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At least 469 records · Page 26Linked to original sources
USGS1986

Maps showing aeromagnetic data and interpretation of the Medford 1 degree by 2 degrees Quadrangle, Oregon-California

These maps are part of a folio of maps of the Medford 1 o x 2 o quadrangle, Oregon, prepared under the Conterminous United States Mineral Assessment Program. Other publications in this folio discuss the geology, geophysics, geochemistry, and mineral assessment of the Medford 1 o x 2 o quadrangle and are listed in the references at the end of this report. The distinctive magnetic properties of the major rock types of the Medford 1 o x 2 o quadrangle over produce explicit magnetic anomalies. For example, contacts between magnetic ophiolitic rocks with nonmagnetic sedimentary rocks cause abrupt aeromagnetic boundaries even though these contacts may be buried at some depth below the topographic surface. Careful study of the aeromagnetic data, therefore, can provide insights about the geology and the mineral resource potential below the mapped surface. For example, aeromagnetic data may indicate the presence of an ultramafic body at shallow depth that is connected to an ultramafic outcrop with known chromite deposits.

Oregon↗
USGS1983

Aeromagnetic map and interpretation of geophysical data from the Condrey Mountain Roadless Area, Siskiyou County, California

The Condrey Mountain Roadless Area lies within the Klamath Mountains geologic province, a province composed of four eastward-dipping imbricate thrust slices or belts consisting predominantly of marine arc-related volcanic and sedimentary rocks, but also including significant amounts of ultramafic and other ophiolitic rocks (Irwin, 1981). From west to east the four Klamath Mountains thrust slices are called the western Jurassic belt, the western Paleozoic and Triassic belt, the central metamorphic belt, and the eastern Klamath belt. The Condrey Mountain Road less Area is located within a structural window in the western Paleozoic and Triassic belt, a window in which the structural dome comprised of the Condrey Mountain Schist is exposed (Coleman and others, 1983). North, east and south of the roadless area, the Condrey Mountain Schist is separated from the overlying western Paleozoic and Triassic belt by a low-angle regional thrust, whereas to the west the two units are in high-angle fault contact (Coleman and others, 1983). The Condrey Mountain schist consists mainly of sedimentary and volcanic rocks metamorphosed to greenschist facies. Metasedimentary rocks are exposed over most of the eastern and central parts of the structural window. Metavolcanic rocks occupy the western part of the window but also occur in small exposures within the metasedimentary rocks and along the eastern and southern margins of the window. Tabular bodies of metaserpentinite, the largest of which crops out near White Mountain, are contained within the metasedimentary rocks. Densities of hand samples from 11 sites scattered throughout the Condrey Mountain window average 2.66±0.05 g/cm 3 . The four samples of metavolcanic rocks yielded a higher average density than the seven samples of metasedimentary rocks (2.71±0.04 g/cm 3 versus 2.63±0.03 g/cm 3 ). Along the western edge of the Condrey Mountain Road less Area, numerous narrow north-trending zones of mineralized schist extend from near Copper Butte on the south, northward to Elliot Creek (Coleman and others, 1983). These zones contain abundant pyrite mineralization associated with pyrrhotite, chalcopyrite, qalena, and sphalerite. The Blue Ledge mine area, 2 mi north-northeast of Copper Butte, is located in a zone of mineralized schist. The western Paleozoic and Triassic belt that nearly surrounds the Condrey Mountain Schist is a melange of sedimentary, volcanic, and ultramafic rocks metamorphosed to amphibolite facies (Coleman and others, 1983). Only two samples of the metamorphic melange were collected near the Condrcy Mountain Road less Area, but extensive sampling of this unit southwest of the roadless area yielded an average sample density of 2.86±0.15 g/cm 3 (112 samples) (Jachens and others, 1983).

California↗
USGS1984

Aeromagnetic, Bouguer gravity, and interpretation maps of the Sheep Hole-Cadiz Wilderness Study Area (CDCA-305), San Bernardino County, California

The Federal Land Policy and Management Act (Public Law 94-579, October 21, 1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral surveys on certain areas to determine their mineral resource potential. Results must be made available to the public and be submitted to the President and the Congress. These maps presents the results of a mineral survey of the Sheep Hole-Cadiz Wilderness Study Area (CDCA-305), California Desert Conservation Area, San Bernardino County, California. The U.S. Bureau of Mines conducted a mineral survey of the Sheep Hole-Cadiz Wilderness Study Area, which encompasses approximately 200,000 acres including enclosed private lands, in south-central San Bernardino County, California. The U.S. Bureau of Mines studied the mineral resources of mines, prospects, and mineralized areas; geologic, geochemical, and geophysical investigations were conducted by the U.S. Geological Survey. The study area is located in the Mojave Desert 13 miles east of Amboy, California, 20 miles east of Twentynine Palms, California, and 90 miles east of San Bernardino, and encompasses parts of the Dale Lake, Bristol Lake, Cadiz Valley and Cadiz Lake 15-minute quadrangles. Its borders are defined by the Amboy Road and a gas pipeline service road on the northwest, the unimproved Cadiz Valley access road on the east, State Route 62 along the south, and the Iron Age mine road and an unimproved powerline service road on the west. Major access from the east and west is provided by State Route 62 and access from the north is provided by the Amboy Road. Companion reports to this one describe the mineral resource potential (March and others, 1982), the geology (Howard and John, 1984), and hydrothermal alteration studies (Raines, 1983).

California↗
USGS1994

Maps showing interpretation, using R-mode factor analysis, of trace-element abundances in heavy-mineral concentrate samples, Delta 1° x 2° quadrangle, Utah

A set of heavy-mineral concentrate data for the Delta 1° x 2° quadrangle, Utah Conterminous U.S. Mineral Assessment Program (CUSMAP) project was compiled from results of analyses of samples collected during the National Uranium Resource Evaluation Program (SURE), as well as results obtained from samples collected more recently by the USGS. Data results, sampling methods, and analytical methods are provided in Abrogast and others, 1993; 1990; 1988a; 1988b). A similar report, discussing results obtained from stream-sediment samples, is presented in Zimbelman (1993a). The Delta 1° x 2° quadrangle, Utah (figure 1) contains a variety of hydrothermal mineral deposit types, including porphyry-, vein-, replacement-, and Carlin-type deposits. These deposit types have been worked for commodities including gold, silver, beryllium, uranium, lead, zinc, copper, manganese, and cadmium (Lindsey, 1977; Morris and Mogensen, 1978; Zimbelman and others, 1990; Zimbelman and others, 1988). Heavy-mineral concentrate and stream-sediment samples derived from these hydrothermally altered rocks typically contain many geochemical anomalies (for example, see Zimbelman 1993b, c, d). Element associations characterizing lithology and hydrothermal mineral deposits can be distinguished using R-mode factor analysis. This tool often is useful in reconnaissance-scale surveys where sample anomalies are often weak. and single-element distributions may not help to delineate targets. R-mode factors analysis can help identify geologic trends and areas most likely to contain the mineral deposits. R-mode factor analysis was performed on a data set of results of analyses for 19 elements in 643 samples and produced a six-factor model. These six factors represent the geochemical contributions to the data set provided by lithologic and mineralization processes, The distribution of samples that contain high scores for mineralization-related factors is widespread in the Delta quadrangle. These sample sites are though to relate to both known prospect and mineralization areas, as well as define new areas that are geochemically favorable to contain altered or mineralized rocks.

Utah↗
USGS1994

Map showing large structures interpreted from geophysical data in the vicinity of New Madrid, Missouri

This is one of a series of five seismotectonic maps of the seismically active New Madrid area in southeast Missouri and adjacent parts of Arkansas, Kentucky, and Tennessee (table 1). We cannot legibly show all the seismotectonic data on a single map, therefore each of the five maps in this series groups a different type of related information. Rhea and others (1994) summarized the background and purpose of the seismotectonic map folio.

Missouri↗