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Late Cenozoic volcanism, geochronology, and structure of the Coso Range, Inyo County, California

May 10, 1980

The Coso Range lies at the west edge of the Great Basin, adjacent to the southern part of the Sierra Nevada. A basement complex of pre‐Cenozoic plutonic and metamorphic rocks is partly buried by ∼35 km3 of late Cenozoic volcanic rocks that were erupted during two periods, as defined by K‐Ar dating: (1) 4.0–2.5 m.y., ∼31 km3 of basalt, rhyodacite, dacite, andesite, and rhyolite, in descending order of abundance, and (2) ≤1.1 m.y., nearly equal amounts of basalt and rhyolite, most of the rhyolite being ≤0.3 m.y. old. Vents for the volcanic rocks of the younger period are localized on and near a horst of basement rocks within a concavity defined by the distribution of vents of the older period. The alignment of many vents and the presence of a considerable number of roughly north‐trending normal faults of late Cenozoic age reflect basin and range tectonics dominated by roughly east‐west lithospheric extension. Fumaroles, intermittently active thermal springs, and associated altered rocks occur within and immediately east of the central part of the field of Quaternary rhyolite, in an area characterized by various geophysical anomalies that are evidently related to an active hot‐water geothermal system. This system apparently is heated by a reservoir of silicic magma at ≥8‐km depth, itself produced and sustained through partial melting of crustal rocks by thermal energy contained in mantle‐derived basaltic magma that intrudes the crust in response to lithospheric extension.

Citation Information

Publication Year 1980
Title Late Cenozoic volcanism, geochronology, and structure of the Coso Range, Inyo County, California
DOI 10.1029/JB085iB05p02381
Authors Wendell A. Duffield, Charles R. Bacon, G. Brent Dalrymple
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geophysical Research B: Solid Earth
Index ID 70200638
Record Source USGS Publications Warehouse
USGS Organization Volcano Science Center

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