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At least 847 records · Page 47Linked to original sources
USGS1983

Selective concentration of cesium in analcime during hydrothermal alteration, Yellowstone National Park, Wyoming

Chemical and mineralogical studies of fresh and hydrothermally altered rhyolitic material in Upper and Lower Geyser Basins, Yellowstone National Park, show that all the altered rocks are enriched in Cs and that Cs is selectively concentrated in analcime. The Cs content of unaltered rhyolite lava flows, including those from which the altered sediments are derived, ranges from 2.5 to 7.6 ppm. The Cs content of analcime-bearing altered sedimentary rocks is as high as 3000 ppm, and in clinoptilolite-bearing altered sedimentary rocks Cs content is as high as 180 ppm. Altered rhyolite lava flows which were initially vitrophyres, now contain up to 250 ppm Cs, and those which were crystallized prior to hydrothermal alteration contain up to 14 ppm. Mineral concentrates of analcime contain as much as 4700 ppm Cs. The Cs must have been incorporated into the analcime structure during crystallization, rather than by later cation substitution, because analcime does not readily exchange Cs. The Cs Cl "> CsCl of the fluids circulating through the hydrothermal system varies, suggesting that Cs is not always a conservative ion and that Cs is lost from upflowing thermal waters due to water-rock interaction resulting in crystallization of Cs-bearing analcime. The source of Cs for Cs enrichment of the altered rocks is from leaching of rhyolitic rocks underlying the geyser basins, and from the top of the silicic magma chamber that underlies the area. Analcime is an important natural Cs sink, and the high Cs concentrations reported here may prove to be an important indicator of the environment of analcime crystallization.

Geochimica et Cosmochimica Acta↗
USGS2015

Uranium in the Islamic Republic of Mauritania (phase V, deliverable 81)

Mauritania has 80 known uranium mineral occurrences and is the current focus of active exploration for uranium by a number of private companies. Seventeen occurrences have had resource estimates published and can be considered as mineral deposits. Fourteen of these are calcrete-type deposits with a total resource of 138.3 million tonnes at an average grade of 331 ppm U3O8. The three bedrock-hosted deposits are granite hosted vein/shear zone type deposits with a total resource of 46.5 million tonnes at a grade of 248 ppm U3O8. All of the deposits and the majority of the other uranium occurrences are found in the Paleoproterozoic Rgueïbat Shield in areas underlain by the Cortege de Yetti, the Complexe de Tmeïmichatt Ghallamane and the Complexe d'Adam Esseder. This area is also visible in the PRISM airborne radiometric data as an extensive >4 ppm equivalent uranium anomaly. Uranium occurrences are also reported in the Tasiast-Tijirit Terrane of the Archean Rgueïbat Shield, the Mauritanide Belt, and the Coastal Basin. Geologic environments permissive for eight types of uranium deposits are recognized in Mauritania. These deposit types include: calcrete, granite-hosted vein/shear, alkaline intrusive, unconformity-associated, quartz pebble conglomerate, phosphate, sandstone, and red bed-type uranium deposits.

Open-File Report↗
USGS1981

Proceedings of the Symposium on Mineral Deposits of the Pacific Northwest: Geological Society of America, Cordilleran Section meeting at Corvallis, Oregon, March 20-21, 1980

Stratiform and volcanogenic zinc-lead-barium deposits occur within the pelagic Kagvik sequence in the Red Dog Creek and Drenchwater Creek areas in the DeLong Mountains and Howard Pass quadrangles. The sulfide deposits occur together with barite, tuff, sandstone, shale, chert, and keratophyre flows and sills. The three main occurrences of the stratiform zinc-lead-barium deposits in the Red Dog Creek area are: (1) thinly-bedded stratiform sulfide minerals in organic-rich Mississippian shale and chert; (2) massive sulfide vein and breccia fillings in Mississippian shale; and (3) massive stratiform barite lenses and nodules in chert and shale of the Siksikpuk Formation. The Drenchwater Creek area has only the first type. Sulfide-bearing zones of up to several thousand meters long occur in both areas with up to 19.5 percent Zn, 9.5 percent Pb, and locally more than 150 ppm Ag. Radiolaria from sulfide-bearing chert indicate in the Red Dog Creek area a Mississippian age of sulfide deposition. K/Ar ages of 319 + 10 m.y. and 330 + 17 m.y. obtained from biotite in keratophyre associated with sulfide-bearing tuff and chert in the Drenchwater Creek area indicate a Mississippian age of sulfide deposition. Sulfur isotope analyses of sulfur-bearing minerals from the Red Dog Creek area indicate that a combination of sea water sulfate and deep-seated sulfur was probably the source of the barite sulfate whereas sulfur in the sulfide minerals may have had a deep-seated source. Sulfur isotope values for sphalerite and galena are similar in vein and stratiform occurrences. Using sulfur isotope geothermetry, spalerite-galena pairs yield paleotemperatures of between 115° and 305° C. Lead isotope analyses of galena from both the Red Dog Creek and Drenchwater Creek areas yield Triassic model ages of approximately 200 m.y. Lead isotope data from both areas approximate typical orogene, i.e., Andean-type arc, or mature island-arc values and exclude ocean floor rifting for the generation of lead. The isotopic, petrologic, and field data indicate the stratiform zinc-lead-barium deposits in the Red Dog Creek and Drenchwater Creek areas formed during a short-lived period of Mississippian submarine volcanism in either an incipient Andean-type arc, or mature island arc environment.

Alaska, British Columbia, California↗
USGS1983

Comparative anatomy of epithermal precious- and base-metal districts hosted by volcanic rocks: A talk presented at the GAC/MSC/GGU Joint Annual Meeting, May 11-13, 1983, Victoria, British Columbia

In order to distinguish dissimilar from similar features of epithermal districts, lithotectonic, mineralogical and geochemical traits are compiled for 15 such districts. The districts occur in structurally complex settings associated with silicic to intermediate volcanics. Affiliation with subduction environments on a continental scale and caldera settings on a regional scale is common but is not demonstrable for all districts. Most deposits formed near the end of major volcanism, but some formed considerably later. Paleodepth to the top of the ore is 300-600m for most districts, although Au-rich districts appear to be shallower. The lateral extent of the ore zone is highly variable and far exceeds the limited vertical range (300-800m). Most ore was deposited from dominantly meteoric fluids ranging in temperature from 220°-290°C. Salinities ranged from 0-13 wt% NaCl equiv., and typical values were 1-3 wt%. Although noted for eight deposits, boiling is clearly associated with precious-metal deposition in only two deposits. Four districts, typified by Goldfield, Nev., are characterized by a highly sulfidized mineral assemblage, advanced argillic alteration, and ore deposition closely following emplacement of the host rock. The remaining eleven districts highlight a second, discrete type of deposit. They contain adularia, exhibit sericitic ± argillic alteration, and were mineralized significantly after emplacement of the host rock. The latter category includes two subgroups: Ag- and base-metal-rich deposits (e.g., Creede, Colo.), and Au-rich, base-metal-poor deposits (e.g., Round Mtn., Nev.).

Open-File Report↗
USGS2025

Advancing current understanding of Martian impact-generated hydrothermal systems through novel coupled modeling: Insights from Gale, Jezero, and other craters

Impact-generated hydrothermal systems are considered potentially habitable environments on Mars, Earth, and other planetary bodies for microbial life. However, there is an ongoing debate regarding what geological features on Mars provide definitive evidence for such systems. Although earlier studies have modeled hydrothermal processes in Martian craters, they often lacked integration with shock physics hydrocodes to constrain initial impact conditions. The importance of this two-code coupling was demonstrated by successfully replicating alteration signatures in the Earth's Haughton impact structure. In this study, we use a similar two-code approach, combining the iSALE hydrocode with the HYDROTHERM hydrothermal model to simulate the full evolution of impact-generated hydrothermal systems. We apply this method to craters the size of Jezero (∼50 km) and Gale (∼154 km) in diameter. Although Jezero's interior is largely buried, our results align with hypothesized hydrothermal vents and alteration minerals near central uplifts in similarly sized exposed craters, such as Toro and Auki. Furthermore, our models correspond to alteration patterns observed by the Curiosity in the lower layers of Mount Sharp, which may represent remnants of impact-driven hydrothermal activity. A key finding is that these systems may persist much longer than previously estimated. Our simulations suggest that a Jezero-sized system could remain habitable for thermophiles for approximately 720,000 years, whereas a Gale-sized system could persist for nearly 2 million years. Additionally, simulations under unsaturated crustal conditions reveal that air-dominated near-surface layers can suppress vertical fluid flow, enabling deep subsurface alteration without producing detectable mineral signatures at the surface.

Journal of Geophysical Research - Planets↗
USGS2001

Leg 188 synthesis: Transitions in the glacial history of the Prydz Bay region, East Antarctica, from ODP drilling

Drilling during Leg 119 (1988) and Leg 188 (2000; Sites 1165–1167) of the Ocean Drilling Program (ODP) provides direct evidence for long- and short-term changes in Cenozoic paleoenvironments in the Prydz Bay region. Cores from across the continental margin reveal that in preglacial times the present shelf was an alluvial plain system with austral conifer woodland in the Late Cretaceous that changed to cooler Nothofagus rainforest scrub by the middle to late Eocene (Site 1166). Earliest recovered evidence of nearby mountain glaciation is seen in late Eocene–age grain textures in fluvial sands. In the late Eocene to early Oligocene, Prydz Bay permanently shifted from being a fluvio-deltaic complex to an exclusively marine continental shelf environment. This transition is marked by a marine flooding surface later covered by overcompacted glacial sediments that denote the first advance of the ice sheet onto the shelf. Cores do not exist for the early Oligocene to early Miocene, and seismic data are used to infer the transition from a shallow to normal depth prograding continental shelf with submarine canyons on the slope and channel/levees on the rise. Cores from the continental rise at Site 1165 show long-term (millions of years) early Miocene and younger decreases in sedimentation rates as well as short-term (Milankovitch periods) cyclicity between principally biogenic and terrigenous sediment supply—resulting from the cyclic presence of onshore glaciers and changes in ocean circulation. Middle Miocene transitions include rapid decreases in sedimentation rates, increased ice-rafted debris, shifts in clays and other minerals, and regional erosion of the slope and rise. These transitions may reflect enhanced glacial erosion and reduced glacial meltwater from progressively colder ice. At this time, seismic data show that depocenters began to shift from the outer continental rise to the base of the continental slope coincident with the initial stages of the glacial erosion and overdeepening of the continental shelf. During the late Miocene to early Pliocene there was a transition to greater subglacial activity on the shelf and more pronounced cyclic facies variations on the continental rise. At this time, severe glacial morphologies initiated on the shelf with the erosion of Prydz Channel and other troughs by fast-moving ice and the deposition of overcompacted glacial diamictons by slow-moving ice on adjacent banks. The Prydz trough-mouth fan also began to form with alternating deposition of debris flows (ice at shelf edge) and muddy units (reduced ice) (Site 1167). The fan also records a transition during the late Pleistocene for times younger than 780 k.y. when short-term glacial variations continued but ice reached the shelf edge only a few times. Both short-term and long-term transitions characterize the Cenozoic evolution of the Prydz Bay region from the Cretaceous nonglacial to late Neogene full-glacial paleoenvironments. These transitions are known only from ODP cores, and further insights will require additional drilling.

Prydz Bay region↗
USGS2018

Geochemistry and microbiology of groundwater and solids from extraction and monitoring wells and their relation to well efficiency at a Federally operated confined disposal facility, East Chicago, Indiana

In cooperation with the U.S. Army Corps of Engineers, Chicago District, the U.S. Geological Survey investigated the processes affecting water quality, geochemistry, and microbiology in representative extraction and monitoring wells at a confined disposal facility (CDF) in East Chicago, Indiana. The CDF is a 140-acre Federally-managed facility that was the former location of an oil refinery and is now used for the long-term disposal and storage of dredge material from the Indiana Harbor and Indiana Harbor Canal. Residual petroleum hydrocarbons and leachate from the CDF are contained within the facility by use of a groundwater cutoff wall. The wall consists of a soil-bentonite slurry and a gradient control system made up of an automated network of 96 extraction wells, 42 monitoring wells, and 2 ultrasonic sensors that maintain an inward hydraulic gradient at the site. The pumps in the extraction wells require vigilant maintenance and must be replaced when unable to withdraw water at a rate sufficient to maintain the required inward gradient. The wells are screened in the Calumet aquifer, a coarse-grained sand and gravel unit that extends approximately 35 feet below the land surface and is not utilized for drinking-water supply at the CDF or in the surrounding area. This study was initiated to identify the cause of decreased pump discharges and to identify potential mitigation strategies. For this study, the U.S. Geological Survey collected groundwater and solids from monitoring and extraction wells. Groundwater samples were collected during June 2014 for precautionary health screening and on four occasions during September 2014 through November 2014. Groundwater samples collected from two extraction wells during June 2014 were analyzed for concentrations of anthropogenic organic constituents. During September through November 2014, groundwater samples were collected from one additional extraction well, and samples from three monitoring wells were analyzed for concentrations of inorganic and organic constituents, dissolved gases, and bacterial abundance and diversity. Solid samples were collected during April 2014, during September 2014 through November 2014, and during November 2016. Solid samples were collected from the exterior of extraction-well pumps and as flocculent from water samples. Solid samples were collected from 10 wells, including 1 extraction well and 3 monitoring wells sampled for water quality. Solid samples were analyzed for mineralogy, solid-phase habit, geochemistry, and organic composition. The following is a list of observations that were made during this study: (1) the water quality is substantially variable among the six well locations sampled as part of this study—lower (more negative) redox values and higher concentrations of many constituents (including calcium, magnesium, sodium, and sulfate) and properties (including dissolved solids, hardness, and turbidity) were detected in sampled wells located near the extraction wells with the highest frequency of failure; (2) water-level drawdown is variable between extraction wells—wells with the greatest drawdown may pull deeper groundwater into the borehole; (3) dissolved gas results indicate reducing oxidation-reduction processes in the aquifer material that can feasibly contribute iron, carbon dioxide, and other byproducts from hydrocarbon degradation to precipitates and solids that accumulate on and impair pump operation; (4) crystalline and amorphous solid-phase minerals are precipitating in the borehole; (5) several types of bacteria are present in water pumped from extraction wells and are likely responsible for bonding mineral and microbiologic matter to the pump (and other well components); and (6) bacteria may create microenvironments that facilitate precipitation of solids or inhibit dissolution of unstable minerals once the bacteria adhere to biofilm attached to the pump. Results of the study indicate that bacteria may be accumulating and entrapping solid material on the exterior of pumps. This accumulation reduces heat transfer and water discharge from the pump and may lead to decreased efficiency or mechanical failure. Observations could not be made on the well screen, gravel pack, or surrounding geologic formation; therefore, mitigating measures in the borehole may not solve well-productivity issues. Remedies for the pump fouling problems were derived from the review and interpretation of data collected during this study and from information documented in other sources about groundwater well fouling. Potential remedies to problems associated with pump fouling at the CDF may include the following: (1) reducing attractiveness of the extraction wells for microbiological growth by modifying the chemical or physical environment of the well, (2) modifying the pump exterior to decrease microbiological adherence, (3) changing the pumping regime to control the chemistry of water entering the well from the surrounding aquifer material, (4) modifying the pumps to be less physically and thermally attractive, and (5) removing hydrocarbons from groundwater and the aquifer material surrounding the wells or adding surfactants to make them more mobile. Pilot scale testing may be necessary to identify the most effective treatment or combination of treatments.

Indiana↗
USGS2023

Sources and chemical stability of soil organic carbon in natural and created coastal marshes of Louisiana

Coastal marshes are globally important for sequestering carbon, yet sea-level rise and anthropogenic stressors can reduce their capacity as carbon sinks. Marsh restoration can offset a portion of carbon loss through the degradation of natural marshes, but potential differences in the sources and stability of soil organic carbon (SOC) between created and natural marshes may affect their function as a long-term carbon sink. Here, we examine the sources and chemical stability of SOC in natural and created marshes across the Gulf coast of Louisiana, USA. Marshes were examined along an estuarine salinity gradient in a former interdistributary basin of the Mississippi River Delta and in six created marshes across a 32-year chronosequence and a natural reference marsh ( n = 6) in the Chenier Plain. Carbon source was assessed using δ 13 C analysis and chemical stability was determined through an acid hydrolysis digestion that removed labile carbon (LC). Soil δ 13 C values suggested that the local vegetation dominated SOC in all natural marshes although brackish marshes had a mix of sources and degradation of SOC. Recalcitrant carbon (RC) was 72.2 ± 0.5 % of SOC across fresh, brackish and saline marshes. The depth-averaged RC accumulation rate was almost three times greater than LC accumulation rate, yet both contributed significantly to accretion and long-term SOC accumulation (124–132 g m −2 y −1 in natural marshes). RC and SOC accumulation rate increased with mineral sediment accumulation rate. For the created marshes, SOC became increasingly recalcitrant due to an increase in in-situ plant inputs, but accumulation rates were lower than the natural marshes. Overall, this study illustrates that natural marshes have a large stock of RC from the vegetation while dredge sediment created marshes have no plant-derived carbon initially, which accumulates slowly thereafter. Restoration practices may be improved by preserving and augmenting these deteriorating but carbon-rich natural marshes.

Louisiana↗
USGS1991

Vanadium accumulation in carbonaceous rocks: A review of geochemical controls during deposition and diagenesis

Published data relevant to the geochemistry of vanadium were used to evaluate processes and conditions that control vanadium accumulation in carbonaceous rocks. Reduction, adsorption, and complexation of dissolved vanadium favor addition of vanadium to sediments rich in organic carbon. Dissolved vanadate (V(V)) species predominate in oxic seawater and are reduced to vanadyl ion (V(IV)) by organic compounds or H2S. Vanadyl ion readily adsorbs to particle surfaces and is added to the sediment as the particles settle. The large vanadium concentrations of rocks deposited in marine as compared to lacustrine environments are the result of the relatively large amount of vanadium provided by circulating ocean water compared to terrestrial runoff. Vanadium-rich carbonaceous rocks typically have high contents of organically bound sulfur and are stratigraphically associated with phosphate-rich units. A correspondence between vanadium content and organically bound sulfur is consistent with high activities of H2S during sediment deposition. Excess H2S exited the sediment into bottom waters and favored reduction of dissolved V(V) to V(IV) or possibly V(III). The stratigraphic association of vanadiferous and phosphatic rocks reflects temporal and spatial shifts in bottom water chemistry from suboxic (phosphate concentrated) to more reducing (euxinic?) conditions that favor vanadium accumulation. During diagenesis some vanadium-organic complexes migrate with petroleum out of carbonaceous rocks, but significant amounts of vanadium are retained in refractory organic matter or clay minerals. As carbon in the rock evolves toward graphite during metamorphism, vanadium is incorporated into silicate minerals. ?? 1991.

Chemical Geology↗
USGS2021

Acetylene-fueled trichloroethene reductive dechlorination in a groundwater enrichment culture

In aquifers, acetylene (C 2 H 2 ) is a product of abiotic degradation of trichloroethene (TCE) catalyzed by in situ minerals. C 2 H 2 can, in turn, inhibit multiple microbial processes including TCE dechlorination and metabolisms that commonly support dechlorination, in addition to supporting the growth of acetylenotrophic microorganisms. Previously, C 2 H 2 was shown to support TCE reductive dechlorination in synthetic, laboratory-constructed cocultures containing the acetylenotroph Pelobacter sp. strain SFB93 and Dehalococcoides mccartyi strain 195 or strain BAV1. In this study, we demonstrate TCE and perchloroethene (PCE) reductive dechlorination by a microbial community enriched from contaminated groundwater and amended with C 2 H 2 as the sole electron donor and organic carbon source. The metagenome of the stable, enriched community was analyzed to elucidate putative community functions. A novel anaerobic acetylenotroph in the phylum Actinobacteria was identified using metagenomic analysis. These results demonstrate that the coupling of acetylenotrophy and reductive dechlorination can occur in the environment with native bacteria and broaden our understanding of biotransformation at contaminated sites containing both TCE and C 2 H 2 .

mBio↗
USGS2008

Uranium in surface waters and sediments affected by historical mining in the Denver West 1:100,000 Quadrangle, Colorado

Geochemical sampling of 82 stream waters and 87 stream sediments within mountainous areas immediately west of Denver, Colorado, was conducted by the U.S. Geological Survey in October 1994. The primary purpose was to evaluate regionally the effects of geology and past mining on the concentration and distribution of uranium. The study area contains uranium- and thorium-rich bedrock, numerous noneconomic occurrences of uranium minerals, and several uranium deposits of variable size and production history. During the sampling period, local streams had low discharge and were more susceptible to uranium-bearing acid drainage originating from historical mines of base- and precious-metal sulfides. Results indicated that the spatial distribution of Precambrian granites and metamorphic rocks strongly influences the concentration of uranium in stream sediments. Within-stream transport increases the dispersion of uranium- and thorium rich mineral grains derived primarily from granitic source rocks. Dissolved uranium occurs predominantly as uranyl carbonate complexes, and concentrations ranged from less than 1 to 65 micrograms per liter. Most values were less than 5 micrograms per liter, which is less than the current drinking water standard of 30 micrograms per liter and much less than locally applied aquatic-life toxicity standards of several hundred micrograms per liter. In local streams that are affected by uranium-bearing acid mine drainage, dissolved uranium is moderated by dilution and sorptive uptake by stream sediments. Sorbents include mineral alteration products and chemical precipitates of iron- and aluminum-oxyhydroxides, which form where acid drainage enters streams and is neutralized. Suspended uranium is relatively abundant in some stream segments affected by nearby acid drainage, which likely represents mobilization of these chemical precipitates. The 234U/238U activity ratio of acid drainage (0.95-1.0) is distinct from that of local surface waters (more than 1.05), and this distinctive isotopic composition may be preserved in iron-oxyhydroxide precipitates of acid drainage origin. The study area includes a particularly large vein-type uranium deposit (Schwartzwalder mine) with past uranium production. Stream water and sediment collected downstream from the mine's surface operations have locally anomalous concentrations of uranium. Fine-grained sediments downstream from the mine contain rare minute particles (10-20 micrometers) of uraninite, which is unstable in a stream environment and thus probably of recent origin related to mining. Additional rare particles of very fine grained (less than 5 micrometer) barite likely entered the stream as discharge from settling ponds in which barite precipitation was formerly used to scavenge dissolved radium from mine effluent.

Colorado↗
USGS2007

Ecological Investigations of the Federally Endangered Shivwits Milk-Vetch (Astragalus ampullarioides)--2006 Annual Report

Astragalus ampullarioides (Welsh) Welsh, the Shivwits milk-vetch, is an herbaceous perennial legume that was listed as federally endangered in September 2001. Known populations of this edaphic endemic species are restricted to Washington County, Utah, with the majority of occurrences found on gently sloping outcrops of the Triassic Petrified Forest Member of the Chinle Formation at the edge of the Mojave Desert. At the time of listing in 2001, surveys estimated a total of 1000 individuals for the species. In April-May 2006, surveys estimated approximately 4205 individuals distributed among six populations. Of the total number of individuals estimated in spring 2006, over 75 percent were distributed among three subpopulations in Zion National Park and approximately 60 percent occurred at a single 0.3-ha site in the Park. In addition to small population sizes and limited geographic distributions, the species is threatened to varying degrees by urbanization, livestock grazing, off-road vehicle use, and invasive exotic plants. In April 2006, the U.S. Geological Survey (USGS) initiated ecological investigations of the Shivwits milk-vetch to support conservation management and recovery of the species by the National Park Service (NPS; Zion National Park), the U.S. Fish and Wildlife Service (USFWS), the Bureau of Land Management (BLM), the Shivwits Band of the Paiute Tribe, and other cooperators such as The Nature Conservancy of Utah (TNC). To date, funding for this research has been provided by the Southwest Biological Science Center of the USGS Biological Resources Discipline, the USGS-NPS Park-Oriented Biological Support Project, and the Earth Surface Dynamics Program of the USGS Geologic Discipline. Additional logistical support has been provided by the Bureau of Land Management, Grand Staircase-Escalante National Monument. General objectives of this research are (1) to develop a better understanding of species-environment relations to support habitat modelling, future surveys for additional recovery populations, and potential efforts to establish new recovery populations; and (2) to evaluate effects of invasive exotic plants on habitat conditions and measures of milk-vetch performance. Specific objectives are to: Describe the distribution and abundance of milk-vetch populations and associated invasive exotic plant species within and outside of Zion National Park (Zion NP) in relation to geologic / geomorphic setting, soil properties, and plant community composition. In a field setting in Zion NP, conduct experiments to evaluate effects of invasive exotic plants on reproductive output and seedling establishment of A. ampullarioides across a gradient of exotic species biomass. Conduct greenhouse studies and analyze soils to evaluate effects of invasive exotic plants on soil biological properties (including mycorrhizal inocculation potential) that affect cycling and plant uptake of essential mineral nutrients. Based on environmental characteristics of known population locations, use Geographic Information System (GIS) tools to prepare a predictive habitat model that can be used to guide future surveys and efforts to evaluate sites for reintroduction efforts. This report describes 2006 progress and future plans for achieving these four objectives.

Open-File Report↗
USGS2014

Mercury speciation in the Mt. Amiata mining district (Italy): interplay between urban activities and mercury contamination

A fundamental step to evaluate the biogeochemical and eco-toxicological significance of Hg dispersion in the environment is to determine speciation of Hg in solid matrices. In this study, several analytical techniques such as scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), sequential chemical extractions (SCEs), and X-ray absorption spectroscopy (XANES) were used to identify Hg compounds and Hg speciation in samples collected from the Mt. Amiata Hg mining district, southern Tuscany, Italy. Different geological materials, such as mine waste calcine (retorted ore), soil, stream sediment, and stream water suspended particulate matter were analyzed. Results show that the samples were generally composed of highly insoluble Hg compounds such as sulphides (HgS, cinnabar and metacinnabar), and more soluble Hg halides such as those associated with the mosesite group. Other moderately soluble Hg compounds, HgCl 2 , HgO and Hg 0 , were also identified in stream sediments draining the mining area. The presence of these minerals suggests active and continuous runoff of soluble Hg compounds from calcines, where such Hg compounds form during retorting, or later in secondary processes. Specifically, we suggest that, due to the proximity of Hg mines to the urban center of Abbadia San Salvatore, the influence of other anthropogenic activities was a key factor for Hg speciation, resulting in the formation of unusual Hg-minerals such as mosesite.

Tuscany↗
USGS1981

Composition of tidal flat sediments, Willapa Bay, Washington

The purpose of this study was to characterize the modern sediments of sandy tidal flats in Willapa Bay, Washington based on their composition. Generally, clay comprises less than five percent of the sediment. Clay content increases upslope and up-estuary. Principal clay minerals are montmorillanite, illite, and chlorite; two clay mineral suites are present: (1) muddy flat suite with clay containing 44% montmorillonite, and (2) sandy flat suite with clay composition of 88% montmorillonite. Heavy minerals make up approximately four percent of the tidal flat sediment. Distribution of heavy minerals reflect their source with (1) heavy minerals most abundant near the beach on flats to the north where they were eroded out of terrace deposits, and (2) relatively greater heavy mineral concentrations (supplied by the Naselle River) across the entire flat to the south. The composition of the heavy mineral suite is mainly clinopyroxene, orthopyroxene, hornblende, epidote, and opaque minerals. This mineral suite represents several sources including rivers, ocean and ocean beaches, and reworked local Tertiary and Quaternary deposits. Tidal flat sediments are approximately 90% light minerals, mostly quartz. The light fraction also contains small quantities of lithic fragments, pumice, vegetation, and biogenic shell fragments. Tertiary and Quaternary terrace deposits are the major source of most of the light material. Fossils make up less than one percent of the bottom sediment. Two foram assemblages are present: (1) a modern shallow-water assemblage characterized by Trochammina inflata, found mainly in muddy flats near rivers, and (2) a relic deep-water assemblage (Eocene to Cretaceous) characterized by such species as Bathysiphon and Cyclammina found predominantly on the sandy flats. Macrofossils consists of shells of the modern tidal flat mollusc assemblage. Organic sediments were mostly carbon (1%). The highest concentrations of organic carbon are associated with muddy sediments near the Palix River and Pickernell Creek; overall, organic carbon concentration increased up-estuary. C/N ratios are transitional between open marine environments and marsh deposits of estuaries.

Washington↗
USGS2011

Sulfate threshold target to control methylmercury levels in wetland ecosystems

Sulfate contamination has a significant environmental implication through the stimulation of toxic hydrogen sulfide and methylmercury (MeHg) production. High levels of MeHg are a serious problem in many wetland ecosystems worldwide. In the Florida Everglades, it has been demonstrated that increasing MeHg occurrence is due to a sulfate contamination problem. A promising strategy of lowering the MeHg occurrence is to reduce the amount of sulfate entering the ecosystem. High surface water sulfate concentrations in the Everglades are mainly due to discharges from the Everglades Agricultural Area (EAA) canals. Water and total sulfur mass balances indicated that total sulfur released by soil oxidation, Lake Okeechobee and agricultural application were the major sources contributing 49,169, 35,217 and 11,775mtonsyear-1, respectively. Total sulfur loads from groundwater, levees, and atmospheric deposition contributed to a lesser extent: 4055; 5858 and 4229mtonsyear-1, respectively. Total sulfur leaving the EAA into Water Conservation Areas (WCAs) through canal discharge was estimated at 116,360mtonsyear-1, and total sulfur removed by sugarcane harvest accounted for 23,182mtonsyear-1. Furthermore, a rise in the mineral content and pH of the EAA soil over time, suggested that the current rates of sulfur application would increase as the buffer capacity of the soil increases. Therefore, a site specific numeric criterion for sulfate of 1mgL-1 was recommended for the protection of the Everglades; above this level, mercury methylation is enhanced. In parallel, sulfide concentrations in the EAA exceeded the 2??gL-1 criterion for surface water already established by the U.S. Environmental Protection Agency (EPA). ?? 2011 Elsevier B.V.

Science of the Total Environment↗
USGS1981

A lithologic-tectonic framework for the metallogenic provinces of California

The lithologic-tectonic framework of California developed principally during Mesozoic time when various terranes of oceanic crust and island-arc crust were accreted to older sialic crust, resulting in westward growth of the continent. Emplacement of great batholithic masses of granitoid rocks cutting all these crustal types also took place during the Mesozoic period. The discrete tectonostratigraphic terranes that resulted from these events and subsequent Tertiary and Quaternary volcanic events are characterized by specific types of metallic mineral deposits or, in some terranes, by the virtual absence of deposits. Lead-silver-zinc replacement-type deposits are common in the Paleozoic carbonate terrane in the eastern part of the state and occur sporadically elsewhere in the miogeoclinal and cratonal terranes but are absent from the oceanic and island-arc terranes. The vast majority of contact metasomatic tungsten deposits, including all the large ones, are in pendants of miogeoclinal rocks in the Sierra Nevada batholith, but the important Atolia deposits reside in granitoid rocks that invade oceanic terrane. Molybdenum distribution closely follows that of tungsten. All the large contact metasomatic iron deposits in California are in craton and miogeoclinal terranes, but sparse small deposits of this type also occur in island-arc terranes of the northern Sierra Nevada and eastern Klamath Mountains. Lode gold deposits, although widely scattered, show a marked preference for oceanic and island-arc terranes that have been invaded by granitoid plutons. All the major deposits, including late Tertiary bonanza deposits such as Bodie, are in such terranes. It appears that magmatic processes were responsible for mobilizing and transporting the gold, but the metal was perhaps derived from the eugeosynclinal rocks, notably the mafic volcanics. Most mercury deposits are found in the Coast Ranges, where they commonly occur in silica-carbonate rock, an alteration product of serpentinite. The deposits appear to be spatially related to the Coast Range thrust, and the source of the mercury may have been sedimentary rocks of the underlying Franciscan assemblage. Epigenetic mineralization occurred at several different times during the Mesozoic, and again during Miocene and Pliocene time. The timing of mineralization events and the distribution of various deposit types indicate that no broad-scale zoning of epigenetic deposits exists around the Sierra Nevada batholith.Syngenetic deposits are represented mainly by massive sulfides, chert-associated manganese, and chromite. The massive sulfide deposits, with one exception, are restricted to island-arc terranes, and nearly all of these deposits are in silicic volcanic rocks. They are interpreted to be syngenetic with the enclosing rocks, although some redistribution of metals may have occurred after the original deposition. The deposits occur in volcanic sequences of at least five different ages ranging from Early Devonian to Late Jurassic or Early Cretaceous and, along with their enclosing rocks, were probably formed at some distance from their present sites. Chert-associated manganese deposits occur mainly in exotic blocks of oceanic crust in melange and probably formed in fairly deep ocean environments. Chromite is confined to ultramafic rock, much of which occupies suture zones separating various accreted terranes.

Economic Geology↗
USGS2020

Wildfire-driven changes in hydrology mobilize arsenic and metals from legacy mine waste

Wildfires burning in watersheds that have been mined and since revegetated pose unique risks to downstream water supplies. A wildfire near Boulder, Colorado that burned a forested watershed recovering from mining disturbance that occurred 80-160 years ago allowed us to 1) assess arsenic and metal contamination in streams draining the burned area for a five-year period after the wildfire and 2) determine the fire-affected hydrologic drivers that convey arsenic and metals to surface water. Most metal concentrations were low in the circumneutral waters draining the burned area. Water and sediment collected from streams downstream of the burned area had elevated arsenic concentrations during and after post-fire storms. Mining-related deposits were the main source of arsenic to streams. An increased proportion of overland flow relative to infiltration after the fire mobilized arsenic- and metal- rich surface deposits and wildfire ash into streams within and downstream of the burned area. The deposition of this sediment into stream channels resulted in the remobilization of arsenic for the five-year post-fire study period. It is also possible that enhanced subsurface flow after the fire increased contact of water with arsenic-bearing minerals exposed in underground mine workings. Other studies have reported that wildfire ash can be an important source of arsenic and metals to surface waters, but wildfire ash was not an important source of arsenic in this study. Predicted increases in frequency, size, and intensity of wildfires in the western U.S., a region with widely dispersed historical mines, suggest that the intersection of legacy mining and post-wildfire hydrologic response poses an increasing risk for water supplies.

Colorado↗
USGS2009

Ultra-deep oxidation and exotic copper formation at the late pliocene boyongan and bayugo porphyry copper-gold deposits, surigao, philippines: Geology, mineralogy, paleoaltimetry, and their implications for Geologic, physiographic, and tectonic controls

The Boyongan and Bayugo porphyry copper-gold deposits are part of an emerging belt of intrusion-centered gold-rich deposits in the Surigao district of northeast Mindanao, Philippines. Exhumation and weathering of these Late Pliocene-age deposits has led to the development of the world's deepest known porphyry oxidation profile at Boyongan (600 m), and yet only a modest (30-70 m) oxidation profile at adjacent Bayugo. Debris flows, volcanic rocks, and fluviolacustrine sediments accumulating in the actively extending Mainit graben subsequently covered the deposits and preserved the supergene profiles. At Boyongan and Bayugo, there is a vertical transition from shallower supergene copper oxide minerals (malachite + azurite + cuprite) to deeper sulfide-stable assemblages (chalcocite ?? hypogene sulfides). This transition provides a time-integrated proxy for the position of the water table at the base of the saturated zone during supergene oxidation. Contours of the elevation of the paleopotentiometric surface based on this min- eralogical transition show that the thickest portions of the unsaturated zone coincided with a silt-sand matrix diatreme breccia complex at Boyongan. Within the breccia complex, the thickness of the unsaturated zone approached 600 in, whereas outside the breccia complex (e.g., at Bayugo), the thickness averaged 50 m. Contours of the paleopotentiometric surface suggest that during weathering, groundwater flowed into the breccia complex from the north, south, and east, and exited along a high permeability zone to the west. The high relief (>550 m) on the elevation of the paleopotentiometric surface is consistent with an environment of high topographic relief, and the outflow zone to the west of the breccia complex probably reflects proximity to a steep scarp intersecting the western breccia complex margin. Stable isotope paleoaltimetry has enabled estimation of the elevation of the land surface, which further constrains the physiographic setting during supergene oxidation. Isotopic measurements of oxygen in supergene kaolinite from Boyongan suggest that local paleometeoric water involved in weathering had a ??180 composition of approximately -5.7 per mil. At the latitude of the southern Philippines, this value corresponds to Pleistocene rain water condensing at elevations between 750 and 1,050 m above contemporary sea level, providing a maximum estimate for the surface elevation during weathering of the porphyry systems. Physiographic reconstuctions suggest that the deep oxidation profile at Boyongan formed in an environment of high topographic relief immediately east of a prominent (>550 m) escarpment. The high permeability contrast between the breccia complex and the surrounding wall rocks, coupled with the proximity of the breccia complex to the escarpment, led to a depressed groundwater table and a vertically extensive unsaturated zone in the immediate vicinity of Boyongan. This thick vadose zone and the low hypogene pyrite/copper sulfide ratios (0.6) at Boyongan promoted in situ oxidation of copper sulfides with only modest (<200 m) supergene remobilization of copper. In contrast, higher hypogene pyrite/chalcopyrite ratios (2.3) at Bayugo led to greater acid production during weathering and more complete leaching of copper above the base of oxidation. This process promoted significant (600 m) lateral dispersion of copper down the paleohydraulic gradient into the diatreme breccia comple, ultimately leading to the formation of an exotic copper deposit. ?? 2009 Society of Economices Geologists, Inc.

Economic Geology↗