T204 Best Student Geologic Mapping Competition (Posters)
Tuesday, 24 September 2019
9:00 AM - 6:30 PM
Hall AB, North Building
DISCOVERY AND ANALYSIS OF A BLIND GEOTHERMAL SYSTEM IN SOUTHEASTERN GABBS VALLEY, WESTERN NEVADA
Paper number: T204-1
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM
Authors
Abstract
This study assessed the potential for high-temperature (≥130°C) blind geothermal systems in southeastern Gabbs Valley, Nevada, an area with no previously known geothermal activity or geothermal exploration, by integration of geologic, geophysical, and geochemical datasets. Gabbs Valley is a complex, tectonically active basin within the Great Basin on the boundary between the transtensional central Walker Lane domain and extensional Basin and Range province. The termination of the Petrified Springs fault, a major dextral fault of the central Walker Lane, into an array of normal faults indicates that the area occupies a displacement transfer zone, which is a favorable structural setting for geothermal activity. A substantial northwest-trending gravity high within the south-central part of the basin is produced from offsets along concealed northwest-striking dextral-normal faults that intersect strands of north-northeast-striking normal faults. Multiple lines of direct and indirect evidence suggest the presence of a blind geothermal system in this area, including collocated intersecting gravity gradients, magnetic-low, low-resistivity, and 2-m temperature anomaly. Potentially related, warm (32°C) water samples from agricultural wells 7 km northwest of the 2-m temperature anomaly yield geothermometers indicating subsurface fluid temperatures of 130-140°C. Six temperature-gradient holes were drilled to target the extent of the shallow-temperature and geophysical anomalies. Two wells contained high temperatures exceeding boiling with bottom-hole temperatures of 114.5°C and 124.9°C, and the remaining wells displayed elevated to background temperatures ranging from 79.2°C to 28.7°C. The observed temperature gradients for the two hottest drill holes necessitate intercepts of hydrothermal fluids and establish the discovery of a blind geothermal system that may be capable of supporting a power plant.
Geological Society of America Abstracts with Programs. Vol. 51, No. 5
doi: 10.1130/abs/2019AM-337585
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