Geochemical variations during development of the 5.46 Ma Broadwell Mesa basaltic volcanic field, California
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Abstract
The 5.46±0.04 Ma Broadwell Mesa basalt and associated basaltic volcanic field in the western Bristol Mountains, California, formed a ~6 km2 volcanic flow field with architecture including numerous lava flows, a ~1.1 km2 lava lake, and a ~0.17 km2 cinder cone. The local number of lava flows varies from one along the margins of the field to as many as 18 that are stacked vertically, onlapped by younger flows, or are laterally adjacent to each other. Geochemical plots of 40 hand samples indicate that all lava flows are basalt and that the field is slightly compositionally zoned. Typically, there is a progressive change in composition in sequentially overlying lava flows, although in some flow sequences, the overlying flow has an “across trend” step in composition, and a few have an “against trend” step in composition. The progressive compositional change indicates that the magmatic composition evolved during the history of the field, and the “across trend” and minor “against trend” steps probably represent periods of crystal fractionation or reinjection of magma during hiatuses in eruptions. The lack of clastic sedimentary rocks or even aeolianite interstratified with the lava flows probably indicates that the Broadwell Mesa volcanic field was short-lived.
Suggested Citation
Buesch, D.C., 2017, Geochemical variations during development of the 5.46 Ma Broadwell Mesa basaltic volcanic field, California, in ECSZ does it: Revisiting the Eastern California Shear Zone 2017 Desert Symposium Field Guide and Proceedings, p. 103-117.
| Publication type | Conference Paper |
|---|---|
| Publication Subtype | Conference Paper |
| Title | Geochemical variations during development of the 5.46 Ma Broadwell Mesa basaltic volcanic field, California |
| Year Published | 2017 |
| Language | English |
| Publisher | California State University Desert Studies Center |
| Contributing office(s) | Geology, Minerals, Energy, and Geophysics Science Center |
| Description | 15 p. |
| Larger Work Type | Book |
| Larger Work Subtype | Conference publication |
| Larger Work Title | ECSZ does it: Revisiting the Eastern California Shear Zone 2017 Desert Symposium Field Guide and Proceedings |
| First page | 103 |
| Last page | 117 |
| Conference Title | 2017 Desert Symposium |