Late mesozoic-quaternary plate tectonics and the Geysers-Clear Lake geothermal anomaly, Northern Coast Ranges, California (Abstract)

Journal Article · Tue Feb 01 04:00:00 EST 1977 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:5445156

McLaughlin, J R

The development of structures related to the Geysers-Clear Lake geothermal anomaly can be explained in terms of relative motions of the North American and Pacific plates. Hypothetically, plate convergence during Late Jurassic to mid-Tertiary time produced a west-stepping subduction zone that thrust successively younger plates of sediments and volcanic rocks of the Franciscan assemblage eastward beneath oceanic crust and depositionally overlying sediments of the Great Valley sequence. East of this subduction zone, elements of previously subducted Franciscan plates were uplifted and faulted into the basal part of the ophiolite in response to regional compression. Some of the faults bounding the uplifted wedges died out upward into northwest-trending folds in the overlying ophiolite sheet, and others formed imbricate thrusts along which wedges of Franciscan rocks pierced the ophiolite. Many of these thrusts were later reactivated as strike-slip faults as motion between the Pacific and North American plates changed. Postulated rates of right-lateral motion between the Pacific and North American plates for the past 5 to 6 million years indicate that subduction and associated processes leading to partial melting deep in the subduction zone terminated in the Clear Lake region about 3 million years ago, with passage of the Mendocino triple junction. Following local termination of subduction, about 0.5 million years elapsed before eruption of the first Clear Lake volcanic rocks, during which time magma moved upward to mid-crustal levels, and extensional and strike-slipfaulting established conduits for venting of magma. This tectonic model implies that any significant new sources of geothermal energy in the Coast Ranges are most likely to be found north and northwest of the Clear Lake region, where subduction has recently been or is now active.

• Research Organization: US Geological Survey, Menlo Park, CA
• OSTI ID: 5445156
• Journal Information: Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 9:4; ISSN GAAPB
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150201* -- Geology & Hydrology of Geothermal Systems-- USA-- (-1989)
CALIFORNIA
CENOZOIC ERA
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC STRUCTURES
GEOLOGICAL SURVEYS
GEOLOGY
GEOTHERMAL FIELDS
GEYSERS GEOTHERMAL FIELD
IGNEOUS ROCKS
LAKES
MAGMA
MESOZOIC ERA
NORTH AMERICA
PLATE TECTONICS
QUATERNARY PERIOD
ROCKS
SEDIMENTS
SURFACE WATERS
TECTONICS
USA
VOLCANIC ROCKS