Geochemical variations during development of the 5.46 Ma Broadwell Mesa basaltic volcanic field, California

By:

Links

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.

Additional publication details

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