Publications

The mineral sector plays a key role in the economies of Guinea, Liberia, and Sierra Leone. The onset of the Ebola virus disease (EVD) outbreak in early 2014, together with changes in mineral market conditions, raised questions regarding the status of mining operations and of mineral development and exploration projects in all three countries. Mineral projects were the underpinnings of...

A thick Quaternary alluvial section fills a sedimentary basin beneath the Santa Clara Valley, California, located within the San Andreas Fault system at the south end of San Francisco Bay. This section consists of an upper sequence about 1,000 feet thick containing eight sedimentary cycles and a lower fine-grained unit as thick as several hundred feet. Together these constitute the...

A natural smoky quartz crystal from Shandong province, China, was characterised by laser ablation ICP-MS, electron probe microanalysis (EPMA) and solution ICP-MS to determine the concentration of twenty-four trace and ultra trace elements. Our main focus was on Ti quantification because of the increased use of this element for titanium-in-quartz (TitaniQ) thermobarometry. Pieces of a...

A reconnaissance investigation of the Carboniferous Lisburne Group in the Cobblestone Creek area, Chandler Lake Quadrangle, yields insights into its resource potential and regional relations. Locally porous vuggy dolostone with hydrocarbon reservoir potential occurs in the lower Lisburne in the three most southerly of five thrust sheets, and contains traces of dead oil in two of these...

A modeling approach that was used to predict the toxicity of dissolved single and multiple metals to trout is extended to stream benthic macroinvertebrates, freshwater zooplankton, and Daphnia magna. The approach predicts the accumulation of toxicants (H, Al, Cd, Cu, Ni, Pb, and Zn) in organisms using 3 equilibrium accumulation models that define interactions between dissolved cations...

The U.S. Geological Survey collaborated with international colleagues to assess undiscovered resources in porphyry copper deposits in the Central Asian Orogenic Belt and eastern Tethysides. These areas host 20 known porphyry copper deposits, including the world class Oyu Tolgoi deposit in Mongolia that was discovered in the late 1990s. The study area covers major parts of the world’s...

The induced magnetic field and the remanent magnetic field of rock masses are important to geologic modeling based on Earth’s magnetic field data. The orientation of the induced magnetic field is approximately parallel to the orientation of Earth’s geomagnetic field and its intensity can be derived from measured magnetic susceptibilities of rocks in a study area. The orientation and...

Global dependence on a limited number of countries for specific mineral commodities could lead to sudden supply disruptions for the United States, and barite is one such commodity. Analyses of barite supply amounts and sources for the United States are demonstrative of mineral commodities on which the country is import reliant. Mineral commodity trade flows can be analyzed more easily...

The U.S. Geological Survey has completed a series of geologic, mineral resource, and environmental assessment studies in the Rocky Mountains of central Colorado, from Leadville eastward to the range front and from New Mexico to the Wyoming border. Regional stream-sediment geochemical maps, useful for assessing mineral resources and environmental effects of historical mining activities...

Independent researchers working in the Talladega belt, Ashland-Wedowee-Emuckfaw belt, and Opelika Complex of Alabama, as well as the Dahlonega gold belt and western Inner Piedmont of Alabama, Georgia, and the Carolinas, have mapped stratigraphic sequences unique to each region. Although historically considered distinct terranes of disparate origin, a synthesis of data suggests that each...

Correlating laboratory resistivity measurements with geophysical resistivity models helps constrain these models to the geology and lithology of an area. Throughout the Fort Irwin National Training Center area, 111 samples from both cored boreholes and surface outcrops were collected and processed for laboratory measurements. These samples represent various lithologic types that include...

The purpose of this report is to present geochronologic data for unaltered volcanic rocks, hydrothermally altered volcanic rocks, and mineral deposits of the Miocene Bodie Hills and Pliocene to Pleistocene Aurora volcanic fields of east-central California and west-central Nevada. Most of the data presented here were derived from samples collected between 2000–13, but some of the...