HR: 0830h
AN: V51H-0367    [PDF]
TI: Understanding the Chemical and Structural Dynamics of a Geothermal System Using Hyperspectral Imaging and Field Observations, Dixie Meadows, Nevada
AU: * Kennedy-Bowdoin, T J
EM: Tbowdoin@es.ucsc.edu
AF: University of California at Santa Cruz, Department of Earth Sciences, UCSC, 1156 High St., Santa Cruz, CA 95064 United States
AU: Silver, E A
EM: Esilver@es.ucsc.edu
AF: University of California at Santa Cruz, Department of Earth Sciences, UCSC, 1156 High St., Santa Cruz, CA 95064 United States
AU: Martini, B A
EM: Martini@hyvista.com
AF: HyVista Corporation, P.O. Box 437, Baulkham Hills, NSW 1755 Australia
AU: Pickles, W L
EM: Pickles1@llnl.gov
AF: Lawrence Livermore National Labs, University of California, 7000 East St., L-644, Livermore, CA 94550-8080 United States
AB: Dixie Valley hosts the largest geothermal plant in the state of Nevada. As part of an exploration program to evaluate other geothermal sites we mapped a 16 km swath of the eastern front of the Stillwater Range, including the Dixie Valley Fault system (Caskey et al. 1996) and Dixie Hot Springs. This visibly hydrothermally altered portion of the range front is located 25 km south of the existing plant and 10 km north of a major bend in the Dixie Valley Fault System. We used hyperspectral (HyMAP) data to locate outcrops of high temperature, hydrothermally altered minerals (including alunite, kaolinite, dickite, jarosite, and hematite). Several outcrops of these altered minerals exist in the mapped region, and one area of roughly 1 square kilometer shows abundant high temperature alteration. We also utilized an ASD field spectrometer to ground-truth our image interpretation and to map more subtle mineral distributions. These spectra support the locations of the mapped high temperature mineralization based on the hyperspectral data, and show that other high temperature minerals, such as vein chalcedony are present on scales below the spectral resolution of the HyMap data (3 m). At active fumaroles near the range front, acidic vapor-phase mineralization is occurring, and we measured ground temperatures of up to 94 §C. Approximately 1 km into the valley, at Dixie Valley Hot Springs, we measured alkaline liquid discharge to have a pH of 8.4 and a temperature of 75 §C. We also carried out structural analysis using a DEM, hyperspectral-based mineral mapping, and field observations. We find that this outcrop is bounded on all sides by a set of cross-cutting faults. We hypothesize that extension related to the release of the bend to the south has resulted in increased permeability, and as result, greater geothermal activity. Both the intense alteration in this area, including the presence of active fumeroles and hotsprings, and the high permeability introduced by cross-cutting faults support this hypothesis. We suggest that this region is a prime candidate for further geothermal exploration.
DE: 8010 Fractures and faults
DE: 8040 Remote sensing
DE: 8045 Role of fluids
DE: 8109 Continental tectonics--extensional (0905)
DE: 8424 Hydrothermal systems (8135)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting