Structural Controls of Lee Hot Springs, Southern Churchill County, Western Nevada: A Small Pull-Apart in the Dextral Shear Zone of the Walker Lane

Abstract

Allen Springs and Lee Hot Springs provide an opportunity to evaluate a geothermal reservoir model relative to structures of the Walker Lane. Allen Springs is a cool-temperature, natural seep, and Lee Hot Springs is a hot spring, emanating from a well drilled in the 1930s. These springs have been used for livestock water for much of the past century, and thermal applications have been explored periodically since the 1930s. Both springs are probably part of a single geothermal system with a reservoir temperature estimated at ~170º C. Detailed geologic mapping and geophysical investigations were used to investigate the structural controls of these springs. The study area is cut by multiple northeast-striking, southeast dipping normal faults that repeat Tertiary volcanic sequences. A series of northwest-striking dextral faults intersect these normal faults. Geologic and geophysical data suggest that these normal and dextral faults comprise a right step or small pull-apart, in a northwest-striking dextral shear zone of the Walker Lane. The geothermal reservoir is hosted in shallow basement rocks, and fluid flow is controlled by the northeast-striking normal faults with greatest documented displacement. The distribution of spring deposits along this normal fault indicate that fluid flow is also concentrated along intersections with the northwest-striking dextral faults.