The central Sierra Nevada volcanic field of California: A geochemical study of a transitional arc

Central Sierra Nevada (CSN) lavas record an arc/post-arc transition that took place around 10 Ma. Analysis shows changes in the style of volcanism, post 6 Ma. I also show that Sierra Nevada Batholith, slab fluids, and sediments from the subducting slab did not contribute greatly to CSN trace element compositions.; Major oxide and trace element analyses of 42 volcanic rock samples were collected to assess the characteristics of ancestral Cascade volcanism. CSN samples display high total alkalis (Na2O + K2O), medium to high K2O, and range from 50--75 wt% SiO2; all key signatures of Cascade volcanism. We looked for distinct geochemical signatures to test for an arc influence. The CSN volcanic field contains Ba/Nb ratio between 52 and 151, high La/Nb ratios, and high Sr/P2O5 ratios, which generally agree with the criteria that characterize subduction-related lavas.; Two models were tested to explain the evolution of the CSN suite: fractional crystallization (FC) and assimilation-fractional crystallization (AFC). FC better explains both major oxide and trace element variations, when compared to AFC.