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Sample records for active hydrothermal sites

  1. Discovery of Active Hydrothermal Sites Along the Mariana Volcanic Arc, Western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Baker, E. T.; Embley, R. W.; Resing, J. A.; Lupton, J. E.; Massoth, G. J.; de Ronde, C. E.; Nakamura, K.; Walker, S. L.

    2003-12-01

    Some 20,000 km of volcanic arcs, roughly one-third the total length of the global midocean ridge (MOR) system, rim the western Pacific Ocean. But compared to 25 years of hydrothermal investigations along MORs, exploration of similar activity on the estimated 600 submarine arc volcanoes is only beginning. In February 2003, as part of the Submarine Ring of Fire project funded by NOAA's Ocean Exploration Program, we made the first systematic survey of hydrothermal activity along the 1270-km-long Mariana intraoceanic volcanic arc, which lies almost entirely within the US EEZ. Prior fieldwork had documented active (but low-temperature) hydrothermal discharge on only three volcanoes: Kasuga 2, Kasuga 3, and Esmeralda Bank. During the cruise, we conducted 70 CTD operations over more than 50 individual volcanoes from 13° N to 23° N, plus a continuous CTD survey along 75 km of the back-arc spreading center (13° 15'N to 13° 41'N) adjacent to the southern end of the arc. We found evidence for active hydrothermal venting at 11 submarine volcanoes with summit (or caldera floor) depths ranging from 50 to 1550 m. Two additional sites were identified on the back-arc spreading center. Ongoing analyses of collected water samples could increase these totals. Our results confirmed continuing hydrothermal activity at Kasuga 2 (but not Kasuga 3) and Esmeralda Bank, in addition to newly discovered sites on nine other volcanoes. Many of these sites produce intense and widely dispersed plumes indicative of vigorous, high-temperature discharge. The volcanoes with active hydrothermal systems are about equally divided between those with and without summit calderas. The addition of the Marianas data greatly improves our view of hydrothermal sources along arcs. The 20,000 km of Pacific arcs can be divided between 6380 km of intraoceanic (i.e., mostly submarine) arcs and 13,880 km of island (i.e., mostly subaerial) arcs. At present, ˜15% of the total length of Pacific arcs has been surveyed

  2. Deep-Sea Magnetics on Active and Fossil Hydrothermal Sites: a Tool to Detect and Characterize Submarine Ore Deposits

    NASA Astrophysics Data System (ADS)

    Dyment, J.; Szitkar, F.; Fouquet, Y.; Choi, Y.

    2011-12-01

    Since the first discoveries of hydrothermal sites at mid-ocean ridges in the 70s, international efforts in the deep seafloor exploration have unravelled a wide variety of hydrothermal sites in terms of geological settings, physical parameters, and biological communities as well. Such efforts, coordinated in the InterRidge program since 1992, are becoming even more important when the increasing need in metals for developing economies makes the exploitation of metal sulfides accumulated at deep-sea hydrothermal sites a realistic target. The usual method to find hydrothermal sites is to detect the associated chemical plumes enriched in manganese, methane, hydrogen, helium 3, in the water column. How efficient it has been proven, such a method is limited to the search for active hydrothermal vents. Active vents, however, are not the best places for mining the seafloor, because (1) they host massive sulfides deposits in the making and may not represent the largest accumulation; (2) they are still very hot and would rapidly damage the mining tools; and, last but not the least, (3) they host fragile and precious ecosystem that could be dramatically affected by mining operations. Methods to find fossil hydrothermal sites (i.e. colder and devoid of specific ecosystems) include systematic rock sampling - a very tedious endeavour - and high resolution, near seafloor geophysical surveys. Existing magnetic surveys on basalt-hosted, peridotite-hosted and sediment-hosted sites revealed different types of signatures, which reflect the magnetizations of the host rock and the ore deposit, among others. Basalt-hosted sites exhibit negative magnetic anomalies, i.e. a deficit of magnetization, due to thermal demagnetization and hydrothermal alteration of the highly magnetic basalt, whereas both peridotite-hosted and sediment-hosted sites show positive anomalies, i.e. an excess of magnetization, clearly associated with the ore deposit. Results from recent cruises Serpentine (R

  3. Hydrothermal Activity on the Mid-Cayman Rise: ROV Jason sampling and site characterization at the Von Damm and Piccard hydrothermal fields

    NASA Astrophysics Data System (ADS)

    German, C. R.

    2012-12-01

    In January 2012 our multi-national and multi-disciplinary team conducted a series of 10 ROV Jason dives to conduct first detailed and systematic sampling of the Mid Cayman Rise hydrothermal systems at the Von Damm and Piccard hydrothermal fields. At Von Damm, hydrothermal venting is focused at and around a large conical structure that is approximately 120 m in diameter and rises at least 80m from the surrounding, largely sedimented seafloor. Clear fluids emitted from multiple sites around the flanks of the mound fall in the temperature range 110-130°C and fall on a common mixing line with hotter (>200°C) clear fluids emitted from an 8m tall spire at the summit which show clear evidence of ultramafic influence. Outcrop close to the vent-site is rare and the cone itself appear to consist of clay minerals derived from highly altered host rock. The dominant fauna at the summit of Von Damm are a new species of chemosynthetic shrimp but elsewhere the site also hosts two distinct species of chemosynthetic tube worm as well as at least one species of gastropod. The adjacent Piccard site, at ~5000m depth comprises 7 distinct sulfide mounds, 3 of which are currently active: Beebe Vents, Beebe Woods and Beebe Sea. Beebe Vents consists of 5 vigorous black smoker chimneys with maximum temperatures in the range 400-403°C while at Beebe Woods a more highly colonized thicket of up to 8m tall chimneys includes predominantly beehive diffusers with rare black smokers emitting fluids up to 353°C. Beebe Sea a diffuse site emitting fluids at 38°C Tmax, is the largest of the currently active mounds and immediately abuts a tall (8m) rift that strikes NE-SW bisecting the host Axial Volcanic Ridge. The fauna at Piccard are less diverse than at Von Damm and, predominantly, comprise the same species of MCR shrimp, a distinct gastropod species and abundant anemones.

  4. Enceladus: Starting Hydrothermal Activity

    NASA Technical Reports Server (NTRS)

    Matson, D. L.; Castillo-Rogez, J. C.; Johnson, T. V.; Lunine, J. I.; Davies, A. G.

    2011-01-01

    We describe a process for starting the hydrothermal activity in Enceladus' South Polar Region. The process takes advantage of fissures that reach the water table, about 1 kilometer below the surface. Filling these fissures with fresh ocean water initiates a flow of water up from an ocean that can be self-sustaining. In this hypothesis the heat to sustain the thermal anomalies and the plumes comes from a slightly warm ocean at depth. The heat is brought to the surface by water that circulates up, through the crust and then returns to the ocean.

  5. Geological framework of an active hydrothermal site in the North Fiji Basin: Starmer cruise of the submersible Nautile

    SciTech Connect

    Auzende, J. )

    1990-06-01

    During the summer of 1989 the French submersible Nautile carried out a diving cruise on the North Fiji Basin ridge axis in the frame of the Starmer French-Japanese joint project. The diving sites were selected using the Seapso 3, Kaiyo 87, and Kaiyo 88 cruises Seabeam surveys. They are located around 17{degree}S in the axial graben at the northern end of the N15 ridge. The axis consists of an 18 km wide, N15 elongated dome cut by a 2 km wide axial graben. The elevation of the dome with respect to adjacent oceanic floor is 500-600 m. It culminates at less than 1,900 m, which is higher than a normal oceanic ridge. The axial graben width (2 km) is also unusual compared to oceanic ridge with intermediate spreading rates such as the EPR at 21{degree}N. Six Nautile dives have been devoted to the detailed exploration of the axial graben between 16{degree}58'S and 17{degree}00'S in order to locate the hydrothermal vents in the inferred most active part of the axial graben. A structural map has been established on the basis of dive observation. Between 17{degree}S and 16{degree}58'S, the axis shows a succession of N15-trending horsts and grabens paralleling the main orientation of the ridge. Two main lateral grabens and a central graben can be recognized. The central graben shows remarkably constant width (200 m) and depth (2,000 m). It is bounded by two small horsts, few tens of meters wide. Observed tectonic features include N15 normal fault scarps and abundant open fissures with the same direction. The whole area is dusted with sediments indicating that volcanism was not active recently. Evidence of recent hydrothermal activity such as oxide staining, dead munch, dead chimney is abundant all along the central graben.

  6. Chemosynthetic microbial activity at Mid-Atlantic Ridge hydrothermal vent sites

    NASA Astrophysics Data System (ADS)

    Wirsen, Carl O.; Jannasch, Holger W.; Molyneaux, Stephen J.

    1993-06-01

    Chemosynthetic production of microbial biomass, determined by 14CO2 fixation and enzymatic (RuBisCo) activity, at the Mid-Atlantic Ridge (MAR) 23° and 26°N vent sites was found in various niches: warm water emissions, loosely rock-attached flocculent material, dense morphologically diverse bacterial mats covering the surfaces of polymetal sulfide deposits, and filamentous microbes on the carapaces of shrimp (Rimicaris exoculata). The bacterial mats on polymetal sulfide surfaces contained unicellular and filamentous bacteria which appeared to use as their chemolithotrophic electron or energy source either dissolved reduced minerals from vent emissions, mainly sulfur compounds, or solid metal sulfide deposits, mainly pyrite. Moderately thermophilic Chemosynthetic activity was observed in carbon dioxide fixation experiments and in enrichments, but no thermophilic aerobic sulfur oxidizers could be isolated. Both obligate and facultative chemoautotrophs growing at mesophilic temperatures were isolated from all chemosynthetically active surface scrapings. The obligate autotrophs could oxidize sterilized MAR natural sulfide deposits as well as technical pyrite at near neutral pH, in addition to dissolved reduced sulfur compounds. While the grazing by shrimp on the surface mats of MAR metal sulfide deposits was observed and deemed important, the animals' primary occurrence in dense swarms near vent emissions suggests that they were feeding at these sites, where conditions for Chemosynthetic growth of their filamentous microbial epiflora were optimal. The data show that the transformation of geothermal energy at the massive polymetal sulfide deposits of the MAR is based on the lithoautotrophic oxidation of soluble sulfides and pyrites into microbial biomass.

  7. Arctic Ocean: hydrothermal activity on Gakkel Ridge.

    PubMed

    Jean-Baptiste, Philippe; Fourré, Elise

    2004-03-01

    In the hydrothermal circulation at mid-ocean ridges, sea water penetrates the fractured crust, becomes heated by its proximity to the hot magma, and returns to the sea floor as hot fluids enriched in various chemical elements. In contradiction to earlier results that predict diminishing hydrothermal activity with decreasing spreading rate, a survey of the ultra-slowly spreading Gakkel Ridge (Arctic Ocean) by Edmonds et al. and Michael et al. suggests that, instead of being rare, the hydrothermal activity is abundant--exceeding by at least a factor of two to three what would be expected by extrapolation from observation on faster spreading ridges. Here we use helium-3 (3He), a hydrothermal tracer, to show that this abundance of venting sites does not translate, as would be expected, into an anomalous hydrothermal 3He output from the ridge. Because of the wide implications of the submarine hydrothermal processes for mantle heat and mass fluxes to the ocean, these conflicting results call for clarification of the link between hydrothermal activity and crustal production at mid-ocean ridges.

  8. Correlation of the changes in the framework and active Cu sites for typical Cu/CHA zeolites (SSZ-13 and SAPO-34) during hydrothermal aging.

    PubMed

    Su, Wenkang; Li, Zhenguo; Peng, Yue; Li, Junhua

    2015-11-21

    The relative framework stability of Cu/CHA zeolites (SAPO-34 and SSZ-13) was studied during hydrothermal aging at 800 °C, and the fundamental mechanism for the framework change was investigated. Additionally, the relationship between the variation in the framework and active SCR reaction sites was established. SAPO-34 showed stronger stability during hydrothermal aging than SSZ-13. The results showed that dealumination occurred in the SSZ-13 zeolite, leading to the loss of crystallinity and a severe decrease of the Brönsted acid sites. Simultaneously, the detached Al(OH)3 species deactivated the Cu species by the transformation of isolated Cu(2+) ions to CuAlOx species. While the vacancy in the SAPO-34 framework caused by desilication could be healed with the migration of extra-framework Al and P atoms to the defects. And the Cu species showed a certain degree of aggregation with the improved redox ability of the aged Cu/SAPO-34 zeolite and the acidic properties were well maintained. PMID:26462874

  9. High-Temperature Hydrothermal Vent Field of Kolumbo Submarine Volcano, Aegean Sea: Site of Active Kuroko-Type Mineralization

    NASA Astrophysics Data System (ADS)

    Sigurdsson, H.; Carey, S.; Alexandri, M.; Vougioukalakis, G.; Croff, K.; Roman, C.; Sakellariou, D.; Anagnostou, C.; Rousakis, G.; Ioakim, C.; Gogou, A.; Ballas, D.; Misaridis, T.; Nomikou, P.

    2006-12-01

    Kolumbo submarine volcano is located 7 km north-east of the island of Santorini in the Hellenic arc (Greece), and comprises one of about twenty submarine cones in a NE-trending rift zone. Kolumbo erupted explosively in 1649-50AD, causing 70 fatalities on Santorini. Kolumbo's crater is 1700 m in diameter, with a crater rim at 10 m below sea level and crater floor at depth of 505 m. Recent marine geological investigations, using ROVs, reveal a very active high-temperature hydrothermal vent field in the northeastern part of the Kolumbo crater floor, about 25,000 m2. Vent chimneys up to 4 m high are vigorously emitting colorless gas plumes up to 10 m high in the water column. Temperatures up to 220oC are recorded in vent fluids. Some vents are in crater- like depressions, containing debris from collapsed extinct chimneys. The entire crater floor of Kolumbo is mantled by a reddish-orange bacterial mat, and bacterial filaments of a variety of colors cling to chimneys in dense clusters. Glassy tunicates and anemones are common in lower-temperature environments on the crater floor. Most chimneys show a high porosity, with a central conduit surrounded by an open and very permeable framework of sulfides and sulfates, aiding fluid flow through the chimney walls. In the sulfate-rich samples, blades of euhedral barite and anhydrite crystals coat the outside of the chimney wall, and layers of barite alternate with sulfide in the interior. The dominant sulfides are pyrite, sphalerite, wurtzite, marcasite and galena. Crusts on extinct and lower-temperature chimneys are composed of amorphous silica, goethite and halite. Sulfur isotope composition of sulfates is virtually at sea water values, whereas the sulfides are more depleted. Elevated levels of copper, gold and silver are observed in bulk composition of chimney samples. Both the structural setting, character of the vent field and sulfide/sulfate mineralogy and geochemistry indicate on-going Kuroko-type mineralization in the

  10. Ongoing hydrothermal activities within Enceladus.

    PubMed

    Hsu, Hsiang-Wen; Postberg, Frank; Sekine, Yasuhito; Shibuya, Takazo; Kempf, Sascha; Horányi, Mihály; Juhász, Antal; Altobelli, Nicolas; Suzuki, Katsuhiko; Masaki, Yuka; Kuwatani, Tatsu; Tachibana, Shogo; Sirono, Sin-iti; Moragas-Klostermeyer, Georg; Srama, Ralf

    2015-03-12

    Detection of sodium-salt-rich ice grains emitted from the plume of the Saturnian moon Enceladus suggests that the grains formed as frozen droplets from a liquid water reservoir that is, or has been, in contact with rock. Gravitational field measurements suggest a regional south polar subsurface ocean of about 10 kilometres thickness located beneath an ice crust 30 to 40 kilometres thick. These findings imply rock-water interactions in regions surrounding the core of Enceladus. The resulting chemical 'footprints' are expected to be preserved in the liquid and subsequently transported upwards to the near-surface plume sources, where they eventually would be ejected and could be measured by a spacecraft. Here we report an analysis of silicon-rich, nanometre-sized dust particles (so-called stream particles) that stand out from the water-ice-dominated objects characteristic of Saturn. We interpret these grains as nanometre-sized SiO2 (silica) particles, initially embedded in icy grains emitted from Enceladus' subsurface waters and released by sputter erosion in Saturn's E ring. The composition and the limited size range (2 to 8 nanometres in radius) of stream particles indicate ongoing high-temperature (>90 °C) hydrothermal reactions associated with global-scale geothermal activity that quickly transports hydrothermal products from the ocean floor at a depth of at least 40 kilometres up to the plume of Enceladus. PMID:25762281

  11. Ongoing hydrothermal activities within Enceladus.

    PubMed

    Hsu, Hsiang-Wen; Postberg, Frank; Sekine, Yasuhito; Shibuya, Takazo; Kempf, Sascha; Horányi, Mihály; Juhász, Antal; Altobelli, Nicolas; Suzuki, Katsuhiko; Masaki, Yuka; Kuwatani, Tatsu; Tachibana, Shogo; Sirono, Sin-iti; Moragas-Klostermeyer, Georg; Srama, Ralf

    2015-03-12

    Detection of sodium-salt-rich ice grains emitted from the plume of the Saturnian moon Enceladus suggests that the grains formed as frozen droplets from a liquid water reservoir that is, or has been, in contact with rock. Gravitational field measurements suggest a regional south polar subsurface ocean of about 10 kilometres thickness located beneath an ice crust 30 to 40 kilometres thick. These findings imply rock-water interactions in regions surrounding the core of Enceladus. The resulting chemical 'footprints' are expected to be preserved in the liquid and subsequently transported upwards to the near-surface plume sources, where they eventually would be ejected and could be measured by a spacecraft. Here we report an analysis of silicon-rich, nanometre-sized dust particles (so-called stream particles) that stand out from the water-ice-dominated objects characteristic of Saturn. We interpret these grains as nanometre-sized SiO2 (silica) particles, initially embedded in icy grains emitted from Enceladus' subsurface waters and released by sputter erosion in Saturn's E ring. The composition and the limited size range (2 to 8 nanometres in radius) of stream particles indicate ongoing high-temperature (>90 °C) hydrothermal reactions associated with global-scale geothermal activity that quickly transports hydrothermal products from the ocean floor at a depth of at least 40 kilometres up to the plume of Enceladus.

  12. Introduction to Atlantic Hydrothermal Activity

    NASA Astrophysics Data System (ADS)

    Rona, Peter A.; Thompson, Geoffrey

    1993-06-01

    Seafloor hydrothermal research has advanced rapidly from local to global scope through a sequence of discoveries. Hydrothermal research at seafloor spreading centers began in the mid-1960s with the discovery of hot metalliferous brines and sediments ponded in deeps along the slow spreading (half rate 1 cm yr-1) axis of the Red Sea [Chamock, 1964; Miller, 1964; Swallow and Crease, 1965; Miller et al., 1966; Hunt et al., 1967; Bischoff, 1969]. At the same time a hydrothermal metalliferous component was identified in sediments of the East Pacific Rise [Skomyakova, 1965; Arrhenins and Bonatti, 1965; Boström and Peterson, 1966]. Geophysicists recognized that heat flow measurements at spreading centers could only be explained by convective cooling of the crust with circulating seawater [Elder, 1967; Lister, 1972].

  13. Hydrothermal Activity in the Northern Guaymas Basin

    NASA Astrophysics Data System (ADS)

    Berndt, C.; Hensen, C.; Mortera-Gutierrez, C. A.; Sarkar, S.; Geilert, S.; Schmidt, M.; Liebetrau, V.; Kipfer, R.; Scholz, F.; Doll, M.; Muff, S.; Karstens, J.; Böttner, C.; Chi, W. C.; Moser, M.; Behrendt, R.; Fiskal, A.; Evans, T.; Planke, S.; Lizarralde, D.; Lever, M. A.

    2015-12-01

    Rift-related magmatism in the Guaymas Basin, Gulf of California induces hydrothermal activity within the basin sediments. Mobilized fluids migrate to the seafloor where they are emitted into the water column changing ocean chemistry and fuelling chemosynthetic ecosystems. New seismic and geochemical data from the northern rift arm of the Guaymas Basin document the variety of fluid expulsion phenomena from large-scale subsurface sediment mobilization related to contact metamorphosis to focused small-scale structures. The geochemical composition of emitted fluids depends largely on the age of the fluid escape structures with respect to the underlying intrusions. Whereas, old structures are dominated by methane emission, young vent sites are characterized by hot fluids that carry a wide range of minerals in solution. The overall high geothermal gradient within the basin (mainly between 160 and 260 °C/km) leads to a thin gas hydrate stability zone. Thus, deep hydrothermal fluid advection affects the gas hydrate system and makes it more dynamic than in colder sedimentary basins.

  14. The Trans-Atlantic Geotraverse hydrothermal field: A hydrothermal system on an active detachment fault

    NASA Astrophysics Data System (ADS)

    Humphris, Susan E.; Tivey, Margaret K.; Tivey, Maurice A.

    2015-11-01

    Over the last ten years, geophysical studies have revealed that the Trans-Atlantic Geotraverse (TAG) hydrothermal field (26°08‧N on the Mid-Atlantic Ridge) is located on the hanging wall of an active detachment fault. This is particularly important in light of the recognition that detachment faulting accounts for crustal accretion/extension along a significant portion of the Mid-Atlantic Ridge, and that the majority of confirmed vent sites on this slow-spreading ridge are hosted on detachment faults. The TAG hydrothermal field is one of the largest sites of high-temperature hydrothermal activity and mineralization found to date on the seafloor, and is comprised of active and relict deposits in different stages of evolution. The episodic nature of hydrothermal activity over the last 140 ka provides strong evidence that the complex shape and geological structure of the active detachment fault system exerts first order, but poorly understood, influences on the hydrothermal circulation patterns, fluid chemistry, and mineral deposition. While hydrothermal circulation extracts heat from a deep source region, the location of the source region at TAG is unknown. Hydrothermal upflow is likely focused along the relatively permeable detachment fault interface at depth, and then the high temperature fluids leave the low-angle portion of the detachment fault and rise vertically through the highly fissured hanging wall to the seafloor. The presence of abundant anhydrite in the cone on the summit of the TAG active mound and in veins in the crust beneath provides evidence for a fluid circulation system that entrains significant amounts of seawater into the shallow parts of the mound and stockwork. Given the importance of detachment faulting for crustal extension at slow spreading ridges, the fundamental question that still needs to be addressed is: How do detachment fault systems, and the structure at depth associated with these systems (e.g., presence of plutons and/or high

  15. Hydrothermal Mineralization Along the Volcanically Active Mariana Arc

    NASA Astrophysics Data System (ADS)

    de Ronde, C. E.; Hein, J. R.; Embley, R. W.; Stern, R. J.

    2004-12-01

    In March and April, 2004, ROPOS ROV dives took place from the R/V T.G. Thompson along the volcanically active Mariana arc to ground truth CTD data collected a year earlier that indicated hydrothermal activity. Dives took place on seven volcanoes, six of which showed hydrothermal activity. We present data on samples collected from NW Rota-1 (14° , 36'N, 144° , 46'E), E. Diamante (15° , 56'N, 145° , 41'E), and NW Eifuku (21° , 29'N, 144° , 03'E), the three sites most studied. All the hydrothermal systems found are associated with volcano summits, or with resurgent domes inside a caldera. Brimstone vent at NW Rota-1 provided a dramatic display of thick, bellowing, yellow plumes that contained ash and molten sulfur. This site occurs at 500 m water depth and clearly shows closely associated magmatic-hydrothermal discharge. Sulfur was the dominant hydrothermal mineral deposited around the vent and occurs as spheres in the surrounding volcaniclastic sediment, fracture fill and veins, and massive deposits. The Black Forest vent field at E Diamante consists of a sulfide-sulfate chimney system developed at about 650 m water depth. This is the only mature system discovered and consists of numerous tall (up to 9 m) chimneys. The measured fluid temperature of 240° C produces boiling at the depth of the vents. The chimneys and mounds are composed of varying amounts of pyrite, sphalerite, chalcopyrite, barite, and anhydrite. Hydrothermal Mn oxides occur on the surface of inactive chimneys. This mineralogy contrasts with the other two systems, which deposit sulfur as the dominant hydrothermal product. The Cu-Zn-Fe-Ba mineralization is perhaps largely controlled by water/rock interaction. A unique hydrothermal field (Champagne field) was found at NW Eifuku where liquid CO2 is discharging from focused- and diffuse-flow vents at 1600 m water depth. The focused-flow vents consist of small chimneys and mounds up to a meter high that are composed of sulfur and yet to be

  16. Active and relict sea-floor hydrothermal mineralization at the TAG hydrothermal field, Mid-Atlantic Ridge

    SciTech Connect

    Rona, P.A. . Atlantic Oceanographic and Meteorological Labs.); Hannington, M.D. ); Raman, C.V. ); Thompson, G.; Tivey, M.K.; Humphris, S.E. ); Lalou, C. . Lab. CNRS-CEA); Petersen, S. Aachen Univ. of Technology )

    1993-12-01

    The TAG hydrothermal field is a site of major active and inactive volcanic-hosted hydrothermal mineralization in the rift valley of the slow-spreading Mid-Atlantic Ridge at 26[degree]N. The axial high is the principal locus of present magmatic intrusions. The TAG field contains three main areas of present and past hydrothermal activity: (1) an actively venting high-temperature sulfide mound; (2) two former high-temperature vent areas; (3) a zone of low-temperature venting and precipitation of Fe and Mn oxide deposits. The volcanic centers occur at the intersections between ridge axis-parallel normal faults and projected axis-transverse transfer faults. The intersections of these active fault systems may act as conduits both for magmatic intrusions from sources beneath the axial high that build the volcanic centers and for hydrothermal upwelling that taps the heat sources. Radiometric dating of sulfide samples and manganese crusts in the hydrothermal zones and dating of sediments intercalated with pillow lava flows in the volcanic center adjacent to the active sulfide mound indicate multiple episodes of hydrothermal activity throughout the field driven by heat supplied by episodic intrusions over a period of at least 140 [times] 10[sup 3] yr. The sulfide deposits are built by juxtaposition and superposition during relatively long residence times near episodic axial heat sources counterbalanced by mass wasting in the tectonically active rift valley of the slow-spreading oceanic ridge. Hydrothermal reworking of a relict hydrothermal zone by high-temperature hydrothermal episodes has recrystallized sulfides and concentrated the first visible primary gold reported in a deposit at an oceanic ridge.

  17. Post-drilling hydrothermal vent and associated biological activities seen through artificial hydrothermal vents in the Iheya North field, Okinawa Trough

    NASA Astrophysics Data System (ADS)

    Takai, K.; Kawagucci, S.; Miyazaki, J.; Watsuji, T.; Ishibashi, J.; Yamamoto, H.; Nozaki, T.; Kashiwabara, T.; Shibuya, T.

    2012-12-01

    In 2010, IODP Expedition 331 was conducted in the Iheya North Field, the Okinawa Trough and drilled several sites in hydrothermally active subseafloor. In addition, during the IODP Expedition 331, four new hydrothermal vents were created. These post-drilling artificial hydrothermal vents provide excellent opportunities to investigate the physical, chemical and microbiological characteristics of the previously unexplored subseafloor hydrothermal fluid reservoirs, and to monitor and estimate how the anthropogenic drilling behaviors affect the deep-sea hydrothermal vent ecosystem. We were very much interested in the difference of hydrothermal fluid chemistry between the natural hydrothermal vents and the artificial hydrothermal vents. The IODP porewater chemistry of the cores pointed to the density-driven stratification of the phase-separated hydrothermal fluids and the natural vent fluids were likely derived only from the shallower vapor-enriched phases. However, the artificial hydrothermal vents had deeper fluid sources in the subseafloor hydrothermal fluid reservoirs composed of vapor-lost (Cl-enriched) phases. The fluids from the artificial hydrothermal vents were sampled by ROV at 5, 12 and 18 months after the IODP expedition. The artificial hydrothermal vent fluids were slightly enriched with Cl as compared to the natural hydrothermal vent fluids. Thus, the artificial hydrothermal vents successfully entrained the previously unexplored subseafloor hydrothermal fluids. The newly created hydrothermal vents also hosted the very quickly grown, enormous chimney structures, of which mineral compositions were highly variable among the vents. However, the quickly grown C0016B and C0016D vent chimneys were found to be typical Kuroko ore even though the chimney growth rates in the artificial vents were extremely faster than those in the natural vents. In addition, the IODP drilling operation not only created new hydrothermal vents by deep drilling but also induced the

  18. Experimental constraints on hydrothermal activities in Enceladus

    NASA Astrophysics Data System (ADS)

    Sekine, Y.; Shibuya, T.; Suzuki, K.; Kuwatani, T.

    2012-12-01

    One of the most remarkable findings by the Cassini-Huygens mission is perhaps water-rich plumes erupting from the south-pole region of Enceladus [1]. Given such geological activity and the detection of sodium salts in the plume, the interior of Enceladus is highly likely to contain an interior ocean interacting with the rock core [2]. A primary question regarding astrobiology and planetary science is whether Enceladus has (or had) hydrothermal activities in the interior ocean. Because N2 might be formed by thermal dissociation of primordial NH3 [3], the presence of N2 in the plume may be a possible indicator for the presence of hydrothermal activities in Enceladus. However, the Cassini UVIS revealed that the plumes do not contain large amounts of N2 [4]. Although these observations may not support the presence of hydrothermal activities, whether NH3 dissociation proceeds strongly depends on the kinetics of hydrothermal reactions and interactions with the rock components, which remain largely unknown. Furthermore, the Cassini CDA recently showed that small amounts of SiO2 might have been included in the plume dusts [5]. Formation of amorphous SiO2 usually occurs when high-temperature and/or high-pH solution with high concentrations of dissolved SiO2 cools and/or is neutralized. Thus, the presence of SiO2 in the plume dusts may suggest the presence of a temperature and/or pH gradient in the ocean. However, no laboratory experiments have investigated what processes control pH and SiO2 concentrations in hydrothermal fluids possibly existing in Enceladus. Here, we show the results of laboratory experiments simulating hydrothermal systems on Enceladus. As the initial conditions, we used both aqueous solution of high concentrations (0.01-2%) of NH3 and NaHCO3 and powdered olivine as an analog for the rock components. Our experimental results show that formation of N2 from NH3 is kinetically and thermodynamically inhibited even under high temperature conditions (< 400

  19. Hydrothermal activity at the Arctic mid-ocean ridges

    NASA Astrophysics Data System (ADS)

    Pedersen, Rolf B.; Thorseth, Ingunn H.; Nygård, Tor Eivind; Lilley, Marvin D.; Kelley, Deborah S.

    Over the last 10 years, hydrothermal activity has been shown to be abundant at the ultraslow spreading Arctic Mid-Ocean Ridges (AMOR). Approximately 20 active and extinct vent sites have been located either at the seafloor, as seawater anomalies, or by dredge sampling hydrothermal deposits. Decreasing spreading rates and decreasing influence of the Icelandic hot spot toward the north along the AMOR result in a north-south change from a shallow and magmatically robust to a deep and magmatically starved ridge system. This contrast gives rise to large variability in the ridge geology and in the nature of the associated hydrothermal systems. The known vent sites at the southern part of the ridge system are either low-temperature or white smoker fields. At the deep, northern parts of the ridge system, a large black smoker field has been located, and seawater anomalies and sulfide deposits suggest that black smoker-type venting is common. Several of these fields may be peridotite-hosted. The hydrothermal activity at parts of the AMOR exceeds by a factor of 2 to 3 what would be expected by extrapolating from observations on faster spreading ridges. Higher fracture/fault area relative to the magma volume extracted seems a likely explanation for this. Many of the vent fields at the AMOR are associated with axial volcanic ridges. Strong focusing of magma toward these ridges, deep rifting of the ridges, and subsequent formation of long-lived detachment faults that are rooted below the ridges may be the major geodynamic mechanisms causing the unexpectedly high hydrothermal activity.

  20. Preliminary results from Submarine Ring of Fire 2012 - NE Lau: First explorations of hydrothermally active volcanoes across the supra-subduction zone and a return to the West Mata eruption site

    NASA Astrophysics Data System (ADS)

    Resing, J.; Embley, R. W.

    2012-12-01

    Several expeditions in the past few years have shown that the NE Lau basin has one of the densest concentrations of volcanically and hydrothermally active volcanoes on the planet. In 2008 two active submarine volcanic eruptions were discovered during a one week period and subsequent dives with the Jason remotely operated vehicle at one of the sites (West Mata) revealed an active boninite eruption taking place at 1200 m depth. Two dives at the other revealed evidence for recent eruption along the NE Lau Spreading Center. Several more expeditions in 2010-11 discovered additional evidence about the extent and types of hydrothermal activity in this area. Data from CTDO (conductivity, temperature, depth, optical) vertical casts, tow-yos, and towed camera deployments revealed more than 15 hydrothermal sites at water depths from ~800 to 2700 m that include sites from the magmatic arc, the "rear arc," and the back arc spreading centers. These sites range from high temperature black smoker sulfide-producing systems to those dominated by magmatic degassing. Dives by remotely operated vehicle (Quest 4000) in September 2012 will explore these sites and return samples for chemical, biological and geologic studies. One of the dives will be a return visit to West Mata volcano, the site of the deepest submarine eruption yet observed (in 2009). Recent multibeam data reveal large changes in West Mata's summit, suggesting that the nature of the eruption and the location of the erupting vents may have changed. In addition to the preliminary results from the science team, we will also discuss our use and experience with continuous live video transmission (through the High Definition video camera on the Quest 4000) back to shore via satellite and through the internet. Submarine Ring of Fire 2012 Science Team: Bradley Tebo, Bill Chadwick, Ed Baker, Ken Rubin, Susan Merle, Timothy Shank, Sharon Walker, Andra Bobbitt, Nathan Buck, David Butterfield, Eric Olson, John Lupton, Richard Arculus

  1. Martian Magmatic-Driven Hydrothermal Sites: Potential Sources of Energy, Water, and Life

    NASA Technical Reports Server (NTRS)

    Anderson, R. C.; Dohm, J. M.; Baker, V. R.; Ferris, J. C.; Hare, T. M.; Tanaka, K. L.; Klemaszewski, J. E.; Skinner, J. A.; Scott, D. H.

    2000-01-01

    Magmatic-driven processes and impact events dominate the geologic record of Mars. Such recorded geologic activity coupled with significant evidence of past and present-day water/ice, above and below the martian surface, indicate that hydrothermal environments certainly existed in the past and may exist today. The identification of such environments, especially long-lived magmatic-driven hydrothermal environments, provides NASA with significant target sites for future sample return missions, since they (1) could favor the development and sustenance of life, (2) may comprise a large variety of exotic mineral assemblages, and (3) could potentially contain water/ice reservoirs for future Mars-related human activities. If life developed on Mars, the fossil record would presumably be at its greatest concentration and diversity in environments where long-term energy sources and water coexisted such as at sites where long-lived, magmatic-driven hydrothermal activity occurred. These assertions are supported by terrestrial analogs. Small, single-celled creatures (prokaryotes) are vitally important in the evolution of the Earth; these prokaryotes are environmentally tough and tolerant of environmental extremes of pH, temperature, salinity, and anoxic conditions found around hydrothermal vents. In addition, there is a great ability for bacteria to survive long periods of geologic time in extreme conditions, including high temperature hydrogen sulfide and sulfur erupted from Mount St. Helens volcano. Our team of investigators is conducting a geological investigation using multiple mission-derived datasets (e.g., existing geologic map data, MOC imagery, MOLA, TES image data, geophysical data, etc.) to identify prime target sites of hydrothermal activity for future hydrological, mineralogical, and biological investigations. The identification of these sites will enhance the probability of success for future missions to Mars.

  2. Seafloor Hydrothermal Activity at the Galapagos Triple Junction, East Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Li, H.; Yu, Z.; Zhang, G.; Tao, C.; Chen, S.

    2014-12-01

    Since the first discovery of black smokers on the Gaplapgaos spreading center, over 500 hydrothermal sites have been confirmed on the mid-ocean ridge, arc and back-arc settings (Beaulieu et al., 2013). However, the hydrothermal activity at triple-junction has not received much attention. Consequently, there are outstanding questions regarding the features of the hydrothermal system, and the effect of the hydrothermal circulation on the tectonic activity of the triple-junction. In 2009, the Chinese Dayang Cruise 21 discovered the Precious Stone field (PSF) on the Dietz Semount at the southern flank of the Galapagos triple junction (GTJ). Most studies of the GTJ focus on the topographictectonic and stresssimulation, which suggest that the GTJ had complex evoluation(Smith et al., 2011, 2013; Mitchell et al., 2011,Schouten et al., 2012). Water anomay were clear detected and samples of hydrothermal deposit and rocks were collected by TV-Grab (Figure.1). This study aims to understand the geological features of the PSF related hydrothermal activity. Hydrothermal mineralization Three types of sedimentary hydrothermal deposits representing three different hydrothermal activity stages (Figure 1)are confirmed in the PSF: 1) sediments with native sulfur and pyrite clasts(Type I), 2) Fe—Mn oxides (Type II), and 3) clay minerals mainlynontronite(Type III). Type II sedimentsprecipitate early and the source comprises of clasts of distal hydrothermal plume. The nontronite-rich sediments propably derive from the low-temperature alteration of Fe—Mn oxides. Type 1 sediments are found on the active hydrothermal venting field. Hydrothermal plume Water anomaly were detected at the southewestern PSF. We observed widespreadsedimentary hydrothermal depositsin the western PSF, but no water anomaly. According to the results of five water anomaly dectection lines, we predicted the existence of three hydrothermal vents in the PSF. Seafloor type inversion Multi-beam backscatter data were

  3. Hydrothermal and tectonic activity in northern Yellowstone Lake, Wyoming

    USGS Publications Warehouse

    Johnson, S.Y.; Stephenson, W.J.; Morgan, L.A.; Shanks, Wayne C.; Pierce, K.L.

    2003-01-01

    Yellowstone National Park is the site of one of the world's largest calderas. The abundance of geothermal and tectonic activity in and around the caldera, including historic uplift and subsidence, makes it necessary to understand active geologic processes and their associated hazards. To that end, we here use an extensive grid of high-resolution seismic reflection profiles (???450 km) to document hydrothermal and tectonic features and deposits in northern Yellowstone Lake. Sublacustrine geothermal features in northern Yellowstone Lake include two of the largest known hydrothermal explosion craters, Mary Bay and Elliott's. Mary Bay explosion breccia is distributed uniformly around the crater, whereas Elliott's crater breccia has an asymmetric distribution and forms a distinctive, ???2-km-long, hummocky lobe on the lake floor. Hydrothermal vents and low-relief domes are abundant on the lake floor; their greatest abundance is in and near explosion craters and along linear fissures. Domed areas on the lake floor that are relatively unbreached (by vents) are considered the most likely sites of future large hydrothermal explosions. Four submerged shoreline terraces along the margins of northern Yellowstone Lake add to the Holocene record or postglacial lake-level fluctuations attributed to "heavy breathing" of the Yellowstone magma reservoir and associated geothermal system. The Lake Hotel fault cuts through northwestern Yellowstone Lake and represents part of a 25-km-long distributed extensional deformation zone. Three postglacial ruptures indicate a slip rate of ???0.27 to 0.34 mm/yr. The largest (3.0 m slip) and most recent event occurred in the past ???2100 yr. Although high heat flow in the crust limits the rupture area of this fault zone, future earthquakes of magnitude ???5.3 to 6.5 are possible. Earthquakes and hydrothermal explosions have probably triggered landslides, common features around the lake margins. Few high-resolution seismic reflection surveys have

  4. First hydrothermal discoveries on the Australian-Antarctic Ridge: Discharge sites, plume chemistry, and vent organisms

    NASA Astrophysics Data System (ADS)

    Hahm, Doshik; Baker, Edward T.; Siek Rhee, Tae; Won, Yong-Jin; Resing, Joseph A.; Lupton, John E.; Lee, Won-Kyung; Kim, Minjeong; Park, Sung-Hyun

    2015-09-01

    The Australian-Antarctic Ridge (AAR) is one of the largest unexplored regions of the global mid-ocean ridge system. Here, we report a multiyear effort to locate and characterize hydrothermal activity on two first-order segments of the AAR: KR1 and KR2. To locate vent sites on each segment, we used profiles collected by Miniature Autonomous Plume Recorders on rock corers during R/V Araon cruises in March and December of 2011. Optical and oxidation-reduction-potential anomalies indicate multiple active sites on both segments. Seven profiles on KR2 found 3 sites, each separated by ˜25 km. Forty profiles on KR1 identified 17 sites, some within a few kilometer of each other. The spatial density of hydrothermal activity along KR1 and KR2 (plume incidence of 0.34) is consistent with the global trend for a spreading rate of ˜70 mm/yr. The densest area of hydrothermal activity, named "Mujin," occurred along the 20 km-long inflated section near the segment center of KR1. Continuous plume surveys conducted in January-February of 2013 on R/V Araon found CH4/3He (1 - 15 × 106) and CH4/Mn (0.01-0.5) ratios in the plume samples, consistent with a basaltic-hosted system and typical of ridges with intermediate spreading rates. Additionally, some of the plume samples exhibited slightly higher ratios of H2/3He and Fe/Mn than others, suggesting that those plumes are supported by a younger hydrothermal system that may have experienced a recent eruption. The Mujin-field was populated by Kiwa crabs and seven-armed Paulasterias starfish previously recorded on the East Scotia Ridge, raising the possibility of circum-Antarctic biogeographic connections of vent fauna.

  5. Hydrothermal fluid-mineral interactions within volcanic sediment layer revealed by shallow drilling in active seafloor hydrothermal fields in the mid-Okinawa

    NASA Astrophysics Data System (ADS)

    Ishibashi, J.; Miyoshi, Y.; Tanaka, K.; Omori, E.; Takahashi, Y.; Furuzawa, Y.; Yamanaka, T.; Kawagucci, S.; Yoshizumi, R.; Urabe, T.

    2012-12-01

    TAIGA11 Expedition of R/V Hakurei-maru No.2 was conducted in June, 2011 to study subseafloor environment below active hydrothermal fields using a shallow drilling system (called as Benthic Multi-coring System, BMS). Three active hydrothermal fields at Iheya North Knoll (27 47'N, 126 54'E), at Izena Hole Jade site (27 16'N, 127 05'E) and at Izena Hole Hakurei site (27 15'N, 127 04'E) were selected as exploration targets, to focus on a hydrothermal fluid circulation system that develops in sediment consists of volcaniclastic and hemipelagic materials. In this presentation, we will report mineralogy of hydrothermal precipitates and altered clay minerals together with geochemistry of pore fluids, to discuss hydrothermal interactions beneath an active hydrothermal field. In the Iheya North Knoll hydrothermal field, the BMS drilling successfully attained to 453 cmbsf at the station 200 meters apart from the central mound area. The obtained core consisted almost entirely of grayish white altered mud that was identified as kaolinite by XRD. Pore fluid from the corresponding depth showed enrichment in major cations (Na, K, Ca and Mg) and Cl, which may be explained as a result of involvement of water into the kaolinite. Since kaolinite is considered as stable in rather acidic environment, its abundant occurrence beneath the seafloor would be attributed to a unique hydrothermal interaction. A possible scenario is intrusion of the vapor-rich hydrothermal component that has experienced phase separation. In the Jade hydrothermal fields in the Izena Hole, the BMS drilling successfully attained to 529 cmbsf at the marginal part of a hydrothermal field. The obtained core comprised grayish white hydrothermal altered mud below 370 cmbsf. Occurrence of native sulphur is also identified. Unfortunately, pore fluid could not be extracted from the intense alteration layer. In the Hakurei hydrothermal fields in the Izena Hole, the BMS drilling successfully attained to 610 cmbsf near one of

  6. Discovery of New Hydrothermal Venting Sites in the Lau Basin, Tonga Back Arc

    NASA Astrophysics Data System (ADS)

    Crowhurst, P. V.; Arculus, R. J.; Massoth, G. J.; Baptista, L.; Stevenson, I.; Angus, R.; Baker, E. T.; Walker, S. L.; Nakamura, K.

    2009-12-01

    Between 22 April and 25 June 2009, a systematic search for hydrothermal venting along 1340 km of back-arc features was conducted throughout the Lau Basin aboard the CSIRO owned RV Southern Surveyor. The selection of survey areas was based on bathymetry, sidescan and water column anomaly datasets collected during previous marine science research and commercial exploration voyages. During 54 operational days, 76 CTD tows were completed using real-time plume mapping protocols, augmented with mini autonomous plume recorders, to discern anomalies in light scattering, and oxidation-reduction potential with water samples collected within the peak anomalies. Coincident with CTD towing at an average speed of 1.1 knots high resolution EM300 bathymetry and backscatter data was collected which significantly enhanced geological interpretation of possible source sites for follow up cross tows. 32 venting sites were detected, 24 of which are believed to be new discoveries. 13 dredge operations were conducted on 7 of these sites. Sulfides were recovered from 2 sites, one being a new discovery on the NE Lau spreading centre, ~14 km north of the commercial discovery by Teck and ~7km north of the eruption site discovery during a RV Thompson NOAA survey, both during 2008. The new venting field discoveries at North Mata, northern extent of the CLSC and far southern Valu Fa ridge are beyond any previously known areas of hydrothermal activity and further enhances the reputation of the Lau Basin as one of the most productive back arc regions for hydrothermally active spreading centers. A significant number of filter residue samples collected from the vent sites yielded greater than background values for metals including Cu and Zn, which is interpreted to imply they were sourced from active seafloor massive sulfide systems rather than volcanic activity.

  7. Subaerial and sublacustrine hydrothermal activity at Lake Rotomahana

    NASA Astrophysics Data System (ADS)

    Stucker, Valerie K.; de Ronde, Cornel E. J.; Scott, Bradley J.; Wilson, Nathaniel J.; Walker, Sharon L.; Lupton, John E.

    2016-03-01

    Lake Rotomahana is a crater lake in the Okataina Volcanic Centre (New Zealand) that was significantly modified by the 1886 Tarawera Rift eruption. The lake is host to numerous sublacustrine hydrothermal vents. Water column studies were conducted in 2011 and 2014 along with sampling of lake shore hot springs and crater lakes in Waimangu Valley to complement magnetic, seismic, bathymetric and heat flux surveys. Helium concentrations below 50 m depth are higher in 2014 compared to 2011 and represent some of the highest concentrations measured, at 6 × 10- 7 ccSTP/g, with an end-member 3He/4He value of 7.1 RA. The high concentrations of helium, when coupled with pH anomalies due to high dissolved CO2 content, suggest the dominant chemical input to the lake is derived from magmatic degassing of an underlying magma. The lake shore hot spring waters show differences in source temperatures using a Na-K geothermometer, with inferred reservoir temperatures ranging between 197 and 232 °C. Water δ18O and δD values show isotopic enrichment due to evaporation of a steam heated pool with samples from nearby Waimangu Valley having the greatest enrichment. Results from this study confirm both pre-1886 eruption hydrothermal sites and newly created post-eruption sites are both still active.

  8. Hydrothermal Activity on ultraslow Spreading Ridge: new hydrothermal fields found on the Southwest Indian ridge

    NASA Astrophysics Data System (ADS)

    Tao, C.; Li, H.; Deng, X.; Lei, J.; Wang, Y.; Zhang, K.; Zhou, J.; Liu, W.

    2014-12-01

    Ultraslow spreading ridge makes up about 25% of global mid-ocean ridge length. Previous studies believed that hydrothermal activity is not widespread on the ultraslow spreading ridge owing to lower magma supply. Southwest Indian ridge (SWIR) with the spreading rate between 1.2cm/a to 1.4cm/a, represents the ultraslow spreading ridge. In 2007, Chinese Cruise (CC) 19th discovered the Dragon Flag deposit (DFD) on the SWIR, which is the first active hydrothermal field found on the ultraslow spreading ridge. In recent years, over 10 hydrothermal fields have been found on the SWIR between Indomed and Gallieni transform faults by the Chinese team. Tao et al. (2012) implied that the segment sections with excess heat from enhanced magmatism and suitable crustal permeability along slow and ultraslow ridges might be the most promising areas for searching for hydrothermal activities. In 2014, CC 30thdiscovered five hydrothermal fields and several hydrothermal anomalies on the SWIR. Dragon Horn Area (DHA). The DHA is located on the southern of segment 27 SWIR, with an area of about 400 km2. The geophysical studies indicated that the DHA belongs to the oceanic core complex (OCC), which is widespread on the slow spreading ridges (Zhao et al., 2013). The rocks, such as gabbro, serpentinized peridotite, and consolidated carbonate were collected in the DHA, which provide the direct evidence with the existence of the OCC. However, all rock samples gathered by three TV-grab stations are basalts on the top of the OCC. A hydrothermal anomaly area, centered at 49.66°E,37.80° S with a range of several kms, is detected in the DHA. It is probably comprised of several hydrothermal fields and controlled by a NW fault. New discovery of hydrothermal fields. From January to April 2014, five hydrothermal fields were discovered on the SWIR between 48°E to 50°E during the leg 2&3 of the CC 30th, which are the Su Causeway field (48.6°E, 38.1°S), Bai Causeway field (48.8°E, 37.9 °S), Dragon

  9. Seafloor Hydrothermal Activity in the Southern Gulf of California

    NASA Astrophysics Data System (ADS)

    Paduan, J. B.; Clague, D. A.; Caress, D. W.; Lundsten, L.; Zierenberg, R. A.; Troni, G.; Wheat, C. G.; Spelz, R. M.

    2015-12-01

    Active hydrothermal venting was previously unknown between Guaymas Basin and 21°N on the East Pacific Rise. MBARI AUV surveys and ROV dives in 2012 and 2015 discovered 7 hydrothermal vent sites with diverse and varied vent communities within that gap. One field in the Pescadero Basin vents clear shimmering fluids at 3685 m depth and four vigorous black smoker fields and several extinct chimney fields are between 2225 and 2400 m depth on the Alarcón Rise. Low-temperature vent sites are present on both of the Pescadero and Tamayo Transforms. The chimneys were discovered in 1-m resolution AUV bathymetric data, with some indicated to be active based on temperature anomalies in the AUV CTD data and confirmed during later ROV dives. The low-temperature vent sites on the transform faults were found on ROV dives while exploring young lava flows and sediment hills uplifted by sill intrusions. Pescadero Basin is a deep extensional basin in the southern Gulf. The smooth, subtly faulted floor is filled with at least 150 m of sediment, as determined from sub-bottom profiles collected by the AUV. Three large chimneys (named Auka by our Mexican collaborators) and several broad mounds are located on the SW margin of the basin. Temperatures to 290°C were measured, the fluids are clear, neutral pH, and contain elevated Na. The chimneys are delicate, white, predominantly Ca-carbonate; barite, sparse sulfides, and some aromatic hydrocarbons are also present. Three active vent fields (Ja Sít, Pericú, and Meyibó) at Alarcón Rise are located near the eruptive fissure of an extensive young sheet flow. The fourth field (Tzab-ek) is 1.1 km NW of the axis on older pillow lavas. The largest chimneys are in the Tzab-ek field: 31 and 33 m tall, with flanges and upside-down waterfalls. They rise from a sulfide mound, suggesting a long-lived hydrothermal system, in contrast to the near-axis fields where the chimneys grow directly on basalt. The Alarcón chimneys are Zn and Cu-rich sulfides

  10. Comparative assessment of five potential sites for hydrothermal-magma systems: energy transport

    SciTech Connect

    Hardee, H.C.

    1980-09-01

    A comparative assessment of five sites is being prepared as part of a Continental Scientific Drilling Program (CSDP) review of thermal regimes for the purpose of scoping areas for future research and drilling activities. This background report: discusses the various energy transport processes likely to be encountered in a hydrothermal-magma system, reviews related literature, discusses research and field data needs, and reviews the sites from an energy transport viewpoint. At least three major zones exist in the magma-hydrothermal transport system: the magma zone, the hydrothermal zone, and the transition zone between the two. Major energy transport questions relate to the nature and existence of these zones and their evolution with time. Additional energy transport questions are concerned with the possible existence of critical state and super-critical state permeable convection in deep geothermal systems. A review of thermal transport models emphasizes the fact that present transport models and computational techniques far outweigh the scarcity and quality of deep field data.

  11. Diffuse versus discrete venting at the Tour Eiffel vent site, Lucky Strike hydrothermal field

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, E. L.; Escartin, J.; Gracias, N.; Olive, J. L.; Barreyre, T.; Davaille, A. B.; Cannat, M.

    2010-12-01

    Two styles of fluid flow at the seafloor are widely recognized: (1) localized outflows of high temperature (>300°C) fluids, often black or grey color in color (“black smokers”) and (2) diffuse, lower temperature (<100°C), fluids typically transparent and which escape through fractures, porous rock, and sediment. The partitioning of heat flux between these two types of hydrothermal venting is debated and estimates of the proportion of heat carried by diffuse flow at ridge axes range from 20% to 90% of the total axial heat flux. Here, we attempt to improve estimates of this partitioning by carefully characterizing the heat fluxes carried by diffuse and discrete flows at a single vent site, Tour Eiffel in the Lucky Strike hydrothermal field along the Mid-Atlantic Ridge. Fluid temperature and video data were acquired during the recent Bathyluck’09 cruise to the Lucky Strike hydrothermal field (September, 2009) by Victor aboard “Pourquoi Pas?” (IFREMER, France). Temperature measurements were made of fluid exiting discrete vents, of diffuse effluents immediately above the seafloor, and of vertical temperature gradients within discrete hydrothermal plumes. Video data allow us to calculate the fluid velocity field associated with these outflows: for diffuse fluids, Diffuse Flow Velocimetry tracks the displacement of refractive index anomalies through time; for individual hydrothermal plumes, Particle Image Velocimetry tracks eddies by cross-correlation of pixels intensities between subsequent images. Diffuse fluids exhibit temperatures of 8-60°C and fluid velocities of ~1-10 cm s-1. Discrete outflows at 204-300°C have velocities of ~1-2 m s-1. Combined fluid flow velocities, temperature measurements, and full image mosaics of the actively venting areas are used to estimate heat flux of both individual discrete vents and diffuse outflow. The total integrated heat flux and the partitioning between diffuse and discrete venting at Tour Eiffel, and its

  12. Geophysical Constraints On Enceladus' Hydrothermal Activity

    NASA Astrophysics Data System (ADS)

    Matson, D.; Castillo, J. C.; Johnson, T. V.; Lunine, J. I.; Davies, A. G.

    2011-12-01

    Cassini-Huygens discovered many eruptive plumes and a heat flow of about 15 GW [1] in the South Polar Region of Enceladus. The plume material is believed to come from an ocean [2]. We have modeled the heat and chemicals as coming to the surface via the circulation of relatively warm ocean water [3]. The major challenge for our work is to explain how circulation of water can be maintained in the very cold crust. The upper boundary condition is relatively simple. Where seawater contacts surface ice the temperature is ~-2 C. Also, under the right conditions, tidally induced fissures in the surface ice can fill with water that freezes, producing new ice. The lower boundary temperature is difficult to characterize precisely. The ocean is several degrees warmer than the ice. Consequently there will be some melting at the bottom of the crust. The melt water is less dense than seawater and floats on it. As a result, an ice-ocean interface layer is formed. This layer is stable against Rayleigh-Bénard convection. The layer regulates the rate at which heat is transferred and the temperature at which melt water is produced through temperature and salinity gradients. Currents in the ocean below and other variables influence the extent and shape of the interface layer. A somewhat similar interface layer (thermal gradient only) has been discussed and modeled for Europa [4] and many of those considerations apply to Enceladus. In the Europa case a layer thickness of ~200 m was suggested and that should be roughly what one might also expect for Enceladus. We demonstrate that it is feasible to keep this hydrothermal activity going over the long-term, as long as it is powered by a deep source of heat whose origin is still to be determined. This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2011 Caltech.

  13. Origin of magnetic highs at ultramafic hosted hydrothermal systems: Insights from the Yokoniwa site of Central Indian Ridge

    NASA Astrophysics Data System (ADS)

    Fujii, Masakazu; Okino, Kyoko; Sato, Taichi; Sato, Hiroshi; Nakamura, Kentaro

    2016-05-01

    High-resolution vector magnetic measurements were performed on an inactive ultramafic-hosted hydrothermal vent field, called Yokoniwa Hydrothermal Field (YHF), using a deep-sea manned submersible Shinkai6500 and an autonomous underwater vehicle r2D4. The YHF has developed at a non-transform offset massif of the Central Indian Ridge. Dead chimneys were widely observed around the YHF along with a very weak venting of low-temperature fluids so that hydrothermal activity of the YHF was almost finished. The distribution of crustal magnetization from the magnetic anomaly revealed that the YHF is associated with enhanced magnetization, as seen at the ultramafic-hosted Rainbow and Ashadze-1 hydrothermal sites of the Mid-Atlantic Ridge. The results of rock magnetic analysis on seafloor rock samples (including basalt, dolerite, gabbro, serpentinized peridotite, and hydrothermal sulfide) showed that only highly serpentinized peridotite carries high magnetic susceptibility and that the natural remanent magnetization intensity can explain the high magnetization of Yokoniwa. These observations reflect abundant and strongly magnetized magnetite grains within the highly serpentinized peridotite. Comparisons with the Rainbow and Ashadze-1 suggest that in ultramafic-hosted hydrothermal systems, strongly magnetized magnetite and pyrrhotite form during the progression of hydrothermal alteration of peridotite. After the completion of serpentinization and production of hydrogen, pyrrhotites convert into pyrite or nonmagnetic iron sulfides, which considerably reduces their levels of magnetization. Our results revealed origins of the magnetic high and the development of subsurface chemical processes in ultramafic-hosted hydrothermal systems. Furthermore, the results highlight the use of near-seafloor magnetic field measurements as a powerful tool for detecting and characterizing seafloor hydrothermal systems.

  14. Interactions Between Serpentinization, Hydrothermal Activity and Microbial Community at the Lost City Hydrothermal Field

    NASA Astrophysics Data System (ADS)

    Delacour, A.; Frueh-Green, G. L.; Bernasconi, S. M.; Schaeffer, P.; Frank, M.; Gutjahr, M.; Kelley, D. S.

    2008-12-01

    Seafloor investigations of slow- and ultraslow-spreading ridges have reported many occurrences of exposed mantle peridotites and gabbroic rocks on the ocean floor. Along the Mid-Atlantic Ridge, these uplifted portions of oceanic crust host high-temperature black smoker-type hydrothermal systems (e.g., Rainbow, Logatchev, Saldanha), and the more distinct low-temperature Lost City Hydrothermal Field (LCHF). Built on a southern terrace of the Atlantis Massif, the LCHF is composed of carbonate-brucite chimneys that vent alkaline and low-temperature (40-90°C) hydrothermal fluids. These fluids are related to serpentinization of mantle peridotites, which together with minor gabbroic intrusions form the basement of the LCHF. Long-lived hydrothermal activity at Lost City led to extensive seawater-rock interaction in the basement rocks, as indicated by seawater-like Sr- and mantle to unradiogenic Nd-isotope compositions of the serpentinites. These high fluid fluxes in the southern part of the massif influenced the conditions of serpentinization and have obliterated the early chemical signatures in the serpentinites, especially those of carbon and sulfur. Compared to reducing conditions commonly formed during the first stages of serpentinization, serpentinization at Lost City is characterized by relatively oxidizing conditions resulting in a predominance of magnetite, the mobilization/dissolution and oxidation of igneous sulfides to secondary pyrite, and the incorporation of seawater sulfate, all leading to high bulk-rock S-isotope compositions. The Lost City hydrothermal fluids contain high concentrations in methane, hydrogen, and low-molecular weight hydrocarbons considered as being produced abiotically. In contrast, organic compounds in the serpentinites are dominated by the occurrences of isoprenoids (pristane, phytane, and squalane), polycyclic compounds (hopanes and steranes), and higher abundances of C16 to C20 n-alkanes indicative of a marine organic input. We

  15. Hydrothermal activity along the slow-spreading Lucky Strike ridge segment (Mid-Atlantic Ridge): Distribution, heatflux, and geological controls

    NASA Astrophysics Data System (ADS)

    Escartin, J.; Barreyre, T.; Cannat, M.; Garcia, R.; Gracias, N.; Deschamps, A.; Salocchi, A.; Sarradin, P.-M.; Ballu, V.

    2015-12-01

    We have reviewed available visual information from the seafloor, and recently acquired microbathymetry for several traverses across the Lucky Strike segment, to evaluate the distribution of hydrothermal activity. We have identified a new on-axis site with diffuse flow, Ewan, and an active vent structure ∼1.2 km from the axis, Capelinhos. These sites are minor relative to the Main field, and our total heatflux estimate for all active sites (200-1200 MW) is only slightly higher than previously published estimates. We also identify fossil sites W of the main Lucky Strike field. A circular feature ∼200 m in diameter located on the flanks of a rifted off-axis central volcano is likely a large and inactive hydrothermal edifice, named Grunnus. We find no indicator of focused hydrothermal activity elsewhere along the segment, suggesting that the enhanced melt supply and the associated melt lenses, required to form central volcanoes, also sustain hydrothermal circulation to form and maintain large and long-lived hydrothermal fields. Hydrothermal discharge to the seafloor occurs along fault traces, suggesting focusing of hydrothermal circulation in the shallow crust along permeable fault zones.

  16. Searching for evidence of hydrothermal activity at Apollinaris Mons, Mars

    USGS Publications Warehouse

    El Maarry, M.R.; Dohm, J.M.; Marzo, G.A.; Fergason, R.; Goetz, W.; Heggy, E.; Pack, A.; Markiewicz, W.J.

    2012-01-01

    A multidisciplinary approach involving various remote sensing instruments is used to investigate Apollinaris Mons, a prominent volcano on Mars, as well as the surrounding plains for signs of prolonged hydrologic and volcanic, and possibly hydrothermal activity. The main findings include (1) evidence from laser altimetry indicating the large thickness (1.5-2. km at some locations) of the fan deposits draping the southern flank contrary to previous estimates, coupled with possible layering which point to a significant emplacement phase at Apollinaris Mons, (2) corroboration of Robinson et al. (Robinson, M.S., Mouginis-Mark, P.J., Zimbelman, J.R., Wu, S.S.C., Ablin, K.K., Howington-Kraus, A.E. [1993]. Icarus 104, 301-323) hypothesis regarding the formation of incised valleys on the western flanks by density current erosion which would indicate magma-water interaction or, alternatively, volatile-rich magmas early in the volcano's history, (3) mounds of diverse geometric shapes, many of which display summit depressions and occur among faults and fractures, possibly marking venting, (4) strong indicators on the flanks of the volcano for lahar events, and possibly, a caldera lake, (5) ubiquitous presence of impact craters displaying fluidized ejecta in both shield-forming (flank and caldera) materials and materials that surround the volcano that are indicative of water-rich target materials at the time of impact, (6) long-term complex association in time among shield-forming materials and Medusae Fossae Formation.The findings point to a site of extensive volcanic and hydrologic activity with possibly a period of magma-water interaction and hydrothermal activity. Finally, we propose that the mound structures around Apollinaris should be prime targets for further in situ exploration and search for possible exobiological signatures. ?? 2011 Elsevier Inc..

  17. Searching for evidence of hydrothermal activity at Apollinaris Mons, Mars

    USGS Publications Warehouse

    El Maarry, M. Ramy; Dohm, James M.; Marzo, Giuseppe A.; Fergason, Robin; Goetz, Walter; Heggy, Essam; Pack, Andreas; Markiewicz, Wojciech J.

    2012-01-01

    A multidisciplinary approach involving various remote sensing instruments is used to investigate Apollinaris Mons, a prominent volcano on Mars, as well as the surrounding plains for signs of prolonged hydrologic and volcanic, and possibly hydrothermal activity. The main findings include (1) evidence from laser altimetry indicating the large thickness (1.5–2 km at some locations) of the fan deposits draping the southern flank contrary to previous estimates, coupled with possible layering which point to a significant emplacement phase at Apollinaris Mons, (2) corroboration of Robinson et al. (Robinson, M.S., Mouginis-Mark, P.J., Zimbelman, J.R., Wu, S.S.C., Ablin, K.K., Howington-Kraus, A.E. [1993]. Icarus 104, 301–323) hypothesis regarding the formation of incised valleys on the western flanks by density current erosion which would indicate magma–water interaction or, alternatively, volatile-rich magmas early in the volcano’s history, (3) mounds of diverse geometric shapes, many of which display summit depressions and occur among faults and fractures, possibly marking venting, (4) strong indicators on the flanks of the volcano for lahar events, and possibly, a caldera lake, (5) ubiquitous presence of impact craters displaying fluidized ejecta in both shield-forming (flank and caldera) materials and materials that surround the volcano that are indicative of water-rich target materials at the time of impact, (6) long-term complex association in time among shield-forming materials and Medusae Fossae Formation. The findings point to a site of extensive volcanic and hydrologic activity with possibly a period of magma–water interaction and hydrothermal activity. Finally, we propose that the mound structures around Apollinaris should be prime targets for further in situ exploration and search for possible exobiological signatures.

  18. Modeling the hydrothermal circulation and the hydrogen production at the Rainbow site with Cast3M

    NASA Astrophysics Data System (ADS)

    Perez, F.; Mügler, C.; Charlou, J.; Jean-baptiste, P.

    2012-12-01

    On the Mid-Atlantic Ridge, the Rainbow venting site is described as an ultramafic-hosted active hydrothermal site and releases high fluxes of methane and hydrogen [1, 2]. This behavior has first been interpreted as the result of serpentinization processes. But geochemical reactions involving olivine and plagioclase assemblages, and leading to chlorite, tremolite, talc and magnetite assemblages, could contribute to the observed characteristics of the exiting fluid [2]. The predominance of one of these geochemical reactions or their coexistence strongly depend on the hydrothermal fluid circulation. We developed and validated a 2D/3D numerical model using a Finite Volume method to simulate heat driven fluid flows in the framework of the Cast3M code [3, 4]. We also developed a numerical model for hydrogen production and transport that is based on experimental studies of the serpentinization processes [5-6]. This geochemical model takes into account the exothermic and water-consuming behavior of the serpentinization reaction and it can be coupled to our thermo-hydrogeological model. Our simulations provide temperatures, mass fluxes and venting surface areas very close to those estimated in-situ [7]. We showed that a single-path model [8] was necessary to simulate high values such as the in-situ measured temperatures and estimated water mass fluxes of the Rainbow site [7]. This single-path model will be used to model the production and transport of hydrogen at the Rainbow hydrothermal site. References [1]Charlou et al. (2010) AGU Monograph series. [2]Seyfried et al. (2011) Geochim. Cosmochim. Acta 75, 1574-1593. [3]http://www-cast3m.cea.fr. [4]Martin & Fyfe (1970) Chem. Geol. 6, 185-202. [5] Marcaillou et al. (2011) Earth and Planet. Sci. Lett. 303, 281-290. [6]Malvoisin et al. (2012) JGR, 117, B01104. [7]Perez et al. (2012) submited to Computational Geosciences. [8]Lowell & Germanovich (2004) AGU, Washington DC, USA.

  19. Hydrothermal activity along the slow-spreading Lucky Strike ridge segment (Mid-Atlantic Ridge): Distribution, heatflux, and geological controls

    NASA Astrophysics Data System (ADS)

    Escartin, J.; Barreyre, T.; Cannat, M.; Garcia, R.; Gracias, N.; Deschamps, A.; Salocchi, A.; Sarradin, P. M.; Ballu, V.

    2015-12-01

    We have reviewed available visual information from the seafloor, and recently acquired microbathymetry for several traverses across the Lucky Strike segment to evaluate the distribution of hydrothermal activity. The Lucky Strike segment hosts three active hydrothermal fields: Capelinhos, Ewan, and the known Main Lucky Strike Hydrothermal Field (MLSHF). Capelinhos is located 1.3 km E of the axis and the MLSHF, and consists of a ~20 m sulfide mound with black smoker vents. Ewan is located ~1.8 km south from the MLSHF along the axial graben, and displays only diffuse flow along and around scarps of collapse structures associated with fault scarps. At the MLSHF we have identified an inactive site, thus broadening the extent of this field. Heat flux estimates from these new sites are relatively low and correspond to ~10% of the heat flux estimated for the Main field, with an integrated heatflux of 200-1200 MW. Overall, most of the flux (up to 80-90%) is associated with diffuse outflow, with the Ewan site showing solely diffuse flow and Capelinhos mostly focused flow. Microbathymetry also reveals a large, off-axis (~2.4 km) hydrothermal field, similar to the TAG mound in size, on the flanks of a rifted volcano. The association of these fields to a central volcano, and the absence of indicators of hydrothermal activity along the ridge segment, suggest that sustained hydrothermal activity is maintained by the enhanced melt supply and the associated magma chamber(s) required to build central volcanoes. Hydrothermal outflow zones at the seafloor are systematically controlled by faults, indicating that hydrothermal circulation in the shallow crust exploits permeable fault zones. Central volcanoes are thus associated with long-lived hydrothermal activity, and these sites may play a major role in the distribution and biogeography of vent communities.

  20. Quantifying diffuse and discrete venting at the Tour Eiffel vent site, Lucky Strike hydrothermal field

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, Eric; EscartíN, Javier; Gracias, Nuno; Olive, Jean-Arthur; Barreyre, Thibaut; Davaille, Anne; Cannat, Mathilde; Garcia, Rafael

    2012-04-01

    The relative heat carried by diffuse versus discrete venting of hydrothermal fluids at mid-ocean ridges is poorly constrained and likely varies among vent sites. Estimates of the proportion of heat carried by diffuse flow range from 0% to 100% of the total axial heat flux. Here, we present an approach that integrates imagery, video, and temperature measurements to accurately estimate this partitioning at a single vent site, Tour Eiffel in the Lucky Strike hydrothermal field along the Mid-Atlantic Ridge. Fluid temperatures, photographic mosaics of the vent site, and video sequences of fluid flow were acquired during the Bathyluck'09 cruise (Fall, 2009) and the Momarsat'10 cruise (Summer, 2010) to the Lucky Strike hydrothermal field by the ROV Victor6000 aboard the French research vessel the "Pourquoi Pas"? (IFREMER, France). We use two optical methods to calculate the velocities of imaged hydrothermal fluids: (1) for diffuse venting, Diffuse Flow Velocimetry tracks the displacement of refractive index anomalies through time, and (2) for discrete jets, Particle Image Velocimetry tracks eddies by cross-correlation of pixel intensities between subsequent images. To circumvent video blurring associated with rapid velocities at vent orifices, exit velocities at discrete vents are calculated from the best fit of the observed velocity field to a model of a steady state turbulent plume where we vary the model vent radius and fluid exit velocity. Our results yield vertical velocities of diffuse effluent between 0.9 cm s-1 and 11.1 cm s-1 for fluid temperatures between 3°C and 33.5°C above that of ambient seawater, and exit velocities of discrete jets between 22 cm s-1 and 119 cm s-1 for fluid temperatures between 200°C and 301°C above ambient seawater. Using the calculated fluid velocities, temperature measurements, and photo mosaics of the actively venting areas, we calculate a heat flux due to diffuse venting from thin fractures of 3.15 ± 2.22 MW, discrete venting of

  1. Hydrothermal activity in the Northwest Lau Backarc Basin: Evidence from water column measurements

    NASA Astrophysics Data System (ADS)

    Lupton, J. E.; Arculus, R. J.; Resing, J.; Massoth, G. J.; Greene, R. R.; Evans, L. J.; Buck, N.

    2012-05-01

    The Northwest Lau Backarc Basin, consisting of the Northwest Lau Spreading Center (NWLSC) and the Rochambeau Rifts (RR), is unique in having elevated 3He/4He ratios (up to 28 Ra) in the erupted lavas, clearly indicating a hot spot or ocean island basalt (OIB)-type signature. This OIB-type helium signature does not appear in any other part of the Lau Basin. Water column plume surveys conducted in 2008 and 2010 identified several sites of active hydrothermal discharge along the NWLSC-RR and showed that the incidence of hydrothermal activity is high, consistent with the high spreading rate of ˜100 mm/year. Hydrocasts into the Central Caldera and Southern Caldera of the NWLSC detected elevated3He/4He (δ3He = 55% and 100%, respectively), trace metals (TMn, TFe), and suspended particles, indicating localized hydrothermal venting at these two sites. Hydrocasts along the northern rift zone of the NWLSC also had excess δ3He, TMn, and suspended particles suggesting additional sites of hydrothermal activity. The RR are dominated by Lobster Caldera, a large volcano with four radiating rift zones. Hydrocasts into Lobster Caldera in 2008 detected high δ3He (up to 239%) and suspended particle and TMn signals, indicating active venting within the caldera. A repeat survey of Lobster in 2010 confirmed the site was still active two years later. Plumes at Lobster Caldera and Central Caldera have end-member3He/4He ratios of 19 Ra and 11 Ra, respectively, confirming that hot spot-type helium is also present in the hydrothermal fluids.

  2. Hydrothermal reservoir beneath Taal Volcano (Philippines): Implications to volcanic activity

    NASA Astrophysics Data System (ADS)

    Nagao, T.; Alanis, P. B.; Yamaya, Y.; Takeuchi, A.; Bornas, M. V.; Cordon, J. M.; Puertollano, J.; Clarito, C. J.; Hashimoto, T.; Mogi, T.; Sasai, Y.

    2012-12-01

    Taal Volcano is one of the most active volcanoes in the Philippines. The first recorded eruption was in 1573. Since then it has erupted 33 times resulting in thousands of casualties and large damages to property. In 1995, it was declared as one of the 15 Decade Volcanoes. Beginning in the early 1990s it has experienced several phases of abnormal activity, including seismic swarms, episodes of ground deformation, ground fissuring and hydrothermal activities, which continues up to the present. However, it has been noted that past historical eruptions of Taal Volcano may be divided into 2 distinct cycles, depending on the location of the eruption center, either at Main Crater or at the flanks. Between 1572-1645, eruptions occurred at the Main Crater, in 1707 to 1731, they occurred at the flanks. In 1749, eruptions moved back to the Main Crater until 1911. During the 1965 and until the end of the 1977 eruptions, eruptive activity once again shifted to the flanks. As part of the PHIVOLCS-JICA-SATREPS Project magnetotelluric and audio-magnetotelluric surveys were conducted on Volcano Island in March 2011 and March 2012. Two-dimensional (2-D) inversion and 3-D forward modeling reveals a prominent and large zone of relatively high resistivity between 1 to 4 kilometers beneath the volcano almost directly beneath the Main Crater, surrounded by zones of relatively low resistivity. This anomalous zone of high resistivity is hypothesized to be a large hydrothermal reservoir filled with volcanic fluids. The presence of this large hydrothermal reservoir could be related to past activities of Taal Volcano. In particular we believe that the catastrophic explosion described during the 1911 eruption was the result of the hydrothermal reservoir collapsing. During the cycle of Main Crater eruptions, this hydrothermal reservoir is depleted, while during a cycle of flank eruptions this reservoir is replenished with hydrothermal fluids.

  3. The Sasquatch Hydrothermal Field: Linkages Between Seismic Activity, Hydrothermal Flow, and Geology

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    The Sasquatch Hydrothermal Field is the most northern known vent field along the central Endeavour Segment of the Juan de Fuca Ridge, located 6 km north of the Main Endeavour Field (MEF) near 47° 59.8'N, 129° 4.0'W. It was discovered in 2000, after two large earthquake swarms in June 1999 and January 2000 caused increased venting temperatures in the MEF and significant changes in volatile composition along the entire axis [Johnson et al., 2000; Lilley et al., 2003; Proskurowski et al., 2004]. From 2004-2006, Sasquatch and the surrounding axial valley were comprehensively mapped with SM2000 multibeam sonar system and Imagenex scanning sonar at a resolution of 1-5 m. These data were combined with visual imagery from Alvin and ROV dives to define the eruptive, hydrothermal, and tectonic characteristics of the field and distal areas. Based on multibeam sonar results, bathymetric relief of the segment near Sasquatch is subdued. The broad axial valley is split by a central high that rises 30-40 m above the surrounding seafloor. Simple pattern analysis of the valley shows two fundamentally different regions, distinguished by low and high local variance. Areas of low variance correspond to a collapse/drainback landscape characterized by ropy sheet flow, basalt pillars, and bathtub rings capped by intact and drained lobate flows. Areas of high variance generally correspond to three types of ridge structures: 1) faulted basalt ridges composed of truncated pillow basalt, rare massive flows, and widespread pillow talus; 2) constructional basalt ridges composed of intact pillow flow fronts; and 3) extinct sulfide ridges covered by varying amounts of sulfide talus and oxidized hydrothermal sediment. Sasquatch is located in a depression among truncated pillow ridges, and is comprised of ~10, 1-6 m high, fragile sulfide chimneys that vent fluids up to 289°C. The active field extends only ~25 x 25 m, although a linear, N-S trending ridge of nearly continuous extinct sulfide

  4. Stabilization of dissolved trace metals at hydrothermal vent sites: Impact on their marine biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Sander, Sylvia G.; Powell, Zach D.; Koschinsky, Andrea; Kuzmanovski, Stefan; Kleint, Charlotte

    2014-05-01

    Hydrothermal vents have long been neglected as a significant source of several bioactive trace metals as it was assumed that elements such as Fe, Mn, and Cu etc., precipitate in extensor forming poly-metallic sulfide and oxy-hydroxy sediments in the relative vicinity of the emanation site. However, recently this paradigm has been reviewed since the stabilization of dissolved Fe and Cu from hydrothermal vents was observed [1, 2] and increased concentrations of trace metals can be traced from their hydrothermal source thousands of kilometres through the ocean basins [3]. Furthermore several independent modelling attempts have shown that not only a stabilization of dissolved hydrothermal Fe and Cu is possible [4] but also that hydrothermalism must be a significant source of Fe to be able to balance the Fe-biogeochemical cycle [5]. Here we present new data that gives further evidence of the presence of copper stabilising organic and inorganic compounds in samples characterized by hydrothermal input. We can show that there are systematic differences in copper-complexing ligands at different vent sites such as 5°S on the Mid Atlantic Ridge, Brother Volcano on the Kermadec Arc, and some shallow hydrothermal CO2 seeps in the Bay of Plenty, New Zealand and the Mediterranean Sea. Quantitative and qualitative voltammetric data convincingly indicates that inorganic sulphur and organic thiols form the majority of the strong copper-complexing ligand pool in many of these hydrothermal samples. On average, the high temperature vents had a significantly higher copper binding capacity than the diffuse vents due to higher inorganic sulphur species concentrations. References: [1] Sander, S. G., et al. 2007. Organic complexation of copper in deep-sea hydrothermal vent systems. Environmental Chemistry 4: 81-89 [2] Bennett, S. A., et al. 2008. The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes. Earth and Planetary Science Letters 270: 157-167. [3] Wu J

  5. Lithosphere-biosphere interaction at a shallow-sea hydrothermal vent site; Hot Lake, Panarea, Italy

    NASA Astrophysics Data System (ADS)

    Huang, Chia-I.; Amann, Rudolf; Amend, Jan P.; Bach, Wolfgang; Brunner, Benjamin; Meyerdierks, Anke; Price, Roy E.; Schubotz, Florence; Summons, Roger; Wenzhöfer, Frank

    2010-05-01

    Deep-Sea hydrothermal systems are unique habitats for microbial life with primary production based on chemosynthesis and are considered to be windows to the subsurface biosphere. It is often overlooked, however, that their far more accessible shallow-sea counterparts are also valuable targets to study the effects of hydrothermal activity on geology, seawater chemistry and finally, on microbial life. Such an area of shallow marine hydrothermal venting is observed approximately 2.5 km east of Panarea Island (Sicily, Italy). This system is characterized by fluid temperatures of up to 135° C, gas emissions dominated by CO2 and precipitation of elemental sulfur on the seafloor. In an interdisciplinary project to investigate the influence of geofuels on marine microbiota, sediment cores and pore fluids were sampled for geological and geochemical analyses. An attempt was made to link these geochemical data with a characterization of the microbial community. One of the investigated sites (Lago Caldo, Hot Lake) is an oval-shaped (~10 by 6 meters) shallow (~2.5 m deep) depression covered by elemental sulfur. The sediments in this depression are strongly affected by hydrothermal activity: the pH of pore fluids is in a range between 5 and 6; the salinity is approximately two times higher than seawater. In situ temperatures of 36° C and 74° C (10 cm sediment depth) at two different locations within Hot Lake indicate variability in hydrothermal flux. The sediment surface layer is anoxic, and with increasing depth from the sediment-water interface, sulfate concentrations decrease from ~30 mM to less than 10 mM, whereas sulfide concentrations increase from less than 50 μm to ~1000 μm at 25 cm sediment depth, thus suggesting a higher potential for energy gain based on sulfur disequilibrium. As indicated by the variability in the sediment temperatures at 10 cm, fluid fluxes and mixing with seawater is not found to be uniform at Hot Lake. This is reflected in variability of the

  6. Time-variation of hydrothermal discharge at selected sites in the Western United States: Implications for monitoring

    USGS Publications Warehouse

    Ingebritsen, S.E.; Galloway, D.L.; Colvard, E.M.; Sorey, M.L.; Mariner, R.H.

    2001-01-01

    We compiled time series of hydrothermal discharge consisting of 3593 chloride- or heat-flux measurements from 24 sites in the Yellowstone region, the northern Oregon Cascades, Lassen Volcanic National Park and vicinity, and Long Valley, California. At all of these sites the hydrothermal phenomena are believed to be as yet unaffected by human activity, though much of the data collection was driven by mandates to collect environmental-baseline data in acticipation of geothermal development. The time series average 19 years in length and some of the Yellowstone sites have been monitored intermittently for over 30 years. Many sites show strong seasonality but few show clear long-term trends, and at most sites statistically significant decadal-scale trends are absent. Thus, the data provide robust estimates of advective heat flow ranging from ~130 MW in the north-central Oregon Cascades to ~6100 MW in the Yellowstone region, and also document Yellowstone hydrothermal chloride and arsenic fluxes of 1740 and 15-20 g/s, respectively. The discharge time series show little sensitivity to regional tectonic events such as earthquakes or inflation/deflation cycles. Most long-term monitoring to date has focused on high-chloride springs and low-temperature fumaroles. The relative stability of these features suggests that discharge measurements done as part of volcano-monitoring programs should focus instead on high-temperature fumaroles, which may be more immediately linked to the magmatic heat source. ?? 2001 Elsevier Science B.V. All rights reserved.

  7. Hydrothermal activity in Tertiary Icelandic crust: Implication for cooling processes along slow-spreading mid-ocean ridges

    NASA Astrophysics Data System (ADS)

    Pałgan, D.; Devey, C. W.; Yeo, I. A.

    2015-12-01

    Known hydrothermal activity along the Mid-Atlantic Ridge is mostly high-temperature venting, controlled by volcano-tectonic processes confined to ridge axes and neotectonic zones ~15km wide on each side of the axis (e.g. TAG or Snake Pit). However, extensive exploration and discoveries of new hydrothermal fields in off-axis regions (e.g. Lost City, MAR) show that hydrothermalism may, in some areas, be dominated by off-axis venting. Little is known about nature of such systems, including whether low-temperature "diffuse" venting dominates rather than high-temperature black-smokers. This is particularly interesting since such systems may transport up to 90% of the hydrothermal heat to the oceans. In this study we use Icelandic hot springs as onshore analogues for off-shore hydrothermal activity along the MAR to better understand volcano-tectonic controls on their occurrence, along with processes supporting fluid circulation. Iceland is a unique laboratory to study how new oceanic crust cools and suggests that old crust may not be as inactive as previously thought. Our results show that Tertiary (>3.3 Myr) crust of Iceland (Westfjords) has widespread low-temperature hydrothermal activity. Lack of tectonism (indicated by lack of seismicity), along with field research suggest that faults in Westfjords are no longer active and that once sealed, can no longer support hydrothermal circulation, i.e. none of the hot springs in the area occur along faults. Instead, dyke margins provide open and permeable fluid migration pathways. Furthermore, we suggest that the Reykjanes Ridge (south of Iceland) may be similar to Westfjords with hydrothermalism dominated by off-axis venting. Using bathymetric data we infer dyke positions and suggest potential sites for future exploration located away from neotectonic zone. We also emphasise the importance of biological observations in seeking for low-temperature hydrothermal activity, since chemical or optical methods are not sufficient.

  8. Comparative assessment of five potential sites for hydrothermal-magma systems: summary

    SciTech Connect

    Luth, W.C.; Hardee, H.C.

    1980-11-01

    A comparative assessment of five potential hydrothermal-magma sites for this facet of the Thermal Regimes part of the CSDP has been prepared for the DOE Office of Basic Energy Sciences. The five sites are: The Geysers-Clear Lake, CA, Long Valley, CA, Rio Grande Rift, NM, Roosevelt Hot Springs, UT, and Salton Trough, CA. This site assessment study has drawn together background information (geology, geochemistry, geophysics, and energy transport) on the five sites as a preliminary stage to site selection. Criteria for site selection are that potential sites have identifiable, or likely, hydrothermal systems and associated magma sources, and the important scientific questions can be identified and answered by deep scientific holes. Recommendations were made.

  9. Macrobenthos community structure and trophic relationships within active and inactive Pacific hydrothermal sediments

    NASA Astrophysics Data System (ADS)

    Levin, Lisa A.; Mendoza, Guillermo F.; Konotchick, Talina; Lee, Raymond

    2009-09-01

    Hydrothermal fluids passing through sediments create a habitat hypothesized to influence the community structure of infaunal macrobenthos. Here we characterize the density, biomass, species composition, diversity, distributions, lifestyle, and nutritional sources of macroinfauna in hydrothermal sediments in NE and SW Pacific settings, and draw comparisons in search of faunal attributes characteristic of this habitat. There is increasing likelihood that seafloor massive sulfide deposits, associated with active and inactive hydrothermal venting, will be mined commercially. This creates a growing imperative for a more thorough understanding of the structure, dynamics, and resilience of the associated sediment faunas, and has stimulated the research presented here. Macrobenthic assemblages were studied at Manus Basin (1430-1634 m, Papua New Guinea [PNG]) as a function of location (South Su vs. Solwara 1), and hydrothermal activity (active vs. inactive), and at Middle Valley (2406-2411 m, near Juan de Fuca Ridge) as a function of habitat (active clam bed, microbial mat, hot mud, inactive background sediment). The studies conducted in PNG formed part of the environmental impact assessment work for the Solwara 1 Project of Nautilus Minerals Niugini Limited. We hypothesized that hydrothermally active sites should support (a) higher densities and biomass, (b) greater dominance and lower diversity, (c) a higher fraction of deposit feeders, and (d) greater isotopic evidence for chemosynthetic food sources than inactive sites. Manus Basin macrofauna generally had low density (<1000 ind. m -2) and low biomass (0.1-1.07 g m -2), except for the South Su active site, which had higher density (3494 ind. m -2) and biomass (11.94 g m -2), greater dominance (R1D=76%), lower diversity and more spatial (between-core) homogeneity than the Solwara 1 and South Su inactive sites. Dominant taxa at Manus Basin were Spionidae ( Prionospio sp.) in active sediments, and tanaids and deposit

  10. Hydrothermal regimes of the dry active layer

    NASA Astrophysics Data System (ADS)

    Ishikawa, Mamoru; Zhang, Yinsheng; Kadota, Tsutomu; Ohata, Tetsuo

    2006-04-01

    Evaporation and condensation in the soil column clearly influence year-round nonconductive heat transfer dynamics in the dry active layer underlying semiarid permafrost regions. We deduced this from heat flux components quantified using state-of-the-art micrometeorological data sets obtained in dry and moist summers and in winters with various snow cover depths. Vapor moves easily through large pores, some of which connect to the atmosphere, allowing (1) considerable active layer warming driven by pipe-like snowmelt infiltration, and (2) direct vapor linkage between atmosphere and deeper soils. Because of strong adhesive forces, water in the dry active layer evaporates with great difficulty. The fraction of latent heat to total soil heat storage ranged from 26 to 45% in dry and moist summers, respectively. These values are not negligible, despite being smaller than those of arctic wet active layer, in which only freezing and thawing were considered.

  11. IODP Expedition 331: Strong and Expansive Subseafloor Hydrothermal Activities in the Okinawa Trough

    NASA Astrophysics Data System (ADS)

    Takai, K.; Mottl, M. J.; Nielsen, S. H. H.; IODP Expedition 331 Scientists, the

    2012-04-01

    Integrated Ocean Drilling Program (IODP) Expedition 331 drilled into the Iheya North hydrothermal system in the middle Okinawa Trough in order to investigate active subseafloor microbial ecosystems and their physical and chemical settings. We drilled five sites during Expedition 331 using special guide bases at three holes for reentry, casing, and capping, including installation of a steel mesh platform with valve controls for postcruise sampling of fluids. At Site C0016, drilling at the base of the North Big Chimney (NBC) mound yielded low recovery, but core included the first Kuroko-type black ore ever recovered from the modern subseafloor. The other four sites yielded interbedded hemipelagic and strongly pumiceous volcaniclastic sediment, along with volcanogenic breccias that are variably hydrothermally altered and mineralized. At most sites, analyses of interstitial water and headspace gas yielded complex patterns with depth and lateral distance of only a few meters. Documented processes included formation of brines and vapor-rich fluids by phase separation and segregation, uptake of Mg and Na by alteration minerals in exchange for Ca, leaching of K at high temperature and uptake at low temperature, anhydrite precipitation, potential microbial oxidation of organic matter and anaerobic oxidation of methane utilizing sulfate, and methanogenesis. Shipboard analyses have found evidence for microbial activity in sediments within the upper 10-30 m below seafloor (mbsf) where temperatures were relatively low, but little evidence in the deeper hydrothermally altered zones and hydrothermal fluid regime. doi:10.2204/iodp.sd.13.03.2011

  12. Refractory Organic Compounds in Enceladus' Ice Grains and Hydrothermal Activity

    NASA Astrophysics Data System (ADS)

    Postberg, F.; Khawaja, N.; Hsu, H. W.; Sekine, Y.; Shibuya, T.

    2015-12-01

    Cassini's Cosmic Dust Analyzer (CDA) generates time-of-flight mass spectra of individual grains impinging on the instruments target-plate. Following the analysis of salt rich ice grains emitted by Enceladus that indicated a salt-water ocean in contact with the moon's rocky core [1,2] a recent CDA analysis of nano-phase silica particles pointed at hydrothermal activity at the moon's rock/water interface [3]. The results imply temperatures above 80 - 90°C and alkaline pH values around 10 reminiscent of alkaline hydrothermal vents on Earth like the Lost City Hydrothermal Field. In this context the compositional analysis of organic components in CDA mass spectra of the ejected ice grains is of particular relevance. A multitude of volatile organic species has already been identified in the gas component of the plume [4]. As expected, we find more complex organic molecules in ice grains than in the gas indicating aromatic species, amines, and carbonyl group species. The composition of organic-bearing ice grains displays a great diversity indicating a variety of different organic species in varying concentrations. Recent spatially resolved CDA in situ measurements inside Enceladus' plume indicate that these organic compounds are especially frequent in 'young' ice grains that have just been ejected by high velocity jets. We investigate the implications of our findings with respect to ice grain formation at the water surface and inside the icy vents. We constrain the generation of organic compounds at the rock/water interface in the light of hydrothermal activity and the potential for the formation of life precursor molecules in Enceladus' ocean. Ref:[1] Postberg et al., Nature 459, 1098-1101 (2009). [2] Postberg et al., Nature 474, 620-622 (2011). [3]. Hsu, Postberg, Sekine et al., Nature, 519, 207-210 (2015). [4] Waite et al., Nature 460, 487-490 (2009).

  13. Free-living nematode species (Nematoda) dwelling in hydrothermal sites of the North Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Tchesunov, Alexei V.

    2015-12-01

    Morphological descriptions of seven free-living nematode species from hydrothermal sites of the Mid-Atlantic Ridge are presented. Four of them are new for science: Paracanthonchus olgae sp. n. (Chromadorida, Cyatholaimidae), Prochromadora helenae sp. n. (Chromadorida, Chromadoridae), Prochaetosoma ventriverruca sp. n. (Desmodorida, Draconematidae) and Leptolaimus hydrothermalis sp. n. (Plectida, Leptolaimidae). Two species have been previously recorded in hydrothermal habitats, and one species is recorded for the first time in such an environment. Oncholaimus scanicus (Enoplida, Oncholaimidae) was formerly known from only the type locality in non-hydrothermal shallow milieu of the Norway Sea. O. scanicus is a very abundant species in Menez Gwen, Lucky Strike and Lost City hydrothermal sites, and population of the last locality differs from other two in some morphometric characteristics. Desmodora marci (Desmodorida, Desmodoridae) was previously known from other remote deep-sea hydrothermal localities in south-western and north-eastern Pacific. Halomonhystera vandoverae (Monhysterida, Monhysteridae) was described and repeatedly found in mass in Snake Pit hydrothermal site. The whole hydrothermal nematode assemblages are featured by low diversity in comparison with either shelf or deep-sea non-hydrothermal communities. The nematode species list of the Atlantic hydrothermal vents consists of representatives of common shallow-water genera; the new species are also related to some shelf species. On the average, the hydrothermal species differ from those of slope and abyssal plains of comparable depths by larger sizes, diversity of buccal structures, presence of food content in the gut and ripe eggs in uteri.

  14. Tide-related variability of TAG hydrothermal activity observed by deep-sea monitoring system and OBSH

    NASA Astrophysics Data System (ADS)

    Fujioka, Kantaro; Kobayashi, Kazuo; Kato, Kazuhiro; Aoki, Misumi; Mitsuzawa, Kyohiko; Kinoshita, Masataka; Nishizawa, Azusa

    1997-12-01

    Hydrothermal activities were monitored by an ocean bottom seismometer with hydrophone (OBSH) and a composite measuring system (Manatee) including CTD, current meter, transmission meter and cameras at a small depression on the TAG hydrothermal mound in the Mid-Atlantic Ridge. Low-frequency pressure pulses detected by the hydrophone with semi-diurnal periodicity seem to correspond to cycles of hydrothermal upflow from a small and short-lived smoker vent close to the observing site. The peaks of pressure pulses are synchronous with the maximum gradient of areal strain decrease due to tidal load release. Microearthquakes with very near epicenters occur sporadically and do not appear to be directly correlatable to hydrothermal venting. Temporal variations in bottom water temperature also have semi-diurnal periodicity but are more complicated than the pressure events. Temperatures may be affected both by upwelling of hot water and by lateral flow of the bottom current changing its directions with ocean tide.

  15. Antimicrobial Activity of Marine Bacterial Symbionts Retrieved from Shallow Water Hydrothermal Vents.

    PubMed

    Eythorsdottir, Arnheidur; Omarsdottir, Sesselja; Einarsson, Hjorleifur

    2016-06-01

    Marine sponges and other sessile macro-organisms were collected at a shallow water hydrothermal site in Eyjafjörður, Iceland. Bacteria were isolated from the organisms using selective media for actinomycetes, and the isolates were screened for antimicrobial activity. A total of 111 isolates revealed antimicrobial activity displaying different antimicrobial patterns which indicates production of various compounds. Known test strains were grown in the presence of ethyl acetate extracts from one selected isolate, and a clear growth inhibition of Staphylococcus aureus was observed down to 0.1 % extract concentration in the medium. Identification of isolates shows different species of Actinobacteria with Streptomyces sp. playing the largest role, but also members of Bacilli, Alphaproteobacteria and Gammaproteobacteria. Sponges have an excellent record regarding production of bioactive compounds, often involving microbial symbionts. At the hydrothermal vents, however, the majority of active isolates originated from other invertebrates such as sea anemones or algae. The results indicate that antimicrobial assays involving isolates in full growth can detect activity not visible by other methods. The macro-organisms inhabiting the Eyjafjörður hydrothermal vent area host diverse microbial species in the phylum Actinobacteria with antimicrobial activity, and the compounds responsible for the activity will be subject to further research. PMID:27147438

  16. Antimicrobial Activity of Marine Bacterial Symbionts Retrieved from Shallow Water Hydrothermal Vents.

    PubMed

    Eythorsdottir, Arnheidur; Omarsdottir, Sesselja; Einarsson, Hjorleifur

    2016-06-01

    Marine sponges and other sessile macro-organisms were collected at a shallow water hydrothermal site in Eyjafjörður, Iceland. Bacteria were isolated from the organisms using selective media for actinomycetes, and the isolates were screened for antimicrobial activity. A total of 111 isolates revealed antimicrobial activity displaying different antimicrobial patterns which indicates production of various compounds. Known test strains were grown in the presence of ethyl acetate extracts from one selected isolate, and a clear growth inhibition of Staphylococcus aureus was observed down to 0.1 % extract concentration in the medium. Identification of isolates shows different species of Actinobacteria with Streptomyces sp. playing the largest role, but also members of Bacilli, Alphaproteobacteria and Gammaproteobacteria. Sponges have an excellent record regarding production of bioactive compounds, often involving microbial symbionts. At the hydrothermal vents, however, the majority of active isolates originated from other invertebrates such as sea anemones or algae. The results indicate that antimicrobial assays involving isolates in full growth can detect activity not visible by other methods. The macro-organisms inhabiting the Eyjafjörður hydrothermal vent area host diverse microbial species in the phylum Actinobacteria with antimicrobial activity, and the compounds responsible for the activity will be subject to further research.

  17. Significant role of climatic trends on hydrothermal activity Coso Hot Springs, California

    SciTech Connect

    Lofgren, B.E. )

    1990-05-01

    The hydrothermal features of Coso Hot Springs have attracted visitors for 130 yr and scientific investigators for two decades. In 1978, anticipating effects of major geothermal developments nearby, the Naval Weapons Center (NWC) initiated a comprehensive monitoring program at a dozen hydrothermal sites in the Coso Hot Springs area. Nine years of monitoring preceded power production in the nearby Coso geothermal field in July 1987. During this period, steam was rising from numerous vents and gently boiling mud pots. Local rainfall caused increased boiling activity in several mud pots, with some overflowing during wet periods. Then in August 1988, a year after geothermal power production began major changes in hot spring activity commenced. Small mud pots and steamers started to grow and coalesce. In March 1989, mud-pot activity became more violent. Many buried wells failed causing surface activity in other areas to diminish. During ensuing months, large mud cones developed and much of the steam and boiling water occurred in a few major pots. Because the abrupt changes in hydrothermal activity followed so closely after nearby geothermal production began, the obvious cause has been attributed to geothermal developments. Studies of NWC baseline monitoring data indicate, however, that no effects of geothermal developments have been felt in the hot springs area. Rainfall and barometric effects account for most of the fluctuations in records of the past decade. Early accounts and field evidence suggest similar changes have occurred in the past.

  18. The Third Dimension of an Active Back-arc Hydrothermal System: ODP Leg 193 at PACMANUS

    NASA Astrophysics Data System (ADS)

    Binns, R.; Barriga, F.; Miller, D.

    2001-12-01

    This first sub-seafloor examination of an active hydrothermal system hosted by felsic volcanics, at a convergent margin, obtained drill core from a high-T "smoker" site (penetrated to sim200 mbsf) and a low-T site of diffuse venting (~400mbsf). We aimed to delineate the lateral and vertical variability in mineralisation and alteration patterns, so as to understand links between volcanological, structural and hydrothermal phenomena and the sources of fluids, and to establish the nature and extent of microbial activity within the system. Technological breakthroughs included deployment of a new hard-rock re-entry system, and direct comparison in a hardrock environment of structural images obtained by wireline methods and logging-while-drilling. The PACMANUS hydrothermal site, at the 1700m-deep crest of a 500m-high layered sequence of dacitic lavas, is notable for baritic massive sulfide chimneys rich in Cu, Zn, Au and Ag. Below an extensive cap 5-40m thick of fresh dacite-rhyodacite, we found unexpectedly pervasive hydrothermal alteration of vesicular and flow-banded precursors, accompanied by variably intense fracturing and anhydrite-pyrite veining. Within what appears one major hydrothermal event affecting the entire drilled sequence, there is much overprinting and repetition of distinctly allochemical argillaceous (illite-chlorite), acid-sulfate (pyrophyllite-anhydrite) and siliceous assemblages. The alteration profiles include a transition from metastable cristobalite to quartz at depth, and are similar under low-T and high-T vent sites but are vertically condensed in a manner suggesting higher thermal gradients beneath the latter. The altered rocks are surprisingly porous (average 25%). Retention of intergranular pore spaces and open vesicles at depth implies elevated hydrothermal pressures, whereas evidence from fluid inclusions and hydrothermal brecciation denotes local or sporadic phase separation. A maximum measured temperature of 313 degC measured 8 days

  19. An authoritative global database for active submarine hydrothermal vent fields

    NASA Astrophysics Data System (ADS)

    Beaulieu, Stace E.; Baker, Edward T.; German, Christopher R.; Maffei, Andrew

    2013-11-01

    The InterRidge Vents Database is available online as the authoritative reference for locations of active submarine hydrothermal vent fields. Here we describe the revision of the database to an open source content management system and conduct a meta-analysis of the global distribution of known active vent fields. The number of known active vent fields has almost doubled in the past decade (521 as of year 2009), with about half visually confirmed and others inferred active from physical and chemical clues. Although previously known mainly from mid-ocean ridges (MORs), active vent fields at MORs now comprise only half of the total known, with about a quarter each now known at volcanic arcs and back-arc spreading centers. Discoveries in arc and back-arc settings resulted in an increase in known vent fields within exclusive economic zones, consequently reducing the proportion known in high seas to one third. The increase in known vent fields reflects a number of factors, including increased national and commercial interests in seafloor hydrothermal deposits as mineral resources. The purpose of the database now extends beyond academic research and education and into marine policy and management, with at least 18% of known vent fields in areas granted or pending applications for mineral prospecting and 8% in marine protected areas.

  20. Near-bottom magnetic surveys around hydrothermal sites in the southern Mariana Trough

    NASA Astrophysics Data System (ADS)

    Nogi, Y.; Mochizuki, N.; Okino, K.; Asada, M.

    2011-12-01

    Near-bottom magnetic survey is an effective method to reveal detailed magnetic anomaly features of seafloor. The measurements of three-components of the geomagnetic field by using AUV "URASHIMA" were conducted during the YK-09-08 cruise in the southern Mariana Trough in order to detect signals of hydrothermally altered rocks. During the cruise, vector geomagnetic field are successfully obtained along the all dive tracks with the information of the vehicle's attitude. Total intensities of geomagnetic field by the overhauser magnetometer were also conducted, but the data are only collected along almost E-W oriented observation lines due to the sensitivity of the sensor. The distribution of crustal magnetization are estimated using downward component of magnetic anomalies by the inversion method. The distribution of low crustal magnetization are almost coincide with the area around hydrothermal vent sites from on ridge to off ridge area, and most likely indicate signs of hydrothermally altered rocks. The distribution of low crustal magnetization on ridge are almost parallel to the the strike of ridge axis implying tectonic control of hydrothermal vent sites.

  1. Organic Analysis of Peridotite Rocks from the Ashadze and Logatchev Hydrothermal Sites

    PubMed Central

    Bassez, Marie-Paule; Takano, Yoshinori; Ohkouchi, Naohiko

    2009-01-01

    This article presents an experimental analysis of the organic content of two serpentinized peridotite rocks of the terrestrial upper mantle. The samples have been dredged on the floor of the Ashadze and Logatchev hydrothermal sites on the Mid-Atlantic Ridge. In this preliminary analysis, amino acids and long chain n-alkanes are identified. They are most probably of biological/microbial origin. Some peaks remain unidentified. PMID:19742180

  2. Organic analysis of peridotite rocks from the Ashadze and Logatchev hydrothermal sites.

    PubMed

    Bassez, Marie-Paule; Takano, Yoshinori; Ohkouchi, Naohiko

    2009-06-01

    This article presents an experimental analysis of the organic content of two serpentinized peridotite rocks of the terrestrial upper mantle. The samples have been dredged on the floor of the Ashadze and Logatchev hydrothermal sites on the Mid-Atlantic Ridge. In this preliminary analysis, amino acids and long chain n-alkanes are identified. They are most probably of biological/microbial origin. Some peaks remain unidentified. PMID:19742180

  3. Organic analysis of peridotite rocks from the Ashadze and Logatchev hydrothermal sites.

    PubMed

    Bassez, Marie-Paule; Takano, Yoshinori; Ohkouchi, Naohiko

    2009-07-03

    This article presents an experimental analysis of the organic content of two serpentinized peridotite rocks of the terrestrial upper mantle. The samples have been dredged on the floor of the Ashadze and Logatchev hydrothermal sites on the Mid-Atlantic Ridge. In this preliminary analysis, amino acids and long chain n-alkanes are identified. They are most probably of biological/microbial origin. Some peaks remain unidentified.

  4. Modelling of hydrothermal fluid circulation in a heterogeneous medium: Application to the Rainbow Vent site (Mid-Atlantic-Ridge, 36°14N)

    NASA Astrophysics Data System (ADS)

    Perez, F.; Mügler, C.; Jean-Baptiste, P.; Charlou, J. L.

    2012-04-01

    Hydrothermal activity at the axis of mid-ocean ridges is a key driver for energy and matter transfer from the interior of the Earth to the ocean floor. At mid-ocean ridges, seawater penetrates through the permeable young crust, warms at depth and exchanges chemicals with the surrounding rocks. This hot fluid focuses and flows upwards, then is expelled from the crust at hydrothermal vent sites in the form of black or white smokers completed by diffusive emissions. We developed a new numerical tool in the Cast3M software framework to model such hydrothermal circulations. Thermodynamic properties of one-phase pure water were calculated from the IAPWS formulation. This new numerical tool was validated on several test cases of convection in closed-top and open-top boxes. Simulations of hydrothermal circulation in a homogeneous-permeability porous medium also gave results in good agreement with already published simulations. We used this new numerical tool to construct a geometric and physical model configuration of the Rainbow Vent site at 36°14'N on the Mid-Atlantic Ridge. In this presentation, several configurations will be discussed, showing that high temperatures and high mass fluxes measured at the Rainbow site cannot be modelled with hydrothermal circulation in a homogeneous-permeability porous medium. We will show that these high values require the presence of a fault or a preferential pathway right below the venting site. We will propose and discuss a 2-D one-path model that allows us to simulate both high temperatures and high mass fluxes. This modelling of the hydrothermal circulation at the Rainbow site constitutes a first but necessary step to understand the origin of high concentrations of hydrogen issued from this ultramafic-hosted vent field.

  5. Pb isotopes in sulfides from mid-ocean ridge hydrothermal sites

    SciTech Connect

    LeHuray, A.P.; Church, S.E.; Koski, R.A.; Bouse, R.M.

    1988-04-01

    The authors report Pb isotope ratios of sulfides deposited at seven recently active mid-ocean ridge (MOR) hydrothermal vents. Sulfides from three sediment-starved sites on the Juan de Fuca Ridge contain Pb with isotope ratios identical to their local basaltic sources. Lead in two deposits from the sediment-covered Escanaba Trough, Gorda Ridge, is derived from the sediments and does not appear to contain any basaltic component. There is a range of isotope ratios in a Guaymas Basin deposit, consistent with a mixture of sediment and MOR basalt Pb. Lead in a Galapagos deposit differs slightly from known Galapagos basalt Pb isotope values. The faithful record of Pb isotope signatures of local sources in MOR sulfides indicates that isotope ratios from ancient analogues ca be used as accurate reflections of ancient oceanic crustal values in ophiolite-hosted deposits and continental crustal averages in sediment-hosted deposits. The preservation of primary ophiolitic or continental crustal Pb isotope signatures in ancient MOR sulfides provides a powerful tool for investigation of crustal evolution and for fingerprinting ancient terranes.

  6. High-resolution water column survey to identify active sublacustrine hydrothermal discharge zones within Lake Rotomahana, North Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Walker, Sharon L.; de Ronde, Cornel E. J.; Fornari, Daniel; Tivey, Maurice A.; Stucker, Valerie K.

    2016-03-01

    Autonomous underwater vehicles were used to conduct a high-resolution water column survey of Lake Rotomahana using temperature, pH, turbidity, and oxidation-reduction potential (ORP) to identify active hydrothermal discharge zones within the lake. Five areas with active sublacustrine venting were identified: (1) the area of the historic Pink Terraces; (2) adjacent to the western shoreline subaerial "Steaming Cliffs," boiling springs and geyser; (3) along the northern shoreline to the east of the Pink Terrace site; (4) the newly discovered Patiti hydrothermal system along the south margin of the 1886 Tarawera eruption rift zone; and (5) a location in the east basin (northeast of Patiti Island). The Pink Terrace hydrothermal system was active prior to the 1886 eruption of Mount Tarawera, but venting along the western shoreline, in the east basin, and the Patiti hydrothermal system appear to have been initiated in the aftermath of the eruption, similar to Waimangu Valley to the southwest. Different combinations of turbidity, pH anomalies (both positive and negative), and ORP responses suggest vent fluid compositions vary over short distances within the lake. The seasonal period of stratification limits vertical transport of heat to the surface layer and the hypolimnion temperature of Lake Rotomahana consequently increases with an average warming rate of ~ 0.010 °C/day due to both convective hydrothermal discharge and conductive geothermal heating. A sudden temperature increase occurred during our 2011 survey and was likely the response to an earthquake swarm just 11 days prior.

  7. A fluorescein tracer release experiment in the hydrothermally active crater of Vailulu'u volcano, Samoa

    NASA Astrophysics Data System (ADS)

    Hart, S. R.; Staudigel, H.; Workman, R.; Koppers, A. A. P.; Girard, A. P.

    2003-08-01

    On 3 April 2001, a 20 kg point source of fluorescein dye was released 30 m above the bottom of the active summit caldera of Vailulu'u submarine volcano, Samoa. Vailulu'u crater is 2000 m wide and at water depths of 600-1000 m, with the bottom 200 m completely enclosed; it thus provides an ideal site to study the hydrodynamics of an active hydrothermal system. The magmatically driven hydrothermal system in the crater is currently exporting massive amounts of particulates, manganese, and helium. The dispersal of the dye was tracked for 4 days with a fluorimeter in tow-yo mode from the U.S. Coast Guard icebreaker Polar Sea. Lateral dispersion of the dye ranged from 80 to 500 m d-1; vertical dispersion had two components: a diapycnal diffusivity component averaging 21 cm2 s-1, and an advective component averaging 0.025 cm s-1. These measurements constrain the mass export of water from the crater during this period to be 8-1.3+4.6 × 107 m3 d-1, which leads to a "turnover" time for water in the crater of ˜3.2 days. Coupled with temperature data from CTD profiles and Mn analyses of water samples, the power output from the crater is 610-100+350 MW, and the manganese export flux is ˜240 kg d-1. The Mn/Heat ratio of 4.7 ng J-1 is significantly lower than ratios characteristic of hot smokers and diffuse hydrothermal flows on mid-ocean ridges and points to phase separation processes in this relatively shallow hydrothermal system.

  8. Effects of hydrothermal alteration on Pb in the active PACMANUS hydrothermal field, ODP Leg 193, Manus Basin, Papua New Guinea: A LA-ICP-MS study

    NASA Astrophysics Data System (ADS)

    Beaudoin, Yannick; Scott, Steven D.; Gorton, Michael P.; Zajacz, Zoltan; Halter, Werner

    2007-09-01

    The conventional model of leaching volcanic rocks as a source of metals in a seafloor hydrothermal systems has been tested by examining the behavior of Pb and other trace elements during hydrothermal alteration. ODP Leg 193 drill sites 1188 (Snowcap) and 1189 (Roman Ruins) on Pual Ridge in the eastern Manus Basin offshore eastern Papua New Guinea provide a unique three-dimensional window into an active back-arc hydrothermal system. We investigate by means of a LA-ICP-MS microbeam technique the capacity of Pb to be leached from a host volcanic rock exposed to various types and intensities of alteration. Our results are in general agreement with previous studies that utilized bulk analytical techniques but provide a more detailed explanation of the processes. Fresh representative dacitic lavas from the Pual Ridge have an average whole rock Pb content of 5.2 ppm, an average interstitial glass Pb content of 5.6 ppm and an average plagioclase Pb content of 1.0 ppm. Altered matrix samples have highly variable Pb values ranging from 0 to 52.4 ppm. High Pb values in altered samples are associated with a low temperature chlorite and clay mineral assemblage, in some cases overprinted by a high temperature (up to 350 °C) silica-rich "bleaching" alteration. Only the most highly altered matrix samples have REE patterns that differ from the fresh Pual Ridge dacite. This may represent either different lava histories or alteration characteristics that have affected normally immobile REEs. Altered samples with the highest Pb values have similar REE patterns to those of the local unaltered lavas. They are compositionally similar to typical Pual Ridge dacites indicating a genetic relationship between the main regional volcanic suite and the subseafloor hydrothermally altered, Pb-enriched material. Relative loss/gain for Pb between the analyzed altered samples and a calculated precursor show a maximum relative gain of 901%. Samples with relative Pb gain from both drill sites are

  9. Comparative assessment of five potential sites for magma: hydrothermal systems - geophysics

    SciTech Connect

    Kasameyer, P.

    1980-09-02

    As part of a comparative assessment for the Continental Scientific Drilling Program, geophysical data were used, to characterize and evaluate potential magma-hydrothermal targets at five drill sites in the western United States. The sites include Roosevelt Hot Springs, Utah, the Rio Grande Rift, New Mexico, and The Geysers-Clear Lake, Long Valley, and Salton Trough areas, California. This summary discusses the size, depth, temperature, and setting of each potential target, as well as relvant scientific questions about their natures and the certainty of their existence.

  10. Liquid Carbon Dioxide Venting at the Champagne Hydrothermal Site, NW Eifuku Volcano, Mariana Arc

    NASA Astrophysics Data System (ADS)

    Lupton, J.; Lilley, M.; Butterfield, D.; Evans, L.; Embley, R.; Olson, E.; Proskurowski, G.; Resing, J.; Roe, K.; Greene, R.; Lebon, G.

    2004-12-01

    In March/April 2004, submersible dives with the remotely-operated vehicle ROPOS discovered an unusual CO2-rich hydrothermal system near the summit of NW Eifuku, a submarine volcano located at 21.49° N, 144.04° E in the northern Mariana Arc. Although several sites of hydrothermal discharge were located on NW Eifuku, the most intense venting was found at 1600-m depth at the Champagne site, slightly west of the volcano summit. The Champagne site was found to be discharging two distinct fluids into the ocean: a) several small white chimneys were emitting milky 103° C gas-rich hydrothermal fluid with at least millimolar levels of H2S and b) cold (< 4° C) droplets coated with a milky skin were rising slowly from the sediment. These droplets were later determined to consist mainly of liquid CO2, with H2S as a probable secondary component. The droplets were sticky, and did not tend to coalesce into larger droplets, even though they adhered to the ROV like clumps of grapes. The film coating the droplets was assumed to be CO2 hydrate (or clathrate) which is known to form whenever liquid CO2 contacts water under these P,T conditions. Samples of the 103° C hydrothermal fluids were collected in special gas-tight titanium sampling bottles that were able to withstand the high internal pressures created by the dissolved gases. The Champagne hydrothermal fluids contained a surprising 2.3 moles/kg of CO2, an order of magnitude higher than any CO2 values previously reported for submarine hydrothermal fluids. The overall gas composition was 87% CO2, < 0.1% CH4, < 2 ppm H2, 0.012 mM/kg 4He, with the remaining 13% (322 mM/kg) assumed to be sulfur gases (H2S, SO2, etc.). (Additional analyses planned will confirm the speciation of this sulfur gas component). The helium had R/RA = 7.3, typical of subduction zone systems (R = 3He/4He and RA = Rair). Isotopic analysis of the CO2 yielded δ 13C = -1.75 ‰ , much heavier than the -6.0 ‰ typical for carbon in MOR vent fluids. The C/3He

  11. Hydrothermal synthesis and photocatalytic activity of zinc oxide hollow spheres.

    PubMed

    Yu, Jiaguo; Yu, Xiaoxiao

    2008-07-01

    ZnO hollow spheres with porous crystalline shells were one-pot fabricated by hydrothermal treatment of glucose/ZnCl2 mixtures at 180 degrees C for 24 h, and then calcined at different temperatures for 4 h. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption isotherms. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic decolorization of Rhodamine B aqueous solution at ambient temperature. The results indicated that the average crystallite size, shell thickness, specific surface areas, pore structures, and photocatalytic activity of ZnO hollow spheres could be controlled by varying the molar ratio of glucose to zinc ions (R). With increasing R, the photocatalytic activity increases and reaches a maximum value at R = 15, which can be attributed to the combined effects of several factors such as specific surface area, the porous structure and the crystallite size. Further results show that hollow spheres can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and reused than conventional powder photocatalyst. After many recycles for the photodegradation of RhB, the catalyst does not exhibit any great loss in activity, confirming ZnO hollow spheres is stability and not photocorroded. The prepared ZnO hollow spheres are also of great interest in solar cell, catalysis, separation technology, biomedical engineering, and nanotechnology.

  12. Fluid inclusion petrology and microthermometry of the Cocos Ridge hydrothermal system, IODP Expedition 344 (CRISP 2), Site U1414

    PubMed Central

    Brandstätter, Jennifer; Krenn, Kurt; Micheuz, Peter

    2016-01-01

    Abstract In this study, we present new data from microthermometry of fluid inclusions entrapped in hydrothermal veins along the Cocos Ridge from the IODP Expedition 344 Site U1414. The results of our study concern a primary task of IODP Expedition 344 to evaluate fluid/rock interaction linked with the tectonic evolution of the incoming Cocos Plate from the Early Miocene up to recent times. Aqueous, low saline fluids are concentrated within veins from both the Cocos Ridge basalt and the overlying lithified sediments of Unit III. Mineralization and crosscutting relationships give constraints for different vein generations. Isochores from primary, reequilibrated, and secondary fluid inclusions crossed with litho/hydrostatic pressures indicate an anticlockwise PT evolution during vein precipitation and modification by isobaric heating and subsequent cooling at pressures between ∼210 and 350 bar. Internal over and underpressures in the inclusions enabled decrepitation and reequilibration of early inclusions but also modification of vein generations in the Cocos Ridge basalt and in the lithified sediments. We propose that lithification of the sediments was accompanied with a first stage of vein development (VU1 and VC1) that resulted from Galapagos hotspot activity in the Middle Miocene. Heat advection, either related to the Cocos‐Nazca spreading center or to hotspot activity closer to the Middle America Trench, led to subsequent vein modification (VC2, VU2/3) related to isobaric heating. The latest mineralization (VC3, VU3) within aragonite and calcite veins and some vesicles of the Cocos Ridge basalt occurred during crustal cooling up to recent times. Fluid inclusion analyses and published isotope data show evidence for communication with deeper sourced, high‐temperature hydrothermal fluids within the Cocos Plate. The fluid source of the hydrothermal veins reflects aqueous low saline pore water mixed with invaded seawater. PMID:27570496

  13. Fluid inclusion petrology and microthermometry of the Cocos Ridge hydrothermal system, IODP Expedition 344 (CRISP 2), Site U1414

    NASA Astrophysics Data System (ADS)

    Brandstätter, Jennifer; Kurz, Walter; Krenn, Kurt; Micheuz, Peter

    2016-04-01

    In this study, we present new data from microthermometry of fluid inclusions entrapped in hydrothermal veins along the Cocos Ridge from the IODP Expedition 344 Site U1414. The results of our study concern a primary task of IODP Expedition 344 to evaluate fluid/rock interaction linked with the tectonic evolution of the incoming Cocos Plate from the Early Miocene up to recent times. Aqueous, low saline fluids are concentrated within veins from both the Cocos Ridge basalt and the overlying lithified sediments of Unit III. Mineralization and crosscutting relationships give constraints for different vein generations. Isochores from primary, reequilibrated, and secondary fluid inclusions crossed with litho/hydrostatic pressures indicate an anticlockwise PT evolution during vein precipitation and modification by isobaric heating and subsequent cooling at pressures between ˜210 and 350 bar. Internal over and underpressures in the inclusions enabled decrepitation and reequilibration of early inclusions but also modification of vein generations in the Cocos Ridge basalt and in the lithified sediments. We propose that lithification of the sediments was accompanied with a first stage of vein development (VU1 and VC1) that resulted from Galapagos hotspot activity in the Middle Miocene. Heat advection, either related to the Cocos-Nazca spreading center or to hotspot activity closer to the Middle America Trench, led to subsequent vein modification (VC2, VU2/3) related to isobaric heating. The latest mineralization (VC3, VU3) within aragonite and calcite veins and some vesicles of the Cocos Ridge basalt occurred during crustal cooling up to recent times. Fluid inclusion analyses and published isotope data show evidence for communication with deeper sourced, high-temperature hydrothermal fluids within the Cocos Plate. The fluid source of the hydrothermal veins reflects aqueous low saline pore water mixed with invaded seawater.

  14. Extensive and Diverse Submarine Volcanism and Hydrothermal Activity in the NE Lau Basin

    NASA Astrophysics Data System (ADS)

    Embley, R. W.; Merle, S. G.; Lupton, J. E.; Resing, J.; Baker, E. T.; Lilley, M. D.; Arculus, R. J.; Crowhurst, P. V.

    2009-12-01

    The northeast Lau basin, the NE “corner” of the Tonga subduction zone, has an unusual concentration of young submarine volcanism and hydrothermal activity. The area is bounded on the west by overlapping spreading centers opening at rates up to 120 mm/yr, on the north by the E-W trending Tonga trench and on the east by the Tofua arc front. From the south, the Fonualei rift spreading center (FRSC) overlaps with the southern rift of The Mangatolo triple junction spreading center (MTJSC). The northern arm of the MTJSC overlaps with the northeast Lau spreading center (NELSC). Surveys of the area with an EM300 sonar system in November 2008 show high backscatter over the 10-20 km wide neovolcanic zones of the FRSC, MTJSC and NELSC. High backscatter is also associated with: (1) a 10-km diameter, hydrothermally active, volcanic caldera/cone (Volcano “O”) lying between the NELSC and the northern Tofua arc front; (2) a rift zone extending north from volcano “O” and intersecting the NELSC near the Tonga trench; and (3) a series of volcanoes constructed along SW-NE trending crustal tears in the northernmost backarc near the east-west portion of the Tonga Trench. Two eruptions were detected in November 2008 during hydrothermal plume surveys of the area. Subsequent dives with the remotely operated vehicle Jason 2 in May 2009 revealed that the southern NELSC eruption was a short-lived, primarily effusive eruption. The second eruption was detected on the summit of the largest SW-NE trending volcano (West Mata) and was ongoing when Jason 2 arrived on site more than 6 months later. It was producing both pillow lavas and abundant volcaniclastic debris streams that have a characteristic appearance on the sonar backscatter map. There is also an unusual series of lava flows emanating from ridges and scarps between Volcano “O” and West Mata. These flows contain drained-out lava ponds up to 2 km in diameter. The apparent high level of volcanic activity in the NE Lau basin

  15. Distribution of Hydrothermal Activity at the Lau ISS: Possible Controlling Parameters

    NASA Astrophysics Data System (ADS)

    Martinez, F.; Baker, E. T.; Resing, J. A.; Edwards, M. H.; Walker, S. L.; Buck, N.

    2008-12-01

    Seismic tomographic studies of intermediate to fast spreading rate mid-ocean ridges (MORs) interpret zones of rapid crustal cooling a few (3-4) km off axis surrounding the axial seismic low velocity zone (LVZ). These zones of rapid cooling also broadly correlate with the initiation and growth of large abyssal hill faults. The close association of both high thermal gradients and development of fault permeability at crustal scales suggests the hypothesis that these areas may be favorable locations for off-axis high temperature hydrothermal activity. In March-May 2008 on R/V Kilo Moana we conducted a near-bottom sidescan sonar and oceanographic survey along the Eastern Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) in the Lau back-arc basin to map the distribution of hydrothermal activity within this region. The survey utilized the deep-towed DSL120A (IMI120) sonar, an array of miniature autonomous plume recorders (MAPRs) attached to the tow cable and tethered beneath the sonar's depressor weight, an in situ chemical scanner (VISA) and 23 CTD hydrocasts (see Baker et al., this session). At the ELSC the survey spanned ~100 x 10 km area encompassing the ABE, Tow Cam and Kilo Moana vent fields with ~ 1 km spaced lines overall and ~500 m spaced lines in the area of the ABE vent field. On the VFR the survey spanned a distance of ~100 km along axis by ~5 km across axis with 700 m spaced lines encompassing the Vai Lili, Mariner and Tui Malila vent sites. Initial results identified particle plumes, indicative of high temperature venting, only within about a km of the ridge axis at the ELSC and VFR with possible diffuse venting indicated by MAPR oxidation-reduction potential (ORP) measurements at flank sites at VFR. The expanded sonar coverage better defines the volcano-tectonic context of the hydrothermal signals and previously mapped vent sites. Initial results suggest, however, no high-T venting more than about 1 km from the ridge axis, an apparently negative test of

  16. Microbial Activity and Volatile Fluxes in Seafloor Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Corrigan, R. S.; Lowell, R. P.

    2013-12-01

    Understanding geographically and biologically the production or utilization of volatile chemical species such as CO2, CH4, and H2 is crucial not only for understanding hydrothermal processes but also for understanding life processes in the oceanic crust. To estimate the microbial effect on the transport of these volatiles, we consider a double-loop single pass model as shown in Figure 1 to estimate the mass fluxes shown. We then use a simple mixing formulation: C4Q4 = C3 (Q1 -Q3)+ C2Q2, where C2 is the concentration of the chemical in seawater, C3 is the average concentration of the chemical in high temperature focused flow, C4 is the expected concentration of the chemical as a result of mixing, and the relevant mass flows are as shown in Figure 1. Finally, we compare the calculated values of CO2, CH4, and H2 in diffuse flow fluids to those observed. The required data are available for both the Main Endeavour Field on the Juan de Fuca Ridge and the East Pacific Rise 9°50' N systems. In both cases we find that, although individual diffuse flow sites have observed concentrations of some elements that are greater than average, the average concentration of these volatiles is smaller in all cases than the concentration that would be expected from simple mixing. This indicates that subsurface microbes are net utilizers of these chemical constituents at the Main Endeavour Field and at EPR 9°50' N on the vent field scale. Figure 1. Schematic of a 'double-loop' single-pass model above a convecting, crystallizing, replenished AMC (not to scale). Heat transfer from the vigorously convecting, cooling, and replenished AMC across the conductive boundary layer δ drives the overlying hydrothermal system. The deep circulation represented by mass flux Q1 and black smoker temperature T3 induces shallow circulation noted by Q2. Some black smoker fluid mixes with seawater resulting in diffuse discharge Q4, T4, while the direct black smoker mass flux with temperature T3 is reduced

  17. Hydrothermal Processes

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

    found at more than 40 locations throughout the Pacific, North Atlantic, and Indian Oceans (e.g., Van Dover et al., 2002) with further evidence - from characteristic chemical anomalies in the ocean water column - of its occurrence in even the most remote and slowly spreading ocean basins ( Figure 3), from the polar seas of the Southern Ocean (German et al., 2000; Klinkhammer et al., 2001) to the extremes of the ice-covered Arctic ( Edmonds et al., 2003). (61K)Figure 3. Schematic map of the global ridge crest showing the major ridge sections along which active hydrothermal vents have already been found (red circles) or are known to exist from the detection of characteristic chemical signals in the overlying water column (orange circles). Full details of all known hydrothermally active sites and plume signals are maintained at the InterRidge web-site: http://triton.ori.u-tokyo.ac.jp/~intridge/wg-gdha.htm The most spectacular manifestation of seafloor hydrothermal circulation is, without doubt, the high-temperature (>400 °C) "black smokers" that expel fluids from the seafloor along all parts of the global ocean ridge crest. In addition to being visually compelling, vent fluids also exhibit important enrichments and depletions when compared to ambient seawater. Many of the dissolved chemicals released from the Earth's interior during venting precipitate upon mixing with the cold, overlying seawater, generating thick columns of black metal-sulfide and oxide mineral-rich smoke - hence the colloquial name for these vents: "black smokers" (Figure 4). In spite of their common appearance, high-temperature hydrothermal vent fluids actually exhibit a wide range of temperatures and chemical compositions, which are determined by subsurface reaction conditions. Despite their spectacular appearance, however, high-temperature vents may only represent a small fraction - perhaps as little as 10% - of the total hydrothermal heat flux close to ridge axes. A range of studies - most notably

  18. Diversity of Active Seafloor Hydrothermal Mineralization in the Manus Back-Arc Basin, Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Gena, K.; Chiba, H.

    2004-12-01

    The Manus back-arc basin in the Western Pacific hosts three contrasting style of mineralization called Vienna Wood, Pacmanus and Onsen site. The three deposits have distinct geology and geochemical characteristics. The Vienna Wood site in the Central Manus Basin (CMB) is hosted by mid-oceanic ridge type basalt. The mineralization is dominated by wurtzite, marcasite, pyrite, chalcopyrite, Fe-oxide and gangue minerals of anhydrite, gypsum and quartz. The filling temperatures and salinities of the inclusion range from 200-260_E#8249;C and 4.8-6.6 NaCl equiv. wt% respectively. Bulk chemical analyses of the ores indicate that the mineralization in the Vienna Wood site can be classified into the Zn-Cu type. The simple mineral assemblage indicates simple basalt-seawater interaction and is a modern analogue of the ophiolite hosted VVMS deposits. The mineralization in the Pacmanus site is hosted by dacitic lavas is characterised by a complex mineral assemblage of marcasite, pyrite, chalcopyrite, sphalerite, bornite, enargite, covellite, chalcocite, digenite, galena, tennantite, native gold, PbAs-sulfosalts and gangue minerals of barite, rare silica, anhydrite and native sulphur. The temperature of mineralization ranges from 230-280_E#8249;C. Bulk chemical composition of the ore samples indicates that the mineralization in the Pacmanus site can be classified into the Zn-Cu-Pb-Au type. The mineral assemblage, character of the ores and tectonic setting resembles those of ancient Kuroko and currently forming hydrothermal deposits in Lau Basin and in Okinawa Trough. The Onsen hydrothermal site in the Desmos caldera is hosted by basaltic andesite. The advanced argillic alteration is characterised by both high and low temperature acid stable minerals of pyrophyllite, natroalunite, quartz, cristobalite, amorphous silica, anhydrite, gypsum, pyrite, marcasite, enargite, covellite and native sulphur. The mineralization occurs at a temperature range of 240 to 340_E#8249;C. The high

  19. High-resolution magnetics reveal the deep structure of a volcanic-arc-related basalt-hosted hydrothermal site (Palinuro, Tyrrhenian Sea)

    NASA Astrophysics Data System (ADS)

    Szitkar, Florent; Petersen, Sven; Caratori Tontini, Fabio; Cocchi, Luca

    2015-06-01

    High-resolution magnetic surveys have been acquired over the partially sedimented Palinuro massive sulfide deposits in the Aeolian volcanic arc, Tyrrhenian Sea. Surveys flown close to the seafloor using an autonomous underwater vehicle (AUV) show that the volcanic-arc-related basalt-hosted hydrothermal site is associated with zones of lower magnetization. This observation reflects the alteration of basalt affected by hydrothermal circulation and/or the progressive accumulation of a nonmagnetic deposit made of hydrothermal and volcaniclastic material and/or a thermal demagnetization of titanomagnetite due to the upwelling of hot fluids. To discriminate among these inferences, estimate the shape of the nonmagnetic deposit and the characteristics of the underlying altered area—the stockwork—we use high-resolution vector magnetic data acquired by the AUV Abyss (GEOMAR) above a crater-shaped depression hosting a weakly active hydrothermal site. Our study unveils a relatively small nonmagnetic deposit accumulated at the bottom of the depression and locked between the surrounding volcanic cones. Thermal demagnetization is unlikely but the stockwork extends beyond the limits of the nonmagnetic deposit, forming lobe-shaped zones believed to be a consequence of older volcanic episodes having contributed in generating the cones.

  20. Hydrothermal Plume Mapping Along the Hotspot-affected Galapagos Spreading Center Finds High-Temperature Vent Sites are Anomalously Scarce

    NASA Astrophysics Data System (ADS)

    Baker, E. T.; Resing, J. A.; Walker, S. L.; Lebon, G. T.; Nakamura, K.; Haymon, R. M.; White, S. M.; MacDonald, K. C.

    2006-12-01

    Systematic searches for hydrothermal activity along midocean ridges (MORs) demonstrate that the spatial density of hydrothermal activity is a robust linear function of spreading rate. This trend argues that the availability of mantle heat is the first order control on the distribution of seafloor vent fields. However, some crustal thermal models predict that the thicker, hotter, more ductile crust associated with hotspots substantially reduces convective hydrothermal cooling, explaining observations of axial magma chambers (AMC) at shallower depths than found on normal MORs. In Dec-Jan 2006 we tested this hypothesis by mapping hydrothermal plumes overlying the hotspot-affected Galapagos Spreading Center (GSC) from 95°-89.6°W, using a dual-pass, side-scan deep tow with an array of plume sensors spanning 50- 250 m above bottom. The western GSC near 91°-92.5°W has axial-high morphology, shallow and quasi-continuous AMC, and thick (8 km) crust, changing to a transitional morphology, deeper and more discontinuous AMC, and normal (6 km) crust from 93° to 95°W. The eastern GSC, 90.5°- 89.6°W is also an axial high and presumably has crustal characteristics similar to the western GSC at 91°-92.5°W. We identified hydrothermal plumes by anomalies in light backscattering (NTU) from a vertical array of MAPR sensors along the tow line, plus redox potential (Eh) measured continuously in-situ on the tow body at a nominal elevation of 100 m. Many plumes were subsequently confirmed by CTD tows and sampling. Only three areas of extensive and intense plumes were observed: 90.52°-90.63°W, 91.78°- 91.96°W, and 94°-94.1°W. Maximum plume rise at the latter two sites exceeded 200 m, indicative of high-temperature venting that was confirmed by camera tows. Some 25 other NTU and Eh anomalies were detected along ~1000 km of trackline, but none were >5 km in length. The primary result of our survey is that hydrothermal plumes were scarce for a ridge spreading at ~60 mm

  1. Post-Impact Hydrothermal Activity at the Haughton Impact Structure, Devon Island, Nunavut, Canada

    NASA Technical Reports Server (NTRS)

    Osinski, G. R.; Spray, J. G.; Bunch, T. E.; Grieve, R. A. F.; Schutt, J. W.; Lee, P.

    2000-01-01

    Evidence for impact-generated hydrothermal activity is reported from the Haughton crater, Canada. Two distinct settings have been found: (1) pipe structures with marcasite, pyrite and minor chalcopyrite; (2) cavity and fracture fillings with marcasite predominant.

  2. Absolute magnetization of the seafloor at a basalt-hosted hydrothermal site: Insights from a deep-sea submersible survey

    NASA Astrophysics Data System (ADS)

    Szitkar, Florent; Dyment, Jérôme; Fouquet, Yves; Choi, Yujin; Honsho, Chie

    2015-02-01

    The analysis of high-resolution vector magnetic data acquired by deep-sea submersibles (DSSs) requires the development of specific approaches adapted to their uneven tracks. We present a method that takes advantage of (1) the varying altitude of the DSS above the seafloor and (2) high-resolution multibeam bathymetric data acquired separately, at higher altitude, by an Autonomous Underwater Vehicle, to estimate the absolute magnetization intensity and the magnetic polarity of the shallow subseafloor along the DSS path. We apply this method to data collected by DSS Nautile on a small active basalt-hosted hydrothermal site. The site is associated with a lack of magnetization, in agreement with previous findings at the same kind of sites: the contrast between nonmagnetic sulfide deposits/stockwork zone and strongly magnetized basalt is sufficient to explain the magnetic signal observed at such a low altitude. Both normal and reversed polarities are observed in the lava flows surrounding the site, suggesting complex history of accumulating volcanic flows.

  3. New evidence for persistent impact-generated hydrothermal activity in the Miocene Ries impact structure, Germany

    NASA Astrophysics Data System (ADS)

    Arp, Gernot; Kolepka, Claudia; Simon, Klaus; Karius, Volker; Nolte, Nicole; Hansen, Bent T.

    2013-12-01

    The extent of impact-generated hydrothermal activity in the 24 km sized Ries impact structure has been controversially discussed. To date, mineralogical and isotopic investigations point to a restriction of hydrothermal activity to the impact-melt bearing breccias, specifically the crater-fill suevite. Here, we present new petrographic, geochemical, and isotopic data of postimpact carbonate deposits, which indicate a hydrothermal activity more extended than previously assumed. Specifically, carbonates of the Erbisberg, a spring mound located upon the inner crystalline ring of the crater, show travertine facies types not seen in any of the previously investigated sublacustrine soda lake spring mounds of the Ries basin. In particular, the streamer carbonates, which result from the encrustation of microbial filaments in subaerial spring effluents between 60 and 70 °C, are characteristic of a hydrothermal origin. While much of the primary geochemical and isotopic signatures in the mound carbonates have been obliterated by diagenesis, a postimpact calcite vein from brecciated gneiss of the subsurface crater floor revealed a flat rare earth element pattern with a clear positive Eu anomaly, indicating a hydrothermal fluid convection in the crater basement. Finally, the strontium isotope stratigraphic correlation of the travertine mound with the crater basin succession suggests a hydrothermal activity for about 250,000 yr after the impact, which would be much longer than previously assumed.

  4. Hydrothermal activity at slow-spreading ridges: variability and importance of magmatic controls

    NASA Astrophysics Data System (ADS)

    Escartin, Javier

    2016-04-01

    Hydrothermal activity along mid-ocean ridge axes is ubiquitous, associated with mass, chemical, and heat exchanges between the deep lithosphere and the overlying envelopes, and sustaining chemiosynthetic ecosystems at the seafloor. Compared with hydrothermal fields at fast-spreading ridges, those at slow spreading ones show a large variability as their location and nature is controlled or influenced by several parameters that are inter-related: a) tectonic setting, ranging from 'volcanic systems' (along the rift valley floor, volcanic ridges, seamounts), to 'tectonic' ones (rift-bounding faults, oceanic detachment faults); b) the nature of the host rock, owing to compositional heterogeneity of slow-spreading lithosphere (basalt, gabbro, peridotite); c) the type of heat source (magmatic bodies at depth, hot lithosphere, serpentinization reactions); d) and the associated temperature of outflow fluids (high- vs.- low temperature venting and their relative proportion). A systematic review of the distribution and characteristics of hydrothermal fields along the slow-spreading Mid-Atlantic Ridge suggests that long-lived hydrothermal activity is concentrated either at oceanic detachment faults, or along volcanic segments with evidence of robust magma supply to the axis. A detailed study of the magmatically robust Lucky Strike segment suggests that all present and past hydrothermal activity is found at the center of the segment. The association of these fields to central volcanos, and the absence of indicators of hydrothermal activity along the remaining of the ridge segment, suggests that long-lived hydrothermal activity in these volcanic systems is maintained by the enhanced melt supply and the associated magma chamber(s) required to build these volcanic edifices. In this setting, hydrothermal outflow zones at the seafloor are systematically controlled by faults, indicating that hydrothermal fluids in the shallow crust exploit permeable fault zones to circulate. While

  5. An in situ vapour phase hydrothermal surface doping approach for fabrication of high performance Co3O4 electrocatalysts with an exceptionally high S-doped active surface.

    PubMed

    Tan, Zhijin; Liu, Porun; Zhang, Haimin; Wang, Yun; Al-Mamun, Mohammad; Yang, Hua Gui; Wang, Dan; Tang, Zhiyong; Zhao, Huijun

    2015-04-01

    A facile in situ vapour phase hydrothermal (VPH) surface doping approach has been developed for fabrication of high performance S-doped Co3O4 electrocatalysts with an unprecedentedly high surface S content (>47%). The demonstrated VPH doping approach could be useful for enrichment of surface active sites for other metal oxide electrocatalysts. PMID:25714902

  6. The hydrophysical evidence for hydrothermal activity intensification in the subtropical MAR in summer, 2002

    NASA Astrophysics Data System (ADS)

    Aleynik, D. L.

    2003-04-01

    The adequate evaluations of heat and matter flux on the ocean - bottom boundary are required as for determination of the overall ocean thermal budget, so for the expected climate transformations. The hydrophysical measurements were obtained by rosette equipped with CTD, nephelometer, pinger and 30-liter bottles, which were deployed from R/V “Ak. M. Keldysh” in a tow-yo regime. The data were supplemented by visual and instrumental observations from submersibles “MIR”. These results at six hydrothermal vent sites of MAR from 23.3 to 37.3 deg. N were compared with data of similar surveys, fulfilled during previous decade. The hydrothermal matter influx irregularity leads to fluctuations in the parameters of the neutral buoyant plumes above five sites (Snake Pit, TAG, Broken Spur, Lucky Strike and Rainbow). The absence of the plume above the Lost City was detected. In July, 2002, northeastern-more off the most active field Rainbow the sizes of the neutral plume again (as well as during the RRS “Discovery” expedition in 1997) increased in three times (up to 6-7 kms along SW-NE line and more than 4 kms across) in contrast to the data of detail survey in autumn, 1999. Now this plume covers the whole peak of Rainbow axial Ridge. The waters contained in this rift valley (160 cubic kms) are remarkably more heated than ambient ocean waters (at depth 2650 m the difference is near 0.5 deg. C). The author thanks crews of R/V “AMK” and submersibles “MIR” for their help in measurements.

  7. Tidal bottom current modulation of chemical environment in the Suiyo hydrothermal site in the Izu-Ogasawara (Bonin) Arc.

    NASA Astrophysics Data System (ADS)

    Nakamura, K.

    2002-12-01

    Intense seafloor observatory studies were done at the Suiyo hydrothermal site in the summer of 2001 and 2002. Deployed instruments on the seafloor were CTD (Idronaut, Ocean Seven 316), Digiquartz precision pressure sensor and its recorder, 3-D acoustic current meters (NOBSKA, MAVS3), high temperature and redox recorders at the vents, in-situ laser particle analyzer (Sequoia Scientific, LISST-Deep), methane sensor (CAPSUM METS) with its data logger, etc. The Suiyo Seamount hydrothermal site is located in the summit caldera of Izu-Ogasawara (Bonin) Arc (1380 m deep, 28.572 N, 140.643 E). The tide is mixed type dominant with semi-diurnal component. There is no tidal components in temperature and redox records neither at high temperature vents (300 deg C) nor at low temperature vents (less than 200 deg C). Whereas the temperature, redox, methane concentration in the seawater, particle characters measured just above the seafloor had strong semi-diurnal components. The methane concentration varies from several micro mol/litter to several tens of micro mol/litter associated with 200 mV redox change in the central part of the hydrothermal site. Semi-diurnal strong bottom current over 40 cm/sec appeared several hours after high tides introduced entrainment of ambient waters in the marginal part of hydrothermal site and accelerated mixing of vent water with bottom water in the central part of the hydrothermal site. This research was funded by the "Archaean Park" Project (International research project on interaction between sub-vent biosphere and geo environment funded by Special Coordination Fund of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The R/V Natsushima cruise with the sub "Shinkai 2000" was a part of the Deep Sea Research project of the Japan Marine Science and Technology Center (JAMSTEC).

  8. 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

    NASA Astrophysics Data System (ADS)

    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

  9. Hydrothermal Activity and Volcanism on the Southern Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Haase, K. M.; Scientific Party, M.

    2005-12-01

    In April 2005 four recently discovered different hydrothermal fields on the slow-spreading Mid-Atlantic Ridge (MAR) south of the Equator were studied and sampled using a remotely operated vehicle (ROV) during cruise METEOR 64/1. Three of these hydrothermally active fields (called Turtle Pits, Red Lion, and Wideawake) occur at about 3000 m water depth in the centre of a MAR segment at 4° 48'S which appears to be volcanically very active. The youngest lava flow partly covers the low-temperature, diffuse flow Wideawake mussel field and is thus probably only a few years old. The high-temperature Turtle Pits hydrothermal field with four active vent structures lies some 300 m west of the diffuse vent field and is characterized by boiling fluids with temperatures close to 400° C. The mineral assemblage recovered from inactive hydrothermal mounds includes massive magnetite+hematite+sulfate and differs from that of the presently active vents and indicates more oxidizing conditions during the earlier activity. The vent fluids at Turtle Pits contain relatively high contents of hydrogen which may have formed during iron oxidation processes when basaltic magmas crystallized. The high fluid temperatures, the change to more reducing conditions, and the relatively high hydrogen contents in the fluids are most likely due to the ascent of magmas from the mantle that fed the very recent eruption. The high-temperature Red Lion hydrothermal field lies some 2 km north of the Turtle Pits field and consists of at least four active black smokers surrounded by several inactive sulfide mounds. The composition of the Red Lion fluids differs significantly from the Turtle Pits fluids, possibly owing largely to a difference in the temperature of the two systems. The fourth hydrothermally active field on the southern MAR, the Liliput field, was discovered near 9° 33'S in a water depth of 1500 m and consists of several low-temperature vents. A shallow hydrothermal plume in the water column

  10. Hydrothermal Cooling Within the Lau Integrated Study Site: No Evidence for Off-axis Discharge

    NASA Astrophysics Data System (ADS)

    Baker, E. T.; Resing, J. A.; Martinez, F.; Walker, S. L.; Buck, N.; Edwards, M. H.; Nakamura, K.

    2008-12-01

    Decades of intensive hydrothermal surveying, overwhelmingly concentrated within hundreds of meters of the axes of ridge crests, has supported the view that discrete fluid discharge is predominantly concentrated in this same region. This simple view, however, conflicts with emerging evidence for a crustal high-temperature, low-velocity volume (LVV) that extends 2-3 km beyond the ridge crest and generates strongly focused hydrothermal cooling along its off-axis vertical boundaries. In March/April 2008, we used high-resolution sampling of near-bottom waters along 175 km of the hydrothermally active Valu Fa Ridge (VFR) and Eastern Lau Spreading Center (ELSC) to comprehensively test the hypothesis that hydrothermal discharge is predominantly near-axis. Our sampling array included a suite of Miniature Autonomous Plume Recorders (temperature, light scattering, oxidation-reduction potential (ORP)) attached above (to a nominal altitude of 400 m) and below the deep-towed IMI120 sonar, plus CTDs and sensors at the bottom of the string (50 m) and on the clump weight (120 m). The ELSC between 19.9° and 21°S (spreading ~80 mm/yr) grades from a broad, flat valley in the north to a shallow high in the south. Ten survey lines at 1 km spacing were centered on the axis, plus five interleaved lines around the axial high of the ABE vent field (1300 km of track). The VFR from 21.9° to 22.4°S (~50 mm/yr) is a sharp ridge that deepens ~200 m within 1 km of the axis. Seven survey lines were run at 0.7 km spacing, plus two shorter lines adjacent to a broad overlapping spreading center (390 km). CTD tows and casts supplemented the IMI120 surveys. The surveys detected emissions from the several known on-axis vent fields, and also identified a substantial unexplored field near 20.65°S, ~10 km north of the ABE field. In neither survey area, however, did we detect evidence of high-temperature discharge beyond the near-axis (±1 km) zone. Because off-axis discharge may be largely low

  11. Microbial control of silver mineralization at a sea-floor hydrothermal site on the northern Gorda Ridge

    USGS Publications Warehouse

    Zierenberg, R.A.; Schiffman, P.

    1990-01-01

    THE Sea Cliff hydrothermal field, on the northern Gorda Ridge, contains mounds and chimneys of hydrothermally precipitated sulphide and sulphate minerals typical of sea-floor hydrothermal vent sites1. In addition, large areas of the sea floor are covered by subhorizontal hydrothermal crusts. Samples of the crust recovered by submersible are composed of intensely altered fragments of basalt and basaltic hyaloclastite cemented by amorphous silica and chalcedony with less abundant barite, and minor amounts of base-metal sulphide minerals2. Some surfaces of the crust were formerly colonized by bacterial mats, which are locally preserved by replacement and overgrowth of the bacterial filaments by metal sulphide minerals and amorphous silica. The bacterial filaments are selectively replaced by prousite (Ag3AsS3), pearceite3 (Ag14.7-XCu1.3+xAs2S11), chalcopyrite (CuFeS2) and rarely by galena (PbS). Our observations suggest that bacterially mediated processes selectively precipitate silver, arsenic and copper, and that biological processes may contribute to precious-metal enrichment in some sea-floor hydrothermal base-metal sulphide deposits.

  12. Application of radium isotopes to determine crustal residence times of hydrothermal fluids from two sites on the Reykjanes Peninsula, Iceland

    NASA Astrophysics Data System (ADS)

    Kadko, David; Gronvold, Karl; Butterfield, David

    2007-12-01

    Radium isotopes were used to determine the crustal residence times of hydrothermal fluids from two geothermal wells (Svartsengi and Reykjanes) from the Reykjanes Peninsula, Iceland. The availability of rock samples from the subsurface (to depths of 2400 m) allowed direct comparison of the radium isotopic characteristics of the fluids with those of the rocks within the high temperature and pressure reaction zone. The 226Ra activity of the Svartsengi fluid was ˜one-fourth of the Reykjanes fluid and the 228Ra/ 226Ra ratio of the Svartsengi fluid was ˜twice that of Reykjanes. The fluid isotopic characteristics were relatively stable for both sites over the 6 years (2000-2006) of the study. It was determined, using a model that predicts the evolution of the fluid 228Ra/ 226Ra ratio with time, that both sites had fluid residence times, from the onset of high temperature water-rock reaction, of less than 5 years. Measurement of the short-lived 224Ra and 223Ra allowed estimation of the recoil input parameter used in the model. The derived timescale is consistent with results from similar studies of fluids from submarine systems, and has implications for the use of terrestrial systems in Iceland as an exploited energy resource.

  13. Present-day submarine hydrothermal activity in the Taupo-Rotorua Zone (Bay of Plenty, New Zealand)

    SciTech Connect

    Osipenko, A.B.; Egorov, Yu.O.; Fazlullin, S.M.; Gavrilenko, G.M.; Shul`kin, V.I.; Chertkova, L.V.

    1994-09-01

    We made detailed descriptions of the structure and material composition of sedimentary and water columns in the vicinity of active submarine hydrothermal activity in the southern part of the Bay of Plenty (North Island, New Zealand). Geophysical methods revealed that the hydrothermal system is confined to a tectonically distinct zone with a sedimentary cover characterized by complex structure. Chemical and mineralogical investigations confirmed that the activity of underwater vents exerts no substantial regional influence on the composition and features of ore mineralization in these formations. It is shown that essentially hydrothermal formations distinguishable within areas of otherwise monotypic sediments directly coincide with zones of hydrothermal discharge in the ocean floor. The absence of pronounced hydrothermal anomalies, together with the presence of {open_quotes}tongues{close_quotes} of anomalous concentrations of water-soluble gases suggests that the discharges are primarily hydrothermal in character.

  14. Biogeographical distribution of Rimicaris exoculata resident gut epibiont communities along the Mid-Atlantic Ridge hydrothermal vent sites.

    PubMed

    Durand, Lucile; Roumagnac, Marie; Cueff-Gauchard, Valérie; Jan, Cyrielle; Guri, Mathieu; Tessier, Claire; Haond, Marine; Crassous, Philippe; Zbinden, Magali; Arnaud-Haond, Sophie; Cambon-Bonavita, Marie-Anne

    2015-10-01

    Rimicaris exoculata is a deep-sea hydrothermal vent shrimp whose enlarged gill chamber houses a complex trophic epibiotic community. Its gut harbours an autochthonous and distinct microbial community. This species dominates hydrothermal ecosystem megafauna along the Mid-Atlantic Ridge, regardless of contrasting geochemical conditions prevailing in them. Here, the resident gut epibiont community at four contrasted hydrothermal vent sites (Rainbow, TAG, Logatchev and Ashadze) was analysed and compiled with previous data to evaluate the possible influence of site location, using 16S rRNA surveys and microscopic observations (transmission electron microscopy, scanning electron microscopy and fluorescence in situ hybridization analyses). Filamentous epibionts inserted between the epithelial cell microvilli were observed on all examined samples. Results confirmed resident gut community affiliation to Deferribacteres, Mollicutes, Epsilonproteobacteria and to a lesser extent Gammaproteobacteria lineages. Still a single Deferribacteres phylotype was retrieved at all sites. Four Mollicutes-related operational taxonomic units were distinguished, one being only identified on Rainbow specimens. The topology of ribotype median-joining networks illustrated a community diversification possibly following demographic expansions, suggesting a more ancient evolutionary history and/or a larger effective population size at Rainbow. Finally, the gill chamber community distribution was also analysed through ribotype networks based on sequences from R. exoculata collected at the Rainbow, Snake Pit, TAG, Logatchev and Ashadze sites. Results allow the refining of hypotheses on the epibiont role and transmission pathways.

  15. Biogeographical distribution of Rimicaris exoculata resident gut epibiont communities along the Mid-Atlantic Ridge hydrothermal vent sites.

    PubMed

    Durand, Lucile; Roumagnac, Marie; Cueff-Gauchard, Valérie; Jan, Cyrielle; Guri, Mathieu; Tessier, Claire; Haond, Marine; Crassous, Philippe; Zbinden, Magali; Arnaud-Haond, Sophie; Cambon-Bonavita, Marie-Anne

    2015-10-01

    Rimicaris exoculata is a deep-sea hydrothermal vent shrimp whose enlarged gill chamber houses a complex trophic epibiotic community. Its gut harbours an autochthonous and distinct microbial community. This species dominates hydrothermal ecosystem megafauna along the Mid-Atlantic Ridge, regardless of contrasting geochemical conditions prevailing in them. Here, the resident gut epibiont community at four contrasted hydrothermal vent sites (Rainbow, TAG, Logatchev and Ashadze) was analysed and compiled with previous data to evaluate the possible influence of site location, using 16S rRNA surveys and microscopic observations (transmission electron microscopy, scanning electron microscopy and fluorescence in situ hybridization analyses). Filamentous epibionts inserted between the epithelial cell microvilli were observed on all examined samples. Results confirmed resident gut community affiliation to Deferribacteres, Mollicutes, Epsilonproteobacteria and to a lesser extent Gammaproteobacteria lineages. Still a single Deferribacteres phylotype was retrieved at all sites. Four Mollicutes-related operational taxonomic units were distinguished, one being only identified on Rainbow specimens. The topology of ribotype median-joining networks illustrated a community diversification possibly following demographic expansions, suggesting a more ancient evolutionary history and/or a larger effective population size at Rainbow. Finally, the gill chamber community distribution was also analysed through ribotype networks based on sequences from R. exoculata collected at the Rainbow, Snake Pit, TAG, Logatchev and Ashadze sites. Results allow the refining of hypotheses on the epibiont role and transmission pathways. PMID:26324855

  16. ESR dating of submarine hydrothermal activities using barite in sulfide deposition

    NASA Astrophysics Data System (ADS)

    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

  17. Submarine hydrothermal environments as sites for the origin and evolution of life

    NASA Technical Reports Server (NTRS)

    Hoffman, S.; Baross, J.

    1985-01-01

    That life formed and evolved in hydrothermal environments is proposed. This hypothesis is plausible in terms of the tectonic, paleontological, and degassing history of the Earth. Submarine hydrothermal vents are the only contemporary geological environment which may truly be called primeval and which today continue to be a major source of gases and dissolved elements to the ocean. The microbial assemblages in present day hydrothermal systems therefore could be living analogues of the earliest microbial communities to develop on Earth. The evidence for the hypothesis is reviewed.

  18. Silica nanoparticles as indicator of hydrothermal activities at Enceladus ocean floor

    NASA Astrophysics Data System (ADS)

    Postberg, F.; Hsu, S.; Sekine, Y.; Kempf, S.; Juhasz, A.; Horanyi, M.; Moragas-Klostermeyer, G.; Srama, R.

    2013-12-01

    Silica nanoparticles as indicator of hydrothermal activities at Enceladus ocean floor F. Postberg, H.-W. Hsu, Y. Sekine, S. Kempf, A. Juhasz, M. Horanyi, G. Moragas-Klostermeyer, R. Srama Silica serves as a unique indicator of hydrothermal activities on Earth as well as on Mars. Here we report the Cassini Cosmic Dust Analyser (CDA) observation of nanosilica particles from the Saturnian system. Based on their interaction with the solar wind electromagnetic fields, these charged nanosilica particles, so-called stream particles, are found to be originated in Saturn's E ring, indicating Enceladus being their ultimate source. CDA stream particle mass spectra reveal a metal-free but silicon-rich composition that is only plausible for nearly pure silica particles. The size range derived from our measurements confines the size of these particles to a radius of 2 - 8 nm. The unique properties of nano-grains with the observed composition and size are a well-known phenomenon on Earth and their formation requires specific hydrothermal rock-water interactions. The observation of Saturnian nanosilica particles thus serves as an evidence of hydrothermal activities at the interface of Enceladus subsurface ocean and its rocky core. Considering plasma erosion as the major mechanism of releasing embedded nanosilica particles from their carriers, the much larger E ring ice grains, our dynamical model and CDA observation provide a lower limit on the average nanosilica concentration in E ring grains. Together with dedicated hydrothermal experiments (Sekine at al., 2013) this can be translated into constraints on the hydrothermal activities on Enceladus. Measurements and experiments both point at dissolved silica concentrations at the ocean floor in the order of 1 - 3 mMol. The hydrothermal reactions likely take place with a pristine, chondritic rock composition at temperature higher than 130°C (Sekine at al. 2013). Colloidal nano-silica forms upon supersaturation during cooling of the

  19. Metagenome and Metatranscriptome Revealed a Highly Active and Intensive Sulfur Cycle in an Oil-Immersed Hydrothermal Chimney in Guaymas Basin.

    PubMed

    He, Ying; Feng, Xiaoyuan; Fang, Jing; Zhang, Yu; Xiao, Xiang

    2015-01-01

    The hydrothermal vent system is a typical chemosynthetic ecosystem in which microorganisms play essential roles in the geobiochemical cycling. Although it has been well-recognized that the inorganic sulfur compounds are abundant and actively converted through chemosynthetic pathways, the sulfur budget in a hydrothermal vent is poorly characterized due to the complexity of microbial sulfur cycling resulting from the numerous parties involved in the processes. In this study, we performed an integrated metagenomic and metatranscriptomic analysis on a chimney sample from Guaymas Basin to achieve a comprehensive study of each sulfur metabolic pathway and its hosting microorganisms and constructed the microbial sulfur cycle that occurs in the site. Our results clearly illustrated the stratified sulfur oxidation and sulfate reduction at the chimney wall. Besides, sulfur metabolizing is closely interacting with carbon cycles, especially the hydrocarbon degradation process in Guaymas Basin. This work supports that the internal sulfur cycling is intensive and the net sulfur budget is low in the hydrothermal ecosystem.

  20. Hydrothermal changes related to earthquake activity at Mud Volcano, Yellowstone National Park, Wyoming

    SciTech Connect

    Pitt, A.M.; Hutchinson, R.A.

    1982-04-10

    The Mud Volcano hydrothermal area in Yellowstone National Park is near the intersection of a 20-km-long zone of northeast trending normal faults with the eastern resurgent dome within the 600,000-year-odd Yellowstone caldera. Recent crustal uplift along the northeast trending axis of the caldera is at a maximum (700 mm since 1923) near the Mud Volcano area. From 1973 through April 1978, less than 10 earthquakes (largest M 2.4) were located within 3 km of the Mud Volcano area. In May 1978, earthquakes began occurring beneath the hydrothermal area at depths of 1 to 5 km. The seismic activity continued until the end of November with intense swarms (100 events per hour) occurring on October 23 and November 7. The largest event (M 3.1) occured on November 14 and at least 8 events were M 2.5 or larger. In December 1978, heat flux in the Mud Volcano hydrothermal features began increasing along a 2-km-long northeast trending zone. Existing mud cauldrons became more active, new mud cauldrons and fumeroles were formed, and vegetation (primarily lodgepole pine) was killed by increased soil temperature. The increase in heat flux continued through July 1979 then gradually declined, reaching the early 1978 level by June 1980. The spatial and temporal association of earthquakes and increased hydrothermal activity at Mud Volcano suggests that the seismic activity expanded preexisting fracture systems, premitting increased fluid flow from depths of several kilometers.

  1. Exploring an active hydrothermal system - An analogue study from the Swiss Alps

    NASA Astrophysics Data System (ADS)

    Egli, Daniel; Herwegh, Marco; Berger, Alfons; Baron, Ludovic

    2016-04-01

    Understanding the detailed flow paths in hydrothermal reservoirs is crucial for successful exploration of naturally porous and permeable rock masses for energy production. However, due to the common inaccessibility of active hydrothermal systems of suitable depth, e.g. in the northern Alpine foreland of the European Alps, direct observations are normally impossible and the knowledge about such systems is still insufficient. For that reason, a known fault-bound hydrothermal system in the crystalline basement of the Aar Massif serves as an analogue for potential geothermal reservoirs in the deep crystalline subsurface of the northern Alpine foreland. During summer 2015, a 125 m hole has been drilled across this active hydrothermal zone on the Grimsel Pass for in-situ characterization of its structural, petrophysical, mechanical as well as geophysical parameters. With this information, this project aims at improving the knowledge of natural hydrothermal systems as a potentially exploitable energy source. The investigated system is characterized by a central breccia zone surrounded by different types of cataclasites and localized high strain zones. The surrounding includes different altered and deformed granitoid host rocks. In this study, we focus on the ductile and brittle deformation (shear zones, fractures, joints) that provides the main fluid pathways. Their spatial distribution around a central water-bearing breccia zone as well as their continuity and permeability provide constraints on the water flow paths in such structurally controlled hydrothermal systems. The aim will be the connection of detailed structural data with petrophysical parameters such as porosities and permeabilities. The drillcore shows the high variability of deformation structures and related fluid pathways at different scales (millimeter-decameter) demonstrating the urgent need for an improved understanding of the link between mechanical evolution, associated deformation structures as well

  2. Immunomodulatory N-acyl Dopamine Glycosides from the Icelandic Marine Sponge Myxilla incrustans Collected at a Hydrothermal Vent Site.

    PubMed

    Einarsdottir, Eydis; Liu, Hong-Bing; Freysdottir, Jona; Gotfredsen, Charlotte Held; Omarsdottir, Sesselja

    2016-06-01

    A chemical investigation of the sponge (Porifera) Myxilla incrustans collected from the unique submarine hydrothermal vent site Strytan, North of Iceland, revealed a novel family of closely related N-acyl dopamine glycosides. Three new compounds, myxillin A (1), B (2) and C (3), were isolated and structurally elucidated using several analytical techniques, such as HR-MS, 1D and 2D NMR spectroscopy. Myxillin A (1) and B (2)were shown to be structurally similar, composed of a dopamine moiety, but differ in the acyl chain length and saturation. The myxillin C (3) has a dehydrotyrosine moiety composing the same acyl chain and glycosylation as myxillin B (2). Myxillins A (1) and C (3) were tested for immunomodulating activity in an in vitro dendritic cell model. Dendritic cells matured and stimulated in the presence of myxillin A (1) secreted lower levels of IL-12p40, whilst dendritic cells matured and stimulated in the presence of myxillin C (3) secreted lower levels of IL-10 compared with dendritic cells matured and stimulated in the presence of the solvent alone. These opposing results indicate that the structural differences in the aromatic ring part of the molecules could have an impact on the immunological effects of dendritic cells. These molecules could, therefore, prove to be important in preventing inflammatory diseases on the one hand, and inducing a response to fight tumors and/or pathogens on the other hand. Further studies will be needed to confirm these potential uses. PMID:27135626

  3. Hydrothermal activity recorded in post Noachian-aged impact craters on Mars

    NASA Astrophysics Data System (ADS)

    Turner, Stuart M. R.; Bridges, John C.; Grebby, Stephen; Ehlmann, Bethany L.

    2016-04-01

    Hydrothermal systems have previously been reported in ancient Noachian and Hesperian-aged craters on Mars using CRISM but not in Amazonian-aged impact craters. However, the nakhlite meteorites do provide evidence of Amazonian hydrothermal activity. This study uses CRISM data of 144 impact craters of ≥7 km diameter and 14 smaller craters (3-7 km diameter) within terrain mapped as Amazonian to search for minerals that may have formed as a result of impact-induced hydrothermal alteration or show excavation of ancient altered crust. No evidence indicating the presence of hydrated minerals was found in the 3-7 km impact craters. Hydrated minerals were identified in three complex impact craters, located at 52.42°N, 39.86°E in the Ismenius Lacus quadrangle, at 8.93°N, 141.28°E in Elysium, and within the previously studied Stokes crater. These three craters have diameters 20 km, 62 km, and 51 km. The locations of the hydrated mineral outcrops and their associated morphology indicate that two of these three impact craters—the unnamed Ismenius Lacus Crater and Stokes Crater—possibly hosted impact-induced hydrothermal systems, as they contain alteration assemblages on their central uplifts that are not apparent in their ejecta. Chlorite and Fe serpentine are identified within alluvial fans in the central uplift and rim of the Ismenius Lacus crater, whereas Stokes crater contains a host of Fe/Mg/Al phyllosilicates. However, excavation origin cannot be precluded. Our work suggests that impact-induced hydrothermalism was rare in the Amazonian and/or that impact-induced hydrothermal alteration was not sufficiently pervasive or spatially widespread for detection by CRISM.

  4. Plume indications from hydrothermal activity on Kawio Barat Submarine Volcano, Sangihe Talaud Sea, North Sulawesi, Indonesia

    NASA Astrophysics Data System (ADS)

    Makarim, S.; Baker, E. T.; Walker, S. L.; Wirasantosa, S.; Permana, H.; Sulistiyo, B.; Shank, T. M.; Holden, J. F.; Butterfield, D.; Ramdhan, M.; Adi, R.; Marzuki, M. I.

    2010-12-01

    Kawio Barat submarine volcano has formed in response to the active tectonic conditions in Sangihe Talaud, an area that lies in the subduction zone between the Molucca Sea Plate and Celebes Sea Plate. Submarine volcanic activity in the western Sangihe volcanic arc is controlled by the west-dipping Molucca Sea Plate as it subducts beneath the Sangihe Arc. A secondary faulting system on Kawio Barat is in a northwest - southeast direction, and creates a network of deep cracks that facilitate hydrothermal discharge in this area. Hydrothermal activity on Kawio Barat was first discovered by joint Indonesia/Australian cruises in 2003. In 2010, as part of the joint US/Indonesian INDEX-SATAL expedition, we conducted CTD casts that confirmed continuing activity. Hydrothermal plumes were detected by light -scattering (LSS) and oxidation-reduction potential (ORP) sensors on the CTD package. LSS anomalies were found between 1600-1900 m, with delta NTU levels of 0.020-0.040. ORP anomalies coincident with the LSS anomalies indicate strong concentrations of reduced species such as H2S and Fe, confirming the hydrothermal origin of the plumes. Images of hydrothermal vents on Kawio Barat Submarine volcano, recorded by high- definition underwater cameras on the ROV “Little Hercules” operated from the NOAA ship Okeanos Explorer, confirmed the presence and sources of the detected vent plumes in the northern and southwest part of the summit in 1800-1900 m depth. In southwest part of this summit chimney, drips of molten sulfur were observed in the proximity of microbal staining.

  5. Submarine Hydrothermal Activity on the Aeolian Arc: New Evidence from Helium Isotopes

    NASA Astrophysics Data System (ADS)

    Lupton, J.; de Ronde, C.; Baker, E.; Sprovieri, M.; Bruno, P.; Italiano, F.; Walker, S.; Faure, K.; Leybourne, M.; Britten, K.; Greene, R.

    2008-12-01

    In November 2007 we conducted a water-column and seafloor mapping study of the submarine volcanoes of the Aeolian Arc in the southern Tyrrhenian Sea aboard the R/V Urania. A total of 26 CTD casts were completed, 13 vertical casts and 13 tows. In addition to in situ measurements of temperature, conductivity, pressure and suspended particles, we also collected discrete samples for helium isotopes, methane, and trace metals. The helium isotope ratio, which is known to be an unambiguous indicator of hydrothermal input, showed a clear excess above background at 5 out of the 10 submarine volcanoes surveyed. We found the strongest helium anomaly over Marsili seamount, where the 3He/4He ratio reached maximum values of δ3He = 23% at 610 m depth compared with background values of ~7%. We also found smaller but distinct δ3He anomalies over Enerato, Eolo, Palinuro, and Secca del Capo. We interpret these results as indicating the presence of hydrothermal activity on these 5 seamounts. Hydrothermal venting has been documented at subsea vents offshore of the islands of Panarea, Stromboli, and Vulcano (Dando et al., 1999; Di Roberto et al., 2008), and hydrothermal deposits have been sampled on many of the submarine volcanoes of the Aeolian Arc (Dekov and Savelli, 2004). However, as far as we know this is the first evidence of present day hydrothermal activity on Marsili, Enerato, and Eolo. Samples collected over Filicudi, Glabro, Lamentini, Sisifo, and Alcioni had δ3He very close to the regional background values, suggesting either absence of or very weak hydrothermal activity on these seamounts. Helium isotope measurements from the background hydrocasts positioned between the volcanoes revealed the presence of an excess in 3He throughout the SE Tyrrhenian Sea. These background profiles reach a consistent maximum of about δ3He = 11% at 2300 m depth. Historical helium profiles collected in the central and northern Tyrrhenian Sea in 1987 and 1997 do not show this deep 3He

  6. Vibrio diabolicus challenge in Bathymodiolus azoricus populations from Menez Gwen and Lucky Strike hydrothermal vent sites.

    PubMed

    Martins, Eva; Santos, Ricardo Serrão; Bettencourt, Raul

    2015-12-01

    Menez Gwen (MG) and Lucky Strike (LS) deep-sea hydrothermal vents are located at 850 m and 1730 m depths respectively and support chemosynthesis-based ecosystems partially differing in heavy metal concentration, temperature range, and faunistic composition. The successfully adapted deep-sea vent mussel Bathymodiolus azoricus is found at both vent locations. In such inhospitable environments survival strategies rely on the establishment of bacteria-vent animal symbiosis In spite of the toxic nature of deep-sea vents, the problem of microbial threat and the need for immunity exist in B. azoricus. This study aims at investigating the immune system of B. azoricus from MG and LS populations by comparing immune gene expressions profiles using the deep-sea vent-related Vibrio diabolicus. Expression of nineteen immune genes was analyzed from gill, digestive gland and mantle tissues upon 3 h, 12 h and 24 h V. diabolicus challenges. Based on quantitative-Polymerase Chain Reaction (qPCR) significant gene expression differences were found among MG and LS populations and challenge times MG mussels revealed that gill and digestive gland gene expression levels were remarkably higher than those from LS mussels. Expression of Carcinolectin, Serpin-2, SRCR, IRGs, RTK, TLR2, NF-κB, HSP70 and Ferritin genes was greater in MG than LS mussels. In contrast, mantle tissue from LS mussels revealed the highest peak of expression at 24 h for most genes analyzed. The activation of immune signaling pathways demonstrated that gene expression profiles are distinct between the two mussel populations. These differences may possibly ensue from intrinsic immune transcriptional activities upon which host responses are modulated in presence of V. diabolicus. mRNA transcript variations were assessed during 24 h acclimatization taking into account the partial depuration to which mussels were subjected to. Additionally, gene expression differences may reflect still accountable effects from the presence

  7. Vibrio diabolicus challenge in Bathymodiolus azoricus populations from Menez Gwen and Lucky Strike hydrothermal vent sites.

    PubMed

    Martins, Eva; Santos, Ricardo Serrão; Bettencourt, Raul

    2015-12-01

    Menez Gwen (MG) and Lucky Strike (LS) deep-sea hydrothermal vents are located at 850 m and 1730 m depths respectively and support chemosynthesis-based ecosystems partially differing in heavy metal concentration, temperature range, and faunistic composition. The successfully adapted deep-sea vent mussel Bathymodiolus azoricus is found at both vent locations. In such inhospitable environments survival strategies rely on the establishment of bacteria-vent animal symbiosis In spite of the toxic nature of deep-sea vents, the problem of microbial threat and the need for immunity exist in B. azoricus. This study aims at investigating the immune system of B. azoricus from MG and LS populations by comparing immune gene expressions profiles using the deep-sea vent-related Vibrio diabolicus. Expression of nineteen immune genes was analyzed from gill, digestive gland and mantle tissues upon 3 h, 12 h and 24 h V. diabolicus challenges. Based on quantitative-Polymerase Chain Reaction (qPCR) significant gene expression differences were found among MG and LS populations and challenge times MG mussels revealed that gill and digestive gland gene expression levels were remarkably higher than those from LS mussels. Expression of Carcinolectin, Serpin-2, SRCR, IRGs, RTK, TLR2, NF-κB, HSP70 and Ferritin genes was greater in MG than LS mussels. In contrast, mantle tissue from LS mussels revealed the highest peak of expression at 24 h for most genes analyzed. The activation of immune signaling pathways demonstrated that gene expression profiles are distinct between the two mussel populations. These differences may possibly ensue from intrinsic immune transcriptional activities upon which host responses are modulated in presence of V. diabolicus. mRNA transcript variations were assessed during 24 h acclimatization taking into account the partial depuration to which mussels were subjected to. Additionally, gene expression differences may reflect still accountable effects from the presence

  8. Site-related differences in gene expression and bacterial densities in the mussel Bathymodiolus azoricus from the Menez Gwen and Lucky Strike deep-sea hydrothermal vent sites.

    PubMed

    Bettencourt, Raul; Rodrigues, Mónica; Barros, Inês; Cerqueira, Teresa; Freitas, Cátia; Costa, Valentina; Pinheiro, Miguel; Egas, Conceição; Santos, Ricardo Serrão

    2014-08-01

    The deep-sea hydrothermal vent mussel Bathymodiolus azoricus is a symbiont bearing bivalve that is found in great abundance at the Menez Gwen and Lucky Strike hydrothermal vent sites and in close vicinity of the Azores region near the Mid-Atlantic Ridge (MAR). The physiological relationships that vent mussels have developed with their physical and chemical environments are likely to influence global gene expression profiles providing thus the means to investigate distinct biological markers predicting the origin of Bathymodiolus sp. irrespectively of their geographical localization. Differences found at gene expression levels, and between fluorescence in situ hybridization (FISH) and 16S rRNA amplicon sequencing results provided experimental evidence for the distinction of both Menez Gwen and Lucky Strike vent mussel individuals based on bacterial and vent mussel gene expression signatures and on the constitutive distribution and relative abundance of endosymbiotic bacteria within gill tissues. Our results confirmed the presence of methanotroph endosymbionts in Menez Gwen vent mussels whereas Lucky Strike specimens seem to harbor a different bacterial morphotype when a methane monooxygenase gene specific probe was used. No qualitative differences could be visualized between Menez Gwen and Lucky Strike individuals when tested with a sulfur-oxidizing-related probe. Quantitative PCR (qPCR) studies revealed different gene expression profiles in both Menez Gwen and Lucky Strike mussel gill tissues for the immune genes selected. Genes encoding transcription factors presented noticeably low levels of fold expression whether in Menez Gwen or Lucky Strike animals whereas the genes encoding effector molecules appeared to have higher levels expression in gill tissues from Menez Gwen animals. The peptidoglycan recognition molecule encoding gene, PGRP, presented the highest level of transcriptional activity among the genes analyzed in Menez Gwen mussel gill tissues, seconded by

  9. Site-related differences in gene expression and bacterial densities in the mussel Bathymodiolus azoricus from the Menez Gwen and Lucky Strike deep-sea hydrothermal vent sites.

    PubMed

    Bettencourt, Raul; Rodrigues, Mónica; Barros, Inês; Cerqueira, Teresa; Freitas, Cátia; Costa, Valentina; Pinheiro, Miguel; Egas, Conceição; Santos, Ricardo Serrão

    2014-08-01

    The deep-sea hydrothermal vent mussel Bathymodiolus azoricus is a symbiont bearing bivalve that is found in great abundance at the Menez Gwen and Lucky Strike hydrothermal vent sites and in close vicinity of the Azores region near the Mid-Atlantic Ridge (MAR). The physiological relationships that vent mussels have developed with their physical and chemical environments are likely to influence global gene expression profiles providing thus the means to investigate distinct biological markers predicting the origin of Bathymodiolus sp. irrespectively of their geographical localization. Differences found at gene expression levels, and between fluorescence in situ hybridization (FISH) and 16S rRNA amplicon sequencing results provided experimental evidence for the distinction of both Menez Gwen and Lucky Strike vent mussel individuals based on bacterial and vent mussel gene expression signatures and on the constitutive distribution and relative abundance of endosymbiotic bacteria within gill tissues. Our results confirmed the presence of methanotroph endosymbionts in Menez Gwen vent mussels whereas Lucky Strike specimens seem to harbor a different bacterial morphotype when a methane monooxygenase gene specific probe was used. No qualitative differences could be visualized between Menez Gwen and Lucky Strike individuals when tested with a sulfur-oxidizing-related probe. Quantitative PCR (qPCR) studies revealed different gene expression profiles in both Menez Gwen and Lucky Strike mussel gill tissues for the immune genes selected. Genes encoding transcription factors presented noticeably low levels of fold expression whether in Menez Gwen or Lucky Strike animals whereas the genes encoding effector molecules appeared to have higher levels expression in gill tissues from Menez Gwen animals. The peptidoglycan recognition molecule encoding gene, PGRP, presented the highest level of transcriptional activity among the genes analyzed in Menez Gwen mussel gill tissues, seconded by

  10. Lake-floor sediment texture and composition of a hydrothermally-active, volcanic lake, Lake Rotomahana

    NASA Astrophysics Data System (ADS)

    Pittari, A.; Muir, S. L.; Hendy, C. H.

    2016-03-01

    Young volcanic lakes undergo a transition from rapid, post-eruptive accumulation of volcaniclastic sediment to slower pelagic settling under stable lake conditions, and may also be influenced by sublacustrine hydrothermal systems. Lake Rotomahana is a young (129 year-old), hydrothermally-active, volcanic lake formed after the 1886 Tarawera eruption, and provides a unique insight into the early evolution of volcanic lake systems. Lake-bottom sediment cores, 20-46 cm in length, were taken along a transect across the lake and characterised with respect to stratigraphy, facies characteristics (i.e., grain size, componentry) and pore water silica concentrations. The sediments generally comprise two widespread facies: (i) a lower facies of light grey to grey, very fine lacustrine silt derived from the unconsolidated pyroclastic deposits that mantled the catchment area immediately after the eruption, which were rapidly reworked and redeposited into the lake basin; and (ii) an upper facies of dark, fine-sandy diatomaceous silt, that settled from the pelagic zone of the physically stable lake. Adjacent to sublacustrine hydrothermal vents, the upper dark facies is absent, and the upper part of the light grey to grey silt is replaced by a third localised facies comprised of hydrothermally altered pale yellow to yellowish brown, laminated silt with surface iron-rich encrustations. Microspheres, which are thought to be composed of amorphous silica, although some may be halloysite, have precipitated from pore water onto sediment grains, and are associated with a decrease in pore water silicon concentration. Lake Rotomahana is an example of a recently-stabilised volcanic lake, with respect to sedimentation, that shows signs of early sediment silicification in the presence of hydrothermal activity.

  11. The study of active submarine volcanoes and hydrothermal vents in the Southernmost Part of Okinawa Trough

    NASA Astrophysics Data System (ADS)

    Lee, Y.; Tsai, C.; Lee, C.

    2004-12-01

    The study area is located in the Southernmost Part of Okinawa Trough (SPOT), which is a back-arc basin formed by extension of Eurasian plate. Previous research indicated two extensional stages in SPOT area. Many normal-fault structures were come into existence during both extensional processes. The SPOT is presently in an activity tectonic episode. Therefore, the area becomes a frequent earthquake and abundant magmatism. The purpose of this study is to discuss which relationship between tectonics, submarine volcanoes and hydrothermal vents in SPOT area. The investigations are continued from 1998 to 2004, we have found at least twelve active hydrothermal vents in study area. Compare the locations hydrothermal vents with fault systems, we find both of them have highly correlated. We can distinguish them into two shapes, pyramidal shape and non-pyramidal shape. According to plumes height, we are able to divide these vents into two groups near east longitude 122.5° . East of this longitude, the hydrothermal plumes are more powerful and west of it are the weaker. This is closely related to the present extensional axis (N80° E) of the southern part of the Okinawa Trough. This can be explained the reason of why the more powerful vents coming out of the east group. The east group is associated with the present back-arc spreading system. West of 122.5° , the spreading system are in a primary stage. The andesitic volcanic island, the Turtle Island, is a result of N60° E extensional tectonism with a lot of faults. Besides the pyramidal shape, this can be proved indirectly. The vents located in the west side were occurred from previous extensional faults and are weaker than the eastern. Therefore, we suggest that if last the extension keeps going on, the hydrothermal vents located at the west side of the longitude 122.5° will be intensified.

  12. Hydrodynamic modeling of magmatic-hydrothermal activity at submarine arc volcanoes, with implications for ore formation

    NASA Astrophysics Data System (ADS)

    Gruen, Gillian; Weis, Philipp; Driesner, Thomas; Heinrich, Christoph A.; de Ronde, Cornel E. J.

    2014-10-01

    Subduction-related magmas have higher volatile contents than mid-ocean ridge basalts, which affects the dynamics of associated submarine hydrothermal systems. Interaction of saline magmatic fluids with convecting seawater may enhance ore metal deposition near the seafloor, making active submarine arcs a preferred modern analogue for understanding ancient massive sulfide deposits. We have constructed a quantitative hydrological model for sub-seafloor fluid flow based on observations at Brothers volcano, southern Kermadec arc, New Zealand. Numerical simulations of multi-phase hydrosaline fluid flow were performed on a two-dimensional cross-section cutting through the NW Caldera and the Upper Cone sites, two regions of active venting at the Brothers volcanic edifice, with the former hosting sulfide mineralization. Our aim is to explore the flow paths of saline magmatic fluids released from a crystallizing magma body at depth and their interaction with seawater circulating through the crust. The model includes a 3×2 km sized magma chamber emplaced at ∼2.5 km beneath the seafloor connected to the permeable cone via a ∼200 m wide feeder dike. During the simulation, a magmatic fluid was temporarily injected from the top of the cooling magma chamber into the overlying convection system, assuming hydrostatic conditions and a static permeability distribution. The simulations predict a succession of hydrologic regimes in the subsurface of Brothers volcano, which can explain some of the present-day hydrothermal observations. We find that sub-seafloor phase separation, inferred from observed vent fluid salinities, and the temperatures of venting at Brothers volcano can only be achieved by input of a saline magmatic fluid at depth, consistent with chemical and isotopic data. In general, our simulations show that the transport of heat, water, and salt from magmatic and seawater sources is partly decoupled. Expulsion of magmatic heat and volatiles occurs within the first few

  13. Anomalous quartz from the Roter Kamm impact crater, Namibia - Evidence for post-impact hydrothermal activity?

    NASA Technical Reports Server (NTRS)

    Koeberl, Christian; Fredriksson, Kurt; Goetzinger, Michael; Reimold, Wolf Uwe

    1989-01-01

    Quartz pebbles from the Roter Kamm impact crater (the Namib Desert, SWA/Namibia) were examined for evidence of impact-induced hydrothermal activity, using results from microprobe analyses, neutron activation analyses, transmission IR spectroscopy, and X-ray diffractometry. It was found that the pebbles consisted of pure quartz, which contains three different types of fluid inclusions. These were identified as primary inclusions (5-10 microns) that record the formation conditions of the quartz, very small (less than 1 micron) secondary inclusions associated with the grain boundaries, and late inclusions of irregular size. It is concluded that the quartz and the primary inclusions may provide evidence for a postimpact phase of extensive hydrothermal activity, generated by the residual heat from the kinetic energy of the impact.

  14. Living with the Heat. Submarine Ring of Fire--Grades 5-6. Hydrothermal Vent Ecology.

    ERIC Educational Resources Information Center

    National Oceanic and Atmospheric Administration (DOC), Rockville, MD.

    This activity is designed to teach about hydrothermal vent ecology. Students are expected to describe how hydrothermal vents are formed and characterize the physical conditions at these sites, explain chemosynthesis and contrast this process with photosynthesis, identify autotrophic bacteria as the basis for food webs in hydrothermal vent…

  15. Microwave-assisted hydrothermal synthesis of marigold-like ZnIn2S4 microspheres and their visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Chen, Zhixin; Li, Danzhen; Xiao, Guangcan; He, Yunhui; Xu, Yi-Jun

    2012-02-01

    Marigold-like ZnIn2S4 microspheres were synthesized by a microwave-assisted hydrothermal method with the temperature ranging from 80 to 195 °C. X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen sorption analysis, UV-visible spectroscopy, scanning electron microscopy and transmission electron microscopy were used to characterize the products. It was found that the crystallographic structure and optical property of the products synthesized at different temperatures were almost the same. The degradation of methyl orange (MO) under the visible light irradiation has been used as a probe reaction to investigate the photocatalytic activity of as-prepared ZnIn2S4, which shows that the ZnIn2S4 sample synthesized at 195 °C shows the best photocatalytic activity for MO degradation. In addition, the photocatalytic activities of all the samples prepared by the microwave-assisted hydrothermal method are better than those prepared by a normal hydrothermal method, which could be attributed to the formation of more defect sites during the microwave-assisted hydrothermal treatment.

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

    SciTech Connect

    Murphy, William M.

    2007-07-01

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

  17. Seafloor hydrothermal activity and spreading rates: the Eocene carbon dioxide greenhouse revisted.

    PubMed

    Kasting, J F; Richardson, S M

    1985-01-01

    A suggestion has been made that enhanced rates of hydrothermal activity during the Eocene could have caused a global warming by adding calcium to the ocean and pumping CO2 into the atmosphere (Owen and Rea, 1984). This phenomenon was purported to be consistent with the predictions of the CO2 geochemical cycle model of Berner, Lasaga and Garrels (1983) (henceforth BLAG). In fact, however, the BLAG model predicts only a weak connection between hydrothermal activity and atmospheric CO2 levels. By contrast, it predicts a strong correlation between seafloor spreading rates and pCO2, since the release rate of CO2 from carbonate metamorphism is assumed to be proportional to the mean spreading rate. The Ecocene warming can be conveniently explained if the BLAG model is extended by assuming that the rate of carbonate metamorphism is also proportional to the total length of the midocean ridges from which the spreading originates.

  18. Seafloor hydrothermal activity and spreading rates: the Eocene carbon dioxide greenhouse revisted

    NASA Technical Reports Server (NTRS)

    Kasting, J. F.; Richardson, S. M.

    1985-01-01

    A suggestion has been made that enhanced rates of hydrothermal activity during the Eocene could have caused a global warming by adding calcium to the ocean and pumping CO2 into the atmosphere (Owen and Rea, 1984). This phenomenon was purported to be consistent with the predictions of the CO2 geochemical cycle model of Berner, Lasaga and Garrels (1983) (henceforth BLAG). In fact, however, the BLAG model predicts only a weak connection between hydrothermal activity and atmospheric CO2 levels. By contrast, it predicts a strong correlation between seafloor spreading rates and pCO2, since the release rate of CO2 from carbonate metamorphism is assumed to be proportional to the mean spreading rate. The Ecocene warming can be conveniently explained if the BLAG model is extended by assuming that the rate of carbonate metamorphism is also proportional to the total length of the midocean ridges from which the spreading originates.

  19. Seafloor hydrothermal activity and spreading rates - The Eocene carbon dioxide greenhouse revisited

    NASA Technical Reports Server (NTRS)

    Kasting, J. F.; Richardson, S. M.

    1985-01-01

    A suggestion has been made that enhanced rates of hydrothermal activity during the Eocene could have caused a global warming by adding calcium to the ocean and pumping CO2 into the atmosphere (Owen and Rea, 1984). This phenomenon was purported to be consistent with the predictions of the CO2 geochemical cycle model of Berner, Lasaga and Garrels (1983) (henceforth BLAG). In fact, however, the BLAG model predicts only a weak connection between hydrothermal activity and atmospheric CO2 levels. By contrast, it predicts a strong correlation between seafloor spreading rates and pCO2, since the release rate of CO2 from carbonate metamorphism is assumed to be proportional to the mean spreading rate. The Eocene warming can be conveniently explained if the BLAG model is extended by assuming that the rate of carbonate metamorphism is also proportional to the total length of the midocean ridges from which the spreading originates.

  20. Seafloor hydrothermal activity and spreading rates: the Eocene carbon dioxide greenhouse revisted.

    PubMed

    Kasting, J F; Richardson, S M

    1985-01-01

    A suggestion has been made that enhanced rates of hydrothermal activity during the Eocene could have caused a global warming by adding calcium to the ocean and pumping CO2 into the atmosphere (Owen and Rea, 1984). This phenomenon was purported to be consistent with the predictions of the CO2 geochemical cycle model of Berner, Lasaga and Garrels (1983) (henceforth BLAG). In fact, however, the BLAG model predicts only a weak connection between hydrothermal activity and atmospheric CO2 levels. By contrast, it predicts a strong correlation between seafloor spreading rates and pCO2, since the release rate of CO2 from carbonate metamorphism is assumed to be proportional to the mean spreading rate. The Ecocene warming can be conveniently explained if the BLAG model is extended by assuming that the rate of carbonate metamorphism is also proportional to the total length of the midocean ridges from which the spreading originates. PMID:11539654

  1. Impact Crater Hydrothermal Niches for Life on Mars: Question of Scale

    NASA Technical Reports Server (NTRS)

    Pope, K. O.; Ames, D. E.; Kieffer, S. W.; Ocampo, A. C.

    2000-01-01

    A major focus in the search for fossil life on Mars is on ancient hydrothermal deposits. Nevertheless, remote sensing efforts have not found mineral assemblages characteristic of hydrothermal activity. Future remote sensing work, including missions with higher spatial resolution, may detect localized hydrothermal deposits, but it is possible that dust mantles will prohibit detection from orbit and lander missions will be required. In anticipation of such missions, it is critical to develop a strategy for selecting potential hydrothermal sites on Mars. Such a strategy is being developed for volcanogenic hydrothermal systems, and a similar strategy is needed for impact hydrothermal systems.

  2. Salt site performance assessment activities

    SciTech Connect

    Kircher, J.F.; Gupta, S.K.

    1983-01-01

    During this year the first selection of the tools (codes) for performance assessments of potential salt sites have been tentatively selected and documented; the emphasis has shifted from code development to applications. During this period prior to detailed characterization of a salt site, the focus is on bounding calculations, sensitivity and with the data available. The development and application of improved methods for sensitivity and uncertainty analysis is a focus for the coming years activities and the subject of a following paper in these proceedings. Although the assessments to date are preliminary and based on admittedly scant data, the results indicate that suitable salt sites can be identified and repository subsystems designed which will meet the established criteria for protecting the health and safety of the public. 36 references, 5 figures, 2 tables.

  3. Active Volcanic and Hydrothermal Processes at NW Rota-1 Submarine Volcano: Mariana Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Embley, R. W.; Baker, E. T.; Butterfield, D. A.; Chadwick, W. W.; de Ronde, C.; Dower, J.; Evans, L.; Hein, J.; Juniper, K.; Lebon, G.; Lupton, J. E.; Merle, S.; Metaxas, A.; Nakamura, K.; Resing, J. E.; Roe, K.; Stern, R.; Tunnicliffe, V.

    2004-12-01

    Dives with the remotely operated vehicle ROPOS in March/April 2004 documented a volcanic eruption at NW Rota-1, a submarine volcano of basaltic composition located at 14\\deg 36.0'N, 144\\deg 46.5'E lying 65 km northwest of Rota Island in the Commonwealth of the Northern Mariana Islands. The site was chosen as a dive target because of the of the high concentrations of H2S and alunite in the hydrothermal plume overlying its summit in February 2003. The summit of the volcano is composed of curvilinear volcanic ridge oriented NW-SE bounded by NE-SW trending normal faults. Lavas collected on the upper part of the edifice are primitive to moderately fractionated basalts (Mg# = 51-66). The eruptive activity is occurring within a small crater (Brimstone Pit) located on the upper south flank of the volcano at 550 m, about 30 m below the summit. The crater is approximately 15 m wide and at least 20 meters deep. The ROPOS's cameras observed billowing clouds of sulfur-rich fluid rising out of the crater, punctuated by frequent bursts of several minutes duration that entrained glassy volcanic ejecta up to at least 2 cm in diameter. ROPOS recorded a temperature of 38\\degC within the plume. The volcanic activity had substantial temporal variability on the scale of minutes. ROPOS was sometimes completely enveloped by the plume while on the rim of the crater, and its surfaces were coated with large sulfur droplets. Black glassy fragments were entrained in the plume up to least 50 m above the crater and deposits of this material were on ledges and tops of outcrops up to several hundred meters from Brimstone Pit. The pit crater fluids have an extremely high content of particulate sulfur and extremely acidic, with pH around 2.0. This strongly implicates magmatic degassing of SO2 and disproportionation into elemental S and sulfuric acid. Diffuse venting of clear fluids was also present on the summit of the volcano, with temperatures exceeding 100\\degC in volcaniclastic sands

  4. Transfer and partitioning of energy and mass through seafloor hydrothermal systems: comparative studies at the Ridge2000 Integrated Study Sites (ISS) (Invited)

    NASA Astrophysics Data System (ADS)

    Tivey, M. K.

    2010-12-01

    Seafloor hydrothermal systems are major players in the transfer of mass and energy from the mantle and crust to the ocean and biosphere. Over the past thirty years, much has been learned about this transfer to the ocean, but considerably less is known about the transfer to the biosphere. Study of hydrothermal systems in a diverse range of geologic settings has shown relationships between spreading rate and hydrothermal heat flux, substrate composition (including rock geochemistry, presence/absence of sediment) and hydrothermal fluid composition, and magmatic/tectonic events and temporal variability of fluid composition (e.g., German and Von Damm, Treatise On Geochemistry, 2004; Baker et al. AGU Monograph Series 91, 1995). Studies in arc and back-arc settings are documenting the effects of magmatic acid volatiles on fluid-rock reaction and fluid and vent deposit compositions (e.g., Ishibashi and Urabe, Backarc Basins: Tectonics and Magmatism, 1995). These comparative studies in a wide range of geologic settings, including at the three Ridge2000 ISS, have provided a fairly good understanding of the flux of heat and many elements to the ocean associated with high temperature seafloor hydrothermal systems. Considerably less is known, however, about the partitioning of heat and mass (particularly metals and sulfur) in hydrothermal systems. The deposits that form at vent sites are intimately linked within paths of energy and mass transport from the mantle and crust to the oceans. Transport differs greatly through different types of deposits (e.g., black smokers, white smokers/diffusers, flanges). Estimates of heat flux from measured temperatures of flow (unless integrated over and around an entire vent field) require an understanding of the partitioning of flow between focused black smokers and more diffuse flow from diffusers, flanges, and surfaces of deposits, and from the igneous substrate. Estimates of mass flux into the ocean require an understanding of the

  5. Cu-SSZ-39, an active and hydrothermally stable catalyst for the selective catalytic reduction of NOx.

    PubMed

    Moliner, Manuel; Franch, Cristina; Palomares, Eduardo; Grill, Marie; Corma, Avelino

    2012-08-25

    A Cu-exchanged SSZ-39 zeolite has been synthesized and tested for the selective catalytic reduction (SCR) of NOx. This material shows an excellent catalytic activity, and most importantly, an extraordinary hydrothermal stability.

  6. A reduced crustal magnetization zone near the first observed active hydrothermal vent field on the Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Zhu, Jian; Lin, Jian; Chen, Yongshun J.; Tao, Chunhui; German, Christopher R.; Yoerger, Dana R.; Tivey, Maurice A.

    2010-09-01

    Inversion of near-bottom magnetic data reveals a well-defined low crustal magnetization zone (LMZ) near a local topographic high (37°47‧S, 49°39‧E) on the ultraslow-spreading Southwest Indian Ridge (SWIR). The magnetic data were collected by the autonomous underwater vehicle ABE on board R/V DaYangYiHao in February-March 2007. The first active hydrothermal vent field observed on the SWIR is located in Area A within and adjacent to the LMZ at the local topographic high, implying that this LMZ may be the result of hydrothermal alteration of magnetic minerals. The maximum reduction in crustal magnetization is 3 A/M. The spatial extent of the LMZ is estimated to be at least 6.7 × 104 m2, which is larger than that of the LMZs at the TAG vent field on the Mid-Atlantic Ridge (MAR), as well as the Relict Field, Bastille, Dante-Grotto, and New Field vent-sites on the Juan de Fuca Ridge (JdF). The calculated magnetic moment, i.e., the product of the spatial extent and amplitude of crustal magnetization reduction is at least -3 × 107 Am2 for the LMZ on the SWIR, while that for the TAG field on the MAR is -8 × 107 Am2 and that for the four individual vent fields on the JdF range from -5 × 107 to -3 × 107 Am2. Together these results indicate that crustal demagnetization is a common feature of basalt-hosted hydrothermal vent fields at mid-ocean ridges of all spreading rates. Furthermore, the crustal demagnetization of the Area A on the ultraslow-spreading SWIR is comparable in strength to that of the TAG area on the slow-spreading MAR.

  7. Time Series Studies of Faunal Colonization and Temperature Variations at Diffuse-Flow Hydrothermal Vent Sites Near 9° 50'N, EPR

    NASA Astrophysics Data System (ADS)

    Shank, T. M.; Scheirer, D.; Fornari, D. J.

    2001-12-01

    The April 1991 discovery of newly-formed hydrothermal vents in areas of intense volcanic activity along the East Pacific Rise (EPR) between 9\\deg 45' and 9\\deg 52'N provided a unique opportunity to follow temporal changes in biological community structure and vent fluid temperature and chemistry since the birth of numerous deep-sea hydrothermal vents. Discrete high resolution biological imaging and fluid chemistry samples have been collected in conjunction with autonomous temperature probe arrays that have monitored the fluid temperature at 10-15 minute intervals since 1993, within four diffuse-flow regions of the BioTransect at 9\\deg 50'N on the EPR. During ~1 year deployments between 1993 and 2000, active vent invertebrate colonization by greater than 500 individuals (representing 8 species) occurred on more than 60 recovered temperature probes comprising 12 arrays. On each temperature probe, the position and length of individual organisms were mapped to correlate the position of settlement and growth rates with the environmental temperatures experienced by these colonists. Regressions of colonization parameters with temperature measures (such as average, minimum, and maximum T) from multiple communities, along with size-frequency histograms and growth rates, indicate that the abundance of the vestimentiferan Tevnia jerichonana was greater than Riftia pachyptila tube worms and bathymodiolid mussels on temperature probes bathed in significantly higher average and maximum temperatures. Results strongly suggest that Tevnia has a greater physiological tolerance to higher temperatures and elevated geochemical concentrations (e.g., sulfide species) than Riftia and mussels. Significant differential colonization onto probes within an array demonstrates thermal and chemical habitat preferences by vestimentiferan tubeworms and mussels. Thus, patterns of active faunal colonization in hydrothermal areas vary with differing temperature regimes and associated environmental

  8. Acoustic mapping of diffuse flow at a seafloor hydrothermal site: Monolith Vent, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Rona, P. A.; Jackson, D. R.; Wen, T.; Jones, C.; Mitsuzawa, K.; Bemis, K. G.; Dworski, J. G.

    Diffuse flow of hydrothermal solutions commonly occurs in patchy areas up to tens of meters in diameter in seafloor hydrothermal fields. It is recognized as a quantitatively significant component of thermal and chemical fluxes, yet is elusive to map. We report a new acoustic method to detect and map areas of diffuse flow using phase-coherent correlation techniques. The sonar system was modified to record phase information and mounted on DSV SEA CLIFF. The submersible occupied a stationary position on the seafloor and the transducer scanned the seafloor surrounding Monolith Vent, a sulfide edifice venting black smokers, at a nominal range of 17 m at a depth of 2249 m on the Juan de Fuca Ridge. Patchy areas of uncorrelated returns clearly stood out from a background of returns that exhibited ping-to-ping correlation. The areas of uncorrelated returns coincided with areas of diffuse flow as mapped by a video survey with the Navy's Advanced Tethered Vehicle (ATV). Correlated returns were backscattered from invariant seafloor. Uncorrelated returns were distorted by index of refraction inhomogeneities as they passed through diffuse flow between the seafloor and the transducer. The acoustic method presented can synoptically map areas of diffuse flow. When combined with standard in situ measurement and sampling methods the acoustic mapping will facilitate accurate determination of diffuse thermal and chemical fluxes in seafloor hydrothermal fields.

  9. Meteorite organics in planetary environments: hydrothermal release, surface activity, and microbial utilization.

    PubMed

    Mautner, M N; Leonard, R L; Deamer, D W

    1995-01-01

    Up to 50% of the organics in the Murchison meteorite, possibly including some of the polymer, is released in high temperature and pressure aqueous environments, to 350 degrees C and 250 bar, that simulate submarine volcanic, hydrothermal or impact-induced conditions. Meteorite organics of prebiotic significance, such as nonanoic acid, glycine, and pyrene survive the hydrothermal conditions. The released material is surface active with surface pressures up to 19.8 x 10(-3) N m-1, and exhibits an extended surface tension isotherm which suggests a mixture of amphiphilic components. One component, nonanoic acid, is shown to form vesicles. The materials extracted under mild conditions, at 120 degrees C, are nutrients for the humic acid bacterium Pseudomonas maltophilia and efficient nutrients for the oligotroph Flavobacterium oryzihabitans, demonstrating the capability of microorganisms to metabolize extraterrestrial organics.

  10. Meteorite organics in planetary environments: hydrothermal release, surface activity, and microbial utilization.

    PubMed

    Mautner, M N; Leonard, R L; Deamer, D W

    1995-01-01

    Up to 50% of the organics in the Murchison meteorite, possibly including some of the polymer, is released in high temperature and pressure aqueous environments, to 350 degrees C and 250 bar, that simulate submarine volcanic, hydrothermal or impact-induced conditions. Meteorite organics of prebiotic significance, such as nonanoic acid, glycine, and pyrene survive the hydrothermal conditions. The released material is surface active with surface pressures up to 19.8 x 10(-3) N m-1, and exhibits an extended surface tension isotherm which suggests a mixture of amphiphilic components. One component, nonanoic acid, is shown to form vesicles. The materials extracted under mild conditions, at 120 degrees C, are nutrients for the humic acid bacterium Pseudomonas maltophilia and efficient nutrients for the oligotroph Flavobacterium oryzihabitans, demonstrating the capability of microorganisms to metabolize extraterrestrial organics. PMID:11538427

  11. Meteorite organics in planetary environments: hydrothermal release, surface activity, and microbial utilization

    NASA Astrophysics Data System (ADS)

    Mautner, Michael N.; Leonard, Robert L.; Deamer, David W.

    1995-02-01

    Up to 50% of the organics in the Murchison meteorite, possibly including some of the polymer, is released in high temperature and pressure aqueous environments, to 350°C and 250 bar, that simulate submarine volcanic, hydrothermal or impact-induced conditions. Meteorite organics of prebiotic significance, such as nonanoic acid, glycine, and pyrene survive the hydrothermal conditions. The released material is surface active with surface pressures up to 19.8 × 10 -3 N m -1, and exhibits an extended surface tension isotherm which suggests a mixture of amphiphilic components. One component, nonanoic acid, is shown to form vesicles. The materials extracted under mild conditions, at 120°C, are nutrients for the humic acid bacterium Pseudomonas maltophilia and efficient nutrients for the oligotroph Flavobacterium oryzihabitans, demonstrating the capability of micro-organisms to metabolize extraterrestrial organics.

  12. Meteorite organics in planetary environments: hydrothermal release, surface activity, and microbial utilization

    NASA Technical Reports Server (NTRS)

    Mautner, M. N.; Leonard, R. L.; Deamer, D. W.

    1995-01-01

    Up to 50% of the organics in the Murchison meteorite, possibly including some of the polymer, is released in high temperature and pressure aqueous environments, to 350 degrees C and 250 bar, that simulate submarine volcanic, hydrothermal or impact-induced conditions. Meteorite organics of prebiotic significance, such as nonanoic acid, glycine, and pyrene survive the hydrothermal conditions. The released material is surface active with surface pressures up to 19.8 x 10(-3) N m-1, and exhibits an extended surface tension isotherm which suggests a mixture of amphiphilic components. One component, nonanoic acid, is shown to form vesicles. The materials extracted under mild conditions, at 120 degrees C, are nutrients for the humic acid bacterium Pseudomonas maltophilia and efficient nutrients for the oligotroph Flavobacterium oryzihabitans, demonstrating the capability of microorganisms to metabolize extraterrestrial organics.

  13. Electrical Resistivity Monitoring of an Active Hydrothermal Degassing Area at Solfatara, Phlegrean Fields.

    NASA Astrophysics Data System (ADS)

    Vandemeulebrouck, J.; Byrdina, S.; Grangeon, J.; Lebourg, T.; Bascou, P.; Mangiacapra, A.

    2015-12-01

    Campi Flegrei caldera (CFc) is an active volcanic complex covering a ~100 km² densely populated area in the western part of Naples (Italy) that is presently showing clear signs of unrest. Solfatara volcano, a tuff cone crater formed ~4000 yrs B.P. ago by phreato-magmatic eruptions represents the main degassing outflow of CFc. Magmatic gases which are exsolved from a ~8 km deep magmatic reservoir mix at 4 km depth with meteoric hydrothermal fluids then reach the surface in the Solfatara area. These hydrothermal and magmatic gases, mainly H2O and CO2, are released through both diffuse degassing structures and fumaroles. In the frame of the MedSuv (Mediterranean Supervolcanoes) FP7 european project , we are performing a time-lapse electrical resistivity monitoring of an active degassing area of Solfatara. Using a 500-m-long cable and 48 electrodes, an electrical resistivity tomography (ERT) is performed on a two-day basis since May 2013. The time-lapse inversion of the ERT gives an image of the temporal variations of resistivity up to 100 m depth that can be compared with the variations of ground deformation, CO2 flux, soil temperature and seismic ambient noise. Resistivity variations can originate from fluid composition, gas ratio and temperature. For example, the abrupt change of resistivity that was observed mid-2014 during a period of uplift and gas flux increase, could be associated with the rise of hydrothermal fluids.

  14. Phylogenetic diversity of sulfate-reducing prokaryotes in active deep-sea hydrothermal vent chimney structures.

    PubMed

    Nakagawa, Tatsunori; Nakagawa, Satoshi; Inagaki, Fumio; Takai, Ken; Horikoshi, Koki

    2004-03-19

    The phylogenetic diversity of sulfate-reducing prokaryotes occurring in active deep-sea hydrothermal vent chimney structures was characterized based on the deduced amino acid sequence analysis of the polymerase chain reaction-amplified dissimilatory sulfite reductase (DSR) gene. The DSR genes were successfully amplified from microbial assemblages of the chimney structures, derived from three geographically and geologically distinct deep-sea hydrothermal systems in the Central Indian Ridge (CIR), in the Izu-Bonin Arc (IBA), and the Okinawa Trough (OT), respectively. Phylogenetic analysis revealed seven major phylogenetic groups. More than half of the clones from the CIR chimney structure were related to DSR amino acid sequences of the hyperthermophilic archaeal members of the genus Archaeoglobus, and those of environmental DSR clones within the class Thermodesulfobacteria. From the OT chimney structure, a different group was obtained, which comprised a novel, deep lineage associated with the DSRs of the thermophilic sulfate-reducing bacterium Thermodesulfovibrio. Most of the DSR clones from the IBA chimney structure were phylogenetically associated with the delta-proteobacterial sulfate-reducing bacteria represented by the genus Desulfobulbus. Sequence analysis of DSR clones demonstrated a diverse sulfate-reducing prokaryotic community in the active deep-sea hydrothermal chimney structures.

  15. Linking geology, fluid chemistry, and microbial activity of basalt- and ultramafic-hosted deep-sea hydrothermal vent environments.

    PubMed

    Perner, M; Hansen, M; Seifert, R; Strauss, H; Koschinsky, A; Petersen, S

    2013-07-01

    Hydrothermal fluids passing through basaltic rocks along mid-ocean ridges are known to be enriched in sulfide, while those circulating through ultramafic mantle rocks are typically elevated in hydrogen. Therefore, it has been estimated that the maximum energy in basalt-hosted systems is available through sulfide oxidation and in ultramafic-hosted systems through hydrogen oxidation. Furthermore, thermodynamic models suggest that the greatest biomass potential arises from sulfide oxidation in basalt-hosted and from hydrogen oxidation in ultramafic-hosted systems. We tested these predictions by measuring biological sulfide and hydrogen removal and subsequent autotrophic CO2 fixation in chemically distinct hydrothermal fluids from basalt-hosted and ultramafic-hosted vents. We found a large potential of microbial hydrogen oxidation in naturally hydrogen-rich (ultramafic-hosted) but also in naturally hydrogen-poor (basalt-hosted) hydrothermal fluids. Moreover, hydrogen oxidation-based primary production proved to be highly attractive under our incubation conditions regardless whether hydrothermal fluids from ultramafic-hosted or basalt-hosted sites were used. Site-specific hydrogen and sulfide availability alone did not appear to determine whether hydrogen or sulfide oxidation provides the energy for primary production by the free-living microbes in the tested hydrothermal fluids. This suggests that more complex features (e.g., a combination of oxygen, temperature, biological interactions) may play a role for determining which energy source is preferably used in chemically distinct hydrothermal vent biotopes.

  16. Mineralogical and geochemical evidence for hydrothermal activity at the west wall of 12°50′N core complex (Mid-Atlantic ridge): a new ultramafic-hosted seafloor hydrothermal deposit?

    USGS Publications Warehouse

    Dekov, Vesselin; Boycheva, Tanya; Halenius, Ulf; Billstrom, Kjell; Kamenov, George D.; Shanks, Wayne C.; Stummeyer, Jens

    2011-01-01

    Dredging along the west wall of the core complex at 12°50′N Mid-Atlantic Ridge sampled a number of black oxyhydroxide crusts and breccias cemented by black and dark brown oxyhydroxide matrix. Black crusts found on top of basalt clasts (rubble) are mainly composed of Mn-oxides (birnessite, 10-Å manganates) with thin films of nontronite and X-ray amorphous FeOOH on their surfaces. Their chemical composition (low trace- and rare earth-element contents, high Li and Ag concentrations, rare earth element distribution patterns with negative both Ce and Eu anomalies), Sr–Nd–Pb-isotope systematic and O-isotope data suggest low-temperature (~ 20 °C) hydrothermal deposition from a diffuse vent area on the seafloor. Mineralogical, petrographic and geochemical investigations of the breccias showed the rock clasts were hydrothermally altered fragments of MORBs. Despite the substantial mineralogical changes caused by the alteration the Sr–Nd–Pb-isotope ratios have not been significantly affected by this process. The basalt clasts are cemented by dark brown and black matrix. Dark brown cement exhibits geochemical features (very low trace- and rare earth- element contents, high U concentration, rare earth element distribution pattern with high positive Eu anomaly) and Nd–Pb-isotope systematics (similar to that of MORB) suggesting that the precursor was a primary, high-temperature Fe-sulfide, which was eventually altered to goethite at ambient seawater conditions. The data presented in this work points towards the possible existence of high- and low-temperature hydrothermal activity at the west wall of the core complex at 12°50′N Mid-Atlantic Ridge. Tectonic setting at the site implies that the proposed hydrothermal field is possibly ultramafic-hosted.

  17. Distributions and contents of the organic carbon and major heavy metals in aquatic environment surrounding the active submarine hydrothermal vent in the Northwestern Pacific

    NASA Astrophysics Data System (ADS)

    Lee, S.; Iizasa, K.; Shimoda, G.

    2009-12-01

    Since seafloor massive sulfides (SMSs) were firstly found in the central Red Sea in the middle of 20 century, many SMSs have been reported in the settings of oceanic ridges and island arcs. Although seafloor mining of SMSs is likely to be realized in the near future, there are some concerns on hydrothermal biota and ambient environments after seafloor mining. As biota and ambient environments will be affected by the mining of SMSs in direct, researches on the aquatic environment surrounding submarine hydrothermal vents are strongly needed. Because submarine hydrothermal activities are not stable and their life times are relatively short, it is conceivable that the aquatic environments in the hydrothermal field are different from the other site. Therefore, the regular and the long term monitoring in the aquatic environment of the hydrothermal field be strongly required for the more exact and detailed knowledge about the submarine hydrothermal environment. The distributions and the contents of organic carbon and major heavy metals in the seawater columns around hydrothermal fields will be discussed in the present study. In recent, the submarine hydrothermal activities are presumed as one of the factors causing the seasonal fluctuation in concentration of the total organic carbon in the subtropical Northwestern Pacific, but the practical demonstration about this was not carried out yet. The discussion about the distributions and the contents of major heavy metals in the seawater columns around hydrothermal fields will help to understanding of the diffusion through the plume discharged from hydrothermal vents to ambient environments. The samples were collected at and around the hydrothermal fields of the Bayonnaise Knoll caldera on the back-arc rift and the Myojin Knoll and Myojinsho in the Izu-Ogasawara arc, and the Izena cauldron in Okinawa Trough, during at summer in 2008 and 2009 throughout the HT08 cruise by Hakurei-maru and KT09-12 cruise by Tansei-maru. Seawater

  18. Observations of Flatfish "Spas" From Three Hydrothermally Active Seamounts in the Mariana Arc

    NASA Astrophysics Data System (ADS)

    Dower, J.; Tunnicliffe, V.; Tyler, J.; Juniper, K.; Stevens, C.; Kouris, A.; Takano, B.

    2006-12-01

    During a cruise to the Mariana Islands in spring 2004, dense aggregations of small flatfish were recorded from areas of diffuse flow on two hydrothermally active seamounts known as Kasuga-2 and Daikoku. This is quite novel, as flatfish are not known to be part of vent faunas elsewhere. Based on a single specimen, it was determined to be a new species of tonguefish in the genus Symphurus, and is currently under description. In October 2005, we returned to the Mariana Arc and collected about 60 specimens from Kasuga-2, Daikoku, and a third site, Nikko Seamount. Interestingly, the Nikko specimens were about twice as large as the flatfish from Kasuga-2 and Daikoku. Current molecular work (using the Barcode of Life Data System) will determine the relationship among these populations, and verify whether they are the same species. Under the microscope, the sandy sediments from the flatfish habitat were found to be full of tiny nematodes and polychaete worms. Our current hypothesis is that the fish are feeding on both and, thus, are ultimately supported by chemosynthesis, since the worms likely feed on bacteria in the sediments. However, during our most recent cruise in May 2006, we also observed several instances in which dead (or nearly dead) mid-water fish and shrimp fell out of the water column onto the bottom, after which they were almost immediately fed upon by the flatfish. This suggests that there may also be an additional energy subsidy to the seamount benthos from the water column. We hypothesize that sulfite (or some other toxic chemical) in the plume overlying these active volcanoes either kills or anesthetizes small pelagics that get advected over the seamount summit while feeding in near-surface waters at night. Stable isotope and lipid analysis of samples from these "fish spas" are currently underway to establish trophic relationships. We hope to use otolith microstructure analyses to quantify individual growth trajectories and population age structure of

  19. Hydrothermal alteration of a chevkinite-group mineral to a bastnäsite-(Ce)-ilmenite- columbite-(Fe) assemblage: interaction with a F-, CO2-rich fluid

    NASA Astrophysics Data System (ADS)

    Macdonald, Ray; Bagiński, Bogusław; Kartashov, Pavel M.; Zozulya, Dmitry; Dzierżanowski, Piotr; Jokubauskas, Petras

    2015-12-01

    The results are presented of a textural and mineral chemical study of a previously undescribed type of hydrothermal alteration of chevkinite-(Ce) which occurs in a syenitic pegmatite from the Vishnevye Mountains, Urals Region, Russia. The progressive alteration of the chevkinite to a bastnäsite-(Ce)-ilmenite-columbite-(Fe) assemblage through a series of texturally complex intermediate stages is described and electron microprobe analyses are given of all the major phases. Unusual Nb ± Th-rich phases formed late in the alteration sequence provide evidence of local Nb mobility. The main compositional fluxes are traced, especially of the REE, HFSE, Th and U. It appears that almost all elements, with the exception of La, released from the chevkinite-(Ce) were reincorporated into later phases, such that they did not leave the alteration crust in significant amounts. The hydrothermal fluids are inferred to have been F- and CO2-rich, with variable levels of Ca activity, and with fO2 mainly between the nickel-nickel oxide and magnetite-hematite buffers. This occurrence represents a new paragenesis for a columbite-group mineral.

  20. Isolation and complete genome sequence of the thermophilic Geobacillus sp. 12AMOR1 from an Arctic deep-sea hydrothermal vent site.

    PubMed

    Wissuwa, Juliane; Stokke, Runar; Fedøy, Anita-Elin; Lian, Kjersti; Smalås, Arne Oskar; Steen, Ida Helene

    2016-01-01

    Members of the genus Geobacillus have been isolated from a wide variety of habitats worldwide and are the subject for targeted enzyme utilization in various industrial applications. Here we report the isolation and complete genome sequence of the thermophilic starch-degrading Geobacillus sp. 12AMOR1. The strain 12AMOR1 was isolated from deep-sea hot sediment at the Jan Mayen hydrothermal Vent Site. Geobacillus sp. 12AMOR1 consists of a 3,410,035 bp circular chromosome and a 32,689 bp plasmid with a G + C content of 52 % and 47 %, respectively. The genome comprises 3323 protein-coding genes, 88 tRNA species and 10 rRNA operons. The isolate grows on a suite of sugars, complex polysaccharides and proteinous carbon sources. Accordingly, a versatility of genes encoding carbohydrate-active enzymes (CAZy) and peptidases were identified in the genome. Expression, purification and characterization of an enzyme of the glycoside hydrolase family 13 revealed a starch-degrading capacity and high thermal stability with a melting temperature of 76.4 °C. Altogether, the data obtained point to a new isolate from a marine hydrothermal vent with a large bioprospecting potential. PMID:26913091

  1. Isolation and complete genome sequence of the thermophilic Geobacillus sp. 12AMOR1 from an Arctic deep-sea hydrothermal vent site.

    PubMed

    Wissuwa, Juliane; Stokke, Runar; Fedøy, Anita-Elin; Lian, Kjersti; Smalås, Arne Oskar; Steen, Ida Helene

    2016-01-01

    Members of the genus Geobacillus have been isolated from a wide variety of habitats worldwide and are the subject for targeted enzyme utilization in various industrial applications. Here we report the isolation and complete genome sequence of the thermophilic starch-degrading Geobacillus sp. 12AMOR1. The strain 12AMOR1 was isolated from deep-sea hot sediment at the Jan Mayen hydrothermal Vent Site. Geobacillus sp. 12AMOR1 consists of a 3,410,035 bp circular chromosome and a 32,689 bp plasmid with a G + C content of 52 % and 47 %, respectively. The genome comprises 3323 protein-coding genes, 88 tRNA species and 10 rRNA operons. The isolate grows on a suite of sugars, complex polysaccharides and proteinous carbon sources. Accordingly, a versatility of genes encoding carbohydrate-active enzymes (CAZy) and peptidases were identified in the genome. Expression, purification and characterization of an enzyme of the glycoside hydrolase family 13 revealed a starch-degrading capacity and high thermal stability with a melting temperature of 76.4 °C. Altogether, the data obtained point to a new isolate from a marine hydrothermal vent with a large bioprospecting potential.

  2. Silica nanoparticles in E ring ice grains as an indicator for hydrothermal activities at Enceladus

    NASA Astrophysics Data System (ADS)

    Postberg, F.; Hsu, H. W.; Sekine, Y.

    2013-09-01

    Since 2004 the Cosmic Dust Analyser (CDA) on board the Cassini spacecraft detects nano-meter sized dust particles, so called stream particles, in the Saturnian system. Recently it has been shown that they are released from E ring ice grains in which they were previously embedded [1]. As a consequence the nanograins must have been generated at Saturns active moon Enceladus which feeds the E ring by its spectacular jets of vapour and ice grains. Liquid water below the moons icy crust is known to be the dominant source of these jets [2, 3]. New results from CDA presented here indicate that stream particles actually are nano-silica grains. The most prominent geological process which produces nano-phase silica are hydrothermal rock-water interactions. This process has recently been intensely studied for hydrothermal systems on Earth [e.g. 4, 5]. The measured concentration, composition and size range observed at in the Saturnian system precisely matches a hydrothermal synthesis origin. Thus, we propose nano-colloidal silica to be present at mMol concentrations in Enceladus' subsurface waters. We were able to reproduce the proposed hydrothermal serpentinisation processes in a geochemical long term experiment in the laboratory. As there are no alternative formation scenarios which are in agreement with the CDA observations our results indicate ongoing rock-water interactions inside Enceladus at temperatures clearly exceeding 100°C. We discuss implications for Enceladus geochemistry, like salinity, possible ranges of temperature and pH, as well as the mineral composition of the Enceladian rock core.

  3. Geochemical studies on the biodiversity and hydrothermal activity; mineralogy, chemistry, and age determination of hydrothermal chimney collected from Suiyo seamount, Izu-Bonin arc

    NASA Astrophysics Data System (ADS)

    Noguchi, T.; Oomori, T.; Taira, N.; Takada, J.; Urabe, T.

    2004-12-01

    Hydrothermal chimney structure has the steep environmental gradients of temperature, redox potential, pH and chemical concentration, which will provide diverse microhabitats for microbial communities (K.Takai et al. 2001, Hermie J.M. Harmsen et al. 1997). It is important for detailed understanding of the biodiversity to determine the chimney structural environment. Suiyo seamount is located 28.57° N, 140.66° E, where is suitable to compare with the Mid-ocean ridge hydrothermal field, because of few influence of terrestrial sediment. It was reported that the magma chamber below the seamount was very shallow ( ˜1 km), and high temperature hydrothermal fluid chamber was underlying just below the seafloor sealed with anhydrite and barite. Chimney samples used in this study were collected by Dive 1222-1225 of SHINKAI 2000 (JAMSTEC) in 2000. We measured the chemical composition with neutron activation analysis (NAA) and X-ray fluorescence analysis (XRF), mineral composition with X-ray diffraction analysis (XRD), and the precipitation age measurements ( ˜200 years) of these chimneys with γ -ray spectrometry (210Pb/Pb method, 228Th/228Ra method, and 210Pb/226Ra method). The mineral composition of the Suiyo seamount chimney were contained barite (BaSO4), sphalerite ((Zn,Fe)S), pyrite (FeS2), and chalcopyrite (CuFeS2) as a major mineral constituents. The chemical composition shows that gold contents in the chimney collected from Suiyo seamount were much higher (maximum 166 ppm) than other hydrothermal field. The chronological study showed that the precipitation ages of sulfide chimney samples (ranged in 37.2-79.6 years before 2002 by 210Pb/Pb method) were older than barite chimney ((ranged in 2.9-8.2 years before 2002 by 228Th/228Ra method). We will discuss about the process of chimney formation, the temporal variation of the past hydrothermal activity and the difference from other submarine hydrothermal fields (EPR, MAR, Okinawa trough, Loihi seamount).

  4. Volcanic and Hydrothermal Activity of the North Su Volcano: New Insights from Repeated Bathymetric Surveys and ROV Observations

    NASA Astrophysics Data System (ADS)

    Thal, J.; Bach, W.; Tivey, M.; Yoerger, D.

    2013-12-01

    Bathymetric data from cruises in 2002, 2006, and 2011 were combined and compared to determine the evolution of volcanic activity, seafloor structures, erosional features and to identify and document the distribution of hydrothermal vents on North Su volcano, SuSu Knolls, eastern Manus Basin (Papua New Guinea). Geologic mapping based on ROV observations from 2006 (WHOI Jason-2) and 2011 (MARUM Quest-4000) combined with repeated bathymetric surveys from 2002 and 2011 are used to identify morphologic features on the slopes of North Su and to track temporal changes. ROV MARUM Quest-4000 bathymetry was used to develop a 10 m grid of the top of North Su to precisely depict recent changes. In 2006, the south slope of North Su was steeply sloped and featured numerous white smoker vents discharging acid sulfate waters. These vents were covered by several tens of meters of sand- to gravel-sized volcanic material in 2011. The growth of this new cone changed the bathymetry of the south flank of North Su up to ~50 m and emplaced ~0.014 km3 of clastic volcanic material. This material is primarily comprised of fractured altered dacite and massive fresh dacite as well as crystals of opx, cpx, olivine and plagioclase. There is no evidence for pyroclastic fragmentation, so we hypothesize that the fragmentation is likely related to hydrothermal explosions. Hydrothermal activity varies over a short (~50 m) lateral distance from 'flashing' black smokers to acidic white smoker vents. Within 2 weeks of observation time in 2011, the white smoker vents varied markedly in activity suggesting a highly episodic hydrothermal system. Based on ROV video recordings, we identified steeply sloping (up to 30°) slopes exposing pillars and walls of hydrothermal cemented volcaniclastic material representing former fluid upflow zones. These features show that hydrothermal activity has increased slope stability as hydrothermal cementation has prevented slope collapse. Additionally, in some places

  5. Hydrothermal mineralogy and fluid inclusions chemistry to understand the roots of active geothermal systems

    NASA Astrophysics Data System (ADS)

    Chambefort, I. S.; Dilles, J. H.; Heinrich, C.

    2013-12-01

    An integrated study to link magmatic textures, magmatic mineral compositions, hydrothermal alteration zoning, hydrothermal mineral chemistry, and fluid inclusion compositions has been undertaken to link an intrusive complex and its degassing alteration halo with their surface equivalent in an active geothermal system. Ngatamariki geothermal system, New Zealand, presents a unique feature in the Taupo Volcanic Zone (TVZ). Drilling intercepted an intrusive complex with a high temperature alteration halo similarly to what is observed in magmatic-derived ore deposits. Thus it presents the perfect opportunity to study the magmatic-hydrothermal transition of the TVZ by characterizing the nature of the deep magmatic fluids link to the heat source of the world known geothermal fields. The record of magmatic-hydrothermal fluid-rock interactions preserved at Ngatamariki may be analogous of processes presently occurring at depth beneath TVZ geothermal systems. The intrusive complex consists of over 5 km3 of tonalite, diorite, basalt and aplitic dykes. Evidence of undercooling subsolidus magmatic textures such as myrmekite and skeletal overgrowth are commonly observed and often linked to volatile loss. The fluids released during the crystallization of the intrusive complex are interpreted to be at the origin of the surrounding high temperature alteration halo. Advanced argillic to potassic alteration and high temperature acidic assemblage is associated with high-temperature quartz veining at depth and vuggy silica at the paleo-surface. Major element compositions of the white micas associated with the high temperature halo show a transition from, muscovite to phengite, muscovitic illite away from the intrusion, with a transition to pyrophyllite and/ or topaz, and andalusite characteristic of more acidic conditions. Abundant high-density (up to 59 wt% NaCl eq and homogenization temperatures of 550 degree Celsius and above) coexist with low-density vapor fluid inclusions. This

  6. Identification and activity of acetate-assimilating bacteria in diffuse fluids venting from two deep-sea hydrothermal systems.

    PubMed

    Winkel, Matthias; Pjevac, Petra; Kleiner, Manuel; Littmann, Sten; Meyerdierks, Anke; Amann, Rudolf; Mußmann, Marc

    2014-12-01

    Diffuse hydrothermal fluids often contain organic compounds such as hydrocarbons, lipids, and organic acids. Microorganisms consuming these compounds at hydrothermal sites are so far only known from cultivation-dependent studies. To identify potential heterotrophs without prior cultivation, we combined microbial community analysis with short-term incubations using (13)C-labeled acetate at two distinct hydrothermal systems. We followed cell growth and assimilation of (13)C into single cells by nanoSIMS combined with fluorescence in situ hybridization (FISH). In 55 °C-fluids from the Menez Gwen hydrothermal system/Mid-Atlantic Ridge, a novel epsilonproteobacterial group accounted for nearly all assimilation of acetate, representing the first aerobic acetate-consuming member of the Nautiliales. In contrast, Gammaproteobacteria dominated the (13) C-acetate assimilation in incubations of 37 °C-fluids from the back-arc hydrothermal system in the Manus Basin/Papua New Guinea. Here, 16S rRNA gene sequences were mostly related to mesophilic Marinobacter, reflecting the high content of seawater in these fluids. The rapid growth of microorganisms upon acetate addition suggests that acetate consumers in diffuse fluids are copiotrophic opportunists, which quickly exploit their energy sources, whenever available under the spatially and temporally highly fluctuating conditions. Our data provide first insights into the heterotrophic microbial community, catalyzing an under-investigated part of microbial carbon cycling at hydrothermal vents.

  7. Investigating the active hydrothermal field of Kolumbo Volcano using CTD profiling

    NASA Astrophysics Data System (ADS)

    Eleni Christopoulou, Maria; Mertzimekis, Theo; Nomikou, Paraskevi; Papanikolaou, Dimitrios; Carey, Steve

    2014-05-01

    The submarine Kolumbo volcano NE of Santorini Island and the unique active hydrothermal vent field on its crater field (depth ~ 500 m) have been recently explored in multiple cruises aboard E/V Nautilus. ROV explorations showed the existence of extensive vent activity and almost completely absence of vent-specific macrofauna. Gas discharges have been found to be 99%-rich in CO2, which is sequestered at the bottom of the crater due to a special combination of physicochemical and geomorphological factors. The dynamic conditions existing along the water column in the crater have been studied in detail by means of temperature, salinity and conductivity depth profiles for the first time. CTD sensors aboard the ROV Hercules were employed to record anomalies in those parameters in an attempt to investigate several active and inactive vent locations. Temporal CTD monitoring inside and outside of the crater was carried out over a period of two years. Direct comparison between the vent field and locations outside the main cone, where no hydrothermal activity is known to exist, showed completely different characteristics. CTD profiles above the active vent field (NNE side) are correlated to Kolumbo's cone morphology. The profiles suggest the existence of four distinct zones of physicochemical properties in the water column. The layer directly above the chimneys exhibit gas discharges highly enriched in CO2. Continuous gas motoring is essential to identify the onset of geological hazards in the region.

  8. Microwave hydrothermal synthesis of AgInS{sub 2} with visible light photocatalytic activity

    SciTech Connect

    Zhang, Wenjuan; Li, Danzhen; Chen, Zhixin; Sun, Meng; Li, Wenjuan; Lin, Qiang; Fu, Xianzhi

    2011-07-15

    Highlights: {yields} AgInS{sub 2} nanoparticles were synthesized by a microwave hydrothermal method. {yields} This method involves no organic solvents, catalysts, or surfactants. {yields} AgInS{sub 2} showed higher activity for photocatalytic degradation MO than TiO{sub 2-x}N{sub x}. {yields} Holes, O{sub 2}{center_dot}{sup -}, and H{sub 2}O{sub 2} played an important role in the photocatalytic process. -- Abstract: AgInS{sub 2} nanoparticles with superior visible light photocatalytic activity were successfully synthesized by a microwave hydrothermal method. This method is a highly efficient and rapid route that involves no organic solvents, catalysts, or surfactants. The photocatalytic activity of AgInS{sub 2} nanoparticles was investigated through the degradation of dyes under visible light irradiation. Compared with TiO{sub 2-x}N{sub x}, AgInS{sub 2} has exhibited a superior activity for photocatalytic degradation MO under the same condition. The experiment results showed that superoxide radicals (O{sub 2}{center_dot}{sup -}), hydrogen peroxides (H{sub 2}O{sub 2}) and holes (h{sup +}) were the mainly active species for the degradation of organic pollutants over AgInS{sub 2}. Through the determination of flat band potential, the energy band structure of the sample was obtained. A possible mechanism for the degradation of organic pollutant over AgInS{sub 2} was proposed.

  9. Subaqueous cryptodome eruption, hydrothermal activity and related seafloor morphologies on the andesitic North Su volcano

    NASA Astrophysics Data System (ADS)

    Thal, Janis; Tivey, Maurice; Yoerger, Dana R.; Bach, Wolfgang

    2016-09-01

    North Su is a double-peaked active andesite submarine volcano located in the eastern Manus Basin of the Bismarck Sea that reaches a depth of 1154 m. It hosts a vigorous and varied hydrothermal system with black and white smoker vents along with several areas of diffuse venting and deposits of native sulfur. Geologic mapping based on ROV observations from 2006 and 2011 combined with morphologic features identified from repeated bathymetric surveys in 2002 and 2011 documents the emplacement of a volcanic cryptodome between 2006 and 2011. We use our observations and rock analyses to interpret an eruption scenario where highly viscous, crystal-rich andesitic magma erupted slowly into the water-saturated, gravel-dominated slope of North Su. An intense fragmentation process produced abundant blocky clasts of a heterogeneous magma (olivine crystals within a rhyolitic groundmass) that only rarely breached through the clastic cover onto the seafloor. Phreatic and phreatomagmatic explosions beneath the seafloor cause mixing of juvenile and pre-existing lithic clasts and produce a volcaniclastic deposit. This volcaniclastic deposit consists of blocky, non-altered clasts next, variably (1-100%) altered clasts, hydrothermal precipitates and crystal fragments. The usually applied parameters to identify juvenile subaqueous lava fragments, i.e. fluidal shape or chilled margin, were not applicable to distinguish between pre-existing non-altered clasts and juvenile clasts. This deposit is updomed during further injection of magma and mechanical disruption. Gas-propelled turbulent clast-recycling causes clasts to develop variably rounded shapes. An abundance of blocky clasts and the lack of clasts typical for the contact of liquid lava with water is interpreted to be the result of a cooled, high-viscosity, crystal-rich magma that failed as a brittle solid upon stress. The high viscosity allows the lava to form blocky and short lobes. The pervasive volcaniclastic cover on North Su is

  10. Geological setting of hydrothermal activity at 12°50'N on the East Pacific Rise: A submersible study

    NASA Astrophysics Data System (ADS)

    Ballard, R. D.; Hekinian, Roger; Francheteau, Jean

    1984-07-01

    A detailed submersible investigation of a 20-km segment of the East Pacific Rise near 12°50'N between the Orozco and Clipperton fracture zones has resulted in the localization of 24 active hydrothermal vent fields and over 80 sites of sulfide accumulations. The active vents range from low-temperature vents characterized by exotic benthic communities to high-temperature "black smokers" and the deposition of polymetallic sulfides. The study is based upon a combination of fine scale topography obtained using the SEABEAM sonar system on N/O "Jean Charcot", camera lowerings along the axis using the RAIE vehicle, and 32 dives by the submersible "Cyana" operating from N/O "Le Suroit". The observations made between the Orozco and Clipperton fracture zones show topographic highs situated along the strike of the accreting plate segment separated by a small ridge offset at 11°49'N. This offset divides this portion of the ridge into two separate spreading segments each of which has a primary topographic high along strike. Secondary highs are associated with each segment of the ridge separated by either small offsets (or relay zones) or in some cases, zones where spreading centers overlap. Dives made on the tops of both primary highs (12°50'N and 11°30'N) confirm the presence inferred from previous surface work of high-temperature vent fields while one reconnaissance dive (14°20'N) near the Orozco fracture zone/ridge axis intersection reveals the absence of any hydrothermal activity in the present or recent past. The vast majority of vent fields investigated were found at the topographic high near 12°50'N, are associated with the most recent period of volcanism, and are confined to lava ponds situated within the axial graben.

  11. Fluid inclusion petrography and microthermometry of the Cocos Ridge hydrothermal system, IODP Expedition 344 (CRISP 2), Site U1414

    NASA Astrophysics Data System (ADS)

    Brandstätter, J.; Kurz, W.; Krenn, K.; Micheuz, P.

    2015-12-01

    We present new data from microthermometric analyses of fluid inclusions entrapped in hydrothermal veins within lithified sediments and Cocos Ridge (CCR) basalt from IODP Expedition 344 site U1414 (Costa Rica) and concern on a primary task of Expedition 344, i.e. to evaluate fluid/rock interaction, the hydrologic system, and the geochemical processes (indicated by composition and volume of fluids) active within the incoming Cocos Plate. Mineralization of the veins and crosscutting relationships gives constraints for the different generation of veins. Calcium carbonate, commonly aragonite in the upper part and calcite in the lower part of the igneous basement, is usually present in veins as a late phase following the quartz precipitation and the clay minerals formation. The sequence of vein generations in the lithified sediments close to the contact within the CCR basalt is characterized by smaller veins filled by quartz, followed by massive intersecting calcite veins. A high fluid pressure can be concluded, due to wall rock fragments embedded within the filling and fractured mineral grains in the ground mass, which are close to the veins. This requires that the magmatic basement and the lithified sediments were covered by sequences of low permeability sediments forming a barrier that enabled build up elevated fluid pressure. The investigation of fluid inclusions in the lowest units of borehole 344-U1414, give clues about the source of the fluids and about the vein evolution within the incoming Cocos Plate close to Middle American Trench. The microthermometric analyses of the primary, almost aqueous, inclusions indicate a temperature range during entrapment between 200 and 420°C. The data indicate that seawater within the Cocos Ridge aquifer communicated with high-temperature fluids and/or were modified by heat advection. We consider the Galapagos hotspot and/ or the Cocos-Nazca spreading center as heat source. Fluids originated from mobilized sediment pore water

  12. Identification and characterization of the active hydrothermal deposits in Okinawa Trough, SW Japan: Estimates from logging-while-drilling

    NASA Astrophysics Data System (ADS)

    Saito, S.; Sanada, Y.; Moe, K.; Kido, Y. N.; Hamada, Y.; Kumagai, H.; Nozaki, T.; Takai, K.; Suzuki, K.

    2015-12-01

    A scientific drilling expedition was conducted at an active hydrothermal field on the Iheya-North Knoll by D/V Chikyu in 2014 (Expedition 907) as a part of "Next-generation Technology for Ocean Resources Survey" of the Cross-ministerial Strategic Innovation Promotion Program. During the expedition logging while drilling (LWD) was deployed to constrain the area of the fluid reservoir beneath seafloor followed by three coring holes down to 150 meter below the seafloor (mbsf). The LWD system is composed of arcVISION for resistivity and natural gamma ray measurement and TeleScope for real-time transmission of drilling parameters and arcVISION data. Five sites (C9011-15) at the Iheya-North Original Site and one site (C9016) at Aki Site were drilled with LWD. At C9012 and C9016, the arcVISION detected temperature anomaly up to 84℃ at 234 mbsf and up to 39℃ at 80 mbsf, respectively. The temperature quickly increases at that depth and it would reflect the existence of high-temperature heat source along borehole. Due to the continuous fluid circulation during drilling, the measured temperature does not indicate in-situ temperature, but it reflects the heat disturbed by the cold circulated water instead. High quality resistivity and natural gamma ray data were acquired at six sites. The log curves at Site C9016 show characteristic response; the natural gamma ray log exhibits extremely high radiation (>500 gAPI) at 7-13 and 23-31 mbsf (Zone A). In the underlying interval of 31-40 mbsf, the resistivity log exhibits extremely low value (<0.2 ohm-m) (Zone B). Then the resistivity log exhibits higher value (~10 ohm-m) and the natural gamma ray log shows very low radiation (<50 gAPI) at the interval of 41-48 mbsf (Zone C). The log characteristics in Zone A, B, and C can be interpreted as a series of K-rich alteration zone, sulfide zone, and low-K hard (silicified) sediments, respectively. The LWD-based lithological interpretation was confirmed by the following core description

  13. Evolution of magmatic and hydrothermal activity in the western Arctic and North Atlantic regions

    NASA Astrophysics Data System (ADS)

    Sorokhtin, N. O.; Lobkovsky, L. I.; Novikov, G. V.; Kozlov, E. E.; Bogdanova, O. Yu.; Nikiforov, S. L.

    2016-07-01

    This paper discusses the geodynamic evolution of the lithosphere in the Arctic region during the Phaneorozic and its polyphase lithotectonic reorganization. Spatiotemporal patterns of the mosaic junction of lithospheric plates of different age are presented for the Caledonian-Hercynian stage and for the Cenozoic evolution of the North Atlantic and Arctic oceanic basins. Special attention is given to the intersections of fault systems with different kinematics, which control the manifestation of peculiar magmatism and the formation of numerous mineral deposits. It is shown that the hydrothermal activity of the region is related to the ocean opening in the Eocene and is confined to the mid-ocean ridge.

  14. 30,000 years of hydrothermal activity at the lost city vent field.

    PubMed

    Früh-Green, Gretchen L; Kelley, Deborah S; Bernasconi, Stefano M; Karson, Jeffrey A; Ludwig, Kristin A; Butterfield, David A; Boschi, Chiara; Proskurowski, Giora

    2003-07-25

    Strontium, carbon, and oxygen isotope data and radiocarbon ages document at least 30,000 years of hydrothermal activity driven by serpentinization reactions at Lost City. Serpentinization beneath this off-axis field is estimated to occur at a minimum rate of 1.2 x 10(-4) cubic kilometers per year. The access of seawater to relatively cool, fresh peridotite, coupled with faulting, volumetric expansion, and mass wasting processes, are crucial to sustain such systems. The amount of heat produced by serpentinization of peridotite massifs, typical of slow and ultraslow spreading environments, has the potential to drive Lost City-type systems for hundreds of thousands, possibly millions, of years.

  15. Discovery of hydrothermally active and extinct talc mounds on the Mid-Cayman Rise

    NASA Astrophysics Data System (ADS)

    Hodgkinson, M.; Murton, B. J.; Roberts, S.

    2013-12-01

    Since 1977, hydrothermal vents have been the subject of intense scientific interest due to their role in cooling the oceanic crust and global geochemical cycles. Until now, two types of hydrothermal system have been identified: one, driven by magmatic heat extruding ';black smoker' fluids; and another, involving serpentinisation of ultramafic rocks and the precipitation of carbonate/brucite chimneys. Here, we present details of a new, off-axis type of hydrothermal system consisting of mounds of predominately botryoidal talc (a magnesium-silicate) with accessory silica and copper sulphides, and chimneys exhaling fluids of moderate temperature and pH. Discovered on the Mid-Cayman Rise (MCR) in 2010, the Von Damm Vent Field (VDVF) features a NNW-ESE-trending line of four overlapping cones, the largest of which is 75 m high by 150 m in diameter. The VDVF is hosted in the gabbroic footwall of the Mount Dent Oceanic Core Complex (MDOCC), which includes serpentinised peridotite at depth. The largest cone vents clear fluids from two main orifices at its summit, with primary temperatures of 215°C. Elsewhere, both focussed and diffuse flow areas emit fluids with temperatures of up to 150°C. The surrounding ~1 m thick pelagic sediment contains abundant pockmarks that emit methane-rich fluids at temperatures of less than 10°C. During the return to the MCR in early 2013, several other talc mounds were discovered within a kilometre of the active VDVF. These inactive mounds also comprise an assemblage of botryoidal talc, silica, disseminated sulphides (including chalcopyrite) and sulphates. One of these mounds (Mystic Mount) is double the volume of the active VDVF. The unique dominance of talc as the major mineral forming the hydrothermal structures indicates unusual vent fluid compositions that are able to carry both copper (at high-temperatures) and precipitate magnesium silicate. Thermodynamic modelling indicates that talc precipitates on mixing a moderately acidic, silica

  16. Crustal magnetization and the subseafloor structure of the ASHES vent field, Axial Seamount, Juan de Fuca Ridge: Implications for the investigation of hydrothermal sites

    NASA Astrophysics Data System (ADS)

    Caratori Tontini, Fabio; Crone, Timothy J.; Ronde, Cornel E. J.; Fornari, Daniel J.; Kinsey, James C.; Mittelstaedt, Eric; Tivey, Maurice

    2016-06-01

    High-resolution geophysical data have been collected using the Autonomous Underwater Vehicle (AUV) Sentry over the ASHES (Axial Seamount Hydrothermal Emission Study) high-temperature (~348°C) vent field at Axial Seamount, on the Juan de Fuca Ridge. Multiple surveys were performed on a 3-D grid at different altitudes above the seafloor, providing an unprecedented view of magnetic data resolution as a function of altitude above the seafloor. Magnetic data derived near the seafloor show that the ASHES field is characterized by a zone of low magnetization, which can be explained by hydrothermal alteration of the host volcanic rocks. Surface manifestations of hydrothermal activity at the ASHES vent field are likely controlled by a combination of local faults and fractures and different lava morphologies near the seafloor. Three-dimensional inversion of the magnetic data provides evidence of a vertical, pipe-like upflow zone of the hydrothermal fluids with a vertical extent of ~100 m.

  17. Key Factors Influencing Rates of Heterotrophic Sulfate Reduction in Active Seafloor Hydrothermal Massive Sulfide Deposits.

    PubMed

    Frank, Kiana L; Rogers, Karyn L; Rogers, Daniel R; Johnston, David T; Girguis, Peter R

    2015-01-01

    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, [Formula: see text], 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.

  18. Hydrothermal activity and subsurface soil complexity: implication for outgassing processes at Solfatara crater, Campi Flegrei caldera

    NASA Astrophysics Data System (ADS)

    Montanaro, Cristian; Mayer, Klaus; Scheu, Bettina; Isaia, Roberto; Mangiacapra, Annarita; Gresse, Marceau; Vandemeulebrouck, Jean; Moretti, Roberto; Dingwell, Donald B.

    2016-04-01

    The Solfatara area and its fumaroles are the main surface phenomena of the vigorous hydrothermal activity within the active Campi Flegrei caldera system. The existing fault system appears to have a major control on outgassing which in turn leads to a strong alteration of the volcanic products. Moreover the maar-nature of the crater, and its filling by more recent volcanic deposits, resulted in a complex fractured and multilayered cap to the rising gases. As a consequence the hydrothermal alteration differently affects the rocks within the crater, including pyroclastic fallout ash beds, pyroclastic density current deposits, breccias and lavas. The induced changes in both original microstructure and physical and mechanical properties of the rocks control the outgassing behavior. Here, we report results from a measurement survey conducted in July 2015, and aimed to characterize the in-situ physical (temperature, humidity) and mechanical (permeability, strength, stiffness) properties. The survey also included a mapping of the surficial hydrothermal features and their distributions. Chemical analyses and laboratory measurements (porosity, granulometry) of selected samples were additionally performed. Results show that the crater floor area comprises very different kinds of soils, from fine grained, thin laminated deposits around the two bubbling Fangaia mud pools, to crusted hummock formations along the SE and NE border of the crater. Dry and solid alunite-rich deposits are present in the western and southern part. Furthermore we observed evidences of a beginning of crust formation within the central part of the crater. A large range of surface temperatures, from boiling point to ambient temperature, were measured throughout the surveyed area. Outgassing occurs mainly along the crack system, which has also generated the crusted hummocks. Elsewhere the fluid circulation in the subsoil is favored by the presence of coarse and highly porous sulfur-hardened levels, whereas

  19. Key Factors Influencing Rates of Heterotrophic Sulfate Reduction in Active Seafloor Hydrothermal Massive Sulfide Deposits

    PubMed Central

    Frank, Kiana L.; Rogers, Karyn L.; Rogers, Daniel R.; Johnston, David T.; Girguis, Peter R.

    2015-01-01

    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. PMID:26733984

  20. Key Factors Influencing Rates of Heterotrophic Sulfate Reduction in Active Seafloor Hydrothermal Massive Sulfide Deposits.

    PubMed

    Frank, Kiana L; Rogers, Karyn L; Rogers, Daniel R; Johnston, David T; Girguis, Peter R

    2015-01-01

    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, [Formula: see text], 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. PMID:26733984

  1. Hydrothermal Spinel, Corundum and Diaspore in Gabbroic Rocks from the Hess Deep Rift, IODP Site U1415

    NASA Astrophysics Data System (ADS)

    Nozaka, T.; Meyer, R.; Wintsch, R. P.

    2014-12-01

    Hydrothermal alteration of oceanic lower crust has significant implications on geophysical properties of oceanic plates and global-scale geochemical cycles. A first order observation on the hydrothermal alteration at fast-spreading ridges is provided by the gabbroic rocks recovered from the Integrated Ocean Drilling Program (IODP) Site U1415 at the Hess Deep Rift near the East Pacific Rise. Shipboard observations of these rocks have revealed an alteration sequence formed under temperature conditions ranging from amphibolite to zeolite facies with mineral assemblages including amphibole, secondary clinopyroxene, chlorite, talc, serpentine, prehnite, zeolite and clay minerals (Gillis et al., 2014). Amphibolite-facies alteration is illustrated by the tremolite-chlorite corona textures between primary olivine and plagioclase in primitive olivine gabbro or troctolite lithologies (Nozaka and Fryer, 2011). The abundance of these alteration mineral assemblages within some sampled intervals suggests localized high-temperature fluid flow near the spreading axis. Our post-cruise studies prove that some of the coronitic amphiboles, particularly those of incipient-stage corona have hornblendic compositions, suggesting a somewhat higher-temperature formation condition than tremolite. We report here another set of alteration products from Site U1415: that is, Al-spinel, corundum and diaspore. They occur in intensely altered parts of the drilled troctolites. The Al-spinel is associated with An-rich plagioclase and pargasitic amphibole that points to even higher temperature conditions than the amphibole-chlorite corona formation. The Al-spinel is partly replaced by corundum, and the corundum, in turn, is pseudomorphically replaced by diaspore. From modes of occurrence and chemical compositions of minerals, and thermodynamic calculations of the stability conditions for these mineral assemblages, we conclude that the highly aluminous phases were formed by localized fluid flow at

  2. Microwave-assisted hydrothermal synthesis of marigold-like ZnIn{sub 2}S{sub 4} microspheres and their visible light photocatalytic activity

    SciTech Connect

    Chen Zhixin; Li Danzhen; Xiao Guangcan; He Yunhui; Xu Yijun

    2012-02-15

    Marigold-like ZnIn{sub 2}S{sub 4} microspheres were synthesized by a microwave-assisted hydrothermal method with the temperature ranging from 80 to 195 Degree-Sign C. X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen sorption analysis, UV-visible spectroscopy, scanning electron microscopy and transmission electron microscopy were used to characterize the products. It was found that the crystallographic structure and optical property of the products synthesized at different temperatures were almost the same. The degradation of methyl orange (MO) under the visible light irradiation has been used as a probe reaction to investigate the photocatalytic activity of as-prepared ZnIn{sub 2}S{sub 4}, which shows that the ZnIn{sub 2}S{sub 4} sample synthesized at 195 Degree-Sign C shows the best photocatalytic activity for MO degradation. In addition, the photocatalytic activities of all the samples prepared by the microwave-assisted hydrothermal method are better than those prepared by a normal hydrothermal method, which could be attributed to the formation of more defect sites during the microwave-assisted hydrothermal treatment. - Graphical abstract: Marigold-like ZnIn{sub 2}S{sub 4} microspheres were synthesized by a fast microwave-assisted hydrothermal method at 80-195 Degree-Sign C with a very short reaction time of 10 min. The as-prepared ZnIn{sub 2}S{sub 4} sample can be used as visible light photocatalyst for degradation of organic dyes. Highlights: Black-Right-Pointing-Pointer ZnIn{sub 2}S{sub 4} microspheres were synthesized by microwave-assisted hydrothermal method. Black-Right-Pointing-Pointer The crystal structure and optical property of the products were almost the same. Black-Right-Pointing-Pointer Increment of the temperature renders high surface area due to the bubbling effect. Black-Right-Pointing-Pointer The ZnIn{sub 2}S{sub 4} synthesized at 195 Degree-Sign C shows the best visible catalytic activity for MO.

  3. Enhanced hydrothermal activity along the East Pacific Rise during the last two glacial terminations

    NASA Astrophysics Data System (ADS)

    Lund, D. C.; Asimow, P. D.; Farley, K. A.

    2015-12-01

    Mid-ocean ridge magmatism is driven by seafloor spreading and decompression melting of the upper mantle. Scaling estimates [1-2] and model results [3-4] indicate that glacial-interglacial changes in sea level should modulate melt production at mid-ocean ridges, an idea that has been confirmed with detailed surveys of ridge bathymetry [4-5]. The nature and timing of associated changes in hydrothermal activity have remained unknown, however, precluding a clear understanding of whether ridge magmatism can act as a negative feedback on ice sheet size. Here we present multiple records of hydrothermal sedimentation spanning 1300 km of the East Pacific Rise (EPR). At each location, the flux of Fe, Mn, and As increased beginning at ~25 kyr BP, reached maximum values by 15 kyr BP, and then decreased into the Holocene. Lateral sediment focusing is an unlikely explanation given the similar signal in multiple cores and the lack of evidence for anomalous horizontal transport in 3He-based focusing factors. Coherent variations in Fe, Mn, and As suggest that diagenetic overprinting is not the primary driver of the down core signal. Elevated metal fluxes also occur during Termination II. The time series of hydrothermal sedimentation bear a strong resemblance to a record of seafloor bathymetry from 17ºS [5], suggesting that both have a common driver. The simplest explanation is glacial-interglacial variations in sea level, which apparently modulates sub-ridge melting, seafloor bathymetry, and hydrothermal activity at the EPR. Our results imply that geothermal heat flux from ridges increases during the last two glacial terminations, which should act to erode the deep ocean stratification, enhance the abyssal circulation, and transmit excess heat to the Southern Ocean, thereby setting the stage for deglaciation. [1] Lund and Asimow (2008) AGU Fall Meeting, Abstract #PP11D-08. [2] Huybers and Langmuir (2009) Earth and Planetary Science Letters 286, 479-491. [3] Lund and Asimow (2011

  4. Discovery of new hydrothermal activity and chemosynthetic fauna on the Central Indian Ridge at 18°-20° S.

    PubMed

    Nakamura, Kentaro; Watanabe, Hiromi; Miyazaki, Junichi; Takai, Ken; Kawagucci, Shinsuke; Noguchi, Takuro; Nemoto, Suguru; Watsuji, Tomo-o; Matsuzaki, Takuya; Shibuya, Takazo; Okamura, Kei; Mochizuki, Masashi; Orihashi, Yuji; Ura, Tamaki; Asada, Akira; Marie, Daniel; Koonjul, Meera; Singh, Manvendra; Beedessee, Girish; Bhikajee, Mitrasen; Tamaki, Kensaku

    2012-01-01

    Indian Ocean hydrothermal vents are believed to represent a novel biogeographic province, and are host to many novel genera and families of animals, potentially indigenous to Indian Ocean hydrothermal systems. In particular, since its discovery in 2001, much attention has been paid to a so-called 'scaly-foot' gastropod because of its unique iron-sulfide-coated dermal sclerites and the chemosynthetic symbioses in its various tissues. Despite increasing interest in the faunal assemblages at Indian Ocean hydrothermal vents, only two hydrothermal vent fields have been investigated in the Indian Ocean. Here we report two newly discovered hydrothermal vent fields, the Dodo and Solitaire fields, which are located in the Central Indian Ridge (CIR) segments 16 and 15, respectively. Chemosynthetic faunal communities at the Dodo field are emaciated in size and composition. In contrast, at the Solitaire field, we observed faunal communities that potentially contained almost all genera found at CIR hydrothermal environments to date, and even identified previously unreported taxa. Moreover, a new morphotype of 'scaly-foot' gastropod has been found at the Solitaire field. The newly discovered 'scaly-foot' gastropod has similar morphological and anatomical features to the previously reported type that inhabits the Kairei field, and both types of 'scaly-foot' gastropods genetically belong to the same species according to analyses of their COI gene and nuclear SSU rRNA gene sequences. However, the new morphotype completely lacks an iron-sulfide coating on the sclerites, which had been believed to be a novel feature restricted to 'scaly-foot' gastropods. Our new findings at the two newly discovered hydrothermal vent sites provide important insights into the biodiversity and biogeography of vent-endemic ecosystems in the Indian Ocean. PMID:22431990

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

    NASA Astrophysics Data System (ADS)

    Konn, C.; Fourré, E.; Jean-Baptiste, P.; Donval, J. P.; Guyader, V.; Birot, D.; Alix, A. S.; Gaillot, A.; Perez, F.; Dapoigny, A.; Pelleter, E.; Resing, J. A.; Charlou, J. L.; Fouquet, Y.

    2016-10-01

    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. Based on geochemical (CH4, TDM, 3He) and geophysical (nephelometry) tracer surveys: (1) no hydrothermal activity could be found on the Futuna Spreading Centre (FSC) which sets the western limit of hydrothermal activity; (2) four distinct hydrothermal active areas were identified: Kulo Lasi Caldera, Amanaki Volcano, Fatu Kapa and Tasi Tulo areas; (3) extensive and diverse hydrothermal manifestations were observed and especially a 2D distribution of the sources. At Kulo Lasi, our data and especially tracer ratios (CH4/3He 50×106 and CH4/TDM 4.5) reveal a transient CH4 input, with elevated levels of CH4 measured in 2010, that had vanished in 2011, most likely caused by an eruptive magmatic event. By contrast at Amanaki, vertical tracer profiles and tracer ratios point to typical seawater/basalt interactions. Fatu Kapa is characterised by a substantial spatial variability of the hydrothermal water column anomalies, most likely due to widespread focused and diffuse hydrothermal discharge in the area. In the Tasi Tulo zone, the hydrothermal signal is characterised by a total lack of turbidity, although other tracer anomalies are in the same range as in nearby Fatu Kapa. The background data set revealed the presence of a Mn and 3He chronic plume due to the extensive and cumulative venting over the entire area. To that respect, we believe that the joined domain composed of our active area and the nearby active area discovered in the East by Lupton et al. (2012) highly contribute to the

  6. Tectonic Windows Reveal Off-axis Volcanic and Hydrothermal Activity and Along-strike Variations in Eruption Effusion Rates

    NASA Astrophysics Data System (ADS)

    MacDonald, K. C.

    2005-12-01

    steady increase in the number of isolated volcanic cones in the region 5-20 km off-axis (White et al, 1998, Alexander and Macdonald, 1996). Intact lobate and sheet flows are only observed in the top 5-10 m of the cross-sections. Below this, lobate and sheet flows are crushed to rubble by the overburden of later flows. When these rubble layers are correctly identified as crushed lobate/sheet flows, then the percentages of pillows/sheet flows/lobate flows seen in section are essentially the same as those reported in on-axis areal surveys, and are consistent with the along-strike variations documented by White et al. Whereas, the off-axis excess of pillow lavas is mostly explained by off-axis volcanism. In addition something unexpected was found: evidence for hydrothermal activity and associated microbial activity 26 km off-axis on the East Pacific Rise in the EPR R2K Integrated Studies Site area. This is the first documented off-axis hydrothermal field on a fast-spreading ridge that is not on a seamount (Haymon et al 2005). This activity is characterized by large areas (>100×100m) of mossy microbial floc containing hyperthermophiles associated with high-temperature metal-sulfide mineral particles. Visually similar floc was observed at a number of other locations off-axis on the Mid-Atlantic Ridge, Juan de Fuca Ridge and East Pacific Rise. This may provide opportunities for further exploration of off-axis hydrothermal activity in a variety of environments.

  7. Hydrothermal synthesis of Graphene-TiO2 nanowire with an enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Wu, Huitong; Fan, Jun; Yang, Yuhao; Liu, Enzhou; Hu, Xiaoyun; Ma, Yongning; Fan, Xiao; Tang, Chunni

    2015-07-01

    The hydrothermal method was used to synthesize TiO2 nanowire (NW) and then fabricate graphene-TiO2 nanowire nanocomposite (GNW). Graphene oxide (GO) was prepared via improved Hummers'method. GO reduction to graphene and hybridization between NW and graphene by forming chemical bonding. The as-prepared composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM), and ultraviolet visible (UV-Vis) diffuse reflectance spectra. The photocatalytic activity was evaluated by the photodegradation of methylene blue (MB). The prepared GNW nanocomposite has superior photocatalytic activity in the degradation test, showing an impressive photocatalytic enhancement over NW. At the same time, in comparison with Graphene-TiO2 nanoparticle (NP) nanocomposite (GNP), GNW have a better activity which because NW have more uniform dispersion on graphene with less agglomeration.

  8. Evidence of hydrothermal activity on Marsili Seamount, Tyrrhenian Basin. Technical report

    SciTech Connect

    Uchupi, E.; Ballard, R.D.

    1989-01-01

    In this paper we describe the finding of what appears to be an extensive hydrothermal mineral deposit on the crest of Marsili Seamount in the Tyrrhenian Basin, western Mediterranean Sea. The deposit on the seamount was discovered during a study of the geology of the Tyrrhenian Basin with the Argo video system (HARRIS and BALLARD, 1986) aboard the R.V. Starella during June 1988. Mounted on the vehicle were three Silicon Intensified target (SIT) cameras, a digital charge Couple Device (CCD) camera and a 35 mm camera with a 16 mm lens. The site was revisited in mid August aboard the R.V. Knorr during a cruise to test the dynamic position system on the Knorr.

  9. Biogeography of bacteriophages at four hydrothermal vent sites in the Antarctic based on g23 sequence diversity.

    PubMed

    Millard, Andrew D; Pearce, David; Zwirglmaier, Katrin

    2016-04-01

    In this study, which was carried out within the ChEsSO consortium project (Chemosynthetically driven ecosystems south of the Polar Front), we sampled two hydrothermal vent sites on the East Scotia Ridge, Scotia Sea, one in the Kemp Caldera, South Sandwich Arc and one in the Bransfield Strait, north-west of the Antarctic Peninsula, which exhibit strong differences in their chemical characteristics. We compared a subset of their bacteriophage population by Sanger- and 454-sequencing of g23, which codes for the major capsid protein of T4likeviruses. We found that the sites differ vastly in their bacteriophage diversity, which reflects the differences in the chemical conditions and therefore putatively the differences in microbial hosts living at these sites. Comparing phage diversity in the vent samples to other aquatic samples, the vent samples formed a distinct separate cluster, which also included the non-vent control samples that were taken several hundred meters above the vent chimneys. This indicates that the influence of the vents on the microbial population and therefore also the bacteriophage population extends much further than anticipated.

  10. Biogeography of bacteriophages at four hydrothermal vent sites in the Antarctic based on g23 sequence diversity.

    PubMed

    Millard, Andrew D; Pearce, David; Zwirglmaier, Katrin

    2016-04-01

    In this study, which was carried out within the ChEsSO consortium project (Chemosynthetically driven ecosystems south of the Polar Front), we sampled two hydrothermal vent sites on the East Scotia Ridge, Scotia Sea, one in the Kemp Caldera, South Sandwich Arc and one in the Bransfield Strait, north-west of the Antarctic Peninsula, which exhibit strong differences in their chemical characteristics. We compared a subset of their bacteriophage population by Sanger- and 454-sequencing of g23, which codes for the major capsid protein of T4likeviruses. We found that the sites differ vastly in their bacteriophage diversity, which reflects the differences in the chemical conditions and therefore putatively the differences in microbial hosts living at these sites. Comparing phage diversity in the vent samples to other aquatic samples, the vent samples formed a distinct separate cluster, which also included the non-vent control samples that were taken several hundred meters above the vent chimneys. This indicates that the influence of the vents on the microbial population and therefore also the bacteriophage population extends much further than anticipated. PMID:26903011

  11. Activity and hydrothermal stability of CeO₂-ZrO₂-WO₃ for the selective catalytic reduction of NOx with NH₃.

    PubMed

    Song, Zhongxian; Ning, Ping; Zhang, Qiulin; Li, Hao; Zhang, Jinhui; Wang, Yancai; Liu, Xin; Huang, Zhenzhen

    2016-04-01

    A series of CeO2-ZrO2-WO3 (CZW) catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction (SCR) of NO with NH3 over a wide temperature of 150-550°C. The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H2O. The fresh catalyst showed above 90% NOx conversion at 201-459°C, which is applicable to diesel exhaust NOx purification (200-440°C). The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures (below 300°C), while the activity was notably enhanced at high temperature (above 450°C). The aged CZW catalyst (hydrothermal aging at 700°C for 8 hr) showed almost 80% NOx conversion at 229-550°C, while the V2O5-WO3/TiO2 catalyst presented above 80% NOx conversion at 308-370°C. The effect of structural changes, acidity, and redox properties of CZW on the SCR activity was investigated. The results indicated that the excellent hydrothermal stability of CZW was mainly due to the CeO2-ZrO2 solid solution, amorphous WO3 phase and optimal acidity. In addition, the formation of WO3 clusters increased in size as the hydrothermal aging temperature increased, resulting in the collapse of structure, which could further affect the acidity and redox properties.

  12. Multiple techniques for mineral identification on Mars:. a study of hydrothermal rocks as potential analogues for astrobiology sites on Mars

    NASA Astrophysics Data System (ADS)

    Bishop, Janice L.; Murad, Enver; Lane, Melissa D.; Mancinelli, Rocco L.

    2004-06-01

    Spectroscopic studies of Mars analog materials combining multiple spectral ranges and techniques are necessary in order to obtain ground truth information for interpretation of rocks and soils on Mars. Two hydrothermal rocks from Yellowstone National Park, Wyoming, were characterized here because they contain minerals requiring water for formation and they provide a possible niche for some of the earliest organisms on Earth. If related rocks formed in hydrothermal sites on Mars, identification of these would be important for understanding the geology of the planet and potential habitability for life. XRD, thermal properties, VNIR, mid-IR, and Raman spectroscopy were employed to identify the mineralogy of the samples in this study. The rocks studied here include a travertine from Mammoth Formation that contains primarily calcite with some aragonite and gypsum and a siliceous sinter from Octopus Spring that contains a variety of poorly crystalline to amorphous silicate minerals. Calcite was detected readily in the travertine rock using any one of the techniques studied. The small amount of gypsum was uniquely identified using XRD, VNIR, and mid-IR, while the aragonite was uniquely identified using XRD and Raman. The siliceous sinter sample was more difficult to characterize using each of these techniques and a combination of all techniques was more useful than any single technique. Although XRD is the historical standard for mineral identification, it presents some challenges for remote investigations. Thermal properties are most useful for minerals with discrete thermal transitions. Raman spectroscopy is most effective for detecting polarized species such as CO 3, OH, and CH, and exhibits sharp bands for most highly crystalline minerals when abundant. Mid-IR spectroscopy is most useful in characterizing Si-O (and metal-O) bonds and also has the advantage that remote information about sample texture (e.g., particle size) can be determined. Mid-IR spectroscopy is also

  13. Hydrothermal activity on near-arc sections of back-arc ridges: Results from the Mariana Trough and Lau Basin

    NASA Astrophysics Data System (ADS)

    Baker, Edward T.; Massoth, Gary J.; Nakamura, Ko-Ichi; Embley, Robert W.; de Ronde, Cornel E. J.; Arculus, Richard J.

    2005-09-01

    The spatial density of hydrothermal venting is strongly correlated with spreading rate on mid-ocean ridges (with the interesting exception of hot spot-affected ridges), evidently because spreading rate is a reliable proxy for the magma budget. This correlation remains untested on spreading ridges in back-arc basins, where the magma budget may be complicated by subduction-induced variations of the melt supply. To address this uncertainty, we conducted hydrothermal plume surveys along slow-spreading (40-60 mm/yr) and arc-proximal (10-60 km distant) sections of the southern Mariana Trough and the Valu Fa Ridge (Lau Basin). On both sections we found multiple plumes overlying ˜15-20% of the total length of each section, a coverage comparable to mid-ocean ridges spreading at similar rates. These conditions contrast with earlier reported results from the two nearest-arc segments of a faster spreading (60-70 mm/yr) back-arc ridge, the East Scotia Ridge, which approaches no closer than 100 km to its arc. There, hydrothermal venting is relatively scarce (˜5% plume coverage) and the ridge characteristics are distinctly slow-spreading: small central volcanic highs bookended by deep median valleys, and axial melt lenses restricted to the volcanic highs. Two factors may contribute to an unexpectedly low hydrothermal budget on these East Scotia Ridge segments: they may lie too far from the adjacent arc to benefit from near-arc sources of melt supply, and subduction-aided migration of mantle from the Bouvet hot spot may reduce hydrothermal circulation by local crustal warming and thickening, analogous to the Reykjanes Ridge. Thus the pattern among these three ridge sections appears to mirror the larger global pattern defined by mid-ocean ridges: a well-defined trend of spreading rate versus hydrothermal activity on most ridge sections, plus a subset of ridge sections where unusual melt delivery conditions diminish the expected hydrothermal activity.

  14. Different TDM/CH4 hydrothermal plume signatures: TAG site at 26N and serpentinized ultrabasic diapir at 15 degrees 05'N on the Mid-Atlantic ridge

    SciTech Connect

    Charlou, J.L.; Bougault, H. ); Appriou, P. ); Nelsen, T.; Rona, P. )

    1991-11-01

    As a part of the 1988 NOAA VENTS Program, CH{sub 4} and Mn tracers were used to identify and compare hydrothermal plumes found above the TAG Field (26{degrees}N) and in the rift valley at 15{degrees}N close to the eastern intersection of the ridge axis with the 15{degrees}20'N Fracture Zone at the Mid-Atlantic Ridge (MAR). Active hydrothermal venting was confirmed at TAG, based on elevated concentrations of total dissolved Mn (TDM up to 30 nmol/kg), high CH{sub 4} concentrations (up to 200 nL/L), and elevated nephelometry signals. Plumes of a different composition were identified at 15{degree}N with high CH{sub 4} concentrations (up to 400 nL/L), low total dissolved Mn concentrations (TDM < 1 nmol/kg) and no significant nephelometry signal. The different properties of these tracers and the different tracer ratios can be used to deduce vent fluid characteristics and compare one hydrothermal area to another. TDM/CH{sub 4} and Nephel/CH{sub 4} ratios at TEG are of the same order of magnitude as those observed at other spreading axis hydrothermal fields. At 15{degrees}N, the low TDM/CH{sub 4} ratio provides evidence of fluid circulation into ultrabasic rocks and offers a potentially useful and single method of exploring for hydrothermal activity associated with serpentinization. Mantle degassing through hydrothermal activity associated with serpentinization is an important process with respect to chemical and thermal exchanges between the upper mantle and the ocean. Different ratios of hydrothermal tracers (i.e., TDM/CH{sub 4}) provide a useful framework for identifying subseafloor processes along mid-oceanic ridges.

  15. Early Solar System hydrothermal activity in chondritic asteroids on 1-10-year timescales.

    PubMed

    Dyl, Kathryn A; Bischoff, Addi; Ziegler, Karen; Young, Edward D; Wimmer, Karl; Bland, Phil A

    2012-11-01

    Chondritic meteorites are considered the most primitive remnants of planetesimals from the early Solar System. As undifferentiated objects, they also display widespread evidence of water-rock interaction on the parent body. Understanding this history has implications for the formation of planetary bodies, the delivery of water to the inner Solar System, and the formation of prebiotic molecules. The timescales of water-rock reactions in these early objects, however, are largely unknown. Here, we report evidence for short-lived water-rock reactions in the highly metamorphosed ordinary chondrite breccia Villalbeto de la Peña (L6). An exotic clast (d = 2cm) has coexisting variations in feldspar composition and oxygen isotope ratios that can only result from hydrothermal conditions. The profiles were modeled at T = 800 °C and P(H(2)O) = 1 bar using modified grain-boundary diffusion parameters for oxygen self-diffusion and reaction rates of NaSiCa(-1)Al(-1) exchange in a fumarole. The geochemical data are consistent with hydrothermal activity on the parent body lasting only 1-10 y. This result has wide-ranging implications for the geological history of chondritic asteroids.

  16. Early Solar System hydrothermal activity in chondritic asteroids on 1–10-year timescales

    PubMed Central

    Dyl, Kathryn A.; Bischoff, Addi; Ziegler, Karen; Young, Edward D.; Wimmer, Karl; Bland, Phil A.

    2012-01-01

    Chondritic meteorites are considered the most primitive remnants of planetesimals from the early Solar System. As undifferentiated objects, they also display widespread evidence of water–rock interaction on the parent body. Understanding this history has implications for the formation of planetary bodies, the delivery of water to the inner Solar System, and the formation of prebiotic molecules. The timescales of water–rock reactions in these early objects, however, are largely unknown. Here, we report evidence for short-lived water–rock reactions in the highly metamorphosed ordinary chondrite breccia Villalbeto de la Peña (L6). An exotic clast (d = 2cm) has coexisting variations in feldspar composition and oxygen isotope ratios that can only result from hydrothermal conditions. The profiles were modeled at T = 800 °C and P(H2O) = 1 bar using modified grain-boundary diffusion parameters for oxygen self-diffusion and reaction rates of NaSiCa-1Al-1 exchange in a fumarole. The geochemical data are consistent with hydrothermal activity on the parent body lasting only 1–10 y. This result has wide-ranging implications for the geological history of chondritic asteroids. PMID:23093668

  17. Bacteria dominate the ammonia-oxidizing community in a hydrothermal vent site at the Mid-Atlantic Ridge of the South Atlantic Ocean.

    PubMed

    Xu, Wei; Li, Meng; Ding, Jie-Fei; Gu, Ji-Dong; Luo, Zhu-Hua

    2014-09-01

    Ammonia oxidation is the first and rate-limiting step of nitrification, which is carried out by two groups of microorganisms: ammonia-oxidizing bacteria (AOB) and the recently discovered ammonia-oxidizing archaea (AOA). In this study, diversity and abundance of AOB and AOA were investigated in five rock samples from a deep-sea hydrothermal vent site at the Mid-Atlantic Ridge (MAR) of the South Atlantic Ocean. Both bacterial and archaeal ammonia monooxygenase subunit A (amoA) gene sequences obtained in this study were closely related to the sequences retrieved from deep-sea environments, indicating that AOB and AOA in this hydrothermal vent site showed typical deep ocean features. AOA were more diverse but less abundant than AOB. The ratios of AOA/AOB amoA gene abundance ranged from 1/3893 to 1/242 in all investigate samples, indicating that bacteria may be the major members responding to the aerobic ammonia oxidation in this hydrothermal vent site. Furthermore, diversity and abundance of AOA and AOB were significantly correlated with the contents of total nitrogen and total sulfur in investigated samples, suggesting that these two environmental factors exert strong influences on distribution of ammonia oxidizers in deep-sea hydrothermal vent environment.

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

    PubMed

    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. PMID:24126286

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

    PubMed Central

    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. PMID:24126286

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

    PubMed

    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.

  1. Near-bottom water column anomalies associated with active hydrothermal venting at Aeolian arc volcanoes, Tyrrhenian Sea, Italy

    NASA Astrophysics Data System (ADS)

    Walker, S. L.; Carey, S.; Bell, K. L.; Baker, E. T.; Faure, K.; Rosi, M.; Marani, M.; Nomikou, P.

    2012-12-01

    several active sites along the 50-km-long summit. The distribution of ORP anomalies seen during these dives correlates quite well with the locations of anomalous helium samples from 2007. An ORP anomaly of -160 mv was located at the west end of Palinuro where vent fluids up to 54°C were found. Living tubeworms, bacterial mats of various colors and textures, and small chimneys and globular spires coated with iron oxide having bright-green interiors indicative of the iron-rich hydrothermal clay nontronite were found at actively venting areas on Palinuro. ORP anomalies were generally only detected in the near-bottom MAPR mounted on Hercules. In a few locations the MAPRs on Argus (10-30 meters above bottom) and 25 meters above Argus registered anomalies not seen by the MAPR on Hercules indicating active venting nearby, but not observed along the trackline of the ROV. Only the higher-temperature vent site at the west end of Palinuro generated a plume that had an appreciable particle anomaly and rise height (seen by the Argus+25m MAPR). No anomalies were measured by the MAPR located 50 meters above Argus.

  2. Fluids in early stage hydrothermal alteration of high-sulfidation epithermal systems: A view from the Vulcano active hydrothermal system (Aeolian Island, Italy)

    NASA Astrophysics Data System (ADS)

    Boyce, Adrian J.; Fulignati, Paolo; Sbrana, Alessandro; Fallick, Anthony E.

    2007-10-01

    High-sulfidation (HS) epithermal systems have elements in common with passively degassing volcanoes associated with high T, acid fumarole fields or acid crater lakes. They are considered to form in two stages, the first of which involves advanced argillic alteration resulting from intense, strongly acidic fluid-rock interaction. The La Fossa hydrothermal system (Vulcano Island) represents a classic example of such an active HS system and can be considered as a modern analogue of this early stage of alteration, resulting in a core of intense silicic (90-95% pure SiO 2) alteration surrounded by alunitic alteration zones. This paper focuses on a geochemical and stable isotope study of the surficial alteration facies of Vulcano - particularly the horizon characterized by strong silicic alteration - and on deep seated xenoliths ejected during the last eruption of La Fossa volcano (1888-90) that can be considered as representative of fragments of the deep conduit system of La Fossa volcano. Using directly measured temperatures at the sites of sampling, we have calculated fluid composition in isotopic equilibrium with the alteration products. The large range of measured silica δ18O (12.3 to 29‰) reflects the wide range of formation temperatures (80-240 °C). The fluid compositions calculated for intense silicic alteration vary from - 0.9 to + 6.5‰. These are significantly heavier than local meteoric water (- 6‰), and are consistent with derivation from the condensation of high-temperature fumarolic gases, dominated by magmatic fluids and rich in acid gases (SO 2, H 2S, HCl, HF), into shallow groundwaters of meteoric origin, with dynamically variable ratios of fumarolic steam/meteoric water. The calculated δ18O and δD of water in equilibrium with alunite also suggest the mixing of magmatic and meteoric waters for the fluids involved in the genesis of advanced argillic alteration facies. The calculated δ18O of water in equilibrium with hedenbergitic clinopyroxene

  3. Submarine Hydrothermal Sites in Arc Volcanic-Back Arc Environment: Insight from Recent Marine Geophysical Investigations in the Southern Tyrrhenian Sea.

    NASA Astrophysics Data System (ADS)

    Cocchi, L.; Ligi, M.; Bortoluzzi, G.; Petersen, S.; Plunkett, S.; Muccini, F.; Canese, S.; Caratori Tontini, F.; Carmisciano, C.

    2014-12-01

    Hydrothermal alteration processes involve mineralogical and chemical changes, which are reflected in a major modification of potential field patterns observed over hydrothermal areas. Basalt-hosted hydrothermal sites exhibit characteristic responses with magnetic lows and minima of the gravity field. Near bottom AUV (Autonomous Underwater Vehicle) based potential field surveys have become a very effective technique in deep sea exploration. Here we present results of recent ship-borne and near seafloor magnetic and gravity investigations at deep (Marsili and Palinuro seamounts) and shallow (Panarea, Basiluzzo and Secca del Capo) hydrothermal sites in the Southern Tyrrhenian Sea including multibeam bathymetry, seafloor reflectivity and seismic profiles. At Marsili seamount, a large Fe-Mn-oxyhydroxides-rich chimney field is located at the summit (500 m depth). This site is correlated with pronounced magnetic and gravity lows (0 A/m and 2.0 g/cm3). Deep tow magnetic survey (Cruise MAVA11) revealed strong association between the complicated magnetization pattern and the main volcano-tectonic features of the ridge. Hydrothermal manifestations at Palinuro seamount occur mainly on the western sector within the rim of a caldera structure at depth of 600m. Recent AUV based magnetic surveys (Cruise POS442, 2012 using AUV "Abyss") detailed a magnetization low interpreted to represent the local distribution of subseafloor hydrothermal alteration (potentially massive sulfide deposits), and also mapped previously undiscovered inactive chimney fields. Hydrothermal sites observed at the arc-related volcanic islands (Panarea, Basiluzzo, Eolo and Secca del Capo) are confined to shallow depths (less then 300m) and associated with large ochreaceous mounds, vents and chimney fields such as those observed E of Basiluzzo Island. At this site a recent magnetic survey (Cruise PANA13_ASTREA) combined with Remote Operated Vehicle (ROV) investigations revealed that the submarine geothermal

  4. Using in situ voltammetry as a tool to identify and characterize habitats of iron-oxidizing bacteria: from fresh water wetlands to hydrothermal vent sites.

    PubMed

    MacDonald, Daniel J; Findlay, Alyssa J; McAllister, Sean M; Barnett, Josh M; Hredzak-Showalter, Patricia; Krepski, Sean T; Cone, Shane G; Scott, Jarrod; Bennett, Sarah K; Chan, Clara S; Emerson, David; Luther Iii, George W

    2014-09-20

    Iron-oxidizing bacteria (FeOB) likely play a large role in the biogeochemistry of iron, making the detection and understanding of the biogeochemical processes FeOB are involved in of critical importance. By deploying our in situ voltammetry system, we are able to measure a variety of redox species, specifically Fe(ii) and O2, simultaneously. This technique provides significant advantages in both characterizing the environments in which microaerophilic FeOB are found, and finding diverse conditions in which FeOB could potentially thrive. Described here are four environments with different salinities [one fresh groundwater seep site, one beach-groundwater mixing site, one hydrothermal vent site (Mid-Atlantic Ridge), and one estuary (Chesapeake Bay)] where in situ voltammetry was deployed, and where the presence of FeOB were confirmed by either culturing methods or molecular data. The sites varied in both O2 and Fe(ii) content with O2 ranging from below the 3 μM detection limit of the electrodes at the Chesapeake Bay suboxic zone, to as high 150 μM O2 at the vent site. In addition, a range of Fe(ii) concentrations supported FeOB communities, from 3 μM Fe(ii) in the Chesapeake Bay to 300 μM in the beach aquifer. In situ electrochemistry provides the means to quickly measure these redox gradients at appropriate resolution, making it possible in real time to detect niches likely inhabited by microaerophilic FeOB, then accurately sample for proof of FeOB presence and activity. This study demonstrates the utility of this approach while also greatly expanding our knowledge of FeOB habitats. PMID:24924809

  5. Using in situ voltammetry as a tool to identify and characterize habitats of iron-oxidizing bacteria: from fresh water wetlands to hydrothermal vent sites.

    PubMed

    MacDonald, Daniel J; Findlay, Alyssa J; McAllister, Sean M; Barnett, Josh M; Hredzak-Showalter, Patricia; Krepski, Sean T; Cone, Shane G; Scott, Jarrod; Bennett, Sarah K; Chan, Clara S; Emerson, David; Luther Iii, George W

    2014-09-20

    Iron-oxidizing bacteria (FeOB) likely play a large role in the biogeochemistry of iron, making the detection and understanding of the biogeochemical processes FeOB are involved in of critical importance. By deploying our in situ voltammetry system, we are able to measure a variety of redox species, specifically Fe(ii) and O2, simultaneously. This technique provides significant advantages in both characterizing the environments in which microaerophilic FeOB are found, and finding diverse conditions in which FeOB could potentially thrive. Described here are four environments with different salinities [one fresh groundwater seep site, one beach-groundwater mixing site, one hydrothermal vent site (Mid-Atlantic Ridge), and one estuary (Chesapeake Bay)] where in situ voltammetry was deployed, and where the presence of FeOB were confirmed by either culturing methods or molecular data. The sites varied in both O2 and Fe(ii) content with O2 ranging from below the 3 μM detection limit of the electrodes at the Chesapeake Bay suboxic zone, to as high 150 μM O2 at the vent site. In addition, a range of Fe(ii) concentrations supported FeOB communities, from 3 μM Fe(ii) in the Chesapeake Bay to 300 μM in the beach aquifer. In situ electrochemistry provides the means to quickly measure these redox gradients at appropriate resolution, making it possible in real time to detect niches likely inhabited by microaerophilic FeOB, then accurately sample for proof of FeOB presence and activity. This study demonstrates the utility of this approach while also greatly expanding our knowledge of FeOB habitats.

  6. Geochemical constraints on the diversity and activity of H2 -oxidizing microorganisms in diffuse hydrothermal fluids from a basalt- and an ultramafic-hosted vent.

    PubMed

    Perner, Mirjam; Petersen, Jillian M; Zielinski, Frank; Gennerich, Hans-Hermann; Seifert, Richard

    2010-10-01

    Mixing processes of reduced hydrothermal fluids with oxygenated seawater and fluid-rock reactions contribute to the chemical signatures of diffuse venting and likely determine the geochemical constraints on microbial life. We examined the influence of fluid chemistry on microbial diversity and activity by sampling diffuse fluids emanating through mussel beds at two contrasting hydrothermal vents. The H(2) concentration was very low at the basalt-hosted Clueless site, and mixing models suggest O(2) availability throughout much of the habitat. In contrast, effluents from the ultramafic-hosted Quest site were considerably enriched in H(2) , while O(2) is likely limited to the mussel layer. Only two different hydrogenase genes were identified in clone libraries from the H(2) -poor Clueless fluids, but these fluids exhibited the highest H(2) uptake rates in H(2) -spiked incubations (oxic conditions, at 18 °C). In contrast, a phylogenetically diverse H(2) -oxidizing potential was associated with distinct thermal conditions in the H(2) -rich Quest fluids, but under oxic conditions, H(2) uptake rates were extremely low. Significant stimulation of CO(2) fixation rates by H(2) addition was solely illustrated in Quest incubations (P-value <0.02), but only in conjunction with anoxic conditions (at 18 °C). We conclude that the factors contributing toward differences in the diversity and activity of H(2) oxidizers at these sites include H(2) and O(2) availability.

  7. Fluid Geochemistry of the Capelinhos Vent Site. A Key to Understand the Lucky Strike Hydrothermal Vent Field (37°N, MAR).

    NASA Astrophysics Data System (ADS)

    Leleu, T.; Chavagnac, V.; Cannat, M.; Ceuleneer, G.; Castillo, A.; Menjot, L.

    2015-12-01

    The Lucky Strike hydrothermal field is situated at the mid-Atlantic ridge, south of the Azores, on top of a central volcano within the axial valley. The volcano is composed of a fossil lava lake surrounded by three volcanic cones. An Axial Magma Chamber (AMC) is reported 3.4km below the seafloor. The active venting sites are situated around the fossil lava lake and are directly linked to the heat supplied by the AMC. High temperature fluids from the Lucky Strike field were sampled in 2013, 2014 and 2015 in order to document the depth of the reaction zone, subsurface mixing, geographical control and magmatic degassing. A new active site named Capelinhos was discovered approximately 1.5km eastward from the lava lake, during exploration by ROV Victor6000 - MoMARsat cruise, 2013. It is composed of 10m-high chimneys discharging black smoker-type fluid. Fluid temperatures were 328°C in 2013 and decreased to 318°C in 2014 and 2015. Capelinhos fluids are Cl-depleted by 55% compared to seawater indicating phase separation at depth. In comparison, the other sites range from 6% enrichment (2608/Y3 site) to 22% depletion (Eiffel tower site). Si geothermobarometry of Y3 site estimates quartz equilibration at P=300 bars and T=360-380°C, coherent with Fe/Mn geothermometer (T=370±10°C). For Capelinhos, Fe/Mn suggests 398°C (±10°C) which is close to the critical point of seawater (P=300 bars and T=407°C). Other geothermobarometer uses Si/Cl vapor-like fluid to constrain depth of the top of reaction zone and predicts significant bias due to mixing along the up-flow zone. Application gives P=~370 bars, T=~435°C at Capelinhos and P=~390 bars, T=~440°C at Eiffel tower. This is further sustained by end-member 87Sr/86Sr=0.7038, which indicates little interaction of Capelinhos vent fluids with seawater-derived fluid, compared to other vapor-like sites with 87Sr/86Sr=0.7043. Because of its external location, Capelinhos site isn't influenced by the complex tectonic context of the

  8. Enhanced East Pacific Rise hydrothermal activity during the last two glacial terminations

    NASA Astrophysics Data System (ADS)

    Lund, D. C.; Asimow, P. D.; Farley, K. A.; Rooney, T. O.; Seeley, E.; Jackson, E. W.; Durham, Z. M.

    2016-01-01

    Mid-ocean ridge magmatism is driven by seafloor spreading and decompression melting of the upper mantle. Melt production is apparently modulated by glacial-interglacial changes in sea level, raising the possibility that magmatic flux acts as a negative feedback on ice-sheet size. The timing of melt variability is poorly constrained, however, precluding a clear link between ridge magmatism and Pleistocene climate transitions. Here we present well-dated sedimentary records from the East Pacific Rise that show evidence of enhanced hydrothermal activity during the last two glacial terminations. We suggest that glacial maxima and lowering of sea level caused anomalous melting in the upper mantle and that the subsequent magmatic anomalies promoted deglaciation through the release of mantle heat and carbon at mid-ocean ridges.

  9. ESR dating of barite in sulphide deposits formed by the sea-floor hydrothermal activities.

    PubMed

    Toyoda, Shin; Fujiwara, Taisei; Uchida, Ai; Ishibashi, Jun-ichiro; Nakai, Shun'ichi; Takamasa, Asako

    2014-06-01

    Barite is a mineral newly found to be practically useful for electron spin resonance (ESR) dating of sulphide deposits formed by the sea-floor hydrothermal activities. The recent studies for the properties of the ESR dating signal in barite are summarised in the present paper as well as the formulas for corrections for accurate dose-rate estimation are developed including the dose-rate conversion factors, shape correction for gamma-ray dose and decay of (226)Ra. Although development of the techniques for ESR dating of barite has been completed, further comparative studies with other dating techniques such as U-Th and (226)Ra-(210)Pb dating are necessary for the technique to be widely used.

  10. 30,000 years of hydrothermal activity at the lost city vent field.

    PubMed

    Früh-Green, Gretchen L; Kelley, Deborah S; Bernasconi, Stefano M; Karson, Jeffrey A; Ludwig, Kristin A; Butterfield, David A; Boschi, Chiara; Proskurowski, Giora

    2003-07-25

    Strontium, carbon, and oxygen isotope data and radiocarbon ages document at least 30,000 years of hydrothermal activity driven by serpentinization reactions at Lost City. Serpentinization beneath this off-axis field is estimated to occur at a minimum rate of 1.2 x 10(-4) cubic kilometers per year. The access of seawater to relatively cool, fresh peridotite, coupled with faulting, volumetric expansion, and mass wasting processes, are crucial to sustain such systems. The amount of heat produced by serpentinization of peridotite massifs, typical of slow and ultraslow spreading environments, has the potential to drive Lost City-type systems for hundreds of thousands, possibly millions, of years. PMID:12881565

  11. Enhanced East Pacific Rise hydrothermal activity during the last two glacial terminations.

    PubMed

    Lund, D C; Asimow, P D; Farley, K A; Rooney, T O; Seeley, E; Jackson, E W; Durham, Z M

    2016-01-29

    Mid-ocean ridge magmatism is driven by seafloor spreading and decompression melting of the upper mantle. Melt production is apparently modulated by glacial-interglacial changes in sea level, raising the possibility that magmatic flux acts as a negative feedback on ice-sheet size. The timing of melt variability is poorly constrained, however, precluding a clear link between ridge magmatism and Pleistocene climate transitions. Here we present well-dated sedimentary records from the East Pacific Rise that show evidence of enhanced hydrothermal activity during the last two glacial terminations. We suggest that glacial maxima and lowering of sea level caused anomalous melting in the upper mantle and that the subsequent magmatic anomalies promoted deglaciation through the release of mantle heat and carbon at mid-ocean ridges. PMID:26823422

  12. Dramatic activity of mixed-phase TiO2 photocatalyst synthesized by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Li, Huiquan; Xu, Bolian; Fan, Yining

    2013-02-01

    The mixed-phase TiO2 photocatalysts with different anatase/rutile/brookite ratios and high specific surface area (157-218 m2/g) were prepared by hydrothermal method at 100 °C and the effect of rutile content in TiO2 on the BET surface area, light absorption and separation efficiency of photogenerated charge carriers was studied and correlated to the photocatalytic activity of TiO2. Rutile content increased from 0% to 100% by increasing the amount of TiCl4 in aqueous phase and the initial pH value of reaction solution played an important role in the phase composition of TiO2. The photocatalytic mechanism of mixed-phase TiO2 was discussed.

  13. Synthesis of pyrite FeS2 nanorods by simple hydrothermal method and its photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Morales-Gallardo, M. V.; Ayala, A. M.; Pal, Mou; Cortes Jacome, M. A.; Toledo Antonio, J. A.; Mathews, N. R.

    2016-09-01

    In this work, FeS2 nanorods were synthetized by hydrothermal method. The advantages of our process were the high yield, simplicity and reproducibility. The material was studied in detail using different experimental tools such as XRD, SEM, HRTEM, EDXS, XPS, Raman, and UV-vis reflectance. XRD pattern and Raman data revealed good crystalline quality for the as synthesized pyrite FeS2. SEM analysis displayed the rod-like morphologies of FeS2 which seemed to grow radially from a center giving a flower-like appearance. From TEM images the approximate length and diameter of nano-rods were determined as 275 and 15 nm respectively. The material showed excellent photocatalytic activity which was assessed from the degradation of the methlyene blue.

  14. Amino acids assisted hydrothermal synthesis of hierarchically structured ZnO with enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Guo, Yanxia; Lin, Siwen; Li, Xuan; Liu, Yuping

    2016-10-01

    Novel hierarchically structured ZnO, including rose-like, dandelion-like and flower-like, have been synthesized through a simple hydrothermal process using different amino acids (glutamine, histidine and glycine) as structure-directing agents and urea as deposition agent, followed by subsequent calcination. Amino acids played a crucial role in the formation of hierarchically structured ZnO, and different amino acids could induce different exquisite shapes and assembly ways, as well as more oxygen defects. The prepared hierarchically structured ZnO exhibited excellent photocatalytic activities for the photodegradation of Rhodamine B, which was associated with their special hierarchical structures, large BET surface area and the existence of more oxygen defects. Amino acid-assisted growth mechanism of hierarchically structured ZnO was also discussed.

  15. Enhanced East Pacific Rise hydrothermal activity during the last two glacial terminations.

    PubMed

    Lund, D C; Asimow, P D; Farley, K A; Rooney, T O; Seeley, E; Jackson, E W; Durham, Z M

    2016-01-29

    Mid-ocean ridge magmatism is driven by seafloor spreading and decompression melting of the upper mantle. Melt production is apparently modulated by glacial-interglacial changes in sea level, raising the possibility that magmatic flux acts as a negative feedback on ice-sheet size. The timing of melt variability is poorly constrained, however, precluding a clear link between ridge magmatism and Pleistocene climate transitions. Here we present well-dated sedimentary records from the East Pacific Rise that show evidence of enhanced hydrothermal activity during the last two glacial terminations. We suggest that glacial maxima and lowering of sea level caused anomalous melting in the upper mantle and that the subsequent magmatic anomalies promoted deglaciation through the release of mantle heat and carbon at mid-ocean ridges.

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

    NASA Astrophysics Data System (ADS)

    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

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

    USGS Publications Warehouse

    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

  18. Differential gene expression in the mussel Bathymodiolus azoricus from the Menez Gwen and Lucky Strike deep-sea hydrothermal vent sites

    NASA Astrophysics Data System (ADS)

    Bettencourt, R.; Rodrigues, M. I.; Barros, I.; Cerqueira, T.; Freitas, C.; Costa, V.; Pinheiro, M.; Egas, C.; Santos, R. S.

    2013-02-01

    The deep-sea hydrothermal vent mussel Bathymodiolus azoricus is a symbiont bearing bivalve that is found in great abundance at the Menez Gwen and Lucky Strike vent sites and in close vicinity off the Azores region near the Mid-Atlantic Ridge (MAR). The distinct relationships that vent mussels have developed with their physical and chemical environments are likely reflected in global gene expression profiles providing thus a means to distinguish geographically distinct vent mussels on the basis of gene expression studies, fluorescence in situ hybridization (FISH) experiments and 16S rRNA amplicon sequencing, to assess the natural expression of bacterial genes and vent mussel immune genes and the constitutive distribution and relative abundance of endosymbiotic bacteria within gill tissues. Our results confirmed the presence of methanotroph-related endosymbionts in Menez Gwen vent mussels whereas Lucky Strike specimens seem to harbor a different bacterial morphotype when a methane monooxygenase gene specific probe was used. No qualitative differences could be visualized between Menez Gwen and Lucky Strike individuals when tested with sulfur-oxidizing-related nucleic-acid probe. Quantitative PCR (qPCR) studies revealed varied gene expression profiles in both Menez Gwen and Lucky Strike mussel gill tissues for the immune genes selected. Genes encoding transcription factors presented noticeably low levels of fold expression whether in MG or LS animals whereas the genes encoding effector molecules appeared to have higher levels expression in MG gill tissues. The peptidoglycan recognition molecule, encoding gene, PGRP presented the highest level of transcriptional activity among the genes analyzed in MG gill tissues, seconded by carcinolectin and thus denoting the relevance of immune recognition molecules in early stage of the immune responses onset. Genes regarded as encoding molecules involved in signaling pathways were consistently expressed in both MG and LS gill

  19. Topographic control of a dispersing hydrothermal plume

    NASA Astrophysics Data System (ADS)

    German, C. R.; Richards, K. J.; Rudnicki, M. D.; Lam, M. M.; Charlou, J. L.; Flame Scientific Party

    1998-03-01

    Deep-sea hydrothermal vents represent a major source of heat and chemicals to the oceans and support endemic chemosynthetic biological communities. To fully understand the impact of hydrothermal activity upon the oceans, however, requires investigation of both the physical and the biogeochemical processes which are active in hydrothermal plumes and which serve to determine the net hydrothermal flux to the oceans. We have recently conducted a detailed multidisciplinary study of the lateral dispersion of the hydrothermal plume emitted from the Rainbow vent site near 36°15'N, Mid-Atlantic Ridge. Combining velocity measurements from a lowered ADCP, optical back scatter measurements from a deep-tow CTD and methane measurements from bottle samples we are able, for the first time in the Atlantic, to trace a neutrally buoyant plume for a distance of over 50 km. The path of the plume is seen to be heavily controlled by the local topography with a general northeast movement of water. Both particle and methane concentrations decrease downstream over the length of the observed plume. The dataset provides an excellent opportunity to study the mixing and biogeochemical processes active in a hydrothermal plume and estimate fluxes of biogeochemical constituents.

  20. METEORIC-HYDROTHERMAL SYSTEMS.

    USGS Publications Warehouse

    Criss, Robert E.; Taylor, Hugh P.

    1986-01-01

    This paper summarizes the salient characteristics of meteoric-hydrothermal systems, emphasing the isotopic systematics. Discussions of permeable-medium fluid dynamics and the geology and geochemistry of modern geothermal systems are also provided, because they are essential to any understanding of hydrothermal circulation. The main focus of the paper is on regions of ancient meteoric-hydrothermal activity, which give us information about the presently inaccessible, deep-level parts of modern geothermal systems. It is shown oxygen and hydrogen isotopes provide a powerful method to discover and map fossil hydrothermal systems and to investigate diverse associated aspects of rock alteration and ore deposition.

  1. Fine-scale heat flow, shallow heat sources, and decoupled circulation systems at two sea-floor hydrothermal sites, Middle Valley, northern Juan de Fuca Ridge

    SciTech Connect

    Stein, J.S.; Fisher, A.T.; Langseth, M.; Jin, W.; Iturrino, G.; Davis, E.

    1998-12-01

    Fine-scale heat-flow patterns at two areas of active venting in Middle Valley, a sedimented rift on the northern Juan de Fuca Ridge, provide thermal evidence of shallow hydrothermal reservoirs beneath the vent fields. The extreme variability of heat flow is explained by conductive heating immediately adjacent to vents and shallow circulation within sediments above the reservoir. This secondary circulation is hydrologically separated from the deeper system feeding the vents by a shallow conductive lid within the sediments. A similar separation of shallow and deep circulation may also occur at sediment-free ridge-crest hydrothermal environments.

  2. Preliminary results of trace elements mobility in soils and plants from the active hydrothermal area of Nisyros island (Greece)

    NASA Astrophysics Data System (ADS)

    Daskalopoulou, Kyriaki; Calabrese, Sergio; Milazzo, Silvia; Brusca, Lorenzo; D'Alessandro, Walter; Kyriakopoulos, Konstantinos; Tassi, Franco; Parello, Francesco

    2014-05-01

    Trace elements, i.e. chemical constituents of rocks with concentration <1000 ppm, play a structural role in the organisms and use proteins as a carrier to their target site. Their toxicity depends on their concentration, speciation and reactions with other elements. In volcanic environments, significant amounts of trace elements discharged from gas emissions, contribute to produce air particulate. Nisyros Island is a stratovolcano located at the South Aegean active Volcanic Arc. Intense hydrothermal activity characterise the Lakki caldera. In particular, the fumaroles located in the craters of Stefanos, Kaminakia, Lofos Dome and the area comprising Phlegeton, Polyvotes Micros and Polyvotes Megalos discharge hydrothermal fluids rich in H2O (91- 99%), SO2 and H2S. Their temperatures are almost 100o C and H2S is highly abundant accounting for 8-26 % of the released dry gas phase. On June 2013, during a multidisciplinary field trip on Nisyros island, 39 samples of top soils and 31 of endemic plants (Cistus Creticus and Salvifolius and Erica Arborea and Manipuliflora) were collected in the caldera area, with the aim to investigate the distribution of concentrations of trace elements related to the contribution of deep originated fluids. Moreover, one sample of plant and soil was collected outside the caldera as local background, for comparison. All the soil samples were powdered avoiding metal contamination and they were extracted twice, using HNO3 + HCl for one extraction (closed microwave digestion) and ultrapure de- ionized water for the other one (leaching extraction). The leaves of plants were gently isolated, dried and powdered for acid microwave extraction (HNO3 + H2O2). All the solutions were analysed for major and trace elements contents by using ionic chromatography (IC) and inductively plasma spectrometry (ICP-MS and ICP-OES). The preliminary results showed high enrichment of many trace elements both in plant and soils respect to the local background, in

  3. Age, Episodicity and Migration of Hydrothermal Activity within the Axial Valley, Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Jamieson, J. W.; Hannington, M. D.; Kelley, D. S.; Clague, D. A.; Holden, J. F.; Tivey, M. K.; Delaney, J. R.

    2011-12-01

    Hydrothermal sulfide deposits record the history of high-temperature venting along the Endeavour Segment. Active venting is currently located within five discreet vent fields, with minor diffuse venting occurring between the fields. However, inactive and/or extinct sulfide structures are found throughout the entire axial valley of the ridge segment, suggesting that hydrothermal activity has been more vigorous in the past or focused venting has migrated with time. Here, we present age constraints from U-series dating of 44 sulfide samples collected by manned submersible from between the Mothra Field in the south to Sasquatch in the north. Samples are dated using 226Ra/Ba ratios from hydrothermal barite that precipitates along with the sulfide minerals. Most samples have been collected from within or near the active vent fields. Fifteen samples from the Main Endeavour Field (MEF) show a spectrum of ages from present to 2,430 years old, indicating that this field has been continuously active for at least ~2,400 years. MEF appears to be oldest currently active field. This minimum value for the age of hydrothermal activity also provides a minimum age of the axial valley itself. Ages from thirteen samples from the High-Rise Field indicate continuous venting for at least the past ~1,250 years. These age data are used in conjunction with age constraints of the volcanic flows to develop an integrated volcanic, hydrothermal and tectonic history of the Endeavour Segment. The total volume of hydrothermal sulfide within the axial valley, determined from high-resolution bathymetry, is used in conjunction with the age constraints of the sulfide material to determine the mass accumulation rates of sulfide along the Endeavour Segment. These data can be used to calibrate the efficiency of sulfide deposition from the hydrothermal vents, and provide a time-integrated history of heat, fluid and chemical fluxes at the ridge-segment scale. The comparison of time-integrated rates with

  4. NeMO-Net: A System for Near Real-Time Remote Sensing of Hydrothermal and Biological Activity in the Caldera of an Active Submarine Volcano

    NASA Astrophysics Data System (ADS)

    Hammond, S. R.; Butterfield, D.; Embley, R. W.; Meinig, C.; Stalin, S.

    2001-12-01

    In July of 2000, a camera and three temperature sensors were placed on the seafloor near a hydrothermal vent located in the caldera of an active submarine volcano. The volcano's summit lies at a depth of about 1500 m and is located at 46° N, 130° W, approximately 250 nautical miles off the Oregon coast. The volcano is the site of a long-term interdisciplinary study focused in part on discovering relationships between submarine volcanic and hydrothermal activity and a microbial biosphere which exists beneath the sea floor within the volcano's summit caldera. NeMO-Net utilizes an acoustic modem to communicate with a surface mooring anchored nearby. The mooring, in turn, is linked from the ocean surface to the Pacific Marine Environmental Laboratory by means of satellite systems. A unique feature of NeMO-Net is that it enables shore-based investigators to interrogate and command the system to perform specific tasks, the results of which are then reported back typically within several minutes . In the initial year-long deployment, photographic images, along with hourly readings from the three temperature probes, were available on a website which was updated every 24 hours. During the year, the camera documented a dynamic vent biological community as well as water temperature variations due to the influence of tides, and possibly with changing vent fluid temperatures The NeMO-Net system is under continuing development with particular emphasis on linking it to multiple sea floor instruments including near-real-time chemical and water samplers. Near-future plans also call for NeMO Net to be linked to a resident sea floor AUV.

  5. Three-dimensional sea-urchin-like hierarchical TiO{sub 2} microspheres synthesized by a one-pot hydrothermal method and their enhanced photocatalytic activity

    SciTech Connect

    Zhou, Yi; Huang, Yan; Li, Dang; He, Wenhong

    2013-07-15

    Graphical abstract: SEM images of the samples synthesized at different hydrothermal temperatures for 8 h: (a) 75; (b) 100; (c) 120; and (d) 140°C, followed by calcination at 450 °C for 2 h. Highlights: ► Effects of calcination temperature on the phase transformation were studied. ► Effects of hydrothermal temperature and time on the morphology growth were studied. ► A two-stage reaction mechanism for the formation was presented. ► The photocatalytic activity was evaluated under sunlight irradiation. ► Effects of calcination temperature on the photocatalytic activity were studied. - Abstract: Novel three-dimensional sea-urchin-like hierarchical TiO{sub 2} superstructures were synthesized on a Ti plate in a mixture of H{sub 2}O{sub 2} and NaOH aqueous solution by a facile one-pot hydrothermal method at a low temperature, followed by protonation and calcination. The results of series of electron microscopy characterizations suggested that the hierarchical TiO{sub 2} superstructures consisted of numerous one-dimensional nanostructures. The microspheres were approximately 2–4 μm in diameter, and the one-dimensional TiO{sub 2} nanostructures were up to 600–700 nm long. A two-stage reaction mechanism, i.e., initial growth and then assembly, was proposed for the formation of these architectures. The three-dimensional sea-urchin-like hierarchical TiO{sub 2} microstructures showed excellent photocatalytic activity for the degradation of Rhodamine B aqueous solution under sunlight irradiation, which was attributed to the special three-dimensional hierarchical superstructure, and increased number of surface active sites. This novel superstructure has promising use in practical aqueous purification.

  6. Cinnabar, arsenian pyrite and thallium-enrichment in active shallow submarine hydrothermal vents at Paleochori Bay, Milos Island, Greece

    NASA Astrophysics Data System (ADS)

    Kati, Marianna; Voudouris, Panagiotis; Valsami-Jones, Eugenia; Magganas, Andreas; Baltatzis, Emmanouil; Kanellopoulos, Christos; Mavrogonatos, Constantinos

    2015-04-01

    We herein report the discovery of active cinnabar-depositing hydrothermal vents in a submarine setting at Paleochori Bay, within the offshore southeastern extension of the Milos Island Geothermal Field, South Aegean Active Volcanic Arc. Active, low temperature (up to 115 °C) hydrothermal venting through volcaniclastic material has led to a varied assemblage of sulfide and alteration mineral phases in an area of approximately 1 km2. Our samples recovered from Paleochori Bay are hydrothermal edifices composed of volcaniclastic detrital material cemented by pyrite, or pure sulfide (mainly massive pyrite) mounts. Besides pyrite and minor marcasite, the hydrothermal minerals include cinnabar, amorphous silica, hydrous ferric oxides, carbonates (aragonite and calcite), alunite-jarosite solid solution and Sr-rich barite. Among others, growth textures, sieve-textured pyrite associated with barite, alunite-jarosite solid solution and hydrous ferric oxides rims colloform-banded pyrite layers. Overgrowths of arsenian pyrite layers (up to 3.2 wt. % As and/or up to 1.1 wt. % Mn) onto As-free pyrite indicate fluctuation in As content of the hydrothermal fluid. Mercury, in the form of cinnabar, occurs in up to 5 μm grains within arsenian pyrite layers, usually forming distinct cinnabar-enriched micro-layers. Hydrothermal Sr-rich barite (barite-celestine solid solution), pseudocubic alunite-jarosite solid solution and Mn- and Sr-enriched carbonates occur in various amounts and closely associated with pyrite and/or hydrous ferric oxides. Thallium-bearing sulfides and/or sulfosalts were not detected during our study; however, hydrous ferric oxides show thallium content of up to 0.5 wt. % Tl. The following scenarios may have played a role in pyrite precipitation at Paleochori: (a) H2S originally dissolved in the deep fluid but separated upon boiling could have reacted with oxygenated seawater under production of sulphuric acid, thus causing leaching and dissolution of primary iron

  7. Molecular Diversity and Activity of Methanogens in the Subseafloor at Deep-Sea Hydrothermal Vents of the Pacific Ocean (Invited)

    NASA Astrophysics Data System (ADS)

    Huber, J. A.; Merkel, A.; Holden, J. F.; Lilley, M. D.; Butterfield, D. A.

    2009-12-01

    Methanogenesis is thought to represent one of the most ancient metabolic pathways on Earth, and methanogens may serve as important primary producers in warm crustal habitats at deep-sea hydrothermal vents. Many of these obligate chemolithoautotrophs depend solely on geochemically-derived energy and carbon sources and grow at high temperatures under strictly anaerobic conditions. A combined geochemical and microbiological approach was used to determine the distribution and molecular diversity of methanogens in low temperature diffuse vent fluids from the Endeavour Segment R2K ISS site, as well as Axial Seamount and volcanoes of the Mariana Arc. Geochemical data from hot and adjacent warm diffuse vent fluids provided chemical indicators to guide sample selection for detailed polymerase chain reaction (PCR)-based analysis of the key enzyme for methane formation, methyl-coenzyme M reductase (mcrA), as well as archaeal 16S rRNA genes. At most Endeavour vent sites, hydrogen concentrations were too low to support hydrogenotrophic methanogensis directly and only one diffuse site, Easter Island, had a positive signal for the mcrA gene. These sequences were most closely related to members of the order Methanococcales, as well as anaerobic methane oxidizers (ANME-1). The presence of ANME, which are rarely found in non-sedimented marine environments, is another line of evidence supporting the occurrence of buried sediments at Endeavour. At Axial, a number of diffuse vents have strong chemical indicators of methanogenesis. Methanogenic communities were detected at 3 sites on the southeast side of the caldera: the northern end of the 1998 lava flow, the International District, and on the pre-1987 lava flow. Time series work at Marker 113 showed that in 4 different years over the last 6 years methanogenic communities are active and abundant, suggesting a stable anaerobic, warm subseafloor habitat. Results show that members of the order Methanococcales dominate at this site

  8. Hydrothermal Processing

    SciTech Connect

    Elliott, Douglas C.

    2011-03-11

    This chapter is a contribution to a book on Thermochemical Conversion of Biomass being edited by Prof. Robert Brown of Iowa State University. It describes both hydrothermal liquefaction and hydrothermal gasification of biomass to fuels.

  9. Hydrothermal synthesis of ZTO/graphene nanocomposite with excellent photocatalytic activity under visible light irradiation.

    PubMed

    Ben Ali, Monaam; Yolcu, Haci Hasan; Elhouichet, Habib; Sieber, Brigitte; Addad, Ahmed; Boussekey, Luc; Moreau, Myriam; Férid, Mokhtar; Szunerits, Sabine; Boukherroub, Rabah

    2016-07-01

    A facile and efficient one-step hydrothermal approach for the synthesis of Zn2SnO4 nanoparticles/reduced graphene oxide (ZTO/rGO) nanocomposites using zinc acetate, tin chloride and graphene oxide (GO) as precursors, and sodium hydroxide as reducing agent has been developed. This approach allows simultaneous reduction of GO and growth of spinel ZTO nanoparticles (NPs) on the rGO sheets. The morphology and microstructure characterizations of ZTO/rGO nanocomposites revealed that this method leads to close interfacial contact of ZTO NPs and rGO and efficient dispersion of ZTO NPs on the surface of rGO sheets. The photocatalytic activity of the ZTO/rGO nanocomposite was investigated for the reduction of rhodamine B under visible light irradiation. Compared to pure ZTO NPs, ZTO/rGO nanocomposite exhibited superior photocatalytic activity with a full degradation of rhodamine B within 15min. The enhanced photocatalytic performance of ZTO/rGO was mainly attributed to excellent electron trapping and effective adsorption properties of rGO.

  10. Anomalous quartz from the Roter Kamm impact crater, Namibia: Evidence for post-impact hydrothermal activity

    SciTech Connect

    Koeberl, C. Univ. of Vienna ); Fredriksson, K. ); Goetzinger, M. ); Reimold, W.U. )

    1989-08-01

    Centimeter-sized quartz pebbles have been found on the rim of the Roter Kamm impact crater. The Roter Kamm crater has a diameter of about 2.5 km and is situated in the Namib Desert, SWA/Namibia. Because of the sand coverage, impact products are exposed exclusively in the form of ejecta on the crater rim. The quartz pebbles were found close to the main deposits of the impact breccias and show signs of wind abrasion. Thin sections revealed that the pebbles consist of individual quartz domains that are up to 1 mm in size. Under crossed nicols (polarized light), all individual domains show extinction almost simultaneously within {plus minus}2{degree}, which is a rare phenomenon. Microprobe studies, neutron activation analyses, and X-ray diffractometry confirmed that the material consists of pure quartz. The quartz contains three different types of fluid inclusions: primary inclusions that record the formation conditions of the quartz, very small (<1 {mu}m) secondary inclusions associated with the grain boundaries, and late inclusions of irregular size. Freezing point depression measurements of the primary inclusions indicate fluid salinities between 18.3 and 19.6 wt% NaCl. Homogenization temperatures (T{sub h}) for the primary inclusions range from 165 to 250{degree}C. The quartz and the primary inclusions may provide evidence for a post-impact phase of extensive hydrothermal activity, generated by the residual heat from the kinetic energy of the impact.

  11. Hydrothermal synthesis of ZTO/graphene nanocomposite with excellent photocatalytic activity under visible light irradiation.

    PubMed

    Ben Ali, Monaam; Yolcu, Haci Hasan; Elhouichet, Habib; Sieber, Brigitte; Addad, Ahmed; Boussekey, Luc; Moreau, Myriam; Férid, Mokhtar; Szunerits, Sabine; Boukherroub, Rabah

    2016-07-01

    A facile and efficient one-step hydrothermal approach for the synthesis of Zn2SnO4 nanoparticles/reduced graphene oxide (ZTO/rGO) nanocomposites using zinc acetate, tin chloride and graphene oxide (GO) as precursors, and sodium hydroxide as reducing agent has been developed. This approach allows simultaneous reduction of GO and growth of spinel ZTO nanoparticles (NPs) on the rGO sheets. The morphology and microstructure characterizations of ZTO/rGO nanocomposites revealed that this method leads to close interfacial contact of ZTO NPs and rGO and efficient dispersion of ZTO NPs on the surface of rGO sheets. The photocatalytic activity of the ZTO/rGO nanocomposite was investigated for the reduction of rhodamine B under visible light irradiation. Compared to pure ZTO NPs, ZTO/rGO nanocomposite exhibited superior photocatalytic activity with a full degradation of rhodamine B within 15min. The enhanced photocatalytic performance of ZTO/rGO was mainly attributed to excellent electron trapping and effective adsorption properties of rGO. PMID:27054768

  12. Effects of pH and temperature on photocatalytic activity of PbTiO3 synthesized by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Li, Yongyu; Sun, Haijie; Wang, Ning; Fang, Wenxue; Li, Zhongjun

    2014-11-01

    PbTiO3 photocatalyst was synthesized successfully by facile hydrothermal method. The effects of the hydrothermal reaction temperatures and the pH values of the systems on the photocatalytic activities of PbTiO3 were investigated in detail. The photocatalytic activities of samples were evaluated by the degradation of methyl orange (MO) aqueous solution under simulated solar irradiation. The as-obtained PbTiO3 sample exhibits anisotropical growth along the (0 0 1) plane, and its photocatalytic activity is about 3 times higher than that of PbTiO3 prepared by precipitation method. Moreover, the as-prepared PbTiO3 has high stability during photocatalytic oxidation process, and does not cause secondary pollution.

  13. Geochemistry of Phosphorus and Nitrogen in Volcanic Rocks Altered by Submarine Hydrothermal Activities at the Suiyo Seamount in Japan

    NASA Astrophysics Data System (ADS)

    Noda, M.; Kakegawa, T.; Naraoka, H.; Marumo, K.; Urabe, T.

    2002-12-01

    Phosphorus and nitrogen are essential major elements for all microorganisms. In order to understand the ecological conditions of subvent microorganisms and thermophilic microorganisms on ocean floor, it is necessary to understand the behavior of bio-essential elements not only in hydrothermal fluids but also in the subvent environment. Nine sites of hydrothermal discharging area were drilled in the Suiyo volcanic caldera, Izu-Ogasawara (Bonin) island-arc, western Pacific. Approximately 2 to 10 m deep drill core samples were recovered in the last two years. Chemical compositions and hydrothermal mineral assemblages in the drilled core samples were determined by XRF, ICP-MS, and XRD. Morphology of phosphorous-bearing minerals and their chemistry were examined by electron microprobe. Nitrogen isotopes were measured by the EA-IRMS system. Primary igneous-rock texture (such as euhedral plagioclase phenocryst) is found in the less altered rocks. They often associated with montmorillonite. Highly altered rocks are divided into two groups. First group is characterized by extensive (up to 90%) replacement of primary igneous mineral assemblage by chlorite, mica and sulfide. Second group is cemented with large amounts of sulfates with sulfide (mainly pyrite). It is found in a few drill core sections that hydrothermal hydrous silicate minerals change with depth from montmorillonite to chlorite and mica through mixed layer of chlorite/montmorillonite. This may suggest the more extensive and higher temperature alteration in deeper zones in a certain area. Electron microprobe analyses and bulk chemical composition indicate that the depletion of phosphorous in altered rocks (below 0.1 wt%) but enrichment of phosphorous in sulfide zones. This suggests that phosphorous was easily dissolved from igneous rocks by hydrothermal process, but readily precipitated with sulfides. The reason for co-precipitation of phosphates with sulfides is not certain, but such co-precipitation mechanism

  14. Tin-bearing chalcopyrite and platinum-bearing bismuthinite in the active Tiger sulfide chimney, Yonaguni Knoll IV seafloor hydrothermal system, Okinawa Trough, Japan

    NASA Astrophysics Data System (ADS)

    Gena, K.; Kase, K.; Chiba, H.; Nakashima, K.

    2005-12-01

    The active submarine hydrothermal field at the Yonaguni Knoll IV is located in the southern Okinawa Trough, behind the Ryukyu trench-arc system, Japan. This field consists of seven active hydrothermal venting sites (Mosquito chimney, Carp Chimney, Abyss vent, Shallow Chimney, Tiger Chimney, Lion Chimney, Crystal Chimney) which are hosted by thick sediments and an underlying felsic volcanic rock of rhyolitic composition. The sulfides from the flank of the Tiger chimney consist of chalcopyrite, bismuthinite, pyrite, galena, sphalerite and gangue mineral of anhydrite which is slightly different to the mineral assemblage of sphalerite, pyrite, wurtzite, chalcopyrite, galena, tennanite-tetrahedrite series, stibnite, As-Sb-Tl-Hg-S bearing phase, bornite, covellite, nukundamite, alabandite and gangue minerals of barite, anhydrite, calcite, and rhodocrosite seen in the other chimneys in this field. Electron microprobe analysis of the chalcopyrite and bismuthinite from the flank of the Tiger chimney, indicates that the chalcopyrite and bismuthinite contain significantly high tin (0.51 to 2.40wt.% Sn, n = 16 ) and platinum (1.30 to 1.69 wt.% Pt, n = 9)respectively and are quite different to the sulfide chemistry of the other chimneys in this field The high Sn and Pt content in chalcopyrite and bismuthinite respectively, are significantly high and has never been reported previously for the submarine hydrothermal systems. The high Sn content in chalcopyrite confirms that the Sn enters the chalcopyrite as a solid solution towards stannite by the coupled substitution of Sn4+Fe2+ for Fe3+Fe3+ while the high Pt content in bismuthinite might indicate that Pt probably enters the bismuthinite by interstitial substitution of Pt2+Cu1+ for Bi3+ although very limited published data is available to verify this observation. Fluid inclusion data of anhydrite (297-313°C) and measured end-member temperature of the vent fluid (325°C) does not exceed 400°C. Previous experimental studies

  15. Catalysis: Elusive active site in focus

    NASA Astrophysics Data System (ADS)

    Labinger, Jay A.

    2016-08-01

    The identification of the active site of an iron-containing catalyst raises hopes of designing practically useful catalysts for the room-temperature conversion of methane to methanol, a potential fuel for vehicles. See Letter p.317

  16. State of the hydrothermal activity of Soufrière of Guadeloupe volcano inferred by VLF surveys

    NASA Astrophysics Data System (ADS)

    Zlotnicki, J.; Vargemezis, G.; Mille, A.; Bruère, F.; Hammouya, G.

    2006-04-01

    La Soufrière (1467 m) is the active island arc volcano of Guadeloupe Island in the Lesser Antilles arc. Its historical eruptions are more or less violent phreatic outbursts the last of which, in 1976-1977, led to the evacuation of nearly 70 000 persons. The subsurface structure of the volcano consists of calderas, craters, and avalanche amphitheatres nested within the composite pile of eruptive products. Since the last magmatic eruption, dated ca. 1440 AD, the four phreatic eruptions have developed radial fractures on Soufrière dome favouring the development of a huge active hydrothermal system emphasized by a tropical environment. After the eruptions, the thermal state and the stable ground water flow are completely disorganised during several years during which the slow mineralization of rocks is becoming again preponderant. Sealing of fractures and decay of rocks permeability act as a cap for upward thermal transfers. Therefore Soufrière dome operates as a valve, resealing the hydrothermal system underlying the volcano thus providing over pressurization that could lead to the next phreatic eruption. In 1992 new small seismic swarms have appeared. Several of them are recorded every year while the emission of acid gas slowly increases. In order to recognise the superficial electrical resistive and conductive zones (less than 100 m depth) as well as the cavities on Soufrière volcano, we have made Very Low Frequency (VLF) surveys in 2000. Electrical conductive zones are clearly associated with major radial faults starting from the summit in which the hydrothermal activity takes place. In the continuation of these active hydrothermal fractures hot springs are located down slope. Conversely some of the resistive zones are associated with inactive clayed and sealed or opened faults. The distribution of the conductive zones allows detailing the state of the superficial part of the hydrothermal system of La Soufrière. The distribution of vertical clayed zones

  17. The magmatic- and hydrothermal-dominated fumarolic system at the Active Crater of Lascar volcano, northern Chile

    NASA Astrophysics Data System (ADS)

    Tassi, F.; Aguilera, F.; Vaselli, O.; Medina, E.; Tedesco, D.; Delgado Huertas, A.; Poreda, R.; Kojima, S.

    2009-03-01

    Low-to-high temperature fumaroles discharging from the Active Crater of Lascar volcano (northern Chile) have been collected in November 2002, May 2005 and October 2006 for chemical and isotopic analysis to provide the first geochemical survey on the magmatic-hydrothermal system of this active volcano. Chemical and isotopic gas composition shows direct addition of high-temperature fluids from magmatic degassing, mainly testified by the very high contents of SO2, HCl and HF (up to 87,800, 29,500 and 2,900 μmol/mol) and the high R/Ra values (up to 7.29). Contributions from a hydrothermal source, mainly in gas discharges of the Active Crater rim, has also been detected. Significant variations in fluid chemistry, mainly consisting of a general decrease of magmatic-related compounds, i.e. SO2, have affected the fumarolic system during the period of observation, indicating an increase of the influence of the hydrothermal system surrounding the ascending deep fluids. The chemical composition of Active Crater fumaroles has been used to build up a geochemical model describing the main processes that regulate the fluid circulation system of Lascar volcano to be utilized in volcanic surveillance.

  18. Discovery of sublacustrine hydrothermal activity and associated massive sulfides and hydrocarbons in the north Tanganyika trough, East African Rift

    SciTech Connect

    Tiercelin, J.J.; Mondeguer, A. ); Thouin, C. ); Kalala, T. )

    1989-11-01

    Massive sulfides and carbonate mineral deposits associated with sublacustrine thermal springs were recently discovered along the Zaire side of the north Tanganyika trough, western branch of the East African Rift. This hydrothermal activity, investigated by scuba diving at a maximum depth of 20 m, is located at the intersection of major north-south normal faults and northwest-southeast faults belonging to the Tanganyika-Rukwa-Malawi (TRM) strike-slip fault zone. The preliminary results presented here come from analyses of sulfide deposits, hydrothermal fluids, and associated hydrocarbons that result from geothermal activity in this part of the East African Rift filled by a thick pile of sediment, the north Tanganyika trough.

  19. In vitro evaluation of H2O2 hydrothermal treatment of aged titanium surface to enhance biofunctional activity.

    PubMed

    Yoneyama, Yuya; Matsuno, Tomonori; Hashimoto, Yoshiya; Satoh, Tazuko

    2013-01-01

    Surface modification of titanium has been extensively investigated in implant science and technology in an effort to improve its osteoconductivity. The rate of protein adsorption on titanium surfaces is known to vary depending on the chemistry, structure, morphology, and titanium-specific biological aging of the surface. It is thus desirable to modify smooth titanium surfaces of miniimplants used as orthodontic anchors immediately prior to use. In this study, we have developed a simple surface modification of titanium alloy that improves its biofunctional activity. The surface of a Ti-6Al-4V disk was modified by applying 3% H(2)O(2) hydrothermal treatment using an autoclave. A nanostructured porous network TiO(2) was observed on the treated surface. Treated surfaces exhibited higher hydrophilicity, protein adsorption, and cell proliferation than untreated surfaces. 3% H(2)O(2) hydrothermal treatment is thought to provide biofunctional activity for aged titanium surface.

  20. Trophic regions of a hydrothermal plume dispersing away from an ultramafic-hosted vent-system: Von Damm vent-site, Mid-Cayman Rise

    NASA Astrophysics Data System (ADS)

    Bennett, Sarah A.; Coleman, Max; Huber, Julie A.; Reddington, Emily; Kinsey, James C.; McIntyre, Cameron; Seewald, Jeffrey S.; German, Christopher R.

    2013-02-01

    Abstract Deep-sea ultramafic-hosted vent systems have the potential to provide large amounts of metabolic energy to both autotrophic and heterotrophic microorganisms in their dispersing <span class="hlt">hydrothermal</span> plumes. Such vent-systems release large quantities of hydrogen and methane to the water column, both of which can be exploited by autotrophic microorganisms. Carbon cycling in these <span class="hlt">hydrothermal</span> plumes may, therefore, have an important influence on open-ocean biogeochemistry. In this study, we investigated an ultramafic-hosted system on the Mid-Cayman Rise, emitting metal-poor and hydrogen sulfide-, methane-, and hydrogen-rich <span class="hlt">hydrothermal</span> fluids. Total organic carbon concentrations in the plume ranged between 42.1 and 51.1 μM (background = 43.2 ± 0.7 μM (n = 5)) and near-field plume samples with elevated methane concentrations imply the presence of chemoautotrophic primary production and in particular methanotrophy. In parts of the plume characterized by persistent potential temperature anomalies but lacking elevated methane concentrations, we found elevated organic carbon concentrations of up to 51.1 μM, most likely resulting from the presence of heterotrophic communities, their extracellular products and vent larvae. Elevated carbon concentrations up to 47.4 μM were detected even in far-field plume samples. Within the Von Damm <span class="hlt">hydrothermal</span> plume, we have used our data to hypothesize a microbial food web in which chemoautotrophy supports a heterotrophic community of microorganisms. Such an <span class="hlt">active</span> microbial food web would provide a source of labile organic carbon to the deep ocean that should be considered in any future studies evaluating sources and sinks of carbon from <span class="hlt">hydrothermal</span> venting to the deep ocean.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMOS34A..08P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMOS34A..08P"><span id="translatedtitle">Microearthquakes at the <span class="hlt">active</span> Trans-Atlantic Geotraverse (TAG) <span class="hlt">hydrothermal</span> mound, Mid-Atlantic Ridge, 26°08'N</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pontbriand, C.; Reves-Sohn, R. A.</p> <p>2010-12-01</p> <p>A small 200 m aperture network of five ocean bottom seismometers around the periphery the <span class="hlt">active</span> TAG <span class="hlt">hydrothermal</span> mound on the Mid-Atlantic Ridge (26°08’N) detected microearthquake events that may be associated with the subsurface hydraulics of the massive <span class="hlt">hydrothermal</span> deposit. Seismic data were sampled at 100 Hz for a period of eight months spanning June, 2003 to February, 2004, during which time 24,191 locatable events were detected. Microearthquake hypocenters are concentrated within a 300 m radius of the sulfide mound in the top 250 m of crust, and exhibit a conical shape with the deepest events beneath the mound center. Event rates are steady at 180 events per day at the beginning of the study period and decline slightly to 116 events per day after whale calls elevate background noise levels about 2/3 of the way through the deployment. The mean local magnitude of events is -1.2 with a range of -2.9≦ML≦0.3. We suggest that events may be largely due to hydraulic fracturing of clogged flow conduits in the mineral deposit, which provides the possibility of using the microearthquake data to constrain subsurface flow parameters and the permeability structure of the <span class="hlt">active</span> TAG deposit. Figure: A bathymetric map of the TAG area depicts a small aperture network of 5 ocean bottom seismometers (white triangles) around the periphery of the <span class="hlt">active</span> TAG <span class="hlt">hydrothermal</span> mound. High resolution bathymetry is from Roman and Singh, 2005.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012BGeo....9.4661B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012BGeo....9.4661B"><span id="translatedtitle"><span class="hlt">Activity</span> and abundance of denitrifying bacteria in the subsurface biosphere of diffuse <span class="hlt">hydrothermal</span> vents of the Juan de Fuca Ridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bourbonnais, A.; Juniper, S. K.; Butterfield, D. A.; Devol, A. H.; Kuypers, M. M. M.; Lavik, G.; Hallam, S. J.; Wenk, C. B.; Chang, B. X.; Murdock, S. A.; Lehmann, M. F.</p> <p>2012-11-01</p> <p>Little is known about fixed nitrogen (N) transformation and elimination at diffuse <span class="hlt">hydrothermal</span> vents where anoxic fluids are mixed with oxygenated crustal seawater prior to discharge. Oceanic N sinks that remove bio-available N ultimately affect chemosynthetic primary productivity in these ecosystems. Using 15N paired isotope techniques, we determined potential rates of fixed N loss pathways (denitrification, anammox) and dissimilatory nitrate reduction to ammonium (DNRA) in sulfidic <span class="hlt">hydrothermal</span> vent fluids discharging from the subsurface at several <span class="hlt">sites</span> at Axial Volcano and the Endeavour Segment on the Juan de Fuca Ridge. We also measured physico-chemical parameters (i.e., temperature, pH, nutrients, H2S and N2O concentrations) as well as the biodiversity and abundance of chemolithoautotrophic nitrate-reducing, sulfur-oxidizing γ-proteobacteria (SUP05 cluster) using sequence analysis of amplified small subunit ribosomal RNA (16S rRNA) genes in combination with taxon-specific quantitative polymerase chain reaction (qPCR) assays. Denitrification was the dominant N loss pathway in the subsurface biosphere of the Juan de Fuca Ridge, with rates of up to ~1000 nmol N l-1 day-1. In comparison, anammox rates were always < 5 nmol N l-1 day-1 and below the detection limit at most of the <span class="hlt">sites</span>. DNRA rates were up to ~150 nmol N l-1 day-1. These results suggest that bacterial denitrification out-competes anammox in sulfidic <span class="hlt">hydrothermal</span> vent waters. Taxon-specific qPCR revealed that γ-proteobacteria of the SUP05 cluster sometimes dominated the microbial community (SUP05/total bacteria up to 38%). Significant correlations were found between fixed N loss (i.e., denitrification, anammox) rates and in situ nitrate and dissolved inorganic nitrogen (DIN) deficits in the fluids, indicating that DIN availability may ultimately regulate N loss in the subsurface. Based on our rate measurements, and on published data on <span class="hlt">hydrothermal</span> fluid fluxes and residence times, we estimated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012BGD.....9.4177B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012BGD.....9.4177B"><span id="translatedtitle"><span class="hlt">Activity</span> and abundance of denitrifying bacteria in the subsurface biosphere of diffuse <span class="hlt">hydrothermal</span> vents of the Juan de Fuca Ridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bourbonnais, A.; Juniper, S. K.; Butterfield, D. A.; Devol, A. H.; Kuypers, M. M. M.; Lavik, G.; Hallam, S. J.; Wenk, C. B.; Chang, B. X.; Murdock, S. A.; Lehmann, M. F.</p> <p>2012-04-01</p> <p>Little is known about nitrogen (N) transformations in general, and the elimination of N in particular, at diffuse vents where anoxic <span class="hlt">hydrothermal</span> fluids have mixed with oxygenated crustal seawater prior to discharge. Oceanic N sinks that remove bio-available N ultimately affect chemosynthetic primary productivity in these ecosystems. Using 15N paired isotope techniques, we determined potential rates of fixed N-loss pathways (denitrification, anammox) and dissimilative nitrate reduction to ammonium (DNRA) in sulfidic <span class="hlt">hydrothermal</span> vent fluids discharging from the subsurface at several <span class="hlt">sites</span> at Axial Volcano and the Endeavour Segment on the Juan de Fuca Ridge. We also measured physico-chemical parameters (i.e. temperature, pH, nutrients, H2S and N2O concentrations) as well as the biodiversity and abundance of chemolithotrophic nitrate-reducing, sulfur-oxidizing γ-proteobacteria (SUP05 cluster) using sequence analysis of amplified small subunit ribosomal RNA (16S rRNA) genes in combination with taxon-specific quantitative polymerase chain reaction (qPCR) assays. Denitrification was the dominant N-loss pathway in the subsurface biosphere of the Juan de Fuca Ridge, with rates of up to ~1000 nmol N l-1 day-1. In comparison, anammox rates were always <5 nmol N l-1 day-1 and below the detection limit at most of the <span class="hlt">sites</span>. DNRA rates were up to 152 nmol N l-1 day-1. These results suggest that bacterial denitrification out-competes anammox in sulfidic <span class="hlt">hydrothermal</span> vent waters. Taxon-specific qPCR revealed that γ-proteobacteria of the SUP05 cluster sometimes dominated the microbial community (SUP05/total bacteria up to 38%). Significant correlation existed between fixed N-loss (i.e., denitrification, anammox) rates and in-situ nitrate and dissolved inorganic nitrogen (DIN) deficits in the fluids, indicating that DIN availability may ultimately regulate N-loss in the subsurface. Based on our rate measurements, and on published data on <span class="hlt">hydrothermal</span> fluid fluxes and residence</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=15757','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=15757"><span id="translatedtitle">Low dielectric response in enzyme <span class="hlt">active</span> <span class="hlt">site</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mertz, Edward L.; Krishtalik, Lev I.</p> <p>2000-01-01</p> <p>The kinetics of charge transfer depend crucially on the dielectric reorganization of the medium. In enzymatic reactions that involve charge transfer, atomic dielectric response of the <span class="hlt">active</span> <span class="hlt">site</span> and of its surroundings determines the efficiency of the protein as a catalyst. We report direct spectroscopic measurements of the reorganization energy associated with the dielectric response in the <span class="hlt">active</span> <span class="hlt">site</span> of α-chymotrypsin. A chromophoric inhibitor of the enzyme is used as a spectroscopic probe. We find that water strongly affects the dielectric reorganization in the <span class="hlt">active</span> <span class="hlt">site</span> of the enzyme in solution. The reorganization energy of the protein matrix in the vicinity of the <span class="hlt">active</span> <span class="hlt">site</span> is similar to that of low-polarity solvents. Surprisingly, water exhibits an anomalously high dielectric response that cannot be described in terms of the dielectric continuum theory. As a result, sequestering the <span class="hlt">active</span> <span class="hlt">site</span> from the aqueous environment inside low-dielectric enzyme body dramatically reduces the dielectric reorganization. This reduction is particularly important for controlling the rate of enzymatic reactions. PMID:10681440</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22215590','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22215590"><span id="translatedtitle">Low-temperature <span class="hlt">hydrothermal</span> synthesis of BiFeO{sub 3} microcrystals and their visible-light photocatalytic <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wei, Jie; Zhang, Chao; Xu, Zhuo</p> <p>2012-11-15</p> <p>Highlights: ► Urea-assisted <span class="hlt">hydrothermal</span> synthesis of pure BiFeO{sub 3} at 120 °C was reported. ► Possible formation mechanism of pure phase BiFeO{sub 3} at low temperature was illuminated. ► BiFeO{sub 3} microcrystals exhibited efficient visible-light photocatalytic <span class="hlt">activity</span>. -- Abstract: Pure BiFeO{sub 3} (BFO) microcrystals were synthesized at the temperature as low as 120 °C via a urea-assisted <span class="hlt">hydrothermal</span> process. The crystal structure, morphology and photocatalytic property of BFO microcrystals were investigated. The analysis reveals that the hydrolysis of urea in the <span class="hlt">hydrothermal</span> process plays a key role in the synthesis of pure phase BFO microcrystals. FE-SEM and TEM results show that these BFO microcrystals present a nearly spherical microstructure, and specially exhibit superstructures consisting of large amounts of small particles with the size of 100–150 nm by further observation. Moreover, these BFO microcrystals exhibit efficient photocatalytic <span class="hlt">activity</span> under visible-light irradiation, suggesting their promising applications as photocatalysts and related fields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70016071','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70016071"><span id="translatedtitle">Recent uplift and <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at Tangkuban Parahu volcano, west Java, Indonesia</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Dvorak, J.; Matahelumual, J.; Okamura, A.T.; Said, H.; Casadevall, T.J.; Mulyadi, D.</p> <p>1990-01-01</p> <p>Tangkuban Parahu is an <span class="hlt">active</span> stratovolcano located 17 km north of the city of Bandung in the province west Java, Indonesia. All historical eruptive <span class="hlt">activity</span> at this volcano has been confined to a complex of explosive summit craters. About a dozen eruptions-mostly phreatic events- and 15 other periods of unrest, indicated by earthquakes or increased thermal <span class="hlt">activity</span>, have been noted since 1829. The last magmatic eruption occurred in 1910. In late 1983, several small phreatic explosions originated from one of the summit craters. More recently, increased <span class="hlt">hydrothermal</span> and earthquake <span class="hlt">activity</span> occurred from late 1985 through 1986. Tilt measurements, using a spirit-level technique, have been made every few months since February 1981 in the summit region and along the south and east flanks of the volcano. Measurements made in the summit region indicated uplift since the start of these measurements through at least 1986. From 1981 to 1983, the average tilt rate at the edges of the summit craters was 40-50 microradians per year. After the 1983 phreatic <span class="hlt">activity</span>, the tilt rate decreased by about a factor of five. Trilateration surveys across the summit craters and on the east flank of the volcano were conducted in 1983 and 1986. Most line length changes measured during this three-year period did not exceed the expected uncertainty of the technique (4 ppm). The lack of measurable horizontal strain across the summit craters seems to contradict the several years of tilt measurements. Using a point source of dilation in an elastic half-space to model tilt measurements, the pressure center at Tangkuban Parahu is located about 1.5 km beneath the southern part of the summit craters. This is beneath the epicentral area of an earthquake swarm that occurred in late 1983. The average rate in the volume of uplift from 1981 to 1983 was 3 million m3 per year; from 1983 to 1986 it averaged about 0.4 million m3 per year. Possible causes for this uplift are increased pressure within a very</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008DSRI...55..203G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008DSRI...55..203G"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> exploration with the Autonomous Benthic Explorer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>German, Christopher R.; Yoerger, Dana R.; Jakuba, Michael; Shank, Timothy M.; Langmuir, Charles H.; Nakamura, Ko-ichi</p> <p></p> <p>We describe a three-phase use of the Woods Hole Oceanographic Institution's Autonomous Benthic Explorer ( ABE), to locate, map and photograph previously undiscovered fields of high temperature submarine <span class="hlt">hydrothermal</span> vents. Our approach represents both a complement to and a significant advance beyond the prior state of the art. Previously, <span class="hlt">hydrothermal</span> exploration relied upon deep-tow instruments equipped with sensors that could locate <span class="hlt">sites</span> of <span class="hlt">active</span> "black smoker" venting to within a few kilometers. Follow-on CTD tow-yos could then resolve the <span class="hlt">sites</span> of seafloor venting to length scales of less than a kilometer but rarely to better than a few hundreds of meters. In our new approach ABE: (i) uses sensors to locate the center of a dispersing non-buoyant <span class="hlt">hydrothermal</span> plume 100-400 m above the seabed; (ii) makes high-resolution maps of the seafloor beneath the plume center whilst simultaneously detecting interception of any rising, buoyant <span class="hlt">hydrothermal</span> plumes; and (iii) dives to the seafloor to take photographs in and around any new vent <span class="hlt">site</span> to characterize its geologic setting and reveal the nature of any chemosynthetic ecosystems it may host. By conducting all of the above under long-baseline navigation, precise <span class="hlt">sites</span> of venting can be determined to within 5 m. Our approach can be used both to address important scientific issues in their own right and to ensure much more efficient use of other deep-submergence assets such as human occupied vehicles (HOVs) and remotely operated vehicles (ROVs) during follow-on studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMOS34A..02T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMOS34A..02T"><span id="translatedtitle">Investigating microbial colonization in <span class="hlt">actively</span> forming <span class="hlt">hydrothermal</span> deposits using thermocouple arrays</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tivey, M. K.; Reysenbach, A. L.; Hirsch, M.; Steinberg, J.; Flores, G. E.</p> <p>2010-12-01</p> <p>Investigations of microbial colonization of very young <span class="hlt">hydrothermal</span> deposits were carried out in 2009 at <span class="hlt">hydrothermal</span> vents in the Lau Basin (SW Pacific), and in Guaymas Basin, Gulf of California, with a test deployment at the Rainbow vent field on the Mid-Atlantic Ridge in 2008. Our method entailed razing <span class="hlt">active</span> chimneys and placing arrays of temperature probes (8 titanium-encased probes with their tips placed within a titanium cage) over the <span class="hlt">active</span> flow. The chimneys that grew back through each array, encasing the temperature probe tips, were recovered after 2 to 15 days, along with temperature records. Molecular phylogenetic methods are being used to reveal the members of the microbial communities that developed in each chimney of known age and thermal history. A total of 15 array deployments were made at 10 vents in 6 different vent fields. Similar morphology beehives (with porous fine-grained interiors and steep temperature gradients across the outermost more-consolidated “wall”) formed at 2 of the 3 vents in Guaymas Basin (in 2 and 5 days at one vent and 3 and 15 days at a second), and at one vent each in the Kilo Moana (in 3 days), Tahi Moana (in 2.5 days), and Tui Malila (in 3 and 8 days) vent fields in the Lau Basin. In contrast, open conduit, thin walled chimneys grew within arrays at the Mariner vent field, Lau Basin, at 3 different vents (in 3 days at one vent, in 3 and 11 days at a second vent, and in 13 days at a third vent). A lower temperature (<280C) diffuser/spire with a filamentous biofilm formed in 15 days in an array at a hydrocarbon-rich vent in the Guaymas Basin. A similar biofilm formed after 6 days within an array placed earlier at this same vent, with little mineralization. Preliminary diversity data from the 6 and 15 day Guaymas deployments show an increased diversity of bacteria with time with initial colonizers being primarily sulfur-oxidizing Epsilonproteobacteria, with members of the Aquificales and Deltaproteobacteria appearing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70024075','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70024075"><span id="translatedtitle">Geochemistry of fluid phases and sediments: Relevance to <span class="hlt">hydrothermal</span> circulation in Middle Valley, ODP Legs 139 and 169</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Gieskes, J.M.; Simoneit, B.R.T.; Shanks, Wayne C.; Goodfellow, W.D.; James, R.H.; Baker, P.A.; Ishibashi, J.-I.</p> <p>2002-01-01</p> <p>Geochemical and isotopic studies of pore fluids and solid phases recovered from the Dead Dog and Bent Hill <span class="hlt">hydrothermal</span> <span class="hlt">sites</span> in Middle Valley (Ocean Drilling Program Leg 169) have been compared with similar data obtained previously from these <span class="hlt">sites</span> during Ocean Drilling Program Leg 139. Although generally the <span class="hlt">hydrothermal</span> systems reflect non-steady state conditions, the data allow an assessment of the history of the <span class="hlt">hydrothermal</span> processes. Sediment K/A1 ratios as well as the distribution of anhydrite in the sediments suggest that the Dead Dog <span class="hlt">hydrothermal</span> field has been, and still is, <span class="hlt">active</span>. In contrast, similar data in the Bent Hill <span class="hlt">hydrothermal</span> field indicate a waning of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>. Pore fluid and <span class="hlt">hydrothermal</span> vent data in the Dead Dog <span class="hlt">hydrothermal</span> field are similar in nature to the data collected during ODP Leg 139. In the area of the Bent Hill sulfide deposit, however, the pore water data indicate that recent wholesale flushing of the sediment column with relatively unaltered seawater has obliterated a previous record of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> in the pore fluids. Data from the deepest part of Hole 1035A in the Bent Hill locality show the presence of <span class="hlt">hydrothermal</span> fluids at greater depths in this area. This suggests the origin of the <span class="hlt">hydrothermal</span> fluids found to be emanating from Hole 1035F, which constitutes one of the first man made <span class="hlt">hydrothermal</span> vents in the Middle Valley <span class="hlt">hydrothermal</span> system. Similarly, CORKed Hole 858G, because of seal failures, has acted as a <span class="hlt">hydrothermal</span> vent, with sulfide deposits forming inside the CORK. ?? 2002 Elsevier Science Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008E%26PSL.273..332G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008E%26PSL.273..332G"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> <span class="hlt">activity</span> on the southern Mid-Atlantic Ridge: Tectonically- and volcanically-controlled venting at 4 5°S</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>German, C. R.; Bennett, S. A.; Connelly, D. P.; Evans, A. J.; Murton, B. J.; Parson, L. M.; Prien, R. D.; Ramirez-Llodra, E.; Jakuba, M.; Shank, T. M.; Yoerger, D. R.; Baker, E. T.; Walker, S. L.; Nakamura, K.</p> <p>2008-09-01</p> <p>We report results from an investigation of the geologic processes controlling <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> along the previously-unstudied southern Mid-Atlantic Ridge (3-7°S). Our study employed the NOC (UK) deep-tow sidescan sonar instrument, TOBI, in concert with the WHOI (USA) autonomous underwater vehicle, ABE, to collect information concerning <span class="hlt">hydrothermal</span> plume distributions in the water column co-registered with geologic investigations of the underlying seafloor. Two areas of high-temperature <span class="hlt">hydrothermal</span> venting were identified. The first was situated in a non-transform discontinuity (NTD) between two adjacent second-order ridge-segments near 4°02'S, distant from any neovolcanic <span class="hlt">activity</span>. This geologic setting is very similar to that of the ultramafic-hosted and tectonically-controlled Rainbow vent-<span class="hlt">site</span> on the northern Mid-Atlantic Ridge. The second <span class="hlt">site</span> was located at 4°48'S at the axial-summit centre of a second-order ridge-segment. There, high-temperature venting is hosted in an ˜ 18 km 2 area of young lava flows which in some cases are observed to have flowed over and engulfed pre-existing chemosynthetic vent-fauna. In both appearance and extent, these lava flows are directly reminiscent of those emplaced in Winter 2005-06 at the East Pacific Rise, 9°50'N and reference to global seismic catalogues reveals that a swarm of large (M 4.6-5.6) seismic events was centred on the 5°S segment over a ˜ 24 h period in late June 2002, perhaps indicating the precise timing of this volcanic eruptive episode. Temperature measurements at one of the vents found directly adjacent to the fresh lava flows at 5°S MAR (Turtle Pits) have subsequently revealed vent-fluids that are <span class="hlt">actively</span> phase separating under conditions very close to the Critical Point for seawater, at ˜ 3000 m depth and 407 °C: the hottest vent-fluids yet reported from anywhere along the global ridge crest.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1167674','SCIGOV-DOEDE'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1167674"><span id="translatedtitle">Calibrated <span class="hlt">Hydrothermal</span> Parameters, Barrow, Alaska, 2013</span></a></p> <p><a target="_blank" href="http://www.osti.gov/dataexplorer">DOE Data Explorer</a></p> <p>Atchley, Adam; Painter, Scott; Harp, Dylan; Coon, Ethan; Wilson, Cathy; Liljedahl, Anna; Romanovsky, Vladimir</p> <p>2015-01-29</p> <p>A model-observation-experiment process (ModEx) is used to generate three 1D models of characteristic micro-topographical land-formations, which are capable of simulating present <span class="hlt">active</span> thaw layer (ALT) from current climate conditions. Each column was used in a coupled calibration to identify moss, peat and mineral soil <span class="hlt">hydrothermal</span> properties to be used in up-scaled simulations. Observational soil temperature data from a tundra <span class="hlt">site</span> located near Barrow, AK (Area C) is used to calibrate thermal properties of moss, peat, and sandy loam soil to be used in the multiphysics Advanced Terrestrial Simulator (ATS) models. Simulation results are a list of calibrated <span class="hlt">hydrothermal</span> parameters for moss, peat, and mineral soil <span class="hlt">hydrothermal</span> parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013HMR....67..535W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013HMR....67..535W"><span id="translatedtitle">Intertidal rocky shore seaweed communities subject to the influence of shallow water <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> in São Miguel (Azores, Portugal)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wallenstein, Francisco M.; Couto, Ruben P.; Torrão, Daniel F.; Neto, Ana I.; Rodrigues, Armindo S.; Wilkinson, Martin</p> <p>2013-09-01</p> <p>The volcanic origin of the Azores archipelago (Portugal) gives rise to <span class="hlt">active</span> deep sea and shallow water <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> that affects benthic communities. Intertidal seaweed surveys were conducted at two shores affected by intense shallow water <span class="hlt">hydrothermal</span> vents. Water temperature, acidity and salinity were monitored. Seaweed communities were found to be species poor and have a disproportionally larger number of filamentous early successional species on shores that are subject to the effect of hot and acidic freshwater of volcanic origin. There is an ecological resemblance between <span class="hlt">hydrothermally</span> affected seaweed communities in the Azores and those affected by acid mine drainage in the UK, thus indicating that <span class="hlt">hydrothermalism</span> can be a useful scenario for pollution studies under conditions of ocean warming and acidification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFMOS21B0450S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFMOS21B0450S"><span id="translatedtitle">Aqueous Volatiles in <span class="hlt">Hydrothermal</span> fluids from the Main Endeavour Vent Field: Temporal Variability Following Earthquake <span class="hlt">Activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seewald, J. S.; Cruse, A. M.; Saccocia, P. J.</p> <p>2001-12-01</p> <p>Volatile species play a critical role in a broad spectrum of physical, chemical, and biological processes associated with <span class="hlt">hydrothermal</span> circulation at oceanic spreading centers. Earthquake <span class="hlt">activity</span> at the Main Endeavour vent field, northern Juan de Fuca Ridge in June 1999 [1] provided and opportunity to assess factors that regulate the flux of volatile species from the oceanic crust to the water column following a rapid change in subsurface reaction zone conditions. High temperature vent fluids were collected in gas-tight samplers at the Main Endeavour field in September 1999, approximately four months after the earthquakes, and again in July 2000, and were analyzed for the abundance of aqueous volatile and non-volatile species. Measured concentrations of aqueous H2, H2S, and CO2 increased substantially in September 1999 relative to pre-earthquake values [2,3], and subsequently decreased in July 2000, while aqueous Cl concentrations initially decreased in 1999 and subsequently increased in 2000. Concentrations of Cl in all fluids were depleted relative to seawater values. Aqueous CH4 and NH3 concentrations decreased in both the 1999 and 2000 samples relative to pre- earthquake values. Variations in Cl concentration of Endeavour fluids reflect varying degrees of phase separation under near critical temperature and pressure conditions. Because volatile species efficiently partition into the vapor phase, variations in their abundance as a function of Cl concentration can be used to constrain conditions of phase separation and fluid-rock interaction. For example, concentrations of volatile species that are not readily incorporated into minerals (CH4 and NH3) correlated weakly with Cl suggesting phase separation was occurring under supercritical conditions after the earthquake <span class="hlt">activity</span>. In contrast, compositional data for fluids prior to the earthquakes indicate a strong negative correlation between these species and Cl suggesting phase separation under subcritical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.B31C0430T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.B31C0430T"><span id="translatedtitle">Hg Isotopic Compositions of Chimneys and Pelagic Sediments at <span class="hlt">Active</span> Submarine <span class="hlt">Hydrothermal</span> Field in the Okinawa Trough, Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takeuchi, A.; Marumo, K.; Tomiyasu, T.; Yamamoto, M.; Komuro, K.</p> <p>2012-12-01</p> <p>Mercury (Hg) is a globally distributed and highly toxic pollutant in the environment. It is known that a submarine <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> is one of the natural processes to emit Hg to marine environment. In order to estimate the degree to which the Hg found in the marine environment is from anthropogenic versus natural sources, it is important to characterize the Hg from the <span class="hlt">hydrothermal</span> vents. Samples of chimneys and a ~20 cm sediment core, collected by a deep-sea remotely operated vehicle, from Iheya North <span class="hlt">hydrothermal</span> field in Okinawa Trough, Japan, were analyzed for Hg concentrations and Hg isotopic compositions. Total Hg concentrations of chimneys range between 8.2 and 16.9 mg/kg, whereas seafloor sediment total Hg concentrations are from 3.8 to 34.8 mg/kg. Approximately 0.4 to 1.1 μg/kg of monomethyl Hg (MMHg) was detected in the top 6 cm sediment cores. Hg isotopic compositions (δ202Hg) of chimneys are between -0.30 and -0.96 ‰, whereas δ202Hg values of sediment samples range from -0.85 to -1.60 ‰. Neither chimneys nor sediment samples exhibit the significant mass independent fractionations in Hg isotopes (Δ201Hg > ± 0.10). The chimney δ202Hg values are slightly higher than the δ202Hg values of sediments. This may indicate that the heavier Hg isotopes tend to be incorporated with mercury-bearing sulfides in chimneys, and the lighter isotopes tend to be remained in the <span class="hlt">hydrothermal</span> fluid and distributed in the surrounding sediments. Also, the sediment samples from the upper portion of cores demonstrate approximately 0.4 - 0.5 ‰ lower δ202Hg values than those from the lower part. This isotopic fractionation may be resulted from a demethylated process of MMHg by microbes. Several studies have previously demonstrated the rapid demethylation of MMHg by microbes in Hg-contaminated aquatic sediments, and range of the isotopic fractionation is similar to that of the experimentally determined isotopic fractionation of MMHg by bacterial reduction</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUSM.V43B..09H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUSM.V43B..09H"><span id="translatedtitle">Sulfur Isotope Chemistry of the Uzon Caldera <span class="hlt">Active</span> <span class="hlt">Hydrothermal</span> System, Kamchatka, Far-East Russia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hollingsworth, E. R.; Crowe, D. E.</p> <p>2006-05-01</p> <p>The Uzon Caldera is an <span class="hlt">actively</span> precipitating As-Sb-Au epithermal system located on the Kamchatka Peninsula of Far-East Russia. Present at the surface of the caldera is a remarkable diversity of thermal fluid types discharging within the geothermal fields. These fluids have subsequently produced a broad array of S- bearing alteration minerals both within and around pools, hotsprings, mudpots, and fumaroles. Using the δD/δ18O/δ34S and dissolved ion chemistry of the thermal fluids, three types were distinguished as follows: 1) an acid sulfate type with δD/δ18O/δ34S values ranging between -74.66‰ to -100.33‰, - 2.30‰ to -9.57‰, and -0.3‰ to 0.3‰ respectively with sulfate being the dominant anion ranging between 504ppm and 3439ppm 2) an alkali chloride type with δD/δ18O/δ34S values ranging between -97.22‰ to -104.37‰, - 8.8‰ to -11.43‰ respectively with chloride being the dominant anion ranging between 1090ppm to 2405ppm, and 3) a dilute type resulting from the mixture of the alkali-chloride endmember with the cold meteoric waters present at the surface subsequently generating δD/δ18O/δ34S values ranging between -82.00‰ to -119.34‰, -6.02‰ to -15.76‰, and +1.9‰ to +13.5‰ with dissolved ion concentrations falling along a mixing line between the two endmember components. The interpretations made from the presence of these three fluid types were used in conjunction with the δ34S of the S-bearing alteration minerals from within and around the various water and gas sources (values ranging between -1.94‰ to +5.7‰ and -5.19‰ to +1.6‰ respectively) to construct a sulfur evolution model for the Uzon's <span class="hlt">hydrothermal</span> system. Results of the model show the chemical and isotopic processes responsible for the speciation and isotopic signature of the S-bearing phases collected at the surface (both aqueous and mineral) are not only dictated by the geologic processes at depth, but are also influenced by microbiological processes at the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21707671','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21707671"><span id="translatedtitle">Comparison of microbial communities associated with three Atlantic ultramafic <span class="hlt">hydrothermal</span> systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Roussel, Erwan G; Konn, Cécile; Charlou, Jean-Luc; Donval, Jean-Pierre; Fouquet, Yves; Querellou, Joël; Prieur, Daniel; Bonavita, Marie-Anne Cambon</p> <p>2011-09-01</p> <p>The distribution of Archaea and methanogenic, methanotrophic and sulfate-reducing communities in three Atlantic ultramafic-hosted <span class="hlt">hydrothermal</span> systems (Rainbow, Ashadze, Lost City) was compared using 16S rRNA gene and functional gene (mcrA, pmoA and dsrA) clone libraries. The overall archaeal community was diverse and heterogeneously distributed between the <span class="hlt">hydrothermal</span> <span class="hlt">sites</span> and the types of samples analyzed (seawater, <span class="hlt">hydrothermal</span> fluid, chimney and sediment). The Lost City <span class="hlt">hydrothermal</span> field, characterized by high alkaline warm fluids (pH>11; T<95 °C), harbored a singular archaeal diversity mostly composed of unaffiliated Methanosarcinales. The archaeal communities associated with the recently discovered Ashadze 1 <span class="hlt">site</span>, one of the deepest <span class="hlt">active</span> <span class="hlt">hydrothermal</span> fields known (4100 m depth), showed significant differences between the two different vents analyzed and were characterized by putative extreme halophiles. Sequences related to the rarely detected Nanoarchaeota phylum and Methanopyrales order were also retrieved from the Rainbow and Ashadze <span class="hlt">hydrothermal</span> fluids. However, the methanogenic Methanococcales was the most widely distributed hyper/thermophilic archaeal group among the hot and acidic ultramafic-hosted <span class="hlt">hydrothermal</span> system environments. Most of the lineages detected are linked to methane and hydrogen cycling, suggesting that in ultramafic-hosted <span class="hlt">hydrothermal</span> systems, large methanogenic and methanotrophic communities could be fuelled by <span class="hlt">hydrothermal</span> fluids highly enriched in methane and hydrogen.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JAfES..58..812C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JAfES..58..812C"><span id="translatedtitle">A geophysical multi-parametric analysis of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at Dallol, Ethiopia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carniel, Roberto; Jolis, Ester Muñoz; Jones, Josh</p> <p>2010-12-01</p> <p>During December 2003, three seismic stations were installed close to the hornitos of the <span class="hlt">hydrothermal</span> system at Dallol, complemented by radiometer and infrasonic measurements. A combined geophysical data set was collected for about three days. During this period thermal, seismic and acoustic records indicate the presence of two regimes characterized by a different energy distribution in frequency. Few volcano-tectonic events appear superimposed to the continuous <span class="hlt">hydrothermal</span> tremor. The continuous data indicate variable shallow processes most likely related with variations in temperature and degassing processes within the shallow geothermal system. This alternation of low and high regimes shows significant similarities with other volcanic systems of different nature, although at Dallol the transition is more evident in the thermal than in the seismic and acoustic data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5290771','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5290771"><span id="translatedtitle">Stratigraphic development and <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> in the central western Cascade Range, Oregon</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cummings, M.L.; Bull, M.K. ); Pollock, J.M. ); Thompson, G.D. )</p> <p>1990-11-10</p> <p>Two volcanic sequences bounded by erosional unconformities compose the stratigraphy of the North Santiam mining district, Western Cascade Range, Oregon. Diorite, grandodiorite, and leucocratic quartz porphyry dikes, stocks, and sills intrude the breccias, flows, and tuffs of a volcanic center in the older Sardine Formation. Tourmaline-bearing breccia pipes are associated with the porphyritic granodiorite intrusions. An erosional unconformity separates the Sardine Formation from the overlying Elk Lake formation. The alteration patterns in the two formations are consistent with the development of <span class="hlt">hydrothermal</span> systems during the eruption of each formation. However, the development of the two <span class="hlt">hydrothermal</span> systems is separated by a period of erosion of the older volcanic pile. Early formation of mineralization that resembles porphyry copper deposits occurred within the Sardine Formation, and later, after eruption of the Elk Lake formation, epithermal veins and alteration developed along faults, fractures, and the margins of dikes in the Sardine Formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26872039','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26872039"><span id="translatedtitle">Coupled RNA-SIP and metatranscriptomics of <span class="hlt">active</span> chemolithoautotrophic communities at a deep-sea <span class="hlt">hydrothermal</span> vent.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fortunato, Caroline S; Huber, Julie A</p> <p>2016-08-01</p> <p>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 <span class="hlt">activity</span> 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 <span class="hlt">active</span> autotrophic bacteria and archaea and their pathways present in low-temperature <span class="hlt">hydrothermal</span> fluids from Axial Seamount, an <span class="hlt">active</span> 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 <span class="hlt">activity</span> of distinct chemolithoautotrophic communities across a thermal gradient of a deep-sea <span class="hlt">hydrothermal</span> vent. PMID:26872039</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5029171','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5029171"><span id="translatedtitle">Coupled RNA-SIP and metatranscriptomics of <span class="hlt">active</span> chemolithoautotrophic communities at a deep-sea <span class="hlt">hydrothermal</span> vent</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fortunato, Caroline S; Huber, Julie A</p> <p>2016-01-01</p> <p>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 <span class="hlt">activity</span> 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 <span class="hlt">active</span> autotrophic bacteria and archaea and their pathways present in low-temperature <span class="hlt">hydrothermal</span> fluids from Axial Seamount, an <span class="hlt">active</span> 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 13C 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 <span class="hlt">activity</span> of distinct chemolithoautotrophic communities across a thermal gradient of a deep-sea <span class="hlt">hydrothermal</span> vent. PMID:26872039</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22490563','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22490563"><span id="translatedtitle">Photocatalytic <span class="hlt">activity</span> of BiFeO{sub 3} nanoparticles synthesized through <span class="hlt">hydrothermal</span> method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dhanalakshmi, Radhalayam; Muneeswaran, M.; Vanga, Pradeep Reddy; Ashok, M.; Giridharan, N. V.</p> <p>2015-06-24</p> <p>Multiferroic BiFeO{sub 3} (BFO) nanoparticles (Nps) were synthesized using <span class="hlt">hydrothermal</span> method. From the X-Ray diffraction analysis (XRD), the synthesized Nps were found to having rhombohedral structure with R3c space group confirmed by Rietveld analysis. Fourier transform infrared spectroscopy (FTIR) analysis was carried out to identify the chemical bonds present in the BFO Nps. Photocatalytic properties of synthesized Nps were studied for the degradation of Methylene Blue (MB) dye under visible light of 150W.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/8204','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/8204"><span id="translatedtitle">Field Trip Guide to Serpentinite, Silica-Carbonate Alteration, and Related <span class="hlt">Hydrothermal</span> <span class="hlt">Activity</span> in the Clear Lake Region, California</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fraser Goff; George Guthrie</p> <p>1999-06-01</p> <p>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 <span class="hlt">hydrothermal</span> alteration and Quarternary volcanic <span class="hlt">activity</span>. Stanley et al. (1998) summarized geophysical characteristics of the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984ESRv...20....1R&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984ESRv...20....1R&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> mineralization at seafloor spreading centers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rona, Peter A.</p> <p>1984-01-01</p> <p>The recent recognition that metallic mineral deposits are concentrated by <span class="hlt">hydrothermal</span> processes at seafloor spreading centers constitutes a scientific breakthrough that opens <span class="hlt">active</span> <span class="hlt">sites</span> at seafloor spreading centers as natural laboratories to investigate ore-forming processes of such economically useful deposits as massive sulfides in volcanogenic rocks on land, and that enhances the metallic mineral potential of oceanic crust covering two-thirds of the Earth both beneath ocean basins and exposed on land in ophiolite belts. This paper reviews our knowledge of processes of <span class="hlt">hydrothermal</span> mineralization and the occurrence and distribution of <span class="hlt">hydrothermal</span> mineral deposits at the global oceanic ridge-rift system. Sub-seafloor <span class="hlt">hydrothermal</span> convection involving circulation of seawater through fractured rocks of oceanic crust driven by heat supplied by generation of new lithosphere is nearly ubiquitous at seafloor spreading centers. However, ore-forming <span class="hlt">hydrothermal</span> systems are extremely localized where conditions of anomalously high thermal gradients and permeability increase <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> from the ubiquitous low-intensity background level (⩽ 200°C) to high-intensity characterized by high temperatures ( > 200-c.400°C), and a rate and volume of flow sufficient to sustain chemical reactions that produce acid, reducing, metal-rich primary <span class="hlt">hydrothermal</span> solutions. A series of mineral phases with sulfides and oxides as high- and low-temperature end members, respectively, are precipitated along the upwelling limb and in the discharge zone of single-phase systems as a function of increasing admixture of normal seawater. The occurrence of <span class="hlt">hydrothermal</span> mineral deposits is considered in terms of spatial and temporal frames of reference. Spatial frames of reference comprise structural features along-axis (linear sections that are the loci of seafloor spreading alternating with transform faults) and perpendicular to axis (axial zone of volcanic extrusion and marginal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6216758','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6216758"><span id="translatedtitle"><span class="hlt">Active</span> <span class="hlt">Sites</span> Environmental Monitoring Program: Action levels</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ashwood, J.S.; Ashwood, T.L.</p> <p>1991-10-01</p> <p>The <span class="hlt">Active</span> <span class="hlt">Sites</span> Environmental Monitoring Program (ASEMP) was established at Oak Ridge National Laboratory to provide for early leak detection and to monitor performance of the <span class="hlt">active</span> low-level waste disposal facilities in Solid Waste Storage Area (SWSA) 6 and the transuranic waste storage areas in SWSA 5 North. Early leak detection is accomplished by sampling runoff, groundwater, and perched water in burial trenches. Sample results are compared to action levels that represent background contamination by naturally occurring and fallout-derived radionuclides. 15 refs., 3 figs., 12 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFMOS13D1761S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFMOS13D1761S&link_type=ABSTRACT"><span id="translatedtitle">Characterization of <span class="hlt">Active</span> <span class="hlt">Hydrothermal</span> Fluid Discharge and Recharge Zones in the Endeavour Axial Valley, Juan de Fuca Ridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salmi, M.; Hutnak, M.; Hearn, C.; Tivey, M.; Bjorklund, T.; Johnson, H. P.</p> <p>2012-12-01</p> <p><span class="hlt">Sites</span> where warm <span class="hlt">hydrothermal</span> fluid vents at mid-ocean spreading centers are important for understanding a wide range of critical oceanic processes, but discharge zones represent a very limited portion of crustal fluid circulation pathways. Mapping the distribution of both fluid recharge and discharge <span class="hlt">sites</span> within the axial valley provides wider insight into the larger scale features of <span class="hlt">hydrothermal</span> circulation. Our 2011 survey consisted of 180 conductive heat flow stations within the Endeavour axial valley in roughly a 400 m by 1000 m grid, extending across the entire axial valley from the outer flank of the western boundary ridge to the eastern wall. Data acquisition used thermal blankets which measured conductive heat flow without requiring substantial sediment cover. A surprising result from this survey was zones of high heat flow extending across-strike, from the summit of the west valley wall across the entire axial valley floor. This trend was correlated with anomalously low seafloor magnetization from a near-bottom survey with the ROV JASON. Unexpectedly, over half of the axial valley floor was anomalously low at <50 mW m-2, while a small portion of the <span class="hlt">sites</span> within the 'warm zone' had heat flow values >1 W m-2. The areas of extremely low heat flow values are interpreted as being directly influenced by recharge zones. Based on MCS estimates of partial melt depth below the axial valley and the assumption of no fluid advection, the purely conductive heat flow for this region should be on the order of 1 W m-2.The observation that conductive heat flux is suppressed over large portions of the axial valley floor suggests that heat transfer within the crustal sub-surface fluid reservoir is widespread, and impacts a large portion of our survey area. The largely bi-modal distribution of high and low conductive heat flow, coupled with geophysical and video observations, suggest current Endeavour axial valley crustal fluid circulation models need to be re-evaluated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1984ESRv...20....1R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1984ESRv...20....1R"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> mineralization at seafloor spreading centers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rona, Peter A.</p> <p>1984-01-01</p> <p>The recent recognition that metallic mineral deposits are concentrated by <span class="hlt">hydrothermal</span> processes at seafloor spreading centers constitutes a scientific breakthrough that opens <span class="hlt">active</span> <span class="hlt">sites</span> at seafloor spreading centers as natural laboratories to investigate ore-forming processes of such economically useful deposits as massive sulfides in volcanogenic rocks on land, and that enhances the metallic mineral potential of oceanic crust covering two-thirds of the Earth both beneath ocean basins and exposed on land in ophiolite belts. This paper reviews our knowledge of processes of <span class="hlt">hydrothermal</span> mineralization and the occurrence and distribution of <span class="hlt">hydrothermal</span> mineral deposits at the global oceanic ridge-rift system. Sub-seafloor <span class="hlt">hydrothermal</span> convection involving circulation of seawater through fractured rocks of oceanic crust driven by heat supplied by generation of new lithosphere is nearly ubiquitous at seafloor spreading centers. However, ore-forming <span class="hlt">hydrothermal</span> systems are extremely localized where conditions of anomalously high thermal gradients and permeability increase <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> from the ubiquitous low-intensity background level (⩽ 200°C) to high-intensity characterized by high temperatures ( > 200-c.400°C), and a rate and volume of flow sufficient to sustain chemical reactions that produce acid, reducing, metal-rich primary <span class="hlt">hydrothermal</span> solutions. A series of mineral phases with sulfides and oxides as high- and low-temperature end members, respectively, are precipitated along the upwelling limb and in the discharge zone of single-phase systems as a function of increasing admixture of normal seawater. The occurrence of <span class="hlt">hydrothermal</span> mineral deposits is considered in terms of spatial and temporal frames of reference. Spatial frames of reference comprise structural features along-axis (linear sections that are the loci of seafloor spreading alternating with transform faults) and perpendicular to axis (axial zone of volcanic extrusion and marginal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.B43G0497A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.B43G0497A"><span id="translatedtitle">Distribution, <span class="hlt">activity</span> and function of short-chain alkane degrading phylotypes in <span class="hlt">hydrothermal</span> vent sediments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adams, M. M.; Joye, S. B.; Hoarfrost, A.; Girguis, P. R.</p> <p>2012-12-01</p> <p>Global geochemical analyses suggest that C2-C4 short chain alkanes are a common component of the utilizable carbon pool in deep-sea sediments worldwide and have been found in diverse ecosystems. From a thermodynamic standpoint, the anaerobic microbial oxidation of these aliphatic hydrocarbons is more energetically yielding than the anaerobic oxidation of methane (AOM). Therefore, the preferential degradation of these hydrocarbons may compete with AOM for the use of oxidants such as sulfate, or other potential oxidants. Such processes could influence the fate of methane in the deep-sea. Sulfate-reducing bacteria (SRB) from hydrocarbon seep sediments of the Gulf of Mexico and Guaymas Basin have previously been enriched that anaerobically oxidize short chain alkanes to generate CO2 with the preferential utilization of 12C-enriched alkanes (Kniemeyer et al. 2007). Different temperature regimens along with multiple substrates were tested and a pure culture (deemed BuS5) was isolated from mesophilic enrichments with propane or n-butane as the sole carbon source. Through comparative sequence analysis, strain BuS5 was determined to cluster with the metabolically diverse Desulfosarcina / Desulfococcus cluster, which also contains the SRB found in consortia with anaerobic, methane-oxidizing archaea in seep sediments. Enrichments from a terrestrial, low temperature sulfidic hydrocarbon seep also corroborated that propane degradation occurred with most bacterial phylotypes surveyed belonging to the Deltaproteobacteria, particularly Desulfobacteraceae (Savage et al. 2011). To date, no microbes capable of ethane oxidation or anaerobic C2-C4 alkane oxidation at thermophilic temperature have been isolated. The sediment-covered, <span class="hlt">hydrothermal</span> vent systems found at Middle Valley (Juan de Fuca Ridge, eastern Pacific Ocean) are a prime environment for investigating mesophilic to thermophilic anaerobic oxidation of short-chain alkanes, given the elevated temperatures and dissolved</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/548615','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/548615"><span id="translatedtitle">Characterization of <span class="hlt">active</span> <span class="hlt">sites</span> in zeolite catalysts</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Eckert, J.; Bug, A.; Nicol, J.M.</p> <p>1997-11-01</p> <p>This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Atomic-level details of the interaction of adsorbed molecules with <span class="hlt">active</span> <span class="hlt">sites</span> in catalysts are urgently needed to facilitate development of more effective and/or environmentally benign catalysts. To this end the authors have carried out neutron scattering studies combined with theoretical calculations of the dynamics of small molecules inside the cavities of zeolite catalysts. The authors have developed the use of H{sub 2} as a probe of adsorption <span class="hlt">sites</span> by observing the hindered rotations of the adsorbed H{sub 2} molecule, and they were able to show that an area near the four-rings is the most likely adsorption <span class="hlt">site</span> for H{sub 2} in zeolite A while adsorption of H{sub 2} near cations located on six-ring <span class="hlt">sites</span> decreases in strength as Ni {approximately} Co > Ca > Zn {approximately} Na. Vibrational and rotational motions of ethylene and cyclopropane adsorption complexes were used as a measure for zeolite-adsorbate interactions. Preliminary studies of the binding of water, ammonia, and methylamines were carried out in a number of related guest-host materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007GGG.....8.7007D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007GGG.....8.7007D"><span id="translatedtitle">Submarine <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> along the mid-Kermadec Arc, New Zealand: Large-scale effects on venting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Ronde, C. E. J.; Baker, E. T.; Massoth, G. J.; Lupton, J. E.; Wright, I. C.; Sparks, R. J.; Bannister, S. C.; Reyners, M. E.; Walker, S. L.; Greene, R. R.; Ishibashi, J.; Faure, K.; Resing, J. A.; Lebon, G. T.</p> <p>2007-07-01</p> <p>The 2,500-km Kermadec-Tonga arc is the longest submarine arc on the planet. Here, we report on the second of a series of cruises designed to investigate large-scale controls on <span class="hlt">active</span> <span class="hlt">hydrothermal</span> venting on this arc. The 2002 NZAPLUME II cruise surveyed 12 submarine volcanic centers along ~580 km of the middle Kermadec arc (MKA), extending a 1999 cruise that surveyed 260 km of the southern Kermadec arc (SKA). Average spacing between volcanic centers increases northward from 30 km on backarc crust along the SKA, to 45 km on backarc crust along the southern MKA, to 58 km where the MKA joins the Kermadec Ridge. Volcanic cones dominate in the backarc, and calderas dominate the Kermadec Ridge. The incidence of venting is higher along the MKA (83%, 10 of 12 volcanic centers) than the SKA (67%, 8 of 12), but the relative intensity of venting, as given by plume thickness, areal extent, and concentration of dissolved gases and ionic species, is generally weaker in the MKA. This pattern may reflect subduction of the ~17-km-thick oceanic Hikurangi Plateau beneath the SKA. Subduction of this basaltic mass should greatly increase fluid loss from the downgoing slab, initiating extensive melting in the upper mantle wedge and invigorating the <span class="hlt">hydrothermal</span> systems of the SKA. Conversely, volcanic centers in the southern MKA are starved of magma replenishment and so their <span class="hlt">hydrothermal</span> systems are waning. Farther north, where the MKA centers merge with the Kermadec Ridge, fewer but larger magma bodies accumulate in the thicker (older) crust, ensuring more widely separated, caldera-dominated volcanic centers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017161','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017161"><span id="translatedtitle">Mass transfer constraints on the chemical evolution of an <span class="hlt">active</span> <span class="hlt">hydrothermal</span> system, Valles caldera, New Mexico</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>White, A.F.; Chuma, N.J.; Goff, F.</p> <p>1992-01-01</p> <p>Partial equilibrium conditions occur between fluids and secondary minerals in the Valles <span class="hlt">hydrothermal</span> system, contained principally in the Tertiary rhyolitic Bandelier Tuff. The mass transfer processes are governed by reactive phase compositions, surface areas, water-rock ratios, reaction rates, and fluid residence times. Experimental dissolution of the vitric phase of the tuff was congruent with respect to Cl in the solid and produced reaction rates which obeyed a general Arrhenius release rate between 250 and 300??C. The 18O differences between reacted and unreacted rock and fluids, and mass balances calculations involving Cl in the glass phase, produced comparable water-rock ratios of unity, confirming the importance of irreversible reaction of the vitric tuff. A fluid residence time of approximately 2 ?? 103 years, determined from fluid reservoir volume and discharge rates, is less than 0.2% of the total age of the <span class="hlt">hydrothermal</span> system and denotes a geochemically and isotopically open system. Mass transfer calculations generally replicated observed reservoir pH, Pco2, and PO2 conditions, cation concentrations, and the secondary mineral assemblage between 250 and 300??C. The only extraneous component required to maintain observed calcite saturation and high Pco2 pressures was carbon presumably derived from underlying Paleozoic limestones. Phase rule constraints indicate that Cl was the only incompatible aqueous component not controlled by mineral equilibrium. Concentrations of Cl in the reservoir directly reflect mass transport rates as evidenced by correlations between anomalously high Cl concentrations in the fluids and tuff in the Valles caldera relative to other <span class="hlt">hydrothermal</span> systems in rhyolitic rocks. ?? 1992.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MinDe..49..535D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MinDe..49..535D"><span id="translatedtitle">Timing and duration of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at the Los Bronces porphyry cluster: an update</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deckart, K.; Silva, W.; Spröhnle, C.; Vela, I.</p> <p>2014-06-01</p> <p>New geochronological data from the Los Bronces cluster of the Río Blanco-Los Bronces mega-porphyry Cu-Mo district establish a wide range of magmatism, <span class="hlt">hydrothermal</span> alteration, and mineralization ages, both in terms of areal extent and time. The northern El Plomo and southernmost Los Piches exploration areas contain the oldest barren porphyritic intrusions with U-Pb ages of 10.8 ± 0.1 Ma and 13.4 ± 0.1 Ma, respectively. A hypabyssal barren intrusion adjacent northwesterly to the main pit area yields a slightly younger age of 10.2 ± 0.3 Ma (San Manuel sector, U-Pb), whereas in the Los Bronces (LB) open-pit area, the present day mineral extraction zone, porphyries range from 8.49 to 6.02 Ma (U-Pb). <span class="hlt">Hydrothermal</span> biotite and sericite ages are up to 0.5 Ma younger but consistent with the cooling of the corresponding intrusion events of each area. Two quartz-molybdenite B-type veins from the LB open pit have Re-Os molybdenite ages of 5.65 ± 0.03 Ma and 5.35 ± 0.03 Ma consistent with published data for the contiguous Río Blanco cluster. The San Manuel exploration area within the Los Bronces cluster, located about 1.5-2 km southeast of the open-pit extraction zone, shows both the oldest <span class="hlt">hydrothermal</span> biotite (7.70 ± 0.07 Ma; 40Ar/39Ar) and breccia cement molybdenite ages (8.36 ± 0.06 Ma; Re-Os) registered in the entire Río Blanco-Los Bronces district. These are also older than those reported from the El Teniente porphyry Cu(-Mo) deposit, suggesting that mineralization in the late Miocene to early Pliocene porphyry belt of Central Chile commenced 2 Ma before the previously accepted age of 6.3 Ma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V53A4839S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V53A4839S"><span id="translatedtitle">Heat Source for <span class="hlt">Active</span> Venting at the Lost City <span class="hlt">Hydrothermal</span> Field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, J. E.; Germanovich, L. N.; Lowell, R. P.</p> <p>2014-12-01</p> <p>Located at the inside corner high of the Mid-Atlantic Ridge (MAR), 30°N and the Atlantis Transform Fault (ATF), the Atlantis Massif has been uplifted over the past ~2 my. The Southern Ridge of this massif hosts the Lost City <span class="hlt">Hydrothermal</span> Field (LCHF), an off-axis <span class="hlt">hydrothermal</span> vent field with carbonate chimney ages surpassing 120,000 yrs. The fluids discharging at LCHF carry geochemical signals that show a direct interaction with serpentinites. However, mineralogical evidence suggests that peridotite hydration began early in the formation of oceanic core complexes and previous modeling results indicate that serpentinization is unlikely to generate the heat necessary to maintain current levels of discharge at LCHF. This work develops a model for the LCHF venting based on the evidence of tectonic strain, detachment faulting, serpentinization, and convective fluid flow. We constrain fluid flow at the LCHF by vent geochemistry, vent temperature, seismically inferred faulting, and expected geothermal gradient ≈100°C/km. Present understanding of tectonic processes at the intersection of MAR and ATF suggests that unroofing of the footwall and crustal flexing of the massif induced normal faults, which run parallel to the MAR, throughout the Southern Ridge. In the absence of the evidence of magmatism, we test the feasibility of the geothermal gradient to cause fluid circulation in the high-permeability, sub-vertical fault zone. Fluid circulation in the fault zone is complemented by the bulk porous flow driven through the Southern Ridge by the lateral temperature gradient between the cold water on the steep face along the ATF side and the hot interior of the massif. In this scenario, the high pH <span class="hlt">hydrothermal</span> fluids pass through the serpentinized zone before discharging as both high-temperature focused flow (40°-91°C) and low-temperature (≈15°C) diffuse flow at the LCHF.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/107732','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/107732"><span id="translatedtitle">Stable isotope geochemistry of clay minerals from fossil and <span class="hlt">active</span> <span class="hlt">hydrothermal</span> systems, southwestern Hokkaido, Japan</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Marumo, Katsumi; Longstaffe, F.J.; Matsubaya, Osamu</p> <p>1995-06-01</p> <p>Miocene submarine to Quaternary terrestrial volcanism in southwestern Hokkaido, Japan, is associated with <span class="hlt">hydrothermal</span> clay alteration and mineralization, including Kuroko-type deposits at Kagenosawa (14.2 Ma, Cu > Zn, Pb > Au) and Minamishiraoi (12.5 Ma, Ba > Zn, Pb, Cu), vein-style at Noboribetsu ({le} 1.8 Ma). The {delta}D and {delta}{sup 18}O values of mica (sericite), mica-smectite, chlorite, chlorite-smectite, nacrite, dickite, kaolinite, and smectite were used to deduce the type(s) of <span class="hlt">hydrothermal</span> fluid at each locality. Calculated compositions for Minamishiraoi and Kagenosawa fluids suggest that seawater was dominant, but some mixing with magmatic water is also indicated, particularly for the polymetallic Kagenosawa deposit. <span class="hlt">Hydrothermal</span> fluids at Date, Chitose, and the Noboribetsu geothermal area were dominated by meteoric water. The {delta}D and {delta}{sup 18}O values of modern hot-spring waters at Noboribetsu closely parallel fluid compositions calculated for the clay alteration at Date, Chitose, and Noboribetsu. In vacuo TG patterns of other smectitic clays suggested gradual loss of hydroxyl-groups beginning near 200{degrees}C, rather than the more typical distinct separation between interlayer water at <200{degrees}C and hydroxyl-groups at >400{degrees}C. This behaviour constrains the maximum temperature that can be used for in vacuo preheating. Furthermore, shifts to lower {delta}D values (by as much as 19{per_thousand}) were obtained when this smectite was dispersed in low-D water for three weeks, perhaps indicating isotopic exchange. However, with appropriate care, {delta}D values obtained by conventional procedures (including preheating to {le}200{degrees}C) normally reproduced natural compositions of the smectitic clays with acceptable accuracy and precision.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JEMat..45.4215H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JEMat..45.4215H"><span id="translatedtitle">Enhanced Visible-Light Photocatalytic <span class="hlt">Activity</span> of C/Ce-Codoped ZnO Nanoellipsoids Synthesized by <span class="hlt">Hydrothermal</span> Method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ha, Luu Thi Viet; Dai, Luu Minh; Nhiem, Dao Ngoc; Van Cuong, Nguyen</p> <p>2016-08-01</p> <p>C/Ce-codoped ZnO nanomaterial has been synthesized by a <span class="hlt">hydrothermal</span> method and its physical properties and characterization investigated using thermogravimetric and differential thermal analysis (TG-DTA), x-ray diffraction (XRD) analysis, Fourier-transform infrared (FTIR) spectroscopy, energy-dispersive x-ray (EDX) spectroscopy, UV-Vis diffuse reflectance spectroscopy, and scanning electron microscopy (SEM). The photocatalytic <span class="hlt">activity</span> of the nanomaterial was examined using methylene blue as organic dye under visible-light source. The results show that the C/Ce-codoped ZnO nanomaterial exhibited higher photocatalytic <span class="hlt">activity</span> under visible-light irradiation compared with undoped ZnO, Ce-doped ZnO or C-doped ZnO nanomaterials. Such enhancement of the photocatalytic <span class="hlt">activity</span> of C/Ce-codoped ZnO under visible-light irradiation suggests that these nanoparticles might have good applications in optoelectronics and wastewater treatment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26433479','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26433479"><span id="translatedtitle">Tunable ZnO spheres with high anti-biofilm and antibacterial <span class="hlt">activity</span> via a simple green <span class="hlt">hydrothermal</span> route.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Patrinoiu, Greta; Calderón-Moreno, José Maria; Chifiriuc, Carmen Mariana; Saviuc, Crina; Birjega, Ruxandra; Carp, Oana</p> <p>2016-01-15</p> <p>A family of distinct ZnO morphologies - hollow, compartmented, core-shell and full solid ZnO spheres, dispersed or interconnected - is obtained by a simple <span class="hlt">hydrothermal</span> route, in the presence of the starch biopolymer. The zinc-carbonaceous precursors were characterized by infrared spectroscopy, thermal analysis and scanning electron microscopy, while the ZnO spheres, obtained after the thermal processing, were investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, UV-VIS spectroscopy, photoluminescence measurements, antimicrobial, anti-biofilm and flow cytometry tests. The formation mechanism proposed for this versatile synthesis route is based on the gelling ability of amylose, one of the starch template constituents, responsible for the effective embedding of zinc cations into starch prior to its <span class="hlt">hydrothermal</span> carbonization. The simple variation of the raw materials concentration dictates the type of ZnO spheres. The micro-sized ZnO spheres exhibit high antibacterial and anti-biofilm <span class="hlt">activity</span> against Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa) reference and methicillin resistant clinical strains especially for Gram-negative biofilms (P. aeruginosa), demonstrating great potential for new ZnO anti-biofilm formulations. PMID:26433479</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5024310','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5024310"><span id="translatedtitle">Muon dynamic radiography of density changes induced by <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at the La Soufrière of Guadeloupe volcano</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jourde, Kevin; Gibert, Dominique; Marteau, Jacques; de Bremond d’Ars, Jean; Komorowski, Jean-Christophe</p> <p>2016-01-01</p> <p>Imaging geological structures through cosmic muon radiography is a newly developed technique which shows a great potential in volcanology. Here we demonstrate that muon radiography permits to detect and characterize mass movements in shallow <span class="hlt">hydrothermal</span> systems of low-energy <span class="hlt">active</span> volcanoes like the La Soufrière lava dome. We present an experiment conducted on this volcano during the Summer 2014 and bring evidence that very important density changes occurred in three domains of the lava dome. Depending on their position and on the medium porosity the volumes of these domains vary from 1 × 106 m3 to 7 × 106 m3. However, the total mass budget remains approximately constant : two domains show a mass loss (Δm∈ [−0.8;−0.4] × 109 kg) and the third one a mass gain (Δm∈ [1.5; 2.5] × 109 kg). We attribute the negative mass changes to the formation of steam in shallow <span class="hlt">hydrothermal</span> reservoir previously partly filled with liquid water. This coincides with the emergence of new fumaroles on top of the volcano. The positive mass change is synchronized with the negative mass changes indicating that liquid water probably flowed from the two reservoirs invaded by steam toward the third reservoir. PMID:27629497</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JESS..123..887S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JESS..123..887S"><span id="translatedtitle">Mineralogical and chemical characteristics of newer dolerite dyke around Keonjhar, Orissa: Implication for <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> in subduction zone setting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sengupta, Piyali; Ray, Arijit; Pramanik, Sayantani</p> <p>2014-06-01</p> <p>The newer dolerite dykes around Keonjhar within the Singbhum Granite occur in NE-SW, NW-SE and NNE-SSW trends. The mafic dykes of the present study exhibit several mineralogical changes like clouding of plagioclase feldspars, bastitisation of orthopyroxene, and development of fibrous amphibole (tremolite-actinolite) from clinopyroxene, which are all considered products of <span class="hlt">hydrothermal</span> alterations. This alteration involves addition and subtraction of certain elements. Graphical analyses with Alteration index and elemental abundances show that elements like Rb, Ba, Th, La and K have been added during the alteration process, whereas elements like Sc, Cr, Co, Ni, Si, Al, Fe, Mg and Ca have been removed. It is observed that in spite of such chemical alteration, correlation between major and trace elements, characteristic of petrogenetic process, is still preserved. This might reflect systematic Alteration (addition or subtraction) of elements without disturbing the original element to element correlation. It has also been established by earlier workers that the evolution of newer dolerite had occurred in an arc-back arc setting which may also be true for newer dolerites of the present study. This is evident from plots of pyroxene composition and whole rock composition of newer dolerite samples in different tectonic discrimination diagrams using immobile elements. The newer dolerite dykes of the Keonjhar area may thus be considered to represent an example of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> on mafic rocks in an arc setting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27629497','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27629497"><span id="translatedtitle">Muon dynamic radiography of density changes induced by <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at the La Soufrière of Guadeloupe volcano.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jourde, Kevin; Gibert, Dominique; Marteau, Jacques; de Bremond d'Ars, Jean; Komorowski, Jean-Christophe</p> <p>2016-01-01</p> <p>Imaging geological structures through cosmic muon radiography is a newly developed technique which shows a great potential in volcanology. Here we demonstrate that muon radiography permits to detect and characterize mass movements in shallow <span class="hlt">hydrothermal</span> systems of low-energy <span class="hlt">active</span> volcanoes like the La Soufrière lava dome. We present an experiment conducted on this volcano during the Summer 2014 and bring evidence that very important density changes occurred in three domains of the lava dome. Depending on their position and on the medium porosity the volumes of these domains vary from 1 × 10(6) m(3) to 7 × 10(6) m(3). However, the total mass budget remains approximately constant : two domains show a mass loss (Δm∈ [-0.8;-0.4] × 10(9) kg) and the third one a mass gain (Δm∈ [1.5; 2.5] × 10(9) kg). We attribute the negative mass changes to the formation of steam in shallow <span class="hlt">hydrothermal</span> reservoir previously partly filled with liquid water. This coincides with the emergence of new fumaroles on top of the volcano. The positive mass change is synchronized with the negative mass changes indicating that liquid water probably flowed from the two reservoirs invaded by steam toward the third reservoir. PMID:27629497</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27629497','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27629497"><span id="translatedtitle">Muon dynamic radiography of density changes induced by <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at the La Soufrière of Guadeloupe volcano.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jourde, Kevin; Gibert, Dominique; Marteau, Jacques; de Bremond d'Ars, Jean; Komorowski, Jean-Christophe</p> <p>2016-09-15</p> <p>Imaging geological structures through cosmic muon radiography is a newly developed technique which shows a great potential in volcanology. Here we demonstrate that muon radiography permits to detect and characterize mass movements in shallow <span class="hlt">hydrothermal</span> systems of low-energy <span class="hlt">active</span> volcanoes like the La Soufrière lava dome. We present an experiment conducted on this volcano during the Summer 2014 and bring evidence that very important density changes occurred in three domains of the lava dome. Depending on their position and on the medium porosity the volumes of these domains vary from 1 × 10(6) m(3) to 7 × 10(6) m(3). However, the total mass budget remains approximately constant : two domains show a mass loss (Δm∈ [-0.8;-0.4] × 10(9) kg) and the third one a mass gain (Δm∈ [1.5; 2.5] × 10(9) kg). We attribute the negative mass changes to the formation of steam in shallow <span class="hlt">hydrothermal</span> reservoir previously partly filled with liquid water. This coincides with the emergence of new fumaroles on top of the volcano. The positive mass change is synchronized with the negative mass changes indicating that liquid water probably flowed from the two reservoirs invaded by steam toward the third reservoir.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...633406J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...633406J"><span id="translatedtitle">Muon dynamic radiography of density changes induced by <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at the La Soufrière of Guadeloupe volcano</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jourde, Kevin; Gibert, Dominique; Marteau, Jacques; de Bremond D’Ars, Jean; Komorowski, Jean-Christophe</p> <p>2016-09-01</p> <p>Imaging geological structures through cosmic muon radiography is a newly developed technique which shows a great potential in volcanology. Here we demonstrate that muon radiography permits to detect and characterize mass movements in shallow <span class="hlt">hydrothermal</span> systems of low-energy <span class="hlt">active</span> volcanoes like the La Soufrière lava dome. We present an experiment conducted on this volcano during the Summer 2014 and bring evidence that very important density changes occurred in three domains of the lava dome. Depending on their position and on the medium porosity the volumes of these domains vary from 1 × 106 m3 to 7 × 106 m3. However, the total mass budget remains approximately constant : two domains show a mass loss (Δm∈ [‑0.8‑0.4] × 109 kg) and the third one a mass gain (Δm∈ [1.5; 2.5] × 109 kg). We attribute the negative mass changes to the formation of steam in shallow <span class="hlt">hydrothermal</span> reservoir previously partly filled with liquid water. This coincides with the emergence of new fumaroles on top of the volcano. The positive mass change is synchronized with the negative mass changes indicating that liquid water probably flowed from the two reservoirs invaded by steam toward the third reservoir.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/7164178','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/7164178"><span id="translatedtitle">A national drilling program to study the roots of <span class="hlt">active</span> <span class="hlt">hydrothermal</span> systems related to young magmatic intrusions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1984-01-01</p> <p>The importance of studies of <span class="hlt">active</span> <span class="hlt">hydrothermal</span>-magma systems as part of a national continental scientific drilling program has been emphasized in numerous workshops and symposia. The present report, prepared by the Panel on Thermal Regimes of the Continental Scientific Drilling Committee, both reinforces and expands on earlier recommendations. The US Geodynamics Committee 1979 report of the Los Almos workshop, Continental Scientific Drilling Program, placed major emphasis on maximizing the scientific value of current and planned drilling by industry and government, supplementing these efforts with holes drilled solely for scientific purposes. Although the present report notes the importance of opportunities for scientific investigations that may be added on to current, mission-oriented drilling <span class="hlt">activities</span>, the Panel on Thermal Regimes recognizes that such opportunities are limited and thus focused its study on holes dedicated to broad scientific objectives. 16 refs., 2 figs., 4 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25820327','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25820327"><span id="translatedtitle">Microwave-assisted <span class="hlt">hydrothermal</span> synthesis of Cu/Cu2O hollow spheres with enhanced photocatalytic and gas sensing <span class="hlt">activities</span> at room temperature.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zou, Xinwei; Fan, Huiqing; Tian, Yuming; Zhang, Mingang; Yan, Xiaoyan</p> <p>2015-05-01</p> <p>Cu/Cu2O nano-heterostructure hollow spheres with a submicron diameter (200-500 nm) were prepared by a microwave-assisted <span class="hlt">hydrothermal</span> method using Cu(OAc)2·H2O, PVP and ascorbic acid solution as the precursors. The morphology of the products could evolve with the <span class="hlt">hydrothermal</span> time from solid spheres to thick-shell hollow spheres, then to thin-shell hollow spheres, and finally to nanoparticles. Moreover, the content of Cu in the products could be controlled by adjusting the <span class="hlt">hydrothermal</span> time. The spontaneous forming of the hollow structure spheres was found to result from the Ostwald ripening effect during the low temperature (100 °C) <span class="hlt">hydrothermal</span> reaction process. The photocatalytic degradation <span class="hlt">activities</span> on MO under visible-light irradiation and the gas sensing <span class="hlt">activities</span> toward the oxidizing NO2 gas of different Cu/Cu2O nano-heterostructure hollow spheres were investigated. As a result, the Cu/Cu2O nano-heterostructure hollow spheres obtained at the <span class="hlt">hydrothermal</span> time of 30 min, with a rough/porous thin-shell structure and a Cu content of about 10.5 wt%, exhibited the best photocatalytic and gas sensing performances compared with others.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004EOSTr..85...37E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004EOSTr..85...37E"><span id="translatedtitle">Explorations of Mariana Arc Volcanoes Reveal New <span class="hlt">Hydrothermal</span> Systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Embley, R. W.; Baker, E. T.; Chadwick, W. W., Jr.; Lupton, J. E.; Resing, J. A.; Massoth, G. J.; Nakamura, K.</p> <p>2004-01-01</p> <p>Some 20,000 km of volcanic arcs, roughly one-third the length of the global mid-ocean ridge (MOR) system, rim the western Pacific Ocean. Compared to 25 years of <span class="hlt">hydrothermal</span> investigations along MORs, exploration of similar <span class="hlt">activity</span> on the estimated ~600 submarine arc volcanoes is only beginning [Ishibashi and Urabe, 1995; De Ronde et al., 2003]. To help alleviate this under-sampling, the R/V T. G. Thompson was used in early 2003 (9 February to 5 March) to conduct the first complete survey of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> along 1200 km of the Mariana intra-oceanic volcanic arc. This region includes both the Territory of Guam and the Commonwealth of the Northern Mariana Islands. The expedition mapped over 50 submarine volcanoes with stunning new clarity (Figures 1 and 2) and found <span class="hlt">active</span> <span class="hlt">hydrothermal</span> discharge at 12 <span class="hlt">sites</span>, including the southern back-arc <span class="hlt">site</span>. This includes eight new <span class="hlt">sites</span> along the arc (West Rota, Northwest Rota, E. Diamante, Zealandia Bank, Maug Caldera, Ahyi, Daikoku, and Northwest Eifuku) and four <span class="hlt">sites</span> of previously known <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> (Seamount X, Esmeralda, Kasuga 2, and Nikko) (Figures 1 and 2). The mapping also fortuitously provided a ``before'' image of the submarine flanks of Anatahan Island, which had its first historical eruption on 10 May 2003 (Figures 1 and 3).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6381611','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6381611"><span id="translatedtitle"><span class="hlt">Active</span> <span class="hlt">site</span> of ribulosebisphosphate carboxylase/oxygenase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hartman, F.C.; Stringer, C.D.; Milanez, S.; Lee, E.H.</p> <p>1985-01-01</p> <p>Previous affinity labeling studies and comparative sequence analyses have identified two different lysines at the <span class="hlt">active</span> <span class="hlt">site</span> of ribulosebisphosphate carboxylase/oxygenase and have suggested their essentiality to function. The essential lysines occupy positions 166 and 329 in the Rhodospirillum rubrum enzyme and positions 175 and 334 in the spinach enzyme. Based on the pH-dependencies of inactivations of the two enzymes by trinitrobenzene sulfonate, Lys-166 (R. rubrum enzyme) exhibits a pK/sub a/ of 7.9 and Lys-334 (spinach enzyme) exhibits a pK/sub a/ of 9.0. These low pK/sub a/ values as well as the enhanced nucleophilicities of the lysyl residues argue that both are important to catalysis rather than to substrate binding. Lys-166 may correspond to the essential base that initiates catalysis and that displays a pK/sub a/ of 7.5 in the pH-curve for V/sub max//K/sub m/. Cross-linking experiments with 4,4'-diisothiocyano-2,2'-disulfonate stilbene demonstrate that the two <span class="hlt">active-site</span> lysines are within 12 A. 50 refs., 7 figs., 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JVGR..130...31P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JVGR..130...31P"><span id="translatedtitle">Drill core-based facies reconstruction of a deep-marine felsic volcano hosting an <span class="hlt">active</span> <span class="hlt">hydrothermal</span> system (Pual Ridge, Papau New Guinea, ODP Leg 193)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paulick, H.; Vanko, D. A.; Yeats, C. J.</p> <p>2004-02-01</p> <p>Pual Ridge is a deep-marine, felsic volcanic edifice in the eastern Manus back-arc basin (Papua New Guinea) with an estimated volume of ˜6 to 9 km 3. It is 1-1.5 km wide, 20 km long and rises 500-600 m above the surrounding ocean floor. The <span class="hlt">active</span> PACMANUS <span class="hlt">hydrothermal</span> field on the crest of Pual Ridge at 1640-1690 m below sea level was the target of Ocean Drilling Program Leg 193. Variably altered dacite lavas have been recovered from the subsurface of a low-T discharge <span class="hlt">site</span> (Snowcap) and a high-T black smoker <span class="hlt">site</span> (Roman Ruins) reaching a maximum depth of 380 m below seafloor (mbsf). Volcanic facies interpretation of these cores is difficult due to incomplete recovery and widespread pseudoclastic textures generated by fracturing and multi-phase, incomplete fluid-dacite interaction. However, distinction of genuine volcaniclastic facies and facies with alteration-related clastic appearance is important in order to define paleo-seafloor positions within the volcanic stratigraphy, that may be prospective for massive sulfide mineralization. This has been accomplished using remnant primary characteristics indicative of transportation such as polymictic composition, grading or textural evidence for differential movement of individual clasts. Three phases of volcanic <span class="hlt">activity</span> can be distinguished and a proximal facies association dominated by coherent facies of dacite lavas exists below Snowcap. At Roman Ruins, a medial facies association consists of lava flows with about equal proportions of coherent and volcaniclastic facies. Endogenous growth was an important process during lava flow emplacement and groundmass textures such as perlite, flow banding and spherulites indicate that cooling rates were variable, locally allowing for high-temperature devitrification. A tube pumice breccia unit is interpreted as the resedimented facies of a quench fragmented, highly vesicular dacite lava carapace. Sulfide accumulations in the subsurface are restricted to Roman Ruins</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.680..211B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.680..211B"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> fluids circulation and travertine deposition in an <span class="hlt">active</span> tectonic setting: Insights from the Kamara geothermal area (western Anatolia, Turkey)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brogi, Andrea; Alçiçek, M. Cihat; Yalçıner, Cahit Çağlar; Capezzuoli, Enrico; Liotta, Domenico; Meccheri, Marco; Rimondi, Valentina; Ruggieri, Giovanni; Gandin, Anna; Boschi, Chiara; Büyüksaraç, Aydin; Alçiçek, Hülya; Bülbül, Ali; Baykara, Mehmet Oruç; Shen, Chuan-Chou</p> <p>2016-06-01</p> <p>Coexistence of thermal springs, travertine deposits and tectonic <span class="hlt">activity</span> is a recurring feature for most geothermal areas. Although such a certainty, their relationships are debated mainly addressing on the role of the tectonic <span class="hlt">activity</span> in triggering and controlling fluids flow and travertine deposition. In this paper, we present the results of an integrated study carried out in a geothermal area located in western Anatolia (Turkey), nearby the well-known Pamukkale area (Denizli Basin). Our study focused on the relationships among <span class="hlt">hydrothermal</span> fluids circulation, travertine deposition and tectonic <span class="hlt">activity</span>, with particular emphasis on the role of faults in controlling fluids upwelling, thermal springs location and deposition of travertine masses. New field mapping and structural/kinematics analyses allowed us to recognize two main faults systems (NW- and NE-trending), framed in the Neogene-Quaternary extensional tectonic evolution of western Anatolia. A geo-radar (GPR) prospection was also provided in a key-area, permitting us to reconstruct a buried fault zone and its relationships with the development of a fissure-ridge travertine deposit (Kamara fissure-ridge). The integration among structural and geophysical studies, fluids inclusion, geochemical, isotopic data and 230 Th/238 U radiometric age determination on travertine deposits, depict the characteristics of the geothermal fluids and their pathway, up to the surface. Hydrological and seismological data have been also taken in account to investigate the relation between local seismicity and fluid upwelling. As a main conclusion we found strict relationships among tectonic <span class="hlt">activity</span>, earthquakes occurrence, and variation of the physical/chemical features of the <span class="hlt">hydrothermal</span> fluids, presently exploited at depth, or flowing out in thermal springs. In the same way, we underline the tectonic role in controlling the travertine deposition, making travertine (mainly banded travertine) a useful proxy to reconstruct the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.8487B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.8487B"><span id="translatedtitle">Distribution, structure and temporal variability of <span class="hlt">hydrothermal</span> outflow at a slow-spreading <span class="hlt">hydrothermal</span> field from seafloor image mosaics.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barreyre, Thibaut; Escartin, Javier; Cannat, Mathilde; Garcia, Rafael; Science Party, Momar'08; Science Party, Bathyluck'09</p> <p>2010-05-01</p> <p>The Lucky Strike <span class="hlt">hydrothermal</span> <span class="hlt">site</span>, located South of the Azores along the Mid-Atlantic Ridge, is one of the largest and best-known <span class="hlt">active</span> <span class="hlt">hydrothermal</span> fields along the ridge system. This <span class="hlt">site</span> within the MoMAR area is also the target for the installation in 2010 of a pilot deep-sea observatory with direct telemetry to land, to be part of the European Seafloor Observatory Network (ESONET). The Lucky Strike <span class="hlt">hydrothermal</span> <span class="hlt">site</span> has seen extensive high-resolution, near-bottom geophysical surveys in 1996 (Lustre'96), 2006 (Momareto06), 2008 (MOMAR08) and 2009 (Bathyluck09). Vertically acquired black-and-white electronic still camera images have been projected and georeferenced to obtain 3 image mosaics covering the zone of <span class="hlt">active</span> venting, extending ~ 700x800 m2, and with full image resolution (~10 mm pixels). These data allow us to study how <span class="hlt">hydrothermal</span> outflow is structured, including the relationships between the zones of <span class="hlt">active</span> high-temperature venting, areas of diffuse outflow, and the geological structure (nature of the substrate, faults and fissures, sediments, etc.). <span class="hlt">Hydrothermal</span> outflow is systematically associated with bacterial mats that are easily identified in the imagery, allowing us to study temporal variability at two different scales. Over the 13-year period we can potentially track changes in both the geometry and intensity of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> throughout the system; our preliminary study of the Eiffel Tower, White Castle and Mt Segur indicate that <span class="hlt">activity</span> has been sustained in recent times, with small changes in the detailed geometry of the diffuse outflow and its intensity. At longer times scales (hundreds to 1000 years?) imagery also shows evidence of areas of venting that are no longer <span class="hlt">active</span>, often associated with the <span class="hlt">active</span> structures. In combination with the high-resolution bathymetry, the imagery data thus allow us to characterize the shallow structure of <span class="hlt">hydrothermal</span> outflow at depth, the structural and volcanic control, and ultimately</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70037202','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70037202"><span id="translatedtitle">River solute fluxes reflecting <span class="hlt">active</span> <span class="hlt">hydrothermal</span> chemical weathering of the Yellowstone Plateau Volcanic Field, USA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hurwitz, S.; Evans, William C.; Lowenstern, J. B.</p> <p>2010-01-01</p> <p>In the past few decades numerous studies have quantified the load of dissolved solids in large rivers to determine chemical weathering rates in orogenic belts and volcanic areas, mainly motivated by the notion that over timescales greater than ~100kyr, silicate hydrolysis may be the dominant sink for atmospheric CO2, thus creating a feedback between climate and weathering. Here, we report the results of a detailed study during water year 2007 (October 1, 2006 to September 30, 2007) in the major rivers of the Yellowstone Plateau Volcanic Field (YPVF) which hosts Earth's largest "restless" caldera and over 10,000 thermal features. The chemical compositions of rivers that drain thermal areas in the YPVF differ significantly from the compositions of rivers that drain non-thermal areas. There are large seasonal variations in river chemistry and solute flux, which increases with increasing water discharge. The river chemistry and discharge data collected periodically over an entire year allow us to constrain the annual solute fluxes and to distinguish between low-temperature weathering and <span class="hlt">hydrothermal</span> flux components. The TDS flux from Yellowstone Caldera in water year 2007 was 93t/km2/year. Extensive magma degassing and <span class="hlt">hydrothermal</span> interaction with rocks accounts for at least 82% of this TDS flux, 83% of the cation flux and 72% of the HCO3- flux. The low-temperature chemical weathering rate (17t/km2/year), calculated on the assumption that all the Cl- is of thermal origin, could include a component from low-temperature hydrolysis reactions induced by CO2 ascending from depth rather than by atmospheric CO2. Although this uncertainty remains, the calculated low-temperature weathering rate of the young rhyolitic rocks in the Yellowstone Caldera is comparable to the world average of large watersheds that drain also more soluble carbonates and evaporates but is slightly lower than calculated rates in other, less-silicic volcanic regions. Long-term average fluxes at</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008epsc.conf..900P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008epsc.conf..900P"><span id="translatedtitle">Targeting organic molecules in <span class="hlt">hydrothermal</span> environments on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parnell, J.; Bowden, S. A.; Lindgren, P.; Wilson, R.; Cooper, J. M.</p> <p>2008-09-01</p> <p><span class="hlt">Hydrothermal</span> deposits on Mars <span class="hlt">Hydrothermal</span> systems are proposed as environments that could support organic synthesis, the evolution of life or the maintenance of life [1,2,3]. They have therefore been suggested as primary targets for exploration on Mars [1,2,4,].There is now confidence that <span class="hlt">hydrothermal</span> deposits occur at the martian surface. This is based on a range of criteria that could point towards <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>, including volcanic <span class="hlt">activity</span>, magmatic-driven tectonism, impact cratering in icy terrains, hydrous alteration of minerals and typical <span class="hlt">hydrothermal</span> mineralogies [4]. The proposals to search for evidence of life at martian <span class="hlt">hydrothermal</span> <span class="hlt">sites</span> have been focussed on seeking morphological evidence of microbial <span class="hlt">activity</span> [5]. Here we discuss the potential to seek a chemical signature of organic matter in <span class="hlt">hydrothermal</span> systems. Organics in terrestrial <span class="hlt">hydrothermal</span> systems Terrestrial <span class="hlt">hydrothermal</span> systems can have large quantities of organic matter because they intersect organic-rich sedimentary rocks or oil reservoirs. Thus the signatures that they contain reflect some preexisting concentration of fossil organic compounds, rather than life which was <span class="hlt">active</span> in the <span class="hlt">hydrothermal</span> system. If any extant life was incorporated in these <span class="hlt">hydrothermal</span> systems, it is swamped by the fossil molecules. Examples of environments where organic materials may become entrained include subsurface <span class="hlt">hydrothermal</span> mineral deposits, generation of <span class="hlt">hydrothermal</span> systems by igneous intrusions, and hot fluid venting at the seafloor. Nevertheless, there is value in studying the interactions of <span class="hlt">hydrothermal</span> systems with fossil organic matter, for information about the survivability of organic compounds, phase relationships between carbonaceous and noncarbonaceous materials, and where in <span class="hlt">hydrothermal</span> deposits to find evidence of organic matter. Microbial colonization of hot spring systems is feasible at depth within the systems and at the surface where the <span class="hlt">hydrothermal</span> waters discharge</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRB..120.2821F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRB..120.2821F"><span id="translatedtitle">High-resolution magnetic signature of <span class="hlt">active</span> <span class="hlt">hydrothermal</span> systems in the back-arc spreading region of the southern Mariana Trough</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujii, Masakazu; Okino, Kyoko; Honsho, Chie; Dyment, Jerome; Szitkar, Florent; Mochizuki, Nobutatsu; Asada, Miho</p> <p>2015-05-01</p> <p>High-resolution vector magnetic measurements were performed on five <span class="hlt">hydrothermal</span> vent fields of the back-arc spreading region of the southern Mariana Trough using Shinkai 6500, a deep-sea manned submersible. A new 3-D forward scheme was applied that exploits the surrounding bathymetry and varying altitudes of the submersible to estimate absolute crustal magnetization. The results revealed that magnetic-anomaly-derived absolute magnetizations show a reasonable correlation with natural remanent magnetizations of rock samples collected from the seafloor of the same region. The distribution of magnetic-anomaly-derived absolute magnetization suggests that all five andesite-hosted <span class="hlt">hydrothermal</span> fields are associated with a lack of magnetization, as is generally observed at basalt-hosted <span class="hlt">hydrothermal</span> <span class="hlt">sites</span>. Furthermore, both the Pika and Urashima <span class="hlt">sites</span> were found to have their own distinct low-magnetization zones, which could not be distinguished in magnetic anomaly data collected at higher altitudes by autonomous underwater vehicle due to their limited extension. The spatial extent of the resulting low magnetization is approximately 10 times wider at off-axis <span class="hlt">sites</span> than at on-axis <span class="hlt">sites</span>, possibly reflecting larger accumulations of nonmagnetic sulfides, stockwork zones, and/or alteration zones at the off-axis <span class="hlt">sites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5789340','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5789340"><span id="translatedtitle"><span class="hlt">Active</span> <span class="hlt">Sites</span> Environmental Monitoring Program: Program plan</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ashwood, T.L.; Wickliff, D.S.; Morrissey, C.M.</p> <p>1992-02-01</p> <p>The <span class="hlt">Active</span> <span class="hlt">Sites</span> Environmental Monitoring Program (ASEMP), initiated in 1989, provides early detection and performance monitoring of transuranic (TRU) waste and <span class="hlt">active</span> low-level waste (LLW) facilities at Oak Ridge National Laboratory (ORNL) in accordance with US Department of Energy (DOE) Order 5820.2A. <span class="hlt">Active</span> LLW facilities in Solid Waste Storage Area (SWSA) 6 include Tumulus I and Tumulus II, the Interim Waste Management Facility (IWMF), LLW silos, high-range wells, asbestos silos, and fissile wells. The tumulus pads and IWMF are aboveground, high-strength concrete pads on which concrete vaults containing metal boxes of LLW are placed; the void space between the boxes and vaults is filled with grout. Eventually, these pads and vaults will be covered by an engineered multilayered cap. All other LLW facilities in SWSA 6 are below ground. In addition, this plan includes monitoring of the Hillcut Disposal Test Facility (HDTF) in SWSA 6, even though this facility was completed prior to the data of the DOE order. In SWSA 5 North, the TRU facilities include below-grade engineered caves, high-range wells, and unlined trenches. All samples from SWSA 6 are screened for alpha and beta <span class="hlt">activity</span>, counted for gamma-emitting isotopes, and analyzed for tritium. In addition to these analytes, samples from SWSA 5 North are analyzed for specific transuranic elements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5075710','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5075710"><span id="translatedtitle">Green synthesis of silver nanoparticles in aloe vera plant extract prepared by a <span class="hlt">hydrothermal</span> method and their synergistic antibacterial <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Phromviyo, Nutthakritta; Boueroy, Parichart; Chompoosor, Apiwat</p> <p>2016-01-01</p> <p>Background There is worldwide interest in silver nanoparticles (AgNPs) synthesized by various chemical reactions for use in applications exploiting their antibacterial <span class="hlt">activity</span>, even though these processes exhibit a broad range of toxicity in vertebrates and invertebrates alike. To avoid the chemical toxicity, biosynthesis (green synthesis) of metal nanoparticles is proposed as a cost-effective and environmental friendly alternative. Aloe vera leaf extract is a medicinal agent with multiple properties including an antibacterial effect. Moreover the constituents of aloe vera leaves include lignin, hemicellulose, and pectins which can be used in the reduction of silver ions to produce as AgNPs@aloe vera (AgNPs@AV) with antibacterial <span class="hlt">activity</span>. Methods AgNPs were prepared by an eco-friendly <span class="hlt">hydrothermal</span> method using an aloe vera plant extract solution as both a reducing and stabilizing agent. AgNPs@AV were characterized using XRD and SEM. Additionally, an agar well diffusion method was used to screen for antimicrobial <span class="hlt">activity</span>. MIC and MBC were used to correlate the concentration of AgNPs@AV its bactericidal effect. SEM was used to investigate bacterial inactivation. Then the toxicity with human cells was investigated using an MTT assay. Results The synthesized AgNPs were crystalline with sizes of 70.70 ± 22-192.02 ± 53 nm as revealed using XRD and SEM. The sizes of AgNPs can be varied through alteration of times and temperatures used in their synthesis. These AgNPs were investigated for potential use as an antibacterial agent to inhibit pathogenic bacteria. Their antibacterial <span class="hlt">activity</span> was tested on S. epidermidis and P. aeruginosa. The results showed that AgNPs had a high antibacterial which depended on their synthesis conditions, particularly when processed at 100 oC for 6 h and 200 oC for 12 h. The cytotoxicity of AgNPs was determined using human PBMCs revealing no obvious cytotoxicity. These results indicated that AgNPs@AV can be effectively utilized in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1203906','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1203906"><span id="translatedtitle">Catalytic <span class="hlt">Hydrothermal</span> Gasification</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Elliott, Douglas C.</p> <p>2015-05-31</p> <p>The term “hydrothermal” used here refers to the processing of biomass in water slurries at elevated temperature and pressure to facilitate the chemical conversion of the organic structures in biomass into useful fuels. The process is meant to provide a means for treating wet biomass materials without drying and to access ionic reaction conditions by maintaining a liquid water processing medium. Typical <span class="hlt">hydrothermal</span> processing conditions are 523-647K of temperature and operating pressures from 4-22 MPa of pressure. The temperature is sufficient to initiate pyrolytic mechanisms in the biopolymers while the pressure is sufficient to maintain a liquid water processing phase. <span class="hlt">Hydrothermal</span> gasification is accomplished at the upper end of the process temperature range. It can be considered an extension of the <span class="hlt">hydrothermal</span> liquefaction mechanisms that begin at the lowest <span class="hlt">hydrothermal</span> conditions with subsequent decomposition of biopolymer fragments formed in liquefaction to smaller molecules and eventually to gas. Typically, <span class="hlt">hydrothermal</span> gasification requires an <span class="hlt">active</span> catalyst to accomplish reasonable rates of gas formation from biomass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26675848','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26675848"><span id="translatedtitle">Antioxidant <span class="hlt">activities</span> of crude extracts of fucoidan extracted from Sargassum glaucescens by a compressional-puffing-<span class="hlt">hydrothermal</span> extraction process.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huang, Chun-Yung; Wu, Shu-Jing; Yang, Wen-Ning; Kuan, Ai-Wei; Chen, Cheng-Yo</p> <p>2016-04-15</p> <p>Fucoidan, a multifunctional marine polymer, is normally extracted from brown algae via extensive use of acid, solvent or high temperature water and a long reaction time. In present study, we developed a novel compressional-puffing-<span class="hlt">hydrothermal</span> extraction (CPHE) process which primarily decomposes the cellular structure of algae and facilitates the release of fucoidan by hot water extraction. The CPHE process provides a number of advantages including simple procedure, reactant-saving, reduced pollution, and feasibility for continuous production. Sargassum glaucescens (SG) was utilized in this study, and the maximum extraction yield of polysaccharide was approximately 9.83 ± 0.11% (SG4). Thin layer chromatography (TLC), Fourier transform infrared (FTIR) analysis, and measurements of monosaccharide composition, fucose, sulfate, and uronic acid contents revealed that the extracted polysaccharide showed characteristics of fucoidan. All extracts exhibited antioxidant <span class="hlt">activities</span>, and thus, further exploration of these extracts as potential natural and safe antioxidant agents is warranted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26675848','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26675848"><span id="translatedtitle">Antioxidant <span class="hlt">activities</span> of crude extracts of fucoidan extracted from Sargassum glaucescens by a compressional-puffing-<span class="hlt">hydrothermal</span> extraction process.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huang, Chun-Yung; Wu, Shu-Jing; Yang, Wen-Ning; Kuan, Ai-Wei; Chen, Cheng-Yo</p> <p>2016-04-15</p> <p>Fucoidan, a multifunctional marine polymer, is normally extracted from brown algae via extensive use of acid, solvent or high temperature water and a long reaction time. In present study, we developed a novel compressional-puffing-<span class="hlt">hydrothermal</span> extraction (CPHE) process which primarily decomposes the cellular structure of algae and facilitates the release of fucoidan by hot water extraction. The CPHE process provides a number of advantages including simple procedure, reactant-saving, reduced pollution, and feasibility for continuous production. Sargassum glaucescens (SG) was utilized in this study, and the maximum extraction yield of polysaccharide was approximately 9.83 ± 0.11% (SG4). Thin layer chromatography (TLC), Fourier transform infrared (FTIR) analysis, and measurements of monosaccharide composition, fucose, sulfate, and uronic acid contents revealed that the extracted polysaccharide showed characteristics of fucoidan. All extracts exhibited antioxidant <span class="hlt">activities</span>, and thus, further exploration of these extracts as potential natural and safe antioxidant agents is warranted. PMID:26675848</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70034150','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70034150"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> processes above the Yellowstone magma chamber: Large <span class="hlt">hydrothermal</span> systems and large <span class="hlt">hydrothermal</span> explosions</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Morgan, L.A.; Shanks, W.C. Pat; Pierce, K.L.</p> <p>2009-01-01</p> <p><span class="hlt">Hydrothermal</span> 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. <span class="hlt">Hydrothermal</span> 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, <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> 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 <span class="hlt">active</span> Norris-Mammoth tectonic corridor. In Yellowstone, at least 20 large (>100 m in diameter) <span class="hlt">hydrothermal</span> explosion craters have been identifi ed; the scale of the individual associated events dwarfs similar features in geothermal areas elsewhere in the world. Large <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> explosion deposits are extensively altered, indicating that explosions occur in areas subjected to intense <span class="hlt">hydrothermal</span> processes; (4) many lithic clasts contained in explosion breccia deposits preserve evidence of repeated fracturing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GGG....17..375D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GGG....17..375D"><span id="translatedtitle">Geologic evolution of the Lost City <span class="hlt">Hydrothermal</span> Field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Denny, Alden R.; Kelley, Deborah S.; Früh-Green, Gretchen L.</p> <p>2016-02-01</p> <p>The Lost City <span class="hlt">Hydrothermal</span> 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. <span class="hlt">Hydrothermal</span> <span class="hlt">activity</span> is focused at the 60 m tall, 100 m across, massive carbonate edifice "Poseidon," which is venting 91°C fluid. <span class="hlt">Hydrothermal</span> <span class="hlt">activity</span> 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 <span class="hlt">hydrothermal</span> flow is characterized by egress of diffuse fluids from narrow fissures within a low-angle, anastomosing mylonite zone. South of the area of current <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>, there is evidence of two discrete previously unrecognized relict fields. <span class="hlt">Active</span> venting <span class="hlt">sites</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JGRB..108.2475B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JGRB..108.2475B"><span id="translatedtitle">Dynamics of <span class="hlt">active</span> magmatic and <span class="hlt">hydrothermal</span> systems at Taal Volcano, Philippines, from continuous GPS measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bartel, Beth A.; Hamburger, Michael W.; Meertens, Chuck M.; Lowry, Anthony R.; Corpuz, Ernesto</p> <p>2003-10-01</p> <p>A dense network of continuous single- and dual-frequency GPS receivers at Taal Volcano, Philippines, reveals four major stages of volcanogenic deformation: deflation, from installation in June 1998 to December 1998; inflation, from January to March 1999; deflation, from April 1999 to February 2000; and inflation, from February to November 2000. The largest displacements occurred during the February-November 2000 period of inflation, which was characterized by ˜120 mm of uplift of the center of Volcano Island relative to the northern caldera rim at average rates up to 216 mm/yr. Deformation sources were modeled using a constrained least squares inversion algorithm. The source of 1999 deflation and inflation in 2000 were modeled as contractional and dilatational Mogi point sources centered at 4.2 and 5.2 km depth, respectively, beneath Volcano Island. The locations of the inflationary and deflationary sources are indistinguishable within the 95% confidence estimates. Modeling using a running 4-month time window from June 1999 to March 2001 reveals little evidence for source migration. We suggest that the two periods of inflation observed at Taal result from episodic intrusions of magma into a shallow reservoir centered beneath Volcano Island. Subsequent deflation may result from exsolution of magmatic fluids and/or gases into an overlying, unconfined <span class="hlt">hydrothermal</span> system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70013393','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70013393"><span id="translatedtitle">Crater lake and post-eruption <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>, El Chichón Volcano, Mexico</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Casadevall, Thomas J.; de la Cruz-Reyna, Servando; Rose, William I.; Bagley, Susan; Finnegan, David L.; Zoller, William H.</p> <p>1984-01-01</p> <p>Explosive eruptions of Volcán El Chichón in Chiapas, Mexico on March 28 and April 3–4, 1982 removed 0.2 km3 of rock to form a 1-km-wide 300-m-deep summit crater. By late April 1982 a lake had begun to form on the crater floor, and by November 1982 it attained a maximum surface area of 1.4 × 105 m2 and a volume of 5 × 106 m3. Accumulation of 4–5 m of rainfall between July and October 1982 largely formed the lake. In January 1983, temperatures of fumaroles on the crater floor and lower crater walls ranged from 98 to 115°C; by October 1983 the maximum temperature of fumarole emissions was 99°C. In January 1983 fumarole gas emissions were greater than 99 vol. % H2O with traces of CO2, SO2, and H2S. The water of the lake was a hot (T = 52–58°C), acidic (pH = 0.5), dilute solution (34,046 mg L−1 dissolved solids; Cl/S = 20.5). Sediment from the lake contains the same silicate minerals as the rocks of the 1982 pyroclastic deposits, together with less than 1% of elemental sulfur. The composition and temperature of the lake water is attributed to: (1) solution of fumarole emissions; (2) reaction of lake water with hot rocks beneath the lake level; (3) sediments washed into the lake from the crater walls; (4) <span class="hlt">hydrothermal</span> fluids leaching sediments and formational waters in sedimentary rocks of the basement; (5) evaporation; and (6) precipitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS23C2027C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS23C2027C"><span id="translatedtitle">Detection of <span class="hlt">active</span> <span class="hlt">hydrothermal</span> vent fields in the Pescadero Basin and on the Alarcon Rise using AUV multibeam and CTD data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caress, D. W.; Troni, G.; Clague, D. A.; Paduan, J. B.; Martin, J. F.; Thomas, H. J.; Thompson, D.; Conlin, D.; Martin, E. J.; meneses-Quiroz, E.; Nieves-Cardoso, C.; Angel Santa Rosa del Rio, M.</p> <p>2015-12-01</p> <p>The MBARI AUV D. Allan B. collected high resolution bathymetry, sidescan, and subbottom profiles along the neovolcanic zone of the Alarcon Rise and across the southern Pescadero Basin during 2012 and 2015 MBARI expeditions to the Gulf of California (GOC). The combination of high resolution multibeam bathymetry and seawater temperature data has proven effective in identifying <span class="hlt">active</span> high temperature vent fields, as validated by inspection and sampling during ROV dives. The AUV carries a 200 kHz multibeam sonar, 110 kHz chirp sidescan sonar, a 1-6 kHz chirp subbottom profiler, and a conductivity, temperature and depth (CTD) sensor for ~17-hour duration missions. Flying at 5.4 km/hr at 50 m altitude, the processed AUV bathymetry has a 0.1 m vertical precision and a 1 m lateral resolution. Chimneys taller than 1.5 m are sufficiently distinctive to allow provisional identification. The CTD temperature data have a nominal 0.002°C accuracy. Following calculation of potential temperature and correcting for average local variation of potential temperature with depth, anomalies greater than 0.05 °C can be reliably identified using a spike detection filter. MBARI AUV mapping surveys are typically planned using a 150 m survey line spacing, so the CTD data may be collected as much as 75 m away from any vent plume source. Five <span class="hlt">active</span> high temperature vent fields were discovered in the southern GOC, with the Auka Field in the southern Pescadero Basin, and the Ja Sít, Pericú, Meyibó, and Tzab-ek Fields along the Alarcon Rise. In all five cases, <span class="hlt">hydrothermal</span> vent chimneys are readily identifiable in the multibeam bathymetry, and temperature anomalies are observed above background variability. Other apparent <span class="hlt">hydrothermal</span> chimneys were observed in the bathmetry that did not exhibit water temperature anomalies; most of these were visited during ROV dives and confirmed to be inactive <span class="hlt">sites</span>. The maximum water column anomalies are 0.13°C observed above the Meyibó field and 0.25</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5657932','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5657932"><span id="translatedtitle">Control of <span class="hlt">active</span> <span class="hlt">sites</span> in flocculation: Concept of equivalent <span class="hlt">active</span> <span class="hlt">sites</span>''</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Behl, S.; Moudgil, B.M. . Dept. of Materials Science and Engineering)</p> <p>1993-12-01</p> <p>Flocculation and dispersion of solids are strong functions of the amount and conformation of the adsorbed polymer. Regions of dispersion and flocculation of solids with particular polymer molecules may be deduced from saturation adsorption data. The concept of equivalent <span class="hlt">active</span> <span class="hlt">sites</span>'' is proposed to explain flocculation and dispersion behavior irrespective of the amount or conformation of the adsorbed polymer. The concept has been further extended to study the selective flocculation process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26377214','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26377214"><span id="translatedtitle">Comparative study of photocatalytic <span class="hlt">activities</span> of <span class="hlt">hydrothermally</span> grown ZnO nanorod on Si(001) wafer and FTO glass substrates.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jeon, Eun Hee; Yang, Sena; Kim, Yeonwoo; Kim, Namdong; Shin, Hyun-Joon; Baik, Jaeyoon; Kim, Hyun Sung; Lee, Hangil</p> <p>2015-12-01</p> <p>ZnO nanorods have been grown on Si(001) wafer and fluorine-doped tin oxide (FTO) glass substrates for 1 and 4 h with the <span class="hlt">hydrothermal</span> methods. The morphologies and photocatalytic <span class="hlt">activities</span> of the ZnO nanorods were found to depend on the substrates. We investigated their properties by using spectroscopic analysis and demonstrated that the shape of nanorod and the ratios of external defects can be controlled by varying the substrates. Our experiments revealed that the nanorods grown on Si(001) have a single-crystalline wurtzite structure with (002) facets and that the number of surface oxygen defects increases with their length as the growth time increases. The nanorods grown on Si(001) have different facets, in particular wider (002) facets, and a higher ratio of the oxygen defect than the nanorods on FTO glass substrate. Moreover, the photocatalytic <span class="hlt">activities</span> with respect to 2-aminothiophenol (2-ATP) of these nanorods were investigated with high-resolution photoemission spectroscopy (HRPES). We demonstrated that their photocatalytic <span class="hlt">activity</span> is influenced by the ratios of surface oxygen defects, which varies with the substrate surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NRL....10..361J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NRL....10..361J"><span id="translatedtitle">Comparative study of photocatalytic <span class="hlt">activities</span> of <span class="hlt">hydrothermally</span> grown ZnO nanorod on Si(001) wafer and FTO glass substrates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jeon, Eun Hee; Yang, Sena; Kim, Yeonwoo; Kim, Namdong; Shin, Hyun-Joon; Baik, Jaeyoon; Kim, Hyun Sung; Lee, Hangil</p> <p>2015-09-01</p> <p>ZnO nanorods have been grown on Si(001) wafer and fluorine-doped tin oxide (FTO) glass substrates for 1 and 4 h with the <span class="hlt">hydrothermal</span> methods. The morphologies and photocatalytic <span class="hlt">activities</span> of the ZnO nanorods were found to depend on the substrates. We investigated their properties by using spectroscopic analysis and demonstrated that the shape of nanorod and the ratios of external defects can be controlled by varying the substrates. Our experiments revealed that the nanorods grown on Si(001) have a single-crystalline wurtzite structure with (002) facets and that the number of surface oxygen defects increases with their length as the growth time increases. The nanorods grown on Si(001) have different facets, in particular wider (002) facets, and a higher ratio of the oxygen defect than the nanorods on FTO glass substrate. Moreover, the photocatalytic <span class="hlt">activities</span> with respect to 2-aminothiophenol (2-ATP) of these nanorods were investigated with high-resolution photoemission spectroscopy (HRPES). We demonstrated that their photocatalytic <span class="hlt">activity</span> is influenced by the ratios of surface oxygen defects, which varies with the substrate surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1713809B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1713809B"><span id="translatedtitle">Microbial bio-mineralization processes in <span class="hlt">hydrothermal</span> travertine: the case study of two <span class="hlt">active</span> travertine systems (Tuscany, Italy).</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barilaro, Federica; Bontognali, Tomaso R. R.; Mc Kenzie, Judith A.; Vasconcelos, Crisogono</p> <p>2015-04-01</p> <p>Modern <span class="hlt">hydrothermal</span> travertine deposits, occurring today at Bagni San Filippo (Radicofani Basin) and at Bagni di Saturnia (Albegna Valley) in Tuscany, Central Italy, have been investigated with the main purpose to improve the understanding of the processes that control calcium carbonate precipitation in <span class="hlt">hydrothermal</span>-spring settings. Present-day thermal <span class="hlt">activity</span> at Bagni di Saturnia is characterized by a 37.5°C thermal spring with a rate of about 800 l/s, with a pH of ca. 6.4. Thermal water discharges at Bagni San Filippo reach a rate of 20 litres per second at a maximum temperature of 50°C and a pH of ca. 7. The springs expel water enriched in H2S-CO2-SO42- and HCO3- and divalent cations (Ca and Mg). In the studied areas, travertine precipitation occurs in association with living microbial mats and biofilms, composed of a heterogeneous community of green algae, filamentous cyanobacteria and other types of prokaryotes, anoxygenic photosynthetic bacteria and heterotrophic heat-tolerant bacteria, with a variable amount of extracellular polymeric substances (EPS). Nine categories of fabric types, dominantly calcite and aragonite in composition, showing a wide range of macro- and micro-porosity, have been identified. High magnification analysis of dendritic and laminated boundstone, crystalline crust cementstone, raft boundstone, coated bubble boundstone, micrite mudstone and coated reed boundstone fabric types, suggests that precipitation occurs in association with organic matter. Diatoms, cyanobacteria filaments and other bacteria are then associated with the EPS and often appear totally or partially entombed (passively or <span class="hlt">actively</span>) in it. Organic extracellular polymeric substances (EPS) and often the external surface of cyanobacterial sheaths are the location where the calcite minerals nucleate and grow. Precipitation begins with organomineral nano-globules consisting of nanometre-size, from sub-spherical to globular-like, raised structures (5 to 80 nm diameter</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.V21C2737W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.V21C2737W"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> plumes in the NE Lau basin: A regional perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walker, S. L.; Baker, E. T.</p> <p>2013-12-01</p> <p>Exploration for mineral resources and the presence of an extensive plume of excess 3He centered at 1750 m water depth in the Samoa-Tonga-Fiji region (Lupton, 2004) have motivated exploration for <span class="hlt">active</span> <span class="hlt">hydrothermal</span> vent <span class="hlt">sites</span> in the NE Lau basin during the past decade. The region is tectonically complex with back-arc spreading centers, rift zones, and volcanic centers, all of which potentially host <span class="hlt">active</span> venting and/or <span class="hlt">active</span> volcanism. To date, 400 km of the three back-arc spreading centers in the NE Lau basin (FRSC, Fonualei Rift and Spreading Center; MTJ, Mangatolu Triple Junction; and NELSC, Northeastern Lau Spreading Center) plus several volcanic centers have been systematically surveyed for <span class="hlt">hydrothermal</span> plumes using towed CTD or MAPR arrays that include both optical backscatter and oxidation-reduction potential (ORP) sensors. The FRSC, where spreading rates range from 47 mm/a in the south to 85 mm/a in the north, has 5 <span class="hlt">active</span> <span class="hlt">sites</span> (plume depths ranging from 1300-2200 m) distributed one every ~40 km over its 200 km length. There is evidence for 4 <span class="hlt">active</span> <span class="hlt">sites</span> (plume depths range from 1950-2380 m) along the 150 km combined length of the MTJ segments, however plumes were optically weak (dNTU < 0.02) and except for one location along the northeastern limb, no ORP anomalies were detected. Plumes were observed off-axis to the MTJ at a bathymetric high adjacent to the northeastern limb (1700 m) as well as over the summit of a cratered volcanic edifice east of the central junction (1200-1300 m). The southern segment of the NELSC was the <span class="hlt">site</span> of an <span class="hlt">active</span> eruption in 2008 which injected event plumes throughout the water column (900-1600 m depth range) in addition to the chronic plume from the Maka massive sulfide vent <span class="hlt">site</span> (1500 m). There is evidence for at least two additional <span class="hlt">active</span> areas along the northern segments of the NELSC (1800-1900 m). Several volcanoes in the region are <span class="hlt">hydrothermally</span> <span class="hlt">active</span> ranging from the northernmost volcano on the Tonga arc (Niua</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22275859','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22275859"><span id="translatedtitle">Synthesis of ZnO nanorod–nanosheet composite via facile <span class="hlt">hydrothermal</span> method and their photocatalytic <span class="hlt">activities</span> under visible-light irradiation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tan, Wai Kian; Abdul Razak, Khairunisak; Lockman, Zainovia; Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori</p> <p>2014-03-15</p> <p>ZnO composite films consisting of ZnO nanorods and nanosheets were prepared by low-temperature <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> 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 <span class="hlt">activity</span> during degradation of aqueous methylene blue under visible-light irradiation. -- Graphical abstract: Schematic illustration of ZnO nanorod–nanosheet composite structure formation by <span class="hlt">hydrothermal</span> at low-temperature of 80 °C against time. Highlights: • Novel simultaneous formation of ZnO nanorods and nanosheets composite structure. • Facile single <span class="hlt">hydrothermal</span> step formation at low-temperature. • Photoluminescence showed ultraviolet and visible emission. • Feasible application on substrates with low temperature stability. • Improved photocatalytic <span class="hlt">activity</span> under visible</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25167333','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25167333"><span id="translatedtitle">Mineral elements, lipoxygenase <span class="hlt">activity</span>, and antioxidant capacity of okara as a byproduct in <span class="hlt">hydrothermal</span> processing of soy milk.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stanojevic, Sladjana P; Barac, Miroljub B; Pesic, Mirjana B; Zilic, Sladjana M; Kresovic, Mirjana M; Vucelic-Radovic, Biljana V</p> <p>2014-09-10</p> <p>Minerals and antioxidative capacity of raw okara that was obtained as a byproduct from six soybean varieties during <span class="hlt">hydrothermal</span> cooking (HTC) of soy milk were assessed. Lipoxygenase (Lox), an enzyme deteriorating the sensory characteristics of okara, was also investigated. All genotypes had very similar concentrations of Lox (4.32-5.62%). Compared to raw soybeans, the applied HTC significantly reduced Lox content in okara (0.54-0.19%) and lowered its <span class="hlt">activity</span> to 0.004-0.007 μmol g(-1) min (-1). Correlation between the content of Lox in soybeans and that in okara (r = 0.21;p < 0.05) was not registered. This indicates that the content of this enzyme in okara depended much more on the technological process than on soybean genotype. Very strong correlation (r = 0.99; p < 0.05) between okara Lox content and its <span class="hlt">activity</span> was found. The most abundant minerals in raw okara were potassium (1.04-1.21 g/100g), phosphorus (0.45-0.50 g/100 g), calcium (0.26-0.39 g/100 g), and iron (5.45-10.95 mg/100 g). A very high antioxidant capacity (19.06-29.36 mmol Trolox kg(-1)) contributes to the nutritional value of raw okara. PMID:25167333</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ApSS..258.7448L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ApSS..258.7448L"><span id="translatedtitle">High-temperature <span class="hlt">hydrothermal</span> synthesis of crystalline mesoporous TiO2 with superior photo catalytic <span class="hlt">activities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Fujian; Liu, Chun-Lin; Hu, Baowei; Kong, Wei-Ping; Qi, Chen-Ze</p> <p>2012-07-01</p> <p>Mesoporous titanium dioxide with crystalline mesopore walls (M-TiO2-ns) have been successfully synthesized through the self-assembly of poly 4-Vinylpyridine template and tetrabutyl titanate precursor based on their complex bond interaction under high temperature (180 °C) <span class="hlt">hydrothermal</span> conditions. X-ray diffraction shows that M-TiO2-ns have highly crystalline mesopore walls with anatase phase characters; N2 sorption-desorption isotherms, SEM and TEM images show that M-TiO2-ns have high BET surface areas (85 and 120 m2/g, respectively), large pore volumes (0.32 and 0.34 cm3/g, respectively) and crystalline mesopore walls, which exhibit monolithic morphology with crystal sizes around 3-5 μm. Interestingly, M-TiO2-ns exhibit much higher catalytic <span class="hlt">activities</span> and good recyclability in both induced reduction of decabromodiphenyl and oxidation of Rhodamine B under UV light than those of nonporous crystalline TiO2 and M-TiO2 templated by hydrocarbon surfactant of F127, which is even comparable with that of commercial P25. Combination of the unique characters such as crystallinity, stable mesostructure, large BET surface areas and superior photo catalytic <span class="hlt">activities</span> make M-TiO2-ns a kind of potentially important material for removing of organic pollutions in environment through green photo irradiation processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27427614','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27427614"><span id="translatedtitle">Low Temperature <span class="hlt">Hydrothermal</span> Synthesis of Visible-Light-<span class="hlt">Activated</span> I-Doped TiO2 for Improved Dye Degradation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Dongting; Li, Jianwen; Zhou, Guangsheng; Wang, Wenxu; Zhang, Xianxi; Pan, Xu</p> <p>2016-06-01</p> <p>Iodine doped TiO2 with different iodine/Ti molar ratios has been firstly synthesized with a low temperature <span class="hlt">hydrothermal</span> route and has been studied systematically in photocatalysis under visible light condition. The resulting iodine doped TiO2 were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (TEM), diffuse reflectance spectrum (DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic performance investigations were conducted by means of the degradation of Rhodamine B (RhB) under the visible light irradiation in aqueous solution. Under an optimized I/Ti doping ratio of 10 mol%, the photocatalytic performance is greatly better, with degradation efficiency of 95%, which is almost double that of pure TiO2. The superior photocatalytic <span class="hlt">activity</span> of iodine-doped TiO2 could be mainly attributed to extended visible light absorption originated from the formation of continuous states existed in the band gap of the doped TiO2 introduced by iodine. <span class="hlt">Active</span> oxygen species, that is, *OH and O2-, were evidenced to be involved in the degradation process and a possible mechanism was also proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27427614','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27427614"><span id="translatedtitle">Low Temperature <span class="hlt">Hydrothermal</span> Synthesis of Visible-Light-<span class="hlt">Activated</span> I-Doped TiO2 for Improved Dye Degradation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Dongting; Li, Jianwen; Zhou, Guangsheng; Wang, Wenxu; Zhang, Xianxi; Pan, Xu</p> <p>2016-06-01</p> <p>Iodine doped TiO2 with different iodine/Ti molar ratios has been firstly synthesized with a low temperature <span class="hlt">hydrothermal</span> route and has been studied systematically in photocatalysis under visible light condition. The resulting iodine doped TiO2 were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (TEM), diffuse reflectance spectrum (DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic performance investigations were conducted by means of the degradation of Rhodamine B (RhB) under the visible light irradiation in aqueous solution. Under an optimized I/Ti doping ratio of 10 mol%, the photocatalytic performance is greatly better, with degradation efficiency of 95%, which is almost double that of pure TiO2. The superior photocatalytic <span class="hlt">activity</span> of iodine-doped TiO2 could be mainly attributed to extended visible light absorption originated from the formation of continuous states existed in the band gap of the doped TiO2 introduced by iodine. <span class="hlt">Active</span> oxygen species, that is, *OH and O2-, were evidenced to be involved in the degradation process and a possible mechanism was also proposed. PMID:27427614</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003E%26PSL.216..575S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003E%26PSL.216..575S"><span id="translatedtitle">Aqueous volatiles in <span class="hlt">hydrothermal</span> fluids from the Main Endeavour Field, northern Juan de Fuca Ridge: temporal variability following earthquake <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seewald, Jeffrey; Cruse, Anna; Saccocia, Peter</p> <p>2003-12-01</p> <p>The Main Endeavour Field, northern Juan de Fuca Ridge, experienced intense seismic <span class="hlt">activity</span> in June 1999. <span class="hlt">Hydrothermal</span> vent fluids were collected from sulfide structures in September 1999 and July 2000 and analyzed for the abundance of H2, H2S, CH4, CO2, NH3, Mg and Cl to document temporal and spatial changes following the earthquakes. Dissolved concentrations of CO2, H2, and H2S increased dramatically in the September 1999 samples relative to pre-earthquake abundances, and subsequently decreased during the following year. In contrast, dissolved NH3 and CH4 concentrations in 1999 and 2000 were similar to or less than pre-earthquake values. Aqueous Cl abundances showed large decreases immediately following the earthquakes followed by increases to near pre-earthquake values. The abundances of volatile species at the Main Endeavour Field were characterized by strong inverse correlations with chlorinity. Phase separation can account for 20-50% enrichments of CO2, CH4, and NH3 in low-chlorinity fluids, while temperature- and pressure-dependent fluid-mineral equilibria at near-critical conditions are responsible for order of magnitude greater enrichments in dissolved H2S and H2. The systematic variation of dissolved gas concentrations with chlorinity likely reflects mixing of a low-chlorinity volatile-enriched vapor generated by supercritical phase separation with a cooler gas-poor <span class="hlt">hydrothermal</span> fluid of seawater chlorinity. Decreased abundances of sediment-derived NH3 and CH4 in 1999 indicate an earthquake-induced change in subsurface hydrology. Elevated CO2 abundances in vent fluids collected in September 1999 provide evidence that supports a magmatic origin for the earthquakes. Temperature-salinity relationships are consistent with intrusion of a shallow dike and suggest that the earthquakes were associated with movement of magma beneath the ridge crest. These data demonstrate the large and rapid response of chemical fluxes at mid-ocean ridges to magmatic <span class="hlt">activity</span> and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010GMS...188...27E&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010GMS...188...27E&link_type=ABSTRACT"><span id="translatedtitle">Chemical signatures from <span class="hlt">hydrothermal</span> venting on slow spreading ridges</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edmonds, Henrietta N.</p> <p></p> <p>At least 24 <span class="hlt">sites</span> of <span class="hlt">active</span> venting have been confirmed on slow and ultraslow spreading ridges, with dozens more indicated on the basis of <span class="hlt">hydrothermal</span> plume distributions and/or dredge recovery of massive sulfides. Fluid chemistry data have been published for 13 <span class="hlt">sites</span>: 8 on the northern Mid-Atlantic Ridge, 3 on the southern Mid-Atlantic Ridge, and 2 on the Central Indian Ridge. Three of these 13 <span class="hlt">sites</span> (Rainbow, Logatchev, and Lost City) are known to be hosted in ultramafic terrain, and their fluid chemistries reflect the influence of serpentinization reactions, including elevated hydrogen and methane, and low silica concentrations. This brief review presents the published fluid chemistry for all 13 <span class="hlt">sites</span>, including time series where available, and demonstrates the diversity of chemical compositions engendered by the myriad settings (near and off axis, young volcanic to ultramafic terrain, and depths up to 4100 m) of <span class="hlt">hydrothermal</span> systems on slow and ultraslow spreading ridges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/240930','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/240930"><span id="translatedtitle">Multiple episodes of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> and epithermal mineralization in the southwestern Nevada volcanic field and their relations to magmatic <span class="hlt">activity</span>, volcanism and regional extension</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Weiss, S.I.; Noble, D.C.; Jackson, M.C.</p> <p>1994-12-31</p> <p>Volcanic rocks of middle Miocene age and underlying pre-Mesozoic sedimentary rocks host widely distributed zones of <span class="hlt">hydrothermal</span> alteration and epithermal precious metal, fluorite and mercury deposits within and peripheral to major volcanic and intrusive centers of the southwestern Nevada volcanic field (SWNVF) in southern Nevada, near the southwestern margin of the Great Basin of the western United States. Radiometric ages indicate that episodes of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> mainly coincided with and closely followed major magmatic pulses during the development of the field and together spanned more than 4.5 m.y. Rocks of the SWNVF consist largely of rhyolitic ash-flow sheets and intercalated silicic lava domes, flows and near-vent pyroclastic deposits erupted between 15.2 and 10 Ma from vent areas in the vicinity of the Timber Mountain calderas, and between about 9.5 and 7 Ma from the outlying Black Mountain and Stonewall Mountain centers. Three magmatic stages can be recognized: the main magmatic stage, Mountain magmatic stage (11.7 to 10.0 Ma), and the late magmatic stage (9.4 to 7.5 Ma).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/140776','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/140776"><span id="translatedtitle">The Timber Mountain magmato-thermal event: An intense widespread culmination of magmatic and <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at the southwestern Nevada volcanic field</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jackson, M.R. Jr.</p> <p>1988-05-01</p> <p>Eruption of the Rainier Mesa and Ammonia Tanks Members Timber Mountain Tuff at about 11.5 and 11.3 Ma, respectively, resulted in formation of the timber Mountain (TM) caldera; new K-Ar ages show that volcanism within and around the TM caldera continued for about 1 m.y. after collapse. Some TM age magmatic <span class="hlt">activity</span> took place west and southeast of the TM caldera in the Beatty -- Bullfrog Hills and Shoshone Mountain areas, suggesting that volcanic <span class="hlt">activity</span> at the TM caldera was an intense expression of an areally extensive magmatic system <span class="hlt">active</span> from about 11.5 to 10Ma. Epithermal Au-Ag, Hg and fluorite mineralization and <span class="hlt">hydrothermal</span> alteration are found in both within and surrounding the Timber Mountain -- Oasis Valley caldera complex. New K-Ar ages date this <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> between about 13 and 10 Ma, largely between about 11.5 and 10 Ma, suggesting a genetic relation of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> to the TM magmatic system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26790096','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26790096"><span id="translatedtitle"><span class="hlt">Activity</span> of antioxidant enzymes in response to atmospheric pressure induced physiological stress in deep-sea <span class="hlt">hydrothermal</span> vent mussel Bathymodiolus azoricus.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Martins, Inês; Romão, Célia V; Goulart, Joana; Cerqueira, Teresa; Santos, Ricardo S; Bettencourt, Raul</p> <p>2016-03-01</p> <p>Deep sea <span class="hlt">hydrothermal</span> Bathymodiolus azoricus mussels from Portuguese EEZ Menez Gwen <span class="hlt">hydrothermal</span> field possess the remarkable ability to overcome decompression and survive successfully at atmospheric pressure conditions. We investigated the potential use of antioxidant defense enzymes in mussel B. azoricus as biomarkers of oxidative stress induced by long term acclimatization to atmospheric pressure conditions. Mussels collected at Menez Gwen <span class="hlt">hydrothermal</span> field were acclimatized for two weeks in three distinct conditions suitable of promoting physiological stress, (i) in plain seawater for concomitant endosymbiont bacteria loss, (ii) in plain seawater under metal iron exposure, (iii) constant bubbling methane and pumped sulfide for endosymbiont bacteria survival. The enzymatic <span class="hlt">activities</span> of superoxide dismutase (SOD), catalase (CAT), and iron storage proteins in addition to electrophoretic profiles were examined in vent mussel gills and digestive gland. Gills showed approximately 3 times more SOD specific <span class="hlt">activity</span> than digestive glands. On the other hand, digestive glands showed approximately 6 times more CAT specific <span class="hlt">activity</span> than gills. Iron storage proteins were identified in gill extracts from all experimental conditions mussels. However, in digestive gland extracts only fresh collected mussels and after 2 weeks in FeSO4 showed the presence of iron storage proteins. The differences between SOD, CAT specific <span class="hlt">activities</span> and the presence of iron storage proteins in the examined tissues reflect dissimilar metabolic and antioxidant <span class="hlt">activities</span>, as a result of tissue specificities and acclimatization conditions influences on the organism. PMID:26790096</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5281083','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5281083"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> processes at seafloor spreading centers,</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rona, P.A.; Bostrom, K.; Laubier, L.; Smith, K.L.</p> <p>1983-01-01</p> <p>This book examines research on the description and interpretation of <span class="hlt">hydrothermal</span> and associated phenomena at seafloor spreading centers. An interdisciplinary overview of the subject is presented, including geological, geophysical, geochemical, and biological discoveries. The implications of the discoveries for understanding the earth's heat transfer, geochemical mass balances and cycles, mineralization, and biological adaptation are discussed. Topics considered include geologic setting (e.g., the four dimensions of the spreading axis, geological processes of the mid-ocean ridge), <span class="hlt">hydrothermal</span> convection (e.g., oxygen and hydrogen isotope studies, the basic physics of water penetration into hot rock), Iceland and oceanic ridges (e.g., chemical evidence from Icelandic geothermal systems, the physical environment of <span class="hlt">hydrothermal</span> systems), mass balances and cycles (e.g., reduced gases and bacteria in <span class="hlt">hydrothermal</span> fluids, the effects of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> on sedimentary organic matter), ferromanganese deposits, <span class="hlt">hydrothermal</span> mineralization, and the biology of <span class="hlt">hydrothermal</span> vents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999PrOce..44..333D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999PrOce..44..333D"><span id="translatedtitle"><span class="hlt">Hydrothermalism</span> in the Mediterranean Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dando, P. R.; Stüben, D.; Varnavas, S. P.</p> <p>1999-08-01</p> <p><span class="hlt">Hydrothermalism</span> in the Mediterranean Sea results from the collision of the African and European plates, with the subduction of the oceanic part of the African plate below Europe. High heat flows in the resulting volcanic arcs and back-arc extensional areas have set-up <span class="hlt">hydrothermal</span> convection systems. Most of the known <span class="hlt">hydrothermal</span> <span class="hlt">sites</span> are in shallow coastal waters, <200 m depth, so that much of the reported fluid venting is of the gasohydrothermal type. The <span class="hlt">hydrothermal</span> liquids are of varying salinities, both because of phase separation as a result of seawater boiling at the low pressures and because of significant inputs of rainfall into the <span class="hlt">hydrothermal</span> reservoirs at some <span class="hlt">sites</span>. The major component of the vented gas is carbon dioxide, with significant quantities of sulphur dioxide, hydrogen sulphide, methane and hydrogen also being released. Acid leaching of the underlying rocks leads to the mobilisation of heavy metals, many of which are deposited sub-surface although there is a conspicuous enrichment of metals in surficial sediments in venting areas. Massive polymetalic sulphides have been reported from some <span class="hlt">sites</span>. No extant vent-specific fauna have been described from Mediterranean <span class="hlt">sites</span>. There is a reduced diversity of fauna within the sediments at the vents. In contrast, a high diversity of epifauna has been reported and the vent <span class="hlt">sites</span> are areas of settlement for exotic thermophilic species. Large numbers of novel prokaryotes, especially hyperthermophilic crenarchaeota, have been isolated from Mediterranean <span class="hlt">hydrothermal</span> vents. However, their distribution in the subsurface biosphere and their role in the biogeochemistry of the <span class="hlt">sites</span> has yet to be studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARX41005H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARX41005H"><span id="translatedtitle">Dissecting the <span class="hlt">active</span> <span class="hlt">site</span> of a photoreceptor protein</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoff, Wouter; Hara, Miwa; Ren, Jie; Moghadam, Farzaneh; Xie, Aihua; Kumauchi, Masato</p> <p></p> <p>While enzymes are quite large molecules, functionally important chemical events are often limited to a small region of the protein: the <span class="hlt">active</span> <span class="hlt">site</span>. The physical and chemical properties of residues at such <span class="hlt">active</span> <span class="hlt">sites</span> are often strongly altered compared to the same groups dissolved in water. Understanding such effects is important for unraveling the mechanisms underlying protein function and for protein engineering, but has proven challenging. Here we report on our ongoing efforts on using photoactive yellow protein (PYP), a bacterial photoreceptor, as a model system for such effects. We will report on the following questions: How many residues affect <span class="hlt">active</span> <span class="hlt">site</span> properties? Are these residues in direct physical contact with the <span class="hlt">active</span> <span class="hlt">site</span>? Can functionally important residues be recognized in the crystal structure of a protein? What structural resolution is needed to understand <span class="hlt">active</span> <span class="hlt">sites</span>? What spectroscopic techniques are most informative? Which weak interactions dominate <span class="hlt">active</span> <span class="hlt">site</span> properties?</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.V11F..08G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.V11F..08G"><span id="translatedtitle">On the Interaction of a Vigorous <span class="hlt">Hydrothermal</span> System with an <span class="hlt">Active</span> Magma Chamber: The Puna Magma Chamber, Kilauea East Rift, Hawaii</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gregory, R. T.; Marsh, B. D.; Teplow, W.; Fournelle, J.</p> <p>2009-12-01</p> <p>The extent of the interaction between <span class="hlt">hydrothermal</span> systems and <span class="hlt">active</span> magma chambers has long been of fundamental interest to the development of ore deposits, cooling of magma chambers, and dehydration of the subducting lithosphere. As volatiles build up in the residual magma in the trailing edge of magmatic solidification fronts, is it possible that volatiles are transferred from the <span class="hlt">active</span> magma to the <span class="hlt">hydrothermal</span> system and vice versa? Does the external fracture front associated with vigorous <span class="hlt">hydrothermal</span> systems sometimes propagate into the solidification front, facilitating volatile exchange? Or is the magma always sealed at temperatures above some critical level related to rock strength and overpressure? The degree of <span class="hlt">hydrothermal</span> interaction in igneous systems is generally gauged in post mortem studies of δ18O and δD, where it has been assumed that a fracture front develops about the magma collapsing inward with cooling. H.P. Taylor and D. Norton's (1979; J. Petrol.)seminal work inferred that rocks are sealed with approach to the solidus and there is little to no direct interaction with external volatiles in the <span class="hlt">active</span> magma. In <span class="hlt">active</span> lava lakes a fracture front develops in response to thermal contraction of the newly formed rock once the temperature drops to ~950°C (Peck and Kinoshita,1976;USGS PP935A); rainfall driven <span class="hlt">hydrothermal</span> systems flash to steam near the 100 °C isotherm in the solidified lake and have little effect on the cooling history (Peck et al., 1977; AJS). Lava lakes are fully degassed magmas and until the recent discovery of the Puna Magma Chamber (Teplow et al., 2008; AGU) no <span class="hlt">active</span> magma was known at sufficiently great pressure to contain original volatiles. During the course of routine drilling of an injection well at the Puna Geothermal Venture (PGV) well-field, Big Island, Hawaii, a 75-meter interval of diorite containing brown glass inclusions was penetrated at a depth of 2415 m, continued drilling to 2488 m encountered a melt</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.V21D0755M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.V21D0755M"><span id="translatedtitle">Emission of CO2 from seafioor <span class="hlt">hydrothermal</span> systems at Mariana Trough</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maeda, Y.; Shitashima, K.</p> <p>2007-12-01</p> <p><span class="hlt">Hydrothermal</span> vent fluids are highly enriched in CO2 and the CO2 rich fluids are released into the ocean as a <span class="hlt">hydrothermal</span> plume. Especially, the emission of <span class="hlt">hydrothermal</span>-related liquid CO2 from the seafloor (about 1500m) was discovered at the Okinawa Trough and Mariana Trough. At these areas, it is considered that the liquid CO2 rises up to shallow depth as a CO2 droplet and that the rising CO2 droplet dissolves gradually in ambient seawater. The observation of the <span class="hlt">hydrothermal</span>-related CO2 would provide the opportunity for understanding the physic-chemical behavior and diffusion process of liquid CO2 in the ocean. Newly developed in-situ pH/pCO2 sensor can detect precisely and rapidly the changes of pH and pCO2 derived from high CO2 concentration. At southern Mariana Trough, the pH/pCO2 sensor was installed onto the manned submersible and in-situ pH and pCO2 data were measured every 10 seconds during the operation on the <span class="hlt">hydrothermal</span> <span class="hlt">active</span> <span class="hlt">site</span>. Mapping survey of low pH and pCO2 distribution was performed on the <span class="hlt">hydrothermal</span> <span class="hlt">active</span> <span class="hlt">site</span> by the grid navigation of the manned submersible that installed the pH/pCO2 sensor. The results of pH mapping survey showed only localized pH depression at the <span class="hlt">hydrothermal</span> <span class="hlt">active</span> <span class="hlt">site</span>. At NW Eifuku submarine volcano, <span class="hlt">hydrothermal</span>-related liquid CO2 dispersion was observed by using a towing multi-layer monitoring system. This system can observe the dispersion behavior of CO2 by towing several in-situ pH/pCO2 sensors and SSBL transponders in the high CO2 plume. Low pH plume of 100m high and 200m wide was detected above the summit of NW Eifuku submarine volcano.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.minsocam.org/MSA/AmMin/TOC/2016/index.html?issue_number=02','USGSPUBS'); return false;" href="http://www.minsocam.org/MSA/AmMin/TOC/2016/index.html?issue_number=02"><span id="translatedtitle">The Lassen <span class="hlt">hydrothermal</span> system</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ingebritsen, Steven E.; Bergfeld, Deborah; Clor, Laura; Evans, William C.</p> <p>2016-01-01</p> <p>The <span class="hlt">active</span> Lassen <span class="hlt">hydrothermal</span> system includes a central vapor-dominated zone or zones beneath the Lassen highlands underlain by ~240 °C high-chloride waters that discharge at lower elevations. It is the best-exposed and largest <span class="hlt">hydrothermal</span> system in the Cascade Range, discharging 41 ± 10 kg/s of steam (~115 MW) and 23 ± 2 kg/s of high-chloride waters (~27 MW). The Lassen system accounts for a full 1/3 of the total high-temperature <span class="hlt">hydrothermal</span> heat discharge in the U.S. Cascades (140/400 MW). <span class="hlt">Hydrothermal</span> heat discharge of ~140 MW can be supported by crystallization and cooling of silicic magma at a rate of ~2400 km3/Ma, and the ongoing rates of heat and magmatic CO2 discharge are broadly consistent with a petrologic model for basalt-driven magmatic evolution. The clustering of observed seismicity at ~4–5 km depth may define zones of thermal cracking where the <span class="hlt">hydrothermal</span> system mines heat from near-plastic rock. If so, the combined areal extent of the primary heat-transfer zones is ~5 km2, the average conductive heat flux over that area is >25 W/m2, and the conductive-boundary length <50 m. Observational records of <span class="hlt">hydrothermal</span> discharge are likely too short to document long-term transients, whether they are intrinsic to the system or owe to various geologic events such as the eruption of Lassen Peak at 27 ka, deglaciation beginning ~18 ka, the eruptions of Chaos Crags at 1.1 ka, or the minor 1914–1917 eruption at the summit of Lassen Peak. However, there is a rich record of intermittent <span class="hlt">hydrothermal</span> measurement over the past several decades and more-frequent measurement 2009–present. These data reveal sensitivity to climate and weather conditions, seasonal variability that owes to interaction with the shallow hydrologic system, and a transient 1.5- to twofold increase in high-chloride discharge in response to an earthquake swarm in mid-November 2014.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000088617','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000088617"><span id="translatedtitle">Mars Surveyor Project Landing <span class="hlt">Site</span> <span class="hlt">Activities</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gulick, Virginia C.; Briggs, Geoffrey; Saunders, R. Stephen; Gilmore, Martha; Soderblom, Larry</p> <p>1999-01-01</p> <p>The Mars Surveyor Program --now a cooperative program led by NASA and CNES along with other international partners -- is underway. It has the primary science objective of furthering our understanding of the biological potential and possible biological history of Mars and has the complementary objective of improving our understanding of martian climate evolution and planetary history The missions will develop technology and acquire data necessary for eventual human Exploration. Launches of orbiters, landers and rovers will take place in 2001 and in 2003; in 2005 a complete system will be launched capable of returning samples to Earth by 2008. A key aspect of the program is the selection of landing <span class="hlt">sites</span>. This abstract 1) reports on the status of the landing <span class="hlt">site</span> selection process that begins with the 2001 lander mission and 2) outlines be opportunities for the Mars community to provide input into the landing <span class="hlt">site</span> selection process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000092080','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000092080"><span id="translatedtitle">Mars Surveyor Project Landing <span class="hlt">Site</span> <span class="hlt">Activities</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gulick, V. C.; Briggs, Geoffrey; Saunders, R. Stephen; Gilmore, Martha; Soderblom, Larry</p> <p>1999-01-01</p> <p>The Mars Surveyor Program -- now a cooperative program led by NASA and CNES along with other international partners -- is underway. It has the primary science objective of furthering our understanding of the biological potential and possible biological history of Mars and has the complementary objective of improving our understanding of martian climate evolution and planetary history. The missions will develop technology and acquire data necessary for eventual human exploration. Launches of orbiters, landers and rovers will take place in 2001 and in 2003; in 2005 a complete system will be launched capable of returning samples to Earth by 2008. A key aspect of the program is the selection of landing <span class="hlt">sites</span>. This abstract 1) reports on the status of the landing <span class="hlt">site</span> selection process that begins with the 2001 lander mission and 2) outlines the opportunities for the Mars community to provide input into the landing <span class="hlt">site</span> selection process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApSS..359..805Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApSS..359..805Z"><span id="translatedtitle">NaF-assisted <span class="hlt">hydrothermal</span> synthesis of Ti-doped hematite nanocubes with enhanced photoelectrochemical <span class="hlt">activity</span> for water splitting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zheng, Chong; Zhu, Zezhou; Wang, Sibo; Hou, Yidong</p> <p>2015-12-01</p> <p>Ti-doped α-Fe2O3 nanocubes on FTO substrate was prepared by <span class="hlt">hydrothermal</span> deposition β-FeOOH onto FTO glass with a solution of FeCl3, TiOCl2 and NaF, followed by an appropriate annealing. In comparison to Ti-doped α-Fe2O3 nanorods Ti-doped α-Fe2O3 nanocubes showed an enhanced photoelectrochemical <span class="hlt">activity</span> for water splitting, with a remarkable IPCE of 25.2% at 340 nm at the potential of 1.23 V vs. RHE. The hematite films were studied in detail by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis absorption spectroscopy and electrochemical impedance spectroscopy. On the basis of the obtained results, the improved performance of Ti-doped α-Fe2O3 nanocubes can be ascribed to the porous structure, good electrical conductivity and fast charge transportation of hematite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22136425','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22136425"><span id="translatedtitle">Nitrogen-doped graphene/ZnSe nanocomposites: <span class="hlt">hydrothermal</span> synthesis and their enhanced electrochemical and photocatalytic <span class="hlt">activities</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Ping; Xiao, Tian-Yuan; Li, Hui-Hui; Yang, Jing-Jing; Wang, Zheng; Yao, Hong-Bin; Yu, Shu-Hong</p> <p>2012-01-24</p> <p>Nitrogen-doped graphene (GN) has great potential applications in many fields because doping with nitrogen can alter the electrical properties of graphene. It is still a challenge to develop a convenient method for synthesis of GN sheets. In this paper, we first report the synthesis of a nitrogen-doped graphene/ZnSe nanocomposite (GN-ZnSe) by a one-pot <span class="hlt">hydrothermal</span> process at low temperature using graphene oxide nanosheets and [ZnSe](DETA)(0.5) nanobelts as precursors. ZnSe nanorods composed of ZnSe nanoparticles were found to deposit on the surface of the GN sheets. The results demonstrated that [ZnSe](DETA)(0.5) nanobelts were used not only as the source of ZnSe nanoparticles but also as the nitrogen source. Interestingly, it was found that the as-prepared nanocomposites exhibit remarkably enhanced electrochemical performance for oxygen reduction reaction and photocatalytic <span class="hlt">activities</span> for the bleaching of methyl orange dye under visible-light irradiation. This facile and catalyst-free approach for depositing ZnSe nanoparticles onto the graphene sheets may provide an alternative way for preparation of other nanocomposites based on GN sheets under mild conditions, which show their potential applications in wastewater treatment, fuel cells, energy storage, nanodevices, and so on. PMID:22136425</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3366505','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3366505"><span id="translatedtitle"><span class="hlt">Activation</span> of Inhibitors by Sortase Triggers Irreversible Modification of the <span class="hlt">Active</span> <span class="hlt">Site*S</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Maresso, Anthony W.; Wu, Ruiying; Kern, Justin W.; Zhang, Rongguang; Janik, Dorota; Missiakas, Dominique M.; Duban, Mark-Eugene; Joachimiak, Andrzej; Schneewind, Olaf</p> <p>2011-01-01</p> <p>Sortases anchor surface proteins to the cell wall of Gram-positive pathogens through recognition of specific motif sequences. Loss of sortase leads to large reductions in virulence, which identifies sortase as a target for the development of antibacterials. By screening 135,625 small molecules for inhibition, we report here that aryl (β-amino)ethyl ketones inhibit sortase enzymes from staphylococci and bacilli. Inhibition of sortases occurs through an irreversible, covalent modification of their <span class="hlt">active</span> <span class="hlt">site</span> cysteine. Sortases specifically <span class="hlt">activate</span> this class of molecules via β-elimination, generating a reactive olefin intermediate that covalently modifies the cysteine thiol. Analysis of the three-dimensional structure of Bacillus anthracis sortase B with and without inhibitor provides insights into the mechanism of inhibition and reveals binding pockets that can be exploited for drug discovery. PMID:17545669</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/10551856','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/10551856"><span id="translatedtitle">The bifunctional <span class="hlt">active</span> <span class="hlt">site</span> of s-adenosylmethionine synthetase. Roles of the <span class="hlt">active</span> <span class="hlt">site</span> aspartates.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Taylor, J C; Markham, G D</p> <p>1999-11-12</p> <p>S-Adenosylmethionine (AdoMet) synthetase catalyzes the biosynthesis of AdoMet in a unique enzymatic reaction. Initially the sulfur of methionine displaces the intact tripolyphosphate chain (PPP(i)) from ATP, and subsequently PPP(i) is hydrolyzed to PP(i) and P(i) before product release. The crystal structure of Escherichia coli AdoMet synthetase shows that the <span class="hlt">active</span> <span class="hlt">site</span> contains four aspartate residues. Aspartate residues Asp-16* and Asp-271 individually provide the sole protein ligand to one of the two required Mg(2+) ions (* denotes a residue from a second subunit); aspartates Asp-118 and Asp-238* are proposed to interact with methionine. Each aspartate has been changed to an uncharged asparagine, and the metal binding residues were also changed to alanine, to assess the roles of charge and ligation ability on catalytic efficiency. The resultant enzyme variants all structurally resemble the wild type enzyme as indicated by circular dichroism spectra and are tetramers. However, all have k(cat) reductions of approximately 10(3)-fold in AdoMet synthesis, whereas the MgATP and methionine K(m) values change by less than 3- and 8-fold, respectively. In the partial reaction of PPP(i) hydrolysis, mutants of the Mg(2+) binding residues have >700-fold reduced catalytic efficiency (k(cat)/K(m)), whereas the D118N and D238*N mutants are impaired less than 35-fold. The catalytic efficiency for PPP(i) hydrolysis by Mg(2+) <span class="hlt">site</span> mutants is improved by AdoMet, like the wild type enzyme. In contrast AdoMet reduces the catalytic efficiency for PPP(i) hydrolysis by the D118N and D238*N mutants, indicating that the events involved in AdoMet <span class="hlt">activation</span> are hindered in these methionyl binding <span class="hlt">site</span> mutants. Ca(2+) uniquely <span class="hlt">activates</span> the D271A mutant enzyme to 15% of the level of Mg(2+), in contrast to the approximately 1% Ca(2+) <span class="hlt">activation</span> of the wild type enzyme. This indicates that the Asp-271 side chain size is a discriminator between the <span class="hlt">activating</span> ability of Ca(2+) and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.V23B0606K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.V23B0606K"><span id="translatedtitle">Liquid CO2 venting on the seafloor: Yonaguni Knoll IV <span class="hlt">hydrothermal</span> system, Okinawa Trough</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Konno, U.; Tsunogai, U.; Nakagawa, F.; Nakaseama, M.; Ishibashi, J.; Nunoura, T.; Nakamura, K.</p> <p>2006-12-01</p> <p>In 2000, an <span class="hlt">active</span> <span class="hlt">hydrothermal</span> <span class="hlt">site</span>, venting high-temperature fluid up to 300 oC, was discovered by Shinkai 6500 on the top of Yonaguni Knoll IV during YK 00-06 cruise in Okinawa Trough. During the subsequent subseafloor survey using Shinkai 6500 in 2003 (YK03-05), vents of liquid CO2 droplets were found at the <span class="hlt">site</span>. Similar liquid CO2 droplets had previously been found at the <span class="hlt">active</span> <span class="hlt">hydrothermal</span> <span class="hlt">sites</span> at JADE <span class="hlt">hydrothermal</span> field, Okinawa Trough, during the extensive seafloor survey using submersibles in 1989 [Sakai et al., 1990]. Besides, similar liquid CO2 venting has also been recognized in NW Eifuku <span class="hlt">hydrothermal</span> <span class="hlt">site</span> on Izu-Bonin- Mariana arc. It thus appears that liquid CO2 venting might be usual phenomenon in some submarine arc volcanoes. The detailed relation between seafloor venting liquid CO2 and the surrounding high-temperature <span class="hlt">hydrothermal</span> fluid, however, was not clarified in their studies. Furthermore, no definite evidence was obtained for the presence of CO2-hydrate in the subsurface. In this study, in order to discuss the subseafloor processes responsible for producing liquid CO2 at the Yonaguni Knoll IV <span class="hlt">site</span>, as well as the possibility of the occurrence of solid CO2-hydrate within the sediments, we determined the chemical and isotopic compositions of the liquid CO2 found on the <span class="hlt">site</span>, as well as those in <span class="hlt">hydrothermal</span> fluid venting from the surrounding chimneys. In consequence, the ^13C of both CO2 and CH4 in the liquid CO2 almost coincide with those in the <span class="hlt">hydrothermal</span> fluid, suggesting that the liquid CO2 must be derived from the <span class="hlt">hydrothermal</span> fluid. While showing homogeneous ^13C, the <span class="hlt">hydrothermal</span> fluids exhibit wide variation in gas contents. <span class="hlt">Active</span> phase separation must be taking place within the conduits. Besides, H2-depletion in the liquid CO2 suggests formation of solid CO2-hydrate must also precede the venting of liquid CO2. In conclusion, liquid CO2 must be produced through following subseafloor processes: phase separation of <span class="hlt">hydrothermal</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27394009','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27394009"><span id="translatedtitle">Visible light induced bactericidal and photocatalytic <span class="hlt">activity</span> of <span class="hlt">hydrothermally</span> synthesized BiVO4 nano-octahedrals.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sharma, Rishabh; Uma; Singh, Sonal; Verma, Ajit; Khanuja, Manika</p> <p>2016-09-01</p> <p>In the present work, monoclinic bismuth vanadate (m-BiVO4) nanostructures have been synthesized via simple <span class="hlt">hydrothermal</span> method and employed for visible light driven antimicrobial and photocatalytic <span class="hlt">activity</span>. Morphology (octahedral) and size (200-300nm) of the m-BiVO4 are studied using transmission electron microscopy (TEM). The crystal structure of m-BiVO4 (monoclinic scheelite structure) is confirmed by high resolution-TEM (HRTEM) and X-ray diffraction (XRD) studies. The band gap of m-BiVO4 was estimated to be ca. 2.42eV through Kubelka-Munk function F(R∞) using diffuse reflectance spectroscopy (DRS). Antimicrobial action of m-BiVO4 is anticipated by (i) shake flask method, (ii) MTT [3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide] assay for cytotoxicity. SEM analysis has been carried on Escherichia coli (E.coli) before and after treatment with nanostructure materials to reveal the mechanism underlying the antimicrobial action. Antimicrobial <span class="hlt">activity</span> is studied as a function of m-BiVO4 concentration viz. 20, 40, 60 and 80ppm. The bacterial growth is decreased 80% to 96%, with the increase in m-BiVO4 concentration from 20ppm to 80ppm, respectively, in 2h. Photocatalytic <span class="hlt">activity</span> and rate kinetics of m-BiVO4 nanostructures have been studied as a function of time on methylene blue (MB) dye degradation which is one of the waste products of textile industries and responsible for water pollution. PMID:27394009</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Nanos...712392W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Nanos...712392W"><span id="translatedtitle">Morphology-dependent photocatalytic <span class="hlt">activity</span> of octahedral anatase particles prepared by ultrasonication-<span class="hlt">hydrothermal</span> reaction of titanates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, Zhishun; Kowalska, Ewa; Verrett, Jonathan; Colbeau-Justin, Christophe; Remita, Hynd; Ohtani, Bunsho</p> <p>2015-07-01</p> <p>Octahedral anatase particles (OAPs) were prepared by an ultrasonication (US)-<span class="hlt">hydrothermal</span> (HT) reaction of partially proton-exchanged potassium titanate nanowires (TNWs). The structural/physical properties of OAP-containing samples, including specific surface area, crystallinity, crystallite size, particle aspect ratio, composition and total OAP content, were analyzed. Photocatalytic <span class="hlt">activities</span> of samples were measured under irradiation (>290 nm) for oxidative decomposition of acetic acid (CO2 system) and dehydrogenation of methanol (H2 system) under aerobic and deaerated conditions, respectively. Total density of electron traps (ETs) was measured by double-beam photoacoustic spectroscopy (DB-PAS). Mobility and lifetime of charge carriers (electrons) were investigated by the time-resolved microwave conductivity (TRMC) method. The effects of synthesis parameters, i.e., HT duration, HT temperature and US duration, on properties and photocatalytic <span class="hlt">activities</span> of final products were examined in detail. The sample prepared with 1 h US duration and 6 h HT duration at 433 K using 267 mg of TNWs in 80 mL of Milli-Q water exhibited the highest photocatalytic <span class="hlt">activity</span>. It was found that change in HT duration or HT temperature while keeping the other conditions the same resulted in changes in all properties and photocatalytic <span class="hlt">activity</span>. On the other hand, duration of US treatment, before HT reaction, influenced the morphology of both the reagent (by TNWs breaking) and final products (change in total OAP content); samples prepared with various US durations exhibited almost the same structural/physical properties evaluated in this study but were different in morphology and photocatalytic <span class="hlt">activity</span>. This enabled clarification of the correlation between morphology and photocatalytic <span class="hlt">activity</span>, i.e., the higher the total OAP content was, the higher was the level of photocatalytic <span class="hlt">activity</span>, especially in the CO2 system. Although the decay after maximum TRMC signal intensity (Imax) was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V13C3140I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V13C3140I"><span id="translatedtitle">Vapor Discharges On Nevado Del Ruiz During The Recent <span class="hlt">Activity</span>: Clues On The Composition Of The Deep <span class="hlt">Hydrothermal</span> System And Its Effects On Thermal Springs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Inguaggiato, S.; Federico, C.; Chacon, Z.; Londono, J. M.; Alzate, D. M.; Gil, E.</p> <p>2015-12-01</p> <p>The Nevado del ruiz volcano (NdR, 5321m asl), one of the most <span class="hlt">active</span> in Colombia, threatens about 600,000 people. The existence of an ice cap and several streams channeling in some main rivers increase the risk of lahars and mudflows in case of unrest, as occurred during the November 1985 eruption, which caused 20,000 casualties. The involvement of the local <span class="hlt">hydrothermal</span> system has also produced in the past phreatic and phreatomagmatic <span class="hlt">activity</span>, as in 1985 and 1989. After more than 7 years of relative stability, since 2010, the still ongoing phase of unrest has produced two small eruption in 2012, and still maintains in high levels of seismicity and SO2 degassing. In October 2013, a sampling campaign has been performed on thermal springs and streamwater, located at 2600-5000 m asl, analyzed for water chemistry and stable isotopes. By applying a model of steam-heating, based on mass and enthalpy balances, we have estimated the mass rate of steam discharging in the different steam-heated springs. The composition of the hottest thermal spring (Botero Londoño) is probably representative of a marginal part of the <span class="hlt">hydrothermal</span> system, having a temperature of 250°C and low salinity (Cl ~1500 mg/l), which suggest a chiefly meteoric origin, as also confirmed by the isotope composition retrieved for the <span class="hlt">hydrothermal</span> water. The vapour discharged at the steam vent "Nereidas" (3600 m asl) is hypothesised to be separated from a high-temperature hyrothermal system. Based on its composition and on literature data on fluid inclusions, we have retrieved the P-T-X conditions of the deep <span class="hlt">hydrothermal</span> system, as well as its pH and fO2. The vapour feeding Nereidas would separate from a byphasic <span class="hlt">hydrothermal</span> system characterised by the follow parameters: t= 315°C, P=19 MPa, NaCl= 15 %, CO2 = 9%, and similar proportion between liquid and vapour. Considering also the equilibria involving S-bearing gases and HCl, we obtain pH=2, fO2 fixed by FeO-Fe2O3 buffer, and [Cl]=12000 mg/l. Changes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6074751','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6074751"><span id="translatedtitle">The <span class="hlt">active</span> <span class="hlt">site</span> of ribulose-bisphosphate carboxylase/oxygenase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hartman, F.C.</p> <p>1991-01-01</p> <p>The <span class="hlt">active</span> <span class="hlt">site</span> of ribulose-bisphosphate carboxylase/oxygenase requires interacting domains of adjacent, identical subunits. Most <span class="hlt">active-site</span> residues are located within the loop regions of an eight-stranded {beta}/{alpha}-barrel which constitutes the larger C-terminal domain; additional key residues are located within a segment of the smaller N-terminal domain which partially covers the mouth of the barrel. <span class="hlt">Site</span>-directed mutagenesis of the gene encoding the enzyme from Rhodospirillum rubrum has been used to delineate functions of <span class="hlt">active-site</span> residues. 6 refs., 2 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10123124','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10123124"><span id="translatedtitle">Savannah River <span class="hlt">Site</span> prioritization of transition <span class="hlt">activities</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Finley, R.H.</p> <p>1993-11-01</p> <p>Effective management of SRS conversion from primarily a production facility to other missions (or Decontamination and Decommissioning (D&D)) requires a systematic and consistent method of prioritizing the transition <span class="hlt">activities</span>. This report discusses the design of a prioritizing method developed to achieve systematic and consistent methods of prioritizing these <span class="hlt">activities</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10114220','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10114220"><span id="translatedtitle">DOE <span class="hlt">site</span> performance assessment <span class="hlt">activities</span>. Radioactive Waste Technical Support Program</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1990-07-01</p> <p>Information on performance assessment capabilities and <span class="hlt">activities</span> was collected from eight DOE <span class="hlt">sites</span>. All eight <span class="hlt">sites</span> either currently dispose of low-level radioactive waste (LLW) or plan to dispose of LLW in the near future. A survey questionnaire was developed and sent to key individuals involved in DOE Order 5820.2A performance assessment <span class="hlt">activities</span> at each <span class="hlt">site</span>. The <span class="hlt">sites</span> surveyed included: Hanford <span class="hlt">Site</span> (Hanford), Idaho National Engineering Laboratory (INEL), Los Alamos National Laboratory (LANL), Nevada Test <span class="hlt">Site</span> (NTS), Oak Ridge National Laboratory (ORNL), Paducah Gaseous Diffusion Plant (Paducah), Portsmouth Gaseous Diffusion Plant (Portsmouth), and Savannah River <span class="hlt">Site</span> (SRS). The questionnaire addressed all aspects of the performance assessment process; from waste source term to dose conversion factors. This report presents the information developed from the <span class="hlt">site</span> questionnaire and provides a comparison of <span class="hlt">site</span>-specific performance assessment approaches, data needs, and ongoing and planned <span class="hlt">activities</span>. All <span class="hlt">sites</span> are engaged in completing the radioactive waste disposal facility performance assessment required by DOE Order 5820.2A. Each <span class="hlt">site</span> has achieved various degrees of progress and have identified a set of critical needs. Within several areas, however, the <span class="hlt">sites</span> identified common needs and questions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21144233','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21144233"><span id="translatedtitle">Safety Oversight of Decommissioning <span class="hlt">Activities</span> at DOE Nuclear <span class="hlt">Sites</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zull, Lawrence M.; Yeniscavich, William</p> <p>2008-01-15</p> <p>The Defense Nuclear Facilities Safety Board (Board) is an independent federal agency established by Congress in 1988 to provide nuclear safety oversight of <span class="hlt">activities</span> at U.S. Department of Energy (DOE) defense nuclear facilities. The <span class="hlt">activities</span> under the Board's jurisdiction include the design, construction, startup, operation, and decommissioning of defense nuclear facilities at DOE <span class="hlt">sites</span>. This paper reviews the Board's safety oversight of decommissioning <span class="hlt">activities</span> at DOE <span class="hlt">sites</span>, identifies the safety problems observed, and discusses Board initiatives to improve the safety of decommissioning <span class="hlt">activities</span> at DOE <span class="hlt">sites</span>. The decommissioning of former defense nuclear facilities has reduced the risk of radioactive material contamination and exposure to the public and <span class="hlt">site</span> workers. In general, efforts to perform decommissioning work at DOE defense nuclear <span class="hlt">sites</span> have been successful, and contractors performing decommissioning work have a good safety record. Decommissioning <span class="hlt">activities</span> have recently been completed at <span class="hlt">sites</span> identified for closure, including the Rocky Flats Environmental Technology <span class="hlt">Site</span>, the Fernald Closure Project, and the Miamisburg Closure Project (the Mound <span class="hlt">site</span>). The Rocky Flats and Fernald <span class="hlt">sites</span>, which produced plutonium parts and uranium materials for defense needs (respectively), have been turned into wildlife refuges. The Mound <span class="hlt">site</span>, which performed R and D <span class="hlt">activities</span> on nuclear materials, has been converted into an industrial and technology park called the Mound Advanced Technology Center. The DOE Office of Legacy Management is responsible for the long term stewardship of these former EM <span class="hlt">sites</span>. The Board has reviewed many decommissioning <span class="hlt">activities</span>, and noted that there are valuable lessons learned that can benefit both DOE and the contractor. As part of its ongoing safety oversight responsibilities, the Board and its staff will continue to review the safety of DOE and contractor decommissioning <span class="hlt">activities</span> at DOE defense nuclear <span class="hlt">sites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2144750','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2144750"><span id="translatedtitle">Mutations of fumarase that distinguish between the <span class="hlt">active</span> <span class="hlt">site</span> and a nearby dicarboxylic acid binding <span class="hlt">site</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Weaver, T.; Lees, M.; Banaszak, L.</p> <p>1997-01-01</p> <p>Two mutant forms of fumarase C from E. coli have been made using PCR and recombinant DNA. The recombinant form of the protein included a histidine arm on the C-terminal facilitating purification. Based on earlier studies, two different carboxylic acid binding <span class="hlt">sites</span>, labeled A- and B-, were observed in crystal structures of the wild type and inhibited forms of the enzyme. A histidine at each of the <span class="hlt">sites</span> was mutated to an asparagine. H188N at the A-<span class="hlt">site</span> resulted in a large decrease in specific <span class="hlt">activity</span>, while the H129N mutation at the B-<span class="hlt">site</span> had essentially no effect. From the results, we conclude that the A-<span class="hlt">site</span> is indeed the <span class="hlt">active</span> <span class="hlt">site</span>, and a dual role for H188 as a potential catalytic base is proposed. Crystal structures of the two mutant proteins produced some unexpected results. Both mutations reduced the affinity for the carboxylic acids at their respective <span class="hlt">sites</span>. The H129N mutant should be particularly useful in future kinetic studies because it sterically blocks the B-<span class="hlt">site</span> with the carboxyamide of asparagine assuming the position of the ligand's carboxylate. In the H188N mutation at the <span class="hlt">active</span> <span class="hlt">site</span>, the new asparagine side chain still interacts with an <span class="hlt">active</span> <span class="hlt">site</span> water that appears to have moved slightly as a result of the mutation. PMID:9098893</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SuMi...81..226M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SuMi...81..226M"><span id="translatedtitle">Synthesis of nanostructured and microstructured ZnO and Zn(OH)2 on <span class="hlt">activated</span> carbon cloth by <span class="hlt">hydrothermal</span> and microwave-assisted chemical bath deposition methods</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mosayebi, Elham; Azizian, Saeid; Hajian, Ali</p> <p>2015-05-01</p> <p>Nanostructured and microstructured ZnO and Zn(OH)2 loaded on <span class="hlt">activated</span> carbon cloth were synthesized by microwave-assisted chemical bath deposition and <span class="hlt">hydrothermal</span> methods. By <span class="hlt">hydrothermal</span> method the deposited sample on carbon fiber is pure ZnO with dandelion-like nanostructures. By microwave-assisted chemical bath method the structure and composition of deposited sample depends on solution pH. At pH = 9.8 the deposited sample on carbon fiber is pure ZnO with flower-like microstructure; but at pH = 10.8 the sample is a mixture of ZnO and Zn(OH)2 with flower-like and rhombic microstructures, respectively. The mechanism of crystal grow by microwave-assisted chemical bath method was investigated by SEM method at both pH.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70013764','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70013764"><span id="translatedtitle">Acoustic stratigraphy and <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> within Epi Submarine Caldera, Vanuatu, New Hebrides Arc</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Greene, H. Gary; Exon, N.F.</p> <p>1988-01-01</p> <p>Geological and geophysical surveys of <span class="hlt">active</span> submarine volcanoes offshore and southeast of Epi Island, Vanuatu, New Hebrides Arc, have delineated details of the structure and acoustic stratigraphy of three volcanic cones. These submarine cones, named Epia, Epib, and Epic, are aligned east-west and spaced 3.5 km apart on the rim of a submerged caldera. At least three acoustic sequences, of presumed Quaternary age, can be identified on single-channel seismic-reflection profiles. Rocks dredged from these cones include basalt, dacite, and cognate gabbroic inclusions with magmatic affinities similar to those of the Karua (an <span class="hlt">active</span> submarine volcano off the southeastern tip of Epi) lavas. ?? 1988 Springer-Verlag New York Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5348702','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5348702"><span id="translatedtitle">Current California legislative and regulatory <span class="hlt">activity</span> impacting geothermal <span class="hlt">hydrothermal</span> commercialization: a monitoring report. Report No. 1017</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1980-01-20</p> <p>Four key geothermal-impacting bills presently before the California legislature are described. Two deal with state financial backing for geothermal projects. The third relates to the use of the state's share of the BLM geothermal revenues and the fourth to the protection of sensitive hot springs. The current regulatory <span class="hlt">activities</span> of the California Energy Commission, the California Division of Oil and Gas, and the counties are discussed. (MHR)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3360948','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3360948"><span id="translatedtitle">Ionizable Side Chains at Catalytic <span class="hlt">Active</span> <span class="hlt">Sites</span> of Enzymes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jimenez-Morales, David; Liang, Jie</p> <p>2012-01-01</p> <p>Catalytic <span class="hlt">active</span> <span class="hlt">sites</span> of enzymes of known structure can be well defined by a modern program of computational geometry. The CASTp program was used to define and measure the volume of the catalytic <span class="hlt">active</span> <span class="hlt">sites</span> of 573 enzymes in the Catalytic <span class="hlt">Site</span> Atlas database. The <span class="hlt">active</span> <span class="hlt">sites</span> are identified as catalytic because the amino acids they contain are known to participate in the chemical reaction catalyzed by the enzyme. Acid and base side chains are reliable markers of catalytic <span class="hlt">active</span> <span class="hlt">sites</span>. The catalytic <span class="hlt">active</span> <span class="hlt">sites</span> have 4 acid and 5 base side chains, in an average volume of 1072 Å3. The number density of acid side chains is 8.3 M (in chemical units); the number density of basic side chains is 10.6 M. The catalytic <span class="hlt">active</span> <span class="hlt">site</span> of these enzymes is an unusual electrostatic and steric environment in which side chains and reactants are crowded together in a mixture more like an ionic liquid than an ideal infinitely dilute solution. The electrostatics and crowding of reactants and side chains seems likely to be important for catalytic function. In three types of analogous ion channels, simulation of crowded charges accounts for the main properties of selectivity measured in a wide range of solutions and concentrations. It seems wise to use mathematics designed to study interacting complex fluids when making models of the catalytic <span class="hlt">active</span> <span class="hlt">sites</span> of enzymes. PMID:22484856</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9208H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9208H"><span id="translatedtitle">Double, double, (but mostly) toil, and trouble: A multidisciplinary approach to quantify the permeability of an <span class="hlt">active</span> volcanic <span class="hlt">hydrothermal</span> system (Whakaari volcano, New Zealand)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heap, Michael; Kennedy, Ben; Farquharson, Jamie; Ashworth, James; Mayer, Klaus; Letham-Brake, Mark; Reuschlé, Thierry; Gilg, Albert; Scheu, Betty; Lavallée, Yan; Siratovich, Paul; Cole, Jim; Jolly, Art; Dingwell, Donald</p> <p>2016-04-01</p> <p>Our multidisciplinary approach, which combines field techniques and traditional laboratory methods, aims to better understand the permeability of an <span class="hlt">active</span> volcanic <span class="hlt">hydrothermal</span> system, a vital prerequisite for understanding and modelling the behaviour of <span class="hlt">hydrothermal</span> systems worldwide. Whakaari volcano (an <span class="hlt">active</span> stratovolcano located 48 km off New Zealand's North Island) hosts an open, highly reactive <span class="hlt">hydrothermal</span> system (hot springs and mud pools, fumaroles, acid streams and lakes) and represents an ideal natural laboratory to undertake such a study. We first gained an appreciation of the different lithologies at Whakaari and (where possible) their lateral and vertical extent through reconnaissance by land, sea, and air. Due to the variable nature of these altered lithologies (mainly lavas and tuffs), we measured porosity-permeability for in excess of a hundred rock hand samples using field techniques. We also measured the permeability of recent, unconsolidated deposits using a field soil permeameter. Our field measurements were then groundtruthed on a subset of these samples (~40-50) using traditional laboratory techniques: helium pycnometry and measurements of permeability using a benchtop permeameter, including measurements under increasing confining pressure (i.e., depth). In all, our measurements highlight that the porosity of the materials at Whakaari can vary from ~0.01 to ~0.6, and permeability can vary by eight orders of magnitude. However, our data show no discernable trend between porosity and permeability. A combination of macroscopic and microscopic observations, chemistry (XRF), mineralogy (XRD), and mercury porosimetry highlight that the absence of a robust porosity-permeability relationship is the product of an insane variability in alteration and microstructure (pore size, particle size, pore connectivity, presence/absence of microcracks, layering, amongst others). While our systematic study offers the most complete porosity-permeability dataset</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21580075','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21580075"><span id="translatedtitle">Synthesis of large surface area nano-sized BiVO{sub 4} by an EDTA-modified <span class="hlt">hydrothermal</span> process and its enhanced visible photocatalytic <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sun Wanting; Xie Mingzheng; Jing Liqiang; Luan Yunbo; Fu Honggang</p> <p>2011-11-15</p> <p>In this work, monoclinic scheelite-type BiVO{sub 4} nanoparticle with large surface area has been successfully synthesized, using Bi(NO{sub 3}){sub 3} and NH{sub 4}VO{sub 3} as raw materials, through a <span class="hlt">hydrothermal</span> process in the presence of ethylene diamine tetraacetic acid (EDTA). It is demonstrated that the nanoparticle size of as-prepared BiVO{sub 4} becomes small by decreasing <span class="hlt">hydrothermal</span> temperature, shortening <span class="hlt">hydrothermal</span> reaction time and increasing EDTA amount used. The resulting BiVO{sub 4} nanoparticle with large surface area exhibits a good photocatalytic performance for degrading phenol solution as a model organic pollutant under visible illumination. The key of this method is the chelating role of EDTA group in the synthetic process that it can greatly control the concentration of Bi{sup 3+}, leading to the growth inhibition of BiVO{sub 4} crystallite. The work provides a route for the synthesis of Bi-containing nano-sized composite oxides with large surface area. - Graphical abstract: High visible <span class="hlt">active</span> nano-sized BiVO{sub 4} photocatalyst with large surface area is successfully synthesized, which is attributed to the chelating role of EDTA group inhibiting the growth of BiVO{sub 4} crystallites. Highlights: > Monoclinic scheelite-type BiVO{sub 4} nanoparticle with large surface area has been synthesized by a <span class="hlt">hydrothermal</span> process. > Key of this method is the chelating role of EDTA group inhibiting the growth of BiVO{sub 4} crystallites. > Resulting nano-sized BiVO{sub 4} exhibits a good photocatalytic <span class="hlt">activity</span> for degrading phenol under visible illumination.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998ApPhL..73..478X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998ApPhL..73..478X"><span id="translatedtitle">Luminescence characteristics of impurities-<span class="hlt">activated</span> ZnS nanocrystals prepared in microemulsion with <span class="hlt">hydrothermal</span> treatment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, S. J.; Chua, S. J.; Liu, B.; Gan, L. M.; Chew, C. H.; Xu, G. Q.</p> <p>1998-07-01</p> <p>Cu-, Eu-, or Mn-doped ZnS nanocrystalline phosphors were prepared at room temperature using a chemical synthesis method. Transmission electron microscopy observation shows that the size of the ZnS clusters is in the 3-18 nm range. New luminescence characteristics such as strong and stable visible-light emissions with different colors were observed from the doped ZnS nanocrystals at room temperature. These results strongly suggest that impurities, especially transition metals and rare-earth metals-<span class="hlt">activated</span> ZnS nanoclusters form a new class of luminescent materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910031951&hterms=Pegmatite&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DPegmatite','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910031951&hterms=Pegmatite&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DPegmatite"><span id="translatedtitle">A discussion of 'Anomalous quartz from the Roter Kamm impact crater, Namibia - Evidence for post-impact <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>?'</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roedder, Edwin</p> <p>1990-01-01</p> <p>This paper presents arguments against the statement made by Koeberl et al. (1989) to the effect that various differences between the quartz of the three quartz pebbles from the Roter Kamm impact crater (Namibia) and the quartz of the pegmatites present in the basement rocks of this crater can be best interpreted as evidence that the pebbles were formed (or 'recrystallized') by a post-impact <span class="hlt">hydrothermal</span> system. Arguments are presented that suggest that the three quartz pebbles are, most likely, fragments of a preimpact vein quartz of <span class="hlt">hydrothermal</span> origin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005M%26PS...40.1859O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005M%26PS...40.1859O"><span id="translatedtitle">A case study of impact-induced <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>: The Haughton impact structure, Devon Island, Canadian High Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Osinski, Gordon R.; Lee, Pascal; Parnell, John; Spray, John G.; Baron, Martin</p> <p>2005-12-01</p> <p>The well-preserved state and excellent exposure at the 39 Ma Haughton impact structure, 23 km in diameter, allows a clearer picture to be made of the nature and distribution of <span class="hlt">hydrothermal</span> deposits within mid-size complex impact craters. A moderate- to low-temperature <span class="hlt">hydrothermal</span> system was generated at Haughton by the interaction of groundwaters with the hot impact melt breccias that filled the interior of the crater. Four distinct settings and styles of <span class="hlt">hydrothermal</span> mineralization are recognized at Haughton: a) vugs and veins within the impact melt breccias, with an increase in intensity of alteration towards the base; b) cementation of brecciated lithologies in the interior of the central uplift; c) intense veining around the heavily faulted and fractured outer margin of the central uplift; and d) <span class="hlt">hydrothermal</span> pipe structures or gossans and mineralization along fault surfaces around the faulted crater rim. Each setting is associated with a different suite of <span class="hlt">hydrothermal</span> minerals that were deposited at different stages in the development of the <span class="hlt">hydrothermal</span> system. Minor, early quartz precipitation in the impact melt breccias was followed by the deposition of calcite and marcasite within cavities and fractures, plus minor celestite, barite, and fluorite. This occurred at temperatures of at least 200 °C and down to ˜100-120 °C. <span class="hlt">Hydrothermal</span> circulation through the faulted crater rim with the deposition of calcite, quartz, marcasite, and pyrite, occurred at similar temperatures. Quartz mineralization within breccias of the interior of the central uplift occurred in two distinct episodes (˜250 down to ˜90 °C, and <60 °C). With continued cooling (<90 °C), calcite and quartz were precipitated in vugs and veins within the impact melt breccias. Calcite veining around the outer margin of the central uplift occurred at temperatures of ˜150 °C down to <60 °C. Mobilization of hydrocarbons from the country rocks occurred during formation of the higher</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Nanot..26f5603L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Nanot..26f5603L"><span id="translatedtitle">Reduced graphene oxide supported platinum nanocubes composites: one-pot <span class="hlt">hydrothermal</span> synthesis and enhanced catalytic <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Fumin; Gao, Xueqing; Xue, Qi; Li, Shuni; Chen, Yu; Lee, Jong-Min</p> <p>2015-02-01</p> <p>Reduced graphene oxide (rGO) supported platinum nanocubes (Pt-NCs) composites (Pt-NCs/rGO) were synthesized successfully by a water-based co-chemical reduction method, in which polyallylamine hydrochloride acted as a multi-functional molecule for the functionalization of graphene oxide, anchorage of PtII precursor, and control of Pt crystal facets. The morphology, structure, composition, and catalytic property of Pt-NCs/rGO composites were characterized in detail by various spectroscopic techniques. Transmission electron microscopy images showed well-defined Pt-NCs with an average size of 9 nm uniformly distributed on the rGO surface. The as-prepared Pt-NCs/rGO composites had excellent colloidal stability in the aqueous solution, and exhibited superior catalytic <span class="hlt">activity</span> towards the hydrogenation reduction of nitro groups compared to commercial Pt black. The improved catalytic <span class="hlt">activity</span> originated from the abundant exposed Pt{100} facets of Pt-NCs, excellent dispersion of Pt-NCs on the rGO surface, and synergistic effect between Pt-NCs and rGO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1251034','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1251034"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> Alteration of Glass from Underground Nuclear Tests: Formation and Transport of Pu-clay Colloids at the Nevada National Security <span class="hlt">Site</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zavarin, M.; Zhao, P.; Joseph, C.; Begg, J.; Boggs, M.; Dai, Z.; Kersting, A. B.</p> <p>2015-05-27</p> <p>The testing of nuclear weapons at the Nevada National Security <span class="hlt">Site</span> (NNSS), formerly the Nevada Test <span class="hlt">Site</span> (NTS), has led to the deposition of substantial quantities of plutonium into the environment. Approximately 2.8 metric tons (3.1×10<sup>4</sup> TBq) of Pu were deposited in the NNSS subsurface as a result of underground nuclear testing. While <sup>3</sup>H is the most abundant anthropogenic radionuclide deposited in the NNSS subsurface (4.7×10<sup>6</sup> TBq), plutonium is the most abundant from a molar standpoint. The only radioactive elements in greater molar abundance are the naturally occurring K, Th, and U isotopes. <sup>239</sup>Pu and <sup>240</sup>Pu represent the majority of alpha-emitting Pu isotopes. The extreme temperatures associated with underground nuclear tests and the refractory nature of Pu results in most of the Pu (98%) being sequestered in melted rock, referred to as nuclear melt glass (Iaea, 1998). As a result, Pu release to groundwater is controlled, in large part, by the leaching (or dissolution) of nuclear melt glass over time. The factors affecting glass dissolution rates have been studied extensively. The dissolution of Pu-containing borosilicate nuclear waste glasses at 90ºC has been shown to lead to the formation of dioctahedral smectite colloids. Colloid-facilitated transport of Pu at the NNSS has been observed. Recent groundwater samples collected from a number of contaminated wells have yielded a wide range of Pu concentrations from 0.00022 to 2.0 Bq/L. While Pu concentrations tend to fall below the Maximum Contaminant Level (MCL) established by the Environmental Protection Agency (EPA) for drinking water (0.56 Bq/L), we do not yet understand what factors limit the Pu concentration or its transport behavior. To quantify the upper limit of Pu concentrations produced as a result of melt glass dissolution and determine the nature of colloids and Pu associations, we performed a 3 year nuclear melt glass dissolution experiment</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/993489','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/993489"><span id="translatedtitle">Response to"Analysis of the Treatment, by the U.S. Department of Energy, of the FEP <span class="hlt">Hydrothermal</span> <span class="hlt">Activity</span> in the Yucca Mountain Performance Assessment" by Yuri Dublyansky</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Houseworth, J.E.; Hardin, E.</p> <p>2008-11-17</p> <p>This paper presents a rebuttal to Dublyansky (2007), which misrepresents technical issues associated with <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> 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 <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> are reviewed and the justification for exclusion of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> from performance assessment is presented. The hypothesis that <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at Yucca Mountain over the 10,000-year regulatory period would be negligible. The conclusion that <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> was incorrectly excluded from performance assessment as asserted in Dublyansky (2007) is contradicted by the available technical and regulatory information.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS23A1166P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS23A1166P"><span id="translatedtitle">Diffused vs. Focused Flow - Metaproteogenomic Insights into Effects of <span class="hlt">Hydrothermal</span> Fluid Flow on Metal-Sulfide Chimney Colonizing Biofilms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pjevac, P.; Markert, S.; Richter, M.; Gruber-Vodicka, H.; Schweder, T.; Amann, R.; Meyerdierks, A.</p> <p>2014-12-01</p> <p>At many <span class="hlt">sites</span> of <span class="hlt">hydrothermal</span> discharge in the deep-sea, the deposition of metal sulfides from <span class="hlt">hydrothermal</span> fluids leads to the formation of geological structures known as <span class="hlt">hydrothermal</span> chimneys. The mixing of reduced <span class="hlt">hydrothermal</span> fluids with oxygenated seawater leads to the formation of steep redox gradients within the chimney walls. These gradients facilitate the co-existence of metabolically diverse microorganisms in the narrow habitable zone of <span class="hlt">hydrothermal</span> chimney walls. However, the overall composition of chimney-associated microbial community is usually of low complexity and represents an environment suitable for metaomic-based studies. We used metagenomic and metaproteomic tools to compare microbial communities colonizing two metal-sulfide chimneys from the Manus Basin back-arc spreading center in the Bismarck Sea off Papua New Guinea. These chimneys were supplied by the same source <span class="hlt">hydrothermal</span> fluids, but exhibited different fluid flow regimes. One chimney (RMR5) had a focused venting edifice, while the other (RMR-D) displayed diffuse fluid efflux on its entire outer surface. Although the microbial diversity of both chimneys is similar and dominated by mesophilic Epsilonproteobacteria, our results indicate a strong structuring effect of <span class="hlt">hydrothermal</span> fluid flow regime on chimney-associated biofilms. The microbial community composition indicates a homogeneous colonization of the diffuse chimney walls. In contrast, the walls of the focused venting chimney appear to be colonized in layers reflecting different temperature tolerances of the dominant microorganisms. Sulfide-oxidation is likely the key metabolism in both chimneys, which is in line with the high sulfide content of the source <span class="hlt">hydrothermal</span> fluid. However, preliminary metaproteome analysis indicates high <span class="hlt">activity</span> of low-abundant methanotrophic Bacteria in the diffuser chimney walls. This finding is particularly interesting in light of the very low methane content of the source <span class="hlt">hydrothermal</span> fluid</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPSC...10..816P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPSC...10..816P"><span id="translatedtitle">The latest on <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> on Enceladus from Cassini and Laboratory work</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Postberg, F.; Hsu, H. W.; Sekine, Y.; Shibuya, T.</p> <p>2015-10-01</p> <p>Various observations from the Cassini spacecraft [1,2,3], suggest the existence of subsurface water beneath the south polar region of Saturn's geologically <span class="hlt">active</span> icy moon Enceladus. They provide information on the composition and physical conditions of water reservoirs occurring at shallow depth from which the plumes emerge [1,2,4], and about the dimensions of the south polar ocean beneath the ice crust at a depth of about 50km [3]. However, constraints on the physical and chemical conditions at the interface of the rocky core and the deep ocean are sparse. We report in situ measurements of tiny grains, so called stream particles, by Cassini's Cosmic Dust Analyser (CDA) in the Saturnian system. CDA data shows that these nano-particles are composed of silica that were initially embedded in larger μm-sized icy grains emitted from Enceladus subsurface waters and released by sputter erosion in Saturn's E ring. Comprehensive long- term laboratory experiments and model calculations were carried out to investigate the reaction conditions at the bottom of Enceladus' ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22012137','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22012137"><span id="translatedtitle">Rapid microwave <span class="hlt">hydrothermal</span> synthesis of ZnGa{sub 2}O{sub 4} with high photocatalytic <span class="hlt">activity</span> toward aromatic compounds in air and dyes in liquid water</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sun Meng; Li Danzhen; Zhang Wenjuan; Chen Zhixin; Huang Hanjie; Li Wenjuan; He Yunhui; Fu Xianzhi</p> <p>2012-06-15</p> <p>ZnGa{sub 2}O{sub 4} was synthesized from Ga(NO{sub 3}){sub 3} and ZnCl{sub 2} via a rapid and facile microwave-assisted <span class="hlt">hydrothermal</span> method. The photocatalytic properties of the as-prepared ZnGa{sub 2}O{sub 4} were evaluated by the degradation of pollutants in air and aqueous solution under ultraviolet (UV) light illumination. The results demonstrated that ZnGa{sub 2}O{sub 4} had exhibited efficient photocatalytic <span class="hlt">activities</span> higher than that of commercial P25 (Degussa Co.) in the degradation of benzene, toluene, and ethylbenzene, respectively. In the liquid phase degradation of dyes (methyl orange, Rhodamine B, and methylene blue), ZnGa{sub 2}O{sub 4} has also exhibited remarkable <span class="hlt">activities</span> higher than that of P25. After 32 min of UV light irradiation, the decomposition ratio of methyl orange (10 ppm, 150 mL) over ZnGa{sub 2}O{sub 4} (0.06 g) was up to 99%. The TOC tests revealed that the mineralization ratio of MO (10 ppm, 150 mL) was 88.1% after 90 min of reaction. A possible mechanism of the photocatalysis over ZnGa{sub 2}O{sub 4} was also proposed. - Graphical abstract: In the degradation of RhB under UV light irradiation, ZnGa{sub 2}O{sub 4} had exhibited efficient photo-<span class="hlt">activity</span>, and after only 24 min of irradiation the decomposition ratio was up to 99.8%. Highlights: Black-Right-Pointing-Pointer A rapid and facile M-H method to synthesize ZnGa{sub 2}O{sub 4} photocatalyst. Black-Right-Pointing-Pointer The photocatalyst exhibits high <span class="hlt">activity</span> toward benzene and dyes. Black-Right-Pointing-Pointer The catalyst possesses more surface hydroxyl <span class="hlt">sites</span> than TiO{sub 2} (P25). Black-Right-Pointing-Pointer Deep oxidation of different aromatic compounds and dyes over catalyst.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JVGR..258...74Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JVGR..258...74Y"><span id="translatedtitle">Shallow submarine <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> with significant contribution of magmatic water producing talc chimneys in the Wakamiko Crater of Kagoshima Bay, southern Kyushu, Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamanaka, Toshiro; Maeto, Kotaro; Akashi, Hironori; Ishibashi, Jun-Ichiro; Miyoshi, Youko; Okamura, Kei; Noguchi, Takuroh; Kuwahara, Yoshihiro; Toki, Tomohiro; Tsunogai, Urumu; Ura, Tamaki; Nakatani, Takeshi; Maki, Toshihiro; Kubokawa, Kaoru; Chiba, Hitoshi</p> <p>2013-05-01</p> <p><span class="hlt">Active</span> <span class="hlt">hydrothermal</span> venting from shallow seafloor (200-m depth) with talc chimneys has been discovered at the Wakamiko Crater floor in the Aira Caldera, southern Kyushu, Japan. The major chemical composition of the fluids suggests that the fluids are supplied from a single reservoir. The fluid is characterized by a low chloride concentration, low δD value, and a high δ18O value, suggesting that the endmember <span class="hlt">hydrothermal</span> fluid is a mixture of seawater and andesitic water and possibly contribution of meteoric water and/or phase separation. Such noticeable magmatic input may be supported by high helium isotopic ratio (6.77 RA) of fumarolic gas discharging from the crater. Silica and alkaline geothermometers indicate that the fluid-rock interaction in the reservoir occurs in the temperature range of 230 to 250 °C. The high alkalinity and high ammonium and dissolved organic matter concentrations in the fluid indicate interaction of the fluid with organic matter in sedimentary layers. At least three <span class="hlt">hydrothermal</span> vents have been observed in the crater. Two of these have similar cone-shaped chimneys. The chimneys have a unique mineralogy and consist dominantly of talc (kerolite and hydrated talc) with lesser amounts of carbonate (dolomite and magnesite), anhydrite, amorphous silica, and stibnite. The precipitation temperature estimated from δ18O values of talc was almost consistent with the observed fluid temperature. Geochemical modeling calculations also support the formation of talc and carbonate upon mixing of the endmember <span class="hlt">hydrothermal</span> fluid with seawater and suggest that the talc chimneys are currently growing from venting fluid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5768035','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5768035"><span id="translatedtitle"><span class="hlt">Active</span> <span class="hlt">site</span> - a <span class="hlt">site</span> of binding of affinity inhibitors in baker's yeast inorganic pyrophosphatase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Svyato, I.E.; Sklyankina, V.A.; Avaeva, S.M.</p> <p>1986-03-20</p> <p>The interaction of the enzyme-substrate complex with methyl phosphate, O-phosphoethanolamine, O-phosphopropanolamine, N-acetylphosphoserine, and phosphoglyolic acid, as well as pyrophosphatase, modified by monoesters of phosphoric acid, with pyrophosphate and tripolyphosphate, was investigated. It was shown that the enzyme containing the substrate in the <span class="hlt">active</span> <span class="hlt">site</span> does not react with monophosphates, but modified pyrophosphatase entirely retains the ability to bind polyanions to the regulatory <span class="hlt">site</span>. It is concluded that the inactivation of baker's yeast inorganic pyrophosphatase by monoesters of phosphoric acid, which are affinity inhibitors of it, is the result of modification of the <span class="hlt">active</span> <span class="hlt">site</span> of the enzyme.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/14997541','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/14997541"><span id="translatedtitle">A novel approach to predict <span class="hlt">active</span> <span class="hlt">sites</span> of enzyme molecules.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chou, Kuo-Chen; Cai, Yu-dong</p> <p>2004-04-01</p> <p>Enzymes are critical in many cellular signaling cascades. With many enzyme structures being solved, there is an increasing need to develop an automated method for identifying their <span class="hlt">active</span> <span class="hlt">sites</span>. However, given the atomic coordinates of an enzyme molecule, how can we predict its <span class="hlt">active</span> <span class="hlt">site</span>? This is a vitally important problem because the core of an enzyme molecule is its <span class="hlt">active</span> <span class="hlt">site</span> from the viewpoints of both pure scientific research and industrial application. In this article, a topological entity was introduced to characterize the enzymatic <span class="hlt">active</span> <span class="hlt">site</span>. Based on such a concept, the covariant discriminant algorithm was formulated for identifying the <span class="hlt">active</span> <span class="hlt">site</span>. As a paradigm, the serine hydrolase family was demonstrated. The overall success rate by jackknife test for a data set of 88 enzyme molecules was 99.92%, and that for a data set of 50 independent enzyme molecules was 99.91%. Meanwhile, it was shown through an example that the prediction algorithm can also be used to find any typographic error of a PDB file in annotating the constituent amino acids of catalytic triad and to suggest a possible correction. The very high success rates are due to the introduction of a covariance matrix in the prediction algorithm that makes allowance for taking into account the coupling effects among the key constituent atoms of <span class="hlt">active</span> <span class="hlt">site</span>. It is anticipated that the novel approach is quite promising and may become a useful high throughput tool in enzymology, proteomics, and structural bioinformatics. PMID:14997541</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006PhyA..371...92S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PhyA..371...92S"><span id="translatedtitle">Growth exponents in surface models with non-<span class="hlt">active</span> <span class="hlt">sites</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santos, M.; Figueiredo, W.; Aarão Reis, F. D. A.</p> <p>2006-11-01</p> <p>In this work, we studied the role played by the inactive <span class="hlt">sites</span> present on the substrate of a growing surface. In our model, one particle sticks at the surface if the <span class="hlt">site</span> where it falls is an <span class="hlt">active</span> <span class="hlt">site</span>. However, we allow the deposited particle to diffuse along the surface in accordance with some mechanism previously defined. Using Monte Carlo simulations, and some analytical results, we have investigated the model in (1+1) and (2+1) dimensions considering different relaxation mechanisms. We show that the consideration of non-<span class="hlt">active</span> <span class="hlt">sites</span> is a crucial point in the model. In fact, we have seen that the saturation regime is not observed for any value of the density of inactive <span class="hlt">sites</span>. Besides, the growth exponent β turns to be one, at long times, whatever the mechanism of diffusion we consider in one and two dimensions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V24A..01L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V24A..01L"><span id="translatedtitle">SeaVOICE: Sea-going Experiments to Test Potential Linkages among Sea Level Change, Ocean Ridge Volcanism, and <span class="hlt">Hydrothermal</span> <span class="hlt">Activity</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Langmuir, C. H.; Carbotte, S. M.; Huybers, P. J.; McManus, J. F.; Mukhopadhyay, S.; Winckler, G.; Boulahanis, B.; Costa, K.; Ferguson, D.; Katz, R. F.; Li, Y.; Middleton, J. L.</p> <p>2015-12-01</p> <p>Changes in sea level influence the pressure of the solid Earth over entire ocean basins. While the absolute changes in sea level caused by glacial cycles are small relative to ocean depths, the temporal variations in sea level can lead to pressure changes of similar order to mantle upwelling rates, with the potential to significantly perturb short term rates of melt production at ocean ridges (Huybers and Langmuir, EPSL, 2009). Such changes could then lead to fluctuations in crustal thickness, magma composition and <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>. To investigate possible relationships between glacial cycles and ocean ridge processes, we carried out an 18 day cruise of mapping and sediment coring to the Cleft Segment of the Juan de Fuca ridge. High resolution bathymetry was obtained on the west side of the ridge axis to beyond 1Ma to test whether abyssal hill fabric shows periodicities consistent with glacial cycles. Nine successful piston cores up to 7.6m in length provide a sedimentary record back to more than 600kyr to test for spatial and temporal variations in <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>. Oxygen isotope stratigraphy on these cores is systematic and provides good age constraints. Short cores near the ridge axis provide a record of the current trace of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> in youngest sediments. Several of the cores impacted basement and recovered a basement sample. Above basement, basaltic glass shards were recovered in the bottom meter of sediment, raising the possibility of temporal records of basalt chemical compositions using the age constraints the sediments provide. The glass samples provide a unique and new perspective on ridge volcanism, since previous off-axis samples were restricted to dredging old fault scarps. Cores can be taken anywhere, raising the potential for global time series studies of ridge volcanism. The coupled bathymetry, sediment geochemistry and magmatic glass compositions hold the promise of a definitive advance in our understanding of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3424543','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3424543"><span id="translatedtitle">A small ribozyme with dual-<span class="hlt">site</span> kinase <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Biondi, Elisa; Maxwell, Adam W.R.; Burke, Donald H.</p> <p>2012-01-01</p> <p>Phosphoryl transfer onto backbone hydroxyls is a recognized catalytic <span class="hlt">activity</span> of nucleic acids. We find that kinase ribozyme K28 possesses an unusually complex <span class="hlt">active</span> <span class="hlt">site</span> that promotes (thio)phosphorylation of two residues widely separated in primary sequence. After allowing the ribozyme to radiolabel itself by phosphoryl transfer from [γ-32P]GTP, DNAzyme-mediated cleavage yielded two radiolabeled cleavage fragments, indicating phosphorylation <span class="hlt">sites</span> within each of the two cleavage fragments. These <span class="hlt">sites</span> were mapped by alkaline digestion and primer extension pausing. Enzymatic digestion and mutational analysis identified nucleotides important for <span class="hlt">activity</span> and established the <span class="hlt">active</span> structure as being a constrained pseudoknot with unusual connectivity that may juxtapose the two reactive <span class="hlt">sites</span>. Nuclease sensitivities for nucleotides near the pseudoknot core were altered in the presence of GTPγS, indicating donor-induced folding. The 5′ target <span class="hlt">site</span> was more strongly favored in full-length ribozyme K28 (128 nt) than in truncated RNAs (58 nt). Electrophoretic mobilities of self-thiophosphorylated products on organomercurial gels are distinct from the 5′ mono-thiophosphorylated product produced by reaction with polynucleotide kinase, potentially indicating simultaneous labeling of both <span class="hlt">sites</span> within individual RNA strands. Our evidence supports a single, compact structure with local dynamics, rather than global rearrangement, as being responsible for dual-<span class="hlt">site</span> phosphorylation. PMID:22618879</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001M%26PS...36..731O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001M%26PS...36..731O"><span id="translatedtitle">Impact-induced <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> within the Haughton impact structure, arctic Canada: generation of a transient, warm, wet oasis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Osinski, Gordon R.; Spray, John G.</p> <p>2001-05-01</p> <p>Field studies and analytical scanning electron microscopy indicate that a <span class="hlt">hydrothermal</span> system was created by the interaction of water with hot, impact-generated rocks following formation of the 24 km-diameter, 23 Ma Haughton impact structure. <span class="hlt">Hydrothermal</span> alteration is recognized in two settings: within polymict impact breccias overlying the central portion of the structure, and within localized pipes in impact-generated concentric fault systems. The intra-breccia alteration comprises three varieties of cavity and fracture filling: (a) sulfide with carbonate, (b) sulfate, and (c) carbonate. These are accompanied by subordinate celestite, barite, fluorite, quartz and marcasite. Selenite is also developed, particularly in the lower levels of the impact breccia sheet. The fault-related <span class="hlt">hydrothermal</span> alteration occurs in 1-7 m diameter subvertical pipes that are exposed for lengths of up 20 m. The pipes are defined by a monomict quartz-carbonate breccia showing pronounced Fe-hydroxide alteration. Associated sulfides include marcasite, pyrite and chalcopyrite. We propose three distinct stages in the evolution of the <span class="hlt">hydrothermal</span> system: (1) Early Stage (>200 degC), with the precipitation of quartz (vapour phase dominated); (2) Main Stage (200-100 deg C), with the development of a two phase (vapour plus liquid) zone, leading to calcite, celestite, barite, marcasite and fluorite precipitation, and (3) Late Stage (<100 degC), with selenite and fibroferrite development through liquid phase-dominanted precipitation. We estimate that it took several tens of thousands of years to cool below 50 deg C following impact. During this time, Haughton supported a 14 km diameter crater lake and subsurface water system, providing a warmer, wetter niche relative to the surrounding terrain. The results also reveal how understanding the internal structure of impact craters is necessary in order to determine their plumbing and cooling systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/60547','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/60547"><span id="translatedtitle">Behavior of nuclear waste elements during <span class="hlt">hydrothermal</span> alteration of glassy rhyolite in an <span class="hlt">active</span> geothermal system: Yellowstone National Park, Wyoming</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sturchio, N.C.; Seitz, M.G.</p> <p>1984-12-31</p> <p>The behavior of a group of nuclear waste elements (U, Th, Sr, Zr, Sb, Cs, Ba, and Sm) during <span class="hlt">hydrothermal</span> alteration of glassy rhyolite is investigated through detailed geochemical analyses of whole rocks, glass and mineral separates, and thermal waters. Significant mobility of U, Sr, Sb, Cs, and Ba is found, and the role of sorption processes in their observed behavior is identified. Th, Zr, and Sm are relatively immobile, except on a microscopic scale. 9 references, 2 figures, 2 tables.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015QSRv..112..230G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015QSRv..112..230G"><span id="translatedtitle">A reassessment of the evidence for <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> in the Neogene-Quaternary lacustrine environments of the Baza basin (Betic Cordillera, SE Spain) and its paleoecological implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>García-Aguilar, José Manuel; Guerra-Merchán, Antonio; Serrano, Francisco; Flores-Moya, Antonio; Delgado-Huertas, Antonio; Espigares, M. Patrocinio; Ros-Montoya, Sergio; Martínez-Navarro, Bienvenido; Palmqvist, Paul</p> <p>2015-03-01</p> <p>In a recent paper, García-Aguilar et al. (2014) reported on lithological, mineralogical and geochemical evidence of intense, tectonically-induced <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> during the continental sedimentary infilling of the Baza basin, a postorogenic, intramontane area developed on the boundary between the Internal and External Zones of the Betic Cordillera, Southeast Spain (Fig. 1). This evidence includes the finding of sulfur contents, magnesium clays, fluorspar and celestine deposits, thermogene stromatolites and travertine growths in the latest Miocene (Turolian) to Middle Pleistocene lacustrine sediments and is particularly concentrated at certain stages and places (e.g. at Calabrian times in the Orce area).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011A%26G....52d...7.','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011A%26G....52d...7."><span id="translatedtitle">News and Views: Betelgeuse bubbles up dust; <span class="hlt">Hydrothermal</span> <span class="hlt">activity</span> on early asteroids; Is this a record? Galaxy evolution in 3D; LOFAR looks farther; IOPD makes plans</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p></p> <p>2011-08-01</p> <p>Red supergiant star Betelgeuse is surrounded by a vast halo of silicate and aluminium dust, visible in false colour in this infrared image from the European Southern Observatory's Very Large Telescope. This material may eventually form planets around a new star. Biochemical analysis of the Tagish Lake meteorites, some of the most pristine samples of carbonaceous chondrites known, suggests that much of the variation in organic matter between different meteorite samples can be ascribed to <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> on meteorite parent bodies. European Southern Observatory astronomers have discovered the most distant quasar yet - and reckon it is one of the brightest objects in the early universe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.B32B..02P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.B32B..02P"><span id="translatedtitle">Bioavailability, Bioaccumulation and Biotransformation of arsenic in coral reef organisms surrounding an arsenic-rich marine shallow-water <span class="hlt">hydrothermal</span> vent system in the coastal waters of Ambitle Island, Papua New Guinea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pichler, T.; Wallschläger, D.; Price, R. E.</p> <p>2009-12-01</p> <p>Marine shallow-water <span class="hlt">hydrothermal</span> systems are often enriched in biologically toxic elements, thus making them ideal natural analogs for coastal anthropogenic pollution. Here, we report our investigation of the bioavailability, bioaccumulation, and biotransformation of <span class="hlt">hydrothermally</span>-derived arsenic into several coral reef organisms from the arsenic-rich marine shallow-water <span class="hlt">hydrothermal</span> system of Tutum Bay, Ambitle Island, in northeastern Papua New Guinea. <span class="hlt">Hydrothermal</span> venting provided bioavailable As by two major pathways throughout Tutum Bay: 1) easily-exchangeable As from <span class="hlt">hydrothermally</span> influenced sediments to as far away as 200 m from focused venting, and 2) in surface seawaters, which may allow for biological uptake by phytoplankton and transfer up the food web. The soft coral Clavularia sp., the calcareous algae Halimeda sp., and the tunicate Polycarpa sp. collected from the <span class="hlt">hydrothermal</span> area each displayed distinctly higher (up to 20 times) total arsenic compared to the control <span class="hlt">site</span>, with increasing trends while approaching focused <span class="hlt">hydrothermal</span> venting. Organic and inorganic arsenic species were extracted intact from the tissues of each organism, separated by anion exchange chromatography, and analyzed by inductively-coupled plasma-dynamic reaction cell-mass spectrometry. Overall, speciation patterns for Clavularia were similar for the control <span class="hlt">site</span> versus the <span class="hlt">hydrothermal</span> <span class="hlt">site</span>, although the concentrations were much higher. Elevated concentrations of DMA and cationic forms of arsenic, most likely AB, in Clavularia, both from the control <span class="hlt">site</span> and from the <span class="hlt">hydrothermal</span> area suggest its metabolic pathway is not altered due to <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>, and is similar to other marine organisms. Arsenic speciation patterns in Polycarpa were also similar for both <span class="hlt">sites</span>, and suggests uptake of arsenic via food chain, containing neither As(III) nor As(V), but abundant excluded As and DMA. It is unclear if methylation is taking place within this organism or prior to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3474877','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3474877"><span id="translatedtitle">Architecture and <span class="hlt">active</span> <span class="hlt">site</span> of particulate methane monooxygenase</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Culpepper, Megen A.; Rosenzweig, Amy C.</p> <p>2012-01-01</p> <p>Particulate methane monooxygenase (pMMO) is an integral membrane metalloenzyme that oxidizes methane to methanol in methanotrophic bacteria, organisms that live on methane gas as their sole carbon source. Understanding pMMO function has important implications for bioremediation applications and for the development of new, environmentally friendly catalysts for the direct conversion of methane to methanol. Crystal structures of pMMOs from three different methanotrophs reveal a trimeric architecture, consisting of three copies each of the pmoB, pmoA, and pmoC subunits. There are three distinct metal centers in each protomer of the trimer, mononuclear and dinuclear copper <span class="hlt">sites</span> in the periplasmic regions of pmoB and a mononuclear <span class="hlt">site</span> within the membrane that can be occupied by copper or zinc. Various models for the pMMO <span class="hlt">active</span> <span class="hlt">site</span> have been proposed within these structural constraints, including dicopper, tricopper, and diiron centers. Biochemical and spectroscopic data on pMMO and recombinant soluble fragments, denoted spmoB proteins, indicate that the <span class="hlt">active</span> <span class="hlt">site</span> involves copper and is located at the <span class="hlt">site</span> of the dicopper center in the pmoB subunit. Initial spectroscopic evidence for O2 binding at this <span class="hlt">site</span> has been obtained. Despite these findings, questions remain about the <span class="hlt">active</span> <span class="hlt">site</span> identity and nuclearity and will be the focus of future studies. PMID:22725967</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JVGR..325...70R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JVGR..325...70R"><span id="translatedtitle">Chlorine isotope and Cl-Br fractionation in fluids of Poás volcano (Costa Rica): Insight into an <span class="hlt">active</span> volcanic-<span class="hlt">hydrothermal</span> system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rodríguez, Alejandro; Eggenkamp, H. G. M.; Martínez-Cruz, María; van Bergen, Manfred J.</p> <p>2016-10-01</p> <p>Halogen-rich volcanic fluids issued at the surface carry information on properties and processes operating in shallow <span class="hlt">hydrothermal</span> systems. This paper reports a long-term record of Cl-Br concentrations and δ37Cl signatures of lake water and fumaroles from the <span class="hlt">active</span> crater of Poás volcano (Costa Rica), where surface expressions of magmatic-<span class="hlt">hydrothermal</span> <span class="hlt">activity</span> have shown substantial periodic changes over the last decades. Both the hyperacid water of its crater lake (Laguna Caliente) and subaerial fumaroles show significant temporal variability in Cl-Br concentrations, Br/Cl ratios and δ37Cl, reflecting variations in the mode and magnitude of volatile transfer. The δ37Cl signatures of the lake, covering the period 1985-2012, show fluctuations between + 0.02 ± 0.06‰ and + 1.15 ± 0.09‰. Condensate samples from adjacent fumaroles on the southern shore, collected during the interval (2010-2012) with strong changes in gas temperature (107-763°C), display a much larger range from - 0.43 ± 0.09‰ to + 14.09 ± 0.08‰. Most of the variations in Cl isotope, Br/Cl and concentration signals can be attributed to interaction between magma-derived gas and liquid water in the volcanic-<span class="hlt">hydrothermal</span> system below the crater. The δ37Cl were lowest and closest to magmatic values in (1) fumarolic gas that experienced little or no interaction with subsurface water and followed a relatively dry pathway, and (2) water that captured the bulk of magmatic halogen output so that no phase separation could induce fractionation. In contrast, elevated δ37Cl can be explained by partial scavenging and fractionation during subsurface gas-liquid interaction. Hence, strong Cl isotope fractionation leading to very high δ37Cl in Poás' fumaroles indicates that they followed a wet pathway. Highest δ37Cl values in the lake water were found mostly in periods when it received a significant input from subaqueous fumaroles or when high temperatures and low pH caused HCl evaporation. It is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4326222','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4326222"><span id="translatedtitle">Morphology of <span class="hlt">hydrothermally</span> synthesized ZnO nanoparticles tethered to carbon nanotubes affects electrocatalytic <span class="hlt">activity</span> for H2O2 detection</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wayu, Mulugeta B.; Spidle, Ryan T.; Devkota, Tuphan; Deb, Anup K.; Delong, Robert K.; Ghosh, Kartik C.; Wanekaya, Adam K.; Chusuei, Charles C.</p> <p>2013-01-01</p> <p>We describe the synthesis of zinc oxide (ZnO) nanoparticles and demonstrate their attachment to multiwalled carbon tubes, resulting in a composite with a unique synergistic effect. Morphology and size of ZnO nanostructures were controlled using <span class="hlt">hydrothermal</span> synthesis, varying the <span class="hlt">hydrothermal</span> treatment temperature, prior to attachment to carboxylic acid functionalized multi-walled carbon nanotubes for sensing applications. A strong dependence of electrocatalytic <span class="hlt">activity</span> on nanosized ZnO shape was shown. High <span class="hlt">activity</span> for H2O2 reduction was achieved when nanocomposite precursors with a roughly semi-spherical morphology (no needle-like particles present) formed at 90 °C. A 2.4-fold increase in cyclic voltammetry current accompanied by decrease in overpotential from the composites made from the nanosized, needle-like-free ZnO shapes was observed as compared to those composites produced from needle-like shaped ZnO. Electrocatalytic <span class="hlt">activity</span> varied with pH, maximizing at pH 7.4. A stable, linear response for H2O2 concentrations was observed in the 1–20 mM concentration range. PMID:25684785</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApSS..319..256D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApSS..319..256D"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> fabrication of N-doped (BiO)2CO3: Structural and morphological influence on the visible light photocatalytic <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dong, Fan; Wang, Rui; Li, Xinwei; Ho, Wing-Kei</p> <p>2014-11-01</p> <p>Various 3D N-doped (BiO)2CO3 (N-BOC) hierarchical superstructures self-assembled with 2D nanosheets were fabricated by one-step <span class="hlt">hydrothermal</span> treatment of bismuth citrate and urea. The as-obtained samples were characterized by XRD, XPS, FT-IR, SEM, N2 adsorption-desorption isotherms and UV-vis DRS. The <span class="hlt">hydrothermal</span> 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)2CO3 samples with corresponding attractive persimmon-like, flower-like and nanoflakes nano/microstructures. The photocatalytic <span class="hlt">activities</span> of the samples were evaluated by removal of NO under visible and solar light irradiation. The results revealed that the N-doped (BiO)2CO3 hierarchical superstructures showed enhanced visible light photocatalytic <span class="hlt">activity</span> compared to pure (BiO)2CO3 and TiO2-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 <span class="hlt">activity</span> of photocatalyst for better environmental pollution control.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26908655','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26908655"><span id="translatedtitle">Methanopyrus kandleri topoisomerase V contains three distinct AP lyase <span class="hlt">active</span> <span class="hlt">sites</span> in addition to the topoisomerase <span class="hlt">active</span> <span class="hlt">site</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rajan, Rakhi; Osterman, Amy; Mondragón, Alfonso</p> <p>2016-04-20</p> <p>Topoisomerase V (Topo-V) is the only topoisomerase with both topoisomerase and DNA repair <span class="hlt">activities</span>. The topoisomerase <span class="hlt">activity</span> is conferred by a small alpha-helical domain, whereas the AP lyase <span class="hlt">activity</span> is found in a region formed by 12 tandem helix-hairpin-helix ((HhH)2) domains. Although it was known that Topo-V has multiple repair <span class="hlt">sites</span>, only one had been mapped. Here, we show that Topo-V has three AP lyase <span class="hlt">sites</span>. The atomic structure and Small Angle X-ray Scattering studies of a 97 kDa fragment spanning the topoisomerase and 10 (HhH)2 domains reveal that the (HhH)2 domains extend away from the topoisomerase domain. A combination of biochemical and structural observations allow the mapping of the second repair <span class="hlt">site</span> to the junction of the 9th and 10th (HhH)2 domains. The second <span class="hlt">site</span> is structurally similar to the first one and to the <span class="hlt">sites</span> found in other AP lyases. The 3rd AP lyase <span class="hlt">site</span> is located in the 12th (HhH)2 domain. The results show that Topo-V is an unusual protein: it is the only known protein with more than one (HhH)2 domain, the only known topoisomerase with dual <span class="hlt">activities</span> and is also unique by having three AP lyase repair <span class="hlt">sites</span> in the same polypeptide. PMID:26908655</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4838376','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4838376"><span id="translatedtitle">Methanopyrus kandleri topoisomerase V contains three distinct AP lyase <span class="hlt">active</span> <span class="hlt">sites</span> in addition to the topoisomerase <span class="hlt">active</span> <span class="hlt">site</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rajan, Rakhi; Osterman, Amy; Mondragón, Alfonso</p> <p>2016-01-01</p> <p>Topoisomerase V (Topo-V) is the only topoisomerase with both topoisomerase and DNA repair <span class="hlt">activities</span>. The topoisomerase <span class="hlt">activity</span> is conferred by a small alpha-helical domain, whereas the AP lyase <span class="hlt">activity</span> is found in a region formed by 12 tandem helix-hairpin-helix ((HhH)2) domains. Although it was known that Topo-V has multiple repair <span class="hlt">sites</span>, only one had been mapped. Here, we show that Topo-V has three AP lyase <span class="hlt">sites</span>. The atomic structure and Small Angle X-ray Scattering studies of a 97 kDa fragment spanning the topoisomerase and 10 (HhH)2 domains reveal that the (HhH)2 domains extend away from the topoisomerase domain. A combination of biochemical and structural observations allow the mapping of the second repair <span class="hlt">site</span> to the junction of the 9th and 10th (HhH)2 domains. The second <span class="hlt">site</span> is structurally similar to the first one and to the <span class="hlt">sites</span> found in other AP lyases. The 3rd AP lyase <span class="hlt">site</span> is located in the 12th (HhH)2 domain. The results show that Topo-V is an unusual protein: it is the only known protein with more than one (HhH)2 domain, the only known topoisomerase with dual <span class="hlt">activities</span> and is also unique by having three AP lyase repair <span class="hlt">sites</span> in the same polypeptide. PMID:26908655</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1229945','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1229945"><span id="translatedtitle">Effects of Alkali and Alkaline Earth Cocations on the <span class="hlt">Activity</span> and <span class="hlt">Hydrothermal</span> Stability of Cu/SSZ-13 NH3-SCR Catalysts</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gao, Feng; Wang, Yilin; Washton, Nancy M.; Kollar, Marton; Szanyi, Janos; Peden, Charles HF</p> <p>2015-10-13</p> <p>Using a three-step aqueous solution ion-exchange method, cocation modified Cu/SSZ-13 SCR catalysts were synthesized. These catalysts, in both fresh and <span class="hlt">hydrothermally</span> aged forms, were characterized with several methods including temperature-programmed reduction by H2 (H2-TPR), temperature-programmed desorption of NH3 (NH3-TPD), and 27Al solid-state nuclear magnetic resonance (NMR) and diffuse reflectance Infrared Fourier Transform (DRIFT) spectroscopies. Their catalytic performance was probed using steady-state standard NH3-SCR. Characterization results indicate that cocations weaken interactions between Cu-ions and the CHA framework making them more readily reducible. By removing a portion of Brønsted acid <span class="hlt">sites</span>, cocations also help to mitigate hydrolysis of the zeolite catalysts during <span class="hlt">hydrothermal</span> aging as evidenced from 27Al NMR. Reaction tests show that certain cocations, especially Li+ and Na+, promote low-temperature SCR rates while others show much less pronounced effects. In terms of applications, our results indicate that introducing cocations can be a viable strategy to improve both low- and high-temperature performance of Cu/SSZ-13 SCR catalysts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.P31G..02R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.P31G..02R"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> Occurrences in Gusev Crater</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruff, S. W.; Farmer, J. D.; Milliken, R.; Mills, V. W.; Shock, E.</p> <p>2011-12-01</p> <p>Exploration of the Gusev crater landing <span class="hlt">site</span> by the Spirit rover has revealed for the first time, in situ evidence of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> on Mars. Most compelling are eroded outcrops of opaline silica found adjacent to "Home Plate" [1], an eroded stack of volcaniclastic deposits stratigraphically overlain by a vesicular basalt unit [2]. Recent work [3] demonstrates that the silica outcrops occur in a stratiform unit that possibly surrounds Home Plate. The outcrops are dominated by opal-A with no evidence for diagenesis to other silica phases. No other hydrous or alteration phases have been identified within the outcrops; most notable is a lack of sulfur phases. The outcrops have porous and in some cases, brecciated microtextures. Taken together, these observations support the interpretation that the opaline silica outcrops were produced in a hot spring or perhaps geyser environment. In this context, they are silica sinter deposits precipitated from silica-rich <span class="hlt">hydrothermal</span> fluids, possibly related to the volcanism that produced the Home Plate volcanic rocks. On Earth, debris aprons in which sinter is brecciated, reworked, and cemented, are common features of hot springs and geysers and are good analogs for the Martian deposits. An alternative hypothesis is that the silica resulted from acid-sulfate leaching of precursor rocks by fumarolic steam condensates. But stratigraphic, textural, and chemical observations tend to diminish this possibility [3]. We are conducting extensive laboratory and field investigations of silica from both hot spring/geyser and fumarole environments to understand the full range of mineralogical, chemical, textural, and morphological variations that accompany its production, in order to shed more light on the Home Plate occurrence. The recent discovery of abundant Mg-Fe carbonate (16-34 wt%) in outcrops named Comanche provides possible evidence for additional <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> in Gusev [4]. However, the carbonate is hosted by olivine</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20228114','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20228114"><span id="translatedtitle">Biogeography and biodiversity in sulfide structures of <span class="hlt">active</span> and inactive vents at deep-sea <span class="hlt">hydrothermal</span> fields of the Southern Mariana Trough.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kato, Shingo; Takano, Yoshinori; Kakegawa, Takeshi; Oba, Hironori; Inoue, Kazuhiko; Kobayashi, Chiyori; Utsumi, Motoo; Marumo, Katsumi; Kobayashi, Kensei; Ito, Yuki; Ishibashi, Jun-ichiro; Yamagishi, Akihiko</p> <p>2010-05-01</p> <p>The abundance, diversity, <span class="hlt">activity</span>, and composition of microbial communities in sulfide structures both of <span class="hlt">active</span> and inactive vents were investigated by culture-independent methods. These sulfide structures were collected at four <span class="hlt">hydrothermal</span> fields, both on- and off-axis of the back-arc spreading center of the Southern Mariana Trough. The microbial abundance and <span class="hlt">activity</span> in the samples were determined by analyzing total organic content, enzymatic <span class="hlt">activity</span>, and copy number of the 16S rRNA gene. To assess the diversity and composition of the microbial communities, 16S rRNA gene clone libraries including bacterial and archaeal phylotypes were constructed from the sulfide structures. Despite the differences in the geological settings among the sampling points, phylotypes related to the Epsilonproteobacteria and cultured hyperthermophilic archaea were abundant in the libraries from the samples of <span class="hlt">active</span> vents. In contrast, the relative abundance of these phylotypes was extremely low in the libraries from the samples of inactive vents. These results suggest that the composition of microbial communities within sulfide structures dramatically changes depending on the degree of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>, which was supported by statistical analyses. Comparative analyses suggest that the abundance, <span class="hlt">activity</span> and diversity of microbial communities within sulfide structures of inactive vents are likely to be comparable to or higher than those in <span class="hlt">active</span> vent structures, even though the microbial community composition is different between these two types of vents. The microbial community compositions in the sulfide structures of inactive vents were similar to those in seafloor basaltic rocks rather than those in marine sediments or the sulfide structures of <span class="hlt">active</span> vents, suggesting that the microbial community compositions on the seafloor may be constrained by the available energy sources. Our findings provide helpful information for understanding the biogeography, biodiversity and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20228114','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20228114"><span id="translatedtitle">Biogeography and biodiversity in sulfide structures of <span class="hlt">active</span> and inactive vents at deep-sea <span class="hlt">hydrothermal</span> fields of the Southern Mariana Trough.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kato, Shingo; Takano, Yoshinori; Kakegawa, Takeshi; Oba, Hironori; Inoue, Kazuhiko; Kobayashi, Chiyori; Utsumi, Motoo; Marumo, Katsumi; Kobayashi, Kensei; Ito, Yuki; Ishibashi, Jun-ichiro; Yamagishi, Akihiko</p> <p>2010-05-01</p> <p>The abundance, diversity, <span class="hlt">activity</span>, and composition of microbial communities in sulfide structures both of <span class="hlt">active</span> and inactive vents were investigated by culture-independent methods. These sulfide structures were collected at four <span class="hlt">hydrothermal</span> fields, both on- and off-axis of the back-arc spreading center of the Southern Mariana Trough. The microbial abundance and <span class="hlt">activity</span> in the samples were determined by analyzing total organic content, enzymatic <span class="hlt">activity</span>, and copy number of the 16S rRNA gene. To assess the diversity and composition of the microbial communities, 16S rRNA gene clone libraries including bacterial and archaeal phylotypes were constructed from the sulfide structures. Despite the differences in the geological settings among the sampling points, phylotypes related to the Epsilonproteobacteria and cultured hyperthermophilic archaea were abundant in the libraries from the samples of <span class="hlt">active</span> vents. In contrast, the relative abundance of these phylotypes was extremely low in the libraries from the samples of inactive vents. These results suggest that the composition of microbial communities within sulfide structures dramatically changes depending on the degree of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>, which was supported by statistical analyses. Comparative analyses suggest that the abundance, <span class="hlt">activity</span> and diversity of microbial communities within sulfide structures of inactive vents are likely to be comparable to or higher than those in <span class="hlt">active</span> vent structures, even though the microbial community composition is different between these two types of vents. The microbial community compositions in the sulfide structures of inactive vents were similar to those in seafloor basaltic rocks rather than those in marine sediments or the sulfide structures of <span class="hlt">active</span> vents, suggesting that the microbial community compositions on the seafloor may be constrained by the available energy sources. Our findings provide helpful information for understanding the biogeography, biodiversity and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V21A4722T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V21A4722T"><span id="translatedtitle">Geochemical Evidence for Recent <span class="hlt">Hydrothermal</span> Alteration of Marine Sediments in Mid-Okinawa Trough, Southwest Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tanaka, A.; Abe, G.; Yamaguchi, K. E.</p> <p>2014-12-01</p> <p>Recent studies have shown that submarine <span class="hlt">hydrothermal</span> system supports diverse microbial life. Bio-essential metals supporting such microbial communities were released from basalts by high-temperature water-rock interaction in deeper part of the oceanic crust and carried by submarine fluid flow. Its total quantity in global <span class="hlt">hydrothermal</span> settings has been estimated to be on the order of ~1019 g/yr, which is surprisingly on the same order of the total river flows (Urabe et al., 2011). Therefore, it is important to explore how submarine river system works, i.e., to understand mechanism and extent of elemental transport, which should lead to understanding of the roles of <span class="hlt">hydrothermal</span> circulation in oceanic crust in controlling elemental budget in the global ocean and geochemical conditions to support deep hot biosphere.  We performed REE analysis of marine sediments influenced by submarine <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> in Mid-Okinawa Trough. The sediment samples used in this study are from IODP <span class="hlt">site</span> at Iheya North region and JADE <span class="hlt">site</span> at Izena region. The samples show alternation between volcanic and clastic sediments. <span class="hlt">Hydrothermal</span> fluids of this area contain elevated concentrations of volatile components such as H2, CO2, CH4, NH4+, and H2S, supporting diverse chemoautotrophic microbial community (Nakagawa et al., 2005). The purpose of this study is to examine the effect of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> on the REE signature of the sediments. Chondrite-normalized REE patterns of the samples show relative enrichment of light over heavy REEs, weak positive Ce anomalies, and variable degrees of negative Eu anomalies. The REE patterns suggest the sediments source was mainly basalt, suggesting insignificant input of continental materials. Negative Eu anomalies found in the IODP <span class="hlt">site</span> become more pronounced with increasing depth, suggesting progressive increase of <span class="hlt">hydrothermal</span> alteration where Eu was reductively dissolved into fluids by decomposition of feldspars. Contrary, at the JADE <span class="hlt">site</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.419..143G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.419..143G"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> Fe cycling and deep ocean organic carbon scavenging: Model-based evidence for significant POC supply to seafloor sediments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>German, C. R.; Legendre, L. L.; Sander, S. G.; Niquil, N.; Luther, G. W.; Bharati, L.; Han, X.; Le Bris, N.</p> <p>2015-06-01</p> <p>Submarine <span class="hlt">hydrothermal</span> venting has recently been identified to have the potential to impact ocean biogeochemistry at the global scale. This is the case because processes <span class="hlt">active</span> in <span class="hlt">hydrothermal</span> plumes are so vigorous that the residence time of the ocean, with respect to cycling through <span class="hlt">hydrothermal</span> plumes, is comparable to that of deep ocean mixing caused by thermohaline circulation. Recently, it has been argued that seafloor venting may provide a significant source of bio-essential Fe to the oceans as the result of a close coupling between Fe and organic carbon in <span class="hlt">hydrothermal</span> plumes. But a complementary question remains to be addressed: does this same intimate Fe-Corg association in <span class="hlt">hydrothermal</span> plumes cause any related impact to the global C cycle? To address this, SCOR-InterRidge Working Group 135 developed a modeling approach to synthesize <span class="hlt">site</span>-specific field data from the East Pacific Rise 9°50‧ N <span class="hlt">hydrothermal</span> field, where the range of requisite data sets is most complete, and combine those inputs with global estimates for dissolved Fe inputs from venting to the oceans to establish a coherent model with which to investigate <span class="hlt">hydrothermal</span> Corg cycling. The results place new constraints on submarine Fe vent fluxes worldwide, including an indication that the majority of Fe supplied to <span class="hlt">hydrothermal</span> plumes should come from entrainment of diffuse flow. While this same entrainment is not predicted to enhance the supply of dissolved organic carbon to <span class="hlt">hydrothermal</span> plumes by more than ∼10% over background values, what the model does indicate is that scavenging of carbon in association with Fe-rich <span class="hlt">hydrothermal</span> plume particles should play a significant role in the delivery of particulate organic carbon to deep ocean sediments, worldwide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006GeoRL..3316607K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006GeoRL..3316607K"><span id="translatedtitle">Liquid CO2 venting on the seafloor: Yonaguni Knoll IV <span class="hlt">hydrothermal</span> system, Okinawa Trough</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Konno, Uta; Tsunogai, Urumu; Nakagawa, Fumiko; Nakaseama, Miwako; Ishibashi, Jun-ichiro; Nunoura, Takuro; Nakamura, Ko-ichi</p> <p>2006-08-01</p> <p>We determined the chemical and isotopic compositions of the liquid CO2 found on Yonaguni IV knoll <span class="hlt">hydrothermal</span> <span class="hlt">site</span>, as well as those in <span class="hlt">hydrothermal</span> fluid venting from the surrounding chimneys. The δ13C of both CO2 and CH4 in the liquid CO2 almost coincide with those in the <span class="hlt">hydrothermal</span> fluid, suggesting that the liquid CO2 must be derived from the <span class="hlt">hydrothermal</span> fluid. While showing homogeneous δ13C, the <span class="hlt">hydrothermal</span> fluids exhibit wide variation in gas contents. <span class="hlt">Active</span> phase separation must be taking place within the conduits. Besides, H2-depletion in the liquid CO2 suggests formation of solid CO2-hydrate must also precede the venting of liquid CO2. In conclusion, liquid CO2 must be produced through following subseafloor processes: phase separation of <span class="hlt">hydrothermal</span> fluid due to boiling, formation of solid CO2-hydrate due to cooling of vapor phase, and melting of the solid CO2-hydrate to liquid CO2 due to a temperature increase within the sedimentary layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5163744','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5163744"><span id="translatedtitle">REE/Fe variations in <span class="hlt">hydrothermal</span> sediments: Implications for the REE content of seawater</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Olivarez, A.M.; Owen, R.M. )</p> <p>1989-03-01</p> <p>Seafloor <span class="hlt">hydrothermal</span> vent solutions exhibit rare earth element (REE) enrichments ranging between one to three orders of magnitude greater than average seawater. To assess the impact of these <span class="hlt">hydrothermal</span> inputs on ocean chemistry, the authors have examined he behavior of REEs for <span class="hlt">hydrothermal</span> sediments collected adjacent to two Pacific spreading ridge <span class="hlt">sites</span>: the East Pacific Rise at 19{degree}S, and the Southern Juan de Fuca Ridge at 45{degree}N. In general, the REE/Fe ratios for both proximal and distal <span class="hlt">hydrothermal</span> sediments are greater than vent solutions by a factor of 2 to 500, and these ratios increase with increasing distance away from the ridge axis. An evaluation of these results in the context of previous models of REE behavior indicates that, in fact, seawater experiences a net depletion in REEs as a result of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>. This is due primarily to the large scavenging capacity of iron oxyhydroxides which precipitate from these solutions. Such an interpretation explains why the REE content of seawater collected in the vicinity of <span class="hlt">hydrothermal</span> vents is anomalously lower than normal seawater sampled from a comparable depth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17654787','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17654787"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> petroleum from lacustrine sedimentary organic matter in the East African Rift.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Simoneit, B R; Aboul-Kassim, T A; Tiercelin, J J</p> <p>2000-03-01</p> <p>Cape Kalamba oil seeps occur at the south end of the Ubwari Peninsula, at the intersection of faults controlling the morphology of the northern basin of the Tanganyika Rift, East Africa. Oil samples collected at the surface of the lake 3-4 km offshore from Cape Kalamba have been studied. The aliphatic hydrocarbon and biomarker compositions, with the absence of the typical suite of polynuclear aromatic hydrocarbons, indicate an origin from <span class="hlt">hydrothermal</span> alteration of immature microbial biomass in the sediments. These data show a similarity between a tar sample from the beach and the petroleum from the oil seeps, and confirm that the source of these oils is from organic matter consisting mainly of bacterial and degraded algal biomass, altered by <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>. The compositions also demonstrate a < 200 degrees C temperature for formation/generation of this <span class="hlt">hydrothermal</span> petroleum, similar to the fluid temperature identified for the Pemba <span class="hlt">hydrothermal</span> <span class="hlt">site</span> located 150 km north of Cape Kalamba. The 14C age of 25.6 ka B.P. obtained for the tar ball suggests that Pleistocene lake sediments could be the source rock. <span class="hlt">Hydrothermal</span> generation may have occurred slightly before 25 ka B.P., during a dry climatic environment, when the lake level was lower than today. These results also suggest that the Cape Kalamba <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> did not occur in connection with an increased flux of meteoric water, higher water tables and lake levels as demonstrated in the Kenya Rift and for the Pemba <span class="hlt">site</span>. <span class="hlt">Hydrothermal</span> petroleum formation is a facile process also in continental rift systems and should be considered in exploration for energy resources in such locales. PMID:17654787</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17654787','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17654787"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> petroleum from lacustrine sedimentary organic matter in the East African Rift.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Simoneit, B R; Aboul-Kassim, T A; Tiercelin, J J</p> <p>2000-03-01</p> <p>Cape Kalamba oil seeps occur at the south end of the Ubwari Peninsula, at the intersection of faults controlling the morphology of the northern basin of the Tanganyika Rift, East Africa. Oil samples collected at the surface of the lake 3-4 km offshore from Cape Kalamba have been studied. The aliphatic hydrocarbon and biomarker compositions, with the absence of the typical suite of polynuclear aromatic hydrocarbons, indicate an origin from <span class="hlt">hydrothermal</span> alteration of immature microbial biomass in the sediments. These data show a similarity between a tar sample from the beach and the petroleum from the oil seeps, and confirm that the source of these oils is from organic matter consisting mainly of bacterial and degraded algal biomass, altered by <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>. The compositions also demonstrate a < 200 degrees C temperature for formation/generation of this <span class="hlt">hydrothermal</span> petroleum, similar to the fluid temperature identified for the Pemba <span class="hlt">hydrothermal</span> <span class="hlt">site</span> located 150 km north of Cape Kalamba. The 14C age of 25.6 ka B.P. obtained for the tar ball suggests that Pleistocene lake sediments could be the source rock. <span class="hlt">Hydrothermal</span> generation may have occurred slightly before 25 ka B.P., during a dry climatic environment, when the lake level was lower than today. These results also suggest that the Cape Kalamba <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> did not occur in connection with an increased flux of meteoric water, higher water tables and lake levels as demonstrated in the Kenya Rift and for the Pemba <span class="hlt">site</span>. <span class="hlt">Hydrothermal</span> petroleum formation is a facile process also in continental rift systems and should be considered in exploration for energy resources in such locales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6035481','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6035481"><span id="translatedtitle"><span class="hlt">Active</span> <span class="hlt">Sites</span> Environmental Monitoring Program: Mid-FY 1991 report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ashwood, T.L.; Wickliff, D.S.; Morrissey, C.M.</p> <p>1991-10-01</p> <p>This report summarizes the <span class="hlt">activities</span> of the <span class="hlt">Active</span> <span class="hlt">Sites</span> Environmental Monitoring Program (ASEMP) from October 1990 through March 1991. The ASEMP was established in 1989 by Solid Waste Operations and the Environmental Sciences Division to provide early detection and performance monitoring at <span class="hlt">active</span> low-level radioactive waste (LLW) disposal <span class="hlt">sites</span> in Solid Waste Storage Area (SWSA) 6 and transuranic (TRU) waste storage <span class="hlt">sites</span> in SWSA 5 as required by chapters II and III of US Department of Energy Order 5820.2A. Monitoring results continue to demonstrate the no LLW is being leached from the storage vaults on the tumulus pads. Loading of vaults on Tumulus II began during this reporting period and 115 vaults had been loaded by the end of March 1991.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5641454','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5641454"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> industrialization electric-power systems development. Final report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1982-03-01</p> <p>The nature of <span class="hlt">hydrothermal</span> resources, their associated temperatures, geographic locations, and developable capacity are described. The parties involved in development, required <span class="hlt">activities</span> and phases of development, regulatory and permitting requirements, environmental considerations, and time required to complete development <span class="hlt">activities</span> ae examined in detail. These <span class="hlt">activities</span> are put in proper perspective by detailing development costs. A profile of the geothermal industry is presented by detailing the participants and their operating characteristics. The current development status of geothermal energy in the US is detailed. The work on market penetration is summarized briefly. Detailed development information is presented for 56 high temperature <span class="hlt">sites</span>. (MHR)</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27243042','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27243042"><span id="translatedtitle"><span class="hlt">Active</span> chemisorption <span class="hlt">sites</span> in functionalized ionic liquids for carbon capture.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cui, Guokai; Wang, Jianji; Zhang, Suojiang</p> <p>2016-07-25</p> <p>Development of novel technologies for the efficient and reversible capture of CO2 is highly desired. In the last decade, CO2 capture using ionic liquids has attracted intensive attention from both academia and industry, and has been recognized as a very promising technology. Recently, a new approach has been developed for highly efficient capture of CO2 by <span class="hlt">site</span>-containing ionic liquids through chemical interaction. This perspective review focuses on the recent advances in the chemical absorption of CO2 using <span class="hlt">site</span>-containing ionic liquids, such as amino-based ionic liquids, azolate ionic liquids, phenolate ionic liquids, dual-functionalized ionic liquids, pyridine-containing ionic liquids and so on. Other <span class="hlt">site</span>-containing liquid absorbents such as amine-based solutions, switchable solvents, and functionalized ionic liquid-amine blends are also investigated. Strategies have been discussed for how to <span class="hlt">activate</span> the existent reactive <span class="hlt">sites</span> and develop novel reactive <span class="hlt">sites</span> by physical and chemical methods to enhance CO2 absorption capacity and reduce absorption enthalpy. The carbon capture mechanisms of these <span class="hlt">site</span>-containing liquid absorbents are also presented. Particular attention has been paid to the latest progress in CO2 capture in multiple-<span class="hlt">site</span> interactions by amino-free anion-functionalized ionic liquids. In the last section, future directions and prospects for carbon capture by <span class="hlt">site</span>-containing ionic liquids are outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27243042','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27243042"><span id="translatedtitle"><span class="hlt">Active</span> chemisorption <span class="hlt">sites</span> in functionalized ionic liquids for carbon capture.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cui, Guokai; Wang, Jianji; Zhang, Suojiang</p> <p>2016-07-25</p> <p>Development of novel technologies for the efficient and reversible capture of CO2 is highly desired. In the last decade, CO2 capture using ionic liquids has attracted intensive attention from both academia and industry, and has been recognized as a very promising technology. Recently, a new approach has been developed for highly efficient capture of CO2 by <span class="hlt">site</span>-containing ionic liquids through chemical interaction. This perspective review focuses on the recent advances in the chemical absorption of CO2 using <span class="hlt">site</span>-containing ionic liquids, such as amino-based ionic liquids, azolate ionic liquids, phenolate ionic liquids, dual-functionalized ionic liquids, pyridine-containing ionic liquids and so on. Other <span class="hlt">site</span>-containing liquid absorbents such as amine-based solutions, switchable solvents, and functionalized ionic liquid-amine blends are also investigated. Strategies have been discussed for how to <span class="hlt">activate</span> the existent reactive <span class="hlt">sites</span> and develop novel reactive <span class="hlt">sites</span> by physical and chemical methods to enhance CO2 absorption capacity and reduce absorption enthalpy. The carbon capture mechanisms of these <span class="hlt">site</span>-containing liquid absorbents are also presented. Particular attention has been paid to the latest progress in CO2 capture in multiple-<span class="hlt">site</span> interactions by amino-free anion-functionalized ionic liquids. In the last section, future directions and prospects for carbon capture by <span class="hlt">site</span>-containing ionic liquids are outlined. PMID:27243042</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1133638','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1133638"><span id="translatedtitle">Studies on the <span class="hlt">active</span> <span class="hlt">site</span> of pig plasma amine oxidase.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Collison, D; Knowles, P F; Mabbs, F E; Rius, F X; Singh, I; Dooley, D M; Cote, C E; McGuirl, M</p> <p>1989-01-01</p> <p>Amine oxidase from pig plasma (PPAO) has two bound Cu2+ ions and at least one pyrroloquinoline quinone (PQQ) moiety as cofactors. It is shown that recovery of <span class="hlt">activity</span> by copper-depleted PPAO is linear with respect to added Cu2+ ions. Recovery of e.s.r. and optical spectral characteristics of <span class="hlt">active-site</span> copper parallel the recovery of catalytic <span class="hlt">activity</span>. These results are consistent with both Cu2+ ions contributing to catalysis. Further e.s.r. studies indicate that the two copper <span class="hlt">sites</span> in PPAO, unlike those in amine oxidases from other sources, are chemically distinct. These comparative studies establish that non-identity of the Cu2+ ions in PPAO is not a requirement for amine oxidase <span class="hlt">activity</span>. It is shown through the use of a new assay procedure that there are two molecules of PQQ bound per molecule of protein in PPAO; only the more reactive of these PQQ moieties is required for <span class="hlt">activity</span>. PMID:2559715</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Litho.263...66A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Litho.263...66A"><span id="translatedtitle">High-temperature <span class="hlt">hydrothermal</span> <span class="hlt">activities</span> around suboceanic Moho: An example from diopsidite and anorthosite in Wadi Fizh, Oman ophiolite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Akizawa, Norikatsu; Tamura, Akihiro; Fukushi, Keisuke; Yamamoto, Junji; Mizukami, Tomoyuki; Python, Marie; Arai, Shoji</p> <p>2016-10-01</p> <p>Reaction products between <span class="hlt">hydrothermal</span> fluids and uppermost mantle harzburgite-lowermost crustal gabbro have been reported along Wadi Fizh, northern Oman ophiolite. They are named mantle diopsidite (MD) or crustal diopsidite (CD) depending on the stratigraphic level. They construct network-like dikes crosscutting structures of the surrounding harzburgite or gabbro. The MD is mainly composed of diopsidic clinopyroxene, whereas the CD is of diopsidic clinopyroxene and anorthitic plagioclase. Here, we report a new reaction product, crustal anorthosite (CA), from the lowermost crustal section. The CA is always placed in the center of the CD network, and mainly consists of anorthitic plagioclase with minor titanite and chromian minerals such as chromite and uvarovite. Aqueous fluid inclusions forming negative crystals are evenly distributed in minerals of the CA. The fluid inclusions contain angular-shaped or rounded daughter minerals as calcite or calcite-anhydrite composite, which were identified by Raman spectroscopic analysis. We estimated their captured temperature at 530 °C at least by conducting microthermometric analysis of the fluid inclusions. Furthermore, we examined their chemical characteristics by direct laser-shot sampling conducted by laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS). The results indicate that the trapped aqueous fluids contain an appreciable amount of Na, but no K and Cr. <span class="hlt">Hydrothermal</span> fluids involved in the CA formation transported Cr, which was probably taken up from chromite seams in the uppermost mantle section. Cr got soluble by forming complexes with anions as SO42-, CO32- and Cl-. In addition, these <span class="hlt">hydrothermal</span> fluids transported Fe, Mg and trace elements (Ti, Sr, Y, Zr and rare-earth elements) governing whole-rock chemical compositions of the MDs, CDs and CAs. Our estimation for the condition of CA formation yielded rather low temperatures (530-600 °C), which indicates a later stage production of the CA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014JGRB..119.7389T&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014JGRB..119.7389T&link_type=ABSTRACT"><span id="translatedtitle">High-resolution near-bottom vector magnetic anomalies over Raven <span class="hlt">Hydrothermal</span> Field, Endeavour Segment, Juan de Fuca Ridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tivey, Maurice A.; Johnson, H. Paul; Salmi, Marie S.; Hutnak, Michael</p> <p>2014-10-01</p> <p>High-resolution, near-bottom vector magnetic data were collected by remotely operated vehicle Jason over the Raven <span class="hlt">hydrothermal</span> vent field (47°57.3'N 129°5.75'W) located north of Main Endeavour vent field on the Endeavour segment of the Juan de Fuca Ridge. The survey was part of a comprehensive heat flow study of the Raven <span class="hlt">site</span> using innovative thermal blanket technology to map the heat flux and crustal fluid pathways around a solitary <span class="hlt">hydrothermal</span> vent field. Raven <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> is presently located along the western axial valley wall, while additional inactive <span class="hlt">hydrothermal</span> deposits are found to the NW on the upper rift valley wall. Magnetic inversion results show discrete areas of reduced magnetization associated with both <span class="hlt">active</span> and inactive <span class="hlt">hydrothermal</span> vent deposits that also show high conductive heat flow. Higher spatial variability in the heat flow patterns compared to the magnetization is consistent with the heat flow reflecting the currently <span class="hlt">active</span> but ephemeral thermal environment of fluid flow, while crustal magnetization is representative of the static time-averaged effect of <span class="hlt">hydrothermal</span> alteration. A general NW to SE trend in reduced magnetization across the Raven area correlates closely with the distribution of <span class="hlt">hydrothermal</span> deposits and heat flux patterns and suggests that the fluid circulation system at depth is likely controlled by local crustal structure and magma chamber geometry. Magnetic gradient tensor components computed from vector magnetic data improve the resolution of the magnetic anomaly source and indicate that the <span class="hlt">hydrothermally</span> altered zone directly beneath the Raven <span class="hlt">site</span> is approximately 15 × 106 m3 in volume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013MinDe..48..233C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013MinDe..48..233C"><span id="translatedtitle">Migration of <span class="hlt">hydrothermal</span> systems in an evolving collisional orogen, New Zealand</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Craw, D.; Upton, P.; Horton, T.; Williams, J.</p> <p>2013-02-01</p> <p>The Pacific-Australian tectonic plate boundary through the South Island of New Zealand consists of the transpressional Southern Alps mountain belt and the transcurrent Marlborough Fault System, both of which have <span class="hlt">active</span> tectonically driven <span class="hlt">hydrothermal</span> systems, with topographically driven meteoric incursion and warm springs. The Southern Alps <span class="hlt">hydrothermal</span> system is relatively diffuse, with little or no fault control, and is channelled through scattered extensional <span class="hlt">sites</span> beneath the mountains, where gold mineralisation is occurring locally. The <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> along the Marlborough Fault System is controlled by the principal faults in well-defined valleys separated by narrow high ridges. Lateral evolution of Marlborough fault strands southwestwards into the Southern Alps has caused diversion of diffuse Southern Alps <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> into the structural superimposition zone, where fluid flow is increasingly being controlled by faults. This <span class="hlt">hydrothermal</span> diversion was accompanied by major topographic reorientation and river drainage reversal in the late Quaternary. Vein swarms now exposed in the remnants of the Southern Alps north of the superimposition zone formed at shallow levels, with some evidence for fluid boiling, from a mixture of meteoric and deep-sourced fluid. These veins, some of which contain gold, are part of an abandoned <1 million-year-old <span class="hlt">hydrothermal</span> zone beneath the fossil topographic divide of the Southern Alps that has now been dismembered by lateral incursion of the Marlborough fault strands. Observations on this <span class="hlt">active</span> plate boundary provide some insights into processes that controlled orogenic gold mineralisation in ancient belts, particularly with respect to relationships between <span class="hlt">hydrothermal</span> fluid flow, structure and topography.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009DSRII..56.1577E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009DSRII..56.1577E"><span id="translatedtitle">Evidence for a chemoautotrophically based food web at inactive <span class="hlt">hydrothermal</span> vents (Manus Basin)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erickson, K. L.; Macko, S. A.; Van Dover, C. L.</p> <p>2009-09-01</p> <p><span class="hlt">Hydrothermal</span> vents are ephemeral systems. When venting shuts down, sulfide-dependent taxa die off, and non-vent taxa can colonize the hard substrata. In Manus Basin (Papua New Guinea), where <span class="hlt">hydrothermally</span> <span class="hlt">active</span> and inactive <span class="hlt">sites</span> are interspersed, hydroids, cladorhizid sponges, barnacles, bamboo corals, and other invertebrate types may occupy inactive <span class="hlt">sites</span>. Carbon and nitrogen isotopic compositions of animals occupying inactive <span class="hlt">sites</span> are consistent with nutritional dependence on either chemoautotrophically or photosynthetically produced organic material, but sulfur isotopic compositions of these animals point to a chemoautotrophic source of sulfur from dissolved sulfide in vent fluids rather than sulfur derived from seawater sulfate through photosynthesis. Given that suspension-feeding and micro-carnivorous invertebrates are the biomass dominants at inactive <span class="hlt">sites</span>, the primary source of chemoautotrophic nutrition is likely suspended particulates and organisms delivered from nearby <span class="hlt">active</span> vents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/447585','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/447585"><span id="translatedtitle">Computer simulation of the <span class="hlt">active</span> <span class="hlt">site</span> of human serum cholinesterase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kefang Jiao; Song Li; Zhengzheng Lu</p> <p>1996-12-31</p> <p>The first 3D-structure of acetylchelinesterase from Torpedo California electric organ (T.AChE) was published by JL. Sussman in 1991. We have simulated 3D-structure of human serum cholinesterase (H.BuChE) and the <span class="hlt">active</span> <span class="hlt">site</span> of H.BuChE. It is discovered by experiment that the residue of H.BuChE is still <span class="hlt">active</span> <span class="hlt">site</span> after a part of H.BuChE is cut. For example, the part of 21KD + 20KD is <span class="hlt">active</span> <span class="hlt">site</span> of H.BuChE. The 20KD as it is. Studies on these peptides by Hemelogy indicate that two <span class="hlt">active</span> peptides have same negative electrostatic potential maps diagram. These negative electrostatic areas attached by acetyl choline with positive electrostatic potency. We predict that 147...236 peptide of AChE could be <span class="hlt">active</span> <span class="hlt">site</span> because it was as 20KD as with negative electrostatic potential maps. We look forward to proving from other ones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T43D2704F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T43D2704F"><span id="translatedtitle">Magnetic Structure of Backarc Spreading Axis with <span class="hlt">Hydrothermal</span> Vents; the Southern Mariana Trough</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujii, M.; Okino, K.; Mochizuki, N.; Honsho, C.; Szitkar, F.; Dyment, J.; Nakamura, K.</p> <p>2012-12-01</p> <p>Seafloor <span class="hlt">hydrothermal</span> systems are important in relation to global heat and chemical fluxes as well as habitat of microbial communities. The substantial variation of <span class="hlt">hydrothermal</span> systems in various tectonic settings has important implications for the magnetic structure of oceanic crust. It has been very difficult to detect the geophysical signature of <span class="hlt">hydrothermal</span> systems from sea-surface data because the small scale of <span class="hlt">hydrothermal</span> systems is below the limit of resolution. The advance of near-bottom survey methods using a submersible, deep-tow, ROV and AUV has made possible high-resolution geophysical mapping around <span class="hlt">hydrothermal</span> areas. Near-bottom magnetic surveys can provide direct information on the magnetization of the shallower oceanic crust, implying <span class="hlt">hydrothermal</span> alteration both in <span class="hlt">active</span> and fossil vent <span class="hlt">sites</span>. Near-bottom three component magnetic measurements on submersible Shinkai 6500 were carried out at <span class="hlt">hydrothermal</span> fields in the Southern Mariana Trough, a slow spreading backarc basin. Fourteen dive surveys were conducted during cruises YK11-10 and YK10-11. We investigated the magnetic structure of four <span class="hlt">hydrothermal</span> systems located at on- and off-axis to clarify how the geophysical and geological setting controls the fluid circulation at small scale. Recent researches at slow spreading ridges showed a relationship between crustal magnetic structure and host rock around <span class="hlt">hydrothermal</span> vents (e.g. Tivey and Dyment, 2010), but no observation at backarc spreading axis has been reported so far. We carefully corrected the effects of induced and permanent magnetizations of the submersible by applying the method of Isezaki [1986] with dumped least-square method (Honsho et al., 2009). After subtracting the IGRF from the corrected observed data, we obtained geomagnetic vector anomalies in geographical coordinate. For three transects of the axis, we applied three methods; 2D inversion technique (Parker and Huestis, 1972), 2D forward modeling technique (Honsho et al</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SurSc.645...41C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SurSc.645...41C"><span id="translatedtitle">Resonant <span class="hlt">active</span> <span class="hlt">sites</span> in catalytic ammonia synthesis: A structural model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cholach, Alexander R.; Bryliakova, Anna A.; Matveev, Andrey V.; Bulgakov, Nikolai N.</p> <p>2016-03-01</p> <p>Adsorption <span class="hlt">sites</span> Mn consisted of n adjacent atoms M, each bound to the adsorbed species, are considered within a realistic model. The sum of bonds Σ lost by atoms in a <span class="hlt">site</span> in comparison with the bulk atoms was used for evaluation of the local surface imperfection, while the reaction enthalpy at that <span class="hlt">site</span> was used as a measure of <span class="hlt">activity</span>. The comparative study of Mn <span class="hlt">sites</span> (n = 1-5) at basal planes of Pt, Rh, Ir, Fe, Re and Ru with respect to heat of N2 dissociative adsorption QN and heat of Nad + Had → NHad reaction QNH was performed using semi-empirical calculations. Linear QN(Σ) increase and QNH(Σ) decrease allowed to specify the resonant Σ for each surface in catalytic ammonia synthesis at equilibrium Nad coverage. Optimal Σ are realizable for Ru2, Re2 and Ir4 only, whereas other centers meet steric inhibition or unreal crystal structure. Relative <span class="hlt">activity</span> of the most <span class="hlt">active</span> <span class="hlt">sites</span> in proportion 5.0 × 10- 5: 4.5 × 10- 3: 1: 2.5: 3.0: 1080: 2270 for a sequence of Pt4, Rh4, Fe4(fcc), Ir4, Fe2-5(bcc), Ru2, Re2, respectively, is in agreement with relevant experimental data. Similar approach can be applied to other adsorption or catalytic processes exhibiting structure sensitivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2453504','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2453504"><span id="translatedtitle">Multi-<span class="hlt">site</span> Phosphorylation Regulates Bim Stability and Apoptotic <span class="hlt">Activity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hübner, Anette; Barrett, Tamera; Flavell, Richard A.; Davis, Roger J.</p> <p>2008-01-01</p> <p>The pro-apoptotic BH3-only protein Bim is established to be an important mediator of signaling pathways that induce cell death. Multi-<span class="hlt">site</span> phosphorylation of Bim by several members of the MAP kinase group is implicated as a regulatory mechanism that controls the apoptotic <span class="hlt">activity</span> of Bim. To test the role of Bim phosphorylation in vivo, we constructed mice with a series of mutant alleles that express phosphorylation-defective Bim proteins. We show that mutation of the phosphorylation <span class="hlt">site</span> Thr-112 causes decreased binding of Bim to the anti-apoptotic protein Bcl2 and can increase cell survival. In contrast, mutation of the phosphorylation <span class="hlt">sites</span> Ser-55, Ser-65, and Ser-73 can cause increased apoptosis because of reduced proteasomal degradation of Bim. Together, these data indicate that phosphorylation can regulate Bim by multiple mechanisms and that the phosphorylation of Bim on different <span class="hlt">sites</span> can contribute to the sensitivity of cellular apoptotic responses. PMID:18498746</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS13A1712Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS13A1712Y"><span id="translatedtitle">What is the constraint on formation of oil-starved <span class="hlt">hydrothermal</span> systems in the sediment-rich Okinawa Trough, southwestern Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamanaka, T.; Akashi, H.; Mitsunari, T.</p> <p>2012-12-01</p> <p>Petroleum generation associated with seafloor <span class="hlt">hydrothermal</span> systems was first identified at the Guaymas Basin, Gulf of California in 1978 (Simoneit et al., 1979). Since the first discovery, <span class="hlt">hydrothermal</span> petroleums have been discovered at other seafloor <span class="hlt">hydrothermal</span> fields, Escanaba Trough, Middle Valley, and the Red Sea, where thick sedimentary layer overlay the <span class="hlt">active</span> spreading center. Simoneit (1990) suggested that <span class="hlt">hydrothermal</span> petroleum can be occurred any <span class="hlt">hydrothermal</span> systems as a result of interaction between hot <span class="hlt">hydrothermal</span> fluid and organic mater in the sedimentary layer. In the middle Okinawa Trough, where typical sediment-hosted <span class="hlt">hydrothermal</span> systems distribute, occurrence of <span class="hlt">hydrothermal</span> petroleum has not been found. In 2010 IODP Exp. 331 had been performed, and then five <span class="hlt">sites</span> were drilled at the Iheya North <span class="hlt">hydrothermal</span> system. However, <span class="hlt">hydrothermal</span> petroleum generation has not been reported even at that time. On the other hand, significant <span class="hlt">hydrothermal</span> petroleum generation has been observed at a shallow-seafloor <span class="hlt">hydrothermal</span> system in the Kagoshima Bay, north extension of Okinawa Trough (Yamanaka et al., 1999). It is an interesting subject why <span class="hlt">hydrothermal</span> petroleum can not be found in the Okinawa Trough. So we considered what is the most critical constraint on occurrence of <span class="hlt">hydrothermal</span> petroleum based on comparison with the well known <span class="hlt">hydrothermal</span> fields occurred <span class="hlt">hydrothermal</span> petroleum. Three major control factors for petroleum generation at seafloor <span class="hlt">hydrothermal</span> systems are expected; (i) temperature, (ii) elapsed time, (iii) type of sediment. High temperature is essential for maturation of organic matter, but under extremely high temperature condition pyrolysis to gaseous hydrocarbon and other low-molecular weight product may be prevailed. Dissolved organic matter (DOM) and methane concentrations may reflect the temperature condition, because methane generation may continue under extreme condition but DOM, especially low-molecular weight organic acid</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JVGR..288...94G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JVGR..288...94G"><span id="translatedtitle">Towards understanding the puzzling lack of acid geothermal springs in Tibet (China): Insight from a comparison with Yellowstone (USA) and some <span class="hlt">active</span> volcanic <span class="hlt">hydrothermal</span> systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guo, Qinghai; Kirk Nordstrom, D.; Blaine McCleskey, R.</p> <p>2014-11-01</p> <p>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 <span class="hlt">active</span> 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 <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3149774','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3149774"><span id="translatedtitle">Water in the <span class="hlt">Active</span> <span class="hlt">Site</span> of Ketosteroid Isomerase</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hanoian, Philip; Hammes-Schiffer, Sharon</p> <p>2011-01-01</p> <p>Classical molecular dynamics simulations were utilized to investigate the structural and dynamical properties of water in the <span class="hlt">active</span> <span class="hlt">site</span> of ketosteroid isomerase (KSI) to provide insight into the role of these water molecules in the enzyme-catalyzed reaction. This reaction is thought to proceed via a dienolate intermediate that is stabilized by hydrogen bonding with residues Tyr16 and Asp103. A comparative study was performed for the wild-type (WT) KSI and the Y16F, Y16S, and Y16F/Y32F/Y57F (FFF) mutants. These systems were studied with three different bound ligands: equilenin, which is an intermediate analog, and the intermediate states of two steroid substrates. Several distinct water occupation <span class="hlt">sites</span> were identified in the <span class="hlt">active</span> <span class="hlt">site</span> of KSI for the WT and mutant systems. Three additional <span class="hlt">sites</span> were identified in the Y16S mutant that were not occupied in WT KSI or the other mutants studied. The number of water molecules directly hydrogen bonded to the ligand oxygen was approximately two waters in the Y16S mutant, one water in the Y16F and FFF mutants, and intermittent hydrogen bonding of one water molecule in WT KSI. The molecular dynamics trajectories of the Y16F and FFF mutants reproduced the small conformational changes of residue 16 observed in the crystal structures of these two mutants. Quantum mechanical/molecular mechanical calculations of 1H NMR chemical shifts of the protons in the <span class="hlt">active</span> <span class="hlt">site</span> hydrogen-bonding network suggest that the presence of water in the <span class="hlt">active</span> <span class="hlt">site</span> does not prevent the formation of short hydrogen bonds with far-downfield chemical shifts. The molecular dynamics simulations indicate that the <span class="hlt">active</span> <span class="hlt">site</span> water molecules exchange much more frequently for WT KSI and the FFF mutant than for the Y16F and Y16S mutants. This difference is most likely due to the hydrogen-bonding interaction between Tyr57 and an <span class="hlt">active</span> <span class="hlt">site</span> water molecule that is persistent in the Y16F and Y16S mutants but absent in the FFF mutant and significantly less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25453233','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25453233"><span id="translatedtitle"><span class="hlt">Activation</span> of phenylalanine hydroxylase by phenylalanine does not require binding in the <span class="hlt">active</span> <span class="hlt">site</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Roberts, Kenneth M; Khan, Crystal A; Hinck, Cynthia S; Fitzpatrick, Paul F</p> <p>2014-12-16</p> <p>Phenylalanine hydroxylase (PheH), a liver enzyme that catalyzes the hydroxylation of excess phenylalanine in the diet to tyrosine, is <span class="hlt">activated</span> by phenylalanine. The lack of <span class="hlt">activity</span> at low levels of phenylalanine has been attributed to the N-terminus of the protein's regulatory domain acting as an inhibitory peptide by blocking substrate access to the <span class="hlt">active</span> <span class="hlt">site</span>. The location of the <span class="hlt">site</span> at which phenylalanine binds to <span class="hlt">activate</span> the enzyme is unknown, and both the <span class="hlt">active</span> <span class="hlt">site</span> in the catalytic domain and a separate <span class="hlt">site</span> in the N-terminal regulatory domain have been proposed. Binding of catecholamines to the <span class="hlt">active-site</span> iron was used to probe the accessibility of the <span class="hlt">active</span> <span class="hlt">site</span>. Removal of the regulatory domain increases the rate constants for association of several catecholamines with the wild-type enzyme by ∼2-fold. Binding of phenylalanine in the <span class="hlt">active</span> <span class="hlt">site</span> is effectively abolished by mutating the <span class="hlt">active-site</span> residue Arg270 to lysine. The k(cat)/K(phe) value is down 10⁴ for the mutant enzyme, and the K(m) value for phenylalanine for the mutant enzyme is >0.5 M. Incubation of the R270K enzyme with phenylalanine also results in a 2-fold increase in the rate constants for catecholamine binding. The change in the tryptophan fluorescence emission spectrum seen in the wild-type enzyme upon <span class="hlt">activation</span> by phenylalanine is also seen with the R270K mutant enzyme in the presence of phenylalanine. Both results establish that <span class="hlt">activation</span> of PheH by phenylalanine does not require binding of the amino acid in the <span class="hlt">active</span> <span class="hlt">site</span>. This is consistent with a separate allosteric <span class="hlt">site</span>, likely in the regulatory domain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=cysteine&id=EJ717237','ERIC'); return false;" href="http://eric.ed.gov/?q=cysteine&id=EJ717237"><span id="translatedtitle">Chemical Modification of Papain and Subtilisin: An <span class="hlt">Active</span> <span class="hlt">Site</span> Comparison</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>St-Vincent, Mireille; Dickman, Michael</p> <p>2004-01-01</p> <p>An experiment using methyle methanethiosulfonate (MMTS) and phenylmethylsulfonyl flouride (PMSF) to specifically modify the cysteine and serine residues in the <span class="hlt">active</span> <span class="hlt">sites</span> of papain and subtilism respectively is demonstrated. The covalent modification of these enzymes and subsequent rescue of papain shows the beginning biochemist that proteins…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/238906','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/238906"><span id="translatedtitle">Energy transfer at the <span class="hlt">active</span> <span class="hlt">sites</span> of heme proteins</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dlott, D.D.; Hill, J.R.</p> <p>1995-12-31</p> <p>Experiments using a picosecond pump-probe apparatus at the Picosecond Free-electron Laser Center at Stanford University, were performed to investigate the relaxation of carbon monoxide bound to the <span class="hlt">active</span> <span class="hlt">sites</span> of heme proteins. The significance of these experiments is two-fold: (1) they provide detailed information about molecular dynamics occurring at the <span class="hlt">active</span> <span class="hlt">sites</span> of proteins; and (2) they provide insight into the nature of vibrational relaxation processes in condensed matter. Molecular engineering is used to construct various molecular systems which are studied with the FEL. We have studied native proteins, mainly myoglobin obtained from different species, mutant proteins produced by genetic engineering using recombinant DNA techniques, and a variety of model systems which mimic the structures of the <span class="hlt">active</span> <span class="hlt">sites</span> of native proteins, which are produced using molecular synthesis. Use of these different systems permits us to investigate how specific molecular structural changes affect dynamical processes occurring at the <span class="hlt">active</span> <span class="hlt">sites</span>. This research provides insight into the problems of how different species needs are fulfilled by heme proteins which have greatly different functionality, which is induced by rather small structural changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPCS...92...11Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPCS...92...11Z"><span id="translatedtitle">One-pot synthesis of Ag+ doped BiVO4 microspheres with enhanced photocatalytic <span class="hlt">activity</span> via a facile <span class="hlt">hydrothermal</span> method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, Shiwen; Li, Quanguo; Li, Feng; Cao, Wei; Li, Taohai</p> <p>2016-05-01</p> <p>The Ag+/BiVO4 photocatalyst was fabricated through a facile <span class="hlt">hydrothermal</span> method by using K6V10O28·9H2O as the vanadium source. The impact of Ag+ on the product's structure and morphology was studied. It was shown that the amount of Ag+ has no effect on the product's crystal phases but plays an important role on the morphology of the nanoparticles that construct the shell of BiVO4 microspheres. In addition, the Ag+-doped photocatalysts have much higher photocatalytic <span class="hlt">activities</span> in removing RhB and MB under the UV light illumination than the pure BiVO4. A possible photocatalytic mechanism was proposed in photoexcitation of the BiVO4 electrons which subsequently captured by the dopant. The present work may offer a novel route to reach higher photocatalytic <span class="hlt">activity</span> by doping the Ag+ in the semiconductor catalysts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23968356','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23968356"><span id="translatedtitle">General one-pot template-free <span class="hlt">hydrothermal</span> method to metal oxide hollow spheres and their photocatalytic <span class="hlt">activities</span> and lithium storage properties.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Di; Qin, Qing; Duan, Xiaochuan; Yang, Jiaqin; Guo, Wei; Zheng, Wenjun</p> <p>2013-09-25</p> <p>A general and facile one-pot template-free <span class="hlt">hydrothermal</span> strategy has been developed to synthesize various metal oxide (TiO2, SnO2 and α-Fe2O3) hollow spheres with unified morphologies. The formation of hollow structure involves a trifluoroacetic acid (TFA)-assisted Ostwald ripening process. Photocatalytic <span class="hlt">activities</span> of the as-prepared TiO2 product are evaluated by the photodegradation of Rhodamine B (RhB), which the TiO2 hollow spheres obtained from 450 °C thermal treatment exhibit higher photocatalytic <span class="hlt">activity</span> than Degussa P25. In addition, electrochemical measurements demonstrate that all of the as-prepared metal oxides hollow spheres have the potential applications in lithium-ion battery. We have a great expectation that this synthesis strategy can afford a new universal route for functional metal oxide hollow materials preparation without using template.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/543373','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/543373"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> vents is Lake Tanganyika, East African Rift system</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tiercelin, J.J.; Pflumio, C.; Castrec, M.</p> <p>1993-06-01</p> <p>Sublacustrine <span class="hlt">hydrothermal</span> vents with associated massive sulfides were discovered during April 1987 at Pemba and Cape Banza on the Zaire side of the northern basin of Lake Tanganyika, East African Rift system. New investigations by a team of ten scuba divers during the multinational (France, Zaire, Germany, and Burundi) TANGANYDRO expedition (August-October 1991) found <span class="hlt">hydrothermal</span> vents down to a depth of 46 m along north-trending <span class="hlt">active</span> faults bounding the Tanganyika rift on the western side. Temperatures from 53 to 103 {degrees}C were measured in <span class="hlt">hydrothermal</span> fluids and sediments. Veins of massive sulfides 1-10 cm thick (pyrite and marcasite banding) were found associated with vents at the Pemba <span class="hlt">site</span>. At Cape Banza, <span class="hlt">active</span> vents are characterized by 1-70-cm-high aragonite chimneys, and there are microcrystalline pyrite coatings on the walls of <span class="hlt">hydrothermal</span> pipes. <span class="hlt">Hydrothermal</span> fluid end members show distinctive compositions at the two <span class="hlt">sites</span>. The Pemba end member is a NaHCO{sub 3}-enriched fluid similar to the NaHCO{sub 3} thermal fluids form lakes Magadi and Bogoria in the eastern branch of the rift. The Cape Banza end member is a solution enriched in NaCl. Such brines may have a deep-seated basement origin, as do the Uvinza NaCl brines on the eastern flank of the Tanganyika basin. Geothermometric calculations have yielded temperatures of fluid-rock interaction of 219 and 179 {degrees}C in the Pemba and Cape Banza systems, respectively. Abundant white or reddish-brown microbial colonies resembling Beggiatoa mats were found surrounding the <span class="hlt">active</span> vents. Thermal fluid circulation is permitted by opening of cracks related to 130{degrees}N normal-dextral faults that intersect the north-south major rift trend. The sources of heat for such <span class="hlt">hydrothermal</span> systems may relate to the existence of magmatic bodies under the rift, which is suggested by the isotopic composition of carbon dioxide released at Pemba and Cape Banza. 21 refs., 2 figs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70117573','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70117573"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> monitoring in a quiescent volcanic arc: Cascade Range, northwestern United States</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ingebritsen, S.E.; Randolph-Flagg, N. G.; Gelwick, K.D.; Lundstrom, E.A.; Crankshaw, I.M.; Murveit, A.M.; Schmidt, M.E.; Bergfeld, D.; Spicer, K.R.; Tucker, D.S.; Mariner, R.H.; Evans, William C.</p> <p>2014-01-01</p> <p>Ongoing (1996–present) volcanic unrest near South Sister, Oregon, is accompanied by a striking set of <span class="hlt">hydrothermal</span> anomalies, including elevated temperatures, elevated major ion concentrations, and 3He/4He ratios as large as 8.6 RA in slightly thermal springs. These observations prompted the US Geological Survey to begin a systematic <span class="hlt">hydrothermal</span>-monitoring effort encompassing 25 <span class="hlt">sites</span> and 10 of the highest-risk volcanoes in the Cascade volcanic arc, from Mount Baker near the Canadian border to Lassen Peak in northern California. A concerted effort was made to develop hourly, multiyear records of temperature and/or <span class="hlt">hydrothermal</span> solute flux, suitable for retrospective comparison with other continuous geophysical monitoring data. Targets included summit fumarole groups and springs/streams that show clear evidence of magmatic influence in the form of high 3He/4He ratios and/or anomalous fluxes of magmatic CO2 or heat. As of 2009–2012, summit fumarole temperatures in the Cascade Range were generally near or below the local pure water boiling point; the maximum observed superheat was 3 during periods of hourly record. <span class="hlt">Hydrothermal</span> responses to these small seismic stimuli were generally undetectable or ambiguous. Evaluation of multiyear to multidecadal trends indicates that whereas the <span class="hlt">hydrothermal</span> system at Mount St. Helens is still fast-evolving in response to the 1980–present eruptive cycle, there is no clear evidence of ongoing long-term trends in <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at other Cascade Range volcanoes that have been <span class="hlt">active</span> or restless during the past century (Baker, South Sister, and Lassen). Experience gained during the Cascade Range <span class="hlt">hydrothermal</span>-monitoring experiment informs ongoing efforts to capture entire unrest cycles at more <span class="hlt">active</span> but generally less accessible volcanoes such as those in the Aleutian arc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.V21D0759K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.V21D0759K"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> fountains imaged by high resolution side-scan sonar equipped on a cruising AUV, URASHIMA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumagai, H.; Tsukioka, S.; Yamamoto, H.; Shitashima, K.; Yamamoto, F.; Sawa, T.; Hyakudome, T.; Kasaya, T.; Kinoshita, M.</p> <p>2007-12-01</p> <p>Mapping of an area and intensities of <span class="hlt">activity</span> at a particular <span class="hlt">hydrothermal</span> field has required huge effort so far, typically several tens of dives of manned submersibles and/or ROVs to obtain detailed locality map with needed resolutions. Thus, appropriate remote sensing techniques have been desired since the discovery of seafloor <span class="hlt">hydrothermal</span> field. A series of successful trials has been performed by ABE of WHOI equipped with a Eh-sensor (Yoerger et al., Oceanography, 2007). A 100kHz side-scan sonar (SSS) equipped on a cruising AUV, URASHIMA, caught detailed structural image of <span class="hlt">hydrothermal</span> fountains rooting <span class="hlt">active</span> chimneys during YK07-07 Cruise off Okinawa Isl. (May 6-18, 2007). The URASHIMA AUV is a 10-m-length cylindrical-shaped one that originally optimized to long distance cruise. In the expedition, she cruised near the sea floor with 50-100 m altitude, at the area of 1000-1500 m in WD. She has currently basic oceanographic/CTD sensors, a 400kHz echo-sounder and sonars of 100400 kHz side-scan sonar and up to 6 kHz sub-bottom profiler. In this operation, pH and ORP sensors (CRIEPI) were also attached in front of AUV. On the pre-processing image of SSS, numbers of filament-shape echoes were recorded within water column zone. The reason why they should be the echo from <span class="hlt">hydrothermal</span> plumes are as folows; 1) the echoes in the water column were limitedly recorded above the <span class="hlt">active</span> <span class="hlt">hydrothermal</span> field; 2) CTD and pH sensors show temperature and pH anomaly corresponding to the record of echoes; 3) some of the root of the filament-shape echoes correspond to the <span class="hlt">hydrothermal</span> mound recognized in the detailed bathymetry obtained with SeaBat7125 MNBES. This-like technique should revolute the mapping work prior to the sampling at the particular <span class="hlt">hydrothermal</span> <span class="hlt">site</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27551082','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27551082"><span id="translatedtitle">Changes in <span class="hlt">active</span> <span class="hlt">site</span> histidine hydrogen bonding trigger cryptochrome <span class="hlt">activation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ganguly, Abir; Manahan, Craig C; Top, Deniz; Yee, Estella F; Lin, Changfan; Young, Michael W; Thiel, Walter; Crane, Brian R</p> <p>2016-09-01</p> <p>Cryptochrome (CRY) is the principal light sensor of the insect circadian clock. Photoreduction of the Drosophila CRY (dCRY) flavin cofactor to the anionic semiquinone (ASQ) restructures a C-terminal tail helix (CTT) that otherwise inhibits interactions with targets that include the clock protein Timeless (TIM). All-atom molecular dynamics (MD) simulations indicate that flavin reduction destabilizes the CTT, which undergoes large-scale conformational changes (the CTT release) on short (25 ns) timescales. The CTT release correlates with the conformation and protonation state of conserved His378, which resides between the CTT and the flavin cofactor. Poisson-Boltzmann calculations indicate that flavin reduction substantially increases the His378 pKa Consistent with coupling between ASQ formation and His378 protonation, dCRY displays reduced photoreduction rates with increasing pH; however, His378Asn/Arg variants show no such pH dependence. Replica-exchange MD simulations also support CTT release mediated by changes in His378 hydrogen bonding and verify other responsive regions of the protein previously identified by proteolytic sensitivity assays. His378 dCRY variants show varying abilities to light-<span class="hlt">activate</span> TIM and undergo self-degradation in cellular assays. Surprisingly, His378Arg/Lys variants do not degrade in light despite maintaining reactivity toward TIM, thereby implicating different conformational responses in these two functions. Thus, the dCRY photosensory mechanism involves flavin photoreduction coupled to protonation of His378, whose perturbed hydrogen-bonding pattern alters the CTT and surrounding regions. PMID:27551082</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4676079','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4676079"><span id="translatedtitle">Conformational Transitions in Human AP Endonuclease 1 and Its <span class="hlt">Active</span> <span class="hlt">Site</span> Mutant during Abasic <span class="hlt">Site</span> Repair†</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kanazhevskaya, Lyubov Yu.; Koval, Vladimir V.; Zharkov, Dmitry O.; Strauss, Phyllis R.; Fedorova, Olga S.</p> <p>2010-01-01</p> <p>AP endonuclease 1 (APE 1) is a crucial enzyme of the base excision repair pathway (BER) in human cells. APE1 recognizes apurinic/apyrimidinic (AP) <span class="hlt">sites</span> and makes a nick in the phosphodiester backbone 5′ to them. The conformational dynamics and presteady-state kinetics of wild-type APE1 and its <span class="hlt">active</span> <span class="hlt">site</span> mutant, Y171F-P173L-N174K, have been studied. To observe conformational transitions occurring in the APE1 molecule during the catalytic cycle, we detected intrinsic tryptophan fluorescence of the enzyme under single turnover conditions. DNA duplexes containing a natural AP <span class="hlt">site</span>, its tetrahydrofuran analogue, or a 2′-deoxyguanosine residue in the same position were used as specific substrates or ligands. The stopped-flow experiments have revealed high flexibility of the APE1 molecule and the complexity of the catalytic process. The fluorescent traces indicate that wild-type APE1 undergoes at least four conformational transitions during the processing of abasic <span class="hlt">sites</span> in DNA. In contrast, nonspecific interactions of APE1 with undamaged DNA can be described by a two-step kinetic scheme. Rate and equilibrium constants were extracted from the stopped-flow and fluorescence titration data for all substrates, ligands, and products. A replacement of three residues at the enzymatic <span class="hlt">active</span> <span class="hlt">site</span> including the replacement of tyrosine 171 with phenylalanine in the enzyme <span class="hlt">active</span> <span class="hlt">site</span> resulted in a 2 × 104-fold decrease in the reaction rate and reduced binding affinity. Our data indicate the important role of conformational changes in APE1 for substrate recognition and catalysis. PMID:20575528</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NatSR...3E3487I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NatSR...3E3487I"><span id="translatedtitle">Fungal colonization of an Ordovician impact-induced <span class="hlt">hydrothermal</span> system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivarsson, Magnus; Broman, Curt; Sturkell, Erik; Ormö, Jens; Siljeström, Sandra; van Zuilen, Mark; Bengtson, Stefan</p> <p>2013-12-01</p> <p>Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced <span class="hlt">hydrothermal</span> convection. Impact-generated <span class="hlt">hydrothermal</span> systems have been suggested to possess the same life supporting capability as <span class="hlt">hydrothermal</span> systems associated with volcanic <span class="hlt">activity</span>. However, evidence of fossil microbial colonization in impact-generated <span class="hlt">hydrothermal</span> systems is scarce in the literature. Here we report of fossilized microorganisms in association with cavity-grown <span class="hlt">hydrothermal</span> minerals from the 458 Ma Lockne impact structure, Sweden. Based on morphological characteristics the fossilized microorganisms are interpreted as fungi. We further infer the kerogenization of the microfossils, and thus the life span of the fungi, to be contemporaneous with the <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> and migration of hydrocarbons in the system. Our results from the Lockne impact structure show that <span class="hlt">hydrothermal</span> systems associated with impact structures can support colonization by microbial life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3864048','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3864048"><span id="translatedtitle">Fungal colonization of an Ordovician impact-induced <span class="hlt">hydrothermal</span> system</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ivarsson, Magnus; Broman, Curt; Sturkell, Erik; Ormö, Jens; Siljeström, Sandra; van Zuilen, Mark; Bengtson, Stefan</p> <p>2013-01-01</p> <p>Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced <span class="hlt">hydrothermal</span> convection. Impact-generated <span class="hlt">hydrothermal</span> systems have been suggested to possess the same life supporting capability as <span class="hlt">hydrothermal</span> systems associated with volcanic <span class="hlt">activity</span>. However, evidence of fossil microbial colonization in impact-generated <span class="hlt">hydrothermal</span> systems is scarce in the literature. Here we report of fossilized microorganisms in association with cavity-grown <span class="hlt">hydrothermal</span> minerals from the 458 Ma Lockne impact structure, Sweden. Based on morphological characteristics the fossilized microorganisms are interpreted as fungi. We further infer the kerogenization of the microfossils, and thus the life span of the fungi, to be contemporaneous with the <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> and migration of hydrocarbons in the system. Our results from the Lockne impact structure show that <span class="hlt">hydrothermal</span> systems associated with impact structures can support colonization by microbial life. PMID:24336641</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24336641','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24336641"><span id="translatedtitle">Fungal colonization of an Ordovician impact-induced <span class="hlt">hydrothermal</span> system.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ivarsson, Magnus; Broman, Curt; Sturkell, Erik; Ormö, Jens; Siljeström, Sandra; van Zuilen, Mark; Bengtson, Stefan</p> <p>2013-12-16</p> <p>Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced <span class="hlt">hydrothermal</span> convection. Impact-generated <span class="hlt">hydrothermal</span> systems have been suggested to possess the same life supporting capability as <span class="hlt">hydrothermal</span> systems associated with volcanic <span class="hlt">activity</span>. However, evidence of fossil microbial colonization in impact-generated <span class="hlt">hydrothermal</span> systems is scarce in the literature. Here we report of fossilized microorganisms in association with cavity-grown <span class="hlt">hydrothermal</span> minerals from the 458 Ma Lockne impact structure, Sweden. Based on morphological characteristics the fossilized microorganisms are interpreted as fungi. We further infer the kerogenization of the microfossils, and thus the life span of the fungi, to be contemporaneous with the <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> and migration of hydrocarbons in the system. Our results from the Lockne impact structure show that <span class="hlt">hydrothermal</span> systems associated with impact structures can support colonization by microbial life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24336641','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24336641"><span id="translatedtitle">Fungal colonization of an Ordovician impact-induced <span class="hlt">hydrothermal</span> system.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ivarsson, Magnus; Broman, Curt; Sturkell, Erik; Ormö, Jens; Siljeström, Sandra; van Zuilen, Mark; Bengtson, Stefan</p> <p>2013-01-01</p> <p>Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced <span class="hlt">hydrothermal</span> convection. Impact-generated <span class="hlt">hydrothermal</span> systems have been suggested to possess the same life supporting capability as <span class="hlt">hydrothermal</span> systems associated with volcanic <span class="hlt">activity</span>. However, evidence of fossil microbial colonization in impact-generated <span class="hlt">hydrothermal</span> systems is scarce in the literature. Here we report of fossilized microorganisms in association with cavity-grown <span class="hlt">hydrothermal</span> minerals from the 458 Ma Lockne impact structure, Sweden. Based on morphological characteristics the fossilized microorganisms are interpreted as fungi. We further infer the kerogenization of the microfossils, and thus the life span of the fungi, to be contemporaneous with the <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> and migration of hydrocarbons in the system. Our results from the Lockne impact structure show that <span class="hlt">hydrothermal</span> systems associated with impact structures can support colonization by microbial life. PMID:24336641</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014QSRv...96..204G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014QSRv...96..204G"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> <span class="hlt">activity</span> and its paleoecological implications in the latest Miocene to Middle Pleistocene lacustrine environments of the Baza Basin (Betic Cordillera, SE Spain)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>García-Aguilar, José Manuel; Guerra-Merchán, Antonio; Serrano, Francisco; Palmqvist, Paul; Flores-Moya, Antonio; Martínez-Navarro, Bienvenido</p> <p>2014-07-01</p> <p>The continental sedimentary record of the Baza Basin (Guadix-Baza Depression, Betic Cordillera, SE Spain) shows six sedimentary units of lacustrine origin deposited from the latest Miocene to the Middle Pleistocene. Depending on the interval considered, the lacustrine deposits are mainly composed of marls, carbonates or gypsiferous evaporites, showing lithological, mineralogical and geochemical features (i.e., magnesium, strontium and sulfur contents, celestine deposits and travertine growths) that are evidence of intense, tectonically-induced <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>. According to the high concentrations of strontium and sulfur as well as the abundance of travertines and magnesium clays, the supply of hot waters was greater during the Zanclean, the Gelasian and the Calabrian, as a result of tectonic <span class="hlt">activity</span>. <span class="hlt">Hydrothermal</span> <span class="hlt">activity</span> has continued until the present time and is responsible of the hot springs that are nowadays <span class="hlt">active</span> in the Guadix-Baza Depression. The paleoenvironmental consequences of these sublacustrine hot springs were that during some intervals the lakes maintained a relatively permanent water table, not subject to periodic desiccations in the dry season, and warmer temperatures throughout the year. This resulted in a high level of organic productivity, especially for the Calabrian, which allowed the development of a rich and well diversified mammalian community, similar to those of modern African savannas with tree patches. In this mild environment, the permanent water sheet favored the presence of drought intolerant megaherbivores such as the giant extinct hippo Hippopotamus antiquus. The high standing crop biomass of ungulates resulted in the availability of abundant carcasses for scavengers such as hyenas and hominins, which explains the very high densities of skeletal remains preserved in the sediments distributed along the lake surroundings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25681182','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25681182"><span id="translatedtitle">Quantitative PCR analysis of functional genes in iron-rich microbial mats at an <span class="hlt">active</span> <span class="hlt">hydrothermal</span> vent system (Lō'ihi Seamount, Hawai'i).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jesser, Kelsey J; Fullerton, Heather; Hager, Kevin W; Moyer, Craig L</p> <p>2015-05-01</p> <p>The chemolithotrophic Zetaproteobacteria represent a novel class of Proteobacteria which oxidize Fe(II) to Fe(III) and are the dominant bacterial population in iron-rich microbial mats. Zetaproteobacteria were first discovered at Lō'ihi Seamount, located 35 km southeast off the big island of Hawai'i, which is characterized by low-temperature diffuse <span class="hlt">hydrothermal</span> venting. Novel nondegenerate quantitative PCR (qPCR) assays for genes associated with microbial nitrogen fixation, denitrification, arsenic detoxification, Calvin-Benson-Bassham (CBB), and reductive tricarboxylic acid (rTCA) cycles were developed using selected microbial mat community-derived metagenomes. Nitrogen fixation genes were not detected, but all other functional genes were present. This suggests that arsenic detoxification and denitrification processes are likely cooccurring in addition to two modes of carbon fixation. Two groups of microbial mat community types were identified by terminal restriction fragment length polymorphism (T-RFLP) and were further described based on qPCR data for zetaproteobacterial abundance and carbon fixation mode preference. qPCR variance was associated with mat morphology but not with temperature or sample <span class="hlt">site</span>. Geochemistry data were significantly associated with sample <span class="hlt">site</span> and mat morphology. Together, these qPCR assays constitute a functional gene signature for iron microbial mat communities across a broad array of temperatures, mat types, chemistries, and sampling <span class="hlt">sites</span> at Lō'ihi Seamount.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4393452','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4393452"><span id="translatedtitle">Quantitative PCR Analysis of Functional Genes in Iron-Rich Microbial Mats at an <span class="hlt">Active</span> <span class="hlt">Hydrothermal</span> Vent System (Lō'ihi Seamount, Hawai'i)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jesser, Kelsey J.; Fullerton, Heather; Hager, Kevin W.</p> <p>2015-01-01</p> <p>The chemolithotrophic Zetaproteobacteria represent a novel class of Proteobacteria which oxidize Fe(II) to Fe(III) and are the dominant bacterial population in iron-rich microbial mats. Zetaproteobacteria were first discovered at Lō'ihi Seamount, located 35 km southeast off the big island of Hawai'i, which is characterized by low-temperature diffuse <span class="hlt">hydrothermal</span> venting. Novel nondegenerate quantitative PCR (qPCR) assays for genes associated with microbial nitrogen fixation, denitrification, arsenic detoxification, Calvin-Benson-Bassham (CBB), and reductive tricarboxylic acid (rTCA) cycles were developed using selected microbial mat community-derived metagenomes. Nitrogen fixation genes were not detected, but all other functional genes were present. This suggests that arsenic detoxification and denitrification processes are likely cooccurring in addition to two modes of carbon fixation. Two groups of microbial mat community types were identified by terminal restriction fragment length polymorphism (T-RFLP) and were further described based on qPCR data for zetaproteobacterial abundance and carbon fixation mode preference. qPCR variance was associated with mat morphology but not with temperature or sample <span class="hlt">site</span>. Geochemistry data were significantly associated with sample <span class="hlt">site</span> and mat morphology. Together, these qPCR assays constitute a functional gene signature for iron microbial mat communities across a broad array of temperatures, mat types, chemistries, and sampling <span class="hlt">sites</span> at Lō'ihi Seamount. PMID:25681182</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B13C0479H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B13C0479H"><span id="translatedtitle">Microbial and Mineral Descriptions of the Interior Habitable Zones of <span class="hlt">Active</span> <span class="hlt">Hydrothermal</span> Chimneys from the Endeavour Segment, Juan de Fuca Ridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holden, J. F.; Lin, T.; Ver Eecke, H. C.; Breves, E.; Dyar, M. D.; Jamieson, J. W.; Hannington, M. D.; Butterfield, D. A.; Bishop, J. L.; Lane, M. D.</p> <p>2013-12-01</p> <p><span class="hlt">Actively</span> venting <span class="hlt">hydrothermal</span> chimneys and their associated <span class="hlt">hydrothermal</span> fluids were collected from the Endeavour Segment, Juan de Fuca Ridge to determine the mineralogy, chemistry and microbial community composition of their interiors. To characterize the mineralogy, Mössbauer, FTIR, VNIR and thermal emission spectroscopies were used for the first time on this type of sample in addition to thin-section petrography, x-ray diffraction and elemental analyses. A chimney from the Bastille edifice was Fe-sulfide rich and composed primarily of chalcopyrite, marcasite-sphalerite, and pyrrhotite while chimneys from the Dante and Hot Harold edifices were Fe-sulfide poor and composed primarily of anhydrite. The bulk emissivity and reflectance spectroscopies corroborated well with the petrography and XRD analyses. The microbial community in the interior of Bastille was most closely related to mesophilic-to-thermophilic anaerobes of the deltaproteobacteria and hyperthermophilic archaea while those in the interiors of Dante and Hot Harold were most closely related to mesophilic-to-thermophilic aerobes of the beta-, gamma- and epsilonproteobacteria. The fluid temperatures (282-321°C) and chemistries of the three chimneys were very similar suggesting that differences in mineralogy and microbial community compositions were more dependent on fluid flow characteristics and paragenesis within the chimney. Thin-section petrography of the interior of another <span class="hlt">hydrothermal</span> chimney collected from the Dante edifice (emitting 336°C fluid) shows a thin coat of Fe3+ oxide associated with amorphous silica on the exposed outer surfaces of pyrrhotite, sphalerite and chalcopyrite in pore spaces, along with anhydrite precipitation in the pores that is indicative of seawater ingress. The Fe-sulfide minerals were likely oxidized to ferrihydrite with increasing pH and Eh due to cooling and seawater exposure, providing reactants for bioreduction. Culture-based most-probable-number estimates of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/1968086','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/1968086"><span id="translatedtitle">N-methyl-D-aspartate recognition <span class="hlt">site</span> ligands modulate <span class="hlt">activity</span> at the coupled glycine recognition <span class="hlt">site</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hood, W F; Compton, R P; Monahan, J B</p> <p>1990-03-01</p> <p>In synaptic plasma membranes from rat forebrain, the potencies of glycine recognition <span class="hlt">site</span> agonists and antagonists for modulating [3H]1-[1-(2-thienyl)cyclohexyl]piperidine ([3H]TCP) binding and for displacing strychnine-insensitive [3H]glycine binding are altered in the presence of N-methyl-D-aspartate (NMDA) recognition <span class="hlt">site</span> ligands. The NMDA competitive antagonist, cis-4-phosphonomethyl-2-piperidine carboxylate (CGS 19755), reduces [3H]glycine binding, and the reduction can be fully reversed by the NMDA recognition <span class="hlt">site</span> agonist, L-glutamate. Scatchard analysis of [3H]glycine binding shows that in the presence of CGS 19755 there is no change in Bmax (8.81 vs. 8.79 pmol/mg of protein), but rather a decrease in the affinity of glycine (KD of 0.202 microM vs. 0.129 microM). Similar decreases in affinity are observed for the glycine <span class="hlt">site</span> agonists, D-serine and 1-aminocyclopropane-1-carboxylate, in the presence of CGS 19755. In contrast, the affinity of glycine antagonists, 1-hydroxy-3-amino-2-pyrrolidone and 1-aminocyclobutane-1-carboxylate, at this [3H]glycine recognition <span class="hlt">site</span> increases in the presence of CGS 19755. The functional consequence of this change in affinity was addressed using the modulation of [3H]TCP binding. In the presence of L-glutamate, the potency of glycine agonists for the stimulation of [3H]TCP binding increases, whereas the potency of glycine antagonists decreases. These data are consistent with NMDA recognition <span class="hlt">site</span> ligands, through their interactions at the NMDA recognition <span class="hlt">site</span>, modulating <span class="hlt">activity</span> at the associated glycine recognition <span class="hlt">site</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998DSRII..45..319V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998DSRII..45..319V"><span id="translatedtitle">Naked in toxic fluids: A nudibranch mollusc from <span class="hlt">hydrothermal</span> vents</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Valdés, Ángel; Bouchet, Philippe</p> <p>1998-01-01</p> <p>A new species of the nudibranch genus Dendronotus (Mollusca, Opisthobranchia) is reported from a <span class="hlt">hydrothermal</span> vent at the Lucky Strike area, on the Mid-Atlantic Ridge. This is the first species of nudibranch recorded with certainty from a vent <span class="hlt">site</span>. Other species of Dendronotus are distributed in temperate waters on the continental shelf of the northern hemisphere. Two factors that probably account for the occurrence of a nudibranch in this <span class="hlt">hydrothermal</span> field are that the Lucky Strike area presents potential hydroid prey, and that nudibranchs apparently inhabit a lower <span class="hlt">activity</span> area. It is hypothesized that the new species, which lacks eyes, is a permanent resident of vent fields on the Mid-Atlantic Ridge, but is probably not restricted to that environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.V43B2880G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.V43B2880G"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> Monitoring in a Quiescent Volcanic Arc: Cascade Range, Northwestern United States</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gelwick, K.; Randolph-Flagg, N. G.; Crankshaw, I. M.; McCulloch, C. L.; Lundstrom, E. A.; Murveit, A. M.; Bergfeld, D.; Spicer, K.; Tucker, D.; Schmidt, M. E.; Mariner, R. H.; Evans, W.; Ingebritsen, S.</p> <p>2013-12-01</p> <p>Ongoing (1996-present) volcanic unrest near South Sister, Oregon, is accompanied by a striking set of <span class="hlt">hydrothermal</span> anomalies, including elevated temperatures, elevated major-ion concentrations, and 3He/4He ratios as large as 8.6 RA in slightly thermal springs. These observations prompted the U.S. Geological Survey to begin a systematic <span class="hlt">hydrothermal</span>-monitoring effort encompassing 25 <span class="hlt">sites</span> and 10 of the highest-risk volcanoes in the Cascade Range volcanic arc, from Mount Baker near the Canadian border to Mount Lassen in northern California. A concerted effort was made to develop hourly records of temperature and (or) <span class="hlt">hydrothermal</span> solute flux spanning multiple years, suitable for comparison with other continuous geophysical monitoring data. Monitored <span class="hlt">sites</span> included summit-fumarole groups and springs/streams that show clear evidence of magmatic influence in the form of high 3He/4He ratios and (or) large fluxes of magmatic CO2 or heat. As of 2009-2012 measured summit-fumarole temperatures in the Cascade Range were generally near or below the local pure-water boiling point; the maximum observed superheat was <+2.5°C at Mount Baker. Temporal variability in ground-temperature records from the summit-fumarole <span class="hlt">sites</span> is temperature-dependent, with the hottest <span class="hlt">sites</span> tending to show less variability. Seasonal variability in the flux of <span class="hlt">hydrothermally</span> sourced major anions from the springs varied from essentially undetectable to a factor of 5-10. This range of observed behavior owes mainly to the local climate regime, with strongly snowmelt-influenced springs and streams exhibiting more variability. As of the end of the 2012 field season, there had been 87 occurrences of local seismic energy densities ~>0.001 J/m3 during periods of hourly record. <span class="hlt">Hydrothermal</span> responses to these small seismic stimuli were generally undetectable or ambiguous. Evaluation of multiyear to multi-decadal trends indicates that whereas the <span class="hlt">hydrothermal</span> system at Mount St. Helens is still fast-evolving in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26684507','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26684507"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> Conditions and the Origin of Cellular Life.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Deamer, David W; Georgiou, Christos D</p> <p>2015-12-01</p> <p>The conditions and properties of <span class="hlt">hydrothermal</span> vents and <span class="hlt">hydrothermal</span> fields are compared in terms of their ability to support processes related to the origin of life. The two <span class="hlt">sites</span> can be considered as alternative hypotheses, and from this comparison we propose a series of experimental tests to distinguish between them, focusing on those that involve concentration of solutes, self-assembly of membranous compartments, and synthesis of polymers. Key Word: <span class="hlt">Hydrothermal</span> systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26684507','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26684507"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> Conditions and the Origin of Cellular Life.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Deamer, David W; Georgiou, Christos D</p> <p>2015-12-01</p> <p>The conditions and properties of <span class="hlt">hydrothermal</span> vents and <span class="hlt">hydrothermal</span> fields are compared in terms of their ability to support processes related to the origin of life. The two <span class="hlt">sites</span> can be considered as alternative hypotheses, and from this comparison we propose a series of experimental tests to distinguish between them, focusing on those that involve concentration of solutes, self-assembly of membranous compartments, and synthesis of polymers. Key Word: <span class="hlt">Hydrothermal</span> systems. PMID:26684507</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.4085H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.4085H"><span id="translatedtitle">Postcaldera volcanism and <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> revealed by autonomous underwater vehicle surveys in Myojin Knoll caldera, Izu-Ogasawara arc</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Honsho, Chie; Ura, Tamaki; Kim, Kangsoo; Asada, Akira</p> <p>2016-06-01</p> <p>Myojin Knoll caldera, one of the submarine silicic calderas lying on the volcanic front of the northern Izu-Ogasawara arc, has attracted increasing attention since the discovery of a large <span class="hlt">hydrothermal</span> field called the Sunrise deposit. Although numerous submersible surveys have been conducted in Myojin Knoll caldera, they have not sufficiently explored areas to produce a complete picture of the caldera and understand the origin of the Sunrise deposit. We conducted comprehensive deep-sea surveys using an autonomous underwater vehicle and obtained high-resolution bathymetric and magnetic data and sonar images from ~70% of the caldera. The detailed bathymetric map revealed that faulting and magma eruptions, possibly associated with an inflation-deflation cycle of the magma reservoir during postcaldera volcanism, had generally occurred in the caldera wall. The main dome of the central cone was covered with lava flows and exhibits exogenous growth, which is unusual for rhyolitic domes. The magnetization distribution in the central cone indicates preferential magma intrusion along a NW-SE direction. It is presumed that magma migrated along this direction and formed a rhyolite dome at the foot of the southeastern caldera wall, where the Sunrise deposit occurs. The Sunrise deposit is composed mainly of three ridges extending in slope directions and covers ~400 × ~400 m. Magnetization reduction in the deposit area is small, indicating that the alteration zone beneath the Sunrise deposit is slanting rather than vertical. It is presumed that several slanting and near-vertical volcanic vents serve as pathways of <span class="hlt">hydrothermal</span> fluid in Myojin Knoll caldera.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5531936','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5531936"><span id="translatedtitle">Control of <span class="hlt">active</span> <span class="hlt">sites</span> in selective flocculation: I -- Mathematical model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Behl, S.; Moudgil, B.M.; Prakash, T.S. . Dept. of Materials Science and Engineering)</p> <p>1993-12-01</p> <p>Heteroflocculation has been determined to be another major reason for loss in selectivity for flocculation process. In a mathematical model developed earlier, conditions for controlling heteroflocculation were discussed. Blocking <span class="hlt">active</span> <span class="hlt">sites</span> to control selective adsorption of a flocculant oil a desirable solid surface is discussed. It has been demonstrated that the lower molecular weight fraction of a flocculant which is incapable of flocculating the particles is an efficient <span class="hlt">site</span> blocking agent. The major application of selective flocculation has been in mineral processing but many potential uses exist in biological and other colloidal systems. These include purification of ceramic powders, separating hazardous solids from chemical waste, and removal of deleterious components from paper pulp.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70111059','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70111059"><span id="translatedtitle">Dynamics of the Yellowstone <span class="hlt">hydrothermal</span> system</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hurwitz, Shaul; Lowenstern, Jacob B.</p> <p>2014-01-01</p> <p>The Yellowstone Plateau Volcanic Field is characterized by extensive seismicity, episodes of uplift and subsidence, and a <span class="hlt">hydrothermal</span> system that comprises more than 10,000 thermal features, including geysers, fumaroles, mud pots, thermal springs, and <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> explosions and their relation to glacial cycles, defining possible links between <span class="hlt">hydrothermal</span> <span class="hlt">activity</span>, deformation, and seismicity; quantifying geyser dynamics; and the discovery of extensive <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> in Yellowstone Lake. Discussion of these many advances forms the basis of this review.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/1799660','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/1799660"><span id="translatedtitle">The <span class="hlt">site</span> of <span class="hlt">activation</span> of factor X by cancer procoagulant.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gordon, S G; Mourad, A M</p> <p>1991-12-01</p> <p>Cancer procoagulant (CP) is a cysteine proteinase found in a variety of malignant cells and tissues and in human amnion-chorion tissue. It initiates coagulation by <span class="hlt">activating</span> factor X. However, the amino acid sequence of the substrate protein that determines the cleavage <span class="hlt">site</span> of cysteine proteinases is different from that of the serine proteinases that normally <span class="hlt">activate</span> factor X, such as factor IXa, VIIa and Russell's Viper Venom (RVV). Therefore, it was of interest to determine the <span class="hlt">site</span> of cleavage of human factor X by CP. Purified CP was incubated with purified factor X and the reaction mixture was electrophoresed on a 10% Tris-tricine SDS-PAGE gel. The proteins were electroeluted on to a polyvinylidene difluoride (PVDF) membrane, and stained with Coomassie blue. The heavy chain of <span class="hlt">activated</span> factor X was cut out of the PVDF membrane and sequenced with an Applied Biosystems 477A with on-line HPLC. The primary cleavage sequence was Asp-Ala-Ala-Asp-Leu-Asp-Pro-; two other secondary sequences Ser-Ile-Thr-Trp-Lys-Pro- and Glu-Asn-Pro-Phe-Asp-Leu were found. The penultimate amino acid on the carbonyl side of the hydrolysed amide bond plays a critical role for the recognition of the cleavage <span class="hlt">site</span> of cysteine proteinases. These data indicate that the penultimate amino acid for the primary cleavage <span class="hlt">site</span> of factor X by CP is proline-20 and for the secondary <span class="hlt">sites</span>, proline-13 and proline-28. This is in contrast to arginine-52 that determines the specificity of the cleavage by normal serine proteinase <span class="hlt">activation</span>.(ABSTRACT TRUNCATED AT 250 WORDS)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1028515','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1028515"><span id="translatedtitle"><span class="hlt">Active-Site</span>-Accessible, Porphyrinic Metal;#8722;Organic Framework Materials</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Farha, Omar K.; Shultz, Abraham M.; Sarjeant, Amy A.; Nguyen, SonBinh T.; Hupp, Joseph T.</p> <p>2012-02-06</p> <p>On account of their structural similarity to cofactors found in many metallo-enzymes, metalloporphyrins are obvious potential building blocks for catalytically <span class="hlt">active</span>, metal-organic framework (MOF) materials. While numerous porphyrin-based MOFs have already been described, versions featuring highly accessible <span class="hlt">active</span> <span class="hlt">sites</span> and permanent microporosity are remarkably scarce. Indeed, of the more than 70 previously reported porphyrinic MOFs, only one has been shown to be both permanently microporous and contain internally accessible <span class="hlt">active</span> <span class="hlt">sites</span> for chemical catalysis. Attempts to generalize the design approach used in this single successful case have failed. Reported here, however, is the synthesis of an extended family of MOFs that directly incorporate a variety of metalloporphyrins (specifically Al{sup 3+}, Zn{sup 2+}, Pd{sup 2+}, Mn{sup 3+}, and Fe{sup 3+} complexes). These robust porphyrinic materials (RPMs) feature large channels and readily accessible <span class="hlt">active</span> <span class="hlt">sites</span>. As an illustrative example, one of the manganese-containing RPMs is shown to be catalytically competent for the oxidation of alkenes and alkanes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17793659','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17793659"><span id="translatedtitle">Catastrophic volcanic collapse: relation to <span class="hlt">hydrothermal</span> processes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>López, D L; Williams, S N</p> <p>1993-06-18</p> <p>Catastrophic volcanic collapse, without precursory magmatic <span class="hlt">activity</span>, is characteristic of many volcanic disasters. The extent and locations of <span class="hlt">hydrothermal</span> discharges at Nevado del Ruiz volcano, Colombia, suggest that at many volcanoes collapse may result from the interactions between <span class="hlt">hydrothermal</span> fluids and the volcanic edifice. Rock dissolution and <span class="hlt">hydrothermal</span> mineral alteration, combined with physical triggers such as earth-quakes, can produce volcanic collapse. Hot spring water compositions, residence times, and flow paths through faults were used to model potential collapse at Ruiz. Caldera dimensions, deposits, and alteration mineral volumes are consistent with parameters observed at other volcanoes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/3010866','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/3010866"><span id="translatedtitle">Functional constituents of the <span class="hlt">active</span> <span class="hlt">site</span> of human neutrophil collagenase.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mookhtiar, K A; Wang, F; Van Wart, H E</p> <p>1986-05-01</p> <p>A series of chemical modification reactions has been carried out to identify functional constituents of the <span class="hlt">active</span> <span class="hlt">site</span> of human neutrophil collagenase. The enzyme is reversibly inhibited by the transition metal chelating agent 1,10-phenanthroline, and inhibition is fully reversed by zinc. Removal of weakly bound metal ions by gel filtration inactivates collagenase, and <span class="hlt">activity</span> is fully restored on immediate readdition of calcium. The enzyme is unaffected by reagents that modify serine, cysteine, and arginine residues. However, reaction with the carboxyl reagents cyclohexylmorpholinocarbodiimide and Woodward's Reagent K lowers the <span class="hlt">activity</span> of the enzyme substantially. Acetylimidazole inactivates the enzyme, but <span class="hlt">activity</span> is completely restored on addition of hydroxylamine. The enzyme is also inactivated by tetranitromethane, indicating that it contains an essential tyrosine residue. Acylation of collagenase with diethyl pyrocarbonate, diketene, acetic anhydride, or trinitrobenzenesulfonate inactivates the enzyme, and <span class="hlt">activity</span> is not restored on addition of hydroxylamine, indicating the presence of an essential lysine residue.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AGUFM.V21A4726X&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AGUFM.V21A4726X&link_type=ABSTRACT"><span id="translatedtitle">Modeling mid-ocean ridge <span class="hlt">hydrothermal</span> response to earthquakes, tides, and ocean currents: a case study at the Grotto mound, Endeavour Segment, Juan de Fuca Ridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, G.; Bemis, K. G.</p> <p>2014-12-01</p> <p>Seafloor <span class="hlt">hydrothermal</span> systems feature intricate interconnections among oceanic, geological, <span class="hlt">hydrothermal</span>, and biological processes. The advent of the NEPTUNE observatory operated by Ocean Networks Canada at the Endeavour Segment, Juan de Fuca Ridge enables scientists to study these interconnections through multidisciplinary, continuous, real-time observations. The multidisciplinary observatory instruments deployed at the Grotto Mound, a major study <span class="hlt">site</span> of the NEPTUNE observatory, makes it a perfect place to study the response of a seafloor <span class="hlt">hydrothermal</span> system to geological and oceanic processes. In this study, we use the multidisciplinary datasets recorded by the NEPTUNE Observatory instruments as observational tools to demonstrate two different aspects of the response of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at the Grotto Mound to geological and oceanic processes. First, we investigate a recent increase in venting temperature and heat flux at Grotto observed by the Benthic and Resistivity Sensors (BARS) and the Cabled Observatory Vent Imaging Sonar (COVIS) respectively. This event started in Mar 2014 and is still evolving by the time of writing this abstract. An initial interpretation in light of the seismic data recorded by a neighboring ocean bottom seismometer on the NEPTUNE observatory suggests the temperature and heat flux increase is probably triggered by local seismic <span class="hlt">activities</span>. Comparison of the observations with the results of a 1-D mathematical model simulation of <span class="hlt">hydrothermal</span> sub-seafloor circulation elucidates the potential mechanisms underlying <span class="hlt">hydrothermal</span> response to local earthquakes. Second, we observe significant tidal oscillations in the venting temperature time series recorded by BARS and the acoustic imaging of <span class="hlt">hydrothermal</span> plumes by COVIS, which is evidence for <span class="hlt">hydrothermal</span> response to ocean tides and currents. We interpret the tidal oscillations of venting temperature as a result of tidal loading on a poroelastic medium. We then invoke poroelastic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1110443H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1110443H"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> mixing: Fuel for life in the deep-sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hentscher, M.; Bach, W.; Amend, J.; McCollom, T.</p> <p>2009-04-01</p> <p>Deep-sea <span class="hlt">hydrothermal</span> vent systems show a wide range of fluid compositions and temperatures. They reach from highly alkaline and reducing, like the Lost City <span class="hlt">hydrothermal</span> field, to acidic and reducing conditions, (e. g., the Logatchev <span class="hlt">hydrothermal</span> field) to acidic and oxidizing conditions (e. g., island arc hosted systems). These apparently hostile vent systems are generally accompanied by high microbial <span class="hlt">activity</span> forming the base of a food-web that often includes higher organisms like mussels, snails, or shrimp. The primary production is boosted by mixing of chemically reduced <span class="hlt">hydrothermal</span> vent fluids with ambient seawater, which generates redox disequilibria that serve as energy source for chemolithoautotrophic microbial life. We used geochemical reaction path models to compute the affinities of catabolic (energy-harvesting) and anabolic (biosynthesis) reactions along trajectories of batch mixing between vent fluids and 2 °C seawater. Geochemical data of endmember <span class="hlt">hydrothermal</span> fluids from 12 different vent fields (Lost City, Rainbow, Logatchev, TAG, EPR 21 °N, Manus Basin, Mariana Arc, etc.) were included in this reconnaissance study of the variability in metabolic energetics in global submarine vent systems. The results show a distinction between ultramafic-hosted and basalt-hosted <span class="hlt">hydrothermal</span> systems. The highest energy yield for chemolithotrophic catabolism in ultramafic-hosted <span class="hlt">hydrothermal</span> systems is reached at low temperature and under slightly aerobic to aerobic conditions. The dominant reactions, for example at Rainbow or Lost City, are the oxidation of H2, Fe2+ and methane. At temperatures >60 °C, anaerobic metabolic reactions, e. g., sulphate reduction and methanogenesis, become more profitable. In contrast, basalt-hosted systems, such as TAG and 21 °N EPR uniformly indicate H2S oxidation to be the catabolically dominant reaction over the entire microbial-relevant temperature range. Affinities were calculated for the formation of individual cellular</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930034010&hterms=organic+synthesis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dorganic%2Bsynthesis','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930034010&hterms=organic+synthesis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dorganic%2Bsynthesis"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> organic synthesis experiments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shock, Everett L.</p> <p>1992-01-01</p> <p>Ways in which heat is useful in organic synthesis experiments are described, and experiments on the <span class="hlt">hydrothermal</span> destruction and synthesis of organic compounds are discussed. It is pointed out that, if heat can overcome kinetic barriers to the formation of metastable states from reduced or oxidized starting materials, abiotic synthesis under <span class="hlt">hydrothermal</span> conditions is a distinct possibility. However, carefully controlled experiments which replicate the descriptive variables of natural <span class="hlt">hydrothermal</span> systems have not yet been conducted with the aim of testing the hypothesis of <span class="hlt">hydrothermal</span> organic systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMOS22A..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMOS22A..07S"><span id="translatedtitle">Discovery of Nascent Vents and Recent Colonization Associated with(Re)<span class="hlt">activated</span> <span class="hlt">Hydrothermal</span> Vent Fields by the GALREX 2011 Expedition on the Galápagos Rift</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shank, T. M.; Holden, J. F.; Herrera, S.; Munro, C.; Muric, T.; Lin, J.; Stuart, L.</p> <p>2011-12-01</p> <p>GALREX 2011 was a NOAA OER telepresence cruise that explored the diverse habitats and geologic settings of the deep Galápagos region. The expedition made12 Little Hercules ROV dives in July 2011.Abundant corals and a strong depth zonation of species (including deepwater coral communities) were found near 500 m depth on Paramount Seamount, likely influenced by past low sea level states, wave-cut terrace processes, and the historical presence of shallow reef structures. At fresh lava flows with associated (flocculent) <span class="hlt">hydrothermal</span> venting near 88° W, now known as Uka Pacha and Pegasus Vent Fields, rocks were coated with white microbial mat and lacked sessile fauna, with few mobile fauna (e.g., bythograeid crabs, alvinocarid shrimp, polynoid worms, zoarcid fish, and dirivultid copepods). This suggests a recent creation of <span class="hlt">hydrothermal</span> habitats through volcanic eruptions and/or diking events, which may have taken place over a 15 km span separating the two vent fields. The Rosebud vent field at 86°W was not observed and may have been covered with lava since last visited in 2005. A <span class="hlt">hydrothermal</span> vent field near 86°W was discovered that is one of the largest vent fields known on the Rift (120m by 40m). Low-temperature vent habitats were colonized by low numbers of tubeworms including Riftia, Oasisia, and a potential Tevnia species (the latter not previously observed on the Galapagos Rift). Patches of tubeworms were observed with individuals less than 2cm in length, and the relatively few large Riftia had tube lengths near 70cm long. Large numbers of small (< 3cm long) bathymodiolin mussels lined cracks and crevices throughout the <span class="hlt">active</span> part of the field. Live clams, at least four species of gastropod limpets, three species of polynoid polychaetes, juvenile and adult alvinocarid shrimp, actinostolid anemones, and white microbial communities were observed on the underside and vertical surfaces of basalt rock surfaces. There were at least 13 species of vent-endemic fauna</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70022212','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70022212"><span id="translatedtitle">Nest predation increases with parental <span class="hlt">activity</span>: Separating nest <span class="hlt">site</span> and parental <span class="hlt">activity</span> effects</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Martin, T.E.; Scott, J.; Menge, C.</p> <p>2000-01-01</p> <p>Alexander Skutch hypothesized that increased parental <span class="hlt">activity</span> can increase the risk of nest predation. We tested this hypothesis using ten open-nesting bird species in Arizona, USA. Parental <span class="hlt">activity</span> was greater during the nestling than incubation stage because parents visited the nest frequently to feed their young during the nestling stage. However, nest predation did not generally increase with parental <span class="hlt">activity</span> between nesting stages across the ten study species. Previous investigators have found similar results. We tested whether nest <span class="hlt">site</span> effects might yield higher predation during incubation because the most obvious <span class="hlt">sites</span> are depredated most rapidly. We conducted experiments using nest <span class="hlt">sites</span> from the previous year to remove parental <span class="hlt">activity</span>. Our results showed that nest <span class="hlt">sites</span> have highly repeatable effects on nest predation risk; poor nest <span class="hlt">sites</span> incurred rapid predation and caused predation rates to be greater during the incubation than nestling stage. This pattern also was exhibited in a bird species with similar (i.e. controlled) parental <span class="hlt">activity</span> between nesting stages. Once nest <span class="hlt">site</span> effects are taken into account, nest predation shows a strong proximate increase with parental <span class="hlt">activity</span> during the nestling stage within and across species. Parental <span class="hlt">activity</span> and nest <span class="hlt">sites</span> exert antagonistic influences on current estimates of nest predation between nesting stages and both must be considered in order to understand current patterns of nest predation, which is an important source of natural selection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GGG....15.3430D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GGG....15.3430D"><span id="translatedtitle">Insights into magmatic processes and <span class="hlt">hydrothermal</span> alteration of in situ superfast spreading ocean crust at ODP/IODP <span class="hlt">site</span> 1256 from a cluster analysis of rock magnetic properties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dekkers, Mark J.; Heslop, David; Herrero-Bervera, Emilio; Acton, Gary; Krasa, David</p> <p>2014-08-01</p> <p>analyze magnetic properties from Ocean Drilling Program (ODP)/Integrated ODP (IODP) Hole 1256D (6°44.1' N, 91°56.1' W) on the Cocos Plate in ˜15.2 Ma oceanic crust generated by superfast seafloor spreading, the only drill hole that has sampled all three oceanic crust layers in a tectonically undisturbed setting. Fuzzy c-means cluster analysis and nonlinear mapping are utilized to study down-hole trends in the ratio of the saturation remanent magnetization and the saturation magnetization, the coercive force, the ratio of the remanent coercive force and coercive force, the low-field magnetic susceptibility, and the Curie temperature, to evaluate the effects of magmatic and <span class="hlt">hydrothermal</span> processes on magnetic properties. A statistically robust five cluster solution separates the data predominantly into three clusters that express increasing <span class="hlt">hydrothermal</span> alteration of the lavas, which differ from two distinct clusters mainly representing the dikes and gabbros. Extensive alteration can obliterate magnetic property differences between lavas, dikes, and gabbros. The imprint of thermochemical alteration on the iron-titanium oxides is only partially related to the porosity of the rocks. Thus, the analysis complements interpretation based on electrofacies analysis. All clusters display rock magnetic characteristics compatible with an ability to retain a stable natural remanent magnetization suggesting that the entire sampled sequence of ocean crust can contribute to marine magnetic anomalies. Paleointensity determination is difficult because of the propensity of oxyexsolution during laboratory heating and/or the presence of intergrowths. The upper part of the extrusive sequence, the granoblastic dikes, and moderately altered gabbros may contain a comparatively uncontaminated thermoremanent magnetization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22475901','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22475901"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> synthesis and photocatalytic <span class="hlt">activities</span> of Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} composite micro-platelets</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhao, Wei Wang, Hongxing; Feng, Xiangning; Jiang, Wangyang; Zhao, Dan; Li, Jiyuan</p> <p>2015-10-15</p> <p>Highlights: • Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} composite was fabricated by combining <span class="hlt">hydrothermal</span> reaction and molten salt method. • Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} exhibits higher photocatalytic <span class="hlt">activity</span> than pure Bi{sub 4}Ti{sub 3}O{sub 12}. • The absorption light of Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} has been broadened to visible light. - Abstract: In this study, Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} micro-platelets were successfully synthesized by using <span class="hlt">hydrothermal</span> and molten salt methods, and the morphology and photocatalytic degradation performance of Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} was characterized. The results indicated a much higher degradation rate of methylene blue and methylene orange, reaching more than 90% and 65%, respectively, within 3 h under visible-light irradiation. Compared with pure Bi{sub 4}Ti{sub 3}O{sub 12}, the photocatalytic <span class="hlt">activity</span> of Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} was significantly better, due to the micron–submicron heterojunction with SrTiO{sub 3} reducing the band gap of Bi{sub 4}Ti{sub 3}O{sub 12}. In addition, the perovskite structure layer facilitates the mobility of the photogenerated carriers and hampers their recombination, which were affected the photocatalytic properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23211727','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23211727"><span id="translatedtitle"><span class="hlt">Active</span> <span class="hlt">sites</span>, deactivation and stabilization of Fe-ZSM-5 for the selective catalytic reduction (SCR) of NO with NH(3).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kröcher, Oliver; Brandenberger, Sandro</p> <p>2012-01-01</p> <p>Fe-ZSM-5 has been systematically investigated as catalyst for the selective catalytic reduction (SCR) of NO with NH(3), concentrating on the <span class="hlt">active</span> <span class="hlt">sites</span>, the deactivation mechanism during <span class="hlt">hydrothermal</span> aging and the chemical possibilities to stabilize this type of SCR catalyst. Regarding the <span class="hlt">active</span> SCR <span class="hlt">sites</span>, it could be shown that monomeric species start to become <span class="hlt">active</span> at the lowest temperatures (E(a,app) ≈ 36.3 ± 0.2 kJ/mol), followed by dimeric species at intermediate temperatures (E(a,app) ≈ 77 ± 16 kJ/mol) and oligomeric species at high temperatures. Experiments with Fe-ZSM-5 samples, in which the Brønsted acidity was specifically removed, proved that Brønsted acidity is not required for high SCR <span class="hlt">activity</span> and that NH(3) can also be adsorbed on other acidic <span class="hlt">sites</span> on the zeolite surface. The <span class="hlt">hydrothermal</span> deactivation of Fe-ZSM-5 could be explained by the migration of <span class="hlt">active</span> iron ions from the exchange <span class="hlt">sites</span>. Parallel to the iron migration dealumination of the zeolite framework occurs, which has to be regarded as an independent process. The migration of iron can be reduced by the targeted reaction of the aluminum hydroxide groups in the lattice with trimethylaluminium followed by calcination. With respect to the application of iron zeolites in the SCR process in diesel vehicles, the most efficient stabilization method would be to switch from the ZSM-5 to the BEA structure type. The addition of NO(2) to the feed gas is another effective measure to increase the <span class="hlt">activity</span> of even strongly deactivated iron zeolites tremendously.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5760343','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5760343"><span id="translatedtitle"><span class="hlt">Active</span> <span class="hlt">sites</span> in char gasification: Final technical report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wojtowicz, M.; Lilly, W.D.; Perkins, M.T.; Hradil, G.; Calo, J.M.; Suuberg, E.M.</p> <p>1987-09-01</p> <p>Among the key variables in the design of gasifiers and combustors is the reactivity of the chars which must be gasified or combusted. Significant loss of unburned char is unacceptable in virtually any process; the provision of sufficient residence time for complete conversion is essential. A very wide range of reactivities are observed, depending upon the nature of the char in a process. The current work focuses on furthering the understanding of gasification reactivities of chars. It has been well established that the reactivity of char to gasification generally depends upon three principal factors: (1) the concentration of ''<span class="hlt">active</span> <span class="hlt">sites</span>'' in the char; (2) mass transfer within the char; and (3) the type and concentration of catalytic impurities in the char. The present study primarily addresses the first factor. The subject of this research is the origin, nature, and fate of <span class="hlt">active</span> <span class="hlt">sites</span> in chars derived from parent hydrocarbons with coal-like structure. The nature and number of the <span class="hlt">active</span> <span class="hlt">sites</span> and their reactivity towards oxygen are examined in ''model'' chars derived from phenol-formaldehyde type resins. How the <span class="hlt">active</span> <span class="hlt">sites</span> are lost by the process of thermal annealing during heat treatment of chars are studied, and actual rate for the annealing process is derived. Since intrinsic char reactivities are of primary interest in the present study, a fair amount of attention was given to the model char synthesis and handling so that the effect of catalytic impurities and oxygen-containing functional groups in the chemical structure of the material were minimized, if not completely eliminated. The project would not be considered complete without comparing characteristic features of synthetic chars with kinetic behavior exhibited by natural chars, including coal chars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22420026','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22420026"><span id="translatedtitle">Brownian aggregation rate of colloid particles with several <span class="hlt">active</span> <span class="hlt">sites</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nekrasov, Vyacheslav M.; Yurkin, Maxim A.; Chernyshev, Andrei V.; Polshchitsin, Alexey A.; Yakovleva, Galina E.; Maltsev, Valeri P.</p> <p>2014-08-14</p> <p>We theoretically analyze the aggregation kinetics of colloid particles with several <span class="hlt">active</span> <span class="hlt">sites</span>. Such particles (so-called “patchy particles”) are well known as chemically anisotropic reactants, but the corresponding rate constant of their aggregation has not yet been established in a convenient analytical form. Using kinematic approximation for the diffusion problem, we derived an analytical formula for the diffusion-controlled reaction rate constant between two colloid particles (or clusters) with several small <span class="hlt">active</span> <span class="hlt">sites</span> under the following assumptions: the relative translational motion is Brownian diffusion, and the isotropic stochastic reorientation of each particle is Markovian and arbitrarily correlated. This formula was shown to produce accurate results in comparison with more sophisticated approaches. Also, to account for the case of a low number of <span class="hlt">active</span> <span class="hlt">sites</span> per particle we used Monte Carlo stochastic algorithm based on Gillespie method. Simulations showed that such discrete model is required when this number is less than 10. Finally, we applied the developed approach to the simulation of immunoagglutination, assuming that the formed clusters have fractal structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6992554','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6992554"><span id="translatedtitle"><span class="hlt">Active</span> <span class="hlt">Sites</span> Environmental Monitoring Program: FY 1991 report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ashwood, T.L.; Hicks, D.S.; Morrissey, C.M.</p> <p>1992-11-01</p> <p>This report summarizes the <span class="hlt">activities</span> of the <span class="hlt">Active</span> <span class="hlt">Sites</span> Environmental Monitoring Program (ASEMP) from April 1991 through September 1991. The ASEMP was established in 1989 by Solid Waste Operations (SWO) and the Environmental Sciences Division, both of Oak Ridge National Laboratory, to provide early detection and performance monitoring at <span class="hlt">active</span> low-level (radioactive) waste (LLW) disposal <span class="hlt">sites</span> in Solid Waste Storage Area (SWSA) 6 and transuranic (TRU) waste storage <span class="hlt">sites</span> in SWSA 5 as required by chapters II and III of US Department of Energy Order 5820.2A. A new set of action levels was developed on the basis of a statistical analysis of background contamination. These new action levels have been used to evaluate results in this report. Results of ASEMP monitoring continue to demonstrate that no LLW (except [sup 3]H) is being leached from the storage vaults on the tumulus pads. Loading of vaults on Tumulus II, which began in early FY 1991, was >90% complete at the end of September 1991. Results of sampling of groundwater and surface waters is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/2924773','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/2924773"><span id="translatedtitle">Inhibition and <span class="hlt">active-site</span> modelling of prolidase.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>King, G F; Crossley, M J; Kuchel, P W</p> <p>1989-03-15</p> <p>Consideration of the <span class="hlt">active-site</span> model of prolidase led us to examine azetidine, pyrrolidine and piperidine substrate analogs as potential in vivo inhibitors of the enzyme. One of these, N-benzyloxycarbonyl-L-proline, was shown to be a potent competitive inhibitor of porcine kidney prolidase (Ki = 90 microM); its rapid protein-mediated permeation of human and sheep erythrocytes suggests that it may be effective in vivo. The higher homolog, N-benzyloxycarbonyl-L-pipecolic acid, was also a potent inhibitor of the enzyme while the antihypertensive drugs, captopril and enalaprilat, were shown to have mild and no inhibitory effects, respectively. Analysis of inhibitor action and consideration of X-ray crystallographic data of relevant Mn2+ complexes allowed the <span class="hlt">active-site</span> model of prolidase to be further refined; a new model is presented in which the substrate acts as a bidentate ligand towards the <span class="hlt">active-site</span> manganous ion. Various aspects of the new model help to explain why Mn2+ has been 'chosen' by the enzyme in preference to other biologically available metal ions. PMID:2924773</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5158533','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5158533"><span id="translatedtitle">Rare earth element systematics in <span class="hlt">hydrothermal</span> fluids</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Michard, A. )</p> <p>1989-03-01</p> <p>Rare earth element concentrations have been measured in <span class="hlt">hydrothermal</span> solutions from geothermal fields in Italy, Dominica, Valles Caldera, Salton Sea and the Mid-Atlantic Ridge. The measured abundances show that <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> is not expected to affect the REE balance of either continental or oceanic rocks. The REE enrichment of the solutions increases when the pH decreases. High-temperature solutions (> 230{degree}C) percolating through different rock types may show similar REE patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5347450','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5347450"><span id="translatedtitle"><span class="hlt">Hydrothermal</span> industrialization: direct heat development. Final report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1982-05-01</p> <p>A description of <span class="hlt">hydrothermal</span> resources suitable for direct applications, their associated temperatures, geographic distribution and developable capacity are given. An overview of the <span class="hlt">hydrothermal</span> direct-heat development infrastructure is presented. Development <span class="hlt">activity</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3705409','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3705409"><span id="translatedtitle">Unusual Glycosaminoglycans from a Deep Sea <span class="hlt">Hydrothermal</span> Bacterium Improve Fibrillar Collagen Structuring and Fibroblast <span class="hlt">Activities</span> in Engineered Connective Tissues</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Senni, Karim; Gueniche, Farida; Changotade, Sylvie; Septier, Dominique; Sinquin, Corinne; Ratiskol, Jacqueline; Lutomski, Didier; Godeau, Gaston; Guezennec, Jean; Colliec-Jouault, Sylvia</p> <p>2013-01-01</p> <p>Biopolymers produced by marine organisms can offer useful tools for regenerative medicine. Particularly, HE800 exopolysaccharide (HE800 EPS) secreted by a deep-sea <span class="hlt">hydrothermal</span> bacterium displays an interesting glycosaminoglycan-like feature resembling hyaluronan. Previous studies demonstrated its effectiveness to enhance in vivo bone regeneration and to support osteoblastic cell metabolism in culture. Thus, in order to assess the usefulness of this high-molecular weight polymer in tissue engineering and tissue repair, in vitro reconstructed connective tissues containing HE800 EPS were performed. We showed that this polysaccharide promotes both collagen structuring and extracellular matrix settle by dermal fibroblasts. Furthermore, from the native HE800 EPS, a low-molecular weight sulfated derivative (HE800 DROS) displaying chemical analogy with heparan-sulfate, was designed. Thus, it was demonstrated that HE800 DROS mimics some properties of heparan-sulfate, such as promotion of fibroblast proliferation and inhibition of matrix metalloproteinase (MMP) secretion. Therefore, we suggest that the HE800EPS family can be considered as an innovative biotechnological source of glycosaminoglycan-like compounds useful to design biomaterials and drugs for tissue engineering and repair. PMID:23612369</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.B12B..02P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.B12B..02P&link_type=ABSTRACT"><span id="translatedtitle">Seawater bicarbonate removal during <span class="hlt">hydrothermal</span> circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Proskurowski, G. K.; Seewald, J.; Sylva, S. P.; Reeves, E.; Lilley, M. D.</p> <p>2013-12-01</p> <p>High temperature fluids sampled at <span class="hlt">hydrothermal</span> vents represent a complex alteration product of water-rock reactions on a multi-component mixture of source fluids. Sources to high-temperature <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> circulation. Here we present data from a suite of samples collected over the past 15 years from high-temperature <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> 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 <span class="hlt">hydrothermal</span> vent chemistry. Nature 422(6934):878-881. 2. Seewald J, Cruse A, & Saccocia P (2003) Aqueous volatiles in <span class="hlt">hydrothermal</span> fluids from the Main Endeavour Field, northern Juan de Fuca Ridge: temporal variability following earthquake <span class="hlt">activity</span>. Earth and Planetary Science Letters 216(4):575-590.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5053377','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5053377"><span id="translatedtitle">Druggability analysis and classification of protein tyrosine phosphatase <span class="hlt">active</span> <span class="hlt">sites</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ghattas, Mohammad A; Raslan, Noor; Sadeq, Asil; Al Sorkhy, Mohammad; Atatreh, Noor</p> <p>2016-01-01</p> <p>Protein tyrosine phosphatases (PTP) play important roles in the pathogenesis of many diseases. The fact that no PTP inhibitors have reached the market so far has raised many questions about their druggability. In this study, the <span class="hlt">active</span> <span class="hlt">sites</span> of 17 PTPs were characterized and assessed for its ability to bind drug-like molecules. Consequently, PTPs were classified according to their druggability scores into four main categories. Only four members showed intermediate to very druggable pocket; interestingly, the rest of them exhibited poor druggability. Particularly focusing on PTP1B, we also demonstrated the influence of several factors on the druggability of PTP <span class="hlt">active</span> <span class="hlt">site</span>. For instance, the open conformation showed better druggability than the closed conformation, while the tight-bound water molecules appeared to have minimal effect on the PTP1B druggability. Finally, the allosteric <span class="hlt">site</span> of PTP1B was found to exhibit superior druggability compared to the catalytic pocket. This analysis can prove useful in the discovery of new PTP inhibitors by assisting researchers in predicting hit rates from high throughput or virtual screening and saving unnecessary cost, time, and efforts via prioritizing PTP targets according to their predicted druggability. PMID:27757011</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MRE.....3g5602S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MRE.....3g5602S"><span id="translatedtitle">Effects of TiO2 content on the microstructure, mechanical properties and photocatalytic <span class="hlt">activity</span> of three dimensional TiO2-Graphene composite prepared by <span class="hlt">hydrothermal</span> reaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shi, Xiangru; Chen, Jian; Wang, Wenxiu; Wang, Zengmei; Zhang, Yao; Guo, Xinli</p> <p>2016-07-01</p> <p>A series of three dimensional (3D) porous TiO2-graphene (TGR) hydrogel samples with different mass ratio of graphene to TiO2 were obtained using a one-step <span class="hlt">hydrothermal</span> method. Their microstructure, mechanical properties, and photocatalytic <span class="hlt">activity</span> were investigated. The TGR samples exhibited well defined interconnected 3D porous network microstructure and good mechanical strength. Moreover, the pore size and the compressive strength could be easily adjusted by changing the content of TiO2, showing a decreasing tendency with the increase of the relative content of TiO2. The results of the photodegradation of methylene blue indicated that the photocatalytic <span class="hlt">activity</span> of the TGR samples can be significantly enhanced, compared to the pure TiO2 nanoparticles. The TGR sample also showed good durability and reusability. The mechanisms resulting in the improvement of photocatalytic <span class="hlt">activity</span> were investigated with DRS, PL spectra, and adsorption experiment under dark conditions. It was found that adsorption is the dominant factor for the enhanced photocatalytic <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22131225','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22131225"><span id="translatedtitle">Microwave assisted <span class="hlt">hydrothermal</span> synthesis of Ag/AgCl/WO{sub 3} photocatalyst and its photocatalytic <span class="hlt">activity</span> under simulated solar light</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Adhikari, Rajesh; Gyawali, Gobinda; Sekino, Tohru; Wohn Lee, Soo</p> <p>2013-01-15</p> <p>Simulated solar light responsive Ag/AgCl/WO{sub 3} composite photocatalyst was synthesized by microwave assisted <span class="hlt">hydrothermal</span> process. The synthesized powders were characterized by X-Ray Diffraction (XRD) spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), Diffuse Reflectance Spectroscopy (UV-Vis DRS), and BET surface area analyzer to investigate the crystal structure, morphology, chemical composition, optical properties and surface area of the composite photocatalyst. This photocatalyst exhibited higher photocatalytic <span class="hlt">activity</span> for the degradation of rhodamine B under simulated solar light irradiation. Dye degradation efficiency of composite photocatalyst was found to be increased significantly as compared to that of the commercial WO{sub 3} nanopowder. Increase in photocatalytic <span class="hlt">activity</span> of the photocatalyst was explained on the basis of surface plasmon resonance (SPR) effect caused by the silver nanoparticles present in the composite photocatalyst. Highlights: Black-Right-Pointing-Pointer Successful synthesis of Ag/AgCl/WO{sub 3} nanocomposite. Black-Right-Pointing-Pointer Photocatalytic experiment was performed under simulated solar light. Black-Right-Pointing-Pointer Nanocomposite photocatalyst was very <span class="hlt">active</span> as compared to WO{sub 3} commercial powder. Black-Right-Pointing-Pointer SPR effect due to Ag nanoparticles enhanced the photocatalytic <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12529639','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12529639"><span id="translatedtitle">Discovery of abundant <span class="hlt">hydrothermal</span> venting on the ultraslow-spreading Gakkel ridge in the Arctic Ocean.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Edmonds, H N; Michael, P J; Baker, E T; Connelly, D P; Snow, J E; Langmuir, C H; Dick, H J B; Mühe, R; German, C R; Graham, D W</p> <p>2003-01-16</p> <p>Submarine <span class="hlt">hydrothermal</span> venting along mid-ocean ridges is an important contributor to ridge thermal structure, and the global distribution of such vents has implications for heat and mass fluxes from the Earth's crust and mantle and for the biogeography of vent-endemic organisms. Previous studies have predicted that the incidence of <span class="hlt">hydrothermal</span> venting would be extremely low on ultraslow-spreading ridges (ridges with full spreading rates <2 cm x yr(-1)-which make up 25 per cent of the global ridge length), and that such vent systems would be hosted in ultramafic in addition to volcanic rocks. Here we present evidence for <span class="hlt">active</span> <span class="hlt">hydrothermal</span> venting on the Gakkel ridge, which is the slowest spreading (0.6-1.3 cm x yr(-1)) and least explored mid-ocean ridge. On the basis of water column profiles of light scattering, temperature and manganese concentration along 1,100 km of the rift valley, we identify <span class="hlt">hydrothermal</span> plumes dispersing from at least nine to twelve discrete vent <span class="hlt">sites</span>. Our discovery of such abundant venting, and its apparent localization near volcanic centres, requires a reassessment of the geologic conditions that control <span class="hlt">hydrothermal</span> circulation on ultraslow-spreading ridges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6885919','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6885919"><span id="translatedtitle">Current <span class="hlt">activities</span> handbook: formerly utilized <span class="hlt">sites</span> remedial action program</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p></p> <p>1981-02-27</p> <p>This volume is one of a series produced under contract with the DOE, by Politech Corporation to develop a legislative and regulatory data base to assist the FUSRAP management in addressing the institutional and socioeconomic issues involved in carrying out the Formerly Utilized <span class="hlt">Sites</span> Remedial Action Program. This Information Handbook series contains information about all relevant government agencies at the Federal and state levels, the pertinent programs they administer, each affected state legislature, and current Federal and state legislative and regulatory initiatives. This volume is a compilation of information about the <span class="hlt">activities</span> each of the thirteen state legislatures potentially affected by the Formerly Utilized <span class="hlt">Sites</span> Remedial Action Program. It contains a description of the state legislative procedural rules and a schedule of each legislative session; a summary of pending relevant legislation; the name and telephone number of legislative and state agency contacts; and the full text of all bills identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950057138&hterms=Hydrocyanic+acid&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2528Hydrocyanic%2Bacid%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950057138&hterms=Hydrocyanic+acid&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2528Hydrocyanic%2Bacid%2529"><span id="translatedtitle">Thermodynamics of Strecker synthesis in <span class="hlt">hydrothermal</span> systems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schulte, Mitchell; Shock, Everett</p> <p>1995-01-01</p> <p>Submarine <span class="hlt">hydrothermal</span> systems on the early Earth may have been the <span class="hlt">sites</span> from which life emerged. The potential for Strecker synthesis to produce biomolecules (amino and hydroxy acids) from starting compounds (ketones, aldehydes, HCN and ammonia) in such environments is evaluated quantitatively using thermodynamic data and parameters for the revised Helgeson-Kirkham-Flowers (HKF) equation of state. Although there is an overwhelming thermodynamic drive to form biomolecules by the Strecker synthesis at <span class="hlt">hydrothermal</span> conditions, the availability and concentration of starting compounds limit the efficiency and productivity of Strecker reactions. Mechanisms for concentrating reactant compounds could help overcome this problem, but other mechanisms for production of biomolecules may have been required to produce the required compounds on the early Earth. Geochemical constraints imposed by <span class="hlt">hydrothermal</span> systems provide important clues for determining the potential of these and other systems as <span class="hlt">sites</span> for the emergence of life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19557339','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19557339"><span id="translatedtitle">Microbial diversity of a sulfide black smoker in main endeavour <span class="hlt">hydrothermal</span> vent field, Juan de Fuca Ridge.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhou, Huaiyang; Li, Jiangtao; Peng, Xiaotong; Meng, Jun; Wang, Fengping; Ai, Yuncan</p> <p>2009-06-01</p> <p>Submarine <span class="hlt">hydrothermal</span> vents are among the least-understood habitats on Earth but have been the intense focus of research in the past 30 years. An <span class="hlt">active</span> <span class="hlt">hydrothermal</span> sulfide chimney collected from the Dudley <span class="hlt">site</span> in the Main Endeavour vent Field (MEF) of Juan de Fuca Ridge was investigated using mineralogical and molecular approaches. Mineral analysis indicated that the chimney was composed mainly of Fe-, Zn-and Cu-rich sulfides. According to phylogenetic analysis, within the Crenarchaeota, clones of the order Desulfurococcales predominated, comprising nearly 50% of archaeal clones. Euryarchaeota were composed mainly of clones belonging to Thermococcales and deep-sea <span class="hlt">hydrothermal</span> vent Euryarchaeota (DHVE), each of which accounted for about 20% of all clones. Thermophilic or hyperthermophilic physiologies were common to the predominant archaeal groups. More than half of bacterial clones belonged to epsilon-Proteobacteria, which confirmed their prevalence in <span class="hlt">hydrothermal</span> vent environments. Clones of Proteobacteria (gamma-, delta-, beta-), Cytophaga-Flavobacterium-Bacteroides (CFB) and Deinococcus-Thermus occurred as well. It was remarkable that methanogens and methanotrophs were not detected in our 16S rRNA gene library. Our results indicated that sulfur-related metabolism, which included sulfur-reducing <span class="hlt">activity</span> carried out by thermophilic archaea and sulfur-oxidizing by mesophilic bacteria, was common and crucial to the vent ecosystem in Dudley <span class="hlt">hydrothermal</span> <span class="hlt">site</span>. PMID:19557339</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1816742H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1816742H"><span id="translatedtitle">The influence of isotropic and anisotropic crustal permeability on <span class="hlt">hydrothermal</span> flow at fast spreading ridges</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hasenclever, Jörg; Rüpke, Lars; Theissen-Krah, Sonja; Morgan, Jason</p> <p>2016-04-01</p> <p> <span class="hlt">activity</span>. We also explore the effect of anisotropic permeability that is likely to be a feature of the diking region above the melt lens where the repeated emplacement of meter-size dikes should lead to higher permeability in vertical and along-ridge direction and to lower permeability across the ridge. We further study the effect of along-ridge depth-variations of the axial melt lens on the distribution of <span class="hlt">hydrothermal</span> vent <span class="hlt">sites</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25634941','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25634941"><span id="translatedtitle">Methanocaldococcus bathoardescens sp. nov., a hyperthermophilic methanogen isolated from a volcanically <span class="hlt">active</span> deep-sea <span class="hlt">hydrothermal</span> vent.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stewart, Lucy C; Jung, Jong-Hyun; Kim, You-Tae; Kwon, Soon-Wo; Park, Cheon-Seok; Holden, James F</p> <p>2015-04-01</p> <p>A hyperthermophilic methanogen, strain JH146(T), was isolated from 26 °C <span class="hlt">hydrothermal</span> vent fluid emanating from a crack in basaltic rock at Marker 113 vent, Axial Seamount in the northeastern Pacific Ocean. It was identified as an obligate anaerobe that uses only H2 and CO2 for growth. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain is more than 97% similar to other species of the genus Methanocaldococcus . Therefore, overall genome relatedness index analyses were performed to establish that strain JH146(T) represents a novel species. For each analysis, strain JH146(T) was most similar to Methanocaldococcus sp. FS406-22, which can fix N2 and also comes from Marker 113 vent. However, strain JH146(T) differs from strain FS406-22 in that it cannot fix N2. The average nucleotide identity score for strain JH146(T) was 87%, the genome-to-genome direct comparison score was 33-55% and the species identification score was 93%. For each analysis, strain JH146(T) was below the species delineation cut-off. Full-genome gene synteny analysis showed that strain JH146(T) and strain FS406-22 have 97% genome synteny, but strain JH146(T) was missing the operons necessary for N2 fixation and assimilatory nitrate reduction that are present in strain FS406-22. Based on its whole genome sequence, strain JH146(T) is suggested to represent a novel species of the genus Methanocaldococcus for which the name Methanocaldococcus bathoardescens is proposed. The type strain is JH146(T) ( = DSM 27223(T) = KACC 18232(T)).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25634941','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25634941"><span id="translatedtitle">Methanocaldococcus bathoardescens sp. nov., a hyperthermophilic methanogen isolated from a volcanically <span class="hlt">active</span> deep-sea <span class="hlt">hydrothermal</span> vent.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stewart, Lucy C; Jung, Jong-Hyun; Kim, You-Tae; Kwon, Soon-Wo; Park, Cheon-Seok; Holden, James F</p> <p>2015-04-01</p> <p>A hyperthermophilic methanogen, strain JH146(T), was isolated from 26 °C <span class="hlt">hydrothermal</span> vent fluid emanating from a crack in basaltic rock at Marker 113 vent, Axial Seamount in the northeastern Pacific Ocean. It was identified as an obligate anaerobe that uses only H2 and CO2 for growth. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain is more than 97% similar to other species of the genus Methanocaldococcus . Therefore, overall genome relatedness index analyses were performed to establish that strain JH146(T) represents a novel species. For each analysis, strain JH146(T) was most similar to Methanocaldococcus sp. FS406-22, which can fix N2 and also comes from Marker 113 vent. However, strain JH146(T) differs from strain FS406-22 in that it cannot fix N2. The average nucleotide identity score for strain JH146(T) was 87%, the genome-to-genome direct comparison score was 33-55% and the species identification score was 93%. For each analysis, strain JH146(T) was below the species delineation cut-off. Full-genome gene synteny analysis showed that strain JH146(T) and strain FS406-22 have 97% genome synteny, but strain JH146(T) was missing the operons necessary for N2 fixation and assimilatory nitrate reduction that are present in strain FS406-22. Based on its whole genome sequence, strain JH146(T) is suggested to represent a novel species of the genus Methanocaldococcus for which the name Methanocaldococcus bathoardescens is proposed. The type strain is JH146(T) ( = DSM 27223(T) = KACC 18232(T)). PMID:25634941</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22143193','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22143193"><span id="translatedtitle">One-step <span class="hlt">hydrothermal</span> synthesis of N-doped TiO2/C nanocomposites with high visible light photocatalytic <span class="hlt">activity</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Dong-Hong; Jia, Li; Wu, Xi-Lin; Lu, Li-Qiang; Xu, An-Wu</p> <p>2012-01-21</p> <p>N-doped TiO(2) nanoparticles modified with carbon (denoted N-TiO(2)/C) were successfully prepared by a facile one-pot <span class="hlt">hydrothermal</span> treatment in the presence of L-lysine, which acts as a ligand to control the nanocrystal growth and as a source of nitrogen and carbon. As-prepared nanocomposites were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR) spectra, and N(2) adsorption-desorption analysis. The photocatalytic <span class="hlt">activities</span> of the as-prepared photocatalysts were measured by the degradation of methyl orange (MO) under visible light irradiation at λ≥ 400 nm. The results show that N-TiO(2)/C nanocomposites increase absorption in the visible light region and exhibit a higher photocatalytic <span class="hlt">activity</span> than pure TiO(2), commercial P25 and previously reported N-doped TiO(2) photocatalysts. We have demonstrated that the nitrogen was doped into the lattice and the carbon species were modified on the surface of the photocatalysts. N-doping narrows the band gap and C-modification enhances the visible light harvesting and accelerates the separation of the photo-generated electrons and holes. As a consequence, the photocatalytic <span class="hlt">activity</span> is significantly improved. The molar ratio of L-lysine/TiCl(4) and the pH of the <span class="hlt">hydrothermal</span> reaction solution are important factors affecting the photocatalytic <span class="hlt">activity</span> of the N-TiO(2)/C; the optimum molar ratio of L-lysine/TiCl(4) is 8 and the optimum pH is ca. 4, at which the catalyst exhibits the highest reactivity. Our findings demonstrate that the as-obtained N-TiO(2)/C photocatalyst is a better and more promising candidate than well studied N-doped TiO(2) alternatives as visible light photocatalysts for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/175621','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/175621"><span id="translatedtitle">Thermal and tectonic history in the steamboat hills geothermal field: Determination of the age of <span class="hlt">active</span> <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> by application of AFTA{sup {trademark}} (apatite fission track analysis)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Duddy, I.R.; Green, P.F.; Kamp, P.C. van de</p> <p>1995-12-31</p> <p>This study, in the Steamboat Hills area of the Carson segment of the northern Walker Lane Belt, was initiated to provide a regional thermal history framework and to investigate the age of the <span class="hlt">active</span> local <span class="hlt">hydrothermal</span> system. Seven outcrop samples, representing ?Cretaceous granodiorite and ?Triassic Peavine sequence metamorphosed volcanic flow and volcaniclastic rocks plus six samples of Peavine rocks in vertical sequence from an 0.8 km deep geothermal corehole have been analyzed using AFTA (apatite fission track analysis) and zircon fission track analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/2664781','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/2664781"><span id="translatedtitle">Electrostatic fields in the <span class="hlt">active</span> <span class="hlt">sites</span> of lysozymes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, D P; Liao, D I; Remington, S J</p> <p>1989-07-01</p> <p>Considerable experimental evidence is in support of several aspects of the mechanism that has been proposed for the catalytic <span class="hlt">activity</span> of lysozyme. However, the enzymatically catalyzed hydrolysis of polysaccharides proceeds over 5 orders of magnitude faster than that of model compounds that mimic the configuration of the substrate in the <span class="hlt">active</span> <span class="hlt">site</span> of the enzyme. Although several possible explanations for this rate enhancement have been discussed elsewhere, a definitive mechanism has not emerged. Here we report striking results obtained by classical electrodynamics, which suggest that bond breakage and the consequent separation of charge in lysozyme is promoted by a large electrostatic field across the <span class="hlt">active</span> <span class="hlt">site</span> cleft, produced in part by a very asymmetric distribution of charged residues on the enzyme surface. Lysozymes unrelated in amino acid sequence have similar distributions of charged residues and electric fields. The results reported here suggest that the electrostatic component of the rate enhancement is greater than 9 kcal.mol-1. Thus, electrostatic interactions may play a more important role in the enzymatic mechanism than has generally been appreciated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/6458322','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/6458322"><span id="translatedtitle">Histidine at the <span class="hlt">active</span> <span class="hlt">site</span> of Neurospora tyrosinase.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pfiffner, E; Lerch, K</p> <p>1981-10-13</p> <p>The involvement of histidyl residues as potential ligands to the binuclear <span class="hlt">active-site</span> copper of Neurospora tyrosinase was explored by dye-sensitized photooxidation. The enzymatic <span class="hlt">activity</span> of the holoenzyme was shown to be unaffected by exposure to light in the presence of methylene blue; however, irradiation of the apoenzyme under the same conditions led to a progressive loss of its ability to be reactivated with Cu2+. This photoinactivation was paralleled by a decrease in the histidine content whereas the number of histidyl residues in the holoenzyme remained constant. Copper measurements of photooxidized, reconstituted apoenzyme demonstrated the loss of binding of one copper atom per mole of enzyme as a consequence of photosensitized oxidation of three out of nine histidine residues. Their sequence positions were determined by a comparison of the relative yields of the histidine containing peptides of photooxidized holo- and apotyrosinases. The data obtained show the preferential modification of histidyl residues 188, 193, and 289 and suggest that they constitute metal ligands to one of the two <span class="hlt">active-site</span> copper atoms. Substitution of copper by cobalt was found to afford complete protection of the histidyl residues from being modified by dye-sensitized photooxidation. PMID:6458322</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFMOS22A..01E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFMOS22A..01E"><span id="translatedtitle">Sulphur Cycling at the Mid-Atlantic Ridge: Isotopic Evidence From the Logatchev and Turtle Pits <span class="hlt">Hydrothermal</span> Fields</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eickmann, B.; Strauss, H.; Koschinsky, A.; Kuhn, T.; Petersen, S.; Schmidt, K.</p> <p>2005-12-01</p> <p>Mid-ocean ridges and associated <span class="hlt">hydrothermal</span> vent systems represent a unique scenario in which the interaction of hydrosphere, lithosphere and biosphere and the related element cycling can be studied. Sulphur participates in inorganic and microbially driven processes and plays, thus, an important role at these vent <span class="hlt">sites</span>. The sulphur isotopic compositions of different sulphur-bearing minerals as well as dissolved sulphur compounds provide a tool for identifying the sulphur source and pertinent processes of sulphur cycling. Here, we present sulphur isotope data from an ongoing study of the Logatchev <span class="hlt">hydrothermal</span> field at 14°45' N and the Turtle Pits <span class="hlt">hydrothermal</span> field at 4°48' S. The former is located in 2900 to 3060 m water depth, hosted by ultramafic rocks, while the latter is situated in 2990 m water depth, hosted by basaltic rocks. Different metal sulphides (chalcopyrite, pyrite, pyrrhotite, various copper sulphides), either particles from the emanating hot fluid itself or pieces of <span class="hlt">active</span> and inactive black smokers, display δ34S values between +2 and +9 ‰. So far, no significant difference is discernible between mineral precipitates from both <span class="hlt">hydrothermal</span> fields. However, differences exist between different generations of sulphide precipitates. Based on respective data from other <span class="hlt">sites</span> of <span class="hlt">hydrothermal</span> <span class="hlt">activity</span> at mid-ocean ridges, this sulphur isotope range suggests that sulphur in the <span class="hlt">hydrothermal</span> fluid and mineral precipitates represents a mixture between mantle sulphur and reduced seawater sulphate. Anhydrite precipitates from <span class="hlt">hydrothermal</span> chimneys, located inside sulphide conduits, and obvious late stage gypsum needles from voids, yielded sulphur isotope values between +17.5 and +20.0 ‰. This clearly identifies seawater sulphate as the principal sulphur source. Variable, but generally low abundances of sulphide and sulphate in differently altered mafic and ultramafic rocks point to a complex fluid-rock interaction. Sulphur isotope values for total</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFM.V12D1009Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFM.V12D1009Z"><span id="translatedtitle">Decline of a <span class="hlt">Hydrothermal</span> Vent Field - Escanaba Trough 12 Years Later</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zierenberg, R. A.; Clague, D. A.; Davis, A. S.; Lilley, M. D.; McClain, J. S.; Olson, E. S.; Ross, S. L.; Von Damm, K. L.</p> <p>2001-12-01</p> <p><span class="hlt">Hydrothermal</span> venting was discovered in Escanaba Trough, the southern sediment-covered portion of the Gorda Ridge, in 1988. Large pyrrhotite-rich massive sulfide mounds are abundant at each of the volcanic/intrusive centers that have been investigated in Escanaba Trough, but the only area of known <span class="hlt">hydrothermal</span> venting is the NESCA <span class="hlt">site</span> along the ridge axis at 41\\deg N. <span class="hlt">Hydrothermal</span> fluids venting at 217\\deg C and 108\\deg C were sampled in 1988 on two sulfide mounds separated by about 275 m. The end-member fluid compositions were indistinguishable within analytical errors. Several sulfide mounds were observed in 1988 which had diffusely venting low temperature (< 20\\deg C) fluids that supported extensive vent communities dominated by fields of Ridgia. Nine holes were drilled in the NESCA area in 1996 on ODP Leg 169, including Hole 1036I that penetrated to basaltic basement at 405 m below sea floor (mbsf). Surveys of the area using the drill string camera located only one area of <span class="hlt">active</span> venting at the same mound where 217\\deg C vent fluids were sampled from two <span class="hlt">active</span> vents in 1988. Drill hole 1036A was spudded between the two <span class="hlt">active</span> vents on this sulfide mound (approximately 4 and 8 m away) and penetrated to 115 mbsf. The NESCA <span class="hlt">site</span> was revisited in 2000 using MBARI's R/V Western Flyer and ROV Tiburon. The <span class="hlt">hydrothermal</span> vents appeared essentially identical to observations made from the drill string camera in 1996 despite the presence of a drill hole within meters of the two vents. The maximum vent temperature measured in 2000 was 212\\deg C. Fluid samples have major element and isotopic compositions very similar to those collected in 1988. The vent fluids have higher methane ( ~19 mmol/kg) than those from the geologically similar Middle Valley vent field, but lower values than those at Guaymas Basin. Drill hole 1036A was weakly venting, but the diffuse <span class="hlt">hydrothermal</span> fluids could not be sampled with the equipment available. The walls of the drill hole were</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MS%26E..123a2030H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MS%26E..123a2030H"><span id="translatedtitle">Effect of temperature and concentration of precursors on morphology and photocatalytic <span class="hlt">activity</span> of zinc oxide thin films prepared by <span class="hlt">hydrothermal</span> route</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heinonen, S.; Nikkanen, J.-P.; Hakola, H.; Huttunen-Saarivirta, E.; Kannisto, M.; Hyvärinen, L.; Järveläinen, M.; Levänen, E.</p> <p>2016-04-01</p> <p>Zinc oxide (ZnO) is an important semiconductive material due to its potential applications, such as conductive gas sensors, transparent conductive electrodes, solar cells, and photocatalysts. Photocatalytic <span class="hlt">activity</span> can be exploited in the decomposition of hazardous pollutants from environment. In this study, we produced zinc oxide thin films on stainless steel plates by <span class="hlt">hydrothermal</span> method varying the precursor concentration (from 0.029 M to 0.16 M) and the synthesis temperature (from 70 °C to 90 °C). Morphology of the synthesized films was examined using field-emission scanning electron microscopy (FESEM) and photocatalytic <span class="hlt">activity</span> of the films was characterized using methylene blue decomposition tests. It was found that the morphology of the nanostructures was strongly affected by the precursor concentration and the temperature of the synthesis. At lower concentrations zinc oxide grew as thin needlelike nanorods of uniform length and shape and aligned perpendicular to the stainless steel substrate surface. At higher concentrations the shape of the rods transformed towards hexagon shaped units and further on towards flaky platelets. Temperature changes caused variations in the coating thickness and the orientation of the crystal units. It was also observed, that the photocatalytic <span class="hlt">activity</span> of the prepared films was clearly dependent on the morphology of the surfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70016266','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70016266"><span id="translatedtitle">Hydrocarbon geochemistry of <span class="hlt">hydrothermally</span> generated petroleum from Escanaba trough, offshore Californi U.S.A.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Kvenvolden, K.A.; Rapp, J.B.; Hostettler, F.D.</p> <p>1990-01-01</p> <p>In 1986, three samples of sulfide-rich sediments, impregnated with <span class="hlt">hydrothermally</span> derived, asphaltic petroleum, were recovered in a dredge and by submersible from Escanaba Trough, the sediment-covered, southern end of the Gorda Ridge spreading axis, offshore northern California. The molecular distributions of hydrocarbons in the two pyrrhotite-rich samples recovered by submersible are similar and compare well the hydrocarbon composition of the first pyrrhotite-rich samples containing petroleum discovered at a 1985 dredge <span class="hlt">site</span> about 30 km to the south of the <span class="hlt">site</span> of the submersible dive. In contrast, the 1986 dredge sample, composed of a polymetallic assemblage of sulfides, containes petroleum in which the distribution of hydrocarbons indicates a slightly higher of maturity relative to the other samples. The observation that petroleum of variable composition occurs with metallic sulfides at two and probably more distinct <span class="hlt">site</span> indicates that petroleum generation may be a common process in the <span class="hlt">hydrothermally</span> <span class="hlt">active</span> Escanaba Trough. ?? 1990.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/7873527','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/7873527"><span id="translatedtitle">Trichodiene synthase. Identification of <span class="hlt">active</span> <span class="hlt">site</span> residues by <span class="hlt">site</span>-directed mutagenesis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cane, D E; Shim, J H; Xue, Q; Fi