Structural Analysis of the Desert Peak-Brady Geothermal Fields, Northwestern Nevada: Implications for Understanding Linkages Between Northeast-Trending Structures and Geothermal Reservoirs in the Humboldt Structural Zone

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Conference Paper: Structural Analysis of the Desert Peak-Brady Geothermal Fields, Northwestern Nevada: Implications for Understanding Linkages Between Northeast-Trending Structures and Geothermal Reservoirs in the Humboldt Structural Zone

Abstract
Detailed geologic mapping, delineation of Tertiary strata, analysis of faults and folds, and a new gravity survey have elucidated the structural controls on the Desert Peak and Brady geothermal fields in the Hot Springs Mountains of northwestern Nevada. The fields lie within the Humboldt structural zone, a region of high heat flow characterized by east-northeast to north northeast- striking fault zones. The Tertiary section consists of late Oligocene ash-flow tuffs overlain by sequences of interfingering basalt lavas, diatomite, siltstone, sandstone, and limestone. The strata are fragmented into multiple north-northeast-trending fault blocks, which are bounded by en echelon, overlapping north-northeast- striking faults, most of which dip west-northwest. Slip data obtained from fault surfaces show that the north-northeast-striking faults generally accommodated dip-slip normal displacement, which is suggestive of a west-northwest-trending least principal stress. The strata are also deformed into north-northeast-trending, gently plunging folds. The folds are typically asymmetric with steeper and narrower west-dipping limbs found proximal to major west-dipping normal faults. These relations suggest that most folds resulted from a combination of east-tilting of fault blocks and drag along the west-dipping normal faults. The Brady field occurs along and near the north-northeast-striking, west-northwest- dipping, Brady fault zone, whereas the Desert Peak field may be localized near the northern end of the north-northeast-striking, west-northwest-dipping Rhyolite Ridge fault zone, which breaks into several strands (horse tails) as it loses displacement northward in the northern Hot Springs Mountains. Left-lateral shear along east-northeast-striking fault zones within the Humboldt structural zone may accentuate west-northwest-directed regional extension in the Hot Springs Mountains. This, combined with a greater density of faults and fractures induced by the transfer of strain between the en echelon overlapping normal faults, may promote deep circulation of fluids along the north-northeast-striking fault zones. Similar relations may characterize other geothermal fields within the Humboldt structural zone.

Authors 
James E. Faulds, Larry J. Garside and Gary L. Oppliger






Conference 
GRC Annual Meeting; Morelia, Mexico; 2003/10/12


Published 
Geothermal Resources Council, 2003





DOI 
Not Provided
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Online 
Internet link for Structural Analysis of the Desert Peak-Brady Geothermal Fields, Northwestern Nevada: Implications for Understanding Linkages Between Northeast-Trending Structures and Geothermal Reservoirs in the Humboldt Structural Zone

Citation

James E. Faulds,Larry J. Garside,Gary L. Oppliger. 2003. Structural Analysis of the Desert Peak-Brady Geothermal Fields, Northwestern Nevada: Implications for Understanding Linkages Between Northeast-Trending Structures and Geothermal Reservoirs in the Humboldt Structural Zone. In: Transactions. GRC Annual Meeting; 2003/10/12; Morelia, Mexico. Davis, CA: Geothermal Resources Council; p. 859-864