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Title: Three-Dimensional Geologic Characterization of a Great Basin Geothermal System: Astor Pass, Nevada

The Great Basin, western USA, exhibits anomalously high heat flow (~75±5 mWm-2) and active faulting and extension, resulting in ~430 known geothermal systems. Recent studies have shown that steeply dipping normal faults in transtensional pull-aparts are a common structural control of these Great Basin geothermal systems. The Astor Pass blind (no surface expression) geothermal system, Nevada, lies along the boundary between the Basin and Range to the east and the Walker Lane to the west. Across this boundary, strain is transferred from dextral shear in the Walker Lane to west-northwest directed extension in the Basin and Range, resulting in a transtensional setting consisting of both northwest-striking, left-stepping dextral faults and northerly striking normal faults. Previous studies indicate that Astor Pass was controlled by the intersection of a northwest-striking dextral normal fault and north-northwest striking normal-dextral fault bounding the western side of the Terraced Hills. Drilling (to ~1200 m) has revealed fluid temperatures of ~94°C, confirming a blind geothermal system. Expanding upon previous work and employing interpretation of 2D seismic reflection data, additional detailed geologic mapping, and well cuttings analysis, a 3-dimensional geologic model of the Astor Pass geothermal system was constructed. The 3D model indicates a complex interaction/intersection area ofmore » three discrete fault zones: a northwest-striking dextral-normal fault, a north-northwest-striking normal-dextral fault, and a north-striking west-dipping normal fault. These two discrete, critically-stressed intersection areas plunge moderately to steeply to the NW-NNW and probably act as conduits for upwelling geothermal fluids.« less
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Publication Date:
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Report Number(s):
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Resource Relation:
Conference: Rocky Mountain Rendezvous of Geoscience Students and Employers
Research Org:
Rocky Mountain Rendezvous Student Expo
Sponsoring Org:
USDOE; USDOE EE Office of Geothermal Technologies (EE-2C)
Contributing Orgs:
Nevada Bureau of Mines and Geology, University of Nevada, Reno Mackay School of Earth Science and Engineering, University of Nevada, Reno
Country of Publication:
United States
15 GEOTHERMAL ENERGY Geothermal, faults, Astor Pass, Pyramid Lake Paiute, 3D Geologic Model, structural controls, Great Basin