from the Potato Peak, Paramount-Bald Peak, and Cinnabar Canyon-US 395 alteration zones; a native sulfur resource in the Cinnabar Canyon-US 395 alteration zone has been identified by drilling. There are no known mineral resources in the other six alteration zones, Red Wash-East Walker River, East Brawley Peak, Sawtooth Ridge, Aurora Canyon, Four Corners, and Spring Peak. The mining districts and alteration zones formed between 13.4 and 8.1 Ma in predominantly ~15–9 Ma volcanic rocks of the Bodie Hills volcanic field. Ages of hydrothermal minerals in the districts and zones are the same as, or somewhat younger than, the ages of volcanic host rocks.

Coastal submarine hydrothermal activity off northern Baja California: 2. Evolutionary history and isotope geochemistry

Science.gov (United States)

Vidal, Victor M. V.; Vidal, Francisco V.; Isaacs, John D.

1981-10-01

A geochemical model of the Punta Banda submarine hydrothermal system (PBSHS) and Ensenada quadrangle subaerial hot springs is developed using 18O/16O, D/H, 34S/32S, 3H, water and gas chemistry. The PBSHS water is a primary high temperature, acid, reducing fluid of old seawater origin which has been titrated by cold, alkaline groundwater of meteoric origin. The final exiting solutions represent a 1 : 1 mixture of the two primary mixing components. In contrast, the subaerial hot spring waters are of unmixed meteoric origin. The subaerial hot spring gas is predominantly atmospheric N2, while the PBSHS contains large amounts of CH4 and N2 derived from trapped marine sediments of Cretaceous age; δS34 values of sampled hydrothermal waters are similar to Cretaceous marine sulfate values and suggest that the waters contacted Cretaceous marine sedimentary strata. The presence of the Alisitos and Rosario marine sedimentary formations of Cretaceous age within the Ensenada-Punta Banda quadrangle renders support to the above hypothesis. The data also demonstrate that pyrite mineralization and deposition in submarine hydrothermal environments result from the complexing of ferrous iron with elemental sulfur and sulfide and that submarine hydrothermal activity acts as a major source of silica, Ca2+, and trace metals and as a major sink for seawater Mg2+ and SO42-.

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

We report new whole rock U-Th and in-situ oxygen isotope compositions for partially melted (0–50 vol% melt), low-δ18O Pleistocene granitoid blocks ejected during the ∼7.7 ka caldera-forming eruption of Mt. Mazama (Crater Lake, Oregon). The blocks are interpreted to represent wall rocks of the climactic magma chamber that, prior to eruption, experienced variable amounts of exchange with meteoric hydrothermal fluids and subsequent partial melting. U-Th and oxygen isotope results allow us to examine the timescales of hydrothermal circulation and partial melting, and provide an “outside in” perspective on the buildup to the climactic eruption of Mt. Mazama. Oxygen isotope compositions measured in the cores and rims of individual quartz (n = 126) and plagioclase (n = 91) crystals, and for transects across ten quartz crystals, document zonation in quartz (Δ18OCore-Rim ≤ 0.1–5.5‰), but show homogeneity in plagioclase (Δ18OCore-Rim ≤ ±0.8‰). We propose that oxygen isotope zonation in quartz records hydrothermal exchange followed by high-temperature exchange in response to partial melting caused by injection of basaltic to andesitic recharge magma into the deeper portions of the chamber. Results of modeling of oxygen diffusion in quartz indicates that hydrothermal exchange in quartz occurred over a period of ∼1000–63,000 years. Models also suggest that the onset of melting of the granitoids occurred a minimum of ∼10–200 years prior to the Mazama climactic eruption, an inference which is broadly consistent with results for magnetite homogenization and for Zr diffusion in melt previously reported by others.Uranium-thorium isotope compositions of most granitoid blocks are in 238U excess, and are in agreement with a 238U enriched array previously measured for volcanic rocks at Mt. Mazama. Uranium excess in the granitoids is likely due to enrichment via hydrothermal circulation, given their low δ18O values. The sample with the

Soil gas composition from the 2001-2002 fissure in the Lakki Plain (Nisyros Island, Greece): evidences for shallow hydrothermal fluid circulation

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Venturi, Stefania; Tassi, Franco; Kanellopoulos, Christos; Vaselli, Orlando; Caponi, Chiara; Ricci, Andrea; Raspanti, Alessio; Gallorini, Andrea; Cabassi, Jacopo; Vougioukalakis, Georges

2016-04-01

Nisyros volcano (Aegean Sea, Greece) is currently classified in the "Very High Threat" category (Kinvig et al., 2010). Although the last volcanic activity, consisting of phreatic eruptions, occurred in the 19th century, Nisyros experienced an intense seismic activity during 1996-1998 accompanied by ground deformation and changes in the chemistry of fumarolic gases (Chiodini et al., 2002), pointing to a renewed unrest. Between November 2001 and December 2002, a NNE-oriented 600 m long fissure opened in the vegetated central part of the Lakki Plain. The fissure, 1-5 m wide and up to 15-20 m deep, showed neither vertical displacements nor gas release. No changes in the seismic and volcanic activity were observed during or after this event, which was interpreted as related to collapse of the upper caldera floor fine sediment cover (permeable sediment cover in the Lakki Plain conceals the underneath hydrothermal gas flow, preventing the typical surface manifestations (high temperature and CO2 flux), the chemistry of the interstitial gases reveals that deep-sourced fluids circulate within the deep permeable layers beneath the Lakki Plain enhancing alteration processes and formation of shallow collapsing structures. Chiodini G., Brombach T., Caliro S., Cardellini C., 2002. Geophys Res Lett, 29(16), 1759. Kinvig H.S., Winson A., Gottsmann J., 2010. Nat Hazards Earth Syst Sci, 10. Vougioukalakis G.E., Fytikas M., 2005. In Fytikas M., Vougioukalakis G.E. (Eds.), The South Aegean Active Volcanic Arc, Present Knowledge and Future Perspectives, Developments in Volcanology, Elsevier, Amsterdam The Netherlands, 2005, pp. 161-163.

The radiogenic and stable Sr isotope geochemistry of basalt weathering in Iceland: Role of hydrothermal calcite and implications for long-term climate regulation

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Andrews, M. Grace; Jacobson, Andrew D.

2017-10-01

Several studies have examined the geochemistry of Icelandic rivers to quantify the relationship between basalt weathering and long-term climate regulation. Recent research has suggested that the chemical weathering of hydrothermal and metamorphic calcite contributes significant quantities of HCO3- to the Icelandic riverine flux (Jacobson et al., 2015). Because the HCO3- derives from volcanic CO2 that was sequestered in mineral form prior to atmospheric injection, the strength of the basalt weathering feedback occurring in Iceland may be lower than previously realized. To test these hypotheses, we analyzed the radiogenic and stable Sr isotope composition (87Sr/86Sr and δ88/86Sr) of the same suite of water, rock, and mineral samples as examined in Jacobson et al. (2015), and we developed a simple model of the long-term C cycle that considers the transformation of volcanic CO2 to HCO3- during subsurface silicate weathering, which is a precursor to hydrothermal calcite formation. Interpretations based on 87Sr/86Sr and Ca/Sr ratios suggest that conservative, three-component mixing between basalt, calcite, and atmospheric deposition adequately explains river geochemistry. On average, the δ88/86Sr values of glacial and non-glacial rivers (0.414‰ and 0.388‰, respectively) are generally higher than those for basalt (0.276‰); however, calcite δ88/86Sr values (0.347‰) are also higher than those for basalt and span the range of riverine values. Thus, riverine δ88/86Sr values are also consistent three-component mixing between basalt, calcite, and atmospheric deposition. Isotopic fractionation is not required to explain riverine trends. Finally, model equations for the long-term C cycle demonstrate that subsurface silicate weathering reduces the magnitude of the volcanic CO2 degassing flux, which in turn causes the atmosphere to stabilize at lower pCO2 values compared to the case where no subsurface silicate weathering occurs. However, the proportion of the net

Xenopumice erupted on 15 October 2011 offshore of El Hierro (Canary Islands): a subvolcanic snapshot of magmatic, hydrothermal and pyrometamorphic processes

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Del Moro, S.; Di Roberto, A.; Meletlidis, S.; Pompilio, M.; Bertagnini, A.; Agostini, S.; Ridolfi, F.; Renzulli, A.

2015-06-01

On 15 October 2011, a submarine eruption offshore of El Hierro Island gave rise to floating volcanic products, known as xenopumices, i.e., pumiceous xenoliths partly mingled and coated with the juvenile basanitic magma. Over the last few years, no consensus in the scientific community in explaining the origin of these products has been reached. In order to better understand the formation of xenopumice, we present a textural, mineralogical, and geochemical study of the possible magmatic, hydrothermal, and pyrometamorphic processes, which usually operate in the plumbing systems of active volcanoes. We carried out a comprehensive SEM investigation and Sr-Nd-Pb isotope analyses on some samples representative of three different xenopumice facies. All the data were compared with previous studies, new data for El Hierro extrusives and a literature dataset of Canary Islands igneous and sedimentary rocks. In the investigated xenopumices, we emphasize the presence of restitic magmatic phases as well as crystallization of minerals (mainly olivine + pyroxene + magnetite aggregates) as pseudomorphs after pre-existing mafic phenocrysts, providing evidence of pyrometamorphism induced by the high-T juvenile basanitic magma. In addition, we identify veins consisting of zircon + REE-oxides + mullite associated with Si-rich glass and hydrothermal quartz, which indicate the fundamental role played by hydrothermal fluid circulation in the xenopumice protolith. The petrological data agree with a pre-syneruptive formation of the xenopumice, when El Hierro basanite magma intruded hydrothermally altered trachyandesite to trachyte rocks and triggered local partial melting. Therefore, the El Hierro xenopumice represents a snapshot of the transient processes at the magma-wall rock interface, which normally occurs in the feeding system of active volcanoes.

Water column imaging on hydrothermal vent in Central Indian Ridge

Science.gov (United States)

Koh, J.; Park, Y.

2017-12-01

Water column imaging with Multibeam echosounder systems (MBES) is recently becoming of increasing interest for oceanographic studies. Especially gas bubbles and hot water exposed from hydrothermal vents make acoustic impedance anomalies in cold seawater, water column imaging is very useful for the researchers who want to detect some kinds of hydrothermal activity. We conducted a hydrothermal exploration program, called "INVENT17", using the MBES system, KONGBERG EM122 (12kHz, 1°×1°), mounted on R/V ISABU and we deployed other equipments including video guided hydraulic grab, tow-yo CTD and general CTD with MAPR (Miniature Autonomous Plume Recorder) in 2017. First, to evaluate its capabilities of detection of hydrothermal vent, the surveys using the MBES were conducted at the Solitaire Field, previously identified hydrothermal area of the Central Indian Ridge. The bathymetric data obtained from MBES provided information about detailed morphology of seafloor, but we were not able to achieve the information from the water column imaging data. But the clue of existence of active hydrothermal vent was detected through the values of ΔNTU, dEh/dt, and OPR gained from MAPR, the data means that the hydrothermal activity affects 100m from the seafloor. It could be the reason that we can't find the hydrothermal activity because the range resolution of water column imaging is pretty rough so that the size of 100m-scaled activity has low possibility to distinguish from seafloor. The other reason is there are no sufficient objects to cause strong scattering like as CO2 bubbles or droplets unlike in the mid-Okinawa Trough. And this suggests that can be a important standard to identify properties of hydrothermal vent sites depending on the presence of scattering objects in water mass. To justify this, we should perform more chemical analysis of hot water emanating from hydrothermal vent and collected several bottles of water sample to do that.

Chronology of the 2015 eruption of Hakone volcano, Japan: geological background, mechanism of volcanic unrest and disaster mitigation measures during the crisis

Science.gov (United States)

Mannen, Kazutaka; Yukutake, Yohei; Kikugawa, George; Harada, Masatake; Itadera, Kazuhiro; Takenaka, Jun

2018-04-01

The 2015 eruption of Hakone volcano was a very small phreatic eruption, with total erupted ash estimated to be in the order of only 102 m3 and ballistic blocks reaching less than 30 m from the vent. Precursors, however, had been recognized at least 2 months before the eruption and mitigation measures were taken by the local governments well in advance. In this paper, the course of precursors, the eruption and the post-eruptive volcanic activity are reviewed, and a preliminary model for the magma-hydrothermal process that caused the unrest and eruption is proposed. Also, mitigation measures taken during the unrest and eruption are summarized and discussed. The first precursors observed were an inflation of the deep source and deep low-frequency earthquakes in early April 2015; an earthquake swarm then started in late April. On May 3, steam wells in Owakudani, the largest fumarolic area on the volcano, started to blowout. Seismicity reached its maximum in mid-May and gradually decreased; however, at 7:32 local time on June 29, a shallow open crack was formed just beneath Owakudani as inferred from sudden tilt change and InSAR analysis. The same day mud flows and/or debris flows likely started before 11:00 and ash emission began at about 12:30. The volcanic unrest and the eruption of 2015 can be interpreted as a pressure increase in the hydrothermal system, which was triggered by magma replenishment to a deep magma chamber. Such a pressure increase was also inferred from the 2001 unrest and other minor unrests of Hakone volcano during the twenty-first century. In fact, monitoring of repeated periods of unrest enabled alerting prior to the 2015 eruption. However, since open crack formation seems to occur haphazardly, eruption prediction remains impossible and evacuation in the early phase of volcanic unrest is the only way to mitigate volcanic hazard.[Figure not available: see fulltext.

Concentration and distribution of dissolved amino acids in a shallow hydrothermal system, Vulcano Island (Italy)

Energy Technology Data Exchange (ETDEWEB)

Svensson, E.; Skoog, A. [University of Connecticut, Groton, CT (United States). Dept. of Marine Sciences; Amend, J.P. [Washington University, St. Louis, MO (United States). Dept. of Earth and Planetary Sciences

2004-09-01

Hydrothermal systems are known to harbour a large number of microorganisms, but the organic chemical composition of the solution that comprises their potential substrate is largely unknown. Concentrations and distributions of dissolved free amino acids (DFAA) and dissolved combined amino acids (DCAA) were determined in fluids from the moderate-temperature (42-89{sup o}C), shallow hydrothermal system on the volcanically active island of Vulcano, Italy. The seven samples represent three different geological settings on the island; shallow ({approx} 1 m) submarine vents, geothermal wells, and seeps in heated beach sediments, in addition to ambient local seawater from the bay, Baia di Levante. All hydrothermal sites, with one exception, had TDAA concentrations that were 3-114 times higher than local seawater in Baia di Levante. There were large similarities in amino acid concentration and composition among samples from the same geological setting. The highest amino acid concentrations were found at sites with acidic and reducing conditions, which also had the largest freshwater component. An unusually high fraction of the TDAA pool was represented by DFAA (33-87%), possibly due to in situ acid hydrolysis of DCAA to DFAA. Both DFAA and DCAA concentrations were correlated to DOC, indicating similar source and sink functions for these pools. The yield of TDAA (TDAA-carbon as fraction of organic carbon) ranged from 2% to 25%, which is high compared with non-hydrothermal settings, and indicates high biological lability. The mole fraction of {beta}-alanine plus {gamma}-aminobutyric acid (% BALA + GABA) was 2-2.7% of TDAA, also indicating high biological lability. Owing to the high over-all amino acid concentrations, the high fraction of DFAAs, and the high biological lability of the organic matter, organic matter in general and amino acids specifically could represent significant carbon and energy sources for archaea and bacteria in this hydrothermal system. The clear

ASI-Volcanic Risk System (SRV): a pilot project to develop EO data processing modules and products for volcanic activity monitoring, first results.

Science.gov (United States)

Silvestri, M.; Musacchio, M.; Buongiorno, M. F.; Dini, L.

2009-04-01

The Project called Sistema Rischio Vulcanico (SRV) is funded by the Italian Space Agency (ASI) in the frame of the National Space Plan 2003-2005 under the Earth Observations section for natural risks management. The SRV Project is coordinated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) which is responsible at national level for the volcanic monitoring. The project philosophy is to implement, by incremental versions, specific modules which allow to process, store and visualize through Web GIS tools geophysical parameters suitable for volcanic risk management. The ASI-SRV is devoted to the development of an integrated system based on Earth Observation (EO) data to respond to specific needs of the Italian Civil Protection Department (DPC) and improve the monitoring of Italian active volcanoes during all the risk phases (Pre Crisis, Crisis and Post Crisis). The ASI-SRV system provides support to risk managers during the different volcanic activity phases and its results are addressed to the Italian Civil Protection Department (DPC). SRV provides the capability to manage the import many different EO data into the system, it maintains a repository where the acquired data have to be stored and generates selected volcanic products. The processing modules for EO Optical sensors data are based on procedures jointly developed by INGV and University of Modena. This procedures allow to estimate a number of parameters such as: surface thermal proprieties, gas, aerosol and ash emissions and to characterize the volcanic products in terms of composition and geometry. For the analysis of the surface thermal characteristics, the available algorithms allow to extract information during the prevention phase and during the Warning and Crisis phase. In the prevention phase the thermal analysis is directed to the identification of temperature variation on volcanic structure which may indicate a change in the volcanic activity state. At the moment the only sensor that

Preparation high photocatalytic activity of CdS/halloysite nanotubes (HNTs) nanocomposites with hydrothermal method

Science.gov (United States)

Xing, Weinan; Ni, Liang; Huo, Pengwei; Lu, Ziyang; Liu, Xinlin; Luo, Yingying; Yan, Yongsheng

2012-10-01

A novel nanocatalyst CdS/halloysite nanotubes (HNTs) was synthesized by hydrothermal method with direct growth of CdS nanoparticles on the surface of HNTs. The as-prepared photocatalysts had been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis DRS), Fourier transform infrared (FT-IR) and the thermo gravimetric analysis (TGA). The photocatalytic activity of the sample was evaluated by the degradation of tetracycline (TC) under visible light irradiation. Benefit from the excellent properties of CdS and HNTs, the photocatalyst exhibited good photocatalytic activity and stability. In order to find out the optimum synthesis condition to obtain the best photocatalytic activity, a series of experiments were performed with different CdS loading capacity, different sources of sulfide and different hydrothermal temperatures, etc. The best photodegradation rate could reach 93% in 60 min under visible light irradiation. Therefore, the combination of CdS nanoparticles with HNTs endowed this material with a potential use in environmental treatments in industries.

New structural, hydrogeological and hydrothermal insights on Cumbre Vieja (La Palma, Canary Islands, Spain)

Science.gov (United States)

Barde-Cabusson, S.; Finizola, A.; Torres, P.; Víctor Villasante-Marcos, V.; Abella, R.; Aragó, S.; Berthod, C.; Ibarra, P.; Geyer Traver, A.

2013-12-01

Determining the link between shallow structure and volcanism is a topic of interest in Volcanology. We carried out a geophysical study devoted to the characterization of the major structural limits influencing volcanic hydrothermal activity and underground meteoric circulations in La Palma (Canary Islands). Since 1 Ma volcanic activity concentrates at the southern half of the island, on the Cumbre Vieja volcanic rift-zone. During the 1949 eruption a N-S fault system, facing west, developed in the summit area of Cumbre Vieja. This was interpreted as the surface expression of an incipient deformation zone on the western flank. The distribution of the recent activity and faulting indicate that a discontinuity may be present beneath the western flank of Cumbre Vieja, along which a future collapse may occur. Our study, which combines the application of self-potential and soil temperature measurements, provides new information to characterize and locate the limits guiding upward or downward fluid circulation and possibly associated to future failures and potential landslides on the Cumbre Vieja rift-zone. We found a clear asymmetry of the self-potential signal between the eastern and the western flanks of Cumbre Vieja. Strong infiltration of meteoric water seems to affect most of the summit axis while we observe poor variation in the self-potential values on the western flank. This could be explained by a constant thickness of the vadose zone on this flank, i.e., the presence of an impermeable layer at constant depth. This layer could correspond to the landslide interface associated to the previous Cumbre Nueva edifice destruction, on which Cumbre Vieja is currently growing. This constant self-potential pattern is interrupted by at least one other main infiltration zone, near Tajuya volcano, at 1200 m a.s.l. on the western flank, where field observation allowed identifying a small horst-graben system. However it is not clear if this fault system results from local

Galileo SSI Observations of Volcanic Activity at Tvashtar Catena, Io

Science.gov (United States)

Milazzo, M. P.; Keszthely, L. P.; Radebaugh, J.; Davies, A. G.; Turtle, E. P.; Geissler, P.; Klaasen, K. P.; McEwen, A. S.

2005-01-01

Introduction: We report on the analysis of the Galileo SSI's observations of the volcanic activity at Tvashtar Catena, Io as discussed by Milazzo et al. Galileo's Solid State Imager (SSI) observed Tvashtar Catena (63 deg N, 120 deg W) four times between November 1999 and October 2001, providing a unique look at the distinctive high latitude volcanism on Io. The November 1999 observation spatially resolved, for the first time, an active extraterrestrial fissure eruption. The brightness temperature of the lavas at the November 1999 fissure eruption was 1300 K. The second observation (orbit I27, February 2000) showed a large (approx. 500 sq km) region with many, small spots of hot, active lava. The third observation was taken in conjunction with a Cassini observation in December 2000 and showed a Pele-like plume deposition ring, while the Cassini images revealed a 400 km high Pele-type plume above the Catena. The final Galileo SSI observation of Tvashtar was acquired in October 2001, and all obvious (to SSI) activity had ceased, although data from Galileo's Near Infrared Mapping Spectrometer (NIMS) indicated that there was still significant thermal emission from the Tvashtar region. We have concentrated on analyzing the style of eruption during orbit I27 (February 2000). Comparison with a lava flow cooling model indicates that the behavior of the Tvashtar eruption during I27 does not match that of "simple" advancing lava flows. Instead, it may be an active lava lake or a complex set of lava flows with episodic, overlapping (in time and space) eruptions.

International Collaboration on Building Local Technical Capacities for Monitoring Volcanic Activity at Pacaya Volcano, Guatemala.

Science.gov (United States)

Escobar-Wolf, R. P.; Chigna, G.; Morales, H.; Waite, G. P.; Oommen, T.; Lechner, H. N.

2015-12-01

Pacaya volcano is a frequently active and potentially dangerous volcano situated in the Guatemalan volcanic arc. It is also a National Park and a major touristic attraction, constituting an important economic resource for local municipality and the nearby communities. Recent eruptions have caused fatalities and extensive damage to nearby communities, highlighting the need for risk management and loss reduction from the volcanic activity. Volcanic monitoring at Pacaya is done by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH), instrumentally through one short period seismic station, and visually by the Parque Nacional Volcan de Pacaya y Laguna de Calderas (PNVPLC) personnel. We carry out a project to increase the local technical capacities for monitoring volcanic activity at Pacaya. Funding for the project comes from the Society of Exploration Geophysicists through the Geoscientists Without Borders program. Three seismic and continuous GPS stations will be installed at locations within 5 km from the main vent at Pacaya, and one webcam will aid in the visual monitoring tasks. Local educational and outreach components of the project include technical workshops on data monitoring use, and short thesis projects with the San Carlos University in Guatemala. A small permanent exhibit at the PNVPLC museum or visitor center, focusing on the volcano's history, hazards and resources, will also be established as part of the project. The strategy to involve a diverse group of local collaborators in Guatemala aims to increase the chances for long term sustainability of the project, and relies not only on transferring technology but also the "know-how" to make that technology useful. Although not a primary research project, it builds on a relationship of years of joint research projects at Pacaya between the participants, and could be a model of how to increase the broader impacts of such long term collaboration partnerships.

Investigation of the thermal regime and geologic history of the Cascade volcanic arc: First phase of a program for scientific drilling in the Cascade Range

Energy Technology Data Exchange (ETDEWEB)

Priest, G.R.

1987-01-01

A phased, multihole drilling program with associated science is proposed as a means of furthering our understanding of the thermal regime and geologic history of the Cascade Range of Washington, Oregon, and northern California. The information obtained from drilling and ancillary geological and geophysical investigations will contribute to our knowledge in the following general areas: (1) the magnitude of the regional background heat flow of parts of the Quaternary volcanic belt dominated by the most abundant volcanic rock types, basalt and basaltic andesite; (2) the nature of the heat source responsible for the regional heat-flow anomaly; (3) the characteristics of the regional hydrothermal and cold-water circulation; the rates of volcanism for comparison with models for the rate and direction of plate convergence of the Cascades; (5) the history of deformation and volcanism in the volcanic arc that can be related to subduction; (6) the present-day stress regime of the volcanic arc and the relation of these stresses to plate interactions and possible large earthquakes; and the current geometry of the subducted oceanic plate below the Cascade Range and the relationship of the plate to the distribution of heat flow, Quaternary volcanism, and Quaternary deformation. Phase I research will be directed toward a detailed investigation of the Santiam Pass segment. In concert with the Santiam Pass research, a detailed study of the nearby Breitenbush Hot Springs area is also recommended as a component of Phase I. The object of the Breitenbush research is to study one of the hottest known Cascade hydrothermal systems, which coincidentally also has a good geological and geophysical data base. A coordinated program of drilling, sampling, subsurface measurements, and surface surveys will be associated with the drilling of several holes.

Significant discharge of CO2 from hydrothermalism associated with the submarine volcano of El Hierro Island

Science.gov (United States)

Santana-Casiano, J. M.; Fraile-Nuez, E.; González-Dávila, M.; Baker, E. T.; Resing, J. A.; Walker, S. L.

2016-05-01

The residual hydrothermalism associated with submarine volcanoes, following an eruption event, plays an important role in the supply of CO2 to the ocean. The emitted CO2 increases the acidity of seawater. The submarine volcano of El Hierro, in its degasification stage, provided an excellent opportunity to study the effect of volcanic CO2 on the seawater carbonate system, the global carbon flux, and local ocean acidification. A detailed survey of the volcanic edifice was carried out using seven CTD-pH-ORP tow-yo studies, localizing the redox and acidic changes, which were used to obtain surface maps of anomalies. In order to investigate the temporal variability of the system, two CTD-pH-ORP yo-yo studies were conducted that included discrete sampling for carbonate system parameters. Meridional tow-yos were used to calculate the amount of volcanic CO2 added to the water column for each surveyed section. The inputs of CO2 along multiple sections combined with measurements of oceanic currents produced an estimated volcanic CO2 flux = 6.0 105 ± 1.1 105 kg d-1 which is ~0.1% of global volcanic CO2 flux. Finally, the CO2 emitted by El Hierro increases the acidity above the volcano by ~20%.

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.

Hydrogeochemical surveillance of La Soufriere de Guadeloupe volcano (F. W. I. ), 1979-1985: activity decrease or confining

Energy Technology Data Exchange (ETDEWEB)

Bigot, S.; Hammouya, G.

1987-04-07

Since the 1975-1977 crisis, changes in physico-chemical characters of La Soufriere's hot springs are observed. These variations have dual origin: - decrease in exchanges between volatile compounds from deep origin and phreatic waters, because of fissures filling by hydrothermal deposits in the whole dome that involves progresive confining: - decrease of volcanic activity.

Comparison of hydrothermal activity between the Adriatic and the Red Sea rift margins

Science.gov (United States)

Ball, Philip; Incerpi, Nicolò; Birkle, Peter; Lacsamana, Elizabeth; Manatschal, Gianreto; Agar, Susan; Zhang, Shuo; Borsato, Ron

2017-04-01

Detailed field studies, and access to high-quality seismic reflection and refraction data have led to an improved understanding of the architecture and evolution of magma poor and magma rich margins. Associated with the spatial-temporal evolution of the rift, it is evident that there are evolving, extensive, fluid-rock interactions due to the infiltration of fluids within the sediment, basement and lithospheric mantle. Key questions therefore arise: What are the different fluid-rock reactions that can be typed to different geodynamic stages of the rift evolution? What are their compositions and how do they interact with their environment (basement, sediments, evaporites, hydrosphere, and magmatism)? What are the implications for the evolution of the margin rheology, thermal structure, depositional environments/organic matter maturity, and reservoir quality? The Adriatic paleo-rifted margin is preserved in both SE Switzerland and northern Italy. The field exposures provide a unique opportunity to study the fluid flow history of a hyperextended magma poor extensional margin. Analysis of breccias, cement veins and replacement minerals reveal that the margin records a complex, long-lasting history of dolomitization, calcification and silicification during the Jurassic rifting. The Red Sea by contrast is a young rifted margin. It differs from the paleo-Adriatic margin by several characteristics: volcanism is more evident, and syn-tectonic sediments, including evaporites (halite and anhydrite) are thicker. Several core and fluid samples are available from both onshore and offshore wells, which reveal rift-related hydrothermal alteration. In addition, we find evidence for the presence of an extreme dynamic hydraulic system with infiltration of surface water into sub-salt units during Late Pleistocene. In this study we present results from petrographic and geochemical analysis of basement and sedimentary rocks from Adriatic field-derived samples and core/subsurface fluid

Study of the structure changes caused by volcanic activity in Mexico applying the lineament analysis to the Aster (Terra) satellite data.

Science.gov (United States)

Arellano-Baeza, A. A.; Garcia, R. V.; Trejo-Soto, M.; Molina-Sauceda, E.

Mexico is one of the most volcanically active regions in North America Volcanic activity in central Mexico is associated with the subduction of the Cocos and Rivera plates beneath the North American plate Periods of enhanced microseismic activity associated with the volcanic activity of the Colima and Popocapetl volcanoes are compared to some periods of low microseismic activity We detected changes in the number and orientation of lineaments associated with the microseismic activity due to lineament analysis of a temporal sequence of high resolution satellite images of both volcanoes 15 m resolution multispectral images provided by the ASTER VNIR instrument were used The Lineament Extraction and Stripes Statistic Analysis LESSA software package was employed for the lineament extraction

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.

Transition of neogene arc volcanism in central-western Hokkaido, viewed from K-Ar ages, style of volcanic activity, and bulk rock chemistry

Energy Technology Data Exchange (ETDEWEB)

Hirose, Wataru; Iwasaki, Miyuki; Nakagawa, Mitsuhiro [Hokkaido Univ., Sapporo (Japan)

2000-02-01

Spatial and temporal variations in late Cenozoic volcanism of southwestern Hokkaido at the northern end of NE-Japan arc have been clarified by 261 K-Ar and 76 FT ages including 49 newly determined K-Ar ages, volcanic stratigraphy, physical volcanology and whole-rock geochemistry. Arc volcanism characterized by rocks with low-Ti and Nb, and by across-arc increase in K{sub 2}O content in these rocks has continued at least since 12 Ma. Based on volcanic stratigraphy, physical volcanology and whole-rock geochemistry, volcanism after 12 Ma can be subdivided into 4 stages, 12-5, 5-1.7, and 1.7-0 Ma. The volcanism from 12 Ma to 5 Ma extended northward widely compared with distribution of Quaternary arc volcanism (1.7-0 Ma). This suggests that the arc trench junction between Kuril and NE-Japan arc's trenches was located about 100 km northward from the present position. Since around 5 Ma until 1.7 Ma, different type of volcanism under local extension field, characterized by a group of monogenetic volcanoes of alkali basalt and shield volcanoes of calc-alkaline andesite, had occurred at northern end of the volcanic region (Takikawa-Mashike region). During and after this volcanism, the northern edge of arc volcanism in the area has migrated southward. This suggests that the trench junction has migrated about 100 km southward since {approx}5 Ma. The quaternary arc volcanism (1.7-0 Ma) has been restricted at the southern part of the region. The volcanism since 12 Ma might be influenced by oblique subduction of Pacific plate beneath Kuril arc, resulting in the formation of local back arc basin at the junction and to southward migration of the trench junction. (author)

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).

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)

Seismicity and volcanic activity in Japan based on crustal thermal activity. 1; Chikaku no netsukatsudo ni motozuku Nippon no jishin kazan katsudo. 1

Energy Technology Data Exchange (ETDEWEB)

Hayakawa, M [Tokai Univ., Tokyo (Japan). School of Marine Science and Technology

1996-05-01

This paper describes the following matters about correlation between seismic and volcanic activities and thermal energy. Investigations on the status of seismic and volcanic activities in the Japanese archipelago during about 400 years in the past reveals the following matters: noticing earthquakes with magnitudes of upper M6 to about M7, flows of energy going outward from deep crust of the earth repeat ups and downs, whereas several prominent rising periods having certain time widths can be seen; volcanic activities are included in the rising period at the same rank as seismic activities; with regard to years 1900 and on, the similar fact can be seen if the Japanese archipelago is divided into a north portion, a south portion, and an extremely south portion southern than the Hiuga area; and the present time is going toward a period of rise in energy flows. In other words, it is thought that the crust and the uppermost portion of the mantle form one body like an organic body, making an action like a geyser releasing the energy outward. 3 refs., 2 figs., 1 tab.

Native gold and gold-rich sulfide deposits in a submarine basaltic caldera, Higashi-Aogashima hydrothermal field, Izu-Ogasawara frontal arc, Japan

Science.gov (United States)

Iizasa, Kokichi; Asada, Akira; Mizuno, Katsunori; Katase, Fuyuki; Lee, Sangkyun; Kojima, Mitsuhiro; Ogawa, Nobuhiro

2018-04-01

Sulfide deposits with extremely high Au concentrations (up to 275 ppm; avg. 102 ppm, n = 15), high Au/Ag ratios (0.24, n = 15), and low Cu/(Cu + Zn) ratios (0.03, n = 15) were discovered in 2015 in active hydrothermal fields at a water depth of 760 m in a basalt-dominated submarine caldera in the Izu-Ogasawara frontal arc, Japan. Native gold grains occur in massive sulfide fragments, concretions, and metalliferous sediments from a sulfide mound (40 m across and 20 m high) with up to 30-m-high black smoker chimneys. Tiny native gold grains up to 14 μm in diameter are mainly present in sulfide fallouts from chimney orifices and plumes. Larger native gold grains up to 150 μm long occur mostly as discrete particles and/or with amorphous silica and sulfides. The larger gold grains are interpreted to represent direct precipitation from Au-bearing hydrothermal fluids circulating in and/or beneath the unconsolidated sulfide mound deposits. Sulfur isotope compositions from a limited number of sulfide separates (n = 4) range from 4.3 to 5.8‰ δ34S, similar to the quaternary volcanic rocks of the arc. Barite separates have values of 22.2 and 23.1‰, close to modern seawater values, and indicate probable seawater sulfate origin. The Cu, Zn, and Pb concentrations in bulk samples of sulfide-rich rocks are similar to those of volcanogenic massive sulfides formed in continental crustal environments. The gold is interpreted to have formed by low-temperature hydrothermal activity, perhaps genetically different from systems with documented magmatic contributions or from seafloor hydrothermal systems in other island arc settings. Its presence suggests that basalt-dominated submarine calderas situated on relatively thick continental crust in an intraoceanic arc setting such as the Higashi-Aogashima knoll caldera may be perspective for gold mineralization.

Late Pleistocene and Holocene activity of the Atacazo-Ninahuilca Volcanic Complex (Ecuador)

NARCIS (Netherlands)

Hidalgo, Silvana; Monzier, Michel; Almeida, Eduardo; Chazot, Gilles; Eissen, Jean-Philippe; van der Plicht, Johannes; Hall, Minard L.

2008-01-01

The Atacazo-Ninahuilca Volcanic Complex (ANVC) is located in the Western Cordillera of Ecuador, 10 km southwest of Quito. At least six periods of Pleistocene to Holocene activity (N1 to N6) have been preserved in the geologic record as tephra fallouts and pyroclastic flow deposits. New field data,

Relationship between the latest activity of mare volcanism and topographic features of the Moon

Science.gov (United States)

Kato, Shinsuke; Morota, Tomokatsu; Yamaguchi, Yasushi; Watanabe, Sei-ichiro; Otake, Hisashi; Ohtake, Makiko

2016-04-01

Lunar mare basalts provide insights into compositions and thermal history of lunar mantle. According to crater counting analysis with remote sensing data, the model ages of mare basalt units indicate a second peak of magma activity at the end of mare volcanism (~2 Ga), and the latest eruptions were limited in the Procellarum KREEP Terrane (PKT), which has high abundances of heat-producing elements. In order to understand the mechanism for causing the second peak and its magma source, we examined the correlation between the titanium contents and eruption ages of mare basalt units using compositional and chronological data updated by SELENE/Kaguya. Although no systematic relationship is observed globally, a rapid increase in mean titanium (Ti) content occurred at 2.3 Ga in the PKT, suggesting that the magma source of mare basalts changed at that time. The high-Ti basaltic eruption, which occurred at the late stage of mare volcanism, can be correlated with the second peak of volcanic activity at ~2 Ga. The latest volcanic activity can be explained by a high-Ti hot plume originated from the core-mantle boundary. If the hot plume was occurred, the topographic features formed by the hot plume may be remained. We calculated the difference between topography and selenoid and found the circular feature like a plateau in the center of the PKT, which scale is ~1000 km horizontal and ~500 m vertical. We investigated the timing of ridge formation in the PKT by using stratigraphic relationship between mare basalts and ridges. The ridges were formed before and after the high-Ti basaltic eruptions and seem to be along with the plateau. These results suggest that the plateau formation is connected with the high-Ti basaltic eruptions.

Catastrophic debris flows transformed from landslides in volcanic terrains : mobility, hazard assessment and mitigation strategies

Science.gov (United States)

Scott, Kevin M.; Macias, Jose Luis; Naranjo, Jose Antonio; Rodriguez, Sergio; McGeehin, John P.

2001-01-01

Communities in lowlands near volcanoes are vulnerable to significant volcanic flow hazards in addition to those associated directly with eruptions. The largest such risk is from debris flows beginning as volcanic landslides, with the potential to travel over 100 kilometers. Stratovolcanic edifices commonly are hydrothermal aquifers composed of unstable, altered rock forming steep slopes at high altitudes, and the terrain surrounding them is commonly mantled by readily mobilized, weathered airfall and ashflow deposits. We propose that volcano hazard assessments integrate the potential for unanticipated debris flows with, at active volcanoes, the greater but more predictable potential of magmatically triggered flows. This proposal reinforces the already powerful arguments for minimizing populations in potential flow pathways below both active and selected inactive volcanoes. It also addresses the potential for volcano flank collapse to occur with instability early in a magmatic episode, as well as the 'false-alarm problem'-the difficulty in evacuating the potential paths of these large mobile flows. Debris flows that transform from volcanic landslides, characterized by cohesive (muddy) deposits, create risk comparable to that of their syneruptive counterparts of snow and ice-melt origin, which yield noncohesive (granular) deposits, because: (1) Volcano collapses and the failures of airfall- and ashflow-mantled slopes commonly yield highly mobile debris flows as well as debris avalanches with limited runout potential. Runout potential of debris flows may increase several fold as their volumes enlarge beyond volcanoes through bulking (entrainment) of sediment. Through this mechanism, the runouts of even relatively small collapses at Cascade Range volcanoes, in the range of 0.1 to 0.2 cubic kilometers, can extend to populated lowlands. (2) Collapse is caused by a variety of triggers: tectonic and volcanic earthquakes, gravitational failure, hydrovolcanism, and

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.

Toward a pro-active scientific advice on global volcanic activity within the multi-hazard framework of the EU Aristotle project

Science.gov (United States)

Barsotti, Sara; Duncan, Melanie; Loughlin, Susan; Gísladóttir, Bryndis; Roberts, Matthew; Karlsdóttir, Sigrún; Scollo, Simona; Salerno, Giuseppe; Corsaro, Rosa Anna; Charalampakis, Marinos; Papadopoulos, Gerassimos

2017-04-01

The demand for timely analysis and advice on global volcanic activity from scientists is growing. At the same time, decision-makers require more than an understanding of hazards; they need to know what impacts to expect from ongoing and future events. ARISTOTLE (All Risk Integrated System TOwards Trans-boundary hoListic Early-warning) is a two-year EC funded pilot project designed to do just that. The Emergency Response Coordination Centre (ERCC) works to support and coordinate response to disasters both inside and outside Europe using resources from the countries participating in the European Union Civil Protection Mechanism. Led by INGV and ZAMG, the ARISTOTLE consortium comprises 15 institutions across Europe and aims to deliver multi-hazard advice on natural events, including their potential interactions and impact, both inside and outside of Europe to the ERCC. Where possible, the ERCC would like a pro-active provision of scientific advice by the scientific group. Iceland Met Office leads the volcanic hazards work, with BGS, INGV and NOA comprising the volcano observatory team. At this stage, the volcanology component of the project comprises mainly volcanic ash and gas dispersal and potential impact on population and ground-based critical infrastructures. We approach it by relying upon available and official volcano monitoring institutions' reporting of activity, existing assessments and global databases of past events, modelling tools, remote-sensing observational systems and official VAAC advisories. We also make use of global assessments of volcanic hazards, country profiles, exposure and proxy indicators of threat to livelihoods, infrastructure and economic assets (e.g. Global Volcano Model outputs). Volcanic ash fall remains the only hazard modelled at the global scale. Volcanic risk assessments remain in their infancy, owing to challenges related to the multitude of hazards, data availability and model representation. We therefore face a number of

The volcanic acidification of glacial Lake Caviahue, Province of Neuquen, Argentina

Science.gov (United States)

Varekamp, Johan C.

2008-12-01

Lake Caviahue (northern Patagonia, Argentina) is a large glacial lake acidified by volcanic fluids from Copahue volcano. The lake and the feeding rivers were sampled annually from 1997 till early 2006, including the eruptive period of 2000. Lake Caviahue waters evolved over time, with the most concentrated waters in 2000 during the eruptive period, followed by gradual dilution that was interrupted by renewed acidification in 2003-2004. Inversion of the lake water data and application of a dynamic non-steady state model for the lake provides our best quantitative estimates for the variation in element fluxes over the 9-year period. The model flux results agree well with most of the measured fluxes. The Copahue hydrothermal system had gently declining element fluxes between 1997 and mid-1999, although the lake was still becoming more concentrated. About 2-3 months before the 2000 eruption, element fluxes increased strongly, but the hydrothermal fluxes almost shutoff directly after the main eruptive events. The fluxes of several elements recovered post-2001, with an increase in element fluxes in 2003-2004; the lake became more dilute between 2004 and 2006. The intrusion of new magma into the hydrothermal system just prior to the 2000 eruption led to enhanced water rock interaction, with higher concentrations of the rock forming elements in the fluids, and the hot spring flow rate increased as a result of the higher pressure in the reservoir. The fluids became saturated in alunite and jarosite, and they were already saturated with anhydrite. Precipitation of these minerals possibly led to a decreased permeability of the hydrothermal reservoir, leading to the strongly reduced element fluxes just after the eruption. In addition, K, Al and S were retained in the newly precipitated minerals as well, further diminishing their export. The acidification in 2003-2004 may have resulted from a new small intrusion of magma or resulted from seismic activity that created new

Developing International Guidelines on Volcanic Hazard Assessments for Nuclear Facilities

Science.gov (United States)

Connor, Charles

2014-05-01

Worldwide, tremendous progress has been made in recent decades in forecasting volcanic events, such as episodes of volcanic unrest, eruptions, and the potential impacts of eruptions. Generally these forecasts are divided into two categories. Short-term forecasts are prepared in response to unrest at volcanoes, rely on geophysical monitoring and related observations, and have the goal of forecasting events on timescales of hours to weeks to provide time for evacuation of people, shutdown of facilities, and implementation of related safety measures. Long-term forecasts are prepared to better understand the potential impacts of volcanism in the future and to plan for potential volcanic activity. Long-term forecasts are particularly useful to better understand and communicate the potential consequences of volcanic events for populated areas around volcanoes and for siting critical infrastructure, such as nuclear facilities. Recent work by an international team, through the auspices of the International Atomic Energy Agency, has focused on developing guidelines for long-term volcanic hazard assessments. These guidelines have now been implemented for hazard assessment for nuclear facilities in nations including Indonesia, the Philippines, Armenia, Chile, and the United States. One any time scale, all volcanic hazard assessments rely on a geologically reasonable conceptual model of volcanism. Such conceptual models are usually built upon years or decades of geological studies of specific volcanic systems, analogous systems, and development of a process-level understanding of volcanic activity. Conceptual models are used to bound potential rates of volcanic activity, potential magnitudes of eruptions, and to understand temporal and spatial trends in volcanic activity. It is these conceptual models that provide essential justification for assumptions made in statistical model development and the application of numerical models to generate quantitative forecasts. It is a

Soil gas radon and volcanic activity at El Hierro (Canary Islands) before and after the 2011-2012 submarine eruption

Science.gov (United States)

Barrancos, J.; Padilla, G.; Hernandez Perez, P. A.; Padron, E.; Perez, N.; Melian Rodriguez, G.; Nolasco, D.; Dionis, S.; Rodriguez, F.; Calvo, D.; Hernandez, I.

2012-12-01

El Hierro is the youngest and southernmost island of the Canarian archipelago and represents the summit of a volcanic shield elevating from the surrounding seafloor at depth of 4000 m to up to 1501 m above sea level. The island is believed to be near the present hotspot location in the Canaries with the oldest subaerial rocks dated at 1.12 Ma. The subaerial parts of the El Hierro rift zones (NE, NW and S Ridges) are characterized by tightly aligned dyke complexes with clusters of cinder cones as their surface expressions. Since July 16, 2011, an anomalous seismicity at El Hierro Island was recorded by IGN seismic network. Volcanic tremor started at 05:15 hours on October 10, followed on the afternoon of October 12 by a green discolouration of seawater, strong bubbling and degassing indicating the initial stage of submarine volcanic eruption at approximately 2 km off the coast of La Restinga, El Hierro. Soil gas 222Rn and 220Rn activities were continuously measured during the period of the recent volcanic unrest occurred at El Hierro, at two different geochemical stations, HIE02 and HIE03. Significant increases in soil 222Rn activity and 222Rn/220Rn ratio from the soil were observed at both stations prior the submarine eruption off the coast of El Hierro, showing the highest increases before the eruption onset and the occurrence of the strongest seismic event (M=4.6). A statistical analysis showed that the long-term trend of the filtered data corresponded closely to the seismic energy released during the volcanic unrest. The observed increases of 222Rn are related to the rock fracturing processes (seismic activity) and the magmatic CO2 outflow increase, as observed in HIE03 station. Under these results, we find that continuous soil radon studies are important for evaluating the volcanic activity of El Hierro and they demonstrate the potential of applying continuous monitoring of soil radon to improve and optimize the detection of early warning signals of future

Chemistry of a serpentinization-controlled hydrothermal system at the Lost City hydrothermal vent field

Science.gov (United States)

Ludwig, K. A.; Kelley, D. S.; Butterfield, D. A.; Nelson, B. K.; Karson, J. A.

2003-12-01

The Lost City Hydrothermal Field (LCHF), at 30° N near the Mid-Atlantic Ridge, is an off-axis, low temperature, high-pH, ultramafic-hosted vent system. Within the field, carbonate chimneys tower up to 60 m above the seafloor, making them the tallest vent structures known. The chemistry of the vent structures and fluids at the LCHF is controlled by reactions between seawater and ultramafic rocks beneath the Atlantis massif. Mixing of warm alkaline vent fluids with seawater causes precipitation of calcium carbonate and growth of the edifaces, which range from tall, graceful pinnacles to fragile flanges and colloform deposits. Geochemical and petrological analyses of the carbonate rocks reveal distinct differences between the active and extinct structures. Actively venting chimneys and flanges are extremely porous, friable formations composed predominantly of aragonite and brucite. These structures provide important niches for well-developed microbial communities that thrive on and within the chimney walls. Some of the active chimneys may also contain the mineral ikaite, an unstable, hydrated form of calcium carbonate. TIMS and ICP-MS analyses of the carbonate chimneys show that the most active chimneys have low Sr isotope values and that they are low in trace metals (e.g., Mn, Ti, Pb). Active structures emit high-pH, low-Mg fluids at 40-90° C. The fluids also have low Sr values, indicating circulation of hydrothermal solutions through the serpentinite bedrock beneath the field. In contrast to the active structures, extinct chimneys are less porous, are well lithified, and they are composed predominantly of calcite that yields Sr isotopes near seawater values. Prolonged lower temperature seawater-hydrothermal fluid interaction within the chimneys results in the conversion of aragonite to calcite and in the enrichment of some trace metals (e.g., Mn, Ti, Co, Zn). It also promotes the incorporation of foraminifera within the outer, cemented walls of the carbonate

Geological interpretation of volcanism and segmentation of the Mariana back-arc spreading center between 12.7°N and 18.3°N

Science.gov (United States)

Anderson, Melissa O.; Chadwick, William W.; Hannington, Mark D.; Merle, Susan G.; Resing, Joseph A.; Baker, Edward T.; Butterfield, David A.; Walker, Sharon L.; Augustin, Nico

2017-06-01

The relationships between tectonic processes, magmatism, and hydrothermal venting along ˜600 km of the slow-spreading Mariana back-arc between 12.7°N and 18.3°N reveal a number of similarities and differences compared to slow-spreading mid-ocean ridges. Analysis of the volcanic geomorphology and structure highlights the complexity of the back-arc spreading center. Here, ridge segmentation is controlled by large-scale basement structures that appear to predate back-arc rifting. These structures also control the orientation of the chains of cross-arc volcanoes that characterize this region. Segment-scale faulting is oriented perpendicular to the spreading direction, allowing precise spreading directions to be determined. Four morphologically distinct segment types are identified: dominantly magmatic segments (Type I); magmatic segments currently undergoing tectonic extension (Type II); dominantly tectonic segments (Type III); and tectonic segments currently undergoing magmatic extension (Type IV). Variations in axial morphology (including eruption styles, neovolcanic eruption volumes, and faulting) reflect magma supply, which is locally enhanced by cross-arc volcanism associated with N-S compression along the 16.5°N and 17.0°N segments. In contrast, cross-arc seismicity is associated with N-S extension and increased faulting along the 14.5°N segment, with structures that are interpreted to be oceanic core complexes—the first with high-resolution bathymetry described in an active back-arc basin. Hydrothermal venting associated with recent magmatism has been discovered along all segment types.

Volcanic eruptions on Io

Science.gov (United States)

Strom, R. G.; Schneider, N. M.; Terrile, R. J.; Hansen, C.; Cook, A. F.

1981-01-01

Nine eruption plumes which were observed during the Voyager 1 encounter with Io are discussed. During the Voyager 2 encounter, four months later, eight of the eruptions were still active although the largest became inactive sometime between the two encounters. Plumes range in height from 60 to over 300 km with corresponding ejection velocities of 0.5 to 1.0 km/s and plume sources are located on several plains and consist of fissures or calderas. The shape and brightness distribution together with the pattern of the surface deposition on a plume 3 is simulated by a ballistic model with a constant ejection velocity of 0.5 km/s and ejection angles which vary from 0-55 deg. The distribution of active and recent eruptions is concentrated in the equatorial regions and indicates that volcanic activity is more frequent and intense in the equatorial regions than in the polar regions. Due to the geologic setting of certain plume sources and large reservoirs of volatiles required for the active eruptions, it is concluded that sulfur volcanism rather than silicate volcanism is the most likely driving mechanism for the eruption plumes.

A new Bayesian Event Tree tool to track and quantify volcanic unrest and its application to Kawah Ijen volcano

Science.gov (United States)

Tonini, Roberto; Sandri, Laura; Rouwet, Dmitri; Caudron, Corentin; Marzocchi, Warner; Suparjan

2016-07-01

Although most of volcanic hazard studies focus on magmatic eruptions, volcanic hazardous events can also occur when no migration of magma can be recognized. Examples are tectonic and hydrothermal unrest that may lead to phreatic eruptions. Recent events (e.g., Ontake eruption on September 2014) have demonstrated that phreatic eruptions are still hard to forecast, despite being potentially very hazardous. For these reasons, it is of paramount importance to identify indicators that define the condition of nonmagmatic unrest, in particular for hydrothermal systems. Often, this type of unrest is driven by movement of fluids, requiring alternative monitoring setups, beyond the classical seismic-geodetic-geochemical architectures. Here we present a new version of the probabilistic BET (Bayesian Event Tree) model, specifically developed to include the forecasting of nonmagmatic unrest and related hazards. The structure of the new event tree differs from the previous schemes by adding a specific branch to detail nonmagmatic unrest outcomes. A further goal of this work consists in providing a user-friendly, open-access, and straightforward tool to handle the probabilistic forecast and visualize the results as possible support during a volcanic crisis. The new event tree and tool are here applied to Kawah Ijen stratovolcano, Indonesia, as exemplificative application. In particular, the tool is set on the basis of monitoring data for the learning period 2000-2010, and is then blindly applied to the test period 2010-2012, during which significant unrest phases occurred.

Volcanic eruption plumes on Io

International Nuclear Information System (INIS)

Strom, R.G.; Terrile, R.J.; Masursky, H.; Hansen, C.

1979-01-01

The detection of an umbrella-shaped plume extending about 280 km above the bright limb of Io was one of the most important discoveries made during the Voyager 1 encounter with the jovian system. This discovery proves that Io is volcanically active at present, and the number and magnitude of these eruptions indicate that Io is the most volcanically active body so far discovered in the Solar System. Preliminary analyses of these eruptive plumes are presented. (U.K.)

Raman-IR vibrational and XRD characterization of ancient and modern mineralogy from volcanic eruption in Tenerife Island: Implication for Mars

Directory of Open Access Journals (Sweden)

E.A. Lalla

2016-07-01

Full Text Available A detailed vibrational Raman-IR spectroscopic and diffractional analyses have been performed on basalts from two locations from Tenerife Island: (1 the Arenas Negras volcano which belongs to the historical eruption not showing visible alteration and (2 Pillow Lavas zone from Anaga Massif which shows a clearly fluid-rock interaction caused by submarine alteration. These places have been extensively studied due to its similarity with the surface of Mars. The analysis is based on the mineral detection of selected samples by a Micro-Raman study of the materials. The complementary techniques have confirmed the mineralogy detected by the Raman measurement. The results show a volcanic environment behavior with primary phases like olivine, pyroxene, and feldspar/plagioclase. Moreover, the presence of accessory minerals or secondary mineralization like phosphate, iron oxides, zeolite or carbonates shows the alteration processes on each outcrop. The variation in the crystallinity and amorphous phases is related to fluid-rock interaction caused by hydrothermal episodes and external weathering processes, which shows several analogies with the ancient volcanic activity from Mars.

Response to"Analysis of the Treatment, by the U.S. Department of Energy, of the FEP Hydrothermal Activity in the Yucca Mountain Performance Assessment" by Yuri Dublyansky

Energy Technology Data Exchange (ETDEWEB)

Houseworth, J.E.; Hardin, E.

2008-11-17

This paper presents a rebuttal to Dublyansky (2007), which misrepresents technical issues associated with hydrothermal activity at the proposed Yucca Mountain nuclear waste repository and their importance to the long-term performance of the repository. In this paper, questions associated with hydrothermal activity are reviewed and the justification for exclusion of hydrothermal activity from performance assessment is presented. The hypothesis that hydrothermal upwelling into the present-day unsaturated zone has occurred at Yucca Mountain is refuted by the unambiguous evidence that secondary minerals and fluid inclusions in the unsaturated zone formed in an unsaturated environment from downward percolating meteoric waters. The thermal history at Yucca Mountain, inferred from fluid inclusion and isotopic data, is explained in terms of the tectonic extensional environment and associated silicic magmatism. The waning of tectonic extension over millions of years has led to the present-day heat flux in the Yucca Mountain region that is below average for the Great Basin. The long time scales of tectonic processes are such that any effects of a resumption of extension or silicic magmatism on hydrothermal activity at Yucca Mountain over the 10,000-year regulatory period would be negligible. The conclusion that hydrothermal activity was incorrectly excluded from performance assessment as asserted in Dublyansky (2007) is contradicted by the available technical and regulatory information.

Mineralogy and Acid-Extractable Geochemistry from the Loki's Castle Hydrothermal Field, Norwegian Sea at 74 degrees N (South Knipovich Ridge)

Science.gov (United States)

Barriga, F. J.; Fonseca, R.; Dias, S.; Cruz, I.; Carvalho, C.; Relvas, J. M.; Pedersen, R.

2010-12-01

The Loki’s Castle hydrothermal vent field was discovered in the summer of 2008 during a cruise led by the Centre of Geobiology of the University of Bergen, integrated in the H2Deep Project (Eurocores, ESF; see Pedersen et al., 2010, AGU Fall Meeting, Session OS26). Fresh volcanic glasses analyzed by EPMA are basalts. The vent site is composed of several active, over 10 m tall chimneys, producing up to 320 C fluid, at the top of a very large sulfide mound (estimated diameter 200 m). Mineralogy: The main sulfide assemblage in chimneys consists of sphalerite (Sp), pyrite (Py) and pyrrhotite, with lesser chalcopyrite (Ccp). Sulphide-poor selected samples collected at the base of chimneys are mostly composed of anhydrite (Anh), gypsum and talc (Tlc). Association of quartz, anhydrite, gypsum and barite were also found in some of the samples. The sulphide-poor samples from the base of the chimneys denote seawater interaction with the hydrothermal fluid and consequent decrease in temperature, precipitating sulfates. Sphalerite compositions are Zn(0.61-0.70)Fe(0.39-0.30)S. The variations in Fe content are consistent with those of hot, reduced hydrothermal fluids. The observed sulfide assemblage is consistent with the temperature of 320C measured in Loki’s Castle vents. Compositional zonation in sphalerites suggests different pulses of activity of the hydrothermal system, with higher contents of Zn in the center of the crystals. Geochemistry: Here we report preliminary data part of a major analytical task of sequential extraction of metals from sediments in the vicinity of Loki’s Castle, in an attempt to detect correlations with microbial populations and/or subseafloor mineralized intervals. The abundances of Cu, Pb, Ni, Cr, Zn, Fe, Mn and Co in sediments were determined by aqua regia extraction on subsamples from 7 gravity cores. Several anomalous intervals were sampled, in which Cu<707ppm, Ni shows many weak peaks (<50ppm), Cr shows 6 peaks (<121ppm), Zn shows 4 well

Geochemical and geophysical monitoring activities in Campo de Calatrava Volcanic Field (Spain)

Science.gov (United States)

Luengo-Oroz, Natividad; Villasante-Marcos, Víctor; López-Díaz, Rubén; Calvo, Marta; Albert, Helena; Domínguez Cerdeña, Itahiza

2017-04-01

The Campo de Calatrava Volcanic Field (CCVF) or Spanish Central Volcanic Zone is located in central continental Spain (Ciudad Real province) and covers about 5000 km2. It includes around 240 eruptive centers, mainly monogenetic basaltic cones but also explosive maar structures. According to K-Ar geochronology, its main activity phase occurred during Pliocene and Pleistocene epochs (between 5 and 1.7 Ma) and involved alkaline to ultraalkaline magmas, although an older ultrapotassic phase is dated around 8.7-6.4 Ma. However, some recent works have proposed Holocene ages for some of the volcanic products, opening the possibility of considering the CCVF "active" according to international standards. Responding to this situation, the Instituto Geográfico Nacional (IGN) has initiated geochemical and geophysical monitoring activities in the CCVF. Here, we describe these ongoing efforts and we report results about groundwater geochemistry at several natural highly-gaseous springs in the area (hervideros), as well as soil temperature, CO2 diffuse flux from the soil and electrical self-potential data mapped on a small degassing structure called La Sima. In order to analyze microseismicity or any seismic anomaly in the CCVF, a seismic station has also been installed close to this degassing structure. Physicochemical parameters (temperature, pH, Eh and electric conductivity) were measured in situ in four springs and samples were taken in order to analyze major ions and trace elements. Total composition of dissolved gases and helium isotopic ratios were also determined. To complete soil temperature, self-potential and gas prospections performed in La Sima, soil gases were sampled at the bottom of the structure at a depth of 20 cm. Analysis of the total gas composition found 957400 ppm of CO2. Low values of O2 and N2 were also detected (5600 and 24800 ppm respectively).

Evidence for recent hydrothermal activity in the Central Indian Basin

Digital Repository Service at National Institute of Oceanography (India)

Iyer, S.D.; ShyamPrasad, M.; Gupta, S.M.; Charan, S.N.

fracturing provide conditions conducive to hydrothermal discharge and accumulation of the resultant hydrothermal precipitates (Alt et al., 1987). Bonatti and Joensuu (1966) were among the first to report on the occurrence of spongy iron-oxides from a...-S fracture zones, traverse at 73”E, 76”3O’E and 79”E in the basin (Kamesh Raju, 1993). Many seamounts dot the floor of the CIB (Mukhopadhyay and Khadge, 1990; Kamesh Raju et al., 1993), some of them having caldera (Kodagali, 1991; Kodagali, pers. commun...

Review of the Cambrian volcanic activity in Morocco: geochemical fingerprints and geotectonic implications for the rifting of West Gondwana

Science.gov (United States)

Pouclet, André; El Hadi, Hassan; Álvaro, J. Javier; Bardintzeff, Jacques-Marie; Benharref, Mohammed; Fekkak, Abdelilah

2018-03-01

Volcanic activities related to the opening of a Cambrian rift in Morocco were widespread from the Fortunian to the Cambrian Epoch 3. Numerous data are available from northwestern volcanic sites, particularly in the western High Atlas, but they are scarce from the southeastern sites. New data are documented here from the volcanic formations exposed in the Jbel Tazoult n'Ouzina of the Tafilalt Province, eastern Anti-Atlas and dated to Cambrian Epoch 2-3. The Cambrian volcanic activities recorded in the High Atlas, Anti-Atlas, and Coastal Meseta are synthesized to refine their stratigraphic setting and to characterize their magmatic affinities and fingerprints. Six volcanic pulses are determined as tholeiitic, transitional, and alkaline suites. The tholeiitic and transitional magmas originated from primitive mantle and E-MORB-type sources with a spinel- and garnet-bearing lherzolite composition. Some of them were modified by assimilation-fractional crystallisation processes during crust-mantle interactions. The alkaline magmas fit with an OIB-type and a garnet-bearing lherzolite source. The palaeogeographic distribution of the magmatic suites was controlled by the lithospheric thinning of the Cambrian Atlas Rift and lithospheric constraints of the Pan-African metacraton and West African craton.

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.

Magmatic activity stages of the El'brus volcanic center (Great Caucasus): isotope geochronological data

International Nuclear Information System (INIS)

Chernyshev, I.V.; Lebedev, V.A.; Bubnov, S.N.; Arakelyants, M.M.; Gol'tsman, Yu.V.

2001-01-01

The age of volcanites in the Elbrus volcanic center was determined by the methods of K-Ar- and Rb-Sr-dating to ascertain stages of magmatic activity in the area. The data obtained suggest existence of at least two stages of magmatic activity: Middle Neopleistocene (225-180 thous. years) and Late Neopleistocene-Holocene ( [ru

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.

The 2012-2014 eruptive cycle of Copahue Volcano, Southern Andes. Magmatic-Hydrothermal system interaction and manifestations.

Science.gov (United States)

Morales, Sergio; Alarcón, Alex; Basualto, Daniel; Bengoa, Cintia; Bertín, Daniel; Cardona, Carlos; Córdova, Maria; Franco, Luis; Gil, Fernando; Hernandez, Erasmo; Lara, Luis; Lazo, Jonathan; Mardones, Cristian; Medina, Roxana; Peña, Paola; Quijada, Jonathan; San Martín, Juan; Valderrama, Oscar

2015-04-01

deformation of the volcanic edifice detected by GPS network. In this new eruptive process, the record of tremor was followed by particular seismic quiescence, as precursors of explosive activity which evolved from low acoustic energy signals toward more energetic signals with impulsive first arrivals and strong attenuation, joined to night incandescence in the main vent without evident juvenile material ejected, which could be associated to the temporal depression of the hydrothermal system located in the volcano system. The recent eruptive episode at Copahue Volcano is a good example of the complex temporal evolution of the interaction between magmatic and hydrothermal systems.

Seismic and GPS constraints on the dynamics and kinematics of the Yellowstone volcanic field

Science.gov (United States)

Smith, R. B.; Farrell, J.; Jordan, M.; Puskas, C.; Waite, G. P.

2007-12-01

The seismically and volcanically Yellowstone hotspot resulted from interaction of a mantle plume with the overriding North America plate. This feature and related processes have modified continental lithosphere producing the Yellowstone-Snake River Plain-Newberry silicic volcanic field (YSRPN) system, with its NE volcanically active Yellowstone volcanic field. The size and accessibility of the Yellowstone area has allowed a range of geophysical experiments including earthquake monitoring and seismic and GPS imaging of this system. Seismicity is dominated by small-magnitude normal- to oblique-slip faulting earthquake swarms with shallow focal depths, maximum of ~5 km, restricted by high temperatures and a weak elastic layer. There is developing evidence of non-double couple events. Outside the caldera, earthquakes are deeper, ~20 km, and capable of M 7+ earthquakes. We integrate the results from a multi-institution experiment that recorded data from 110 seismic stations and 180 GPS stations for 1999-2004. The tomographic images confirm the existence of a low Vp-body beneath the Yellowstone caldera at depths greater than 8 km, possibly representing hot, crystallizing magma. A key result of our study is a volume of anomalously low Vp and Vp/Vs in the northwestern part of the volcanic field at shallow depths of stress field inverted from seismic and GPS data is dominated by regional SW extension with superimposed volumetric expansion and uplift from local volcanic sources. Mantle tomography derived from integrated inversion of teleseismic and local earthquake data constrained by geoid, crustal structure, discontinuity structure reveals an upper-mantle low P and S velocity body extends from 80 km to ~250 km directly beneath Yellowstone and then continues to 650 km with unexpected westward tilt to the west at ~60° with a 1% to 2% melt. This geometry is consistent with the ascent of the buoyant magma entrained in eastward return-flow of the upper mantle. Some remaining

Collateral variations between the concentrations of mercury and other water soluble ions in volcanic ash samples and volcanic activity during the 2014-2016 eruptive episodes at Aso volcano, Japan

Science.gov (United States)

Marumoto, Kohji; Sudo, Yasuaki; Nagamatsu, Yoshizumi

2017-07-01

During 2014-2016, the Aso volcano, located in the center of the Kyushu Islands, Japan, erupted and emitted large amounts of volcanic gases and ash. Two episodes of the eruption were observed; firstly Strombolian magmatic eruptive episodes from 25 November 2014 to the middle of May 2015, and secondly phreatomagmatic and phreatic eruptive episodes from September 2015 to February 2016. Bulk chemical analyses on total mercury (Hg) and major ions in water soluble fraction in volcanic ash fall samples were conducted. During the Strombolian magmatic eruptive episodes, total Hg concentrations averaged 1.69 ± 0.87 ng g- 1 (N = 33), with a range from 0.47 to 3.8 ng g- 1. In addition, the temporal variation of total Hg concentrations in volcanic ash varied with the amplitude change of seismic signals. In the Aso volcano, the volcanic tremors are always observed during eruptive stages and quiet interludes, and the amplitudes of tremors increase at eruptive stages. So, the temporal variation of total Hg concentrations could provide an indication of the level of volcanic activity. During the phreatomagmatic and phreatic eruptive episodes, on the other hand, total Hg concentrations in the volcanic ash fall samples averaged 220 ± 88 ng g- 1 (N = 5), corresponding to 100 times higher than those during the Strombolian eruptive episode. Therefore, it is possible that total Hg concentrations in volcanic ash samples are largely varied depending on the eruptive type. In addition, the ash fall amounts were also largely different among the two eruptive episodes. This can be also one of the factors controlling Hg concentrations in volcanic ash.

Permeability changes due to mineral diagenesis in fractured crust: implications for hydrothermal circulation at mid-ocean ridges

Science.gov (United States)

Fontaine, Fabrice Jh.; Rabinowicz, Michel; Boulègue, Jacques

2001-01-01

black or white 'smokers'. We show that the development of this front is independent of the Rayleigh number of the hydrothermal flow, indicating that the mineral precipitation causes cold, diffusive vents. Finally, we present a model suggesting that the development of smokers is possible when successive tectonic/volcanic events produce a network of new permeable fissures that can overcome the permeability decrease caused by mineral precipitation. Such a model is consistent with recent seismic data showing hydrothermal vents located at seismologically active ridge segments.

Geochronology of Hydrothermal Processes Leading to the Formation of the Au–U Mineralization at the Rompas Prospect, Peräpohja Belt, Northern Finland: Application of Paired U–Pb Dating of Uraninite and Re–Os Dating of Molybdenite to the Identification of Multiple Hydrothermal Events in a Metamorphic Terrane

Directory of Open Access Journals (Sweden)

Ferenc Molnár

2017-09-01

Full Text Available The Peräpohja belt comprises a greenschist to amphibolite facies; multiply-folded supracrustal sequence of quartzites; mafic volcanics; carbonate rocks; black shales; mica schists and greywackes deposited from ca. 2.44 Ga to 1.92 Ga; during protracted rifting of the Archaean basement. Metamorphism and multiple folding of the basin fill occurred during the Svecofennian orogeny (1.92–1.80 Ga. The Rompas Au–U mineralization is hosted within deformed and metamorphosed calcsilicate veins in mafic volcanics. Textural evidence suggests that deposition and periods of uraninite re-mobilization were followed by localized hydrocarbon-bearing fluid flow which produced pyrobitumen crusts around grains of uraninite. Gold precipitated during the latest hydrothermal event at around 1.75 Ga. In situ U–Pb dating of uraninite by laser ablation inductively coupled mass spectroscopy (LA-ICP-MS, and Re–Os dating of molybdenite, indicate that primary hydrothermal uranium mineralization forms two age clusters; about 2.03–2.01 and 1.95–1.94 Ga. Resetting of the U–Pb system and precipitation of new generations of uraninite are associated with major deformation and metamorphic stages of the Svecofennian orogeny at 1.91–1.89 Ga, 1.85 Ga, and 1.80 Ga. Gold deposition was synchronous with the emplacement of the 1.75–1.78 Ga late/post-orogenic granitoids. The gold-producing hydrothermal event is also recorded by Re–Os dating of molybdenite from the gold-bearing Mg-metasomatized metasedimentary and metavolcanic units at the Palokas prospect; a few kilometres from Rompas. Results of this study confirm that some domains in the structure of uraninite may preserve the original crystallization age, despite an overprinting amphibolite facies metamorphic and other hydrothermal events. The study supports the utility of in situ U–Pb dating of uraninite and the ability of Re–Os dating to assist in sorting out different hydrothermal events in areas with complex

Structural control on arc volcanism: The Caviahue Copahue complex, Central to Patagonian Andes transition (38°S)

Science.gov (United States)

Melnick, Daniel; Folguera, Andrés; Ramos, Victor A.

2006-11-01

This paper describes the volcanostratigraphy, structure, and tectonic implications of an arc volcanic complex in an oblique subduction setting: the Caviahue caldera Copahue volcano (CAC) of the Andean margin. The CAC is located in a first-order morphotectonic transitional zone, between the low and narrow Patagonian and the high and broad Central Andes. The evolution of the CAC started at approximately 4-3 Ma with the opening of the 20 × 15 km Caviahue pull-apart caldera; Las Mellizas volcano formed inside the caldera and collapsed at approximately 2.6 Ma; and the Copahue volcano evolved in three stages: (1) 1.2-0.7 Ma formed the approximately 1 km thick andesitic edifice, (2) 0.7-0.01 Ma erupted andesitic-dacitic subglacial pillow lavas, and (3) 0.01-0 Ma erupted basaltic-andesites and pyroclastic flows from fissures, aligned cones, and summit craters. Magma ascent has occurred along planes perpendicular to the least principal horizontal stress, whereas hydrothermal activity and hot springs also occur along parallel planes. At a regional scale, Quaternary volcanism concentrates along the NE-trending, 90 km long Callaqui-Copahue-Mandolegüe lineament, the longest of the southern volcanic zone, which is here interpreted as an inherited crustal-scale transfer zone from a Miocene rift basin. At a local scale within the CAC, effusions are controlled by local structures that formed at the intersection of regional fault systems. The Central to Patagonian Andes transition occurs at the Callaqui-Copahue-Mandolegüe lineament, which decouples active deformation from the intra-arc strike-slip Liquiñe-Ofqui fault zone to the south and the backarc Copahue-Antiñir thrust system.

δ18O and δD variations in some volcanic lakes on the Cameroon Volcanic Line (West-Africa: generating isotopic baseline data for volcano monitoring and surveillance in Cameroon

Directory of Open Access Journals (Sweden)

. Issa

2014-06-01

Full Text Available Based on geo-anthropological and geochemical studies, catastrophes similar to the unprecedented gas explosions in the mid-1980s from the Cameroonian killer lakes Nyos and Monoun, might occur in any of the 37 other lakes located along the Cameroon Volcanic Line (CVL. Because people could suffer loss and desolation from predictable catastrophes in the future, monitoring/surveillance policies must be established. Due to their location, crater lakes integrate the geochemical processes that develop in the Earth’s crust due to magmatic activities. Therefore, monitoring the surface manifestations of those deep seated and/or hydrothermal processes might reveal increases/decreases in magmatic activities. The anomalous changes in a volcanic lake induced by mixing with exogenous fluids that have a specific δ18O and δD compositional fingerprint (magmatic, metamorphic, etc. could be utilized to predict volcanic hazards. If the steady state of a lake environment and the external and intrinsic parameters that control its hydrodynamics are clearly identified and reasonably understood, the anomalous evolutionary processes that compromise its stability can be identified. This study attempts to collect the δ18O and δD data from 17 Cameroonian lakes to help establish a volcano-related monitoring/surveillance network. This work identifies the processes that control the isotopic composition of the lakes and assesses the intra-/inter- and spatial δ18O/δD variations. Almost all of the lakes contain meteoric water. These lakes are mostly isotopically stratified; epilimnia is generally more positive than the hypolimnia. However, although the rainfall is gradually depleted in heavy isotopes when moving from the South to the North due to the latitude effect, the lakes become more enriched (0.6‰/100 km due to evaporation. The evaluated impact of several parameters on the isotopic variation suggests that the hydrological setting may play an important, albeit not

Mercury as a proxy for volcanic activity during extreme environmental turnover

DEFF Research Database (Denmark)

Sial, A.N.; Lacerda, L.D.; Ferreira, V.P.

2013-01-01

(KTB) and was, perhaps, responsible for dramatic climatic changes and decrease in biodiversity and mass extinction. We have used Hg concentrations as a proxy for volcanic activity and atmospheric Hg and CO2 buildup across the KTB at three localities. In the Salta Basin, Argentina, Hg contents display...... close to) this transition. At Stevns Klint, Denmark, Hg contents reached almost 250 ng·g− 1 within a 5 cm thick-clay layer, the Fiskeler Member (‘Fish Clay’) that comprises the KTB. Some co-variation between Hg and Al2O3 contents has been observed in all of the studied sections across the KTB......, suggesting that Hg is probably adsorbed onto clays. Thermo-desorption experiments in selected samples from the Yacoraite Formation showed Hg+ 2 as the major species present, which is in agreement with a volcanic origin. Combined Hg and C-isotope chemostratigraphy may become a powerful tool for the eventual...

Acoustic waves in the atmosphere and ground generated by volcanic activity

International Nuclear Information System (INIS)

Ichihara, Mie; Lyons, John; Oikawa, Jun; Takeo, Minoru

2012-01-01

This paper reports an interesting sequence of harmonic tremor observed in the 2011 eruption of Shinmoe-dake volcano, southern Japan. The main eruptive activity started with ashcloud forming explosive eruptions, followed by lava effusion. Harmonic tremor was transmitted into the ground and observed as seismic waves at the last stage of the effusive eruption. The tremor observed at this stage had unclear and fluctuating harmonic modes. In the atmosphere, on the other hand, many impulsive acoustic waves indicating small surface explosions were observed. When the effusion stopped and the erupted lava began explosive degassing, harmonic tremor started to be transmitted also to the atmosphere and observed as acoustic waves. Then the harmonic modes became clearer and more stable. This sequence of harmonic tremor is interpreted as a process in which volcanic degassing generates an open connection between the volcanic conduit and the atmosphere. In order to test this hypothesis, a laboratory experiment was performed and the essential features were successfully reproduced.

Acoustic waves in the atmosphere and ground generated by volcanic activity

Energy Technology Data Exchange (ETDEWEB)

Ichihara, Mie; Lyons, John; Oikawa, Jun; Takeo, Minoru [Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032 (Japan); Instituto Geofisico, Escuela Politecnica Nacional, Ladron de Guevara E11-253, Aptdo 2759, Quito (Ecuador); Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032 (Japan)

2012-09-04

This paper reports an interesting sequence of harmonic tremor observed in the 2011 eruption of Shinmoe-dake volcano, southern Japan. The main eruptive activity started with ashcloud forming explosive eruptions, followed by lava effusion. Harmonic tremor was transmitted into the ground and observed as seismic waves at the last stage of the effusive eruption. The tremor observed at this stage had unclear and fluctuating harmonic modes. In the atmosphere, on the other hand, many impulsive acoustic waves indicating small surface explosions were observed. When the effusion stopped and the erupted lava began explosive degassing, harmonic tremor started to be transmitted also to the atmosphere and observed as acoustic waves. Then the harmonic modes became clearer and more stable. This sequence of harmonic tremor is interpreted as a process in which volcanic degassing generates an open connection between the volcanic conduit and the atmosphere. In order to test this hypothesis, a laboratory experiment was performed and the essential features were successfully reproduced.

Degassing of different magma batches as the main controlling factor for fumarolic fluid chemistry at the Planchón-Peteroa-Azufre Volcanic Complex (Argentina-Chile) in 2010-2015

Science.gov (United States)

Tassi, Franco; Aguilera, Felipe; Benavente, Oscar; Paonita, Antonio; Chiodini, Giovanni; Caliro, Stefano; Agusto, Mariano; Gutierrez, Francisco; Capaccioni, Bruno; Vaselli, Orlando; Caselli, Alberto

2016-04-01

This study presents the first geochemical data of gas discharges collected during five sampling campaigns (February 2010 to March 2015), from the NNE-oriented Planchón-Peteroa-Azufre Volcanic Complex (PPAVC), located in the Transitional Southern Volcanic Zone (TSVZ) at the border between Argentina and Chile. In 2012, the acidic gas species of the low temperature (up to 102 °C) fumaroles from the Peteroa summit showed a huge increase (SO2>CO2) with respect to the 2010-2011 period, whereas the typical hydrothermal compounds (CH4 and light hydrocarbons) decreased. Such a dramatic compositional change was apparently indicating a pulse of magmatic fluids. By contrast, the temporal evolution of the δ18O-H2O, δD-H2O, R/Ra and 13C-CO2 values suggested an enhanced fluid contribution from a shallow source. In 2014-2015, the dominant hydrothermal signature characterizing the 2010-2011 fumaroles was almost completely restored. The temporary decoupling of the chemical and isotopic parameters can only be reconciled by admitting the occurrence of a double source of magmatic fluids: a basaltic batch, controlling the fumarolic chemistry in 2010-2011 and 2014-2015, and a small, shallower dacitic batch, likely affected by a significant crustal contamination, whose contribution to the fumarolic fluid emissions achieved its maximum in 2012. It cannot be ruled out that the phreatic to phreatomagmatic eruptions (VEI ≤2) that have affected Peteroa volcano from January 2010 to July 2011 have played a significant role for the modification of the deep feeding source of the fumarolic gases. The disturbance created by the volcanic events and the related seismic activity (MW<3), possibly related to the devastating Maule earthquake occurred on February 27 2010, could have activated a silent dacitic magma batch that in 2012 imposed over that of basaltic composition. Although this scenario provides a reliable explanation for the peculiar compositional changes that affected the Peteroa

Seismic evidence for arc segmentation, active magmatic intrusions and syn-rift fault system in the northern Ryukyu volcanic arc

Science.gov (United States)

Arai, Ryuta; Kodaira, Shuichi; Takahashi, Tsutomu; Miura, Seiichi; Kaneda, Yoshiyuki

2018-04-01

Tectonic and volcanic structures of the northern Ryukyu arc are investigated on the basis of multichannel seismic (MCS) reflection data. The study area forms an active volcanic front in parallel to the non-volcanic island chain in the eastern margin of the Eurasian plate and has been undergoing regional extension on its back-arc side. We carried out a MCS reflection experiment along two across-arc lines, and one of the profiles was laid out across the Tokara Channel, a linear bathymetric depression which demarcates the northern and central Ryukyu arcs. The reflection image reveals that beneath this topographic valley there exists a 3-km-deep sedimentary basin atop the arc crust, suggesting that the arc segment boundary was formed by rapid and focused subsidence of the arc crust driven by the arc-parallel extension. Around the volcanic front, magmatic conduits represented by tubular transparent bodies in the reflection images are well developed within the shallow sediments and some of them are accompanied by small fragments of dipping seismic reflectors indicating intruded sills at their bottoms. The spatial distribution of the conduits may suggest that the arc volcanism has multiple active outlets on the seafloor which bifurcate at crustal depths and/or that the location of the volcanic front has been migrating trenchward over time. Further distant from the volcanic front toward the back-arc (> 30 km away), these volcanic features vanish, and alternatively wide rift basins become predominant where rapid transitions from normal-fault-dominant regions to strike-slip-fault-dominant regions occur. This spatial variation in faulting patterns indicates complex stress regimes associated with arc/back-arc rifting in the northern Okinawa Trough.[Figure not available: see fulltext.

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.

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.

Volcanic risk

International Nuclear Information System (INIS)

Rancon, J.P.; Baubron, J.C.

1995-01-01

This project follows the previous multi-disciplinary studies carried out by the French Bureau de Recherches Geologiques et Minieres (BRGM) on the two active volcanoes of the French lesser Antilles: Mt Pelee (Martinique) and Soufriere (Guadeloupe) for which geological maps and volcanic risk studies have been achieved. The research program comprises 5 parts: the study of pyroclastic deposits from recent eruptions of the two volcanoes for a better characterization of their eruptive phenomenology and a better definition of crisis scenarios; the study of deposits and structures of active volcanoes from Central America and the study of eruptive dynamics of andesite volcanoes for a transposition to Antilles' volcanoes; the starting of a methodological multi-disciplinary research (volcanology, geography, sociology...) on the volcanic risk analysis and on the management of a future crisis; and finally, the development of geochemical survey techniques (radon, CO 2 , H 2 O) on active volcanoes of Costa-Rica and Europe (Fournaise, Furnas, Etna) and their application to the Soufriere. (J.S.). 9 refs., 3 figs

The geochemical characteristics of basaltic and acidic volcanics around the Myojin depression in the Izu arc, Japan

Science.gov (United States)

Haraguchi, S.; Tamaki, K.; Kato, Y.; Machida, S.

2012-12-01

Around the Myojin Depression, westside of the Myojin-sho caldera in the Izu arc, seamounts are circular distributed and hydrothermal activity with sulfide deposition are found from the Baiyonneise Caldera, one of seamounts at the northern side. Some knoll chains distribute in the eastside of the Myojin Depression, and connect between these knolls. This circulator distribution of seamounts and connected knoll chains considered to the dykes are similar to the geographical features of the Kuroko Depositions in the Hokuroku Region, Northwest Japan (Tanahashi et al., 2008). Hydrothermal activities are also found from the other rifts (Urabe and Kusakabe 1990). Based on these observations, the cruise KT09-12 by R/V Tansei-Maru, Ocean Research Institute (ORI), University of Tokyo, investigated in the Myojin Rift. During the cruise, basaltic to dacitic volcanic rocks and some acidic plutonic rocks were recovered by dredge system. Herein, we present petrographical and chemical analyses of these rock samples with sample dredged by the cruise MW9507 by R/V MOANA WAVE, and consider the association with hydrothermal activities and depositions. Dredges during the cruise KT09-12 were obtained at the Daini-Beiyonneise Knoll at the northern side, Daisan-Beiyonneise Knoll at the southern side, and the Dragonborn Hill, small knoll chains, at the southeastern side of the depression. Many volcanic rocks are basalt, and recovered mainly from the Dragonborn Hill. Andesite and dacite was recovered from the Daini- and the Daini-Bayonneise Knoll. Tonalites were recovered from the Daisan-Bayonneise Knoll. Basalts from the Dragonborn Hill show less than 50% of SiO2 and more than 6 wt% and 0.88 wt% of MgO and TiO2 content. Basalts from the rift zone show depleted in the volcanic front (VF) side and enriched in the reararc (RA) side. The Dragonborn Hill is distributed near the VF, and basalts show depleted geochemical characteristics. However, these characteristics are different from the basalts

Radon gas as a tracer for volcanic processes

International Nuclear Information System (INIS)

Thomas, D.M.

1990-01-01

Radon emissions from volcanic systems have been under investigation for several decades. Soil gas and groundwater radon activities have been used to map faults and to characterize geothermal systems, and measurements of atmospheric radon and radon daughter concentrations have been used to estimate the volume of magma chambers feeding active eruptions. Several studies have also shown that temporal variations in radon concentration have been associated with the onset of volcanic eruptions or changes in the rates or character of an eruption. Some of these studies have been able to clearly define the cause of the radon anomalies but others have proposed models of radon emission and transport that are not well supported by the known physical and chemical processes that occur in a volcanic system. In order to better characterize the processes that control radon activities in volcanic systems, it is recommended that future radon monitoring programs attempt to maintain continuous recording of radon activities; individual radon measurements should be made over the shortest time intervals possible that are consistent with acceptable counting statistics and geophysical, meteorological, and hydrological parameters should be measured in order to better define the physical processes that affect radon activities in volcanic systems. (author). 63 refs

Classifcation of volcanic structure in mesozoic era in the Fuzhou-Shaoxing area

International Nuclear Information System (INIS)

Zhang Fengqi.

1989-01-01

The volcanic structure in the Fuzhou-Shaoxing area can be classified into IV grades: the grade I be the zone of volcanic activity; the grade II be the second zone of volcanic activity; the grade III be the positive, negative volcanic structure; the grade IV be volcanic conduit, volcanic crater, concealed eruption breccia pipe. Based on the geological situation in this area, the different types of volcanic structure are also dealt with. In the mean time, both the embossed type in the depression area and the depressed type in the embossed area in the volcanic basin are pointed out. It is of great advantage to Uranium mineralization

Structural control of monogenetic volcanism in the Garrotxa volcanic field (Northeastern Spain) from gravity and self-potential measurements

Science.gov (United States)

Barde-Cabusson, S.; Gottsmann, J.; Martí, J.; Bolós, X.; Camacho, A. G.; Geyer, A.; Planagumà, Ll.; Ronchin, E.; Sánchez, A.

2014-01-01

We report new geophysical observations on the distribution of subsurface structures associated with monogenetic volcanism in the Garrotxa volcanic field (Northern Spain). As part of the Catalan Volcanic Zone, this Quaternary volcanic field is associated with the European rifts system. It contains the most recent and best preserved volcanic edifices of the Catalan Volcanic Zone with 38 monogenetic volcanoes identified in the Garrotxa Natural Park. We conducted new gravimetric and self-potential surveys to enhance our understanding of the relationship between the local geology and the spatial distribution of the monogenetic volcanoes. The main finding of this study is that the central part of the volcanic field is dominated by a broad negative Bouguer anomaly of around -0.5 mGal, within which a series of gravity minima are found with amplitudes of up to -2.3 mGal. Inverse modelling of the Bouguer data suggests that surficial low-density material dominates the volcanic field, most likely associated with effusive and explosive surface deposits. In contrast, an arcuate cluster of gravity minima to the NW of the Croscat volcano, the youngest volcano of this zone, is modelled by vertically extended low-density bodies, which we interpret as a complex ensemble of fault damage zones and the roots of young scoria cones. A ground-water infiltration zone identified by a self-potential anomaly is associated with a steep horizontal Bouguer gravity gradient and interpreted as a fault zone and/or magmatic fissure, which fed the most recent volcanic activity in the Garrotxa. Gravimetric and self-potential data are well correlated and indicate a control on the locations of scoria cones by NNE-SSW and NNW-SSE striking tectonic features, which intersect the main structural boundaries of the study area to the north and south. Our interpretation of the data is that faults facilitated magma ascent to the surface. Our findings have major implications for understanding the relationship

Protocols for geologic hazards response by the Yellowstone Volcano Observatory

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,

2010-01-01

The Yellowstone Plateau hosts an active volcanic system, with subterranean magma (molten rock), boiling, pressurized waters, and a variety of active faults with significant earthquake hazards. Within the next few decades, light-to-moderate earthquakes and steam explosions are certain to occur. Volcanic eruptions are less likely, but are ultimately inevitable in this active volcanic region. This document summarizes protocols, policies, and tools to be used by the Yellowstone Volcano Observatory (YVO) during earthquakes, hydrothermal explosions, or any geologic activity that could lead to a volcanic eruption.

Hydrothermal activity, functional diversity and chemoautotrophy are major drivers of seafloor carbon cycling

NARCIS (Netherlands)

Bell, J.B.; Woulds, C.; van Oevelen, D.

2017-01-01

Hydrothermal vents are highly dynamic ecosystems and are unusually energy rich in the deep-sea. Insitu hydrothermal-based productivity combined with sinking photosynthetic organic matter in a softsedimentsetting creates geochemically diverse environments, which remain poorly studied. Here,we use

A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000-10

Science.gov (United States)

Patrick, Matthew R.; Smellie, John L.

2015-01-01

Of the more than twenty historically active volcanoes in Antarctica and the sub-Antarctic region only two, to our knowledge, host any ground-based monitoring instruments. Moreover, because of their remoteness, most of the volcanoes are seldom visited, thus relegating the monitoring of volcanism in this region almost entirely to satellites. In this study, high temporal resolution satellite data from the Hawaii Institute of Geophysics and Planetology's MODVOLC system using MODIS (Moderate Resolution Imaging Spectroradiometer) are complemented with high spatial resolution data (ASTER, or Advanced Spaceborne Thermal Emission and Reflection Radiometer, and similar sensors) to document volcanic activity throughout the region during the period 2000–10. Five volcanoes were observed in eruption (Mount Erebus, Mount Belinda, Mount Michael, Heard Island and McDonald Island), which were predominantly low-level and effusive in nature. Mount Belinda produced tephra, building a cinder cone in addition to an extensive lava field. Five volcanoes exhibited detectable thermal, and presumed fumarolic, activity (Deception, Zavodovski, Candlemas, Bristol, and Bellingshausen islands). A minor eruption reported at Marion Island was not detected in our survey due to its small size. This study also discovered a new active vent on Mount Michael, tracked dramatic vent enlargement on Heard Island, and provides an improved picture of the morphology of some of the volcanoes.

Self-potential, geoelectric and magnetotelluric studies in Italian active volcanic areas

OpenAIRE

Di Mai, R.; Mauriello, P.; Patella, D.; Petrillo, Z.; Piscitelli, S.; Siniscalchi, A.; Veneruso, M.

1997-01-01

We present the results of self-potential, geoelectric and magnetotelluric studies in Italian active volcanic areas as essential contributions both to structural modeling and to hazard evaluation. On Mt. Etna and Mt. Somma-Vesuvius complexes structural modeling was emphasized due to a lack of global information involving the whole apparatuses, at least from the electrical point of view. Hazard investigation was, instead, investigated with high resolution techniques on the island of Vulcano, wh...

Tectonic environments and local geologic controls of potential hydrothermal fields along the Southern Mid-Atlantic Ridge (12-14°S)

Science.gov (United States)

Li, Bing; Shi, Xuefa; Wang, Jixin; Yan, Quanshu; Liu, Chenguang; DY125-21 (Leg 3) Science Party; DY125-22 (Legs 2-5) Science Party; DY125-26 (Leg 3) Science Party

2018-05-01

Systematic hydrothermal exploration and multi-beam bathymetry mapping have been conducted along a 220-km-long section of the Southern Mid-Atlantic Ridge (SMAR) from 12°S (Bode Verde Fracture Zone) to 14°S (Cardno Fracture Zone), and previously reported deposits (Tao et al., 2011) are now being thoroughly investigated. Here, we present the characterization of three possible hydrothermal fields, a complete bathymetry data set of the ridge segment, gravity data, and the petrologic characteristics of collected rock samples. The magmatism characteristics, evolution of the ridge segment, and the local geological controls of the possible hydrothermal fields are then discussed. The studied segment can be divided into two segments by a Non-Transform Discontinuity (NTD). Our morphotectonic analysis shows significant along-axis heterogeneity in the surveyed segments: three distinctive cross-axis grabens were identified in the northern segment, and two were identified in the southern segment. Moreover, based on the gravity data (a relatively low spherical Bouguer anomaly) and petrologic data (low Mg# values and relatively low FeO and relatively high Al2O3 and CaO contents compared to nearby seafloor samples), a volcanic feature, the ZouYu seamount, on this segment is considered to be associated with strong magmatic activity, and the magmatic activity of the inside corner at the southern end of the segment has increased and decreased. The three possible hydrothermal fields occur in different local geological settings: a shallow magmatic seamount (ZouYu), an NTD (TaiJi), and an inside-corner high (CaiFan). These potential hydrothermal fields are significantly different from other fields in similar tectonic settings in terms of local geologic controls and products. The ZouYu field is primarily related to a newly formed cone, resulting in the production of sulfides, and differs from other fields on shallow magmatic seamounts. The TaiJi field is largely controlled by the tectonic

Noble Gas geochemistry of the newly discovered hydrothermal fields in the Gulf of California: preliminary He-isotope ratios from the Alarcon Rise and Pescadero basin vent sites

Science.gov (United States)

Spelz, R. M.; Lupton, J. E.; Evans, L. J.; Zierenberg, R. A.; Clague, D. A.; Neumann, F.; Paduan, J. B.

2015-12-01

Numerous submarine deep-sea hydrothermal vents related to volcanic activity of the East Pacific Rise (EPR) are situated along the Pacific margins of Mexico. Until recently, active hydrothermal venting was unknown between the Guaymas Basin and 21°N on the EPR. MBARI's recent oceanographic surveys have added 7 new active vent sites. In this study, we aimed to sample the high-temperature hydrothermal fluids emanating from two distinct vent sites, named Meyibo and Auka, located in the Alarcon Rise and Pescadero Basin, respectively. Mantle-derived He have long been identified in hydrothermal fluid releases. The presence of He in aqueous fluids with 3He/4He ratios greater than in-situ production values (~0.05 RA, where RA = air He or 1.4 x 10-6) indicates the presence of mantle-derived melts. Preliminary analyses of He-isotope ratios derived from the newly discovered Meyibo and Auka hydrothermal fields show high 3He/4He ratios (~8RA), typical of MORB's. Auka vent field, characterized by chimneys composed of light carbonate minerals and oil-like hydrocarbons, and temperatures between 250-290oC, show average values of ~7.87RA. In contrast, the black-smokers at the Meyibo field, composed of dark sulfide minerals and temperatures over 350oC, yielded a higher He ratio of ~8.24RA. Recently, it has become clear that regional maximum mantle He values correlate with the velocity structure in the mantle, therefore, He has the potential to map regions of the underlying mantle that are undergoing partial melting. Seismic records could then be compared with the geochemical He ratio signal and supply information regarding tectonics and other processes involved in the generation of these gases. The data presented here will be completing a totally new inventory of He results from hydrothermal vents in the EPR and fault-termination basins distributed along the P-NA plate boundary in the Gulf of California. The results will be further coupled with the analysis of other geochemical

Martian volcanism: A review

International Nuclear Information System (INIS)

Carr, M.H.

1987-01-01

Martian volcanism is reviewed. It is emphasized that lava plains constitute the major type of effusive flow, and can be differentiated by morphologic characteristics. Shield volcanoes, domes, and patera constitute the major constructional landforms, and recent work has suggested that explosive activity and resulting pyroclastic deposits may have been involved with formation of some of the small shields. Analysis of morphology, presumed composition, and spectroscopic data all indicate that Martian volcanism was dominantly basaltic in composition

First volcanic CO2 budget estimate for three actively degassing volcanoes in the Central American Volcanic Arc

Science.gov (United States)

Robidoux, Philippe; Aiuppa, Alessandro; Conde, Vladimir; Galle, Bo; Giudice, Gaetano; Avard, Geoffroy; Muñoz, Angélica

2014-05-01

CO2 is a key chemical tracer for exploring volcanic degassing mechanisms of basaltic magmatic systems (1). The rate of CO2 release from sub-aerial volcanism is monitored via studies on volcanic plumes and fumaroles, but information is still sparse and incomplete for many regions of the globe, including the majority of the volcanoes in the Central American Volcanic Arc (2). Here, we use a combination of remote sensing techniques and in-situ measurements of volcanic gas plumes to provide a first estimate of the CO2 output from three degassing volcanoes in Central America: Turrialba, in Costa Rica, and Telica and San Cristobal, in Nicaragua. During a field campaign in March-April 2013, we obtained (for the three volcanoes) a simultaneous record of SO2 fluxes (from the NOVAC network (3)) and CO2 vs. SO2 concentrations in the near-vent plumes (obtained via a temporary installed fully-automated Multi-GAS instrument (4)). The Multi-GAS time-series allowed to calculate the plume CO2/SO2 ratios for different intervals of time, showing relatively stable gas compositions. Distinct CO2 - SO2 - H2O proportions were observed at the three volcanoes, but still within the range of volcanic arc gas (5). The CO2/SO2 ratios were then multiplied by the SO2 flux in order to derive the CO2 output. At Turrialba, CO2/SO2 ratios fluctuated, between March 12 and 19, between 1.1 and 5.7, and the CO2flux was evaluated at ~1000-1350 t/d (6). At Telica, between March 23 and April 8, a somewhat higher CO2/SO2 ratio was observed (3.3 ± 1.0), although the CO2 flux was evaluated at only ~100-500 t/d (6). At San Cristobal, where observations were taken between April 11 and 15, the CO2/SO2 ratio ranged between 1.8 and 7.4, with a mean CO2 flux of 753 t/d. These measurements contribute refining the current estimates of the total CO2 output from the Central American Volcanic Arc (7). Symonds, R.B. et al., (2001). J. Volcanol. Geotherm. Res., 108, 303-341 Burton, M. R. et al. (2013). Reviews in

Volcanism, Iron, and Phytoplankton in the Heard and McDonald Islands Region, Southern Indian Ocean

Science.gov (United States)

Coffin, M. F.; Arculus, R. J.; Bowie, A. R.; Chase, Z.; Robertson, R.; Trull, T. W.; Heobi in2016 v01 Shipboard Party, T.

2016-12-01

Phytoplankton supply approximately half of the oxygen in Earth's atmosphere, and iron supply limits the growth of phytoplankton in the anemic Southern Ocean. Situated entirely within the Indian Ocean sector of the Southern Ocean are Australia's only active subaerial volcanoes, Heard and McDonald islands (HIMI) on the central Kerguelen Plateau, a large igneous province. Widespread fields of submarine volcanoes, some of which may be active, extend for distances of up to several hundred kilometers from the islands. The predominantly eastward-flowing Antarctic Circumpolar Current sweeps across the central Kerguelen Plateau, and extensive blooms of phytoplankton are observed on the Plateau down-current of HIMI. The goal of RV Investigator voyage IN2016_V01, conducted in January/February 2016, is to test the hypothesis that hydrothermal fluids, which cool active submarine volcanoes in the HIMI region, ascend from the seafloor and fertilise surface waters with iron, thereby enhancing biological productivity beginning with phytoplankton. Significant initial shipboard results include: Documentation, for the first time, of the role of active HIMI and nearby submarine volcanoes in supplying iron to the Southern Ocean. Nearshore waters had elevated dissolved iron levels. Although biomass was not correspondingly elevated, fluorescence induction data indicated highly productive resident phytoplankton. Discovery of >200 acoustic plumes emanating from the seafloor and ascending up to tens of meters into the water column near HIMI. Deep tow camera footage shows bubbles rising from the seafloor in an acoustic plume field north of Heard Island. Mapping 1,000 km2 of uncharted seafloor around HIMI. Submarine volcanic edifices punctuate the adjacent seafloor, and yielded iron-rich rocks similar to those found on HIMI, respectively. Acoustic plumes emanating from some of these features suggest active seafloor hydrothermal systems.

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.

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.

Micro-seismic earthquakes characteristics at natural and exploited hydrothermal systems in West Java, Indonesia

Science.gov (United States)

Jousset, P. G.; Jaya, M. S.; Sule, R.; Diningrat, W.; Gassner, A.; Akbar, F.; Ryannugroho, R.; Hendryana, A.; Kusnadi, Y.; Syahbana, D.; Nugraha, A. D.; Umar, M.; Indrinanto, Y.; Erbas, K.

2013-12-01

The assessment of geothermal resources requires the understanding of the structure and the dynamics of geothermal reservoirs. We deployed a multidisciplinary geophysical network around geothermal areas in the south of Bandung, West Java, Indonesia. The first deployment included a network of 30 broadband and 4 short-period seismic stations with Güralp and Trillium sensors (0.008 - 100 Hz) since October 2012. In a second step, we extended the network in June 2013 with 16 short-period (1 Hz) seismometers. We describe the set-up of the seismic networks and discuss first observations and results. The co-existence of a large variety of intense surface manifestations like geysers, hot-steaming grounds, hot water pools, and active volcanoes suggest an intimate coupling between volcanic, tectonic and hydrothermal processes in this area. Preliminary location of earthquakes is performed using a non-linear algorithm, which allows us to define at least 3 seismic clusters. We discuss this seismic pattern within the geothermal fields.

Key factors influencing rates of heterotrophic sulfate reduction in active seafloor hydrothermal massive sulfide deposits

Directory of Open Access Journals (Sweden)

Kiana Laieikawai Frank

2015-12-01

Full Text Available Hydrothermal vents are thermally and geochemically dynamic habitats, and the organisms therein are subject to steep gradients in temperature and chemistry. To date, the influence of these environmental dynamics on microbial sulfate reduction has not been well constrained. Here, via multivariate experiments, we evaluate the effects of key environmental variables (temperature, pH, H2S, SO42-, DOC on sulfate reduction rates and metabolic energy yields in material recovered from a hydrothermal flange from the Grotto edifice in the Main Endeavor Field, Juan de Fuca Ridge. Sulfate reduction was measured in batch reactions across a range of physico-chemical conditions. Temperature and pH were the strongest stimuli, and maximum sulfate reduction rates were observed at 50 °C and pH 6, suggesting that the in situ community of sulfate-reducing organisms in Grotto flanges may be most active in a slightly acidic and moderate thermal/chemical regime. At pH 4, sulfate reduction rates increased with sulfide concentrations most likely due to the mitigation of metal toxicity. While substrate concentrations also influenced sulfate reduction rates, energy-rich conditions muted the effect of metabolic energetics on sulfate reduction rates. We posit that variability in sulfate reduction rates reflect the response of the active microbial consortia to environmental constraints on in situ microbial physiology, toxicity, and the type and extent of energy limitation. These experiments help to constrain models of the spatial contribution of heterotrophic sulfate reduction within the complex gradients inherent to seafloor hydrothermal deposits.

Volcanic complexes in the eastern ridge of the Canary Islands: the Miocene activity of the island of Fuerteventura

Science.gov (United States)

Ancochea, E.; Brändle, J. L.; Cubas, C. R.; Hernán, F.; Huertas, M. J.

1996-03-01

Fuerteventura has been since early stages of its growth the result of three different adjacent large volcanic complexes: Southern, Central and Northern. The definition of these volcanic complexes and their respective growing episodes is based on volcano-stratigraphic, morphological and structural criteria, particularly radial dyke swarms. Each complex has its own prolonged history that might be longer than 10 m.y. During that time, several periods of activity alternating with gaps accompanied by important erosion took place. The evolution of each volcanic complex has been partially independent but all the three are affected by at least three Miocene tectonic phases that controlled considerably their activity. The volcanic complexes are deeply eroded and partially submerged. In the core of the Northern and the Central volcanic complexes there is a set of submarine and plutonic rocks intensely traversed by a dyke swarm, known as the Basal Complex. The Basal Complex has been interpreted in different ways but all previous authors have considered it to be prior to the subaerial shield stage of the island. Here we advance the idea that the Basal Complex represent the submarine growing stage of the volcanic complexes and the hypabyssal roots (plutons and dykes) of their successive subaerial growing episodes. Two seamounts situated nearby, southwest of the island, might be interpreted as remains of two other major volcanoes. These two volcanoes, together with those forming the present emerged island of Fuerteventura, and finally those of Famara and Los Ajaches situated further north on Lanzarote constitute a chain of volcanoes located along a lineation which is subparallel to the northwestern African coastline and which may relate to early Atlantic spreading trends in the area.

Venus - Volcanic features in Atla Region

Science.gov (United States)

1991-01-01

This Magellan image from the Atla region of Venus shows several types of volcanic features and superimposed surface fractures. The area in the image is approximately 350 kilometers (217 miles) across, centered at 9 degrees south latitude, 199 degrees east longitude. Lava flows emanating from circular pits or linear fissures form flower-shaped patterns in several areas. A collapse depression approximately 20 kilometers by 10 kilometers (12 by 6 miles) near the center of the image is drained by a lava channel approximately 40 kilometers (25 miles) long. Numerous surface fractures and graben (linear valleys) criss-cross the volcanic deposits in north to northeast trends. The fractures are not buried by the lavas, indicating that the tectonic activity post-dates most of the volcanic activity.

A geochemical approach for assessing the possible uses of the geothermal resource in the eastern sector of the Sabatini Volcanic District (Central Italy)

Science.gov (United States)

Cinti, Daniele; Tassi, Franco; Procesi, Monia; Brusca, Lorenzo; Cabassi, Jacopo; Capecchiacci, Francesco; Delgado Huertas, Antonio; Galli, Gianfranco; Grassa, Fausto; Vaselli, Orlando; Voltattorni, Nunzia

2017-04-01

The Sabatini Volcanic District (SVD) hosts a hydrothermal reservoir heated by the post-magmatic activity that affected the peri-Tyrrhenian sector of central Italy, giving rise to a number of thermal and mineral discharges. In this study, a complete geochemical and isotopic dataset based on the composition of 215 water and 9 bubbling gases, collected from the eastern sector of this huge hydrothermal system, is reported. The main aims are to (i) investigate the fluid sources and the main chemical-physical processes controlling the fluid chemistry and (ii) construct a conceptual fluid circulation model to provide insights into the possible use(s) of the geothermal resource. The fluid discharges are fed by two main aquifers, characterized by: (1) a Ca-HCO3 to Ca(Na)-HCO3 composition, typical of a shallow hydrological circuit within volcanic and sedimentary formations, and (2) a Ca-HCO3(SO4) to Na(Ca)-HCO3(Cl) composition, produced by the interaction of CO2-rich fluids with Mesozoic and Triassic carbonate-evaporite rocks. A thick sequence of low-permeability volcanic products represents a physical barrier between the two fluid reservoirs. As commonly occurring in central-southern Italy, CO2 is mainly produced by thermo-metamorphic decarbonation within the carbonate-evaporite reservoir, with minor contribution of mantle CO2. A dominant crustal source is also indicated by the relatively low R/Ra values (0.07-1.04). Methane and light hydrocarbons are mostly thermogenic, whereas H2S derives from thermogenic reduction of the Triassic anhydrites. Slightly positive 15N/14N values suggest minor N2 contribution from deep sedimentary sources. On the whole, a comparison of these geochemical features with those of the thermal fluids from the western portion of SVD highlights an eastward increasing influence of the shallow aquifer on the deep-originated fluids, likely caused by the proximity of the Apennine range from where the meteoric water, recharging the hydrothermal system

The Volcanism Ontology (VO): a model of the volcanic system

Science.gov (United States)

Myer, J.; Babaie, H. A.

2017-12-01

We have modeled a part of the complex material and process entities and properties of the volcanic system in the Volcanism Ontology (VO) applying several top-level ontologies such as Basic Formal Ontology (BFO), SWEET, and Ontology of Physics for Biology (OPB) within a single framework. The continuant concepts in BFO describe features with instances that persist as wholes through time and have qualities (attributes) that may change (e.g., state, composition, and location). In VO, the continuants include lava, volcanic rock, and volcano. The occurrent concepts in BFO include processes, their temporal boundaries, and the spatio-temporal regions within which they occur. In VO, these include eruption (process), the onset of pyroclastic flow (temporal boundary), and the space and time span of the crystallization of lava in a lava tube (spatio-temporal region). These processes can be of physical (e.g., debris flow, crystallization, injection), atmospheric (e.g., vapor emission, ash particles blocking solar radiation), hydrological (e.g., diffusion of water vapor, hot spring), thermal (e.g., cooling of lava) and other types. The properties (predicates) relate continuants to other continuants, occurrents to continuants, and occurrents to occurrents. The ontology also models other concepts such as laboratory and field procedures by volcanologists, sampling by sensors, and the type of instruments applied in monitoring volcanic activity. When deployed on the web, VO will be used to explicitly and formally annotate data and information collected by volcanologists based on domain knowledge. This will enable the integration of global volcanic data and improve the interoperability of software that deal with such data.

Evaluation on changes caused by volcanic activities in the groundwater environment as a natural barrier for the HLW disposal. Literature survey and groundwater observation conducted at Mt. Iwate

International Nuclear Information System (INIS)

Mahara, Yasunori; Nakata, Eiji; Tanaka, Kazuhiro

2000-01-01

It is very important in the site characterization for the HLW disposal to understand changes in geochemical performances caused by volcanic activities in the groundwater environment as the natural barrier. The various effects and its magnitude of changes were listed up and were filed from literature surveys of the correlation between volcanic activities and hydrological can geochemical changes (e.g. water temperature, water pressure, water level, dissolved gas concentration of He and Rn, isotopic ratio of He, and chloride concentration) in volcanic aquifer. However, it is difficult to evaluate the magnitude of impacts, which volcanic activities will give to the groundwater environment in the natural barrier, through only the literature surveys. We have started monitoring of groundwater level and changes in groundwater quality, since volcanic activities have enhanced at Mt. Iwate from June in 1998. Judging from variation of isotopic ratio of dissolved He in groundwater, a prompt and sharp signals indicating volcanic activities will easily be found in shallow groundwater and discharged ponds. On the other hands, geochemical conditions in deep groundwater surroundings from some 100 m to 1000 m deep will be very stable, if the area being more than 5 km apart from the volcanic active center. Consequently, our observed results suggest that the groundwater environment which is not directly disturbed by the underground magmatic activities spreads under the area that is connected to trench side of the volcanic front. (author)

Synthesis of ZnO nanorod–nanosheet composite via facile hydrothermal method and their photocatalytic activities under visible-light irradiation

Energy Technology Data Exchange (ETDEWEB)

Tan, Wai Kian [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Abdul Razak, Khairunisak; Lockman, Zainovia [School of Materials and Mineral Resources, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Pulau Pinang (Malaysia); Kawamura, Go; Muto, Hiroyuki [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Matsuda, Atsunori, E-mail: matsuda@ee.tut.ac.jp [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan)

2014-03-15

ZnO composite films consisting of ZnO nanorods and nanosheets were prepared by low-temperature hydrothermal processing at 80 °C on seeded glass substrates. The seed layer was coated on glass substrates by sol–gel dip-coating and pre-heated at 300 °C for 10 min prior to hydrothermal growth. The size of the grain formed after pre-heat treatment was ∼40 nm. A preferred orientation seed layer at the c-axis was obtained, which promoted vertical growth of the ZnO nanorod arrays and formation of the ZnO nanosheets. X-ray diffraction patterns and high-resolution transmission electron microscope (HR-TEM) images confirmed that the ZnO nanorods and nanosheets consist of single crystalline and polycrystalline structures, respectively. Room temperature photoluminescence spectra of the ZnO nanorod–nanosheet composite films exhibited band-edge ultraviolet (UV) and visible emission (blue and green) indicating the formation of ZnO crystals with good crystallinity and are supported by Raman scattering results. The formation of one-dimensional (1D) ZnO nanorod arrays and two-dimensional (2D) ZnO nanosheet films using seeded substrates in a single low-temperature hydrothermal step would be beneficial for realization of device applications that utilize substrates with limited temperature stability. The ZnO nanorods and nanosheets composite structure demonstrated higher photocatalytic activity during degradation of aqueous methylene blue under visible-light irradiation. -- Graphical abstract: Schematic illustration of ZnO nanorod–nanosheet composite structure formation by hydrothermal at low-temperature of 80 °C against time. Highlights: • Novel simultaneous formation of ZnO nanorods and nanosheets composite structure. • Facile single hydrothermal step formation at low-temperature. • Photoluminescence showed ultraviolet and visible emission. • Feasible application on substrates with low temperature stability. • Improved photocatalytic activity under visible

Layered hydrothermal barite-sulfide mound field, East Diamante Caldera, Mariana volcanic arc

Science.gov (United States)

Hein, James R.; de Ronde, Cornel E. J.; Koski, Randolph A.; Ditchburn, Robert G.; Mizell, Kira; Tamura, Yoshihiko; Stern, Robert J.; Conrad, Tracey; Ishizuka, Osamu; Leybourne, Matthew I.

2014-01-01

East Diamante is a submarine volcano in the southern Mariana arc that is host to a complex caldera ~5 × 10 km (elongated ENE-WSW) that is breached along its northern and southwestern sectors. A large field of barite-sulfide mounds was discovered in June 2009 and revisited in July 2010 with the R/V Natsushima, using the ROV Hyper-Dolphin. The mound field occurs on the northeast flank of a cluster of resurgent dacite domes in the central caldera, near an active black smoker vent field. A 40Ar/39Ar age of 20,000 ± 4000 years was obtained from a dacite sample. The mound field is aligned along a series of fractures and extends for more than 180 m east-west and >120 m north-south. Individual mounds are typically 1 to 3 m tall and 0.5 to 2 m wide, with lengths from about 3 to 8 m. The mounds are dominated by barite + sphalerite layers with the margins of each layer composed of barite with disseminated sulfides. Rare, inactive spires and chimneys sit atop some mounds and also occur as clusters away from the mounds. Iron and Mn oxides are currently forming small (caldera, mineralization resulted from focused flow along small segments of linear fractures rather than from a point source, typical of hydrothermal chimney fields. Based on the mineral assemblage, the maximum fluid temperatures were ~260°C, near the boiling point for the water depths of the mound field (367–406 m). Lateral fluid flow within the mounds precipitated interstitial sphalerite, silica, and Pb minerals within a network of barite with disseminated sulfides; silica was the final phase to precipitate. The current low-temperature precipitation of Fe and Mn oxides and silica may represent rejuvenation of the system.

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.

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.

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.

Active spreading processes at ultraslow mid-ocean ridges: The 1999-2001 seismo-volcanic episode at 85°E Gakkel ridge, Arctic Ocean

Science.gov (United States)

Schlindwein, Vera; Riedel, Carsten; Korger, Edith; Läderach, Christine

2010-05-01

The rate of magma and crustal production at mid-ocean ridges is thought to decrease with decreasing spreading rate. At ultraslow spreading rates below 10-20 mm/y full rate, heat loss by conduction greatly reduces melt production with less melt produced at increasingly greater depths. Gakkel Ridge, the actively spreading mid-ocean ridge in the Arctic Ocean, opens at rates of 14 mm/y in the west decreasing to less than 6 mm/y at its eastern termination and demonstrates that magma production is not only a function of spreading rate. Whereas amagmatic spreading takes place at rates of about 12-10 mm/y, focussed melt production occurs at even lower spreading rates in long-lived discrete volcanic centres. One such centre is the 85°E volcanic complex at eastern Gakkel ridge where in 1999 a teleseismically recorded earthquake swarm consisting of more than 250 earthquakes over 9 months signalled the onset of an active spreading episode. The earthquake swarm is believed to be associated with volcanic activity although no concurrent lava effusion was found. We analysed the teleseismic earthquake swarm together with visual observation and microseismic data recorded at this site in 2001 and 2007 and noted the following characteristics which may be indicative for volcanic spreading events at the still poorly explored ultraslow spreading ridges: - unusual duration: The 1999 earthquake swarm lasted over 9 months rather than a few weeks as observed on faster spreading ridges. In addition, in 2001 seismoacoustic sounds which we interpret as gas discharge in Strombolian eruptions and a giant event plume maintained over more than one year indicate waxing and waning volcanic activity since 1999. - unusual strength: The earthquake swarm was detected at teleseismic distances of more than 1000 km and included 11 events with a magnitude >5. No other confirmed mid-ocean ridge eruption released a comparable seismic moment. Rather than focussing in a narrow area or showing pronounced

Mineralogy and geological significance of hydrothermal deposits from the Okinawa Trough

Science.gov (United States)

Zhang, Xia; Zhai, Shikui; Yu, Zenghui; Wang, Shujie; Cai, Zongwei

2018-04-01

The study of hydrothermal deposits in the Okinawa Trough can help us to uncover the hydrothermal mineralization characteristics in the back-arc basin during the early expanding stage. Mineralogy and geological significance of hydrothermal deposits from both the middle and southern trough are studied in this paper. First of all, using optical microscope to confirm the mineral compositions, characteristics of crystal shape, paragenetic relationship and minerals crystallization order. Then the minerals chemical composition were analyzed in virtue of electron microprobe. On these basis, the paragenetic sequence and the mineralization characteristics of the hydrothermal deposits were discussed. The results show that the hydrothermal deposit from the mid-Okinawa Trough belongs to Zn-Cu-rich type, consisting dominantly of sulfide minerals such as sphalerite, chalcopyrite, pyrite, etc. The minerals crystallization order is first generation pyrite(PyI)-sphalerite-chalcopyrite-galena-second generation pyrite(PyII)-amorphous silica. While the deposit from the southern Okinawa Trough is Ba-Zn-Pb-rich type mainly composing of barite, sphalerite, galena, etc. The minerals crystallization order is barite-pyrite-sphalerite-tetrahedrite-galena-chalcopyrite-amorphous silica. Hydrothermal fluid temperature in the mid-Okinawa Trough undergoes a process from high to low, which is high up to 350 °C in the early stage, but decreasing gradually with the evolution of hydrothermal fluid. On the contrary, the hydrothermal activity in the southern Okinawa Trough is low temperature dominated, but the mineralization environment is unstable and the fluid temperature changes drastically during the period of hydrothermal activity.

An oxygen isotope study on hydrothermal sources of granite-type uranium deposits in South China

International Nuclear Information System (INIS)

Yongfei, Z.

1987-01-01

The usefulness of oxygen isotope measurements in solving problems of hydrothermal sources has been demonstrated in a number of detailed studies of the granite type uranium deposits in this paper. Remarkly the granite-type uranium deposits in Southr China have been shown to have formed from magmatic water, meteoric water, of mixtures of both the above, and origin of waters in the ore-forming fluid may be different for differing uranium deposits ore differing stages of the mineralization. Consequences obtained in this study for typical uranium deposits of different age and geologic sitting agree well with that obtained by other geologic-geochemical investigation. Furthermore, not only meteoric water is of importance to origin and evolution of the ore-forming fluid, but also mixing of waters from different sources is considered to be one of the most characteristic features of many hydrothermal uranium deposits related to granitoids or volcanics. (C.D.G.) [pt

Integrated thermal infrared imaging and Structure-from-Motion photogrametry to map apparent temperature and radiant hydrothermal heat flux at Mammoth Mountain, CA USA

Science.gov (United States)

Lewis, Aaron; George Hilley,; Lewicki, Jennifer L.

2015-01-01

This work presents a method to create high-resolution (cm-scale) orthorectified and georeferenced maps of apparent surface temperature and radiant hydrothermal heat flux and estimate the radiant hydrothermal heat emission rate from a study area. A ground-based thermal infrared (TIR) camera was used to collect (1) a set of overlapping and offset visible imagery around the study area during the daytime and (2) time series of co-located visible and TIR imagery at one or more sites within the study area from pre-dawn to daytime. Daytime visible imagery was processed using the Structure-from-Motion photogrammetric method to create a digital elevation model onto which pre-dawn TIR imagery was orthorectified and georeferenced. Three-dimensional maps of apparent surface temperature and radiant hydrothermal heat flux were then visualized and analyzed from various computer platforms (e.g., Google Earth, ArcGIS). We demonstrate this method at the Mammoth Mountain fumarole area on Mammoth Mountain, CA. Time-averaged apparent surface temperatures and radiant hydrothermal heat fluxes were observed up to 73.7 oC and 450 W m-2, respectively, while the estimated radiant hydrothermal heat emission rate from the area was 1.54 kW. Results should provide a basis for monitoring potential volcanic unrest and mitigating hydrothermal heat-related hazards on the volcano.

Synthesis of zeolitic materials from volcanic ash in presence and absence of cetyltrimethylammonium bromide

Energy Technology Data Exchange (ETDEWEB)

Sanhueza N, V. M.; Bennun T, L. D., E-mail: vsanhuez@udec.cl [Universidad de Concepcion, Facultad de Ciencias Quimicas, Edmundo Larenas 129, Region del Biobio (Chile)

2015-07-01

Zeolitic materials as Na-phillipsite, Na-K-phillipsite-like zeolites and the mixtures of zeolites (phillipsite+analcime and phillipsite+chabazite+analcime) were synthesized from volcanic ash, either in presence and absence of cetiltrimetilamonium bromide (CTAB). The ash sample used in the laboratory experiments contains 75.36% SiO{sub 2} and 14.11% Al{sub 2}O{sub 3}, abundances. The reaction time as well as the influence of CTAB were studied in the zeolitic materials crystallization. The experiments were carried out under hydrothermal conditions, autogenic pressure and temperature of 150 grades C, as well as reaction time from 8 to 116 h. Products from this hydrothermal treatment were identified by X-ray diffraction (XRD) and characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy (Sem-EDS). Of the zeolitic materials obtained the Na-K-phillipsite-like zeolite was found to be the most effective for the retention of cations Pb{sup 2+}, Zn{sup 2+} and Ba{sup 2+}. (Author)

Abrupt climatic changes as triggering mechanisms of massive volcanic collapses: examples from Mexico (Invited)

Science.gov (United States)

Capra, L.

2010-12-01

Climate changes have been considered to be a triggering mechanism for large magmatic eruptions. However they can also trigger volcanic collapses, phenomena that cause the destruction of the entire sector of a volcano, including its summit. During the past 30 ka, major volcanic collapses occurred just after main glacial peaks that ended with a rapid deglaciation. Glacial debuttressing, load discharge and fluid circulation coupled with the post-glacial increase of humidity and heavy rains can activate the failure of unstable edifices. Looking at the synchronicity of the maximum glaciations during the late Pleistocene and Holocene in the northern and southern hemispheres it is evident that several volcanic collapses are absent during a glacial climax, but start immediately after it during a period of rapid retreat. Several examples can be detected around the world and Mexico is not an exception. The 28 ka Nevado de Toluca volcanic collapse occurred during an intraglacial stage, under humid conditions as evidenced by paleoclimatic studies on lacustrine sediments of the area. The debris avalanche deposit associated to this event clearly shows evidence of a large amount of water into the mass previous to the failure that enhanced its mobility. It also contains peculiar, plastically deformed, m-sized fragment of lacustrine sediments eroded from glacial berms. The 17 ka BP collapse of the Colima Volcano corresponds to the initial stage of glacial retreat in Mexico after the Last Glacial Maximum (22-17.5ka). Also in this case the depositional sequence reflects high humidity conditions with voluminous debris flow containing a large amount logs left by pine trees. The occurrence of cohesive debris flows originating from the failure of a volcanic edifice can also reflect the climatic conditions, indicating important hydrothermal alteration and fluid circulation from ice-melting at an ice-capped volcano, as observed for example at the Pico de Orizaba volcano for the Tetelzingo

Salt shell fallout during the ash eruption at the Nakadake crater, Aso volcano, Japan: evidence of an underground hydrothermal system surrounding the erupting vent

Science.gov (United States)

Shinohara, Hiroshi; Geshi, Nobuo; Yokoo, Akihiko; Ohkura, Takahiro; Terada, Akihiko

2018-03-01

A hot and acid crater lake is located in the Nakadake crater, Aso volcano, Japan. The volume of water in the lake decreases with increasing activity, drying out prior to the magmatic eruptions. Salt-rich materials of various shapes were observed, falling from the volcanic plume during the active periods. In May 2011, salt flakes fell from the gas plume emitted from an intense fumarole when the acid crater lake was almost dry. The chemical composition of these salt flakes was similar to those of the salts formed by the drying of the crater lake waters, suggesting that they originated from the crater lake water. The salt flakes are likely formed by the drying up of the crater lake water droplets sprayed into the plume by the fumarolic gas jet. In late 2014, the crater lake dried completely, followed by the magmatic eruptions with continuous ash eruptions and intermittent Strombolian explosions. Spherical hollow salt shells were observed on several occasions during and shortly after the weak ash eruptions. The chemical composition of the salt shells was similar to the salts formed by the drying of the crater lake water. The hollow structure of the shells suggests that they were formed by the heating of hydrothermal solution droplets suspended by a mixed stream of gas and ash in the plume. The salt shells suggest the existence of a hydrothermal system beneath the crater floor, even during the course of magmatic eruptions. Instability of the magmatic-hydrothermal interface can cause phreatomagmatic explosions, which often occur at the end of the eruptive phase of this volcano.

Volcanic alert system (VAS) developed during the 2011-2014 El Hierro (Canary Islands) volcanic process

Science.gov (United States)

García, Alicia; Berrocoso, Manuel; Marrero, José M.; Fernández-Ros, Alberto; Prates, Gonçalo; De la Cruz-Reyna, Servando; Ortiz, Ramón

2014-06-01

The 2011 volcanic unrest at El Hierro Island illustrated the need for a Volcanic Alert System (VAS) specifically designed for the management of volcanic crises developing after long repose periods. The VAS comprises the monitoring network, the software tools for analysis of the monitoring parameters, the Volcanic Activity Level (VAL) management, and the assessment of hazard. The VAS presented here focuses on phenomena related to moderate eruptions, and on potentially destructive volcano-tectonic earthquakes and landslides. We introduce a set of new data analysis tools, aimed to detect data trend changes, as well as spurious signals related to instrumental failure. When data-trend changes and/or malfunctions are detected, a watchdog is triggered, issuing a watch-out warning (WOW) to the Monitoring Scientific Team (MST). The changes in data patterns are then translated by the MST into a VAL that is easy to use and understand by scientists, technicians, and decision-makers. Although the VAS was designed specifically for the unrest episodes at El Hierro, the methodologies may prove useful at other volcanic systems.

Coupled RNA-SIP and metatranscriptomics of active chemolithoautotrophic communities at a deep-sea hydrothermal vent.

Science.gov (United States)

Fortunato, Caroline S; Huber, Julie A

2016-08-01

The chemolithoautotrophic microbial community of the rocky subseafloor potentially provides a large amount of organic carbon to the deep ocean, yet our understanding of the activity and metabolic complexity of subseafloor organisms remains poorly described. A combination of metagenomic, metatranscriptomic, and RNA stable isotope probing (RNA-SIP) analyses were used to identify the metabolic potential, expression patterns, and active autotrophic bacteria and archaea and their pathways present in low-temperature hydrothermal fluids from Axial Seamount, an active submarine volcano. Metagenomic and metatranscriptomic results showed the presence of genes and transcripts for sulfur, hydrogen, and ammonium oxidation, oxygen respiration, denitrification, and methanogenesis, as well as multiple carbon fixation pathways. In RNA-SIP experiments across a range of temperatures under reducing conditions, the enriched (13)C fractions showed differences in taxonomic and functional diversity. At 30 °C and 55 °C, Epsilonproteobacteria were dominant, oxidizing hydrogen and primarily reducing nitrate. Methanogenic archaea were also present at 55 °C, and were the only autotrophs present at 80 °C. Correspondingly, the predominant CO2 fixation pathways changed from the reductive tricarboxylic acid (rTCA) cycle to the reductive acetyl-CoA pathway with increasing temperature. By coupling RNA-SIP with meta-omics, this study demonstrates the presence and activity of distinct chemolithoautotrophic communities across a thermal gradient of a deep-sea hydrothermal vent.

The regional metallogenesis and optimum selection of prospecting target for superlarge uranium deposit in metallogenic area of erguna

International Nuclear Information System (INIS)

Luo Yi; Wang Zhengbang; Hou Huiqun; Zhou Dean; Qi Fucheng; Xiao Xiangping

1995-06-01

The study area, an activation zone of the median Massif in Xingmeng geosynclinal area, geologically underwent the multiple tectono-magmatic reworking of granitizations during Shinagan, Caledonia and Hercynian periods and of continental rift volcanism in the Mesozoic-Cenozoic era. It is an important potential area for uranium metallogenesis in volcanic basin in North China. The study identifies that four stages of uranium preconcentration and three phases of hydrothermal superimposed-reworking uranium metallogenesis occurred along with the regional geological elevation process. Studies on the U-Pb isotope and induced fission track of various kinds of basement rocks from the area indicate that the basement composed of crustal source remelting type Caledonian and Hercynian granites is favourable for uranium metallogenesis in volcanic basin, and that the late Jurassic intermediate-acid volcano-rock directly act as the source of uranium and that Cretaceous-Tertiary extension-rift basalt magmatic activation supply an important hydrothermal reworking condition for the uranium metallogenesis in volcanic basin. Based on comparative study on the metallogenetic conditions of typical large-scale volcanic uranium deposits at home and abroad, nine prospecting criteria are summarized, the polygenetic mixing hydrothermal uranium metallogenetic model for penetrable volcano-collapse basin is presented, and the main prospecting targets of uranium deposits are pointed out. (2 figs.)

Spatial distribution of helium isotopes in volcanic gases and thermal waters along the Vanuatu (New Hebrides) volcanic arc

Science.gov (United States)

Jean-Baptiste, P.; Allard, P.; Fourré, E.; Bani, P.; Calabrese, S.; Aiuppa, A.; Gauthier, P. J.; Parello, F.; Pelletier, B.; Garaebiti, E.

2016-08-01

We report the first helium isotope survey of volcanic gases, hot springs and some olivine phenocrysts along the Vanuatu island arc, from Tanna in the south to Vanua Lava in the north. Low CO2 content and low 3He/4He ratios in thermal fluids of Epi (4.0 ± 0.1 Ra), Efate (4.5 ± 0.1 Ra) and Pentecost (5.3 ± 0.5 Ra) islands coherently indicate reduced mantle gas leakage and crustal contamination by radiogenic helium on these extinct volcanic systems of the former (Pliocene) arc. Instead, presently active Vanuatu volcanoes display 3He/4He and C/3He ratios typical of subduction-related volcanic arcs: 3He/4He ratios range from 6.4 ± 0.5 Ra in southernmost Tanna and 7.23 ± 0.09 Ra in northernmost Vanua Lava to typical MORB values in the central islands of Gaua (7.68 ± 0.06 Ra), Ambrym (7.6 ± 0.8 Ra) and Ambae (7 ± 2 Ra in groundwaters, 7.9 ± 1.4 Ra in olivine phenocrysts, and 8.0 ± 0.1 Ra in summit fumaroles of Aoba volcano). On Ambrym, however, we discover that hydrothermal manifestations separated by only 10-15 km on both sides of a major E-W transverse fault zone crossing the island are fed by two distinct helium sources, with different 3He/4He signatures: while fluids in southwest Ambrym (Baiap and Sesivi areas) have typical arc ratios (7.6 ± 0.8 Ra), fluids on the northwest coast (Buama Bay area) display both higher 3He/4He ratios (9.8 ± 0.2 Ra in waters to 10.21 ± 0.08 Ra in bubbling gases) and lower C/3He ratios that evidence a hotspot influence. We thus infer that the influx of Indian MORB mantle beneath the central Vanuatu arc, from which Ambrym magmas originate, also involves a 3He-rich hotspot component, possibly linked to a westward influx of Samoan hotspot material or another yet unknown local source. This duality in magmatic He source at Ambrym fits with the bimodal composition and geochemistry of the erupted basalts, implying two distinct magma sources and feeding systems. More broadly, the wide He isotopic variations detected along the Vanuatu

Characteristics of volcanic gas correlated to the eruption activity; Case study in the Merapi Volcano, periods of 1990-1994

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Priatna Priatna

2014-06-01

Full Text Available http://dx.doi.org/10.17014/ijog.vol2no4.20074Volcanic gases, collected from Gendol and Woro solfatara fields, the summit of Merapi Volcano during 1990-1994, show an increase in chemical composition of H , CO, CO , SO , and HCl prior to the volcanic events, on the contrary to the drastic decreasing water vapour. The carbon/sulfur ratio of the volcanic gases lies between 1.5 and 5.7 which means that they were derived from the fresh magma. The Apparent Equilibrium Temperature (AET which is calculated from chemical compositions of volcanic gases using reaction of SO +3H = H S+2H O showed an increasing value prior to the volcanic events. The Merapi activities lasted during August 1990 to November 1994 showed a significant increase in ratio SO /H S prior to the November 1994 pyroclastic flow. The isotopic composition of volcanic gas condensates indicates that water vapour in Gendol is directly derived from the fresh magma. On the other hand, the contamination and cooling by the subsurface water occurred around the Woro field at a shallow part. 

Global volcanic aerosol properties derived from emissions, 1990-2014, using CESM1(WACCM): VOLCANIC AEROSOLS DERIVED FROM EMISSIONS

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Mills, Michael J. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Schmidt, Anja [School of Earth and Environment, University of Leeds, Leeds UK; Easter, Richard [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Solomon, Susan [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge Massachusetts USA; Kinnison, Douglas E. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Ghan, Steven J. [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Neely, Ryan R. [School of Earth and Environment, University of Leeds, Leeds UK; National Centre for Atmospheric Science, University of Leeds, Leeds UK; Marsh, Daniel R. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Conley, Andrew [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Bardeen, Charles G. [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA; Gettelman, Andrew [Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder Colorado USA

2016-03-06

Accurate representation of global stratospheric aerosol properties from volcanic and non-volcanic sulfur emissions is key to understanding the cooling effects and ozone-loss enhancements of recent volcanic activity. Attribution of climate and ozone variability to volcanic activity is of particular interest in relation to the post-2000 slowing in the apparent rate of global average temperature increases, and variable recovery of the Antarctic ozone hole. We have developed a climatology of global aerosol properties from 1990 to 2014 calculated based on volcanic and non-volcanic emissions of sulfur sources. We have complied a database of volcanic SO2 emissions and plume altitudes for eruptions between 1990 and 2014, and a new prognostic capability for simulating stratospheric sulfate aerosols in version 5 of the Whole Atmosphere Community Climate Model, a component of the Community Earth System Model. Our climatology shows remarkable agreement with ground-based lidar observations of stratospheric aerosol optical depth (SAOD), and with in situ measurements of aerosol surface area density (SAD). These properties are key parameters in calculating the radiative and chemical effects of stratospheric aerosols. Our SAOD climatology represents a significant improvement over satellite-based analyses, which ignore aerosol extinction below 15 km, a region that can contain the vast majority of stratospheric aerosol extinction at mid- and high-latitudes. Our SAD climatology significantly improves on that provided for the Chemistry-Climate Model Initiative, which misses 60% of the SAD measured in situ. Our climatology of aerosol properties is publicly available on the Earth System Grid.

Neogene volcanism in Gutai Mts. (Eastern Carpathains: a review

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Marinel Kovacs

2003-04-01

Full Text Available Two types of volcanism developed in Gutâi Mts. (inner volcanic chain of Eastern Carpathians: a felsic, extensional/“back-arc” type and an intermediate, arc type. The felsic volcanism of explosive origin, consisting of caldera-related rhyolitic ignimbrites and resedimented volcaniclastics, had taken place during Early-Middle Badenian and Early Sarmatian. The intermediate volcanism, consisting of extrusive (effusive and explosive and intrusive activity, had developed during Sarmatian and Pannonian (13.4-7.0 Ma. It is represented by typical calc-alkaline series, from basalts to rhyolites. Lava flows of basaltic andesites and andesites are predominant, often emplaced in subaqueous environment. Extrusive domes, mainly composed of dacites, are associated to the andesitic volcanic structures. The intermediate volcanism, consisting of extrusive (effusive and explosive and intrusive activity, had developed during Sarmatian and Pannonian (13.4-7.0 Ma. It is represented by typical calc-alkaline series, from basalts to rhyolites. Lava flows of basaltic andesites and andesites are predominant, often emplaced in subaqueous environment. Extrusive domes, mainly composed of dacites, are associated to the andesitic volcanic structures. The geochemical study on the volcanic rocks shows the calc-alkaline character of both felsic and intermediate volcanism and typical subduction zones geochemical signatures for the intermediate one. The felsic volcanism shows affinities with subduction-related rocks as well. The main petrogenetic process in Gutâi Mts. was crustal assimilation, strongly constrained by trace element and isotope geochemistry.

Strike-slip pull-apart process and emplacement of Xiangshan uranium-producing volcanic basin

International Nuclear Information System (INIS)

Qiu Aijin; Guo Lingzhi; Shu Liangshu

2001-01-01

Xiangshan volcanic basin is one of the famous uranium-producing volcanic basins in China. Emplacement mechanism of Xiangshan uranium-producing volcanic basin is discussed on the basis of the latest research achievements of deep geology in Xiangshan area and the theory of continental dynamics. The study shows that volcanic activity in Xiangshan volcanic basin may be divided into two cycles, and its emplacement is controlled by strike-ship pull-apart process originated from the deep regional faults. Volcanic apparatus in the first cycle was emplaced in EW-trending structure activated by clockwise strike-slipping of NE-trending deep fault, forming the EW-trending fissure-type volcanic effusion belt. Volcanic apparatus in the second cycle was emplaced at junction points of SN-trending pull-apart structure activated by sinistral strike-slipping of NE-trending deep faults and EW-trending basement faults causing the center-type volcanic magma effusion and extrusion. Moreover, the formation mechanism of large-rich uranium deposits is discussed as well

Environmental changes during Frasnian-Famennian transition in south China: A multiproxy approach

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Xu, Bing; Gu, Zhaoyan; Han, Jingtai; Wang, Chengyuan

2008-12-01

This study presents high-resolution multiproxy analyses on two Late Devonian sequences for characterizing the environmental changes during the Frasnian-Famennian (F-F) transition in south China. Carbon isotope signatures of the carbonate and organic matter consistently show two positive excursions in the late rhenana zone and around the F-F boundary, implying two increased organic carbon burial events. These observations are consistent with the records from other continents, providing further support for the documented perturbations of the global carbon cycle. Redox indices, mainly of the Cu/Al and U/Al ratios, and hydrothermal-volcanic proxies, Al/(Al + Fe) and Zr/Al, indicate reducing conditions and increased hydrothermal-volcanic activities during these carbon isotope excursions. High-resolution investigations revealed that the reducing conditions predate the onset of the carbon isotope excursions, suggesting that the two positive carbon isotope shifts are likely caused by the expansion of anoxic conditions. The low Al/(Al + Fe) ratio around the F-F boundary leads the U/Al and Cu/Al anomalies in timing, implying that this anoxic event might have resulted from a long-term cumulative effect of intense hydrothermal-volcanic activities. In the late rhenana zone, enhanced hydrothermal activity also seems responsible for the reducing conditions.

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.

Self-potential, geoelectric and magnetotelluric studies in Italian active volcanic areas

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A. Siniscalchi

1997-06-01

Full Text Available We present the results of self-potential, geoelectric and magnetotelluric studies in Italian active volcanic areas as essential contributions both to structural modeling and to hazard evaluation. On Mt. Etna and Mt. Somma-Vesuvius complexes structural modeling was emphasized due to a lack of global information involving the whole apparatuses, at least from the electrical point of view. Hazard investigation was, instead, investigated with high resolution techniques on the island of Vulcano, where intense unrest phenomena have long been recorded.

Recurrence models of volcanic events: Applications to volcanic risk assessment

International Nuclear Information System (INIS)

Crowe, B.M.; Picard, R.; Valentine, G.; Perry, F.V.

1992-01-01

An assessment of the risk of future volcanism has been conducted for isolation of high-level radioactive waste at the potential Yucca Mountain site in southern Nevada. Risk used in this context refers to a combined assessment of the probability and consequences of future volcanic activity. Past studies established bounds on the probability of magmatic disruption of a repository. These bounds were revised as additional data were gathered from site characterization studies. The probability of direct intersection of a potential repository located in an eight km 2 area of Yucca Mountain by ascending basalt magma was bounded by the range of 10 -8 to 10 -10 yr -1 2 . The consequences of magmatic disruption of a repository were estimated in previous studies to be limited. The exact releases from such an event are dependent on the strike of an intruding basalt dike relative to the repository geometry, the timing of the basaltic event relative to the age of the radioactive waste and the mechanisms of release and dispersal of the waste radionuclides in the accessible environment. The combined low probability of repository disruption and the limited releases associated with this event established the basis for the judgement that the risk of future volcanism was relatively low. It was reasoned that that risk of future volcanism was not likely to result in disqualification of the potential Yucca Mountain site

Magmatic Activity Beneath the Quiescent Three Sisters Volcanic Center, Central Oregon Cascade Range, USA, Inferred from Satellite InSAR

Science.gov (United States)

Wicks, C. W.; Dzurisin, D.; Ingebritsen, S.; Thatcher, W.; Lu, Z.; Iverson, J.

2001-12-01

Images from satellite interferometric synthetic aperture radar (InSAR) reveal uplift of a broad ~10 km by 20 km area in the Three Sisters volcanic center of the central Oregon Cascade Range, ~130 km south of Mt. St. Helens. The uplift is centered ~5 km west of South Sister volcano, the youngest stratovolcano in the volcanic center. The center has been volcanically inactive since the last eruption ~1500 years ago. Multiple European Space Agency ERS-1 and 2 satellite images from 1992 through 2000, used in this study, were selected based on orbital separation and time of year. Summer and early autumn scenes were necessary to avoid decorrelation from snow cover. Interferograms generated from these images indicate that most if not all of ~100 mm of observed uplift occurred between September 1998 and October 2000. We interpret the uplift as inflation caused by an apparently ongoing episode of magma intrusion at a depth of ~6.5 km. Geochemical (water chemistry) anomalies, first noted ~1990, coincide with the area of uplift and suggest the existence of a magma reservoir prior to the uplift. High chloride and sulfate concentrations, and a positive correlation between chloride concentration and spring temperature were found within the uplift area, with larger SO4/Cl ratios in springs at higher elevations. These findings are indicative of a high-temperature hydrothermal system driven by magma intrusions. The current inflation episode observed with InSAR may lead to an eruption, but the more persistent geochemical evidence suggests that the episode is likely the latest in a series of hitherto undetected magma intrusions. We do not yet know if the inflation has abated, is continuing, or has accelerated since October 2000--we only know that the highest rate of uplift occurred in the last year for which ERS-2 data was available (1999- 2000). In May of 2001, a continuous GPS receiver and seismometer were installed by the USGS within the Three Sisters Wilderness to monitor the

Surface heat flow and CO2 emissions within the Ohaaki hydrothermal field, Taupo Volcanic Zone, New Zealand

Science.gov (United States)

Rissmann, C.; Christenson, B.; Werner, C.; Leybourne, M.; Cole, J.; Gravley, D.

2012-01-01

Carbon dioxide emissions and heat flow have been determined from the Ohaaki hydrothermal field, Taupo Volcanic Zone (TVZ), New Zealand following 20a of production (116MW e). Soil CO2 degassing was quantified with 2663 CO2 flux measurements using the accumulation chamber method, and 2563 soil temperatures were measured and converted to equivalent heat flow (Wm -2) using published soil temperature heat flow functions. Both CO2 flux and heat flow were analysed statistically and then modelled using 500 sequential Gaussian simulations. Forty subsoil CO 2 gas samples were also analysed for stable C isotopes. Following 20a of production, current CO2 emissions equated to 111??6.7T/d. Observed heat flow was 70??6.4MW, compared with a pre-production value of 122MW. This 52MW reduction in surface heat flow is due to production-induced drying up of all alkali-Cl outflows (61.5MW) and steam-heated pools (8.6MW) within the Ohaaki West thermal area (OHW). The drying up of all alkali-Cl outflows at Ohaaki means that the soil zone is now the major natural pathway of heat release from the high-temperature reservoir. On the other hand, a net gain in thermal ground heat flow of 18MW (from 25MW to 43.3??5MW) at OHW is associated with permeability increases resulting from surface unit fracturing by production-induced ground subsidence. The Ohaaki East (OHE) thermal area showed no change in distribution of shallow and deep soil temperature contours despite 20a of production, with an observed heat flow of 26.7??3MW and a CO 2 emission rate of 39??3T/d. The negligible change in the thermal status of the OHE thermal area is attributed to the low permeability of the reservoir beneath this area, which has limited production (mass extraction) and sheltered the area from the pressure decline within the main reservoir. Chemistry suggests that although alkali-Cl outflows once contributed significantly to the natural surface heat flow (~50%) they contributed little (99% of the original CO 2

Sustained effects of volcanic ash on biofilm stoichiometry, enzyme activity and community composition in North- Patagonia streams.

Science.gov (United States)

Carrillo, Uara; Díaz-Villanueva, Verónica; Modenutti, Beatriz

2018-04-15

Volcanic eruptions are extreme perturbations that affect ecosystems. These events can also produce persistent effects in the environment for several years after the eruption, with increased concentrations of suspended particles and the introduction of elements in the water column. On 4th June 2011, the Puyehue-Cordón Caulle Volcanic Complex (40.59°S-72.11°W, 2200m.a.s.l.) erupted explosively in southern Chile. The area affected by the volcano was devastated; a thick layer of volcanic ash (up to 30cm) was deposited in areas 50 km east of the volcano towards Argentina. The aim of the present study was to evaluate the effect of volcanic ash deposits on stream ecosystems four years after the eruption, comparing biofilm stoichiometry, alkaline phosphatase activity, and primary producer's assemblage in streams which were severely affected by the volcano with unaffected streams. We confirmed in the laboratory that ash deposited in the catchment of affected streams still leach phosphorus (P) into the water four years after eruption. Results indicate that affected streams still receive volcanic particles and that these particles release P, thus stream water exhibits high P concentration. Biofilm P content was higher and the C:P ratio lower in affected streams compared to unaffected streams. As a consequence of less P in unaffected streams, the alkaline phosphatase activity was higher compared to affected streams. Cyanobacteria increased their abundances (99.9% of total algal biovolume) in the affected streams suggesting that the increase in P may positively affect this group. On the contrary, unaffected streams contained a diatom dominant biofilm. In this way, local heterogeneity was created between sub-catchments located within 30 km of each other. These types of events should be seen as opportunities to gather valuable ecological information about how severe disturbances, like volcanic eruptions, shape landscapes and lotic systems for several years after the event

Evolution of the Mothra Hydrothermal Field, Endeavour Segment of the Juan de Fuca Ridge

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Glickson, D.; Kelley, D. S.; Delaney, J.

2005-12-01

The Mothra Hydrothermal Field (MHF) is a 600 m long, high-temperature hydrothermal field. It is located 2.7 km south of the Main Endeavour Field at the southern end of the central Endeavour Segment. Mothra is the most areally extensive field along the Endeavour Segment, composed of six active sulfide clusters that are 40-200 m apart. Each cluster contains rare black smokers (venting up to 319°C), numerous diffusely venting chimneys, and abundant extinct chimneys and sulfide talus. From north to south, these clusters include Cauldron, Twin Peaks, Faulty Towers, Crab Basin, Cuchalainn, and Stonehenge. As part of the Endeavour Integrated Study Site (ISS), the MHF is a site of intensive interdisciplinary studies focused on linkages among geology, geochemistry, fluid chemistry, seismology, and microbiology. Axial valley geology at MHF is structurally complex, consisting of lightly fissured flows that abut the walls and surround a core of extensively fissured, collapsed terrain. Fissure abundance and distribution indicates that tectonism has been the dominant process controlling growth of the axial graben. Past magmatic activity is shown by the 200 m long chain of collapse basins between Crab Basin and Stonehenge, which may have held at least ~7500 m3 of lava. Assuming a flow thickness of 0.5 m, this amount of lava could cover over half the valley floor during a single volcanic event. At a local scale, MHF clusters vary in size, activity, and underlying geology. They range in size from 400-1600 m2 and consist of isolated chimneys and/or coalesced cockscomb arrays atop ramps of sulfide talus. In the northern part of the field, Cauldron, Twin Peaks, Faulty Towers, and Crab Basin are located near the western valley wall, bounded by basalt talus and a combination of collapsed sheet flows, intermixed lobate and sulfide, disrupted terrain, and isolated pillow ridges. The southern clusters, Cuchalainn and Stonehenge, are associated with collapse basins in the central valley

Comprehensive geophysical survey technique in exploration for deep-buried hydrothermal type uranium deposits in Xiangshan volcanic basin, China

International Nuclear Information System (INIS)

Ke, D.

2014-01-01

According to recent drilling results, uranium mineralization has been found underground more than 1000 m deep in the Xiangshan volcanic basin, in where uranium exploration has been carried out for over 50 years. This paper presents a comprehensive geophysical survey technique, including audio magnetotelluric method (AMT), high resolution ground magnetic and radon survey, which aim to prospect deep-buried and concealed uranium deposits in Xiangshan volcanic basin. Based on research and application, a comprehensive geophysical technique consisting of data acquisition, processing and interpretation has been established. Concealed rock and ore-controlling structure buried deeper than 1000 m can be detected by using this technique. Moreover, one kind of anti-interference technique of AMT survey is presented, which can eliminate the interference induced by the high-voltage power lines. Result of AMT in Xiangshan volcanic basin is demonstrated as high-low-high mode, which indicates there are three layers in geology. The upper layer with high resistivity is mainly the react of porphyroclastic lava. The middle layer with low resistivity is metamorphic schists or dellenite whereas the lower layer with high resistivity is inferred as granite. The interface between middle and lower layer is recognized as the potential zone for occurrence of uranium deposits. According to the corresponding relation of the resistivity and magnetic anomaly with uranium ore bodies, the tracing model of faults and interfaces between the different rocks, and the forecasting model of advantageous area for uranium deposits have been established. In terms of the forecasting model, some significant sections for uranium deposits were delineated in the west of the Xiangshan volcanic basin. As a result, some achievements on uranium prospecting have been acquired. High grade economic uranium ore bodies have been found in several boreholes, which are located in the forecasted zones. (author)

A new model for the development of the active Afar volcanic margin

Science.gov (United States)

Pik, Raphaël; Stab, Martin; Bellahsen, Nicolas; Leroy, Sylvie

2016-04-01

Volcanic passive margins, that represent more than the three quarters of continental margins worldwide, are privileged witnesses of the lithospheric extension processes thatform new oceanic basins. They are characterized by voluminous amounts of underplated, intruded and extruded magmas, under the form of massive lavas prisms (seaward-dipping reflectors, or SDR) during the course of thinning and stretching of the lithosphere, that eventually form the ocean-continent transition. The origin and mechanisms of formation of these objects are still largely debated today. We have focussed our attention in the last few years on the Afar volcanic province which represents an active analogue of such volcanic margins. We explored the structural and temporal relationships that exist between the development of the major thinning and stretching structures and the magmatic production in Central Afar. Conjugate precise fieldwork analysis along with lavas geochronology allowed us to revisit the timing and style of the rift formation, since the early syn-rift period of time in the W-Afar marginal area to present days. Extension is primarily accommodated over a wide area at the surface since the very initial periods of extension (~ 25 Ma) following the emplacement of Oligocene CFBs. We propose in our reconstruction of central Afar margin history that extension has been associated with important volumes of underplated mafic material that compensate crustal thinning. This has been facilitated by major crustal-scale detachments that help localize the thinning and underplating at depth. In line with this 'magmatic wide-rift' mode of extension, we demonstrate that episodic extension steps alternate with more protracted magmatic phases. The production of syn-rift massive flood basalts (~ 4 Ma) occurs after early thinning of both the crust and the lithosphere, which suggests that SDR formation, is controlled by previous tectonic event. We determined how the melting regime evolved in

Spontaneous and Widespread Electricity Generation in Natural Deep-Sea Hydrothermal Fields.

Science.gov (United States)

Yamamoto, Masahiro; Nakamura, Ryuhei; Kasaya, Takafumi; Kumagai, Hidenori; Suzuki, Katsuhiko; Takai, Ken

2017-05-15

Deep-sea hydrothermal vents discharge abundant reductive energy into oxidative seawater. Herein, we demonstrated that in situ measurements of redox potentials on the surfaces of active hydrothermal mineral deposits were more negative than the surrounding seawater potential, driving electrical current generation. We also demonstrated that negative potentials in the surface of minerals were widespread in the hydrothermal fields, regardless of the proximity to hydrothermal fluid discharges. Lab experiments verified that the negative potential of the mineral surface was induced by a distant electron transfer from the hydrothermal fluid through the metallic and catalytic properties of minerals. These results indicate that electric current is spontaneously and widely generated in natural mineral deposits in deep-sea hydrothermal fields. Our discovery provides important insights into the microbial communities that are supported by extracellular electron transfer and the prebiotic chemical and metabolic evolution of the ocean hydrothermal systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Origin and Distribution of Thiophenes and Furans in Gas Discharges from Active Volcanoes and Geothermal Systems

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Franco Tassi

2010-03-01

Full Text Available The composition of non-methane organic volatile compounds (VOCs determined in 139 thermal gas discharges from 18 different geothermal and volcanic systems in Italy and Latin America, consists of C2–C20 species pertaining to the alkanes, alkenes, aromatics and O-, S- and N-bearing classes of compounds. Thiophenes and mono-aromatics, especially the methylated species, are strongly enriched in fluids emissions related to hydrothermal systems. Addition of hydrogen sulphide to dienes and electrophilic methylation involving halogenated radicals may be invoked for the formation of these species. On the contrary, the formation of furans, with the only exception of C4H8O, seems to be favoured at oxidizing conditions and relatively high temperatures, although mechanisms similar to those hypothesized for the production of thiophenes can be suggested. Such thermodynamic features are typical of fluid reservoirs feeding high-temperature thermal discharges of volcanoes characterised by strong degassing activity, which are likely affected by conspicuous contribution from a magmatic source. The composition of heteroaromatics in fluids naturally discharged from active volcanoes and geothermal areas can then be considered largely dependent on the interplay between hydrothermal vs. magmatic contributions. This implies that they can be used as useful geochemical tools to be successfully applied in both volcanic monitoring and geothermal prospection.

Origin and distribution of thiophenes and furans in gas discharges from active volcanoes and geothermal systems.

Science.gov (United States)

Tassi, Franco; Montegrossi, Giordano; Capecchiacci, Francesco; Vaselli, Orlando

2010-03-31

The composition of non-methane organic volatile compounds (VOCs) determined in 139 thermal gas discharges from 18 different geothermal and volcanic systems in Italy and Latin America, consists of C(2)-C(20) species pertaining to the alkanes, alkenes, aromatics and O-, S- and N-bearing classes of compounds. Thiophenes and mono-aromatics, especially the methylated species, are strongly enriched in fluids emissions related to hydrothermal systems. Addition of hydrogen sulphide to dienes and electrophilic methylation involving halogenated radicals may be invoked for the formation of these species. On the contrary, the formation of furans, with the only exception of C(4)H(8)O, seems to be favoured at oxidizing conditions and relatively high temperatures, although mechanisms similar to those hypothesized for the production of thiophenes can be suggested. Such thermodynamic features are typical of fluid reservoirs feeding high-temperature thermal discharges of volcanoes characterised by strong degassing activity, which are likely affected by conspicuous contribution from a magmatic source. The composition of heteroaromatics in fluids naturally discharged from active volcanoes and geothermal areas can then be considered largely dependent on the interplay between hydrothermal vs. magmatic contributions. This implies that they can be used as useful geochemical tools to be successfully applied in both volcanic monitoring and geothermal prospection.

A high-temperature hydrothermal deposit on the East Pacific Rise near 70N

International Nuclear Information System (INIS)

Boulegue, J.; Stouff, P.; Perseil, E.A.; Bernat, M.; Dupre, B.; Francheteau, J.

1984-01-01

A SEABEAM survey of the East Pacific Rise (EPR) led to the selection of several sites having structural characteristics favorable for hydrothermal activity. Dredging of such an area located at 7 0 N on the EPR resulted in the recovery of sulfides, oxides and fresh basalt. Chemical analyses and isotopic compositions showed that the recovered pyrites were probably precipitated directly from hot vent hydrothermal waters. Chemical analyses and isotopic composition of manganese-iron oxides indicated that they too were of hydrothermal origin. 210 Pb/Pb measurements yielded ages of 90 +- 10 years for the deposits. This site may still be undergoing hydrothermal activity. (orig.)

Hydrothermal fabrication of N-doped (BiO){sub 2}CO{sub 3}: Structural and morphological influence on the visible light photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Dong, Fan, E-mail: dfctbu@126.com [Chongqing Key Laboratory of Catalysis and Functional Organic Molecules, College of Environmental and Biological Engineering, Chongqing Technology and Business University, Chongqing 400067 (China); Wang, Rui; Li, Xinwei [Chongqing Key Laboratory of Catalysis and Functional Organic Molecules, College of Environmental and Biological Engineering, Chongqing Technology and Business University, Chongqing 400067 (China); Ho, Wing-Kei [Department of Science and Environmental Studies, The Centre for Education in Environmental Sustainability, The Hong Kong Institute of Education, Hong Kong (China)

2014-11-15

Graphical abstract: - Highlights: • Persimmon-like, flower-like N-doped (BiO){sub 2}CO{sub 3} superstructures were prepared. • The superstructures were fabricated by one-step hydrothermal method. • The hydrothermal temperature controlled the morphological structure. • N-doped (BiO){sub 2}CO{sub 3} superstructure showed enhanced photocatalytic activity. • The high activity can be ascribed to doped nitrogen and hierarchical structure. - Abstract: Various 3D N-doped (BiO){sub 2}CO{sub 3} (N-BOC) hierarchical superstructures self-assembled with 2D nanosheets were fabricated by one-step hydrothermal treatment of bismuth citrate and urea. The as-obtained samples were characterized by XRD, XPS, FT-IR, SEM, N{sub 2} adsorption–desorption isotherms and UV–vis DRS. The hydrothermal temperature plays a crucial role in tuning the crystal and morphological structure of the samples. Adjusting the reaction temperature to 150, 180 and 210 °C, we obtained N-doped (BiO){sub 2}CO{sub 3} samples with corresponding attractive persimmon-like, flower-like and nanoflakes nano/microstructures. The photocatalytic activities of the samples were evaluated by removal of NO under visible and solar light irradiation. The results revealed that the N-doped (BiO){sub 2}CO{sub 3} hierarchical superstructures showed enhanced visible light photocatalytic activity compared to pure (BiO){sub 2}CO{sub 3} and TiO{sub 2}-based visible light photocatalysts. The outstanding photocatalytic performance of N-BOC samples can be ascribed to the doped nitrogen and the special hierarchical structure. The present work could provide new perspectives in controlling the morphological structure and photocatalytic activity of photocatalyst for better environmental pollution control.

Diffuse CO2 degassing studies to reveal hidden geothermal resources in oceanic volcanic islands: The Canarian archipelago case study

Science.gov (United States)

Rodríguez, F.; Perez, N. M.; García-Merino, M.; Padron, E.; Melián, G.; Asensio-Ramos, M.; Hernandez Perez, P. A.; Padilla, G.; Barrancos, J.; Cótchico, M. A.

2016-12-01

The Canary Islands, owing to their recent volcanism, are the only Spanish territory with potential high enthalpy geothermal resources. The final goal of geothermal exploration in a specific area is to locate and define the size, shape, structure of hidden geothermal resources, and determine their characteristics (fluid type, temperature, chemical composition an ability to produce energy). At those areas where there is not any evidence of endogenous fluids manifestations at surface, that traditionally evidence the presence of an active geothermal system) the geochemical methods for geothermal exploration must include soil gas surveys. This is the case of five mining licenses for geothermal exploration in the Canay Islands, four in Tenerife and one in Gran Canaria Island. We report herein the results of diffuse CO2 emission studies in the five mining licenses during 2011-2014. The primary objective of the study was to sort the possible geothermal potential of these five mining licenses, thus reducing the uncertainty inherent to the selection of the areas with highest geothermal potential for future exploration works. The criterion used to sort the different areas was the contribution of volcano-hydrothermal CO2 in the degassing at each study area. Several hundreds of measurements of diffuse CO2 emission, soil CO2 concentration and isotopic composition were performed at each study area. Based in three different endmembers (biogenic, atmospheric and deep-seated CO2) with different CO2 concentrations (100, 0.04 and 100% respectively) and isotopic compositions (-20, -8 and -3 per mil vs. VPDB respectively) a mass balance to distinguish the different contribution of each endmember in the soil CO2 at each sampling site was made. The percentage of the volcano-hydrothermal contribution in the current diffuse CO2 degassing was in the range 2-19%.The Abeque mining license, that comprises part of the north-west volcanic rift of Tenerife, seemed to show the highest geothermal

Holocene volcanic geology, volcanic hazard, and risk on Taveuni, Fiji

International Nuclear Information System (INIS)

Cronin, S.J.; Neall, V.E.

2001-01-01

The Holocene volcanic geology of Taveuni has been mapped in order to produce a volcanic hazard and risk assessment for the island. Taveuni is the third-largest island of the Fiji group and home to 14,500 people. At least cubic km 2.7 of olivine-alkali-basalt magma was erupted from over 100 events throughout the Holocene. Vents are concentrated along a northeast-striking rift zone that is parallel to other regional structural trends. There is an overall trend of younging southward along the rift. Holocene lavas and tephras are grouped within six newly defined eruptive periods, established on a basis of radiocarbon dating. Within these periods, 14 tephra layers, useful as local marker horizons, are recognised. At least 58% of Holocene eruptions produced lava flows, while almost all produced some tephra. Individual eruption event volumes ranged between 0.001 and cubic km 0.20 (dense rock equivalent). Many eruptions involved at least some phases of phreatic and/or phreato-magmatic activity, although dominant hydrovolcanic activity was limited to only a few events. A volcanic hazard map is presented, based on the Holocene geology map and statistical analyses of eruption recurrence. The highest levels of ground-based and near-vent hazards are concentrated along the southern portion of the island's rift axis, with the paths of initial lava flows predicted from present topography. Tephra fall hazards are based on eruption parameters interpreted from mapped Holocene tephra layers. Hawaiian explosive-style eruptions appear to be a dominant eruptive process, with prevailing low-level (<3 km) southeasterly winds dispersing most tephra to the northwestern quadrant. Vulnerable elements (population centres, infrastructure, and economy) on Taveuni have been considered in deriving a volcanic risk assessment for the island. A number of infrastructural and subdivision developments are either under way or planned for the island, driven by its highly fertile soils and availability of

New K-Ar ages of volcanic rocks and associated mineralization in Canada Honda district, San Luis, Argentina

International Nuclear Information System (INIS)

Urbina, N.E.; Oggier, F.P

2001-01-01

New K-Ar ages in the Late Tertiary gold-bearing volcanic belt of the Sierras Pampeanas of San Luis, Argentina are presented. At Canada Honda district, an age of 8.49±0.2 Ma yielded by Cerro del Valle andesite indicates that the dome emplacement postdates the Diente Verde eruptive event. An even younger age of 7.3±0.2 Ma was obtained for illite from hydrothermal alteration at La Reynela mineralization which is hosted by Cerro del Valle andesite (au)

Assessment of volcanic hazards, vulnerability, risk and uncertainty (Invited)

Science.gov (United States)

Sparks, R. S.

2009-12-01

A volcanic hazard is any phenomenon that threatens communities . These hazards include volcanic events like pyroclastic flows, explosions, ash fall and lavas, and secondary effects such as lahars and landslides. Volcanic hazards are described by the physical characteristics of the phenomena, by the assessment of the areas that they are likely to affect and by the magnitude-dependent return period of events. Volcanic hazard maps are generated by mapping past volcanic events and by modelling the hazardous processes. Both these methods have their strengths and limitations and a robust map should use both approaches in combination. Past records, studied through stratigraphy, the distribution of deposits and age dating, are typically incomplete and may be biased. Very significant volcanic hazards, such as surge clouds and volcanic blasts, are not well-preserved in the geological record for example. Models of volcanic processes are very useful to help identify hazardous areas that do not have any geological evidence. They are, however, limited by simplifications and incomplete understanding of the physics. Many practical volcanic hazards mapping tools are also very empirical. Hazards maps are typically abstracted into hazards zones maps, which are some times called threat or risk maps. Their aim is to identify areas at high levels of threat and the boundaries between zones may take account of other factors such as roads, escape routes during evacuation, infrastructure. These boundaries may change with time due to new knowledge on the hazards or changes in volcanic activity levels. Alternatively they may remain static but implications of the zones may change as volcanic activity changes. Zone maps are used for planning purposes and for management of volcanic crises. Volcanic hazards maps are depictions of the likelihood of future volcanic phenomena affecting places and people. Volcanic phenomena are naturally variable, often complex and not fully understood. There are