Geothermal exploration with remote sensing from 0.45--2.5 mum over Brady-Desert Peak, Churchill County, Nevada

The purpose of this study was to use the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Hymap (hyperspectral mapper) to remotely map unique geothermal identifiers over the Brady-Desert Peak geothermal fields. Both of these instruments detect reflected solar energy in the 0.45--2.5 mum wavelength region. Geothermal-related minerals display diagnostic characteristics in this wavelength region. The Brady-Desert Peak geothermal fields are located about 80 km east of Reno, Nevada in the Hot Springs Mountains. North-northeast-striking en-echelon faults act upon Tertiary volcanic and lacustrine rocks. The 20 MWe Brady geothermal plant is located in the hanging wall of the north-northeast-striking Brady's fault and is expressed by numerous fumaroles and mudpots for a distance of over 4 km. The 6.5 MWe Desert Peak geothermal plant is located in the hanging wall of the north-northeast-striking Rhyolite Ridge fault zone, which unlike Brady's fault shows no active thermal expression. Basalt, carbonate, and lacustrine units were discriminated with image transforms applied to ASTER bands covering the 0.45--2.5mu region. Known opaline sinter outcrops were also mapped with ASTER. The Hymap data was used to identify, gypsum, carbonate, kaolinite, and rocks composed of opaline silica, all serving as unique geothermal identifiers. Mapping results were synthesized with other spatial data in a geographic information systems (GIS) data base. This led to new structural interpretations Brady-Desert Peak. The same processing methods can be applied to new ASTER and Hymap data sets for future exploration in the Great Basin, especially in areas that lack active thermal expressions.