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Results for “Mineral Resources of the United States”

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At least 541 records · Page 30Linked to original sources

USGS1996

Mineral nitrogen transformations in and under seasonal snow in a high-elevation catchment in the Rocky Mountains, United States

In an effort to understand sources of nitrate (NO 3 − ) in surface waters of high-elevation catchments, nitrogen (N) transformations in and under seasonal snow were investigated from 1993 to 1995 on Niwot Ridge, an alpine ecosystem at 3,500 m located in the Colorado Front Range of the Rocky Mountains. Ammonium (NH 4 + ) and NO 3 − labeled with 15 N applied as nonconservative tracers to the snow showed no evidence of nitrification in the snowpack. Furthermore, NH 4 + movement through the amended snowpack was highly correlated with a conservative chloride tracer ( r 2 = 0.99). In an unamended snowpack NH 4 + concentrations in meltwater before contact with the ground were highly correlated with NO 3 − concentrations ( r 2 = 0.98), which is consistent with no nitrification in the snowpack. The isotopically labeled 15 NH + 4 applied to the snowpack was found in underlying soils, showing that NH 4 + released from snow can be rapidly immobilized. Resin bag (mixed-bed ion-exchange resins) measurements (n = 22) showed that 80% of the mobile inorganic N in unamended subnivial soils was NO 3 − . Measurements of KCl-extractable inorganic N from surface soils showed that highest values were prior to the initiation of snowmelt and lowest values were during the growing season. The natural δ 15 N abundance of unamended soils was negative and ranged from −12 to −2, suggesting that atmospheric deposition of δ 15 N-depleted N is an important component of N cycling in these alpine soils. These results suggest that soil mineralization under seasonal snow, rather than snowmelt release of NO 3 − , may control NO 3 − concentrations in surface waters of high-elevation catchments.

Water Resources Research↗

USGS2011

Groundwater chemistry near an impoundment for produced water, Powder River Basin, Wyoming, USA

The Powder River Basin is one of the largest producers of coal-bed natural gas (CBNG) in the United States. An important environmental concern in the Basin is the fate of the large amounts of groundwater extracted during CBNG production. Most of this produced water is disposed of in unlined surface impoundments. A 6-year study of groundwater flow and water chemistry at one impoundment, Skewed Reservoir, has produced the most detailed data set for any impoundment in the Basin. Data were collected from a network of 21 observation wells and three suction lysimeters. A groundwater mound formed atop bedrock within initially unsaturated, unconsolidated deposits underlying the reservoir. Heterogeneity in physical and chemical properties of sediments resulted in complex groundwater flow paths and highly variable groundwater chemistry. Sulfate, bicarbonate, sodium, and magnesium were the dominant ions in all areas, but substantial variability existed in relative concentrations; pH varied from less than 3 to more than 9, and total dissolved solids concentrations ranged from less than 5000 to greater than 100,000 mg/L. Selenium was a useful tracer of reservoir water; selenium concentrations exceeded 300 μg/L in samples obtained from 18 of the 24 sampling points. Groundwater travel time from the reservoir to a nearby alluvial aquifer (a linear distance of 177 m) was calculated at 474 days on the basis of selenium concentrations. The produced water is not the primary source of solutes in the groundwater. Naturally occurring salts and minerals within the unsaturated zone, dissolved and mobilized by infiltrating impoundment water, account for most of the solute mass in groundwater. Gypsum dissolution, cation-exchange, and pyrite oxidation appear to be important reactions. The complex geochemistry and groundwater flow paths at the study site underscore the difficulty in assessing effects of surface impoundments on water resources within the Powder River Basin.

Wyoming↗

USGS1962

Bismuth in the United States, exclusive of Alaska and Hawaii

The bismuth-bearing deposits in the United States (exclusive of Alaska and Hawaii) are shown on the accompanying map. In compiling the map the deposits were classified into two categories: 1) those that have produced bismuth or are regarded as potential sources based on available information (in general, this category includes the minable base- and precious-metal depos its whose ores or concentrates are reported to contain at least 0.02 percent bismuth); and 2) deposits that have been reported to contain bismuth but which are either unappraised or are regarded as having no potential importance as sources of the metal. The map also shows by stipple pattern various segments of the southern Piedmont gold belt, which extends from northern Virginia southwestward to Alabama. Numerous gold deposits within this belt contain very minor quantities of bismuth and are, therefore, of general interest. Each deposit or group of deposits is numbered on the map by state and identified in the index. The index gives the name of each locality, the coordinates to the nearest minute of latitude and longitude, the principal metals in the ore, a very brief geologic description, and references to published reports if any. Both published and unpublished data have been used in compiling this map.

Mineral Investigations Resource Map↗

USGS1988

The ecology of the soft-bottom benthos of San Francisco Bay: a community profile

This profile, part of a series of profiles concerning coastal habitats of the United States, is a detailed examination of the soft-bottom benthos of San Francisco Bay. A U.S. Fish and Wildlife Service and California Department of Fish and Game report (1979) entitled "Protection and Restoration of San Francisco Bay Fish and Wildlife Habitat" provides clear recognition of the importance of intertidal and subtidal soft-bottom habitats and their associated organisms to the bay's birds and fishes and to the overall functioning of the estuary. The purpose of this profile is to provide a description of the structure and functioning of the benthic community in San Francisco Bay (exclusive of its tidal marshes, which are discussed by M. Josselyn [1983] in another profile). The habitats covered in this volume include all nonvegetated soft-bottom intertidal and subtidal areas of the bay between the Golden Gate and the mouths of the Sacramento and San Joaquin Rivers to the northeast, and to the southern extremity of the bay. The profile provides a reference to the scientific information concerning the animals and plants of the bay's benthic communities, their importance to the bay ecosystem, and their value as a resource measured in human terms. Because there have been few process-oriented studies of the benthos of San Francisco Bay (e.g., field and laboratory rate-measurement experiments), the material presented herein is largely descriptive. Nonetheless, we have described the processes that interconnect the various physical, chemical, and biological components of the benthic environment, and the important couplings between this environment and the water column above, with reference to research results from other estuaries where necessary. We consider the role of the benthic community as a food source for fish, aquatic birds, and humans; as a consumer or degrader of organic materials including wastes; as a recycler of minerals and nutrients; and as an accumulator of pollutants.

California↗

USGS2012

Montana Valley and Foothill Prairies Ecoregion: Chapter 6 in Status and trends of land change in the Western United States--1973 to 2000

The Montana Valley and Foothill Prairies Ecoregion comprises numerous intermountain valleys and low-elevation foothill prairies spread across the western half of Montana, on both sides of the Continental Divide (Omernik, 1987; U.S. Environmental Protection Agency, 1997). The ecoregion, which covers approximately 64,658 km 2 (24,965 mi 2 ), includes the Flathead Valley and the valleys surrounding Helena, Missoula, Bozeman, Billings, Anaconda, Dillon, and Lewistown (fig. 1). These valleys are generally characterized by shortgrass prairie vegetation and are flanked by forested mountains (Woods and others, 1999); thus, the valleys’ biotas with regards to fish and insects are comparable. In many cases, the valleys are conduits for some of the largest rivers in the state, including Clark Fork and the Missouri, Jefferson, Madison, Flathead, Yellowstone, Gallatin, Smith, Big Hole, Bitterroot, and Blackfoot Rivers (fig. 2). The Montana Valley and Foothill Prairies Ecoregion also includes the “Rocky Mountain front,” an area of prairies along the eastern slope of the northern Rocky Mountains. Principal land uses within the ecoregion include farming, grazing, and mining. The valleys serve as major transportation and utility corridors and also contain the majority of Montana’s human population. The Montana Valley and Foothill Prairies Ecoregion extends into 17 mostly rural counties throughout western Montana. Only three of the counties—Carbon, Yellowstone, and Missoula—are part of a metropolitan statistical area with contiguous built-up areas tied to an employment center. Nearly two-thirds of Montana residents live in nonmetropolitan counties (Albrecht, 2008). Ten of the counties within the ecoregion had population growth rates greater than national averages (9–13 percent) between 1970 and 2000 (table 1). Ravalli and Gallatin Counties had the highest growth rates. Population growth was largely due to amenity-related inmigration and an economy dependent on tourism, health care, and services. Counties that had population declines, such as Deer Lodge, Silver Bow, and Meagher Counties, also had declines in agriculture and mining activity, and they had railroad closures as well. Climate varies from north to south and from the east side of the Continental Divide to the west side. However, all areas are semiarid with long cold winters and short growing seasons. In the western part of the ecoregion, Beaverhead, Bitterroot, Flathead, and Lolo National Forests provide the natural resources, particularly timber, that form the economic base for towns within nearby valleys. Mineral resources from mines in and around Anaconda, Deer Lodge, and Butte have long provided an economic base for these towns (fig. 3).

Idaho;Montana;Wyoming↗

USGS1987

Oblique map of the northern Sierra Nevada, California, showing location of gold-bearing areas

More than a third of the gold produced by the United States was mined in California. The bulk of this gold was recovered from the western slope of the northern half of the Sierra Nevada between the Merced River in the south and the Feather River to the north, a distance of about 170 mi. Gold was first discovered, in this region, on the American River at Coloma in 1848, triggering the famed California gold rush. Mining was continuously active, somewhere in the area, from the discovery of gold until World War II when mining was legally prohibited. Dramatic increases in gold prices in the past decade coupled with recent advances in extractive techniques have revitalized prospecting, and major deposits are currently being explored and developed. Gold has been found in a variety of geologic environments in the region. In addition to production from the complex vein systems of the historically famous Mother Lode and associated East Gold Belt and West Gold Belt, large amounts of gold have also been recovered from the Grass Valley-Nevada City and other isolated lode districts and from Tertiary river channels and Quaternary alluvium. This oblique map illustrates the relation of the different gold-bearing environments to each other and to the general terrain of the northern Sierra Nevada. The map was derived from the 1970 U.S. Geological Survey 1:500,000-scale topographic map of California and the 1976 U.S. Geological Survey 1:500,000-scale topographic map of Nevada, using an isometrograph, a mechanical instrument that produces an oblique framework by tracing individual contours. Form lines sketched over this framework graphically portray the physiographic configuration of the region. Relief on the oblique map has a 3:1 vertical exaggeration and appears as if viewed from a 30° angle above the horizon. Locations of lode gold prospects and mines shown on the map were obtained from the U.S. Geological Survey's Mineral Resource Data System (MRDS), a computerized mineral-resource information file, and plotted in their respective locations (D.F. Huber, written commun., 1986). Some locations from two northern counties, missing from the MRDS retrival, were added. The twenty lode mines believed to be the most productive are cited in table 1. A total of nearly 4,000 sites, including both prospects and mines, were initially plotted, but about a third of those were obscured by topography on the oblique map. Locations of Tertiary river channels and gold-dredging fields were taken from published general references modified by examining specific sources and by cursory field examination. Seven of the major dredge fields are identified in table 2.

California↗

USGS1992

A geochemical investigation of selected areas in Greenville and Laurens Counties, South Carolina: Implications for mineral resources

The purpose of this study is to geochemically evaluate three areas within the Greenville 1° x 2° quadrangle (see index map) that have been shown by previous studies to contain anomalously high amounts of tin. Jackson and Moore (1992) reported the presence of cassiterite (SnO 2 )-bearing heavy-mineral concentrates from stream sediment samples that were collected during a regional geochemical reconnaissance of the Greenville 1° x 2° quadrangle. The data reported here confirm identified in selected heavy-mineral concentrate samples. In addition, anomalously high concentrations of barium, beryllium, lanthanum, and thorium are also reported for parts of the same areas. No significant mineral deposits are known to occur in the study areas. There was, however, minor production of monazite from several nearby localities (Sloan, 1908), and gold was produced from deposits in the northeastern part of Greenville County and nearby Spartanburg County (McCauley and Butler, 1966). The three areas selected for resampling are located in the Inner Piedmont physiographic province of South Carolina (see index map). The generalized tectonic setting of the region and the locations of the study is just north of Greenville, S.C. Much of it is within the moderately to steeply sloped terrane of Paris Mountain State Park where elevations reach approximately 600 m. Simpsonville, S.C., is neat the center of the second study area, and the southernmost study area is near Hickory Tavern, S.C. Both the Simpsonville and Hickory Tavern study areas are in more gently rolling Piedmont terrane. Each of the sampled areas is drained by tributaries of the Enoree and Reedy Rivers. Parts of three different thrust sheets underlie the region covered by this study (fig. 1); in ascending structural position, they are the Six Mile, Paris Mountain, and Laurens thrust sheets (Nelson and others, 1987). Nelson (1988, p. 7) described the contacts between these sheets as being along unnamed faults. The rocks in and around the study areas have undergone sillimanite-muscovite-grade metamorphism (Nelson, 1988, p. 9). Nelson (1988, p. 13) reports that the Six Mile thrust sheet was metamorphosed about 344 Ma. The geology of these sheets as described in this study, including geologic contacts, rock descriptions, and unit names, generally follows that of Nelson and others (1987, 1989). Within the Paris Mountain study area, rocks of the Paris Mountain thrust sheet predominate (fig. 2) and consist of a biotite-muscovite-sillimanite schist (EZsp) that has extensive lenses of fine- to medium- grained biotite granite gneiss (Pzgp). Areas of biotite granite gneiss that occur in the southern part of the Paris Mountain study area contain extensive pegmatitic and leucogranitic phases. These pegmatitic zones consist mostly of coarse-grained microcline feldspar and quartz with minor amounts of muscovite, biotite, and garnet. Smaller pegmatite lenses (<0.5 m thick) that occur within the biotite-muscovite-sillimanite schist of the Paris Mountain study area are generally of similar mineralogy, although some contain tourmaline crystals up to 5 cm in length. The Six Mile thrust sheet underlies the northern edge of the Paris Mountain study area, where it is composed of gneissic biotitic granites of the Caesars Head Granite (figs. 1 and 2). The northwestern part of the Simpsonville study area (figs. 1 and 3), within the Paris Mountain thrust sheet, is underlain by a biotite-muscovite-sillimanite schist (EZsp) that contains lenses of biotite granite gneiss (Pzgp). In the southeastern part of the Simpsonville study area, within the Laurens thrust sheet, biotite gneiss (EZgl), biotite granite gneiss (Pzgf), and minor amphibolite (EZal) are interlayered biotite (EZgl), granite gneiss (Dgg), and amphibolite (EZal) of the Laurens thrust sheet (fig. 4).

South Carolina↗

USGS2007

Geochemistry of Selected Coal Samples from Sumatra, Kalimantan, Sulawesi, and Papua, Indonesia

Introduction Indonesia is an archipelago of more than 17,000 islands that stretches astride the equator for about 5,200 km in southeast Asia (figure 1) and includes major Cenozoic volcano-plutonic arcs, active volcanoes, and various related onshore and offshore basins. These magmatic arcs have extensive Cu and Au mineralization that has generated much exploration and mining in the last 50 years. Although Au and Ag have been mined in Indonesia for over 1000 years (van Leeuwen, 1994), it was not until the middle of the nineteenth century that the Dutch explored and developed major Sn and minor Au, Ag, Ni, bauxite, and coal resources. The metallogeny of Indonesia includes Au-rich porphyry Cu, porphyry Mo, skarn Cu-Au, sedimentary-rock hosted Au, epithermal Au, laterite Ni, and diamond deposits. For example, the Grasberg deposit in Papua has the world's largest gold reserves and the third-largest copper reserves (Sillitoe, 1994). Coal mining in Indonesia also has had a long history beginning with the initial production in 1849 in the Mahakam coal field near Pengaron, East Kalimantan; in 1891 in the Ombilin area, Sumatra, (van Leeuwen, 1994); and in South Sumatra in 1919 at the Bukit Asam mine (Soehandojo, 1989). Total production from deposits in Sumatra and Kalimantan, from the 19thth century to World War II, amounted to 40 million metric tons (Mt). After World War II, production declined due to various factors including politics and a boom in the world-wide oil economy. Active exploration and increased mining began again in the 1980's mainly through a change in Indonesian government policy of collaboration with foreign companies and the global oil crises (Prijono, 1989). This recent coal revival (van Leeuwen, 1994) has lead Indonesia to become the largest exporter of thermal (steam) coal and the second largest combined thermal and metallurgical (coking) coal exporter in the world market (Fairhead and others, 2006). The exported coal is desirable as it is low sulfur and ash (generally <1 and < 10 wt.%, respectively). Coal mining for both local use and for export has a very strong future in Indonesia although, at present, there are concerns about the strong need for a major revision in mining laws and foreign investment policies (Wahju, 2004; United States Embassy Jakarta, 2004). The World Coal Quality Inventory (WoCQI) program of the U.S. Geological Survey (Tewalt and others, 2005) is a cooperative project with about 50 countries (out of 70 coal-producing countries world-wide). The WoCQI initiative has collected and published extensive coal quality data from the world's largest coal producers and consumers. The important aspects of the WoCQI program are; (1) samples from active mines are collected, (2) the data have a high degree of internal consistency with a broad array of coal quality parameters, and (3) the data are linked to GIS and available through the world-wide-web. The coal quality parameters include proximate and ultimate analysis, sulfur forms, major-, minor-, and trace-element concentrations and various technological tests. This report contains geochemical data from a selected group of Indonesian coal samples from a range of coal types, localities, and ages collected for the WoCQI program.

Open-File Report↗

USGS2023

A novel non-destructive workflow for examining germanium and co-substituents in ZnS

A suite of complementary techniques was used to examine germanium (Ge), a byproduct critical element, and co-substituent trace elements in ZnS and mine wastes from four mineral districts where germanium is, or has been, produced within the United States. This contribution establishes a comprehensive workflow for characterizing Ge and other trace elements, which captures the full heterogeneity of samples through extensive pre-characterization. This process proceeded from optical microscopy, to scanning electron microscopy and cathodoluminescence (CL) imaging, to electron microprobe analysis, prior to synchrotron-based investigations. Utilizing non-destructive techniques enabled reanalysis, which proved essential for verifying observations and validating unexpected results. In cases where the Fe content was <0.3 wt% in ZnS, cathodoluminescence imaging proved to be an efficient means to qualitatively identify trace element zonation that could then be further explored by other micro-focused techniques. Micro-focused X-ray diffraction was used to map the distribution of the non-cubic ZnS polymorph, whereas micro-focused X-ray fluorescence (μ-XRF) phase mapping distinguished between Ge 4+ hosted in primary ZnS and a weathering product, hemimorphite [Zn 4 Si 2 O 7 (OH) 2 ·H 2 O]. Microprobe data and μ-XRF maps identified spatial relationships among trace elements in ZnS and implied substitutional mechanisms, which were further explored using Ge and copper (Cu) X-ray absorption near-edge spectroscopy (XANES). Both oxidation states of Ge (4+ and 2+) were identified in ZnS along with, almost exclusively, monovalent Cu. However, the relative abundance of Ge oxidation states varied among mineral districts and, sometimes, within samples. Further, bulk XANES measurements typically agreed with micro-focused XANES (μ-XANES) spectra, but unique micro-environments were detected, highlighting the importance of complementary bulk and micro-focused measurements. Some Ge μ-XANES utilized a high energy resolution fluorescence detector, which improved spectral resolution and spectral signal-to-noise ratio. This detector opens new opportunities for exploring byproduct critical elements in complex matrices. Overall, the non-destructive workflow employed here can be extended to other byproduct critical elements to more fully understand fundamental ore enrichment processes, which have practical implications for critical element exploration, resource quantification, and extraction.

Frontiers in Earth Science↗

USGS2017

Formation of Fe-Mn crusts within a continental margin environment

This study examines Fe-Mn crusts that form on seamounts along the California continental-margin (CCM), within the United States 200 nautical mile exclusive economic zone. The study area extends from approximately 30° to 38° North latitudes and from 117° to 126° West longitudes. The area of study is a tectonically active northeast Pacific plate boundary region and is also part of the North Pacific Subtropical Gyre with currents dominated by the California Current System. Upwelling of nutrient-rich water results in high primary productivity that produces a pronounced oxygen minimum zone. Hydrogenetic Fe-Mn crusts forming along the CCM show distinct chemical and mineral compositions compared to open-ocean crusts. On average, CCM crusts contain more Fe relative to Mn than open-ocean Pacific crusts. The continental shelf and slope release both Fe and Mn under low-oxygen conditions. Silica is also enriched relative to Al compared to open-ocean crusts. This is due to the North Pacific silica plume and enrichment of Si along the path of deep-water circulation, resulting in Si enrichment in bottom and intermediate waters of the eastern Pacific. The CCM Fe-Mn crusts have a higher percentage of birnessite than open-ocean crusts, reflecting lower dissolved seawater oxygen that results from the intense coastal upwelling and proximity to zones of continental slope pore-water anoxia. Carbonate fluorapatite (CFA) is not present and CCM crusts do not show evidence of phosphatization, even in the older sections. The mineralogy indicates a suboxic environment under which birnessite forms, but in which pH is not high enough to facilitate CFA deposition. Growth rates of CCM crusts generally increase with increasing water depth, likely due to deep-water Fe sources mobilized from reduced shelf and slope sediments. Many elements of economic interest including Mn, Co, Ni, Cu, W, and Te have slightly or significantly lower concentrations in CCM crusts relative to crusts from the Pacific Prime Crust Zone and other open-ocean basins. However, concentrations of total rare earth elements and yttrium average only slightly lower contents and in the future may be a strategic resource for the U.S.

California↗

USGS2010

Geologic map of the Bartlett Springs Fault Zone in the vicinity of Lake Pillsbury and adjacent areas of Mendocino, Lake, and Glenn Counties, California

The Lake Pillsbury area lies in the eastern part of the northern California Coast Ranges, along the east side of the transform boundary between the Pacific and North American plates (fig. 1). The Bartlett Springs Fault Zone is a northwest-trending zone of faulting associated with this eastern part of the transform boundary. It is presently active, based on surface creep (Svarc and others, 2008), geomorphic expression, offset of Holocene units (Lienkaemper and Brown, 2009), and microseismicity (Bolt and Oakeshott, 1982; Dehlinger and Bolt, 1984; DePolo and Ohlin, 1984). Faults associated with the Bartlett Springs Fault Zone at Lake Pillsbury are steeply dipping and offset older low to steeply dipping faults separating folded and imbricated Mesozoic terranes of the Franciscan Complex and interleaved rocks of the Coast Range Ophiolite and Great Valley Sequence. Parts of this area were mapped in the late 1970s and 1980s by several investigators who were focused on structural relations in the Franciscan Complex (Lehman, 1978; Jordan, 1975; Layman, 1977; Etter, 1979). In the 1980s the U.S. Geological Survey (USGS) mapped a large part of the area as part of a mineral resource appraisal of two U.S. Forest Service Roadless areas. For evaluating mineral resource potential, the USGS mapping was published at a scale of 1:62,500 as a generalized geologic summary map without a topographic base (Ohlin and others, 1983; Ohlin and Spear, 1984). The previously unpublished mapping with topographic base is presented here at a scale of 1:30,000, compiled with other mapping in the vicinity of Lake Pillsbury. The mapping provides a geologic framework for ongoing investigations to evaluate potential earthquake hazards and structure of the Bartlett Springs Fault Zone. This geologic map includes part of Mendocino National Forest (the Elk Creek Roadless Area) in Mendocino, Glenn, and Lake Counties and is traversed by several U.S. Forest Service Routes, including M1 and M6 (fig. 2). The study area is characterized by northwest-trending ridges separated by steep-sided valleys. Elevations in this part of the Coast Ranges vary from 1,500 ft (457 m) to 6,600 ft (2,012 m), commonly with gradients of 1,000 ft per mile (90 m per km). The steep slopes are covered by brush, grass, oak, and conifer forests. Access to most of the area is by county roads and Forest Service Route M6 from Potter Valley to Lake Pillsbury and by county road and Forest Service Route M6 and M1 from Upper Lake and State Highway 20. From the north, State Highway 261 provides access from Covelo. Forest Service Route M1 trends roughly north from its intersection with Route M6 south of Hull Mountain and through the Elk Creek and Black Butte Roadless areas to State Highway 261. Side roads used for logging and jeep trails provide additional access in parts of the area.

Open-File Report↗

USGS1983

Hydrogeologic and water-quality characteristics of the Prairie du Chien-Jordan aquifer, Southeast Minnesota

Quality of water in the Prairie du Chien-Jordan aquifer is generally good, except for some localized contamination, Coal-tar derivatives that contaminate the aquifer in St. Louis Park, a western suburb in the Twin Cities Metropolitan Area, pose the most serious threat to water quality. High hardness and iron concentration limit suitability for municipal and industrial use in parts of extreme southeast Minnesota. Confining beds of bedrock and drift, however, protect most of the aquifer from surface pollutants. The Prairie du Chien-Jordan aquifer is part of a sequence of sedimentary bedrock units in southeast Minnesota. The Jordan Sandstone is a white to yellow, fine- to coarse-grained sandstone. The Prairie du Chien Group comprises two dolomitic formations that are vuggy and fractured and interbedded with thin layers of shale. The aquifer formations were deposited in Paleozoic seas that occupied the Hollandale embayment. The aquifer dips toward the interior of the embayment where it is as deep as 750 feet below land surface and as thick as 500 feet. Permeability is secondary in the Prairie du Chien Group because of solution cavities and fractures, and intergranular in the Jordan Sandstone. Water in the aquifer is confined except in the eastern part. Water generally flows to the north and east into the Minnesota and Mississippi Rivers. A ground-water divide separates part of the flow southward into Iowa. This aquifer supplies more water than any other bedrock one in the State. Calcium magnesium bicarbonate type water is most common in the aquifer. Calcium and sulfate and, to a lesser degree sodium and magnesium, increase in concentration toward the southwestern part of the study area. Bicarbonate concentration, on the other hand, decreases toward the southwestern corner of the study area. Leakage from overlying Cretaceous deposits is the source of much of the sulfate and other minerals in the southwest. This report is one of a series on the hydrogeology and water quality of the 14 principal aquifers in Minnesota prepared by the U. S. Geological Survey. The U. S. Environmental Protection Agency requested these studies because of the need for information to develop its Underground Injection Control Program.

Minnesota↗

USGS2006

Submarine ground-water discharge: nutrient loading and nitrogen transformations

Eutrophication of coastal waters due to nonpoint source land-derived nitrogen (N) loads is a worldwide phenomenon and perhaps the greatest agent of change altering coastal ecology (National Research Council, 2000; Howarth and others, 2000). Within the United States, a majority of estuaries have been determined to be moderately to severely impaired by eutrophication associated with increasing nutrient loads (Bricker and others, 1999). In coastal watersheds with soils of high hydraulic conductivity and permeable coastal sediments, ground water is a major route of transport of freshwater and its solutes from land to sea. Freshwater flowing downgradient from aquifers may either discharge from a seepage face near the intertidal zone, or flow directly into the sea as submarine ground-water discharge (SGD) (fig. 1). In the coastal aquifer, entrainment of saline pore water occurs prior to discharge, producing a gradient in ground-water salinity from land to sea, referred to as a subterranean estuary (Moore, 1999). In addition, processes including density-driven flow and tidal pumping create brackish and saline ground-water circulation. Hence, submarine ground-water discharge often consists of a substantial amount of recirculating seawater. Mixing of fresh and saline ground waters in the context of coastal sediments may alter the chemical composition of the discharging fluid. Depending on the biogeochemical setting, removal of fixed N due to processes leading to N 2 (dinitrogen gas) production in the nearshore aquifer and subterranean estuary may significantly attenuate land-derived N loads; or, processes such as ion exchange and tidal pumping in the subterranean estuary may substantially accelerate the transport of both land-derived and sediment re-mineralized N to estuarine water columns. As emphasized by Burnett and others (2001, 2002), a fundamental problem in evaluating the importance of ground-water discharge in marine geochemical budgets is the difficulty of collecting samples across the salinity gradients of coastal aquifers. In addition, locating and quantifying rates of submarine ground-water discharge remains a challenge due to the diffuse and spatially and temporally heterogeneous nature of discharge. As a result, with regard to the study of biogeochemical cycles and chemical loads to coastal waters, the seepage face and subterranean estuary are relatively new and under-studied zones in the aquatic cascade from watershed to sea. Processes occurring in those zones must be understood and considered for proper modeling and management of coastal water resources.

Fact Sheet↗

USGS2017

Rare-earth elements

The rare-earth elements (REEs) are 15 elements that range in atomic number from 57 (lanthanum) to 71 (lutetium); they are commonly referred to as the “lanthanides.” Yttrium (atomic number 39) is also commonly regarded as an REE because it shares chemical and physical similarities and has affinities with the lanthanides. Although REEs are not rare in terms of average crustal abundance, the concentrated deposits of REEs are limited in number. Because of their unusual physical and chemical properties, the REEs have diverse defense, energy, industrial, and military technology applications. The glass industry is the leading consumer of REE raw materials, which are used for glass polishing and as additives that provide color and special optical properties to the glass. Lanthanum-based catalysts are used in petroleum refining, and cerium-based catalysts are used in automotive catalytic converters. The use of REEs in magnets is a rapidly increasing application. Neodymium-iron-boron magnets, which are the strongest known type of magnets, are used when space and weight are restrictions. Nickel-metal hydride batteries use anodes made of a lanthanum-based alloys. China, which has led the world production of REEs for decades, accounted for more than 90 percent of global production and supply, on average, during the past decade. Citing a need to retain its limited REE resources to meet domestic requirements as well as concerns about the environmental effects of mining, China began placing restrictions on the supply of REEs in 2010 through the imposition of quotas, licenses, and taxes. As a result, the global rare-earth industry has increased its stockpiling of REEs; explored for deposits outside of China; and promoted new efforts to conserve, recycle, and substitute for REEs. New mine production began at Mount Weld in Western Australia, and numerous other exploration and development projects noted in this chapter are ongoing throughout the world. The REE-bearing minerals are diverse and often complex in composition. At least 245 individual REE-bearing minerals are recognized; they are mainly carbonates, fluorocarbonates, and hydroxylcarbonates (n = 42); oxides (n = 59); silicates (n = 85); and phosphates (n = 26). Many of the world’s significant REE deposits occur in carbonatites, which are carbonate igneous rocks. The REEs also have a strong genetic association with alkaline magmatism. The systematic geologic and chemical processes that explain these observations are not well understood. Economic or potentially economic REE deposits have been found in (a) carbonatites, (b) peralkaline igneous systems, (c) magmatic magnetite-hematite bodies, (d) iron oxide-copper-gold (IOCG) deposits, (e) xenotime-monazite accumulations in mafic gneiss, (f) ion-absorption clay deposits, and (g) monazite-xenotime-bearing placer deposits. Carbonatites have been the world’s main source for the light REEs since the 1960s. Ion-adsorption clay deposits in southern China are the world’s primary source of the heavy REEs. Monazite-bearing placer deposits were important sources of REEs before the mid-1960s and may be again in the future. In recent years, REEs have been produced from large carbonatite bodies mined at the Mountain Pass deposit in California and, in China, at the Bayan Obo deposit in Nei Mongol Autonomous Region, the Maoniuping deposit in Sichuan Province, the Daluxiang deposit in Sichuan Province, and the Weishan deposit in Anhui Province. Alkaline igneous complexes have recently been targeted for exploration because of their enrichments in the heavy REEs. Information relevant to the environmental aspects of REE mining is limited. Little is known about the aquatic toxicity of REEs. The United States lacks drinking water standards for REEs. The concentrations of REEs in environmental media are influenced by their low abundances in crustal rocks and their limited solubility in most groundwaters and surface waters. The scarcity of sulfide minerals, including pyrite, minimizes or eliminates concerns about acid-mine drainage for carbonatite-hosted deposits and alkaline-intrusion-related REE deposits. For now, insights into environmental responses of REE mine wastes must rely on predictive models.

Professional Paper↗

USGS1984

Geologic and hydrologic characterization and evaluation of the Basin and Range Province relative to the disposal of high-level radioactive waste: Part I, Introduction and guidelines

The U.S. Geological Survey's program for geologic and hydrologic evaluation of physiographic provinces to identify areas potentially suitable for locating repository sites for disposal of high-level nuclear wastes was announced to the Governors of the eight States in the Basin and Range Province on May 5, 1981. Representatives of Arizona, California, Idaho, New Mexico, Nevada, Oregon, Texas, and Utah, were invited to cooperate with the Federal Government in the evaluation process. Each Governor was requested to nominate an Earth scientist to represent the State in a province working group composed of State and U.S. Geological Survey representatives. This report, Part I of a three-part report, provides the background, introduction and scope of the study. This part also includes a discussion of geologic and hydrologic guidelines that will be used in the evaluation process and illustrates geohydrologic environments and the effect of individual factors in providing multiple natural barriers to radionuclide migration. Part II is a reconnaissance characterization of the geologic and hydrologic factors to be used in the initial screening of the Basin and Range Province. Part III will be the initial evaluation of the Province and will identify regions that appear suitable for further study. The plan for study of the Province includes a stepwise screening process by which successively smaller land units are considered in increasing detail. Each step involves characterization of the geology and hydrology and selection of subunits for more intensive characterization. Selection of subunits for further study is by evaluation of geologic and hydrologic conditions following a set of guidelines. By representation on the Province Working Group, the States participate in a consultation and review role in: (1) Establishing geologic and hydrologic guidelines, and (2) characterizing and evaluating the Province. The States also participate in compilation of geologic and hydrologic data used in characterizing the Province. The current (1983) needs for a high-level radioactive waste repository include: (1) Disposal in a mined repository; (2) retrievability of the waste for as much as 50 years; and (3) confidence of isolation of the waste from the accessible environment. Isolation of the waste needs to be assured using geologic and hydrologic conditions that: (1) Minimize risk of inadvertent future intrusions by man; (2) minimize the possibility of disturbance by processes that would expose the waste or increase its mobility; and (3) provide a system of natural barriers to the migration of waste by ground water. The guidelines adopted by the Province Working Group are designed to provide a standard with which these conditions can be compared. The guidelines can be grouped into four principal categories: (1) Potential host media, (2) ground-water conditions, (3) tectonic conditions, and. (4) occurrence of natural resources. Ideally the host medium constitutes the first natural barrier to migration of radionculides. The host medium ideally should be a rock type that prevents or retards dissolution and transport of radionuclides. Rocks in both the saturated and unsaturated zones may have desirable characteristics for host media. Rocks-other than the host-in the ground-water flow path from the repository ideally should be major barriers to radionuclide migration. Confining beds of low permeability might be present to retard the rate of flow between more permeable beds. Additionally, sorption of radionuclides by materials such as clays and zeolites in the flow path can further retard the flow of radionuclides by several orders of magnitude. Tectonic conditions in an area should not present a probable cause for exhumation or increased mobility of radioactive waste. Natural resources are a factor for consideration because of the problem of future human intrusion and exposure to radioactivity in the quest for minerals, oil, gas, water, and geothermal resources. The ultimate evaluation of the suitability of a geohydrologic environment for developing a mined repository needs to assess all geologic and hydrologic characteristics and their interaction in providing confidence that a geohydrologic environment will effectively isolate radionuclides from human access. Several hypothetical settings with typical geohydrologic conditions in the Basin and Range Province are used to illustrate the effect of multiple barriers in the isolation of radionuclides.

Arizona, California, Idaho, Nevada, New Mexico, Or↗

USGS1979

Principal thorium resources in the United States

Resources were assessed for thorium in the higher grade and better known deposits in the United States in: (1) veins, (2) massive carbonatites, (3) stream placers of North and South Carolina, and (4) disseminated deposits. Thorium resources for the first three categories were divided into reserves and probable potential resources. Each of these then were separated into the following cost categories: (1) the amount of ThO2 producible at less than $15 per pound, (2) the amount producible at between $15 and $30 per pound, and (3) the amount producible at more than $50 per pound. The type of mining and milling needed at each deposit determines the capital, operating, and fixed costs of both mining and milling. Costs start with the clearing of land and are carried through to the final product, which for all deposits is ThO2. Capital costs of mining are affected most by the type of mining and the size of the mine. Those of milling are affected most by the kind of mill, its size, and whether or not extra circuits are needed for the separation of rare earths or some other byproduct. Veins, massive carbonatites, and stream placers of North and South Carolina have reserves of 188,000 short tons of ThO2 and probable potential resources of 505,000 tons of ThO2. Approximately half of the reserves and probable potential resources can be produced at less than $30 per pound of ThO2. Veins are the highest grade source in the United States and have total reserves of 142,000 tons of ThO2 and probable potential resources of 343,000 tons. About 90 percent of the reserves and 91 percent of the probable potential resources can be produced at less than $15 per pound of ThO2. Seven vein districts were evaluated: (1) Lemhi Pass, Mont.-Idaho, (2) Wet Mountains, Colo., (3) Powderhorn, Colo., (4) Hall Mountain, Idaho, (5) Diamond Creek, Idaho, (6) Bear Lodge Mountains, Wyo. and (7) Mountain Pass, Calif. Eighty-seven percent of the total reserves and probable potential resources are in the Lemhi Pass and Wet Mountains Districts. The first district has reserves of 68,000 tons of ThO2 and probable potential resources of 124,000 tons that can be produced at less than $15 per pound; the second district has 54,000 tons of reserves and 141,000 tons of probable potential resources producible at less than $15 per pound. Rare earths are a common byproduct, and in many veins they are from one-half to several times as abundant as thorium. Massive carbonatite bodies are large-tonnage low-grade deposits. Thorium in these deposits would be a byproduct either of rare earth or of niobium mining. The Iron Hill carbonatite body in the Powderhorn district, Colorado, and the Sulfide Queen carbonatite body in the Mountain Pass district, California, were evaluated. These two deposits contain 40,800 tons of ThO2 in reserves and 125,000 tons of ThO2 in probable potential resources. More than 80 percent of this total is in the Iron Hill carbonatite. This thorium is entirely a byproduct and is producible at less than $15 per pound of ThO2. The Sulphide Queen massive carbonatite deposit was being mined in 1977 for rare earths, and thorium could be recovered by adding an extra circuit to the existing mill. Stream placers in North and South Carolina occur both in the Piedmont and just east of the Fall Line. The reserves of these deposits total 5,270 tons of ThO2, and the probable potential resources are 36,800 tons of ThO2. The Piedmont placers are all too small to produce ThO2 at a cost of less than $50 per pound. One placer on Hollow Creek, S.C., just east of the Fall Line had reserves of 2,040 tons of ThO2 that is producible at between $15 and $30 per pound. Thorium occurs in monazite in these placers. Other heavy minerals that would be recovered with the monazite include rutile, zircon, and ilmenite. In addition to thorium, monazite contains large amounts of rare earths and small amounts of uranium; both can be recovered during the process that separates thorium fr

Circular↗

USGS1979

Summary appraisals of the nation's ground-water resources– South Atlantic-Gulf region

Precipitation in the 270,000-square-mile South Atlantic-Gulf Region ranges from 44 to 80 inches, and the average runoff is about 15 inches. The ground-water discharge that forms the base flow of streams is conservatively estimated to be about 78,000 million gallons per day the equivalent of about 6 inches of precipitation. On this basis, the regional sustained ground-water supply is about 286,000 gallons per day per square mile. Projected water use through 2020 indicates that about 10 percent of the supply will meet the region's requirement for ground water. Enormous quantities of ground water are available in the South Atlantic-Gulf States in the extensive aquifers that underlie the Coastal Plain province. Large supplies of ground water can be developed also in places in the Cumberland Plateau and the Valley and Ridge provinces. In the Piedmont and Blue Ridge provinces ground water is available only in modest quantities. The principal Coastal Plain aquifers consist largely of deltaic sand and gravel deposits of Cretaceous to Quaternary age; however, a notable exception is the highly permeable Tertiary limestone aquifer, which underlies parts of four States. Ground water in the Blue Ridge and the Valley and Ridge provinces is available from openings along fissures and joints in consolidated rocks and from the unconsolidated sand and gravel in the residuum and alluvium that overlie the bedrock. In parts of these areas faulting and folding has created favorable conditions for the development of moderate supplies of ground water. In the Piedmont province modest quantities of water are available from joints and fractures. Solution cavities in massive limestone units in some areas underlying the Cumberland Plateau section yield very large quantities of ground water. Most of the major Coastal Plain aquifers are recharged where they are exposed and water moves downdip to the south. The general direction of ground-water movement in the Coastal Plain aquifers is seaward. There is, however, movement of water vertically and laterally that affects pressure and quality in every aquifer. Ground water of good chemical and physical quality is available generally except in a small area in western Alabama and eastern Mississippi and in some small coastal areas. Freshwater extends to depths of slightly more than 3,000 feet in some areas. In many areas, water can be produced that does not require any treatment for general use. The more common objectionable constituents or properties are excessive iron, fluoride, hardness, color, and acidity. Contamination or pollution of ground water is not a major regional problem, but it is significant in local areas. Many of these local problems of contamination were the result of earlier improper disposal of oil-field and industrial waste. Saltwater intrusion either directly from the sea or from estuaries has been reported in every State in the region, and the potential for the proliferation of this problem is very large. The relationship of ground water and surface water is significant at many places in the region where large ground-water withdrawals affect swamps, lakes, and the flow of streams and springs. There is a potential in some areas for using ground water during dry periods for low-flow augmentation of stream supplies. In other areas it is feasible to recharge ground-water reservoirs artificially by means of injection wells, pits, and water spreading. Although large water-level declines caused by withdrawals have occurred locally, water-level changes have been small or modest when considered on a regional basis owing to the abundant rainfall and favorable recharge conditions. The saline-water resources of the region are known to be extremely large. In some areas where the availability of freshwater is limited, saline ground water is available for desalinization to supplement freshwater supplies. Also, the saline aquifers are potential storage sites for injected freshwater. Ground-water problems generally are not severe. Critical situations are restricted to areas where large quantities of ground water are being withdrawn or where aquifers are contaminated by oil-field or industrial waste. Large withdrawals in coastal areas have caused some saltwater intrusion. In other localities, highly mineralized water may have migrated along fault zones to freshwater aquifers. Many of the present problems can be resolved or ameliorated by redistributing withdrawals or developing alternative water sources.

Alabama, Florida, Georgia, Mississippi, North Caro↗

USGS2017

Tin

Tin (Sn) is one of the first metals to be used by humans. Almost without exception, tin is used as an alloy. Because of its hardening effect on copper, tin was used in bronze implements as early as 3500 B.C. The major uses of tin today are for cans and containers, construction materials, transportation materials, and solder. The predominant ore mineral of tin, by far, is cassiterite (SnO 2 ). In 2015, the world’s total estimated mine production of tin was 289,000 metric tons of contained tin. Total world reserves at the end of 2016 were estimated to be 4,700,000 metric tons. China held about 24 percent of the world’s tin reserves and accounted for 38 percent of the world’s 2015 production of tin. The proportion of scrap used in tin production is between 10 and 25 percent. Unlike many metals, tin recycling is relatively efficient, and the fraction of tin in discarded products that get recycled is greater than 50 percent. Only about 20 percent of the world’s identified tin resources occur as primary hydrothermal hard-rock veins, or lodes. These lodes contain predominantly high-temperature minerals and almost invariably occur in close association with silicic, peraluminous granites. About 80 percent of the world’s identified tin resources occur as unconsolidated secondary or placer deposits in riverbeds and valleys or on the sea floor. The largest concentration of both onshore and offshore placers is in the extensive tin belt of Southeast Asia, which stretches from China in the north, through Thailand, Burma (also referred to as Myanmar), and Malaysia, to the islands of Indonesia in the south. Furthermore, tin placers are almost always found closely allied to the granites from which they originate. Other countries with significant tin resources are Australia, Bolivia, and Brazil. Most hydrothermal tin deposits belong to what can be thought of as a superclass of porphyry-greisen deposits. The hydrothermal tin deposits are all characterized by a close spatial, temporal, and genetic association with highly differentiated, peraluminous porphyritic granite intrusions. The intrusions form pegmatites; disseminated ore; parallel or subparallel, greisen-bordered sheeted veins that either cross-cut the intrusion or are peripheral to it; skarns; and (or) limestone replacements that contain different amounts of cassiterite, molybdenite, and wolframite. The tectonic settings of tin-bearing granites are relatively well understood and of limited variety. Tin and tungsten deposits and their associated igneous rocks are found mainly in continental settings. Historically, prospecting for tin has been carried out by the time-honored methods of panning, drilling, trenching, and assaying. Geophysical and geochemical surveys have been employed to cover large areas more rapidly, isolating areas of possible tin deposits so that drilling can be more effective and less costly. Elemental concentrations and relationships of the lithophile elements, especially barium, lithium, niobium, potassium, rubidium, and zirconium, are the most reliable chemical indicators of ore-forming processes and tin-bearing potential. The average human diet includes an intake of about 10 milligrams per day of tin. Ingestion of tin in significantly greater amounts than 10 milligrams per day may lead to a stomach ache, anemia, and liver and kidney problems. Exposure to some organo-tin compounds can interfere with brain and nervous system function and, in severe cases, can cause death. Extended inhalation of tin oxide—an issue mainly for those people who work in the tin industry—results in a higher potential to develop stannosis, which is a mild disease of the lungs caused by the inhalation of tin-bearing dust. Inorganic tin is poorly absorbed by the body, and no evidence exists for the carcinogenicity of metallic tin and tin compounds in humans. Most placer tin deposits are mined by open pit and (or) dredging methods. Mining of alluvial placers in modern streambeds and riverbeds is likely to increase the amount of sediment delivered downstream. This, combined with potential diversion of rivers and streams, may negatively affect downstream ecosystems. Many of the placer deposits located in Burma, Indonesia, Malaysia, and Thailand are located offshore. Most offshore placer tin deposits are mined by dredging methods, which have the potential to negatively affect benthic, midwater, and pelagic ecosystems. In a congressionally mandated U.S. Department of Defense study of strategic minerals published in 2013, tin has the greatest shortfall amount (insufficient supply to meet demand) at \$416 million; this amount is more than twice that of antimony ($182 million), which is the strategic mineral with the next largest shortfall amount (U.S. Department of Defense, 2013). The United States imported 75 percent of its tin supply in 2015. During the period 2012–15, these imports were from, in descending order of amount imported, Peru, Indonesia, Malaysia, and Bolivia. A promising advancement concerning research into the origin of tin deposits is the recent development of a reliable method of analyzing tin isotopes in cassiterite. Although the mechanism of transport and deposition of tin is fairly well understood, the means by which tin is incorporated into the parent magma at the points of magma generation and ascent needs further investigation. Tin metallogenic provinces worldwide are well known. Consequently, any undiscovered tin deposits will likely be spatially close to known deposits or extensions of the same.

Professional Paper↗