The compositionally bimodal Pleistocene Coso volcanic field is located at the western margin of the Basin and Range province ∼60 km north of the Garlock fault. Thirty-nine nearly aphyric high-silica rhyolite domes were emplaced in the past million years: one at 1 Ma from a transient magma reservoir, one at ∼0·6 Ma, and the rest since ∼0·3 Ma. Over the past 0·6 My, the depth from which the rhyolites erupted has decreased and their temperatures have become slightly higher. Pre-eruptive conditions of the rhyolite magmas, calculated from phenocryst compositions using the two-oxide thermometer and the Al-in-hornblende barometer, ranged from 740°C and 270 MPa (2·7 kbar; ∼10 km depth) for the ∼0·6 Ma magma, to 770°C and 140 MPa (1·4 kbar; ∼5·5 km) for the youngest (∼0·04 Ma) magma. Results are consistent with either a single rhyolitic reservoir moving upward through the crust, or a series of successively shallower reservoirs. As the reservoir has become closer to the surface, eruptions have become both more frequent and more voluminous.
|Publication Subtype||Journal Article|
|Title||Rhyolite themobarometry and the shallowing of the magma reservoir, Coso volcanic field, California|
|Series title||Journal of Petrology|
|Contributing office(s)||Volcano Science Center|
|Other Geospatial||Magma Reservoir, Coso Volcanic Field|
|Google Analytic Metrics||Metrics page|