Geochemical and Petrologic Evolution of the Basic Plutons of the Peninsular Ranges Batholith, Southern California

The basic plutons within the southern California portion of the Peninsular Ranges batholith are multiple intrusive complexes that formed as a result of differentiation of a parental high-alumina basaltic melt at pressures less than 5 kb. The earliest rocks contain abundant plagioclase and lesser amounts of olivine and clinopyroxene as cumulate minerals with interstitial amphibole, orthopyroxene, and opaque minerals. Amphibole-bearing norite and amphibole gabbro represent the middle- and late-stage differentiates, respectively. Small amounts of quartz norite associated with several plutons do not fit compositionally or texturally into the differentiation scheme and may represent a contaminated phase of the parental gabbroic melt. Average values of $$K_{2}O, TiO_{2}$$, and nine trace elements for each pluton do not change with distance of the pluton from the western margin of the batholith. Models generating the granitic rocks of the Peninsular Ranges batholith by crystallization differentiation of the parental gabbroic melt are not supported by the trace element data.