Potassic volcanism near Mono Basin, California; evidence for high water and oxygen fugacities inherited from subduction.
Lange, Rebecca A; Carmichael, Ian S E; Renne, Paul R (1993) Potassic volcanism near Mono Basin, California; evidence for high water and oxygen fugacities inherited from subduction. Geology (Boulder). 21; 10, Pages 949-952. 1993.
| Authors | Lange, Rebecca A; Carmichael, Ian S E; Renne, Paul R |
|---|---|
| Year | 1993 |
| Title | Potassic volcanism near Mono Basin, California; evidence for high water and oxygen fugacities inherited from subduction. |
| Source | Geology (Boulder). 21; 10, Pages 949-952. 1993. |
| Publisher | Geological Society of America (GSA). Boulder, CO, United States. 1993. |
| Document type | Serial |
| ISSN | 0091-7613 |
| GeoRef | 1993-038104 |
| Keywords | absolute-age; California-; Cenozoic-; crystallization-; dates-; east-central-California; fugacity-; geochemistry-; hydration-; K-Ar; lava-; Long-Valley-Caldera; magmas-; mantle-; Mono-Basin; Mono-County-California; Neogene-; oxidation-; oxygen-; plate-tectonics; Pliocene-; potassic-composition; Quaternary-; subduction-; Tertiary-; United-States; upper-mantle; volcanism-; water- |
Abstract
Exposed around the margins of Mono basin and the periphery of Long Valley caldera are approximately 100 km (super 3) of potassic, basic to intermediate lavas that record high water and oxygen fugacities. Most eruptions occurred between 4 and 2 Ma, although sporadic potassic volcanism continued into the Quaternary with a pulse between 0.1 and 0.5 Ma, approximately 15 km northeast of Mono basin. The lava types include absarokite, minette, hornblende lamprophyre, trachybasalt, and trachyandesite. Estimated water contents for lavas without hydrous phenocrysts range between 2 and 3 wt%, considerably more than mid-ocean ridge, oceanic island, or back-arc magmas. Calculated f O (sub 2) values fall between -0.4 and +1.2 log units of the Ni-NiO buffer. Although this potassic suite was erupted in an extensional tectonic setting at the western margin of the Basin and Range province, its high K (sub 2) O/TiO (sub 2) and low Zr/Ba ratios suggest a subduction-modified mantle source. If subduction was the process that enriched the lithospheric mantle in large-ion lithophile elements (K, Ba, etc.), it was also a mechanism for mantle oxidation and hydration. October 1993.