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At least 685 records · Page 38Linked to original sources
USGS1964

Bottom sediments of Saginaw Bay, Michigan

Saginaw Bay is a southwest extension of Lake Huron on the east shore of the Southern Peninsula of Michigan. It is a shallow-water derivative of the Pleistocene Lake Saginaw. Sixty-one bottom samples were collected on a semigrid pattern and analyzed physically. Findings were treated statistically. Sediments range in size from large pebbles to clay. Medium- to fine-grained clear quartz sand is common to all parts of the bay. Currents and wave action are primarily responsible for both median diameter and sorting distribution patterns. Only a very general correlation can be established between depth and median diameter. Heavy minerals occur in abundance locally and show an affinity to shallow-water areas subject to prevailing currents. Shape also locally determines heavy mineral concentrations. Only general conclusions can be established from roundness and sphericity and acid-soluble content. Increased organic content is correlative with quiet water environments. The shallow-water, heterogeneous nature of Saginaw Bay is not conducive to the recognition of sedimentary criteria suitable for correlations in other than a local environment.

Journal of Sedimentary Petrology↗
USGS1998

Landslide Hazards in Glacial Lake Clays - Tully Valley, New York

At approximately midday on April 27, 1993, a large landslide occurred along the foot of Bare Mountain in LaFayette, Onondaga County, New York, about 12 miles south of Syracuse (figs. 1, 2). The slide moved rapidly east toward the middle of the Tully Valley and impacted approximately 50 acres of land, destroyed three homes, and resulted in the evacuation of four other homes. Debris from the slide, consisting mostly of remolded clay, covered Tully Farms Road with up to 15 feet of earth for a length of some 1,200 feet. Springs that developed near the top of the slide discharged either freshwater or brackish water, which contained concentrations of dissolved evaporites (salt and gypsum) and other minerals. The total volume of earth moved by the slide is estimated to be about 1.3 million cubic yards. According to the New York State Geological Survey, this slide is the largest to have occurred in the State in more than 75 years. Most residents were away from their homes at the time of the slide, and so there were no fatalities or serious injuries caused by the slide.

Fact Sheet↗
USGS1956

Geology of the Ralston Buttes district, Jefferson County, Colorado: a preliminary report

The Ralston Buttes district in Jefferson County is one of the most significant new uranium districts located east of the Continental Divide in Colorado. The district is east of the Colorado Front Range mineral belt, along the east front of the range. From November 1953 through October 1956, about 10,000 tons of uranium ore, much of which was high-grade pitchblende-bearing vein material, was shipped from the district. The ore occurs in deposits that range in size from bodies containing less than 50 tons to ore shoots containing over 1,000 tons. The only other mining activity in the area has been a sporadic production of beryl, feldspar, and scrap mica from Precambrian pegmatites, and quarrying of dimension stone, limestone, and clay from sedimentary rocks. Most of the Ralston Buttes district consists of complexly folded Precambrian metamorphic and igneous rocks - gneiss, schist, quartzite, amphibolite, and granodiorite. Paleozoic and Mesozoic sedimentary rocks crop out in the northeastern part of the district. These rocks are cut by northwesterly-trending fault systems of Laramide age and by small bodies of intrusive rocks that are Tertiary in age. The typical uranium deposits in the district are hydrothermal veins occupying openings in Laramide fault breccias or related fractures that cut the Precambrian rocks. Pitchblende and lesser amounts of secondary uranium minerals are associated with sparse base-mental sulfides in a gangue of carbonate minerals, potash feldspar, and, more rarely, quartz. Less common types of deposits consist of pitchblende and secondary uranium minerals that occupy fractures cutting pegmatites and quartz veins. The uranium deposits are concentrated in two areas, the Ralston Creek area and the Golden Gate Canyon area. The deposits in the Ralston Creek area are located along the Rogers fault system, and the deposits in the Golden Gate Canyon area are along the Hurricane Hill fault system. Two geologic factors were important to the localization of the uranium deposits: (1) favorable structural environment and (2) favorable host rocks. The deposits in each of the two major areas are located where a northwesterly-trending Laramide fault system splits into a complex network of faults. Also, most of the deposits appear to be localized where the faults cut Precambrian rocks rich in hornblende, biotite, or garnet and biotite. The ore controls recognized in this relatively new uranium district may have wider application in areas of similar geology elsewhere in the Front Range.

Colorado↗
USGS1998

Additional descriptive models of industrial mineral deposits

This report includes previously written, but unpublished descriptive industrial mineral deposit models not released in earlier reports (Cox and Singer, 1986; Orris, 1992; Orris and Bliss, 1991, 1992). Although some of the models are preliminary, recent and repeated requests for several of the models has led to their release in this compilation. Initial drafts of the clay models were written for individual U.S. deposits or districts by J.W. Hosterman2 of the U.S. Geological Survey (USGS) in the late 1980/s. All of the models in this report have been modified from their original unpublished versions; for most models, the modifications have consisted of additional geologic detail, economic information, and (or) health and environmental considerations related to the deposit type. More extensive alterations have been made to the clay models written by Hosterman, which were put into standard format and extensively revised by G.J. Orris. As much as two-thirds of the information in the current versions of the models post-dates Hosterman's contributions and these models are shown as jointly authored.

Open-File Report↗
USGS2005

Direct observation of heavy metal-mineral association from the Clark Fork River Superfund Complex: Implications for metal transport and bioavailability

Two sets of samples from riverbeds and adjacent floodplains, separated by 80 river kilometers, were collected from the Clark Fork River Superfund Complex, Montana, (the largest Superfund site in the United States), and studied primarily with transmission electron microscopy (TEM) with several supporting techniques to determine heavy metal-mineral association. Seven of the eight samples studied were strongly influenced by material that once resided in mining and smelting dumps and impoundments; this material was transported downstream sometime during the last century and a half from the Butte/Anaconda areas. The eighth sample was from a deeper floodplain level and dates to premining days. The TEM observations afford a direct look, down to the nanometer level, at secondary mineral formation as a result of the breakdown of sulfides and silicates in the acid environment of this massive mine-drainage system. In the shallow, oxic floodplain sediments, heavy metals of concern in this system (As, Cu, Pb, and Zn) are taken up by the formation of sulfates (particularly Pb in jarosite), as well as hydrous metal oxides (As, Cu, Pb, and Zn in and on ferrihydrite, and a possibly new vernadite-like mineral). The oxides are long-lived in these systems, as they were also found in the anoxic riverbeds. Metals are also taken up by the formation of sulfides in sulfate-reducing environments as observed in the formation of nanoclusters of chalcopyrite and sphalerite. In all samples, clays make up between 5 and 20% of the sediment and carry significant amounts of Cu and Zn. The hydrous oxides, secondary sulfides, and clays provide several routes for metal transport downstream over long distances. Besides the potential bioavailability of heavy metals exchanged on and off the hydrous metal oxides and clays, nanometer-sized sulfides may also be highly reactive in the presence of biologic systems. Copyright ?? 2005 Elsevier Ltd.

Geochimica et Cosmochimica Acta↗
USGS1961

Geology and mineral deposits of the Carlile quadrangle, Crook County, Wyoming

The Carlile quadrangle-is along the northwestern flank of the Black Hills uplift in Crook County, Wyo. The area-is primarily one of canyons and divides that are a result of downcutting by the Belle Fourche River and its tributaries through an alternating succession of sandstone, siltstone, and mudstone or shale beds. The present topography is also influenced by the regional structure, as reflected by the beds that dip gently westward and by the local structural features such as anticlines, domes, synclines, basins, and terraces, which are superimposed upon the regional setting. Rocks exposed include shale and thin limestone and sandstone beds belonging to the Redwater shale member of the Sundance formation and to the Morrison formation, both of Late Jurassic age; sandstone, siltstone, and mudstone of the Lakota and Fall River formations of Early Cretaceous age; and shale and sandstone of the Skull Creek shale, Newcastle sandstone, and Mowry shale, also of Early Cretaceous age. In the southwestern part of the quadrangle rocks of the Upper Cretaceous series are exposed. These include the Belle Fourche shale, Greenhorn formation, and Carlile shale. Gravel terraces, landslide debris, and stream alluvium comprise the surficial deposits. The Lakota and Fall River formations, which make up the Iriyan Kara group, contain uranium deposits locally in the northern Black Hills. These formations were informally subdivided in order to show clearly the vertical and lateral distribution of the sandstone, siltstone, and mudstone facies within them. The Lakota was subdivided into a sandstone unit and an overlying mudstone unit; the Fall River was subdivided, in ascending order, into a siltstone unit, a mudstone unit, a sandstone unit, and an upper unit. The lithologic character of the Lakota changes abruptly locally, and the units are quite inconsistent with respect to composition, thickness, and extent. This is in contrast to a notable consistency in the lithologic character and thickness among all the Fall River units, with the exception of the upper unit. Petrographic studies on selected samples of units from both formations show differences in composition between Lakota and Fall River rocks. The Carlile quadrangle lies immediately east of the monocline that marks the outer limit of the Black Hills uplift, and the rocks in this area have a regional dip of less than 2° outward from the center of the uplift. Superimposed upon the regional uplift are many subordinate structural features anticlines, synclines, domes, basins, and terraces which locally modify the regional features. The most pronounced of these subordinate structural features are the doubly-plunging Pine Ridge, Oil Butte, and Dakota Divide anticlines, and the Eggie Creek syncline. Stress throughout the area was relieved almost entirely through folding; only a few small nearly vertical normal faults were found within the quadrangle. Uranium has been mined from the Carlile deposit, owned by the Homestake Mining Co. The ore minerals, carnotite and tyuyamnuite occur in a sandstone lens that is enclosed within relatively impermeable clayey beds in the mudstone unit of the Lakota formation. The ore also includes unidentified black vanadium minerals and possibly coffinite. Uranium minerals are more abundant in and adjacent to thicker carbonaceous and silty seams in the sandstone lens. A mixture of fine-grained calcium carbonate and calcium sulfate fills the interstices between detrital quartz grains in mineralized sandstone. Selenium and arsenic are more abundant in samples that are high in uranium. Drilling on Thorn Divide about 1 mile west of the Carlile mine has roughly outlined concentrations of a sooty black uranium mineral associated with pyrite In two stratigraphic intervals of the Lakota formation. One is in the same sandstone lens that contains the ore at the Carlile mine; the other is in conglomeratic sandstone near the base of the Lakota. These deposits are relatively deep, and no mining has been attempted. The mineralogy of the Carlile deposits and the lithologic features of the sandstone host rock suggest that uranium and vanadium were transported in the high-valent state by carbonate or sulfate solutions, were extracted from solution by organic material, and were reduced to low-valent states to form an original assemblage of oxides and silicates. These primary minerals were oxidized in place, and the present carnotite-tyuyamunite assemblage was formed. In general, radioactivity analyses correspond fairly closely with chemical analyses of uranium, thus it is believed that only minor solution and migration of uranium has occurred since the present suite of oxidized minerals was formed. The factors responsible for ore localization are not clear, but probably a combination of three lithologic and structural elements contributed to provide a favorable environment for precipitating uranium from aqueous solutions: abundant carbonaceous material or pyrite in a thin, permeable sandstone enclosed within relatively thick impermeable clays; local structural basins; and a regional structural setting involving a broad syncline between two anticlines. The structural features controlled the regional flow of ground water and the lithologic features controlled the local rate of flow and provided the proper chemical environment for uranium deposition. Bentonite has been mined from an opencut in the Mowry shale in the southwest part of the quadrangle. A bentonite bed in the Newcastle sandstone also seems to be of minable thickness and quality. Exploration for petroleum has been unsuccessful within the quadrangle; however, some wells that yielded oil were recently drilled on small anticlines to the west and southeast. It is possible that similar structural features in the Carlile area, that were previously overlooked, may be equally productive.

Wyoming↗
USGS2006

An exploratory method to detect tephras from quantitative XRD scans: Examples from Iceland and east Greenland marine sediments

Tephras, mainly from Iceland, are becoming increasingly important in interpreting leads and lags in the Holocene climate system across NW Europe. Here we demonstrate that Quantitative Phase Analysis of x-ray diffractograms of the < 2 mm of marine sediment fraction (ie, sand, silt and clay) from Iceland and East Greenland can detect peaks in volcanic glass concentrations (weight%) even though discrete tephra layers are not visible; thus it provides a rapid overview of the probable location of volcanic glass within sediment sequences. Experiments in spiking samples from Baffin Bay and an artificial mixture of minerals with known weight% fractions of an Icelandic tephra (Hekla 4) demonstrate a significant correlation (r2 = 0.92 and 0.97) between known and estimated weight percentages, although the slope of the measured to observed weight% is around 0.65 and not 1.0 as expected. In core B997-321PC off North Iceland we identify tephras from point counting in the > 150 um fraction and identify these same peaks in XRD scans - two of these correlate geochemically and chronologically with Hekla 1104 and 3. At a distal site to the WNW of Iceland, on the East Greenland margin (core MD99-2317), the weight% of volcanic glass reaches values of 11% at about the time of the Saksunarvatn tephra. The XRD method identifies the presence of volcanic glass but not its elemental composition; hence it will assist in focusing attention on specific sections of sediment cores for subsequent geochemical fingerprinting of tephras. ?? 2006 SAGE Publications.

Holocene↗
USGS2021

Groundwater hydrology and chemistry of Jamestown Island, Virginia—Potential effects of tides, storm surges, and sea-level rise on archaeological, cultural, and ecological resources

As the site of the first permanent English settlement in North America in 1607, Jamestown Island, Colonial National Historical Park (COLO), Virginia, contains a rich archaeological record that extends from the Paleoindian period (15,000 to 8,000 years ago) through the 20th century. The island is located on the lower James River near the mouth of Chesapeake Bay. Jamestown Island vegetation is dominated by upland forests surrounded by tidal, freshwater-to-oligohaline marshes. Along the Virginia coast, relative sea-level rise was more than 2.5 times the global average during the 20th century. Consequently, the National Park Service (NPS) has identified COLO as one of the 25 national parks most threatened by climate change. Surface waters across the island are hydraulically connected to the laterally continuous Surficial aquifer. The land-surface altitude of the island is low, with two-thirds of the island less than 5 feet (ft) above the North American Vertical Datum of 1988 (NAVD 88). Consequently, sea-level rise, combined with tides and storm surges, threatens the island and its resources as surface-water and groundwater levels rise, saltwater enters the Surficial aquifer, and groundwater chemistry changes. The impact of sea-level rise on the island’s surface-water resources has been well studied, but groundwater effects have been largely ignored. Quantifying the effects of tides, storm surges, and sea-level rise on groundwater levels and chemistry is essential to developing an effective strategy for managing climate-induced changes. The first step in developing a response strategy includes a parkwide general risk assessment for archaeological sites on the island, so that sites can be prioritized for management actions. The U.S. Geological Survey and the NPS began a study in 2015 to develop a long-term groundwater-monitoring program to evaluate this risk and to develop an updated management strategy. The groundwater-monitoring program consists of 45 wells and piezometers in two individual clusters and three transects across the island in different hydrologic and chemical settings. Samples for water quality were collected from the wells and piezometers from October 2015 through September 2018 at variable time intervals. Results of the monitoring identified disparate hydrologic and chemical responses to saltwater intrusion across the island. Specific conductance (an indicator of salinity) of groundwater beneath several marshes responded differently to changes in James River salinity. Groundwater response to changes in James River specific conductance appeared to be controlled by land-surface altitude and slope, differences in lateral and vertical sediment characteristics, distance from surface waters, and the degree of surface water/groundwater connectivity between channels and the aquifer. Groundwater chemistry data from monitoring wells at Black Point, a low-altitude, upland setting, are in contrast with conditions observed in Island House observation wells, a high-altitude, upland setting. Specific conductance (less than 200 microsiemens per centimeter [μS/cm]) and pH (greater than 5.0) of groundwater beneath much of the uplands that characterize the Island House observation wells are typical of groundwater in noncarbonate sedimentary aquifers recharged by precipitation. At Black Point, specific conductance ranged from 2,490 to 15,200 μS/cm, and pH ranged from 3.1 to 6.6 standard units. At the Black Point observation wells, the most saline and dense water was at the water table rather than deeper in the aquifer, causing a density inversion that persisted throughout the study. The density inversion likely resulted from differences in permeability between the shallow clay and fine-grained sands and the deeper coarse-grained sand and gravel. Groundwater with the lowest pH was at the water table. As saline groundwater flows through organic sediment beneath the marshes, bacterial biodegradation of organic matter creates anoxic conditions. Continued biodegradation concomitantly reduces iron-oxide minerals in the sediment and sulfate in saline water. When oxygen is reintroduced into groundwater, iron and sulfur can reoxidize to form sulfuric acid, locally lowering the pH of the water. This report describes the groundwater monitoring network design, rationale for site selection, monitoring approach, and results of monitoring from October 2015 through September 2018. Maps of inundation at selected water-level altitudes are included to identify the risk to archaeological, cultural, and ecological resources. The monitoring results of the hydrology and chemistry data are interpreted, and the different hydrologic and chemical settings are described. The implications of the study results for management decisions are presented, and suggestions for improving the monitoring network are included.

Virginia↗
USGS1985

Experimental chemical weathering of various bedrock types at different pH-values. 1. Sandstone and granite

Experimental chemical weathering of the so-called Old Rag Granite and Massanutten Sandstone, Virginia, U.S.A., has produced a comparison with the natural environment, and prediction of the effect of acid precipitation. The experimental results of the release of elements, dissolution of minerals, total rock weathered and the degree of weathering as function of volume of leachate were plotted. These data were compared with the natural environment. The use of the plots to predict the effect of high levels of rain acidity on weathering of these rocks is demonstrated. A nonexpandable 14-Å clay was developed from the alteration of biotite during the experimental chemical weathering of the granite at pH 4. This interstratified Al(OH)—mica clay resembles those of the soil developed on the granite and sandstone. Hydroxy-Al may be precipitating between the mica interlayers and producing a 14-Å spacing. Development of this clay by chemical alteration of biotite may change the current hypotheses about its origin in the soils of northeastern U.S.A. While Al-hydroxide seems to regulate Al concentrations in stream waters at the present level of rain acidity, it was found that at lower pH and in the presence of high sulfate concentrations, Al solubility may be controlled by Al-sulfate phase(s).

Virginia↗
USGS2007

Thermal infrared reflectance and emission spectroscopy of quartzofeldspathic glasses

This investigation seeks to better understand the thermal infrared (TIR) spectral characteristics of naturally-occurring amorphous materials through laboratory synthesis and analysis of glasses. Because spectra of glass phases differ markedly from their mineral counterparts, examination of glasses is important to accurately determine the composition of amorphous surface materials using remote sensing datasets. Quantitatively characterizing TIR (5-25 ??m) spectral changes that accompany structural changes between glasses and mineral crystals provides the means to understand natural glasses on Earth and Mars. A suite of glasses with compositions analogous to common terrestrial volcanic glasses was created and analyzed using TIR reflectance and emission techniques. Documented spectral characteristics provide a basis for comparison with TIR spectra of other amorphous materials (glasses, clays, etc.). Our results provide the means to better detect and characterize glasses associated with terrestrial volcanoes, as well as contribute toward understanding the nature of amorphous silicates detected on Mars. Copyright 2007 by the American Geophysical Union.

Geophysical Research Letters↗
USGS1993

Heavy metal anomalies in the Tinto and Odiel River and estuary system, Spain

The Tinto and Odiel rivers drain 100 km from the Rio Tinto sulphide mining district, and join at a 20-km long estuary entering the Atlantic Ocean. A reconnaissance study of heavy metal anomalies in channel sand and overbank mud of the river and estuary by semi-quantitative emission dc-arc spectrographic analysis shows the following upstream to downstream ranges in ppm (??g g-1): As 3,000 to <200, Cd 30 to <0.1, Cu 1,500 to 10, Pb 2,000 to <10, Sb 3000 to <150, and Zn 3,000 to <200. Organic-rich (1.3-2.6% total organic carbon, TOC), sandysilty overbank clay has been analyzed to represent suspended load materials. The high content of heavy metals in the overbank clay throughout the river and estuary systems indicates the importance of suspended sediment transport for dispersing heavy metals from natural erosion and anthropogenic mining activities of the sulfide deposit. The organic-poor (0.21-0.37% TOC) river bed sand has been analyzed to represent bedload transport of naturally-occurring sulfide minerals. The sand has high concentrations of metals upstream but these decrease an order of magnitude in the lower estuary. Although heavy metal contamination of estuary mouth beach sand has been diluted to background levels estuary mud exhibits increased contamination apparently related to finer grain size, higher organic carbon content, precipitation of river-borne dissolved solids, and input of anthropogenic heavy metals from industrial sources. The contaminated estuary mud disperses to the inner shelf mud belt and offshore suspended sediment, which exhibit metal anomalies from natural erosion and mining of upstream Rio Tinto sulphide lode sources (Pb, Cu, Zn) and industrial activities within the estuary (Fe, Cr, Ti). Because heavy metal contamination of Tinto-Odiel river sediment reaches or exceeds the highest levels encountered in other river sediments of Spain and Europe, a detailed analysis of metals in water and suspended sediment throughout the system, and epidemiological analysis of heavy metal effects in humans is appropriate. ?? 1993 Estuarine Research Federation.

Estuaries↗
USGS2011

Aqueous mineralogy and stratigraphy at and around the proposed Mawrth Vallis MSL Landing Site: New insights into the aqueous history of the region

In this work, we have confirmed the mineralogical stratigraphy previously inferred by other authors, but also demonstrate the presence of additional minerals, including a possible acid-leaching product near the top of the sequence, an Mh-OH bearing phyllosilicate at the to of the sequence, and potentially a Ca-sulfate at the bottom of the phyllosilicate sequence. The latter has important implications regarding the relative timing of sulfate vs clay formation on Mars.

Mars, The International Journal of Mars Science an↗
USGS2008

Geochemical controls of elevated arsenic concentrations in groundwater, Ester Dome, Fairbanks district, Alaska

Ester Dome, an upland area near Fairbanks, Alaska, was chosen for a detailed hydrogeochemical study because of the previously reported elevated arsenic in groundwater, and the presence of a large set of wells amenable to detailed sampling. Ester Dome lies within the Fairbanks mining district, where gold-bearing quartz veins, typically containing 2–3 vol.% sulfide minerals (arsenopyrite, stibnite, and pyrite), have been mined both underground and in open cuts. Gold-bearing veins on Ester Dome occur in shear zones and the sulfide minerals in these veins have been crushed to fine-grained material by syn- or post-mineralization movement. Groundwater at Ester Dome is circumneutral, Ca–HCO 3 to Ca–SO 4 type, and ranges from dilute (specific conductance of 48 µS/cm) to more concentrated (specific conductance as high as 2070 µS/cm). In general, solute concentrations increase down hydrologic gradient. Redox species indicate that the groundwaters range from oxic to sub-oxic (low dissolved oxygen, Fe(III) reduction, no SO 4 reduction). Waters with the highest Fe concentrations, as high as 10.7 mg/L, are the most anoxic. Dissolved As concentrations range from < 1 to 1160 µg/L, with a median value of 146 µg/L. Arsenic concentrations are not correlated with specific conductance or Fe concentrations, suggesting that neither groundwater residence time, nor reductive dissolution of iron oxyhydroxides, control the arsenic chemistry. Furthermore, As concentrations do not covary with other constituents that form anions and oxyanions in solution (e.g., HCO 3 , Mo, F, or U) such that desorption of arsenic from clays or oxides also does not control arsenic mobility. Oxidation of arsenopyrite and dissolution of scorodite, in the near-surface environment appears to be the primary control of dissolved As in this upland area. More specifically, the elevated As concentrations are spatially associated with sulfidized shear zones and localities of gold-bearing quartz veins. Consistent with this interpretation, elevated dissolved Sb concentrations (as high as 59 µg/L), also correlated with occurrences of hypogene sulfide minerals, were measured in samples with high dissolved As concentrations.

Chemical Geology↗
USGS2017

Wisconsin Glaciation of the Sierra Nevada (79,000-15,000 yr B.P.) as recorded by rock flour in sediments of Owens Lake, California

Chemical analyses of the clay-sized fractions of 564 continuous sediment samples (200-yr resolution) from composite core OL90/92 allow quantification of an abundance of glacial rock flour. Rock flour produced during glacier advances is represented by clay-sized plagioclase, K-feldspar, and biotite in homogeneous internal composition. The abundance of rock flour is deemed proportional to the intensity of glacies advances. Age control for the composite section is provided by combining previously published radiocarbon dates on organics, U/Th dates on ostracode shells, and U/Th dates on saline minerals from nearby Searles Lake correlated to OL92 by pollen. The rock flour record displays three levels of variability: (1) a dominant one of about 20,000 yr related to summer insolation and precipitation; (2) an intermediate one of 3000-5000 yr, perhaps related to North Atlantic Heinrich events; and (3) a minor one of 1000-2000 yr, perhaps related to North Atlantic thermohaline-driven air-temperature variation. ?? 2001 University of Washington.

Quaternary Research↗
USGS1964

Origin of precambrian iron formations

A statistical study of the chemical composition of the Precambrian iron formations of the Canadian Shield affords a new approach to the origin of these unusual formations . The average total iron content of 2,200 samples from the literature and from unpublished mining company analyses is 26.7 percent Fe. The average Fe content for 16 iron formations in the United States and Canada ranges from 24.5 to 34.1 percent. Low contents of A1203, Ti02, P2O5, and CaO characterize the Precambrian iron formations compared to the relatively large amounts of these constituents in the post- Precambrian iron -bearing sediments. The chemical data emphasize that whereas iron , manganese, and silica were transported and deposited together in the cherty iron formations of the Precambrian , these same elements were chemically differentiated in younger geological time in large but separate deposits of iron and silica. Isotopic age determinations indicate that cherty iron formations were deposited during a long interval of geologic time from approximately 1,700 to 3,000 million years ago. A model is proposed to explain the origin of the iron formations of the Lake Superior type based on the absence or marked deficiency of free oxygen in the atmosphere prior to the Late Precambrian . Lateritic weathering under these conditions permitted the transport of iron and manganese together with silica. The weathered mantle effectively retained aluminum, titanium, phosphorus, and colloidal clay. Graphitic material of biogenic origin is closely associated with the Precambrian iron formations . Although it is uncertain whether iron was precipitated directly through biologic processes, the removal of C02 and the liberation of oxygen to the sea water through photosynthesis of primitive plants undoubtedly influenced the energy relationships among the iron minerals. As a result of the variable conditions the iron formations commonly are characterized by nonequilibrium mineral assemblages. In Late Precambrian time a critical level of free oxygen in the atmosphere was attained permitting a marked acceleration in plant growth and in accretion of oxygen. This stage in the development of an oxygenated atmosphere was reached at least 1,200 million years ago and effectively curtailed the development of cherty iron formations of the Lake Superior type.

Economic Geology↗
USGS1983

Preliminary appraisal of the hydrology of the Stigler area, Haskell County, Oklahoma

Bed rock in the Stigler area of southeastern Oklahoma consists principally of shale, siltstone, and sandstone of the McAlester, Savanna, and Boggy Formations of Pennsylvanian age. These rocks have been folded to form the Stigler syncline on the north and the Antioch anticline on the south. An area of several square miles is underlain by terrace deposits, mostly sandy silt, as much as 25 feet thick. Alluvium along the streams is 5 to 10 feet thick and consists mainly of sandy silt. Neither the terrace deposits nor the alluvium are hydrologically significant. Water in the bedrock is under artesian conditions. Well depths range from 34 to 235 feet and average 95 feet. The water level in most wells is less than 30 feet below the land surface. Because the rocks have minimal permeability, well yields probably are less than 5 gallons per minute. Much of the area is provided with water by a rural water district. Based on specific-conductance measurements, dissolved-solids concentrations in ground water are estimated to range from 200 to 2,500 milligrams per liter. Nor relationship between variations in specific conductance and well depth, geographic distribution, or geologic formation is apparent. Streams in the area are ephemeral and extended periods of no flow can be expected. During much of the period of record, streamflow in Taloka Creek was maintained by water pumped from an active coal mine. Water upstream from the mine area had a mean dissolved-solids concentration of 72 milligrams per liter whereas water downstream from the mine area had a mean concentration of 1,323 milligrams per liter. At times, downstream concentrations of some toxic metals exceeded the standards for drinking water set by the U.S. Environmental Protection Agency. Samples of water collected from Taloka Creek since mining ceased did not have excessive concentrations of toxic metals. Maximum suspended-sediment discharge of Taloka Creek was about 1,660 tons per day. Silt-clay particles (diameters less than 0.062 millimeter) were the dominant grain size. Observed and measured effects of surface mining for coal on the hydrologic system include (1) creation of additional water storage in the surface mine pond, (2) disruption of drainage in an area of about 1 square mile, and (3) increased mineralization of water in Taloka Creek. Other possible effects include (4) changes in permeability and storage of water in mine spoil, (5) minor changes in streamflow and runoff characteristics, and (6) temporary increase in the sediment load of Taloka Creek.

Water-Resources Investigations Report↗
USGS1973

Gold-bearing arsenian pyrite determined by microprobe analysis, Cortez and Carlin Gold Mines, Nevada

Studies of polished sections and chemical analyses made by electron microprobe show that gold and arsenic in the unoxidized ores from the Cortez and Carlin mines are most abundant in pyrite. Gold, as particles too small to be seen under the microscope, along with arsenic is concentrated in tiny pyrite grains (<0.005 mm) and in thin rims of larger pyrite grains. It is concentrated also in arsenopyrite which is sparsely distributed in the Cortez ore. Traces of gold are contained in sphalerite and chalcopyrite sparsely disseminated in Carlin ore. Mercury and antimony occur also in the pyrite, and antimony is in illite as well. Little if any gold or arsenic is contained in quartz, carbonate, clay, and carbonaceous material. In oxidized ore, the sulfur and carbonaceous material have been removed and gold and arsenic occur in iron oxide pseudomorphs after pyrite. Gold can be seen in the oxidized ore, indicating that it has been mobilized and concentrated. No association was found between gold and the carbonaceous material. During mineralization, calcite was removed from the fractured silty carbonate of the Roberts Mountains Formation, creating micropore space in which pyrite, quartz, and illite were deposited. The average tenor of the pyrite, if all the gold were in the pyrite, would be 0.10 percent at Cortez and 0.14 percent at Carlin. These calculated values are similar to the analytical values. The calculated tenor of the carbonaceous material, however-if such material were considered to be the mineral host of the gold-would be 0.28 percent at Cortez and 1 percent at Carlin. These figures are unreasonable when compared with the analytical data, which show that the carbonaceous material contains no detectable amounts of gold. © 1973 Society of Economic Geologists, Inc.

Nevada↗
USGS2013

Nickel-cobalt laterites: A deposit model

Nickel-cobalt (Ni-Co) laterite deposits are supergene enrichments of Ni±Co that form from intense chemical and mechanical weathering of ultramafic parent rocks. These regolith deposits typically form within 26 degrees of the equator, although there are a few exceptions. They form in active continental margins and stable cratonic settings. It takes as little as one million years for a laterite profile to develop. Three subtypes of Ni-Co laterite deposits are classified according to the dominant Ni-bearing mineralogy, which include hydrous magnesium (Mg)-silicate, smectite, and oxide. These minerals form in weathering horizons that begin with the unweathered protolith at the base, saprolite next, a smectite transition zone only in profiles where drainage is very poor, followed by limonite, and then capped with ferricrete at the top. The saprolite contains Ni-rich hydrous Mg-silicates, the Ni-rich clays occur in the transition horizon, and Ni-rich goethite occurs in the limonite. Although these subtypes of deposits are the more widely used terms for classification of Ni-Co laterite deposits, most deposits have economic concentrations of Ni in more than one horizon. Because of their complex mineralogy and heterogeneous concentrations, mining of these metallurgically complex deposits can be challenging. Deposits range in size from 2.5 to about 400 million tonnes, with Ni and Co grades of 0.66–2.4 percent (median 1.3) and 0.01–0.15 percent (median 0.08), respectively. Modern techniques of ore delineation and mineralogical identification are being developed to aid in streamlining the Ni-Co laterite mining process, and low-temperature and low-pressure ore processing techniques are being tested that will treat the entire weathered profile. There is evidence that the production of Ni and Co from laterites is more energy intensive than that of sulfide ores, reflecting the environmental impact of producing a Ni-Co laterite deposit. Tailings may include high levels of magnesium, sulfate, and manganese and have the potential to be physically unstable.

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