Petrology of Miocene volcanic rocks in the Resting Spring Range, California

The late Miocene volcanic rocks of the Chicago Valley in the Southern Resting Spring Range consist of alternating basaltic-trachyandesite and trachyandesite lava flows and breccias, a trachydacite dome complex and lava flows, and a trachyandesite cinder cone complex. The presence of compositionally similar dikes, the dome complex, and eroded cinder cones and associated near-vent features (e.g., large bombs) indicate that volcanic rocks were erupted locally. Extensional tilting and erosion have exposed the core of this complex, allowing for a detailed look into the stratigraphy and construction of this syn-extensional magmatic system.; Field and petrographic evidence in the rocks of the study area show evidence of magma mixing. A petrogenetic model involving silicic recharge and magma mixing coupled with fractional crystallization and convective self mixing during mafic recharge best explains the geochemical data and field and petrographic observations.