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.
Citation Information
Publication Year | 2000 |
---|---|
Title | Rhyolite themobarometry and the shallowing of the magma reservoir, Coso volcanic field, California |
DOI | 10.1093/petrology/41.1.149 |
Authors | C.R. Manley, Charles R. Bacon |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Journal of Petrology |
Index ID | 70200567 |
Record Source | USGS Publications Warehouse |
USGS Organization | Volcano Science Center |