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Preliminary geologic map of the Tuscarora geothermal area, Elko County, Nevada [TWO PLATES AND TEXT]
Preliminary geologic map of the Tuscarora geothermal area, Elko County, Nevada TWO PLATES AND TEXT

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Product Code: OF2013-05


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Title: Preliminary geologic map of the Tuscarora geothermal area, Elko County, Nevada
Author: Gregory M. Dering and James E. Faulds
Year: 2013
Series: Open-File Report 2013-05
Format: two plates and text; plate 1: 33 x 24 inches, scale 1:24,000; plate 2: 24 x 33 inches, color, cross sections; text: 4 pages, B/W
Scale: 1:24,000

Tuscarora is an amagmatic geothermal system that lies in the northern part of the Basin and Range province, ~15 km southeast of the Snake River Plain and ~90 km northwest of Elko, Nevada. The Tuscarora area is dominated by late Eocene to middle Miocene volcanic and sedimentary rocks, all overlying Paleozoic metasedimentary rocks. A geothermal power plant was constructed in 2011 and currently produces 18 MWe from an ~170°C reservoir in metasedimentary rocks at a depth of 1740 m. Two distinct structural settings at different scales appear to control the geothermal field. The regional structural setting is a 10-km wide complexly faulted left step or relay ramp in the west-dipping range-bounding Independence–Bull Run Mountains normal fault system. Geothermal activity occurs within the step-over where sets of east- and west-dipping normal faults overlap in a northerly trending accommodation zone. The distribution of hot wells and hydrothermal surface features, including boiling springs, fumaroles, and siliceous sinter, indicate that the geothermal system is restricted to the narrow (< 1 km) axial part of the accommodation zone, where permeability is maintained at depth around complex fault intersections. Shallow up-flow appears to be focused along several closely spaced steeply west-dipping north-northeast-striking normal faults within the axial part of the accommodation zone. The recognition of the axial part of an accommodation zone as a favorable structural setting for geothermal activity may be a useful exploration tool for development of drilling targets in extensional terranes, as well as for developing geologic models of known geothermal fields. In addition, the presence of several high-temperature systems in northeastern Nevada demonstrates the viability of electrical-grade geothermal activity in this region despite low present-day strain rates as indicated by GPS geodetic data. Geothermal exploration potential in northeastern Nevada may therefore be higher than previously recognized.

Original Product Code: OF135