Geochemistry of Sublacustrine Hydrothermal Deposits in Yellowstone Lake—Hydrothermal Reactions, Stable-Isotope Systematics, Sinter Deposition, and Spire Formation

Geochemical and mineralogical studies of hydrothermal deposits and altered vent muds from the floor of Yellowstone Lake indicate that these features form due to hydrothermal fluid quenching in shallow flow conduits or upon egress into bottom waters. Siliceous precipitates occur as conduits within the uppermost sediments, as tabular deposits that form along sedimentary layers, and as spires as much as 8 m tall that grow upward from crater-like depressions on the lake bottom. These deposits are enriched in As, Cs, Hg, Mo, Sb, Tl, and W. Variations in major-element geochemistry indicate that subaerial sinters from West Thumb and spire interiors are nearly pure SiO2, whereas sublacustrine conduits are less SiO2 rich and are similar in some cases to normal Yellowstone Lake sediments due to incorporation of sediments into conduit walls. Vent muds, which are hydrothermally altered lake sediments, and some outer conduit walls show pervasive leaching of silica (~63 weight percent silica removal). This hydrothermal leaching process may explain the occurrence of most sublacustrine vents in holes or vent craters, but sediment winnowing by vent fluids may also be an important process in some cases. Stable-isotope studies indicate that most deposits formed at temperatures between 78°C and 160°C and that vent fluids had oxygen-isotope values of –3.2 to –11.6 per mil, significantly higher than lake waters (–*16.5 per mil). Sulfur-isotope studies indicate that vent waters and lake waters are dominated by sulfur derived from volcanic rocks with δ34S ~ 2.5 per mil. Geochemical reaction modeling indicates that spires form from upwelling hydrothermal fluids that are saturated with amorphous silica at temperatures 80°–96°C. Reaction calculations suggest that silica precipitation on the lake bottom is initially caused by mixing with cold bottom waters. Once a siliceous carapace is established, more rapid silica precipitation occurs by conductive cooling. Silicification of thermophilic bacteria is a very important process in building spire structures

Cycling of sulfur in subduction zones: The geochemistry of sulfur in the Mariana Island Arc and back-arc trough

The sulfur contents and sulfur isotopic compositions of 24 glassy submarine volcanics from the Mariana Island Arc and back-arc Mariana Trough were determined in order to investigate the hypothesis that subducted seawater sulfur ([delta]34S = 21[per mille sign]) is recycled through arc volcanism. Our results for sulfur are similar to those for subaerial arc volcanics: Mariana Arc glasses are enriched in 34S ([delta]34S = up to 10.3[per mille sign], mean = 3.8[per mille sign]) and depleted in S (20-290 ppm, MEAN = 100 ppm) relative to MORB (850 ppm S, [delta]34S = 0.1 +/- 0.5[per mille sign]). The back-arc trough basalts contain 200-930 ppm S and have [delta]34S values of 1.1 +/- 0.5[per mille sign], which overlap those for the arc and MORB. The low sulfur contents of the arc and some of the trough glasses are attributed to (1) early loss of small amounts of sulfur through separation of immiscible sulfide and (2) later vapor-melt equilibrium control of sulfur contents and loss of sulfur in a vapor phase from sulfide-undersaturated melts near the minimum in sulfur solubility at [function of (italic small f)]O2 [approximate] NNO (nickel-nickel oxide). Although these processes removed sulfur from the melts their effects on the sulfur isotopic compositions of the melts were minimal. Positive trends of [delta]34S with 87Sr/86Sr, LILE and LREE contents of the arc volcanics are consistent with a metasomatic seawater sulfur component in the depleted sub-arc mantle source. The lack of a 34S-rich slab signature in the trough lavas may be attributed to equilibration of metasomatic fluid with mantle material along the longer pathway from the slab to the source of the trough volcanics. Sulfur is likely to have been transported into the mantle wedge by metasomatic fluid derived from subducted sediments and pore fluids.Gases extracted from vesicles in arc and back-arc samples are predominantly H2O, with minor CO2 and traces of H2S and SO2. CO2 in the arc and back-arc rocks has [delta]13C values of -2.1 to -13.1[per mille sign], similar to MORB. These data suggest that degassing of CO2 could explain the slightly lower [delta]13C values for some Mariana Trough volcanic glasses, and that incorporation of subduction-derived organic carbon into the Mariana Trough mantle source may not be necessary. More analyses are required to resolve this question, however.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30563/1/0000196.pd

Geological and thermal control of the hydrothermal system in northern Yellowstone Lake: inferences from high-resolution magnetic surveys

Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 125(9), (2020): e2020JB019743, doi:10.1029/2020JB019743.A multiscale magnetic survey of the northern basin of Yellowstone Lake was undertaken in 2016 as part of the Hydrothermal Dynamics of Yellowstone Lake Project (HD‐YLAKE)—a broad research effort to characterize the cause‐and‐effect relationships between geologic and environmental processes and hydrothermal activity on the lake floor. The magnetic survey includes lake surface, regional aeromagnetic, and near‐bottom autonomous underwater vehicle (AUV) data. The study reveals a strong contrast between the northeastern lake basin, characterized by a regional magnetic low punctuated by stronger local magnetic lows, many of which host hydrothermal vent activity, and the northwestern lake basin with higher‐amplitude magnetic anomalies and no obvious hydrothermal activity or punctuated magnetic lows. The boundary between these two regions is marked by a steep gradient in heat flow and magnetic values, likely reflecting a significant structure within the currently active ~20‐km‐long Eagle Bay‐Lake Hotel fault zone that may be related to the ~2.08‐Ma Huckleberry Ridge caldera rim. Modeling suggests that the broad northeastern magnetic low reflects both a shallower Curie isotherm and widespread hydrothermal activity that has demagnetized the rock. Along the western lake shoreline are sinuous‐shaped, high‐amplitude magnetic anomaly highs, interpreted as lava flow fronts of upper units of the West Thumb rhyolite. The AUV magnetic survey shows decreased magnetization at the periphery of the active Deep Hole hydrothermal vent. We postulate that lower magnetization in the outer zone results from enhanced hydrothermal alteration of rhyolite by hydrothermal condensates while the vapor‐dominated center of the vent is less altered.The lake surface and AUV magnetic data were acquired under National Park Service research permit YELL‐2016‐SCI‐7018 and the 2016 aeromagnetic data under research permit YELL‐2016‐SCI‐7056. We thank Sarah Haas, Stacey Gunther, Erik Oberg, Annie Carlson, and Patricia Bigelow at the Yellowstone Center for Resources for assistance with permitting and logistics, Ranger Jackie Sene for assistance with logistics and safety at Bridge Bay, Bob Gresswell for providing us with the U.S. Geological Survey (USGS) boat Alamar, the boat pilot Nick Heredia, and Robert Harris and Shaul Hurwitz for fruitful discussions. We are very thankful to Ocean Floor Geophysics (Brian Claus and Steve Bloomer) who provided the magnetometer for the AUV survey and preprocessed the data, and to the REMUS 600 team (Greg Packard and Greg Kurras) for operating and optimizing the AUV during lake operations. Data from the Newport and Boulder observatories were used to process the survey data. We thank the USGS Geomagnetism Program for supporting their operation and INTERMAGNET for promoting high standards of magnetic observatory practice (www.intermagnet.org). This research was funded by the National Science Foundation's Integrated Earth Systems program EAR‐1516361 (HD‐YLAKE project), USGS Mineral Resource and Volcano Hazard Programs, and benefited from major in‐kind support from the USGS Yellowstone Volcano Observatory. Maurice Tivey was supported under National Science Foundation Grant OCE‐1557455. During the course of this study, Claire Bouligand was a visiting scientist at the USGS in Menlo Park, California, USA, benefited from a delegation to Centre National de la Recherche Scientifique (CNRS), and received funding from CNRS‐INSU program SYSTER. ISTerre is part of Labex OSUG@2020 (ANR10 LABX56). Any use of trade, firm, or product names is for descriptive purposes and does not imply endorsement by the U.S. Government.2021-01-2

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

Processes controlling the composition of seafloor hydrothermal fluids in silicic back-arc or near-arc crustal settings remain poorly constrained despite growing evidence for extensive magmatic–hydrothermal activity in such environments. We conducted a survey of vent fluid compositions from two contrasting sites in the Manus back-arc basin, Papua New Guinea, to examine the influence of variations in host rock composition and magmatic inputs (both a function of arc proximity) on hydrothermal fluid chemistry. Fluid samples were collected from felsic-hosted hydrothermal vent fields located on Pual Ridge (PACMANUS and Northeast (NE) Pual) near the active New Britain Arc and a basalt-hosted vent field (Vienna Woods) located farther from the arc on the Manus Spreading Center. Vienna Woods fluids were characterized by relatively uniform endmember temperatures (273–285 °C) and major element compositions, low dissolved CO2 concentrations (4.4 mmol/kg) and high measured pH (4.2–4.9 at 25 °C). Temperatures and compositions were highly variable at PACMANUS/NE Pual and a large, newly discovered vent area (Fenway) was observed to be vigorously venting boiling (358 °C) fluid. All PACMANUS fluids are characterized by negative δDH2O values, in contrast to positive values at Vienna Woods, suggesting substantial magmatic water input to circulating fluids at Pual Ridge. Low measured pH (25 °C) values (∼2.6–2.7), high endmember CO2 (up to 274 mmol/kg) and negative δ34SH2S values (down to −2.7‰) in some vent fluids are also consistent with degassing of acid-volatile species from evolved magma. Dissolved CO2 at PACMANUS is more enriched in 13C (−4.1‰ to −2.3‰) than Vienna Woods (−5.2‰ to −5.7‰), suggesting a contribution of slab-derived carbon. The mobile elements (e.g. Li, K, Rb, Cs and B) are also greatly enriched in PACMANUS fluids reflecting increased abundances in the crust there relative to the Manus Spreading Center. Variations in alkali and dissolved gas abundances with Cl at PACMANUS and NE Pual suggest that phase separation has affected fluid chemistry despite the low temperatures of many vents. In further contrast to Vienna Woods, substantial modification of PACMANUS/NE Pual fluids has taken place as a result of seawater ingress into the upflow zone. Consistently high measured Mg concentrations as well as trends of increasingly non-conservative SO4 behavior, decreasing endmember Ca/Cl and Sr/Cl ratios with increased Mg indicate extensive subsurface anhydrite deposition is occurring as a result of subsurface seawater entrainment. Decreased pH and endmember Fe/Mn ratios in higher Mg fluids indicate that the associated mixing/cooling gives rise to sulfide deposition and secondary acidity production. Several low temperature (⩽80 °C) fluids at PACMANUS/NE Pual also show evidence for anhydrite dissolution and water–rock interaction (fixation of B) subsequent to seawater entrainment. Hence, the evolution of fluid compositions at Pual Ridge reflects the cumulative effects of water/rock interaction, admixing and reaction of fluids exsolved from silicic magma, phase separation/segregation and seawater ingress into upflow zones

The Floor of Yellowstone Lake is Anything but Quiet—New Discoveries from High-Resolution Sonar Imaging, Seismic- Reflection Profiling, and Submersible Studies

Discoveries from multibeam sonar mapping and seis-mic-reflection surveys of Yellowstone Lake provide new insight into the recent geologic forces that have shaped a large lake at the active front of the Yellowstone hot spot, a region strongly affected by young (\u3c2 \u3em.y.), large-volume (\u3e100–1,000s km3) silicic volcanism, active tectonism, and accompanying uplift. Specifically, our mapping has identified the extent of postcaldera-collapse volcanism and active hydrothermal processes occurring above a large magma chamber beneath the lake floor. Multiple advances and recessions of thick glacial ice have overlapped volcanic and hydrothermal activity leaving a lake basin that has been shaped predominantly by fire and ice. 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 morphology and localization of hydrothermal activity in the northern, West Thumb, and central basins. Many previously unknown features have been identified and include more than 660 hydrothermal vents, several very large (\u3e500-m diameter) hydrothermal-explosion craters, many small hydrothermal-vent craters (~1-to 200-m diameter), domed lacustrine sediments related to hydrothermal activity, elongate fissures cutting postglacial sediments, siliceous hydrothermal-spire structures, sublacustrine landslide deposits, submerged former shorelines, large glacial melting features, incipient faulting along the trace of the Eagle Bay fault zone, 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

The Floor of Yellowstone Lake is Anything but Quiet—New Discoveries from High-Resolution Sonar Imaging, Seismic- Reflection Profiling, and Submersible Studies

Discoveries from multibeam sonar mapping and seis-mic-reflection surveys of Yellowstone Lake provide new insight into the recent geologic forces that have shaped a large lake at the active front of the Yellowstone hot spot, a region strongly affected by young (\u3c2 \u3em.y.), large-volume (\u3e100–1,000s km3) silicic volcanism, active tectonism, and accompanying uplift. Specifically, our mapping has identified the extent of postcaldera-collapse volcanism and active hydrothermal processes occurring above a large magma chamber beneath the lake floor. Multiple advances and recessions of thick glacial ice have overlapped volcanic and hydrothermal activity leaving a lake basin that has been shaped predominantly by fire and ice. 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 morphology and localization of hydrothermal activity in the northern, West Thumb, and central basins. Many previously unknown features have been identified and include more than 660 hydrothermal vents, several very large (\u3e500-m diameter) hydrothermal-explosion craters, many small hydrothermal-vent craters (~1-to 200-m diameter), domed lacustrine sediments related to hydrothermal activity, elongate fissures cutting postglacial sediments, siliceous hydrothermal-spire structures, sublacustrine landslide deposits, submerged former shorelines, large glacial melting features, incipient faulting along the trace of the Eagle Bay fault zone, 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

Geochemical Data for Selected Rivers, Lake Waters, Hydrothermal Vents, and Subaerial Geysers in Yellowstone National Park, Wyoming and Vicinity, 1996–2004

Analyses of more than 400 water samples collected from creeks and rivers draining into Yellowstone Lake, hydrothermal vents and water-column profiles within Yellowstone Lake, and subaerial hot springs and geysers throughout Yellowstone National Park (the Park) are reported. The samples were collected from 1996 to 2004. All of the water samples were collected and analyzed as part of the USGS Mineral Resources Program Project, Integrated Geoscience Studies of the Greater Yellowstone Area. Goals of this study are to provide state-of-the-art chemical determinations of more than 45 elements and species to help understand the influences of hydrothermal processes within Yellowstone National Park. Hydrothermal vents within Yellowstone Lake were sampled during 1996–2004. Sampling of creeks contributing to Yellowstone Lake began in 1997 and continued through 1999. Four water-column profiles were collected within Yellowstone Lake in both 1997 and 1998. Water samples were collected from subaerial geysers and hot springs throughout Yellowstone National Park during 1998–2002. In 1999, mixing experiments were conducted using water samples collected from four subaerial hot springs: three in Norris Geyser Basin and one at West Thumb Geyser Basin. These thermal-water samples were mixed with Yellowstone Lake water to simulate processes at sublacustrine vents and to evaluate conservative–nonconservative behavior of elements during mixing. The results of these experiments are discussed in Balistrieri and others (this volume), and the full data sets are presented here. The data reported in this paper clearly show the influence of hydrothermal processes on waters within Yellowstone National Park. Yellowstone Lake hydrothermal- indicator elements (As, B, Cl, Cs, Cu, Ge, Hg, Li, Mo, Sb, and W) as defined by Balistrieri and others (this volume) delineate areas of hydrothermal influx. The differences in the levels of these elements between the creek data and water-column profiles indicate an influx of hydrothermal water within Yellowstone Lake. The water-column samples have higher values of the hydrothermal-indicator elements than the creeks flowing into the lake; therefore significant input of hydrothermal-indicator elements from the hydrothermal vents within the lake is indicated. There are large variations in the values of the indicator elements among vents in Yellowstone Lake. The values of the hydrothermal-indicator elements are elevated for all of the vent samples, but a group of the West Thumb vents contain the highest values. This could indicate more active vents and (or) less mixing with lake water during sampling or during ascent to the lake floor. The subaerial features in the Park also show considerable variations in the values of the indicator elements. Some thermal features in the Park, such as Porkchop and Green Dragon Geysers in Norris Geyser Basin, have highly elevated hydrothermal- indicator-element values, while other features have values similar to Yellowstone Lake water, which is 99 percent meteoric water. These differences must reflect varying amounts of hydrothermal activity and input in these areas

The Influence of Sublacustrine Hydrothermal Vent Fluids on the Geochemistry of Yellowstone Lake

The geochemical composition of Yellowstone Lake water is strongly influenced by sublacustrine hydrothermal vent activity. The evidence for this conclusion is twofold. First, mass-balance calculations indicate that the outflow from Yellowstone Lake is enriched in dissolved As, B, Cl, Cs, Ge, Li, Mo, Sb, and W relative to inflowing waters. Calculations involving stable isotopes of hydrogen and oxygen (δD and δ18O, respectively) and mass-balances indicate about 13 percent evapoconcentration in the lake, which is inadequate to account for the enrichment of these elements in the water column. Second, linear relationships between the concentration of Cl and many other elements in the lake and in hydrothermal vent fluids suggest that Yellowstone Lake water is a mixture of inflowing surface water and hydrothermal source fluid. The conservative behavior of many elements is further demonstrated in mixing experiments that utilize subaerial geyser fluids and Yellowstone River water sampled at the lake outlet. The hydrothermal source fluid feeding the lake is identified by comparing theoretical predictions of the Cl and δD content of boiled, deep, thermal-reservoir fluid with observed compositions of water-column, pore-water, and vent samples from Yellowstone Lake. This comparison indicates that the hydrothermal source fluid has a temperature of 220°C and a Cl content of 570 mg/kg (~16 mM or millimoles per liter) and it evolved by boiling of a deep reservoir fluid with δD equal to –149 per mil and Cl content of 310 mg/kg. The concentrations of other elements in the hydrothermal source fluid are estimated using the observed linear relationships between Cl and other elements in lake and hydrothermal vent fluids. These concentrations indicate strong enrichment of Cl, Si, B, Li, Na, K, Rb, As, Ge, Mo, Sb, and W in sublacustrine hydrothermal vent fluids. In general, the composition of the hydrothermal source fluid is similar to the composition of subaerial geyser water in Yellowstone National Park (the Park). The Cl concentration in the hydrothermal source fluid indicates that Yellowstone Lake water is about 1 percent hydrothermal source fluid and 99 percent inflowing stream water. The flux of hydrothermal source fluid into the lake is about 8 x 109 kg of water per year, based on mass-balance calculations for Cl. If the concentration of Cl in deep reservoir fluid, rather than in hydrothermal source fluid, is used, then the flow is calculated to be 1.5x1010 kg of water per year. Using the latter estimate, sublacustrine vents in Yellowstone Lake account for ~10 percent of the total flux of deep, thermal reservoir water in the Park, as estimated from Cl in streams (Friedman and Norton, 2000, this volume). Although the volumetric input of water into the lake from hydrothermal vents is small, the impact of the vent fluids on the geochemistry of Yellowstone Lake is large because of the great enrichment of many elements in these fluids. Because about 41 million kg per day of element-enriched deep thermal water flows into the lake, and recent swath sonar studies show the presence of numerous newly recognized hydrothermal features, Yellowstone Lake should be considered one of the most significant hydrothermal basins in the Park

Zoning and controls of mineralization in the southeast Missouri barite district

Master of ScienceGeologyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/114733/1/39015003277012.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/114733/2/39015003277012.pd