Massive collapse of volcano edifices triggered by hydrothermal pressurization

USGS Publications Warehouse

Reid, M.E.

2004-01-01

Catastrophic collapse of steep volcano flanks threatens lives at stratovolcanoes around the world. Although destabilizing shallow intrusion of magma into the edifice accompanies some collapses (e.g., Mount St. Helens), others have occurred without eruption of juvenile magmatic materials (e.g., Bandai). These latter collapses can be difficult to anticipate. Historic collapses without magmatic eruption are associated with shallow hydrothermal groundwater systems at the time of collapse. Through the use of numerical models of heat and groundwater flow, I evaluate the efficacy of hydrothermally driven collapse. Heating from remote magma intrusion at depth can generate temporarily elevated pore-fluid pressures that propagate upward into an edifice. Effective-stress deformation modeling shows that these pressures are capable of destabilizing the core of an edifice, resulting in massive, deep-seated collapse. Far-field pressurization only occurs with specific rock hydraulic properties; however, data from numerous hydrothermal systems illustrate that this process can transpire in realistic settings. ?? 2004 Geological Society of America.

Groundwater flow, heat transport, and water table position within volcanic edifices: Implications for volcanic processes in the Cascade Range

USGS Publications Warehouse

Hurwitz, S.; Kipp, K.L.; Ingebritsen, S.E.; Reid, M.E.

2003-01-01

The position of the water table within a volcanic edifice has significant implications for volcano hazards, geothermal energy, and epithermal mineralization. We have modified the HYDROTHERM numerical simulator to allow for a free-surface (water table) upper boundary condition and a wide range of recharge rates, heat input rates, and thermodynamic conditions representative of continental volcano-hydrothermal systems. An extensive set of simulations was performed on a hypothetical stratovolcano system with unconfined groundwater flow. Simulation results suggest that the permeability structure of the volcanic edifice and underlying material is the dominant control on water table elevation and the distribution of pressures, temperatures, and fluid phases at depth. When permeabilities are isotropic, water table elevation decreases with increasing heat flux and increases with increasing recharge, but when permeabilities are anisotropic, these effects can be much less pronounced. Several conditions facilitate the ascent of a hydrothermal plume into a volcanic edifice: a sufficient source of heat and magmatic volatiles at depth, strong buoyancy forces, and a relatively weak topography-driven flow system. Further, the plume must be connected to a deep heat source through a pathway with a time-averaged effective permeability ???1 ?? 10-16 m2, which may be maintained by frequent seismicity. Topography-driven flow may be retarded by low permeability in the edifice and/or the lack of precipitation recharge; in the latter case, the water table may be relatively deep. Simulation results were compared with observations from the Quaternary stratovolcanoes along the Cascade Range of the western United States to infer hydrothermal processes within the edifices. Extensive ice caps on many Cascade Range stratovolcanoes may restrict recharge on the summits and uppermost flanks. Both the simulation results and limited observational data allow for the possibility that the water table beneath the stratovolcanoes is relatively deep.

Learning about hydrothermal volcanic activity by modeling induced geophysical changes

NASA Astrophysics Data System (ADS)

Currenti, Gilda M.; Napoli, Rosalba

2017-05-01

Motivated by ongoing efforts to understand the nature and the energy potential of geothermal resources, we devise a coupled numerical model (hydrological, thermal, mechanical), which may help in the characterization and monitoring of hydrothermal systems through computational experiments. Hydrothermal areas in volcanic regions arise from a unique combination of geological and hydrological features which regulate the movement of fluids in the vicinity of magmatic sources capable of generating large quantities of steam and hot water. Numerical simulations help in understanding and characterizing rock-fluid interaction processes and the geophysical observations associated with them. Our aim is the quantification of the response of different geophysical observables (i.e. deformation, gravity and magnetic field) to hydrothermal activity on the basis of a sound geological framework (e.g. distribution and pathways of the flows, the presence of fractured zones, caprock). A detailed comprehension and quantification of the evolution and dynamics of the geothermal systems and the definition of their internal state through a geophysical modeling approach are essential to identify the key parameters for which the geothermal system may fulfill the requirements to be exploited as a source of energy. For the sake of illustration only, the numerical computations are focused on a conceptual model of the hydrothermal system of Vulcano Island by simulating a generic 1-year unrest and estimating different geophysical changes. We solved (i) the mass and energy balance equations of flow in porous media for temperature, pressure and density changes, (ii) the elastostatic equation for the deformation field and (iii) the Poisson’s equations for gravity and magnetic potential fields. Under the model assumptions, a generic unrest of 1-year engenders on the ground surface low amplitude changes in the investigated geophysical observables, that are, however, above the accuracies of the modern state-of-the-art instruments. Devising multidisciplinary and easy-to-use computational experiments enable us to learn how the hydrothermal system responds to un unrest and which fingerprints it may leave in the geophysical signals.

Physical inter-relationships between hydrothermal activity, faulting and magmatic processes at the center of a slow-spreading, magma-rich mid-ocean ridge segment: A case study of the Lucky Strike segment (MAR, 37°03'-37‧N)

NASA Astrophysics Data System (ADS)

Fontaine, F. J.; Cannat, M.; Escartin, J.; Crawford, W. C.; Singh, S. C.

2012-12-01

The modalities and efficiency of hydrothermal heat evacuation at mid-ocean ridges (25% of the global heat loss) are controlled by the lithosphere thermal and permeability structures for which we had robust constraints only for fast/intermediate spreading axis until the last past few years during which integrated geophysical, geological and geochemical studies focused on some hydrothermal sites at slow-spreading ridges. At the Lucky Strike vent field of the mid-atlantic ridge - a hydrothermal complex composed of high-temperature (maximum T=340°C), smoker-like vents and associated diffuse flow and extracting a few hundreds MW from the oceanic lithosphere - a seafloor observatory which installation started in 2005 highlights local interactions between hydrothermal, tectonic and magmatic processes. Detailed geophysical and geological investigations stress the role of the local axial fault system on localizing high- and low-temperature ventings around the faulted rim of a paleo lava lake. Microseismic studies bring constraints on the subseafloor hydrology and suggest an along-axis flow pattern, with a privileged recharge area located about a kilometer north off the active discharges. Seismic reflection studies image a central magma chamber fueling the hydrothermal sites and also reveal its along-axis depth variations likely influencing hydrothermal cell organization and flow focusing. Such linkages among hydrothermal dynamics, heat source and crustal permeability geometries usually lack quantitative constraints at mid-ocean ridges in general, and the Lucky Strike segment settings offers a unique opportunity to couple high-resolution geophysical data to hydrodynamic model. Here we develop a series of original two- and three-dimensional numerical and physical models of hydrothermal activity, tailored to this slow-spreading environment. Our results highlight physical linkages among magmatism, tectonics and crustal hydrology stressing the key role of faulting and magma chamber roof-topology in focusing fluid flow at the center of the Lucky Strike segment. They also help identifying some causes of variations in the modalities of hydrothermal heat extraction along the global ridge network.

Geochemical and Visual Indicators of Hydrothermal Fluid Flow through a Sediment-Hosted Volcanic Ridge in the Central Bransfield Basin (Antarctica)

PubMed Central

Aquilina, Alfred; Connelly, Douglas P.; Copley, Jon T.; Green, Darryl R. H.; Hawkes, Jeffrey A.; Hepburn, Laura E.; Huvenne, Veerle A. I.; Marsh, Leigh; Mills, Rachel A.; Tyler, Paul A.

2013-01-01

In the austral summer of 2011 we undertook an investigation of three volcanic highs in the Central Bransfield Basin, Antarctica, in search of hydrothermal activity and associated fauna to assess changes since previous surveys and to evaluate the extent of hydrothermalism in this basin. At Hook Ridge, a submarine volcanic edifice at the eastern end of the basin, anomalies in water column redox potential (Eh) were detected close to the seafloor, unaccompanied by temperature or turbidity anomalies, indicating low-temperature hydrothermal discharge. Seepage was manifested as shimmering water emanating from the sediment and from mineralised structures on the seafloor; recognisable vent endemic fauna were not observed. Pore fluids extracted from Hook Ridge sediment were depleted in chloride, sulfate and magnesium by up to 8% relative to seawater, enriched in lithium, boron and calcium, and had a distinct strontium isotope composition (87Sr/86Sr  = 0.708776 at core base) compared with modern seawater (87Sr/86Sr ≈0.70918), indicating advection of hydrothermal fluid through sediment at this site. Biogeochemical zonation of redox active species implies significant moderation of the hydrothermal fluid with in situ diagenetic processes. At Middle Sister, the central ridge of the Three Sisters complex located about 100 km southwest of Hook Ridge, small water column Eh anomalies were detected but visual observations of the seafloor and pore fluid profiles provided no evidence of active hydrothermal circulation. At The Axe, located about 50 km southwest of Three Sisters, no water column anomalies in Eh, temperature or turbidity were detected. These observations demonstrate that the temperature anomalies observed in previous surveys are episodic features, and suggest that hydrothermal circulation in the Bransfield Strait is ephemeral in nature and therefore may not support vent biota. PMID:23359806

Hydrothermal Processes

NASA Astrophysics Data System (ADS)

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

2003-12-01

What is Hydrothermal Circulation?Hydrothermal circulation occurs when seawater percolates downward through fractured ocean crust along the volcanic mid-ocean ridge (MOR) system. The seawater is first heated and then undergoes chemical modification through reaction with the host rock as it continues downward, reaching maximum temperatures that can exceed 400 °C. At these temperatures the fluids become extremely buoyant and rise rapidly back to the seafloor where they are expelled into the overlying water column. Seafloor hydrothermal circulation plays a significant role in the cycling of energy and mass between the solid earth and the oceans; the first identification of submarine hydrothermal venting and their accompanying chemosynthetically based communities in the late 1970s remains one of the most exciting discoveries in modern science. The existence of some form of hydrothermal circulation had been predicted almost as soon as the significance of ridges themselves was first recognized, with the emergence of plate tectonic theory. Magma wells up from the Earth's interior along "spreading centers" or "MORs" to produce fresh ocean crust at a rate of ˜20 km3 yr-1, forming new seafloor at a rate of ˜3.3 km2 yr-1 (Parsons, 1981; White et al., 1992). The young oceanic lithosphere formed in this way cools as it moves away from the ridge crest. Although much of this cooling occurs by upward conduction of heat through the lithosphere, early heat-flow studies quickly established that a significant proportion of the total heat flux must also occur via some additional convective process (Figure 1), i.e., through circulation of cold seawater within the upper ocean crust (Anderson and Silbeck, 1981). (2K)Figure 1. Oceanic heat flow versus age of ocean crust. Data from the Pacific, Atlantic, and Indian oceans, averaged over 2 Ma intervals (circles) depart from the theoretical cooling curve (solid line) indicating convective cooling of young ocean crust by circulating seawater (after C. A. Stein and S. Stein, 1994). The first geochemical evidence for the existence of hydrothermal vents on the ocean floor came in the mid-1960s when investigations in the Red Sea revealed deep basins filled with hot, salty water (40-60 °C) and underlain by thick layers of metal-rich sediment (Degens and Ross, 1969). Because the Red Sea represents a young, rifting, ocean basin it was speculated that the phenomena observed there might also prevail along other young MOR spreading centers. An analysis of core-top sediments from throughout the world's oceans ( Figure 2) revealed that such metalliferous sediments did, indeed, appear to be concentrated along the newly recognized global ridge crest (Boström et al., 1969). Another early indication of hydrothermal activity came from the detection of plumes of excess 3He in the Pacific Ocean Basin (Clarke et al., 1969) - notably the >2,000 km wide section in the South Pacific ( Lupton and Craig, 1981) - because 3He present in the deep ocean could only be sourced through some form of active degassing of the Earth's interior, at the seafloor. (62K)Figure 2. Global map of the (Al+Fe+Mn):Al ratio for surficial marine sediments. Highest ratios mimic the trend of the global MOR axis (after Boström et al., 1969). One area where early heat-flow studies suggested hydrothermal activity was likely to occur was along the Galapagos Spreading Center in the eastern equatorial Pacific Ocean (Anderson and Hobart, 1976). In 1977, scientists diving at this location found hydrothermal fluids discharging chemically altered seawater from young volcanic seafloor at elevated temperatures up to 17 °C ( Edmond et al., 1979). Two years later, the first high-temperature (380±30 °C) vent fluids were found at 21° N on the East Pacific Rise (EPR) (Spiess et al., 1980) - with fluid compositions remarkably close to those predicted from the lower-temperature Galapagos findings ( Edmond et al., 1979). Since that time, hydrothermal activity has been 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 along the Juan de Fuca Ridge (JdFR) in the NE Pacific Ocean (Rona and Trivett, 1992; Schultz et al., 1992; Ginster et al., 1994) have suggested that, instead, axial hydrothermal circulation may be dominated by much lower-temperature diffuse flow exiting the seafloor at temperatures comparable to those first observed at the Galapagos vent sites in 1977. The relative importance of high- and low-temperature hydrothermal circulation to overall ocean chemistry remains a topic of active debate. (141K)Figure 4. (a) Photograph of a "black smoker" hydrothermal vent emitting hot (>400 °C) fluid at a depth of 2,834 m into the base of the oceanic water column at the Brandon vent site, southern EPR. The vent is instrumented with a recording temperature probe. (b) Diffuse flow hydrothermal fluids have temperatures that are generally <35 °C and, therefore, may host animal communities. This diffuse flow site at a depth of 2,500 m on the EPR at 9°50' N is populated by Riftia tubeworms, mussels, crabs, and other organisms. While most studies of seafloor hydrothermal systems have focused on the currently active plate boundary (˜0-1 Ma crust), pooled heat-flow data from throughout the world's ocean basins (Figure 1) indicate that convective heat loss from the oceanic lithosphere actually continues in crust from 0-65 Ma in age ( Stein et al., 1995). Indeed, most recent estimates would indicate that hydrothermal circulation through this older (1-65 Ma) section, termed "flank fluxes," may be responsible for some 70% or more of the total hydrothermal heat loss associated with spreading-plate boundaries - either in the form of warm (20-65 °C) altered seawater, or as cooler water, which is only much more subtly chemically altered ( Mottl, 2003).When considering the impact of hydrothermal circulation upon the chemical composition of the oceans and their underlying sediments, however, attention returns - for many elements - to the high-temperature "black smoker" systems. Only here do many species escape from the seafloor in high abundance. When they do, the buoyancy of the high-temperature fluids carries them hundreds of meters up into the overlying water column as they mix and eventually form nonbuoyant plumes containing a wide variety of both dissolved chemicals and freshly precipitated mineral phases. The processes active within these dispersing hydrothermal plumes play a major role in determining the net impact of hydrothermal circulation upon the oceans and marine geochemistry.

Hydrothermal Circulation Within and Between Basement Outcrops on a Young Ridge Flank: Numerical Models and Thermal Constraints

NASA Astrophysics Data System (ADS)

Hutnak, M.; Fisher, A. T.; Stauffer, P.; Gable, C. W.

2005-12-01

We use two-dimensional, finite-element models of coupled heat and fluid flow to investigate local and large-scale heat and fluid transport around and between basement outcrops on a young ridge flank. System geometries and properties are based on observations and measurements on the 3.4-3.6 Ma eastern flank of the Juan de Fuca Ridge. A small area of basement exposure (Baby Bare outcrop) experiences focused hydrothermal discharge, whereas a much larger feature (Grizzly Bare outcrop) 50 km to the south is a site of hydrothermal recharge. Observations of seafloor heat flow, subseafloor pressures, and basement fluid geochemistry at and near these outcrops constrain acceptable model results. Single-outcrop simulations suggest that local convection alone (represented by a high Nusselt number proxy) cannot explain the near-outcrop heat flow patterns; rapid through-flow is required. Venting of at least 5 L/s through the smaller outcrop, a volumetric flow rate consistent with earlier estimates based on plume and outcrop measurements, is needed to match seafloor heat flow patterns. Heat flow patterns are more variable and complex near the larger, recharging outcrop. Simulations that include 5-20 L/s of recharge through this feature can replicate first-order trends in the data, but small-scale variations are likely to result from heterogeneous flow paths and vigorous, local convection. Two-outcrop simulations started with a warm hydrostatic initial condition, based on a conductive model, result in rapid fluid flow from the smaller outcrop to the larger outcrop, inconsistent with observations. Flow can be sustained in the opposite (correct) direction if it is initially forced, which generates a hydrothermal siphon between the two features. Free flow simulations maintain rapid circulation at rates consistent with observations (specific discharge of m/yr to tens of m/yr), provided basement permeability is on the order of 10-10 m2 or greater. Lateral flow rates scale inversely with the thickness of the permeable basement layer. The differential pressure needed to drive this circulation, created by the siphon, is on the order of tens to hundreds of kPa, with greater differential pressure needed when basement permeability is lower.

Formation of hydrothermal pits and the role of seamounts in the Guatemala Basin (Equatorial East Pacific) from heat flow, seismic, and core studies

NASA Astrophysics Data System (ADS)

Villinger, H. W.; Pichler, T.; Kaul, N.; Stephan, S.; Pälike, H.; Stephan, F.

2017-01-01

We acquired seismic and heat flow data and collected sediment cores in three areas in the Guatemala Basin (Cocos Plate, Eastern Pacific) to investigate the process by which depressions (pits) in the sedimentary cover on young oceanic crust were formed. Median heat flow of 55 mW/m2 for the three areas is about half of the expected conductive cooling value. The heat deficit is caused by massive recharge of cold seawater into the upper crust through seamounts which is inferred from depressed heat flow in the vicinity of seamounts. Heat flow inside of pits is always elevated, in some cases up to three times (max. 300 mW/m2) relative to background. None of the geochemical pore water profiles from cores inside and outside of the pits show any evidence of active fluid flow inside the pits. All three areas originated within the high productivity equatorial zone and moved northwest over the past 15 to 18 Ma. Pits found in the working areas are likely relict dissolution structures formed by diffuse hydrothermal venting in a zone of high biogenic carbonate production which were sealed when they moved north. It is likely that these pits were discharge sites of "hydrothermal siphons" where recharging seamounts could feed cold seawater via the upper crust to several discharging pits. Probably pit density on the whole Cocos Plate is similar to the three working areas and which may explain the huge heat deficit of the Cocos Plate.

Numerical models of caldera deformation: Effects of multiphase and multicomponent hydrothermal fluid flow

USGS Publications Warehouse

Hutnak, M.; Hurwitz, S.; Ingebritsen, S.E.; Hsieh, P.A.

2009-01-01

Ground surface displacement (GSD) in large calderas is often interpreted as resulting from magma intrusion at depth. Recent advances in geodetic measurements of GSD, notably interferometric synthetic aperture radar, reveal complex and multifaceted deformation patterns that often require complex source models to explain the observed GSD. Although hydrothermal fluids have been discussed as a possible deformation agent, very few quantitative studies addressing the effects of multiphase flow on crustal mechanics have been attempted. Recent increases in the power and availability of computing resources allow robust quantitative assessment of the complex time-variant thermal interplay between aqueous fluid flow and crustal deformation. We carry out numerical simulations of multiphase (liquid-gas), multicomponent (H 2O-CO2) hydrothermal fluid flow and poroelastic deformation using a range of realistic physical parameters and processes. Hydrothermal fluid injection, circulation, and gas formation can generate complex, temporally and spatially varying patterns of GSD, with deformation rates, magnitudes, and geometries (including subsidence) similar to those observed in several large calderas. The potential for both rapid and gradual deformation resulting from magma-derived fluids suggests that hydrothermal fluid circulation may help explain deformation episodes at calderas that have not culminated in magmatic eruption.

Along-axis hydrothermal flow at the axis of slow spreading Mid-Ocean Ridges: Insights from numerical models of the Lucky Strike vent field (MAR)

NASA Astrophysics Data System (ADS)

Fontaine, Fabrice J.; Cannat, Mathilde; Escartin, Javier; Crawford, Wayne C.

2014-07-01

processes and efficiency of hydrothermal heat extraction along the axis of mid-ocean ridges are controlled by lithospheric thermal and permeability structures. Hydrothermal circulation models based on the structure of fast and intermediate spreading ridges predict that hydrothermal cell organization and vent site distribution are primarily controlled by the thermodynamics of high-temperature mid-ocean ridge hydrothermal fluids. Using recent constraints on shallow structure at the slow spreading Lucky Strike segment along the Mid-Atlantic Ridge, we present a physical model of hydrothermal cooling that incorporates the specificities of a magma-rich slow spreading environment. Using three-dimensional numerical models, we show that, in contrast to the aforementioned models, the subsurface flow at Lucky Strike is primarily controlled by across-axis permeability variations. Models with across-axis permeability gradients produce along-axis oriented hydrothermal cells and an alternating pattern of heat extraction highs and lows that match the distribution of microseismic clusters recorded at the Lucky Strike axial volcano. The flow is also influenced by temperature gradients at the base of the permeable hydrothermal domain. Although our models are based on the structure and seismicity of the Lucky Strike segment, across-axis permeability gradients are also likely to occur at faster spreading ridges and these results may also have important implications for the cooling of young crust at fast and intermediate spreading centers.

The physical hydrogeology of ore deposits

USGS Publications Warehouse

Ingebritsen, Steven E.; Appold, M.S.

2012-01-01

Hydrothermal ore deposits represent a convergence of fluid flow, thermal energy, and solute flux that is hydrogeologically unusual. From the hydrogeologic perspective, hydrothermal ore deposition represents a complex coupled-flow problem—sufficiently complex that physically rigorous description of the coupled thermal (T), hydraulic (H), mechanical (M), and chemical (C) processes (THMC modeling) continues to challenge our computational ability. Though research into these coupled behaviors has found only a limited subset to be quantitatively tractable, it has yielded valuable insights into the workings of hydrothermal systems in a wide range of geologic environments including sedimentary, metamorphic, and magmatic. Examples of these insights include the quantification of likely driving mechanisms, rates and paths of fluid flow, ore-mineral precipitation mechanisms, longevity of hydrothermal systems, mechanisms by which hydrothermal fluids acquire their temperature and composition, and the controlling influence of permeability and other rock properties on hydrothermal fluid behavior. In this communication we review some of the fundamental theory needed to characterize the physical hydrogeology of hydrothermal systems and discuss how this theory has been applied in studies of Mississippi Valley-type, tabular uranium, porphyry, epithermal, and mid-ocean ridge ore-forming systems. A key limitation in the computational state-of-the-art is the inability to describe fluid flow and transport fully in the many ore systems that show evidence of repeated shear or tensional failure with associated dynamic variations in permeability. However, we discuss global-scale compilations that suggest some numerical constraints on both mean and dynamically enhanced crustal permeability. Principles of physical hydrogeology can be powerful tools for investigating hydrothermal ore formation and are becoming increasingly accessible with ongoing advances in modeling software.

Exploration and discovery in Yellowstone Lake: Results from high-resolution sonar imaging, seismic reflection profiling, and submersible studies

USGS Publications Warehouse

Morgan, L.A.; Shanks, Wayne C.; Lovalvo, D.A.; Johnson, S.Y.; Stephenson, W.J.; Pierce, K.L.; Harlan, S.S.; Finn, C.A.; Lee, G.; Webring, M.; Schulze, B.; Duhn, J.; Sweeney, R.; Balistrieri, L.

2003-01-01

Discoveries from multi-beam sonar mapping and seismic reflection surveys of the northern, central, and West Thumb basins of Yellowstone Lake provide new insight into the extent of post-collapse volcanism and active hydrothermal processes occurring in a large lake environment above a large magma chamber. Yellowstone Lake has an irregular bottom covered with dozens of features directly related to hydrothermal, tectonic, volcanic, and sedimentary processes. Detailed bathymetric, seismic reflection, and magnetic evidence reveals that rhyolitic lava flows underlie much of Yellowstone Lake and exert fundamental control on lake bathymetry and localization of hydrothermal activity. Many previously unknown features have been identified and include over 250 hydrothermal vents, several very large (>500 m diameter) hydrothermal explosion craters, many small hydrothermal vent craters (???1-200 m diameter), domed lacustrine sediments related to hydrothermal activity, elongate fissures cutting post-glacial sediments, siliceous hydrothermal spire structures, sublacustrine landslide deposits, submerged former shorelines, and a recently active graben. Sampling and observations with a submersible remotely operated vehicle confirm and extend our understanding of the identified features. Faults, fissures, hydrothermally inflated domal structures, hydrothermal explosion craters, and sublacustrine landslides constitute potentially significant geologic hazards. Toxic elements derived from hydrothermal processes also may significantly affect the Yellowstone ecosystem. Published by Elsevier Science B.V.

Amino Acid Stability in the Early Oceans

NASA Technical Reports Server (NTRS)

Parker, E. T.; Brinton, K. L.; Burton, A. S.; Glavin, D. P.; Dworkin, J. P.; Bada, J. L.

2015-01-01

It is likely that a variety of amino acids existed in the early oceans of the Earth at the time of the origin and early evolution of life. "Primordial soup", hydrothermal vent, and meteorite based processes could have contributed to such an inventory. Several "protein" amino acids were likely present, however, based on prebiotic synthesis experiments and carbonaceous meteorite studies, non-protein amino acids, which are rare on Earth today, were likely the most abundant. An important uncertainty is the length of time these amino acids could have persisted before their destruction by abiotic and biotic processes. Prior to life, amino acid concentrations in the oceans were likely regulated by circulation through hydro-thermal vents. Today, the entire ocean circulates through vent systems every 10(exp 7) years. On the early Earth, this value was likely smaller due to higher heat flow and thus marine amino acid life-time would have been shorter. After life, amino acids in the oceans could have been assimilated by primitive organisms.

The Sound Generated by Mid-Ocean Ridge Black Smoker Hydrothermal Vents

PubMed Central

Crone, Timothy J.; Wilcock, William S.D.; Barclay, Andrew H.; Parsons, Jeffrey D.

2006-01-01

Hydrothermal flow through seafloor black smoker vents is typically turbulent and vigorous, with speeds often exceeding 1 m/s. Although theory predicts that these flows will generate sound, the prevailing view has been that black smokers are essentially silent. Here we present the first unambiguous field recordings showing that these vents radiate significant acoustic energy. The sounds contain a broadband component and narrowband tones which are indicative of resonance. The amplitude of the broadband component shows tidal modulation which is indicative of discharge rate variations related to the mechanics of tidal loading. Vent sounds will provide researchers with new ways to study flow through sulfide structures, and may provide some local organisms with behavioral or navigational cues. PMID:17205137

The dynamics of Black Smokers: a heated-salty plume analog.

NASA Astrophysics Data System (ADS)

Maxworthy, Tony

2004-11-01

Experiments have been carried out on the dynamical processes that govern the evolution of hot, salty plumes injected into cold surroundings. Under the appropriate circumstances these are then used as an analoque system to understand some features of particle-laden, deep-ocean, hydrothermal plumes, e.g., Black Smokers. Details of the temperature distributions over a wide range of parameters are presented and these, coupled with flow visualization experiments, have yielded a fairly complete picture of the important features of the flow. As a result it has been concluded that cabelling processes are critical to an understanding of the flow reversals found in a certain parameter range and that double diffusive processes, though present, are of minor importance. As a final exercise an example is worked through in which the circumstances for flow reversal in deep-sea plumes have been estimated based on the best available knowledge of these interesting entities.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yusa, Y.; Ohsawa, S.; Kitaoka, K.

The central part of Kyushu Island, southwest Japan, is located at the junction of the Southwest Japan Arc and the Ryukyu Arc, where a graben (Beppu-Shimabara Graben) has been formed by the rifting tectonic movement. There are many Quaternary volcanoes and active geo- and hydro-thermal fields within the Graben. The Beppu hydrothermal system extends around the Tsurumi-Garandake volcanoes at the eastern end of the Graben. This report will deal with the hydrothermal system beneath the volcanoes specially focusing on Garandake. Modest or violent fumarolic activities are visible near the summit of Garandake (1045 m in height). The total water(steam) outputmore » is 1.4 kg/s and its heat output 3.8 MW, while the heat output from the ground surface of 5.5 x 10{sup 4} m{sup 2} is 19.5 MW estimated by a heat balance analysis based on infrared radiation measurements (Yuhara et al., 1987). Thus the main process of heat discharge from Garandake, totally 23.3 MW, is the radiation from the ground surface. The geothermal gradient observed in a well drilled near the summit indicates that the large heat output is caused by some special process different from conduction because the heat flow by conduction is estimated to be 0.03 MW, which is very small compared with the observed output. Allis and Yusa (1989) suggested that a two-phase flow system is developed in Garandake. The two-phase flow, steam rising and water failing, acts as a heat pipe, by which a large quantity of (latent) heat can be transported upwards. Applying the theory of two-phase flow (Yusa and Oishi, 1989) to the Garandake system, the upflow rate of steam is estimated to be 10.3 kg/s at 100{degrees}C; the temperature near the ground surface, A part of rising steam (1.4 kg/s) flows out through fumaroles, and the remnant condenses to flow downwards. If the system is vapor-dominated, the intrinsic permeability at the shallow part should be about 1 darcy.« less

Using noble gases measured in spring discharge to trace hydrothermal processes in the Norris Geyser Basin, Yellowstone National Park, U.S.A.

USGS Publications Warehouse

Gardner, W.P.; Susong, D.D.; Solomon, D.K.; Heasler, H.P.

2010-01-01

Dissolved noble gas concentrations in springs are used to investigate boiling of hydrothermal water and mixing of hydrothermal and shallow cool water in the Norris Geyser Basin area. Noble gas concentrations in water are modeled for single stage and continuous steam removal. Limitations on boiling using noble gas concentrations are then used to estimate the isotopic effect of boiling on hydrothermal water, allowing the isotopic composition of the parent hydrothermal water to be determined from that measured in spring. In neutral chloride springs of the Norris Geyser Basin, steam loss since the last addition of noble gas charged water is less than 30% of the total hydrothermal discharge, which results in an isotopic shift due to boiling of ?? 2.5% ??D. Noble gas concentrations in water rapidly and predictably change in dual phase systems, making them invaluable tracers of gas-liquid interaction in hydrothermal systems. By combining traditional tracers of hydrothermal flow such as deuterium with dissolved noble gas measurements, more complex hydrothermal processes can be interpreted. ?? 2010 Elsevier B.V.

Microbial processing of carbon in hydrothermal systems (Invited)

NASA Astrophysics Data System (ADS)

LaRowe, D.; Amend, J. P.

2013-12-01

Microorganisms are known to be active in hydrothermal systems. They catalyze reactions that consume and produce carbon compounds as a result of their efforts to gain energy, grow and replace biomass. However, the rates of these processes, as well as the size of the active component of microbial populations, are poorly constrained in hydrothermal environments. In order to better characterize biogeochemical processes in these settings, a quantitative relationship between rates of microbial catalysis, energy supply and demand and population size is presented. Within this formulation, rates of biomass change are determined as a function of the proportion of catabolic power that is converted into biomass - either new microorganisms or the replacement of existing cell components - and the amount of energy that is required to synthesize biomass. The constraints that hydrothermal conditions place on power supply and demand are explicitly taken into account. The chemical composition, including the concentrations of organic compounds, of diffuse and focused flow hydrothermal fluids, hydrothermally influenced sediment pore water and fluids from the oceanic lithosphere are used in conjunction with cell count data and the model described above to constrain the rates of microbial processes that influence the carbon cycle in the Juan de Fuca hydrothermal system.

Exploration and discovery in Yellowstone Lake: results from high-resolution sonar imaging, seismic reflection profiling, and submersible studies

NASA Astrophysics Data System (ADS)

Morgan, L. A.; Shanks, W. C.; Lovalvo, D. A.; Johnson, S. Y.; Stephenson, W. J.; Pierce, K. L.; Harlan, S. S.; Finn, C. A.; Lee, G.; Webring, M.; Schulze, B.; Dühn, J.; Sweeney, R.; Balistrieri, L.

2003-04-01

'No portion of the American continent is perhaps so rich in wonders as the Yellow Stone' (F.V. Hayden, September 2, 1874) Discoveries from multi-beam sonar mapping and seismic reflection surveys of the northern, central, and West Thumb basins of Yellowstone Lake provide new insight into the extent of post-collapse volcanism and active hydrothermal processes occurring in a large lake environment above a large magma chamber. Yellowstone Lake has an irregular bottom covered with dozens of features directly related to hydrothermal, tectonic, volcanic, and sedimentary processes. Detailed bathymetric, seismic reflection, and magnetic evidence reveals that rhyolitic lava flows underlie much of Yellowstone Lake and exert fundamental control on lake bathymetry and localization of hydrothermal activity. Many previously unknown features have been identified and include over 250 hydrothermal vents, several very large (>500 m diameter) hydrothermal explosion craters, many small hydrothermal vent craters (˜1-200 m diameter), domed lacustrine sediments related to hydrothermal activity, elongate fissures cutting post-glacial sediments, siliceous hydrothermal spire structures, sublacustrine landslide deposits, submerged former shorelines, and a recently active graben. Sampling and observations with a submersible remotely operated vehicle confirm and extend our understanding of the identified features. Faults, fissures, hydrothermally inflated domal structures, hydrothermal explosion craters, and sublacustrine landslides constitute potentially significant geologic hazards. Toxic elements derived from hydrothermal processes also may significantly affect the Yellowstone ecosystem.

Coupled cycling of Fe and organic carbon in submarine hydrothermal systems: Modelling approach

NASA Astrophysics Data System (ADS)

Legendre, Louis; German, Christopher R.; Sander, Sylvia G.; Niquil, Nathalie

2014-05-01

It has been recently proposed that hydrothermal plumes may be a significant source of dissolved Fe to the oceans. In order to assess this proposal, we investigated the fate of dissolved Fe released from hydrothermal systems to the overlying ocean using an approach that combined modelling and field values. We based our work on a consensus conceptual model developed by members of SCOR-InterRidge Working Group 135. The model was both complex enough to capture the main processes of dissolved Fe released from hydrothermal systems and chemical transformation in the hydrothermal plume, and simple enough to be parameterized with existing field data. It included the following flows: Fe, water and heat in the high temperature vent fluids, in the fluids diffusing around the vent, and in the entrained seawater in the buoyant plume; Fe precipitation in polymetallic sulphides near the vent; transport of Fe in the non-buoyant plume, and both its precipitation in particles onto the sea bottom away from the vent and dissolution into deep-sea waters. In other words, there were three Fe input flows into the buoyant hydrothermal plume (vent-fluids; entrained diffuse flow; entrained seawater) and three Fe output flows (sedimentation from the buoyant plume as polymetallic sulfides; sedimentation from the non-buoyant plume in particulate form; export to the deep ocean in dissolved or nanoparticulate form). The output flows balanced the input flows. We transformed the conceptual model into equations, and parameterized these with field data. To do so, we assumed that all hydrothermal systems, globally, can be represented by the circumstances that prevail at the EPR 9°50'N hydrothermal field, although we knew this assumption not to be accurate. We nevertheless achieved, by following this approach, two important goals, i.e. we could assemble into a coherent framework, for the first time, several discrete data sets acquired independently over decades of field work, and we could obtain model results that were consistent with recent field observations. We used our model to explore scenarios of Fe emissions and transformations under various constraints. The modelling exercises indicated that the provision of significant amounts of dissolved Fe to the oceans by hydrothermal plumes was consistent with realistic model parameters. This supported the proposition that hydrothermal systems play significant roles in the global biogeochemical Fe cycle.

High-Resolution Photo-Mosaicing of the Rosebud Hydrothermal Vent Site and Surrounding Lava Flows, Galapagos Rift 86W: Techniques and Interpretations

NASA Astrophysics Data System (ADS)

Rzhanov, Y.; Mayer, L.; Fornari, D.; Shank, T.; Humphris, S.; Scheirer, D.; Kinsey, J.; Whitcomb, L.

2003-12-01

The Rosebud hydrothermal vent field was discovered in May 2002 in the Galapagos Rift near 86W during a series of Alvin dives and ABE autonomous vehicle surveys. Vertical-incidence digital imaging using a 3.1 Mpixel digital camera and strobe illumination from altitudes of 3-5m was carried out during the Alvin dives. A complete survey of the Rosebud vent site was carried out on Alvin Dive 3790. Submersible position was determined by post-cruise integration of 1.2 MHz bottom-lock Doppler sonar velocity data logged at 5Hz, integrated with heading and attitude data from a north-seeking fiber-optic gyroscope logged at 10Hz, and initialized with a surveyed-in long-baseline transponder navigation system providing geodetic position fixes at 15s intervals. The photo-mosaicing process consisted of three main stages: pre-processing, pair-wise image co-registration, and global alignment. Excellent image quality allowed us to avoid lens distortion correction, so images only underwent histogram equalization. Pair-wise co-registration of sequential frames was done partially automatically (where overlap exceeded 70 percent we employed a frequency-domain based technique), and partially manually (when overlap did not exceed 15 percent and manual feature extraction was the only way to find transformations relating the frames). Partial mosaics allowed us to determine which non-sequential frames had substantial overlap, and the corresponding transformations were found via feature extraction. Global alignment of the images consisted of construction of a sparse, nonlinear over-constrained system of equations reflecting positions of the frames in real-world coordinates. This system was solved using least squares, and the solution provided globally optimal positions of the frames in the overall mosaic. Over 700 images were mosaiced resulting in resolution of ~3 mm per pixel. The mosaiced area covers approximately 50 m x 60 m and clearly shows several biological zonations and distribution of lava flow morphologies, including what is interpreted as the contact between older lobate lava and the young sheet flow that hosts Rosebud vent communities. Recruitment of tubeworms, mussels, and clams is actively occurring at more than five locations oriented on a NE-SW trend where vent emissions occur through small cracks in the sheet flow. Large-scale views of seafloor hydrothermal vent sites, such as the one produced for Rosebud, are critical to properly understanding spatial relationships between hydrothermal biological communities, sites of focused and diffuse fluid flow, and the complex array of volcanic and tectonic features at mid-ocean ridge crests. These high-resolution perspectives are also critical to time-series studies where quantitative documentation of changes can be related to variations in hydrothermal, magmatic and tectonic processes.

Process Development for Hydrothermal Liquefaction of Algae Feedstocks in a Continuous-Flow Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elliott, Douglas C.; Hart, Todd R.; Schmidt, Andrew J.

Wet algae slurries can be converted into an upgradeable biocrude by hydrothermal liquefaction (HTL). High levels of carbon conversion to gravity-separable biocrude product were accomplished at relatively low temperature (350 °C) in a continuous-flow, pressurized (sub-critical liquid water) environment (20 MPa). As opposed to earlier work in batch reactors reported by others, direct oil recovery was achieved without the use of a solvent and biomass trace components were removed by processing steps so that they did not cause process difficulties. High conversions were obtained even with high slurry concentrations of up to 35 wt% of dry solids. Catalytic hydrotreating wasmore » effectively applied for hydrodeoxygenation, hydrodenitrogenation, and hydrodesulfurization of the biocrude to form liquid hydrocarbon fuel. Catalytic hydrothermal gasification was effectively applied for HTL byproduct water cleanup and fuel gas production from water soluble organics, allowing the water to be considered for recycle of nutrients to the algae growth ponds. As a result, high conversion of algae to liquid hydrocarbon and gas products was found with low levels of organic contamination in the byproduct water. All three process steps were accomplished in bench-scale, continuous-flow reactor systems such that design data for process scale-up was generated.« less

East Pacific rise at 21°N: the volcanic, tectonic, and hydrothermal processes of the central axis

USGS Publications Warehouse

Ballard, Richard D.; Francheteau, Jean; Juteau, Tierre; Rangan, Claude; Normark, William

1981-01-01

Photographs obtained by the ANGUS survey system at 21°N reveal many similarities to the geological processes delineated at other spreading centers and in particular those observed in the Galapagos Rift at 86°W. The region of recent volcanism is restricted to a narrow zone (Zone 1) approximately 1 km wide. This suggests that the width of the magma chamber feeding these flows is also narrow at the top. Variations in sediment cover are used to subdivide the flows within Zone 1 into three sheet-flow/pillow-flow pairs. The youngest pair appears to have erupted form a linear fissure 8 km long running parallel to the valley axis. This fissure is part of a larger en echelon pattern of eruptive fissures. Active hydrothermal vents associated with the youngest flows are situated directly above the apparent eruptive fissure. The high (350°C) temperature for some of the fluids exiting from the vents suggests a highly restricted circulation system involving, at times, little to no mixing with cold seawater. The lava terrain in the remainder of Zone 1 and bordering regions is characterized by extensive fracturing, further suggesting a narrow upper dimension to the magma chamber and also that subsurface hydrothermal deposition of massive sulfides may lead to a reduction in the mixing processes.

East Pacific Rise at 21 °N: The volcanic, tectonic, and hydrothermal processes of the central axis

USGS Publications Warehouse

Ballard, Richard D.; Francheteau, Jean; Juteau, Tierre; Rangan, Claude; Normark, William R.

1981-01-01

Photographs obtained by the ANGUS survey system at 21°N reveal many similarities to the geological processes delineated at other spreading centers and in particular those observed in the Galapagos Rift at 86°W. The region of recent volcanism is restricted to a narrow zone (Zone l) approximately l km wide. This suggests that the width of the magma chamber feeding these flows is also narrow at the top. Variations in sediment cover are used to subdivide the flows within Zone 1 into three sheet-flow/pillow-flow pairs. The youngest pair appears to have erupted form a linear fissure 8 km long running parallel to the valley axis. This fissure is part of a larger en echelon pattern of eruptive fissures. Active hydrothermal vents associated with the youngest flows are situated directly above the apparent eruptive fissure. The high (350°C) temperature for some of the fluids exiting from the vents suggests a highly restricted circulation system involving, at times, little to no mixing with cold seawater. The lava terrain in the remainder of Zone l and bordering regions is characterized by extensive fracturing, further suggesting a narrow upper dimension to the magma chamber and also that subsurface hydrothermal deposition of massive sulfides may lead to a reduction in the mixing processes.

East Pacific rise at 21°N: The volcanic, tectonic, and hydrothermal processes of the central axis

NASA Astrophysics Data System (ADS)

Ballard, Robert D.; Francheteau, Jean; Juteau, Tierre; Rangan, Claude; Normark, William

1981-09-01

Photographs obtained by the ANGUS survey system at 21°N reveal many similarities to the geological processes delineated at other spreading centers and in particular those observed in the Galapagos Rift at 86°W. The region of recent volcanism is restricted to a narrow zone (Zone 1) approximately 1 km wide. This suggests that the width of the magma chamber feeding these flows is also narrow at the top. Variations in sediment cover are used to subdivide the flows within Zone 1 into three sheet-flow/pillow-flow pairs. The youngest pair appears to have erupted form a linear fissure 8 km long running parallel to the valley axis. This fissure is part of a larger en echelon pattern of eruptive fissures. Active hydrothermal vents associated with the youngest flows are situated directly above the apparent eruptive fissure. The high (350°C) temperature for some of the fluids exiting from the vents suggests a highly restricted circulation system involving, at times, little to no mixing with cold seawater. The lava terrain in the remainder of Zone 1 and bordering regions is characterized by extensive fracturing, further suggesting a narrow upper dimension to the magma chamber and also that subsurface hydrothermal deposition of massive sulfides may lead to a reduction in the mixing processes.

WHATS-3: An improved flow-through multi-bottle fluid sampler for deep-sea geofluid research

NASA Astrophysics Data System (ADS)

Miyazaki, Junichi; Makabe, Akiko; Matsui, Yohei; Ebina, Naoya; Tsutsumi, Saki; Ishibashi, Jun-ichiro; Chen, Chong; Kaneko, Sho; Takai, Ken; Kawagucci, Shinsuke

2017-06-01

Deep-sea geofluid systems, such as hydrothermal vents and cold seeps, are key to understanding subseafloor environments of Earth. Fluid chemistry, especially, provides crucial information towards elucidating the physical, chemical and biological processes that occur in these ecosystems. To accurately assess fluid and gas properties of deep-sea geofluids, well-designed pressure-tight fluid samplers are indispensable and as such they are important assets of deep-sea geofluid research. Here, the development of a new flow-through, pressure-tight fluid sampler capable of four independent sampling events (two subsamples for liquid and gas analyses from each) is reported. This new sampler, named WHATS-3, is a new addition to the WHATS-series samplers and a major upgrade from the previous WHATS-2 sampler with improvements in sample number, valve operational time, physical robustness, and ease of maintenance. Routine laboratory-based pressure tests proved that it is suitable for operation up to 35 MPa pressure. Successful field tests of the new sampler were also carried out in five hydrothermal fields, two in Indian Ocean and three in Okinawa Trough (max. depth 3,300 m). Relations of Mg and major ion species demonstrated bimodal mixing trends between a hydrothermal fluid and seawater, confirming the high-quality of fluids sampled. The newly developed WHATS-3 sampler is well-balanced in sampling capability, field usability, and maintenance feasibility, and can serve as one of the best geofluid samplers available at present to conduct efficient research of deep-sea geofluid systems.

Seismological evidence for an along-axis hydrothermal flow at the Lucky Strike hydrothermal vents site

NASA Astrophysics Data System (ADS)

Rai, A.; Wang, H.; Singh, S. C.; Crawford, W. C.; Escartin, J.; Cannat, M.

2010-12-01

Hydrothermal circulation at ocean spreading centres plays fundamental role in crustal accretion process, heat extraction from the earth and helps to maintain very rich ecosystem in deep Ocean. Recently, it has been suggested that hydrothermal circulation is mainly along the ridge axis at fast spreading centres above along axis melt lens (AMC). Using a combination of micro-earthquake and seismic reflection data, we show that the hydrothermal circulation at the Lucky Strike segment of slow spreading Mid-Atlantic Ridge is also along axis in a narrow (~1 km) zone above a wide (2-3 km) AMC. We find that the seismicity mainly lies above the seismically imaged 3 km wide 7 km long melt lens at 3.2 km depth. We observe a vertical plume of seismicity above a weak AMC reflection just north of the hydrothermal vent fields that initiates just above the AMC and continues to the seafloor. This zone is collocated with active rifting of the seafloor in the neo-volcanic zone. Beneath the hydrothermal vents sites, where a strong melt lens is imaged, the seismicity initiates at 500 m above the AMC and continues to the seafloor. Just south of the hydrothermal field, where the AMC is widest and strongest, the seismicity band lies 500 m above the melt lens in a 800 m thick zone, which does not continue to the seafloor. The presence the weak melt lens reflection could be due to a cooled and crystallised AMC (mush) that permits the penetration of hydrothermal fluids down to the top of the AMC indicated by seismicity plume and might be the in-flow zone for hydrothermal circulation. The strong AMC reflection could be due to fresh supply of melt in the AMC (pure melt), which has pushed the cracking front 500 m above the AMC. Beneath the hydrothermal fields, the strong AMC reflection and seismicity 500 above the AMC to the seafloor could represent cracking along the up-flow zone. The 800 m thick zone of seismicity above the pure melt zone could be the zone of hydrothermal cracking zone. We do not observe any seismicity along the main bounding faults. These results suggest that the hydrothermal flow is mainly along the ridge axis in a narrow zone above the AMC, even when the AMC only 7 km long.

A noninvasive method for measuring the velocity of diffuse hydrothermal flow by tracking moving refractive index anomalies

NASA Astrophysics Data System (ADS)

Mittelstaedt, Eric; Davaille, Anne; van Keken, Peter E.; Gracias, Nuno; Escartin, Javier

2010-10-01

Diffuse flow velocimetry (DFV) is introduced as a new, noninvasive, optical technique for measuring the velocity of diffuse hydrothermal flow. The technique uses images of a motionless, random medium (e.g., rocks) obtained through the lens of a moving refraction index anomaly (e.g., a hot upwelling). The method works in two stages. First, the changes in apparent background deformation are calculated using particle image velocimetry (PIV). The deformation vectors are determined by a cross correlation of pixel intensities across consecutive images. Second, the 2-D velocity field is calculated by cross correlating the deformation vectors between consecutive PIV calculations. The accuracy of the method is tested with laboratory and numerical experiments of a laminar, axisymmetric plume in fluids with both constant and temperature-dependent viscosity. Results show that average RMS errors are ˜5%-7% and are most accurate in regions of pervasive apparent background deformation which is commonly encountered in regions of diffuse hydrothermal flow. The method is applied to a 25 s video sequence of diffuse flow from a small fracture captured during the Bathyluck'09 cruise to the Lucky Strike hydrothermal field (September 2009). The velocities of the ˜10°C-15°C effluent reach ˜5.5 cm/s, in strong agreement with previous measurements of diffuse flow. DFV is found to be most accurate for approximately 2-D flows where background objects have a small spatial scale, such as sand or gravel.

Diffuse CO2 degassing at Vesuvio, Italy

NASA Astrophysics Data System (ADS)

Frondini, Francesco; Chiodini, Giovanni; Caliro, Stefano; Cardellini, Carlo; Granieri, Domenico; Ventura, Guido

2004-10-01

At Vesuvio, a significant fraction of the rising hydrothermal-volcanic fluids is subjected to a condensation and separation process producing a CO2-rich gas phase, mainly expulsed through soil diffuse degassing from well defined areas called diffuse degassing structures (DDS), and a liquid phase that flows towards the outer part of the volcanic cone. A large amount of thermal energy is associated with the steam condensation process and subsequent cooling of the liquid phase. The total amount of volcanic-hydrothermal CO2 discharged through diffuse degassing has been computed through a sequential Gaussian simulation (sGs) approach based on several hundred accumulation chamber measurements and, at the time of the survey, amounted to 151 t d-1. The steam associated with the CO2 output, computed assuming that the original H2O/CO2 ratio of hydrothermal fluids is preserved in fumarolic effluents, is 553 t d-1, and the energy produced by the steam condensation and cooling of the liquid phase is 1.47×1012 J d-1 (17 MW). The location of the CO2 and temperature anomalies show that most of the gas is discharged from the inner part of the crater and suggests that crater morphology and local stratigraphy exert strong control on CO2 degassing and subsurface steam condensation. The amounts of gas and energy released by Vesuvio are comparable to those released by other volcanic degassing areas of the world and their estimates, through periodic surveys of soil CO2 flux, can constitute a useful tool to monitor volcanic activity.

The rapid size- and shape-controlled continuous hydrothermal synthesis of metal sulphide nanomaterials

NASA Astrophysics Data System (ADS)

Dunne, Peter W.; Starkey, Chris L.; Gimeno-Fabra, Miquel; Lester, Edward H.

2014-01-01

Continuous flow hydrothermal synthesis offers a cheap, green and highly scalable route for the preparation of inorganic nanomaterials which has predominantly been applied to metal oxide based materials. In this work we report the first continuous flow hydrothermal synthesis of metal sulphide nanomaterials. A wide range of binary metal sulphides, ZnS, CdS, PbS, CuS, Fe(1-x)S and Bi2S3, have been synthesised. By varying the reaction conditions two different mechanisms may be invoked; a growth dominated route which permits the formation of nanostructured sulphide materials, and a nucleation driven process which produces nanoparticles with temperature dependent size control. This offers a new and industrially viable route to a wide range of metal sulphide nanoparticles with facile size and shape control.Continuous flow hydrothermal synthesis offers a cheap, green and highly scalable route for the preparation of inorganic nanomaterials which has predominantly been applied to metal oxide based materials. In this work we report the first continuous flow hydrothermal synthesis of metal sulphide nanomaterials. A wide range of binary metal sulphides, ZnS, CdS, PbS, CuS, Fe(1-x)S and Bi2S3, have been synthesised. By varying the reaction conditions two different mechanisms may be invoked; a growth dominated route which permits the formation of nanostructured sulphide materials, and a nucleation driven process which produces nanoparticles with temperature dependent size control. This offers a new and industrially viable route to a wide range of metal sulphide nanoparticles with facile size and shape control. Electronic supplementary information (ESI) available: Experimental details, refinement procedure, fluorescence spectra of ZnS samples. See DOI: 10.1039/c3nr05749f

Using Image Analysis to Explore Changes In Bacterial Mat Coverage at the Base of a Hydrothermal Vent within the Caldera of Axial Seamount

NASA Astrophysics Data System (ADS)

Knuth, F.; Crone, T. J.; Marburg, A.

2017-12-01

The Ocean Observatories Initiative's (OOI) Cabled Array is delivering real-time high-definition video data from an HD video camera (CAMHD), installed at the Mushroom hydrothermal vent in the ASHES hydrothermal vent field within the caldera of Axial Seamount, an active submarine volcano located approximately 450 kilometers off the coast of Washington at a depth of 1,542 m. Every three hours the camera pans, zooms and focuses in on nine distinct scenes of scientific interest across the vent, producing 14-minute-long videos during each run. This standardized video sampling routine enables scientists to programmatically analyze the content of the video using automated image analysis techniques. Each scene-specific time series dataset can service a wide range of scientific investigations, including the estimation of bacterial flux into the system by quantifying chemosynthetic bacterial clusters (floc) present in the water column, relating periodicity in hydrothermal vent fluid flow to earth tides, measuring vent chimney growth in response to changing hydrothermal fluid flow rates, or mapping the patterns of fauna colonization, distribution and composition across the vent over time. We are currently investigating the seventh scene in the sampling routine, focused on the bacterial mat covering the seafloor at the base of the vent. We quantify the change in bacterial mat coverage over time using image analysis techniques, and examine the relationship between mat coverage, fluid flow processes, episodic chimney collapse events, and other processes observed by Cabled Array instrumentation. This analysis is being conducted using cloud-enabled computer vision processing techniques, programmatic image analysis, and time-lapse video data collected over the course of the first CAMHD deployment, from November 2015 to July 2016.

Basin-scale hydrogeologic modeling

NASA Astrophysics Data System (ADS)

Person, Mark; Raffensperger, Jeff P.; Ge, Shemin; Garven, Grant

1996-02-01

Mathematical modeling of coupled groundwater flow, heat transfer, and chemical mass transport at the sedimentary basin scale has been increasingly used by Earth scientists studying a wide range of geologic processes including the formation of excess pore pressures, infiltration-driven metamorphism, heat flow anomalies, nuclear waste isolation, hydrothermal ore genesis, sediment diagenesis, basin tectonics, and petroleum generation and migration. These models have provided important insights into the rates and pathways of groundwater migration through basins, the relative importance of different driving mechanisms for fluid flow, and the nature of coupling between the hydraulic, thermal, chemical, and stress regimes. The mathematical descriptions of basin transport processes, the analytical and numerical solution methods employed, and the application of modeling to sedimentary basins around the world are the subject of this review paper. The special considerations made to represent coupled transport processes at the basin scale are emphasized. Future modeling efforts will probably utilize three-dimensional descriptions of transport processes, incorporate greater information regarding natural geological heterogeneity, further explore coupled processes, and involve greater field applications.

Conversion of a wet waste feedstock to biocrude by hydrothermal processing in a continuous-flow reactor: grape pomace

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elliott, Douglas C.; Schmidt, Andrew J.; Hart, Todd R.

Wet waste feedstocks present an apt opportunity for biomass conversion to fuels by hydrothermal processing. In this study, grape pomace slurries from two varieties, Montepulciano and cabernet sauvignon, have been converted into a biocrude by hydrothermal liquefaction (HTL) in a bench-scale, continuous-flow reactor system. Carbon conversion to gravity-separable biocrude product up to 56 % was accomplished at relatively low temperature (350 C) in a pressurized (sub-critical liquid water) environment (20 MPa) when using grape pomace feedstock slurry with a 16.8 wt% concentration of dry solids processed at a liquid hourly space velocity of 2.1 h-1. Direct oil recovery was achievedmore » without the use of a solvent and biomass trace mineral components were removed by processing steps so that they did not cause processing difficulties. In addition, catalytic hydrothermal gasification (CHG) was effectively applied for HTL byproduct water cleanup using a Ru on C catalyst in a fixed bed producing a gas composed of methane and carbon dioxide from water soluble organics. Conversion of 99.8% of the chemical oxygen demand (COD) left in the aqueous phase was demonstrated. As a result, high conversion of grape pomace to liquid and gas fuel products was found with residual organic contamination in byproduct water reduced to <150 mg/kg COD.« less

Magnetic fabrics and fluid flow directions in hydrothermal systems. A case study in the Chaillac Ba-F-Fe deposits (France)

NASA Astrophysics Data System (ADS)

Sizaret, Stanislas; Chen, Yan; Chauvet, Alain; Marcoux, Eric; Touray, Jean Claude

2003-02-01

This study presents a possible use of anisotropy of magnetic susceptibility (AMS) to describe the mineralizing process in hydrothermal systems. Ba-F-Fe-rich deposits within the Chaillac Basin are on the southern border of the Paris Basin. In these deposits hydrothermal textures and tectonic structures have been described in veins, sinters, and sandstone cemented by hydrothermal goethite. 278 oriented cores from 24 sites have been collected in these formations. In addition, a lateritic duricrust superimposed on the hydrothermal formation has been sampled. Rock magnetic investigations show that the principal magnetic carrier is goethite for the hydrothermal mineralization and for the laterite level. The AMS measurements show distinguishable behaviors in the different mineralogical and geological contexts. The K1 magnetic lineation (maximum axis) is strongly inclined for the vertical veins. For the horizontally mineralized sinters, the magnetic lineation is almost horizontal with an azimuth similar to the sedimentary flow direction. The AMS of goethite-rich sandstone close to the veins shows strongly inclined K1 as they are probably influenced by the vertical veins; however, when the distance from the vein is larger than 1 m, the AMS presents rather horizontal K1 directions, parallel to the sedimentary flow. The laterite has a foliation dominance of AMS with vertically well-grouped K3 axes and scattered K1 and K2 axes. Field structural observations suggest that the ore deposit is mainly controlled by EW extension tectonics associated with NS trending normal faults. Combining the AMS results on the deposit with vein textures and field data a model is proposed in which AMS results are interpreted in terms of hydrothermal fluid flow. This work opens a new investigation field to constrain hydrodynamic models using the AMS method. Textural study combined with efficient AMS fabric measurements should be used for systematic investigation to trace flow direction in fissures and in sand porosity.

Aerogeophysical measurements of collapse-prone hydrothermally altered zones at Mount Rainier volcano.

PubMed

Finn, C A; Sisson, T W; Deszcz-Pan, M

2001-02-01

Hydrothermally altered rocks can weaken volcanoes, increasing the potential for catastrophic sector collapses that can lead to destructive debris flows. Evaluating the hazards associated with such alteration is difficult because alteration has been mapped on few active volcanoes and the distribution and severity of subsurface alteration is largely unknown on any active volcano. At Mount Rainier volcano (Washington, USA), collapses of hydrothermally altered edifice flanks have generated numerous extensive debris flows and future collapses could threaten areas that are now densely populated. Preliminary geological mapping and remote-sensing data indicated that exposed alteration is contained in a dyke-controlled belt trending east-west that passes through the volcano's summit. But here we present helicopter-borne electromagnetic and magnetic data, combined with detailed geological mapping, to show that appreciable thicknesses of mostly buried hydrothermally altered rock lie mainly in the upper west flank of Mount Rainier. We identify this as the likely source for future large debris flows. But as negligible amounts of highly altered rock lie in the volcano's core, this might impede collapse retrogression and so limit the volumes and inundation areas of future debris flows. Our results demonstrate that high-resolution geophysical and geological observations can yield unprecedented views of the three-dimensional distribution of altered rock.

Aerogeophysical measurements of collapse-prone hydrothermally altered zones at Mount Rainier volcano

USGS Publications Warehouse

Finn, C.A.; Sisson, T.W.; Deszcz-Pan, M.

2001-01-01

Hydrothermally altered rocks can weaken volcanoes, increasing the potential for catastrophic sector collapses that can lead to destructive debris flows1. Evaluating the hazards associated with such alteration is difficult because alteration has been mapped on few active volcanoes1-4 and the distribution and severity of subsurface alteration is largely unknown on any active volcano. At Mount Rainier volcano (Washington, USA), collapses of hydrothermally altered edifice flanks have generated numerous extensive debris flows5,6 and future collapses could threaten areas that are now densely populated7. Preliminary geological mapping and remote-sensing data indicated that exposed alteration is contained in a dyke-controlled belt trending east-west that passes through the volcano's summit3-5,8. But here we present helicopter-borne electromagnetic and magnetic data, combined with detailed geological mapping, to show that appreciable thicknesses of mostly buried hydrothermally altered rock lie mainly in the upper west flank of Mount Rainier. We identify this as the likely source for future large debris flows. But as negligible amounts of highly altered rock lie in the volcano's core, this might impede collapse retrogression and so limit the volumes and inundation areas of future debris flows. Our results demonstrate that high-resolution geophysical and geological observations can yield unprecedented views of the three-dimensional distribution of altered rock.

Numerical Modeling of Multiphase Fluid Flow in Ore-Forming Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Weis, P.; Driesner, T.; Coumou, D.; Heinrich, C. A.

2007-12-01

Two coexisting fluid phases - a variably saline liquid and a vapor phase - are ubiquitous in ore-forming and other hydrothermal systems. Understanding the dynamics of phase separation and the distinct physical and chemical evolution of the two fluids probably plays a key role in generating different ore deposit types, e.g. porphyry type, high and low sulfidation Cu-Mo-Au deposits. To this end, processes within hydrothermal systems have been studied with a refined numerical model describing fluid flow in transient porous media (CSP~5.0). The model is formulated on a mass, energy and momentum conserving finite-element-finite-volume (FEFV) scheme and is capable of simulating multiphase flow of NaCl-H20 fluids. Fluid properties are computed from an improved equation of state (SOWAT~2.0). It covers conditions with temperatures of up to 1000 degrees~C, pressures of up to 500 MPa, and fluid salinities of 0~to 100%~NaCl. In particular, the new set-up allows for a more accurate description of fluid phase separation during boiling of hydrothermal fluids into a vapor and a brine phase. The geometric flexibility of the FEFV-meshes allows for investigations of a large variety of geological settings, ranging from ore-forming processes in magmatic hydrothermal system to the dynamics of black smokers at mid-ocean ridges. Simulations demonstrated that hydrothermal convection patterns above cooling plutons are primarily controlled by the system-scale permeability structure. In porphyry systems, high fluid pressures develop in a stock rising from the magma chamber which can lead to rock failure and, eventually, an increase in permeability due to hydrofracturing. Comparisons of the thermal evolution as inferred from modeling studies with data from fluid inclusion studies of the Pb-Zn deposits of Madan, Bulgaria are in a strikingly good agreement. This indicates that cross-comparisons of field observations, analytical data and numerical simulations will become a powerful tool towards a more thorough understanding of hydrothermal fluid processes. One such attempt will incorporate geometric data of veins in the Bingham porphyry Cu-Mo-Au deposit into our numerical model. The presentation will introduce the numerical model and show examples and first results of the aforementioned applications.

Using the VentCam and Optical Plume Velocimetry to Measure High-Temperature Hydrothermal Fluid Flow Rates in the ASHES Vent Field on Axial Volcano

NASA Astrophysics Data System (ADS)

Crone, T. J.; Mittelstaedt, E. L.; Fornari, D. J.

2014-12-01

Fluid flow rates through high-temperature mid-ocean ridge hydrothermal vents are likely quite sensitive to poroelastic forcing mechanisms such as tidal loading and tectonic activity. Because poroelastic deformation and flow perturbations are estimated to extend to considerable depths within young oceanic crust, observations of flow rate changes at seafloor vents have the potential to provide constraints on the flow geometry and permeability structure of the underlying hydrothermal systems, as well as the quantities of heat and chemicals they exchange with overlying ocean, and the potential biological productivity of ecosystems they host. To help provide flow rate measurements in these challenging environments, we have developed two new optical flow oriented technologies. The first is a new form of Optical Plume Velocimetry (OPV) which relies on single-frame temporal cross-correlation to obtain time-averaged image velocity fields from short video sequences. The second is the VentCam, a deep sea camera system that can collect high-frame-rate video sequences at focused hydrothermal vents suitable for analysis with OPV. During the July 2014 R/V Atlantis/Alvin expedition to Axial Seamount, we deployed the VentCam at the ~300C Phoenix vent within the ASHES vent field and positioned it with DSRV Alvin. We collected 24 seconds of video at 50 frames per second every half-hour for approximately 10 days beginning July 22nd. We are currently applying single-frame lag OPV to these videos to estimate relative and absolute fluid flow rates through this vent. To explore the relationship between focused and diffuse venting, we deployed a second optical flow camera, the Diffuse Effluent Measurement System (DEMS), adjacent to this vent at a fracture within the lava carapace where low-T (~30C) fluids were exiting. This system collected video sequences and diffuse flow measurements at overlapping time intervals. Here we present the preliminary results of our work with VentCam and OPV, and comparisons with results from the DEMS camera.

Various-scale controls of complex subduction dynamics on magmatic-hydrothermal processes in eastern Mediterranean

NASA Astrophysics Data System (ADS)

Menant, Armel; Jolivet, Laurent; Sternai, Pietro; Ducoux, Maxime; Augier, Romain; Rabillard, Aurélien; Gerya, Taras; Guillou-Frottier, Laurent

2014-05-01

In subduction environment, magmatic-hydrothermal processes, responsible for the emplacement of magmatic bodies and related mineralization, are strongly controlled by slab dynamics. This 3D dynamics is often complex, resulting notably in spatial evolution through time of mineralization and magmatism types and in fast kinematic changes at the surface. Study at different scales of the distribution of these magmatic and hydrothermal products is useful to better constrain subduction dynamics. This work is focused on the eastern Mediterranean, where the complex dynamics of the Tethyan active margin since the upper Cretaceous is still largely debated. We propose new kinematic reconstructions of the region also showing the distribution of magmatic products and mineralization in space and time. Three main periods have thus been identified with a general southward migration of magmatic and ore bodies. (1) From late Cretaceous to lower Paleocene, calc-alkaline magmatism and porphyry Cu deposits emplaced notably in the Balkans, along a long linear cordillera. (2) From late Paleocene to Eocene, a barren period occurred while the Pelagonian microcontinent was buried within the subduction zone. (3) Since the Oligocene, Au-rich deposits and related K-rich magmatism emplaced in the Rhodopes, the Aegean and western Anatolian extensional domains in response to fast slab retreat and related mantle flow inducing the partial melting of the lithospheric mantle or the base of the upper crust where Au was previously stored. The emplacement at shallow level of this mineralization was largely controlled by large-scale structures that drained the magmatic-hydrothermal fluids. In the Cyclades for instance, field studies show that Au-rich but also base metal-rich ore deposits are syn-extensional and spatially related to large-scale detachment systems (e.g. on Tinos, Mykonos, Serifos islands), which are recognized as subduction-related structures. These results highlight the importance at different scales of subduction dynamics and related mantle flow on the emplacement of mineralization and magmatic bodies. Indeed, besides a general southward migration of the magmatic-hydrothermal activity since the upper Cretaceous from the Balkans to the present-day Aegean volcanic arc, a secondary westward migration is observed during the Miocene from the Menderes massif to the Cyclades. This feature is a possible consequence of a slab tearing event and related mantle flow, as suggested notably by tomographic models below western Anatolia. To further test the effects of slab retreat and tearing on the flow and temperature field within the mantle, we performed 3D thermo-mechanical numerical modeling. Models suggest that the asthenospheric flow induced by the development of a slab tear controls the migration of magmatic products stored at the base of the crust, influencing the distribution of potentially fertile magmas within the upper crust.

Coupling hydrothermal liquefaction and anaerobic digestion for energy valorization from model biomass feedstocks.

PubMed

Posmanik, Roy; Labatut, Rodrigo A; Kim, Andrew H; Usack, Joseph G; Tester, Jefferson W; Angenent, Largus T

2017-06-01

Hydrothermal liquefaction converts food waste into oil and a carbon-rich hydrothermal aqueous phase. The hydrothermal aqueous phase may be converted to biomethane via anaerobic digestion. Here, the feasibility of coupling hydrothermal liquefaction and anaerobic digestion for the conversion of food waste into energy products was examined. A mixture of polysaccharides, proteins, and lipids, representing food waste, underwent hydrothermal processing at temperatures ranging from 200 to 350°C. The anaerobic biodegradability of the hydrothermal aqueous phase was examined through conducting biochemical methane potential assays. The results demonstrate that the anaerobic biodegradability of the hydrothermal aqueous phase was lower when the temperature of hydrothermal processing increased. The chemical composition of the hydrothermal aqueous phase affected the anaerobic biodegradability. However, no inhibition of biodegradation was observed for most samples. Combining hydrothermal and anaerobic digestion may, therefore, yield a higher energetic return by converting the feedstock into oil and biomethane. Copyright © 2017 Elsevier Ltd. All rights reserved.

The rapid size- and shape-controlled continuous hydrothermal synthesis of metal sulphide nanomaterials.

PubMed

Dunne, Peter W; Starkey, Chris L; Gimeno-Fabra, Miquel; Lester, Edward H

2014-02-21

Continuous flow hydrothermal synthesis offers a cheap, green and highly scalable route for the preparation of inorganic nanomaterials which has predominantly been applied to metal oxide based materials. In this work we report the first continuous flow hydrothermal synthesis of metal sulphide nanomaterials. A wide range of binary metal sulphides, ZnS, CdS, PbS, CuS, Fe(1-x)S and Bi2S3, have been synthesised. By varying the reaction conditions two different mechanisms may be invoked; a growth dominated route which permits the formation of nanostructured sulphide materials, and a nucleation driven process which produces nanoparticles with temperature dependent size control. This offers a new and industrially viable route to a wide range of metal sulphide nanoparticles with facile size and shape control.

High-temperature hydrothermal circulation in the lower oceanic crust at fast spreading ridges: Reconciling geophysical and geochemical constraints

NASA Astrophysics Data System (ADS)

Wilcock, W.

2003-04-01

Hydrothermal circulation is the dominant mechanism for cooling young oceanic crust and knowledge of its depth, extent and timing is critical for our understanding of crustal accretion. At fast-spreading ridges there is considerable controversy regarding the importance of this process in the lower crust. Geochemical data indicate that high-temperature hydrothermal fluids react with the lower crust but they also suggest that the reactions are limited to a narrow temperature interval and involve relatively small volumes of fluid. As a result many geochemical studies conclude that high-temperature hydrothermal circulation plays a relatively small role in heat transport in the lower crust and occurs in a closed system that is isolated from upper crustal hydrothermal cells. In contrast, seismic observations on the fast spreading East Pacific Rise show that the mid-crustal axial magma chamber is underlain by a low velocity zone which is no more than 5-8 km wide throughout the lower crust and is interpreted as a region of elevated temperatures containing relatively low average melt fractions. Irrespective of the style of lower crustal accretion, simple physical considerations suggest that this structure is only thermally feasible if the lower crust cools by extensive hydrothermal circulation. Modeling studies indicate that this requires the permeability of the lower crust to temporarily reach at least ~10-13 m2. In order to reconcile the geochemical and geophysical data it is important to recognize that the thermal constraints do not require pervasive seawater circulation in the lower crust and can be satisfied by focused flow through narrow permeable zones spaced as far as about 1 km apart. Widely spaced regions of flow might be difficult to find in the field especially if the sampling strategies focus on the freshest outcrops. There is a tendency to overestimate the volume of fluid that must circulate through an open single-pass system. The fluid-rock ratios (0.2 - 1) inferred from oxygen isotope studies are often cited as evidence of limited circulation but when interpreted physically they are actually sufficient to transport a substantial proportion of the heat required to solidify and cool the lower crust. Nevertheless the geophysical constraints are also compatible with circulation in a two-layer double diffusive system favored by many researchers, in which the lower crust is cooled by a recirculating brine cell.

Characterization of the paleo-hydrothermal fluids flow in the geothermal province of Limagne. (French Massif Central).

NASA Astrophysics Data System (ADS)

Fréville, K.; Sizaret, S.

2017-12-01

Exploitation of the geothermal energy is a prime target to future energy supply. Understanding the nature and the flow of geothermal fluids is a key objective for describe the functioning of current hydrothermal systems. Located in the French Massif Central, the Limagne basin is a tertiary hemi-graben characterized by a high thermal gradient with numerous occurrences of CO2-rich thermo-mineral waters. This basin has potential for high-temperature geothermal energy, expressed by numerous natural high temperature water sources, as well as at Royat and Vichy were the surface temperature of the water can reach 33°C and 27°C, respectively. In order to better localize this potential, the geological evolution has to be deciphered. In this aim we study the flow processes of the paleo-fluids and estimate the direction and the velocity of the hydrothermal flow from the studies of the growth bands of comb quartz grain localized in vein. In a second time, the studies fluids inclusions within the quartz grain are used to characterize the nature of the fluids involved. Preliminary results show that the flow is discontinuous over the time with changes in velocities and directions during the growth of a single quartz grain. Two main flows were identified, i) a relatively fast upward flow at 10-6,-5 m.s-1; ii) a downward flow at about 10-5,-4 m.s-1. The results allow: (i) to discuss the processes controlling the fluids flow in the Limagne basin; and (ii) to suggest to delimitate the areas with high geothermal potential which integrate the flow variation in time.

Immobilization of LiCl-Li2O pyroprocessing salt wastes in chlorosodalite using glass-bonded hydrothermal and salt-occlusion methods

NASA Astrophysics Data System (ADS)

Riley, Brian J.; Peterson, Jacob A.; Kroll, Jared O.; Frank, Steven M.

2018-04-01

In this study, hydrothermal and salt-occlusion processes were used to make chlorosodalite through reactions with a high-LiCl salt simulating a waste stream generated from pyrochemical treatment of oxide-based used nuclear fuel. Some products were reacted with glass binders to increase chlorosodalite yield through alkali ion exchange and to aid in densification. Hydrothermal processes included reaction of the salt simulant in an autoclave with either zeolite 4A or sodium aluminate and colloidal silica. Chlorosodalite yields in the crystalline products were nearly complete in the glass-bonded materials at values of 100 mass% for the salt-occlusion method, up to 99.0 mass% for the hydrothermal synthesis with zeolite 4A, and up to 96 mass% for the hydrothermal synthesis with sodium aluminate and colloidal silica. These results show promise for using chemically stable chlorosodalite to immobilize oxide reduction salt wastes.

Improvement in the productivity of xylooligosaccharides from waste medium after mushroom cultivation by hydrothermal treatment with suitable pretreatment.

PubMed

Sato, Nobuaki; Shinji, Kazunori; Mizuno, Masahiro; Nozaki, Kouichi; Suzuki, Masayuki; Makishima, Satoshi; Shiroishi, Masahiro; Onoda, Takeru; Takahashi, Fumihiro; Kanda, Takahisa; Amano, Yoshihiko

2010-08-01

The effective xylooligosaccharides (XOs) production from the waste medium after mushroom cultivation (WM) was investigated. The WM contains rich nutrients (protein, etc.) which induce Maillard reaction with reducing sugars under hydrothermal conditions. To improve the productivity of XOs, the suitable pretreatment combined with washing and grinding was investigated, and subsequently hydrothermal treatment was demonstrated with batch type and continuous flow type reactor. The washing pretreatment with hot water of 60 degrees C was effective to remove nutrients from the WM, and it led to prevent brownish discoloration on the hydrothermal treatment. On the basis of experimental data, industrial XOs production processes consisting of the pretreatment, hydrothermal treatment and purification step was designed. During the designed process, 2.3 kg-dry of the purified XOs was produced from 30 kg-wet of the WM (15% yield as dry basis weight). Theoretical yield of XOs attained to 48% as xylan weight in the WM. (c) 2010 Elsevier Ltd. All rights reserved.

Imaging hydrothermal roots along the Endeavour segment of the Juan de Fuca ridge using elastic full waveform inversion.

NASA Astrophysics Data System (ADS)

Arnulf, A. F.; Harding, A. J.; Kent, G. M.

2016-12-01

The Endeavour segment is a 90 km-long, medium-spreading-rate, oceanic spreading center located on the northern Juan de Fuca ridge (JDFR). The central part of this segment forms a 25-km-long volcanic high that hosts five of the most hydrothermally active vent fields on the MOR system, namely (from north to south): Sasquatch, Salty Dawg, High Rise, Main Endeavour and Mothra. Mass, heat and chemical fluxes associated to vigorous hydrothermal venting are large, however the geometry of the fluid circulation system through the oceanic crust remains almost completely undefined. To produce high-resolution velocity/reflectivity structures along the axis of the Endeavour segment, here, we combined a synthetic ocean bottom experiment (SOBE), 2-D traveltime tomography, 2D elastic full waveform and reverse time migration (RTM). We present velocity and reflectivity sections along Endeavour segment at unprecedented spatial resolutions. We clearly image a set of independent, geometrically complex, elongated low-velocity regions linking the top of the magma chamber at depth to the hydrothermal vent fields on the seafloor. We interpret these narrow pipe-like units as focused regions of hydrothermal fluid up-flow, where acidic and corrosive fluids form pipe-like alteration zones as previously observed in Cyprus ophiolites. Furthermore, the amplitude of these low-velocity channels is shown to be highly variable, with the strongest velocity drops observed at Main Endeavour, Mothra and Salty Dawg hydrothermal vent fields, possibly suggesting more mature hydrothermal cells. Interestingly, the near-seafloor structure beneath those three sites is very similar and highlights a sharp lateral transition in velocity (north to south). On the other hand, the High-Rise hydrothermal vent field is characterized by several lower amplitudes up-flow zones and relatively slow near-surface velocities. Last, Sasquatch vent field is located in an area of high near-surface velocities and is not characterized by an obvious low-velocity up-flow region, in good agreement with an extinct vent field.

Inactivation of Escherichia coli Endotoxin by Soft Hydrothermal Processing▿

PubMed Central

Miyamoto, Toru; Okano, Shinya; Kasai, Noriyuki

2009-01-01

Bacterial endotoxins, also known as lipopolysaccharides, are a fever-producing by-product of gram-negative bacteria commonly known as pyrogens. It is essential to remove endotoxins from parenteral preparations since they have multiple injurious biological activities. Because of their strong heat resistance (e.g., requiring dry-heat sterilization at 250°C for 30 min) and the formation of various supramolecular aggregates, depyrogenation is more difficult than sterilization. We report here that soft hydrothermal processing, which has many advantages in safety and cost efficiency, is sufficient to assure complete depyrogenation by the inactivation of endotoxins. The endotoxin concentration in a sample was measured by using a chromogenic limulus method with an endotoxin-specific limulus reagent. The endotoxin concentration was calculated from a standard curve obtained using a serial dilution of a standard solution. We show that endotoxins were completely inactivated by soft hydrothermal processing at 130°C for 60 min or at 140°C for 30 min in the presence of a high steam saturation ratio or with a flow system. Moreover, it is easy to remove endotoxins from water by soft hydrothermal processing similarly at 130°C for 60 min or at 140°C for 30 min, without any requirement for ultrafiltration, nonselective adsorption with a hydrophobic adsorbent, or an anion exchanger. These findings indicate that soft hydrothermal processing, applied in the presence of a high steam saturation ratio or with a flow system, can inactivate endotoxins and may be useful for the depyrogenation of parenterals, including end products and medical devices that cannot be exposed to the high temperatures of dry heat treatments. PMID:19502435

Heat flow, morphology, pore fluids and hydrothermal circulation in a typical Mid-Atlantic Ridge flank near Oceanographer Fracture Zone

NASA Astrophysics Data System (ADS)

Le Gal, V.; Lucazeau, F.; Cannat, M.; Poort, J.; Monnin, C.; Battani, A.; Fontaine, F.; Goutorbe, B.; Rolandone, F.; Poitou, C.; Blanc-Valleron, M.-M.; Piedade, A.; Hipólito, A.

2018-01-01

Hydrothermal circulation affects heat and mass transfers in the oceanic lithosphere, not only at the ridge axis but also on their flanks, where the magnitude of this process has been related to sediment blanket and seamounts density. This was documented in several areas of the Pacific Ocean by heat flow measurements and pore water analysis. However, as the morphology of Atlantic and Indian ridge flanks is generally rougher than in the Pacific, these regions of slow and ultra-slow accretion may be affected by hydrothermal processes of different regimes. We carried out a survey of two regions on the eastern and western flanks of the Mid-Atlantic Ridge between Oceanographer and Hayes fracture zones. Two hundred and eight new heat flow measurements were obtained along six seismic profiles, on 5 to 14 Ma old seafloor. Thirty sediment cores (from which porewaters have been extracted) have been collected with a Kullenberg corer equipped with thermistors thus allowing simultaneous heat flow measurement. Most heat flow values are lower than those predicted by purely conductive cooling models, with some local variations and exceptions: heat flow values on the eastern flank of the study area are more variable than on the western flank, where they tend to increase westward as the sedimentary cover in the basins becomes thicker and more continuous. Heat flow is also higher, on average, on the northern sides of both the western and eastern field regions and includes values close to conductive predictions near the Oceanographer Fracture Zone. All the sediment porewaters have a chemical composition similar to that of bottom seawater (no anomaly linked to fluid circulation has been detected). Heat flow values and pore fluid compositions are consistent with fluid circulation in volcanic rocks below the sediment. The short distances between seamounts and short fluid pathways explain that fluids flowing in the basaltic aquifer below the sediment have remained cool and unaltered. Finally, relief at small-scale is calculated using variogram of bathymetry and compared for different regions affected by hydrothermal circulation.

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

NASA Technical Reports Server (NTRS)

Leif, Roald N.

1993-01-01

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

Seafloor weathering buffering climate: numerical experiments

NASA Astrophysics Data System (ADS)

Farahat, N. X.; Archer, D. E.; Abbot, D. S.

2013-12-01

Continental silicate weathering is widely held to consume atmospheric CO2 at a rate controlled in part by temperature, resulting in a climate-weathering feedback [Walker et al., 1981]. It has been suggested that weathering of oceanic crust of warm mid-ocean ridge flanks also has a CO2 uptake rate that is controlled by climate [Sleep and Zahnle, 2001; Brady and Gislason, 1997]. Although this effect might not be significant on present-day Earth [Caldeira, 1995], seafloor weathering may be more pronounced during snowball states [Le Hir et al., 2008], during the Archean when seafloor spreading rates were faster [Sleep and Zahnle, 2001], and on waterworld planets [Abbot et al., 2012]. Previous studies of seafloor weathering have made significant contributions using qualitative, generally one-box, models, and the logical next step is to extend this work using a spatially resolved model. For example, experiments demonstrate that seafloor weathering reactions are temperature dependent, but it is not clear whether the deep ocean temperature affects the temperature at which the reactions occur, or if instead this temperature is set only by geothermal processes. Our goal is to develop a 2-D numerical model that can simulate hydrothermal circulation and resulting alteration of oceanic basalts, and can therefore address such questions. A model of diffusive and convective heat transfer in fluid-saturated porous media simulates hydrothermal circulation through porous oceanic basalt. Unsteady natural convection is solved for using a Darcy model of porous media flow that has been extensively benchmarked. Background hydrothermal circulation is coupled to mineral reaction kinetics of basaltic alteration and hydrothermal mineral precipitation. In order to quantify seafloor weathering as a climate-weathering feedback process, this model focuses on hydrothermal reactions that influence carbon uptake as well as ocean alkalinity: silicate rock dissolution, calcium and magnesium leaching reactions, carbonate precipitation, and clay formation.

Characterization of Magma-Driven Hydrothermal Systems at Oceanic Spreading Centers

NASA Astrophysics Data System (ADS)

Farough, A.; Lowell, R. P.; Corrigan, R.

2012-12-01

Fluid circulation in high-temperature hydrothermal systems involves complex water-rock chemical reactions and phase separation. Numerical modeling of reactive transport in multi-component, multiphase systems is required to obtain a full understanding of the characteristics and evolution of hydrothermal vent systems. We use a single-pass parameterized model of high-temperature hydrothermal circulation at oceanic spreading centers constrained by observational parameters such as vent temperature, heat output, and vent field area, together with surface area and depth of the sub-axial magma chamber, to deduce fundamental hydrothermal parameters such as mass flow rate, bulk permeability, conductive boundary layer thickness at the base of the system, magma replenishment rate, and residence time in the discharge zone. All of these key subsurface characteristics are known for fewer than 10 sites out of 300 known hydrothermal systems. The principal limitations of this approach stem from the uncertainty in heat output and vent field area. For systems where data are available on partitioning of heat and chemical output between focused and diffuse flow, we determined the fraction of high-temperature vent fluid incorporated into diffuse flow using a two-limb single pass model. For EPR 9°50` N and ASHES, the diffuse flow temperatures calculated assuming conservative mixing are nearly equal to the observed temperatures indicating that approximately 80%-90% of the hydrothermal heat output occurs as high-temperature flow derived from magmatic heat even though most of the heat output appears as low-temperature diffuse discharge. For the Main Endeavour Field and Lucky Strike, diffuse flow fluids show significant conductive cooling and heating respectively. Finally, we calculate the transport of various geochemical constituents in focused and diffuse flow at the vent field scale and compare the results with estimates of geochemical transports from the Rainbow hydrothermal field where diffuse flow is absent.

Microbial community stratification controlled by the subseafloor fluid flow and geothermal gradient at the Iheya North hydrothermal field in the Mid-Okinawa Trough (Integrated Ocean Drilling Program Expedition 331).

PubMed

Yanagawa, Katsunori; Breuker, Anja; Schippers, Axel; Nishizawa, Manabu; Ijiri, Akira; Hirai, Miho; Takaki, Yoshihiro; Sunamura, Michinari; Urabe, Tetsuro; Nunoura, Takuro; Takai, Ken

2014-10-01

The impacts of lithologic structure and geothermal gradient on subseafloor microbial communities were investigated at a marginal site of the Iheya North hydrothermal field in the Mid-Okinawa Trough. Subsurface marine sediments composed of hemipelagic muds and volcaniclastic deposits were recovered through a depth of 151 m below the seafloor at site C0017 during Integrated Ocean Drilling Program Expedition 331. Microbial communities inferred from 16S rRNA gene clone sequencing in low-temperature hemipelagic sediments were mainly composed of members of the Chloroflexi and deep-sea archaeal group. In contrast, 16S rRNA gene sequences of marine group I Thaumarchaeota dominated the microbial phylotype communities in the coarse-grained pumiceous gravels interbedded between the hemipelagic sediments. Based on the physical properties of sediments such as temperature and permeability, the porewater chemistry, and the microbial phylotype compositions, the shift in the physical properties of the sediments is suggested to induce a potential subseafloor recharging flow of oxygenated seawater in the permeable zone, leading to the generation of variable chemical environments and microbial communities in the subseafloor habitats. In addition, the deepest section of sediments under high-temperature conditions (∼90°C) harbored the sequences of an uncultivated archaeal lineage of hot water crenarchaeotic group IV that may be associated with the high-temperature hydrothermal fluid flow. These results indicate that the subseafloor microbial community compositions and functions at the marginal site of the hydrothermal field are highly affected by the complex fluid flow structure, such as recharging seawater and underlying hydrothermal fluids, coupled with the lithologic transition of sediments. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Microbial Community Stratification Controlled by the Subseafloor Fluid Flow and Geothermal Gradient at the Iheya North Hydrothermal Field in the Mid-Okinawa Trough (Integrated Ocean Drilling Program Expedition 331)

PubMed Central

Breuker, Anja; Schippers, Axel; Nishizawa, Manabu; Ijiri, Akira; Hirai, Miho; Takaki, Yoshihiro; Sunamura, Michinari; Urabe, Tetsuro; Nunoura, Takuro; Takai, Ken

2014-01-01

The impacts of lithologic structure and geothermal gradient on subseafloor microbial communities were investigated at a marginal site of the Iheya North hydrothermal field in the Mid-Okinawa Trough. Subsurface marine sediments composed of hemipelagic muds and volcaniclastic deposits were recovered through a depth of 151 m below the seafloor at site C0017 during Integrated Ocean Drilling Program Expedition 331. Microbial communities inferred from 16S rRNA gene clone sequencing in low-temperature hemipelagic sediments were mainly composed of members of the Chloroflexi and deep-sea archaeal group. In contrast, 16S rRNA gene sequences of marine group I Thaumarchaeota dominated the microbial phylotype communities in the coarse-grained pumiceous gravels interbedded between the hemipelagic sediments. Based on the physical properties of sediments such as temperature and permeability, the porewater chemistry, and the microbial phylotype compositions, the shift in the physical properties of the sediments is suggested to induce a potential subseafloor recharging flow of oxygenated seawater in the permeable zone, leading to the generation of variable chemical environments and microbial communities in the subseafloor habitats. In addition, the deepest section of sediments under high-temperature conditions (∼90°C) harbored the sequences of an uncultivated archaeal lineage of hot water crenarchaeotic group IV that may be associated with the high-temperature hydrothermal fluid flow. These results indicate that the subseafloor microbial community compositions and functions at the marginal site of the hydrothermal field are highly affected by the complex fluid flow structure, such as recharging seawater and underlying hydrothermal fluids, coupled with the lithologic transition of sediments. PMID:25063666

Electrochemistry of Prebiotic Early Earth Hydrothermal Chimney Systems

NASA Astrophysics Data System (ADS)

Hermis, N.; Barge, L. M.; Chin, K. B.; LeBlanc, G.; Cameron, R.

2017-12-01

Hydrothermal chimneys are self-organizing chemical garden precipitates generated from geochemical disequilibria within sea-vent environments, and have been proposed as a possible setting for the emergence of life because they contain mineral catalysts and transect ambient pH / Eh / chemical gradients [1]. We simulated the growth of hydrothermal chimneys in early Earth vent systems by using different hydrothermal simulants such as sodium sulfide (optionally doped with organic molecules) which were injected into an early Earth ocean simulant containing dissolved ferrous iron, nickel, and bicarbonate [2]. Chimneys on the early Earth would have constituted flow-through reactors, likely containing Fe/Ni-sulfide catalysts that could have driven proto-metabolic electrochemical reactions. The electrochemical activity of the chimney system was characterized non-invasively by placing electrodes at different locations across the chimney wall and in the ocean to analyze the bulk properties of surface charge potential in the chimney / ocean / hydrothermal fluid system. We performed in-situ characterization of the chimney using electrochemical impedance spectroscopy (EIS) which allowed us to observe the changes in physio-chemical behavior of the system through electrical spectra of capacitance and impedance over a wide range of frequencies during the metal sulfide chimney growth. The electrochemical properties of hydrothermal chimneys in natural systems persist due to the disequilibria maintained between the ocean and hydrothermal fluid. When the injection in our experiment (analogous to fluid flow in a vent) stopped, we observed a corresponding decline in open circuit voltage across the chimney wall, though the impedance of the precipitate remained lor. Further work is needed to characterize the electrochemistry of simulated chimney systems by controlling response factors such as electrode geometry and environmental conditions, in order to simulate electrochemical reactions that may have occurred in similar systems on the early Earth. [1] Russell, MJ et al. 2014. Astrobiology,14, 4, 308-343. [2] Barge, LM et al. (2015) Journal of Visualized Experiments, 105, DOI: 10.3791/53015.

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

NASA Astrophysics Data System (ADS)

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

2005-12-01

The Mothra Hydrothermal Field (MHF) is a 600 m long, high-temperature hydrothermal field. It is located 2.7 km south of the Main Endeavour Field at the southern end of the central Endeavour Segment. Mothra is the most areally extensive field along the Endeavour Segment, composed of six active sulfide clusters that are 40-200 m apart. Each cluster contains rare black smokers (venting up to 319°C), numerous diffusely venting chimneys, and abundant extinct chimneys and sulfide talus. From north to south, these clusters include Cauldron, Twin Peaks, Faulty Towers, Crab Basin, Cuchalainn, and Stonehenge. As part of the Endeavour Integrated Study Site (ISS), the MHF is a site of intensive interdisciplinary studies focused on linkages among geology, geochemistry, fluid chemistry, seismology, and microbiology. Axial valley geology at MHF is structurally complex, consisting of lightly fissured flows that abut the walls and surround a core of extensively fissured, collapsed terrain. Fissure abundance and distribution indicates that tectonism has been the dominant process controlling growth of the axial graben. Past magmatic activity is shown by the 200 m long chain of collapse basins between Crab Basin and Stonehenge, which may have held at least ~7500 m3 of lava. Assuming a flow thickness of 0.5 m, this amount of lava could cover over half the valley floor during a single volcanic event. At a local scale, MHF clusters vary in size, activity, and underlying geology. They range in size from 400-1600 m2 and consist of isolated chimneys and/or coalesced cockscomb arrays atop ramps of sulfide talus. In the northern part of the field, Cauldron, Twin Peaks, Faulty Towers, and Crab Basin are located near the western valley wall, bounded by basalt talus and a combination of collapsed sheet flows, intermixed lobate and sulfide, disrupted terrain, and isolated pillow ridges. The southern clusters, Cuchalainn and Stonehenge, are associated with collapse basins in the central valley and bounded by extensive lobate flows and disrupted terrain. At all clusters, active chimneys stand within meters of extinct chimneys, suggesting that flow in the shallow subsurface is both complex and transient. 1-2 m high mounds of sulfide talus and broken chimneys indicate that focused flow has been concentrated at the clusters for long periods, while extinct sulfide deposits between clusters and in collapse basins demonstrate that flow conduits have been rerouted and/or clogged by mineral precipitation. Two subsurface processes are responsible for hydrothermal venting at the clusters: tapping of magmatic heat near the lava drainbacks and tectonic movement along the steeply dipping, inward-facing normal faults at the western wall boundary. The interplay between these processes and fluid flow is synthesized in an evolutionary model of hydrothermal development at Mothra.

Submarine hydrothermal processes, mirroring the geotectonic evolution of the NE Hungarian Jurassic Szarvaskő Unit

NASA Astrophysics Data System (ADS)

Kiss, Gabriella B.; Zagyva, Tamás; Pásztor, Domokos; Zaccarini, Federica

2018-05-01

The Jurassic pillow basalt of the NE Hungarian Szarvaskő Unit is part of an incomplete ophiolitic sequence, formed in a back-arc- or marginal basin of Neotethyan origin. Different, often superimposing hydrothermal processes were studied aiming to characterise them and to discover their relationship with the geotectonic evolution of the region. Closely packed pillow, pillow-fragmented hyaloclastite breccia and transition to peperitic facies of a submarine lava flow were observed. The rocks underwent primary and cooling-related local submarine hydrothermal processes immediately after eruption at ridge setting. Physico-chemical data of this process and volcanic facies analyses revealed distal formation in the submarine lava flow. A superimposing, more extensive fluid circulation system resulted in intense alteration of basalt and in the formation of mostly sulphide-filled cavities. This lower temperature, but larger-scale process was similar to VMS systems and was related to ridge setting. As a peculiarity of the Szarvaskő Unit, locally basalt may be completely altered to a grossular-bearing mineral assemblage formed by rodingitisation s.l. This unique process observed in basalt happened in ridge setting/during spreading, in the absence of known large ultramafic blocks. Epigenetic veins formed also during Alpine regional metamorphism, related to subduction/obduction. The observed hydrothermal minerals represent different steps of the geotectonic evolution of the Szarvaskő Unit, from the ridge setting and spreading till the subduction/obduction. Hence, studying the superimposing alteration mineral assemblages can be a useful tool for reconstructing the tectonic history of an ophiolitic complex. Though the found mineral parageneses are often similar, careful study can help in distinguishing the processes and characterising their P, T, and X conditions.

Practical development of continuous supercritical fluid process using high pressure and high temperature micromixer

NASA Astrophysics Data System (ADS)

Kawasaki, Shin-Ichiro; Sue, Kiwamu; Ookawara, Ryuto; Wakashima, Yuichiro; Suzuki, Akira

2015-12-01

In the synthesis of metal oxide fine particles by continuous supercritical hydrothermal method, the particle characteristics are greatly affected by not only the reaction conditions (temperature, pressure, residence time, concentration, etc.), but also the heating rate from ambient to reaction temperature. Therefore, the heating method by direct mixing of starting solution at room temperature with supercritical water is a key technology for the particle production having smaller size and narrow distribution. In this paper, mixing engineering study through comparison between conventional T-shaped mixers and recently developed swirl mixers was carried out in the hydrothermal synthesis of NiO nanoparticles from Ni(NO3)2 aqueous solution at 400 °C and 30 MPa. Inner diameter in the mixers and total flow rates were varied. Furthermore, the heating rate was calculated by computational fluid dynamics (CFD) simulation. Relationship between the heating rate and the average particle size were discussed. It was clarified that the miniaturization of mixer inner diameter and the use of the swirl flow were effective for improving mixing performance and contributed to produce small and narrow distribution particle under same experimental condition of flow rate, temperature, pressure, residence time, and concentration of the starting materials. We have focused the mixer optimization due to a difference in fluid viscosity.

Diffuse flow environments within basalt- and sediment-based hydrothermal vent ecosystems harbor specialized microbial communities.

PubMed

Campbell, Barbara J; Polson, Shawn W; Zeigler Allen, Lisa; Williamson, Shannon J; Lee, Charles K; Wommack, K Eric; Cary, S Craig

2013-01-01

Hydrothermal vents differ both in surface input and subsurface geochemistry. The effects of these differences on their microbial communities are not clear. Here, we investigated both alpha and beta diversity of diffuse flow-associated microbial communities emanating from vents at a basalt-based hydrothermal system along the East Pacific Rise (EPR) and a sediment-based hydrothermal system, Guaymas Basin. Both Bacteria and Archaea were targeted using high throughput 16S rRNA gene pyrosequencing analyses. A unique aspect of this study was the use of a universal set of 16S rRNA gene primers to characterize total and diffuse flow-specific microbial communities from varied deep-sea hydrothermal environments. Both surrounding seawater and diffuse flow water samples contained large numbers of Marine Group I (MGI) Thaumarchaea and Gammaproteobacteria taxa previously observed in deep-sea systems. However, these taxa were geographically distinct and segregated according to type of spreading center. Diffuse flow microbial community profiles were highly differentiated. In particular, EPR dominant diffuse flow taxa were most closely associated with chemolithoautotrophs, and off axis water was dominated by heterotrophic-related taxa, whereas the opposite was true for Guaymas Basin. The diversity and richness of diffuse flow-specific microbial communities were strongly correlated to the relative abundance of Epsilonproteobacteria, proximity to macrofauna, and hydrothermal system type. Archaeal diversity was higher than or equivalent to bacterial diversity in about one third of the samples. Most diffuse flow-specific communities were dominated by OTUs associated with Epsilonproteobacteria, but many of the Guaymas Basin diffuse flow samples were dominated by either OTUs within the Planctomycetes or hyperthermophilic Archaea. This study emphasizes the unique microbial communities associated with geochemically and geographically distinct hydrothermal diffuse flow environments.

Diffuse flow environments within basalt- and sediment-based hydrothermal vent ecosystems harbor specialized microbial communities

PubMed Central

Campbell, Barbara J.; Polson, Shawn W.; Zeigler Allen, Lisa; Williamson, Shannon J.; Lee, Charles K.; Wommack, K. Eric; Cary, S. Craig

2013-01-01

Hydrothermal vents differ both in surface input and subsurface geochemistry. The effects of these differences on their microbial communities are not clear. Here, we investigated both alpha and beta diversity of diffuse flow-associated microbial communities emanating from vents at a basalt-based hydrothermal system along the East Pacific Rise (EPR) and a sediment-based hydrothermal system, Guaymas Basin. Both Bacteria and Archaea were targeted using high throughput 16S rRNA gene pyrosequencing analyses. A unique aspect of this study was the use of a universal set of 16S rRNA gene primers to characterize total and diffuse flow-specific microbial communities from varied deep-sea hydrothermal environments. Both surrounding seawater and diffuse flow water samples contained large numbers of Marine Group I (MGI) Thaumarchaea and Gammaproteobacteria taxa previously observed in deep-sea systems. However, these taxa were geographically distinct and segregated according to type of spreading center. Diffuse flow microbial community profiles were highly differentiated. In particular, EPR dominant diffuse flow taxa were most closely associated with chemolithoautotrophs, and off axis water was dominated by heterotrophic-related taxa, whereas the opposite was true for Guaymas Basin. The diversity and richness of diffuse flow-specific microbial communities were strongly correlated to the relative abundance of Epsilonproteobacteria, proximity to macrofauna, and hydrothermal system type. Archaeal diversity was higher than or equivalent to bacterial diversity in about one third of the samples. Most diffuse flow-specific communities were dominated by OTUs associated with Epsilonproteobacteria, but many of the Guaymas Basin diffuse flow samples were dominated by either OTUs within the Planctomycetes or hyperthermophilic Archaea. This study emphasizes the unique microbial communities associated with geochemically and geographically distinct hydrothermal diffuse flow environments. PMID:23898323

Modeling microbial reaction rates in a submarine hydrothermal vent chimney wall

NASA Astrophysics Data System (ADS)

LaRowe, Douglas E.; Dale, Andrew W.; Aguilera, David R.; L'Heureux, Ivan; Amend, Jan P.; Regnier, Pierre

2014-01-01

The fluids emanating from active submarine hydrothermal vent chimneys provide a window into subseafloor processes and, through mixing with seawater, are responsible for steep thermal and compositional gradients that provide the energetic basis for diverse biological communities. Although several models have been developed to better understand the dynamic interplay of seawater, hydrothermal fluid, minerals and microorganisms inside chimney walls, none provide a fully integrated approach to quantifying the biogeochemistry of these hydrothermal systems. In an effort to remedy this, a fully coupled biogeochemical reaction-transport model of a hydrothermal vent chimney has been developed that explicitly quantifies the rates of microbial catalysis while taking into account geochemical processes such as fluid flow, solute transport and oxidation-reduction reactions associated with fluid mixing as a function of temperature. The metabolisms included in the reaction network are methanogenesis, aerobic oxidation of hydrogen, sulfide and methane and sulfate reduction by hydrogen and methane. Model results indicate that microbial catalysis is generally fastest in the hottest habitable portion of the vent chimney (77-102 °C), and methane and sulfide oxidation peak near the seawater-side of the chimney. The fastest metabolisms are aerobic oxidation of H2 and sulfide and reduction of sulfate by H2 with maximum rates of 140, 900 and 800 pmol cm-3 d-1, respectively. The maximum rate of hydrogenotrophic methanogenesis is just under 0.03 pmol cm-3 d-1, the slowest of the metabolisms considered. Due to thermodynamic inhibition, there is no anaerobic oxidation of methane by sulfate (AOM). These simulations are consistent with vent chimney metabolic activity inferred from phylogenetic data reported in the literature. The model developed here provides a quantitative approach to describing the rates of biogeochemical transformations in hydrothermal systems and can be used to constrain the role of microbial activity in the deep subsurface.

The influence of isotropic and anisotropic crustal permeability on hydrothermal flow at fast spreading ridges

NASA Astrophysics Data System (ADS)

Hasenclever, Jörg; Rüpke, Lars; Theissen-Krah, Sonja; Morgan, Jason

2016-04-01

We use 3-D numerical models of hydrothermal fluid flow to assess the magnitude and spatial distribution of hydrothermal mass and energy fluxes within the upper and lower oceanic crust. A better understanding of the hydrothermal flow pattern (e.g. predominantly on-axis above the axial melt lens vs. predominantly off-axis and ridge-perpendicular over the entire crustal thickness) is essential for quantifying the volume of oceanic crust exposed to high-temperature fluid flow and the associated leaching and redistribution of economically interesting metals. The initial setup of all 3-D models is based on our previous 2-D studies (Theissen-Krah et al., 2011), in which we have coupled numerical models for crustal accretion and hydrothermal fluid flow. One result of these 2-D calculations is a crustal permeability field that leads to a thermal structure in the crust that matches seismic tomography data at the East Pacific Rise. Our reference 3-D model for hydrothermal flow at fast-spreading ridges predicts the existence of a hybrid hydrothermal system (Hasenclever et al., 2014) with two interacting flow components that are controlled by different physical mechanisms. Shallow on-axis flow structures develop owing to the thermodynamic properties of water, whereas deeper off-axis flow is strongly shaped by crustal permeability, particularly the brittle-ductile transition. About ˜60% of the discharging fluid mass is replenished on-axis by warm (up to 300oC) recharge flow surrounding the hot thermal plumes. The remaining ˜40%, however, occurs as colder and broader recharge up to several kilometres away from the ridge axis that feeds hot (500-700oC) deep off-axis flow in the lower crust towards the ridge. Both flow components merge above the melt lens to feed ridge-centred vent sites. In a suite of 3-D model calculations we vary the isotropic crustal permeability to quantify its influence on on-axis vs. off-axis hydrothermal fluxes as well as on along-axis hydrothermal activity. 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 hydrothermal vent sites.

Immobilization of LiCl-Li 2 O pyroprocessing salt wastes in chlorosodalite using glass-bonded hydrothermal and salt-occlusion methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riley, Brian J.; Peterson, Jacob A.; Kroll, Jared O.

In this study, salt occlusion and hydrothermal processes were used to make chlorosodalite through reaction with a high-LiCl salt simulating a waste stream following pyrochemical treatment of oxide-based used nuclear fuel. Some products were reacted with glass binders to increase chlorosodalite yield through alkali ion exchange and aide in densification. Hydrothermal processes included reaction of the salt simulant in an acid digestion vessel with either zeolite 4A or sodium aluminate and colloidal silica. Chlorosodalite yields in the crystalline products were nearly complete in the glass-bonded materials at values of 100 mass% for the salt-occlusion method, up to 99.0 mass% formore » the hydrothermal synthesis with zeolite 4A, and up to 96 mass% for the hydrothermal synthesis with sodium aluminate and colloidal silica. These results show promise for using chemically stable chlorosodalite to immobilize oxide reduction salt wastes.« less

Evolutionary Strategies of Viruses, Bacteria and Archaea in Hydrothermal Vent Ecosystems Revealed through Metagenomics

PubMed Central

Anderson, Rika E.; Sogin, Mitchell L.; Baross, John A.

2014-01-01

The deep-sea hydrothermal vent habitat hosts a diverse community of archaea and bacteria that withstand extreme fluctuations in environmental conditions. Abundant viruses in these systems, a high proportion of which are lysogenic, must also withstand these environmental extremes. Here, we explore the evolutionary strategies of both microorganisms and viruses in hydrothermal systems through comparative analysis of a cellular and viral metagenome, collected by size fractionation of high temperature fluids from a diffuse flow hydrothermal vent. We detected a high enrichment of mobile elements and proviruses in the cellular fraction relative to microorganisms in other environments. We observed a relatively high abundance of genes related to energy metabolism as well as cofactors and vitamins in the viral fraction compared to the cellular fraction, which suggest encoding of auxiliary metabolic genes on viral genomes. Moreover, the observation of stronger purifying selection in the viral versus cellular gene pool suggests viral strategies that promote prolonged host integration. Our results demonstrate that there is great potential for hydrothermal vent viruses to integrate into hosts, facilitate horizontal gene transfer, and express or transfer genes that manipulate the hosts’ functional capabilities. PMID:25279954

Faulting and off-axis submarine massive sulfide accumulation at slow spreading mid-ocean ridges: A numerical modeling perspective

NASA Astrophysics Data System (ADS)

Andersen, C.; Theissen-Krah, S.; Hannington, M.; Rüpke, L.; Petersen, S.

2017-06-01

The potential of mining seafloor massive sulfide deposits for metals such as Cu, Zn, and Au is currently debated. One key challenge is to predict where the largest deposits worth mining might form, which in turn requires understanding the pattern of subseafloor hydrothermal mass and energy transport. Numerical models of heat and fluid flow are applied to illustrate the important role of fault zone properties (permeability and width) in controlling mass accumulation at hydrothermal vents at slow spreading ridges. We combine modeled mass-flow rates, vent temperatures, and vent field dimensions with the known fluid chemistry at the fault-controlled Logatchev 1 hydrothermal field of the Mid-Atlantic Ridge. We predict that the 135 kilotons of SMS at this site (estimated by other studies) can have accumulated with a minimum depositional efficiency of 5% in the known duration of hydrothermal venting (58,200 year age of the deposit). In general, the most productive faults must provide an efficient fluid pathway while at the same time limit cooling due to mixing with entrained cold seawater. This balance is best met by faults that are just wide and permeable enough to control a hydrothermal plume rising through the oceanic crust. Model runs with increased basal heat input, mimicking a heat flow contribution from along-axis, lead to higher mass fluxes and vent temperatures, capable of significantly higher SMS accumulation rates. Nonsteady state conditions, such as the influence of a cooling magmatic intrusion beneath the fault zone, also can temporarily increase the mass flux while sustaining high vent temperatures.

Microbial biofilms associated with fluid chemistry and megafaunal colonization at post-eruptive deep-sea hydrothermal vents

NASA Astrophysics Data System (ADS)

O'Brien, Charles E.; Giovannelli, Donato; Govenar, Breea; Luther, George W.; Lutz, Richard A.; Shank, Timothy M.; Vetriani, Costantino

2015-11-01

At deep-sea hydrothermal vents, reduced, super-heated hydrothermal fluids mix with cold, oxygenated seawater. This creates temperature and chemical gradients that support chemosynthetic primary production and a biomass-rich community of invertebrates. In late 2005/early 2006 an eruption occurred on the East Pacific Rise at 9°50‧N, 104°17‧W. Direct observations of the post-eruptive diffuse-flow vents indicated that the earliest colonizers were microbial biofilms. Two cruises in 2006 and 2007 allowed us to monitor and sample the early steps of ecosystem recovery. The main objective of this work was to characterize the composition of microbial biofilms in relation to the temperature and chemistry of the hydrothermal fluids and the observed patterns of megafaunal colonization. The area selected for this study had local seafloor habitats of active diffuse flow (in-flow) interrupted by adjacent habitats with no apparent expulsion of hydrothermal fluids (no-flow). The in-flow habitats were characterized by higher temperatures (1.6-25.2 °C) and H2S concentrations (up to 67.3 μM) than the no-flow habitats, and the microbial biofilms were dominated by chemosynthetic Epsilonproteobacteria. The no-flow habitats had much lower temperatures (1.2-5.2 °C) and H2S concentrations (0.3-2.9 μM), and Gammaproteobacteria dominated the biofilms. Siboglinid tubeworms colonized only in-flow habitats, while they were absent at the no-flow areas, suggesting a correlation between siboglinid tubeworm colonization, active hydrothermal flow, and the composition of chemosynthetic microbial biofilms.

Explosive Deep Sea Volcanism Produces Composite Volcanoes (Stratocones) with Predominantly Diffuse Flow Hydrothermal Ecosystems

NASA Astrophysics Data System (ADS)

Rubin, K. H.; Chadwick, W. C.; Embley, R. W.; Butterfield, D. A.

2018-05-01

Newly-discovered extensive explosive deep sea volcanism produces distinct stratovolcano structures and physical rock characteristics, and host primarily diffuse flow hydrothermal activity, unlike focused flow systems at effusive submarine volcanoes.

An in-situ Mobile pH Calibrator for application with HOV and ROV platform in deep sea environments

NASA Astrophysics Data System (ADS)

Tan, C.; Ding, K.; Seyfried, W. E., Jr.

2014-12-01

Recently, a novel in-situ sensor calibration instrument, Mobile pH Calibrator (MpHC), was developed for application with HOV Alvin. It was specifically designed to conduct in-situ pH measurement in deep sea hydrothermal diffuse fluids with in-situ calibration function. In general, the sensor calibrator involves three integrated electrodes (pH, dissolved H2 and H2S) and a temperature sensor, all of which are installed in a cell with a volume of ~ 1 ml. A PEEK check valve cartridge is installed at the inlet end of the cell to guide the flow path during the measurement and calibration processes. Two PEEK tubes are connected at outlet end of the cell for drawing out hydrothermal fluid and delivering pH buffer fluids. During its measurement operation, the pump draws in hydrothermal fluid, which then passes through the check valve directly into the sensing cell. When in calibration mode, the pump delivers pH buffers into the cell, while automatically closing the check valve to the outside environment. This probe has two advantages compared to our previous unit used during KNOX18RR MAR cruise in 2008 and MARS cabled observatory deployment in 2012. First, in the former design, a 5 cm solenoid valve was equipped with the probe. This enlarged size prevented its application in specific point or small area. In this version, the probe has only a dimension of 1.6 cm for an easy access to hydrothermal biological environments. Secondly, the maximum temperature condition of the earlier system was limited by the solenoid valve precluding operation in excess of 50 ºC. The new design avoids this problem, which improves its temperature tolerance. The upper limit of temperature condition is now up to 100oC, therefore enabling broader application in hydrothermal diffuse flow system on the seafloor. During SVC cruise (AT26-12) in the Gulf of Mexico this year, the MpHC was successfully tested with Alvin dives at the depth up to 2600 m for measuring pH with in-situ calibration in seafloor cold seep environment. The measurement and calibration were also conducted in hydrothermal diffuse flow at temperature condition exceeding 70 ºC with Alvin dives during a recent cruise AT26-17 in ASHES vent field and Main Endeavour Field on Juan de Fuca Ridge. Data from these seagoing deployments will be presented, with emphasis on both technical and scientific aplications.

High-Density Magnetic Recording and Integrated Magneto-Optics: Materials and Devices; Symposium Held in San Francisco, California, on April 12-16 1998

DTIC Science & Technology

1998-04-01

Kido •Solution Flow System for Hydrothermal -Electrochemical Synthesis : New Opportunities for Multilayered Oxide Films 639 VI. Suchanek, T...FLOW SYSTEM FOR HYDROTHERMAL -ELECTROCHEMICAL SYNTHESIS : NEW OPPORTUNITIES FOR MULTTLAYERED OXIDE FILMS W. SUCHANEK, T. WATANABE, B. SAKURAI, M...ABSTRACT A solution flow system for hydrothermal -electrochemical synthesis has been constructed in our laboratory. This equipment can operate at 20

Continent-Wide Maps of Lg Coda Q Variation and Rayleigh-wave Attenuation Variation for Eurasia

DTIC Science & Technology

2007-01-30

lithosphere and crustal strain lead us to infer that fluids, originating by hydrothermal release from subducting lithosphere or other upper mantle heat...relatively low Qo values in the Arabian Peninsula are produced by fluids that have been released in the upper mantle by hydrothermal processes and have...Advection of plumes in mantle flow: Implications for hotspot motion, mantle viscosity and plume distribution, Geophys. J. Int., 132, 412–434. Talebian, M

Major off-axis hydrothermal activity on the northern Gorda Ridge

USGS Publications Warehouse

Rona, Peter A.; Denlinger, Roger P.; Fisk, M. R.; Howard, K. J.; Taghon, G. L.; Klitgord, Kim D.; McClain, James S.; McMurray, G. R.; Wiltshire, J. C.

1990-01-01

The first hydrothermal field on the northern Gorda Ridge, the Sea Cliff hydrothermal field, was discovered and geologic controls of hydrothermal activity in the rift valley were investigated on a dive series using the DSV Sea Cliff. The Sea Cliff hydrothermal field was discovered where predicted at the intersection of axis-oblique and axis-parallel faults at the south end of a linear ridge at mid-depth (2700 m) on the east wall. Preliminary mapping and sampling of the field reveal: a setting nested on nearly sediment-free fault blocks 300 m above the rift valley floor 2.6 km from the axis; a spectrum of venting types from seeps to black smokers; high conductive heat flow estimated to be equivalent to the convective flux of multiple black smokers through areas of the sea floor sealed by a caprock of elastic breccia primarily derived from basalt with siliceous cement and barite pore fillings; and a vent biota with Juan de Fuca Ridge affinites. These findings demonstrate the importance of off-axis hydrothermal activity and the role of the intersection of tectonic lineations in controlling hydrothermal sites at sea-floor spreading centers.

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

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

Sulfur Metabolizing Microbes Dominate Microbial Communities in Andesite-Hosted Shallow-Sea Hydrothermal Systems

PubMed Central

Zhang, Yao; Zhao, Zihao; Chen, Chen-Tung Arthur; Tang, Kai; Su, Jianqiang; Jiao, Nianzhi

2012-01-01

To determine microbial community composition, community spatial structure and possible key microbial processes in the shallow-sea hydrothermal vent systems off NE Taiwan’s coast, we examined the bacterial and archaeal communities of four samples collected from the water column extending over a redoxocline gradient of a yellow and four from a white hydrothermal vent. Ribosomal tag pyrosequencing based on DNA and RNA showed statistically significant differences between the bacterial and archaeal communities of the different hydrothermal plumes. The bacterial and archaeal communities from the white hydrothermal plume were dominated by sulfur-reducing Nautilia and Thermococcus, whereas the yellow hydrothermal plume and the surface water were dominated by sulfide-oxidizing Thiomicrospira and Euryarchaeota Marine Group II, respectively. Canonical correspondence analyses indicate that methane (CH4) concentration was the only statistically significant variable that explains all community cluster patterns. However, the results of pyrosequencing showed an essential absence of methanogens and methanotrophs at the two vent fields, suggesting that CH4 was less tied to microbial processes in this shallow-sea hydrothermal system. We speculated that mixing between hydrothermal fluids and the sea or meteoric water leads to distinctly different CH4 concentrations and redox niches between the yellow and white vents, consequently influencing the distribution patterns of the free-living Bacteria and Archaea. We concluded that sulfur-reducing and sulfide-oxidizing chemolithoautotrophs accounted for most of the primary biomass synthesis and that microbial sulfur metabolism fueled microbial energy flow and element cycling in the shallow hydrothermal systems off the coast of NE Taiwan. PMID:22970260

Sulfur metabolizing microbes dominate microbial communities in Andesite-hosted shallow-sea hydrothermal systems.

PubMed

Zhang, Yao; Zhao, Zihao; Chen, Chen-Tung Arthur; Tang, Kai; Su, Jianqiang; Jiao, Nianzhi

2012-01-01

To determine microbial community composition, community spatial structure and possible key microbial processes in the shallow-sea hydrothermal vent systems off NE Taiwan's coast, we examined the bacterial and archaeal communities of four samples collected from the water column extending over a redoxocline gradient of a yellow and four from a white hydrothermal vent. Ribosomal tag pyrosequencing based on DNA and RNA showed statistically significant differences between the bacterial and archaeal communities of the different hydrothermal plumes. The bacterial and archaeal communities from the white hydrothermal plume were dominated by sulfur-reducing Nautilia and Thermococcus, whereas the yellow hydrothermal plume and the surface water were dominated by sulfide-oxidizing Thiomicrospira and Euryarchaeota Marine Group II, respectively. Canonical correspondence analyses indicate that methane (CH(4)) concentration was the only statistically significant variable that explains all community cluster patterns. However, the results of pyrosequencing showed an essential absence of methanogens and methanotrophs at the two vent fields, suggesting that CH(4) was less tied to microbial processes in this shallow-sea hydrothermal system. We speculated that mixing between hydrothermal fluids and the sea or meteoric water leads to distinctly different CH(4) concentrations and redox niches between the yellow and white vents, consequently influencing the distribution patterns of the free-living Bacteria and Archaea. We concluded that sulfur-reducing and sulfide-oxidizing chemolithoautotrophs accounted for most of the primary biomass synthesis and that microbial sulfur metabolism fueled microbial energy flow and element cycling in the shallow hydrothermal systems off the coast of NE Taiwan.

Seismic Signatures of Hydrothermal Pathways Along the East Pacific Rise Between 9°16' and 9°56'N

NASA Astrophysics Data System (ADS)

Marjanović, Milena; Fuji, Nobuaki; Singh, Satish C.; Belahi, Thomas; Escartín, Javier

2017-12-01

We apply wave equation-based techniques to 2-D seismic data to characterize the nature of zero-age upper crust at the East Pacific Rise from 9°16' to 9°56'N. The final velocity model reveals a number of low-velocity anomalies, complex in shape, extending down to 1 km below the seafloor. We attribute them to the presence of hydrothermal flow. Depending on their spatial correlation with the previously identified tectonic discontinuities in bathymetry and presence of venting, we classify them as downgoing and upgoing pathways, respectively. This distinction is not always clear; within the third-order discontinuities at 9°20' and 9°37'N, both pathways may be present. The region north of 9°44'N, known for its magmatic robustness and volcanic activity, is represented by five low-velocity perturbations. Three of these anomalies are spatially correlated with the fourth-order discontinuities and attributed to the presence of the on-axis recharge zones. The remaining two anomalies underlie two vent clusters, marked as hydrothermally active sites after the last documented eruption event. These velocity anomalies can be thus identified as the up-flow pathways or at least their remnants. By comparing our results to the available interdisciplinary data sets, we show that the interaction between the tectono-magmatic and hydrothermal processes is not straightforward due to different timescales at which they operate. However, for developing, maintaining, and driving vigorous, high-temperature hydrothermal flow, the high crustal permeability and high thermal regime must coexist in time and space.

Conductive heat flux in VC-1 and the thermal regime of Valles caldera, Jemez Mountains, New Mexico ( USA).

USGS Publications Warehouse

Sass, J.H.; Morgan, P.

1988-01-01

Over 5% of heat in the western USA is lost through Quaternary silicic volcanic centers, including the Valles caldera in N central New Mexico. These centers are the sites of major hydrothermal activity and upper crustal metamorphism, metasomatism, and mineralization, producing associated geothermal resources. Presents new heat flow data from Valles caldera core hole 1 (VC-1), drilled in the SW margin of the Valles caldera. Thermal conductivities were measured on 55 segments of core from VC-1, waxed and wrapped to preserve fluids. These values were combined with temperature gradient data to calculate heat flow. Above 335 m, which is probably unsaturated, heat flow is 247 + or - 16 mW m-2. Inteprets the shallow thermal gradient data and the thermal regime at VC-1 to indicate a long-lived hydrothermal (and magmatic) system in the southwestern Valles caldera that has been maintained through the generation of shallow magma bodies during the long postcollapse history of the caldera. High heat flow at the VC-1 site is interpreted to result from hot water circulating below the base of the core hole, and we attribute the lower heat flow in the unsaturated zone is attributed to hydrologic recharge. -from Authors

Effect of Hydrothermal Alteration on Rock Properties in Active Geothermal Setting

NASA Astrophysics Data System (ADS)

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

2012-04-01

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

CAREER: Hydrothermal vent flow and temperature fluctuations: exploring long-term variability through an integrated research and education program

NASA Astrophysics Data System (ADS)

Di Iorio, D.

2011-12-01

An acoustic scintillation system was built in partnership with ASL Environmental Sciences (Sidney BC Canada), which provided a unique opportunity for two engineering undergraduate students to live and work abroad. The acoustic instrumentation was tested in coastal waters and then deployed to study deep-sea hydrothermal plume dynamics. Undergraduate students were involved in the deployment of instrumentation and the development of processing software to give vertical velocities and temperature fluctuations from a vigorous hydrothermal vent. A graduate student thesis has yielded insights into the vertical and azimuthal dependence of entrainment and into plume bending and rise height. Teachers and Ocean Science Bowl students also participated in research cruises describing physical oceanography of estuaries, coastal waters, and deep-sea hydrothermal vents and participated in data collection, processing and analysis. Teachers used the knowledge they gained to develop creative educational curricula at their schools, to present their experiences at national conferences and to publish an article in the National Science Teachers Association - The Science Journal. One of the teachers was recently recognized with the Presidential Award for Excellence in Mathematics and Science Teaching. Working with the ocean bowl team at Oconee County High School has led to top ten placements in the national championships in 2005 (fourth place) and 2006 (sixth place). In order to increase quantitative methods in an undergraduate class, students acquire data from an ocean observatory and analyze the data for specific quantities of interest. One such project led to the calculation of the upper ocean heat content for the Greenland Sea using 7 years of Argo profiles, which showed a 0.04oC/year trend. These results were then published in JGR.

Effets thermique et hydrothermal de la coulée de basalte triasico-liasique sur les argiles du bassin d'Argana (Maroc)Thermal and hydrothermal effects of Triassic Liassic basalt flow deposition on clays (Agana Basin, Morocco)

NASA Astrophysics Data System (ADS)

Daoudi, Lahcen; Pot de Vin, Jean-Luc

Thermal and hydrothermal effects of Triassic-Liassic basalt flow deposition on sedimentary series of the Argana Basin are responsible for major modifications in detrital clays, until 20 m in depth. It expressed by transformation of detrital smectite to corrensite and moreover to chlorite, and by increasing illite crystallinity. On the 2 m of sediments located immediately under the flow, magnesium-rich hydrothermal fluids have caused precipitation of new mineral phases. To cite this article: L. Daoudi, J.-L. Pot de Vin, C. R. Geoscience 334 (2002) 463-468.

Bacterial Diets of Primary Consumers at Hydrothermal Vents

NASA Astrophysics Data System (ADS)

Govenar, B.; Shank, T. M.

2008-12-01

Chemical energy produced by mixing hydrothermal fluids and seawater supports dense biological communities on mid-ocean ridges. The base of the food web at deep-sea hydrothermal vents is formed by chemolithoautotrophic bacteria that use the energy from the oxidation of reduced chemicals to fix inorganic carbon into simple sugars. With the exception of a few species that have chemolithoautotropic bacterial symbionts, most of the vent-endemic macrofauna are heterotrophs that feed on free-living bacteria, protists, and other invertebrates. The most abundant and diverse group of primary consumers in hydrothermal vent communities belong to the Gastropoda, particularly the patellomorph limpets. Gastropod densities can be as high as 2000 individuals m-2, and there can be as many as 13 species of gastropods in a single aggregation of the siboglinid tubeworm Riftia pachyptila and more than 40 species along the East Pacific Rise. Some gastropods are ubiquitous and others are found in specific microhabitats, stages of succession, or associated with different foundation species. To determine the mechanisms of species coexistence (e.g. resource partitioning or competition) among hydrothermal vent primary consumers and to track the flow of energy in hydrothermal vent communities, we employed molecular genetic techniques to identify the gut contents of four species of co-occurring hydrothermal vent gastropods, Eulepetopsis vitrea, Lepetodrilus elevatus, Lepetodrilus ovalis and Lepetodrilus pustulosus, collected from a single diffuse-flow hydrothermal vent site on the East Pacific Rise. Unique haplotypes of the 16S gene that fell among the epsilon-proteobacteria were found in the guts of every species, and two species had gut contents that were similar only to epsilon-proteobacteria. Two species had gut contents that also included haplotypes that clustered with delta-proteobacteria, and one species had gut contents that clustered with alpha- proteobacteria. Differences in the diets of these four hydrothermal vent gastropods may reflect microhabitat conditions where these species typically occur or where they were located at the time of the collection. Results from this work provide insights to the "bottom-up" regulation of primary consumers and tracking chemical fluxes through biological communities at hydrothermal vents.

Long-term hydrothermal temperature and pressure monitoring equipped with a Kuroko cultivation apparatus on the deep-sea artificial hydrothermal vent at the middle Okinawa Trough

NASA Astrophysics Data System (ADS)

Masaki, Y.; Nozaki, T.; Saruhashi, T.; Kyo, M.; Sakurai, N.; Yokoyama, T.; Akiyama, K.; Watanabe, M.; Kumagai, H.; Maeda, L.; Kinoshita, M.

2017-12-01

The middle Okinawa Trough, located along the Ryukyu- arc on the margin of the East China Sea, has several active hydrothermal fields. From February to March 2016, Cruise CK16-01 by D/V Chikyu targeted the Iheya-North Knoll and southern flank of the Iheya Minor Ridge to comprehend sub-seafloor geological structure and polymetallic sulfide mineralization. In this cruise, we installed two Kuroko cultivation apparatuses equipped with P/T sensors, flowmeter and load cell to monitor pressure, temperature and flow rate of hydrothermal fluid discharged from the artificial hydrothermal vent together with weight of hydrothermal precipitate. During Cruise KR16-17 in January 2017, two cultivation cells with sensor loggers were successfully recovered by ROV Kaiko MK-IV and R/V Kairei. We report these physical sensor data obtained by more than 10 months monitoring at two deep-sea artificial hydrothermal vents through many first and challenging operations.Hole C9017B at southern flank of the Iheya Minor Ridge (water depth of 1,500 mbsl), fluid temperature was constant ca. 75 ºC for 5 months from the beginning of monitoring. Then temperature gradually decrease to be 40 ºC. In November 2016, temperature and pressure suddenly dropped and quickly recovered due to the disturbance of subseafloor hydrology, induced by another drilling operation at Hole C9017A which is 10.8 meters northeastward from Hole C9017B during Cruise CK16-05. Temperature data exhibit conspicuous periodic 12.4hour cycles and this is attributable to oceanic tidal response. The amplitude of temperature variations increased along with decline of the temperature variations increased along with decline of the temperature. The average flow rate was 67 L/min for 9 hours from the onset of monitoring.Hole C9024A at the Iheya-North Knoll (water depth of 1,050 msl), the maximum temperature reached 308 ºC, which is similar to the maximum value of 311 ºC obtained from the ROV thermometer. The average flow rate was 289 L/min for 8 days from onset of monitoring.

Locating hydrothermal acoustic sources at Old Faithful Geyser using Matched Field Processing

NASA Astrophysics Data System (ADS)

Cros, E.; Roux, P.; Vandemeulebrouck, J.; Kedar, S.

2011-10-01

In 1992, a large and dense array of geophones was placed around the geyser vent of Old Faithful, in the Yellowstone National Park, to determine the origin of the seismic hydrothermal noise recorded at the surface of the geyser and to understand its dynamics. Old Faithful Geyser (OFG) is a small-scale hydrothermal system where a two-phase flow mixture erupts every 40 to 100 min in a high continuous vertical jet. Using Matched Field Processing (MFP) techniques on 10-min-long signal, we localize the source of the seismic pulses recorded at the surface of the geyser. Several MFP approaches are compared in this study, the frequency-incoherent and frequency-coherent approach, as well as the linear Bartlett processing and the non-linear Minimum Variance Distorsionless Response (MVDR) processing. The different MFP techniques used give the same source position with better focalization in the case of the MVDR processing. The retrieved source position corresponds to the geyser conduit at a depth of 12 m and the localization is in good agreement with in situ measurements made at Old Faithful in past studies.

Contrasted hydrothermal activity along the South-East Indian Ridge (130°E-140°E): From crustal to ultramafic circulation

NASA Astrophysics Data System (ADS)

Boulart, Cédric; Briais, Anne; Chavagnac, Valérie; Révillon, Sidonie; Ceuleneer, Georges; Donval, Jean-Pierre; Guyader, Vivien; Barrere, Fabienne; Ferreira, Nicolas; Hanan, Barry; Hémond, Christophe; Macleod, Sarah; Maia, Marcia; Maillard, Agnès.; Merkuryev, Sergey; Park, Sung-Hyun; Ruellan, Etienne; Schohn, Alexandre; Watson, Sally; Yang, Yun-Seok

2017-07-01

Using a combined approach of seafloor mapping, MAPR and CTD survey, we report evidence for active hydrothermal venting along the 130°-140°E section of the poorly-known South-East Indian Ridge (SEIR) from the Australia-Antarctic Discordance (AAD) to the George V Fracture Zone (FZ). Along the latter, we report Eh and CH4 anomalies in the water column above a serpentinite massif, which unambiguously testify for ultramafic-related fluid flow. This is the first time that such circulation is observed on an intermediate-spreading ridge. The ridge axis itself is characterized by numerous off-axis volcanoes, suggesting a high magma supply. The water column survey indicates the presence of at least ten distinct hydrothermal plumes along the axis. The CH4:Mn ratios of the plumes vary from 0.37 to 0.65 denoting different underlying processes, from typical basalt-hosted to ultramafic-hosted high-temperature hydrothermal circulation. Our data suggest that the change of mantle temperature along the SEIR not only regulates the magma supply, but also the hydrothermal activity. The distribution of hydrothermal plumes from a ridge segment to another implies secondary controls such as the presence of fractures and faults along the axis or in the axial discontinuities. We conclude from these results that hydrothermal activity along the SEIR is controlled by magmatic processes at the regional scale and by the tectonics at the segment scale, which influences the type of hydrothermal circulation and leads to various chemical compositions. Such variety may impact global biogeochemical cycles, especially in the Southern Ocean where hydrothermal venting might be the only source of nutrients.

Geothermal implications of a refined composition-age geologic map for the volcanic terrains of southeast Oregon, northeast California, and southwest Idaho, USA

USGS Publications Warehouse

Burns, Erick; Gannett, Marshall W.; Sherrod, David R.; Keith, Mackenzie K.; Curtis, Jennifer A.; Bartolino, James R.; Engott, John A.; Scandella, Benjamin P.; Stern, Michelle A.; Flint, Alan L.

2017-01-01

Sufficient temperatures to generate steam likely exist under most of the dominantly volcanic terrains of southeast Oregon, northeast California, and southeast Idaho, USA, but finding sufficient permeability to allow efficient advective heat exchange is an outstanding challenge. A new thematic interpretation of existing state-level geologic maps provides an updated and refined distribution of the composition and age of geologic units for the purposes of assessing the implications for measurement and development of geothermal resources. This interpretation has been developed to better understand geothermal and hydrologic resources of the region. Comparison of the new geologic categories with available hydrologic data shows that younger volcanogenic terrains tend to have higher primary permeability than older terrains. Decrease in primary permeability with age is attributable to weathering and hydrothermal alteration of volcanogenic deposits to pore-filling clays and deposition of secondary deposits (e.g., zeolites). Spring density as a function of geology and precipitation can be used to infer groundwater flow path length within the upper aquifers. Beneath the upper aquifers, we postulate that, due to accelerated hydrothermal alteration at temperatures ~>30 °C, primary permeability at depths of geothermal interest will be limited, and that secondary permeability is a more viable target for hydrothermal fluid withdrawal. Because open fractures resulting from tensile stresses will affect all geologic layers, regions with a significant amount of groundwater flow through shallow, structurally controlled secondary permeability may overlay zones of deep secondary permeability. Regardless of whether the shallow permeability is connected with the deep permeability, shallow groundwater flow can mask the presence of deep hydrothermal flow, resulting in blind geothermal systems. Ideally, hydraulic connectivity between shallow and deep secondary permeability is limited, so that shallow groundwater does not cool potential geothermal reservoirs.

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

NASA Astrophysics Data System (ADS)

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

2005-12-01

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

Agro-industrial waste to solid biofuel through hydrothermal carbonization.

PubMed

Basso, Daniele; Patuzzi, Francesco; Castello, Daniele; Baratieri, Marco; Rada, Elena Cristina; Weiss-Hortala, Elsa; Fiori, Luca

2016-01-01

In this paper, the use of grape marc for energy purposes was investigated. Grape marc is a residual lignocellulosic by-product from the winery industry, which is present in every world region where vine-making is addressed. Among the others, hydrothermal carbonization was chosen as a promising alternative thermochemical process, suitable for the treatment of this high moisture substrate. Through a 50 mL experimental apparatus, hydrothermal carbonization tests were performed at several temperatures (namely: 180, 220 and 250 °C) and residence times (1, 3, 8 h). Analyses on both the solid and the gaseous phases obtained downstream of the process were performed. In particular, solid and gas yields versus the process operational conditions were studied and the obtained hydrochar was evaluated in terms of calorific value, elemental analysis, and thermal stability. Data testify that hydrochar form grape marc presents interesting values of HHV (in the range 19.8-24.1 MJ/kg) and physical-chemical characteristics which make hydrochar exploitable as a solid biofuel. In the meanwhile, the amount of gases produced is very small, if compared to other thermochemical processes. This represents an interesting result when considering environmental issues. Statistical analysis of data allows to affirm that, in the chosen range of operational conditions, the process is influenced more by temperature than residence time. These preliminary results support the option of upgrading grape marc toward its energetic valorisation through hydrothermal carbonization. Copyright © 2015 Elsevier Ltd. All rights reserved.

New Marine Heat Flow measurements at the Costa Rica Rift, Panama Basin

NASA Astrophysics Data System (ADS)

Harris, R. N.; Kolandaivelu, K. P.; Gregory, E. P. M.; Alshafai, R.; Lowell, R. P.; Hobbs, R. W.

2016-12-01

We report new heat flow measurements collected along the southern flank of the Costa Rica ridge. This ridge flank has been the site of numerous seismic, heat flow, and ocean drilling experiments and has become an important type location for investigations of off-axis hydrothermal processes. These data were collected as part of an interdisciplinary NERC and NSF-funded collaboration entitled: Oceanographic and Seismic Characterization of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR), to better understand links between crustal evolution, hydrothermal heat loss and the impact of this heat loss and fluid mass discharge on deep ocean circulation. The heat flow measurements are collocated with a newly acquired high-resolution seismic profile collected using a GI-gun source to image the sedimentary and upper crustal section. The profile is tied to ODP Hole 504B and provides robust estimates of the sediment thickness as well as its internal structure. In total five heat flow stations consisting of 67 new heat flow measurements were made, spanning crustal ages between 1.3 and 5.4 Myr. The full spreading rate of 66 mm/yr gives rise to abyssal hill basement relief between 500 and 250 m. Sediment cover is relatively incomplete in this region and varies between 0 and 290 m. The majority of heat flow values fall below half-space cooling models indicating that significant amounts of heat are removed by hydrothermal circulation. Low heat flow values are observed in sediment ponds between abyssal hill relief and high values are generally associated with ridge-ward dipping faults bounding abyssal hills. These faults are likely high permeability pathways where heated fluids are discharging, providing an example where large-scale faulting and block rotation plays a major role in ventilated ridge flank fluid circulation. The heat flow fraction (qobs/qpred) varies between varies between 0.01 and 4.1 and has a mean of 0.3 indicating that on average 70% of the expected heat is advected. The mass flux associated with this heat advection is 5 x 10-6 kg/m2-s assuming temperature discharge on the ridge flank is 10° C above ambient.

High-throughput continuous hydrothermal synthesis of nanomaterials (part II): unveiling the as-prepared CexZryYzO2-δ phase diagram.

PubMed

Quesada-Cabrera, Raul; Weng, Xiaole; Hyett, Geoff; Clark, Robin J H; Wang, Xue Z; Darr, Jawwad A

2013-09-09

High-throughput continuous hydrothermal flow synthesis was used to manufacture 66 unique nanostructured oxide samples in the Ce-Zr-Y-O system. This synthesis approach resulted in a significant increase in throughput compared to that of conventional batch or continuous hydrothermal synthesis methods. The as-prepared library samples were placed into a wellplate for both automated high-throughput powder X-ray diffraction and Raman spectroscopy data collection, which allowed comprehensive structural characterization and phase mapping. The data suggested that a continuous cubic-like phase field connects all three Ce-Zr-O, Ce-Y-O, and Y-Zr-O binary systems together with a smooth and steady transition between the structures of neighboring compositions. The continuous hydrothermal process led to as-prepared crystallite sizes in the range of 2-7 nm (as determined by using the Scherrer equation).

Bench-scale synthesis of nanoscale materials

NASA Technical Reports Server (NTRS)

Buehler, M. F.; Darab, J. G.; Matson, D. W.; Linehan, J. C.

1994-01-01

A novel flow-through hydrothermal method used to synthesize nanoscale powders is introduced by Pacific Northwest Laboratory. The process, Rapid Thermal Decomposition of precursors in Solution (RTDS), uniquely combines high-pressure and high-temperature conditions to rapidly form nanoscale particles. The RTDS process was initially demonstrated on a laboratory scale and was subsequently scaled up to accommodate production rates attractive to industry. The process is able to produce a wide variety of metal oxides and oxyhydroxides. The powders are characterized by scanning and transmission electron microscopic methods, surface-area measurements, and x-ray diffraction. Typical crystallite sizes are less than 20 nanometers, with BET surface areas ranging from 100 to 400 sq m/g. A description of the RTDS process is presented along with powder characterization results. In addition, data on the sintering of nanoscale ZrO2 produced by RTDS are included.

Hydrothermal impacts on trace element and isotope ocean biogeochemistry.

PubMed

German, C R; Casciotti, K A; Dutay, J-C; Heimbürger, L E; Jenkins, W J; Measures, C I; Mills, R A; Obata, H; Schlitzer, R; Tagliabue, A; Turner, D R; Whitby, H

2016-11-28

Hydrothermal activity occurs in all ocean basins, releasing high concentrations of key trace elements and isotopes (TEIs) into the oceans. Importantly, the calculated rate of entrainment of the entire ocean volume through turbulently mixing buoyant hydrothermal plumes is so vigorous as to be comparable to that of deep-ocean thermohaline circulation. Consequently, biogeochemical processes active within deep-ocean hydrothermal plumes have long been known to have the potential to impact global-scale biogeochemical cycles. More recently, new results from GEOTRACES have revealed that plumes rich in dissolved Fe, an important micronutrient that is limiting to productivity in some areas, are widespread above mid-ocean ridges and extend out into the deep-ocean interior. While Fe is only one element among the full suite of TEIs of interest to GEOTRACES, these preliminary results are important because they illustrate how inputs from seafloor venting might impact the global biogeochemical budgets of many other TEIs. To determine the global impact of seafloor venting, however, requires two key questions to be addressed: (i) What processes are active close to vent sites that regulate the initial high-temperature hydrothermal fluxes for the full suite of TEIs that are dispersed through non-buoyant hydrothermal plumes? (ii) How do those processes vary, globally, in response to changing geologic settings at the seafloor and/or the geochemistry of the overlying ocean water? In this paper, we review key findings from recent work in this realm, highlight a series of key hypotheses arising from that research and propose a series of new GEOTRACES modelling, section and process studies that could be implemented, nationally and internationally, to address these issues.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2015 The Authors.

Hydrothermal impacts on trace element and isotope ocean biogeochemistry

PubMed Central

Dutay, J.-C.; Heimbürger, L. E.; Jenkins, W. J.; Measures, C. I.; Mills, R. A.; Obata, H.; Turner, D. R.; Whitby, H.

2016-01-01

Hydrothermal activity occurs in all ocean basins, releasing high concentrations of key trace elements and isotopes (TEIs) into the oceans. Importantly, the calculated rate of entrainment of the entire ocean volume through turbulently mixing buoyant hydrothermal plumes is so vigorous as to be comparable to that of deep-ocean thermohaline circulation. Consequently, biogeochemical processes active within deep-ocean hydrothermal plumes have long been known to have the potential to impact global-scale biogeochemical cycles. More recently, new results from GEOTRACES have revealed that plumes rich in dissolved Fe, an important micronutrient that is limiting to productivity in some areas, are widespread above mid-ocean ridges and extend out into the deep-ocean interior. While Fe is only one element among the full suite of TEIs of interest to GEOTRACES, these preliminary results are important because they illustrate how inputs from seafloor venting might impact the global biogeochemical budgets of many other TEIs. To determine the global impact of seafloor venting, however, requires two key questions to be addressed: (i) What processes are active close to vent sites that regulate the initial high-temperature hydrothermal fluxes for the full suite of TEIs that are dispersed through non-buoyant hydrothermal plumes? (ii) How do those processes vary, globally, in response to changing geologic settings at the seafloor and/or the geochemistry of the overlying ocean water? In this paper, we review key findings from recent work in this realm, highlight a series of key hypotheses arising from that research and propose a series of new GEOTRACES modelling, section and process studies that could be implemented, nationally and internationally, to address these issues. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’. PMID:29035265

HYDROGEOLOGY OF THE THERMAL LANDSLIDE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vantine, J.

1985-01-22

The large Thermal Landslide overlies the initial area of geothermal development at The Geysers. The landslide is waterbearing while the underlying Franciscan formation bedrock units are essentially non-waterbearing except where affected by hydrothermal alteration. Perched ground water moving through the landslide is heated prior to discharge as spring flow.

Chemical environments of submarine hydrothermal systems

NASA Technical Reports Server (NTRS)

Shock, Everett L.

1992-01-01

Perhaps because black-smoker chimneys make tremendous subjects for magazine covers, the proposal that submarine hydrothermal systems were involved in the origin of life has caused many investigators to focus on the eye-catching hydrothermal vents. In much the same way that tourists rush to watch the spectacular eruptions of Old Faithful geyser with little regard for the hydrology of the Yellowstone basin, attention is focused on the spectacular, high-temperature hydrothermal vents to the near exclusion of the enormous underlying hydrothermal systems. Nevertheless, the magnitude and complexity of geologic structures, heat flow, and hydrologic parameters which characterize the geyser basins at Yellowstone also characterize submarine hydrothermal systems. However, in the submarine systems the scale can be considerably more vast. Like Old Faithful, submarine hydrothermal vents have a spectacular quality, but they are only one fascinating aspect of enormous geologic systems operating at seafloor spreading centers throughout all of the ocean basins. A critical study of the possible role of hydrothermal processes in the origin of life should include the full spectrum of probable environments. The goals of this chapter are to synthesize diverse information about the inorganic geochemistry of submarine hydrothermal systems, assemble a description of the fundamental physical and chemical attributes of these systems, and consider the implications of high-temperature, fluid-driven processes for organic synthesis. Information about submarine hydrothermal systems comes from many directions. Measurements made directly on venting fluids provide useful, but remarkably limited, clues about processes operating at depth. The oceanic crust has been drilled to approximately 2.0 km depth providing many other pieces of information, but drilling technology has not allowed the bore holes and core samples to reach the maximum depths to which aqueous fluids circulate in oceanic crust. Such determinations rely on studies of pieces of deep oceanic crust uplifted by tectonic forces such as along the Southwest Indian Ridge, or more complete sections of oceanic crust called ophiolite sequences which are presently exposed on continents owing to tectonic emplacement. Much of what is thought to happen in submarine hydrothermal systems is inferred from studies of ophiolite sequences, and especially from the better-exposed ophiolites in Oman, Cyprus and North America. The focus of much that follows is on a few general features: pressure, temperature, oxidation states, fluid composition and mineral alteration, because these features will control whether organic synthesis can occur in hydrothermal systems.

Application of environmental groundwater tracers at the Sulphur Bank Mercury Mine, California, USA

USGS Publications Warehouse

Engle, M.A.; Goff, F.; Jewett, D.G.; Reller, G.J.; Bauman, J.B.

2008-01-01

Boron, chloride, sulfate, ??D, ??18O, and 3H concentrations in surface water and groundwater samples from the Sulphur Bank Mercury Mine (SBMM), California, USA were used to examine geochemical processes and provide constraints on evaporation and groundwater flow. SBMM is an abandoned sulfur and mercury mine with an underlying hydrothermal system, adjacent to Clear Lake, California. Results for non-3H tracers (i.e., boron, chloride, sulfate, ??D, and ??18O) identify contributions from six water types at SBMM. Processes including evaporation, mixing, hydrothermal water input and possible isotopic exchange with hydrothermal gases are also discerned. Tritium data indicate that hydrothermal waters and other deep groundwaters are likely pre-bomb (before ???1952) in age while most other waters were recharged after ???1990. A boron-based steady-state reservoir model of the Herman Impoundment pit lake indicates that 71-79% of its input is from meteoric water with the remainder from hydrothermal contributions. Results for groundwater samples from six shallow wells over a 6-month period for ??D and ??18O suggests that water from Herman Impoundment is diluted another 3% to more than 40% by infiltrating meteoric water, as it leaves the site. Results for this investigation show that environmental tracers are an effective tool to understand the SBMM hydrogeologic regime. ?? Springer-Verlag 2007.

Oxidative Weathering and Microbial Diversity of an Inactive Seafloor Hydrothermal Sulfide Chimney

PubMed Central

Li, Jiangtao; Cui, Jiamei; Yang, Qunhui; Cui, Guojie; Wei, Bingbing; Wu, Zijun; Wang, Yong; Zhou, Huaiyang

2017-01-01

When its hydrothermal supply ceases, hydrothermal sulfide chimneys become inactive and commonly experience oxidative weathering on the seafloor. However, little is known about the oxidative weathering of inactive sulfide chimneys, nor about associated microbial community structures and their succession during this weathering process. In this work, an inactive sulfide chimney and a young chimney in the early sulfate stage of formation were collected from the Main Endeavor Field of the Juan de Fuca Ridge. To assess oxidative weathering, the ultrastructures of secondary alteration products accumulating on the chimney surface were examined and the presence of possible Fe-oxidizing bacteria (FeOB) was investigated. The results of ultrastructure observation revealed that FeOB-associated ultrastructures with indicative morphologies were abundantly present. Iron oxidizers primarily consisted of members closely related to Gallionella spp. and Mariprofundus spp., indicating Fe-oxidizing species likely promote the oxidative weathering of inactive sulfide chimneys. Abiotic accumulation of Fe-rich substances further indicates that oxidative weathering is a complex, dynamic process, alternately controlled by FeOB and by abiotic oxidization. Although hydrothermal fluid flow had ceased, inactive chimneys still accommodate an abundant and diverse microbiome whose microbial composition and metabolic potential dramatically differ from their counterparts at active vents. Bacterial lineages within current inactive chimney are dominated by members of α-, δ-, and γ-Proteobacteria and they are deduced to be closely involved in a diverse set of geochemical processes including iron oxidation, nitrogen fixation, ammonia oxidation and denitrification. At last, by examining microbial communities within hydrothermal chimneys at different formation stages, a general microbial community succession can be deduced from early formation stages of a sulfate chimney to actively mature sulfide structures, and then to the final inactive altered sulfide chimney. Our findings provide valuable insights into the microbe-involved oxidative weathering process and into microbial succession occurring at inactive hydrothermal sulfide chimney after high-temperature hydrothermal fluids have ceased venting. PMID:28785251

Geophysical image of the hydrothermal system of Merapi volcano

NASA Astrophysics Data System (ADS)

Byrdina, S.; Friedel, S.; Vandemeulebrouck, J.; Budi-Santoso, A.; Suhari; Suryanto, W.; Rizal, M. H.; Winata, E.; Kusdaryanto

2017-01-01

We present an image of the hydrothermal system of Merapi volcano based on results from electrical resistivity tomography (ERT), self-potential, and CO2 flux mappings. The ERT models identify two distinct low-resistivity bodies interpreted as two parts of a probably interconnected hydrothermal system: at the base of the south flank and in the summit area. In the summit area, a sharp resistivity contrast at ancient crater rim Pasar-Bubar separates a conductive hydrothermal system (20-50 Ω m) from the resistive andesite lava flows and pyroclastic deposits (2000-50,000 Ω m). The existence of preferential fluid circulation along this ancient crater rim is also evidenced by self-potential data. The significative diffuse CO2 degassing (with a median value of 400 g m-2 d-1) is observed in a narrow vicinity of the active crater rim and close to the ancient rim of Pasar-Bubar. The total CO2 degassing across the accessible summital area with a surface of 1.4 ṡ 105 m2 is around 20 t d-1. Before the 2010 eruption, Toutain et al. (2009) estimated a higher value of the total diffuse degassing from the summit area (about 200-230 t d-1). This drop in the diffuse degassing from the summit area can be related to the decrease in the magmatic activity, to the change of the summit morphology, to the approximations used by Toutain et al. (2009), or, more likely, to a combination of these factors. On the south flank of Merapi, the resistivity model shows spectacular stratification. While surficial recent andesite lava flows are characterized by resistivity exceeding 100,000 Ω m, resistivity as low as 10 Ω m has been encountered at a depth of 200 m at the base of the south flank and was interpreted as a presence of the hydrothermal system. No evidence of the hydrothermal system is found on the basis of the north flank at the same depth. This asymmetry might be caused by the asymmetry of the heat supply source of Merapi whose activity is moving south or/and to the asymmetry in topography caused by the presence of Merbabu volcano in the north. On the basis of our results we suggest that stratified pyroclastic deposits on the south flank of Merapi screen and separate the flow of hydrothermal fluids with the gaseous part rising through the crater rims, while the liquid part is flowing downwards to the base of the edifice.

Hydrothermal alteration in research drill hole Y-3, Lower Geyser Basin, Yellowstone National Park, Wyoming

USGS Publications Warehouse

Bargar, Keith E.; Beeson, Melvin H.

1985-01-01

Y-3, a U.S. Geological Survey research diamond-drill hole in Lower Geyser Basin, Yellowstone National Park, Wyoming, reached a depth of 156.7 m. The recovered drill core consists of 42.2 m of surficial (mostly glacial) sediments and two rhyolite flows (Nez Perce Creek flow and an older, unnamed rhyolite flow) of the Central Plateau Member of the Pleistocene Plateau Rhyolite. Hydrothermal alteration is fairly extensive in most of the drill core. The surficial deposits are largely cemented by silica and zeolite minerals; and the two rhyolite flows are, in part, bleached by thermal water that deposited numerous hydrothermal minerals in cavities and fractures. Hydrothermal minerals containing sodium as a dominant cation (analcime, clinoptilolite, mordenite, Na-smectite, and aegirine) are more abundant than calcium-bearing minerals (calcite, fluorite, Ca-smectite, and pectolite) in the sedimentary section of the drill core. In the volcanic section of drill core Y-3, calcium-rich minerals (dachiardite, laumontite, yugawaralite, calcite, fluorite, Ca-smectite, pectolite, and truscottite) are predominant over sodium-bearing minerals (aegirine, mordenite, and Na-smectite). Hydrothermal minerals that contain significant amounts of potassium (alunite and lepidolite in the sediments and illitesmectite in the rhyolite flows) are found in the two drill-core intervals. Drill core y:.3 also contains hydrothermal silica minerals (opal, [3-cristobalite, chalcedony, and quartz), other clay minerals (allophane, halloysite, kaolinite, and chlorite), gypsum, pyrite, and hematite. The dominance of calcium-bearing hydrothermal minerals in the lower rhyolitic section of the y:.3 drill core appears to be due to loss of calcium, along with potassium, during adiabatic cooling of an ascending boiling water.

Identifying bubble collapse in a hydrothermal system using hidden Markov models

USGS Publications Warehouse

Dawson, P.B.; Benitez, M.C.; Lowenstern, J. B.; Chouet, B.A.

2012-01-01

Beginning in July 2003 and lasting through September 2003, the Norris Geyser Basin in Yellowstone National Park exhibited an unusual increase in ground temperature and hydrothermal activity. Using hidden Markov model theory, we identify over five million high-frequency (>15Hz) seismic events observed at a temporary seismic station deployed in the basin in response to the increase in hydrothermal activity. The source of these seismic events is constrained to within ???100 m of the station, and produced ???3500-5500 events per hour with mean durations of ???0.35-0.45s. The seismic event rate, air temperature, hydrologic temperatures, and surficial water flow of the geyser basin exhibited a marked diurnal pattern that was closely associated with solar thermal radiance. We interpret the source of the seismicity to be due to the collapse of small steam bubbles in the hydrothermal system, with the rate of collapse being controlled by surficial temperatures and daytime evaporation rates. copyright 2012 by the American Geophysical Union.

Identifying bubble collapse in a hydrothermal system using hiddden Markov models

USGS Publications Warehouse

Dawson, Phillip B.; Benitez, M.C.; Lowenstern, Jacob B.; Chouet, Bernard A.

2012-01-01

Beginning in July 2003 and lasting through September 2003, the Norris Geyser Basin in Yellowstone National Park exhibited an unusual increase in ground temperature and hydrothermal activity. Using hidden Markov model theory, we identify over five million high-frequency (>15 Hz) seismic events observed at a temporary seismic station deployed in the basin in response to the increase in hydrothermal activity. The source of these seismic events is constrained to within ~100 m of the station, and produced ~3500–5500 events per hour with mean durations of ~0.35–0.45 s. The seismic event rate, air temperature, hydrologic temperatures, and surficial water flow of the geyser basin exhibited a marked diurnal pattern that was closely associated with solar thermal radiance. We interpret the source of the seismicity to be due to the collapse of small steam bubbles in the hydrothermal system, with the rate of collapse being controlled by surficial temperatures and daytime evaporation rates.

Hydrothermal activity in the Lau back-arc basin: Sulfides and water chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fouquet, Y.; Charlou, J.L.; Donval, J.P.

1991-04-01

The submersible Nautile completed 22 dives during the Nautilau cruise (R/V Nadir, April 17-May 10, 1989) for a detailed investigation of the southern Lau basin near Tonga. The objective of the scientific team from France, Germany, and Tonga was to understand the process of sea-floor ore formation associated with hydrothermal circulation along the Valu Fa back-arc ridge behind the Tonga-Kermadec trench. The four diving areas, between lat21{degree}25'S and 22{degree}40'S in water{approximately}2000 m deep, were selected on the basis of results from cruises of the R/V Jean Charcot and R/V Sonne. The Nadir cruise provided proof of hydrothermal activity-in all formore » areas, over more than 100 km-as indicated by the widespread occurence of hydrothermal deposits and by heat flow, conductivity, and temperature measurements near the sea bottom. The most spectacular findings were high-temperature white and black smokers and associated fauna and ore deposits. Hydrothermal water chemistry and sulfide composition data presented here indicate that this hydrothermal field is very different from the hydrothermal fields in oceanic ridges. This difference is seen in water chemistry of the hydrothermal fluid (pH=2 and high metal content) and the chemical composition of sulfides (enrichment in Ba, As, and Pb).« less

Near-vent chemical processes in a hydrothermal plume: Insights from an integrated study of the Endeavour segment

NASA Astrophysics Data System (ADS)

Coogan, L. A.; Attar, A.; Mihaly, S. F.; Jeffries, M.; Pope, M.

2017-04-01

The Endeavour segment of the Juan de Fuca mid-ocean ridge is one of the best studied ridge segments and has recently been instrumented as part of Ocean Networks Canada's NEPTUNE cabled observatory. Here we investigate the interaction between high-temperature vent fluids and the overlying water column. A new tow-yo survey found that the average temperature anomaly in the neutrally buoyant plume was ˜0.043°C. The water column temperature and light attenuation anomalies correlate linearly in some areas of the plume but in other areas there is a low light attenuation anomaly relative to the temperature anomaly. This temperature excess is interpreted to reflect heat input through (particle-poor) diffuse flow. If this is correct, about half of the heat flux along the Endeavour segment comes from diffuse flow. Sediment trap and push core data show that the mass accumulation rate of the hydrothermal component of the sediments decreases rapidly with distance from the major vent fields. Large changes in the composition of the hydrothermal component of the sediments also occur with distance from the vent fields. The composition of the sediments indicates (i) sulfides precipitate early and accumulate most rapidly close to the vents with a preferential order of element removal from the plume of Cd > Ag > Cu > Co ˜ Fe; (ii) barite is deposited somewhat further from the vents. Strontium and Pb appear to be strongly incorporated in barite and/or other sulfate minerals; (iii) at most a few percent of the mass of these "insoluble" elements that is vented gets deposited within 1.5 km of the vents.

Using design of experiments to optimize derivatization with methyl chloroformate for quantitative analysis of the aqueous phase from hydrothermal liquefaction of biomass.

PubMed

Madsen, René Bjerregaard; Jensen, Mads Mørk; Mørup, Anders Juul; Houlberg, Kasper; Christensen, Per Sigaard; Klemmer, Maika; Becker, Jacob; Iversen, Bo Brummerstedt; Glasius, Marianne

2016-03-01

Hydrothermal liquefaction is a promising technique for the production of bio-oil. The process produces an oil phase, a gas phase, a solid residue, and an aqueous phase. Gas chromatography coupled with mass spectrometry is used to analyze the complex aqueous phase. Especially small organic acids and nitrogen-containing compounds are of interest. The efficient derivatization reagent methyl chloroformate was used to make analysis of the complex aqueous phase from hydrothermal liquefaction of dried distillers grains with solubles possible. A circumscribed central composite design was used to optimize the responses of both derivatized and nonderivatized analytes, which included small organic acids, pyrazines, phenol, and cyclic ketones. Response surface methodology was used to visualize significant factors and identify optimized derivatization conditions (volumes of methyl chloroformate, NaOH solution, methanol, and pyridine). Twenty-nine analytes of small organic acids, pyrazines, phenol, and cyclic ketones were quantified. An additional three analytes were pseudoquantified with use of standards with similar mass spectra. Calibration curves with high correlation coefficients were obtained, in most cases R (2)  > 0.991. Method validation was evaluated with repeatability, and spike recoveries of all 29 analytes were obtained. The 32 analytes were quantified in samples from the commissioning of a continuous flow reactor and in samples from recirculation experiments involving the aqueous phase. The results indicated when the steady-state condition of the flow reactor was obtained and the effects of recirculation. The validated method will be especially useful for investigations of the effect of small organic acids on the hydrothermal liquefaction process.

Asymmetrical hydrothermal system below Merapi volcano imaged by geophysical data.

NASA Astrophysics Data System (ADS)

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

2017-04-01

A high-resolution image of the hydrothermal system of Merapi volcano is obtained using electrical resistivity tomography (ERT), self-potential, and CO2 flux mappings. The ERT inversions identify two distinct low-resistivity bodies, at the base of the south flank and in the summit area, that represent likely two parts of an interconnected hydrothermal system. In the summit area, the extension of the hydrothermal system is clearly limited by the main geological structures which are actual and ancient craters. A sharp resistivity contrast at ancient crater rim Pasar-Bubar separates a conductive hydrothermal system (20 - 50 Ωm) from the resistive andesite lava flows and pyroclastic deposits (2000 - 50 000 Ωm). High diffuse CO2 degassing (with a median value of 400g m -2 d -1) is observed in a narrow vicinity of the active crater rim and close to the Pasar-Bubar. The existence of preferential fluid circulation along this ancient crater rim is also evidenced by self-potential data. The total CO2 degassing across the accessible summit area with a surface of 1.4 · 10 5 m 2 is around 20 td -1. Before the 2010 eruption, Toutain et al. (2009) estimated a higher value of the total diffuse degassing from the summit area (about 200 - 230 td -1). This drop in the diffuse degassing can be related to the decrease in the magmatic activity, to the change of the summit morphology or to a combination of these factors. On the south flank of Merapi, the resistivity model shows spectacular stratification. While surficial recent andesite lava flows are characterized by resistivity exceeding 100 000 Ωm, resistivity as low as 10 Ωm has been encountered at a depth of 200 m at the base of the south flank and was interpreted as a presence of the hydrothermal system. We suggest that a sandwich-like structure of stratified pyroclastic deposits on the flanks of Merapi screen and separate the flow of hydrothermal fluids with the degassing occurring mostly through the fractured crater rims, while the liquid water flows down to the base of the volcanic dome. Our ERT results suggest the existence of a peripheral hydrothermal system below the south and west flanks in agreement with previous electromagnetic studies. In contrast, no evidence of hydrothermal system is found below the north flank, where the resistivity values are too high to be assigned to a hydrothermal system, at least to the ERT investigation depth. A probable cause of this asymmetry could be a non-axial location of the magmatic heat source. Such non-axial location of the magmatic source relative to the edifice is suggested by the shift of the volcanic activity to the south as proposed in the geological model by Camus et al, (2000). In addition, the hypocenters of seismic events located by Budi-Santoso et al, (2013) seem to be distributed to the SW from the active crater suggesting that the magma conduits and likely, the magmatic source, are shifted to the SW with respect to the actual crater.

Mathematical modeling of the thermal and hydrodynamic structure of the cooling reservoir

NASA Astrophysics Data System (ADS)

Saminskiy, G.; Debolskaya, E.

2012-04-01

Hydrothermal conditions of the cooling reservoir is determined by the heat and mass transfer from the water surface to the atmosphere and the processes of heat transfer directly in the water mass of the reservoir. As the capacity of power plants, the corresponding increase in the volume of heated water and the use of deep lakes and reservoirs as coolers there is a need to develop new, more accurate, and the application of existing methods for the numerical simulation. In calculating the hydrothermal regime it must take into account the effect of wind, density (buoyancy) forces, and other data of the cooling reservoir. In addition to solving practical problems it is important to know not only the magnitude of the average temperature, but also its area and depth distribution. A successful solution can be achieved through mathematical modeling of general systems of equations of transport processes and the correct formulation of the problem, based on appropriate initial data. The purpose of the work is application of software package GETM for simulating the hydrothermal regime of cooling reservoir with an estimate of three-dimensional structure of transfer processes, the effects of wind, the friction of the water surface. Three-dimensional models are rarely applied, especially for far-field problems. If such models are required, experts in the field must develop and apply them. Primary physical processes included are surface heat transfer, short-wave and long-wave radiation and penetration, convective mixing, wind and flow induced mixing, entrainment of ambient water by pumped-storage inflows, inflow density stratification as impacted by temperature and dissolved and suspended solids. The model forcing data consists of the system bathymetry developed into the model grid; the boundary condition flow and temperature; the tributary and flow and temperature; and the system meteorology. Ivankovskoe reservoir belongs to the reservoirs of valley type (Tver region, Russia). It is used as a cooling reservoir for Konakovskaya power plant. It dumps the heated water in the Moshkovichevsky bay. Thermal and hydrodynamic structure of the Moshkovichevsky Bay is particular interest as the object of direct influence of heated water discharge. To study the effect of thermal discharge into the Ivankovskoe reservoir the model of the Moshkovichevsky Bay was built, which is subject to the largest thermal pollution. Step of the calculation grid is 25 meters. For further verification of the model field investigations were conducted in August-September 2011. The modeling results satisfactorily describe the thermal and hydrodynamic structure of the Moshkovichevsky Bay.

High power Nb-doped LiFePO4 Li-ion battery cathodes; pilot-scale synthesis and electrochemical properties

NASA Astrophysics Data System (ADS)

Johnson, Ian D.; Blagovidova, Ekaterina; Dingwall, Paul A.; Brett, Dan J. L.; Shearing, Paul R.; Darr, Jawwad A.

2016-09-01

High power, phase-pure Nb-doped LiFePO4 (LFP) nanoparticles are synthesised using a pilot-scale continuous hydrothermal flow synthesis process (production rate of 6 kg per day) in the range 0.01-2.00 at% Nb with respect to total transition metal content. EDS analysis suggests that Nb is homogeneously distributed throughout the structure. The addition of fructose as a reagent in the hydrothermal flow process, followed by a post synthesis heat-treatment, affords a continuous graphitic carbon coating on the particle surfaces. Electrochemical testing reveals that cycling performance improves with increasing dopant concentration, up to a maximum of 1.0 at% Nb, for which point a specific capacity of 110 mAh g-1 is obtained at 10 C (6 min for the charge or discharge). This is an excellent result for a high power cathode LFP based material, particularly when considering the synthesis was performed on a large pilot-scale apparatus.

Sedimentology, Behavior, and Hazards of Debris Flows at Mount Rainier, Washington

USGS Publications Warehouse

Scott, K.M.; Vallance, J.W.; Pringle, P.T.

1995-01-01

Mount Rainier is potentially the most dangerous volcano in the Cascade Range because of its great height, frequent earthquakes, active hydrothermal system, and extensive glacier mantle. Many debris flows and their distal phases have inundated areas far from the volcano during postglacial time. Two types of debris flows, cohesive and noncohesive, have radically different origins and behavior that relate empirically to clay content. The two types are the major subpopulations of debris flows at Mount Rainier. The behavior of cohesive flows is affected by the cohesion and adhesion of particles; noncohesive flows are dominated by particle collisions to the extent that particle cataclasis becomes common during near-boundary shear. Cohesive debris flows contain more than 3 to 5 percent of clay-size sediment. The composition of these flows changed little as they traveled more than 100 kilometers from Mount Rainier to inundate parts of the now-populated Puget Sound lowland. They originate as deep-seated failures of sectors of the volcanic edifice, and such failures are sufficiently frequent that they are the major destructional process of Mount Rainier's morphologic evolution. In several deposits of large cohesive flows, a lateral, megaclast-bearing facies (with a mounded or hummocky surface) contrasts with a more clay-rich facies in the center of valleys and downstream. Cohesive flows at Mount Rainier do not correlate strongly with volcanic activity and thus can recur without warning, possibly triggered by non-magmatic earthquakes or by changes in the hydrothermal system. Noncohesive debris flows contain less than 3 to 5 percent clay-size sediment. They form most commonly by bulking of sediment in water surges, but some originate directly or indirectly from shallow slope failures that do not penetrate the hydrothermally altered core of the volcano. In contrast with cohesive flows, most noncohesive flows transform both from and to other flow types and are, therefore, the middle segments of flow waves that begin and end as flood surges. Proximally, through the bulking of poorly sorted volcaniclastic debris on the flanks of the volcano, flow waves expand rapidly in volume by transforming from water surges through hyperconcentrated stream flow (20 to 60 percent sediment by volume) to debris flow. Distally, the transformations occur more slowly in reverse order - from debris flow, to hyperconcentrated flow, and finally to normal streamflow with less than 20 percent sediment by volume. During runout of the largest noncohesive flows, hyperconcentrated flow has continued for as much as 40 to 70 kilometers. Lahars (volcanic debris flows and their deposits) have occurred frequently at Mount Rainier over the past several thousand years, and generally they have not clustered within discrete eruptive periods as at Mount St. Helens. An exception is a period of large noncohesive flows during and after construction of the modern summit cone. Deposits from lahar-runout flows, the hyperconcentrated distal phases of lahars, document the frequency and extent of noncohesive lahars. These deposits also record the following transformations of debris flows: (1) the direct, progressive dilution of debris flow to hyperconcentrated flow, (2) deposition of successively finer grained lobes of debris until only the hyperconcentrated tail of the flow remains to continue downstream, and (3) dewatering of coarse debris flow deposits to yield fine-grained debris flow or hyperconcentrated flow. Three planning or design case histories represent different lengths of postglacial time. Case I is representative of large, infrequent (500 to 1,000 years on average) cohesive debris flows. These flows need to be considered in long-term planning in valleys around the volcano. Case II generalizes the noncohesive debris flows of intermediate size and recurrence (100 to 500 years). This case is appropriate for consideration in some structural design. Case III flows are

Hydrothermal Alkalinity in Central Nepal Rivers

NASA Astrophysics Data System (ADS)

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

2002-12-01

Numerous hot springs flow along the base of the Himalayan front, at or near the Main Central Thrust, in the Narayani drainage of central Nepal. The springs are found in a narrow zone characterized by rapid uplift and high incision rates. In this zone, hot rocks are brought to the near-surface where they interact with meteoric waters to produce the hydrothermal system. Water-rock interaction produces springs with high solute loads (TDS up to 8000 mg/L.) The springs drive significant chemical anomalies (e.g. Cl, Na, K and Ge) in the rivers that flow through the hydrothermal zone In order to quantify the impact the springs have on the river chemistry, the spring discharge must be estimated. Direct measurement of the spring discharge is difficult, as the springs often flow within the stream bed itself or are inaccessible. We take advantage of the wide disparity in stream vs. hydrothermal [Ge] to calculate spring discharge by chemical mass balance. The hot springs have [Ge] up to 684 nmol/kg and Ge/Si ratios from 200 to 1000 μmol/mol while river waters have [Ge] near 0.15 nmol/kg and Ge/Si ratios near 0.5 μmol/mol, typical of non-polluted rivers. The discharge calculated from the Ge mass balance for individual springs ranges from 0.03 x 106 to 5.6 x 106 m3/yr, and accounts for a small percentage of the total river discharge (0.03% to 1.9%). The hot spring discharge for all of central Nepal is around 1.5x108 m3/yr, 0.5% of the Narayani river discharge. Distinguishing between silicate and carbonate sources is important to assessing the role of weathering on atmospheric CO2 levels and the relative contributions of silicate and carbonate alkalinity in central Nepal rivers are still not well resolved. The hot springs derive up to 100% of their alkalinity from silicate sources. Using the discharge estimates for the springs, we find that the sum of the silicate alkalinity fluxes from all the spring systems is 2.8 x 108 mol/yr. This implies that the hot springs deliver around 18% of the silicate alkalinity in the Narayani river, and ca. 2% of the total alkalinity. Geothermal activity in this active orogenic belt is an important geochemical flux, directly coupling chemical fluxes to tectonic processes.

Episodic thermal perturbations associated with groundwater flow: An example from Kilauea Volcano, Hawaii

USGS Publications Warehouse

Hurwitz, S.; Ingebritsen, S.E.; Sorey, M.L.

2002-01-01

Temperature measurements in deep drill holes on volcano summits or upper flanks allow a quantitative analysis of groundwater induced heat transport within the edifice. We present a new temperature-depth profile from a deep well on the summit of Kilauea Volcano, Hawaii, and analyze it in conjunction with a temperature profile measured 26 years earlier. We propose two groundwater flow models to interpret the complex temperature profiles. The first is a modified confined lateral flow model (CLFM) with a continuous flux of hydrothermal fluid. In the second, transient flow model (TFM), slow conductive cooling follows a brief, advective heating event. We carry out numerical simulations to examine the timescales associated with each of the models. Results for both models are sensitive to the initial conditions, and with realistic initial conditions it takes between 750 and 1000 simulation years for either model to match the measured temperature profiles. With somewhat hotter initial conditions, results are consistent with onset of a hydrothermal plume ???550 years ago, coincident with initiation of caldera subsidence. We show that the TFM is consistent with other data from hydrothermal systems and laboratory experiments and perhaps is more appropriate for this highly dynamic environment. The TFM implies that volcano-hydrothermal systems may be dominated by episodic events and that thermal perturbations may persist for several thousand years after hydrothermal flow has ceased.

Paleointensity in ignimbrites and other volcaniclastic flows

NASA Astrophysics Data System (ADS)

Bowles, J. A.; Gee, J. S.; Jackson, M. J.

2011-12-01

Ash flow tuffs (ignimbrites) are common worldwide, frequently contain fine-grained magnetite hosted in the glassy matrix, and often have high-quality 40Ar/39Ar ages. This makes them attractive candidates for paleointensity studies, potentially allowing for a substantial increase in the number of well-dated paleointensity estimates. However, the timing and nature of remanence acquisition in ignimbrites are not sufficiently understood to allow confident interpretation of paleointensity data from ash flows. The remanence acquisition may be a complex function of mineralogy and thermal history. Emplacement conditions and post-emplacement processes vary considerably between and within tuffs and may potentially affect the ability to recover ancient field intensity information. To better understand the relevant magnetic recording assemblage(s) and remanence acquisition processes we have collected samples from two well-documented historical ignimbrites, the 1980 ash flows at Mt. St. Helens (MSH), Washington, and the 1912 flows from Mt. Katmai in the Valley of Ten Thousand Smokes (VTTS), Alaska. Data from these relatively small, poorly- to non-welded historical flows are compared to the more extensive and more densely welded 0.76 Ma Bishop Tuff. This sample set enables us to better understand the geologic processes that destroy or preserve paleointensity information so that samples from ancient tuffs may be selected with care. Thellier-type paleointensity experiments carried out on pumice blocks sampled from the MSH flows resulted in a paleointensity of 55.8 μT +/- 0.8 (1 standard error). This compares favorably with the actual value of 56.0 μT. Excluded specimens of poor technical quality were dominantly from sites that were either emplaced at low temperature (<350°C) or were subject to post-emplacement hydrothermal alteration. The VTTS experienced much more wide-spread low-temperature hydrothermal activity than did MSH. Pumice-bearing ash matrix samples from this locality are characterized by at least two magnetic phases, one of which appears to carry a chemical remanent magnetization. Paleointensities derived from the second phase give results that vary widely but which may be correlated with degree of hydrothermal alteration or hydration. Preliminary data from the Bishop Tuff suggests that vapor-phase alteration at high (>600°C) temperatures does not corrupt the paleointensity signal, and additional data will be presented which explores this more fully.

Hyperbaric hydrothermal atomic force microscope

DOEpatents

Knauss, Kevin G.; Boro, Carl O.; Higgins, Steven R.; Eggleston, Carrick M.

2002-01-01

A hyperbaric hydrothermal atomic force microscope (AFM) is provided to image solid surfaces in fluids, either liquid or gas, at pressures greater than normal atmospheric pressure. The sample can be heated and its surface imaged in aqueous solution at temperatures greater than 100.degree. C. with less than 1 nm vertical resolution. A gas pressurized microscope base chamber houses the stepper motor and piezoelectric scanner. A chemically inert, flexible membrane separates this base chamber from the sample cell environment and constrains a high temperature, pressurized liquid or gas in the sample cell while allowing movement of the scanner. The sample cell is designed for continuous flow of liquid or gas through the sample environment.

Hyperbaric Hydrothermal Atomic Force Microscope

DOEpatents

Knauss, Kevin G.; Boro, Carl O.; Higgins, Steven R.; Eggleston, Carrick M.

2003-07-01

A hyperbaric hydrothermal atomic force microscope (AFM) is provided to image solid surfaces in fluids, either liquid or gas, at pressures greater than normal atmospheric pressure. The sample can be heated and its surface imaged in aqueous solution at temperatures greater than 100.degree. C. with less than 1 nm vertical resolution. A gas pressurized microscope base chamber houses the stepper motor and piezoelectric scanner. A chemically inert, flexible membrane separates this base chamber from the sample cell environment and constrains a high temperature, pressurized liquid or gas in the sample cell while allowing movement of the scanner. The sample cell is designed for continuous flow of liquid or gas through the sample environment.

Modeling mid-ocean ridge hydrothermal response to earthquakes, tides, and ocean currents: a case study at the Grotto mound, Endeavour Segment, Juan de Fuca Ridge

NASA Astrophysics Data System (ADS)

Xu, G.; Bemis, K. G.

2014-12-01

Seafloor hydrothermal systems feature intricate interconnections among oceanic, geological, hydrothermal, 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 site of the NEPTUNE observatory, makes it a perfect place to study the response of a seafloor hydrothermal 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 hydrothermal activity 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 activities. Comparison of the observations with the results of a 1-D mathematical model simulation of hydrothermal sub-seafloor circulation elucidates the potential mechanisms underlying hydrothermal response to local earthquakes. Second, we observe significant tidal oscillations in the venting temperature time series recorded by BARS and the acoustic imaging of hydrothermal plumes by COVIS, which is evidence for hydrothermal 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 theories to estimate the crustal permeability, a fundamental property of subsurface hydrothermal circulation, from the phase shift of the tidal oscillations of venting temperature relative to ambient ocean tides. These results together shed light on the influences of seismic and oceanic processes on a seafloor hydrothermal system.

Structure of Hole 1256D: The role of mechanical deformation in superfast-spread crust

NASA Astrophysics Data System (ADS)

Tartarotti, P.; Hayman, N. W.; Anma, R.; Crispini, L.; Veloso Espinosa, E. A.; Galli, L.

2006-12-01

One view of seafloor spreading is that mechanical deformation is not significant at high spreading rates. With recovery of up to 37%, and the vertical axis known for many pieces, shipboard visual core descriptions from Hole 1256D provide an opportunity to evaluate the significance of deformational structures in EPR-, superfast- (~220 mm-yr) spread crust. From top to bottom, the structural characteristics of crustal units are: (1) A relatively flat-lying, ~100-m thick "lava pond" that is largely free of deformational structures; (2) ~184 m of shallowly dipping lava flows remarkable for hyaloclastites and a cooling-related fracture system; (3) ~466 m of massive and sheet flows with flow-related fractures, hydrothermal veins, and (fault-related) cataclastic domains; (3) A ~61 m thick transition zone that contains a well-developed (fault-related) cataclastic domain; (4) A ~346 m thick sheeted dike complex, with abundant hydrothermal veins, local breccias, and magmatic flow features. Recovered chilled dike margins have a mean dip of 70° and range from 41-88°; (5) A ~100 m thick plutonic suite contains gabbroic rocks that intrude the sheeted dikes. Gabbros contain some local brittle structures and minor (largely static) recrystallized domains, but are more noteworthy for their magmatic features: dike/gabbro contacts and flow foliations are modestly dipping (e.g., ~45°) with leucocratic melt patches concentrated toward the top of the section. Brittle structures were subordinate to magmatic processes in accommodating large extensional strain. Brittle deformation was important, however, in accommodating magmatism and hydrothermal fluid flow, thereby affecting the variation of crustal physical properties and the distribution of oceanic alteration.

Transport and deposition processes of the hydrothermal blast of the 6 August 2012 Te Maari eruption, Mt. Tongariro

NASA Astrophysics Data System (ADS)

Breard, E. C. P.; Lube, G.; Cronin, S. J.; Valentine, G. A.

2015-11-01

The 2012 eruption of Tongariro volcano (New Zealand) produced highly mobile, low-temperature, blast-derived pyroclastic density currents after partial collapse of the western flank of the Upper Te Maari crater. Despite a low volume (340,000 m3), the flows traveled up to 2.5 km from source, covering a total area of 6.1 km2. Along one of the blast axes, freshly exposed, proximal-to-distal sedimentary structures and grain-size data suggest emplacement of the fining upward tripartite depositional sequence (massive, stratified, and laminated) under a dilute and strongly longitudinally zoned turbulent density current. While the zoning formed in the deposit in the first 1500 m of runout, the current progressively waned to the extent where it transported a nearly homogenous grain-size mixture at the liftoff position. Our data indicate that after the passage of an erosive flow front, massive unit A was deposited under a rapid-suspension sedimentation regime. Unit B was deposited under a traction-dominated regime generated by a subsequent portion of the flow moving at lower velocities and with lower sediment transport capacity than the portion depositing unit A. The final and slowest flow zone deposited the finest particles under weakly tractive conditions. Transport and emplacement dynamics inferred in this study show strong similarities between hydrothermal explosions, magmatic blasts, and high-energy dilute PDCs. The common occurrence of hydrothermal fields on volcanic flanks points to this hazard being an under-appreciated one at stratovolcanoes worldwide.

Characterizing Normal Groundwater Chemistry in Hawaii

NASA Astrophysics Data System (ADS)

Tachera, D.; Lautze, N. C.; Thomas, D. M.; Whittier, R. B.; Frazer, L. N.

2017-12-01

Hawaii is dependent on groundwater resources, yet how water moves through the subsurface is not well understood in many locations across the state. As marine air moves across the islands water evaporates from the ocean, along with trace amounts of sea-salt ions, and interacts with the anthropogenic and volcanic aerosols (e.g. sulfuric acid, ammonium sulfate, HCl), creating a slightly more acidic rain. When this rain falls, it has a chemical signature distinctive of past processes. As this precipitation infiltrates through soil it may pick up another distinctive chemical signature associated with land use and degree of soil development, and as it flows through the underlying geology, its chemistry is influenced by the host rock. We are currently conducting an investigation of groundwater chemistry in selected aquifer areas of Hawaii, having diverse land use, land cover, and soil development conditions, in an effort to investigate and document what may be considered a "normal" water chemistry for an area. Through this effort, we believe we better assess anomalies due to contamination events, hydrothermal alteration, and other processes; and we can use this information to better understand groundwater flow direction. The project has compiled a large amount of precipitation, soil, and groundwater chemistry data in the three focus areas distributed across in the State of Hawaii. Statistical analyses of these data sets will be performed in an effort to determine what is "normal" and what is anomalous chemistry for a given area. Where possible, results will be used to trace groundwater flow paths. Methods and preliminary results will be presented.

Seismic signatures of up- and down-going hydrothermal pathways along the East Pacific Rise 9ºN

NASA Astrophysics Data System (ADS)

Marjanovic, M.; Fuji, N.; Singh, S. C.; Belahi, T.

2016-12-01

Hydrothermal circulation along divergent plate boundaries plays an important role in the transfer of heat between Earth's lithosphere and deep ocean, evidenced by the presence of hydrothermal vents on the seafloor. Although the spatial distribution of different types of vents or fluid discharge zones is well documented, the distribution of fluid recharge zones and its flow pattern within the oceanic crust are still elusive. Here, we apply seismic elastic full waveform inversion techniques to extrapolated high-fidelity 2D along-axis seismic data collected in 2008 to characterise the nature of zero-age upper crust formed at the East Pacific Rise (EPR) within 9º15-57'N. The resulting velocity model shows prominent perturbation in background velocity in the northern part of the profile, where prolific hydrothermal and volcanic activities have been observed. This, 22 km wide region is represented by five low velocity anomalies (for 300 m/s lower) that are 3 km wide and can be tracked to up to 1 km below the seafloor. Two of the low velocity zones seem to underlay vent clusters centered at 9º47' and 9º50' that we relate to the presence of up-going pathways of the fluid. The three remaining low velocity zones (centered at 9º44', 9º48.5', 9º51') are more prominent and their extent roughly coincides with the previously identified fine-scale tectonic discontinuities. The results suggest these deviations of axial orientation observed in the seafloor, coupled with upper crustal fracturing that can be sustained for several 100s of years as ideal locations for seawater to penetrate more permeable crust on the ridge-axis and establish down-going pathway of hydrothermal flow. Similar scenario was suggested by micro-earthquakes within one small portion of the region during the last eruption. The presence of a strong axial melt lens and associated anomalous velocity zone indicate enhanced thermal regime within the area responsible for establishing and sustaining hydrothermal flow in the upper crust. Although similar low velocity regions are imaged in the vicinity of prominent third-order discontinuities at 9º17' and 9º37'N the underlying AML is shown to be mostly cristalized hindering the hydrothermal circulation process in the area.

Linked hydro-thermo-chemo-microbiological processes within a cool hydrothermal circulation system in 18-24 M.y. old seafloor of the Cocos Plate

NASA Astrophysics Data System (ADS)

Fisher, A. T.; Wheat, C. G.; Lauer, R. M.; Villinger, H. W.; McManus, J.; Orcutt, B.

2017-12-01

We present results from surveys and studies of ridge-flank hydrothermal circulation in part of the Cocos Plate. Fluids flowing into and out of the crust in an area >104 km2 extract most of the lithospheric heat. Water moves in and out of the crust through a few mid-plate seamounts, which penetrate low-permeability sediments, and water flows laterally across tens of kilometers between seamounts. This kind of fluid circulation is common globally, extracting 20-25% of Earth's geothermal heat, but focused fluid discharge from these systems has not previously been found or sampled. Sites of discharge from this cool hydrothermal system (CHS) were found and sampled on Dorado Outcrop, a small volcanic edifice on 23 M.y. old seafloor, using deep-submergence vehicles. Seafloor measurements show that Dorado Outcrop is a local site of elevated geothermal heat flux, and temperatures recorded during outcrop surveys show a pattern of small bottom-water temperature anomalies (≤0.04°C, mainly above the central and southern part of the outcrop). Direct measurements of shimmering fluids discharging from patches of bare rock on Dorado Outcrop indicate temperatures up to 10.5°C warmer than bottom water, whereas heat flux and reflection seismic data show regional reaction temperatures in basement of 15-20 °C. Heat budget calculations and coupled fluid-heat simulations of regional circulation indicate that the net discharge from Dorado Outcrop is on the order of 1,000-5,000 L/s, and direct observations show that spring discharge rates vary with time, likely being modulated by ocean tides. Samples of Dorado Outcrop fluids have concentrations that are indistinguishable from bottom seawater for many major ions, but concentrations of minor and trace elements differ significantly, especially Mo, V, Rb, U, phosphate, Li, and silicate. In addition, CHS fluids discharging from Dorado Outcrop have about 50% of the dissolved oxygen (DO) found in bottom seawater, showing that DO is consumed as it flows through the crust. Analytical calculations show that diffusion alone, into overlying sediments, cannot explain the observed DO concentrations; we therefore infer that biotic and abiotic reactions within the volcanic crust consume oxygen.

In situ study of the factors controlling Fe, Cu and Zn scavenging during the early mixing between hydrothermal fluids and seawater

NASA Astrophysics Data System (ADS)

Cathalot, C.; Laes-Huon, A.; Pelleter, E.; Maillard, L.; Chéron, S.; Boissier, A.; Waeles, M.; Cotte, L.; Pernet-Coudrier, B.; Gayet, N.; Sarrazin, J.; Sarradin, P. M.

2016-12-01

Despite the importance of trace metals for marine ecosystems and in the global carbon cycle, dissolved metal sources in the deep ocean and their export mechanism are, today, still unconstrained. The historical view that dissolved metals are largely removed from hydrothermal plumes through precipitation of a range of iron-bearing minerals is now being challenged. Several potential mechanisms for the delivery of hydrothermally sourced metals to the open ocean have been suggested and require a thorough documentation of the early mixing processes between the hydrothermal fluids and the ambient seawater. The geochemistry of a plume, and specially the rising plume, is dictated by the nature and composition of the host rock, fluid temperature, phase separation at depth and subsurface mixing processes, and thus can vary in temperature, pH, metal and dissolved gases content between spatially close hydrothermal vents. Here, we present in situ chemical conditions during the early mixing gradient between hydrothermal fluids and seawater at the Lucky Strike site (Mid-Atlantic Ridge), using a multi proxy approach targeting both the dissolved and particulate phase and combining in situ measurements and analysis back in the lab. Indeed, in situ O2, H2S and temperature measurements were performed at a 1Hz frequency, coupled to lower frequency analysis of in situ Fe2+. In addition, particulate material filtered in situ was analyzed using Inductive Coupled Plasma - Mass Spectrometry, X-Ray Diffraction, X-Ray Fluorescence and Scanning Electron Microscopy and provided useful insights regarding the reactivity of metals during the mixing processes. Our results show different behavior within the Lucky Strike vent field. Fe and S co-precipitation through chalcopyrite formation at the newly discovered Capelinhos site seem to be the main process. At the White Caste site, on the other hand, wurzite and sphalerite precipitation seems to dominate the dilution processes, H2S being rapidly titrated with the available Zinc early in the mixing. Our results indicate a clear control by subsurface mixing processes, at a very local scale: within a single vent field, temperature outflow of the hydrothermal fluid clearly drives Cu, Fe and Zn scavenging in the particulate phase, and controlling hence the iron stability and export.

Hydrothermal fluid flow models of Campi Flegrei caldera, Italy constrained by InSAR surface deformation time series observations

NASA Astrophysics Data System (ADS)

Lundgren, P.; Lanari, R.; Manzo, M.; Sansosti, E.; Tizzani, P.; Hutnak, M.; Hurwitz, S.

2008-12-01

Campi Flegrei caldera, Italy, located along the Bay of Naples, has a long history of significant vertical deformation, with the most recent large uplift (>1.5m) occurring in 1983-1984. Each episode of uplift has been followed by a period of subsidence that decreases in rate with time and may be punctuated by brief episodes of lesser uplift. The large amplitude of the major uplifts that occur without volcanic activity, and the subsequent subsidence has been argued as evidence for hydrothermal amplification of any magmatic source. The later subsidence and its temporal decay have been argued as due to diffusion of the pressurized caldera fill material into the less porous surrounding country rock. We present satellite synthetic aperture radar (SAR) interferometry (InSAR) time series analysis of ERS and Envisat data from the European Space Agency, based on exploiting the Small Baseline Subset (SBAS) approach [Berardino et al., 2002]; this allows us to generate maps of relative surface deformation though time, beginning in 1992 through 2007, that are relevant to both ascending and descending satellite orbits. The general temporal behavior is one of subsidence punctuated by several lesser uplift episodes. The spatial pattern of deformation can be modeled through simple inflation/deflation sources in an elastic halfspace. Given the evidence to suggest that fluids may play a significant role in the temporal deformation of Campi Flegrei, rather than a purely magmatic or magma chamber-based interpretation, we model the temporal and spatial evolution of surface deformation as a hydrothermal fluid flow process. We use the TOUGH2-BIOT2 set of numerical codes [Preuss et al., 1999; Hsieh, 1996], which couple multi-phase (liquid-gas) and multi-component (H2O-CO2) fluid flow in a porous or fractured media with plane strain deformation and fluid flow in a linearly elastic porous medium. We explore parameters related to the depth and temporal history of fluid injection, fluid composition, circulation geometries, and the physical properties of the media, to explain the InSAR time series. References: Berardino, P., R. Lanari, E. Sansosti (2002), A new Algorithm for surface deformation monitoring based on small baseline differential SAR interferograms, IEEE Transactions on Geoscience and Remote Sensing, 40, 11, 2375-2383. Pruess, L., C. Oldenburg, and G. Moridis (1999), TOUGH2 user's guide, version 2.0, Paper LBNL-43134, Lawrence Berkeley Natl. Lab., Berkeley, Calif. Hsieh, P. A. (1996), Deformation-induced changes in hydraulic head during ground-water withdrawal, Ground Water, 34, 1082-1089.

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

NASA Astrophysics Data System (ADS)

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

2011-12-01

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

Hydrothermal systems in small ocean planets.

PubMed

Vance, Steve; Harnmeijer, Jelte; Kimura, Jun; Hussmann, Hauke; Demartin, Brian; Brown, J Michael

2007-12-01

We examine means for driving hydrothermal activity in extraterrestrial oceans on planets and satellites of less than one Earth mass, with implications for sustaining a low level of biological activity over geological timescales. Assuming ocean planets have olivine-dominated lithospheres, a model for cooling-induced thermal cracking shows how variation in planet size and internal thermal energy may drive variation in the dominant type of hydrothermal system-for example, high or low temperature system or chemically driven system. As radiogenic heating diminishes over time, progressive exposure of new rock continues to the current epoch. Where fluid-rock interactions propagate slowly into a deep brittle layer, thermal energy from serpentinization may be the primary cause of hydrothermal activity in small ocean planets. We show that the time-varying hydrostatic head of a tidally forced ice shell may drive hydrothermal fluid flow through the seafloor, which can generate moderate but potentially important heat through viscous interaction with the matrix of porous seafloor rock. Considering all presently known potential ocean planets-Mars, a number of icy satellites, Pluto, and other trans-neptunian objects-and applying Earth-like material properties and cooling rates, we find depths of circulation are more than an order of magnitude greater than in Earth. In Europa and Enceladus, tidal flexing may drive hydrothermal circulation and, in Europa, may generate heat on the same order as present-day radiogenic heat flux at Earth's surface. In all objects, progressive serpentinization generates heat on a globally averaged basis at a fraction of a percent of present-day radiogenic heating and hydrogen is produced at rates between 10(9) and 10(10) molecules cm(2) s(1).

Ca, Sr, O and D isotope approach to defining the chemical evolution of hydrothermal fluids: example from Long Valley, CA, USA

USGS Publications Warehouse

Brown, Shaun T.; Kennedy, B. Mack; DePaolo, Donald J.; Hurwitz, Shaul; Evans, William C.

2013-01-01

We present chemical and isotopic data for fluids, minerals and rocks from the Long Valley meteoric-hydrothermal system. The samples encompass the presumed hydrothermal upwelling zone in the west moat of the caldera, the Casa Diablo geothermal field, and a series of wells defining a nearly linear, ∼16 km long, west-to-east trend along the likely fluid flow path. Fluid samples were analyzed for the isotopes of water, Sr, and Ca, the concentrations of major cations and anions, alkalinity, and total CO2. Water isotope data conform to trends documented in earlier studies, interpreted as indicating a single hydrothermal fluid mixing with local groundwater. Sr isotopes show subtle changes along the flow path, which requires rapid fluid flow and minimal reaction between the channelized fluids and the wallrocks. Sr and O isotopes are used to calculate fracture spacing using a dual porosity model. Calculated fracture spacing and temperature data for hydrothermal fluids indicate the system is (approximately) at steady-state. Correlated variations among total CO2, and the concentration and isotopic composition of Ca suggest progressive fluid degassing (loss of CO2), which drives calcite precipitation as the fluid flows west-to-east and cools. The shifts in Ca isotopes require that calcite precipitated at temperatures of 150–180 °C is fractionated by ca. −0.3‰ to −0.5‰ relative to aqueous species. Our data are the first evidence that Ca isotopes undergo kinetic fractionation at high temperatures (>100 °C) and can be used to trace calcite precipitation along hydrothermal fluid flow paths.

Multiphase groundwater flow near cooling plutons

USGS Publications Warehouse

Hayba, D.O.; Ingebritsen, S.E.

1997-01-01

We investigate groundwater flow near cooling plutons with a computer program that can model multiphase flow, temperatures up to 1200??C, thermal pressurization, and temperature-dependent rock properties. A series of experiments examines the effects of host-rock permeability, size and depth of pluton emplacement, single versus multiple intrusions, the influence of a caprock, and the impact of topographically driven groundwater flow. We also reproduce and evaluate some of the pioneering numerical experiments on flow around plutons. Host-rock permeability is the principal factor influencing fluid circulation and heat transfer in hydrothermal systems. The hottest and most steam-rich systems develop where permeability is of the order of 10-15 m2. Temperatures and life spans of systems decrease with increasing permeability. Conduction-dominated systems, in which permeabilities are ???10-16m2, persist longer but exhibit relatively modest increases in near-surface temperatures relative to ambient conditions. Pluton size, emplacement depth, and initial thermal conditions have less influence on hydrothermal circulation patterns but affect the extent of boiling and duration of hydrothermal systems. Topographically driven groundwater flow can significantly alter hydrothermal circulation; however, a low-permeability caprock effectively decouples the topographically and density-driven systems and stabilizes the mixing interface between them thereby defining a likely ore-forming environment.

Two-Dimensional NMR Evidence for Cleavage of Lignin and Xylan Substituents in Wheat Straw Through Hydrothermal Pretreatment and Enzymatic Hydrolysis

Treesearch

Daniel J. Yelle; Prasad Kaparaju; Christopher G. Hunt; Kolby Hirth; Hoon Kim; John Ralph; Claus Felby

2012-01-01

Solution-state two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy of plant cell walls is a powerful tool for characterizing changes in cell wall chemistry during the hydrothermal pretreatment process of wheat straw for second-generation bioethanol production. One-bond 13C-1H NMR correlation spectroscopy, via...

Three-Dimensional Electrical Resistivity Tomography of the Solfatara Crater (Italy): Implication for the Multiphase Flow Structure of the Shallow Hydrothermal System

NASA Astrophysics Data System (ADS)

Gresse, Marceau; Vandemeulebrouck, Jean; Byrdina, Svetlana; Chiodini, Giovanni; Revil, André; Johnson, Timothy C.; Ricci, Tullio; Vilardo, Giuseppe; Mangiacapra, Annarita; Lebourg, Thomas; Grangeon, Jacques; Bascou, Pascale; Metral, Laurent

2017-11-01

The Solfatara volcano is the main degassing area of the Campi Flegrei caldera, characterized by 60 years of unrest. Assessing such renewal activity is a challenging task because hydrothermal interactions with magmatic gases remain poorly understood. In this study, we decipher the complex structure of the shallow Solfatara hydrothermal system by performing the first 3-D, high-resolution, electrical resistivity tomography of the volcano. The 3-D resistivity model was obtained from the inversion of 43,432 resistance measurements performed on an area of 0.68 km2. The proposed interpretation of the multiphase hydrothermal structures is based on the resistivity model, a high-resolution infrared surface temperature image, and 1,136 soil CO2 flux measurements. In addition, we realized 27 soil cation exchange capacity and pH measurements demonstrating a negligible contribution of surface conductivity to the shallow bulk electrical conductivity. Hence, we show that the resistivity changes are mainly controlled by fluid content and temperature. The high-resolution tomograms identify for the first time the structure of the gas-dominated reservoir at 60 m depth that feeds the Bocca Grande fumarole through a 10 m thick channel. In addition, the resistivity model reveals a channel-like conductive structure where the liquid produced by steam condensation around the main fumaroles flows down to the Fangaia area within a buried fault. The model delineates the emplacement of the main geological structures: Mount Olibano, Solfatara cryptodome, and tephra deposits. It also reveals the anatomy of the hydrothermal system, especially two liquid-dominated plumes, the Fangaia mud pool and the Pisciarelli fumarole, respectively.

Mid-tertiary ash flow tuff cauldrons, southwestern New Mexico

NASA Technical Reports Server (NTRS)

Elston, W. E.

1984-01-01

Characteristics of 28 known or suspected mid-Tertiary ash-flow tuff cauldrons in New Mexico are described. The largest region is 40 km in diameter, and erosional and block faulting processes have exposed levels as far down as the plutonic roots. The study supports a five-stage process: precursor, caldera collapse, early post-collapse, volcanism, major ring-fracture volcanism, and hydrothermal activity. The stages can repeat or the process can stop at any stage. Post-collapse lavas fell into two categories: cauldron lavas, derived from shallow defluidized residues of caldera-forming ash flow tuff eruption, and framework lavas, evolved from a siliceous pluton below the cauldron complex. The youngest caldera was shallow and formed from asymmetric subsidence and collapse of the caldera walls.

Detection of Abiotic Methane in Terrestrial Continental Hydrothermal Systems: Implications for Methane on Mars

NASA Technical Reports Server (NTRS)

Socki, Richard A.; Niles, Paul B.; Gibson, Everett K., Jr.; Romanek, Christopher S.; Zhang, Chuanlun L.; Bissada, Kadry K.

2008-01-01

The recent detection of methane in the Martian atmosphere and the possibility that its origin could be attributed to biological activity, have highlighted the importance of understanding the mechanisms of methane formation and its usefulness as a biomarker. Much debate has centered on the source of the methane in hydrothermal fluids, whether it is formed biologically by microorganisms, diagenetically through the decomposition of sedimentary organic matter, or inorganically via reduction of CO2 at high temperatures. Ongoing research has now shown that much of the methane present in sea-floor hydrothermal systems is probably formed through inorganic CO2 reduction processes at very high temperatures (greater than 400 C). Experimental results have indicated that methane might form inorganically at temperatures lower still, however these results remain controversial. Currently, methane in continental hydrothermal systems is thought to be formed mainly through the breakdown of sedimentary organic matter and carbon isotope equilibrium between CO2 and CH4 is thought to be rarely present if at all. Based on isotopic measurements of CO2 and CH4 in two continental hydrothermal systems, we suggest that carbon isotope equilibration exists at temperatures as low as 155 C. This would indicate that methane is forming through abiotic CO2 reduction at lower temperatures than previously thought and could bolster arguments for an abiotic origin of the methane detected in the martian atmosphere.

A Sr-isotopic comparison between thermal waters, rocks, and hydrothermal calcites, Long Valley caldera, California

USGS Publications Warehouse

Goff, F.; Wollenberg, H.A.; Brookins, D.C.; Kistler, R.W.

1991-01-01

The 87Sr/86Sr values of thermal waters and hydrothermal calcites of the Long Valley caldera geothermal system are more radiogenic than those of young intracaldera volcanic rocks. Five thermal waters display 87Sr/86Sr of 0.7081-0.7078 but show systematically lighter values from west to east in the direction of lateral flow. We believe the decrease in ratio from west to east signifies increased interaction of deeply circulating thermal water with relatively fresh volcanic rocks filling the caldera depression. All types of pre-, syn-, and post-caldera volcanic rocks in the west and central caldera have (87Sr/86Sr)m between about 0.7060 and 0.7072 and values for Sierra Nevada granodiorites adjacent to the caldera are similar. Sierran pre-intrusive metavolcanic and metasedimentary rocks can have considerably higher Sr-isotope ratios (0.7061-0.7246 and 0.7090-0.7250, respectively). Hydrothermally altered volcanic rocks inside the caldera have (87Sr/86Sr)m slightly heavier than their fresh volcanic equivalents and hydrothermal calcites (0.7068-0.7105) occupy a midrange of values between the volcanic/plutonic rocks and the Sierran metamorphic rocks. These data indicate that the Long Valley geothermal reservoir is first equilibrated in a basement complex that contains at least some metasedimentary rocks. Reequilibration of Sr-isotope ratios to lower values occurs in thermal waters as convecting geothermal fluids flow through the isotopically lighter volcanic rocks of the caldera fill. ?? 1991.

Formation of Hematite fine crystals by hydrothermal alteration of synthetic Martian basalt, static and fluid flow experiments

NASA Astrophysics Data System (ADS)

Kobayashi, K.; Isobe, H.

2011-12-01

Exploration made by Martian rovers and probes provided enormous information on the composition of the Martian surface materials. Origin and formation processes of the Martian surface materials should be various depending on topography and history of the Martian crust. Especially, iron minerals in the Martian soil should have essential role to characterize surface environment of the "red planet". In the present study, experimental reproduction of the Martian soil was carried out by hydrothermal alteration of the synthetic iron-rich basaltic rock. Experimental conditions for temperature and fluid composition followed Isobe and Yoshizawa (2010). Static alteration experiments are carried out at 100 °C and 150 °C, and mass ratio of the starting material to the pH1.0 sulfuric acid solution is 1:50. Run durations are 1, 2, 4 or 8 weeks. Appropriate mass of dry ice was sealed in the experimental vessels to expel atmospheric oxygen with CO2. For the static experiments, powdered starting materials were charged in PFA vial to keep textures of the run products. For the fluid flow experiments, we constructed closed loop with Teflon tube inclined approximately 45°. One of the vertical tube is charged with crushed synthetic basalt and heated approximately 150°C by aluminum block with ribbon heater. Surlfuric acid solution flows through the tube from bottom to top and cooled at the end of the aluminum block. Cooled solution returns to the bottom of the heated tube through another vertical tube without heating block. In the static condition run products, characteristic iron mineral particles are formed for 100°C and 150°C concordant with Isobe and Yoshizawa (2010). These iron minerals distributed not only inside the starting material powder but also on the surface of the reaction vessel and the PFA vial in the reactive solution. The surface of the reaction vessel shows orange and reddish color on 100°C and 150°C run products, respectively. By SEM observation, dissolution of melt and olivine grains were observed, and iron mineral particles substituted olivine partly. Diameters of the iron mineral particles are submicron to several micron meters at 100°C, and slowly increase with run durations and temperatures. In the fluid flow experiment, deposition of the characteristic iron minerals occur inside the heated tube. Distribution of iron minerals corresponds to temperature gradient and fluid flow direction. Iron minerals are partially covered by silica phase with submicron meters in thickness. The occurrence of the iron minerals in the run products of this study suggests that characteristic iron mineral fine particles including hematite and goethite were formed by acidic hydrothermal alteration of iron-rich basaltic rock even at remote region from the source materials.

Numerical Temperature And Fluid-Flow Modelling For The Topographic Effects On Hydrothermal Circulation; A case study in Lucy Strike Vent Field

NASA Astrophysics Data System (ADS)

Erçetin, Engin; Düşünür Doǧan, Doǧa

2017-04-01

The aim of the study is to present a numerical temperature and fluid-flow modelling for the topographic effects on hydrothermal circulation. Bathymetry can create a major disturbance on fluid flow pattern. ANSYS Fluent Computational fluid dynamics software is used for simulations. Coupled fluid flow and temperature quations are solved using a 2-Dimensional control volume finite difference approach. Darcy's law is assumed to hold, the fluid is considered to be anormal Boussinesq incompressible fluid neglecting inertial effects. Several topographic models were simulated and both temperature and fluid flow calculations obtained for this study. The preliminary simulations examine the effect of a ingle bathymetric high on a single plume and the secondary study of simulations investigates the effect of multiple bathymetric highs on multiple plume. The simulations were also performed for the slow spreading Lucky Strike segment along the Mid-Atlantic Ridge (MAR), one of the best studied regions along the MAR, where a 3.4 km deep magma chamber extending 6 km along-axis is found at its center. The Lucky Strike segment displays a transitional morphology between that of the FAMOUS - North FAMOUS segments, which are characterized by well-developed axial valleys typical of slow-spreading segments, and that of the Menez Gwen segment, characterized by an axial high at the segment center. Lucky Strike Segment hosts a central volcano and active vent field located at the segment center and thus constitutes an excellent case study to simulate the effects of bathymetry on fluid flow. Results demonstrate that bathymetric relief has an important influence on hydrothermal flow. Subsurface pressure alterations can be formed by bathymetric highs, for this reason, bathymetric relief ought to be considered while simulating hydrothermal circulation systems. Results of this study suggest the dominant effect of bathymetric highs on fluid flow pattern and Darcy velocities will be presented. Keywords: Hydrothermal Circulation, Lucky Strike, Bathymetry - Topography, Vent Location, Fluid Flow, Numerical Modelling

Specific mineral associations of hydrothermal shale (South Kamchatka)

NASA Astrophysics Data System (ADS)

Rychagov, S. N.; Sergeeva, A. V.; Chernov, M. S.

2017-11-01

The sequence of hydrothermal shale from the East Pauzhet thermal field within the Pauzhet hydrothermal system (South Kamchatka) was studied in detail. It was established that the formation of shale resulted from argillization of an andesitic lava flow under the influence of an acidic sulfate vapor condensate. The horizons with radically different compositions and physical properties compared to those of the overlying homogeneous plastic shale were distinguished at the base of the sequence. These horizons are characterized by high (up to two orders of magnitude in comparison with average values in hydrothermal shale) concentrations of F, P, Na, Mg, K, Ca, Sc, Ti, V, Cr, Cu, and Zn. We suggested a geological-geochemical model, according to which a deep metal-bearing chloride-hydrocarbonate solution infiltrated into the permeable zone formed at the root of the andesitic lava flow beneath plastic shale at a certain stage of evolution of the hydrothermal system.

Time-dependent changes in magmatic and hydrothermal activity at the Costa Rica Rift recorded by variations in oceanic crustal structure

NASA Astrophysics Data System (ADS)

Wilson, D. J.; Peirce, C.; Hobbs, R. W.; Gregory, E. P. M.; Zhang, L.

2016-12-01

Geophysical studies of crustal structure at a diverse range of ridges have provided evidence that the balance between spreading rate and magma supply determines whether spreading predominantly occurs by magmatic accretion of new oceanic crust or through tectonic stretching of the whole lithosphere. Asymmetric spreading, patterns of on- and off-axis volcanism, the evolution of oceanic core complexes and the distribution of hydrothermal systems all indicate that the process of spreading is not constant over geologically short timescales. The structure of the resulting crust reflects this complexity in origin. Studies along flow-lines across ridges spreading at intermediate rates suggest variations in topographic style and crustal structure have periodically occurred, controlled by the interplay between magmatic accretion and tectonic stretching, and coupled to the degree of hydrothermal activity. Seismic reflection images and tomographic models derived from wide-angle seismic data have enabled a detailed examination of the oceanic crust that formed at the fast-to-intermediate-spreading (36 mm yr-1) Costa Rica Rift over the last 6 Ma, to look for any temporal variation in basement topography, upper crust (layer 2) P-wave velocity/density structure and crustal thickness. Coincident marine gravity and magnetic data not only allow us to test the validity of the final velocity-density model but also review variability in half-spreading rate, respectively. Collectively our analyses allow us to investigate the timescale and cyclicity of crustal structure variations and, having determined the spreading rate over time, consider how this may reflect changes in magma supply and/or hydrothermal activity at the Costa Rica Rift, using borehole 504B as the ground-truth. This research is part of a major, interdisciplinary NERC-funded collaboration entitled: Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR).

Development of Vertical Cable Seismic System for Hydrothermal Deposit Survey (2) - Feasibility Study

NASA Astrophysics Data System (ADS)

Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Mikada, H.; Takekawa, J.; Shimura, T.

2010-12-01

In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey system development for Hydrothermal deposit. We proposed the Vertical Cable Seismic (VCS), the reflection seismic survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. . (1) VCS is an effective high-resolution 3D seismic survey within limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of seismic data quality. (4) Various types of marine source are applicable with VCS such as sea-surface source (air gun, water gun etc.) , deep-towed or ocean bottom sources. (5) Autonomous recording system. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN. in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. The result gives clearer image than the conventional surface seismic. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Uncertainty of the source/receiver poisons in water causes the serious problem of the imaging. We used several transducer/transponder to estimate these positions. The VCS seismic records themselves can also provide sensor position using the first break of each trace and we calibrate the positions. We are currently developing the autonomous recording VCS system and planning the trial experiment in actual ocean to establish the way of deployment/recovery and the examine the position through the current flow in November, 2010. The second VCS survey will planned over the actual hydrothermal deposit with deep-towed source in February, 2011.

Passive, off-axis convection through the southern flank of the Costa Rica rift

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fisher, A.T.; Becker, K.; Narasimhan, T.N.

1990-06-10

Pore fluids are passively convecting through young oceanic sediments and crust around Deep Sea Drilling Project (DSDP) site 504 on the southern flank of the Costa Rica Rift, as inferred from a variety of geological, geochemical, and geothermal observations. The presence of a fluid circulation system is supported by new data collected on Ocean Drilling Program (ODP) leg 111 and a predrilling survey cruise over the heavily sedimented, 5.9 Ma site; during the latter, elongated heat flow anomalies were mapped subparallel to structural strike, with individual measurements of twice the regional mean value, and strong lateral and vertical geochemical gradientsmore » were detected in pore waters squeezed from sediment cores. Also, there is a strong correlation between heat flow, bathymetry, sediment thickness, and inferred fluid velocities up through the sediments. Although the forces which drive passive circulation are not well understood, it has generally been thought that the length scale of heat flow variations provides a good indication of the depth of hydrothermal circulation within the oceanic crust. The widely varied geothermal and hydrogeological observations near site 504 are readily explained by a model which combines (1) basement relief, (2) irregular sediment drape, (3) largely conductive heat transfer through the sediments overlying the crust, and (4) thermal and geochemical homogenization of pore fluids at the sediment/basement interface, which results from (5) topographically induced, passive hydrothermal circulation with large aspect ratio, convection cells. This convection involves mainly the permeable, upper 200-300 m of crust; the deeper crust is not involved.« less

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 been conducted in lakes in active volcanic areas. Our data reveal active geothermal features with unprecedented resolution and provide important analogues for recognition of comparable features and potential hazards in other subaqueous geothermal environments.

High-quality fuel from food waste - investigation of a stepwise process from the perspective of technology development.

PubMed

Yin, Ke; Li, Ling; Giannis, Apostolos; Weerachanchai, Piyarat; Ng, Bernard J H; Wang, Jing-Yuan

2017-07-01

A stepwise process (SP) was developed for sustainable energy production from food waste (FW). The process comprised of hydrothermal treatment followed by oil upgrading. Synthetic food waste was primarily used as feedstock in the hydrothermal reactor under subcritical water conditions. The produced hydrochars were analyzed for calorific value (17.0-33.7 MJ/kg) and elemental composition indicating high-quality fuel comparable to coal. Hydrothermal carbonization (e.g. 180°C) would be efficient for oil recovery (>90%) from FW, as compared to hydrothermal liquefaction (320°C) whereby lipid degradation may take place. The recovered oil was upgraded to biodiesel in a catalytic refinery process. Selected biodiesels, that is, B3 and B4 were characterized for density (872.7 and 895.5 kg/m 3 ), kinematic viscosity (3.115 and 8.243 cSt), flash and pour point (30°C and >126°C), micro carbon (0.03% and 0.04%), sulfur (both <0.0016%), and calorific value (38,917 and 39,584 J/g), suggesting similar quality to commercial biodiesel. Fatty acid methyl ethers content was further analyzed to assess the influence of hydrothermal treatment in biodiesel quality, indicating the limited impacts. Overall, the SP provides a promising alternative for sustainable energy recovery through high-quality biofuel and hydrochar production.

Ice patterns and hydrothermal plumes, Lake Baikal, Russia - Insights from Space Shuttle hand-held photography

NASA Technical Reports Server (NTRS)

Evans, Cynthia A.; Helfert, Michael R.; Helms, David R.

1992-01-01

Earth photography from the Space Shuttle is used to examine the ice cover on Lake Baikal and correlate the patterns of weakened and melting ice with known hydrothermal areas in the Siberian lake. Particular zones of melted and broken ice may be surface expressions of elevated heat flow in Lake Baikal. The possibility is explored that hydrothermal vents can introduce local convective upwelling and disrupt a stable water column to the extent that the melt zones which are observed in the lake's ice cover are produced. A heat flow map and photographs of the lake are overlaid to compare specific areas of thinned or broken ice with the hot spots. The regions of known hydrothermal activity and high heat flow correlate extremely well with circular regions of thinned ice, and zones of broken and recrystallized ice. Local and regional climate data and other sources of warm water, such as river inlets, are considered.

Bacterial Diversity and Biogeochemistry of Two Marine Shallow-Water Hydrothermal Systems off Dominica (Lesser Antilles).

PubMed

Pop Ristova, Petra; Pichler, Thomas; Friedrich, Michael W; Bühring, Solveig I

2017-01-01

Shallow-water hydrothermal systems represent extreme environments with unique biogeochemistry and high biological productivity, at which autotrophic microorganisms use both light and chemical energy for the production of biomass. Microbial communities of these ecosystems are metabolically diverse and possess the capacity to transform a large range of chemical compounds. Yet, little is known about their diversity or factors shaping their structure or how they compare to coastal sediments not impacted by hydrothermalism. To this end, we have used automated ribosomal intergenic spacer analysis (ARISA) and high-throughput Illumina sequencing combined with porewater geochemical analysis to investigate microbial communities along geochemical gradients in two shallow-water hydrothermal systems off the island of Dominica (Lesser Antilles). At both sites, venting of hydrothermal fluids substantially altered the porewater geochemistry by enriching it with silica, iron and dissolved inorganic carbon, resulting in island-like habitats with distinct biogeochemistry. The magnitude of fluid flow and difference in sediment grain size, which impedes mixing of the fluids with seawater, were correlated with the observed differences in the porewater geochemistry between the two sites. Concomitantly, individual sites harbored microbial communities with a significantly different community structure. These differences could be statistically linked to variations in the porewater geochemistry and the hydrothermal fluids. The two shallow-water hydrothermal systems of Dominica harbored bacterial communities with high taxonomical and metabolic diversity, predominated by heterotrophic microorganisms associated with the Gammaproteobacterial genera Pseudomonas and Pseudoalteromonas , indicating the importance of heterotrophic processes. Overall, this study shows that shallow-water hydrothermal systems contribute substantially to the biogeochemical heterogeneity and bacterial diversity of coastal sediments.

Bacterial Diversity and Biogeochemistry of Two Marine Shallow-Water Hydrothermal Systems off Dominica (Lesser Antilles)

PubMed Central

Pop Ristova, Petra; Pichler, Thomas; Friedrich, Michael W.; Bühring, Solveig I.

2017-01-01

Shallow-water hydrothermal systems represent extreme environments with unique biogeochemistry and high biological productivity, at which autotrophic microorganisms use both light and chemical energy for the production of biomass. Microbial communities of these ecosystems are metabolically diverse and possess the capacity to transform a large range of chemical compounds. Yet, little is known about their diversity or factors shaping their structure or how they compare to coastal sediments not impacted by hydrothermalism. To this end, we have used automated ribosomal intergenic spacer analysis (ARISA) and high-throughput Illumina sequencing combined with porewater geochemical analysis to investigate microbial communities along geochemical gradients in two shallow-water hydrothermal systems off the island of Dominica (Lesser Antilles). At both sites, venting of hydrothermal fluids substantially altered the porewater geochemistry by enriching it with silica, iron and dissolved inorganic carbon, resulting in island-like habitats with distinct biogeochemistry. The magnitude of fluid flow and difference in sediment grain size, which impedes mixing of the fluids with seawater, were correlated with the observed differences in the porewater geochemistry between the two sites. Concomitantly, individual sites harbored microbial communities with a significantly different community structure. These differences could be statistically linked to variations in the porewater geochemistry and the hydrothermal fluids. The two shallow-water hydrothermal systems of Dominica harbored bacterial communities with high taxonomical and metabolic diversity, predominated by heterotrophic microorganisms associated with the Gammaproteobacterial genera Pseudomonas and Pseudoalteromonas, indicating the importance of heterotrophic processes. Overall, this study shows that shallow-water hydrothermal systems contribute substantially to the biogeochemical heterogeneity and bacterial diversity of coastal sediments. PMID:29255454

A Reference Section through the Lower Fast-spreading Oceanic Crust in the Wadi Gideah (Sumail ophiolite, Sultanate Oman): Drill Sites GT1A and GT2A within the ICDP Oman Drilling Project

NASA Astrophysics Data System (ADS)

Mueller, S.; Koepke, J.; Garbe-Schoenberg, C. D.; Müller, T.; Mock, D.; Strauss, H.; Schuth, S.; Ildefonse, B.

2017-12-01

In the absence of a complete profile through fast-spreading oceanic crust in modern oceans, we established a reference profile through the whole paleocrust of the Sumail Ophiolite (Oman), which is regarded as the best analogue for fast-spreading oceanic crust on land. For establishing a coherent data set, we sampled the Wadi Gideah in the Wadi-Tayin massif from the mantle section up to the pillow basalts and performed different analytical and structural investigations on the same suite of samples (pool sample concept). The whole sample set contains about 400 samples focusing on both primary magmatic rocks and hydrothermal fault zones to characterize initial formation processes and cooling of the crust. The Wadi Gideah hosts the sites GT1A (lower crust) and GT2A (foliated / layered gabbro transition) where 400 m long cores have been drilled in the frame of the ICDP Oman Drilling Project (OmanDP). Thus, the Wadi Gideah crustal transect is well-suited for providing a reference frame for these two drill cores. Major and trace element data on minerals and rocks reveal in-situ crystallization in the deep crust, thus strongly supporting a hybrid accretion model that is characterized by sheeted sill intrusion in the lower part of the plutonic crust and gabbro glacier features in the upper section. This hybrid model is also supported by results on crystallographic preferred orientations (CPO) of the minerals within the gabbros, which call for distinct formation mechanisms in the upper and lower gabbro sections. A requirement for our hybrid model is significant hydrothermal cooling in the lower crust for the consumption of the latent heat of crystallization. This was facilitated by channelled hydrothermal flow zones, preserved today in faulted zones of extensively altered gabbro cutting both layered and foliated gabbros. These gabbros show higher Sr87/Sr86 ratios if compared to the background gabbro, the presence of late stage minerals (amphibole, oxides, orthopyroxene, apatite) and evidence for hydrous partial melting, as consequence of fluid / rock interaction at very high temperatures. Obviously, these fault zones remained active for channelled fluid flow during the entire cooling stage of the oceanic crust down to low-temperature mineral assemblages.

Geothermal energy resources of wadi Al-Lith, Saudi Arabia

NASA Astrophysics Data System (ADS)

Lashin, A.; Chandrasekharam, D.; Al Arifi, N.; Al Bassam, A.; Varun, C.

2014-09-01

The entire western Arabian shield is the domain of both hydrothermal and enhanced geothermal systems associated with volcanic centres (Harrats) and high heat generating granites. The most prominent sites of hydrothermal systems are located around Al-Lith and Jizan. The hydrothermal system in Al Lith is controlled by high heat generating (∼11 μW/m3) post orogenic granites. The high heat flow value of >80 mW/m2 across Al-Lith coast is due to such granite intrusives, presence of dike swarms that intrude into the granites as well as position of Moho at shallow level. Although the thermal waters are chloride rich, Red Sea involvement is not observed. Long residence time and water rock interaction with granites are the main processes responsible for chloride enrichment in the thermal waters. Oxygen isotope shift indicates presence of high temperature geothermal system in the area. The tritium values indicate that the circulating waters are >75 years old.

Influence of hydrothermal processing on functional properties and grain morphology of finger millet.

PubMed

Dharmaraj, Usha; Meera, M S; Reddy, S Yella; Malleshi, Nagappa G

2015-03-01

Finger millet was hydrothermally processed followed by decortication. Changes in color, diameter, density, sphericity, thermal and textural characteristics and also some of the functional properties of the millet along with the grain morphology of the kernels after hydrothermal processing and decortication were studied. It was observed that, the millet turned dark after hydrothermal processing and color improved over native millet after decortication. A slight decrease in grain diameter was observed but sphericity of the grains increased on decortication. The soft and fragile endosperm turned into a hard texture and grain hardness increased by about 6 fold. Hydrothermal processing increased solubility and swelling power of the millet at ambient temperature. Pasting profile indicated that, peak viscosity decreased significantly on hydrothermal processing and both hydrothermally processed and decorticated millet exhibited zero breakdown viscosity. Enthalpy was negative for hydrothermally processed millet and positive for decorticated grains. Microscopic studies revealed that the orderly structure of endosperm changed to a coherent mass after hydrothermal processing and the different layers of seed coat get fused with the endosperm.

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

NASA Astrophysics Data System (ADS)

Roberts, J.; Elmore, R. D.

2017-12-01

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

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

USGS Publications Warehouse

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

2008-01-01

Hydrothermal alteration at Mount Rainier waxed and waned over the 500,000-year episodic growth of the edifice. Hydrothermal minerals and their stable-isotope compositions in samples collected from outcrop and as clasts from Holocene debris-flow deposits identify three distinct hypogene argillic/advanced argillic hydrothermal environments: magmatic-hydrothermal, steam-heated, and magmatic steam (fumarolic), with minor superimposed supergene alteration. The 3.8??km3 Osceola Mudflow (5600??y BP) and coeval phreatomagmatic F tephra contain the highest temperature and most deeply formed hydrothermal minerals. Relatively deeply formed magmatic-hydrothermal alteration minerals and associations in clasts include quartz (residual silica), quartz-alunite, quartz-topaz, quartz-pyrophyllite, quartz-dickite/kaolinite, and quartz-illite (all with pyrite). Clasts of smectite-pyrite and steam-heated opal-alunite-kaolinite are also common in the Osceola Mudflow. In contrast, the Paradise lahar, formed by collapse of the summit or near-summit of the edifice at about the same time, contains only smectite-pyrite and near-surface steam-heated and fumarolic alteration minerals. Younger debris-flow deposits on the west side of the volcano (Round Pass and distal Electron Mudflows) contain only low-temperature smectite-pyrite assemblages, whereas the proximal Electron Mudflow and a < 100??y BP rock avalanche on Tahoma Glacier also contain magmatic-hydrothermal alteration minerals that are exposed in the avalanche headwall of Sunset Amphitheater, reflecting progressive incision into deeper near-conduit alteration products that formed at higher temperatures. The pre-Osceola Mudflow alteration geometry is inferred to have consisted of a narrow feeder zone of intense magmatic-hydrothermal alteration limited to near the conduit of the volcano, which graded outward to more widely distributed, but weak, smectite-pyrite alteration within 1??km of the edifice axis, developed chiefly in porous breccias. The edifice was capped by a steam-heated alteration zone, most of which resulted from condensation of fumarolic vapor and oxidation of H2S in the unsaturated zone above the water table. Weakly developed smectite-pyrite alteration extended into the west and east flanks of the edifice, spatially associated with dikes that are localized in those sectors; other edifice flanks lack dikes and associated alteration. The Osceola collapse removed most of the altered core and upper east flank of the volcano, but intensely altered rocks remain on the uppermost west flank. Major conclusions of this study are that: (1) Hydrothermal-mineral assemblages and distributions at Mount Rainier can be understood in the framework of hydrothermal processes and environments developed from studies of ore deposits formed in analogous settings. (2) Frequent eruptions supplied sufficient hot magmatic fluid to alter the upper interior of the volcano hydrothermally, despite the consistently deep (??? 8??km) magma reservoir which may have precluded formation of economic mineral deposits within or at shallow depths beneath Mount Rainier. The absence of indicator equilibrium alteration-mineral assemblages in the debris flows that effectively expose the volcano to a depth of 1-1.5??km also suggests a low potential for significant high-sulfidation epithermal or porphyry-type mineral deposits at depth. (3) Despite the long and complex history of the volcano, intensely altered collapse-prone rocks were spatially restricted to near the volcano's conduit system and summit, and short distances onto the upper east and west flanks, due to the necessary supply of reactive components carried by ascending magmatic fluids. (4) Intensely altered rocks were removed from the summit, east flank, and edifice interior by the Osceola collapse, but remain on the upper west flank in the Sunset Amphitheater area and present a continuing collapse hazard. (5) Visually conspicuous rocks on the lower east and mid-to-lower

Numerical simulation of magmatic hydrothermal systems

USGS Publications Warehouse

Ingebritsen, S.E.; Geiger, S.; Hurwitz, S.; Driesner, T.

2010-01-01

The dynamic behavior of magmatic hydrothermal systems entails coupled and nonlinear multiphase flow, heat and solute transport, and deformation in highly heterogeneous media. Thus, quantitative analysis of these systems depends mainly on numerical solution of coupled partial differential equations and complementary equations of state (EOS). The past 2 decades have seen steady growth of computational power and the development of numerical models that have eliminated or minimized the need for various simplifying assumptions. Considerable heuristic insight has been gained from process-oriented numerical modeling. Recent modeling efforts employing relatively complete EOS and accurate transport calculations have revealed dynamic behavior that was damped by linearized, less accurate models, including fluid property control of hydrothermal plume temperatures and three-dimensional geometries. Other recent modeling results have further elucidated the controlling role of permeability structure and revealed the potential for significant hydrothermally driven deformation. Key areas for future reSearch include incorporation of accurate EOS for the complete H2O-NaCl-CO2 system, more realistic treatment of material heterogeneity in space and time, realistic description of large-scale relative permeability behavior, and intercode benchmarking comparisons. Copyright 2010 by the American Geophysical Union.

Hydrothermal fluid flow and deformation in large calderas: Inferences from numerical simulations

USGS Publications Warehouse

Hurwitz, S.; Christiansen, L.B.; Hsieh, P.A.

2007-01-01

Inflation and deflation of large calderas is traditionally interpreted as being induced by volume change of a discrete source embedded in an elastic or viscoelastic half-space, though it has also been suggested that hydrothermal fluids may play a role. To test the latter hypothesis, we carry out numerical simulations of hydrothermal fluid flow and poroelastic deformation in calderas by coupling two numerical codes: (1) TOUGH2 [Pruess et al., 1999], which simulates flow in porous or fractured media, and (2) BIOT2 [Hsieh, 1996], which simulates fluid flow and deformation in a linearly elastic porous medium. In the simulations, high-temperature water (350??C) is injected at variable rates into a cylinder (radius 50 km, height 3-5 km). A sensitivity analysis indicates that small differences in the values of permeability and its anisotropy, the depth and rate of hydrothermal injection, and the values of the shear modulus may lead to significant variations in the magnitude, rate, and geometry of ground surface displacement, or uplift. Some of the simulated uplift rates are similar to observed uplift rates in large calderas, suggesting that the injection of aqueous fluids into the shallow crust may explain some of the deformation observed in calderas.

Evolution of fracture permeability of ultramafic rocks undergoing serpentinization at hydrothermal conditions: An experimental study

NASA Astrophysics Data System (ADS)

Farough, A.; Moore, D. E.; Lockner, D. A.; Lowell, R. P.

2016-01-01

We performed flow-through laboratory experiments on five cylindrically cored samples of ultramafic rocks, in which we generated a well-mated through-going tensile fracture, to investigate evolution of fracture permeability during serpentinization. The samples were tested in a triaxial loading machine at a confining pressure of 50 MPa, pore pressure of 20 MPa, and temperature of 260°C, simulating a depth of 2 km under hydrostatic conditions. A pore pressure difference of up to 2 MPa was imposed across the ends of the sample. Fracture permeability decreased by 1-2 orders of magnitude during the 200-330 h experiments. Electron microprobe and SEM data indicated the formation of needle-shaped crystals of serpentine composition along the walls of the fracture, and chemical analyses of sampled pore fluids were consistent with dissolution of ferro-magnesian minerals. By comparing the difference between fracture permeability and matrix permeability measured on intact samples of the same rock types, we concluded that the contribution of the low matrix permeability to flow is negligible and essentially all of the flow is focused in the tensile fracture. The experimental results suggest that the fracture network in long-lived hydrothermal circulation systems can be sealed rapidly as a result of mineral precipitation, and generation of new permeability resulting from a combination of tectonic and crystallization-induced stresses is required to maintain fluid circulation.

Evolution of fracture permeability of ultramafic rocks undergoing serpentinization at hydrothermal conditions: An experimental study

USGS Publications Warehouse

Farough, Aida; Moore, Diane E.; Lockner, David A.; Lowell, R.P.

2016-01-01

We performed flow-through laboratory experiments on five cylindrically cored samples of ultramafic rocks, in which we generated a well-mated through-going tensile fracture, to investigate evolution of fracture permeability during serpentinization. The samples were tested in a triaxial loading machine at a confining pressure of 50 MPa, pore pressure of 20 MPa, and temperature of 260°C, simulating a depth of 2 km under hydrostatic conditions. A pore pressure difference of up to 2 MPa was imposed across the ends of the sample. Fracture permeability decreased by 1–2 orders of magnitude during the 200–330 h experiments. Electron microprobe and SEM data indicated the formation of needle-shaped crystals of serpentine composition along the walls of the fracture, and chemical analyses of sampled pore fluids were consistent with dissolution of ferro-magnesian minerals. By comparing the difference between fracture permeability and matrix permeability measured on intact samples of the same rock types, we concluded that the contribution of the low matrix permeability to flow is negligible and essentially all of the flow is focused in the tensile fracture. The experimental results suggest that the fracture network in long-lived hydrothermal circulation systems can be sealed rapidly as a result of mineral precipitation, and generation of new permeability resulting from a combination of tectonic and crystallization-induced stresses is required to maintain fluid circulation.

Oxygen isotope exchange in rocks and minerals from the Cerro Prieto geothermal system: Indicators of temperature distribution and fluid flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, A.E.; Elders, W.A.

1981-01-01

Oxygen isotopic compositions have been measured in drill cuttings and core samples from more than 40 wells ranging in depth to more than 3.5 km in the Cerro Prieto geothermal field. Profiles of isotopic ratios versus sampling depths provide information on the three-dimensional distribution of temperature and fluid flow. These parameters also indicate variations in the history of hydrothermal processes in different areas of the geothermal field.

The hydrothermal evolution of the Kawerau geothermal system, New Zealand

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents Used in Closed-Loop CO2 Removal Systems

NASA Technical Reports Server (NTRS)

Knox, James C.; Gauto, Hernando; Miller, Lee A.

2015-01-01

The International Space Station Carbon Dioxide Removal Assembly uses zeolite 5A molecular sieve material packed into beds for the capture of cabin CO2. The beds are cyclically heated to drive off the CO2 and restore the removal capacity. Over time, the sorbent material has been found to break down resulting in dust that restricts flow through the beds. Humidity adsorbed in the 5A zeolite when it is heated is a suspected cause of this sorbent degradation. To evaluate the impact of adsorbed water during thermal cycling, the Hydrothermal Stability Test was developed. The test configuration provides comparative side-by-side flow restriction data for two sorbent materials at specifically controlled humidity levels. While the initial focus of the testing is on 5A zeolite materials currently used on the ISS, the system will also be used to evaluate future candidate materials. This paper describes the approach, the test system, current results, and future testing.

Guide to the Revised Ground-Water Flow and Heat Transport Simulator: HYDROTHERM - Version 3

USGS Publications Warehouse

Kipp, Kenneth L.; Hsieh, Paul A.; Charlton, Scott R.

2008-01-01

The HYDROTHERM computer program simulates multi-phase ground-water flow and associated thermal energy transport in three dimensions. It can handle high fluid pressures, up to 1 ? 109 pascals (104 atmospheres), and high temperatures, up to 1,200 degrees Celsius. This report documents the release of Version 3, which includes various additions, modifications, and corrections that have been made to the original simulator. Primary changes to the simulator include: (1) the ability to simulate unconfined ground-water flow, (2) a precipitation-recharge boundary condition, (3) a seepage-surface boundary condition at the land surface, (4) the removal of the limitation that a specified-pressure boundary also have a specified temperature, (5) a new iterative solver for the linear equations based on a generalized minimum-residual method, (6) the ability to use time- or depth-dependent functions for permeability, (7) the conversion of the program code to Fortran 90 to employ dynamic allocation of arrays, and (8) the incorporation of a graphical user interface (GUI) for input and output. The graphical user interface has been developed for defining a simulation, running the HYDROTHERM simulator interactively, and displaying the results. The combination of the graphical user interface and the HYDROTHERM simulator forms the HYDROTHERM INTERACTIVE (HTI) program. HTI can be used for two-dimensional simulations only. New features in Version 3 of the HYDROTHERM simulator have been verified using four test problems. Three problems come from the published literature and one problem was simulated by another partially saturated flow and thermal transport simulator. The test problems include: transient partially saturated vertical infiltration, transient one-dimensional horizontal infiltration, two-dimensional steady-state drainage with a seepage surface, and two-dimensional drainage with coupled heat transport. An example application to a hypothetical stratovolcano system with unconfined ground-water flow is presented in detail. It illustrates the use of HTI with the combination precipitation-recharge and seepage-surface boundary condition, and functions as a tutorial example problem for the new user.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring.

PubMed

de Moor, J Maarten; Aiuppa, A; Avard, G; Wehrmann, H; Dunbar, N; Muller, C; Tamburello, G; Giudice, G; Liuzzo, M; Moretti, R; Conde, V; Galle, B

2016-08-01

Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO 2 -rich gas (CO 2 /S total  > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8-10 km deep, whereas the shallow magmatic gas source is at ~3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H 2 S/SO 2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO 2 and H 2 S/SO 2  > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H 2 S/SO 2  < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high-temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high‐frequency gas monitoring

PubMed Central

Aiuppa, A.; Avard, G.; Wehrmann, H.; Dunbar, N.; Muller, C.; Tamburello, G.; Giudice, G.; Liuzzo, M.; Moretti, R.; Conde, V.; Galle, B.

2016-01-01

Abstract Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high‐frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2‐rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur‐rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8–10 km deep, whereas the shallow magmatic gas source is at ~3–5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO2 and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2 < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high‐temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity. PMID:27774371

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring

NASA Astrophysics Data System (ADS)

de Moor, J. Maarten; Aiuppa, A.; Avard, G.; Wehrmann, H.; Dunbar, N.; Muller, C.; Tamburello, G.; Giudice, G.; Liuzzo, M.; Moretti, R.; Conde, V.; Galle, B.

2016-08-01

Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2-rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is 8-10 km deep, whereas the shallow magmatic gas source is at 3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO2 and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2 < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high-temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.

Hybrid shallow on-axis and deep off-axis hydrothermal circulation at fast-spreading ridges.

PubMed

Hasenclever, Jörg; Theissen-Krah, Sonja; Rüpke, Lars H; Morgan, Jason P; Iyer, Karthik; Petersen, Sven; Devey, Colin W

2014-04-24

Hydrothermal flow at oceanic spreading centres accounts for about ten per cent of all heat flux in the oceans and controls the thermal structure of young oceanic plates. It also influences ocean and crustal chemistry, provides a basis for chemosynthetic ecosystems, and has formed massive sulphide ore deposits throughout Earth's history. Despite this, how and under what conditions heat is extracted, in particular from the lower crust, remains largely unclear. Here we present high-resolution, whole-crust, two- and three-dimensional simulations of hydrothermal flow beneath fast-spreading ridges that predict the existence of two interacting flow components, controlled by different physical mechanisms, that merge above the melt lens to feed ridge-centred vent sites. Shallow on-axis flow structures develop owing to the thermodynamic properties of water, whereas deeper off-axis flow is strongly shaped by crustal permeability, particularly the brittle-ductile transition. About 60 per cent of the discharging fluid mass is replenished on-axis by warm (up to 300 degrees Celsius) recharge flow surrounding the hot thermal plumes, and the remaining 40 per cent or so occurs as colder and broader recharge up to several kilometres away from the axis that feeds hot (500-700 degrees Celsius) deep-rooted off-axis flow towards the ridge. Despite its lower contribution to the total mass flux, this deep off-axis flow carries about 70 per cent of the thermal energy released at the ridge axis. This combination of two flow components explains the seismically determined thermal structure of the crust and reconciles previously incompatible models favouring either shallower on-axis or deeper off-axis hydrothermal circulation.

Geochemical Evidence for Recent Hydrothermal Alteration of Marine Sediments in Mid-Okinawa Trough, Southwest Japan

NASA Astrophysics Data System (ADS)

Tanaka, A.; Abe, G.; Yamaguchi, K. E.

2014-12-01

Recent studies have shown that submarine hydrothermal 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 hydrothermal 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 hydrothermal 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 hydrothermal activity in Mid-Okinawa Trough. The sediment samples used in this study are from IODP site at Iheya North region and JADE site at Izena region. The samples show alternation between volcanic and clastic sediments. Hydrothermal 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 hydrothermal activity 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 site become more pronounced with increasing depth, suggesting progressive increase of hydrothermal alteration where Eu was reductively dissolved into fluids by decomposition of feldspars. Contrary, at the JADE site, magnitude of negative Eu anomalies was variable independent of the sediment depth. This suggests changes in the redox conditions, most likely due to occasional invasions of O2-bearing seawater into sediments. Different regimes of hydrothermal fluid flows govern the chemical environments of marine sediments in active hydrothermal areas.

Alteration and mineralization of an oceanic forearc and the ophiolite-ocean crust analogy

USGS Publications Warehouse

Alt, J.C.; Teagle, D.A.H.; Brewer, T.; Shanks, Wayne C.; Halliday, A.

1998-01-01

Mineralogical, chemical, and isotopic (O, C, S, and Sr) analyses were performed on minerals and bulk rocks from a forearc basement section to understand alteration processes and compare with mid-ocean ridges (MOR) and ophiolites. Ocean Drilling Program Hole 786B in the Izu-Bonin forearc penetrates 103 m of sediment and 725 m into volcanic flows, breccias, and basal dikes. The rocks comprise boninites and andesites to rhyolites. Most of the section was affected by low-temperature (<100??C) seawater alteration, with temperatures increasing downward. The rocks are partly (5-25%) altered to smectite, Fe-oxyhydroxide, calcite, and phillipsite, and exhibit gains of K, Rb, and P, loss of Ca, variable changes in Si, Na, Mg, Fe, Sr, and Y, and elevated ??18O and 87Sr/86Sr. Higher temperatures (???150??C) in the basal dikes below 750 m led to more intense alteration and formation of chlorite-smectite, corrensite, albite, K-feldspar, and quartz (??chlorite). A 5 m thick hydrothermally altered and pyritized zone at 815 m in the basal dikes reacted with mixtures of seawater and hydrothermal fluids to Mg-chlorite, albite, and pyrite, and gained Mg and S and lost Si and Ca. Focused flow of hydrothermal fluids produced sericitization halos (Na-K sericite, quartz, pyrophyllite, K-feldspar, and pyrite) along quartz veins at temperatures of 200??-250??C. High 87Sr/86Sr ratios of chloritized (???0.7055) and sericitized (???0.7065) rocks indicate involvement of seawater via mixing with hydrothermal fluids. Low ??34S of sulfide (???2 to -5.5???) and sulfate (12.5???) are consistent with input of magmatic SO2 into hydrothermal fluids and disproportionation to sulfide and sulfate. Alteration processes were generally similar to those at MORs, but the arc section is more intensively altered, in part because of the presence of abundant glassy rocks and mafic phases. The increase in alteration grade below 750 m and the mineralization in the basal dikes are analogous to changes that occur near the base of the volcanic section in MOR and the Troodos ophiolite.

Magmatism, ash-flow tuffs, and calderas of the ignimbrite flareup in the western Nevada volcanic field, Great Basin, USA

USGS Publications Warehouse

Christopher D. Henry,; John, David A.

2013-01-01

The western Nevada volcanic field is the western third of a belt of calderas through Nevada and western Utah. Twenty-three calderas and their caldera-forming tuffs are reasonably well identified in the western Nevada volcanic field, and the presence of at least another 14 areally extensive, apparently voluminous ash-flow tuffs whose sources are unknown suggests a similar number of undiscovered calderas. Eruption and caldera collapse occurred between at least 34.4 and 23.3 Ma and clustered into five ∼0.5–2.7-Ma-long episodes separated by quiescent periods of ∼1.4 Ma. One eruption and caldera collapse occurred at 19.5 Ma. Intermediate to silicic lavas or shallow intrusions commonly preceded caldera-forming eruptions by 1–6 Ma in any specific area. Caldera-related as well as other magmatism migrated from northeast Nevada to the southwest through time, probably resulting from rollback of the formerly shallow-dipping Farallon slab. Calderas are restricted to the area northeast of what was to become the Walker Lane, although intermediate and effusive magmatism continued to migrate to the southwest across the future Walker Lane.Most ash-flow tuffs in the western Nevada volcanic field are rhyolites, with approximately equal numbers of sparsely porphyritic (≤15% phenocrysts) and abundantly porphyritic (∼20–50% phenocrysts) tuffs. Both sparsely and abundantly porphyritic rhyolites commonly show compositional or petrographic evidence of zoning to trachydacites or dacites. At least four tuffs have volumes greater than 1000 km3, with one possibly as much as ∼3000 km3. However, the volumes of most tuffs are difficult to estimate, because many tuffs primarily filled their source calderas and/or flowed and were deposited in paleovalleys, and thus are irregularly distributed.Channelization and westward flow of most tuffs in paleovalleys allowed them to travel great distances, many as much as ∼250 km (original distance) to what is now the western foothills of the Sierra Nevada, which was not a barrier to westward flow of ash flows at that time. At least three tuffs flowed eastward across a north-south paleodivide through central Nevada. That tuffs could flow significant distances apparently uphill raises questions about the absolute elevation of the region and the elevation, relief, and location of the paleodivide.Calderas are equant to slightly elongate, at least 12 km in diameter, and as much as 35 km in longest dimension. Exceptional exposure of two caldera complexes that resulted from extensional faulting and tilting show that calderas subsided as much as 5 km as large piston-like blocks; caldera walls were vertical to steeply inward dipping to depths ≥4–5 km, and topographic walls formed by slumping of wall rock into the caldera were only slightly outboard (≤1 km) of structural margins.Most calderas show abundant post-collapse magmatism expressed as resurgent intrusions, ring-fracture intrusions, or intracaldera lavas that are closely related temporally (∼0–0.5 Ma younger) to caldera formation. Granitoid intrusions, which were emplaced at paleodepths ranging from <1 to ∼7 km, are compositionally similar to both intracaldera ash-flow tuffs and post-caldera lavas. Therefore in the western Nevada volcanic field, erupted caldera-forming tuffs commonly were the upper parts of large magma chambers that retained considerable volumes of magma after tuff eruption.Several calderas in the western Nevada volcanic field hosted large hydrothermal systems and underwent extensive hydrothermal alteration. Different types of hydrothermal systems (neutral-pH alkali-chloride and acid or low-pH magmatic-hydrothermal) may reflect proximity to (depth of) large resurgent intrusions. With the exception of the giant Round Mountain epithermal gold deposit, few known caldera-related hydrothermal systems are strongly mineralized. Major middle Cenozoic precious and base metal mineral deposits in and along the margins of the western Nevada volcanic field are mostly related to intrusive rocks that preceded caldera-forming eruptions.

Sericitization of illite decreases sorption capabilities for cesium

NASA Astrophysics Data System (ADS)

Choung, S.; Hwang, J.; Han, W.; Shin, W.

2017-12-01

Release of radioactive cesium (137Cs) to environment occurs through nuclear accidents such as Chernobyl and Fukushima. The concern is that 137Cs has long half-life (t1/2 = 30.2 years) with chemical toxicity and γ-radiation. Sorption techniques are mainly applied to remove 137Cs from aquatic environment. In particular, it has been known well that clay minerals (e.g, illite) are effective and economical sorbents for 137Cs. Illite that was formed by hydrothermal alteration exist with sericite through "sericitization" processes. Although sericite has analogous composition and lattice structure with illite, the sorptive characteristics of illite and sericite for radiocesium could be different. This study evaluated the effects of hydrothermal alteration and weathering process on illite cesium sorption properties. Natural illite samples were collected at Yeongdong area in Korea as the world-largest hydrothermal deposits for illite. The samples were analyzed by XRF, XRD and SEM-EDX to determine mineralogy, chemical compositions and morphological characteristics, and used for batch sorption experiments. The Yeongdong illites predominantly consist of illite, sericite, quartz, and albite. The measured cesium sorption distribution coefficients (Kd,Cs) of reference illite and sericite were approximately 6000 and 400 L kg-1 at low aqueous concentration (Cw 10-7 M), respectively. In contrast, Kd,Cs values for the Yeongdong illite samples ranged from 500 to 4000 L kg-1 at identical concentration. The observed narrow and sharp XRD peak of sericite indicated that the sericite has better crystallinity compared to illite. These experimental results suggested that sericitization processes of illite can decline the sorption capabilities of illite for cesium under various hydrothermal conditions. In particular, weathering experiments raised the cesium sorption to illite, which seems to be related to the increase of preferential sorption sites for cesium through crystallinity destruction (i.e., frayed edge sites).

Geochemical features of the geothermal fluids from the Mapamyum non-volcanic geothermal system (Western Tibet, China)

NASA Astrophysics Data System (ADS)

Wang, Peng; Chen, Xiaohong; Shen, Licheng; Wu, Kunyu; Huang, Mingzhi; Xiao, Qiong

2016-06-01

Mapamyum geothermal field (MGF) in western Tibet is one of largest geothermal areas characterized by the occurrence of hydrothermal explosions on the Tibetan Plateau. The geochemical properties of hydrothermal water in the MGF system were investigated to trace the origin of the solutes and to determine the equilibrium temperatures of the feeding reservoir. The study results show that the geochemistry of hydrothermal waters in the MGF system is mainly of the Na-HCO3 type. The chemical components of hydrothermal waters are mainly derived from the minerals in the host rocks (e.g., K-feldspar, albite, Ca-montmorillonite, and Mg-montmorillonite). The hydrothermal waters are slightly supersaturated or undersaturated with respect to aragonite, calcite, dolomite, chalcedony and quartz (saturation indices close to 0), but are highly undersaturated with respect to gypsum and anhydrite (saturation indices < 0). Mixing models and Na-K-Mg ternary diagrams show that strong mixing between cold meteoric water and deeply-seated thermal fluids occurred during the upward flowing process. δD and δ18O data confirm that the meteoric water acts as the water source of the geothermal waters. An 220 °C equilibrated reservoir temperature of hydrothermal spring waters was calculated via both the Na-K-Mg ternary diagrams and the cationic chemical geothermometers. The logpCO2 of hydrothermal waters in the MGF system ranges from - 2.59 to - 0.57 and δ13C of the total dissolved inorganic carbon ranges from - 5.53‰ to - 0.94‰, suggesting that the carrier CO2 in hydrothermal water are mainly of a magmatic or metamorphic CO2 origin.

Contrasting origin of two clay-rich debris flows at Cayambe Volcanic Complex, Ecuador

NASA Astrophysics Data System (ADS)

Detienne, M.; Delmelle, P.; Guevara, A.; Samaniego, P.; Opfergelt, S.; Mothes, P. A.

2017-04-01

We investigate the sedimentological and mineralogical properties of a debris flow deposit west of Cayambe Volcanic Complex, an ice-clad edifice in Ecuador. The deposit exhibits a matrix facies containing up to 16 wt% of clays. However, the stratigraphic relationship of the deposit with respect to the Canguahua Formation, a widespread indurated volcaniclastic material in the Ecuadorian inter-Andean Valley, and the deposit alteration mineralogy differ depending on location. Thus, two different deposits are identified. The Río Granobles debris flow deposit ( 1 km3) is characterised by the alteration mineral assemblage smectite + jarosite, and sulphur isotopic analyses point to a supergene hydrothermal alteration environment. This deposit probably derives from a debris avalanche initiated before 14-21 ka by collapse of a hydrothermally altered rock mass from the volcano summit. In contrast, the alteration mineralogy of the second debris flow deposit, which may itself comprise more than one unit, is dominated by halloysite + smectite and relates to a shallower and more recent (<13 ky) mass movement of high-altitude (>3200 m) volcanic soils. Our study reinforces the significance of hydrothermal alteration in weakening volcano flanks and in favouring rapid transformation of a volcanic debris avalanche into a clay-rich debris flow. It also demonstrates that mineralogical analysis provides crucial information for resolving the origin of a debris flow deposit in volcanic terrains. Finally, we posit that slope instability, promoted by ongoing subglacial hydrothermal alteration, remains a significant hazard at Cayambe Volcanic Complex.

Hierarchical hollow microsphere and flower-like indium oxide: Controllable synthesis and application as H{sub 2}S cataluminescence sensing materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Pingyang, E-mail: cpyxx@163.com; Bai, Wei, E-mail: weibaiscu@gmail.com; Zhang, Lichun, E-mail: lichun0203@yahoo.cn

Graphical abstract: Hierarchical hollow microsphere and flower-like In{sub 2}O{sub 3} were controllable fabricated through a novel and simple hydrothermal process, and the former showed superior cataluminescence sensing performance to H{sub 2}S. Highlights: ► In{sub 2}O{sub 3} hierarchical hollow sphere were prepared via a hydrothermal route. ► The growth process of In{sub 2}O{sub 3} hierarchical hollow sphere has been investigated. ► The sensor based on prepared In{sub 2}O{sub 3} shows good sensing performance to H{sub 2}S. -- Abstract: In the present work, In{sub 2}O{sub 3} hierarchical hollow microsphere and flower-like microstructure were achieved controllably by a hydrothermal process in the sodiummore » dodecyl sulfate (SDS)-N,N-dimethyl-formamide (DMF) system. XRD, SEM, HRTEM and N{sub 2} adsorption measurements were used to characterize the as-prepared indium oxide materials and the possible mechanism for the microstructures formation was briefly discussed. The cataluminescence gas sensor based on the as-prepared In{sub 2}O{sub 3} was utilized to detect H{sub 2}S concentrations in flowing air. Comparative gas sensing results revealed that the sensor based on hierarchical hollow microsphere exhibited much higher sensing sensitivity in detecting H{sub 2}S gas than the sensor based on flower-like microstructure. The present gas sensor had a fast response time of 5 s and a recovery time of less than 25 s, furthermore, the cataluminescence intensity vs. H{sub 2}S concentration was linear in range of 2–20 μg mL{sup −1} with a detection limit of 0.5 μg mL{sup −1}. The present highly sensitive, fast-responding, and low-cost In{sub 2}O{sub 3}-based gas sensor for H{sub 2}S would have many practical applications.« less

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 Mn mineralization. Factor analyses indicate various mixtures of two dominant components: hydrothermal Mn oxide for the stratabound Mn and detrital aluminosilicate for the Mn-cemented sandstone; and two minor components, hydrothermal Fe oxyhydroxide and biocarbonate/biosilica. Our conceptual model shows that Mn mineralization was produced by hydrothermal convection cells within arc volcanoes and sedimentary prisms that occur along, the flanks and within calderas. The main source of hydrothermal fluid was seawater that penetrated through fractures, faults, and permeable volcanic edifices. The fluids were heated by magma, enriched in metals by leaching of basement rocks and sediments, and mixed with magmatic fluids and gases. Dikes and sills may have been another source of heat that drove small-scale circulation within sedimentary prisms. Copyright 2008 by the American Geophysical Union.

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 Mn mineralization. Factor analyses indicate various mixtures of two dominant components: hydrothermal Mn oxide for the stratabound Mn and detrital aluminosilicate for the Mn-cemented sandstone; and two minor components, hydrothermal Fe oxyhydroxide and biocarbonate/biosilica. Our conceptual model shows that Mn mineralization was produced by hydrothermal convection cells within arc volcanoes and sedimentary prisms that occur along the flanks and within calderas. The main source of hydrothermal fluid was seawater that penetrated through fractures, faults, and permeable volcanic edifices. The fluids were heated by magma, enriched in metals by leaching of basement rocks and sediments, and mixed with magmatic fluids and gases. Dikes and sills may have been another source of heat that drove small-scale circulation within sedimentary prisms.

From Geochemistry to Biochemistry: Simulating Prebiotic Chemistry Driven by Geochemical Gradients in Alkaline Hydrothermal Vents

NASA Astrophysics Data System (ADS)

Barge, Laurie

2016-07-01

Planetary water-rock interfaces generate energy in the form of redox, pH, and thermal gradients, and these disequilibria are particularly focused in hydrothermal vent systems where the reducing, heated hydrothermal fluid feeds back into the more oxidizing ocean. Alkaline hydrothermal vents have been proposed as a likely location for the origin of life on the early Earth due to various factors: including the hydrothermal pH / Eh gradients that resemble the ubiquitous electrical / proton gradients in biology, the catalytic hydrothermal precipitates that resemble inorganic catalysts in enzymes, and the presence of electron donors and acceptors in hydrothermal systems (e.g. H2 + CH4 and CO2) that are thought to have been utilized in the earliest metabolisms. Of particular importance for the emergence of metabolism are the mineral "chimneys" that precipitate at the vent fluid / seawater interface. Hydrothermal chimneys are flow-through chemical reactors that form porous and permeable inorganic membranes transecting geochemical gradients; in some ways similar to biological membranes that transect proton / ion gradients and harness these disequilibria to drive metabolism. These emergent chimney structures in the far-from-equilibrium system of the alkaline vent have many properties of interest to the origin of life that can be simulated in the laboratory: for example, they can generate electrical energy and drive redox reactions, and produce catalytic minerals (in particular the metal sulfides and iron oxyhydroxides - "green rust") that can facilitate chemical reactions towards proto-metabolic cycles and biosynthesis. Many of the factors prompting interest in alkaline hydrothermal vents on Earth may also have been present on early Mars, or even presently within icy worlds such as Europa or Enceladus - thus, understanding the disequilibria and resulting prebiotic chemistry in these systems can be of great use in assessing the potential for other environments in the Solar System where life could have emerged.

Diffuse-flow hydrothermal field in an oceanic fracture zone setting, Northeast Pacific: Deposit composition

USGS Publications Warehouse

Hein, J.R.; Koski, R.A.; Embley, R.W.; Reid, J.; Chang, S.-W.

1999-01-01

This is the first reported occurrence of an active hydrothermal field in an oceanic fracture zone setting. The hydrothermal field occurs in a pull-apart basin within the Blanco Fracture Zone (BFZ), which has four distinct mineral deposit types: (1) barite mounds and chimneys, (2) barite stockwork breccia, (3) silica-barite beds, and (4) silica, barite, and Fe-Mn oxyhydroxide in sediments. All deposit types contain minor amounts of sulfides. In barite stockwork, silica-barite beds, and mineralized sediment, Ba, Ph, Ag, S, Au, Zn, Cu, Hg, TI, As, Mo, Sb, U, Cd, and Cu are enriched relative to unmineralized rocks and sediments of the BFZ. Fe and Mn are not enriched in the barite stockwork or silica-barite beds, but along with P, Co, and Mg are enriched in the mineralized sediments. Silver contents in deposits of the hydrothermal field range up to 86 ppm, gold to 0.7 ppm, zinc to 3.2%, copper to 0.8%, and barium to 22%. Mineralization occurred by diffuse, low to intermediate temperature (mostly <250??C) discharge of hydrothermal fluids through pillow lavas and ponds of mixed volcaniclastic and biosiliceous sediments. Bacterial mats were mineralized by silica, barite, and minor Fe hydroxides, or less commonly, by Mn oxyhydroxides. Pervasive mineralization of bacterial mats resulted in formation of silica-barite beds. Silica precipitated from hydrothermal fluids by conductive cooling and mixing with seawater. Sulfate, U, and rare earth elements (REEs) in barite were derived from seawater, whereas the REE content of hydrothermal silica deposits and mineralized sediments is associated with the aluminosilicate detrital fraction. Fe-, Zn-, Cu-, Pb-, and Hg-sulfide minerals, Ba in barite, and Eu in all mineralized deposits were derived from hydrothermal fluids. Manganese oxides and associated elements (Co, Sb, Mo, W, Cl, and Cu) and Fe oxides and associated elements (Be, B, P, and Mo) precipitated as the result of mixing of hydrothermal fluids with seawater. ?? 2001 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.

Controls on Martian Hydrothermal Systems: Application to Valley Network and Magnetic Anomaly Formation

NASA Technical Reports Server (NTRS)

Harrison, Keith P.; Grimm, Robert E.

2002-01-01

Models of hydrothermal groundwater circulation can quantify limits to the role of hydrothermal activity in Martian crustal processes. We present here the results of numerical simulations of convection in a porous medium due to the presence of a hot intruded magma chamber. The parameter space includes magma chamber depth, volume, aspect ratio, and host rock permeability and porosity. A primary goal of the models is the computation of surface discharge. Discharge increases approximately linearly with chamber volume, decreases weakly with depth (at low geothermal gradients), and is maximized for equant-shaped chambers. Discharge increases linearly with permeability until limited by the energy available from the intrusion. Changes in the average porosity are balanced by changes in flow velocity and therefore have little effect. Water/rock ratios of approximately 0.1, obtained by other workers from models based on the mineralogy of the Shergotty meteorite, imply minimum permeabilities of 10(exp -16) sq m2 during hydrothermal alteration. If substantial vapor volumes are required for soil alteration, the permeability must exceed 10(exp -15) sq m. The principal application of our model is to test the viability of hydrothermal circulation as the primary process responsible for the broad spatial correlation of Martian valley networks with magnetic anomalies. For host rock permeabilities as low as 10(exp -17) sq m and intrusion volumes as low as 50 cu km, the total discharge due to intrusions building that part of the southern highlands crust associated with magnetic anomalies spans a comparable range as the inferred discharge from the overlying valley networks.

Length Scales of Reactive Transport in Basalt: Hydrothermal Flow-through Experiments and Anhydrite Precipitation

NASA Astrophysics Data System (ADS)

Los, C.; Kahl, W. A.; Bach, W.

2017-12-01

Hydrothermal circulation is a large contributor to mass and heat exchange between oceanic lithosphere and hydrosphere. Cold, unaltered seawater infiltrates in the shallow basaltic crust, leading to sulfate precipitation and clogging of fluid pathways. Anhydrite (CaSO4) veins are common in hydrothermal discharge zones, where entrained seawater is heated and anhydrite quickly forms. Anhydrite is also found in hydrothermal recharge zones, but questions regarding time and length scale in this setting remain. To investigate element transport and anhydrite precipitation we have conducted flow-through experiments using a gypsum-undersaturated CaSO4 solution in pre-fractured basalt at 95, 110 and 140°C. Each run was terminated upon clogging of the input tubes, which took 2-8 weeks. The rock core was scanned before the run and weekly during the experiment using X-ray tomography. Fluid major element chemistry was analyzed using ICP-OES. Geochemical modeling with the software package EQ3/6 showed that the starting solution became supersaturated in anhydrite (SI=IAP/K of 2.5 or higher) in all cases upon heating to the experimental temperature. The software CRUNCH FLOW was used to analyze chemical effects over the length of the core (3cm). The 95°C run and a first run at 110°C did not show any anhydrite. Instead, hematite rosettes and sulfur-bearing (maximum of 1 wt.%) globular Fe-rich structures were present. Tomography images showed that fractures and pores were slightly thinned over the whole core length. Single pores in a second 110°C run and fractures in the 140°C run did show formation of anhydrite and quartz close to the outlet. CRUNCH FLOW modeling predicts the observed release of Mg, Fe, Si, Al, Na and K due to silicate dissolution close to the inlet, while the outlet area should contain some anhydrite. No other sulfur-bearing phases were predicted. The results of this study show that anhydrite needs a large supersaturation (SI>2.5) to precipitate at temperatures below 110°C. This is easier accomplished close to the outlet, where the largest amount of cations is released from the rock. Iron dissolution from primary phases is fast, but its mobility is low as it is rapidly captured in hematite. Anhydrite and hematite precipitation do not seem to induce fracturing in the surrounding rock but close the pre-existing pore space.

Geologic form and setting of a hydrothermal vent field at lat 10°56‧N, East Pacific Rise: A detailed study using Angus and Alvin

NASA Astrophysics Data System (ADS)

McConachy, T. F.; Ballard, R. D.; Mottl, M. J.; von Herzen, R. P.

1986-04-01

A hydrothermal vent field, here called the Feather Duster site, occurs on the eastern marginal high near the edge of a narrow (95-m) and shallow (15 20-m) axial graben, within an area dominated by sheet flows and collapse features. The sheet flows are intermediate in relative age between younger fluid-flow lavas on the floor of the axial graben and older pillow (constructional) lavas on the marginal highs. Hydrothermal activity occurs in two zones within a 65 by 45 m area. The main zone is located where a fissure system and sulfide-sulfate chimneys vent warm (9 47 °C) and hot (347 °C) hydrothermal fluids. Here, two mounds of massive sulfide totaling about 200 t are forming. One occurs at the base of a 3-m-high scarp which is the wall of a drained lava lake; the other is perched on top of the scarp. *Present address: Department of Geology, University of Toronto, Toronto, Ontario, Canada M5S 1A1

Synthesis of magnetic nickel spinel ferrite nanospheres by a reverse emulsion-assisted hydrothermal process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Jilin; Shi Jianxin, E-mail: chemshijx@163.co; Gong Menglian

2009-08-15

Nickel ferrite nanospheres were successfully synthesized by a reverse emulsion-assisted hydrothermal method. The reverse emulsion was composed of water, cetyltrimethyl ammonium bromide, polyoxyethylene(10)nonyl phenyl ether, iso-amyl alcohol and hexane. During the hydrothermal process, beta-FeO(OH) and Ni{sub 0.75}Fe{sub 0.25}(CO{sub 3}){sub 0.125}(OH){sub 2}.0.38H{sub 2}O (INCHH) nanorods formed first and then transformed into nickel spinel ferrite nanospheres. The phase transformation mechanism is proposed based on the results of X-ray powder diffraction, transmission electron microscopy and energy-dispersive X-ray spectroscopy, etc. Nickel ferrite may form at the end of the INCHH nanorods or from the solution accompanied by the dissolution of beta-FeO(OH) and INCHH nanorods.more » The X-ray photoelectron spectroscopy analysis shows that a few Fe{sup 3+} ions have been reduced to Fe{sup 2+} ions during the formation of nickel ferrite. The maximum magnetization of the nickel ferrite nanospheres obtained after hydrothermal reaction for 30 h is 55.01 emu/g, which is close to that of bulk NiFe{sub 2}O{sub 4}. - Graphical abstract: Nickel ferrite nanospheres were obtained through a reverse emulsion-assisted hydrothermal process. The phase transformation as a function of reaction time was studied based on the XRD, TEM and EDS analyses.« less

Hydrothermally synthesized PZT film grown in highly concentrated KOH solution with large electromechanical coupling coefficient for resonator.

PubMed

Feng, Guo-Hua; Lee, Kuan-Yi

2017-12-01

This paper presents a study of lead zirconate titanate (PZT) films hydrothermally grown on a dome-shaped titanium diaphragm. Few articles in the literature address the implementation of hydrothermal PZT films on curved-diaphragm substrates for resonators. In this study, a 50-μm-thick titanium sheet is embossed using balls of designed dimensions to shape a dome-shaped cavity array. Through single-process hydrothermal synthesis, PZT films are grown on both sides of the processed titanium diaphragm with good adhesion and uniformity. The hydrothermal synthesis process involves a high concentration of potassium hydroxide solution and excess amounts of lead acetate and zirconium oxychloride octahydrate. Varied deposition times and temperatures of PZT films are investigated. The grown films are characterized by X-ray diffraction and scanning electron microscopy. The 10-μm-thick PZT dome-shaped resonators with 60- and 20-μm-thick supporting layers are implemented and further tested. Results for both resonators indicate that large electromechanical coupling coefficients and a series resonance of 95 MHz from 14 MHz can be attained. The device is connected to a complementary metal-oxide-semiconductor integrated circuit for analysis of oscillator applications. The oscillator reaches a Q value of 6300 in air. The resonator exhibits a better sensing stability when loaded with water when compared with air.

Hydrothermally synthesized PZT film grown in highly concentrated KOH solution with large electromechanical coupling coefficient for resonator

PubMed Central

Lee, Kuan-Yi

2017-01-01

This paper presents a study of lead zirconate titanate (PZT) films hydrothermally grown on a dome-shaped titanium diaphragm. Few articles in the literature address the implementation of hydrothermal PZT films on curved-diaphragm substrates for resonators. In this study, a 50-μm-thick titanium sheet is embossed using balls of designed dimensions to shape a dome-shaped cavity array. Through single-process hydrothermal synthesis, PZT films are grown on both sides of the processed titanium diaphragm with good adhesion and uniformity. The hydrothermal synthesis process involves a high concentration of potassium hydroxide solution and excess amounts of lead acetate and zirconium oxychloride octahydrate. Varied deposition times and temperatures of PZT films are investigated. The grown films are characterized by X-ray diffraction and scanning electron microscopy. The 10-μm-thick PZT dome-shaped resonators with 60- and 20-μm-thick supporting layers are implemented and further tested. Results for both resonators indicate that large electromechanical coupling coefficients and a series resonance of 95 MHz from 14 MHz can be attained. The device is connected to a complementary metal–oxide–semiconductor integrated circuit for analysis of oscillator applications. The oscillator reaches a Q value of 6300 in air. The resonator exhibits a better sensing stability when loaded with water when compared with air. PMID:29308260

Hydrothermally synthesized PZT film grown in highly concentrated KOH solution with large electromechanical coupling coefficient for resonator

NASA Astrophysics Data System (ADS)

Feng, Guo-Hua; Lee, Kuan-Yi

2017-12-01

This paper presents a study of lead zirconate titanate (PZT) films hydrothermally grown on a dome-shaped titanium diaphragm. Few articles in the literature address the implementation of hydrothermal PZT films on curved-diaphragm substrates for resonators. In this study, a 50-μm-thick titanium sheet is embossed using balls of designed dimensions to shape a dome-shaped cavity array. Through single-process hydrothermal synthesis, PZT films are grown on both sides of the processed titanium diaphragm with good adhesion and uniformity. The hydrothermal synthesis process involves a high concentration of potassium hydroxide solution and excess amounts of lead acetate and zirconium oxychloride octahydrate. Varied deposition times and temperatures of PZT films are investigated. The grown films are characterized by X-ray diffraction and scanning electron microscopy. The 10-μm-thick PZT dome-shaped resonators with 60- and 20-μm-thick supporting layers are implemented and further tested. Results for both resonators indicate that large electromechanical coupling coefficients and a series resonance of 95 MHz from 14 MHz can be attained. The device is connected to a complementary metal-oxide-semiconductor integrated circuit for analysis of oscillator applications. The oscillator reaches a Q value of 6300 in air. The resonator exhibits a better sensing stability when loaded with water when compared with air.

The Guaymas Basin Hiking Guide to Hydrothermal Mounds, Chimneys, and Microbial Mats: Complex Seafloor Expressions of Subsurface Hydrothermal Circulation

PubMed Central

Teske, Andreas; de Beer, Dirk; McKay, Luke J.; Tivey, Margaret K.; Biddle, Jennifer F.; Hoer, Daniel; Lloyd, Karen G.; Lever, Mark A.; Røy, Hans; Albert, Daniel B.; Mendlovitz, Howard P.; MacGregor, Barbara J.

2016-01-01

The hydrothermal mats, mounds, and chimneys of the southern Guaymas Basin are the surface expression of complex subsurface hydrothermal circulation patterns. In this overview, we document the most frequently visited features of this hydrothermal area with photographs, temperature measurements, and selected geochemical data; many of these distinct habitats await characterization of their microbial communities and activities. Microprofiler deployments on microbial mats and hydrothermal sediments show their steep geochemical and thermal gradients at millimeter-scale vertical resolution. Mapping these hydrothermal features and sampling locations within the southern Guaymas Basin suggest linkages to underlying shallow sills and heat flow gradients. Recognizing the inherent spatial limitations of much current Guaymas Basin sampling calls for comprehensive surveys of the wider spreading region. PMID:26925032

Highly catalytic and stabilized titanium nitride nanowire array-decorated graphite felt electrodes for all vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Wei, L.; Zhao, T. S.; Zeng, L.; Zeng, Y. K.; Jiang, H. R.

2017-02-01

In this work, we prepare a highly catalytic and stabilized titanium nitride (TiN) nanowire array-decorated graphite felt electrode for all vanadium redox flow batteries (VRFBs). Free-standing TiN nanowires are synthesized by a two-step process, in which TiO2 nanowires are first grown onto the surface of graphite felt via a seed-assisted hydrothermal method and then converted to TiN through nitridation reaction. When applied to VRFBs, the prepared electrode enables the electrolyte utilization and energy efficiency to be 73.9% and 77.4% at a high current density of 300 mA cm-2, which are correspondingly 43.3% and 15.4% higher than that of battery assembled with a pristine electrode. More impressively, the present battery exhibits good stability and high capacity retention during the cycle test. The superior performance is ascribed to the significant improvement in the electrochemical kinetics and enlarged active sites toward V3+/V2+ redox reaction.

High-resolution Topography of PACMANUS and DESMOS Hydrothermal Fields in the Manus Basin through ROV "FAXIAN"

NASA Astrophysics Data System (ADS)

Luan, Z.; Ma, X.; Yan, J.; Zhang, X.; Zheng, C.; Sun, D.

2016-12-01

High-resolution topography can help us deeply understand the seabed and related geological processes (e.g. hydrothermal/cold spring systems) in the deep sea areas. However, such studies are rare in China due to the limit of deep-sea detection technology. Here, we report the advances of the application of ROV in China and the newly measured high-resolution topographical data in PACMANUS and DESMOS hydrothermal fields. In June 2015, the ROV "FAXIAN" with a multibeam system (Kongsberg EM2040) was deployed to measure the topography of PACMANUS and DESMOS hydrothermal fields in the Manus basin. A composite positioning system on the ROV provided long baseline (LBL) navigation and positioning during measurements, giving a high positioning accuracy (better than 0.5m). The raw bathymetric data obtained were processed using CARIS HIPS (version 8.1). Based on the high-resolution data, we can describe the topographical details of the PACMANUS and DESMOS hydrothermal fields. High-resolution terrain clearly shows the detailed characters of the topography in the PACMANUS hydrothermal field, and some cones are corresponding to the pre discovered hydrothermal points and volcanic area. Most hydrothermal points in the PACMANUS hydrothermal field mainly developed on the steep slopes with a gradient exceeding 30 °. In contrast, the DESMOS field is a caldera that is approximately 250 m deep in the center with an E-W diameter of approximately1 km and a N-S diameter of approximately 2 km. The seafloor is much steeper on the inner side of the circular fracture. Two highlands occur in the northern and the southern flanks of the caldera. Video record indicated that pillow lava, sulfide talus, breccia, anhydrite, outcrops, and sediment all appeared in the DESMOS field. This is the first time for the ROV "FAXIAN" to be used in near-bottom topography measurements in the hydrothermal fields, opening a window of deep-sea researches in China.

Mathematical Models of Seafloor Hydrothermal Systems Driven by Serpentinization of Peridotite

NASA Astrophysics Data System (ADS)

Lowell, R. P.; Rona, P. A.; Germanovich, L. N.

2001-12-01

Most seafloor hydrothermal systems are driven by heat transfer from subsurface magma bodies. At slow spreading ridges of the Atlantic and Indian oceans, however, magma supply is low; and tectonic activity brings mantle rocks to shallow depths in the crust. Then, the heat of formation released upon serpentinization of peridotite provides the energy source for hydrothermal circulation. This latter class of system has been relatively unstudied, but recent discoveries of peridotite-hosted hydrothermal systems along the Mid-Atlantic Ridge suggest that such systems may play an important role in geochemical cycling and biogeochemical processes. The likelihood that peridotite-hosted hydrothermal systems was more prevalent during the Archean further suggests that such systems may have played a role in the origin of life. We present the first mathematical models of seafloor hydrothermal systems driven by heat released upon serpentinization of peridotite. We assume seawater circulates through a major crack network in the host-peridotite and that cooling of the host-rock leads to the formation of microcracks through which the fluid infiltrates. Reaction of the fluid in microcracks with the host rock results in serpentinization and the heat released upon serpentinization is transported to the seafloor by the fluid circulating in the main crack network. The temperature and heat output of the resulting hydrothermal system is a function of the main network permeability and the rate at which the serpentinization reaction proceeds via diffusion and propagation of the microcracks. Although the temperature of such a system can be quite variable, vent temperatures between 10° C and 100° C are likely for typical crustal parameters.

Lead recovery from scrap cathode ray tube funnel glass by hydrothermal sulphidisation.

PubMed

Yuan, Wenyi; Meng, Wen; Li, Jinhui; Zhang, Chenglong; Song, Qingbin; Bai, Jianfeng; Wang, Jingwei; Li, Yingshun

2015-10-01

This research focused on the application of the hydrothermal sulphidisation method to separate lead from scrap cathode ray tube funnel glass. Prior to hydrothermal treatment, the cathode ray tube funnel glass was pretreated by mechanical activation. Under hydrothermal conditions, hydroxyl ions (OH(-)) were generated through an ion exchange reaction between metal ions in mechanically activated funnel glass and water, to accelerate sulphur disproportionation; no additional alkaline compound was needed. Lead contained in funnel glass was converted to lead sulphide with high efficiency. Temperature had a significant effect on the sulphidisation rate of lead in funnel glass, which increased from 25% to 90% as the temperature increased from 100 °C to 300 °C. A sulphidisation rate of 100% was achieved at a duration of 8 h at 300 °C. This process of mechanical activation and hydrothermal sulphidisation is efficient and promising for the treatment of leaded glass. © The Author(s) 2015.

The origins of Late Quaternary debris avalanche and debris flow deposits from Cofre de Perote volcano, México

USGS Publications Warehouse

Diaz-Castellon, Rodolfo; Hubbard, Bernard E.; Carrasco-Nunez, Gerardo; Rodríguez-Vargas, José Luis

2012-01-01

Cofre de Perote volcano is a compound, shield-like volcano located in the northeastern Trans-Mexican volcanic belt. Large debris avalanche and lahar deposits are associated with the evolution of Cofre. The two best preserved of these debris-avalanche and debris-flow deposits are the ∼42 ka “Los Pescados debris flow” deposit and the ∼11–13 ka “Xico avalanche” deposit, both of which display contrasting morphological and textural characteristics, source materials, origins and emplacement environments. Laboratory X-ray diffraction and visible-infrared reflectance spectroscopy were used to identify the most abundant clay, sulfate, ferric-iron, and silica minerals in the deposits, which were either related to hydrothermal alteration or chemical weathering processes. Cloud-free Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) remote sensing imagery, supporting EO-1 Hyperion image spectra, and field ground truth samples were used to map the mineralogy and distribution of hydrothermally altered rocks on the modern summit of Cofre de Perote. The results were then compared to minerals identified in the two debris-avalanche and debris-flow deposits in order to assess possible source materials and origins for the two deposits.The older Los Pescados debris-flow deposit contains mostly halloysite and hydrous silica minerals, which match the dominant mineralogy of soils and weathered volcanic deposit in the surrounding flanks of Cofre de Perote. Its source materials were most likely derived from initially noncohesive or clay-poor flows, which subsequently bulked with clay-rich valley soils and alluvium in a manner similar to lahars from Nevado del Ruiz in 1985, but on a larger scale. The younger Xico avalanche deposit contains abundant smectite, jarosite, kaolinite, gypsum, and mixed-layered illite/smectite, which are either definitely or most likely of hydrothermal alteration origin. Smectite in particular appears to be the most abundant and spectrally dominant mineral in summit ground truth samples, ASTER mapping results, Xico avalanche deposit, and an older (pre-Xico avalanche) deposit derived from collapse(s) of ancestral Cofre de Perote edifice. However, both Xico avalanche and Los Pescados debris flow deposits show some evidence of secondary, postemplacement weathering and induration, which is evident by the presence of gibbsite, and hydroxyl interlayered minerals, in addition to recently formed halloysite and hydrous silica (i.e., indurating) cements. Field-based, visible infrared image spectroscopy (VIS/IR) spectral measurements offer the possibility of distinguishing primary minerals of hydrothermal alteration origin in debris-avalanche and debris-flow deposits from those produced either by in situ chemical weathering or bulked from weathered source materials.

Methods to enhance the characteristics of hydrothermally prepared slurry fuels

DOEpatents

Anderson, Chris M.; Musich, Mark A.; Mann, Michael D.; DeWall, Raymond A.; Richter, John J.; Potas, Todd A.; Willson, Warrack G.

2000-01-01

Methods for enhancing the flow behavior and stability of hydrothermally treated slurry fuels. A mechanical high-shear dispersion and homogenization device is used to shear the slurry fuel. Other improvements include blending the carbonaceous material with a form of coal to reduce or eliminate the flocculation of the slurry, and maintaining the temperature of the hydrothermal treatment between approximately 300.degree. to 350.degree. C.

Time-lapse characterization of hydrothermal seawater and microbial interactions with basaltic tephra at Surtsey Volcano

NASA Astrophysics Data System (ADS)

Jackson, M. D.; Gudmundsson, M. T.; Bach, W.; Cappelletti, P.; Coleman, N. J.; Ivarsson, M.; Jónasson, K.; Jørgensen, S. L.; Marteinsson, V.; McPhie, J.; Moore, J. G.; Nielson, D.; Rhodes, J. M.; Rispoli, C.; Schiffman, P.; Stefánsson, A.; Türke, A.; Vanorio, T.; Weisenberger, T. B.; White, J. D. L.; Zierenberg, R.; Zimanowski, B.

2015-12-01

A new International Continental Drilling Program (ICDP) project will drill through the 50-year-old edifice of Surtsey Volcano, the youngest of the Vestmannaeyjar Islands along the south coast of Iceland, to perform interdisciplinary time-lapse investigations of hydrothermal and microbial interactions with basaltic tephra. The volcano, created in 1963-1967 by submarine and subaerial basaltic eruptions, was first drilled in 1979. In October 2014, a workshop funded by the ICDP convened 24 scientists from 10 countries for 3 and a half days on Heimaey Island to develop scientific objectives, site the drill holes, and organize logistical support. Representatives of the Surtsey Research Society and Environment Agency of Iceland also participated. Scientific themes focus on further determinations of the structure and eruptive processes of the type locality of Surtseyan volcanism, descriptions of changes in fluid geochemistry and microbial colonization of the subterrestrial deposits since drilling 35 years ago, and monitoring the evolution of hydrothermal and biological processes within the tephra deposits far into the future through the installation of a Surtsey subsurface observatory. The tephra deposits provide a geologic analog for developing specialty concretes with pyroclastic rock and evaluating their long-term performance under diverse hydrothermal conditions. Abstracts of research projects are posted at http://surtsey.icdp-online.org.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

Normal faults cutting oceanic core complexes are observed at the seafloor and through geophysics, and may act as flow pathways for hydrothermal fluids, but we know little about such faults in the subsurface. We present bulk rock geochemistry and stable isotope data for a fault that acted as a hydrothermal upflow zone in a seafloor ultramafic-hosted hydrothermal system in the northern Apennines, Italy. Peridotites were exposed on the seafloor by detachment faulting, intruded by MORB gabbros, and are overlain by MORB lavas and pelagic sediments. North of the village of Reppia are fault shear zones in serpentinite, oriented at a high angle to the detachment surface and extending 300 m below the paleo-seafloor. The paleo-seafloor strikes roughly east-west, dipping 30˚ to the north. At depth the fault zone occurs as an anticlinal form plunging 40˚ to the west. A second fault strikes approximately north-south, with a near vertical dip. The fault rock outcrops as reddish weathered talc + sulfide in 0.1-2 m wide anastomosing bands, with numerous splays. Talc replaces serpentinite in the fault rocks, and the talc rocks are enriched in Si, metals (Fe, Cu, Pb), Light Rare Earth Elements (LREE), have variable Eu anomalies, and have low Mg, Cr and Ni contents. In some cases gabbro dikes are associated with talc-alteration and may have enhanced fluid flow. Sulfide from a fault rock has d34S=5.7‰. The mineralogy and chemistry of the fault rocks indicate that the fault acted as the upflow pathway for high-T black-smoker type fluids. Traverses away from the fault (up to 1 km) and with depth below the seafloor (up to 500 m) reveal variable influences of hydrothermal fluids, but there are no consistent trends with distance. Background serpentinites 500 m beneath the paleoseafloor have LREE depleted trends. Other serpentinites exhibit correlations of LREE with HFSE as the result of melt percolation, but there is significant scatter, and hydrothermal effects include LREE enrichment, positive Eu anomalies, decreased MgO/SiO2, and increases in Sr and Cs. One serpentinite 40 m from the fault has d34S = 4.5‰, consistent with a hydrothermal sulfur source. Far from the fault (1 km) ophicalcites near the paleo-seafloor have negative Ce anomalies indicating seawater alteration, and suggesting a limit to hydrothermal influence on the length scale of 1 km.

Microbial community structure across fluid gradients in the Juan de Fuca Ridge hydrothermal system.

PubMed

Anderson, Rika E; Beltrán, Mónica Torres; Hallam, Steven J; Baross, John A

2013-02-01

Physical and chemical gradients are dominant factors in shaping hydrothermal vent microbial ecology, where archaeal and bacterial habitats encompass a range between hot, reduced hydrothermal fluid and cold, oxidized seawater. To determine the impact of these fluid gradients on microbial communities inhabiting these systems, we surveyed bacterial and archaeal community structure among and between hydrothermal plumes, diffuse flow fluids, and background seawater in several hydrothermal vent sites on the Juan de Fuca Ridge using 16S rRNA gene diversity screening (clone libraries and terminal restriction length polymorphisms) and quantitative polymerase chain reaction methods. Community structure was similar between hydrothermal plumes and background seawater, where a number of taxa usually associated with low-oxygen zones were observed, whereas high-temperature diffuse fluids exhibited a distinct phylogenetic profile. SUP05 and Arctic96BD-19 sulfur-oxidizing bacteria were prevalent in all three mixing regimes where they exhibited overlapping but not identical abundance patterns. Taken together, these results indicate conserved patterns of redox-driven niche partitioning between hydrothermal mixing regimes and microbial communities associated with sinking particles and oxygen-deficient waters. Moreover, the prevalence of SUP05 and Arctic96BD-19 in plume and diffuse flow fluids indicates a more cosmopolitan role for these groups in the ecology and biogeochemistry of the dark ocean. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Fractional Multistage Hydrothermal Liquefaction of Biomass and Catalytic Conversion into Hydrocarbons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cortright, Randy; Rozmiarek, Robert; Dally, Brice

2017-08-31

The objective of this project was to develop an improved multistage process for the hydrothermal liquefaction (HTL) of biomass to serve as a new front-end, deconstruction process ideally suited to feed Virent’s well-proven catalytic technology, which is already being scaled up. This process produced water soluble, partially de-oxygenated intermediates that are ideally suited for catalytic finishing to fungible distillate hydrocarbons. Through this project, Virent, with its partners, demonstrated the conversion of pine wood chips to drop-in hydrocarbon distillate fuels using a multi-stage fractional conversion system that is integrated with Virent’s BioForming® process. The majority of work was in the liquefactionmore » task and included temperature scoping, solvent optimization, and separations.« less

Magmatic-vapor expansion and the formation of high-sulfidation gold deposits: Structural controls on hydrothermal alteration and ore mineralization

USGS Publications Warehouse

Berger, Byron R.; Henley, Richard W.

2011-01-01

High-sulfidation copper–gold lode deposits such as Chinkuashih, Taiwan, Lepanto, Philippines, and Goldfield, Nevada, formed within 1500 m of the paleosurface in volcanic terranes. All underwent an early stage of extensive advanced argillic silica–alunite alteration followed by an abrupt change to spatially much more restricted stages of fracture-controlled sulfide–sulfosalt mineral assemblages and gold–silver mineralization. The alteration as well as ore mineralization stages of these deposits were controlled by the dynamics and history of syn-hydrothermal faulting.At the Sulfate Stage, aggressive advanced argillic alteration and silicification were consequent on the in situ formation of acidic condensate from magmatic vapor as it expanded through secondary fracture networks alongside active faults. The reduction of permeability at this stage due to alteration decreased fluid flow to the surface, and progressively developed a barrier between magmatic-vapor expansion constrained by the active faults and peripheral hydrothermal activity dominated by hot-water flow. In conjunction with the increased rock strength resulting from alteration, subsequent fault-slip inversion in response to an increase in compressional stress generated new, highly permeable fractures localized by the embrittled, altered rock. The new fractures focused magmatic-vapor expansion with much lower heat loss so that condensation occurred. Sulfide Stage sulfosalt, sulfide, and gold–silver deposition then resulted from destabilization of vapor phase metal species due to vapor decompression through the new fracture array. The switch from sulfate to sulfide assemblages is, therefore, a logical consequence of changes in structural permeability due to the coupling of alteration and fracture dynamics rather than to changes in the chemistry of the fluid phase at its magmatic source.

Fracture distribution and porosity in a fault-bound hydrothermal system (Grimsel Pass, Swiss Alps)

NASA Astrophysics Data System (ADS)

Egli, Daniel; Küng, Sulamith; Baumann, Rahel; Berger, Alfons; Baron, Ludovic; Herwegh, Marco

2017-04-01

The spatial distribution, orientation and continuity of brittle and ductile structures strongly control fluid pathways in a rock mass by joining existing pores and creating new pore space (fractures, joints) but can also act as seals to fluid flow (e.g. ductile shear zones, clay-rich fault gouges). In long-lived hydrothermal systems, permeability and the related fluid flow paths are therefore dynamic in space and time. Understanding the evolution and behaviour of naturally porous and permeable rock masses is critical for the successful exploration and sustainable exploitation of hydrothermal systems and can advance methods for planning and implementation of enhanced geothermal systems. This study focuses on an active fault-bound hydrothermal system in the crystalline basement of the Aar Massif (hydrothermal field Grimsel Pass, Swiss Alps) that has been exhumed from few kilometres depth and which documents at least 3 Ma of hydrothermal activity. The explored rock unit of the Aar massif is part of the External Crystalline Massifs that hosts a multitude of thermal springs on its southern border in the Swiss Rhône valley and furthermore represents the exhumed equivalent of potentially exploitable geothermal reservoirs in the deep crystalline subsurface of the northern Alpine foreland basin. This study combines structural data collected from a 125 m long drillhole across the hydrothermal zone, the corresponding drill core and surface mapping. Different methods are applied to estimate the porosity and the structural evolution with regard to porosity, permeability and fracture distribution. Analyses are carried out from the micrometre to decametre scale with main focus on the flow path evolution with time. This includes a large variety of porosity-types including fracture-porosity with up to cm-sized aperture down to grain-scale porosity. Main rock types are granitoid host rocks, mylonites, paleo-breccia and recent breccias. The porosity of the host rock as well as the cemented paleo-hydrothermal breccia is typically very low with values <1%. The high volume of mineralized fractures in the paleo-breccia indicates high porosity in former times, which is today closed by newly developed cements. The preservation of such paleo-breccias allow the investigation of contrasts between the fossil porosity/permeability and the present day active flow path, which is defined by fracture porosity that generally follows the regional deformation pattern and forms a wide network of interconnected fractures of variable orientation.

Synchronized chaotic targeting and acceleration of surface chemistry in prebiotic hydrothermal microenvironments

PubMed Central

Priye, Aashish; Yu, Yuncheng; Hassan, Yassin A.; Ugaz, Victor M.

2017-01-01

Porous mineral formations near subsea alkaline hydrothermal vents embed microenvironments that make them potential hot spots for prebiotic biochemistry. But, synthesis of long-chain macromolecules needed to support higher-order functions in living systems (e.g., polypeptides, proteins, and nucleic acids) cannot occur without enrichment of chemical precursors before initiating polymerization, and identifying a suitable mechanism has become a key unanswered question in the origin of life. Here, we apply simulations and in situ experiments to show how 3D chaotic thermal convection—flows that naturally permeate hydrothermal pore networks—supplies a robust mechanism for focused accumulation at discrete targeted surface sites. This interfacial enrichment is synchronized with bulk homogenization of chemical species, yielding two distinct processes that are seemingly opposed yet synergistically combine to accelerate surface reaction kinetics by several orders of magnitude. Our results suggest that chaotic thermal convection may play a previously unappreciated role in mediating surface-catalyzed synthesis in the prebiotic milieu. PMID:28119504

Subsurface conditions in hydrothermal vents inferred from diffuse flow composition, and models of reaction and transport

NASA Astrophysics Data System (ADS)

Larson, B. I.; Houghton, J. L.; Lowell, R. P.; Farough, A.; Meile, C. D.

2015-08-01

Chemical gradients in the subsurface of mid-ocean ridge hydrothermal systems create an environment where minerals precipitate and dissolve and where chemosynthetic organisms thrive. However, owing to the lack of easy access to the subsurface, robust knowledge of the nature and extent of chemical transformations remains elusive. Here, we combine measurements of vent fluid chemistry with geochemical and transport modeling to give new insights into the under-sampled subsurface. Temperature-composition relationships from a geochemical mixing model are superimposed on the subsurface temperature distribution determined using a heat flow model to estimate the spatial distribution of fluid composition. We then estimate the distribution of Gibb's free energies of reaction beneath mid oceanic ridges and by combining flow simulations with speciation calculations estimate anhydrite deposition rates. Applied to vent endmembers observed at the fast spreading ridge at the East Pacific Rise, our results suggest that sealing times due to anhydrite formation are longer than the typical time between tectonic and magmatic events. The chemical composition of the neighboring low temperature flow indicates relatively uniform energetically favorable conditions for commonly inferred microbial processes such as methanogenesis, sulfate reduction and numerous oxidation reactions, suggesting that factors other than energy availability may control subsurface microbial biomass distribution. Thus, these model simulations complement fluid-sample datasets from surface venting and help infer the chemical distribution and transformations in subsurface flow.

New technology for recyclingmaterials from oily cold rollingmill sludge

NASA Astrophysics Data System (ADS)

Liu, Bo; Zhang, Shen-gen; Tian, Jian-jun; Pan, De-an; Meng, Ling; Liu, Yang

2013-12-01

Oily cold rolling mill (CRM) sludge is one of metallurgical industry solid wastes. The recycle of these wastes can not only protect the environment but also permit their reutilization. In this research, a new process of "hydrometallurgical treatment + hydrothermal synthesis" was investigated for the combined recovery of iron and organic materials from oily CRM sludge. Hydrometallurgical treatment, mainly including acid leaching, centrifugal separation, neutralization reaction, oxidizing, and preparation of hydrothermal reaction precursor, was first utilized for processing the sludge. Then, micaceous iron oxide (MIO) pigment powders were prepared through hydrothermal reaction of the obtained precursor in alkaline media. The separated organic materials can be used for fuel or chemical feedstock. The quality of the prepared MIO pigments is in accordance with the standards of MIO pigments for paints (ISO 10601-2007). This clean, effective, and economical technology offers a new way to recycle oily CRM sludge.

Hydrothermal Processing of Base Camp Solid Wastes To Allow Onsite Recycling

DTIC Science & Technology

2008-09-01

ER D C/ CE R L TR -0 8 -1 3 Hydrothermal Processing of Base Camp Solid Wastes To Allow Onsite Recycling Gary L. Gerdes, Deborah...release; distribution is unlimited. ERDC/CERL TR-08-13 September 2008 Hydrothermal Processing of Base Camp Solid Wastes To Allow Onsite Recycling...a technology to process domestic solid waste using a unique hydrothermal system. The process was successfully demonstrated at Forts Benning and

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

NASA Technical Reports Server (NTRS)

Plumlee, Geoffrey S.; Ridley, W. Ian

1992-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2008-08-01

Hydrothermal alteration at Mount Rainier waxed and waned over the 500,000-year episodic growth of the edifice. Hydrothermal minerals and their stable-isotope compositions in samples collected from outcrop and as clasts from Holocene debris-flow deposits identify three distinct hypogene argillic/advanced argillic hydrothermal environments: magmatic-hydrothermal, steam-heated, and magmatic steam (fumarolic), with minor superimposed supergene alteration. The 3.8 km 3 Osceola Mudflow (5600 y BP) and coeval phreatomagmatic F tephra contain the highest temperature and most deeply formed hydrothermal minerals. Relatively deeply formed magmatic-hydrothermal alteration minerals and associations in clasts include quartz (residual silica), quartz-alunite, quartz-topaz, quartz-pyrophyllite, quartz-dickite/kaolinite, and quartz-illite (all with pyrite). Clasts of smectite-pyrite and steam-heated opal-alunite-kaolinite are also common in the Osceola Mudflow. In contrast, the Paradise lahar, formed by collapse of the summit or near-summit of the edifice at about the same time, contains only smectite-pyrite and near-surface steam-heated and fumarolic alteration minerals. Younger debris-flow deposits on the west side of the volcano (Round Pass and distal Electron Mudflows) contain only low-temperature smectite-pyrite assemblages, whereas the proximal Electron Mudflow and a < 100 y BP rock avalanche on Tahoma Glacier also contain magmatic-hydrothermal alteration minerals that are exposed in the avalanche headwall of Sunset Amphitheater, reflecting progressive incision into deeper near-conduit alteration products that formed at higher temperatures. The pre-Osceola Mudflow alteration geometry is inferred to have consisted of a narrow feeder zone of intense magmatic-hydrothermal alteration limited to near the conduit of the volcano, which graded outward to more widely distributed, but weak, smectite-pyrite alteration within 1 km of the edifice axis, developed chiefly in porous breccias. The edifice was capped by a steam-heated alteration zone, most of which resulted from condensation of fumarolic vapor and oxidation of H 2S in the unsaturated zone above the water table. Weakly developed smectite-pyrite alteration extended into the west and east flanks of the edifice, spatially associated with dikes that are localized in those sectors; other edifice flanks lack dikes and associated alteration. The Osceola collapse removed most of the altered core and upper east flank of the volcano, but intensely altered rocks remain on the uppermost west flank. Major conclusions of this study are that: (1) Hydrothermal-mineral assemblages and distributions at Mount Rainier can be understood in the framework of hydrothermal processes and environments developed from studies of ore deposits formed in analogous settings. (2) Frequent eruptions supplied sufficient hot magmatic fluid to alter the upper interior of the volcano hydrothermally, despite the consistently deep (≥ 8 km) magma reservoir which may have precluded formation of economic mineral deposits within or at shallow depths beneath Mount Rainier. The absence of indicator equilibrium alteration-mineral assemblages in the debris flows that effectively expose the volcano to a depth of 1-1.5 km also suggests a low potential for significant high-sulfidation epithermal or porphyry-type mineral deposits at depth. (3) Despite the long and complex history of the volcano, intensely altered collapse-prone rocks were spatially restricted to near the volcano's conduit system and summit, and short distances onto the upper east and west flanks, due to the necessary supply of reactive components carried by ascending magmatic fluids. (4) Intensely altered rocks were removed from the summit, east flank, and edifice interior by the Osceola collapse, but remain on the upper west flank in the Sunset Amphitheater area and present a continuing collapse hazard. (5) Visually conspicuous rocks on the lower east and mid-to-lower west flanks are not intensely altered and probably have not significantly weakened the rock, and thus do not present significant collapse hazards. (6) Alteration developed most intensely within breccia units, because of their high permeability and porosity. Volcanoes with abundant near-conduit upper-edifice breccias are prone to alteration increasing the possibility of collapse, whereas those that are breccia-poor (e.g., massive domes) are less prone to alteration.

Finding the best windows: An apparent environmental threshold determines which diffuse flows are dominated by subsurface microbes

NASA Astrophysics Data System (ADS)

Olins, H. C.; Rogers, D.; Scholin, C. A.; Preston, C. J.; Vidoudez, C.; Ussler, W.; Pargett, D.; Jensen, S.; Roman, B.; Birch, J. M.; Girguis, P. R.

2014-12-01

Hydrothermal vents are hotspots of microbial primary productivity often described as "windows into the subsurface biosphere." High temperature vents have received the majority of research attention, but cooler diffuse flows are as, if not more, important a source of heat and chemicals to the overlying ocean. We studied patterns of in situ gene expression and co-registered geochemistry in order to 1) describe the diversity and physiological poise of active microbial communities that span thermal and geochemical gradients from active diffuse flow to background vent field seawater, and 2) determine to what extent seawater or subsurface microbes were active throughout this environment. Analyses of multiple metatranscriptomes from 5 geochemically distinct sites (some from samples preserved in situ) show that proximate diffuse flows showed strikingly different transcription profiles. Specifically, caldera background and some diffuse flows were similar, both dominated by seawater-derived Gammaproteobacteria despite having distinct geochemistries. Intra-field community shows evidence of increased primary productivity throughout the entire vent field and not just at individual diffuse flows. In contrast, a more spatially limited, Epsilonproteobacteria-dominated transcription profile from the most hydrothermally-influenced diffuse flow appeared to be driven by the activity of vent-endemic microbes, likely reflecting subsurface microbial activity. We suggest that the microbial activity within many diffuse flow vents is primarily attributable to seawater derived Gammaproteobacterial sulfur oxidizers, while in certain other flows vent-endemic Epsilonproteobactiera are most active. These data reveal a diversity in microbial activity at diffuse flows that has not previously been recognized, and reshapes our thinking about the relative influence that different microbial communities may have on local processes (such as primary production) and potentially global biogeochemical cycles.

Deep-Sea Hydrothermal-Vent Sampler

NASA Technical Reports Server (NTRS)

Behar, Alberto E.; Venkateswaran, Kasthur; Matthews, Jaret B.

2008-01-01

An apparatus is being developed for sampling water for signs of microbial life in an ocean hydrothermal vent at a depth of as much as 6.5 km. Heretofore, evidence of microbial life in deep-sea hydrothermal vents has been elusive and difficult to validate. Because of the extreme conditions in these environments (high pressures and temperatures often in excess of 300 C), deep-sea hydrothermal- vent samplers must be robust. Because of the presumed low density of biomass of these environments, samplers must be capable of collecting water samples of significant volume. It is also essential to prevent contamination of samples by microbes entrained from surrounding waters. Prior to the development of the present apparatus, no sampling device was capable of satisfying these requirements. The apparatus (see figure) includes an intake equipped with a temperature probe, plus several other temperature probes located away from the intake. The readings from the temperature probes are utilized in conjunction with readings from flowmeters to determine the position of the intake relative to the hydrothermal plume and, thereby, to position the intake to sample directly from the plume. Because it is necessary to collect large samples of water in order to obtain sufficient microbial biomass but it is not practical to retain all the water from the samples, four filter arrays are used to concentrate the microbial biomass (which is assumed to consist of particles larger than 0.2 m) into smaller volumes. The apparatus can collect multiple samples per dive and is designed to process a total volume of 10 L of vent fluid, of which most passes through the filters, leaving a total possibly-microbe-containing sample volume of 200 mL remaining in filters. A rigid titanium nose at the intake is used for cooling the sample water before it enters a flexible inlet hose connected to a pump. As the water passes through the titanium nose, it must be cooled to a temperature that is above a mineral-precipitation temperature of 100 C but below the upper working temperature (230 C) of switching valves and tubes in the apparatus. The sample water then passes into a manifold tube, from whence the switching valves can direct the water through either a bypass tube or any one of the filter arrays, without contamination from a previous sample. Each filter array consists of series of filters having pore sizes decreasing in the direction of flow: 90-, 60-, 15-, and 7-micron prefilters and a large-surface-area 0.2-micron collection filter. All the filter taps are located between the intake and the bypass tube so that each time the bypass tube is used, the entire manifold tube is flushed as well.

Cutting through the smoke: the diversity of microorganisms in deep-sea hydrothermal plumes.

PubMed

Djurhuus, Anni; Mikalsen, Svein-Ole; Giebel, Helge-Ansgar; Rogers, Alex D

2017-04-01

There are still notable gaps regarding the detailed distribution of microorganisms between and within insular habitats such as deep-sea hydrothermal vents. This study investigates the community composition of black smoker vent microorganisms in the Southern Hemisphere, and changes thereof along a spatial and chemical gradient ranging from the vent plume to surrounding waters. We sampled two hydrothermal vent fields, one at the South West Indian Ridge (SWIR), the other at the East Scotia Ridge (ESR). Samples were collected across vent fields at varying vertical distances from the origin of the plumes. The microbial data were sequenced on an Illumina MiSeq platform for the 16SrRNA gene. A substantial amount of vent-specific putative chemosynthetic microorganisms were found, particularly in samples from focused hydrothermal venting. Common vent-specific organisms from both vent fields were the genera Arcobacter , Caminibacter and Sulfurimonas from the Epsilonproteobacteria and the SUP05 group from the Gammaproteobacteria. There were no major differences in microbial composition between SWIR and ESR for focused plume samples. However, within the ESR the diffuse flow and focused samples differed significantly in microbial community composition and relative abundance. For Epsilonproteobacteria, we found evidence of niche-specificity to hydrothermal vent environments. This taxon decreased in abundance by three orders of magnitude from the vent orifice to background water. Epsilonproteobacteria distribution followed a distance-decay relationship as vent-effluents mixed with the surrounding seawater. This study demonstrates strong habitat affinity of vent microorganisms on a metre scale with distinct environmental selection.

Understanding Fracturing and Alteration at ODP Borehole 504B: 3D Seismic Structure and Anisotropy of 5.9 Ma Oceanic Crust

NASA Astrophysics Data System (ADS)

Gregory, E. P. M.; Hobbs, R. W.; Peirce, C.; Wilson, D. J.; Zhang, L.

2016-12-01

Faults and fracture networks within the oceanic crust influence the pattern of hydrothermal circulation. This circulation changes the primary composition and structure of the crust as it evolves, particularly the upper crust (layer 2), through the secondary alteration of minerals and the infilling and 'sealing' of cracks. Processes influencing the extent and the depth within the crust of these changes are currently not well known. Alteration can be quantified by observing changes in the seismic velocity structure of the crust, and analysis of seismic anisotropy within the upper crust reveals the nature of ridge-parallel aligned faults and fractures. Here we show a 3D P-wave velocity model and anisotropy maps for 5.9 Ma crust at ODP borehole 504B, situated 200 km south of the Costa Rica Rift, derived from an active-source wide-angle seismic survey in the Panama Basin conducted in 2015. The seismic structure reveals relatively homogeneous, 5 km thick oceanic crust with upper crustal velocity boundaries occurring coincident with alteration fronts observed in 504B. Correlations between basement topography, velocity anomaly and anisotropy indicate that a distinct relationship between hydrothermal alteration, basement ridges, fractures, and the velocity structure of layer 2 exists in this location. A significant difference is seen in the velocity and anisotropic structure between regions to the east and west of the borehole, that correlates with patterns in heat flow observations and indicates that: 1) these two regions of crust have inherited differences in crustal fabric during accretion; and/or 2) different regimes of hydrothermal circulation have been active in each part of the crust as they have aged. This research is part of a major, interdisciplinary NERC-funded research collaboration entitled: Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR).

Soil CO2 emissions as a proxy for heat and mass flow assessment, Taupō Volcanic Zone, New Zealand

USGS Publications Warehouse

Bloomberg, S.; Werner, Cynthia A.; Rissmann, C.F.; Mazot, A.; Horton, Travis B.; Gravley, D; Kennedy, B.; Oze, C

2014-01-01

The quantification of heat and mass flow between deep reservoirs and the surface is important for understanding magmatic and hydrothermal systems. Here, we use high-resolution measurement of carbon dioxide flux (φCO2) and heat flow at the surface to characterize the mass (CO2 and steam) and heat released to the atmosphere from two magma-hydrothermal systems. Our soil gas and heat flow surveys at Rotokawa and White Island in the Taupō Volcanic Zone, New Zealand, include over 3000 direct measurements of φCO2 and soil temperature and 60 carbon isotopic values on soil gases. Carbon dioxide flux was separated into background and magmatic/hydrothermal populations based on the measured values and isotopic characterization. Total CO2 emission rates (ΣCO2) of 441 ± 84 t d−1 and 124 ± 18 t d−1were calculated for Rotokawa (2.9 km2) and for the crater floor at White Island (0.3 km2), respectively. The total CO2 emissions differ from previously published values by +386 t d−1 at Rotokawa and +25 t d−1 at White Island, demonstrating that earlier research underestimated emissions by 700% (Rotokawa) and 25% (White Island). These differences suggest that soil CO2 emissions facilitate more robust estimates of the thermal energy and mass flux in geothermal systems than traditional approaches. Combining the magmatic/hydrothermal-sourced CO2 emission (constrained using stable isotopes) with reservoir H2O:CO2mass ratios and the enthalpy of evaporation, the surface expression of thermal energy release for the Rotokawa hydrothermal system (226 MWt) is 10 times greater than the White Island crater floor (22.5 MWt).

Discovery Of An Extensive Hydrothermal Sulfide/Sulfate Mounds Field In East Diamante Caldera, Mariana Volcanic Arc

NASA Astrophysics Data System (ADS)

Hein, J. R.; de Ronde, C. E.; Ditchburn, R.; Leybourne, M. I.; Tamura, Y.; Stern, R. J.; Conrad, T. A.; Nichols, A. R.; Shukuno, H.; Embley, R. W.; Bloomer, S. H.; Ishizuka, O.; Hirahara, Y.; Senda, R.; Nunokawa, A.; Jordan, E.; Wada, I.

2010-12-01

An elongate field of hydrothermal mounds was discovered along the NE flank of a cluster of resurgent dacite domes in East Diamante Caldera using the ROV Hyper-Dolphin aboard the R.V. Natsushima in June 2009 and July 2010. East Diamante seamount lies about 80 km north of Saipan and is the northernmost volcano of the Southern Seamount Province of the Mariana magmatic arc. East Diamante is an irregular caldera about 10 km x 4 km that is breached on the north and south sides. The caldera floor has a maximum water depth of about 700 m. After caldera collapse, dacitic domes intruded into the center of the caldera providing the heat source for production and circulation of hydrothermal fluids that generated the large mounds field and two nearby chimney fields, one active and one inactive, found in 2004 during a NOAA Ring-of-Fire cruise. The mounds field is more than 100 m long and about 25-30 m wide and occurs along a NE-SW rift valley at water depths of about 365-400 m b.s.l. Individual hydrothermal mounds and ridges along this trend vary in size and the bases of the mounds are buried beneath hydrothermal sediment so that only minimum dimensions can be determined. Mounds are typically 1-3 m tall and 0.5-2 m wide, with lengths of about 3 to more than 5 m. The sulfide/sulfate mounds are layered and an iron- and manganese-oxide subsidiary mound venting low-temperature fluids caps some of them. Some mounds also support inactive sulfide/sulfate chimneys and spires; chimneys rarely occur as independent structures within the mounds field. The mounds are composed primarily of barite layers and sphalerite (high cadmium, low iron) plus galena layers with up to 470 ppm silver and 3 ppm gold. The subsidiary mounds are composed of 7A manganate and goethite that occur around a delicate network of 2-10 mm diameter anastomosing channels. Similar oxides cover the seabed throughout the mounds field and precipitated from diffuse fluid flow throughout the region, but formed by both diffuse and focused flow on top of the layered mounds. Several age dates for one mound show the layered section to have formed about 4,000 years ago while the subsidiary oxides formed during the past 4 years. Mineralization appears to be controlled by proximity to the NE-SW rift or fracture zone. Focused flow occurred along a line source rather than a point source that is typical of most hydrothermal chimney fields. Diffuse flow occurred adjacent to the rift and through the sulfide/sulfate mounds deposited atop the conduit. This field may be in a waning stage of activity with higher temperature fluids having been involved in construction of the main mounds several millennia ago. Alternatively, the present low-temperature activity may represent rejuvenation of the system.

Genifuel Hydrothermal Processing Bench Scale Technology Evaluation Project (WE&RF Report LIFT6T14)

EPA Science Inventory

Hydrothermal Liquefaction (HTL) and Catalytic Hydrothermal Gasification (CHG) proof-of-concept bench-scale tests were performed to assess the potential of the Genifuel hydrothermal process technology for handling municipal wastewater sludge. HTL tests were conducted at 300-350◦C ...

In Search for Diffuse Hydrothermal Venting at North Pond, Western Flank of the Mid-Atlantic-Ridge

NASA Astrophysics Data System (ADS)

Villinger, H. W.; Becker, K.; Hulme, S.; Kaul, N. E.; Müller, P.; Wheat, C. G.

2015-12-01

We present results from temperature measurements made with a ROV temperature lance in sediments deposited on the slopes of abyssal hills and small basins surrounding North Pond. North Pond is a ~8x15 km large sediment basin located on ~7 Ma year old crust west of the Mid-Atlantic Ridge at 23°N. Data were collected with the ROV Jason II during cruise MSM37 on the German RV Maria S. Merian in April 2014. The temperature lance consists of a 60 cm long stainless steel tube (o.d. 12 mm) housing 8 thermistors with a spacing of 80 mm, resulting in an active length of 56 cm. Data are logged with an 8-channel data logger (XR-420-T8, RBR, Ottawa) and transmitted online to the control van of the ROV. Data reduction and temperature gradient calculation is done according to the HFRED algorithm (Villinger & Davis, 1987). 90 sites in total were visited, 88 gave good data for temperature gradient calculation. Calculated gradients are usually of good to very good quality. The gradients vary between less than 20 to more than 1000 mK/m reflecting the very heterogeneous distribution of geothermal heat flow. The expected conductive lithospheric heat flow for North Pond is ~190 mW/m2 (geothermal gradient of ~190 mK/m with a thermal conductivity of 1 W/Km). The highest temperature gradients are measured in places where temperature ~50 cm below the sediment-water boundary exceeds bottom water temperature by ~0.5 K . These high temperature gradients may reflect local hydrothermal circulation within the pillow lavas, however no focused discharge was detected. The analysis of temperature measurements made with the ROV-mounted CTD shows clearly detectable bottom water temperature anomalies. We infer that they are either caused by hydrothermal discharge through the thin sediment cover or through unsedimented pillow basalts nearby. Hydrothermal circulation in a North-Pond-like environment appears to be diffuse in nature, hence very difficult if not impossible to detect and to quantify.

Anhydrite precipitation in seafloor hydrothermal systems

NASA Astrophysics Data System (ADS)

Theissen-Krah, Sonja; Rüpke, Lars H.

2016-04-01

The composition and metal concentration of hydrothermal fluids venting at the seafloor is strongly temperature-dependent and fluids above 300°C are required to transport metals to the seafloor (Hannington et al. 2010). Ore-forming hydrothermal systems and high temperature vents in general are often associated with faults and fracture zones, i.e. zones of enhanced permeabilities that act as channels for the uprising hydrothermal fluid (Heinrich & Candela, 2014). Previous numerical models (Jupp and Schultz, 2000; Andersen et al. 2015) however have shown that high permeabilities tend to decrease fluid flow temperatures due to mixing with cold seawater and the resulting high fluid fluxes that lead to short residence times of the fluid near the heat source. A possible mechanism to reduce the permeability and thereby to focus high temperature fluid flow are mineral precipitation reactions that clog the pore space. Anhydrite for example precipitates from seawater if it is heated to temperatures above ~150°C or due to mixing of seawater with hydrothermal fluids that usually have high Calcium concentrations. We have implemented anhydrite reactions (precipitation and dissolution) in our finite element numerical models of hydrothermal circulation. The initial results show that the precipitation of anhydrite efficiently alters the permeability field, which affects the hydrothermal flow field as well as the resulting vent temperatures. C. Andersen et al. (2015), Fault geometry and permeability contrast control vent temperatures at the Logatchev 1 hydrothermal field, Mid-Atlantic Ridge, Geology, 43(1), 51-54. M. D. Hannington et al. (2010), Modern Sea-Floor Massive Sulfides and Base Metal Resources: Toward an Estimate of Global Sea-Floor Massive Sulfide Potential, in The Challenge of Finding New Mineral Resources: Global Metallogeny, Innovative Exploration, and New Discoveries, edited by R. J. Goldfarb, E. E. Marsh and T. Monecke, pp. 317-338, Society of Economic Geologists. Heinrich, C. A., and P. A. Candela (2014), 13.1 - Fluids and Ore Formation in the Earth's Crust, in Treatise on Geochemistry (Second Edition), edited by H. D. Holland and K. K. Turekian, pp. 1-28, Elsevier, Oxford. Jupp, T., and A. Schultz (2000), A thermodynamic explanation for black smoker temperatures, Nature, 403(6772), 880-883.

Interpretation of Ground Temperature Anomalies in Hydrothermal Discharge Areas

NASA Astrophysics Data System (ADS)

Price, A. N.; Lindsey, C.; Fairley, J. P., Jr.

2017-12-01

Researchers have long noted the potential for shallow hydrothermal fluids to perturb near-surface temperatures. Several investigators have made qualitative or semi-quantitative use of elevated surface temperatures; for example, in snowfall calorimetry, or for tracing subsurface flow paths. However, little effort has been expended to develop a quantitative framework connecting surface temperature observations with conditions in the subsurface. Here, we examine an area of shallow subsurface flow at Burgdorf Hot Springs, in the Payette National Forest, north of McCall, Idaho USA. We present a simple analytical model that uses easily-measured surface data to infer the temperatures of laterally-migrating shallow hydrothermal fluids. The model is calibrated using shallow ground temperature measurements and overburden thickness estimates from seismic refraction studies. The model predicts conditions in the shallow subsurface, and suggests that the Biot number may place a more important control on the expression of near-surface thermal perturbations than previously thought. In addition, our model may have application in inferring difficult-to-measure parameters, such as shallow subsurface discharge from hydrothermal springs.

An approach to modeling coupled thermal-hydraulic-chemical processes in geothermal systems

USGS Publications Warehouse

Palguta, Jennifer; Williams, Colin F.; Ingebritsen, Steven E.; Hickman, Stephen H.; Sonnenthal, Eric

2011-01-01

Interactions between hydrothermal fluids and rock alter mineralogy, leading to the formation of secondary minerals and potentially significant physical and chemical property changes. Reactive transport simulations are essential for evaluating the coupled processes controlling the geochemical, thermal and hydrological evolution of geothermal systems. The objective of this preliminary investigation is to successfully replicate observations from a series of hydrothermal laboratory experiments [Morrow et al., 2001] using the code TOUGHREACT. The laboratory experiments carried out by Morrow et al. [2001] measure permeability reduction in fractured and intact Westerly granite due to high-temperature fluid flow through core samples. Initial permeability and temperature values used in our simulations reflect these experimental conditions and range from 6.13 × 10−20 to 1.5 × 10−17 m2 and 150 to 300 °C, respectively. The primary mineralogy of the model rock is plagioclase (40 vol.%), K-feldspar (20 vol.%), quartz (30 vol.%), and biotite (10 vol.%). The simulations are constrained by the requirement that permeability, relative mineral abundances, and fluid chemistry agree with experimental observations. In the models, the granite core samples are represented as one-dimensional reaction domains. We find that the mineral abundances, solute concentrations, and permeability evolutions predicted by the models are consistent with those observed in the experiments carried out by Morrow et al. [2001] only if the mineral reactive surface areas decrease with increasing clay mineral abundance. This modeling approach suggests the importance of explicitly incorporating changing mineral surface areas into reactive transport models.

Geologic and hydrologic controls on the economic potential of hydrothermal systems associated with upper crustal plutons

NASA Astrophysics Data System (ADS)

Weis, Philipp; Driesner, Thomas; Scott, Samuel; Lecumberri-Sanchez, Pilar

2016-04-01

Heat and mass transport in hydrothermal systems associated with upper crustal magmatic intrusions can result in resources with large economic potential (Kesler, 1994). Active hydrothermal systems can form high-enthalpy geothermal reservoirs with the possibility for renewable energy production. Fossil continental or submarine hydrothermal systems may have formed ore deposits at variable crustal depths, which can be mined near today's surface with an economic profit. In both cases, only the right combination of first-order geologic and hydrologic controls may lead to the formation of a significant resource. To foster exploration for these hydrothermal georesources, we need to improve our understanding of subsurface fluxes of mass and energy by combining numerical process modelling, observations at both active and fossil systems, as well as knowledge of fluid and rock properties and their interactions in natural systems. The presentation will highlight the role of non-linear fluid properties, phase separation, salt precipitation, fluid mixing, permeability structure, hydraulic fracturing and the transition from brittle to ductile rock behavior as major geologic and hydrologic controls on the formation of high-enthalpy and supercritical geothermal resources (Scott et al., 2015), and magmatic-hydrothermal mineral resources, such as porphyry copper, massive sulfide and epithermal gold deposits (Lecumberri-Sanchez et al., 2015; Weis, 2015). References: Kesler, S. E., 1994: Mineral Resources, economics and the environment, New York, McMillan, 391. Lecumberri-Sanchez, P., Steele-MacInnis, M., Weis, P., Driesner, T., Bodnar, R.J. (2015): Salt precipitation in magmatic-hydrothermal systems associated with upper crustal plutons. Geology, v. 43, p. 1063-1066, doi:10.1130/G37163.1 Scott, S., Driesner, T., Weis, P. (2015): Geologic controls on supercritical geothermal resources above magmatic intrusions. Nature Communications, 6:7837 doi: 10.1038/ncomms8837 Weis, P. (2015): The dynamic interplay between saline fluid flow and rock permeability in magmatic-hydrothermal systems. Geofluids, 15, 350-371.

Multispectral Imaging Broadens Cellular Analysis

NASA Technical Reports Server (NTRS)

2007-01-01

Amnis Corporation, a Seattle-based biotechnology company, developed ImageStream to produce sensitive fluorescence images of cells in flow. The company responded to an SBIR solicitation from Ames Research Center, and proposed to evaluate several methods of extending the depth of field for its ImageStream system and implement the best as an upgrade to its commercial products. This would allow users to view whole cells at the same time, rather than just one section of each cell. Through Phase I and II SBIR contracts, Ames provided Amnis the funding the company needed to develop this extended functionality. For NASA, the resulting high-speed image flow cytometry process made its way into Medusa, a life-detection instrument built to collect, store, and analyze sample organisms from erupting hydrothermal vents, and has the potential to benefit space flight health monitoring. On the commercial end, Amnis has implemented the process in ImageStream, combining high-resolution microscopy and flow cytometry in a single instrument, giving researchers the power to conduct quantitative analyses of individual cells and cell populations at the same time, in the same experiment. ImageStream is also built for many other applications, including cell signaling and pathway analysis; classification and characterization of peripheral blood mononuclear cell populations; quantitative morphology; apoptosis (cell death) assays; gene expression analysis; analysis of cell conjugates; molecular distribution; and receptor mapping and distribution.

Template-free synthesis of ZnWO{sub 4} powders via hydrothermal process in a wide pH range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hojamberdiev, Mirabbos, E-mail: mirabbos_uz@yahoo.com; Zhu, Gangqiang; Xu, Yunhua

ZnWO{sub 4} powders with different morphologies were fabricated through a template-free hydrothermal method at 180 {sup o}C for 8 h in a wide pH range. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible and luminescence spectrophotometers were applied to study the effects of pH values on crystallinity, morphology, optical and luminescence properties. The XRD results showed that the WO{sub 3} + ZnWO{sub 4}, ZnWO{sub 4}, and ZnO phases could form after hydrothermal processing at 180 {sup o}C for 8 h with the pH values of 1, 3-11, and 13, respectively. The SEM and TEM observation revealedmore » that the morphological transformation of ZnWO{sub 4} powders occurred with an increase in pH values as follows: star anise-, peony-, and desert rose-like microstructures and soya bean- and rod-like nanostructures. The highest luminescence intensity was found to be in sample consisting of star anise-like crystallites among all the samples due to the presence of larger particles with high crystallinity resulted from the favorable pH under the current hydrothermal conditions.« less

Influence of sward maturity and pre-conditioning temperature on the energy production from grass silage through the integrated generation of solid fuel and biogas from biomass (IFBB): 2. Properties of energy carriers and energy yield.

PubMed

Richter, F; Fricke, T; Wachendorf, M

2011-04-01

In order to determine influencing parameters on energy production of the IFBB process, herbage from a lowland hay meadow (Arrhenaterion) was sampled and ensiled at eight dates between 27 April and 21 June 2007. The silage from each date was processed in six IFBB treatments with and without hydrothermal conditioning at different temperatures. Methane yields and higher heating values were determined and an energy balance was calculated with whole-crop digestion (WCD) of the silage as reference system. Maximum net energy yields were 10.2 MWh ha(-1) for the IFBB treatment without hydrothermal conditioning and 9.0 MWh ha(-1) for the treatment with hydrothermal conditioning at 50 °C. WCD achieved a maximum net energy yield of 3.7 MWh ha(-1). Energy conversion efficiency ranged from 0.24 to 0.54 and was predicted with high accuracy by temperature of hydrothermal conditioning as well as concentration of neutral detergent fibre and dry matter in the silage (R(2)=0.90). Copyright © 2011 Elsevier Ltd. All rights reserved.

A novel microbial habitat in the mid-ocean ridge subseafloor

PubMed Central

Summit, Melanie; Baross, John A.

2001-01-01

The subseafloor at the mid-ocean ridge is predicted to be an excellent microbial habitat, because there is abundant space, fluid flow, and geochemical energy in the porous, hydrothermally influenced oceanic crust. These characteristics also make it a good analog for potential subsurface extraterrestrial habitats. Subseafloor environments created by the mixing of hot hydrothermal fluids and seawater are predicted to be particularly energy-rich, and hyperthermophilic microorganisms that broadly reflect such predictions are ejected from these systems in low-temperature (≈15°C), basalt-hosted diffuse effluents. Seven hyperthermophilic heterotrophs isolated from low-temperature diffuse fluids exiting the basaltic crust in and near two hydrothermal vent fields on the Endeavour Segment, Juan de Fuca Ridge, were compared phylogenetically and physiologically to six similarly enriched hyperthermophiles from samples associated with seafloor metal sulfide structures. The 13 organisms fell into four distinct groups: one group of two organisms corresponding to the genus Pyrococcus and three groups corresponding to the genus Thermococcus. Of these three groups, one was composed solely of sulfide-derived organisms, and the other two related groups were composed of subseafloor organisms. There was no evidence of restricted exchange of organisms between sulfide and subseafloor habitats, and therefore this phylogenetic distinction indicates a selective force operating between the two habitats. Hypotheses regarding the habitat differences were generated through comparison of the physiology of the two groups of hyperthermophiles; some potential differences between these habitats include fluid flow stability, metal ion concentrations, and sources of complex organic matter. PMID:11226209

Chemical, isotopic, and dissolved gas compositions of the hydrothermal system in Twin Falls and Jerome counties, Idaho

USGS Publications Warehouse

Mariner, R.H.; Young, H.W.; Evans, W. E.; Parliman, D.J.

1991-01-01

The chemical, isotopic, and gas compositions of the hydrothermal system in Twin Falls and Jerome counties, Idaho, change systematically as the water moves northward from the Idaho-Nevada boundary toward the Snake River. Sodium, chloride, fluoride, alkalinity, dissolved helium, and carbon-13 increase as calcium and carbon-14 decrease. Water-rock reactions may result in dissolution of plagioclase or volcanic glass and calcite, followed by precipitation of zeolites and clays. On the basis of carbon-14 age dating, apparent water ages range from 2,000 to more than 26,000 years; most apparent ages range from about 4,000 to 10,000 years. The older waters, north of the Snake River, are isotopically depleted in deuterium and are enriched in chloride relative to waters to the south. Thermal waters flowing northward beneath the Snake River may join a westward flow of older thermal water slightly north of the river. The direction of flow in the hydrothermal system seems to parallel the surface drainage.

Computational Fluid Dynamics simulation of hydrothermal liquefaction of microalgae in a continuous plug-flow reactor.

PubMed

Ranganathan, Panneerselvam; Savithri, Sivaraman

2018-06-01

Computational Fluid Dynamics (CFD) technique is used in this work to simulate the hydrothermal liquefaction of Nannochloropsis sp. microalgae in a lab-scale continuous plug-flow reactor to understand the fluid dynamics, heat transfer, and reaction kinetics in a HTL reactor under hydrothermal condition. The temperature profile in the reactor and the yield of HTL products from the present simulation are obtained and they are validated with the experimental data available in the literature. Furthermore, the parametric study is carried out to study the effect of slurry flow rate, reactor temperature, and external heat transfer coefficient on the yield of products. Though the model predictions are satisfactory in comparison with the experimental results, it still needs to be improved for better prediction of the product yields. This improved model will be considered as a baseline for design and scale-up of large-scale HTL reactor. Copyright © 2018 Elsevier Ltd. All rights reserved.

Modelling of hydrothermal fluid flow and structural architecture in an extensional basin, Ngakuru Graben, Taupo Rift, New Zealand

NASA Astrophysics Data System (ADS)

Kissling, W. M.; Villamor, P.; Ellis, S. M.; Rae, A.

2018-05-01

Present-day geothermal activity on the margins of the Ngakuru graben and evidence of fossil hydrothermal activity in the central graben suggest that a graben-wide system of permeable intersecting faults acts as the principal conduit for fluid flow to the surface. We have developed numerical models of fluid and heat flow in a regional-scale 2-D cross-section of the Ngakuru Graben. The models incorporate simplified representations of two 'end-member' fault architectures (one symmetric at depth, the other highly asymmetric) which are consistent with the surface locations and dips of the Ngakuru graben faults. The models are used to explore controls on buoyancy-driven convective fluid flow which could explain the differences between the past and present hydrothermal systems associated with these faults. The models show that the surface flows from the faults are strongly controlled by the fault permeability, the fault system architecture and the location of the heat source with respect to the faults in the graben. In particular, fault intersections at depth allow exchange of fluid between faults, and the location of the heat source on the footwall of normal faults can facilitate upflow along those faults. These controls give rise to two distinct fluid flow regimes in the fault network. The first, a regular flow regime, is characterised by a nearly unchanging pattern of fluid flow vectors within the fault network as the fault permeability evolves. In the second, complex flow regime, the surface flows depend strongly on fault permeability, and can fluctuate in an erratic manner. The direction of flow within faults can reverse in both regimes as fault permeability changes. Both flow regimes provide insights into the differences between the present-day and fossil geothermal systems in the Ngakuru graben. Hydrothermal upflow along the Paeroa fault seems to have occurred, possibly continuously, for tens of thousands of years, while upflow in other faults in the graben has switched on and off during the same period. An asymmetric graben architecture with the Paeroa being the major boundary fault will facilitate the predominant upflow along this fault. Upflow on the axial faults is more difficult to explain with this modelling. It occurs most easily with an asymmetric graben architecture and heat sources close to the graben axis (which could be associated with remnant heat from recent eruptions from Okataina Volcanic Centre). Temporal changes in upflow can also be associated with acceleration and deceleration of fault activity if this is considered a proxy for fault permeability. Other explanations for temporal variations in hydrothermal activity not explored here are different permeability on different faults, and different permeability along fault strike.

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

USGS Publications Warehouse

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

2012-01-01

Carbon dioxide emissions and heat flow have been determined from the Ohaaki hydrothermal field, Taupo Volcanic Zone (TVZ), New Zealand following 20a of production (116MW e). Soil CO2 degassing was quantified with 2663 CO2 flux measurements using the accumulation chamber method, and 2563 soil temperatures were measured and converted to equivalent heat flow (Wm -2) using published soil temperature heat flow functions. Both CO2 flux and heat flow were analysed statistically and then modelled using 500 sequential Gaussian simulations. Forty subsoil CO 2 gas samples were also analysed for stable C isotopes. Following 20a of production, current CO2 emissions equated to 111??6.7T/d. Observed heat flow was 70??6.4MW, compared with a pre-production value of 122MW. This 52MW reduction in surface heat flow is due to production-induced drying up of all alkali-Cl outflows (61.5MW) and steam-heated pools (8.6MW) within the Ohaaki West thermal area (OHW). The drying up of all alkali-Cl outflows at Ohaaki means that the soil zone is now the major natural pathway of heat release from the high-temperature reservoir. On the other hand, a net gain in thermal ground heat flow of 18MW (from 25MW to 43.3??5MW) at OHW is associated with permeability increases resulting from surface unit fracturing by production-induced ground subsidence. The Ohaaki East (OHE) thermal area showed no change in distribution of shallow and deep soil temperature contours despite 20a of production, with an observed heat flow of 26.7??3MW and a CO 2 emission rate of 39??3T/d. The negligible change in the thermal status of the OHE thermal area is attributed to the low permeability of the reservoir beneath this area, which has limited production (mass extraction) and sheltered the area from the pressure decline within the main reservoir. Chemistry suggests that although alkali-Cl outflows once contributed significantly to the natural surface heat flow (~50%) they contributed little (<1%) to pre-production CO 2 emissions due to the loss of >99% of the original CO 2 content due to depressurisation and boiling as the fluids ascended to the surface. Consequently, the soil has persisted as the major (99%) pathway of CO 2 release to the atmosphere from the high temperature reservoir at Ohaaki. The CO 2 flux and heat flow surveys indicate that despite 20a of production the variability in location, spatial extent and magnitude of CO 2 flux remains consistent with established geochemical and geophysical models of the Ohaaki Field. At both OHW and OHE carbon isotopic analyses of soil gas indicate a two-stage fractionation process for moderate-flux (>60gm -2d -1) sites; boiling during fluid ascent within the underlying reservoir and isotopic enrichment as CO 2 diffuses through porous media of the soil zone. For high-flux sites (>300gm -2d -1), the ?? 13CO 2 signature (-7.4??0.3??? OHW and -6.5??0.6??? OHE) is unaffected by near-surface (soil zone) fractionation processes and reflects the composition of the boiled magmatic CO 2 source for each respective upflow. Flux thresholds of <30gm -2d -1 for purely diffusive gas transport, between 30 and 300gm -2d -1 for combined diffusive-advective transport, and ???300gm -2d -1 for purely advective gas transport at Ohaaki were assigned. ?? 13CO 2 values and cumulative probability plots of CO 2 flux data both identified a threshold of ~15gm -2d -1 by which background (atmospheric and soil respired) CO 2 may be differentiated from hydrothermal CO 2. ?? 2011 Elsevier Ltd.

Heat flow in relation to hydrothermal activity in the southern Black Rock Desert, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sass, J.H.; Zoback, M.L.; Galanis, S.P. Jr.

1979-01-01

As part of an investigation of the Gerlach NE KGRA (Known Geothermal Resource Area) a number of heat-flow measurements were made in playa sediments of the southern Black Rock Desert, northwestern Nevada. These data together with additional previously unpublished heat-flow values reveal a complex pattern of heat flow with values ranging between 1.0 to 5.0 HFU (40 to 100 mWm/sup -2/) outside of the hot springs area. The mean heat flow for the 13 reported sites in the southern Black Rock Desert is 1.8 +- 0.15 HFU (75 +- 6 mWm/sup -2/). The complexity of the pattern of heat flowmore » is believed to arise from hydrothermal circulation supporting the numerous hot springs throughout the region. The fact that the lowest observed heat flow occurs in the deepest part of the basin strongly suggests that fluid movement within the basin represents part of the recharge for the hydrothermal system. A thermal balance for the system incorporating both anomalous conductive heat loss and convective heat loss from the spring systems indicate a total energy loss of about 8.0 Mcal/sec or 34 megawatts over an estimated 1000 km/sup 2/ region. Consideration of this additional heat loss yields a mean regional heat flow of 2.5 + HFU (100 + mWm/sup -2/) and warrants inclusion of this region in the Battle Mountain heat-flow high (Lachenbruch and Sass, 1977, 1978).« less

Methane- and Hydrogen-Influenced Microbial Communities in Hydrothermal Plumes above the Atlantis Massif, Mid Atlantic Ridge

NASA Astrophysics Data System (ADS)

Stewart, C. L.; Schrenk, M.

2017-12-01

Ultramafic-hosted hydrothermal systems associated with slow-spreading mid ocean ridges emit copious amounts of hydrogen and methane into the deep-sea, generated through a process known as serpentinization. Hydrothermal plumes carrying the reduced products of water-rock interaction dissipate and mix with deep seawater, and potentially harbor microbial communities adapted to these conditions. Methane and hydrogen enriched hydrothermal plumes were sampled from 3 sites near the Atlantis Massif (30°N, Mid Atlantic Ridge) during IODP Expedition 357 and used to initiate cultivation experiments targeting methanotrophic and hydrogenotrophic microorganisms. One set of experiments incubated the cultures at in situ hydrostatic pressures and gas concentrations resulting in the enrichment of gammaproteobacterial assemblages, including Marinobacter spp. That may be involved in hydrocarbon degradation. A second set of experiments pursued the anaerobic enrichment of microbial communities on solid media, resulting in the enrichment of alphaproteobacteria related to Ruegeria. The most prodigious growth in both case occurred in methane-enriched media, which may play a role as both an energy and carbon source. Ongoing work is evaluating the physiological characteristics of these isolates, including their metabolic outputs under different physical-chemical conditions. In addition to providing novel isolates from hydrothermal habitats near the Lost City Hydrothermal Field, these experiments will provide insight into the ecology of microbial communities from serpentinization influenced hydrothermal systems that may aid in future exploration of these sites.

Recovery Act. Development and Validation of an Advanced Stimulation Prediction Model for Enhanced Geothermal System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gutierrez, Marte

The research project aims to develop and validate an advanced computer model that can be used in the planning and design of stimulation techniques to create engineered reservoirs for Enhanced Geothermal Systems. The specific objectives of the proposal are to: 1) Develop a true three-dimensional hydro-thermal fracturing simulator that is particularly suited for EGS reservoir creation. 2) Perform laboratory scale model tests of hydraulic fracturing and proppant flow/transport using a polyaxial loading device, and use the laboratory results to test and validate the 3D simulator. 3) Perform discrete element/particulate modeling of proppant transport in hydraulic fractures, and use the resultsmore » to improve understand of proppant flow and transport. 4) Test and validate the 3D hydro-thermal fracturing simulator against case histories of EGS energy production. 5) Develop a plan to commercialize the 3D fracturing and proppant flow/transport simulator. The project is expected to yield several specific results and benefits. Major technical products from the proposal include: 1) A true-3D hydro-thermal fracturing computer code that is particularly suited to EGS, 2) Documented results of scale model tests on hydro-thermal fracturing and fracture propping in an analogue crystalline rock, 3) Documented procedures and results of discrete element/particulate modeling of flow and transport of proppants for EGS applications, and 4) Database of monitoring data, with focus of Acoustic Emissions (AE) from lab scale modeling and field case histories of EGS reservoir creation.« less

Recovery Act. Development and Validation of an Advanced Stimulation Prediction Model for Enhanced Geothermal Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gutierrez, Marte

2013-12-31

This research project aims to develop and validate an advanced computer model that can be used in the planning and design of stimulation techniques to create engineered reservoirs for Enhanced Geothermal Systems. The specific objectives of the proposal are to; Develop a true three-dimensional hydro-thermal fracturing simulator that is particularly suited for EGS reservoir creation; Perform laboratory scale model tests of hydraulic fracturing and proppant flow/transport using a polyaxial loading device, and use the laboratory results to test and validate the 3D simulator; Perform discrete element/particulate modeling of proppant transport in hydraulic fractures, and use the results to improve understandmore » of proppant flow and transport; Test and validate the 3D hydro-thermal fracturing simulator against case histories of EGS energy production; and Develop a plan to commercialize the 3D fracturing and proppant flow/transport simulator. The project is expected to yield several specific results and benefits. Major technical products from the proposal include; A true-3D hydro-thermal fracturing computer code that is particularly suited to EGS; Documented results of scale model tests on hydro-thermal fracturing and fracture propping in an analogue crystalline rock; Documented procedures and results of discrete element/particulate modeling of flow and transport of proppants for EGS applications; and Database of monitoring data, with focus of Acoustic Emissions (AE) from lab scale modeling and field case histories of EGS reservoir creation.« less

Ongoing hydrothermal heat loss from the 1912 ash-flow sheet, Valley of Ten Thousand Smokes, Alaska

USGS Publications Warehouse

Hogeweg, N.; Keith, T.E.C.; Colvard, E.M.; Ingebritsen, S.E.

2005-01-01

The June 1912 eruption of Novarupta filled nearby glacial valleys on the Alaska Peninsula with ash-flow tuff (ignimbrite), and post-eruption observations of thousands of steaming fumaroles led to the name 'Valley of Ten Thousand Smokes' (VTTS). By the late 1980s most fumarolic activity had ceased, but the discovery of thermal springs in mid-valley in 1987 suggested continued cooling of the ash-flow sheet. Data collected at the mid-valley springs between 1987 and 2001 show a statistically significant correlation between maximum observed chloride (Cl) concentration and temperature. These data also show a statistically significant decline in the maximum Cl concentration. The observed variation in stream chemistry across the sheet strongly implies that most solutes, including Cl, originate within the area of the VTTS occupied by the 1912 deposits. Numerous measurements of Cl flux in the Ukak River just below the ash-flow sheet suggest an ongoing heat loss of ???250 MW. This represents one of the largest hydrothermal heat discharges in North America. Other hydrothermal discharges of comparable magnitude are related to heat obtained from silicic magma bodies at depth, and are quasi-steady on a multidecadal time scale. However, the VTTS hydrothermal flux is not obviously related to a magma body and is clearly declining. Available data provide reasonable boundary and initial conditions for simple transient modeling. Both an analytical, conduction-only model and a numerical model predict large rates of heat loss from the sheet 90 years after deposition.

Hydrothermal Rock-Fluid Interactions in 15-year-old Submarine Basaltic Tuff at Surtsey Volcano, Iceland

NASA Astrophysics Data System (ADS)

Jackson, M. D.; Couper, S.; Li, Y.; Stan, C. V.; Tamura, N.; Stefansson, A.; Moore, J. G.; Wenk, H. R.

2016-12-01

Basaltic tephra at Surtsey volcano, produced by 1963-1967 eruptions in the offshore SE Icelandic rift zone, record the complex interplay of factors that determine rates of palagonitization and crystallization of authigenic minerals in seafloor basalts worldwide. We investigate how formation of nanocrystalline clay mineral in fresh sideromelane glass influenced crystallization of mineral cements in submarine tuff from a 181 m core drilled in 1979. Synchrotron-based microdiffraction and microfluorescence maps (2x5 µm X-ray beam spot size) at beamline 12.3.2, Advanced Light Source, SEM-EDS compositional analyses, and fluid geochemical models compare processes in lapilli-sized glass fragments, vitric cementing matrix, and fine ash accretions. In lapilli at 137.9 m (100°C), nanocrystalline clay mineral in gel-palagonite has asymetric 14.9-12.6 Å (001) reflections, with Fe and Ti enrichment relative to Si, Al and Ca, compared with adjacent sideromelane. Neighboring fibro-palagonite has symmetric (001) and greater Fe and Ti enrichment. Al-tobermorite, a rare calcium-silicate-hydrate, crystallized in nearby vesicles. The 11.30-11.49 Å (002) interlayer and Ca/(Si+Al) ratio of 0.9-1.0 record release of Si, Al, and Ca in a chemical system relatively isolated from submarine hydrothermal fluid flow. In vitric matrix relatively open to fluid flow, however, phillipsite zeolite cement predominates. Al-tobermorite formed at 88.45 m (130°C) and 102.6 m (140°C), but is associated with fibro-palagonite and analcite, reflecting more rapid palagonitization, and changing cation solubility and pH at higher temperature. Tubular palagonite microstructures show nanocrystalline clay mineral with (001) preferred orientations that wrap around relict microchannels, produced perhaps through biogenic activity. Nanocrystalline clay mineral d-spacings suggest similarities with nontronite, but zeolite in palagonite diffraction patterns and 6-9 wt% MgO suggest a polycrystalline composite with smectite mineral precursor(s). Fifteen years after eruption, Al-tobermorite-zeolite assemblages varied with porosity, pH, and reactive rock mass/liquid volume ratio in submillimeter-scale hydrothermal environments. This initial phase of alteration is rarely preserved in older palagonitized rift zone basalts.

Medusa Sea Floor Monitoring System

NASA Technical Reports Server (NTRS)

Flynn, Michael

2004-01-01

The objective of the research described in this poster presentation is to develop technologies to enable fundamental research into understanding the potential for and limits to chemolithoautotrophic life. The Medusa Isosampler (isobaric sampler), for sampling fluids eminating from deep sea hydrothermal vents and cold seep sites analogous to extraterrestrial environments, is described by the presentation. The following instruments are integrated with the isosampler, and also described: in situ flow-through chemical sensor, intrinsic fluorescent-based microbial detector, isotope ratio spectral detector.

Techno-economic feasibility and life cycle assessment of dairy effluent to renewable diesel via hydrothermal liquefaction.

PubMed

Summers, Hailey M; Ledbetter, Rhesa N; McCurdy, Alex T; Morgan, Michael R; Seefeldt, Lance C; Jena, Umakanta; Hoekman, S Kent; Quinn, Jason C

2015-11-01

The economic feasibility and environmental impact is investigated for the conversion of agricultural waste, delactosed whey permeate, through yeast fermentation to a renewable diesel via hydrothermal liquefaction. Process feasibility was demonstrated at laboratory-scale with data leveraged to validate systems models used to perform industrial-scale economic and environmental impact analyses. Results show a minimum fuel selling price of $4.78 per gallon of renewable diesel, a net energy ratio of 0.81, and greenhouse gas emissions of 30.0g-CO2-eqMJ(-1). High production costs and greenhouse gas emissions can be attributed to operational temperatures and durations of both fermentation and hydrothermal liquefaction. However, high lipid yields of the yeast counter these operational demands, resulting in a favorable net energy ratio. Results are presented on the optimization of the process based on economy of scale and a sensitivity analysis highlights improvements in conversion efficiency, yeast biomass productivity and hydrotreating efficiency can dramatically improve commercial feasibility. Copyright © 2015 Elsevier Ltd. All rights reserved.

Siderophore production in high iron environments

NASA Astrophysics Data System (ADS)

Bennett, S. A.; Hoffman, C. L.; Moffett, J. W.; Edwards, K. J.

2010-12-01

Up until recently, the geochemical cycling of Fe in deep sea hydrothermal plumes has assumed to be inorganically dominated, resulting in quantitative precipitation of all hydrothermally sourced Fe to the seafloor. Recent detection of organic Fe binding ligands within both the dissolved and particulate phase (Bennett et al., 2008; Toner et al., 2009), suggests that hydrothermally sourced Fe may be important on a global scale (Tagliabue et al., 2010). The source of these organic ligands is currently unknown; hypotheses include the possible entrainment of organic carbon from the biologically rich diffuse flow areas, or in-situ production from microbial processes. However, the microbial production of organic ligands is only expected when Fe is a limited micronutrient, which is not the case in the hydrothermal environment. The importance of Fe cycling microorganisms within hydrothermal systems was previously overlooked due to the poor energetics with regards to Fe oxidation and reduction. But their recent detection within the hydrothermal system, both around low temperature Fe rich mineral deposits and within hydrothermal plumes (Edwards et al., 2004; Sylvan et al., In prep) suggests that they may have an important role in the hydrothermal Fe cycle, potentially resulting in an interplay between Fe and organic carbon. Within the laboratory, we have carried out experiments to investigate an Fe oxidizing bacteria in a variety of high Fe environments. We have detected both the production of siderophores and an increase in reduced Fe when the Fe oxidizing bacteria is exposed to both Fe(III) and Fe(II) rich minerals. The role of these microbes in the mineral dissolution of Fe sulfides along the seafloor and within the hydrothermal plume, may have important implications on the speciation of Fe and the role of siderophores in the marine environment. Bennett, S.A. et al. 2008. EPSL, 270: 157-167. Edwards, K.J. et al. 2004. Geomicrobiology Journal, 21: 393-404. Sylvan, J.B. et al. In prep for Geobiology Tagliabue, A. et al. 2010. Nature Geoscience, 3: 252-256. Toner, B.M.,et al. 2009. Nature Geoscience, 2: 197 - 201.

Geochemical constraints on the origin of serpentinization of oceanic mantle

NASA Astrophysics Data System (ADS)

Li, Z.; Lee, C. A.

2004-12-01

The lower seismic zone of double seismic zones in subducting oceanic lithosphere is suggested to be a result of serpentine or chlorite dehydration in the lithospheric mantle (Hacker et al., 2003). However, the mechanism by which oceanic lithospheric mantle is serpentinized is unclear. One way is through hydrothermal circulation where the lithospheric mantle represents part of the circuit through which seawater passes and then returns to the ocean. Another way is to inject seawater into the lithospheric mantle through fractures in the overlying crust without having a return path of water to the ocean. The two mechanisms differ in that the former is an open system process whereas the latter is a closed system process in which the mantle serves as a ¡°sponge¡± for water. Identifying the dominant process is important. For example, if the mantle is part of a hydrothermal circulation cell, the interaction of seawater with the mantle will influence the composition of seawater. This also has important implications for the heat flow out of seafloor. On the other hand, if serpentinization occurs by a closed system process, there will be no influence on seawater composition. Previous studies have suggested that serpentinization of ophiolite bodies was an isochemical process, hence closed system, but it was not clear in these studies whether serpentinization occurred in situ in the oceanic lithosphere. To better understand serpentinization processes in the oceanic lithosphere, we investigated a continuous transition zone of relatively unaltered harzburgite to completely serpentinized harzburgite in the Feather River Ophiolite in northern California. These samples are highly enriched in Na, K, Rb, Cs, U, and Sr, which strongly suggests that serpentinization occurred while the oceanic lithosphere was beneath the ocean. All samples (n=19) have Al2O3 contents ranging from 0.6 to 2.5 wt.% and have extremely depleted light rare-earth element abundances, indicating that these samples are cpx-free harzburgites, which have experienced roughly 20 to 35% melt extraction. The degree of serpentinization was quantified using the concentration of magnetite, a by-product of serpentinization. The lack of antigorite suggests that serpentinization occurred at temperatures lower than 300 C. By comparing Cr and Cr/Al systematics to that predicted from theoretical partial melting calculations and empirical relationships in unaltered peridotite xenoliths, it is shown that Cr and Al are immobile. Al content was thus used to determine the composition of the protolith, which allows us to estimate the amount of depletion/enrichment of a given element by processes other than melt depletion. Most of the harzburgites show no evidence for mantle metasomatism as evidenced by extreme depletions in LREE elements. Consistent with previous studies, we find no depletions in Mg, Fe, or Ca. As seawater is undersaturated in Mg-bearing minerals, an open system process would yield progressive depletion of Mg as is seen in abyssal peridotites, which have been weathered by seawater at the bottom of the seafloor (e.g., Snow et al. 1995). Collectively, this suggests that, except for the addition of seawater and its constituents, serpentinization of the Feather River Ophiolite, was a closed system process. By combining these observations with the results of our field mapping project, we suggest that serpentinization of the lithospheric mantle occurs by local introduction of seawater through fractures extending from the crust and into the mantle. We find no evidence that serpentinized zones in oceanic lithospheric mantle represents an extremely deep hydrothermal circulation cell.

Evaluating the Historical Importance of Impact Induced Hydrothermal Systems on Mars Using the Stable Isotopic Composition of Martian Water

NASA Technical Reports Server (NTRS)

Niles, Paul B.

2010-01-01

The importance of impact events during the early history of Mars is obvious through a simple examination of the character of the martian surface. This ancient, heavily cratered terrain has been shown to be associated with extensive phyllosilicate deposits. This geologic link could suggest that the extensive phyllosilicate-forming alteration may have occurred during early martian history through impact-induced hydrothermal alteration. However, examination of the oxygen isotopic composition of water on Mars suggests that the extensive phyllosilicate deposits were formed primarily through low temperature (<30 C) interactions, and that high temperature weathering in impact-induced hydrothermal systems have not been a dominant process on Mars. The average oxygen isotopic composition of water on Earth is dictated by the nature of water-rock interactions. If these interactions occur at higher temperatures then the water will contain a higher proportion of 18O, while lower temperature interactions will result in water with a lower proportion of 18O. Water on Earth today contains a higher proportion of 18O because of plate tectonics and hydrothermal interaction at mid-ocean ridges. The oxygen isotopic composition of water on early earth, however, may have been quite different, containing a smaller proportion of 18O suggesting much less hydrothermal interaction. Because there are not yet any direct measurements of the oxygen isotopic composition of water on Mars, it needs to be inferred through examination of carbonates preserved in martian meteorites and the isotopic composition of atmospheric CO2. This can be done because the oxygen incorporated into carbonates and CO2 is easily exchanged with liquid water if it is present. Independently, both measurements provide an estimate for the (Sigma)18O of water on Mars to be near -16%. This composition is consistent with low temperature weathering of the silicate crust, and indicates that impact hydrothermal systems did not play an important role in the early alteration of the planet. However, our understanding of impact-induced hydrothermal systems remains unclear. If most of the water mobilized by an impact event remained at relatively low temperatures (<30deg), low-temperature interactions could predominate in these environments. These conditions would be consistent with the isotopic constraints suggested in this study.

Mobility of rare earth element in hydrothermal process and weathering product: a review

NASA Astrophysics Data System (ADS)

Lintjewas, L.; Setiawan, I.

2018-02-01

The Rare Earth Element (REE), consists of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Lu, Ho, Er, Tm, Yb, are important elements to be used as raw materials of advanced technology such as semiconductors, magnets, and lasers. The research of REE in Indonesia has not been done. Several researches were conducted on granitic rocks and weathering product such as Bangka, Sibolga, West Kalimantan, West Sulawesi and Papua. REE can be formed by hydrothermal processes such as Bayan Obo, South China. The REE study on active hydrothermal system (geothermal) in this case also has the potential to produce mineral deposits. The purpose of this review paper is to know the mobility of REE on hydrothermal process and weathering products. Mobility of REE in the hydrothermal process can change the distribution patterns and REE content such as Ce, Eu, La, Lu, Nd, Sm, and Y. Another process besides the hydrothermal is weathering process. REE mobility is influenced by weathering products, where the REE will experience residual and secondary enrichment processes in heavier minerals.

Discovery of a magma chamber and faults beneath a Mid-Atlantic Ridge hydrothermal field.

PubMed

Singh, Satish C; Crawford, Wayne C; Carton, Hélène; Seher, Tim; Combier, Violaine; Cannat, Mathilde; Pablo Canales, Juan; Düsünür, Doga; Escartin, Javier; Miranda, J Miguel

2006-08-31

Crust at slow-spreading ridges is formed by a combination of magmatic and tectonic processes, with magmatic accretion possibly involving short-lived crustal magma chambers. The reflections of seismic waves from crustal magma chambers have been observed beneath intermediate and fast-spreading centres, but it has been difficult to image such magma chambers beneath slow-spreading centres, owing to rough seafloor topography and associated seafloor scattering. In the absence of any images of magma chambers or of subsurface near-axis faults, it has been difficult to characterize the interplay of magmatic and tectonic processes in crustal accretion and hydrothermal circulation at slow-spreading ridges. Here we report the presence of a crustal magma chamber beneath the slow-spreading Lucky Strike segment of the Mid-Atlantic Ridge. The reflection from the top of the magma chamber, centred beneath the Lucky Strike volcano and hydrothermal field, is approximately 3 km beneath the sea floor, 3-4 km wide and extends up to 7 km along-axis. We suggest that this magma chamber provides the heat for the active hydrothermal vent field above it. We also observe axial valley bounding faults that seem to penetrate down to the magma chamber depth as well as a set of inward-dipping faults cutting through the volcanic edifice, suggesting continuous interactions between tectonic and magmatic processes.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

The thermal regime in the resurgent dome of Long Valley Caldera, California: Inferences from precision temperature logs in deep wells

USGS Publications Warehouse

Hurwitz, S.; Farrar, C.D.; Williams, C.F.

2010-01-01

Long Valley Caldera in eastern California formed 0.76Ma ago in a cataclysmic eruption that resulted in the deposition of 600km3 of Bishop Tuff. The total current heat flow from the caldera floor is estimated to be ~290MW, and a geothermal power plant in Casa Diablo on the flanks of the resurgent dome (RD) generates ~40MWe. The RD in the center of the caldera was uplifted by ~80cm between 1980 and 1999 and was explained by most models as a response to magma intrusion into the shallow crust. This unrest has led to extensive research on geothermal resources and volcanic hazards in the caldera. Here we present results from precise, high-resolution, temperature-depth profiles in five deep boreholes (327-1,158m) on the RD to assess its thermal state, and more specifically 1) to provide bounds on the advective heat transport as a guide for future geothermal exploration, 2) to provide constraints on the occurrence of magma at shallow crustal depths, and 3) to provide a baseline for future transient thermal phenomena in response to large earthquakes, volcanic activity, or geothermal production. The temperature profiles display substantial non-linearity within each profile and variability between the different profiles. All profiles display significant temperature reversals with depth and temperature gradients <50??C/km at their bottom. The maximum temperature in the individual boreholes ranges between 124.7??C and 129.5??C and bottom hole temperatures range between 99.4??C and 129.5??C. The high-temperature units in the three Fumarole Valley boreholes are at the approximate same elevation as the high-temperature unit in borehole M-1 in Casa Diablo indicating lateral or sub-lateral hydrothermal flow through the resurgent dome. Small differences in temperature between measurements in consecutive years in three of the wells suggest slow cooling of the shallow hydrothermal flow system. By matching theoretical curves to segments of the measured temperature profiles, we calculate horizontal groundwater velocities in the hydrothermal flow unit under the RD that range from 1.9 to 2.8m/yr, which corresponds to a maximum power flowing through the RD of 3-4MW. The relatively low temperatures and large isothermal segments at the bottom of the temperature profiles are inconsistent with the presence of magma at shallow crustal levels. ?? 2010.

The thermal regime in the resurgent dome of Long Valley Caldera, California: Inferences from precision temperature logs in deep wells

NASA Astrophysics Data System (ADS)

Hurwitz, Shaul; Farrar, Christopher D.; Williams, Colin F.

2010-12-01

Long Valley Caldera in eastern California formed 0.76 Ma ago in a cataclysmic eruption that resulted in the deposition of 600 km 3 of Bishop Tuff. The total current heat flow from the caldera floor is estimated to be ~ 290 MW, and a geothermal power plant in Casa Diablo on the flanks of the resurgent dome (RD) generates ~40 MWe. The RD in the center of the caldera was uplifted by ~ 80 cm between 1980 and 1999 and was explained by most models as a response to magma intrusion into the shallow crust. This unrest has led to extensive research on geothermal resources and volcanic hazards in the caldera. Here we present results from precise, high-resolution, temperature-depth profiles in five deep boreholes (327-1,158 m) on the RD to assess its thermal state, and more specifically 1) to provide bounds on the advective heat transport as a guide for future geothermal exploration, 2) to provide constraints on the occurrence of magma at shallow crustal depths, and 3) to provide a baseline for future transient thermal phenomena in response to large earthquakes, volcanic activity, or geothermal production. The temperature profiles display substantial non-linearity within each profile and variability between the different profiles. All profiles display significant temperature reversals with depth and temperature gradients <50 °C/km at their bottom. The maximum temperature in the individual boreholes ranges between 124.7 °C and 129.5 °C and bottom hole temperatures range between 99.4 °C and 129.5 °C. The high-temperature units in the three Fumarole Valley boreholes are at the approximate same elevation as the high-temperature unit in borehole M-1 in Casa Diablo indicating lateral or sub-lateral hydrothermal flow through the resurgent dome. Small differences in temperature between measurements in consecutive years in three of the wells suggest slow cooling of the shallow hydrothermal flow system. By matching theoretical curves to segments of the measured temperature profiles, we calculate horizontal groundwater velocities in the hydrothermal flow unit under the RD that range from 1.9 to 2.8 m/yr, which corresponds to a maximum power flowing through the RD of 3-4 MW. The relatively low temperatures and large isothermal segments at the bottom of the temperature profiles are inconsistent with the presence of magma at shallow crustal levels.

Combined hydrothermal liquefaction and catalytic hydrothermal gasification system and process for conversion of biomass feedstocks

DOEpatents

Elliott, Douglas C.; Neuenschwander, Gary G.; Hart, Todd R.

2017-09-12

A combined hydrothermal liquefaction (HTL) and catalytic hydrothermal gasification (CHG) system and process are described that convert various biomass-containing sources into separable bio-oils and aqueous effluents that contain residual organics. Bio-oils may be converted to useful bio-based fuels and other chemical feedstocks. Residual organics in HTL aqueous effluents may be gasified and converted into medium-BTU product gases and directly used for process heating or to provide energy.

Cutting through the smoke: the diversity of microorganisms in deep-sea hydrothermal plumes

PubMed Central

Mikalsen, Svein-Ole; Giebel, Helge-Ansgar; Rogers, Alex D.

2017-01-01

There are still notable gaps regarding the detailed distribution of microorganisms between and within insular habitats such as deep-sea hydrothermal vents. This study investigates the community composition of black smoker vent microorganisms in the Southern Hemisphere, and changes thereof along a spatial and chemical gradient ranging from the vent plume to surrounding waters. We sampled two hydrothermal vent fields, one at the South West Indian Ridge (SWIR), the other at the East Scotia Ridge (ESR). Samples were collected across vent fields at varying vertical distances from the origin of the plumes. The microbial data were sequenced on an Illumina MiSeq platform for the 16SrRNA gene. A substantial amount of vent-specific putative chemosynthetic microorganisms were found, particularly in samples from focused hydrothermal venting. Common vent-specific organisms from both vent fields were the genera Arcobacter, Caminibacter and Sulfurimonas from the Epsilonproteobacteria and the SUP05 group from the Gammaproteobacteria. There were no major differences in microbial composition between SWIR and ESR for focused plume samples. However, within the ESR the diffuse flow and focused samples differed significantly in microbial community composition and relative abundance. For Epsilonproteobacteria, we found evidence of niche-specificity to hydrothermal vent environments. This taxon decreased in abundance by three orders of magnitude from the vent orifice to background water. Epsilonproteobacteria distribution followed a distance–decay relationship as vent-effluents mixed with the surrounding seawater. This study demonstrates strong habitat affinity of vent microorganisms on a metre scale with distinct environmental selection. PMID:28484604

New evidence on the hydrothermal system in Long Valley caldera, California, from wells, fluid sampling, electrical geophysics, and age determinations of hot-spring deposits

USGS Publications Warehouse

Sorey, M.L.; Suemnicht, G.A.; Sturchio, N.C.; Nordquist, G.A.

1991-01-01

Data collected since 1985 from test drilling, fluid sampling, and geologic and geophysical investigations provide a clearer definition of the hydrothermal system in Long Valley caldera than was previously available. This information confirms the existence of high-temperature (> 200??C) reservoirs within the volcanic fill in parts of the west moat. These reservoirs contain fluids which are chemically similar to thermal fluids encountered in the central and eastern parts of the caldera. The roots of the present-day hydrothermal system (the source reservoir, principal zones of upflow, and the magmatic heat source) most likely occur within metamorphic basement rocks beneath the western part of the caldera. Geothermometer-temperature estimates for the source reservoir range from 214 to 248??C. Zones of upflow of hot water could exist beneath the plateau of moat rhyolite located west of the resurgent dome or beneath Mammoth Mountain. Lateral flow of thermal water away from such upflow zones through reservoirs in the Bishop Tuff and early rhyolite accounts for temperature reversals encountered in most existing wells. Dating of hot-spring deposits from active and inactive thermal areas confirms previous interpretations of the evolution of hydrothermal activity that suggest two periods of extensive hot-spring discharge, one peaking about 300 ka and another extending from about 40 ka to the present. The onset of hydrothermal activity around 40 ka coincides with the initiation of rhyolitic volcanism along the Mono-Inyo Craters volcanic chain that extends beneath the caldera's west moat. ?? 1991.

Satellite observations of fumarole activity at Aluto volcano, Ethiopia: Implications for geothermal monitoring and volcanic hazard

NASA Astrophysics Data System (ADS)

Braddock, Mathilde; Biggs, Juliet; Watson, Iain M.; Hutchison, William; Pyle, David M.; Mather, Tamsin A.

2017-07-01

Fumaroles are the surface manifestation of hydrothermal circulation and can be influenced by magmatic, hydrothermal, hydrological and tectonic processes. This study investigates the temporal changes in fumarole temperatures and spatial extent on Aluto, a restless volcano in the Main Ethiopian Rift (MER), in order to better understand the controls on fluid circulation and the interaction between the magmatic and hydrothermal systems. Thermal infrared (TIR) satellite images, acquired by the Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) over the period of 2004 to 2016, are used to generate time series of the fumarole temperatures and areas. The thermal anomalies identified in the ASTER images coincide with known fumaroles with temperatures > 80 °C and are located on or close to fault structures, which provide a pathway for the rising fluids. Most of the fumaroles, including those along the major zone of hydrothermal upwelling, the Artu Jawe Fault Zone, have pixel-integrated temperature variations of only 2 ± 1.5 °C. The exception are the Bobesa fumaroles located on a hypothesised caldera ring fault which show pixel-integrated temperature changes of up to 9 °C consistent with a delayed response of the hydrothermal system to precipitation. We conclude that fumaroles along major faults are strongly coupled to the magmatic-hydrothermal system and are relatively stable with time, whereas those along shallower structures close to the rift flank are more strongly influenced by seasonal variations in groundwater flow. The use of remote sensing data to monitor the thermal activity of Aluto provides an important contribution towards understanding the behaviour of this actively deforming volcano. This method could be used at other volcanoes around the world for monitoring and geothermal exploration.

Three-dimensional geophysical mapping of rock alteration and water content at Mount Adams, Washington: Implications for lahar hazards

USGS Publications Warehouse

Finn, C.A.; Deszcz-Pan, M.; Anderson, E.D.; John, D.A.

2007-01-01

Hydrothermally altered rocks, particularly if water saturated, can weaken stratovolcanoes, thereby increasing the potential for catastrophic sector collapses that can lead to far-traveled, destructive debris flows. Evaluating the hazards associated with such alteration is difficult because alteration has been mapped on few active volcanoes and the distribution and intensity of subsurface alteration are largely unknown on any active volcano. At Mount Adams, some Holocene debris flows contain abundant hydrothermal minerals derived from collapse of the altered, edifice. Intense hydrothermal alteration significantly reduces the resistivity and magnetization of volcanic rock, and therefore hydrothermally altered rocks can be identified with helicopter electromagnetic and magnetic measurements. Electromagnetic and magnetic data, combined with geological mapping and rock property measurements, indicate the presence of appreciable thicknesses of hydrothermally altered rock in the central core of Mount Adams north of the summit. We identify steep cliffs at the western edge of this zone as the likely source for future large debris flows. In addition, the electromagnetic data identified water in the brecciated core of the upper 100-200 m of the volcano. Water helps alter the rocks, reduces the effective stress, thereby increasing the potential for slope failure, and acts, with entrained melting ice, as a lubricant to transform debris avalanches into lahars. Therefore knowing the distribution of water is also important for hazard assessments. Our results demonstrate that high-resolution geophysical and geological observations can yield unprecedented views of the three-dimensional distribution of altered rock and shallow pore water aiding evaluation of the debris avalanche hazard.

Microstructure and magnetic properties of MFe2O4 (M = Co, Ni, and Mn) ferrite nanocrystals prepared using colloid mill and hydrothermal method

NASA Astrophysics Data System (ADS)

Wang, Wei; Ding, Zui; Zhao, Xiruo; Wu, Sizhu; Li, Feng; Yue, Ming; Liu, J. Ping

2015-05-01

Three kinds of spinel ferrite nanocrystals, MFe2O4 (M = Co, Ni, and Mn), are synthesized using colloid mill and hydrothermal method. During the synthesis process, a rapid mixing and reduction of cations with sodium borohydride (NaBH4) take place in a colloid mill then through a hydrothermal reaction, a slow oxidation and structural transformation of the spinel ferrite nanocrystals occur. The phase purity and crystal lattice parameters are estimated by X-ray diffraction studies. Scanning electron microscopy and transmission electron microscopy images show the morphology and particle size of the as-synthesized ferrite nanocrystals. Raman spectrum reveals active phonon modes at room temperature, and a shifting of the modes implies cation redistribution in the tetrahedral and octahedral sites. Magnetic measurements show that all the obtained samples exhibit higher saturation magnetization (Ms). Meanwhile, experiments demonstrate that the hydrothermal reaction time has significant effects on microstructure, morphologies, and magnetic properties of the as-synthesized ferrite nanocrystals.

Selection of hydrothermal pre-treatment conditions of waste sludge destruction using multicriteria decision-making.

PubMed

Al-Shiekh Khalil, Wael; Shanableh, Abdullah; Rigby, Portia; Kokot, Serge

2005-04-01

The effectiveness of hydrothermal treatment for the destruction of the organic content of sludge waste was investigated. The sludge sampled in this study contained approximately 2% solids. The experimental program consisted of hydrothermal treatment experiments conducted in a batch reactor at temperatures between 100 and 250 degrees C, with the addition of an oxidant (hydrogen peroxide) in the range of 0-150% with reference to TCOD, and reaction times of up to 60 min. The results suggested that the availability of oxidant, reaction temperature and reaction time were the determining factors for COD removal. A significant fraction of the COD remaining after treatment consisted of the dissolved COD. The results confirmed that hydrothermal treatment proceeds through hydrolysis resulting in the production of dissolved organic products followed by COD removal through oxidation. Two MCDM chemometrics methods, PROMETHEE and GAIA, were applied to process the large data matrix so as to facilitate the selection of the most suitable hydrothermal conditions for sludge destruction. Two possible scenarios were produced from this analysis-one depended on the use of high temperatures and no oxidant, while the second offered a choice of compromise solutions at lower temperatures but with the use of at least some oxidant. Thus, for the final choice of operating conditions, the decision maker needs local knowledge of the costs and available infrastructure. In principle, such information could be added as further criteria to the data matrix and new rankings obtained.

Hydrothermal mineralization at seafloor spreading centers

NASA Astrophysics Data System (ADS)

Rona, Peter A.

1984-01-01

The recent recognition that metallic mineral deposits are concentrated by hydrothermal processes at seafloor spreading centers constitutes a scientific breakthrough that opens active sites 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 hydrothermal mineralization and the occurrence and distribution of hydrothermal mineral deposits at the global oceanic ridge-rift system. Sub-seafloor hydrothermal 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 hydrothermal systems are extremely localized where conditions of anomalously high thermal gradients and permeability increase hydrothermal activity 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 hydrothermal 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 hydrothermal 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 zones of active extension) common to all spreading centers, regional tectonic setting determined by stage (early, advanced), and rate (slow, intermediate-to-fast) of opening of an ocean basin about a spreading center, and local tectonic sub-setting that incorporates anomalous structural and thermal conditions conducive to mineral concentration (thermal gradient, permeability, system geometry, leaky versus tight hydrothermal systems). Temporal frames of reference comprise the relation between mineral concentration and timing of regional plutonic, volcanic and tectonic cycles and of episodic local physical and chemical events (transient stress, fluctuating heat transfer, intrusion-extrusion, fracturing, sealing, etc.). Types of hydrothermal deposits are not uniquely associated with specific tectonic settings and subsettings. Similar types of hydrothermal deposits may occur in different tectonic settings as a consequence of convergence of physical and chemical processes of concentration. Local tectonic sub-settings with conditions conducive to hydrothermal mineralization at slow-spreading centers (half rate ≤ 2cm y -1; length c. 28,000 km), characterized by an estimated average convective heat transfer of 15.1·10 8 cal. cm -2, deep-level ( > 3 km), relative narrow (< 5 km wide at base) magma chambers, and high topographic relief (1-5 km) are: (1) basins along linear sections of the axial zone of volcanic extrusion near transform faults at an early stage of opening, represented by a large stratiform sulfide deposit (estimated 32.5·10 6 metric tons) of the Atlantis II Deep of the Red Sea; (2) the wall along linear sections of the rift valley in the marginal zone of active extension at an advanced stage of opening, represented by encrustations and layered deposits of manganese and iron oxides, hydroxides and silicates inferred to be underlain by stockwork sulfides at the TAG Hydrothermal Field at latitude 26°C on the Mid-Atlantic Ridge; (3) transform faults, especially those with large ridge-ridge offset ( > 30 km), at an advanced stage of opening, represented by stockwork sulfides exposed in the walls of equatorial fracture zones of the Atlantic Ocean and Indian Ocean; (4) the axial zone of volcanic extrusion at an advanced stage of opening. Local tectonic sub-settings with conditions conducive to hydrothermal mineralization at intermediate- to fast-spreading centers (half rate > 2cm y -1; length c. 22,000 km) characterized by an estimated average convective heat transfer of 11.5·10 8 cal. cm -2, relatively wide (up to 20 km at base), shallow-level (c. 1-3 km) magma chambers, and low topographic relief (< 1 km), are: (1) basins along linear sections of the axial zone of volcanic extrusion at an early stage of opening, represented by massive sulfide deposits of the Guaymas Basin of the Gulf of California; (2) the axial zone of volcanic extrusion at an advanced stage of opening, represented by individually small (c. 1·10 3 metric tons), massive sulfide mounds surmounted by chimneys of the East Pacific Rise at latitude 21°N; (3) the marginal zone of active extension at an advanced stage of opening represented by a large, massive sulfide deposit (preliminary tentative estimate c.10·10 6 metric tons) at a double-rifted section of the Galapagos Spreading Center; (4) transform faults, especially those with large ridge-ridge offset ( > 50 km) represented by manganese encrustations in a transform fault at the Galapagos Spreading Center; (5) volcanic seamounts related to persistent hot spots at spreading centers, represented by oxide and sulfide deposits on seamounts off the axis of the East Pacific Rise; (6) portions of spreading centers with anomalous configurations such as multiple, bent or extended rifts, represented by massive sulfide deposits at a double-rifted section of the Galapagos Spreading Center, suggesting the operation of a thermal-structural feedback mechanism indicative of the presence of hydrothermal mineralization; (7) discrete spreading centers in back-arc basins represented by hydrothermal deposits at sites in marginal seas of the western Pacific. Ore-forming processes appear to be least efficient in the axial zone of volcanic extrusion of oceanic ridges at an advanced stage of opening irrespective of spreading rate, where tight hydrothermal systems dissipate a major portion of contained metals by precipitation and dispersion in particulate form from "black smokers" that discharge into the water column. Ore-forming processes appear to be most efficient at sites in basins at linear sections of the axial zone of volcanic extrusion near transform faults during an early stage of opening, and at marginal zones of active extension along linear sections of a spreading center during an advanced stage of opening, irrespective of spreading rate, where both tight and leaky hydrothermal systems may conserve their contained metals to concentrate large sulfide deposits. Resemblances in mineralization between stockwork sulfides at seafloor spreading centers and porphyry copper-type deposits in volcanogenic rocks on land suggest the possibility for the occurrence of large tonnage, low-grade porphyry copper-like deposits concentrated by leaky hydrothermal systems at spreading centers. Systematic application of composite exploration procedures is leading to the discovery of numerous additional deposits. It is inferred from the limited data base available that the occurrence of hydrothermal mineral deposits is more frequent at intermediate-to-fast-than at slow-spreading centers, but the potential for the accumulation of large hydrothermal mineral deposits is greater at slow-spreading centers. Current knowledge of the distribution of hydrothermal mineral deposits at seafloor spreading centers is limited to about 55 sites at this early stage of exploration. Estimates of the distribution of either fields of hydrothermal mineral deposits or high-intensity ore-forming hydrothermal systems at seafloor spreading centers, deduced from various considerations, range from one such occurrence between 15 and 265 km along slow-spreading centers, and 1 and 100 km along intermediate- to fast-spreading centers. However, the distribution of sizable deposits will remain sporadic owing to the special structural and thermal conditions necessary to sustain and to retain high-intensity ore-forming hydrothermal systems.

Measured Fluid Flow in an Active H2O-CO2 Geothermal Well as an Analog to Fluid Flow in Fractures on Mars: Preliminary Report

NASA Technical Reports Server (NTRS)

Kieffer, Susan W.; Brown, K. L.; Simmons, Stuart F.; Watson, Arnold

2004-01-01

Water in the Earth's crust generally contains dissolved gases such as CO2. Models for both 'Blue Mars' (H2O-driven processes) and 'White Mars' (CO2-driven processes) predict liquid H2O with dissolved CO2 at depth. The fate of dissolved CO2 as this mixture rises toward the surface has not been quantitatively explored. Our approach is a variation on NASA's 'Follow the Water' as we 'Follow the Fluid' from depth to the surface in hydrothermal areas on Earth and extrapolate our results to Mars. This is a preliminary report on a field study of fluid flow in a producing geothermal well. For proprietary reasons, the name and location of this well cannot be revealed, so we have named it 'Earth1' for this study.

Basin scale permeability and thermal evolution of a magmatic hydrothermal system

NASA Astrophysics Data System (ADS)

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

2013-12-01

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

Breaking Structural Energy Constraints: Hydrothermal Crystallization of High-Silica Germanosilicates via Building Units Self-Growing Approach.

PubMed

Peng, Mingming; Jiang, Jingang; Liu, Xue; Ma, Yue; Jiao, Meichen; Xu, Hao; Wu, Haihong; He, Mingyuan; Wu, Peng

2018-06-11

Zeolites, a class of crystalline microporous materials, have a wide range of practical applications, in particular serving as key catalysts in petrochemical and finechemical processes. Millions of zeolite topologies are theoretically possible. However, to date, only 235 frameworks with various tetrahedral element compositions have been discovered in nature or artificially synthesized, among which approximately 50 topologies are available in pure silica forms. Germanosilicates are becoming an important zeolite family, with a rapidly increasing number of topological structures with unusual double four-membered-ring (D4R) building units and large-pore or extra large-pore systems. The synthesis of their high-silica analogues with higher (hydro)thermal stability remains a great challenge because the formation of siliceous D4R units is kinetically and thermodynamically unfavorable in hydrothermal systems. Herein, we demonstrate that such D4R-containing high-silica zeolites with unexpected crystalline topologies (ECNU-24-RC and IM-20-RC) are readily constructed through a versatile route. This strategy provides new opportunities for the synthesis of high-silica zeolite catalysts that are hardly obtained by conventional hydrothermal synthesis and it would also facilitate a break-through in increasing the number and types of zeolite materials with practical applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimization of Hydrothermal and Diluted Acid Pretreatments of Tunisian Luffa cylindrica (L.) Fibers for 2G Bioethanol Production through the Cubic Central Composite Experimental Design CCD: Response Surface Methodology

PubMed Central

Ziadi, Manel; Ben Hassen-Trabelsi, Aida; Mekni, Sabrine; Aïssi, Balkiss; Alaya, Marwen; Bergaoui, Latifa; Hamdi, Moktar

2017-01-01

This paper opens up a new issue dealing with Luffa cylindrica (LC) lignocellulosic biomass recovery in order to produce 2G bioethanol. LC fibers are composed of three principal fractions, namely, α-cellulose (45.80%  ± 1.3), hemicelluloses (20.76%  ± 0.3), and lignins (13.15%  ± 0.6). The optimization of LC fibers hydrothermal and diluted acid pretreatments duration and temperature were achieved through the cubic central composite experimental design CCD. The pretreatments optimization was monitored via the determination of reducing sugars. Then, the 2G bioethanol process feasibility was tested by means of three successive steps, namely, LC fibers hydrothermal pretreatment performed at 96°C during 54 minutes, enzymatic saccharification carried out by means of a commercial enzyme AP2, and the alcoholic fermentation fulfilled with Saccharomyces cerevisiae. LC fibers hydrothermal pretreatment liberated 33.55 g/kg of reducing sugars. Enzymatic hydrolysis allowed achieving 59.4 g/kg of reducing sugars. The conversion yield of reducing sugar to ethanol was 88.66%. After the distillation step, concentration of ethanol was 1.58% with a volumetric yield about 70%. PMID:28243606

Direct catalytic hydrothermal liquefaction of spirulina to biofuels with hydrogen

NASA Astrophysics Data System (ADS)

Zeng, Qin; Liao, Hansheng; Zhou, Shiqin; Li, Qiuping; Wang, Lu; Yu, Zhihao; Jing, Li

2018-01-01

We report herein on acquiring biofuels from direct catalytic hydrothermal liquefaction of spirulina. The component of bio-oil from direct catalytic hydrothermal liquefaction was similar to that from two independent processes (including liquefaction and upgrading of biocrude). However, one step process has higher carbon recovery, due to the less loss of carbons. It was demonstrated that the yield and HHV of bio-oil from direct catalytic algae with hydrothermal condition is higher than that from two independent processes.

Sulphide mineralization and wall-rock alteration in ophiolites and modern oceanic spreading centres

USGS Publications Warehouse

Koski, R.A.

1983-01-01

Massive and stockwork Fe-Cu-Zn (Cyprus type) sulphide deposits in the upper parts of ophiolite complexes represent hydrothermal mineralization at ancient accretionary plate boundaries. These deposits are probable metallogenic analogues of the polymetallic sulphide deposits recently discovered along modern oceanic spreading centres. Genetic models for these deposits suggest that mineralization results from large-scale circulation of sea-water through basaltic basement along the tectonically active axis of spreading, a zone of high heat flow. The high geothermal gradient above 1 to 2 km deep magma chambers emplaced below the ridge axis drives the convective circulation cell. Cold oxidizing sea-water penetrating the crust on the ridge flanks becomes heated and evolves into a highly reduced somewhat acidic hydrothermal solvent during interaction with basaltic wall-rock. Depending on the temperature and water/rock ratio, this fluid is capable of leaching and transporting iron, manganese, and base metals; dissolved sea-water sulphate is reduced to sulphide. At the ridge axis, the buoyant hydrothermal fluid rises through permeable wall-rocks, and fluid flow may be focussed along deep-seated fractures related to extensional tectonic processes. Metal sulphides are precipitated along channelways as the ascending fluid undergoes adiabatic expansion and then further cooling during mixing with ambient sub-sea-floor water. Vigorous fluid flow results in venting of reduced fluid at the sea-floor/sea-water interface and deposition of massive sulphide. A comparison of sulphide mineralization and wall-rock alteration in ancient and modern spreading centre environments supports this genetic concept. Massive sulphide deposits in ophiolites generally occur in clusters of closely spaced (< 1-5 km) deposits. Individual deposits are a composite of syngenetic massive sulphide and underlying epigenetic stockwork-vein mineralization. The massive sulphide occurs as concordant tabular, lenticular, or saucer-shaped bodies in pillow lavas and pillow-lava breccia; massive lava flows, hyalcoclastite, tuff, and bedded radolarian chert are less commonly associated rock types. These massive sulphide zones are as much as 700 m long, 200 m wide, and 50 m thick. The pipe-, funnel-, or keel-shaped stockwork zone may extend to a dehpth of 1 km in the sheeted-dike complex. Several deposits in Cyprus are confined to grabens or the hanging wall of premineralization normal faults. Polymetallic massive sulphide deposits and active hydrothermal vents at medium- to fast-rate spreading centres (the East Pacific Rise at lat. 21??N, the Galapagos Spreading Centre at long. 86??W, the Juan de Fuca Ridge at lat. 45??N., and the Southern Trough of Guaymas Basin, Gulf of California) have interdeposit spacings on a scale of tens or hundreds of metres, and are spatially associated with structural ridges or grabens within the narrow (< 5 km) axial valleys of the rift zones. Although the most common substrate for massive sulphide accumulations is stacked sequences of pillow basalt and sheet flows, the sea-floor underlying numerous deposits in Guaymas Basin consists of diatomaceous ooze and terrigenous clastic sediment that is intruded by diabase sills. Mound-like massive sulphide deposits, as much as 30 m wide and 5m high, occur over actively discharging vents on the East Pacific Rise, and many of these deposits serve as the base for narrow chimneys and spires of equal or greater height. Sulphides on the Juan de Fuca Ridge appear to form more widespread blanket deposits in the shallow axial-valley depression. The largest deposit found to date, along the axial ridge of the Galapagos Spreading Centre, has a tabular form and a length of 1000 m, a width of 200 m, and a height of 30 m. The sulphide assemblage in both massive and vein mineralization in Cyprus type deposits is characteristically simple: abundant pyrite or, less commonly, pyrrhotite accompanied by minor marcasite, chalcopyrite

Spontaneous Ignition of Hydrothermal Flames in Supercritical Ethanol Water Solutions

NASA Technical Reports Server (NTRS)

Hicks, Michael C.; Hegde, Uday G.; Kojima, Jun J.

2017-01-01

Results are reported from recent tests where hydrothermal flames spontaneously ignited in a Supercritical Water Oxidation (SCWO) Test Cell. Hydrothermal flames are generally categorized as flames that occur when appropriate concentrations of fuel and oxidizer are present in supercritical water (SCW); i.e., water at conditions above its critical point (218 atm and 374 C). A co-flow injector was used to inject fuel, comprising an aqueous solution of 30-vol to 50-vol ethanol, and air into a reactor held at constant pressure and filled with supercritical water at approximately 240 atm and 425 C. Hydrothermal flames auto-ignited and quickly stabilized as either laminar or turbulent diffusion flames, depending on the injection velocities and test cell conditions. Two orthogonal views, one of which provided a backlit shadowgraphic image, provided visual observations. Optical emission measurements of the steady state flame were made over a spectral range spanning the ultraviolet (UV) to the near infrared (NIR) using a high-resolution, high-dynamic-range spectrometer. Depending on the fuel air flow ratios varying degrees of sooting were observed and are qualitatively compared using light absorption comparisons from backlit images.

Multi-method, multi-scale geophysical observations in the Obsidian Pool Thermal Area, Yellowstone National Park

NASA Astrophysics Data System (ADS)

Holbrook, W. S.; Carr, B.; Pasquet, S.; Sims, K. W. W.; Dickey, K.

2016-12-01

Despite the prominence of Yellowstone as the world's most active hydrothermal province, relatively little is known about the plumbing systems that link deeper hydrothermal fluids to the charismatic hot springs, geysers and mud pots at the surface. We present the results of a multi-method, multi-scale geophysical investigation of the Obsidian Pool Thermal Area (OPTA) in Yellowstone National Park. OPTA hosts acid-sulfate hot springs and mud pots with relatively low pH. We present the results of seismic refraction, electrical resistivity, time-domain EM (TEM), soil conductivity meter (EMI), and GPR data acquired in July 2016. There is a strong contrast in physical properties in the upper 50 m of the subsurface between the low-lying hydrothermal area and surrounding hills: the hydrothermal area has much lower seismic velocities ( 1 km/s vs 3 km/s) and electrical resistivity ( 20 ohm-m vs 300 ohm-m). A prominent zone of very low resistivity (<10 ohm-m) exists at about 20 m depth beneath all hydrothermal features. Poisson's ratio, calculated from P-wave refraction tomography and surface wave inversions, shows low values beneath the "frying pan," where gas is emerging in small fumaroles, suggesting that Poisson's ratio is an effective "gas detector" in hydrothermal areas. Near-surface resistivity mapped from EMI shows a strong correlation with hydrothermal areas previously mapped by heat flow, with areas of high heat flow generally having low resistivity near the surface. Two exceptions are (1) the "frying pan," which shows a central area of high resistivity (corresponding to escaping gas) surrounding by a halo of low resistivity, and (2) a broad area of low resistivity connecting the hydrothermal centers to the lake, which may be clay deposits. TEM data penetrate up to 200 m in depth and suggest that a reservoir of hydrothermal fluids may underlie the entire area, including beneath the forested hills, at depths greater than 100 m, but that they rise toward the surface in a 100-m-wide area just west of the frying pan. Our results show that synoptic, multi-scale geophysical measurements can place important constraints on the subsurface pathways of hydrothermal waters and gas.

Vapor-Liquid Partitioning of Iron and Manganese in Hydrothermal Fluids: An Experimental Investigation with Application to the Integrated Study of Basalt-hosted Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Pester, N. J.; Seyfried, W. E.

2010-12-01

The chemistry of deep-sea hydrothermal vent fluids, expressed at the seafloor, reflects a complex history of physicochemical reactions. After three decades of field and experimental investigations, the processes of fluid-mineral equilibria that transform seawater into that of a typical “black smoker” are generally well described in the literature. Deep crustal fluids, when encountering a given heat source that ultimately drives hydrothermal circulation, routinely intersect the two-phase boundary. This process results in the nearly ubiquitous observations of variable salinity in vent fluids and is often a secondary driver of circulation via the evolution of a more buoyant (i.e. less saline) phase. Phase separation in chemically complex fluids results in the partitioning of dissolved species between the two evolved phases that deviates from simple charge balance calculations and these effects become more prominent with increasing temperature and/or decreasing pressure along the two-phase envelope. This process of partitioning has not been extensively studied and the interplay between the effects of phase separation and fluid-mineral equilibrium are not well understood. Most basalt-hosted hydrothermal systems appear to enter a steady state mode wherein fluids approach the heat source at depth and rise immediately once the two-phase boundary is met. Thus, venting fluids exhibit only modest deviations from seawater bulk salinity and the effects of partitioning are likely minor for all but the most volatile elements. Time series observations at integrated study sites, however, demonstrate dynamic changes in fluid chemistry following eruptions/magmatic events, including order of magnitude increases in gas concentrations and unexpectedly high Fe/Cl ratios. In this case, the time dependence of vapor-liquid partitioning relative to fluid-mineral equilibrium must be considered when attempting to interpret changes in subsurface reaction conditions. The two-phase region of vent fluids (as modeled by the NaCl-H2O system) represents challenging experimental conditions due to the extreme sensitivity to pressure and temperature. Using a novel flow through system that allows pressure and temperature to be controlled within 0.5 bars and 1°C, respectively, we have derived vapor-liquid partition coefficients for several species, including Fe and Mn. Divalent cations partition more drastically into the liquid phase than monovalent species and the demonstrated temperature sensitivity of equilibrium Fe/Mn ratios in basalt alteration experiments make these two elements excellent candidates when attempting to interpret time series changes in the aftermath of eruptions. Our experiments demonstrate that with decreasing vapor salinity, the Fe/Mn ratio can effectively double, relative to the bulk fluid composition, as the vapors approach the extremely low dissolved Cl concentrations observed at both EPR, 9°N and Main Endeavour, JdFR. Our results suggest that phase separation can easily account for the observed deviation from apparent Fe-Mn equilibrium in these fluids and further suggests that it may take more than a year for these hydrothermal systems to return to steady state.

Hydrogen, Oxygen and Silicon Isotope Systematics of Groundwater-Magma Interaction in Icelandic Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Kleine, B. I.; Stefansson, A.; Halldorsson, S. A.; Martin, W.; Barnes, J.; Jónasson, K.; Franzson, H.

2016-12-01

Magma often encounters groundwater (meteoric or seawater derived) when intruded into the crust. Magma-groundwater interactions result in the formation of hydrothermal fluids which can lead to contact metamorphism and elemental transport in the country rock. In fact, magma-hydrothermal fluid interaction (rather than magma-magmatic fluid interaction) may lead to classic contact metamorphic reactions. In order to explore the importance of hydrothermal fluid during contact metamorphism we use stable isotopes (δD, δ18O, δ30Si) from both active and extinct magma chambers and hydrothermal systems from across Iceland. Quartz grains from various hydrothermal systems, from crustal xenoliths from the Askja central volcano and from the Hafnarfjall pluton, as well as quartz grains associated with low-T zeolites were analysed for δ18O and δ30Si in-situ using SIMS. Whole rock material of these samples was analysed for δD values using a TCEA coupled to an IRMS. Our results indicate that low-T quartz (<150°C) are dominated by negative δ30Si values whereas positive δ30Si values prevail in quartz precipitated at higher T (>300°C). Combining the results from the analyses of δ18O and δD allows further division of samples into (i) seawater and/or rock dominated and (ii) meteoric water dominated hydrothermal systems. In order to isolate the effects of fluid-rock interaction, fluid source and formation temperature at the magma-groundwater contact, δD, δ18O and δ30Si values of rocks and fluids were modeled using the PHREEQC software. Comparison of analytical and model results shows that the isotopic compositions are influenced by multiple processes. In some cases, groundwater penetrates the contact zone and causes alteration at >400°C by groundwater-magma heat interaction. Other cases document "baked" contact zones without groundwater. Our analyses and modeling demonstrates that groundwater flow and permeability are crucial in setting the style of contact metamorphism around high T intrusions.

Virtual Investigations of an Active Deep Sea Volcano

NASA Astrophysics Data System (ADS)

Sautter, L.; Taylor, M. M.; Fundis, A.; Kelley, D. S.; Elend, M.

2013-12-01

Axial Seamount, located on the Juan de Fuca spreading ridge 300 miles off the Oregon coast, is an active volcano whose summit caldera lies 1500 m beneath the sea surface. Ongoing construction of the Regional Scale Nodes (RSN) cabled observatory by the University of Washington (funded by the NSF Ocean Observatories Initiative) has allowed for exploration of recent lava flows and active hydrothermal vents using HD video mounted on the ROVs, ROPOS and JASON II. College level oceanography/marine geology online laboratory exercises referred to as Online Concept Modules (OCMs) have been created using video and video frame-captured mosaics to promote skill development for characterizing and quantifying deep sea environments. Students proceed at their own pace through a sequence of short movies with which they (a) gain background knowledge, (b) learn skills to identify and classify features or biota within a targeted environment, (c) practice these skills, and (d) use their knowledge and skills to make interpretations regarding the environment. Part (d) serves as the necessary assessment component of the laboratory exercise. Two Axial Seamount-focused OCMs will be presented: 1) Lava Flow Characterization: Identifying a Suitable Cable Route, and 2) Assessing Hydrothermal Vent Communities: Comparisons Among Multiple Sulfide Chimneys.

High-Resolution Geologic Mapping in the Eastern Manus Basin

NASA Astrophysics Data System (ADS)

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

2011-12-01

AUV-based microbathymetry combined with ROV video data was used to create the first high-resolution geologic maps of two hydrothermal active areas in the eastern Manus Basin: North Su volcano and PACManus hydrothermal field on Pual Ridge. The data were recorded in 2006 and 2011 during the research cruises Magellan-06 operated by the Woods Hole Oceanographic Institution and BAMBUS (SO-216) operated by MARUM / University Bremen. High accuracy underwater navigation transponder-based and Posidonia systems allowed us to combine video data with bathymetry. The navigation on both cruises was very precise (m-scale) and navigation offsets were less than 10 m. We conducted detailed geologic mapping and sampling to identify the seafloor volcanic and hydrothermal features and created highly detailed maps that provide a comprehensive picture of the seafloor and vent distribution in the eastern Manus Basin. Several different types of dacite lava morphology were mapped, including pillow lava, lobate flows and massive block lava. We have compiled all available information on rock chemistry, fluid and temperature measurements, video data, bathymetry and navigation data into a GIS database. We find that, in contrast to the tectonic control on vent distribution at slow spreading mid-ocean ridges, the pathways of upwelling hydrothermal vent fluids at PACManus are dominated by volcanic features, such as lava domes and thick, massive block lava flows. Vent fields are developed preferentially along the margins of major flow units, probably because the cores of these units are impermeable to fluid flow, while the autobrecciated outer parts of the flows are not. In the North Su area, a comparison of seafloor maps from 2006 and 2011 reveals recent volcanic activity, which has strongly modified the bathymetry and hydrothermal vent distribution on the southern flank of the volcano. An ash cone with multiple small craters on the SW flank of the North-Su volcano that didn't exist in 2006 was mapped in 2011. Also, magmatic degassing was much more vigorous in 2011, with large accumulations of liquid sulfur (from disproportionation of magmatic SO2) as well as extensive bubbling of supercritical and liquid CO2.

Changes in Vegetation Reflect Changes in the Mammoth Mountain and Long Valley Caldera Hydrothermal System

NASA Astrophysics Data System (ADS)

Murphy, F.; Diefenbach, A. K.; Evans, W.; Hurwitz, S.

2013-12-01

We examined aerial photographs of the area near Mammoth Lakes, CA taken from 1951 to the present, with the goal of determining if visible changes in vegetation might reflect changes in the upflow of gas or heat through the soil zone. Such changes could be related to magmatic intrusion, the development of geothermal resources, groundwater pumping, earthquakes, or to natural changes in the hydrothermal flow system. We examined the area near Horseshoe Lake at the southern base of Mammoth Mountain where diffuse emissions of carbon dioxide created extensive tree-kill in the 1990s. Analysis of photographs acquired in 1951 suggests that tree density in this area was lower than its surroundings at the time. Whether the low-density tree cover identified in the photographs indicates some lasting effects of a previous episode of tree mortality needs further investigation. We also examine possible effects of geothermal energy production at Casa Diablo that began operation in 1985 on vegetation along the western part of the resurgent dome of Long Valley Caldera. Previous studies have correlated tree-kill in this area with increased steam upflow from the hydrothermal system.

Boiling-induced formation of colloidal gold in black smoker hydrothermal fluids

USGS Publications Warehouse

Gartman, Amy; Hannington, Mark; Jamieson, John W.; Peterkin, Ben; Garbe-Schönberg, Dieter; Findlay, Alyssa J; Fuchs, Sebastian; Kwasnitschka, Tom

2017-01-01

Gold colloids occur in black smoker fluids from the Niua South hydrothermal vent field, Lau Basin (South Pacific Ocean), confirming the long-standing hypothesis that gold may undergo colloidal transport in hydrothermal fluids. Six black smoker vents, varying in temperature from 250 °C to 325 °C, were sampled; the 325 °C vent was boiling at the time of sampling and the 250 °C fluids were diffusely venting. Native gold particles ranging from <50 nm to 2 µm were identified in 4 of the fluid samples and were also observed to precipitate on the sampler during collection from the boiling vent. Total gold concentrations (dissolved and particulate) in the fluid samples range from 1.6 to 5.4 nM in the high-temperature, focused flow vents. Although the gold concentrations in the focused flow fluids are relatively high, they are lower than potential solubilities prior to boiling and indicate that precipitation was boiling induced, with sulfide lost upon boiling to exsolution and metal sulfide formation. Gold concentrations reach 26.7 nM in the 250 °C diffuse flow sample, and abundant native gold particles were also found in the fluids and associated sulfide chimney and are interpreted to be a product of colloid accumulation and growth following initial precipitation upon boiling. These results indicate that colloid-driven precipitation as a result of boiling, the persistence of colloids after boiling, and the accumulation of colloids in diffuse flow fluids are important mechanisms for the enrichment of gold in seafloor hydrothermal systems.

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

NASA Astrophysics Data System (ADS)

Nishimoto, Shoji; Yoshida, Hidekazu

2010-03-01

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

Field guide to hydrothermal alteration in the White River altered area and in the Osceola Mudflow, Washington

USGS Publications Warehouse

John, David A.; Rytuba, James J.; Ashley, Roger P.; Blakely, Richard J.; Vallance, James W.; Newport, Grant R.; Heinemeyer, Gary R.

2003-01-01

The Cenozoic Cascades arcs of southwestern Washington are the product of long-lived, but discontinuous, magmatism beginning in the Eocene and continuing to the present (for example, Christiansen and Yeats, 1992). This magmatism is the result of subduction of oceanic crust beneath the North American continent. The magmatic rocks are divided into two subparallel, north-trending continental-margin arcs, the Eocene to Pliocene Western Cascades, and the Quaternary High Cascades, which overlies, and is east of, the Western Cascades. Both arcs are calc-alkaline and are characterized by voluminous mafic lava flows (mostly basalt to basaltic andesite compositions) and scattered large stratovolcanoes of mafic andesite to dacite compositions. Silicic volcanism is relatively uncommon. Quartz diorite to granite plutons are exposed in more deeply eroded parts of the Western Cascades Arc (for example, Mount Rainier area and just north of Mt. St. Helens). Hydrothermal alteration is widespread in both Tertiary and Quaternary igneous rocks of the Cascades arcs. Most alteration in the Tertiary Western Cascades Arc resulted from hydrothermal systems associated with small plutons, some of which formed porphyry copper and related deposits, including copper-rich breccia pipes, polymetallic veins, and epithermal gold-silver deposits. Hydrothermal alteration also is present on many Quaternary stratovolcanoes of the High Cascades Arc. On some High Cascades volcanoes, this alteration resulted in severely weakened volcanic edifices that were susceptible to failure and catastrophic landslides. Most notable is the sector collapse of the northeast side of Mount Rainier that occurred about 5,600 yr. B.P. This collapse resulted in formation of the clay-rich Osceola Mudflow that traveled 120 km down valley from Mount Rainier to Puget Sound covering more than 200 km2. This field trip examines several styles and features of hydrothermal alteration related to Cenozoic magmatism in the Cascades arcs. The morning of the trip will examine the White River altered area, which includes high-level alteration related to a large, early Miocene magmatic-hydrothermal system exposed about 10 km east of Enumclaw, Washington. Here, vuggy silica alteration is being quarried for silica and advanced argillic alteration has been prospected for alunite. Clay-filled fractures and sulfide-rich, fine-grained sedimentary rocks of hydrothermal origin locally are enriched in precious metals. Many hydrothermal features common in high-sulfidation gold-silver deposits and in advanced argillic alteration zones overlying porphyry copper deposits (for example, Gustafson and Hunt, 1975; Hedenquist and others, 2000; Sillitoe, 2000) are exposed, although no economic base or precious metal mineralized rock has been discovered to date. The afternoon will be spent examining two exposures of the Osceola Mudflow along the White River. The Osceola Mudflow contains abundant clasts of altered Quaternary rocks from Mount Rainier that show various types of hydrothermal alteration and hydrothermal features. The mudflow matrix contains abundant hydrothermal clay minerals that added cohesiveness to the debris flow and helped allow it to travel much farther down valley than other, noncohesive debris flows from Mount Rainier (Crandell, 1971; Vallance and Scott, 1997). The White River altered area is the subject of ongoing studies by geoscientists from Weyerhaeuser Company and the U.S. Geological Survey (USGS). The generalized descriptions of the geology, geophysics, alteration, and mineralization presented here represent the preliminary results of this study (Ashley and others, 2003). Additional field, geochemical, geochronologic, and geophysical studies are underway. The Osceola Mudflow and other Holocene debris flows from Mount Rainier also are the subject of ongoing studies by the USGS (for example, Breit and others, 2003; John and others, 2003; Plumlee and others, 2003, Sisson and others, 2003; Vallance and others, 2003). Studies of hydrothermal alteration in the Osceola Mudflow are being used to better understand fossil hydrothermal systems on Mount Rainier and potential hazards associated with this alteration.

Mass transfer processes in a post eruption hydrothermal system: Parameterisation of microgravity changes at Te Maari craters, New Zealand

NASA Astrophysics Data System (ADS)

Miller, Craig A.; Currenti, Gilda; Hamling, Ian; Williams-Jones, Glyn

2018-05-01

Fluid transfer and ground deformation at hydrothermal systems occur both as a precursor to, or as a result of, an eruption. Typically studies focus on pre-eruption changes to understand the likelihood of unrest leading to eruption; however, monitoring post-eruption changes is important for tracking the return of the system towards background activity. Here we describe processes occurring in a hydrothermal system following the 2012 eruption of Upper Te Maari crater on Mt Tongariro, New Zealand, from observations of microgravity change and deformation. Our aim is to assess the post-eruption recovery of the system, to provide a baseline for long-term monitoring. Residual microgravity anomalies of up to 92 ± 11 μGal per year are accompanied by up to 0.037 ± 0.01 m subsidence. We model microgravity changes using analytic solutions to determine the most likely geometry and source location. A multiobjective inversion tests whether the gravity change models are consistent with the observed deformation. We conclude that the source of subsidence is separate from the location of mass addition. From this unusual combination of observations, we develop a conceptual model of fluid transfer within a condensate layer, occurring in response to eruption-driven pressure changes. We find that depressurisation drives the evacuation of pore fluid, either exiting the system completely as vapour through newly created vents and fumaroles, or migrating to shallower levels where it accumulates in empty pore space, resulting in positive gravity changes. Evacuated pores then collapse, causing subsidence. In addition we find that significant mass addition occurs from influx of meteoric fluids through the fractured hydrothermal seal. Long-term combined microgravity and deformation monitoring will allow us to track the resealing and re-pressurisation of the hydrothermal system and assess what hazard it presents to thousands of hikers who annually traverse the volcano, within 2 km of the eruption site.

Hot water in the Long Valley Caldera—The benefits and hazards of this large natural resource

USGS Publications Warehouse

Evans, William C.; Hurwitz, Shaul; Bergfeld, Deborah; Howle, James F.

2018-03-26

The volcanic processes that have shaped the Long Valley Caldera in eastern California have also created an abundant supply of natural hot water. This natural resource provides benefits to many users, including power generation at the Casa Diablo Geothermal Plant, warm water for a state fish hatchery, and beautiful scenic areas such as Hot Creek gorge for visitors. However, some features can be dangerous because of sudden and unpredictable changes in the location and flow rate of boiling water. The U.S. Geological Survey monitors several aspects of the hydrothermal system in the Long Valley Caldera including temperature, flow rate, and water chemistry.

Kinetic Fractionation of Stable Isotopes in Carbonates on Mars: Terrestrial Analogs

NASA Technical Reports Server (NTRS)

Socki, Richard A.; Gibson, Everett K., Jr.; Golden, D. C.; Ming, Douglas W.; McKay, Gordon A.

2003-01-01

An ancient Martian hydrosphere consisting of an alkali-rich ocean would likely produce solid carbonate minerals through the processes of evaporation and/or freezing. We postulate that both (or either) of these kinetically-driven processes would produce carbonate minerals whose stable isotopic compositions are highly fractionated (enriched) with respect to the source carbon. Various scenarios have been proposed for carbonate formation on Mars, including high temperature formation, hydrothermal alteration, precipitation from evaporating brines, and cryogenic formation. 13C and 18O -fractionated carbonates have previously been shown to form kinetically under some of these conditions, ie.: 1) alteration by hydrothermal processes, 2) low temperature precipitation (sedimentary) from evaporating bicarbonate (brine) solutions, and 3) precipitation during the process of cryogenic freezing of bicarbonate-rich fluids. Here we examine several terrestrial field settings within the context of kinetically controlled carbonate precipitation where stable isotope enrichments have been observed.

Volcano collapse promoted by hydrothermal alteration and edifice shape, Mount Rainier, Washington

USGS Publications Warehouse

Reid, M.E.; Sisson, T.W.; Brien, D.L.

2001-01-01

Catastrophic collapses of steep volcano flanks threaten many populated regions, and understanding factors that promote collapse could save lives and property. Large collapses of hydrothermally altered parts of Mount Rainier have generated far-traveled debris flows; future flows would threaten densely populated parts of the Puget Sound region. We evaluate edifice collapse hazards at Mount Rainier using a new three-dimensional slope stability method incorporating detailed geologic mapping and subsurface geophysical imaging to determine distributions of strong (fresh) and weak (altered) rock. Quantitative three-dimensional slope stability calculations reveal that sizeable flank collapse (>0.1 km3) is promoted by voluminous, weak, hydrothermally altered rock situated high on steep slopes. These conditions exist only on Mount Rainier's upper west slope, consistent with the Holocene debris-flow history. Widespread alteration on lower flanks or concealed in regions of gentle slope high on the edifice does not greatly facilitate collapse. Our quantitative stability assessment method can also provide useful hazard predictions using reconnaissance geologic information and is a potentially rapid and inexpensive new tool for aiding volcano hazard assessments.

Identification of sulfur sources and isotopic equilibria in submarine hot-springs using multiple sulfur isotopes

NASA Astrophysics Data System (ADS)

McDermott, Jill M.; Ono, Shuhei; Tivey, Margaret K.; Seewald, Jeffrey S.; Shanks, Wayne C.; Solow, Andrew R.

2015-07-01

Multiple sulfur isotopes were measured in metal sulfide deposits, elemental sulfur, and aqueous hydrogen sulfide to constrain sulfur sources and the isotopic systematics of precipitation in seafloor hydrothermal vents. Areas studied include the Eastern Manus Basin and Lau Basin back-arc spreading centers and the unsedimented basalt-hosted Southern East Pacific Rise (SEPR) and sediment-hosted Guaymas Basin mid-ocean ridge spreading centers. Chalcopyrite and dissolved hydrogen sulfide (H2S) δ34S values range from -5.5‰ to +5.6‰ in Manus Basin samples, +2.4‰ to +6.1‰ in Lau Basin samples, and +3.7‰ to +5.7‰ in SEPR samples. Values of δ34S for cubic cubanite and H2S range from -1.4‰ to +4.7‰ in Guaymas Basin samples. Multiple sulfur isotope systematics in fluid-mineral pairs from the SEPR and Lau Basin show that crustal host rock and thermochemical reduction of seawater-derived dissolved sulfate (SO4) are the primary sources of sulfur in mid-ocean ridge and some back-arc systems. At PACMANUS and SuSu Knolls hydrothermal systems in the Eastern Manus Basin, a significant contribution of sulfur is derived from disproportionation of magmatic sulfur dioxide (SO2), while the remaining sulfur is derived from crustal host rocks and SO4 reduction. At the sedimented Guaymas Basin hydrothermal system, sulfur sources include crustal host rock, reduced seawater SO4, and biogenic sulfide. Vent fluid flow through fresher, less-mature sediment supplies an increased quantity of reactant organic compounds that may reduce 34S-enriched SO4, while fluid interaction with more highly-altered sediments results in H2S characterized by a small, but isotopically-significant input of 34S-depleted biogenic sulfides. Near-zero Δ33S values in all samples implicate the abiotic processes of SO4 reduction and leaching of host rock as the major contributors to sulfur content at a high temperature unsedimented mid-ocean ridge and at a back-arc system. Δ33S values indicate that SO2 disproportionation is an additional process that contributes sulfur to a different back-arc system and to acid spring-type hydrothermal fluid circulation. At the sedimented Guaymus Basin, near-zero Δ33S values are also observed, despite negative δ34S values that indicate inputs of biogenic pyrite for some samples. In contrast with previous studies reporting isotope disequilibrium between H2S and chalcopyrite, the δ34S values of chalcopyrite sampled from the inner 1-2 mm of a chimney wall are within ±1‰ of δ34S values for H2S in the paired vent fluid, suggesting equilibrium fluid-mineral sulfur isotope exchange at 300-400 °C. Isotopic equilibrium between hydrothermal fluid H2S and precipitating chalcopyrite implies that sulfur isotopes in the chalcopyrite lining across a chimney wall may accurately record past hydrothermal activity.

New fabrication of high-frequency (100-MHz) ultrasound PZT film kerfless linear array.

PubMed

Zhu, Benpeng; Chan, Ngai Yui; Dai, Jiyan; Shung, K Kirk; Takeuchi, Shinichi; Zhou, Qifa

2013-04-01

The paper describes the design, fabrication, and measurements of a high-frequency ultrasound kerfless linear array prepared from hydrothermal lead zirconate titanate (PZT) thick film. The 15-μm hydrothermal PZT thick film with an area of 1 × 1 cm, obtained through a self-separation process from Ti substrate, was used to fabricate a 32-element 100-MHz kerfless linear array with photolithography. The bandwidth at -6 dB without matching layer, insertion loss around center frequency, and crosstalk between adjacent elements were measured to be 39%, -30 dB, and -15 dB, respectively.

Pore Pressure Distribution and Flank Instability in Hydrothermally Altered Stratovolcanoes

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Photosynthetic microbial mats in the 3,416-Myr-old ocean.

PubMed

Tice, Michael M; Lowe, Donald R

2004-09-30

Recent re-evaluations of the geological record of the earliest life on Earth have led to the suggestion that some of the oldest putative microfossils and carbonaceous matter were formed through abiotic hydrothermal processes. Similarly, many early Archaean (more than 3,400-Myr-old) cherts have been reinterpreted as hydrothermal deposits rather than products of normal marine sedimentary processes. Here we present the results of a field, petrographic and geochemical study testing these hypotheses for the 3,416-Myr-old Buck Reef Chert, South Africa. From sedimentary structures and distributions of sand and mud, we infer that deposition occurred in normal open shallow to deep marine environments. The siderite enrichment that we observe in deep-water sediments is consistent with a stratified early ocean. We show that most carbonaceous matter was formed by photosynthetic mats within the euphotic zone and distributed as detrital matter by waves and currents to surrounding environments. We find no evidence that hydrothermal processes had any direct role in the deposition of either the carbonaceous matter or the enclosing sediments. Instead, we conclude that photosynthetic organisms had evolved and were living in a stratified ocean supersaturated in dissolved silica 3,416 Myr ago.

Photosynthetic microbial mats in the 3,416-Myr-old ocean

NASA Astrophysics Data System (ADS)

Tice, Michael M.; Lowe, Donald R.

2004-09-01

Recent re-evaluations of the geological record of the earliest life on Earth have led to the suggestion that some of the oldest putative microfossils and carbonaceous matter were formed through abiotic hydrothermal processes. Similarly, many early Archaean (more than 3,400-Myr-old) cherts have been reinterpreted as hydrothermal deposits rather than products of normal marine sedimentary processes. Here we present the results of a field, petrographic and geochemical study testing these hypotheses for the 3,416-Myr-old Buck Reef Chert, South Africa. From sedimentary structures and distributions of sand and mud, we infer that deposition occurred in normal open shallow to deep marine environments. The siderite enrichment that we observe in deep-water sediments is consistent with a stratified early ocean. We show that most carbonaceous matter was formed by photosynthetic mats within the euphotic zone and distributed as detrital matter by waves and currents to surrounding environments. We find no evidence that hydrothermal processes had any direct role in the deposition of either the carbonaceous matter or the enclosing sediments. Instead, we conclude that photosynthetic organisms had evolved and were living in a stratified ocean supersaturated in dissolved silica 3,416Myr ago.

A theoretical analysis of fluid flow and energy transport in hydrothermal systems

USGS Publications Warehouse

Faust, Charles R.; Mercer, James W.

1977-01-01

A mathematical derivation for fluid flow and energy transport in hydrothermal systems is presented. Specifically, the mathematical model describes the three-dimensional flow of both single- and two-phase, single-component water and the transport of heat in porous media. The derivation begins with the point balance equations for mass, momentum, and energy. These equations are then averaged over a finite volume to obtain the macroscopic balance equations for a porous medium. The macroscopic equations are combined by appropriate constitutive relationships to form two similified partial differential equations posed in terms of fluid pressure and enthalpy. A two-dimensional formulation of the simplified equations is also derived by partial integration in the vertical dimension. (Woodard-USGS)

Using telepresence enabled remote-operated vehicles to assess hydrothermal outflow along a collapse scar near the Kick'em Jenny Volcano

NASA Astrophysics Data System (ADS)

Whitley, S. Z.; Mittelstaedt, E. L.

2016-02-01

During expedition NA054 of the E/V Nautilus from 18 September to 9 October 2014 and as part of the TREET (Transforming Remotely Conducted Research through Ethnography, Education, and Rapidly Evolving Technologies) project, a series of photographic surveys along the shoulder of the Kick'em Jenny volcano were performed under direction of a remote research team located at the University of Rhode Island Inner Space Center. The primary goal of these surveys was to map the distribution and extent of active and extinct hydrothermal activity along a large collapse scar surrounding the current edifice of the Kick'em Jenny volcano. Photomosaic surveys cover a area of 3000 m2 and reveal extensive basalt alteration with areas of active diffuse hydrothermal outflow. The spatial extents of orange-colored alteration and white, bacterial mats, taken to indicate active outflow, are quantified using both manual identification and an automated, supervised classification scheme. Both methods find that alteration covers 7-8% and active outflow 1-3% of the survey region. It is unclear if the observed hydrothermal fluids are part of the fluid circulation network of the nearby Kick'em Jenny volcano or if a separate heat source is driving this flow. To test these two endmember cases, we use a 2D, finite-difference, marker-in-cell code to simulate hydrothermal circulation of a single-phase fluid within the oceanic crust. Parameters varied include the permeability structure (e.g., inclusion of a permeability barrier representing the collapse surface), the depth to the heat source beneath Kick'em Jenny, and the bathymetry. We will discuss results from the photomosaic analysis and our initial models.

Reactive transport model of growth and methane production by high-temperature methanogens in hydrothermal regions of the subseafloor

NASA Astrophysics Data System (ADS)

Stewart, L. C.; Algar, C. K.; Topçuoğlu, B. D.; Fortunato, C. S.; Larson, B. I.; Proskurowski, G. K.; Butterfield, D. A.; Vallino, J. J.; Huber, J. A.; Holden, J. F.

2014-12-01

Hydrogenotrophic methanogens are keystone high-temperature autotrophs in deep-sea hydrothermal vents and tracers of habitability and biogeochemical activity in the hydrothermally active subseafloor. At Axial Seamount, nearly all thermophilic methanogens are Methanothermococcus and Methanocaldococcus species, making this site amenable to modeling through pure culture laboratory experiments coupled with field studies. Based on field microcosm incubations with 1.2 mM, 20 μM, or no hydrogen, the growth of methanogens at 55°C and 80°C is limited primarily by temperature and hydrogen availability, with ammonium amendment showing no consistent effect on total methane output. The Arrhenius constants for methane production by Methanocaldococcus jannaschii (optimum 82°C) and Methanothermococcus thermolithotrophicus (optimum 65°C) were determined in pure culture bottle experiments. The Monod constants for hydrogen concentration were measured by growing both organisms in a 2-liter chemostat at two dilution rates; 55°C, 65°C and 82°C; and variable hydrogen concentrations. M. jannaschii showed higher ks and Vmax constants than M. thermolithotrophicus. In the field, hydrogen and methane concentrations in hydrothermal end-member and low-temperature diffuse fluids were measured, and the concentrations of methanogens that grow at 55°C and 80°C in diffuse fluids were determined using most-probable-number estimates. Methane concentration anomalies in diffuse fluids relative to end-member hydrothermal concentrations and methanogen cell concentrations are being used to constrain a 1-D reactive transport model using the laboratory-determined Arrhenius and Monod constants for methane production by these organisms. By varying flow path length and subseafloor cell concentrations in the model, our goal is to determine solutions for the potential depth of the subseafloor biosphere coupled with the amount of methanogenic biomass it contains.

Hydrothermal exploration of the Mariana Back Arc Basin: Chemical Characterization

NASA Astrophysics Data System (ADS)

Resing, J. A.; Chadwick, B.; Baker, E. T.; Butterfield, D. A.; Baumberger, T.; Buck, N. J.; Walker, S. L.; Merle, S. G.; Michael, S.

2016-12-01

In November and December 2015, we visited the Southern Mariana back-arc on R/V Falkor (cruise FK151121) to explore for hydrothermal and volcanic activity. We conducted our study using the SENTRY AUV, a CTD rosette designed to do tows and vertical casts into the deep back-arc, and a trace metal CTD-package for the upper 1000m of the water column to examine transport form the nearby arc. We conducted 7 SENTRY dives, 12 tow-yos, 7 vertical casts, and 14 trace metal casts. We also mapped 24,050 km2 of the seafloor using the Falkor EM 302 multibeam. We discovered four new hydrothermal vent sites, and at one of them we found that some of the venting was coming from recently erupted lava flows. That lava flow is the deepest contemporary eruption yet discovered (at 4100-4450 m), and the first to be documented on a slow-spreading ridge. In addition, we were able to map the previously known Alice Springs hydrothermal site in unprecedented detail with AUV Sentry. The distribution of hydrothermal activity as well as chemistry of the plumes above them will be discussed. Plume chemistry data will include , Fe, Mn, CH4, H2, and 3He. The ship time for this project was provided by the Schmidt Ocean Institute with science funding provided by NOAA-Ocean Exploration.

Hydrothermal minerals and microstructures in the Silangkitang geothermal field along the Great Sumatran fault zone, Sumatra, Indonesia

USGS Publications Warehouse

Moore, Diane E.; Hickman, S.; Lockner, D.A.; Dobson, P.F.

2001-01-01

Detailed study of core samples of silicic tuff recovered from three geothermal wells along the strike-slip Great Sumatran fault zone near Silangkitang, North Sumatra, supports a model for enhanced hydrothermal circulation adjacent to this major plate-boundary fault. Two wells (A and C) were drilled nearly vertically ??1 km southwest of the eastern (i.e., the principal) fault trace, and the third, directional well (B) was drilled eastward from the site of well A to within ??100 m of the principal fault trace. The examined core samples come from depths of 1650-2120 m at measured well temperatures of 180-320 ??C. The samples collected near the principal fault trace have the highest temperatures, the largest amount of secondary pore space that correlates with high secondary permeability, and the most extensive hydrothermal mineral development. Secondary permeability and the degree of hydrothermal alteration decrease toward the southwestern margin of the fault zone. These features indicate episodic, localized flow of hot, possibly CO2-rich fluids within the fault zone. The microstructure populations identified in the core samples correlate to the subsidiary fault patterns typical of strike-slip faults. The geothermal reservoir appears to be centered on the fault zone, with the principal fault strands and adjoining, highly fractured and hydrothermally altered rock serving as the main conduits for vertical fluid flow and advective heat transport from deeper magmatic sources.

Engineering and economic analysis for the utilization of geothermal fluids in a cane sugar processing plant. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humme, J.T.; Tanaka, M.T.; Yokota, M.H.

1979-07-01

The purpose of this study was to determine the feasibility of geothermal resource utilization at the Puna Sugar Company cane sugar processing plant, located in Keaau, Hawaii. A proposed well site area was selected based on data from surface exploratory surveys. The liquid dominated well flow enters a binary thermal arrangement, which results in an acceptable quality steam for process use. Hydrogen sulfide in the well gases is incinerated, leaving sulfur dioxide in the waste gases. The sulfur dioxide in turn is recovered and used in the cane juice processing at the sugar factory. The clean geothermal steam from themore » binary system can be used directly for process requirements. It replaces steam generated by the firing of the waste fibrous product from cane sugar processing. The waste product, called bagasse, has a number of alternative uses, but an evaluation clearly indicated it should continue to be employed for steam generation. This steam, no longer required for process demands, can be directed to increased electric power generation. Revenues gained by the sale of this power to the utility, in addition to other savings developed through the utilization of geothermal energy, can offset the costs associated with hydrothermal utilization.« less

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

NASA Astrophysics Data System (ADS)

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

2016-09-01

In this study, we unravel the physical, chemical and mineralogical evolution of the active Tolhuaca geothermal system in the Andes of southern Chile. We used temperature measurements in the deep wells and geochemical analyses of borehole fluid samples to constrain present-day fluid conditions. In addition, we reconstructed the paleo-fluid temperatures and chemistry from microthermometry and LA-ICP-MS analysis of fluid inclusions taken from well-constrained parageneses in vein samples retrieved from a 1000 m borehole core. Based on core logging, mineralogical observations and fluid inclusions data we identify four stages (S1-S4) of progressive hydrothermal alteration. An early heating event (S1) was followed by the formation of a clay-rich cap in the upper zone (< 670 m) and the development of a propylitic alteration assemblage at greater depth (S2). Boiling, flashing and brecciation occurred later (S3), followed by a final phase of fluid mixing and boiling (S4). The evolution of hydrothermal alteration at Tolhuaca has produced a mineralogical, hydrological and structural vertical segmentation of the system through the development of a low-permeability, low-cohesion clay-rich cap at shallow depth. The quantitative chemical analyses of fluid inclusions and borehole fluids reveal a significant change in chemical conditions during the evolution of Tolhuaca. Whereas borehole (present-day) fluids are rich in Au, B and As, but Cu-poor (B/Na 100.5, As/Na 10- 1.1, Cu/Na 10- 4.2), the paleofluids trapped in fluid inclusions are Cu-rich but poor in B and As (B/Na 10- 1, As/Na 10- 2.5, Cu/Na 10- 2.5 in average). We interpret the fluctuations in fluid chemistry at Tolhuaca as the result of transient supply of metal-rich, magmatically derived fluids where As, Au and Cu are geochemically decoupled. Since these fluctuating physical and chemical conditions at the reservoir produced a mineralogical vertical segmentation of the system that affects the mechanical and hydrological properties of host rock, we explored the effect of the development of a low-cohesion low-permeability clay cap on the conditions of fault rupture and on the long-term thermal structure of the system. These analyses were performed by using rock failure condition calculations and numerical simulations of heat and fluid flows. Calculations of the critical fluid pressures required to produce brittle rupture indicate that within the clay-rich cap, the creation or reactivation of highly permeable extensional fractures is inhibited. In contrast, in the deep upflow zone the less pervasive formation of clay mineral assemblages has allowed retention of rock strength and dilatant behavior during slip, sustaining high permeability conditions. Numerical simulations of heat and fluid flows support our observations and suggest that the presence of a low permeability clay cap has helped increase the duration of high-enthalpy conditions by a factor of three in the deep upflow zone at Tolhuaca geothermal system, when compared with an evolutionary scenario where a clay cap was not developed. Furthermore, our data demonstrate that the dynamic interplay between fluid flow, crack-seal processes and hydrothermal alteration are key factors in the evolution of the hydrothermal system, leading to the development of a high enthalpy reservoir at the flank of the dormant Tolhuaca volcano.

Morphology-preserving chemical conversion of bioorganic and inorganic templates

NASA Astrophysics Data System (ADS)

Vernon, Jonathan Paul

The generation of nanostructured assemblies with complex (three-dimensional, 3D) self-assembled morphologies and with complex (multicomponent) tailorable inorganic compositions is of considerable technological and scientific interest. This dissertation demonstrates self-assembled 3D organic templates of biogenic origin can be converted into replicas comprised of numerous other functional nanocrystalline inorganic materials. Nature provides a spectacular variety of biologically-assembled 3D organic structures with intricate, hierarchical (macro-to-micro-to-nanoscale) morphologies. Such processing on readily-available structurally complex templates provides a framework for chemical conversion of synthetic organic templates and, potentially, production of organic/inorganic composites. Four specific research thrusts are detailed in this document. First, chemical conversion of a nanostructured bioorganic template into a multicomponent oxide compound (tetragonal BaTiO3) via SSG coating and subsequent morphology-preserving microwave hydrothermal processing is demonstrated. Second, morphology-preserving chemical conversion of bioorganic templates into hierarchical photoluminescent microparticles is demonstrated to reveal both the dramatic change in properties such processing can provide, and the potential utility of chemically transformed templates in anti-counterfeiting / authentication applications. Third, determination of the reaction mechanism(s) for morphology-preserving microwave hydrothermal conversion of TiO2 to BaTiO3, through Au inert markers on single crystal rutile titania, is detailed. Finally, utilization of constructive coating techniques (SSG) and moderate temperature (< 500°C) heat treatments to modify and replicate structural color is coupled with deconstructive focused ion beam microsurgery to prepare samples for microscale structure interrogation. Specifically, the effects of coating thickness and composition on reflection spectra of structurally colored templates are examined. Also, the effects of the replacement of natural material with higher index of refraction inorganic materials on optical properties are discussed. The three processing research thrusts constituting chapters 1, 2 and 4 take advantage of moderate temperature processing to ensure nanocrystalline materials, either for shape preservation or to prevent scattering in optical applications. The research thrust detailed in chapter 3 examines hydrothermal conversion of TiO2 to BaTiO3, not only to identify the reaction mechanism(s) involved in hydrothermal conversion under morphology-preserving conditions, but also to introduce inert marker experiments to the field of microwave hydrothermal processing.

The Plumbing System Feeding the Lusi Eruption Revealed by Ambient Noise Tomography

NASA Astrophysics Data System (ADS)

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

2017-10-01

Lusi is a sediment-hosted hydrothermal system featuring clastic-dominated geyser-like eruption behavior in East Java, Indonesia. We use 10 months of ambient seismic noise cross correlations from 30 temporary seismic stations to obtain a 3-D model of shear wave velocity anomalies beneath Lusi, the neighboring Arjuno-Welirang volcanic complex, and the Watukosek fault system connecting the two. Our work reveals a hydrothermal plume, rooted at a minimum 6 km depth that reaches the surface at the Lusi site. Furthermore, the inversion shows that this vertical anomaly is connected to the adjacent volcanic complex through a narrow ( 3 km wide) low velocity corridor slicing the survey area at a depth of 4-6 km. The NE-SW direction of this elongated zone matches the strike of the Watukosek fault system. Distinct magmatic chambers are also inferred below the active volcanoes. The large-scale tomography features an exceptional example of a subsurface connection between a volcanic complex and a solitary erupting hydrothermal system hosted in a hydrocarbon-rich back-arc sedimentary basin. These results are consistent with a scenario where deep-seated fluids (e.g., magmas and released hydrothermal fluids) flow along a region of enhanced transmissivity (i.e., the Watukosek fault system damage zone) from the volcanic arc toward the back arc basin where Lusi resides. The triggered metamorphic reactions occurring at depth in the organic-rich sediments generated significant overpressure and fluid upwelling that is today released at the spectacular Lusi eruption site.

Converting Y(OH){sub 3} nanofiber bundles to YVO{sub 4} polyhedrons for photodegradation of dye contaminants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Li; School of Chemical Engineering and Materials Engineering, Huainan Normal University, Huainan 232038; Zou, Lei

2015-08-15

Highlights: • YVO{sub 4} polyhedrons were prepared from Y(OH){sub 3} nanofiber bundles through a hydrothermal conversion process. • In contrast to the bulk oxide, the photocatalytic performance of the polyhedrons was much improved. • The main active species involved in photocatalytic oxidative reaction were also investigated. - Abstract: This paper reports a hydrothermal conversion process of rare earth microstructures, Y(OH){sub 3} nanofiber bundles, into YVO{sub 4} polyhedrons, together with the investigation on the related photocatalytic properties. The as-synthesized samples were characterized by a variety of techniques, including XRD, SEM, TEM and UV–vis diffuse reflectance spectroscopy. The photocatalytic activities of YVO{submore » 4} polyhedrons were comparatively evaluated by the photodegradation of Rhodamine B and methylene blue. In contrast to the bulk oxide, the photocatalytic performance of the polyhedrons was much improved. The mechanism and the main active species involved in photocatalytic oxidative reaction were also investigated through the carriers trapping experiments.« less

Hydrothermal activity lowers trophic diversity in Antarctic hydrothermal sediments

NASA Astrophysics Data System (ADS)

Bell, James B.; Reid, William D. K.; Pearce, David A.; Glover, Adrian G.; Sweeting, Christopher J.; Newton, Jason; Woulds, Clare

2017-12-01

Hydrothermal sediments are those in which hydrothermal fluid is discharged through sediments and are one of the least studied deep-sea ecosystems. We present a combination of microbial and biochemical data to assess trophodynamics between and within hydrothermal and background areas of the Bransfield Strait (1050-1647 m of depth). Microbial composition, biomass, and fatty acid signatures varied widely between and within hydrothermally active and background sites, providing evidence of diverse metabolic activity. Several species had different feeding strategies and trophic positions between hydrothermally active and inactive areas, and the stable isotope values of consumers were not consistent with feeding morphology. Niche area and the diversity of microbial fatty acids was lowest at the most hydrothermally active site, reflecting trends in species diversity. Faunal uptake of chemosynthetically produced organics was relatively limited but was detected at both hydrothermal and non-hydrothermal sites, potentially suggesting that hydrothermal activity can affect trophodynamics over a much wider area than previously thought.

Strontium isotope constraints on fluid flow in the sheeted dike complex of fast spreading crust: Pervasive fluid flow at Pito Deep

NASA Astrophysics Data System (ADS)

Barker, A. K.; Coogan, L. A.; Gillis, K. M.; Weis, D.

2008-06-01

Fluid flow through the axial hydrothermal system at fast spreading ridges is investigated using the Sr-isotopic composition of upper crustal samples recovered from a tectonic window at Pito Deep (NE Easter microplate). Samples from the sheeted dike complex collected away from macroscopic evidence of channelized fluid flow, such as faults and centimeter-scale hydrothermal veins, show a range of 87Sr/86Sr from 0.7025 to 0.7030 averaging 0.70276 relative to a protolith with 87Sr/86Sr of ˜0.7024. There is no systematic variation in 87Sr/86Sr with depth in the sheeted dike complex. Comparison of these new data with the two other localities that similar data sets exist for (ODP Hole 504B and the Hess Deep tectonic window) reveals that the extent of Sr-isotope exchange is similar in all of these locations. Models that assume that fluid-rock reaction occurs during one-dimensional (recharge) flow lead to significant decreases in the predicted extent of isotopic modification of the rock with depth in the crust. These model results show systematic misfits when compared with the data that can only be avoided if the fluid flow is assumed to be focused in isolated channels with very slow fluid-rock exchange. In this scenario the fluid at the base of the crust is little modified in 87Sr/86Sr from seawater and thus unlike vent fluids. Additionally, this model predicts that some rocks should show no change from the fresh-rock 87Sr/86Sr, but this is not observed. Alternatively, models in which fluid-rock reaction occurs during upflow (discharge) as well as downflow, or in which fluids are recirculated within the hydrothermal system, can reproduce the observed lack of variation in 87Sr/86Sr with depth in the crust. Minimum time-integrated fluid fluxes, calculated from mass balance, are between 1.5 and 2.6 × 106 kg m-2 for all areas studied to date. However, new evidence from both the rocks and a compilation of vent fluid compositions demonstrates that some Sr is leached from the crust. Because this leaching lowers the fluid 87Sr/86Sr without changing the rock 87Sr/86Sr, these mass balance models must underestimate the time-integrated fluid flux. Additionally, these values do not account for fluid flow that is channelized within the crust.

Integrated geophysical and hydrothermal models of flank degassing and fluid flow at Masaya Volcano, Nicaragua

USGS Publications Warehouse

Sanford, Ward E.; Pearson, S.C.P.; Kiyosugi, K.; Lehto, H.L.; Saballos, J.A.; Connor, C.B.

2012-01-01

We investigate geologic controls on circulation in the shallow hydrothermal system of Masaya volcano, Nicaragua, and their relationship to surface diffuse degassing. On a local scale (~250 m), relatively impermeable normal faults dipping at ~60° control the flowpath of water vapor and other gases in the vadose zone. These shallow normal faults are identified by modeling of a NE-SW trending magnetic anomaly of up to 2300 nT that corresponds to a topographic offset. Elevated SP and CO2 to the NW of the faults and an absence of CO2 to the SE suggest that these faults are barriers to flow. TOUGH2 numerical models of fluid circulation show enhanced flow through the footwalls of the faults, and corresponding increased mass flow and temperature at the surface (diffuse degassing zones). On a larger scale, TOUGH2 modeling suggests that groundwater convection may be occurring in a 3-4 km radial fracture zone transecting the entire flank of the volcano. Hot water rising uniformly into the base of the model at 1 x 10-5 kg/m2s results in convection that focuses heat and fluid and can explain the three distinct diffuse degassing zones distributed along the fracture. Our data and models suggest that the unusually active surface degassing zones at Masaya volcano can result purely from uniform heat and fluid flux at depth that is complicated by groundwater convection and permeability variations in the upper few km. Therefore isolating the effects of subsurface geology is vital when trying to interpret diffuse degassing in light of volcanic activity.

The habitat and nature of early life.

PubMed

Nisbet, E G; Sleep, N H

2001-02-22

Earth is over 4,500 million years old. Massive bombardment of the planet took place for the first 500-700 million years, and the largest impacts would have been capable of sterilizing the planet. Probably until 4,000 million years ago or later, occasional impacts might have heated the ocean over 100 degrees C. Life on Earth dates from before about 3,800 million years ago, and is likely to have gone through one or more hot-ocean 'bottlenecks'. Only hyperthermophiles (organisms optimally living in water at 80-110 degrees C) would have survived. It is possible that early life diversified near hydrothermal vents, but hypotheses that life first occupied other pre-bottleneck habitats are tenable (including transfer from Mars on ejecta from impacts there). Early hyperthermophile life, probably near hydrothermal systems, may have been non-photosynthetic, and many housekeeping proteins and biochemical processes may have an original hydrothermal heritage. The development of anoxygenic and then oxygenic photosynthesis would have allowed life to escape the hydrothermal setting. By about 3,500 million years ago, most of the principal biochemical pathways that sustain the modern biosphere had evolved, and were global in scope.

Microstructure and magnetic properties of MFe{sub 2}O{sub 4} (M = Co, Ni, and Mn) ferrite nanocrystals prepared using colloid mill and hydrothermal method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wei, E-mail: wangwei@mail.buct.edu.cn; Ding, Zui; Zhao, Xiruo

2015-05-07

Three kinds of spinel ferrite nanocrystals, MFe{sub 2}O{sub 4} (M = Co, Ni, and Mn), are synthesized using colloid mill and hydrothermal method. During the synthesis process, a rapid mixing and reduction of cations with sodium borohydride (NaBH{sub 4}) take place in a colloid mill then through a hydrothermal reaction, a slow oxidation and structural transformation of the spinel ferrite nanocrystals occur. The phase purity and crystal lattice parameters are estimated by X-ray diffraction studies. Scanning electron microscopy and transmission electron microscopy images show the morphology and particle size of the as-synthesized ferrite nanocrystals. Raman spectrum reveals active phonon modesmore » at room temperature, and a shifting of the modes implies cation redistribution in the tetrahedral and octahedral sites. Magnetic measurements show that all the obtained samples exhibit higher saturation magnetization (M{sub s}). Meanwhile, experiments demonstrate that the hydrothermal reaction time has significant effects on microstructure, morphologies, and magnetic properties of the as-synthesized ferrite nanocrystals.« less

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

PubMed

Cousins, Claire R; Crawford, Ian A

2011-09-01

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

Evolution of Heat Flow with Age on the Southern Flank of the Costa Rica Rift

NASA Astrophysics Data System (ADS)

Kolandaivelu, K. P.; Harris, R. N.; Lowell, R. P.; Wilson, D. J.; Hobbs, R. W.

2017-12-01

Analysis of 67 new conductive heat flow measurements at five sites ranging between ≈ 1.6 and 5.7 Ma on the southern flank of the Costa Rica Rift yields insight into factors that influence hydrothermal circulation in young oceanic crust. The heat flow measurements were collocated with a high-resolution multi-channel seismic line, extending from the ridge axis to ODP hole 504B. The mean conductive heat flow, qobs, 80 mWm-2, is ≈ 25% of the mean lithospheric heat flux, qth, predicted by half-space conductive cooling model. The ratio qobs/qth varies significantly from site to site indicating that advective heat loss may be influenced by the presence of high-angle, ridge-ward dipping normal faults, surface topography, and sediment thickness, which vary significantly along the profile. The 1.6 Ma heat flow site, which is located between two outcrops separated by 2 km and has thin sediment cover, yields qobs/qth » 0.08. The advective heat loss indicates a mass flux of 3 x 10-5 kgm-2s-1 and upper crustal permeabilities of 4 x 10-11 and 3 x 10-9 m2 for 1000 m and 100 m aquifer thicknesses, respectively. At the 2.6 Ma site with 75 m sediment cover, qobs/qth » 0.18 and heat flow is uniformly low, except for one high value near a fault. At the 3.5 Ma site, qobs/qth » 0.15. The heat flow deficit results from outcrop to outcrop flow, but subcritical cellular convection driven by local basement topography produces small heat flow highs and lows superimposed on the overall trend. At the 4.5 Ma site, qobs/qth » 0.06. The heat flow distribution indicates that discharge occurs through a large, thinly-sedimented topographical high, where estimated mass flux is 3 x 10-5 kgm-2s-1. At the oldest site of 5.7 Ma, qobs/qth » 1, but some heat flow values greater than qth occur near sparsely-sedimented basement outcrops, suggesting redistribution of heat by subsurface convection controlled by basement topography, similar to ODP Hole 504B. That qobs/qth » 1 at a much younger age than indicated by global data suggests that basement burial under a thick sediment cover inhibits advective heat loss through the crust. These data were collected as part of a major interdisciplinary NERC and NSF-funded collaboration entitled: Oceanographic and Seismic Characterization of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR).

Kinetic theory of oxygen isotopic exchange between minerals and water

USGS Publications Warehouse

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

1987-01-01

Kinetic and mass conservation equations are used to describe oxygen isotopic exchange between minerals and water in "closed" and open hydrothermal systems. In cases where n coexisting mineral phases having different reaction rates are present, the exchange process is described by a system of n + 1 simultaneous differential equations consisting of n pseudo first-order rate equations and a conservation of mass equation. The simultaneous solutions to these equations generate curved exchange trajectories on ??-?? plots. Families of such trajectories generated under conditions allowing for different fluid mole fractions, different fluid isotopic compositions, or different fluid flow rates are connected by positive-sloped isochronous lines. These isochrons reproduce the effects observed in hydrothermally exchanged mineral pairs including 1) steep positive slopes, 2) common reversals in the measured fractionation factors (??), and 3) measured fractionations that are highly variable over short distances where no thermal gradient can be geologically demonstrated. ?? 1987.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

Iron-oxidizing bacteria becomes increasingly described in different geological settings from volcanically active seamounts, coastal waters, to diffuse hydrothermal vents near seafloor spreading centers [Emerson et al., 2010]. They have been mostly identified and described in Pacific Ocean, and have been only recently found in hydrothermal systems associated to slow spreading center of the Mid-Atlantic Ridge (MAR) [Scott et al., 2015]. During the MoMARSAT'13 cruise at Lucky Strike hydrothermal field (MAR), a new hydrothermal site was discovered at about 1.5 km eastward from the lava lake and from the main hydrothermal vents. This active venting site, named Capelinhos, is therefore the most distant from the volcano, features many chimneys, both focused and diffuses. The hydrothermal end-member fluids from Capelinhos are different from those of the other sites of Lucky Strike, showing the highest content of iron (Fe/Mn≈3.96) and the lowest chlorinity (270 mmol/l) [Leleu et al., 2015]. Most of the chimneys exhibit rust-color surfaces and bacterial mats near diffuse flows. During the MoMARSAT'15 cruise, an active chimney, a small inactive one, and rust-color bacterial mat near diffuse flow were sampled at Capelinhos. Observations by SEM of the hydrothermal samples revealed the presence of iron oxides in an assemblage of tubular "sheaths", assembled "stalks", helical "stalks" and amorphous aggregates. These features are similar to those described from the Loihi iron-mats deposits and argue for the occurrence of iron-oxidizing bacteria. Cultures under micro-aerobic and neutral pH conditions allowed us to isolate strains from the small inactive chimney. Pyrosequencing of the 16S rRNA gene of the isolates and environmental samples will soon be performed, which should confirm the presence of iron-oxidizing bacteria and reveal the organization of bacterial communities in this original and newly discovered hydrothermal site of the slow spreading Mid-Atlantic Ridge. Emerson, D., et al. (2010), Annu Rev Microbiol, 64(1), 561-583. Leleu, T., et al. (2015), Fluid geochemistry of the Capelinhos Vent Site. A key to understand the Lucky Strike hydrothermal vent field (37°N, MAR), AGU fall meeting Abstract, San Francisco, USA. Scott, J. J.,et al. (2015), PLoS ONE, 10(3), e0119284.

Near-field entrainment in black smoker plumes

NASA Astrophysics Data System (ADS)

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

2013-12-01

In this work, we study the entrainment rate of the ambient fluid into a plume in the extreme conditions of hydrothermal venting at ocean floor depths that would be difficult to reproduce in the laboratory. Specifically, we investigate the flow regime in the lower parts of three black smoker plumes in the Main Endeavour Field on the Juan de Fuca Ridge discharging at temperatures of 249°C, 333°C, and 336°C and a pressure of 21 MPa. Such flow conditions are typical for ocean floor hydrothermal venting but would be difficult to reproduce in the laboratory. The centerline temperature was measured at several heights in the plume above the orifice. Using a previously developed turbine flow meter, we also measured the mean flow velocity at the orifice. Measurements were conducted during dives 4452 and 4518 on the submersible Alvin. Using these measurements, we obtained a range of 0.064 - 0.068 for values of the entrainment coefficient α, which is assumed constant near the orifice. This is half the value of α ≈ 0.12 - 0.13 that would be expected for plume flow regimes based on the existing laboratory results and field measurements in lower temperature and pressure conditions. In fact, α = 0.064 - 0.068 is even smaller than the value of α ≈ 0.075 characteristic of jet flow regimes and appears to be the lowest reported in the literature. Assuming that the mean value α = 0.066 is typical for hydrothermal venting at ocean floor depths, we then characterized the flow regimes of 63 black smoker plumes located on the Endeavor Segment of the Juan de Fuca Ridge. Work with the obtained data is ongoing, but current results indicate that approximately half of these black smokers are lazy in the sense that their plumes exhibit momentum deficits compared to the pure plume flow that develops as the plume rises. The remaining half produces forced plumes that show the momentum excess compared to the pure plumes. The lower value of the entrainment coefficient has important implications for measurements of mass and heat output at mid-oceanic ridges. For example, determining heat output based on the maximum height of plume rise has become a common method of measuring heat flux produced by hydrothermal circulation at mid-oceanic ridges. The fundamental theory for the rise and spreading of turbulent buoyant plumes suggests that the heat output in this method is proportional to α2 and is, therefore, sensitive to the value of α. The considerably different entrainment rates in lazy and forced black smoker plumes may be important for understanding larvae transport mechanism in the life cycle of macrofauna near hydrothermal vents.

High-resolution simulations of multi-phase flow in magmatic-hydrothermal systems with realistic fluid properties

NASA Astrophysics Data System (ADS)

Geiger, S.; Driesner, T.; Matthai, S.; Heinrich, C.

2002-12-01

Realistic modelling of multi-phase fluid flow, energy and component transport in magmatic-hydrothermal systems is very challenging because hydrological properties of fluids and rocks vary over many orders of magnitude and the geometric complexities of such systems. Furthermore, density dependent component transport and transient permeability variations due to P-T changes and fluid-rock interactions introduce additional difficulties. As a result, the governing equations for the hydrodynamics, energy and component transport, and thermodynamics in magmatic hydrothermal systems are highly non-linear and strongly coupled. Essential requirements of a numerical formulation for such a system are: (1) a treatment of the hydrodynamics that can accurately resolve complex geological structures and represent the highly variable fluid velocities herein, (2) a realistic thermodynamic representation of the fluid properties including the wide P-T-X range of liquid+vapour coexistence for the highly saline fluids, and (3) an accurate handling of the highly contrasting transport properties of the two fluids. We are combining higher order finite-element (FE) methods with total variation diminishing finite volume (TVDFV) methods to model the hydrodynamics and energy and component transport of magmatic hydrothermal systems. Combined FE and TVDFV methods are mass and shock preserving, yield great geometric flexibility in 2D and 3D [2]. Furthermore, efficient matrix solvers can be employed to model fluid flow in geologically realistic structures [5]. The governing equations are linearized by operator-splitting and solved sequentially using a Picard iteration scheme. We chose the system water-NaCl as a realistic proxy for natural fluids occurring in magmatic-hydrothermal systems. An in-depth evaluation of the available experimental and theoretical data led to a consistent and accurate set of formulations for the PVTXH relations that are valid from 0 to 800 C, 0 to 500 MPa, and 0 to 1 XNaCl. Dynamic viscosities are currently approximated by the approach of Palliser and McKibbin [4]. The numerical solutions of the governing equations and the equation of state are embedded in our object-oriented C++ code CSP3D4.0 [6]. Comparisons of the numerical solutions carried out with CSP for solute transport with analytical solutions and classical test cases for density dependent flow (i.e., Elder problem [1]) show very good agreement. The numerical solutions carried out with CSP and the established United States Geological Survey code HYDROTHERM [3] for multi-phase flow and energy transport also yield a very good agreement. Fluid inclusion data can be used to constrain the PTX properties of the hydrothermal fluids in numerical solutions. [1] Journal of Fluid Mechanics 27, 609-623 [2] ANU Mathematical Research Report, MRR01-023 [3] USGS Water Investigations Report 94-4045 [4] Transport in Porous Media 33, 155-171 [5] AAPG Bulletin 80, 1763-1779 [6] CSP User's Guide, Dept. of Earth Sciences ETH Zurich

Towards Developing Systematics for Using Periodic Studies of the Hydrothermal Manifestations as Effective Tool for Monitoring Largely 'inaccessible' Volcanoes

NASA Astrophysics Data System (ADS)

Alam, M.

2010-12-01

The San José and Tupungatito volcanoes, located near Santiago (Chile), are the potential hazards, given their geological and historical record of explosive eruptions with pyroclastic flows, most recently in 1960 and 1987 respectively (Global Volcanism Program, Smithsonian Institution). What aggravates the potential risk of these very high (>5290m elevation) snow- and ice-covered volcanoes is their location at the source of relatively narrow mountain drainage systems that feed into the Maipo River, flowing through the southern outskirts of Santiago. Sector-collapse and debris-flow, as a result of volcano-ice/snow interaction, can form lahars causing immense destruction to the life and property in the Maipo Valley (Cajón del Maipo). These lahars can cause submergence and burial of vast downstream areas under several meters thick sediment, as in the case of 1980 eruption of Mount St. Helens, USA. In the event of a major eruption, Santiago city will be at peril, with all the drinking water supply installations either destroyed or contaminated to the extent of being abandoned. Besides, ash and tephra will halt the air traffic in the region, particularly in Santiago-Mendoza sector between Chile and Argentina. In a proposed research project (for which funding is awaited from CONICYT, Chile under its Initiation into Research Funding Competition), hydrothermal systems associated with the aforementioned volcanoes will be periodically studied to monitor these volcanoes, in order to develop a Systematics for using the peripheral hydrothermal manifestations, together with nearby surface water bodies, as means for monitoring the activities of the volcano(es). Basic premise of this proposal is to use the relationship between volcanic and hydrothermal activities. Although this association has been observed at many volcanic centers, no attempt has been made to use this relation effectively as a tool for monitoring the volcanoes. Before an eruption or even with increased solfataric activities, the geochemical signatures of the peripheral hydrothermal systems and nearby surface water bodies change significantly. These geochemical changes can be correlated and verified with the observed volcanic activities. Ground deformation of the volcanoes will be studied through Synthetic Aperture Radar (SAR) Interferometry (InSAR), while thermal infrared remote sensing will be used for monitoring thermal anomalies. The reason for choosing these remote methods over the conventional ground based on-site monitoring, is the difficulty in accessing the aforementioned volcanic centers and risk involved in carrying such instruments for frequent observations, as required for the proposed work. In fact, the idea of developing such a Systematics is because of the risk involved in ground based monitoring of these volcanoes. However, microgravity study, which is relatively easier and safer, will be done to validate the results of the remote sensing studies. The expected outcome of the proposed work will not only help in the mitigation of potential hazard of the aforementioned volcanoes, which are currently unmonitored for the reasons mentioned earlier; but will also serve as a model for monitoring remote and largely ‘inaccessible’ volcanoes elsewhere.

Infrared monitoring of hydrothermal echanges occurring in a fracture

NASA Astrophysics Data System (ADS)

Neuville, Amélie; Flekkøy, Eirik; Galland, Olivier; Gundersen, Olav; Jørgen Måløy, Knut

2014-05-01

We aim to characterize the heat exchange that occurs when water flows through a fracture at a different temperature from that of the surrounding rock. This happens during many man-made or natural processes. For instance, injection of water in the context of geothermal power plants or sudden mechanical movements (e.g. rockfalls, landslides, earthquakes) that transport water. It is presently challenging to estimate the heat transfer and temperature inside a fractured medium where water is flowing, despite various numerical models which have been proposed [Neuville et al, 2010, 2013; Kolditz et Clauser, 1998; Heuer, 1991]. The difficulties arise from the complexity of the fracture network, the fracture topography, as well as complex hydraulic flow (e.g. recirculation) and heat exchanges. As a consequence, various hypotheses were made in the models. More experimental data are required in order to calibrate these models, validate or refute the hypotheses. Our work aims to provide temperature data at the fracture scale, in an experiment where the pressure gradient an fracture topography are controlled, with slow hydraulic flow. This required to develop a setup from scratch. An infrared camera and thermistors are used to monitor the temperature in space and time. Water is injected through a partly natural rough fracture with impermeable walls. The bottom part of the fracture is a larvikite stone with a rough surface (presumably this surface was obtained from mode I fracturing), and the top part is a layer which is transparent in the infrared range. As a consequence the infrared camera is expected to measure the temperature at the interface between this transparent layer and the water. The topography of the surface of the rock was reconstituted using a photogrammetry software [MicMac, IGN], and compared to measurements made with a mechanical profiler. Using this geometry we carefully localize the temperature observations (infrared camera and thermistors) and correlate the temperature variations with the topography. Preliminary comparisons with simulations from a coupled lattice Boltzmann method that solves both the complete Navier-Stokes and advection-diffusion equations in three-dimensions are also presented. N. Heuer, T. Küpper and D. Windelberg, Mathematical model of a Hot Dry Rock system, Geophys. J. Int. 105, 659-664 (1991). O. Kolditz and C. Clauser, Numerical simulation of flow and heat transefer in fractured cristalline rocks: application to the hot dry rock site in Rosemanowes (U.K.), Geothermics, 27, 1, p 1-23, (1998). MicMac, IGN: sofware developed by the French Institut Géographique National (IGN) A. Neuville, R. Toussaint, and J. Schmittbuhl, Hydro-thermal flows in a self-affine rough fracture, Phys. Rev. E, 82, 036,317, (2010). A. Neuville, E.G. Flekkøy, R. Toussaint, Influence of asperities on fluid and thermal flow in a fracture: a coupled Lattice Boltzmann study. Journal of Geophysical Research, 118, 7, 3394-3407, (2013).

Study on optimizing ultrasonic irradiation period for thick polycrystalline PZT film by hydrothermal method.

PubMed

Ohta, Kanako; Isobe, Gaku; Bornmann, Peter; Hemsel, Tobias; Morita, Takeshi

2013-04-01

The hydrothermal method utilizes a solution-based chemical reaction to synthesize piezoelectric thin films and powders. This method has a number of advantages, such as low-temperature synthesis, and high purity and high quality of the product. In order to promote hydrothermal reactions, we developed an ultrasonic assisted hydrothermal method and confirmed that it produces dense and thick lead-zirconate-titanate (PZT) films. In the hydrothermal method, a crystal growth process follows the nucleation process. In this study, we verified that ultrasonic irradiation is effective for the nucleation process, and there is an optimum irradiation period to obtain thicker PZT films. With this optimization, a 9.2-μm-thick PZT polycrystalline film was obtained in a single deposition process. For this film, ultrasonic irradiation was carried out from the beginning of the reaction for 18 h, followed by a 6 h deposition without ultrasonic irradiation. These results indicate that the ultrasonic irradiation mainly promotes the nucleation process. Copyright © 2012 Elsevier B.V. All rights reserved.

Geochemical Tracers of Processes Affecting the Formation of Seafloor Hydrothermal Fluids and Deposits in the Manus Back-Arc Basin

DTIC Science & Technology

2009-02-01

21 ° N East Pacific Rise . In Hydrothermal Processes at Seafloor Spreading Centers (ed. P. Rona, K. Boström, L. Laubier, and K. L. Smith), pp... hydrothermal fluids ( 21 ° N East Pacific Rise ) are taken from Mitra et al (1994) and Klinkhammer et al. (1994). The chemical composition...Measures C. I., Walden B., and Weiss R. F. (1985) Chemistry of submarine hydrothermal solutions at 21 ° N , East

Response of maize germination and growth to HTC filtrate type and concentration

USDA-ARS?s Scientific Manuscript database

Hydrothermal carbonization (HTC) is a thermochemical treatment process that allows for the conversion of biomass slurries into value added products. The option of using HTC filtrate as a liquid based fertilizer for agricultural crop production was evaluated through germination and plant growth studi...

Fracturing And Liquid CONvection

DOE Office of Scientific and Technical Information (OSTI.GOV)

2012-02-29

FALCON has been developed to enable simulation of the tightly coupled fluid-rock behavior in hydrothermal and engineered geothermal system (EGS) reservoirs, targeting the dynamics of fracture stimulation, fluid flow, rock deformation, and heat transport in a single integrated code, with the ultimate goal of providing a tool that can be used to test the viability of EGS in the United States and worldwide. Reliable reservoir performance predictions of EGS systems require accurate and robust modeling for the coupled thermal­hydrological­mechanical processes.

A redox-hydrothermal route to β-MnO 2 hollow octahedra

NASA Astrophysics Data System (ADS)

Zhang, Yange; Chen, Liyong; Zheng, Zhi; Yang, Fengling

2009-07-01

Beta-Manganese dioxides' (β-MnO 2) hollow octahedra have been prepared by a synergetic redox reaction using cuprous chloride (CuCl) and hydrochloric acid (HCl) as reductants and potassium permanganate (KMnO 4) as oxidant through a hydrothermal route. During the process, the self-generated chlorine (Cl 2) gas bubbles and HCl's etching appear to be necessary for the formation of MnO 2 hollow structure. The catalytic efficiency of the prepared β-MnO 2 hollow octahedra was high which has been demonstrated by the catalytic oxidation of methylene blue (MB) dye in the presence of hydrogen peroxide (H 2O 2) under natural light.

Three-dimensional seismic structure of a Mid-Atlantic Ridge segment characterized by active detachment faulting (TAG, 25°55’N-26°20’N)

NASA Astrophysics Data System (ADS)

Zhao, M.; Canales, J.

2009-12-01

The Trans-Atlantic Geotraverse (TAG) segment of the Mid-Atlantic Ridge (MAR) (25°55'N-26°20'N) is characterized by massive active and relict high-temperature hydrothermal deposits. Previous geological and geophysical studies indicate that the active TAG hydrothermal mound sits on the hanging wall of an active detachment fault. The STAG microseismicity study revealed that seismicity associated to detachment faulting extends deep into the crust/uppermost mantle (>6 km), forming an arcuate band (in plan view) extending along ~25 km of the rift valley floor (deMartin et al., Geology, 35, 711-714, 2007). Two-dimensional analysis of the STAG seismic refraction data acquired with ocean bottom seismometers (OBSs) showed that the eastern rift valley wall is associated with high P-wave velocities (>7 km/s) at shallow levels (>1 km depth), indicating uplift of lower crustal and/or upper mantle rocks along the detachment fault (Canales et al., Geochem., Geophys., Geosyst., 8, Q08004, doi:08010.01029/02007GC001629, 2008). Here we present a three-dimensional (3D) seismic tomography analysis of the complete STAG seismic refraction OBS dataset to illuminate the 3D crustal architecture of the TAG segment. Our new results provide, for the first time, a detailed picture of the complex, dome-shaped geometry and structure of a nascent oceanic core complex being exhumed by a detachment fault. Our results show a relatively low-velocity anomaly embedded within the high-velocity body forming the footwall of the detachment fault. The low velocity sits 2-3 km immediately beneath the active TAG hydrothermal mound. Although velocities within the low-velocity zone are too high (6 km/s) to represent partial melt, we speculate that this low velocity zone is intimately linked to hydrothermal processes taking place at TAG. We consider three possible scenarios for its origin: (1) a highly fissured zone produced by extensional stresses during footwall exhumation that may help localize fluid flow; (2) a hot -perhaps partially molten- gabbro pluton intruding the detachment fault footwall, which could provide some of the heat driving hydrothermal circulation at TAG; or (3) serpenitized peridotite, with hydration of the footwall being enhanced by hydrothermal fluid flow. This research was granted by the US-NSF (OCE-0137329) and the Chinese National Natural Science Foundation (40776025). M. Zhao was supported by China Scholarship Council (CSC) for 6 months of cooperative research at WHOI.

Relationship between enhanced dewaterability and structural properties of hydrothermal sludge after hydrothermal treatment of excess sludge.

PubMed

Wang, Liping; Li, Aimin; Chang, Yuzhi

2017-04-01

Hydrothermal treatment is an effective method to enhance the deep dewaterability of excess sludge with low energy consumption. In this study, an insight into the relationship between enhanced dewaterability and structural properties of the produced hydrothermal sludge was presented, aiming at better understanding the effect of hydrothermal process on excess sludge dewatering performance. The results indicated that hydrothermal effect induced the transformation of surface water to interstitial and free water by lowering the binding strength between adjacent water and solid particles and that free water became the main form for moisture existence in hydrothermal sludge as temperature was higher than 180 °C. Increase in temperature of hydrothermal treatment generated a significant size reduction of sludge flocs but treated sludge with a higher rigidity, which not only strengthened the network of hydrothermal sludge but also destroyed the binding of EPS with water. Hydrothermal process caused crevice and pore structures of excess sludge to disappear gradually, which was a main driving force of water removal as temperature was below 150 °C. With the temperature of hydrothermal treatment exceeding 180 °C, the morphology of hydrothermal sludge became rough which linked closely to the solid precipitation of condensation polymerization, and further became smooth at higher temperature (210 °C) due to the coal-like structures with higher aromaticities, indicating that hydrothermal reaction pathways began to play a main role in enhanced dewaterability. Hydrothermal treatment led to more alkyl and aromatic carbon, but lower O-alkyl, carboxyl and carbonyl carbon. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterization of regional cold-hydrothermal inflows enriched in arsenic and associated trace-elements in the southern part of the Duero Basin (Spain), by multivariate statistical analysis.

PubMed

Giménez-Forcada, Elena; Vega-Alegre, Marisol; Timón-Sánchez, Susana

2017-09-01

Naturally occurring arsenic in groundwater exceeding the limit for potability has been reported along the southern edge of the Cenozoic Duero Basin (CDB) near its contact with the Spanish Central System (SCS). In this area, spatial variability of arsenic is high, peaking at 241μg/L. Forty-seven percent of samples collected contained arsenic above the maximum allowable concentration for drinking water (10μg/L). Correlations of As with other hydrochemical variables were investigated using multivariate statistical analysis (Hierarchical Cluster Analysis, HCA and Principal Component Analysis, PCA). It was found that As, V, Cr and pH are closely related and that there were also close correlations with temperature and Na + . The highest concentrations of arsenic and other associated Potentially Toxic Geogenic Trace Elements (PTGTE) are linked to alkaline NaHCO 3 waters (pH≈9), moderate oxic conditions and temperatures of around 18°C-19°C. The most plausible hypothesis to explain the high arsenic concentrations is the contribution of deeper regional flows with a significant hydrothermal component (cold-hydrothermal waters), flowing through faults in the basement rock. Water mixing and water-rock interactions occur both in the fissured aquifer media (igneous and metasedimentary bedrock) and in the sedimentary environment of the CDB, where agricultural pollution phenomena are also active. A combination of multivariate statistical tools and hydrochemical analysis enabled the distribution pattern of dissolved As and other PTGTE in groundwaters in the study area to be interpreted, and their most likely origin to be established. This methodology could be applied to other sedimentary areas with similar characteristics and problems. Copyright © 2017 Elsevier B.V. All rights reserved.

Modeling of biomass fractionation in a lab-scale biorefinery: Solubilization of hemicellulose and cellulose from holm oak wood using subcritical water.

PubMed

Cabeza, A; Piqueras, C M; Sobrón, F; García-Serna, J

2016-01-01

Lignocellulose fractionation is a key biorefinery process that need to be understood. In this work, a comprehensive study on hydrothermal-fractionation of holm oak in a semi-continuous system was conducted. The aim was to develop a physicochemical model in order to reproduce the role of temperature and water flow over the products composition. The experiments involved two sets: at constant flow (6mL/min) and two different ranges of temperature (140-180 and 240-280°C) and at a constant temperature range (180-260°C) and different flows: 11.0, 15.0 and 27.9mL/min. From the results, temperature has main influence and flow effect was observed only if soluble compounds were produced. The kinetic model was validated against experimental data, reproducing the total organic carbon profile (e.g. deviation of 33%) and the physicochemical phenomena observed in the process. In the model, it was also considered the variations of molecular weight of each biopolymer, successfully reproducing the biomass cleaving. Copyright © 2015 Elsevier Ltd. All rights reserved.

Insights into Near-Surface Structural Control of Hydrothermal Fluid Movement at Rabbit Creek Thermal Area, Yellowstone National Park

NASA Astrophysics Data System (ADS)

Carr, B.; Elliot, M.; Sims, K. W. W.

2017-12-01

Recent geophysical imaging efforts at Yellowstone National Park have generated questions about the geologic controls of hydrothermal fluid movement within the parks thermal areas. Currently, faults and lava flow contacts are assumed to be the primary permeability pathways for deeper fluid migration to the surface. Although intuition dictates that these structures are responsible, few studies have definitively shown that this is true. Earlier geophysical imaging efforts of phase separation in Norris Geyser Basin have shown strong evidence for fractures and faulting conducting hydrothermal waters. However, no geologically mapped faults are at the surface to confirm these interpretations. Therefore, during the summer of 2017, UW surface geophysical data acquisition focused on understanding the geologic controls for a thermal area within the well-mapped Rabbit Creek Fault Zone (RCFZ). The RCFZ strikes N-S along the eastern edge of Midway Geyser Basin (i.e. the western edge of the Mallard Lake Dome) about 2.8 Km SE of Grand Prismatic spring. The section of the fault zone within the Rabbit Creek thermal area is exposed on the eastern valley wall and dips steeply to the west. Regardless at our site, this puts the two of the plateau rhyolites (i.e. the Biscuit Basin Flow and Mallard Lake flow) next to each other ( 100 m apart) with a small amount of overlying alluvial, glacial and hydrothermal deposits covering the actual fault trace. Interestingly, at least two mapped reverse faults from the Mallard Lake Dome trend NW-SE into the site and are interpreted to intersect to the RCFZ. At RCFZ, DC resistivity and seismic refraction profiling combined with Self-Potential, Magnetics, and Transient Electromagnetic soundings were acquired to provide images and in situ geophysical properties. These data highlight the variable fracturing and surface expressions of the hydrothermal fluids associated with the RCFZ and the NW trending fault zone associated with the Mallard Lake Dome. Therefore, the shallow geophysics at this one study area indicates faulting is the dominant control for hydrothermal waters reaching the surface.

Reduced and unstratified crust in CV chondrite parent body.

PubMed

Ganino, Clément; Libourel, Guy

2017-08-15

Early Solar System planetesimal thermal models predict the heating of the chondritic protolith and the preservation of a chondritic crust on differentiated parent bodies. Petrological and geochemical analyses of chondrites have suggested that secondary alteration phases formed at low temperatures (<300 °C) by fluid-rock interaction where reduced and oxidized Vigarano type Carbonaceous (CV) chondrites witness different physicochemical conditions. From a thermodynamical survey of Ca-Fe-rich secondary phases in CV3 chondrites including silica activity (aSiO 2 ), here we show that the classical distinction between reduced and oxidized chondrites is no longer valid and that their Ca-Fe-rich secondary phases formed in similar reduced conditions near the iron-magnetite redox buffer at low aSiO 2 (log(aSiO 2 ) <-1) and moderate temperature (210-610 °C). The various lithologies in CV3 chondrites are inferred to be fragments of an asteroid percolated heterogeneously via porous flow of hydrothermal fluid. Putative 'onion shell' structures are not anymore a requirement for the CV parent body crust.Meteorites may unlock the history of the early solar system. Here, the authors find, through Ca-Fe-rich secondary phases, that the distinction between reduced and oxidized CV chondrites is invalid; therefore, CV3 chondrites are asteroid fragments that percolated heterogeneously via porous flow of hydrothermal fluid.

Genesis of the post-caldera eastern Upper Basin Member rhyolites, Yellowstone, WY: from volcanic stratigraphy, geochemistry, and radiogenic isotope modeling

NASA Astrophysics Data System (ADS)

Pritchard, Chad J.; Larson, Peter B.

2012-08-01

An array of samples from the eastern Upper Basin Member of the Plateau Rhyolite (EUBM) in the Yellowstone Plateau, Wyoming, were collected and analyzed to evaluate styles of deposition, geochemical variation, and plausible sources for low δ18O rhyolites. Similar depositional styles and geochemistry suggest that the Tuff of Sulphur Creek and Tuff of Uncle Tom's Trail were both deposited from pyroclastic density currents and are most likely part of the same unit. The middle unit of the EUBM, the Canyon flow, may be composed of multiple flows based on a wide range of Pb isotopic ratios (e.g., 206Pb/204Pb ranges from 17.54 to 17.86). The youngest EUBM, the Dunraven Road flow, appears to be a ring fracture dome and contains isotopic ratios and sparse phenocrysts that are similar to extra-caldera rhyolites of the younger Roaring Mountain Member. Petrologic textures, more radiogenic 87Sr/86Sr in plagioclase phenocrysts (0.7134-0.7185) than groundmass and whole-rock ratios (0.7099-0.7161), and δ18O depletions on the order of 5‰ found in the Tuff of Sulphur Creek and Canyon flow indicate at least a two-stage petrogenesis involving an initial source rock formed by assimilation and fractional crystallization processes, which cooled and was hydrothermally altered. The source rock was then lowered to melting depth by caldera collapse and remelted and erupted. The presence of a low δ18O extra-caldera rhyolite indicates that country rock may have been hydrothermally altered at depth and then assimilated to form the Dunraven Road flow.

Adventive hydrothermal circulation on Stromboli volcano (Aeolian Islands, Italy) revealed by geophysical and geochemical approaches: Implications for general fluid flow models on volcanoes

NASA Astrophysics Data System (ADS)

Finizola, A.; Ricci, T.; Deiana, R.; Cabusson, S. Barde; Rossi, M.; Praticelli, N.; Giocoli, A.; Romano, G.; Delcher, E.; Suski, B.; Revil, A.; Menny, P.; Di Gangi, F.; Letort, J.; Peltier, A.; Villasante-Marcos, V.; Douillet, G.; Avard, G.; Lelli, M.

2010-09-01

On March 15th 2007 a paroxysmal explosion occurred at the Stromboli volcano. This event generated a large amount of products, mostly lithic blocks, some of which impacted the ground as far as down to 200 m a.s.l., about 1.5 km far away from the active vents. Two days after the explosion, a new vapour emission was discovered on the north-eastern flank of the volcanic edifice, at 560 m a.s.l., just above the area called "Nel Cannestrà". This new vapour emission was due to a block impact. In order to investigate the block impact area to understand the appearance of the vapour emission, we conducted on May 2008 a multidisciplinary study involving Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR), Self-Potential (SP), CO 2 soil diffuse degassing and soil temperature surveys. This complementary data set revealed the presence of an anomalous conductive body, probably related to a shallow hydrothermal level, at about 10-15 m depth, more or less parallel to the topography. It is the first time that such a hydrothermal fluid flow, with a temperature close to the water boiling point (76 °C) has been evidenced at Stromboli at this low elevation on the flank of the edifice. The ERT results suggest a possible link between (1) the main central hydrothermal system of Stromboli, located just above the plumbing system feeding the active vents, with a maximum of subsurface soil temperature close to 90 °C and limited by the NeoStromboli summit crater boundary and (2) the investigated area of Nel Cannestrà, at ~ 500 m a.s.l., a buried eruptive fissure active 9 ka ago. In parallel, SP and CO 2 soil diffuse degassing measurements suggest in this sector at slightly lower elevation from the block impact crater a magmatic and hydrothermal fluid rising system along the N41° regional fault. A complementary ERT profile, on May 2009, carried out from the NeoStromboli crater boundary down to the block impact crater displayed a flank fluid flow apparently connected to a deeper system. The concept of shallow hydrothermal level have been compared to similar ERT results recently obtained on Mount Etna and La Fossa cone of Vulcano. This information needs to be taken into account in general fluid flow models on volcanoes. In particular, peripheral thermal waters (as those bordering the north-eastern coast of Stromboli) could be contaminated by hydrothermal and magmatic fluids coming from regional faults but also from the summit.

Structural localization and origin of compartmentalized fluid flow, Comstock lode, Virginia City, Nevada

USGS Publications Warehouse

Berger, B.R.; Tingley, J.V.; Drew, L.J.

2003-01-01

Bonanza-grade orebodies in epithermal-style mineral deposits characteristically occur as discrete zones within spatially more extensive fault and/or fracture systems. Empirically, the segregation of such systems into compartments of higher and lower permeability appears to be a key process necessary for high-grade ore formation and, most commonly, it is such concentrations of metals that make an epithermal vein district world class. In the world-class silver- and gold-producing Comstock mining district, Nevada, several lines of evidence lead to the conclusion that the Comstock lode is localized in an extensional stepover between right-lateral fault zones. This evidence includes fault geometries, kinematic indicators of slip, the hydraulic connectivity of faults as demonstrated by veins and dikes along faults, and the opening of a normal-fault-bounded, asymmetric basin between two parallel and overlapping northwest-striking, lateral- to lateral-oblique-slip fault zones. During basin opening, thick, generally subeconomic, banded quartz-adularia veins were deposited in the normal fault zone, the Comstock fault, and along one of the bounding lateral fault zones, the Silver City fault. As deformation continued, the intrusion of dikes and small plugs into the hanging wall of the Comstock fault zone may have impeded the ability of the stepover to accommodate displacement on the bounding strike-slip faults through extension within the stepover. A transient period of transpressional deformation of the Comstock fault zone ensued, and the early-stage veins were deformed through boudinaging and hydraulic fragmentation, fault-motion inversion, and high- and low-angle axial rotations of segments of the fault planes and some fault-bounded wedges. This deformation led to the formation of spatially restricted compartments of high vertical permeability and hydraulic connectivity and low lateral hydraulic connectivity. Bonanza orebodies were formed in the compartmentalized zones of high permeability and hydraulic connectivity. As heat flow and related hydrothermal activitv waned along the Comstock fault zone, extension was reactivated in the stepover along the Occidental zone of normal faults east of the Comstock fault zone. Volcanic and related intrusive activity in this part of the stepover led to a new episode of hydrothermal activity and formation of the Occidental lodes.

Preliminary Results from an Integrated Airborne EM and Aeromagnetic Survey in Yellowstone National Park

NASA Astrophysics Data System (ADS)

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

2017-12-01

Yellowstone National Park hosts over 10,000 thermal features (e.g. geysers, fumaroles, mud pots, and hot springs), yet little is known about the circulation depth of meteoric water feeding these features, nor the lithological and structural bounds on the pathways that guide deep, hot fluids to the surface. Previous near-surface geophysical studies have been effective in imaging shallow hydrothermal pathways in some areas of the park, but these methods are difficult to conduct over the large areas needed to characterize entire hydrothermal systems. Transient electromagnetic (TEM) soundings and 2D direct current (DC) resistivity profiles show that hydrothermal fluids at active sites have a higher electrical conductivity than the surrounding hydrothermally inactive areas. For that reason, airborne TEM is an effective method to characterize large areas and identify hydrothermally active and inactive zones using electrical conductivity. Aeromagnetic data have been useful in mapping faults that localize hot springs, making the integration of aeromagnetic and EM data effective for structurally characterizing fluid pathways. Here we present the preliminary results from an airborne transient electromagnetic (TEM) and magnetic survey acquired jointly by the U.S. Geological Survey (USGS) and the University of Wyoming (UW) in November 2016. We integrate the EM and magnetic data for the purpose of edge detection of rhyolite flow boundaries as well as source depth of hydrothermal features. The maximum horizontal gradient technique applied on magnetic data is a useful tool that used to estimate source depth as well as indicate faults and fractures. The integration of EM with magnetics allows us to distinguish hydrothermally altered fault systems that guide fluids in the subsurface. We have used preliminary 2D inversions of EM from Aarhus Workbench to delineate rhyolite flow edges in the upper 300-600 meters and cross-checked those boundaries with the aeromagnetic map.

Dissolved gases in hydrothermal (phreatic) and geyser eruptions at Yellowstone National Park, USA

USGS Publications Warehouse

Hurwitz, Shaul; Clor, Laura; McCleskey, R. Blaine; Nordstrom, D. Kirk; Hunt, Andrew G.; Evans, William C.

2016-01-01

Multiphase and multicomponent fluid flow in the shallow continental crust plays a significant role in a variety of processes over a broad range of temperatures and pressures. The presence of dissolved gases in aqueous fluids reduces the liquid stability field toward lower temperatures and enhances the explosivity potential with respect to pure water. Therefore, in areas where magma is actively degassing into a hydrothermal system, gas-rich aqueous fluids can exert a major control on geothermal energy production, can be propellants in hazardous hydrothermal (phreatic) eruptions, and can modulate the dynamics of geyser eruptions. We collected pressurized samples of thermal water that preserved dissolved gases in conjunction with precise temperature measurements with depth in research well Y-7 (maximum depth of 70.1 m; casing to 31 m) and five thermal pools (maximum depth of 11.3 m) in the Upper Geyser Basin of Yellowstone National Park, USA. Based on the dissolved gas concentrations, we demonstrate that CO2 mainly derived from magma and N2 from air-saturated meteoric water reduce the near-surface saturation temperature, consistent with some previous observations in geyser conduits. Thermodynamic calculations suggest that the dissolved CO2 and N2 modulate the dynamics of geyser eruptions and are likely triggers of hydrothermal eruptions when recharged into shallow reservoirs at high concentrations. Therefore, monitoring changes in gas emission rate and composition in areas with neutral and alkaline chlorine thermal features could provide important information on the natural resources (geysers) and hazards (eruptions) in these areas.

PROCESS IMPROVEMENT STUDIES ON THE BATTELLE HYDROTHERMAL COAL PROCESS

EPA Science Inventory

The report gives results of a study to improve the economic viability of the Battelle Hydrothermal (HT) Coal Process by reducing the costs associated with liquid/solid separation and leachant regeneration. Laboratory experiments were conducted to evaluate process improvements for...

Toxicity evaluation of process water from hydrothermal carbonization of sugarcane industry by-products.

PubMed

Fregolente, Laís Gomes; Miguel, Thaiz Batista Azevedo Rangel; de Castro Miguel, Emilio; de Almeida Melo, Camila; Moreira, Altair Benedito; Ferreira, Odair Pastor; Bisinoti, Márcia Cristina

2018-03-29

Hydrothermal carbonization (HTC) is a thermochemical process carried out in an aqueous medium. It is capable of converting biomass into a solid, carbon-rich material (hydrochar), and producing a liquid phase (process water) which contains the unreactive feedstock and/or chemical intermediates from the carbonization reaction. The aim of this study was to evaluate the characteristics of process water generated by HTC from vinasse and sugarcane bagasse produced by sugarcane industry and to evaluate its toxicity to both marine (using Artemia salina as a model organism) and the terrestrial environment (through seed germination studies of maize, lettuce, and tomato). The experiments showed that concentrated process water completely inhibited germination of maize, lettuce, and tomato seeds. On the other hand, diluted process water was able to stimulate seedlings of maize and tomato and enhance root and shoot growth. For Artemia, the LC 50 indicated that the process water is practically non-toxic; however, morphological changes, especially damages to the digestive tube and antennas of Artemia, were observed for the concentration of 1000 mg C L -1 .

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

USGS Publications Warehouse

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

2001-01-01

Communities in lowlands near volcanoes are vulnerable to significant volcanic flow hazards in addition to those associated directly with eruptions. The largest such risk is from debris flows beginning as volcanic landslides, with the potential to travel over 100 kilometers. Stratovolcanic edifices commonly are hydrothermal aquifers composed of unstable, altered rock forming steep slopes at high altitudes, and the terrain surrounding them is commonly mantled by readily mobilized, weathered airfall and ashflow deposits. We propose that volcano hazard assessments integrate the potential for unanticipated debris flows with, at active volcanoes, the greater but more predictable potential of magmatically triggered flows. This proposal reinforces the already powerful arguments for minimizing populations in potential flow pathways below both active and selected inactive volcanoes. It also addresses the potential for volcano flank collapse to occur with instability early in a magmatic episode, as well as the 'false-alarm problem'-the difficulty in evacuating the potential paths of these large mobile flows. Debris flows that transform from volcanic landslides, characterized by cohesive (muddy) deposits, create risk comparable to that of their syneruptive counterparts of snow and ice-melt origin, which yield noncohesive (granular) deposits, because: (1) Volcano collapses and the failures of airfall- and ashflow-mantled slopes commonly yield highly mobile debris flows as well as debris avalanches with limited runout potential. Runout potential of debris flows may increase several fold as their volumes enlarge beyond volcanoes through bulking (entrainment) of sediment. Through this mechanism, the runouts of even relatively small collapses at Cascade Range volcanoes, in the range of 0.1 to 0.2 cubic kilometers, can extend to populated lowlands. (2) Collapse is caused by a variety of triggers: tectonic and volcanic earthquakes, gravitational failure, hydrovolcanism, and precipitation, as well as magmatic activity and eruptions. (3) Risk of collapse begins with initial magmatic activity and increases as intrusion proceeds. An archetypal debris flow from volcanic terrain occurred in Colombia with a tectonic earthquake (M 6.4) in 1994. The Rio Piez conveyed a catastrophic wave of debris flow over 100 kilometers, coalesced from multiple slides of surflcial material weakened both by weathering and by hydrothermal alteration in a large strato- volcano. Similar seismogenic flows occurred in Mexico in 1920 (M -6.5), Chile in 1960 (M 9.2), and Ecuador in 1987 (M 6.1 and 6.9). Velocities of wave fronts in two examples were 60 to 90 km/hr (17-25 meters per second) over the initial 30 kilometers. Volcano flank and sector collapses may produce untransformed debris avalanches, as occurred initially at Mount St. Helens in 1980. However, at least as common is direct transformation of the failed mass to a debris flow. At two other volcanoes in the Cascade Range-- Mount Rainier and Mount Baker--rapid transformation and high mobility were typical of most of at least 15 Holocene flows. This danger exists downstream from many stratovolcanoes worldwide; the population at risk is near 150,000 and increasing at Mount Rainier. The first step in preventing future catastrophes is documenting past flows. Deposits of some debris flows, however, can be mistaken for those of less-mobile debris avalanches on the basis of mounds formed by buoyed megaclasts. Megaclasts may record only the proximal phase of a debris flow that began as a debris avalanche. Runout may have extended much farther, and thus furore flow mobility may be underestimated. Processes and behaviors of megaclast-bearing paleoflows are best inferred from the intermegaclast matrix. Mitigation strategy can respond to volcanic flows regardless of type and trigger by: (1) Avoidance: Limit settlement in flow pathways to numbers that can be evacuated after event warnings (flow is occurring). (2) Instrumental even

Stable isotopes in seafloor hydrothermal systems: Vent fluids, hydrothermal deposits, hydrothermal alteration, and microbial processes

USGS Publications Warehouse

Shanks, Wayne C.

2001-01-01

The recognition of abundant and widespread hydrothermal activity and associated unique life-forms on the ocean floor is one of the great scientific discoveries of the latter half of the twentieth century. Studies of seafloor hydrothermal processes have led to revolutions in understanding fluid convection and the cooling of the ocean crust, the chemical and isotopic mass balance of the oceans, the origin of stratiform and statabound massive-sulfide ore-deposits, the origin of greenstones and serpentinites, and the potential importance of the subseafloor biosphere. Stable isotope geochemistry has been a critical and definitive tool from the very beginning of the modern era of seafloor exploration.

Microwave-Hydrothermal Treated Grape Peel as an Efficient Biosorbent for Methylene Blue Removal

PubMed Central

Ma, Lin; Jiang, Chunhai; Lin, Zhenyu; Zou, Zhimin

2018-01-01

Biosorption using agricultural wastes has been proven as a low cost and efficient way for wastewater treatment. Herein, grape peel treated by microwave- and conventional-hydrothermal processes was used as low cost biosorbent to remove methylene blue (MB) from aqueous solutions. The adsorption parameters including the initial pH value, dosage of biosorbents, contact time, and initial MB concentration were investigated to find the optimum adsorption conditions. The biosorbent obtained by microwave-hydrothermal treatment only for 3 min at 180 °C (microwave-hydrothermal treated grape peel, MGP) showed faster kinetics and higher adsorption capability than that produced by a conventional-hydrothermal process (hydrothermal treated grape peel, HGP) with a duration time of 16 h. The maximum adsorption capability of MGP under the optimum conditions (pH = 11, a dosage of 2.50 g/L) as determined with the Langmuir model reached 215.7 mg/g, which was among the best values achieved so far on biosorbents. These results demonstrated that the grape peel treated by a quick microwave-hydrothermal process can be a very promising low cost and efficient biosorbent for organic dye removal from aqueous solutions. PMID:29385041

Free-living bacterial communities associated with tubeworm (Ridgeia piscesae) aggregations in contrasting diffuse flow hydrothermal vent habitats at the Main Endeavour Field, Juan de Fuca Ridge

PubMed Central

Forget, Nathalie L; Kim Juniper, S

2013-01-01

We systematically studied free-living bacterial diversity within aggregations of the vestimentiferan tubeworm Ridgeia piscesae sampled from two contrasting flow regimes (High Flow and Low Flow) in the Endeavour Hydrothermal Vents Marine Protected Area (MPA) on the Juan de Fuca Ridge (Northeast Pacific). Eight samples of particulate detritus were recovered from paired tubeworm grabs from four vent sites. Most sequences (454 tag and Sanger methods) were affiliated to the Epsilonproteobacteria, and the sulfur-oxidizing genus Sulfurovum was dominant in all samples. Gammaproteobacteria were also detected, mainly in Low Flow sequence libraries, and were affiliated with known methanotrophs and decomposers. The cooccurrence of sulfur reducers from the Deltaproteobacteria and the Epsilonproteobacteria suggests internal sulfur cycling within these habitats. Other phyla detected included Bacteroidetes, Actinobacteria, Chloroflexi, Firmicutes, Planctomycetes, Verrucomicrobia, and Deinococcus–Thermus. Statistically significant relationships between sequence library composition and habitat type suggest a predictable pattern for High Flow and Low Flow environments. Most sequences significantly more represented in High Flow libraries were related to sulfur and hydrogen oxidizers, while mainly heterotrophic groups were more represented in Low Flow libraries. Differences in temperature, available energy for metabolism, and stability between High Flow and Low Flow habitats potentially explain their distinct bacterial communities. PMID:23401293

Dissolution of Olivine, Siderite, and Basalt at 80 Deg C in 0.1 M H2SO4 in a Flow Through Process: Insights into Acidic Weathering on Mars

NASA Technical Reports Server (NTRS)

Golden, D. C.; Ming, D. W.; Hausrath, E. M.; Morris, R. V.; Niles, P. B.; Achilles, C. N.; Ross, D. K.; Cooper, B. L.; Gonzalex, C. P.; Mertzman, S. A.

2012-01-01

The occurrence of jarosite, other sulfates (e.g., Mg-and Ca-sulfates), and hematite along with silicic-lastic materials in outcrops of sedimentary materials at Meridiani Planum (MP) and detection of silica rich deposits in Gusev crater, Mars, are strong indicators of local acidic aqueous processes [1,2,3,4,5]. The formation of sediments at Meridiani Planum may have involved the evaporation of fluids derived from acid weathering of Martian basalts and subsequent diagenesis [6,7]. Also, our previous work on acid weathering of basaltic materials in a closed hydro-thermal system was focused on the mineralogy of the acid weathering products including the formation of jarosite and gray hematite spherules [8,9,10]. The object of this re-search is to extend our earlier qualitative work on acidic weathering of rocks to determine acidic dissolution rates of Mars analog basaltic materials at 80 C using a flow-thru reactor. We also characterized residual phases, including poorly crystalline or amorphous phases and precipitates, that remained after the treatments of olivine, siderite, and basalt which represent likely MP source rocks. This study is a stepping stone for a future simulation of the formation of MP rocks under a range of T and P.

Co-registered Geochemistry and Metatranscriptomics Reveal Unexpected Distributions of Microbial Activity within a Hydrothermal Vent Field

PubMed Central

Olins, Heather C.; Rogers, Daniel R.; Preston, Christina; Ussler, William; Pargett, Douglas; Jensen, Scott; Roman, Brent; Birch, James M.; Scholin, Christopher A.; Haroon, M. Fauzi; Girguis, Peter R.

2017-01-01

Despite years of research into microbial activity at diffuse flow hydrothermal vents, the extent of microbial niche diversity in these settings is not known. To better understand the relationship between microbial activity and the associated physical and geochemical conditions, we obtained co-registered metatranscriptomic and geochemical data from a variety of different fluid regimes within the ASHES vent field on the Juan de Fuca Ridge. Microbial activity in the majority of the cool and warm fluids sampled was dominated by a population of Gammaproteobacteria (likely sulfur oxidizers) that appear to thrive in a variety of chemically distinct fluids. Only the warmest, most hydrothermally-influenced flows were dominated by active populations of canonically vent-endemic Epsilonproteobacteria. These data suggest that the Gammaproteobacteria collected during this study may be generalists, capable of thriving over a broader range of geochemical conditions than the Epsilonproteobacteria. Notably, the apparent metabolic activity of the Gammaproteobacteria—particularly carbon fixation—in the seawater found between discrete fluid flows (the intra-field water) suggests that this area within the Axial caldera is a highly productive, and previously overlooked, habitat. By extension, our findings suggest that analogous, diffuse flow fields may be similarly productive and thus constitute a very important and underappreciated aspect of deep-sea biogeochemical cycling that is occurring at the global scale. PMID:28659879

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…

Liquid and Emulsified Sulfur in Submarine Solfatara Fields of two Northern Mariana Arc Volcanoes.

NASA Astrophysics Data System (ADS)

Nakamura, K.; Embley, R. W.; Chadwick, W. W.; Butterfield, D. A.; Takano, B.; Resing, J. A.; de Ronde, C. E.; Lilley, M. D.; Lupton, J. E.; Merle, S. G.; Inagaki, F.

2006-12-01

Because elemental sulfur melting point is ca 100 deg C (depend on allotropes and heating rate, S8 triple point temperature: 115 deg C), the evidence of liquid sulfur has been known for many subaerial crater lakes and small ponds in geothermal regions throughout the world. But the milky nature of water (sulfur-in- water emulsion in limited water mass) prohibited the direct observation of on-going processes at the bottom of these subaerial lakes. In the passive degassing environment at the summit craters of Daikoku and Nikko Seamounts of the northern Mariana Arc, the continuous flushing of sulfur emulsion by seawater allowed us to observe on- going submarine solfatara processes and associated chemistry through dives with ROVs during the NT05-18 cruise (JAMSTEC R/V Natsushima and ROV hyper-Dolphin) and the Submarine Ring of Fire 2006 cruise (R/V Melville and ROV JASON II). A higher viscosity for liquid elemental sulfur relative to that of seawater, as well as a limited stability of sulfur emulsion (aqueous sulfur sol) at high temperatures in electrolyte solution (seawater), ensures limited mobility of liquid sulfur in the conduits of hydrothermal vents. The subseafloor boiling depth of hydrothermal fluid limits the locus of any liquid sulfur reservoir. It was observed in an exposed liquid sulfur pond that the penetration of gas bubbles (mostly CO2) created sulfur emulsion while collapsing liquid sulfur film between seawater and gas bubbles. Liquid sulfur pits, encrusted sulfur, liquid sulfur fountain structure, sulfur stalactites and stalagmites, mini-pillow lava-like sulfur flows, accretionary sulfur lapilli and sulfur deltas were also observed at the summits of two volcanoes. Note: Solfatara: Italian. A type of fumarole, the gases of which are characteristically sulfurous. In 'Glossary of geology.'

Xylan hydrolysis in Populus trichocarpa × P. deltoides and model substrates during hydrothermal pretreatment.

PubMed

Trajano, Heather L; Pattathil, Sivakumar; Tomkins, Bruce A; Tschaplinski, Timothy J; Hahn, Michael G; Van Berkel, Gary J; Wyman, Charles E

2015-03-01

Previous studies defined easy and difficult to hydrolyze fractions of hemicellulose that may result from bonds among cellulose, hemicellulose, and lignin. To understand how such bonds affect hydrolysis, Populus trichocarpa × Populus deltoides, holocellulose isolated from P. trichocarpa × P. deltoides and birchwood xylan were subjected to hydrothermal flow-through pretreatment. Samples were characterized by glycome profiling, HPLC, and UPLC-MS. Glycome profiling revealed steady fragmentation and removal of glycans from solids during hydrolysis. The extent of polysaccharide fragmentation, hydrolysis rate, and total xylose yield were lowest for P. trichocarpa × P. deltoides and greatest for birchwood xylan. Comparison of results from P. trichocarpa × P. deltoides and holocellulose suggested that lignin-carbohydrate complexes reduce hydrolysis rates and limit release of large xylooligomers. Smaller differences between results with holocellulose and birchwood xylan suggest xylan-cellulose hydrogen bonds limited hydrolysis, but to a lesser extent. These findings imply cell wall structure strongly influences hydrolysis. Copyright © 2014 Elsevier Ltd. All rights reserved.

Geology of the Bir Nifazi Quadrangle, Kingdom of Saudi Arabia

USGS Publications Warehouse

Quick, James E.; Bosch, Paul S.

1990-01-01

A north-trending, 10-km-long belt of gossans crops out within the ophiolite beneath the upper-basalt sequence at Jabal Mardah. Reconnaissance drilling indicates that one of the larger gossans is underlain by a steeply dipping, 15-m-thick, sulfide-rich volcanic wacke that averages 1 percent nickel locally. The ore is composed of pyrite, millerite, polydymite, and minor sphalerite that fill interstices between clasts of the wacke and are intimately intergrown with quartz and nickel-rich epidote and chlorite. These textures and assemblages suggest that the sulfides crystallized in situ from infiltrating hydrothermal fluids. Tuffs and basalt flows appear to have acted as impermeable barriers that channeled the hydrothermal fluids through the more permeable wacke where sulfides were deposited. Carbonate-replaced serpentinized peridotite at the base of the ophiolite is considered a potential source for the nickel. In contrast to most nickel deposits, the mineralized rocks at Jabal Mardah have extremely high Ni/Cu (130 to 260) and negligible concentrations (< 5 ppb) of platinum-group elements.

A comparison of product yields and inorganic content in process streams following thermal hydrolysis and hydrothermal processing of microalgae, manure and digestate.

PubMed

Ekpo, U; Ross, A B; Camargo-Valero, M A; Williams, P T

2016-01-01

Thermal hydrolysis and hydrothermal processing show promise for converting biomass into higher energy density fuels. Both approaches facilitate the extraction of inorganics into the aqueous product. This study compares the behaviour of microalgae, digestate, swine and chicken manure by thermal hydrolysis and hydrothermal processing at increasing process severity. Thermal hydrolysis was performed at 170°C, hydrothermal carbonisation (HTC) was performed at 250°C, hydrothermal liquefaction (HTL) was performed at 350°C and supercritical water gasification (SCWG) was performed at 500°C. The level of nitrogen, phosphorus and potassium in the product streams was measured for each feedstock. Nitrogen is present in the aqueous phase as organic-N and NH3-N. The proportion of organic-N is higher at lower temperatures. Extraction of phosphorus is linked to the presence of inorganics such as Ca, Mg and Fe in the feedstock. Microalgae and chicken manure release phosphorus more easily than other feedstocks. Copyright © 2015. Published by Elsevier Ltd.

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.

Mineral-assisted production of benzene under hydrothermal conditions: Insights from experimental studies on C6 cyclic hydrocarbons

NASA Astrophysics Data System (ADS)

Venturi, Stefania; Tassi, Franco; Gould, Ian R.; Shock, Everett L.; Hartnett, Hilairy E.; Lorance, Edward D.; Bockisch, Christiana; Fecteau, Kristopher M.; Capecchiacci, Francesco; Vaselli, Orlando

2017-10-01

Volatile Organic Compounds (VOCs) are ubiquitously present at low but detectable concentrations in hydrothermal fluids from volcanic and geothermal systems. Although their behavior is strictly controlled by physical and chemical parameters, the mechanisms responsible for the production of most VOCs in natural environments are poorly understood. Among them, benzene, whose abundances were found to be relatively high in hydrothermal gases, can theoretically be originated from reversible catalytic reforming processes, i.e. multi-step dehydrogenation reactions, involving saturated hydrocarbons. However, this hypothesis and other hypotheses are difficult to definitively prove on the basis of compositional data obtained by natural gas discharges only. In this study, therefore, laboratory experiments were carried out to investigate the production of benzene from cyclic hydrocarbons at hydrothermal conditions, specifically 300 °C and 85 bar. The results of experiments carried out in the presence of water and selected powdered minerals, suggest that cyclohexane undergoes dehydrogenation to form benzene, with cyclohexene and cyclohexadiene as by-products, and also as likely reaction intermediates. This reaction is slow when carried out in water alone and competes with isomerization and hydration pathways. However, benzene formation was increased compared to these competing reactions in the presence of sulfide (sphalerite and pyrite) and iron oxide (magnetite and hematite) minerals, whereas no enhancement of any reaction products was observed in the presence of quartz. The production of thiols was observed in experiments involving sphalerite and pyrite, suggesting that sulfide minerals may act both to enhance reactivity and also as reactants after dissolution. These experiments demonstrate that benzene can be effectively produced at hydrothermal conditions through dehydrogenation of saturated cyclic organic structures and highlight the crucial role played by minerals in this process.

Heat flow in the flanks of the Oceanographer-Hayes segment of the Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Le Gal, V.; Lucazeau, F.; Cannat, M.; Battani, A.; Poort, J.; Guichet, X.; Monnin, C.; Fontaine, F. J.; Leroy, S. D.

2016-12-01

It is currently estimated that a third of the oceanic heat loss is due to fluid circulation in the oceanic crust. Besides high and low temperature fluid discharge at ridge axis, off-axis low temperature fluid circulations can affect large volumes of the oceanic crust. Long term investigations of the Eastern Juan de Fuca ridge flank (Hutnak et al.2006) have established a circulation pattern where hydrothermal discharge and recharge occur at basement outcrops and where sediment is mostly impermeable. Here, we present results from the recent Oceanograflu cruise (2013), on the Oceanographer-Hayes segment ridge flanks of the Mid-Atlantic ridge in crust 5 and 12 myrs in age. On both flanks, we obtained 185 temperature gradients and conductivities in-situ, 30 Küllenberg cores (3 to 5 meters long) coupled with temperature gradients in-situ and conductivity measurements onboard. These data are interpreted in terms of heat flow values and are generally lower than the conductive cooling model. Several temperature-depth profiles don't show linear gradients, but rather sigmoid shapes or inverse gradients suggesting superficial circulations through the first meters of sediments. The corresponding heat flow pattern is not similar to the one observed at Juan de Fuca. No systematic links have been observed between basement outcrops and lower or higher heat flow which would point to discharge or recharge sites. Instead, the pattern recalls studies in the North Pond area (Langseth et al.1992), with a clear predominance of low heat flow values over the site. We propose that the North Pond circulation model is applicable to large portions of slow-spreading ridge flanks such as the Atlantic. In this model, seawater cools the uppermost crust below sediments in basins that are typically tens of kms wide, reducing the surface heat flow under cooling model values. Based on subsidence rates, these shallow hydrothermal circulations have a minor impact on the cooling of the diverging plates.

Fault-controlled development of shallow hydrothermal systems: Structural and mineralogical insights from the Southern Andes

NASA Astrophysics Data System (ADS)

Roquer, T.; Arancibia, G.; Rowland, J. V.; Iturrieta, P. C.; Morata, D.; Cembrano, J. M.

2017-12-01

Paleofluid-transporting systems can be recognized as meshes of fracture-filled veins in eroded zones of extinct hydrothermal systems. Here we conducted meso-microstructural analysis and mechanical modeling from two exhumed exposures of the faults governing regional tectonics of the Southern Andes: the Liquiñe-Ofqui Fault System (LOFS) and the Andean Transverse Faults (ATF). A total of 107 fractures in both exposures were analyzed. The ATF specific segment shows two tectonic solutions that can be modeled as Andersonian and non-Andersonian tectonic regimes: (1) shear (mode II/III) failure occurs at differential stresses > 28 MPa and fluid pressures < 40-80% lithostatic in the Andersonian regime; and (2) sporadic hybrid extensional + shear (modes I + II/III) failure occurs at differential stresses < 20 MPa and anomalously high fluid pressures > 85-98% lithostatic in the non-Andersonian regime. Additionally, the LOFS exposure cyclically fails in extension (mode I) or extension + shear (modes I + II/III) in the Andersonian regime, at differential stresses < 28 MPa and fluid pressures > 40-80% lithostatic. In areas of spatial interaction between ATF and LOFS, these conditions might favor: (1) the storage of overpressured fluids in hydrothermal systems associated with the ATF faults, and (2) continuous fluid flow through vertical conduits in the LOFS faults. These observations suggest that such intersections are highly probable locations for concentrated hydrothermal activity, which must be taken into consideration for further geothermal exploration. ACKNOWLEDGEMENTS. PhD CONICYT grants, Centro de Excelencia en Geotermia de los Andes (CEGA-FONDAP/CONICYT Project #15090013), FONDECYT Project #1130030 and Project CONICYT REDES #140036.

Phosphorus reclamation through hydrothermal carbonization of animal manures

USDA-ARS?s Scientific Manuscript database

Projected shortages of global phosphate have prompted investigation of methods that could be employed to capture and recycle phosphate, rather than continue to allow the resource to be essentially irreversibly lost through dilution in surface waters. Hydrothermal carbonization of animal manures from...

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

NASA Astrophysics Data System (ADS)

Zhang, J.

2016-12-01

There is a high temperature hydrothermal activity area in the western plateau of Sichuan. More than 200 hot springs points have been found in the region, including 11 hot spring water temperature above local boiling point. Most of these distribute along Jinshajjiang fracture, Dege-Xiangcheng fracture, Ganzi-Litang fracture as well as Xianshuihe fracture, and form three high-temperature hydrothermal activity strips in the NW-SE direction. Using gravity, magnetic, seismic and helium isotope data, this paper analyzed the crust-mantle heat flow structure, crustal heat source distribution and water heating system. The results show that the geothermal activity mainly controlled by the "hot" crust. The ratio of crustal heat flow and surface heat flow is higher than 60%. In the high temperature hydrothermal activities area, there is lower S wave velocity zone with Vs<3.2 km/s in 15 30 km depth in middle and lower crust. Basing on the S wave velocity inversion temperature of crust-mantle, it has been found that there is a high temperature layer with 850 1000 ° in 20 40 km depth. It is the main heat source of high temperature hydrothermal activity area of western Sichuan. Our argument is that atmospheric precipitation, surface water infiltrated along the fault fracture into the crustal deep, heating by crustal hot source, and circulation to surface become high temperature hot water. Geothermal water mainly reserve in the Triassic strata of the containing water good carbonate rocks, and in the intrusive granite which is along the fault zone. The thermal energy of Surface heat thermal activities mainly comes from the high-temperature hot source which is located in the middle and lower crust. Being in the deep crustal fracture, the groundwater infiltrated to the deep crust and absorbed heat, then, quickly got back to the surface and formed high hot springs.

GALREX 2011: Initial Results of the 2011 NOAA Ocean Exploration Cruise to the Galápagos Rift Using Interactive Telepresence Technology

NASA Astrophysics Data System (ADS)

Holden, J. F.; Baker, E. T.; Embley, R. W.; Hammond, S. R.; Shank, T. M.; Walker, S. L.; White, S. M.; Galrex 2011 Team

2011-12-01

The Galápagos Rift is a classic example of ridge-hotspot interaction. In theory, the increased magma supply to the Rift should create an abundance of active hydrothermal vent sites, and yet previous surveys found that high-temperature vents were more scarce than predicted. The mission goals of GALREX 2011 were to explore the diverse habitats and geological settings of the deep Galápagos region primarily to search for hydrothermal venting, but also to explore other areas of interest. In June 2011, the first multibeam bathymetric map of the Galápagos Rift axis from 101° 18' W to 98° W was made with the EM302 sonar, and an along-axis 'tow-yo' CTD-LSS-ORP hydrocast was conducted for hydrothermal plume signals along with additional EM302 mapping from 89° 18' W to 85° 21' W. In July 2011, the ROV Lil' Hercules explored new sites of hydrothermal venting along the eastern arm of the Rift, the Rosebud hydrothermal vent field, hydrothermal mounds 20 km south of the Rift, one of the Paramount Seamounts for a macrofaunal survey, and a volcano on the Ecuador Rift. Data and ROV video feeds were transmitted by broad-band satellite in real time from the ship to a team of scientists in Seattle, WA; Newport, OR; and Woods Hole, MA. The team evaluated the transmitted data and helped direct seafloor ROV operations in real-time. In total, nearly 4,000 km of seafloor were mapped by EM302, 11 CTD tows covered the entire eastern arm of the Rift, and 12 ROV dives collected > 5 TB of high-definition digital video of the seafloor. The hydrocast survey along the eastern Rift identified two regions with abundant optical and ORP signals directly over the spreading axis. The largest of these was nearly 50 km long between 88° 5' W and 88° 33' W. Five ROV dives near 88° 18' W found recently erupted lobate lava flows and several regions of active diffuse hydrothermal venting. The site had the appearance of a relatively recent eruption as the diffuse venting at the site led to extensive white particles of putative sulfur, presumably of bacterial origin, on the rocks and suspended in the lower water column (hence the high optical signal) and there were only mobile rather than sessile fauna at these vents. Extinct hydrothermal sulfide chimneys over 30 m tall were found within 2 km of the active vents suggesting that the region had previously experienced a period of intense heat loss. Three ROV dives at another plume site near 86° W showed reinvigorated diffuse venting in a once massive clam bed now actively colonized by tubeworms, mussels, and microbial mats and ringed with abundant dandelions. The lack of biota and vitreous, unsedimented lobate flows at the Rosebud diffuse vent field (86° 12' W) suggests that it was paved over by an eruption since 2005. The eastern Galápagos Rift appears to have experienced a series of recent dike injections producing new lava flows and extensive diffuse venting, possibly within the past 5 years. Active, focused high-temperature hydrothermal flow has yet to be found on the eastern Rift, though extinct sulfide chimneys attest that it has occurred.

In situ growth of copper nanocrystals from carbonaceous microspheres with electrochemical glucose sensing properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Xiaoliang; Yan, Zhengguang, E-mail: yanzg2004@gmail.com; Han, Xiaodong, E-mail: xdhan@bjut.edu.cn

2014-02-01

Graphical abstract: In situ growth of copper nanoparticles from hydrothermal copper-containing carbonaceous microspheres was induced by annealing or electron beam irradiation. Obtained micro-nano carbon/copper composite microspheres show electrochemical glucose sensing properties. - Highlights: • We synthesized carbonaceous microspheres containing non-nanoparicle copper species through a hydrothermal route. • By annealing or electron beam irradiation, copper nanoparticles would form from the carbonaceous microspheres in situ. • By controlling the annealing temperature, particle size of copper could be controlled in the range of 50–500 nm. • The annealed carbon/copper hierarchical composite microspheres were used to fabricate an electrochemical glucose sensor. - Abstract: Inmore » situ growth of copper nanocrystals from carbon/copper microspheres was observed in a well-controlled annealing or an electron beam irradiation process. Carbonaceous microspheres containing copper species with a smooth appearance were yielded by a hydrothermal synthesis using copper nitrate and ascorbic acid as reactants. When annealing the carbonaceous microspheres under inert atmosphere, copper nanoparticles were formed on carbon microspheres and the copper particle sizes can be increased to a range of 50–500 nm by altering the heating temperature. Similarly, in situ formation of copper nanocrystals from these carbonaceous microspheres was observed on the hydrothermal product carbonaceous microspheres with electron beam irradiation in a vacuum transmission electron microscopy chamber. The carbon/copper composite microspheres obtained through annealing were used to modify a glassy carbon electrode and tested as an electrochemical glucose sensor.« less

Enrichment of bio-oil after hydrothermal liquefaction (HTL) of microalgae C. vulgaris grown in wastewater: Bio-char and post HTL wastewater utilization studies.

PubMed

Arun, Jayaseelan; Varshini, Padmanabhan; Prithvinath, P Kamath; Priyadarshini, Venkataramani; Gopinath, Kannappan Panchamoorthy

2018-08-01

In this study, bio-oil was produced through hydrothermal liquefaction (HTL) of C. vulgaris biomass cultivated in wastewater and was enriched into transportation fuels. Bio-oil yield was 29.37% wt at 300 °C, 60 min, at 15 g/200 mL biomass loading rate with 3% wt nano ZnO catalyst loading. Applying catalyst reduced oxygen and nitrogen content in bio-oil and increased its calorific value (19.6 ± 0.8 MJ/Kg). Bio-oil was enriched through liquid-liquid extraction (LLE) and higher yield was obtained at 30 °C for dichloromethane solvent (18.2% wt). Compounds of enriched oil were within the petro-diesel range (C 8 -C 21 ). Bio-char after HTL process was activated and used as adsorbent in wastewater treatment process to remove organic pollutants (COD, NO 3 , NH 3 and PO 4 ). Treated wastewater can be supplied as growth medium for microalgae cultivation in further experiments. Nearly 3-4 times the nanocatalyst can be reused in the HTL process. Copyright © 2018 Elsevier Ltd. All rights reserved.

Monitoring Endeavour vent field deep-sea ecosystem dynamics through NEPTUNE Canada seafloor observatory

NASA Astrophysics Data System (ADS)

Matabos, M.; NC Endeavour Science Team

2010-12-01

Mid-ocean ridges are dynamic systems where the complex linkages between geological, biological, chemical, and physical processes are not yet well understood. Indeed, the poor accessibility to the marine environment has greatly limited our understanding of deep-sea ecosystems. Undersea cabled observatories offer the power and bandwidth required to conduct long-term and high-resolution time-series observations of the seafloor. Investigations of mid-ocean ridge hydrothermal ecosystem require interdisciplinary studies to better understand the dynamics of vent communities and the physico-chemical forces that influence them. NEPTUNE Canada (NC) regional observatory is located in the Northeast Pacific, off Vancouver Island (BC, Canada), and spans ecological environments from the beach to the abyss. In September-October 2010, NC will be instrumenting its 5th node, including deployment of a multi-disciplinary suite of instruments in two vent fields on the Endeavour Segment of the Juan de Fuca Ridge. These include a digital camera, an imaging sonar for vent plumes and flow characteristics (i.e. COVIS), temperature resistivity probes, a water sampler and seismometers. In 2011, the TEMPO-mini, a new custom-designed camera and sensor package created by IFREMER for real-time monitoring of hydrothermal faunal assemblages and their ecosystems (Sarrazin et al. 2007), and a microbial incubator, will added to the network in the Main Endeavour and Mothra vent fields. This multidisciplinary approach will involve a scientific community from different institutions and countries. Significant experience aids in this installation. For example, video systems connected to VENUS and NC have led to the development of new experimental protocols for time-series observations using seafloor cameras, including sampling design, camera calibration and image analysis methodologies (see communication by Aron et al. and Robert et al.). Similarly, autonomous deployment of many of the planned instruments has informed their adoption to the cabled instrument array at the Endeavour hydrothermal vents. This provides a unique laboratory for researchers to conduct long-term, integrated studies of hydrothermal vent ecosystem dynamics in relation to environmental variability at different temporal scales. In addition to programmed time-series monitoring, the NC infrastructure will also permit manual and automated modification of observational protocols in response to natural events. This will enhance our ability to document how the entire ecosystem reacts to potentially critical but short-lived environmental forces (e.g. seismic events). Sarrazin et al 2007. TEMPO: a new ecological module for studying deep-sea community dynamics at hydrothermal vents. OCEANS’07 IEEE Aberdeen Conference Proceedings

The Medusa Sea Floor Monitoring System

NASA Astrophysics Data System (ADS)

Flynn, F. T.; Schultz, A.; Gupta, M.; Powers, L.; Klinkhammer, G.

2004-12-01

The Medusa Sea Floor Monitoring System (MSMS) is a technology development project that is designed to enable fundamental research into understanding the potential for and limits to chemolithoautotrophic life. This is life within which inorganic carbon is converted to organic carbon and where only inorganic compounds serve as electron acceptors and electron donors. Such life forms are postulated to be capable of surviving in a Europan ocean. If we can prove that such life forms exist on Earth it would provide credence to the hypothesis that they might exist on other planets or moons in our Solar System. It has been hypothesized that one environment which might foster such life is associated with sub-seafloor hydrothermal vent structures. The goal of the MSMS project is to develop an instrument capable of testing this hypothesis. The MSMS instrument is an evolution of a sea floor monitoring system developed by Dr. Adam Schultz. Its design is the result of many generations of hardware and dive programs. Medusa provides the capability to measure and sample effluent and influent sea floor hydraulic flows associated with hydrothermal vent structures, active sea mounds, and sea floor bore holes. Through this proposal we are developing the next generation Medusa system and initiating the integration of several select chemical and biological sensors into the Medusa backbone. These sensors are an in situ flow-through spectral chemistry system, a cavity ringdown 12C/13C system, and an intrinsic fluorescence instrument. der way. This instrument can be used to target and discriminate between biological samples for automated sample collection

Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation

NASA Astrophysics Data System (ADS)

Hawkes, Jeffrey A.; Rossel, Pamela E.; Stubbins, Aron; Butterfield, David; Connelly, Douglas P.; Achterberg, Eric P.; Koschinsky, Andrea; Chavagnac, Valérie; Hansen, Christian T.; Bach, Wolfgang; Dittmar, Thorsten

2015-11-01

Oceanic dissolved organic carbon (DOC) is an important carbon pool, similar in magnitude to atmospheric CO2, but the fate of its oldest forms is not well understood. Hot hydrothermal circulation may facilitate the degradation of otherwise un-reactive dissolved organic matter, playing an important role in the long-term global carbon cycle. The oldest, most recalcitrant forms of DOC, which make up most of oceanic DOC, can be recovered by solid-phase extraction. Here we present measurements of solid-phase extractable DOC from samples collected between 2009 and 2013 at seven vent sites in the Atlantic, Pacific and Southern oceans, along with magnesium concentrations, a conservative tracer of water circulation through hydrothermal systems. We find that magnesium and solid-phase extractable DOC concentrations are correlated, suggesting that solid-phase extractable DOC is almost entirely lost from solution through mineralization or deposition during circulation through hydrothermal vents with fluid temperatures of 212-401 °C. In laboratory experiments, where we heated samples to 380 °C for four days, we found a similar removal efficiency. We conclude that thermal degradation alone can account for the loss of solid-phase extractable DOC in natural hydrothermal systems, and that its maximum lifetime is constrained by the timescale of hydrothermal cycling, at about 40 million years.

Cell-wall structural changes in wheat straw pretreated for bioethanol production

PubMed Central

Kristensen, Jan B; Thygesen, Lisbeth G; Felby, Claus; Jørgensen, Henning; Elder, Thomas

2008-01-01

Background Pretreatment is an essential step in the enzymatic hydrolysis of biomass and subsequent production of bioethanol. Recent results indicate that only a mild pretreatment is necessary in an industrial, economically feasible system. The Integrated Biomass Utilisation System hydrothermal pretreatment process has previously been shown to be effective in preparing wheat straw for these processes without the application of additional chemicals. In the current work, the effect of the pretreatment on the straw cell-wall matrix and its components are characterised microscopically (atomic force microscopy and scanning electron microscopy) and spectroscopically (attenuated total reflectance Fourier transform infrared spectroscopy) in order to understand this increase in digestibility. Results The hydrothermal pretreatment does not degrade the fibrillar structure of cellulose but causes profound lignin re-localisation. Results from the current work indicate that wax has been removed and hemicellulose has been partially removed. Similar changes were found in wheat straw pretreated by steam explosion. Conclusion Results indicate that hydrothermal pretreatment increases the digestibility by increasing the accessibility of the cellulose through a re-localisation of lignin and a partial removal of hemicellulose, rather than by disruption of the cell wall. PMID:18471316

Mining the earth's heat in the basin and range

USGS Publications Warehouse

Sass, John H.

1995-01-01

The Geothermal Program of the U.S. Geological Survey (USGS) is revisiting the Basin and Range Province after a hiatus of over a decade. The Basin and Range is a region of Neogene extension and generally high, but regionally and locally variable heat flow. The northern Basin and Range (Great Basin) has higher mean elevation and more intense Quaternary extension than does the southern Basin and Range, and a somewhat higher average heat flow. Present geothermal electric power generation (500+ MW) is entirely from hydrothermal systems of the Great Basin. The USGS is seeking industrial partners to investigate the potential for new hydrothermal reservoirs and to develop the technology to enhance the productivity of existing reservoirs.

Mineralization of Alvinella polychaete tubes at hydrothermal vents.

PubMed

Georgieva, M N; Little, C T S; Ball, A D; Glover, A G

2015-03-01

Alvinellid polychaete worms form multilayered organic tubes in the hottest and most rapidly growing areas of deep-sea hydrothermal vent chimneys. Over short periods of time, these tubes can become entirely mineralized within this environment. Documenting the nature of this process in terms of the stages of mineralization, as well as the mineral textures and end products that result, is essential for our understanding of the fossilization of polychaetes at hydrothermal vents. Here, we report in detail the full mineralization of Alvinella spp. tubes collected from the East Pacific Rise, determined through the use of a wide range of imaging and analytical techniques. We propose a new model for tube mineralization, whereby mineralization begins as templating of tube layer and sublayer surfaces and results in fully mineralized tubes comprised of multiple concentric, colloform, pyrite bands. Silica appeared to preserve organic tube layers in some samples. Fine-scale features such as protein fibres, extracellular polymeric substances and two types of filamentous microbial colonies were also found to be well preserved within a subset of the tubes. The fully mineralized Alvinella spp. tubes do not closely resemble known ancient hydrothermal vent tube fossils, corroborating molecular evidence suggesting that the alvinellids are a relatively recent polychaete lineage. We also compare pyrite and silica preservation of organic tissues within hydrothermal vents to soft tissue preservation in sediments and hot springs. © 2014 The Authors. Geobiology Published by John Wiley & Sons Ltd.

Serpentinization and fluid-rock interaction in Jurassic mafic and ultramafic sea-floor: constraints from Ligurian ophiolite sequences

NASA Astrophysics Data System (ADS)

Vogel, Monica; Früh-Green, Gretchen L.; Boschi, Chiara; Schwarzenbach, Esther M.

2014-05-01

The Bracco-Levanto ophiolitic complex (Eastern Liguria) represents one of the largest and better-exposed ophiolitic successions in the Northern Apennines. It is considered to be a fragment of heterogeneous Jurassic lithosphere that records tectono-magmatic and alteration histories similar to those documented along the Mid-Atlantic Ridge, such as at the 15°20'N area and the Atlantis Massif at 30°N. Structural and petrological studies on these rocks provide constraints on metamorphic/deformation processes during formation and hydrothermal alteration of the Jurassic oceanic lithosphere. We present a petrological and geochemical study of deformation processes and fluid-rock interaction in the Bracco-Levanto ophiolitic complex and compare these to modern oceanic hydrothermal systems, such as the Lost City Hydrothermal Field hosted in ultramafic rocks on the Atlantis Massif. A focus is on investigating mass transfer and fluid flow paths during high and low temperature hydrothermal activity, and on processes leading to hydrothermal carbonate precipitation and the formation of ophicalcites, which are characteristic of the Bracco-Levanto sequences. Major element and mineral compositional data allow us to distinguish a multiphase history of alteration characterized by: (1) widespread SiO2 metasomatism during progressive serpentinization, and (2) multiple phases of veining and carbonate precipitation associated with circulation of seawater and high fluid-rock ratios in the shallow ultramafic-dominated portions of the Jurassic seafloor. We observe regional variations in MgO, SiO2 and Al2O3, suggesting Si-flux towards stratigraphically higher units. In general, the ophicalcites have higher Si, Al and Fe concentrations and lower Mg than the serpentinite basement rocks or serpentinites with minimal carbonate veins. Bulk rock trace element data and Sr isotope ratios indicate seawater reacting with rocks of more mafic composition, then channeled towards stratigraphically higher units, leading to Si metasomatism in the serpentinites and ophicalcites. Channelling of Si-rich fluids is also indicated by amphibole and talc growth in shear zones and wall rock around the ophicalcites. δ18O-values of the carbonate veins indicate temperatures up to 150°C and document a decrease in temperature with ongoing serpentinization. Comparison with serpentinites from the Atlantis Massif and 15°20'N indicates a similar degree of Si enrichment in the modern seafloor and suggests that Si-metasomatism may be a fundamental process associated with serpentinization at slow-spreading ridge environments.

Thermal regime of the deep carbonate reservoir of the Po Plain (Italy)

NASA Astrophysics Data System (ADS)

Pasquale, V.; Chiozzi, P.; Verdoya, M.

2012-04-01

Italy is one of the most important countries in the world with regard to high-medium enthalpy geothermal resources, a large part of which is already extracted at relatively low cost. High temperatures at shallow to medium depth occur within a wide belt, several hundred kilometre long, west of the Apennines mountain chain. This belt, affected by recent lithosphere extension, includes several geothermal fields, which are largely exploited for electricity generation. Between the Alps and Apennines ranges, the deeper aquifer, occurring in carbonate rocks of the Po Plain, can host medium enthalpy fluids, which are exploited for district heating. Such a general picture of the available geothermal resources has been well established through several geophysical investigations and drillings. Nevertheless, additional studies are necessary to evaluate future developments, especially with reference to the deep carbonate aquifer of the Po Plain. In this paper, we focus on the eastern sector of the plain and try to gain a better understanding of the thermal regime by using synergically geothermal methodologies and geological information. The analysis of the temperatures recorded to about 6 km depth in hydrocarbon wells supplies basic constraints to outline the thermal regime of the sedimentary basin and to investigate the occurrence and importance of hydrothermal processes in the carbonate layer. After correction for drilling disturbance, temperatures were analysed, together with geological information, through an inversion technique based on a laterally constant thermal gradient model. The inferred thermal gradient changes with depth; it is quite low within the carbonate layer, while is larger in the overlying, practically impermeable formations. As the thermal conductivity variation does not justify such a thermal gradient difference, the vertical change can be interpreted as due to convective processes occurring in the carbonate layer, acting as thermal reservoir. The hydrogeological characteristics hardly permit forced convection in the deep aquifer. Thus, we argue that thermal convection could be the driving mechanism of water flow in the carbonate reservoir. The potential of this mechanism was evaluated by means of the Rayleigh number analysis. A relatively low permeability is required for thermal convection to occur. The carbonate reservoir can be thus envisaged as a hydrothermal convection system of large thickness and extension having a large over-heat ratio. Lateral variation of hydrothermal regime was also tested by using temperature data representing the reservoir thermal conditions. We found that thermal convection is of variable intensity and may more likely occur at an area (Ferrara structural high) where widespread fracturing due to tectonism is expected yielding a local increase in permeability.

Destruction of Energetic Materials in Supercritical Water

DTIC Science & Technology

2002-06-25

PHASE BEHAVIOR UNDER HYDROTHERMAL PROCESSING CONDITIONS...172 E. MODELING TOOLS FOR SOLVATION FREE ENERGIES IN HYDROTHERMAL SYSTEMS...potential equations of state of hydrothermal solutions. Figure 25 shows a schematic of the transient grating experiment. In this experiment, two laser

Heat Flow and Hydrothermal Circulation of the Lucky Strike Segment, Mid Atlantic Ridge

NASA Astrophysics Data System (ADS)

Bonneville, A.; Escartin, J.; Lucazeau, F.; Cannat, M.; Gouze, P.; von Herzen, R. P.; Adam, C.; Le Bars, M.; Monoury, E.; Vidal, V.

2003-12-01

In June 2003, expedition Luckyflux aboard the R/V Poseidon conducted a heat flow survey of a zone centred on the Lucky Strike segment of the Mid Atlantic ridge south of the Azores between ˜35° N and 39° N. Using a 5 m-long lance with 7 outrigger thermal probes, about 150 successful thermal gradient measurements were obtained, 140 of these with in-situ thermal conductivity. Measurements were made at ˜1 mile intervals along several profiles, where adequately sedimented sites were identified using 6-channel and 3.5 kHz seismic data from the previous Sudazores'98 cruise. We conducted heat flow measurements in two areas: a near axis region within the V-shaped ridge of overthickened crust that emanated from the Azores hotspot between ˜14 and 4 Ma, and an off-axis region East of the V-shaped ridge. The off-axis region is characterized by an homogeneous sediment cover, 300-400 m thick, and crustal ages varying between ˜6 and >10 Ma. Long wavelength (tens of km) low heat flow anomalies can be identified but the mean of 160 mWm-2 is comparable to the conductive heat flow expected for a crust of that age. Along two 80-km profiles perpendicular to the ridge, we observed coherent but different patterns. On the first profile, low heat flow values of 20-50 mWm-2 are observed at the base of the V-shaped ridge. These values are 100 mWm-2 below the profile average, showing that hydrothermal circulations can also affect oceanic crust beneath a thick and relatively impermeable sediment cover. On the other profile, heat flow generally decreases from west to east. On both profiles, higher than average values of heat flow are also present, associated on one of them with a nearly outcropping basement elevation. These contrasting overall heat flow patterns in similar geological context indicate that the likely pattern of hydrothermal circulations is mainly 3D, and not driven only by the presence of basement outcrops. In the near-axis region, where the tectonic structure is more complicated and the sediment cover heterogeneous, heat flow data show no clear spatial variation and their mean value, 60 to 90 mWm-2, is systematically lower than theoretical conductive values for young seafloor. These heat flow differences will be used to estimate the importance of advection in the heat budget. This characterization of the regional thermal state around a slow-spreading segment will provide the basis for future long-term studies on the structure, thermal evolution and the hydrothermal systems within the MOMAR (MOnitoring the Mid Atlantic Ridge) project.

The vent microbiome: patterns and drivers

NASA Astrophysics Data System (ADS)

Pachiadaki, M.

2015-12-01

Microbial processes within deep-sea hydrothermal vents affect the global biogeochemical cycles. Still, there are significant gaps in our understanding of the microbiology and the biogeochemistry of deep-sea hydrothermal systems. Vents differ in temperature, host rock composition and fluid chemistry; factors that are hypothesized to shape the distribution of the microbial communities, their metabolic capabilities and their activities. Using large-scale single cell genomics, we obtained insights into the genomic content of several linkages of a diffuse flow vent. The genomes show high metabolic versatility. Sulfur oxidation appears to be predominant but there is the potential of using a variety of e- donors and acceptors to obtain energy. To further assess the ecological importance of the vent auto- and heterotrophs, the global biogeography of the analyzed lineages will be investigated by fragment recruitment of metagenomes produced from the same site as well as other hydrothermal systems. Metatranscriptomic and metaproteomic data will be integrated to examine the expression of the predominant metabolic pathways and thus the main energy sources driving chemoautotrophic production. The comparative analysis of the key players and associated pathways among various vent sites that differ in physicochemical characteristics is anticipated to decipher the patterns and drivers of the global dispersion and the local diversification of the vent microbiome.

A simple, one-step hydrothermal approach to durable and robust superparamagnetic, superhydrophobic and electromagnetic wave-absorbing wood

NASA Astrophysics Data System (ADS)

Wang, Hanwei; Yao, Qiufang; Wang, Chao; Fan, Bitao; Sun, Qingfeng; Jin, Chunde; Xiong, Ye; Chen, Yipeng

2016-10-01

In this work, lamellar MnFe2O4 was successfully planted on a wood surface through the association of hydrogen bonds via the one-pot hydrothermal method. Simultaneously, the fluoroalkylsilane (FAS-17) on the surface of the MnFe2O4 layer formed long-chain or network macromolecules through a poly-condensation process and provided a lower surface energy on the wood surface. The MnFe2O4/wood composite (FMW) presented superior superparamagnetism, superhydrophobicity and electromagnetic wave absorption performance. The results indicated a saturation magnetization of the FMW with excellent superparamagnetism of 28.24 emu·g-1. The minimum value of reflection loss of the FMW reached -8.29 dB at 16.39 GHz with a thickness of 3 mm. Even after mechanical impact and exposure to corrosive liquids, the FMW still maintained a superior superhydrophobicity performance.

Sources and fractionation processes influencing the isotopic distribution of H, O and C in the Long Valley hydrothermal system, California, U.S.A.

USGS Publications Warehouse

White, A.F.; Peterson, M.L.; Wollenberg, H.; Flexser, S.

1990-01-01

The isotopic ratios of H, O and C in water within the Long Valley caldera, California reflect input from sources external to the hydrothermal reservoir. A decrease in ??D in precipitation of 0.5??? km-1, from west to east across Long Valley, is caused by the introduction of less fractionated marine moisture through a low elevation embayment in the Sierra Nevada Mountain Range. Relative to seasonal fluctuations in precipitation (-158 to -35??.), ??D ranges in hot and cold surface and groundwaters are much less variable (-135 to -105??.). Only winter and spring moisture, reflecting higher precipitation rates with lighter isotopic signatures, recharge the hydrological system. The hydrothermal fluids are mixtures of isotopically heavy recharge (??D = - 115???, ??18O = - 15???) derived from the Mammoth embayment, and isotopically lighter cold water (??D = -135???, ??18O = -18???). This cold water is not representative of current local recharge. The ??13C values for dissolved carbon in hot water are significantly heavier (- 7 to - 3???) than in cold water (-18 to -10???) denoting a separate hydrothermal origin. These ??13C values overlie the range generally attributed to magmatic degassing of CO2. However, ??13C values of metamorphosed Paleozoic basement carbonates surrounding Long Valley fall in a similar range, indicating that hydrothermal decarbonization reactions are a probable source of CO2. The ??13C and ??18O values of secondary travertime and vein calcite indicate respective fractionation with CO2 and H2O at temperatures approximating current hydrothermal conditions. ?? 1990.

Integrated model of the shallow and deep hydrothermal systems in the East Mesa area, Imperial Valley, California

USGS Publications Warehouse

Riney, T. David; Pritchett, J.W.; Rice, L.F.

1982-01-01

Geological, geophysical, thermal, petrophysical and hydrological data available for the East Mesa hydrothermal system that are pertinent to the construction of a computer model of the natural flow of heat and fluid mass within the system are assembled and correlated. A conceptual model of the full system is developed and a subregion selected for quantitative modeling. By invoking the .Boussinesq approximation, valid for describing the natural flow of heat and mass in a liquid hydrothermal system, it is found practical to carry computer simulations far enough in time to ensure that steady-state conditions are obtained. Initial calculations for an axisymmetric model approximating the system demonstrate that the vertical formation permeability of the deep East Mesa system must be very low (kv ~ 0.25 to 0.5 md). Since subsurface temperature and surface heat flow data exhibit major deviations from the axisymmetric approximation, exploratory three-dimensional calculations are performed to assess the effects of various mechanisms which might operate to produce such observed asymmetries. A three-dimensional model evolves from this iterative data synthesis and computer analysis which includes a hot fluid convective source distributed along a leaky fault radiating northward from the center of the hot spot and realistic variations in the reservoir formation properties.

Assessment of Japanese Technology in Advanced Glass and Ceramic Fibers

DTIC Science & Technology

1992-06-01

powders and crystals by hydrothermal tech- niques, and they have had their process for the preparation of zirconia powder commercial- ized by the...Masahiro Yoshimura. Whisker-Glass Composites, Hydrothermal Zirconia Powders , Hydrothermal Machining, Super-Conducting Thin Films. Professor Eiichi

The Origin of Carbon-Bearing Volatiles in a Continental Hydrothermal System in the Great Basin: Water Chemistry and Isotope Characterizations

NASA Technical Reports Server (NTRS)

Fu, Qi; Socki, Richard A.; Niles, Paul B.; Romanek, Christopher; Datta, Saugata; Darnell, Mike

2012-01-01

Hydrothermal systems on Earth are active centers in the crust where organic molecules can be synthesized biotically or abiotically under a wide range of physical and chemical conditions [1-3]. Not only are volatile species (CO, CO2, H2, and hydrocarbons) a reflection of deep-seated hydrothermal alteration processes, but they also form an important component of biological systems. Studying carbon-bearing fluids from hydrothermal systems is of specific importance to understanding (bio-)geochemical processes within these systems. With recent detection of methane in the martian atmosphere [4-7] and the possibility of its hydrothermal origin [8, 9], understanding the formation mechanisms of methane may provide constraints on the history of the martian aqueous environments and climate.

Oxygen isotope evidence for hydrothermal alteration within a Quaternary stratovolcano, Lassen Volcanic National Park, California

NASA Astrophysics Data System (ADS)

Rose, Timothy P.; Criss, Robert E.; Mughannam, Andrew J.; Clynne, Michael A.

1994-11-01

Brokeoff volcano, a Quaternary stratocone located in the Lassen volcanic center in northern California, has been deeply eroded, exposing a 10-sq km meteoric hydrothermal alteration zone at the core of the volcano. Portions of the former volcanic edifice are sufficiently well preserved that an unusual opportunity exists wherein the alteration pattern can be correlated with the position of the volcanic cone. The delta(O-18) analyses of more than 100 whole rock samples, consisting primarily of andesitic lavas, vary from +9.8 to +0.6 per mil. The highest delta(O-18) values occur in bleached, solfatarically altered rocks that have interacted with low-pH, fumarolic hot springs associated with the present-day hydrothermal system. Low delta(O-18) values are found in propylitically altered rocks that underwent isotopic exchange with meteoric hydrothermal fluids at elevated temperatures, mostly during the stratovolcanic stage (650-400 ka) of the hydrothermal system, but probably continuing today at depth. Electron microprobe analyses of secondary layer silicate minerals in strongly propylitized samples (delta(O-18) is less than +5.0) revealed the presence of discrete chlorite, suggesting that temperatures up to 200 to 250 C were attained in the shallow levels of the system. Two zones of pervasive meteoric hydrothermal alteration, defined by concentric O-18 contours that are probably interconnected at depth, are located within the original topographic edifice of the volcano. The most intensely altered rocks within these equant zones of alteration define NNW trends that coincide with stream valleys and with regional structural patterns. A comparison of the characteristics of the O-18-depleted zone at Brokeoff with those of more deeply eroded volcanic centers, such as the Comstock Lode mining district (Criss and Champion, 1991), permits the construction of composite O-18 cross sections through a hypothetical intact stratovolcano. At both Brokeoff and Comstock, hydrothermal fluids were strongly focused into plumelike zones of intense O-18 depletion. At Comstock, these low-O-18 plumes are associated with faults. Although major fault displacements are not observed at Brokeoff, the topographic and alteration patterns are consistent with the presence of a linear array of faults that acted as conduits for fluid flow up into the shallow levels of the volcano.

Shape-controlled synthesis and influence of W doping and oxygen nonstoichiometry on the phase transition of VO2

PubMed Central

Chen, Ru; Miao, Lei; Liu, Chengyan; Zhou, Jianhua; Cheng, Haoliang; Asaka, Toru; Iwamoto, Yuji; Tanemura, Sakae

2015-01-01

Monoclinic VO2(M) in nanostructure is a prototype material for interpreting correlation effects in solids with fully reversible phase transition and for the advanced applications to smart devices. Here, we report a facile one-step hydrothermal method for the controlled growth of single crystalline VO2(M/R) nanorods. Through tuning the hydrothermal temperature, duration of the hydrothermal time and W-doped level, single crystalline VO2(M/R) nanorods with controlled aspect ratio can be synthesized in large quantities, and the crucial parameter for the shape-controlled synthesis is the W-doped content. The dopant greatly promotes the preferential growth of (110) to form pure phase VO2(R) nanorods with high aspect ratio for the W-doped level = 2.0 at% sample. The shape-controlled process of VO2(M/R) nanorods upon W-doping are systematically studied. Moreover, the phase transition temperature (Tc) of VO2 depending on oxygen nonstoichiometry is investigated in detail. PMID:26373612

Hydrothermal preparation of hierarchical ZIF-L nanostructures for enhanced CO2 capture.

PubMed

Ding, Bing; Wang, Xianbiao; Xu, Yongfei; Feng, Shaojie; Ding, Yi; Pan, Yang; Xu, Weifan; Wang, Huanting

2018-06-01

A zeolitic imidazolate framework (ZIF-L) with hierarchical morphology was synthesized through hydrothermal method. The hierarchical product consists of ZIF-L leaves with length of several micrometers, width of 1 ∼ 2 μm and thickness of ∼300 nm cross connected symmetrically. It was found that the hydrothermal temperature is crucial for the formation of such hierarchical nanostructure. The formation mechanism was investigated to be a secondary crystal growth process. The hierarchical ZIF-L has larger surface area compared with the two-dimensional (2D) ZIF-L leaves. Subsequently, the hierarchical ZIF-L exhibited enhanced CO 2 adsorption capacity (1.56 mmol·g -1 ) as compared with that of the reported two-dimensional ZIF-L leaves (0.94 mmol·g -1 ). This work not only reveals a new strategy for the formation of hierarchical ZIF-L nanostructures, but also supplies a potential material for CO 2 capture. Copyright © 2018 Elsevier Inc. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

2013-12-01

Near-bottom magnetic profiling using submersible, deep-tow, Remotely Operated Vehicle (ROV) and Autonomous Underwater Vehicle (AUV) make possible to conduct high-resolution surveys and depict detailed magnetic features reflecting, for instance, the presence of fresh lavas or hydrothermal alteration, or geomagnetic paleo-intensity variations. We conducted near-bottom three component magnetic measurements onboard submersible Shinkai 6500 in the Southern Mariana Trough, where five active hydrothermal vent fields (Snail, Yamanaka, Archean, Pica, and Urashima sites) have been found in both on- and off-axis areas of the active back-arc spreading center, to detect signals from hydrothermally altered rock and to distinguish old and new submarine lava flows. Fourteen dives were carried out at an altitude of 1-40 m during the R/V Yokosuka YK10-10 and YK10-11 cruises in 2010. We carefully corrected the effect of the induced and permanent magnetizations of the submersible by applying the correction method for the shipboard three-component magnetometer measurement modified for deep-sea measurement, and subtracted the IGRF values from the corrected data to obtain geomagnetic vector anomalies along the dive tracks. We then calculated the synthetic magnetic vector field produced by seafloor, assumed to be uniformly magnetized, using three dimensional forward modeling. Finally, values of the absolute magnetizations were estimated by using a linear transfer function in the Fourier domain from the observed and synthetic magnetic anomalies. The distribution of estimated absolute magnetization generally shows low values around the five hydrothermal vent sites. This result is consistent with the equivalent magnetization distribution obtained from previous AUV survey data. The areas of low magnetization are also consistent with hydrothermal deposits identified in video records. These results suggest that low magnetic signals are due to hydrothermal alteration zones where host rocks are demagnetized by hydrothermal circulation. The low magnetization zones around the off-axis vent sites are about ten times wider than those surrounding the on-axis sites, possibly reflecting the longer duration of hydrothermal circulation at these sites. Another interesting result is that the absolute magnetization shows extremely high intensities (>80 A/m) at the neo volcanic zones (NVZ) and relatively low intensities (<10 A/m) two to five kilometers away from the NVZ. These variations are quite consistent with those of the Natural Remanent Magnetization measured on basalt samples, suggesting that the low-temperature oxidation of host rock due to the reaction with seawater has completed within a few kilometers distance from the spreading axis. We conclude that the magnetization of the uppermost oceanic crust decreases with age due to the combination of the both hydrothermal rapid alteration and the low-temperature gradual alteration processes.

International Symposium on Stratified Flows (4th) Held in Grenoble, France on June 29-July 2, 1994. Volume 1

DTIC Science & Technology

1994-10-10

Baroclinic Vortex Shedding from Hydrothermal Plumes ", J. Geophys. Res. 96, (C7), 12,511-12,518. Jirka, G.H. (1982), "Turbulent Buoyant Jets in Shallow...boundary layers and transport boundary current - 251 processes effected by buoyancy - 239 D. Obaton, G. Chaben’ dHibres; E. I. Nikitorovich, N . F . Yurchenko...assumed at angle 0 to the vertical, is N 2h cos 0 per unit -iass; which, in opposing the acceleration of fluid (02h/Ot2 )sec 0, gives rise to

The impact of steeping, germination and hydrothermal processing of wheat (Triticum aestivum L.) grains on phytate hydrolysis and the distribution, speciation and bio-accessibility of iron and zinc elements.

PubMed

Lemmens, Elien; De Brier, Niels; Spiers, Kathryn M; Ryan, Chris; Garrevoet, Jan; Falkenberg, Gerald; Goos, Peter; Smolders, Erik; Delcour, Jan A

2018-10-30

Chelation of iron and zinc in wheat as phytates lowers their bio-accessibility. Steeping and germination (15 °C, 120 h) lowered phytate content from 0.96% to only 0.81% of initial dry matter. A multifactorial experiment in which (steeped/germinated) wheat was subjected to different time (2-24 h), temperature (20-80 °C) and pH (2.0-8.0) conditions showed that hydrothermal processing of germinated (15 °C, 120 h) wheat at 50 °C and pH 3.8 for 24 h reduced phytate content by 95%. X-ray absorption near-edge structure imaging showed that it indeed abolished chelation of iron to phytate. It also proved that iron was oxidized during steeping, germination and hydrothermal processing. It was further shown that zinc and iron bio-accessibility were respectively 3 and 5% in wheat and 27 and 37% in hydrothermally processed wheat. Thus, hydrothermal processing of (germinated) wheat paves the way for increasing elemental bio-accessibility in whole grain-based products. Copyright © 2018 Elsevier Ltd. All rights reserved.

Insight from Genomics on Biogeochemical Cycles in a Shallow-Sea Hydrothermal System

NASA Astrophysics Data System (ADS)

Lu, G. S.; Amend, J.

2015-12-01

Shallow-sea hydrothermal ecosystems are dynamic, high-energy systems influenced by sunlight and geothermal activity. They provide accessible opportunities for investigating thermophilic microbial biogeochemical cycles. In this study, we report biogeochemical data from a shallow-sea hydrothermal system offshore Paleochori Bay, Milos, Greece, which is characterized by a central vent covered by white microbial mats with hydrothermally influenced sediments extending into nearby sea grass area. Geochemical analysis and deep sequencing provide high-resolution information on the geochemical patterns, microbial diversity and metabolic potential in a two-meter transect. The venting fluid is elevated in temperature (~70oC), low in pH (~4), and enriched in reduced species. The geochemical pattern shows that the profile is affected by not only seawater dilution but also microbial regulation. The microbial community in the deepest section of vent core (10-12 cm) is largely dominated by thermophilic archaea, including a methanogen and a recently described Crenarcheon. Mid-core (6-8 cm), the microbial community in the venting area switches to the hydrogen utilizer Aquificae. Near the sediment-water interface, anaerobic Firmicutes and Actinobacteria dominate, both of which are commonly associated with subsurface and hydrothermal sites. All other samples are dominated by diverse Proteobacteria. The sulfate profile is strongly correlated with the population size of delta- and episilon-proteobactia. The dramatic decrease in concentrations of As and Mn in pore fluids as a function of distance from the vent suggests that in addition to seawater dilution, microorganisms are likely transforming these and other ions through a combination of detoxification and catabolism. In addition, high concentrations of dissolved Fe are only measurable in the shallow sea grass area, suggesting that iron-transforming microorganisms are controlling Fe mobility, and promoting biomineralization. Taken together, these samples represent the effects of submarine venting on sediment microbial communities both vertically and horizontally in the predicted fluid flow path, and will provide a detailed investigation of genetic potential for biogeochemical cycling at Paleochori Bay.

Some Speculations Concerning The Abitibi Greenstone Belt As A Possible Analog To The Early Martian Crust

NASA Astrophysics Data System (ADS)

Russell, M.; Allwood, A.; Anderson, R. B.; Atkinson, B.; Beaty, D.; Bristow, T. F.; Ehlmann, B. L.; Grotzinger, J. P.; Hand, K. P.; Halevy, I.; Hurowitz, J. A.; Knoll, A.; McCleese, D. J.; Milliken, R.; Stolper, D. A.; Stolper, E. M.; Tosca, N. J.; Agouron Mars Simulation Field Team

2011-12-01

The Noachian crust of Mars comprises basaltic and, potentially, komatiitic lavas derived from a hot mantle slightly more reducing and sulfur-rich than that of the Earth. Ultramafic volcanic sequences of the ~2.7Ga Tisdale Group of the Abitibi Greenstone Belt, Ontario, provide a potential analog to these early martian lavas. The Abitibi rocks are a possible source of quartz veins carrying, in places, pyrite, carbonate and gold. These were hydrothermally introduced into volcanic and sedimentary rocks during greenschist metamorphism. Kilometer-scale talc-magnesite zones, resulting from the carbonation of serpentinized ultramafics, may have been the source and seawater, with some magmatic addition, was probably responsible for the pervasive alteration, although the chemical nature of hydrothermal fluids circulating in such piles depends upon the temperature of wall-rock interactions and is largely independent of fluid origin. Any sulfides and gold in unaltered ultramafic putative source rocks may have been lost to the invasive convective fluids. Given high heat flow and the presence of a hydrosphere, hydrothermal convection cells were probably the main mechanism of heat transfer through the crust on both planets. Exploration of the Abitibi belt provides a template for possible martian exploration strategies. Orbital remote sensing indicates that some ultramafic rocks on Mars have also been serpentinized and isolated areas of magnesite have been recently discovered, overlying altered mafic crust, with characteristic ridges at scales of a few hundred meters. While cogent arguments have been made favoring sedimentary exhalative accumulations of hydrothermal silica of the kind that are known to harbor bacteria on our own planet, no in situ siliceous sinters or even quartz veins have been identified with certainty on Mars. Here, we report on the mineralogic and visible to infrared spectral characteristics of mafic and ultramafic lithologies at Abitibi for comparison to locations on Mars where hydrothermal activity has been proposed.

Biological Sulfate Reduction Rates in Hydrothermal Recharge Zones

NASA Astrophysics Data System (ADS)

Crowell, B.; Lowell, R. P.

2007-12-01

We develop a model to determine the rate of removal of seawater sulfate in the recharge regions of deep-sea hydrothermal systems as a result of biogenic sulfate reduction. The rate of sulfate reduction as a function of temperature derived from laboratory measurements on cores from the Guaymas Basin in Mexico [Jorgensen et al., 1992] is incorporated into a steady state 1-D advection-diffusion temperature equation, and a 1-D, steady- state, advection dominated conservation of solute equation. The diffusivity of sulfate in seawater is on the order of ~ 10-10 m2/s, and unless the flow speeds are < 10-12 m/s, the effects of diffusion are negligible, except within thin diffusive boundary layers. This model is then compared with a model that utilizes Gibbs free energy to quantify biogenic sulfate reduction [Bach and Edwards, 2003] in the upper oceanic crust of aging lithosphere. Using the high rates determined by Jorgensen et al. [1992], our model indicates that biological activity would reduce all seawater sulfate transported into the system within the upper 10 meters or less of the crust, which is inconsistent with the estimates of Bach and Edwards [2003]. Sulfate concentrations from ODP borehole Legs 64 and 168, at the sedimented Guaymas Basin and Juan de Fuca Ridge, respectively, show that most of the seawater sulfate is removed in the upper 100 meters. If the sulfate is assumed to all be reduced biogenically, the sulfate reduction rates at the ODP sites are at least 2 orders of magnitude less than the laboratory estimates of Jorgenson et al. [1992]. Finally, we compare the rate of seawater sulfate removal as a result of the precipitation of anhydrite, with the rate of biogenic sulfate reduction. We find that if hydrothermal recharge occurs rapidly through highly permeable faults, that biogenic sulfate reduction is negligible and that anhydrite precipitation would rapidly clog the recharge zone [Lowell and Yao, 2002]. If recharge occurs through broad zones of slow downwelling (u

Hydrothermal and alkaline hydrothermal pretreatments plus anaerobic digestion of sewage sludge for dewatering and biogas production: Bench-scale research and pilot-scale verification.

PubMed

Li, Chunxing; Wang, Xingdong; Zhang, Guangyi; Yu, Guangwei; Lin, Jingjiang; Wang, Yin

2017-06-15

To test the feasibility and practicability of the process combing hydrothermal pretreatment for dewatering with biogas production for full utilization of sewage sludge, hydrothermal/alkaline hydrothermal pretreatments and in turn anaerobic digestion of the filtrates obtained after dewatering the pretreated sludge were performed at bench- and pilot-scales. The hydrothermal temperature fell within the range of 140 °C-220 °C and the pretreatment time varied from 30 min to 120 min. For the alkaline hydrothermal pretreatment the pH value of the sludge was adjusted to 9.0-11.0 by adding Ca(OH) 2 . The results showed that the dewaterability of the sewage sludge was improved with increasing pretreatment temperature but the impact of the pretreatment time was not significant. The addition of Ca(OH) 2 gave better performance on the subsequent mechanical dewatering of the pretreated sludge compared to pure hydrothermal pretreatment, and the higher the pH value was, the better the dewaterability of the pretreated sludge was. The conditions of 180 °C/30 min and 160 °C/60 min/pH = 10.0 (for hydrothermal and alkaline hydrothermal pretreatments, respectively) resulted in relatively good results in the theoretical energy balance, which were verified in the pilot-scale tests. Based on the data from the pilot tests, the alkaline hydrothermal process realized self-sufficiency in energy at the cost of a proper amount of CaO. Copyright © 2017 Elsevier Ltd. All rights reserved.

A multidisciplinary approach to quantify the permeability of the Whakaari/White Island volcanic hydrothermal system (Taupo Volcanic Zone, New Zealand)

NASA Astrophysics Data System (ADS)

Heap, Michael J.; Kennedy, Ben M.; Farquharson, Jamie I.; Ashworth, James; Mayer, Klaus; Letham-Brake, Mark; Reuschlé, Thierry; Gilg, H. Albert; Scheu, Bettina; Lavallée, Yan; Siratovich, Paul; Cole, Jim; Jolly, Arthur D.; Baud, Patrick; Dingwell, Donald B.

2017-02-01

Our multidisciplinary study aims to better understand the permeability of active volcanic hydrothermal systems, a vital prerequisite for modelling and understanding their behaviour and evolution. Whakaari/White Island volcano (an active stratovolcano at the north-eastern end of the Taupo Volcanic Zone of New Zealand) hosts a highly reactive hydrothermal system 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. The main crater, filled with tephra deposits, is shielded by a volcanic amphitheatre comprising interbedded lavas, lava breccias, and tuffs. We deployed field techniques to measure the permeability and density/porosity of (1) > 100 hand-sized sample blocks and (2) layered unlithified deposits in eight purpose-dug trenches. Our field measurements were then groundtruthed using traditional laboratory techniques on almost 150 samples. Our measurements highlight that the porosity of the materials at Whakaari varies from ∼ 0.01 to ∼ 0.7 and permeability varies by eight orders of magnitude (from ∼ 10-19 to ∼ 10-11 m2). The wide range in physical and hydraulic properties is the result of the numerous lithologies and their varied microstructures and alteration intensities, as exposed by a combination of macroscopic and microscopic (scanning electron microscopy) observations, quantitative mineralogical studies (X-ray powder diffraction), and mercury porosimetry. An understanding of the spatial distribution of lithology and alteration style/intensity is therefore important to decipher fluid flow within the Whakaari volcanic hydrothermal system. We align our field observations and porosity/permeability measurements to construct a schematic cross section of Whakaari that highlights the salient findings of our study. Taken together, the alteration typical of a volcanic hydrothermal system can result in increases (due to alteration-induced dissolution and fracturing) and decreases (due to hydrothermal precipitation) to permeability. Importantly, a decrease in permeability-be it due to fracture sealing in lava, pore-filling alunite precipitation in tuff, near-vent cementation by sulphur, and/or well-sorted layers of fine ash-can result in pore pressure augmentation. An increase in pore pressure could result in ground deformation, seismicity, jeopardise the stability of the volcanic slopes, and/or drive the wide variety of eruptions observed at Whakaari. Our systematic study offers the most complete porosity-permeability dataset for a volcanic hydrothermal system to date. These new data will inform and support modelling, unrest monitoring, and eruption characterisation at Whakaari and other hydrothermally modified volcanic systems worldwide.

Water saturation of hydrothermal smectite-rich clay might have promoted slope instability prior to the 1998 debris avalanche at Casita volcano, Nicaragua

NASA Astrophysics Data System (ADS)

Delmelle, P.; Opfergelt, S.; Boivin, P.; Delvaux, B.

2006-12-01

In October 1998, a relatively small collapse (1 600 000 cubic meters) of a pre-existing scarp occurred on the southern flank of the dormant Casita volcano, Nicaragua. It resulted in a debris avalanche, which quickly transformed into a disastrous debris flow that destroyed two towns and killed more than 2500 people. The failure was shown to be triggered by an excess pore water pressure within highly fractured rocks, following prolonged seasonal rains and precipitations from Hurricane Mitch. This pressure was linked to the water saturation of a hydrothermally-altered clay bedrock impeding in-depth infiltration. Yet, the nature and amounts of the clay material involved in the slope failure were still unknown. Here we report on physical, chemical and mineralogical investigations aimed at quantifying the clay content, and identifying the layer silicates of the hydrothermally-altered clays uncovered by the 1998 debris avalanche. The fine clay material was exceptionally rich in smectite (up to 50 wt. percent), which swells upon wetting and shrinks during dry conditions (Opfergelt et al., 2006, Geophys. Res. Lett., 33 (15), L15305). The smectite belonged to the beidellite-montmorillonite series. The pervasive presence of water-saturated smectitic clay strongly reduced the permeability in depth, and also altered the rheological and mechanical properties of both the pre-failure rock mass and flow materials. The shrink-swell behavior progressively decreased the rock's shear strength, and gradually destabilized the overlying rock mass in the decades and centuries before the landslide, thereby contributing to slope instability. Prolonged intense rainfall led to the formation of incipient weak failure surfaces in the superficial rock mass. As provoked by water saturation, this process was likely favored by the rapid change of the mechanical properties of smectite-rich clays deposited in fracture, joint and gouge interfaces. We suggest that hazard assessments associated with unstable volcanic slopes, especially on volcanoes hosting a long-lived hydrothermal system, should include the potential long and short-term impacts of swelling clays.

Enceladus and Europa: How Does Hydrothermal Activity Begin at the Surface?

NASA Technical Reports Server (NTRS)

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

2011-01-01

The question of how the surface hydrothermal activity (e.g., eruptive plumes and heat flow) is initiated can be addressed within the frame-work of our "Perrier Ocean" model. This model delivers the necessary heat and chemicals to support the heat flow and plumes observed by Cassini in Enceladus' South Polar Region. The model employs closed-loop circulation of water from a sub-surface ocean. The ocean is the main reservoir of heat and chemicals, including dissolved gases. As ocean water moves up toward the surface, pressure is re-duced and gases exsolve forming bubbles. This bub-bly mixture is less dense than the icy crust and the buoyant ocean-water mixture rises toward the surface. Near the surface, heat and chemicals, including some volatiles, are delivered to the chambers in which plumes form and also to shallow reservoirs that keep the surface ice "warm". (Plume operations, per se, are as described by Schmidt et al. and Postberg et al. and are adopted by us.) After transferring heat, the water cools, bubbles contract and dissolve, and the mixture is now relatively dense. It descends through cracks in the crust and returns to the ocean. Once the closed-loop circulation has started it is self-sustaining. Loss of water via the erupting plumes is relatively negligible compared to the amount needed to maintain the heat flow.We note that the activity described herein for the the "Perrier-Ocean" model could, a priori, apply to all small icy bodies that sheltered an interior ocean at some point in their history.

Sill intrusion driven fluid flow and vent formation in volcanic basins: Modeling rates of volatile release and paleoclimate effects

NASA Astrophysics Data System (ADS)

Iyer, Karthik; Schmid, Daniel

2016-04-01

Evidence of mass extinction events in conjunction with climate change occur throughout the geological record and may be accompanied by pronounced negative carbon isotope excursions. The processes that trigger such globally destructive changes are still under considerable debate. These include mechanisms such as poisoning from trace metals released during large volcanic eruptions (Vogt, 1972), CO2 released from lava degassing during the formation of Large Igneous Provinces (LIPs) (Courtillot and Renne, 2003) and CH4 release during the destabilization of sub-seafloor methane (Dickens et al., 1995), to name a few. Thermogenic methane derived from contact metamorphism associated with magma emplacement and cooling in sedimentary basins has been recently gaining considerable attention as a potential mechanism that may have triggered global climate events in the past (e.g. Svensen and Jamtveit, 2010). The discovery of hydrothermal vent complexes that are spatially associated with such basins also supports the discharge of greenhouse gases into the atmosphere (e.g. Jamtveit et al., 2004; Planke et al., 2005; Svensen et al., 2006). A previous study that investigated this process using a fluid flow model (Iyer et al., 2013) suggested that although hydrothermal plume formation resulting from sill emplacement may indeed release large quantities of methane at the surface, the rate at which this methane is released into the atmosphere is too slow to trigger, by itself, some of the negative δ13C excursions observed in the fossil record over short time scales observed in the fossil record. Here, we reinvestigate the rates of gas release during sill emplacement in a case study from the Harstad Basin off-shore Norway with a special emphasis on vent formation. The presented study is based on a seismic line that crosses multiple sill structures emplaced around 55 Ma within the Lower Cretaceous sediments. A single well-defined vent complex is interpreted above the termination of the main sill in the region. We use a 2D, hybrid FEM/FVM model that solves for fully compressible fluid flow to quantify the thermogenic release and transport of methane and to evaluate flow patterns within these systems. Additionally, vent formation in the model is implemented by simple fracture criteria that modify the permeability structure when the fluid pressure exceeds a threshold determined by the lithostatic pressure. The model with fracture formation is able to reproduce a single vent complex at the observed location above the main sill tip. This is very different from hydrothermal plume formation elsewhere in the region and occurs over short time scales (hundreds of years) and results in fluid focusing in that region. The rate of degassing and the resulting negative δ13C excursion from the vent model is then compared to models where only hydrothermal plume formation results in gas transportation. Lastly, variations in the amount of gas liberated in the system are investigated based on kerogen type and other mineral reactions such as limestone decarbonation and halite breakdown in the affected source rock.

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.

Multi-Sensor Mapping of Diffuse Degassing of C-O-H Compounds in Terrestrial Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Schwandner, F. M.; Shock, E. L.

2004-12-01

In-situ single-sensor detection and mapping of diffuse degassing phenomena in hydrothermal and volcanic areas can be used to elucidate subsurface tectonic structures, assess emission rates, and to monitor emission variability (Williams 1985; Chiodini et al. 1996, Werner et al., 2003). More than one technique has been deployed to measure several gas species simultaneously (e.g., Crenshaw et al. 1982), and correlations of one gas species (usually CO2) with physical parameters like heat flux (Brombach et al., 2001), or with one other gas species (Rn, He) have been demonstrated (Barberi & Carapezza 1994; Williams-Jones et al., 2000). Recently, correlations of multiple gas species with one another were reported (Schwandner et al., 2004), leading to the possibility of quantitative mapping of subsurface hydrothermal chemical processes by simultaneous measurement of reaction partners and products that continuously and diffusely degas. In the present study, we joined a fully-quantitative multi-sensor instrument (Draeger Multiwarn II) to a modified accumulation-chamber sensing method (Chiodini et al., 1996) and measured diffuse degassing of CH4, H2, CO2, CO, and H2S. In this approach, each batch of gas that is recirculated through the detector is simultaneously analyzed by all sensors. To test this approach we chose two magmatically influenced, hydrothermally active areas at Yellowstone National Park (USA): Sylvan Springs and the Greater Obsidian Pool Area. The area near Obsidian Pool was previously studied during a diffuse CO2 degassing campaign (Werner & Brantley, 2004). Preliminary results show that elevated reduced gas emissions appear to be most prominent near hydrothermal pools, whereas CO2-dominated degassing anomalies highlight subsurface tectonic structures. This multimodal distribution allows us to distinguish deep degassing sources (CO2 anomalies) from shallow localized hydrothermal processes (reduced gas anomalies). The results permit us to positively identify and partially map a previously-inferred active lineament in the Obsidian Pool area. In addition, reduced gas data are yielding areal ratio distributions of CO/CO2, H2/CH4, and CO/CH4, that may be indicative of reactions such as the catalytic hydrogenation of CO2 (Sabatier-Process) and of CO (Fischer-Tropsch-Process) within the shallow hydrothermal system. Barberi & Carapezza (1994). Bull. Volcanol. 56(5): 335-342. Brombach, et al. (2001). Geophys. Res. Lett. 28(1): 69-72. Crenshaw et al. (1982). Nature 300: 345-346. Chiodini et al. (1996). Bull. Volcanol. 58(1): 41-50. Schwandner et al. (2004). JGR D 109: D04301, doi:10.1029/2003JD003890. Werner & Brantley (2004) JGR B 105: 10,831-10,846. Werner et al. (2003). Earth Planet. Sci. Lett. 210: 561-577. Williams (1985). Science 229(4713): 551-553. Williams-Jones et al. (2000). Bull. Volcanol. 62: 130-142.

The Role of Siliceous Hydrothermal Breccias in the Genesis of Volcanic Massive Sulphide Deposits - Ancient and Recent Systems

NASA Astrophysics Data System (ADS)

Costa, I. A.; Barriga, F. J.; Fouquet, Y.

2014-12-01

Siliceous hydrothermal breccias were sampled in two Mid-Atlantic Ridge active sites: Lucky Strike and Menez Gwen. These hydrothermal fields are located in the border of the Azorean plateau, southwest of the Azores islands where the alteration processes affecting basaltic rocks are prominent (Costa et al., 2003). The hydrothermal breccias are genetically related with the circulation of low temperature hydrothermal fluids in diffuse vents. The groundmass of these breccias precipitates from the fluid and consolidates the clastic fragments mostly composed of basalt. The main sources are the surrounding volcanic hills. Breccias are found near hydrothermal vents and may play an important role in the protection of subseafloor hydrothermal deposits forming an impermeable cap due to the high content in siliceous material. The amorphous silica tends to precipitate when the fluid is conductively cooled as proposed by Fouquet et al. (1998) after Fournier (1983). The process evolves gradually from an initial stage where we have just the fragments and circulating seawater. The ascending hydrothermal fluid mixes with seawater, which favours the precipitation of the sulphide components. Sealing of the initially loose fragments begins, the temperature rises below this crust, and the processes of mixing fluid circulation and conductive cooling are simultaneous. At this stage the fluid becomes oversaturated with respect to amorphous silica. This form of silica can precipitate in the open spaces of the porous sulphides and seal the system. Normally this can happen at low temperatures. At this stage the hydrothermal breccia is formed creating a progressively less permeable, eventually impermeable cap rock at the surface. Once the fluid is trapped under this impermeable layer, conductive cooling is enhanced and mixing with seawater is restricted, making the precipitation of amorphous silica more efficient. Since the first discovery and description of recent mineralized submarine hydrothermal deposits, comparison with ancient volcanic massive sulphide deposits is appropriate. The proposed model can explain some of the processes taking place in the early phase of formation of old deposits where equivalent siliceous material is found in the hanging wall of the ore bodies (e.g. Barriga and Fyfe, 1988).

Life cycle assessment of microalgae to biofuel: Thermochemical processing through hydrothermal liquefaction or pyrolysis

NASA Astrophysics Data System (ADS)

Bennion, Edward P.

Microalgae are currently being investigated as a renewable transportation fuel feedstock based on various advantages that include high annual yields, utilization of poor quality land, does not compete with food, and can be integrated with various waste streams. This study focuses on directly assessing the impact of two different thermochemical conversion technologies on the microalgae-to-biofuel process through life cycle assessment. A system boundary of a "well to pump" (WTP) is defined and includes sub-process models of the growth, dewatering, thermochemical bio-oil recovery, bio-oil stabilization, conversion to renewable diesel, and transport to the pump. Models were validated with experimental and literature data and are representative of an industrial-scale microalgae-to-biofuel process. Two different thermochemical bio-oil conversion systems are modeled and compared on a systems level, hydrothermal liquefaction (HTL) and pyrolysis. The environmental impact of the two pathways were quantified on the metrics of net energy ratio (NER), defined here as energy consumed over energy produced, and greenhouse gas (GHG) emissions. Results for WTP biofuel production through the HTL pathway were determined to be 1.23 for the NER and GHG emissions of -11.4 g CO2 eq (MJ renewable diesel)-1. WTP biofuel production through the pyrolysis pathway results in a NER of 2.27 and GHG emissions of 210 g CO2 eq (MJ renewable diesel)-1. The large environmental impact associated with the pyrolysis pathway is attributed to feedstock drying requirements and combustion of co-products to improve system energetics. Discussion focuses on a detailed breakdown of the overall process energetics and GHGs, impact of modeling at laboratory-scale compared to industrial-scale, environmental impact sensitivity to engineering systems input parameters for future focused research and development, and a comparison of results to literature.

Dissolution of biogenic ooze over basement edifices in the equatorial Pacific with implications for hydrothermal ventilation of the oceanic crust

USGS Publications Warehouse

Bekins, B.A.; Spivack, A.J.; Davis, E.E.; Mayer, L.A.

2007-01-01

Recent observations indicate that curious closed depressions in carbonate sediments overlying basement edifices are widespread in the equatorial Pacific. A possible mechanism for their creation is dissolution by fluids exiting basement vents from off-axis hydrothermal flow. Quantitative analysis based on the retrograde solubility of calcium carbonate and cooling of basement fluids during ascent provides an estimate for the dissolution capacity of the venting fluids. Comparison of the dissolution capacity and fluid flux with typical equatorial Pacific carbonate mass accumulation rates shows that this mechanism is feasible. By maintaining sediment-free basement outcrops, the process may promote widespread circulation of relatively unaltered seawater in the basement in an area where average sediment thicknesses are 300-500 m. The enhanced ventilation can explain several previously puzzling observations in this region, including anomalously low heat flux, relatively unaltered seawater in the basement, and aerobic and nitrate-reducing microbial activity at the base of the sediments. ?? 2007 The Geological Society of America.

Development and characterization of activated hydrochars from orange peels as potential adsorbents for emerging organic contaminants.

PubMed

Fernandez, M E; Ledesma, B; Román, S; Bonelli, P R; Cukierman, A L

2015-05-01

Activated hydrochars obtained from the hydrothermal carbonization of orange peels (Citrus sinensis) followed by various thermochemical processing were assessed as adsorbents for emerging contaminants in water. Thermal activation under flows of CO2 or air as well as chemical activation with phosphoric acid were applied to the hydrochars. Their characteristics were analyzed and related to their ability to uptake three pharmaceuticals (diclofenac sodium, salicylic acid and flurbiprofen) considered as emerging contaminants. The hydrothermal carbonization and subsequent activations promoted substantial chemical transformations which affected the surface properties of the activated hydrochars; they exhibited specific surface areas ranging from 300 to ∼620 m(2)/g. Morphological characterization showed the development of coral-like microspheres dominating the surface of most hydrochars. Their ability to adsorb the three pharmaceuticals selected was found largely dependent on whether the molecules were ionized or in their neutral form and on the porosity developed by the new adsorbents. Copyright © 2015 Elsevier Ltd. All rights reserved.

Ultra-Fast Supercritical Hydrothermal Synthesis of Tobermorite under Thermodynamically Metastable Conditions.

PubMed

Diez-Garcia, Marta; Gaitero, Juan J; Dolado, Jorge S; Aymonier, Cyril

2017-03-13

Tobermorite is a fibrillar mineral of the family of calcium silicates. In spite of not being abundant in nature, its structure and properties are reasonably well known because of its interest in the construction industry. Currently, tobermorite is synthesized by hydrothermal methods at mild temperatures. The problem is that such processes are very slow (>5 h) and temperature cannot be increased to speed them up because tobermorite is metastable over 130 °C. Furthermore the product obtained is generally foil-like and not very crystalline. Herein we propose an alternative synthesis method based on the use of a continuous flow reactor and supercritical water. In spite of the high temperature, the transformation of tobermorite to more stable phases can be prevented by accurately controlling the reaction time. As a result, highly crystalline fibrillar tobermorite can be obtained in just a few seconds under thermodynamically metastable conditions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Axial crustal structure of the Costa Rica Rift: Implications for along-axis hydrothermal circulation

NASA Astrophysics Data System (ADS)

Zhang, L.; Tong, V.; Hobbs, R. W.; Peirce, C.; Lowell, R. P.; Haughton, G.; Murton, B. J.; Morales Maqueda, M. A.; Harris, R. N.; Robinson, A. H.

2017-12-01

In 2015, a multidisciplinary geophysical cruise surveyed the Costa Rica Rift (CRR) in the Panama Basin of the equatorial East Pacific, acquiring a grid of multichannel seismic and wide-angle profiles to determine the mode of oceanic crustal accretion at intermediate-spreading ridges, and how the crustal structure may be influenced by hydrothermal fluid flow. Analysis of 69,000 P-wave first arrivals recorded by 25 ocean-bottom seismographs deployed over a 20 × 20 km area that straddles the ridge axis, reveals a 3D velocity-depth model of upper crustal structure. In particular, the model shows a low velocity anomaly that extends to 2 km below seabed centred on a small-offset non-transform discontinuity (NTD), and a pattern of increasing velocity with distance off-axis that may reflect changes in porosity and permeability in layer 2 of the crust. Assuming the upper crustal velocity anomalies are linked with porosity and hence represent the ability of fluid to flow, comparison of the tomographic model with the volcanic seabed morphology suggests that the broad low velocity zone beneath the NTD may be a region of extensive fracturing. Hence, we infer that this region may provide a primary pathway for the recharge of seawater into the crust. Further west along the axis, beneath the bathymetric dome, which is the shallowest portion along the axis, the low-velocity anomaly is less pronounced, suggesting that fractures are less open and that fluid-rock interaction has encouraged mineral precipitation and alteration, as a result of a longer established hydrothermal fluid flow driven by the axial magma lens observed beneath it. This interpretation is supported by the presence of a plume from an active hydrothermal vent system. Hence, we infer that the variable velocity structure of the upper crust of the CRR is a proxy that reflects the primary porosity, faulting and fracturing related to phases of magma-driven accretion and/or ridge geometry re-adjustment, and that there is along-axis hydrothermal circulation transferring heat and impacting the properties of newly accreted oceanic crust. This research is part of a major, interdisciplinary NERC-funded collaboration entitled: Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR).

Muon dynamic radiography of density changes induced by hydrothermal activity at the La Soufrière of Guadeloupe volcano

NASA Astrophysics Data System (ADS)

Jourde, Kevin; Gibert, Dominique; Marteau, Jacques; de Bremond D'Ars, Jean; Komorowski, Jean-Christophe

2016-09-01

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 hydrothermal systems of low-energy active 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 hydrothermal 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.

Muon dynamic radiography of density changes induced by hydrothermal activity at the La Soufrière of Guadeloupe volcano

PubMed Central

Jourde, Kevin; Gibert, Dominique; Marteau, Jacques; de Bremond d’Ars, Jean; Komorowski, Jean-Christophe

2016-01-01

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 hydrothermal systems of low-energy active 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 hydrothermal 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

Muon dynamic radiography of density changes induced by hydrothermal activity at the La Soufrière of Guadeloupe volcano.

PubMed

Jourde, Kevin; Gibert, Dominique; Marteau, Jacques; de Bremond d'Ars, Jean; Komorowski, Jean-Christophe

2016-09-15

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 hydrothermal systems of low-energy active 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 hydrothermal 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.

Mapping Hydrothermal Alterations in the Muteh Gold Mining Area in Iran by using ASTER satellite Imagery data

NASA Astrophysics Data System (ADS)

Asadi Haroni, Hooshang; Hassan Tabatabaei, Seyed

2016-04-01

Muteh gold mining area is located in 160 km NW of Isfahan town. Gold mineralization is meso-thermal type and associated with silisic, seresitic and carbonate alterations as well as with hematite and goethite. Image processing and interpretation were applied on the ASTER satellite imagery data of about 400 km2 at the Muteh gold mining area to identify hydrothermal alterations and iron oxides associated with gold mineralization. After applying preprocessing methods such as radiometric and geometric corrections, image processing methods of Principal Components Analysis (PCA), Least Square Fit (Ls-Fit) and Spectral Angle Mapper (SAM) were applied on the ASTER data to identify hydrothermal alterations and iron oxides. In this research reference spectra of minerals such as chlorite, hematite, clay minerals and phengite identified from laboratory spectral analysis of collected samples were used to map the hydrothermal alterations. Finally, identified hydrothermal alteration and iron oxides were validated by visiting and sampling some of the mapped hydrothermal alterations.

Sources and drains: Major controls of hydrothermal fluid flow in the Kokanee Range, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Beaudoin, Georges; Therrien, René

1999-10-01

Vein fields are fractured domains of the lithosphere that have been infiltrated by hydrothermal fluids, which deposited minerals in response to changing physico-chemical conditions. Because oxygen is a major component of the infiltrating fluid and the surrounding rock matrix, the oxygen isotope composition of minerals found in veins is used to decipher ancient fluid flow within the lithosphere. We use a numerical model to simulate oxygen isotope transport in the Kokanee Range silver-lead-zinc vein field. The model considers advective, dispersive, and reactive transport in a three-dimensional porous rock matrix intersected by high-permeability planes representing fracture zones. Here we show that it is the geometrical configuration of the sources and of the drains of hydrothermal fluids, combined with the fracture pattern, that exerts the main control on the oxygen isotope distribution. Other factors that affect, to a lesser extent, the values and positions of oxygen isopleths are the fluids and rock-matrix isotopic compositions, the isotopic fractionation, the reaction rate constant, and hydraulic conductivities of the rock matrix and fracture zones.

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

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

Minerals produced during cooling and hydrothermal alteration of ash flow tuff from Yellowstone drill hole Y-5

USGS Publications Warehouse

Keith, T.E.C.; Muffler, L.J.P.

1978-01-01

A rhyolitic ash-flow tuff in a hydrothermally active area within the Yellowstone caldera was drilled in 1967, and cores were studied to determine the nature and distribution of primary and secondary mineral phases. The rocks have undergone a complex history of crystallization and hydrothermal alteration since their emplacement 600,000 years ago. During cooling from magmatic temperatures, the glassy groundmass underwent either devitrification to alkali feldspar + ??-cristobalite ?? tridymite or granophyric crystallization to alkali feldspar + quartz. Associated with the zones of granophyric crystallization are prismatic quartz crystals in cavities similar to those termed miarolitic in plutonic rocks. Vapor-phase alkali feldspar, tridymite, magnetite, and sporadic ??-cristobalite were deposited in cavities and in void spaces of pumice fragments. Subsequently, some of the vapor-phase alkali feldspar crystals were replaced by microcrystalline quartz, and the vapor-phase minerals were frosted by a coating of saccharoidal quartz. Hydrothermal minerals occur primarily as linings and fillings of cavities and fractures and as altered mafic phenocrysts. Chalcedony is the dominant mineral related to the present hydrothermal regime and occurs as microcrystalline material mixed with various amounts of hematite and goethite. The chalcedony displays intricate layering and was apparently deposited as opal from silica-rich water. Hematite and goethite also replace both mafic phenocrysts and vapor-phase magnetite. Other conspicuous hydrothermal minerals include montmorillonite, pyrite, mordenite, calcite, and fluorite. Clinoptilolite, erionite, illite, kaolinite, and manganese oxides are sporadic. The hydrothermal minerals show little correlation with temperature, but bladed calcite is restricted to a zone of boiling in the tuff and clearly was deposited when CO2 was lost during boiling. Fractures and breccias filled with chalcedony are common throughout Y-5 and may have been produced by rapid disruption of rock caused by sudden decrease of fluid pressure in fractures, most likely a result of fracturing during resurgent doming in this part of the Yellowstone caldera. The chalcedony probably was deposited as opal or ??-cristobalite from a pre-existing silica floc that moved rapidly into the fractures and breccias immediately after the sudden pressure drop. ?? 1978.

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Airborne Magnetic and Electromagnetic Data map Rock Alteration and Water Content at Mount Adams, Mount Baker and Mount Rainier, Washington: Implications for Lahar Hazards and Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Finn, C. A.; Deszcz-Pan, M.; Horton, R.; Breit, G.; John, D.

2007-12-01

High resolution helicopter-borne magnetic and electromagnetic (EM) data flown over the rugged, ice-covered, highly magnetic and mostly resistive volcanoes of Mount Rainier, Mount Adams and Mount Baker, along with rock property measurements, reveal the distribution of alteration, water and hydrothermal fluids that are essential to evaluating volcanic landslide hazards and understanding hydrothermal systems. Hydrothermally altered rocks, particularly if water saturated, can weaken stratovolcanoes, thereby increasing the potential for catastrophic sector collapses that can lead to far-traveled, destructive debris flows. Intense hydrothermal alteration significantly reduces the magnetization and resistivity of volcanic rock resulting in clear recognition of altered rock by helicopter magnetic and EM measurements. Magnetic and EM data, combined with geological mapping and rock property measurements, indicate the presence of appreciable thicknesses of hydrothermally altered rock west of the modern summit of Mount Rainier in the Sunset Amphitheater region, in the central core of Mount Adams north of the summit, and in much of the central cone of Mount Baker. We identify the Sunset Amphitheater region and steep cliffs at the western edge of the central altered zone at Mount Adams as likely sources for future debris flows. In addition, the EM data identified water-saturated rocks in the upper 100-200 m of the three volcanoes. The water-saturated zone could extend deeper, but is beyond the detection limits of the EM data. Water in hydrothermal fluids reacts with the volcanic rock to produce clay minerals. The formation of clay minerals and presence of free water reduces the effective stress, thereby increasing the potential for slope failure, and acts, with entrained melting ice, as a lubricant to transform debris avalanches into lahars. Therefore, knowing the distribution of water is also important for hazard assessments. Finally, modeling requires extremely low resistivities (< 20 ohm-m) that laboratory electrical resistivity measurements indicate are most easily explained by sulfuric acid solutions permeating altered rocks. The acid is the result of oxidation of magmatic H2S to sulfuric acid and highlights the continued alteration of volcanoes during periods of relative quiescence. Our results demonstrate that high resolution geophysical and geological observations can yield unprecedented views of the three-dimensional distribution of altered rock and shallow pore water and hydrothermal fluids within active stratovolcanoes.

Water-rock interaction in the magmatic-hydrothermal system of Nisyros Island (Greece)

NASA Astrophysics Data System (ADS)

Ambrosio, Michele; Doveri, Marco; Fagioli, Maria Teresa; Marini, Luigi; Principe, Claudia; Raco, Brunella

2010-04-01

In this work, we investigated the water-rock interaction processes taking place in the hydrothermal reservoir of Nisyros through both: (1) a review of the hydrothermal mineralogy encountered in the deep geothermal borehole Nisyros-2; and (2) a comparison of the analytically-derived redox potentials and acidities of fumarolic-related liquids, with those controlled by redox buffers and pH buffers, involving hydrothermal mineral phases. The propylitic zone met in the deep geothermal borehole Nisyros-2, from 950 to 1547 m (total depth), is characterised by abundant, well crystallised epidote, adularia, albite, quartz, pyrite, chlorite, and sericite-muscovite, accompanied by less abundant anhydrite, stilpnomelane, wairakite, garnet, tremolite and pyroxene. These hydrothermal minerals were produced in a comparatively wide temperature range, from 230 to 300 °C, approximately. Hydrothermal assemblages are well developed from 950 to 1360 m, whereas they are less developed below this depth, probably due to low permeability. Based on the RH values calculated for fumarolic gases and for the deep geothermal fluids of Nisyros-1 and Nisyros-2 wells, redox equilibrium with the (FeO)/(FeO 1.5) rock buffer appears to be closely attained throughout the hydrothermal reservoir of Nisyros. This conclusion may be easily reconciled with the nearly ubiquitous occurrence of anhydrite and pyrite, since RH values controlled by coexistence of anhydrite and pyrite can be achieved by gas separation. The pH of the liquids feeding the fumarolic vents of Stephanos and Polybote Micros craters was computed, by means of the EQ3 code, based on the Cl- δD relationship which is constrained by the seawater-magmatic water mixing occurring at depth in the hydrothermal-magmatic system of Nisyros. The temperature dependence of analytically-derived pH values for the reservoir liquids feeding the fumarolic vents of Stephanos and Polybote Micros craters suggests that some unspecified pH buffer fixes the acidity of these reservoir liquids at values of 4.72-4.85 and 4.88-5.23, respectively. Many of these pH values are lower than those expected for the full-equilibrium condition, although they are close to those of the reservoir liquids of Nisyros-1, 5.16, and Nisyros-2, 4.87. It is likely that this excess of acidity-producing species, chiefly CO 2, promotes release of Fe(II) and Fe(III) to the reservoir liquids through rock dissolution, permitting the attainment of redox equilibrium with the (FeO)/(FeO 1.5) rock buffer, as already suggested by the late Werner Giggenbach.

The characteristics of palm oil plantation solid biomass wastes as raw material for bio oil

NASA Astrophysics Data System (ADS)

Yanti, RN; Hambali, E.; Pari, G.; Suryani, A.

2018-03-01

Indonesia is the largest palm oil plantations estate in the world. It reached 11,30 million hectares in 2015 and increased up to 11,67 million hectares in 2016. The advancement of technology recent, the solid waste of palm oil plantation can be re-produced become bio oil through pyrolysis hydrothermal process and utilized for biofuel. The purpose of this research was to analyze the characteristics of feedstock of bio oil of solid waste of palm oil plantations estate. The feedstock used was derived from solid waste of palm oil plantations in Riau Province. Characteristic analysis of waste oil included chemical compound content (cellulose, hemicellulose, lignin), ultimate analysis (C, H, N, O, S) to know height heating value (HHV). The result of analysis of chemical content showed that solid waste of palm cellulose 31,33 – 66,36 %, hemicellulose 7,54 – 17,94 %, lignin 21,43 - 43,1. The HHV of hydrothermal pyrolysis feedstock was 15,18 kJ/gram - 19,57 kJ/gram. Generally, the solid waste of palm oil plantations estate containing lignocellulose can be utilized as bio oil through hydrothermal pyrolysis. The CG-MS analysis of bio oil indicated hydrocarbon contents such as pentadecane, octadecane, hexadecane and benzene.

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

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

[Effect of sodium carbonate assisted hydrothermal process on heavy metals stabilization in medical waste incinerator fly ash].

PubMed

Jin, Jian; Li, Xiao-dong; Chi, Yong; Yan, Jian-hua

2010-04-01

A sodium carbonate assisted hydrothermal process was induced to stabilize the fly ash from medical waste incinerator. The results showed that sodium carbonate assisted hydrothermal process reduced the heavy metals leachability of fly ash, and the heavy metal waste water from the process would not be a secondary pollution. The leachability of heavy metals studied in this paper were Cd 1.97 mg/L, Cr 1.56 mg/L, Cu 2.56 mg/L, Mn 17.30 mg/L, Ni 1.65 mg/L, Pb 1.56 mg/L and Zn 189.00 mg/L, and after hydrothermal process with the optimal experimental condition (Na2CO3/fly ash dosage = 5/20, reaction time = 8 h, L/S ratio = 10/1) the leachability reduced to < 0.02 mg/L for Cd, Cr, Cu, Mn, Ni, Pb, and 0.05 mg/L for Zn, according to GB 5085.3-2007. Meanwhile, the concentrations of heavy metals in effluent after hydrothermal process were less than 0.8 mg/L. The heavy metals leachability and concentration in effluent reduced with prolonged reaction time. Prolonged aging can affect the leachability of metals as solids become more crystalline, and heavy metals transferred inside of crystalline. The mechanism of heavy metal stabilization can be concluded to the co precipitation and adsorption effect of aluminosilicates formation, crystallization and aging process.

[Elaboration of instant corn flour by hydrothermal process I].

PubMed

Martínez B, F; el-Dahs, A A

1993-12-01

The objective of this research was to investigate a simplified hydrothermal process for the production of instant corn flour and evaluate some variables that affected the degree of gelatinization of corn flour, and evaluate some technological characteristics of the flour. The use of grits of lesser particle diameter and increasing temperature of the soaking water resulted in an increase in the rate of absorption of water of grits, permitting a reduction of soaking time necessary for the process. The instant corn flour prepared by the hydrothermal process using corn grits soaked in water at room temperature (28-30 degrees C) for 5 hours and steaming for 1 minute at 118 degrees C presented characteristics of viscosity, water absorption index and water solubility index similar to that of flours prepared with grits soaked in water at a temperature higher tan room temperature and different steaming time (5 and 15 minutes). The characteristics of color and shelf life of corn flour were improved with the hydrothermal process.

Synthesis of TiO2 nanorods from titania and titanyl sulfate produced from ilmenite dissolution by hydrothermal method

NASA Astrophysics Data System (ADS)

Wahyuningsih, S.; Ramelan, A. H.; Munifa, R. M. I.; Saputri, L. N. M. Z.; Chasanah, U.

2016-11-01

TiO2 powder has been synthesized through hydrolysis-condensation of titanyl sulfate solution to a starting material of TiO2 nanorods formation. This processing was conducted by the solid separation of TiO2 from ilmenite by roasting ilmenite, acidic leaching (hydrolysis), and co-precipitation (condensation). Roasting of ilmenite was carried out by the addition of Na2S at a temperature of 800°C. While the acidic leaching process was conducted by sulfuric acid at a various concentrations of 3, 3.5, 4.5, 6, and 9 M. The result shown that the solubility optimum occurs in H2SO4 6 M condition. Separation of Fe impurities of TiO2 gel from titanyl sulfate (TiOSO4) solution was done through complexation using KCNS addition. The characteristic of TiO2 obtained using X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) showed good crystallinity and purity. Further treatment of the TiO2 is the formation of one-dimensional nano-size (1-D nanorods) through a hydrothermal method under basic condition NaOH 12M solution. TiO2 nanorods were confirmed by Transmission Electron Microscope (TEM) which indicated that the diameter of TiO2 nanorods was about 7.02 nm in size.

Sulphide mineral evolution and metal mobility during alteration of the oceanic crust: Insights from ODP Hole 1256D

NASA Astrophysics Data System (ADS)

Patten, C. G. C.; Pitcairn, I. K.; Teagle, D. A. H.; Harris, M.

2016-11-01

Fluxes of metals during the hydrothermal alteration of the oceanic crust have far reaching effects including buffering of the compositions of the ocean and lithosphere, supporting microbial life and the formation of sulphide ore deposits. The mechanisms responsible for metal mobilisation during the evolution of the oceanic crust are complex and are neither fully constrained nor quantified. Investigations into the mineral reactions that release metals, such as sulphide leaching, would generate better understanding of the controls on metal mobility in the oceanic crust. We investigate the sulphide and oxide mineral paragenesis and the extent to which these minerals control the metal budget in samples from Ocean Drilling Program (ODP) Hole 1256D. The ODP Hole 1256D drill core provides a unique sample suite representative of a complete section of a fast-spreading oceanic crust from the volcanic section down to the plutonic complex. The sulphide population at Hole 1256D is divided into five groups based on mineralogical assemblage, lithological location and texture: the magmatic, metasomatised, high temperature hydrothermal, low temperature and patchy sulphides. The initiation of hydrothermal alteration by downward flow of moderate temperature (250-350 °C) hydrothermal fluids under oxidising conditions leads to metasomatism of the magmatic sulphides in the sheeted dyke and plutonic complexes. Subsequent increase in the degree of hydrothermal alteration at temperatures >350 °C under reducing conditions then leads to the leaching of the metasomatised sulphides by rising hydrothermal fluids. Mass balance calculations show that the mobility of Cu, Se and Au occurs through sulphide leaching during high temperature hydrothermal alteration and that the mobility of Zn, As, Sb and Pb is controlled by silicate rather than sulphide alteration. Sulphide leaching is not complete at Hole 1256D and more advanced alteration would mobilise greater masses of metals. Alteration of oxide minerals does not release significant quantities of metal into the hydrothermal fluid at Hole 1256D. Mixing of rising high temperature fluids with low temperature fluids, either in the upper sheeted dyke section or in the transitional zone, triggers local high temperature hydrothermal sulphide precipitation and trapping of Co, Ni, Cu, Zn, As, Ag, Sb, Se, Te, Au, Hg and Pb. In the volcanic section, low temperature fluid circulation (<150 °C) leads to low temperature sulphide precipitation in the form of pyrite fronts that have high As concentrations due to uptake from the circulating fluids. Deep late low temperature circulation in the sheeted dyke and the plutonic complexes results in local precipitation of patchy sulphides and local metal remobilisation. Control of sulphides over Au, Se and Cu throughout fast-spreading mid-oceanic crust history implies that the generation of hydrothermal fluids enriched in these metals, which can eventually form VMS deposits, is strongly controlled by sulphide leaching.

A mineralogical and granulometric study of Cayambe volcano debris avalanche deposit

NASA Astrophysics Data System (ADS)

Detienne, M.; Delmelle, P.; Guevara, A.; Samaniego, P.; Bustillos, J.; Sonnet, P.; Opfergelt, S.

2013-12-01

Volcano flank/sector collapse represents one of the most catastrophic volcanic hazards. Various volcanic and non-volcanic processes are known to decrease the stability of a volcanic cone, eventually precipitating its gravitational failure. Among them, hydrothermal alteration of volcanic rocks leading to clay mineral formation is recognized as having a large negative impact on rock strength properties. Furthermore, the presence of hydrothermal clays in the collapsing mass influences the behavior of the associated volcanic debris avalanche. In particular, clay-containing debris avalanches seem to travel farther and spread more widely than avalanches of similar volume but which do not incorporate hydrothermally-altered materials. However, the relationship between hydrothermal alteration, flank collapse and debris avalanche behavior is not well understood. The objective of this study is to better determine the volume and composition of hydrothermal clay minerals in the poorly characterized debris avalanche deposit (DAD) of Cayambe composite volcano, located in a densely populated area ~70 km northeast of Quito, Ecuador. Cayambe DAD originated from a sector collapse, which occurred less than 200 ka ago. The DAD is 10-20 m thick and has an estimated total volume of ~0.85 Km3. The H/L ratio (where H is the vertical drop and L is the travel distance of the avalanche) for Cayambe DAD is ~0.095, suggesting a high mobility. In the medial-distal zone, at 9-20 km from its source, the DAD consists of an unstratified and unsorted matrix supporting millimetric to metric clasts. It has a matrix facies (i.e. rich in particles < 2 mm) enriched in hydrothermally-altered materials. Preliminary results of granulometry measurements indicate that the matrix corresponds to ~55 wt.% of the deposit and suggest that the DAD behaved as a cohesive debris flow. Analysis of 13 matrix samples reveals a large variability in particle size distribution. This may reflect poor mixing of the collapsed material during transport. The clay fraction content in the matrix ranges from 15 to 30 wt.%, and does not show a relationship with the sample position in the DAD. Mineralogical determinations are in progress and will be presented.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Phase- and shape-controlled hydrothermal synthesis of CdS nanoparticles, and oriented attachment growth of its hierarchical architectures

NASA Astrophysics Data System (ADS)

Cao, Yali; Hu, Pengfei; Jia, Dianzeng

2013-01-01

Hydrothermal strategies were successfully used to control the phases and morphologies of CdS nanocrystals. In the absence of an external direction-controlling process, the hexagonal and cubic phase well-defined leaf- and flower-like CdS nanocrystals were controlled obtained via adjusting the reaction duration or the concentration of surfactant. Oriented attachment growth modes were suggested for the formation of CdS superstructures, which was clarified through the tracing of temporal evolution of CdS nanoparticles. The CdS superstructures were structured by primary building nanoparticles, and held excellent visible emission with a peak in the green regions. This strategy is very helpful for studying the phase and morphology controlled fabrication of sulfides nanocrystals.

Characteristics of Hydrothermal Mineralization in Ultraslow Spreading Ridges

NASA Astrophysics Data System (ADS)

Zhou, H.; Yang, Q.; Ji, F.; Dick, H. J.

2014-12-01

Hydrothermal activity is a major component of the processes that shape the composition and structure of the ocean crust, providing a major pathway for the exchange of heat and elements between the Earth's crust and oceans, and a locus for intense biological activity on the seafloor and underlying crust. In other hand, the structure and composition of hydrothermal systems are the result of complex interactions between heat sources, fluids, wall rocks, tectonic controls and even biological processes. Ultraslow spreading ridges, including the Southwest Indian Ridge, the Gakkel Ridge, are most remarkable end member in plate-boundary structures (Dick et al., 2003), featured with extensive tectonic amagmatic spreading and frequent exposure of peridotite and gabbro. With intensive surveys in last decades, it is suggested that ultraslow ridges are several times more effective than faster-spreading ridges in sustaining hydrothermal activities. This increased efficiency could attributed to deep mining of heat and even exothermic serpentinisation (Baker et al., 2004). Distinct from in faster spreading ridges, one characteristics of hydrothermal mineralization on seafloor in ultraslow spreading ridges, including the active Dragon Flag hydrothermal field at 49.6 degree of the Southwest Indian Ridge, is abundant and pervasive distribution of lower temperature precipitated minerals ( such as Fe-silica or silica, Mn (Fe) oxides, sepiolite, pyrite, marcasite etc. ) in hydrothermal fields. Structures formed by lower temperature activities in active and dead hydrothermal fields are also obviously. High temperature precipitated minerals such as chalcopyrite etc. are rare or very limited in hydrothermal chimneys. Distribution of diverse low temperature hydrothermal activities is consistence with the deep heating mechanisms and hydrothermal circulations in the complex background of ultraslow spreading tectonics. Meanwhile, deeper and larger mineralization at certain locations along the ultraslow spreading ridges is also presumable.

Event Detection for Hydrothermal Plumes: A case study at Grotto Vent

NASA Astrophysics Data System (ADS)

Bemis, K. G.; Ozer, S.; Xu, G.; Rona, P. A.; Silver, D.

2012-12-01

Evidence is mounting that geologic events such as volcanic eruptions (and intrusions) and earthquakes (near and far) influence the flow rates and temperatures of hydrothermal systems. Connecting such suppositions to observations of hydrothermal output is challenging, but new ongoing time series have the potential to capture such events. This study explores using activity detection, a technique modified from computer vision, to identify pre-defined events within an extended time series recorded by COVIS (Cabled Observatory Vent Imaging Sonar) and applies it to a time series, with gaps, from Sept 2010 to the present; available measurements include plume orientation, plume rise rate, and diffuse flow area at the NEPTUNE Canada Observatory at Grotto Vent, Main Endeavour Field, Juan de Fuca Ridge. Activity detection is the process of finding a pattern (activity) in a data set containing many different types of patterns. Among many approaches proposed to model and detect activities, we have chosen a graph-based technique, Petri Nets, as they do not require training data to model the activity. They use the domain expert's knowledge to build the activity as a combination of feature states and their transitions (actions). Starting from a conceptual model of how hydrothermal plumes respond to daily tides, we have developed a Petri Net based detection algorithm that identifies deviations from the specified response. Initially we assumed that the orientation of the plume would change smoothly and symmetrically in a consistent daily pattern. However, results indicate that the rate of directional changes varies. The present Petri Net detects unusually large and rapid changes in direction or amount of bending; however inspection of Figure 1 suggests that many of the events detected may be artifacts resulting from gaps in the data or from the large temporal spacing. Still, considerable complexity overlies the "normal" tidal response pattern (the data has a dominant frequency of ~12.9 hours). We are in the process of defining several events of particular scientific interest: 1) transient behavioral changes associated with atmospheric storms, earthquakes or volcanic intrusions or eruptions, 2) mutual interaction of neighboring plumes on each other's behavior, and 3) rapid shifts in plume direction that indicate the presence of unusual currents or changes in currents. We will query the existing data to see if these relationships are ever observed as well as testing our understanding of the "normal" pattern of response to tidal currents.Figure 1. Arrows indicate plume orientation at a given time (time axis in days after 9/29/10) and stars indicate times when orientation changes rapidly.

On diagenesis, dolomitisation and mineralisation in the Irish Zn-Pb orefield

NASA Astrophysics Data System (ADS)

Wilkinson, Jamie J.

2003-12-01

Marine calcite cementation and lithification of Carboniferous carbonate sediments hosting Zn-Pb mineralisation in the Irish orefield occurred at or near the seafloor. A relatively early, fine-grained, grey replacive dolomite, preferentially developed in micrite, is widely developed in the Waulsortian Limestone Formation, the main host to mineralisation, and is pervasive in the southeastern Midlands in proximity to the Leinster Massif. This dolomite formed after the first four main stages of calcite cementation but probably also developed within tens of metres of the seafloor as evidenced by incorporation of clasts of dolomite in intraformational sedimentary breccias. Later, coarse-grained white dolomite preferentially replaced coarser components of the Waulsortian Limestone and infilled residual vuggy porosity. Whilst some of this coarse dolomite may be related to the fine replacive dolomite event, a common spatial association with fault zones, coupled with primary fluid inclusion data, suggest that a significant proportion of this phase precipitated during the onset of fault-controlled subsidence and widespread hydrothermal circulation within the Irish Midlands area. Fluids up to ~250 °C and 10-15 wt% NaCl equivalent, sourced from a Lower Palaeozoic basement-equilibrated fluid reservoir, infiltrated the carbonate sequence via faults and fractures. The more localised development of dolomite-cemented breccias (white matrix breccias) that are frequently associated spatially with mineralisation was a consequence of the increased focusing of these hydrothermal fluids. Ore formation was broadly synchronous with development of the white dolomite breccias but only happened where mixing occurred between the hydrothermal ore-fluids and localised, near-surface reservoirs of low-temperature, H2S-rich brine. In the Waulsortian, this process led to the precipitation of a distinctive black dolomite that forms a broad halo to massive sulphides. Although ore-stage sulphides postdate significant diagenesis of the host rocks, and often display "epigenetic" textures, the fact that much of the cementation occurred soon after carbonate deposition means that mineralisation does not have to have formed after significant burial. In fact, the occurrence of clasts of hydrothermal dolomite and sulphides in intraformational debris-flow breccias is only consistent with mineralising processes occurring in the near-seafloor environment, relatively soon after host-rock deposition. The regional development of a distinctive pink dolomite associated with faults and fractures was a post-ore event, and is considered to mark a regional brine migration linked to the onset of the Variscan orogeny. The development of this new tectonic and flow regime may have been responsible for the cessation of economic mineralisation in Ireland.

Reaction of seawater with fresh mid-ocean ridge gabbro creates ';atypical' REE pattern and high REE fluid fluxes: Experiments at 425 and 475 °C, 400 and 1000 bar

NASA Astrophysics Data System (ADS)

Beermann, O.; Garbe-Schönberg, D.; Holzheid, A. D.

2013-12-01

High-temperature MOR hydrothermalism significantly affects ocean chemistry. The Sisters Peak (SP) hydrothermal field at 5°S on the slow-spreading Mid-Atlantic Ridge (MAR) emanates fluids >400°C [1] that have high concentrations of H2, transition metals, and rare earth elements (REE) exhibiting ';atypical' REE pattern characterized by depletions of LREE and HREE relative to MREE and no Eu anomaly [2]. This is in contrast to the ';typical' LREE enrichment and strong positive Eu anomaly known from many MOR vent fluids observed world-wide [e.g., 3]. Besides temperature, the seawater-to-rock ratio (w/r ratio) has significant control on the fluid chemistry [e.g., 4, 5]. To understand how vent fluid REE-signatures are generated during water-rock interaction processes we reacted unaltered gabbro with natural bottom seawater at 425 °C and 400 bar and at 425 and 475 °C at 1000 bar at variable w/r (mass) ratios ranging from 0.5-10 by using cold seal pressure vessels (CSPV). The run durations varied from 3-72 h. Reacted fluids were analysed for major and trace elements by ICP-OES and ICP-MS. In our experiments, ';atypical' REE fluid pattern similar to those of SP fluids were obtained at high w/r ratio (5 and 10) that might be characteristic for focused fluid-flow along e.g., detachment faults at slow-spreading MOR [6]. In contrast, more ';typical'-like REE pattern with elevated LREE and slightly positive Eu anomalies have been reproduced at low w/r ratio (0.5-1). Results of numerical simulations imply that strong positive Eu anomalies of fluids and altered gabbro from high temperature MOR hydrothermal systems can be created by intense rock leaching processes at high w/r ratio (5-10). This suggests that hydrothermal circulation through the ocean crust creates ';typical' REE fluid pattern with strong positive Eu anomalies if seawater reacts with gabbroic host rock that has been already leached in REE at high fluid fluxes. Simulations of the temporal chemical evolution of high temperature MOR hydrothermal systems reveal that rock and fluid REE contents can rapidly decrease within several months particularly at high fluid fluxes. In contrast, the reaction with ';fresh', unaltered rock is evident from the high REE concentration of SP fluids. Both, fluid access to fresh rock and the fluid flux should therefore significantly control chemical fluxes to the ocean. Thus, high chemical fluxes can be expected in particular from early stage high-temperature MOR hydrothermal systems that are assumed to be not uncommon along the slow-spreading MAR. [1] Koschinsky A., Garbe-Schönberg D., Sander S., Schmidt K., Gennerich H.-H., and Strauss H. (2008) Geology 36, 615-618. [2] Schmidt K., Garbe-Schönberg D., Bau M., and Koschinsky A. (2010) Geochim. Cosmochim. Acta 74, 4058-4077. [3] Douville E., Bienvenu P., Charlou J. L., Donval J. P., Fouquet Y., Appriou P., and Gamo T. (1999). Geochim. Cosmochim. Acta 63, 627-643. [4] Seyfried [Jr.] W. E. and Bischoff J. L. (1977) Earth. Planet. Sci. Lett. 34, 71-77. [5] Hajash A. and Chandler G. W. (1981) Contrib. Mineral. Petrol. 78, 240-254. [6] McCaig A.M. and Harris M. (2012) Geology 40, 367-370.

Fault zone hydrogeology

NASA Astrophysics Data System (ADS)

Bense, V. F.; Gleeson, T.; Loveless, S. E.; Bour, O.; Scibek, J.

2013-12-01

Deformation along faults in the shallow crust (< 1 km) introduces permeability heterogeneity and anisotropy, which has an important impact on processes such as regional groundwater flow, hydrocarbon migration, and hydrothermal fluid circulation. Fault zones have the capacity to be hydraulic conduits connecting shallow and deep geological environments, but simultaneously the fault cores of many faults often form effective barriers to flow. The direct evaluation of the impact of faults to fluid flow patterns remains a challenge and requires a multidisciplinary research effort of structural geologists and hydrogeologists. However, we find that these disciplines often use different methods with little interaction between them. In this review, we document the current multi-disciplinary understanding of fault zone hydrogeology. We discuss surface- and subsurface observations from diverse rock types from unlithified and lithified clastic sediments through to carbonate, crystalline, and volcanic rocks. For each rock type, we evaluate geological deformation mechanisms, hydrogeologic observations and conceptual models of fault zone hydrogeology. Outcrop observations indicate that fault zones commonly have a permeability structure suggesting they should act as complex conduit-barrier systems in which along-fault flow is encouraged and across-fault flow is impeded. Hydrogeological observations of fault zones reported in the literature show a broad qualitative agreement with outcrop-based conceptual models of fault zone hydrogeology. Nevertheless, the specific impact of a particular fault permeability structure on fault zone hydrogeology can only be assessed when the hydrogeological context of the fault zone is considered and not from outcrop observations alone. To gain a more integrated, comprehensive understanding of fault zone hydrogeology, we foresee numerous synergistic opportunities and challenges for the discipline of structural geology and hydrogeology to co-evolve and address remaining challenges by co-locating study areas, sharing approaches and fusing data, developing conceptual models from hydrogeologic data, numerical modeling, and training interdisciplinary scientists.

Effect of acid detergent fiber in hydrothermally pretreated sewage sludge on anaerobic digestion process

NASA Astrophysics Data System (ADS)

Takasaki, Rikiya; Yuan, Lee Chang; Kamahara, Hirotsugu; Atsuta, Youichi; Daimon, Hiroyuki

2017-10-01

Hydrothermal treatment is one of the pre-treatment method for anaerobic digestion. The application of hydrothermal treatment to sewage sludge of wastewater treatment plant has been succeeded to enhance the biogas production. The purpose of this study is to quantitatively clarify the effect of hydrothermal treatment on anaerobic digestion process focusing on acid detergent fiber (ADF) in sewage sludge, which is low biodegradability. The hydrothermal treatment experiment was carried out for 15 minutes between 160 °C and 200 °C respectively. The ADF content was decreased after hydrothermal treatment compared with untreated sludge. However, ADF content was increased when raising the treatment temperature from 160 °C to 200 °C. During batch anaerobic digestion experiment, untreated and treated sludge were examined for 10 days under 38 °C, and all samples were fed once based on volatile solids of samples. From batch anaerobic digestion experiment, as ADF content in sewage sludge increased, the total biogas production decreased. It was found that ADF content in sewage sludge influence on anaerobic digestion. Therefore, ADF could be one of the indicator to evaluate the effect of hydrothermal treatment to sewage sludge on anaerobic digestion.

Improving the circular economy via hydrothermal processing of high-density waste plastics.

PubMed

Helmer Pedersen, Thomas; Conti, Federica

2017-10-01

Rising environmental concerns on climate changes are causing an increasing attention on circular economies. The plastic economy, in particular, is in focus due to the accelerating consumption of plastics, mainly derived from virgin feedstock, combined with the lack of plastic recycling strategies. This work presents a novel outlook on the potential of using supercritical hydrothermal processing of waste plastic fractions for tertiary recycling. The study investigates hydrothermal processing of nine different, high-density types of plastics into original resin monomers and other value-added chemical compounds. The outlook presents conversion yields, carbon balances, and chemical details on the products obtained. It is found that all the investigated resins are prone to hydrothermal treatment, and that high yields of monomers and high value compounds (up to nearly 100%), suitable for chemicals and fuels applications, can be obtained. For instance, for polycarbonate, styrene-butadiene, poly(lactic acid), poly(ethylene terephthalate), and poly(butylene terephthalate), original monomeric compounds can be reclaimed for manufacturing new resins. The promising results presented demonstrate that hydrothermal processing of high-density plastics is a prospective technology for increasing the circularity of the plastic economy. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hydrological evolution and chemical structure of a hyper-acidic spring-lake system on Whakaari/White Island, NZ

NASA Astrophysics Data System (ADS)

Christenson, B. W.; White, S.; Britten, K.; Scott, B. J.

2017-10-01

White Island has a long and varied history of acid spring discharge and shallow ephemeral lake formation on its main crater floor. In the 12 months prior to the onset of the 1976-2000 eruptive episode, mass discharge from the spring system increased ca. 10-fold, pointing to a strong coupling of the hydrothermal environment to the evolving magmatic system. Between 1976 and 1978, the formation of numerous eruption vents to 200 m depth in the Western Sub-crater abruptly changed the hydraulic gradients in the volcano, resulting in the reversal of groundwater flow in the massif towards the newly-formed crater(s). This affected not only the style of volcanic activity (leading to phreatic-phreatomagmatic-magmatic eruption cycles), but also led to the demise of the spring system, with discharge from the main crater declining by a factor > 100 by 1979. Eruptive activity ended shortly after a moderate Strombolian eruption in mid-2000, after which ephemeral lakes started to form in the eruption crater complex. Between 2003 and 2015 there were three complete lake filling and evaporative cycles, reflecting varying heat flow through the conduit system beneath the lake. Over these cycles, lake water concentrations of Cl and SO4 varied between ca. 35-150 and 5-45 g/L respectively, with pH values temporally ranging from + 1.5 to - 1. Springs appeared on the Main Crater floor in 2004, and their discharges varied with lake level, pointing to the lake level being a primary control over the piezometric surface in the crater area. Springs closest to the crater complex show direct evidence of crater lake water infiltration into the crater floor aquifer, whereas distal spring discharges show compositional variations reflecting vertical displacement of the interface between shallow, dilute condensate and underlying acidic brine fluids. Source components for the spring fluids include magmatic vapour, dissolved andesitic host rocks, seawater and meteoric water. Lake waters, on the other hand, consist predominantly of magmatic vapour, meteoric water and solutes derived from host andesites and their altered derivatives. δ2H and δ18O signatures of the enclosing acid brine fluids, indicate they are predominantly seawater which have been affected by both vapour loss, but also mixing with arc-type vapour. An interesting finding of this study is that crater floor deformation correlates directly to both lake level and volatile emissions, in an apparent poroelastic response to the establishment of a hydrostatic water column in the eruption crater complex, and a net decrease in permeability owing to hydrothermal mineralization in the conduit (predominantly elemental sulfur and sulfate minerals). The hydrostatic pressurization of the vent environment also leads to increased gas pressures and flows through fumarolic channels, and consequent expansion of fumarolic areas on the main crater floor. A period of unrest, which commenced in August 2012 and lasted until October 2013, included the extrusion of a small dome into the eruption crater complex. This activity, and related high heat flow, led once again to evaporation of the lake, and ongoing phreatic eruption activity which has provided interesting insights into the role which elemental sulfur, associated hydrothermal alteration minerals and of course water play in regulating pressures in the magmatic-hydrothermal environment.

A Hydrothermal Origin for the Sulfate-rich Ocean of Europa

NASA Technical Reports Server (NTRS)

Zolotov, M. Yu.; Shock, E. L.

2001-01-01

Thermodynamic calculations show that formation of a sulfate-rich ocean on Europa might require high-temperature alkaline hydrothermal processes in the oxidized silicate mantle. The ocean on Europa could be thought of as a cooled hydrothermal fluid. Additional information is contained in the original extended abstract.

Scalable continuous flow synthesis of ZnO nanorod arrays in 3-D ceramic honeycomb substrates for low-temperature desulfurization

DOE PAGES

Wang, Sibo; Wu, Yunchao; Miao, Ran; ...

2017-07-26

Scalable and cost-effective synthesis and assembly of technologically important nanostructures in three-dimensional (3D) substrates hold keys to bridge the demonstrated nanotechnologies in academia with industrially relevant scalable manufacturing. In this paper, using ZnO nanorod arrays as an example, a hydrothermal-based continuous flow synthesis (CFS) method is successfully used to integrate the nano-arrays in multi-channeled monolithic cordierite. Compared to the batch process, CFS enhances the average growth rate of nano-arrays by 125%, with the average length increasing from 2 μm to 4.5 μm within the same growth time of 4 hours. The precursor utilization efficiency of CFS is enhanced by 9more » times compared to that of batch process by preserving the majority of precursors in recyclable solution. Computational fluid dynamic simulation suggests a steady-state solution flow and mass transport inside the channels of honeycomb substrates, giving rise to steady and consecutive growth of ZnO nano-arrays with an average length of 10 μm in 12 h. The monolithic ZnO nano-array-integrated cordierite obtained through CFS shows enhanced low-temperature (200 °C) desulfurization capacity and recyclability in comparison to ZnO powder wash-coated cordierite. This can be attributed to exposed ZnO {101¯0} planes, better dispersion and stronger interactions between sorbent and reactant in the ZnO nanorod arrays, as well as the sintering-resistance of nano-array configurations during sulfidation–regeneration cycles. Finally, with the demonstrated scalable synthesis and desulfurization performance of ZnO nano-arrays, a promising, industrially relevant integration strategy is provided to fabricate metal oxide nano-array-based monolithic devices for various environmental and energy applications.« less

Scalable continuous flow synthesis of ZnO nanorod arrays in 3-D ceramic honeycomb substrates for low-temperature desulfurization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Sibo; Wu, Yunchao; Miao, Ran

Scalable and cost-effective synthesis and assembly of technologically important nanostructures in three-dimensional (3D) substrates hold keys to bridge the demonstrated nanotechnologies in academia with industrially relevant scalable manufacturing. In this paper, using ZnO nanorod arrays as an example, a hydrothermal-based continuous flow synthesis (CFS) method is successfully used to integrate the nano-arrays in multi-channeled monolithic cordierite. Compared to the batch process, CFS enhances the average growth rate of nano-arrays by 125%, with the average length increasing from 2 μm to 4.5 μm within the same growth time of 4 hours. The precursor utilization efficiency of CFS is enhanced by 9more » times compared to that of batch process by preserving the majority of precursors in recyclable solution. Computational fluid dynamic simulation suggests a steady-state solution flow and mass transport inside the channels of honeycomb substrates, giving rise to steady and consecutive growth of ZnO nano-arrays with an average length of 10 μm in 12 h. The monolithic ZnO nano-array-integrated cordierite obtained through CFS shows enhanced low-temperature (200 °C) desulfurization capacity and recyclability in comparison to ZnO powder wash-coated cordierite. This can be attributed to exposed ZnO {101¯0} planes, better dispersion and stronger interactions between sorbent and reactant in the ZnO nanorod arrays, as well as the sintering-resistance of nano-array configurations during sulfidation–regeneration cycles. Finally, with the demonstrated scalable synthesis and desulfurization performance of ZnO nano-arrays, a promising, industrially relevant integration strategy is provided to fabricate metal oxide nano-array-based monolithic devices for various environmental and energy applications.« less

Monodisperse spindle-like FeWO{sub 4} nanoparticles: Controlled hydrothermal synthesis and enhanced optical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Jinxue; Zhou, Xiaoyu; Lu, Yibin

2012-12-15

Monodisperse FeWO{sub 4} nanoparticles with specific spindle-like morphology have been synthesized in the presence of citric acid through hydrothermal process. In the synthesis route, citric acid played four roles such as the reducing agent, chelating regents, structure-directing agent and stabilizing agents. In addition, the morphology of FeWO{sub 4} was dramatically tuned by the pH value of the precursor medium. The optical properties of FeWO{sub 4} were investigated with UV-Vis spectra and photoluminescence spectroscopy. The photocatalytic experiments demonstrated that the decomposition efficiency of the monodisperse spindle-like FeWO{sub 4} nanoparticles is 74% after 30 min of UV irradiation, which displayed remarkable enhancedmore » photodegradation activity compared with ordinary FeWO{sub 4} sample (57%) and normal TiO{sub 2} photocatalysts P-25 (56%). - Monodisperse spindle-like FeWO{sub 4} nanoparticles with enhanced photocatalytic activities. Highlights: Black-Right-Pointing-Pointer Monodisperse spindle-like FeWO{sub 4} were synthesized with hydrothermal method. Black-Right-Pointing-Pointer Citric acid plays key roles in the hydrothermal synthesis. Black-Right-Pointing-Pointer Their morphology can be tuned with pH value of the precursor medium. Black-Right-Pointing-Pointer They show enhanced photocatalytic activities with irradiation of UV light.« less

Discovery and Distribution of Black Smokers on the Western Galapagos Spreading Center: Implications for Spatial and Temporal Controls on High Temperature Venting at Ridge/Hotspot Intersections

NASA Astrophysics Data System (ADS)

Haymon, R. M.; Anderson, P. G.; Baker, E. T.; Resing, J. A.; White, S. M.; MacDonald, K. C.

2006-12-01

Though nearly one-fifth of the mid-ocean ridge (MOR) lies on or near hotspots, it has been debated whether hotspots increase or decrease MOR hydrothermal flux, or affect vent biota. Despite hotspot enhancement of melt supply, high-temperature vent plumes are enigmatically sparse along two previously-surveyed ridge- hotspot intersections [Reykjanes Ridge (RR), Southeast Indian Ridge (SEIR)]. This has been attributed to crustal thickening by excess volcanism. During the 2005-06 GalAPAGoS expedition, we conducted nested sonar, plume, and camera surveys along a 540 km-long portion of the Galapagos Spreading Center (GSC) where the ridge intersects the Galapagos hotspot at lon. 94.5 -89.5 deg. W. Although MOR hydrothermal springs were first found along the eastern GSC crest in 1977 near lon. 86 deg. W, the GalAPAGoS smokers are the first active high-temperature vents to be found anywhere along the Cocos-Nazca plate boundary. Active and/or recently-inactive smokers were located beneath plumes at 5 sites on the seafloor between lon. 91 deg. W and 94.5 deg. W (see Anderson et al., this session) during near-bottom, real-time fiber-optic Medea camera surveys. Smokers occur along eruptive seafloor fissures atop axial volcanic ridges near the middles of ridge segments, mainly in areas underlain by relatively shallow, continuous axial magma chamber (AMC) seismic reflectors. These findings (1) support magmatic, rather than tectonic, control of GSC smoker distribution; (2) demonstrate that thick crust at MOR-hotspot intersections does not prevent high-temperature hydrothermal vents from forming; and, (3) appear to be inconsistent with models suggesting that enhanced hydrothermal cooling causes abrupt deepening of the AMC and transition from non-rifted to rifted GSC morphology near lon. 92.7 deg. W. The widely-spaced smoker sites located on different GSC segments exhibit remarkably similar characteristics and seafloor settings. Most sites are mature or extinct, and are on lava flows of visually-similar ages (estimated to be tens-to-hundreds of years old). Possibly a volcanic pulse may have activated the hotspot- affected western GSC, and powered contemporaneous hydrothermal vents that now are waning. It may be that hotspots produce episodes of near-synchronous, extensive ridge volcanism and hydrothermal activity, followed by periods of quiescence. This idea is consistent with: the episodic eruption histories of Hawaii and Iceland; variably anomalous hydrothermal plume incidence (low on RR, SEIR, GSC; high on Mid-Atlantic Ridge near Azores hotspot); models of episodic melt extraction from mantle plumes; and evidence for magma propagation along hotspot-influenced ridges. Our hypothesis potentially can be tested by studies of gene flow between animal communities located on either side of the Galapagos hotspot, and by dating of GSC hydrothermal chimneys and the lava flows on which they are constructed.

Hydrothermal systems and volcano geochemistry

USGS Publications Warehouse

Fournier, R.O.

2007-01-01

The upward intrusion of magma from deeper to shallower levels beneath volcanoes obviously plays an important role in their surface deformation. This chapter will examine less obvious roles that hydrothermal processes might play in volcanic deformation. Emphasis will be placed on the effect that the transition from brittle to plastic behavior of rocks is likely to have on magma degassing and hydrothermal processes, and on the likely chemical variations in brine and gas compositions that occur as a result of movement of aqueous-rich fluids from plastic into brittle rock at different depths. To a great extent, the model of hydrothermal processes in sub-volcanic systems that is presented here is inferential, based in part on information obtained from deep drilling for geothermal resources, and in part on the study of ore deposits that are thought to have formed in volcanic and shallow plutonic environments.

Does serpentinite carbonation occur during recharge or discharge of hydrothermal fluids? A case of study from the Newfoundland margin

NASA Astrophysics Data System (ADS)

Picazo, Suzanne; Malvoisin, Benjamin; Baumgartner, Lukas P.; Bouvier, Anne-Sophie

2017-04-01

Hydrothermal fluid circulation in extensional systems occurrs along the spreading axis of passive, hyper-extended margins and mid-ocean ridges. The most studied feature resulting from hydrothermal circulation is the sub-seafloor chimneys because of their accessibility. Here we focus on the less studied carbonation process of the associated serpentinites. Carbonation of partially to totally serpentinized peridotite i.e. peridotite/serpentinite replacement by carbonate is usually described as a process of veining or matrix formation but not direct replacement of serpentinite. Carbonates that crystallize in veins or as a matrix in a sedimentary setting is known in near-surface environments like Oman (Kelemen et al, 2011), however the processes and timing of carbonation are still not well understood. This study is examins in detail the onset of carbonation in the footwall of the detachment faults responsible for mantle exhumation in hyper-extended rifted margins. It is based on drilled samples from ODP Leg 210 Site 1277 in the Newfoundland margin. We observed calcite grains in the mesh core replacing serpentine and we measured δ18O from core to rim of the calcite grain using the Secondary Ion Mass Spectrometer (SIMS, SwissSIMS facility, University of Lausanne). Ultimately δ18O measurements lead us to infer the temperature of calcite growth. We suplement the study with equilibrium thermodynamic modeling in an open system where fluid can be transported either upwards or downwards. The model allows us determining the influence of fluid flow direction, temperature, pressure and fluid/rock ratio on the stability of carbonates and serpentine, and thus to discuss if carbonation occurs during recharge or discharge of the fluids. Kelemen, P. B., Matter, J., Streit, E. E., Rudge, J. F., Curry, W. B., & Blusztajn, J. (2011). Rates and mechanisms of mineral carbonation in peridotite: natural processes and recipes for enhanced, in situ CO2 capture and storage. Annual Review of Earth and Planetary Sciences, 39, 545-576.

Formation mechanism and optimization of highly luminescent N-doped graphene quantum dots

PubMed Central

Qu, Dan; Zheng, Min; Zhang, Ligong; Zhao, Haifeng; Xie, Zhigang; Jing, Xiabin; Haddad, Raid E.; Fan, Hongyou; Sun, Zaicheng

2014-01-01

Photoluminescent graphene quantum dots (GQDs) have received enormous attention because of their unique chemical, electronic and optical properties. Here a series of GQDs were synthesized under hydrothermal processes in order to investigate the formation process and optical properties of N-doped GQDs. Citric acid (CA) was used as a carbon precursor and self-assembled into sheet structure in a basic condition and formed N-free GQD graphite framework through intermolecular dehydrolysis reaction. N-doped GQDs were prepared using a series of N-containing bases such as urea. Detailed structural and property studies demonstrated the formation mechanism of N-doped GQDs for tunable optical emissions. Hydrothermal conditions promote formation of amide between –NH2 and –COOH with the presence of amine in the reaction. The intramoleculur dehydrolysis between neighbour amide and COOH groups led to formation of pyrrolic N in the graphene framework. Further, the pyrrolic N transformed to graphite N under hydrothermal conditions. N-doping results in a great improvement of PL quantum yield (QY) of GQDs. By optimized reaction conditions, the highest PL QY (94%) of N-doped GQDs was obtained using CA as a carbon source and ethylene diamine as a N source. The obtained N-doped GQDs exhibit an excitation-independent blue emission with single exponential lifetime decay. PMID:24938871

A hydrothermal seep on the Costa Rica margin: middle ground in a continuum of reducing ecosystems

PubMed Central

Levin, Lisa A.; Orphan, Victoria J.; Rouse, Greg W.; Rathburn, Anthony E.; Ussler, William; Cook, Geoffrey S.; Goffredi, Shana K.; Perez, Elena M.; Waren, Anders; Grupe, Benjamin M.; Chadwick, Grayson; Strickrott, Bruce

2012-01-01

Upon their initial discovery, hydrothermal vents and methane seeps were considered to be related but distinct ecosystems, with different distributions, geomorphology, temperatures, geochemical properties and mostly different species. However, subsequently discovered vents and seep systems have blurred this distinction. Here, we report on a composite, hydrothermal seep ecosystem at a subducting seamount on the convergent Costa Rica margin that represents an intermediate between vent and seep ecosystems. Diffuse flow of shimmering, warm fluids with high methane concentrations supports a mixture of microbes, animal species, assemblages and trophic pathways with vent and seep affinities. Their coexistence reinforces the continuity of reducing environments and exemplifies a setting conducive to interactive evolution of vent and seep biota. PMID:22398162

Effect of hydrothermal condition on the formation of multi-component oxides of Ni-based metallic glass under high temperature water near the critical point

DOE PAGES

Kim, J. S.; Kim, S. Y.; Kim, D. H.; ...

2015-07-01

The specific feature of multi-component oxides synthesized by hydrothermal process under high temperature (633 K) and highly pressurized water (18.9 MPa) near critical point. Effects of hydrothermal processing duration times 24 hours and 72 hours, respectively, on the oxide formation of the Ni 59Zr 20Ti 16Si 2Sn 3 metallic glass synthesized by powder metallurgy process were characterized by X-ray diffractometer, differential scanning calorimeter along with the particle size, morphology and crystalline phase of the oxides. The crystallization of the needle-shape NiTiO 3, ZrTiO 4 and ZrSnO 4 ternary oxide phases observed on the surface of metallic glass at below glassmore » transition temperature and the morphology of oxide phases changed to plate-shape around 2 μm in diameter by the increase processing time. This hydrothermal processing in subcritical water provides accelerated dense metal oxide crystals due to the reaction medium being at higher pressure than conventional oxidation processing.« less

A Paleoarchean coastal hydrothermal field inhabited by diverse microbial communities: the Strelley Pool Formation, Pilbara Craton, Western Australia.

PubMed

Sugitani, K; Mimura, K; Takeuchi, M; Yamaguchi, T; Suzuki, K; Senda, R; Asahara, Y; Wallis, S; Van Kranendonk, M J

2015-11-01

The 3.4-Ga Strelley Pool Formation (SPF) at the informally named 'Waterfall Locality' in the Goldsworthy greenstone belt of the Pilbara Craton, Western Australia, provides deeper insights into ancient, shallow subaqueous to possibly subaerial ecosystems. Outcrops at this locality contain a thin (<3 m) unit of carbonaceous and non-carbonaceous cherts and silicified sandstones that were deposited in a shallow-water coastal environment, with hydrothermal activities, consistent with the previous studies. Carbonaceous, sulfide-rich massive black cherts with coniform structures up to 3 cm high are characterized by diverse rare earth elements (REE) signatures including enrichment of light [light rare earth elements (LREE)] or middle rare earth elements and by enrichment of heavy metals represented by Zn. The massive black cherts were likely deposited by mixing of hydrothermal and non-hydrothermal fluids. Coniform structures in the cherts are characterized by diffuse laminae composed of sulfide particles, suggesting that unlike stromatolites, they were formed dominantly through physico-chemical processes related to hydrothermal activity. The cherts yield microfossils identical to previously described carbonaceous films, small and large spheres, and lenticular microfossils. In addition, new morphological types such as clusters composed of large carbonaceous spheroids (20-40 μm across each) with fluffy or foam-like envelope are identified. Finely laminated carbonaceous cherts are devoid of heavy metals and characterized by the enrichment of LREE. This chert locally contains conical to domal structures characterized by truncation of laminae and trapping of detrital grains and is interpreted as siliceous stromatolite formed by very early or contemporaneous silicification of biomats with the contribution of silica-rich hydrothermal fluids. Biological affinities of described microfossils and microbes constructing siliceous stromatolites are under investigation. However, this study emphasizes how diverse the microbial community in Paleoarchean coastal hydrothermal environment was. We propose the diversity is at least partially due to the availability of various energy sources in this depositional environment including reducing chemicals and sunlight. © 2015 John Wiley & Sons Ltd.

Biomolecule-controlled hydrothermal synthesis of C-N-S-tridoped TiO2 nanocrystalline photocatalysts for NO removal under simulated solar light irradiation.

PubMed

Wang, Yawen; Huang, Yu; Ho, Wingkei; Zhang, Lizhi; Zou, Zhigang; Lee, Shuncheng

2009-09-30

In this study, C-N-S-tridoped titanium dioxide (TiO(2)) nanocrystals were synthesized by using a facile hydrothermal method in the presence of a biomolecule l-cysteine. This biomolecule could not only serve as the common source for the carbon, sulfur and nitrogen tridoping, but also could control the final crystal phases and morphology. The resulting materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption and UV-vis diffuse reflectance spectroscopy. XPS analysis revealed that S was incorporated into the lattice of TiO(2) through substituting oxygen atoms, N might coexist in the forms of N-Ti-O and Ti-O-N in tridoped TiO(2) and most C could form a mixed layer of carbonate species deposited on the surface of TiO(2) nanoparticles. The photocatalytic activities of the samples were tested on the removal of NO at typical indoor air level in a flow system under simulated solar light irradiation. The tridoped TiO(2) samples showed much higher removal efficiency than commercial P25 and the undoped counterpart photocatalyst. The enhanced visible light photocatalytic activity of C-N-S-tridoped TiO(2) nanocrystals was explained on the basis of characterizations. The possible formation process of the monodispersed C-N-S-tridoped anatase TiO(2) nanocrystals was also proposed. This study provides a new method to prepare visible light active TiO(2) photocatalyst.

Direct measurement of asperity contact growth in quartz at hydrothermal conditions

USGS Publications Warehouse

Beeler, Nicholas M.; Hickman, Stephen H.

2015-01-01

Earthquake recurrence requires interseismic fault restrengthening which results from solid state deformation in room-temperature friction and indentation experiments. In contrast exhumed fault zones show solution-transport processes such as pressure solution and contact overgrowths influence fault zone properties . In the absence of fluid flow, overgrowths are driven by gradients in surface curvature where material is dissolved, diffuses, and precipitates at the contact without convergence normal to the contact. To determine the rate of overgrowth for quartz, we conducted single contact experiments in an externally heated pressure vessel. Convergence was continuously monitored using reflected-light interferometry through a long-working-distance microscope. Contact normal force was constant with an initial effective normal stress of 1.7 MPa, temperature was between 350 and 530{degree sign}C, and water pressure was constant at 150 MPa. Two control experiments were conducted: one dry at 425{degree sign}C and one bi-material (sapphire) at 425{degree sign}C and 150 MPa water pressure. No contact growth or convergence was observed in the controls. For wet single-phase contacts, growth was initially rapid and then decreased with time. No convergence was observed. Fluid inclusions indicate that the contact is not uniformly wetted. The contact is bounded by small regions of high aperture, reflecting local free-face dissolution as the source for the overgrowth. The apparent activation energy is ~125 kJ/mol. Extrapolation predicts rates of contact area increase orders of magnitude faster than in dry, room-temperature and hydrothermal friction experiments, suggesting that natural strength recovery near the base of the seismogenic zone could be dominated by contact overgrowth.

Characterization of Fractures in the Chicxulub Peak Ring: Preliminary Results from IODP/ICDP Expedition 364

NASA Astrophysics Data System (ADS)

McCall, N.; Gulick, S. P. S.; Morgan, J. V.; Hall, B. J.; Jones, L.; Expedition 364 Science Party, I. I.

2017-12-01

During Expedition 364, IODP/ICDP drilled the peak ring of the Chicxulub impact crater at Site M0077, recovering core from 505.7 to 1334.7 mbsf. The core has been imaged via X-ray Computer Tomography (CT) as a noninvasive method to create a 3-dimensional model of the core, providing information on the density and internal structure at a 0.3 mm resolution. Results from the expedition show that from 748 mbsf and deeper the peak ring is largely composed of uplifted and fractured granitic basement rocks originally sourced from approximately 8-10 km depth. Impact crater modeling suggests the peak ring was formed through dynamic collapse of a rebounding central peak within 10 minutes of impact, requiring the target rocks to temporarily behave as a viscous fluid. The newly recovered core provides a rare opportunity to investigate the cratering process, specifically how the granite was weakened, as well as the extent of the hydrothermal system created after the impact. Based on the CT data, we identify four classes of fractures based on their CT facies deforming the granitoids: pervasive fine fractures, discrete fine fractures, discrete filled fractures, and discrete open fractures. Pervasive fine fractures were most commonly found proximal to dikes and impact melt rock. Discrete filled fractures often displayed a cataclastic texture. We present density trends for the different facies and compare these to petrophysical properties (density, NGR, P-wave seismic velocity). Fractured areas have a lower density than the surrounding granite, as do most filled fractures. This reduction suggests that fluid migrating through the peak ring in the wake of the impact either deposited lower density minerals within the fractures and/or altered the original fracture fill. The extent and duration of fluid flow recorded in these fractures will assist in the characterization of the post-impact hydrothermal system. Future work includes combining information from CT images with thin sections and plug samples at similar depths, refinement of CT facies characterization, examining cross-cutting relationships to determine timing constraints of deformation processes, and measurement of the orientation of the fractures.

Precipitation patterns during channel flow

NASA Astrophysics Data System (ADS)

Jamtveit, B.; Hawkins, C.; Benning, L. G.; Meier, D.; Hammer, O.; Angheluta, L.

2013-12-01

Mineral precipitation during channelized fluid flow is widespread in a wide variety of geological systems. It is also a common and costly phenomenon in many industrial processes that involve fluid flow in pipelines. It is often referred to as scale formation and encountered in a large number of industries, including paper production, chemical manufacturing, cement operations, food processing, as well as non-renewable (i.e. oil and gas) and renewable (i.e. geothermal) energy production. We have studied the incipient stages of growth of amorphous silica on steel plates emplaced into the central areas of the ca. 1 meter in diameter sized pipelines used at the hydrothermal power plant at Hellisheidi, Iceland (with a capacity of ca 300 MW electricity and 100 MW hot water). Silica precipitation takes place over a period of ca. 2 months at approximately 120°C and a flow rate around 1 m/s. The growth produces asymmetric ca. 1mm high dendritic structures ';leaning' towards the incoming fluid flow. A novel phase-field model combined with the lattice Boltzmann method is introduced to study how the growth morphologies vary under different hydrodynamic conditions, including non-laminar systems with turbulent mixing. The model accurately predicts the observed morphologies and is directly relevant for understanding the more general problem of precipitation influenced by turbulent mixing during flow in channels with rough walls and even for porous flow. Reference: Hawkins, C., Angheluta, L., Hammer, Ø., and Jamtveit, B., Precipitation dendrites in channel flow. Europhysics Letters, 102, 54001

Hydrothermal carbonization of animal manures: Processes and energetics

USDA-ARS?s Scientific Manuscript database

Hydrothermal carbonization (HTC) is an emerging technology for thermochemically converting biomass and waste materials into value-added carbonaceous char called hydrochar. HTC is well suited to manage wet feedstocks streams because pre-drying prior to processing is not required as with gasification...

Preparation of anticoagulant PyC biomaterials with super-hydrophobic surface.

PubMed

Ze, Wang; Wen-Sheng, Tan; Ye-Xia; Ming, Zhang; Xiao-Ping, Li; Jian-Guo, Qiu; Xiao-Hong, Yang

2018-01-01

Pyrolytic carbon (PyC) is a kind of biomaterial which is chemically inert and has excellent biocompatibility. In order to obtain a super-hydrophobic PyC surface to improve anticoagulation and inhibit thrombus, this study prepares grating pair structure, microhole array structure, helix structure on PyC surface by nanoseconds laser etching. Rod-like ZnO film and ball-like ZnO film are prepared on the PyC surface by the hydrothermal method; polyvinyl pyrrolidone (PVP) nanofiber film and PVP/TiO 2 complex nanofiber film are prepared on the PyC surface by the electrospinning method; the PyC surface is silanized. Finally, surface microstructure and surface energy are characterized by scanning electron microscopy and contact angle meter (OCA20, German DataPhysics Co.). The periodical microstructures are formed respectively by nanoseconds laser etching. The surface roughness is increased by the hydrothermal and electrospinning method. Through infiltration experiment on rough and smooth PyC surfaces, rough PyC surface with microstructure is super-hydrophobic and has greater than 150° contact angle, which decreases blood flow resistance and inhibits thrombus.

Internal structure, fault rocks, and inferences regarding deformation, fluid flow, and mineralization in the seismogenic Stillwater normal fault, Dixie Valley, Nevada

USGS Publications Warehouse

Caine, Jonathan S.; Bruhn, R.L.; Forster, C.B.

2010-01-01

Outcrop mapping and fault-rock characterization of the Stillwater normal fault zone in Dixie Valley, Nevada are used to document and interpret ancient hydrothermal fluid flow and its possible relationship to seismic deformation. The fault zone is composed of distinct structural and hydrogeological components. Previous work on the fault rocks is extended to the map scale where a distinctive fault core shows a spectrum of different fault-related breccias. These include predominantly clast-supported breccias with angular clasts that are cut by zones containing breccias with rounded clasts that are also clast supported. These are further cut by breccias that are predominantly matrix supported with angular and rounded clasts. The fault-core breccias are surrounded by a heterogeneously fractured damage zone. Breccias are bounded between major, silicified slip surfaces, forming large pod-like structures, systematically oriented with long axes parallel to slip. Matrix-supported breccias have multiply brecciated, angular and rounded clasts revealing episodic deformation and fluid flow. These breccias have a quartz-rich matrix with microcrystalline anhedral, equant, and pervasively conformable mosaic texture. The breccia pods are interpreted to have formed by decompression boiling and rapid precipitation of hydrothermal fluids whose flow was induced by coseismic, hybrid dilatant-shear deformation and hydraulic connection to a geothermal reservoir. The addition of hydrothermal silica cement localized in the core at the map scale causes fault-zone widening, local sealing, and mechanical heterogeneities that impact the evolution of the fault zone throughout the seismic cycle. ?? 2010.

Enhanced performance of wearable piezoelectric nanogenerator fabricated by two-step hydrothermal process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiu, Yu; Lei, Jixue; Yin, Bing

2014-03-17

A simple two-step hydrothermal process was proposed for enhancing the performance of the nanogenerator on flexible and wearable terylene-fabric substrate. With this method, a significant enhancement in output voltage of the nanogenerator from ∼10 mV to 7 V was achieved, comparing with the one by conventional one-step process. In addition, another advantage with the devices synthesized by two-step hydrothermal process was that their output voltages are only sensitive to strain rather than strain rate. The devices with a high output voltage have the ability to power common electric devices and will have important applications in flexible electronics and wearable devices.

Igneous activity and related ore deposits in the western and southern Tushar Mountains, Marysvale volcanic field, west-central Utah

USGS Publications Warehouse

Steven, Thomas A.

1984-01-01

PART A: Igneous activity in the Marysvale volcanic field of western Utah can be separated into many episodes of extrusion, intrusion, and hydrothermal activity. The rocks of the western Tushar Mountains, near the western part of the volcanic field, include intermediate-composition, calc-alkalic volcanic rocks erupted from scattered volcanoes in Oligocene through earliest Miocene time and related monzonitic intrusions emplaced 24-23 m.y. ago. Beginning 22-21 m.y. ago and extending through much of the later Cenozoic, a bimodal basalt-rhyolite assemblage was erupted widely throughout the volcanic field. Only volcanic and intrusive rocks belonging to the rhyolitic end member of this bimodal assemblage are present in the western Tushar Mountains; most of these rocks either fill the Mount Belknap caldera (19 m.y. old) or are part of the rhyolite of Gillies Hill (9---8 m.y. old). Episodic hydrothermal activity altered and mineralized rocks at many places in the western Tushar Mountains during Miocene time. The earliest activity took place in and adjacent to monzonitic calcalkalic intrusions emplaced in the vicinity of Indian Creek and Cork Ridge. These rocks were widely propylitized, and gold-bearing quartz-pyrite-carbonate veins formed in local fractures. Hydrothermal activity associated with the Mount Belknap caldera mobilized and redeposited uranium contained in the caldera-fill rocks and formed primary concentrations of lithophile elements (including molybdenum and uranium) in the vicinity of intrusive bodies. Hydrothermal activity associated with the rhyolite of Gillies Hill altered and mineralized rocks at several places along the fault zone that marks the western margin of the Tushar Mountains; the zoned alunite and gold deposits at Sheep Rock, the gold deposit at the Sunday Mine, and an alunite deposit near Indian Creek were thus produced. Resetting of isotopic ages suggests that another center of hydrothermally altered rocks associated with a buried pluton about 16 m.y. old may exist near Indian Creek just west of the Mount Belknap caldera. Geophysical evidence confirms the probability of a buried pluton near Indian Creek, and also indicates that another buried pluton probably exists beneath the 9-m.y.-old mineralized area at Sheep Rock. The mineral potential of the different hydrothermal systems, and the types of minerals deposited probably vary considerably from one period of mineralization to another and from one depth environment to another within a given system. PART B: The Big John caldera, on the western flank of the Tushar Mountains in the Marysvale volcanic field in west-central Utah, formed 23-22 m.y. ago in response to ash-flow eruptions of the Delano Peak Tuff Member of the Bullion Canyon Volcanics. These eruptions were near the end of the period of Oligocene-early Miocene calc-alkalic igneous activity that built a broad volcanic plateau in this part of Utah. About 22 m.y. ago, the composition of rocks erupted changed to a bimodal assemblage of mafic and silicic volcanics that was erupted episodically through the remainder of Cenozoic time. The alkali rhyolites are uranium rich in part, and are associated with all the known uranium deposits in the Marysvale volcanic field. The Big John caldera was a broad drained basin whose floor was covered by a layer of stream gravels when ash flows from the western source area of the Mount Belknap Volcanics filled the caldera with the Joe Lott Tuff Member about 19 m.y. ago. Devitrified and zeolitized rocks in the caldera fill have lost one-quarter to one-half of the uranium contained in the original magma. This mobilized uranium probably moved into the hydrologic regime, and some may have been redeposited in stream gravels underlying the Joe Lott within the caldera, or in gravels filling the original drainage channel that extended south from the caldera.

Dynamics of the Yellowstone hydrothermal system

USGS Publications Warehouse

Hurwitz, Shaul; Lowenstern, Jacob B.

2014-01-01

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

Seismic structure of oceanic crust at ODP borehole 504B: Investigating anisotropy and layer 2 characteristics

NASA Astrophysics Data System (ADS)

Gregory, E. P. M.; Hobbs, R. W.; Peirce, C.; Wilson, D. J.

2015-12-01

Fracture and fault networks in the upper oceanic crust influence the circulation of hydrothermal fluids and heat transfer between crust and ocean. These fractures form by extensional stresses, with a predominant orientation parallel to the ridge axis, creating porosity- and permeability-derived anisotropy that can be measured in terms of seismic velocity. These properties change as the crust ages and evolves through cooling, alteration and sedimentation. The rate at which these changes occur and their effects on oceanic crustal structure and hydrothermal flow patterns are currently not well constrained. The NERC-funded OSCAR project aims to understand the development of upper oceanic crust, the extent and influence of hydrothermal circulation on the crust, and the behavior of fluids flowing in fractured rock. We show P-wave velocity models centered on DSDP/ODP Hole 504B, located ~200 km south of the Costa Rica Rift, derived from data acquired during a recent integrated geophysics and oceanography survey of the Panama Basin. The data were recorded by 25 four-component OBSs deployed in a grid, that recorded ~10,000 full azimuthal coverage shots fired by a combined high- and low-frequency seismic source. Both reflection and refraction data are integrated to reveal the seismic velocity structure of the crust within the 25 km by 25 km grid. The down-hole geological structure of 6 Ma crust at 504B comprises 571.5 m of extrusive basalts overlying a 209 m transition zone of mixed pillows and dikes containing a clear alteration boundary, which grades to >1050 m of sheeted dikes. Our model results are compared with this lithological structure and other previously published results to better understand the nature of velocity changes within seismic layer 2. The data provide a 3D framework, which together with analysis of the S-wave arrivals and particle motion studies, constrain estimates of the seismic anisotropy and permeability structure of the upper oceanic crust as it ages.

1-Dimensional AgVO3 nanowires hybrid with 2-dimensional graphene nanosheets to create 3-dimensional composite aerogels and their improved electrochemical properties

NASA Astrophysics Data System (ADS)

Liang, Liying; Xu, Yimeng; Lei, Yong; Liu, Haimei

2014-03-01

Three-dimensional (3D) porous composite aerogels have been synthesized via an innovative in situ hydrothermal method assisted by a freeze-drying process. In this hybrid structure, one-dimensional (1D) AgVO3 nanowires are uniformly dispersed on two-dimensional (2D) graphene nanosheet surfaces and/or are penetrated through the graphene sheets, forming 3D porous composite aerogels. As cathode materials for lithium-ion batteries, the composite aerogels exhibit high discharge capacity, excellent rate capability, and good cycling stability.Three-dimensional (3D) porous composite aerogels have been synthesized via an innovative in situ hydrothermal method assisted by a freeze-drying process. In this hybrid structure, one-dimensional (1D) AgVO3 nanowires are uniformly dispersed on two-dimensional (2D) graphene nanosheet surfaces and/or are penetrated through the graphene sheets, forming 3D porous composite aerogels. As cathode materials for lithium-ion batteries, the composite aerogels exhibit high discharge capacity, excellent rate capability, and good cycling stability. Electronic supplementary information (ESI) available: Preparation, characterization, SEM images, XRD patterns, and XPS of AgVO3/GAs. See DOI: 10.1039/c3nr06899d

Hydrothermal synthesis of nanostructured graphene/polyaniline composites as high-capacitance electrode materials for supercapacitors

PubMed Central

Wang, Ronghua; Han, Meng; Zhao, Qiannan; Ren, Zonglin; Guo, Xiaolong; Xu, Chaohe; Hu, Ning; Lu, Li

2017-01-01

As known to all, hydrothermal synthesis is a powerful technique for preparing inorganic and organic materials or composites with different architectures. In this reports, by controlling hydrothermal conditions, nanostructured polyaniline (PANi) in different morphologies were composited with graphene sheets (GNS) and used as electrode materials of supercapacitors. Specifically, ultrathin PANi layers with total thickness of 10–20 nm are uniformly composited with GNS by a two-step hydrothermal-assistant chemical oxidation polymerization process; while PANi nanofibers with diameter of 50~100 nm are obtained by a one-step direct hydrothermal process. Benefitting from the ultrathin layer and porous structure, the sheet-like GNS/PANi composites can deliver specific capacitances of 532.3 to 304.9 F/g at scan rates of 2 to 50 mV/s. And also, this active material showed very good stability with capacitance retention as high as ~99.6% at scan rate of 50 mV/s, indicating a great potential for using in supercapacitors. Furthermore, the effects of hydrothermal temperatures on the electrochemical performances were systematically studied and discussed. PMID:28291246

Deposition conditions and distribution features of native gold individuals in the veins of the Tokur mesothermal deposit, Russia

NASA Astrophysics Data System (ADS)

Ostapenko, N. S.; Neroda, O. N.

2016-05-01

The paper discusses factors in the deposition and concentration of native gold and the spatial distribution of its individuals within the sufide-poor gold-quartz veins at the mesoabyssal Tokur deposit. The major factors in deposition of gold were sealing of the hydrothermal system, a sudden drop in fluid pressure, and repeated immiscibility in the fluid. Native gold was deposited in relation to initial acts of prolonged and discrete opening and preopening of cavities in three mineral assemblages of the productive association II. Most native gold individuals with a visible size of 0.1-1.5 mm were together with the early generation of quartz 2 on cavity walls adjacent to altered rocks. This is caused by the high content of Au complexes in initial hydrothermal solutions favoring rapid oversaturation during cavity formation. Gold fills interstices between grains of quartz 2 throughout the deposit and mineral assemblages. The vertical-flow distribution of gold has been established in economic veins; the upper and middle levels are enriched in gold, and samples with the greatest gold grade of 100-500 g/t or higher are concentrated there. This is caused both by the predominance of mineral association II at these levels and probable natural flotation of gold grains contained in the gold-gas associate for immiscibility of the hydrothermal fluid at the second stage of the ore-forming process.

Survivability and Abiotic Reactions of Selected Amino Acids in Different Hydrothermal System Simulators

NASA Astrophysics Data System (ADS)

Chandru, Kuhan; Imai, Eiichi; Kaneko, Takeo; Obayashi, Yumiko; Kobayashi, Kensei

2013-04-01

We tested the stability and reaction of several amino acids using hydrothermal system simulators: an autoclave and two kinds of flow reactors at 200-250 °C. This study generally showed that there is a variation in the individual amino acids survivability in the simulators. This is mainly attributed to the following factors; heat time, cold quenching exposure, metal ions and also silica. We observed that, in a rapid heating flow reactor, high aggregation and/or condensation of amino acids could occur even during a heat exposure of 2 min. We also monitored their stability in a reflow-type of simulator for 120 min at 20 min intervals. The non-hydrolyzed and hydrolyzed samples for this system showed a similar degradation only in the absence of metal ions.

Hydrothermal Habitats: Measurements of Bulk Microbial Elemental Composition, and Models of Hydrothermal Influences on the Evolution of Dwarf Planets

NASA Astrophysics Data System (ADS)

Neveu, Marc Francois Laurent

Finding habitable worlds is a key driver of solar system exploration. Many solar system missions seek environments providing liquid water, energy, and nutrients, the three ingredients necessary to sustain life. Such environments include hydrothermal systems, spatially-confined systems where hot aqueous fluid circulates through rock by convection. I sought to characterize hydrothermal microbial communities, collected in hot spring sediments and mats at Yellowstone National Park, USA, by measuring their bulk elemental composition. To do so, one must minimize the contribution of non-biological material to the samples analyzed. I demonstrate that this can be achieved using a separation method that takes advantage of the density contrast between cells and sediment and preserves cellular elemental contents. Using this method, I show that in spite of the tremendous physical, chemical, and taxonomic diversity of Yellowstone hot springs, the composition of microorganisms there is surprisingly ordinary. This suggests the existence of a stoichiometric envelope common to all life as we know it. Thus, future planetary investigations could use elemental fingerprints to assess the astrobiological potential of hydrothermal settings beyond Earth. Indeed, hydrothermal activity may be widespread in the solar system. Most solar system worlds larger than 200 km in radius are dwarf planets, likely composed of an icy, cometary mantle surrounding a rocky, chondritic core. I enhance a dwarf planet evolution code, including the effects of core fracturing and hydrothermal circulation, to demonstrate that dwarf planets likely have undergone extensive water-rock interaction. This supports observations of aqueous products on their surfaces. I simulate the alteration of chondritic rock by pure water or cometary fluid to show that aqueous alteration feeds back on geophysical evolution: it modifies the fluid antifreeze content, affecting its persistence over geological timescales; and the distribution of radionuclides, whose decay is a chief heat source on dwarf planets. Interaction products can be observed if transported to the surface. I simulate numerically how cryovolcanic transport is enabled by primordial and hydrothermal volatile exsolution. Cryovolcanism seems plausible on dwarf planets in light of images recently returned by spacecrafts. Thus, these coupled geophysical-geochemical models provide a comprehensive picture of dwarf planet evolution, processes, and habitability.

Defining boundaries for the distribution of microbial communities beneath the sediment-buried, hydrothermally active seafloor

PubMed Central

Yanagawa, Katsunori; Ijiri, Akira; Breuker, Anja; Sakai, Sanae; Miyoshi, Youko; Kawagucci, Shinsuke; Noguchi, Takuroh; Hirai, Miho; Schippers, Axel; Ishibashi, Jun-ichiro; Takaki, Yoshihiro; Sunamura, Michinari; Urabe, Tetsuro; Nunoura, Takuro; Takai, Ken

2017-01-01

Subseafloor microbes beneath active hydrothermal vents are thought to live near the upper temperature limit for life on Earth. We drilled and cored the Iheya North hydrothermal field in the Mid-Okinawa Trough, and examined the phylogenetic compositions and the products of metabolic functions of sub-vent microbial communities. We detected microbial cells, metabolic activities and molecular signatures only in the shallow sediments down to 15.8 m below the seafloor at a moderately distant drilling site from the active hydrothermal vents (450 m). At the drilling site, the profiles of methane and sulfate concentrations and the δ13C and δD isotopic compositions of methane suggested the laterally flowing hydrothermal fluids and the in situ microbial anaerobic methane oxidation. In situ measurements during the drilling constrain the current bottom temperature of the microbially habitable zone to ~45 °C. However, in the past, higher temperatures of 106–198 °C were possible at the depth, as estimated from geochemical thermometry on hydrothermally altered clay minerals. The 16S rRNA gene phylotypes found in the deepest habitable zone are related to those of thermophiles, although sequences typical of known hyperthermophilic microbes were absent from the entire core. Overall our results shed new light on the distribution and composition of the boundary microbial community close to the high-temperature limit for habitability in the subseafloor environment of a hydrothermal field. PMID:27754478

Defining boundaries for the distribution of microbial communities beneath the sediment-buried, hydrothermally active seafloor.

PubMed

Yanagawa, Katsunori; Ijiri, Akira; Breuker, Anja; Sakai, Sanae; Miyoshi, Youko; Kawagucci, Shinsuke; Noguchi, Takuroh; Hirai, Miho; Schippers, Axel; Ishibashi, Jun-Ichiro; Takaki, Yoshihiro; Sunamura, Michinari; Urabe, Tetsuro; Nunoura, Takuro; Takai, Ken

2017-02-01

Subseafloor microbes beneath active hydrothermal vents are thought to live near the upper temperature limit for life on Earth. We drilled and cored the Iheya North hydrothermal field in the Mid-Okinawa Trough, and examined the phylogenetic compositions and the products of metabolic functions of sub-vent microbial communities. We detected microbial cells, metabolic activities and molecular signatures only in the shallow sediments down to 15.8 m below the seafloor at a moderately distant drilling site from the active hydrothermal vents (450 m). At the drilling site, the profiles of methane and sulfate concentrations and the δ 13 C and δD isotopic compositions of methane suggested the laterally flowing hydrothermal fluids and the in situ microbial anaerobic methane oxidation. In situ measurements during the drilling constrain the current bottom temperature of the microbially habitable zone to ~45 °C. However, in the past, higher temperatures of 106-198 °C were possible at the depth, as estimated from geochemical thermometry on hydrothermally altered clay minerals. The 16S rRNA gene phylotypes found in the deepest habitable zone are related to those of thermophiles, although sequences typical of known hyperthermophilic microbes were absent from the entire core. Overall our results shed new light on the distribution and composition of the boundary microbial community close to the high-temperature limit for habitability in the subseafloor environment of a hydrothermal field.

Examining the Effect of Temperature, Pressure, Seismicity and Diffuse Fluid Flow on Floc Events at Axial Seamount

NASA Astrophysics Data System (ADS)

Rahman, M.; Crone, T. J.; Knuth, F.; Garcia, C.; Soule, D. C.; Fatland, R.

2017-12-01

Flocculation (floc) events are characterized by the ejection of bacterial material, possibly associated with thermophiles originating from warmer sub-seafloor habitats, into the water column. These events are anecdotally linked to magmatic and tectonic processes common in mid-ocean ridge seafloor environments. However, little is known about the relationship between flocculation events and other potentially triggering processes. The Cabled Array at Axial Seamount provides a suite of interdisciplinary real-time datasets to examine system-level processes governing the volcanic marine environment. The eruption at Axial Seamount in 2015 creates an opportunity to study this volcanic system as it evolves post eruption and identify the relationships between the temperature, pressure, seismicity and the biological response. The Diffuse Vent Fluid 3-D Temperature Array (TMPSF), located within the ASHES hydrothermal vent field at Axial Seamount, uses 24 separate sensors to provide a 3-dimensional distribution of diffuse flow temperatures near the Mushroom hydrothermal vent. Preliminary analysis suggests that the temperature signal is strongly influenced by tides observed using the ocean bottom pressure sensors, which may be related to either gradual shifts in tidal currents above the seafloor, or related to subsurface flux. CamHD, also located within the ASHES field, produces high definition video data, which we analyze to identify changes in water column floc concentration. These data streams allow us to examine the controls on the temperature signal and the associated correlations with microbial seafloor processes. We are currently examining the flocculation event identified in Crone (2016) to determine its relationship to changes in seawater temperatures near the seafloor, seismic activity and seafloor pressure. We will use this proxy to examine other CamHD data and determine if subsequent flocculation events have occurred and if they have a similar relationship to local thermal and seismic activity.

Layered double hydroxide using hydrothermal treatment: morphology evolution, intercalation and release kinetics of diclofenac sodium

NASA Astrophysics Data System (ADS)

Joy, Mathew; Iyengar, Srividhya J.; Chakraborty, Jui; Ghosh, Swapankumar

2017-12-01

The present work demonstrates the possibilities of hydrothermal transformation of Zn-Al layered double hydroxide (LDH) nanostructure by varying the synthetic conditions. The manipulation in washing step before hydrothermal treatment allows control over crystal morphologies, size and stability of their aqueous solutions. We examined the crystal growth process in the presence and the absence of extra ions during hydrothermal treatment and its dependence on the drug (diclofenac sodium (Dic-Na)) loading and release processes. Hexagonal plate-like crystals show sustained release with ˜90% of the drug from the matrix in a week, suggesting the applicability of LDH nanohybrids in sustained drug delivery systems. The fits to the release kinetics data indicated the drug release as a diffusion-controlled release process. LDH with rod-like morphology shows excellent colloidal stability in aqueous suspension, as studied by photon correlation spectroscopy.

Discovery of a new hydrothermal vent based on an underwater, high-resolution geophysical survey

NASA Astrophysics Data System (ADS)

Nakamura, Kentaro; Toki, Tomohiro; Mochizuki, Nobutatsu; Asada, Miho; Ishibashi, Jun-ichiro; Nogi, Yoshifumi; Yoshikawa, Shuro; Miyazaki, Jun-ichi; Okino, Kyoko

2013-04-01

A new hydrothermal vent site in the Southern Mariana Trough has been discovered using acoustic and magnetic surveys conducted by the Japan Agency for Marine-Earth Science and Technology's (JAMSTEC) autonomous underwater vehicle (AUV), Urashima. The high-resolution magnetic survey, part of a near-bottom geophysical mapping around a previously known hydrothermal vent site, the Pika site, during the YK09-08 cruise in June-July 2009, found that a clear magnetization low extends ˜500 m north from the Pika site. Acoustic signals, suggesting hydrothermal plumes, and 10 m-scale chimney-like topographic highs were detected within this low magnetization zone by a 120 kHz side-scan sonar and a 400 kHz multibeam echo sounder. In order to confirm the seafloor sources of the geophysical signals, seafloor observations were carried out using the deep-sea manned submersible Shinkai 6500 during the YK 10-10 cruise in August 2010. This discovered a new hydrothermal vent site (12°55.30'N, 143°38.89'E; at a depth of 2922 m), which we have named the Urashima site. This hydrothermal vent site covers an area of approximately 300 m×300 m and consists of black and clear smoker chimneys, brownish-colored shimmering chimneys, and inactive chimneys. All of the fluids sampled from the Urashima and Pika sites have chlorinity greater than local ambient seawater, suggesting subseafloor phase separation or leaching from rocks in the hydrothermal reaction zone. End-member compositions of the Urashima and Pika fluids suggest that fluids from two different sources feed the two sites, even though they are located on the same knoll and separated by only ˜500 m. We demonstrate that investigations on hydrothermal vent sites located in close proximity to one another can provide important insights into subseafloor hydrothermal fluid flow, and also that, while such hydrothermal sites are difficult to detect by conventional plume survey methods, high-resolution underwater geophysical surveys provide an effective means.

Fundamental mechanisms and reactions in non-catalytic subcritical hydrothermal processes: A review.

PubMed

Yousefifar, Azadeh; Baroutian, Saeid; Farid, Mohammed M; Gapes, Daniel J; Young, Brent R

2017-10-15

The management and disposal of solid waste is of increasing concern across the globe. Hydrothermal processing of sludge has been suggested as a promising solution to deal with the considerable amounts of sludge produced worldwide. Such a process not only degrades organic compounds and reduces waste volume, but also provides an opportunity to recover valuable substances. Hydrothermal processing comprises two main sub-processes: wet oxidation (WO) and thermal hydrolysis (TH), in which the formation of various free radicals results in the production of different intermediates. Volatile fatty acids (VFAs), especially acetic acid, are usually the main intermediates which remain as a by-product of the process. This paper aims to review the fundamental mechanism for hydrothermal processing of sludge, and the formation of different free radicals and intermediates therein. In addition, the proposed kinetic models for the two processes (WO and TH) from the literature are reviewed and the advantages and disadvantages of each model are outlined. The effect of mass transfer as a critical component of the design and development of the processes, which has been neglected in most of these proposed models, is also reviewed, and the effect of influencing parameters on the processes' controlling step (reaction or mass transfer) is discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Geodiversity of hydrothermal processes along the Mid-Atlantic Ridge and ultramafic-hosted mineralization: A new type of oceanic Cu-Zn-Co-Au volcanogenic massive sulfide deposit

NASA Astrophysics Data System (ADS)

Fouquet, Yves; Cambon, Pierre; Etoubleau, Joël; Charlou, Jean Luc; Ondréas, Hélène; Barriga, Fernando J. A. S.; Cherkashov, Georgy; Semkova, Tatiana; Poroshina, Irina; Bohn, M.; Donval, Jean Pierre; Henry, Katell; Murphy, Pamela; Rouxel, Olivier

Several hydrothermal deposits associated with ultramafic rocks have recently been found along slow spreading ridges with a low magmatic budget. Three preferential settings are identified: (1) rift valley walls near the amagmatic ends of ridge segments; (2) nontransform offsets; and (3) ultramafic domes at inside corners of ridge transform-fault intersections. The exposed mantle at these sites is often interpreted to be a detachment fault. Hydrothermal cells in ultramafic rocks may be driven by regional heat flow, cooling gabbroic intrusions, and exothermic heat produced during serpentinization. Along the Mid-Atlantic Ridge (MAR), hydrothermal deposits in ultramafic rocks include the following: (1) sulfide mounds related to high-temperature low-pH fluids (Logatchev, Rainbow, and Ashadze); (2) carbonate chimneys related to low-temperature, high-pH fluids (Lost City); (3) low-temperature diffuse venting and high-methane discharge associated with silica, minor sulfides, manganese oxides, and pervasive alteration (Saldanha); and (4) stockwork quartz veins with sulfides at the base of detachment faults (15°05'N). These settings are closely linked to preferential circulation of fluid along permeable detachment faults. Compared to mineralization in basaltic environments, sulfide deposits associated with ultramafic rocks are enriched in Cu, Zn, Co, Au, and Ni. Gold has a bimodal distribution in low-temperature Zn-rich and in high-temperature Cu-rich mineral assemblages. The Cu-Zn-Co-Au deposits along the MAR seem to be more abundant than in ophiolites on land. This may be because ultramafic-hosted volcanogenic massive sulfide deposits on slow spreading ridges are usually not accreted to continental margins during obduction and may constitute a specific marine type of mineralization.

The coupled geochemistry of Au and As in pyrite from ore deposits and geothermal fields: monitoring fluid evolution and external forcing factors in hydrothermal systems

NASA Astrophysics Data System (ADS)

Reich, M.; Deditius, A.; Tardani, D.; Sanchez-Alfaro, P.

2014-12-01

Among the many factors influencing the complex process of lava flow emplacement, the interaction with the substrate onto which flow is emplaced plays a central role. Lava flows are rarely emplaced onto smooth or regular surfaces. For example, at Kīlauea Volcano, Hawai'i, lava flows regularly flow over solid rock, vegetation, basaltic or silica sand, and man-made materials, including asphalt and concrete. In situ studies of lava-substrate interactions are inherently difficult, and often dangerous, to carry-out, requiring the design of controllable laboratory experiments. We investigate the effects of substrate grain size, cohesion, and roughness on flow mobility and morphology through a series of flow experiments using analog materials and molten basalt. We have developed a series of experiments that allow for adjustable substrate parameters and analyze their effects on lava flow emplacement. The first set of experiments are performed at the Fluids Mechanics Laboratory at the Lamont-Doherty Earth Observatory and focus on two analog materials: polyethylene glycol (PEG), a commercially available wax, and corn syrup. The fluids were each extruded onto a series of scaled substrate beds to replicate the emplacement of lava in a natural environment. Preliminary experiments demonstrated that irregular topography, particularly topography with a height amplitude similar to that of the flow itself, can affect flow morphology, width, and velocity by acting as local barriers or culverts to the fluid. This is expected from observations of fluid flow in natural environments. A follow-up set of experiments will be conducted in Fall 2015 at the Syracuse University (SU) Lava Project Lab. In this set, we will pour molten basalt directly onto a series of substrates representing natural environments found on the Earth and other rocky bodies in the Solar System. These experiments will allow for analysis of the effects of basaltic composition and high temperatures on lava-substrate heat transfer and mechanical interactions. Results will be used to improve current lava flow prediction models as well as increase our understanding of the evolution of volcanic regions on the Earth and other planets.

Anatomy of a deep sub-surface ridge flank aquifer: The "Red Brick" Horizon in ODP Hole 1256D

NASA Astrophysics Data System (ADS)

Teagle, D. A.; Smith-Duque, C. E.; Harris, M.; Rutter, J.; Coggon, R. M.; Tominaga, M.; Alt, J.; Murphy, B.; Banerjee, N.

2012-12-01

Long-lived conductive heat flow deficits, near isothermal basement temperatures, and sedimentary pore water profiles from mid-ocean ridge flanks provide compelling arguments for the substantial lateral movement of seawater-derived fluids within the upper oceanic crust. However, there are few descriptions of zones within the oceanic basement for which there is strong evidence for sustained low temperature hydrothermal fluid flow and alteration. This paper describes a distinctive horizon of intense low temperature alteration encountered in ODP Hole 1256D. Hole 1256D, located on 15 million-year-old East Pacific Rise crust formed at a superfast spreading rate (>200 mm/yr) provides a reference section for fast spreading ocean crust and is the only well to sample a complete section of lavas, sheeted dikes, and into the upper most gabbros. The volcanic sequences at Hole 1256D are >800 m thick. The Red Brick horizon occurs at ~400 m sub-basement (msb) in massive and sheet flows that overly a ~30 m-thick zone of massive flows. These flows probably crystallized at the base of the ridge axial slope within a few 1000 meters of the ridge axis (Tominaga and Umino, 2010). The Red Brick horizon comprises a 50 cm-thick zone of massive, sparsely olivine-phyric microcrystalline basalt that is very strongly (80 to 90%) hydrothermally altered. Olivine, clinopyroxene, and plagioclase are replaced by beidellite, celadonite, K feldspar and iron oxyhydroxide, imparting blue-green and brick red colors to the rock. These secondary minerals plus quartz and carbonate also fill vugs and pore space. Compared to surrounding basalts that exhibit only background levels of low temperature alteration, the rocks of the Red Brick zone are strongly oxidized (Fe3+/FeTot >0.7), hydrated (>4 wt.%), and have highly elevated concentrations of alkali metals (K, Rb, Cs) and Mg. There are strong reductions in Si, Ca, Mn, Zn and Cu. Bulk rock oxygen isotope (δ18O ~8.5 to 9 per mil) indicate hydrothermal alteration at about 70 °C for a seawater-like fluid. 87Sr/86Sr is significantly elevated (0.7033 to 0.7045) compared to primary igneous values but still rock-dominated. The near complete mineral recrystallization should mean that Sr isotope ratios record the signature of the parent hydrothermal fluid. Intriguingly this range is much less radiogenic than our estimate for Site 1256 paleo-black smoker fluids (0.7051 to 0.7053) indicating that the altering fluids are not seawater-diluted black smoker fluids. The core pieces of the Red Brick zone can be confidently identified in the wireline geophysical measurements by integrating formation micro-scanner and gamma ray logs. The occurrence of intense alteration at the Red Brick horizon appears to result from the occurrence of an impermeable unit of massive basalt with few fractures directly below, that may have acted as a long term channel for the lateral flow of ridge flank hydrothermal fluids.

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

USGS Publications Warehouse

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

2016-01-01

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

Castro ring zone: a 4,500-km2 fossil hydrothermal system in the Challis volcanic field, central Idaho.

USGS Publications Warehouse

Criss, R.E.; Ekren, E.B.; Hardyman, R.F.

1984-01-01

The largest fossil hydrothermal system occupying a 4500 km2 area in central Idaho is revealed by delta 18O studies. The remains of this meteoric-hydrothermal system are preserved within a sharply bounded, 15 km wide, 70-km-diameter annulus of low delta 18O rock (+2.0 to -8.8per mille) termed the Castro ring zone. The zone is centred on a less depleted (+4.5) core zone consisting of granitic rocks of the Castro pluton. This 700-km2 Eocene subvolcanic batholith has intruded, domed, and hydrothermally metamorphosed a thick sequence of Challis Volcanics, the stratigraphically low rocks in the 2000-km2 Van Horn Peak and the 1000-km2 Thunder Mountain cauldron complexes being most strongly altered. Less extreme 18O depletions occur in the youngest major ash-flow sheets of these complexes, indicating a vertical 18O gradient. Water/rock ratios of geothermal systems are surprisingly insensitive to the circulation scale.-L.-di H.

Hydrothermal treatment followed by enzymatic hydrolysis and hydrothermal carbonization as means to valorise agro- and forest-based biomass residues.

PubMed

Wikberg, Hanne; Grönqvist, Stina; Niemi, Piritta; Mikkelson, Atte; Siika-Aho, Matti; Kanerva, Heimo; Käsper, Andres; Tamminen, Tarja

2017-07-01

The suitability of several abundant but underutilized agro and forest based biomass residues for hydrothermal treatment followed by enzymatic hydrolysis as well as for hydrothermal carbonization was studied. The selected approaches represent simple biotechnical and thermochemical treatment routes suitable for wet biomass. Based on the results, the hydrothermal pre-treatment followed by enzymatic hydrolysis seemed to be most suitable for processing of carbohydrate rich corn leaves, corn stover, wheat straw and willow. High content of thermally stable components (i.e. lignin) and low content of ash in the biomass were advantageous for hydrothermal carbonization of grape pomace, coffee cake, Scots pine bark and willow. Copyright © 2017 Elsevier Ltd. All rights reserved.

Aquarius - A Modelling Package for Groundwater Flow and Coupled Heat Transport in the Range 0.1 to 100 MPa and 0.1 to 1000 C

NASA Astrophysics Data System (ADS)

Cook, S. J.

2009-05-01

Aquarius is a Windows application that models fluid flow and heat transport under conditions in which fluid buoyancy can significantly impact patterns and magnitudes of fluid flow. The package is designed as a visualization tool through which users can examine flow systems in environments, both low temperature aquifers and regions with elevated PT regimes such as deep sedimentary basins, hydrothermal systems, and contact thermal aureoles. The package includes 4 components: (1) A finite-element mesh generator/assembler capable of representing complex geologic structures. Left-hand, right-hand and alternating linear triangles can be mixed within the mesh. Planer horizontal, planer vertical and cylindrical vertical coordinate sections are supported. (2) A menu-selectable system for setting properties and boundary/initial conditions. The design retains mathematical terminology for all input parameters such as scalars (e.g., porosity), tensors (e.g., permeability), and boundary/initial conditions (e.g., fixed potential). This makes the package an effective instructional aide by linking model requirements with the underlying mathematical concepts of partial differential equations and the solution logic of boundary/initial value problems. (3) Solution algorithms for steady-state and time-transient fluid flow/heat transport problems. For all models, the nonlinear global matrix equations are solved sequentially using over-relaxation techniques. Matrix storage design allows for large (e.g., 20000) element models to run efficiently on a typical PC. (4) A plotting system that supports contouring nodal data (e.g., head), vector plots for flux data (e.g., specific discharge), and colour gradient plots for elemental data (e.g., porosity), water properties (e.g., density), and performance measures (e.g., Peclet numbers). Display graphics can be printed or saved in standard graphic formats (e.g., jpeg). This package was developed from procedural codes in C written originally to model the hydrothermal flow system responsible for contact metamorphism of Utah's Alta Stock (Cook et al., AJS 1997). These codes were reprogrammed in Microsoft C# to take advantage of object oriented design and the capabilities of Microsoft's .NET framework. The package is available at no cost by e-mail request from the author.

Numerical simulation of hydrothermal circulation in the Cascade Range, north-central Oregon

USGS Publications Warehouse

Ingebritsen, S.E.; Paulson, K.M.

1990-01-01

Alternate conceptual models to explain near-surface heat-flow observations in the central Oregon Cascade Range involve (1) an extensive mid-crustal magmatic heat source underlying both the Quaternary arc and adjacent older rocks or (2) a narrower deep heat source which is flanked by a relatively shallow conductive heat-flow anomaly caused by regional ground-water flow (the lateral-flow model). Relative to the mid-crustal heat source model, the lateral-flow model suggests a more limited geothermal resource base, but a better-defined exploration target. We simulated ground-water flow and heat transport through two cross sections trending west from the Cascade range crest in order to explore the implications of the two models. The thermal input for the alternate conceptual models was simulated by varying the width and intensity of a basal heat-flow anomaly and, in some cases, by introducing shallower heat sources beneath the Quaternary arc. Near-surface observations in the Breitenbush Hot Springs area are most readily explained in terms of lateral heat transport by regional ground-water flow; however, the deep thermal structure still cannot be uniquely inferred. The sparser thermal data set from the McKenzie River area can be explained either in terms of deep regional ground-water flow or in terms of a conduction-dominated system, with ground-water flow essentially confined to Quaternary rocks and fault zones.

The deep structure of a sea-floor hydrothermal deposit

USGS Publications Warehouse

Zierenberg, R.A.; Fouquet, Y.; Miller, D.J.; Bahr, J.M.; Baker, P.A.; Bjerkgard, T.; Brunner, C.A.; Duckworth, R.C.; Gable, R.; Gieskes, J.; Goodfellow, W.D.; Groschel-Becker, H. M.; Guerin, G.; Ishibashi, J.; Iturrino, G.; James, R.H.; Lackschewitz, K.S.; Marquez, L.L.; Nehlig, P.; Peter, J.M.; Rigsby, C.A.; Schultheiss, P.; Shanks, Wayne C.; Simoneit, B.R.T.; Summit, M.; Teagle, D.A.H.; Urbat, M.; Zuffa, G.G.

1998-01-01

Hydrothermal circulation at the crests of mid-ocean ridges plays an important role in transferring heat from the interior of the Earth. A consequence of this hydrothermal circulation is the formation of metallic ore bodies known as volcanic-associated massive sulphide deposits. Such deposits, preserved on land, were important sources of copper for ancient civilizations and continue to provide a significant source of base metals (for example, copper and zinc). Here we present results from Ocean Drilling Program Leg 169, which drilled through a massive sulphide deposit on the northern Juan de Fuca spreading centre and penetrated the hydrothermal feeder zone through which the metal-rich fluids reached the sea floor. We found that the style of feeder-zone mineralization changes with depth in response to changes in the pore pressure of the hydrothermal fluids and discovered a stratified zone of high-grade copper-rich replacement mineralization below the massive sulphide deposit. This copper-rich zone represents a type of mineralization not previously observed below sea-floor deposits, and may provide new targets for land-based mineral exploration.

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

USGS Publications Warehouse

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

2018-01-01

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

Incorporating Density Properties of MgSO4 Brines Into Icy World Ocean Simulations

NASA Astrophysics Data System (ADS)

Goodman, J. C.; Vance, S.

2011-12-01

The structure and flow of the subsurface oceans in icy worlds depends on the sources of buoyancy within these oceans. Buoyancy is determined by the equation of state, in which density is a nonlinear function of temperature, salinity, and pressure. Equations of state for terrestrial seawater (with Na and Cl as the principal dissolved species) are well-developed, but icy world oceans may contain a different balance of species, including Na, Mg, SO4, and NH4 (Kargel et al, 2000). Recent work by Vance and Brown (2011, pers. comm.) has mapped out the density and thermodynamic properties of MgSO4 brines under icy world conditions. We have developed code to incorporate this equation of state data for MgSO4 brines into two different ocean simulation models. First, we investigate a single-column convection model, which is able to find the equilibrium structure and heat transport of an icy world ocean. We explore the heat transport through the ocean subject to a variety of assumptions about ocean salinity and seafloor heat and salt flux. We resolve the paradox posed by Vance and Brown (2004): warm salty MgSO4 brine emitted by a seafloor hydrothermal system may be positively buoyant at the seafloor, but become negatively buoyant (sinking) at lower pressure. How does heat escape the ocean, if it cannot be transported by convection? Second, we add MgSO4 dynamics to a full 3-D time-dependent general circulation model (the MIT GCM), which is able to simulate both the global-scale circulation of the world's ocean and investigate the highly turbulent dynamics of buoyant hydrothermal systems. We ask, "Are buoyancy-driven flows in a MgSO4 brine ocean significantly different than similarly-driven flows in terrestrial seawater?"

Fossil black smoker yields oxygen isotopic composition of Neoproterozoic seawater.

PubMed

Hodel, F; Macouin, M; Trindade, R I F; Triantafyllou, A; Ganne, J; Chavagnac, V; Berger, J; Rospabé, M; Destrigneville, C; Carlut, J; Ennih, N; Agrinier, P

2018-04-13

The evolution of the seawater oxygen isotopic composition (δ 18 O) through geological time remains controversial. Yet, the past δ 18 O seawater is key to assess past seawater temperatures, providing insights into past climate change and life evolution. Here we provide a new and unprecedentedly precise δ 18 O value of -1.33 ± 0.98‰ for the Neoproterozoic bottom seawater supporting a constant oxygen isotope composition through time. We demonstrate that the Aït Ahmane ultramafic unit of the ca. 760 Ma Bou Azzer ophiolite (Morocco) host a fossil black smoker-type hydrothermal system. In this system we analyzed an untapped archive for the ocean oxygen isotopic composition consisting in pure magnetite veins directly precipitated from a Neoproterozoic seawater-derived fluid. Our results suggest that, while δ 18 O seawater and submarine hydrothermal processes were likely similar to present day, Neoproterozoic oceans were 15-30 °C warmer on the eve of the Sturtian glaciation and the major life diversification that followed.

Adsorptive separation and photocatalytic degradation of methylene blue dye on titanate nanotube powders prepared by hydrothermal process using metal Ti particles as a precursor.

PubMed

Hu, Keshui; Xiao, Xin; Cao, Xiufang; Hao, Rong; Zuo, Xiaoxi; Zhang, Xiaojing; Nan, Junmin

2011-08-30

Titanate nanotube powders (TNTPs) with the twofold removal ability, i.e. adsorptive separation and photocatalytic degradation, are synthesized under hydrothermal conditions using metal Ti particles as a precursor in the concentrated alkaline solution, and their morphology, structure, adsorptive and photocatalytic properties are investigated. Under hydrothermal conditions, the titanate nanotubes (TNTs) with pore diameter of 3-4nm are produced on the surface of metal Ti particles, and stacked together to form three-dimensional (3D) network with porous structure. The TNTPs synthesized in the autoclave at 130°C for 24h exhibits a maximum adsorption capability of about 197mg g(-1) in the neutral methylene blue (MB) solution (40mg L(-1)) within 90min, the adsorption process can be described by pseudo second-order kinetics model. Especially, in comparison with the adsorptive and the photocatalytic processes are performed in turn, about 50min can be saved through synchronously utilizing the double removal ability of TNTPs when the removal ratio of MB approaches 95% in MB solution (40mg L(-1)) at a solid-liquid (S/L) ratio of 1:8 under ultraviolet (UV) light irradiation. These 3D TNTPs with the twofold removal properties and easier separation ability for recycling use show promising prospect for the treatment of dye pollutants from wastewaters in future industrial application. Copyright © 2011 Elsevier B.V. All rights reserved.

Hydrothermal preparation of ZnO-reduced graphene oxide hybrid with high performance in photocatalytic degradation

NASA Astrophysics Data System (ADS)

Zhou, Xun; Shi, Tiejun; Zhou, Haiou

2012-06-01

Hydrothermal method was utilized to prepare reduced graphene oxide (RGO) and fabricate ZnO-RGO hybrid (ZnO-RGO) with zinc nitrate hexahydrate and graphene oxide (GO) as raw materials under pH value of 11 adjusted by ammonia water. During the process of reduction of GO, hydrothermal condition with ammonia provided thermal and chemical factors to synthesize RGO. The retained functional groups on RGO planes played an important role in anchoring ZnO to RGO, which was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy and photoluminescence spectra. The various mass ratios of zinc nitrate hexahydrate to GO used to prepare ZnO-RGO impacted significantly on the morphology of ZnO nanostructures such as nanoparticles and nanorods. And, the RGO sheets wrapped ZnO nanoparticles and nanorods very tightly. After the emission of photo electrons from ZnO, RGO in ZnO-RGO can effectively transfer the photo electrons to exhibit a high performance and reproducibility in photocatalytic degradation toward methylene blue (MB) absorbed on the surface of RGO through π-π conjugation.

Enhancing the efficiency of dye-sensitized solar cells by hydrothermal post-treatment in acidic environment

NASA Astrophysics Data System (ADS)

Nathania, A.; Nursam, N. M.; Shobih; Hidayat, J.; Prastomo, N.

2018-03-01

Dye-sensitized solar cell (DSSC) have been extensively studied due to its low production cost and simple production process. In this research, DSSC with improved performance is acquired by modification of TiO2 layer through hydrothermal post-treatment with different hydrochloric acid (HCl) concentrations to obtain various particles and pore sizes. Qualitative and quantitative characterizations of the TiO2 film were conducted using thickness measurement, scanning electron microscope (SEM), and X-ray diffraction (XRD), while the solar cell performances were characterized using current-voltage (I-V) measurement under 0.5 Sun. When hydrothermally treated with 1 mol/L HCl at 180 °C for 3 h, the DSSC showed the most optimum photo-electricity conversion performance of 3.60%, which improved the efficiency of the non-treated DSSC by a factor of 1.2. As the HCl concentration increased, the treated TiO2 film became thinner with smaller particle size and denser structure. It was suspected that the modification in the TiO2 film morphology has led to better light absorption, which consequently resulted in the improvement of DSSC performance.

Facile synthesis of hollow zeolite microspheres through dissolution–recrystallization procedure in the presence of organosilanes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, Haixiang; Ren, Jiawen; Liu, Xiaohui

2013-04-15

Hollow zeolite microspheres have been hydrothermally synthesized in the presence of organosilanes via a dissolution–recrystallization procedure. In the presence of organosilanes, zeolite particles with a core/shell structure formed at the first stage of hydrothermal treatment, then the core was consumed and recrystallized into zeolite framework to form the hollow structure during the second hydrothermal process. The influence of organosilanes was discussed, and a related dissolution–recrystallization mechanism was proposed. In addition, the hollow zeolite microspheres exhibited an obvious advantage in catalytic reactions compared to conventional ZSM-5 catalysts, such as in the alkylation of toluene with benzyl chloride. - Graphical abstract: Hollowmore » zeolite spheres with aggregated zeolite nanocrystals were synthesized via a dissolution–recrystallization procedure in the presence of organosiline. Highlights: ► Hollow zeolite spheres with aggregated zeolite nanocrystals were synthesized via a dissolution–recrystallization procedure. ► Organosilane influences both the morphology and hollow structure of zeolite spheres. ► Hollow zeolite spheres showed an excellent catalytic performance in alkylation of toluene with benzyl chloride.« less

Links between fluid circulation, temperature, and metamorphism in subducting slabs

USGS Publications Warehouse

Spinelli, G.A.; Wang, K.

2009-01-01

The location and timing of metamorphic reactions in subducting lithosph??re are influenced by thermal effects of fluid circulation in the ocean crust aquifer. Fluid circulation in subducting crust extracts heat from the Nankai subduction zone, causing the crust to pass through cooler metamorphic faci??s than if no fluid circulation occurs. This fluid circulation shifts the basalt-to-eclogite transition and the associated slab dehydration 14 km deeper (35 km farther landward) than would be predicted with no fluid flow. For most subduction zones, hydrothermal cooling of the subducting slab will delay eclogitization relative to estimates made without considering fluid circulation. Copyright 2009 by the American Geophysical Union.

Genesis of the Touissit-Bou Beker Mississippi valley-type district (Morocco-Algeria) and its relationship to the Africa-Europe collision

USGS Publications Warehouse

Bouabdellah, M.; Sangster, D.F.; Leach, D.L.; Brown, A.C.; Johnson, C.A.; Emsbo, P.

2012-01-01

The Mississippi Valley-type deposits of the Touissit-Bou Beker district are hosted by a 25 m thick sequence of diagenetically and hydrothermally dolomitized carbonate platform rocks of Aalenian-Bajocian age. The sulfide mineralization consists principally of galena and sphalerite and occurs as open-space fillings of voids and moderate to massive replacement of the medium- to coarse-grained host dolostone. Five types of dolomite have been distinguished, two of which (D 1 and D 2) are of replacement origin, whereas HD 1, HD 2, HD 3 occurring as open-space filling are of hydrothermal affiliation. Main ore controls include stratigraphy and lithology, carbonate dissolution, paleogeography, faults or faulted rocks, and availability of organic matter. Fluid inclusion data, along with Na-Cl-Br leachate, indicate that the ore-forming fluids correspond to evolved NaCl-CaCl 2-KCl-MgCl 2 basin-derived hot (100?? ?? 20??C) saline brines (>20 wt% NaCl equiv) that acquired their high salinities and Ca/Na ratios through evaporation of seawater, and subsequent dolomitization and fluid-rock interactions. Stable isotope data for replacement and hydrothermal dolomites are tightly clustered and overlapping, with ?? 18O and ?? 13C values from 20.5 to 21.2 and 0.2 to 0.7%, respectively. Similarly, sulfides yield ?? 34S values between 11.2 and 1.9%, whereas those corresponding to the nearby Triassic gypsum cluster yield around 14%. Altogether, these isotopic compositions are consistent with a basinal-type fluid with reduced sulfur very likely being derived through thermochemical reduction of dissolved sulfate, resulting in metal precipitation, and carbon of mainly marine Aalenian-Bajocian carbonate origin with a minor biogenic component. 87Sr/ 86Sr values of replacement dolostone are similar to those of ore-related hydrothermal dolomites, ranging from 0.70746 to 0.70833 and from 0.70769 to 0.70828, respectively, and are different from those of the Visean rhyodacite (0.71849-0.72167). Lead isotope ratios ( 206Pb/ 204Pb = 18.319-18.390; 207Pb/ 204Pb = 15.620. 15.680; 208Pb/ 204Pb = 38.452-38.650) of sulfides are consistent with Pb being derived from the Visean rhyodacite and associated volcaniclastic rocks. The intimate link between faults and mineralization suggests the strong possibility of brine flow along both ENE-trending regional-scale faults and NW-SW-trending local-scale faults. The data suggest that MVT mineralization was emplaced during the late Neogene-Quaternary (i.e., ca. 15.0 Ma), possibly as a result of subsurface gravity-driven fluid flow in response to the collision between the African and Eurasian plates. ?? 2012 Society of Economic Geologists, Inc.

Genesis of the Touissit-Bou Beker Mississippi Valley-type district (Morocco-Algeria) and its relation to the Africa-Europe collision

USGS Publications Warehouse

Bouabdellah, Mohammed; Sangster, Donald F.; Leach, David L.; Brown, Alex C.; Johnson, Craig A.; Emsbo, Poul

2012-01-01

The Mississippi Valley-type deposits of the Touissit-Bou Beker district are hosted by a 25 m thick sequence of diagenetically and hydrothermally dolomitized carbonate platform rocks of Aalenian-Bajocian age. The sulfide mineralization consists principally of galena and sphalerite and occurs as open-space fillings of voids and moderate to massive replacement of the medium- to coarse-grained host dolostone. Five types of dolomite have been distinguished, two of which (D1 and D2) are of replacement origin, whereas HD1, HD2, HD3 occurring as open-space filling are of hydrothermal affiliation. Main ore controls include stratigraphy and lithology, carbonate dissolution, paleogeography, faults or faulted rocks, and availability of organic matter. Fluid inclusion data, along with Na-Cl-Br leachate, indicate that the ore-forming fluids correspond to evolved NaCl-CaCl2-KCl-MgCl2 basin-derived hot (100° ± 20°C) saline brines (>20 wt % NaCl equiv) that acquired their high salinities and Ca/Na ratios through evaporation of seawater, and subsequent dolomitization and fluid-rock interactions. Stable isotope data for replacement and hydrothermal dolomites are tightly clustered and overlapping, with δ18O and δ13C values from 20.5 to 21.2 and 0.2 to 0.7‰, respectively. Similarly, sulfides yield δ34S values between 11.2 and 1.9‰, whereas those corresponding to the nearby Triassic gypsum cluster yield around 14‰. Altogether, these isotopic compositions are consistent with a basinal-type fluid with reduced sulfur very likely being derived through thermochemical reduction of dissolved sulfate, resulting in metal precipitation, and carbon of mainly marine Aalenian-Bajocian carbonate origin with a minor biogenic component. 87Sr/86Sr values of replacement dolostone are similar to those of ore-related hydrothermal dolomites, ranging from 0.70746 to 0.70833 and from 0.70769 to 0.70828, respectively, and are different from those of the Visean rhyodacite (0.71849–0.72167). Lead isotope ratios (206Pb/204Pb = 18.319–18.390; 207Pb/204Pb = 15.620–15.680; 208Pb/204Pb = 38.452–38.650) of sulfides are consistent with Pb being derived from the Visean rhyodacite and associated volcaniclastic rocks. The intimate link between faults and mineralization suggests the strong possibility of brine flow along both ENE-trending regional-scale faults and NW-SW-trending local-scale faults. The data suggest that MVT mineralization was emplaced during the late Neogene-Quaternary (i.e., ca. 15–0 Ma), possibly as a result of subsurface gravity-driven fluid flow in response to the collision between the African and Eurasian plates.

The Growth of Berlinite (AlPO4) Single Crystals.

DTIC Science & Technology

1980-03-01

Solubility of AlPO 4 18 6. Solubility Data of Jahn and Kordes on AlPO4 19 7. AlPO 4 Seed Crystal 23 8. Tem-Pres Hydrothermal Research Unit 25 9...Since the vapor pressure of water rises rapidly with temperature, a closed hydrothermal system was used. In a seeded hydrothermal growth process, the...to investigate the hydrothermal growth of Berlinite (AlPO4 ) to determine the optimum growth conditions for large high quality crystals. Over thirty

Three-dimensional oxygen isotope imaging of convective fluid flow around the Big Bonanza, Comstock lode mining district, Nevada

USGS Publications Warehouse

Criss, R.E.; Singleton, M.J.; Champion, D.E.

2000-01-01

Oxygen isotope analyses of propylitized andesites from the Con Virginia and California mines allow construction of a detailed, three-dimensional image of the isotopic surfaces produced by the convective fluid flows that deposited the famous Big Bonanza orebody. On a set of intersecting maps and sections, the δ18O isopleths clearly show the intricate and conformable relationship of the orebody to a deep, ~500 m gyre of meteoric-hydrothermal fluid that circulated along and above the Comstock fault, near the contact of the Davidson Granodiorite. The core of this gyre (δ18O = 0 to 3.8‰) encompasses the bonanza and is almost totally surrounded by rocks having much lower δ18O values (–1.0 to –4.4‰). This deep gyre may represent a convective longitudinal roll superimposed on a large unicellular meteoric-hydrothermal system, producing a complex flow field with both radial and longitudinal components that is consistent with experimentally observed patterns of fluid convection in permeable media.

Using Structure-from-Motion to Quantify Sediment Accumulation and Bedrock Erosion in a Debris-Flow Dominated Channel

NASA Astrophysics Data System (ADS)

Reitman, N. G.; Rengers, F.; Kean, J. W.

2016-12-01

One of the highest frequencies of observed debris flows in the US is located at the Chalk Cliffs in central Colorado. This high rate of debris-flow activity ( 3 per year) is supported by a similarly high rate of sediment supply from rock fall and ravel due to frost weathering of the highly-erodible, hydrothermally-altered quartz monzonite cliffs during the winter months. A first step toward understanding debris-flow initiation, and channel and hillslope evolution, is to quantify the magnitude and spatial distribution of sediment that accumulates by the end of the winter period. Here we test the ability of structure-from-motion photogrammetric surveys to produce high-resolution point clouds in order to quantify sediment deposition, and possibly bedrock erosion. We use point clouds obtained from surveys conducted in late September 2015 and early June 2016 to measure sediment deposition in a 42-m-long channel over one winter. All surveys are co-registered with control points (screws drilled into bedrock) measured in a local coordinate system with a total station. Point clouds derived from these surveys have average point densities >200,000 pts/m2, and accuracies within 2 cm. Initial analysis shows accumulation of 10-50 cm ( 10 m3) of unconsolidated loose sediment over eight months, providing ample material for debris-flow initiation during the following summer season. Sediment accumulated in a spatially-variable pattern dependent on existing channel-bottom bedrock topography. Future surveys are planned in order to measure bedrock erosion by debris flows and variation in sediment deposition rate through time. Our analysis indicates that photogrammetric surveys provide a high level of detail at low cost, and thus are a useful geomorphic monitoring tool that will ultimately lead to better understanding of the processes that contribute to debris-flow activity and landscape evolution.

Impact of hydrothermalism on the ocean iron cycle

PubMed Central

Resing, Joseph

2016-01-01

As the iron supplied from hydrothermalism is ultimately ventilated in the iron-limited Southern Ocean, it plays an important role in the ocean biological carbon pump. We deploy a set of focused sensitivity experiments with a state of the art global model of the ocean to examine the processes that regulate the lifetime of hydrothermal iron and the role of different ridge systems in governing the hydrothermal impact on the Southern Ocean biological carbon pump. Using GEOTRACES section data, we find that stabilization of hydrothermal iron is important in some, but not all regions. The impact on the Southern Ocean biological carbon pump is dominated by poorly explored southern ridge systems, highlighting the need for future exploration in this region. We find inter-basin differences in the isopycnal layer onto which hydrothermal Fe is supplied between the Atlantic and Pacific basins, which when combined with the inter-basin contrasts in oxidation kinetics suggests a muted influence of Atlantic ridges on the Southern Ocean biological carbon pump. Ultimately, we present a range of processes, operating at distinct scales, that must be better constrained to improve our understanding of how hydrothermalism affects the ocean cycling of iron and carbon. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’. PMID:29035256

Impact of hydrothermalism on the ocean iron cycle.

PubMed

Tagliabue, Alessandro; Resing, Joseph

2016-11-28

As the iron supplied from hydrothermalism is ultimately ventilated in the iron-limited Southern Ocean, it plays an important role in the ocean biological carbon pump. We deploy a set of focused sensitivity experiments with a state of the art global model of the ocean to examine the processes that regulate the lifetime of hydrothermal iron and the role of different ridge systems in governing the hydrothermal impact on the Southern Ocean biological carbon pump. Using GEOTRACES section data, we find that stabilization of hydrothermal iron is important in some, but not all regions. The impact on the Southern Ocean biological carbon pump is dominated by poorly explored southern ridge systems, highlighting the need for future exploration in this region. We find inter-basin differences in the isopycnal layer onto which hydrothermal Fe is supplied between the Atlantic and Pacific basins, which when combined with the inter-basin contrasts in oxidation kinetics suggests a muted influence of Atlantic ridges on the Southern Ocean biological carbon pump. Ultimately, we present a range of processes, operating at distinct scales, that must be better constrained to improve our understanding of how hydrothermalism affects the ocean cycling of iron and carbon.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

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

NASA Astrophysics Data System (ADS)

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

2009-12-01

One of Al Hofmann’s many important contributions to our understanding of geochemical cycling in the Earth is the observation that Pb behaves like the light rare earth elements Ce and Nd during melting to form oceanic basalts, but is enriched in the continental crust compared to the LREE by nearly an order of magnitude (Hofmann et al. 1986). This is unusual behavior, and has been called one of the Pb paradoxes, since in most cases, the ratios of elements are effectively the same in the continental crust and oceanic basalts if they show similar mantle melting behavior. One of several mechanisms suggested to mediate this special enrichment is hydrothermal circulation at ocean ridges, which preferentially transports Pb compared to the REE from the interior of the ocean crust to the surface. We confirm the importance of hydrothermal processes at the East Pacific to mediate Pb enrichment at the Trans-Mexican Volcanic Belt (TMVB, through comparison of Pb isotope and Ce/Pb ratios of TMVB lavas with sediments from DSDP Site 487 near the Middle America trench. The lavas of the Trans-Mexican Volcanic Belt include “high Nb” alkali basalts (HNAB), whose trace element patterns lack subduction signatures. The HNAB basalts and hydrothermally affected sediments from DSDP 487, form end-members that bound calcalkaline lavas from volcanoes Colima, Toluca, Popocatépetl, and Malinche in Ce/Pb versus Pb isotope space. The HNAB represent the high Ce/Pb and high Pb-isotope end-member. The hydrothermal sediments have Pb isotopes like Pacific MORB but Ce/Pb ratios typical of the arcs and the continental crust, and an order of magnitude lower than MORB. No analyzed calcalkaline lavas are have compositions outside of the bounds formed by the HNAB and the hydrothermal sediments. The Ce/Pb and Pb isotope ratios show that the calcalkaline lava compositions are inconsistent with contributions from HNAB and EPR MORB, rather the contributions are from HNAB upper mantle and subducted hydrothermal sediments. The Trans-Mexican Volcanic Belt data confirm the two-step process of Pb enrichment in the arc lavas (and more generally in the continental crust). In the first step, hydrothermal processes at the East Pacific Rise preferentially transport Pb from the basaltic oceanic crust to surface sediments. In the second step, during subduction, these sediments are the main source of asthenospheric mantle-derived Pb to the lavas. Our data also confirm the importance of subduction contributions to the Quaternary Mexican arc, despite the >40 km thick continental crust. Ref: Hofmann et al. (1986) EPSL 79 p. 33-45.

Fracturing And Liquid CONvection

DOE Office of Scientific and Technical Information (OSTI.GOV)

2012-02-29

FALCON has been developed to enable simulation of the tightly coupled fluid-rock behavior in hydrothermal and engineered geothermal system (EGS) reservoirs, targeting the dynamics of fracture stimulation, fluid flow, rock deformation, and heat transport in a single integrated code, with the ultimate goal of providing a tool that can be used to test the viability of EGS in the United States and worldwide. Reliable reservoir performance predictions of EGS systems require accurate and robust modeling for the coupled thermal-hydrological-mechanical processes. Conventionally, these types of problems are solved using operator-splitting methods, usually by coupling a subsurface flow and heat transport simulatormore » with a solid mechanics simulator via input files. FALCON eliminates the need for using operator-splitting methods to simulate these systems, and the scalability of the underlying MOOSE architecture allows for simulating these tightly coupled processes at the reservoir scale, allowing for examination of the system as a whole (something the operator-splitting methodologies generally cannot do).« less

Understanding heat and groundwater flow through continental flood basalt provinces: insights gained from alternative models of permeability/depth relationships for the Columbia Plateau, USA

USGS Publications Warehouse

Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.; Voss, Clifford I.; Spane, Frank A.; DeAngelo, Jacob

2015-01-01

Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

From 16th November to 15th December 2016, D/V Chikyu drilled the sea bottom around hydrothermal fields at HAKUREI site in the Izena Hole, Okinawa Trough. Site C9025, C9026, C9027, C9028, and C9032 are located along the transect line from the top of the northern mound of HAKUREI site to the eastward, and Site C9030 for the control site is located about 500 m northwest of the mound. Mg concentrations have generally been used to estimate mixing ratios between hydrothermal end-member and seawater in samples from hydrothermal vents. Higher Mg concentrations, however, were detected in the interstitial water than that of seawater, which could be due to artificially dissolution of Mg-bearing minerals that had formed in in-situ environments, when the cored sediments had become cool after their recovery on ship. Similar features were observed with regard to sulfate concentrations, and it suggests that these chemical species are not suitable to estimate quantitatively the contribution of hydrothermally-derived components. In some layers, chloride concentrations were different from that of seawater, indicating that hydrothermal fluids that had been suffered from phase separation flowed into the layers. The deviation, however, was positive or negative relative to that of seawater for an influence of brine or vapor phase, respectively. Therefore chloride concentrations are also not suitable to evaluate a quantitative contribution of hydrothermal end-member. On the other hand, K and B showed only enrichments relative to the seawater, and their highest concentrations are consistent with the reported hydrothermal end-members of each species at HAKUREI site. Using the concentrations of K and B can be evaluated for an influence of hydrothermal components. Furthermore, the headspace gas data are useful in the layers of sulfide minerals and silicified rocks, even though the interstitial waters could not be obtained because of their hardness. Based on these indices, hydrothermal fluids would be distributed in the upper and lower layers of the ore body. The hydrothermally altered sediment layers above the ore body contain relatively unstable minerals that dissociate immediately in a room temperature, which could play a role as a boundary between hydrothermal fluids and intruded seawater in in-situ environments.

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

NASA Astrophysics Data System (ADS)

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

2014-04-01

Ubinas volcano, the historically most active volcano in Peru straddles a low-relief high plateau and the flank of a steep valley. A multidisciplinary geophysical study has been performed to investigate the internal structure and the fluids flow within the edifice. We conducted 10 self-potential (SP) radial (from summit to base) profiles, 15 audio magnetotelluric (AMT) soundings on the west flank and a detailed survey of SP and soil temperature measurements on the summit caldera floor. The typical “V” shape of the SP radial profiles has been interpreted as the result of a hydrothermal zone superimposed on a hydrogeological zone in the upper parts of the edifice, and depicts a sub-circular SP positive anomaly, about 6 km in diameter. The latter is centred on the summit, and is characterised by a larger extension on the western flank located on the low-relief high plateau. The AMT resistivity model shows the presence of a conductive body beneath the summit at a depth comparable to that of the bottom of the inner south crater in the present-day caldera, where intense hydrothermal manifestations occur. The lack of SP and temperature anomalies on the present caldera floor suggests a self-sealed hydrothermal system, where the inner south crater acts as a pressure release valve. Although no resistivity data exists on the eastern flank, we presume, based on the asymmetry of the basement topography, and the amplitude of SP anomalies on the east flank, which are approximately five fold that on the west flank, that gravitational flow of hydrothermal fluids may occur towards the deep valley of Ubinas. This hypothesis, supported by the presence of hot springs and faults on the eastern foot of the edifice, reinforces the idea that a large part of the southeast flank of the Ubinas volcano may be altered by hydrothermal activity and will tend to be less stable. One of the major findings that stems from this study is that the slope of the basement on which a volcano has grown plays a major role in the geometry of the hydrothermal systems. Another case of asymmetrical composite cone edifice, built on a steep topography, is observed on El Misti volcano (situated 70 km west of Ubinas), which exhibits a similar SP pattern. These types of edifices have a high potential of spreading and sliding along the slope owing to the thicker accumulation of low cohesion and hydrothermally altered volcanic products.

Hydrothermal carbonization of biomass residuals: A comparative review of the chemistry, processes and applications of wet and dry pyrolysis

USDA-ARS?s Scientific Manuscript database

This paper reviews chemistry, processes and application of hydrothermcally carbonized biomass wastes. Potential feedstock for the hydrothermal carbonization (HTC) includes variety of the non-traditional renewable wet agricultural and municipal waste streams. Pyrolysis and HTC show a comparable calor...

Hydrothermal systems are a sink for dissolved black carbon in the deep ocean

NASA Astrophysics Data System (ADS)

Niggemann, J.; Hawkes, J. A.; Rossel, P. E.; Stubbins, A.; Dittmar, T.

2016-02-01

Exposure to heat during fires on land or geothermal processes in Earth's crust induces modifications in the molecular structure of organic matter. The products of this thermogenesis are collectively termed black carbon. Dissolved black carbon (DBC) is a significant component of the oceanic dissolved organic carbon (DOC) pool. In the deep ocean, DBC accounts for 2% of DOC and has an apparent radiocarbon age of 18,000 years. Thus, DBC is much older than the bulk DOC pool, suggesting that DBC is highly refractory. Recently, it has been shown that recalcitrant deep-ocean DOC is efficiently removed during hydrothermal circulation. Here, we hypothesize that hydrothermal circulation is also a net sink for deep ocean DBC. We analyzed DBC in samples collected at different vent sites in the Atlantic, Pacific and Southern oceans. DBC was quantified in solid-phase extracts as benzenepolycarboxylic acids (BPCAs) following nitric acid digestion. Concentrations of DBC were much lower in hydrothermal fluids than in surrounding deep ocean seawater, confirming that hydrothermal circulation acts as a net sink for oceanic DBC. The relative contribution of DBC to bulk DOC did not change during hydrothermal circulation, indicating that DBC is removed at similar rates as bulk DOC. The ratio of the oxidation products benzenehexacarboxylic acid (B6CA) to benzenepentacarboxylic acid (B5CA) was significantly higher in hydrothermally altered samples compared to ratios typically found in the deep ocean, reflecting a higher degree of condensation of DBC molecules after hydrothermal circulation. Our study identified hydrothermal circulation as a quantitatively important sink for refractory DBC in the deep ocean. In contrast to photodegradation of DBC at the sea surface, which is more efficient for more condensed DBC, i.e. decreasing the B6CA/B5CA ratio, hydrothermal processing increases the B6CA/B5CA ratio, introducing a characteristic hydrothermal DBC signature.

Geochemistry of fluid phases and sediments: Relevance to hydrothermal circulation in Middle Valley, ODP Legs 139 and 169

USGS Publications Warehouse

Gieskes, J.M.; Simoneit, B.R.T.; Shanks, Wayne C.; Goodfellow, W.D.; James, R.H.; Baker, P.A.; Ishibashi, J.-I.

2002-01-01

Geochemical and isotopic studies of pore fluids and solid phases recovered from the Dead Dog and Bent Hill hydrothermal sites in Middle Valley (Ocean Drilling Program Leg 169) have been compared with similar data obtained previously from these sites during Ocean Drilling Program Leg 139. Although generally the hydrothermal systems reflect non-steady state conditions, the data allow an assessment of the history of the hydrothermal processes. Sediment K/A1 ratios as well as the distribution of anhydrite in the sediments suggest that the Dead Dog hydrothermal field has been, and still is, active. In contrast, similar data in the Bent Hill hydrothermal field indicate a waning of hydrothermal activity. Pore fluid and hydrothermal vent data in the Dead Dog hydrothermal 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 hydrothermal activity in the pore fluids. Data from the deepest part of Hole 1035A in the Bent Hill locality show the presence of hydrothermal fluids at greater depths in this area. This suggests the origin of the hydrothermal fluids found to be emanating from Hole 1035F, which constitutes one of the first man made hydrothermal vents in the Middle Valley hydrothermal system. Similarly, CORKed Hole 858G, because of seal failures, has acted as a hydrothermal vent, with sulfide deposits forming inside the CORK. ?? 2002 Elsevier Science Ltd. All rights reserved.

New bulk and in situ isotopic and elemental geochemistry of shallow drill core from Atlantis Massif: insights into the sources and paths of fluids and clasts

NASA Astrophysics Data System (ADS)

Bilenker, L.; Weis, D.; Scoates, J. S.

2017-12-01

We present stable Fe and radiogenic isotope and complementary trace element data for samples from Atlantis Massif. This oceanic core complex is located at 30°N where the Atlantis Transform Fault intersects the Mid-Atlantic Ridge (MAR) and is associated with the Lost City Hydrothermal Field (LCHF). It is a unique place to investigate the abiotic and biotic geochemical processes that play a role in the alteration of both crustal and mantle seafloor rocks. The samples analyzed represent a shallow (<15 m) survey of five drill sites (IODP Expedition 357) within Atlantis Massif, varying in distance from the LCHF and MAR. Analyses were performed on a sample set spanning a wide range in degree of alteration and lithology. Bulk measurements involved dissolving whole rock powders, whereas in situ analyses were performed on digested microdrilled samples or by laser ablation. Bulk rock Fe isotope values (n = 34) are correlated with loss-on-ignition (LOI) by sample lithology and location relative to LCHF. Using LOI as a proxy for degree of alteration, this observation indicates that the Fe isotope systematics of seafloor crustal and mantle rocks preserve indicators of fluid flow and source. The Hf and Nd isotope compositions for various lithologies form all analyzed sites are homogeneous, indicating minimal alteration of these isotopic systems. Bulk Sr values provide insight into elemental exchange between seawater and the surface of Atlantis Massif and bulk Pb isotopes allow for fingerprinting of the source of basalt breccias through comparison with published Pb isotope values of MAR basalts. The new results cluster around the Pb, Hf, Nd isotopic composition of mid-ocean ridge basalt from 30.68°N and do not match samples north or south of that location. In situ Fe isotope data within three altered samples reflect varying degrees of hydrothermal and seawater interaction, where the Fe isotope ratios within each sample are likely correlated with extent of exchange or redox. Laser trace element and Pb isotope data in progress will allow us to investigate this further. This study contributes to our understanding of element mobility and mass transfer during chemical reactions within the seafloor, provides insight into the source of the lithological units and fluid flow, and allows for quantification of alteration processes.

Characterization of Particles Created By Laser-Driven Hydrothermal Processing

DTIC Science & Technology

2016-06-01

created by laser-driven hydrothermal processing, an innovative technique used for the ablation of submerged materials. Two naturally occurring...processing, characterization, obsidian, tektite, natural glass 15. NUMBER OF PAGES 89 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT...technique used for the ablation of submerged materials. Two naturally occurring materials, obsidian and tektite, were used as targets for this technique

Intelligent Processing of Ferroelectric Thin Films

DTIC Science & Technology

1993-09-03

the acetate precursors. The results from these experiments involving coprecipitation, hydrothermal , spray pyrolysis and freeze drying have shown that...Spray Pyrolysis (SP) D. Hydrothermal Processing (HP) The powder produced by each process was characterized by X-ray diffraction (XRD) and scanning...precursors were used as described above. Instead of ammonia solution, an oxalic acid solution was used as the3 precipitating agent. The precipitants

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

NASA Astrophysics Data System (ADS)

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

2016-08-01

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

High-pressure homogenization associated hydrothermal process of palygorskite for enhanced adsorption of Methylene blue

NASA Astrophysics Data System (ADS)

Zhang, Zhifang; Wang, Wenbo; Wang, Aiqin

2015-02-01

Palygorskite (PAL) was modified by a high-pressure homogenization assisted hydrothermal process. The effects of modification on the morphology, structure and physicochemical properties of PAL were systematically investigated by Field-emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FTIR), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD) and Zeta potential analysis techniques, and the adsorption properties were systematically evaluated using Methylene blue (MB) as the model dye. The results revealed that the crystal bundles were disaggregated and the PAL nanorods became more even after treated via associated high-pressure homogenization and hydrothermal process, and the crystal bundles were dispersed as nanorods. The intrinsic crystal structure of PAL was remained after hydrothermal treatment, and the pore size calculated by the BET method was increased. The adsorption properties of PAL for MB were evidently improved (from 119 mg/g to 171 mg/g) after modification, and the dispersion of PAL before hydrothermal reaction is favorable to the adsorption. The desorption evaluation confirms that the modified PAL has stronger affinity with MB, which is benefit to fabricate a stable organic-inorganic hybrid pigment.

Turnstiles and bifurcators: the disequilibrium converting engines that put metabolism on the road.

PubMed

Branscomb, Elbert; Russell, Michael J

2013-02-01

The Submarine Hydrothermal Alkaline Spring Theory for the emergence of life holds that it is the ordered delivery of hydrogen and methane in alkaline hydrothermal solutions at a spontaneously precipitated inorganic osmotic and catalytic membrane to the carbon dioxide and other electron acceptors in the earliest acidulous cool ocean that, through these gradients, drove life into being. That such interactions between hydrothermal fuels and potential oxidants have so far not been accomplished in the lab is because some steps along the necessary metabolic pathways are endergonic and must therefore be driven by being coupled to thermodynamically larger exergonic processes. But coupling of this kind is far from automatic and it is not enough to merely sum the ΔGs of two supposedly coupled reactions and show their combined thermodynamic viability. An exergonic reaction will not drive an endergonic one unless 'forced' to do so by being tied to it mechanistically via an organized "engine" of "Free Energy Conversion" (FEC). Here we discuss the thermodynamics of FEC and advance proposals regarding the nature and roles of the FEC devices that could, in principle, have arisen spontaneously in the alkaline hydrothermal context and have forced the onset of a protometabolism. The key challenge is to divine what these initial engines of life were in physicochemical terms and as part of that, what structures provided the first "turnstile-like" mechanisms needed to couple the partner processes in free energy conversion; in particular to couple the dissipation of geochemically given gradients to, say, the reduction of CO(2) to formate and the generation of a pyrophosphate disequilibrium. This article is part of a Special Issue entitled: The evolutionary aspects of bioenergetic systems. Copyright © 2012 Elsevier B.V. All rights reserved.

Impact of heterotrophically stressed algae for biofuel production via hydrothermal liquefaction and catalytic hydrotreating in continuous-flow reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albrecht, Karl O.; Zhu, Yunhua; Schmidt, Andrew J.

Two algal feedstocks were prepared for direct comparison of their properties when converted to liquid hydrocarbon fuel. The first feedstock was prepared by growing an algal strain phototrophically using a bio-film based approach. The second feedstock employed the same algal strain but was stressed heterotrophically to significantly increase the lipid concentration. The algal feedstocks were converted to liquid hydrocarbon fuels. First, the whole algae (i.e. not defatted or lipid extracted) were converted to an intermediate biocrude using continuous hydrothermal liquefaction (HTL) at 350°C and 3000 psig. The biocrudes were subsequently upgraded via catalytic hydrotreating (HT) at 400°C and 1500 psigmore » to remove oxygen and nitrogen as well as increase the hydrogen-to-carbon ratio. The yield and composition of the products from HTL and HT processing of the feedstocks are compared. A techno-economic analysis of the process for converting each feedstock to liquid fuels was also conducted. The capital and operating costs associated with converting the feedstocks to finished transportation fuels are reported. A fuel minimum selling price is presented as a function of the cost of the algal feedstock delivered to the HTL conversion plant.« less

Effect of hydrothermal pre-treatment (HTP) on poultry slaughterhouse waste (PSW) sludge for the enhancement of the solubilization, physical properties, and biogas production through anaerobic digestion.

PubMed

Park, Seyong; Yoon, Young-Man; Han, Seong Kuk; Kim, Daegi; Kim, Ho

2017-06-01

This study is an assessment of the hydrothermal pre-treatment (HTP) of poultry slaughterhouse waste (PSW) sludge for the enhancement of the solubilization, physical properties, and biogas production through anaerobic digestion. This assessment was carried out to ascertain the optimal HTP temperature. The solubilization and physical properties efficacy was investigated by capillary suction time (CST), time to filter (TTF), and particle size. In addition, the anaerobic digestion was investigated through biochemical methane potential (BMP) tests and subsequent statistical analysis using the modified Gompertz model. HTP was found to have improved the solubilization of the PSW sludge with increasing HTP temperature. In addition, the results of the CST, TTF, and particle size decreased with increasing HTP temperature. These results of the assessment that was conducted in this study confirm that the HTP process indeed modifies the physical properties of PSWs to enhance the solubilization of organic solids. Nevertheless, the results of the BMP tests and the modified Gompertz model analysis show that the optimal HTP temperature of PSWs for anaerobic digestion is 190°C. These findings show that to achieve high conversion efficiency, an accurately designed pre-treatment step must be included in the overall anaerobic digestion process for wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

T. H. Brikowski; D. L. Norton; D. D. Blackwell

Final project report of natural state modeling effort for The Geysers geothermal field, California. Initial models examined the liquid-dominated state of the system, based on geologic constraints and calibrated to match observed whole rock delta-O18 isotope alteration. These models demonstrated that the early system was of generally low permeability (around 10{sup -12} m{sup 2}), with good hydraulic connectivity at depth (along the intrusive contact) and an intact caprock. Later effort in the project was directed at development of a two-phase, supercritical flow simulation package (EOS1sc) to accompany the Tough2 flow simulator. Geysers models made using this package show that ''simmering'',more » or the transient migration of vapor bubbles through the hydrothermal system, is the dominant transition state as the system progresses to vapor-dominated. Such a system is highly variable in space and time, making the rock record more difficult to interpret, since pressure-temperature indicators likely reflect only local, short duration conditions.« less

Fluid Pocket Generation in Response to Heterogeneous Reactivity of a Rock Fracture Under Hydrothermal Conditions

NASA Astrophysics Data System (ADS)

Okamoto, A.; Tanaka, H.; Watanabe, N.; Saishu, H.; Tsuchiya, N.

2017-10-01

Fractures are the location of various water-rock interactions within the Earth's crust; however, the impact of the chemical heterogeneity of fractures on hydraulic properties is poorly understood. We conducted flow-through experiments on the dissolution of granite with a tensile fracture at 350°C and fluid pressure of 20 MPa with confining pressure of 40 MPa. The aperture structures were evaluated by X-ray computed tomography before and after the experiments. Under the experimental conditions, quartz grains dissolve rapidly to produce grain-scale pockets on the fracture surface, whereas altered feldspar grains act as asperities to sustain the open cavities. The fracture contained gouge with large surface area. The feedback between fluid flow and the rapid dissolution of gouge material produced large fluid pockets, whereas permeability did not always increase significantly. Such intense hydrological-chemical interactions could strongly influence the porosity-permeability relationship of fractured reservoirs in the crust.

Reconnaissance electrical surveys in the Coso Range, California

NASA Astrophysics Data System (ADS)

Jackson, Dallas B.; O'Donnell, James E.

1980-05-01

Telluric current, audiomagnetotelluric (AMT), and direct current (dc) methods were used to study the electrical structure of the Coso Range and Coso geothermal area. Telluric current mapping outlined major resistivity lows associated with conductive valley fill of the Rose Valley basin, the Coso Basin, and the northern extension of the Coso Basin east of Coso Hot Springs. A secondary resistivity low with a north-south trend runs through the Coso Hot Springs-Devil's Kitchen geothermal area. The secondary low in the geothermal area, best defined by the 7.5-Hz AMT map and dc soundings, is caused by a shallow conductive zone (5-30 ohm m) interpreted to be hydrothermally altered Sierra Nevada basement rocks containing saline water of a hot water geothermal system. This zone of lowest apparent resistivities over the basement rocks lies within a closed contour of a heat flow anomaly where all values are greater than 10 heat flow units.

Rapid hydrothermal flow synthesis and characterisation of carbonate- and silicate-substituted calcium phosphates

PubMed Central

Knowles, Jonathan C; Rehman, Ihtesham; Darr, Jawwad A

2013-01-01

A range of crystalline and nano-sized carbonate- and silicate-substituted hydroxyapatite has been successfully produced by using continuous hydrothermal flow synthesis technology. Ion-substituted calcium phosphates are better candidates for bone replacement applications (due to improved bioactivity) as compared to phase-pure hydroxyapatite. Urea was used as a carbonate source for synthesising phase pure carbonated hydroxyapatite (CO3-HA) with ≈5 wt% substituted carbonate content (sample 7.5CO3-HA) and it was found that a further increase in urea concentration in solution resulted in biphasic mixtures of carbonate-substituted hydroxyapatite and calcium carbonate. Transmission electron microscopy images revealed that the particle size of hydroxyapatite decreased with increasing urea concentration. Energy-dispersive X-ray spectroscopy result revealed a calcium deficient apatite with Ca:P molar ratio of 1.45 (±0.04) in sample 7.5CO3-HA. For silicate-substituted hydroxyapatite (SiO4-HA) silicon acetate was used as a silicate ion source. It was observed that a substitution threshold of ∼1.1 wt% exists for synthesis of SiO4-HA in the continuous hydrothermal flow synthesis system, which could be due to the decreasing yields with progressive increase in silicon acetate concentration. All the as-precipitated powders (without any additional heat treatments) were analysed using techniques including Transmission electron microscopy, X-ray powder diffraction, Differential scanning calorimetry, Thermogravimetric analysis, Raman spectroscopy and Fourier transform infrared spectroscopy. PMID:22983020

Porosity, Fracturing and Alteration of Young Oceanic Crust: New Seismic Analyses at Borehole 504B

NASA Astrophysics Data System (ADS)

Gregory, E. P. M.; Hobbs, R. W.; Peirce, C.; Wilson, D. J.

2017-12-01

DSDP/ODP borehole 504B, drilled 2111 m into 6.9 Ma oceanic crust, provides in-situ core and logging measurements of the lithology, fracturing and porosity of crust originally formed at the Costa Rica Rift and its subsequent alteration by hydrothermal fluids. A recent active seismic survey over the borehole and surrounding area reveals wider spatial variations in velocity that can be related to this porosity and fracturing. Over 10,000 airgun shots were fired in a 30 x 30 km grid over the borehole region, using both high-frequency and low-frequency airgun arrays. The shots were recorded on a 4.5 km-long streamer and 24 ocean-bottom seismographs, each equipped with a three-component geophone and an hydrophone. A vertical hydrophone array recorded the downgoing source wavelet, and underway gravity, magnetic field and multibeam bathymetry data were also recorded. This combined dataset enables the most comprehensive geophysical analysis of this area of crust to date, while the ground-truthing provided by 504B enables us to address the questions of what do the seismic oceanic crustal layers represent and what controls their characteristics as the crust ages? Wide-angle seismic modelling with a Monte Carlo based uncertainty analysis reveals new 2D and 3D Vp and Vs models of the area, which show relatively homogeneous crust around borehole 504B, and place the seismic layer 2B/2C, and seismic layer 2/3 boundaries coincident with fracturing and alteration fronts rather than the lithological boundaries between lavas and dykes, and dykes and gabbros, respectively. Analysis of Poisson's ratio, seismic anisotropy and particle motions reveal patterns in fracturing and porosity across the survey area, and locate possible fossilised hydrothermal circulation cells. These cells appear to have influenced the porosity of the crust through alteration and mineralisation processes, with faults inherited from initial crustal accretion influencing basement topographic highs and providing conduits for mineralising fluids to flow. This research is part of a major, interdisciplinary NERC-funded research collaboration entitled: Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR).

Refining the Subseafloor Circulation Model of the Middle Valley Hydrothermal System Using Fluid Geochemistry

NASA Astrophysics Data System (ADS)

Inderbitzen, K. E.; Wheat, C. G.; Baker, P. A.; Fisher, A. T.

2014-12-01

Currently, fluid circulation patterns and the evolution of rock/fluid compositions as circulation occurs in subseafloor hydrothermal systems are poorly constrained. Sedimented spreading centers provide a unique opportunity to study subsurface flow because sediment acts as an insulating blanket that traps heat from the cooling magma body and limits: (a) potential flow paths for seawater to recharge the aquifer in permeable upper basaltic basement and (b) points of altered fluid egress. This also allows for a range of thermal and geochemical gradients to exist near the sediment-water interface. Models of fluid circulation patterns in this type of hydrologic setting have been generated (eg. Stein and Fisher, 2001); however fluid chemistry datasets have not previously been used to test the model's viability. We address this issue by integrating the existing circulation model with fluid compositional data collected from sediment pore waters and high temperature hydrothermal vents located in Middle Valley on the Juan de Fuca Ridge. Middle Valley hosts a variety of hydrologic regimes: including areas of fluid recharge (Site 855), active venting (Site 858/1036; Dead Dog vent field), recent venting (Site 856/1035; Bent Hill Massive Sulfide deposit) and a section of heavily sedimented basement located between recharge and discharge sites (Site 857). We will present new results based on thermal and geochemical data from the area of active venting (Sites 858 and 1036), that was collected during Ocean Drilling Program Legs 139 and 169 and a subsequent heat flow/gravity coring effort. These results illuminate fine scale controls on secondary recharge and fluid flow within the sediment section at Site 858/1036. The current status of high temperature vents in this area (based on observations made in July, 2014) will also be outlined.

Eruptive and tectonic history of the Endeavour Segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages

USGS Publications Warehouse

Clague, David A.; Dreyer, Brian M; Paduan, Jennifer B; Martin, Julie F; Caress, David W; Gillespie, James B.; Kelley, Deborah S; Thomas, Hans; Portner, Ryan A; Delaney, John R; Guilderson, Thomas P.; McGann, Mary L.

2014-01-01

High-resolution bathymetric surveys from autonomous underwater vehicles ABE and D. Allan B. were merged to create a coregistered map of 71.7 km2 of the Endeavour Segment of the Juan de Fuca Ridge. Radiocarbon dating of foraminifera in cores from three dives of remotely operated vehicle Doc Ricketts provide minimum eruption ages for 40 lava flows that are combined with the bathymetric data to outline the eruptive and tectonic history. The ages range from Modern to 10,700 marine-calibrated years before present (yr BP). During a robust magmatic phase from >10,700 yr BP to ~4300 yr BP, flows erupted from an axial high and many flowed >5 km down the flanks; some partly buried adjacent valleys. Axial magma chambers (AMCs) may have been wider than today to supply dike intrusions over a 2 km wide axial zone. Summit Seamount formed by ~4770 yr BP and was subsequently dismembered during a period of extension with little volcanism starting ~4300 yr BP. This tectonic phase with only rare volcanic eruptions lasted until ~2300 yr BP and may have resulted in near-solidification of the AMCs. The axial graben formed by crustal extension during this period of low magmatic activity. Infrequent eruptions occurred on the flanks between 2620–1760 yr BP and within the axial graben since ~1750 yr BP. This most recent phase of limited volcanic and intense hydrothermal activity that began ~2300 yr BP defines a hydrothermal phase of ridge development that coincides with the present-day 1 km wide AMCs and overlying hydrothermal vent fields.

The origin of life in alkaline hydrothermal vents

NASA Astrophysics Data System (ADS)

Sojo, V.; Herschy, B.; Whicher, A.; Camprubí, E.; Lane, N.

2016-12-01

The origin of life remains one of Science's greatest unresolved questions. The answer will no doubt involve almost all the basic disciplines, including Physics, Chemistry, Astronomy, Geology, and Biology. Chiefly, it is the link between the latter two that must be elucidated: how geochemistry gave rise to biochemistry. Serpentinizing systems such as alkaline hydrothermal vents offer the most robust combination of conditions to have hosted the origin of life on the early Earth, while bearing many parallels to modern living cells. Stark gradients of concentration, pH, oxidation/reduction, and temperature provided the ability to synthesise and concentrate organic products, drive polymerisation reactions, and develop an autotrophic lifestyle independent of foreign sources of organics. In the oxygen-depleted waters of the Hadean, alkaline vents would have acted as electrochemical flow reactors, in which alkaline fluids saturated in H2 mixed with the relatively acidic CO2-rich waters of the ocean, through interconnected micropores made of thin inorganic walls containing catalytic Fe(Ni)S minerals. Perhaps not coincidentally, the unit cells of these Fe(Ni)S minerals closely resemble the active sites of crucial ancestral bioenergetic enzymes. Meanwhile, differences in pH across the thin barriers produced natural proton gradients similar to those used for carbon fixation in modern archaea and bacteria. At the earliest stages, the problem of the origin of life is the problem of the origin of carbon fixation. I will discuss work over the last decade that suggests several possible hypotheses for how simple one-carbon molecules could have given rise to more complex organics, particularly within a serpentinizing alkaline hydrothermal vent. I will discuss the perplexing differences in carbon and energy metabolism in methanogenic archaea and acetogenic bacteria, thought to be the earliest representatives of each domain, to propose a possible ancestral mechanism of CO2 reduction in alkaline hydrothermal vents. Based on this mechanism, I will show that an origin of life in alkaline hydrothermal vents can explain the deep divergence in cell membranes and active ion pumping between archaea and bacteria, from a vent-bound last universal common ancestor (LUCA). Life's most puzzling traits may give a pointer to its origin.

Reduced graphene oxide-induced recrystallization of NiS nanorods to nanosheets and the improved Na-storage properties.

PubMed

Pan, Qin; Xie, Jian; Zhu, Tiejun; Cao, Gaoshao; Zhao, Xinbing; Zhang, Shichao

2014-04-07

Preparation of two-dimensional (2D) graphene-like materials is currently an emerging field in materials science since the discovery of single-atom-thick graphene prepared by mechanical cleavage. In this work, we proposed a new method to prepare 2D NiS, where reduced graphene oxide (rGO) was found to induce the recrystallization of NiS from nanorods to nanosheets in a hydrothermal process. The process and mechanism of recrystallization have been clarified by various characterization techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) mapping, and X-ray photoelectron spectroscopy (XPS). The characterization of ex situ NiS/rGO products by SEM and EDS mapping indicates that the recrystallization of NiS from nanorods to nanosheets is realized actually through an exfoliation process, while the characterization of in situ NiS/rGO products by SEM, TEM, and EDS mapping reveals the exfoliation process. The XPS result demonstrates that hydrothermally assisted chemical bonding occurs between NiS and rGO, which induces the exfoliation of NiS nanorods into nanosheets. The obtained NiS/rGO composite shows promising Na-storage properties.

Investigation of mechanism and critical parameters for removal of arsenic from water using Zr-TiO2 composite.

PubMed

Anđelković, I; Amaizah, N R R; Marković, S B; Stanković, D; Marković, M; Kuzmanović, D; Roglić, G

2017-09-01

Using the microwave-hydrothermal method for the synthesis of composite, high surface density of hydroxyl groups, as an active adsorption sites for arsenic, was obtained. Adsorption mechanisms of As(III) and As(V) onto zirconium-doped titanium dioxide (Zr-TiO 2 ) were investigated and proposed using macroscopic and microscopic methods. Obtained results are suggesting inner-sphere and outer-sphere adsorption mechanisms for As(III) and As(V), respectively. This allowed us to identify parameters that are critical for the successful removal of arsenic from water, which is essential information for further optimization of the removal process. The composite was further applied for the removal of As(III) and As(V) from water in a dynamic flow through the reactor. Column study proved that the removal of both arsenic species below the value recommended by WHO can be achieved. Elution of As(III) and As(V) from the composite can be done by using small amounts of 0.01 M NaOH solution resulting in preconcentration of arsenic species and possible multiple usage of composite.

The Origin of Carbon-bearing Volatiles in Surprise Valley Hot Springs in the Great Basin: Carbon Isotope aud Water Chemistry Characterizations

NASA Technical Reports Server (NTRS)

Fu, Qi; Socki, Richard A.; Niles, Paul B.; Romanek, Christopher; Datta, Saugata; Darnell, Mike; Bissada, Adry K.

2013-01-01

There are numerous hydrothermal fields within the Great Basin of North America, some of which have been exploited for geothermal resources. With methane and other carbon-bearing compounds being observed, in some cases with high concentrations, however, their origins and formation conditions remain unknown. Thus, studying hydrothermal springs in this area provides us an opportunity to expand our knowledge of subsurface (bio)chemical processes that generate organic compounds in hydrothermal systems, and aid in future development and exploration of potential energy resources as well. While isotope measurement has long been used for recognition of their origins, there are several secondary processes that may generate variations in isotopic compositions: oxidation, re-equilibration of methane and other alkanes with CO2, mixing with compounds of other sources, etc. Therefore, in addition to isotopic analysis, other evidence, including water chemistry and rock compositions, are necessary to identify volatile compounds of different sources. Surprise Valley Hot Springs (SVHS, 41º32'N, 120º5'W), located in a typical basin and range province valley in northeastern California, is a terrestrial hydrothermal spring system of the Great Basin. Previous geophysical studies indicated the presence of clay-rich volcanic and sedimentary rocks of Tertiary age beneath the lava flows in late Tertiary and Quaternary. Water and gas samples were collected for a variety of chemical and isotope composition analyses, including in-situ pH, alkalinity, conductivity, oxidation reduction potential (ORP), major and trace elements, and C and H isotope measurements. Fluids issuing from SVHS can be classified as Na-(Cl)-SO4 type, with the major cation and anion being Na+ and SO4 2-, respectively. Thermodynamic calculation using ORP and major element data indicated that sulfate is the most dominant sulfur species, which is consistent with anion analysis results. Aquifer temperatures at depth estimated by both dissolved SiO2 and Na-K-Ca geothermometers are in the range of 125.0 to 135.4 oC, and higher than the values measured at orifices (77.3 to 90.0 oC). CO2 and homologs of straight chain alkanes (C1-C5) were identified in gas samples. Carbon isotope values of alkanes increase with carbon numbers. The 13C fractionation between CO2 and dissolved inorganic carbon suggests they are out of carbon isotope equilibrium. The hypothesis regarding the formation of carbon-bearing compounds in SVHS may involve two processes: 1) Under high heat flow conditions which are caused by regional faulting and crustal extension, original high molecular weight organic compounds (kerogens) in clay-rich rocks decomposed to generate methane and other alkane homologs. 2) The SVHS area is associated with outflow structures, and distant from the heat source. Anaerobic oxidation of methane (AOM) with sulfate at shallow depth (< 90 oC) is suggested as being responsible for the generation of CO2 in SVHS.

The Origin of Carbon-bearing Volatiles in Surprise Valley Hot Springs in the Great Basin: Carbon Isotope and Water Chemistry Characterizations

NASA Technical Reports Server (NTRS)

Fu, Qi; Socki, Richard A.; Niles, Paul B.; Romanek, Christopher; Datta, Saugata; Darnell, Mike; Bissada, Adry K.

2013-01-01

There are numerous hydrothermal fields within the Great Basin of North America, some of which have been exploited for geothermal resources. With methane and other carbon-bearing compounds being observed, in some cases with high concentrations, however, their origins and formation conditions remain unknown. Thus, studying hydrothermal springs in this area provides us an opportunity to expand our knowledge of subsurface (bio)chemical processes that generate organic compounds in hydrothermal systems, and aid in future development and exploration of potential energy resources as well. While isotope measurement has long been used for recognition of their origins, there are several secondary processes that may generate variations in isotopic compositions: oxidation, re-equilibration of methane and other alkanes with CO2, mixing with compounds of other sources, etc. Therefore, in addition to isotopic analysis, other evidence, including water chemistry and rock compositions, are necessary to identify volatile compounds of different sources. Surprise Valley Hot Springs (SVHS, 41 deg 32'N, 120 deg 5'W), located in a typical basin and range province valley in northeastern California, is a terrestrial hydrothermal spring system of the Great Basin. Previous geophysical studies indicated the presence of clay-rich volcanic and sedimentary rocks of Tertiary age beneath the lava flows in late Tertiary and Quaternary. Water and gas samples were collected for a variety of chemical and isotope composition analyses, including in-situ pH, alkalinity, conductivity, oxidation reduction potential (ORP), major and trace elements, and C and H isotope measurements. Fluids issuing from SVHS can be classified as Na-(Cl)-SO4 type, with the major cation and anion being Na+ and SO4(2-), respectively. Thermodynamic calculation using ORP and major element data indicated that sulfate is the most dominant sulfur species, which is consistent with anion analysis results. Aquifer temperatures at depth estimated by both dissolved SiO2 and Na-K-Ca geothermometers are in the range of 125.0 to 135.4 C, and higher than the values measured at orifices (77.3 to 90.0 C). CO2 and homologs of straight chain alkanes (C1-C5) were identified in gas samples. Carbon isotope values of alkanes increase with carbon numbers. The C-13 fractionation between CO2 and dissolved inorganic carbon suggests they are out of carbon isotope equilibrium. The hypothesis regarding the formation of carbon-bearing compounds in SVHS may involve two processes: 1) Under high heat flow conditions which are caused by regional faulting and crustal extension, original high molecular weight organic compounds (kerogens) in clay-rich rocks decomposed to generate methane and other alkane homologs. 2) The SVHS area is associated with outflow structures, and distant from the heat source. Anaerobic oxidation of methane (AOM) with sulfate at shallow depth (< 90 C) is suggested as being responsible for the generation of CO2 in SVHS.

Lithium isotopic systematics of submarine vent fluids from arc and back-arc hydrothermal systems in the western Pacific

NASA Astrophysics Data System (ADS)

Araoka, Daisuke; Nishio, Yoshiro; Gamo, Toshitaka; Yamaoka, Kyoko; Kawahata, Hodaka

2016-10-01

The Li concentration and isotopic composition (δ7Li) in submarine vent fluids are important for oceanic Li budget and potentially useful for investigating hydrothermal systems deep under the seafloor because hydrothermal vent fluids are highly enriched in Li relative to seawater. Although Li isotopic geochemistry has been studied at mid-ocean-ridge (MOR) hydrothermal sites, in arc and back-arc settings Li isotopic composition has not been systematically investigated. Here we determined the δ7Li and 87Sr/86Sr values of 11 end-member fluids from 5 arc and back-arc hydrothermal systems in the western Pacific and examined Li behavior during high-temperature water-rock interactions in different geological settings. In sediment-starved hydrothermal systems (Manus Basin, Izu-Bonin Arc, Mariana Trough, and North Fiji Basin), the Li concentrations (0.23-1.30 mmol/kg) and δ7Li values (+4.3‰ to +7.2‰) of the end-member fluids are explained mainly by dissolution-precipitation model during high-temperature seawater-rock interactions at steady state. Low Li concentrations are attributable to temperature-related apportioning of Li in rock into the fluid phase and phase separation process. Small variation in Li among MOR sites is probably caused by low-temperature alteration process by diffusive hydrothermal fluids under the seafloor. In contrast, the highest Li concentrations (3.40-5.98 mmol/kg) and lowest δ7Li values (+1.6‰ to +2.4‰) of end-member fluids from the Okinawa Trough demonstrate that the Li is predominantly derived from marine sediments. The variation of Li in sediment-hosted sites can be explained by the differences in degree of hydrothermal fluid-sediment interactions associated with the thickness of the marine sediment overlying these hydrothermal sites.

Constraints on hydrocarbon and organic acid abundances in hydrothermal fluids at the Von Damm vent field, Mid-Cayman Rise (Invited)

NASA Astrophysics Data System (ADS)

McDermott, J. M.; Seewald, J.; German, C. R.; Sylva, S. P.

2013-12-01

The generation of organic compounds in vent fluids has been of interest since the discovery of seafloor hydrothermal systems, due to implications for the sustenance of present-day microbial populations and their potential role in the origin of life on early Earth. Possible sources of organic compounds in hydrothermal systems include microbial production, thermogenic degradation of organic material, and abiotic synthesis. Abiotic organic synthesis reactions may occur during active circulation of seawater-derived fluids through the oceanic crust or within olivine-hosted fluid inclusions containing carbon-rich magmatic volatiles. H2-rich end-member fluids at the Von Damm vent field on the Mid-Cayman Rise, where fluid temperatures reach 226°C, provide an exciting opportunity to examine the extent of abiotic carbon transformations in a highly reducing system. Our results indicate multiple sources of carbon compounds in vent fluids at Von Damm. An ultramafic-influenced hydrothermal system located on the Mount Dent oceanic core complex at 2350 m depth, Von Damm vent fluids contain H2, CH4, and C2+ hydrocarbons in high abundance relative to basalt-hosted vent fields, and in similar abundance to other ultramafic-hosted systems, such as Rainbow and Lost City. The CO2 content and isotopic composition in end-member fluids are virtually identical to bottom seawater, suggesting that seawater DIC is unchanged during hydrothermal circulation of seawater-derived fluids. Accordingly, end-member CH4 that is present in slightly greater abundance than CO2 cannot be generated from reduction of aqueous CO2 during hydrothermal circulation. We postulate that CH4 and C2+ hydrocarbons that are abundantly present in Von Damm vent fluids reflect leaching of fluids from carbon- and H2-rich fluid inclusions hosted in plutonic rocks. Geochemical modeling of carbon speciation in the Von Damm fluids suggests that the relative abundances of CH4, C2+ hydrocarbons, and CO2 are consistent with thermodynamic equilibrium at higher temperatures and more reducing conditions than those observed in the Von Damm vent fluids. These findings are consistent with a scenario in which n-alkanes form abiotically within a high-H2, carbon-rich olivine-hosted fluid inclusion, and are subsequently liberated and transported to the seafloor during hydrothermal alteration of the lower crustal rocks exposed at the Mount Dent oceanic core complex. Mixed fluids at Von Damm show depletions in CO2 and H2, relative to conservative mixing. Multiple S isotope measurements indicate that the H2 sink cannot be attributed to sulfate reduction. Thermodynamic constraints indicate that high-H2 conditions support the active formation of formate via reduction of dissolved CO2 during hydrothermal circulation - a process that has also been described at the Lost City vent field - and could account for the concurrent depletions in CO2 and H2. The transformation of inorganic carbon to organic compounds via two distinct pathways in modern seafloor hydrothermal vents validates theoretical and experimental conceptual models regarding processes occurring in the crust and during hydrothermal circulation, and is relevant to supporting life in vent ecosystems.

Continuous flow synthesis of ZSM-5 zeolite on the order of seconds

PubMed Central

Liu, Zhendong; Okabe, Kotatsu; Anand, Chokkalingam; Yonezawa, Yasuo; Zhu, Jie; Yamada, Hiroki; Endo, Akira; Yanaba, Yutaka; Yoshikawa, Takeshi; Ohara, Koji; Okubo, Tatsuya; Wakihara, Toru

2016-01-01

The hydrothermal synthesis of zeolites carried out in batch reactors takes a time so long (typically, on the order of days) that the crystallization of zeolites has long been believed to be very slow in nature. We herein present a synthetic process for ZSM-5, an industrially important zeolite, on the order of seconds in a continuous flow reactor using pressurized hot water as a heating medium. Direct mixing of a well-tuned precursor (90 °C) with the pressurized water preheated to extremely high temperature (370 °C) in the millimeter-sized continuous flow reactor resulted in immediate heating to high temperatures (240–300 °C); consequently, the crystallization of ZSM-5 in a seed-free system proceeded to completion within tens of or even several seconds. These results indicate that the crystallization of zeolites can complete in a period on the order of seconds. The subtle design combining a continuous flow reactor with pressurized hot water can greatly facilitate the mass production of zeolites in the future. PMID:27911823

One-step process of hydrothermal and alkaline treatment of wheat straw for improving the enzymatic saccharification.

PubMed

Sun, Shaolong; Zhang, Lidan; Liu, Fang; Fan, Xiaolin; Sun, Run-Cang

2018-01-01

To increase the production of bioethanol, a two-step process based on hydrothermal and dilute alkaline treatment was applied to reduce the natural resistance of biomass. However, the process required a large amount of water and a long operation time due to the solid/liquid separation before the alkaline treatment, which led to decrease the pure economic profit for production of bioethanol. Therefore, four one-step processes based on order of hydrothermal and alkaline treatment have been developed to enhance concentration of glucose of wheat straw by enzymatic saccharification. The aim of the present study was to systematically evaluated effect for different one-step processes by analyzing the physicochemical properties (composition, structural change, crystallinity, surface morphology, and BET surface area) and enzymatic saccharification of the treated substrates. In this study, hemicelluloses and lignins were removed from wheat straw and the morphologic structures were destroyed to various extents during the four one-step processes, which were favorable for cellulase absorption on cellulose. A positive correlation was also observed between the crystallinity and enzymatic saccharification rate of the substrate under the conditions given. The surface area of the substrate was positively related to the concentration of glucose in this study. As compared to the control (3.0 g/L) and treated substrates (11.2-14.6 g/L) obtained by the other three one-step processes, the substrate treated by one-step process based on successively hydrothermal and alkaline treatment had a maximum glucose concentration of 18.6 g/L, which was due to the high cellulose concentration and surface area for the substrate, accompanying with removal of large amounts of lignins and hemicelluloses. The present study demonstrated that the order of hydrothermal and alkaline treatment had significant effects on the physicochemical properties and enzymatic saccharification of wheat straw. The one-step process based on successively hydrothermal and alkaline treatment is a simple operating and economical feasible method for the production of glucose, which will be further converted into bioethanol.

Geological characteristics of the Shinkai Seep Field, a serpentinite-hosted ecosystem in the Southern Mariana Forearc

NASA Astrophysics Data System (ADS)

Ohara, Y.; Stern, R. J.; Martinez, F.; Michibayashi, K.; Reagan, M. K.; Fujikura, K.; Watanabe, H.; Ishii, T.; Kelley, K. A.

2012-12-01

Most hydrothermal vents along mid-ocean spreading ridges are high-temperature, sulfide-rich, and low pH (acidic environments). For this reason, the discovery of the Lost City hydrothermal field on the Mid-Atlantic Ridge has stimulated interest in the role of serpentinization of peridotite in generating H2- and CH4-rich fluids and associated carbonate chimneys, as well as in the biological communities adapted to highly reduced, alkaline environments. A new serpentinite-hosted ecosystem, the Shinkai Seep Field (SSF), was discovered by a Shinkai 6500 dive in the inner trench slope of the southern Mariana Trench, near the Challenger Deep, during YK10-12 cruise of R/V Yokosuka in September 2010. Abundant chemosynthetic biological communities, principally consisting of vesicomyid clams are associated with serpentinized peridotite in the SSF. Serpentinization beneath several hydrothermal sites on the Mid-Atlantic Ridge is controlled by interacting seawater and peridotite, variably influenced by magmatic heat. In contrast, the SSF is located in a deep inner trench slope where magmatic heat contribution is unlikely. Instead, serpentinization reactions feeding the SSF may be controlled by persistent fluid flow from the subducting slab. Slab-derived fluid flow is probably controlled by flow through fractures because no serpentinite mud volcano can be discerned along the southern Mariana forearc. Deep-towed IMI-30 sonar backscatter imaging during TN273 cruise of R/V Thomas G. Thompson in January 2012 indicates that the SSF is associated with a small, low backscatter feature that may be a small mound. There are 20 or more of these features in the imaged area, the size of which is ~200 m width and ~200 m to ~700 m long. Since the southern Mariana forearc is heavily faulted, with a deep geology that is dominated by peridotite, more SSF-type seeps are likely to exist along the forearc above the Challenger Deep. The discovery of the SSF suggests that serpentinite-hosted vents may be more widespread on the ocean floor than presently known. The discovery further indicates that such serpentinite-hosted low-temperature fluid vents can sustain high-biomass communities and has implications for the chemical budget of the oceans and the distribution of abyssal chemosynthetic life. Since we know nothing about the chemistry and microbiology of the SSF, we hope to return for further studies with Shinkai 6500 in 2013.

The effect of urea on microstructures of tin dioxide grown on Ti plate and its supercapacitor performance

NASA Astrophysics Data System (ADS)

Jinlong, Lv; Meng, Yang; Miura, Hideo

2017-02-01

The effects of urea on microstructures of SnO2 during hydrothermal process and its supercapacitor performance were investigated. The sphere SnO2 was formed on Ti plate in hydrothermal solution without urea, while the SnO2 micro-flowers were assembled by numerous few-layered nanopetals due to adding to urea during hydrothermal process. The separated SnO2 nanopetals arrays showed better electrochemical performance than sphere SnO2. The gap between SnO2 nanopetals promoted penetration of the electrolyte and induced high supercapacitive performance.

Tourmaline as a recorder of ore-forming processes

USGS Publications Warehouse

Slack, John F.; Trumbull, Robert B.

2011-01-01

Tourmaline occurs in diverse types of hydrothermal mineral deposits and can be used to constrain the nature and evolution of ore-forming fl uids. Because of its broad range in composition and retention of chemical and isotopic signatures, tourmaline may be the only robust recorder of original mineralizing processes in some deposits. Microtextures and in situ analysis of compositional and isotopic variations in ore-related tourmaline provide valuable insights into hydrothermal systems in seafl oor, sedimentary, magmatic, and metamorphic environments. Deciphering the hydrothermal record in tourmaline also holds promise for aiding exploration programs in the search for new ore deposits.