Pliocene to Late Pleistocene Magmatism in the Aurora Volcanic Field, Nevada and California, USA: A Petrographic, Geochemical, and Isotopic Study

The Pliocene-Pleistocene Aurora Volcanic Field (AVF) covers 325 km2, stretches across the California-Nevada border north of Mono Lake, and overlaps the Miocene Bodie Hills Volcanic Field (BHVF). It lies within the northwest-striking Walker Lane shear zone at the western margin of the Basin and Range province. Although erupted in a post-subduction setting, normalized incompatible element patterns show a continental arc-like signature, similar to those of other late Cenozoic volcanic fields within the Walker Lane, interpreted to reflect a metasomatized lithospheric mantle source.Petrographic features suggest syn-magmatic open system processes. While trace element compositions show few signs of these processes, the range in isotopic ratios confirm them. The BHVF and the AVF rocks have similar Pb isotope ratios, however, the AVF rocks have higher 87Sr/86Sr, lower 143Nd/144Nd, and stronger correlations between 87Sr/86Sr, silica, and δ18O, indicating that crustal assimilation was a more influential process in the AVF than in the BHVF.