Reconnaissance geophysical studies of the geothermal system in southern Raft River Valley, Idaho
Gravity, aeromagnetic, and telluric current surveys in the southern Raft River have been used to infer the structure and the general lithology underlying the valley. The gravity data indicate the approximate thickness of the Cenozoic rocks and location of the larger normal faults, and the aeromagnetic data indicate the extent of the major Cenozoic volcanic units. The relative ellipse area contour map compiled from the telluric current survey generally conforms to the gravity map except for lower values in the area of the geothermal system. An area of low apparent resistivity values defined by the audiomagnetotelluric (AMT) survey appears to outline the extent of the geothermal reservoir even though the reservoir is deeper than the penetration of the survey. Self-potential anomalies relate to near surface hydrology. The Raft River Valley is underlain by about 2 km of Cenozoic rock, most of which is Tertiary sediments of the Salt Lake formation. On the west side of the valley the Tertiary rocks appear to be separated from the underlying Precambrian basement by a low angle fault along which the Tertiary rocks have slid off a buried basement dome. Subsequent normal faults displace both the basement surface and the Tertiary beds. The geothermal system occurs where these north-trending faults intersect a poorly understood northeast-trending zone that may be a basement shear zone. Apparently deep circulating water at a temperature of about 150/sup 0/C rises in the area of this intersection and then spreads laterally in porous zones near the base of the Tertiary rocks to form the geothermal reservoir. Upward leakage from the reservoir produces shallower effects that were measured by the AMT survey.
- Research Organization:
- Geological Survey, Denver, CO
- OSTI ID:
- 6149280
- Journal Information:
- Geophysics; (United States), Journal Name: Geophysics; (United States) Vol. 43:7; ISSN GPYSA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Geophysical logging case history of the Raft River geothermal system, Idaho
Geology and Hydrothermal Alteration of the Raft River Geothermal System, Idaho
Related Subjects
150301* -- Geothermal Exploration & Exploration Technology-- Geophysical Techniques & Surveys
CENOZOIC ERA
ELECTRICAL SURVEYS
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
GEOTHERMAL SYSTEMS
GRAVITY SURVEYS
HYDROTHERMAL SYSTEMS
IDAHO
LITHOLOGY
MAGNETIC SURVEYS
NORTH AMERICA
PACIFIC NORTHWEST REGION
RAFT RIVER VALLEY
ROCKS
TELLURIC SURVEYS
USA