ACTIVE FAULT MAPPING FOR IDENTIFICATION OF STRUCTURAL PATTERNS AT THE GABBS VALLY, NV, GEOTHERMAL PROSPECT: INTERPRETATIONS FROM LIDAR AND LOW SUN-ANGLE PHOTOGRAPHY ANALYSIS

Recent work has identified 32 out of 37 high-temperature geothermal systems in western Nevada are on or near seismically-active Holocene (<10-13 ka) faults. Active Quaternary fault mapping aids in identification of potential areas of upwelling for deeply circulating geothermal fluids. Broader exploration plans that include field-based datasets such as structural mapping, hydrothermal alteration mineralogy studies, shallow and intermediate depth temperature gradient surveys, and stress orientation can be enhanced by detailed mapping of subtle fault scarps. This type of exploration plan focuses on locating deep drilling targets to prove and utilize a commercial geothermal resource.

The Gabbs Valley geothermal prospect is a blind (i.e. no surface expression), non-magmatic thermal anomaly broadly defined in the 1970’s. The prospect is located in western Nevada, adjacent the Walker Lane Belt, a northwest trending zone of dextral shear, within the Basin and Range. The association of active Holocene faults and high-temperature geothermal systems in the Great Basin, nearby hot springs, and the presence of historical fault ruptures makes this site a good candidate for detailed Quaternary fault mapping. High resolution (0.5 m horizontal resolution, greater than 5 cm vertical accuracy) LiDAR swath mapping and 1:12,000-scale low sun-angle (LSA) aerial photography were used to identify fault scarps. Fieldwork was completed to verify fault scarps mapped with imagery, and to determine their sense of motion.

Two fault sets were identified in the study area striking NNE, one set is right-oblique while the second set is left-oblique. The GPS determined extension direction is roughly N65W and suggests NNE striking structures should be normal faults, but these are observed to be dominantly right-oblique. This discrepancy may be a transition between typical east-west Great Basin extension, and northwest directed Walker Lane Belt dextral shear in the study area. Kinematics from field observations will be used to identify structures of interest. These findings will be integrated with a new shallow temperature survey and precision GPS survey as part of an integrated exploration model to site deep drilling targets.