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At least 1,279 records · Page 71Linked to original sources
USGS2006

Freshwater diatomite deposits in the western United States

Freshwater diatomite deposits in the Western United States are found in lake beds that formed millions of years ago. These diatom-rich sediments are among the Nation's largest commercial diatomite deposits. Each deposit contains billions of tiny diatom skeletons, which are widely used for filtration, absorption, and abrasives. New studies by the U.S. Geological Survey (USGS) are revealing how ancient lakes in the Western States produced such large numbers of diatoms. These findings can be used by both land-use managers and mining companies to better evaluate diatomite resources in the region.

Fact Sheet↗
USGS2010

Historical files from Federal government mineral exploration-assistance programs, 1950 to 1974

Congress enacted the Defense Production Act in 1950 to provide funding and support for the exploration and development of critical mineral resources. From 1950 to 1974, three Department of the Interior agencies carried out this mission. Contracts with mine owners provided financial assistance for mineral exploration on a joint-participation basis. These contracts are documented in more than 5,000 'dockets' now archived online by the U.S. Geological Survey. This archive provides access to unique and difficult to recreate information, such as drill logs, assay results, and underground geologic maps, that is invaluable to land and resource management organizations and the minerals industry. An effort to preserve the data began in 2009, and the entire collection of dockets was electronically scanned. The scanning process used optical character recognition (OCR) when possible, and files were converted into Portable Document Format (.pdf) files, which require Adobe Reader or similar software for viewing. In 2010, the scans were placed online (http://minerals.usgs.gov/dockets/) and are available to download free of charge.

Fact Sheet↗
USGS2010

Chemical analyses in the World Coal Quality Inventory

The main objective of the World Coal Quality Inventory (WoCQI) was to collect and analyze a global set of samples of mined coal during a time period from about 1995 to 2006 (Finkelman and Lovern, 2001). Coal samples were collected by foreign collaborators and submitted to country specialists in the U.S. Geological Survey (USGS) Energy Program. However, samples from certain countries, such as Afghanistan, India, and Kyrgyzstan, were collected collaboratively in the field with USGS personnel. Samples were subsequently analyzed at two laboratories: the USGS Inorganic Geochemistry Laboratory located in Denver, CO and a commercial laboratory (Geochemical Testing, Inc.) located in Somerset, PA. Thus the dataset, which is in Excel (2003) format and includes 1,580 samples from 57 countries, does not have the inter-laboratory variability that is present in many compilations. Major-, minor-, and trace-element analyses from the USGS laboratory, calculated to a consistent analytical basis (dry, whole-coal) and presented with available sample identification information, are sorted alphabetically by country name. About 70 percent of the samples also have data from the commercial laboratory, which are presented on an as-received analytical basis. The USGS initiated a laboratory review of quality assurance in 2008, covering quality control and methodology used in inorganic chemical analyses of coal, coal power plant ash, water, and sediment samples. This quality control review found that data generated by the USGS Inorganic Geochemistry Laboratory from 1996 through 2006 were characterized by quality practices that did not meet USGS requirements commonly in use at the time. The most serious shortcomings were (1) the adjustment of raw sample data to standards when the instrument values for those standards exceeded acceptable limits or (2) the insufficient use of multiple standards to provide adequate quality assurance. In general, adjustment of raw data to account for instrument 'drift' is an acceptable practice within strictly defined limits. During the denoted period, USGS required that the maximum adjustment of instrument values, guided by calibration standards, was not allowed to exceed 10 percent. However, in some cases, the Inorganic Geochemistry Laboratory released data that were adjusted by more than 10 percent and (or) were not constrained by an adequate number of control standards. Original instrument values no longer exist for about 80 percent of the analyses during this period; therefore, the acceptability of drift corrections for most of the samples analyzed cannot be determined. For these reasons, the WoCQI data from the USGS Inorganic Geochemistry Laboratory should be used with care. For more information, individuals may contact laboratory management at EnergyLabs@usgs.gov with specific questions about particular datasets or analytical attributes. Standard USGS sampling methods were provided and recommended to collaborators, but the analyzed samples may or may not be representative of their locale; for some samples, only limited information is available concerning sample provenance. Single samples cannot represent spatial or temporal variability within a coal area. Geochemical datasets of U.S. coals can be found in the COALQUAL database (Bragg and others, 1997) and the National Coal Quality Inventory (Hatch and others, 2006), as only non-U.S. sample data are presented in the WoCQI. Although the WoCQI does not contain worldwide coverage of coal deposits, it is truly a unique and valuable compilation. The information in the WoCQI should prove useful for identifying possible areas for future global coal research.

Open-File Report↗
USGS2010

Water-quality, bed-sediment, and biological data (October 2008 through September 2009) and statistical summaries of long-term data for streams in the Clark Fork basin, Montana

Water, bed sediment, and biota were sampled in streams from Butte to near Missoula, Montana, as part of a long-term monitoring program in the upper Clark Fork basin; additional water samples were collected in the Clark Fork basin from sites near Missoula downstream to near the confluence of the Clark Fork and Flathead River as part of a supplemental sampling program. The sampling programs were conducted by the U.S. Geological Survey in cooperation with the U.S. Environmental Protection Agency to characterize aquatic resources in the Clark Fork basin of western Montana, with emphasis on trace elements associated with historic mining and smelting activities. Sampling sites were located on the Clark Fork and selected tributaries. Water samples were collected periodically at 24 sites from October 2008 through September 2009. Bed-sediment and biota samples were collected once at 13 sites during August 2009. This report presents the analytical results and quality-assurance data for water-quality, bed-sediment, and biota samples collected at all long-term and supplemental monitoring sites from October 2008 through September 2009. Water-quality data include concentrations of selected major ions, trace elements, and suspended sediment. Turbidity was analyzed for water samples collected at the four sites where seasonal daily values of turbidity were being determined as well as at Clark Fork above Missoula. Nutrients also were analyzed at all the supplemental water-quality sites, except for Clark Fork Bypass, near Bonner. Daily values of suspended-sediment concentration and suspended-sediment discharge were determined for four sites. Bed-sediment data include trace-element concentrations in the fine-grained fraction. Biological data include trace-element concentrations in whole-body tissue of aquatic benthic insects. Statistical summaries of long-term water-quality, bed-sediment, and biological data for sites in the upper Clark Fork basin are provided for the period of record since 1985.

Open-File Report↗
USGS2012

Water-quality, bed-sediment, and biological data (October 2009 through September 2010) and statistical summaries of data for streams in the Clark Fork basin, Montana

Water, bed sediment, and biota were sampled in streams from Butte to near Missoula, Montana, as part of a monitoring program in the upper Clark Fork basin. The sampling program was conducted by the U.S. Geological Survey in cooperation with the U.S. Environmental Protection Agency to characterize aquatic resources in the Clark Fork basin of western Montana, with emphasis on trace elements associated with historic mining and smelting activities. Sampling sites were located on the Clark Fork and selected tributaries. Water samples were collected periodically at 20 sites from October 2009 through September 2010. Bed-sediment and biota samples were collected once at 13 sites during August 2010. This report presents the analytical results and quality-assurance data for water-quality, bed-sediment, and biota samples collected at sites from October 2009 through September 2010. Water-quality data include concentrations of selected major ions, trace elements, and suspended sediment. Turbidity was analyzed for water samples collected at the four sites where seasonal daily values of turbidity were being determined. Daily values of suspended-sediment concentration and suspended-sediment discharge were determined for four sites. Bed-sediment data include trace-element concentrations in the fine-grained fraction. Biological data include trace-element concentrations in whole-body tissue of aquatic benthic insects. Statistical summaries of water-quality, bed-sediment, and biological data for sites in the upper Clark Fork basin are provided for the period of record since 1985.

Montana↗
USGS2016

Estimation of daily mean streamflow for ungaged stream locations in the Delaware River Basin, water years 1960–2010

The ability to characterize baseline streamflow conditions, compare them with current conditions, and assess effects of human activities on streamflow is fundamental to water-management programs addressing water allocation, human-health issues, recreation needs, and establishment of ecological flow criteria. The U.S. Geological Survey, through the National Water Census, has developed the Delaware River Basin Streamflow Estimator Tool (DRB-SET) to estimate baseline (minimally altered) and altered (affected by regulation, diversion, mining, or other anthropogenic activities) and altered streamflow at a daily time step for ungaged stream locations in the Delaware River Basin for water years 1960–2010. Daily mean baseline streamflow is estimated by using the QPPQ method to equate streamflow expressed as a percentile from the flow-duration curve (FDC) for a particular day at an ungaged stream location with the percentile from a FDC for the same day at a hydrologically similar gaged location where streamflow is measured. Parameter-based regression equations were developed for 22 exceedance probabilities from the FDC for ungaged stream locations in the Delaware River Basin. Water use data from 2010 is used to adjust the baseline daily mean streamflow generated from the QPPQ method at ungaged stream locations in the Delaware River Basin to reflect current, or altered, conditions. To evaluate the effectiveness of the overall QPPQ method contained within DRB-SET, a comparison of observed and estimated daily mean streamflows was performed for 109 reference streamgages in and near the Delaware River Basin. The Nash-Sutcliffe efficiency (NSE) values were computed as a measure of goodness of fit. The NSE values (using log 10 streamflow values) ranged from 0.22 to 0.98 (median of 0.90) for 45 streamgages in the Upper Delaware River Basin and from -0.37 to 0.98 (median of 0.79) for 41 streamgages in the Lower Delaware River Basin.

Delaware River Basin↗
USGS2019

Time-domain electromagnetic soundings for the delineation of saline groundwater in the Genesee River Valley, Western New York, 2016-2017

The U.S. Geological Survey, in cooperation with the New York State Department of Environmental Conservation, is investigating the distribution of saline groundwater in the Genesee River Valley near the former Retsof salt mine (fig. 1). As part of this study, paired time-domain electromagnetic (TEM) soundings and horizontal-to-vertical spectral ratio (HVSR) seismic soundings were made at 39 locations during the fall of 2016 to determine the presence of saline groundwater and depth to the bedrock surface, respectively. All measurement sites were west of Geneseo, New York, on the Genesee River valley floor north and south of the sinkhole area that developed as a result of the roof collapse and flooding of the Retsof mine in 1994 (fig. 1). An integrated analysis of the TEM and HVSR soundings with borehole logs, coupled with groundwater-sample data from previous investigations, allowed the delineation of zones of high electrical conductivity associated with saline water in the lower part of the valley fill and underlying bedrock to depths greater than 1,000 feet (ft). This article describes the TEM sounding method and its application in the ongoing investigation, presents results of the TEM analysis at two of the sounding sites, and identifies proposed sites for additional TEM/HVSR sounding data collection during the fall of 2017. Supporting data for this study are available in a separate data release (Johnson and others, 2017).

New York↗
USGS2017

Streamflow distribution maps for the Cannon River drainage basin, southeast Minnesota, and the St. Louis River drainage basin, northeast Minnesota

Streamflow distribution maps for the Cannon River and St. Louis River drainage basins were developed by the U.S. Geological Survey, in cooperation with the Legislative-Citizen Commission on Minnesota Resources, to illustrate relative and cumulative streamflow distributions. The Cannon River was selected to provide baseline data to assess the effects of potential surficial sand mining, and the St. Louis River was selected to determine the effects of ongoing Mesabi Iron Range mining. Each drainage basin (Cannon, St. Louis) was subdivided into nested drainage basins: the Cannon River was subdivided into 152 nested drainage basins, and the St. Louis River was subdivided into 353 nested drainage basins. For each smaller drainage basin, the estimated volumes of groundwater discharge (as base flow) and surface runoff flowing into all surface-water features were displayed under the following conditions: (1) extreme low-flow conditions, comparable to an exceedance-probability quantile of 0.95; (2) low-flow conditions, comparable to an exceedance-probability quantile of 0.90; (3) a median condition, comparable to an exceedance-probability quantile of 0.50; and (4) a high-flow condition, comparable to an exceedance-probability quantile of 0.02. Streamflow distribution maps were developed using flow-duration curve exceedance-probability quantiles in conjunction with Soil-Water-Balance model outputs; both the flow-duration curve and Soil-Water-Balance models were built upon previously published U.S. Geological Survey reports. The selected streamflow distribution maps provide a proactive water management tool for State cooperators by illustrating flow rates during a range of hydraulic conditions. Furthermore, after the nested drainage basins are highlighted in terms of surface-water flows, the streamflows can be evaluated in the context of meeting specific ecological flows under different flow regimes and potentially assist with decisions regarding groundwater and surface-water appropriations. Presented streamflow distribution maps are foundational work intended to support the development of additional streamflow distribution maps that include statistical constraints on the selected flow conditions.

Minnesota↗
USGS2005

Stratabound copper-silver deposits of the Mesoproterozoic Revett Formation, Montana and Idaho, with a section on databases and spatial-data files for the geology and mineral deposits of the Revett Formation

The western Montana copper belt in western Montana and northern Idaho contains several large stratabound copper-silver deposits in fine- to medium-grained quartzite beds of the Revett Formation of the Mesoproterozoic (1,470-1,401 Ma) Belt Supergroup. Production from the deposits at the Troy Mine and lesser production from the Snowstorm Mine has yielded 222,237 tons Cu and 1,657.4 tons Ag. Estimates of undeveloped resources, mostly from the world-class Rock Creek-Montanore deposits, as well as lesser amounts at the Troy Mine, total more than 2.9 million tons Cu and 2,600 tons Ag in 406 million tons of ore.The Rock Creek-Montanore and Troy deposits, which are currently the most significant undeveloped resources identified in the copper belt, are also among the largest stratabound copper-silver deposits in North America and contain about 15 percent of the copper in such deposits in North America. Worldwide, stratabound copper-silver deposits contain 23 percent of all copper resources and are the second-most important global source of the metal after porphyry copper deposits.The Revett Formation, which consists of subequal amounts of argillite, siltite, and quartzite, is informally divided into lower, middle, and upper members on the basis of the proportions of the dominant rock types. The unit thickness increases from north to south, from 1,700 ft near the Troy Mine, 55 mi north of Wallace, Idaho, to more than 5,300 ft at Wallace, Idaho, in the Coeur d'Alene Trough south of the Osburn Fault, a major right-lateral strike-slip fault.Mineral deposits in the Revett Formation occur mostly in the A-D beds of the lower member and in the middle quartzite of the upper member. The deposits are concentrated along a preore pyrite/hematite interface in relatively coarse grained, thick quartzite beds that acted as paleoaquifers for ore fluids. The deposits are characterized by mineral zones (alteration-mineral assemblages) that are a useful guide to the locations of mineral deposits. In particular, the gradational zone between the chalcopyrite-ankerite and pyrite-calcite zones is the site of most mineral deposits. Detailed information on the geology and mineral deposits of the Revett Formation is presented in the accompanying files that include (1) a tab-delimited text file providing details of the geologic and mineral-resource data for 57 Revett-subtype stratabound copper-silver deposits, occurrences, and prospects; (2) the stratigraphic records of 40 diamond-drill cores and 86 measured sections, totaling 150,752 ft of true thickness, which are provided in Excel spreadsheet and Adobe Portable Document Format files; and (3) spatial geologic data consisting of geologic maps of the Revett Formation, the subsurface locations of resources in Revett-subtype stratabound copper-silver deposits based on diamond-drill-core data, and the locations of diamond-drill holes and measured sections. The spatial data are contained in Arc/Info interchange files. Spatial information derived from these data includes the locations of mineral zones, a digital database showing untested exploration areas, and a digital database of permissive tracts for undiscovered mineral deposits.

Idaho, Montana↗
USGS2024

Geologic map and structure sections along the southern part of the Bartlett Springs Fault Zone and adjacent areas from Cache Creek to Lake Berryessa, northern Coast Ranges, California

Introduction Located in the Coast Ranges of northern California, the Bartlett Springs Fault Zone is the easternmost fault in the San Andreas Fault system in northern California. The fault is a right-lateral, strike-slip structure considered capable of producing an earthquake of moment magnitude 7. The purpose of this mapping is to better characterize the geology and earthquake hazards associated with the southern part of the Bartlett Springs Fault Zone and to help identify any evidence of active uplift on the faults bounding the Coast Ranges. Although the area immediately surrounding the Bartlett Springs Fault Zone is sparsely populated, its southern segment presents a potential seismic hazard to northern California communities as far away as the San Francisco Bay region and Sacramento. There are also nearby water resources, mineral resources, and public lands used for public recreation. The Coast Ranges of northern California are a series of northwest-southeast-oriented mountain ranges and valleys located north of the San Francisco Bay region, between the Pacific Ocean to the west and the Sacramento Valley to the east. The region has rugged terrain, high mountain peaks that reach more than 2,400 meters above sea level, isolated and narrow valley bottoms on which most human settlements are located, and large drainage systems that tend to follow the northwest-southeast-oriented topographic grain. The physiographic character of the region is shaped by its bedrock geology, deformational history, and active faulting. The basement rocks of the northern Coast Ranges consist of the Franciscan Complex and the Great Valley complex, the latter of which consists of two informal units, the Coast Range ophiolite and the Great Valley sequence. The Franciscan Complex and the Great Valley complex are in structural contact along the Coast Range Fault, a regional-scale structure and fundamental crustal boundary. The Franciscan Complex and the Great Valley complex are superposed by active, northwest-southeast-striking strike-slip faults that are associated with seismicity swarms. These active strike-slip faults can produce moderate to large earthquakes that have moment magnitudes of 7–8. In places, these active structures bound large ranges and valleys, suggesting that much of the modern topographic expression is the result of active deformation processes. This report contains new 1:24,000-scale geologic mapping along the southern part of the Bartlett Springs Fault Zone between Clear Lake and Lake Berryessa. The map area spans 738 square kilometers in northern Napa County, southern Lake County, and parts of Yolo and Colusa Counties. The south and east borders of the map are 90 kilometers north of San Francisco and 70 kilometers west of Sacramento, respectively. The map area is within the Knoxville mining district, which has a history of mercury and gold mining dating back to the mid-19th century. The two main towns in the region, Lower Lake and Clearlake, California, are west-northwest of the map area. Approximately 71,000 people live in the cities and rural communities located within a 40-kilometer radius of the center of the map area. The bedrock geology, cross sections, and structural data presented herein are critical for evaluating the long-term evolution of the Bartlett Springs Fault Zone. This work will supplement studies on local seismic hazards, liquefaction potential, landslide hazards, earthquake geology, natural resources, groundwater resources, engineering geology, and tectonic history by providing the background information for site-specific investigations on these subjects.

California↗
USGS2003

Geology and timing of mineralization at the Cangshang gold deposit, north-western Jiaodong Peninsula, China

The Cangshang gold deposit of the north-western Jiaodong Peninsula contains reserves of greater than 50 tonnes (t) and is developed by the largest open pit gold mine in China. This deposit is a Jiaojia-style (i.e. disseminated-and-veinlet) deposit. It is controlled by the San-Cang fault zone, which trends ~040° and dips 40–75°SE at the mine site. The main (no. 1) orebody lies between a hanging wall of Precambrian metamorphic rocks (mainly amphibolite) of the Fenzishan Group and a footwall composed of the Mesozoic Linglong granitoid. The ore zone is mainly composed of pyritized, sericitized and silicified granitoid, which has undergone variable degrees of cataclasis. SHRIMP U–Pb dating of zircon indicates that the protolith of the hanging wall amphibolite was formed at 2530±17 Ma and underwent metamorphism at 1852±37 Ma. The footwall granodiorite has been dated at 166±4 Ma, whereas zircons from the ore zone yield a younger age of 154±5 Ma. Cathodoluminescence images of zircons from the granodiorite and ore zone show oscillatory zonation indicative of an igneous origin for both and the ages of these zircons, therefore, are all interpreted to be representative of magmatic crystallization. Dating of sericite by 40 Ar– 39 Ar has been used to directly determine the timing of formation of the Cangshang deposit, providing the first time absolute age on formation of the Jiaojia-style gold deposits. The well-defined age of 121.3±0.2 Ma provides the precise timing of gold mineralization at the Cangshang deposit. This age is consistent with those of Linglong-style (vein type) gold mineralization, also from the north-western Jiaodong Peninsula, at between 126 and 120 Ma. Therefore, our work indicates that both styles of gold deposits in the Jiaodong Peninsula were formed during the same mineralization event.

Jiaodong Peninsula↗
USGS1998

Oreshoot zoning in the Carlin-type Betze orebody, Goldstrike Mine, Eureka County, Nevada

Field and laboratory investigations of the giant Betze gold orebody, the largest Carlin-type deposit known, in the north-central Carlin trend, Nevada document that the orebody is composed of individual high-grade oreshoots that contain different geologic, mineralogic, and textural characteristics. The orebody is typical of many structurally controlled Carlin-type deposits, and is hosted in thin-bedded, impure carbonate or limy siltstone, breccia bodies, and intrusive or calc-silicate rock. Most ores in the Betze orebody are highly sheared or brecciated and show evidence of syndeformational hydrothermal deposition. The interplay between rock types and pre- and syn-structural events accounts for most of the distribution and zoning of the oreshoots. Hydrothermal alteration is scale dependent, either in broad, pervasive alteration patterns, or in areas related to various oreshoots. Alteration includes decarbonatization (~decalcification) of carbonate units, argillization (illite-clay), and silicification. Patterns of alteration zoning in and surrounding the Betze orebody define a large porous, dilated volume of rock where high fluid flow predominated. Local restriction of alteration to narrow illite- and clay-rich selvages around unaltered marble or calc-silicate rock phacoids implies that fluid flow favored permeable structures and deformed zones. Gold mainly is present as disseminated sub-micron-sized particles, commonly associated with Asñrich pyrite, although one type of oreshoot contains micron-size free gold. Oreshoots form a three-dimensional zoning pattern in the orebody within a WNW-striking structural zone of shearing and shear folding, termed the Dillon deformation zone (DDZ). Main types of oreshoots are: (1) rutile-bearing siliceous oreshoots; (2) illite-clay-pyrite oreshoots; (3) realgar- and orpiment-bearing oreshoots; (4) stibnite-bearing siliceous oreshoots; and (5) polymetallic oreshoots. Zoning patterns result from paragenetically early development of illite-clay-pyrite oreshoots during movement along the DDZ, and subsequent silicification and brecciation, associated with formation of the realgar- and orpiment-bearing, and stibnite-bearing oreshoots. Additional shear movement along the DDZ followed. Polymetallic oreshoots, which contain minerals rich in Hg, Cu, Zn, Ag, and native Au, were the last ores to form and overprint most earlier oreshoots. Ore textures, gouge, phyllonitic rock, alteration style, and previously documented isotopic and fluid-inclusion data, all indicate a weakly to moderately saline fluid that ascended and cooled during structural displacements. Changing conditions, due to water-wall rock reactions and P-T changes during deformation, are probably responsible for fluid variation that resulted in zoning of the different oreshoots during dynamic interaction of the Au-bearing fluid with the wall rock. This investigation indicates that isolated As-, Sb-, and Hg-rich ores are separate parts of a larger single gold system. This large gold system was contemporaneous with post-Jurassic brittle-ductile deformation, on the basis of deformed mineralized pods of the Jurassic Goldstrike pluton, and large-scale hydrothermal flow, and together they appear to be an integral part of the formation of some Carlin-type gold deposits in north-central Nevada.

Nevada↗
USGS1911

Geology and ore deposits of the Breckenridge district, Colorado

The Breckenridge district is situated in Summit County, Colo., 60 miles. west-southwest of Denver, near the crest of the Continental Divide, and is drained by Blue River, a tributary of the Grand. Placer mining began here in 1860, but it was not until about 1879 that attention was turned to lode mining. During the last five years gold dredging, after many failures, has become established as an important industry.

Colorado↗
USGS1976

Statistical studies of selected trace elements with reference to geology and genesis of the Carlin gold deposit, Nevada

Linear regression and discriminant analyses techniques were applied to gold, mercury, arsenic, antimony, barium, copper, molybdenum, lead, zinc, boron, tellurium, selenium, and tungsten analyses from drill holes into unoxidized gold ore at the Carlin gold mine near Carlin, Nev. The statistical treatments employed were used to judge proposed hypotheses on the origin and geochemical paragenesis of this disseminated gold deposit.

Professional Paper↗
USGS2004

Interseismic strain and rotation rates in the northeast Mojave domain, eastern California

The northeast Mojave domain, a type locality for bookshelf faulting, is a region of east striking, left-lateral faults in the northeast corner of the Mojave block, a block otherwise dominated by ∼N40°W striking, right-lateral faults. Paleomagnetic evidence suggests that blocks within the domain have rotated clockwise about a vertical axis as much as 60° since 12.8 Ma [Schermer et al., 1996] . In 1994, and again in 2002, the U.S. Geological Survey surveyed an array of 14 geodetic monuments distributed across the northeast Mojave domain. The 2002 survey results were adjusted to remove the coseismic offsets imposed by the nearby Hector Mine earthquake (16 October 1999, M w = 7.1). The adjusted deformation across the array appears to be uniform and can be approximated by the principal strain rates ε 1 = 28.9 ± 9.1 N77.2°W ± 4.8° and ε 2 = −48.2 ± 8.9 N12.8°E ± 4.8° nstrain yr −1 ; extension reckoned positive, and quoted uncertainties are standard deviations. That strain accumulation could be released by slip on faults striking N32°W but not by bookshelf faulting on the east striking faults alone. The vertical axis rotation rate of the northeast Mojave domain as a whole relative to fixed North America is 71.0 ± 6.4 nrad yr −1 (4.07° ± 0.37° Myr −1 ) clockwise, about twice the maximum tensor shear strain rate. The observed rotation rate acting over 12.8 Myr would produce a clockwise rotation of 52.1° ± 4.7°, exclusive of possible coseismic rotations. That rotation is in rough agreement with the paleomagnetic rotation accumulated in the individual fault blocks within the northeast Mojave domain since 12.8 Ma.

California↗
USGS2019

Petrographic, geochemical, and geochronologic data for cenozoic volcanic rocks of the Tonopah, Divide, and Goldfield Mining Districts, Nevada

The purpose of this report is to summarize geochemical, petrographic, and geochronologic data for samples, principally those of unmineralized Tertiary volcanic rocks, from the Tonopah, Divide, and Goldfield mining districts of west-central Nevada (fig. 1). Much of the data presented here for the Tonopah and Divide districts are for samples collected by Bonham and Garside (1979) during geologic mapping in and around those districts, whereas much of that for samples from the Goldfield district were obtained by Ashley (1974; 1979; 1990a). Additional data were derived from samples collected between 2012–2015, as part of the Mineral Resources Program funded project titled: “Magmatic-tectonic history and component sources of major precious metal deposits in the southern Walker Lane”. A small amount of additional geochemical data for samples from each of the districts were compiled from other sources. Individual sample collectors are identified by appropriate entries in the “Collector” field (appendix 1) and published sources of geochemical data are defined by entries in the “Chem_Src” data field (appendix 1).

California, Nevada↗
USGS2010

Co-Cu-Au deposits in metasedimentary rocks-A preliminary report

A compilation of data on global Co-Cu-Au deposits in metasedimentary rocks refines previous descriptive models for their occurrence and provides important information for mineral resource assessments and exploration programs. This compilation forms the basis for a new classification of such deposits, which is speculative at this early stage of research. As defined herein, the Co-Cu-Au deposits contain 0.1 percent or more by weight of Co in ore or mineralized rock, comprising disseminated to semi-massive Co-bearing sulfide minerals with associated Fe- and Cu-bearing sulfides, and local gold, concentrated predominantly within rift-related, siliciclastic metasedimentary rocks of Proterozoic age. Some deposits have appreciable Ag ? Bi ? W ? Ni ? Y ? rare earth elements ? U. Deposit geometry includes stratabound and stratiform layers, lenses, and veins, and (or) discordant veins and breccias. The geometry of most deposits is controlled by stratigraphic layering, folds, axial-plane cleavage, shear zones, breccias, or faults. Ore minerals are mainly cobaltite, skutterudite, glaucodot, and chalcopyrite, with minor gold, arsenopyrite, pyrite, pyrrhotite, bismuthinite, and bismuth; some deposits have appreciable tetrahedrite, uraninite, monazite, allanite, xenotime, apatite, scheelite, or molybdenite. Magnetite can be abundant in breccias, veins, or stratabound lenses within ore or surrounding country rocks. Common gangue minerals include quartz, biotite, muscovite, K-feldspar, albite, chlorite, and scapolite; many deposits contain minor to major amounts of tourmaline. Altered wall rocks generally have abundant biotite or albite. Mesoproterozoic metasedimentary successions constitute the predominant geologic setting. Felsic and (or) mafic plutons are spatially associated with many deposits and at some localities may be contemporaneous with, and involved in, ore formation. Geoenvironmental data for the Blackbird mining district in central Idaho indicate that weathering of abundant Fe, S, As, Co, and Cu in sulfide minerals of the deposits produces acidic waters, especially in pyrite-rich deposits; mine runoff has high concentrations of Fe, Cu, and Mn that exceed U.S. drinking water or aquatic life standards.

Open-File Report↗
USGS1987

Hydrologic monitoring of selected streams in coal fields of central and southern Utah — Summary of data collected, August 1978-September 1984

The U.S. Geological Survey conducted a coal-hydrology monitoring program in coal-field areas of central and southern Utah during August 1978-September 1984 to determine possible hydrologic impacts of future mining and to provide a better understanding of the hydrologic systems of the coal resource areas monitored. Data were collected at 19 gaging stations--18 stations in the Price, San Rafael, and Dirty Devil River basins, and 1 in the Kanab Creek Basin. Streamflow data were collected continuously at 11 stations and seasonally at 5 stations. At the other three stations streamflow data were collected continuously during the 1979 water year and then seasonally for the rest of their periods of record. Types of data collected at each station included quantity and quality of streamflow; suspended sediment concentrations; and descriptions of stream bottom sediments, benthic invertebrate, and phytoplankton samples. Also, base flow measurements were made annually upstream from 12 of the gaging stations. Stream bottom sediment sampled at nearly all the monitoring sites contained small to moderate quantities of coal, which may be attributed chiefly to pre-monitoring mining. Streamflow sampled at several sites contained large concentrations of sulfate and dissolved solids. Also, concentrations of various trace elements at 10 stations, and phenols at 18 stations, exceeded the criteria of the EPA for drinking water. This may be attributed to contemporary (water years 1979-84) mine drainage activities. The data collected during the complete water years (1979-84) of monitoring do provide a better understanding of the hydrologic systems of the coal field areas monitored. The data also provide a definite base by which to evaluate hydrologic impacts of continued or increased coal mining in those areas. (Author 's abstract)

Utah↗