Field Mapping At Coso Geothermal Area (1980)

GEOTHERMAL ENERGY

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Exploration Activity: Field Mapping At Coso Geothermal Area (1980)

Exploration Activity Details
Location	Coso Geothermal Area
Exploration Technique	Field Mapping
Activity Date	1980
Usefulness	not indicated
DOE-funding	Unknown

Exploration Basis

Determine the areal extent of the magma reservoir

Notes

The distribution of quaternary rhyolite dome of the Coso Range was analyzed. Thirty-eight separate domes and flows of phenocryst-poor, high-silica rhyolite of similar major element chemical composition were erupted over the past 1 m.y. from vents arranged in a crudely S-shaped array atop a granitic horst in the Coso Range, California. The immediate source of heat for the surficial geothermal phenomena is probably a silicic magma reservoir that may still contain molten or partially molten material at a depth of around 8 km beneath the central part of the rhyolite field. Outlying rhyolite extrusions probably reflect the presence of feeder dikes emanating from the reservoir beneath the central region. Azimuths of dikes appear to be parallel to the regional tectonic axis of maximum horizontal compression, analogous to some dike-fed flank eruptions on basaltic shields and andesitic strato-volcanoes.

References

• Bacon, C.R.; Duffield, W.A.; Nakamura, K.   (10 May 1980) Distribution of quaternary rhyolite dome of the Coso Range, California: Implications for extent of the geothermal anomaly