Publications
Publications from the staff of the Geology, Minerals, Energy, and Geophysics Science Center
Filter Total Items: 2354
Geophysical framework of the northern San Francisco Bay region, California
We use geophysical data to examine the structural framework of the northern San Francisco Bay region, an area that hosts the northward continuation of the East Bay fault system. Although this fault system has accommodated ∼175 km of right-lateral offset since 12 Ma, how this offset is partitioned north of the bay is controversial and important for understanding where and how strain is accommodated
Authors
Victoria E. Langenheim, Russell W. Graymer, Robert C. Jachens, Robert J. McLaughlin, D.L. Wagner, Donald S. Sweetkind
In vitro studies evaluating leaching of mercury from mine waste calcine using simulated human body fluids
In vitro bioaccessibility (IVBA) studies were carried out on samples of mercury (Hg) mine-waste calcine (roasted Hg ore) by leaching with simulated human body fluids. The objective was to estimate potential human exposure to Hg due to inhalation of airborne calcine particulates and hand-to-mouth ingestion of Hg-bearing calcines. Mine waste calcines collected from Hg mines at Almadén, Spain, and Te
Authors
John E. Gray, Geoffrey S. Plumlee, Suzette A. Morman, Pablo L. Higueras, James G. Crock, Heather A. Lowers, Mark L. Witten
Calibration and filtering strategies for frequency domain electromagnetic data
echniques for processing frequency-domain electromagnetic (FDEM) data that address systematic instrument errors and random noise are presented, improving the ability to invert these data for meaningful earth models that can be quantitatively interpreted. A least-squares calibration method, originally developed for airborne electromagnetic datasets, is implemented for a ground-based survey in order
Authors
Burke J. Minsley, Bruce D. Smith, Richard Hammack, James I. Sams, Garret Veloski
It's not just about climate change - What about soils?
Vladimir Vernadsky was one of the giants of geochemistry. Considered the founder of the fi eld of biogeochemistry and a true pioneer in “whole Earth” studies, he realized by 1945 that “Man under our very eyes is becoming a mighty and ever-growing geological force.” In the intervening 65 years, his “ever-growing force” has become a tidal wave. The global population has been increasing exponentially
Authors
Martin B. Goldhaber
Are modern geothermal waters in northwest Nevada forming epithermal gold deposits?
Hydrothermal systems currently are active near some gold deposits in northwestern Nevada. Possible links of these modern systems to gold mineralization were evaluated by chemically and isotopically analyzing water samples from the Brady, Dixie Valley, Humboldt House, San Emidio-Empire, Soda Lake, and Wabuska geothermal areas. In addition, quartz veins from Humboldt House and the adjacent Florida C
Authors
George N. Breit, Andrew G. Hunt, Ruth E. Wolf, Alan E. Koenig, Richard Fifarek, Mark F. Coolbaugh
Transient electromagnetic mapping of clay units in the San Luis Valley, Colorado
Transient electromagnetic soundings were used to obtain information needed to refine hydrologic models of the San Luis Valley, Colorado. The soundings were able to map an aquitard called the blue clay that separates an unconfined surface aquifer from a deeper confined aquifer. The blue clay forms a conductor with an average resistivity of 6.9 ohm‐m. Above the conductor are found a mixture of gray
Authors
David V. Fitterman, V. J. S. Grauch
Strontium isotope detection of brine contamination in the East Poplar oil field, Montana
Brine contamination of groundwater in the East Poplar oil field was first documented in the mid-1980s by the U.S. Geological Survey by using hydrochemistry, with an emphasis on chloride (Cl) and total dissolved solids concentrations. Supply wells for the City of Poplar are located downgradient from the oil field, are completed in the same shallow aquifers that are documented as contaminated, and t
Authors
Zell E. Peterman, Joanna N. Thamke, Kiyoto Futa, Thomas A. Oliver
Thermal state of permafrost in North America: A contribution to the international polar year
A snapshot of the thermal state of permafrost in northern North America during the International Polar Year (IPY) was developed using ground temperature data collected from 350 boreholes. More than half these were established during IPY to enhance the network in sparsely monitored regions. The measurement sites span a diverse range of ecoclimatic and geological conditions across the continent and
Authors
S.L. Smith, V.E. Romanovsky, A.G. Lewkowicz, C.R. Burn, M. Allard, G.D. Clow, K. Yoshikawa, J. Throop
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), g
Authors
Henry N. Ohlin, Robert J. McLaughlin, Barry C. Moring, Thomas L. Sawyer
Colloidal and physical transport textures exhibited by electrum and naumannite in bonanza epithermal veins from western USA, and their significance
It is reasonably clear that disequilibrium or “far-from equilibrium” conditions lead to the formation of silica colloids and their deposition in many epithermal deposits. This implies ore-forming solutions had elevated concentrations of dissolved silica, well in excess of amorphous silica saturation. We have previously demonstrated that such colloidal silica particles were deposited in epithermal
Authors
James A. Saunders, Peter G. Vikre, Derick L. Unger, Lee Beasley
Fluid flow, solution collapse, and massive dissolution at detachment faults, Mormon Mountains, Nevada
Dissolution has removed large volumes of rock at low-angle normal faults, i.e., detachment faults, in the Mormon Mountains and the Tule Springs Hills in the eastern Basin and Range Province, southeastern Nevada. Evidence for major dissolution includes widespread solution-collapse breccias, meter-scale stylolite structures, and high-angle accommodation faults that terminate at or merge with dissolu
Authors
Sharon F. Diehl, R. Ernest Anderson, J. D. Humphrey
Geology of the Lake Mead region: An overview
The Lake Mead region contains major Miocene disruptions of structures formed during Mesozoic tectonic shortening. Erosion by the Colorado River and its tributaries has produced exceptional exposures of diverse structures and basin deposits recording the disruptions. Here we provide an overview of the results of studies of these features that started in earnest in 1934 when Chester Longwell began a
Authors
R. Ernest Anderson, L. Sue Beard