EARLY SIERRA NEVADA MAGMATISM EXAMINED USING SHRIMP-RG U-Pb AGES AND TRACE ELEMENT COMPOSITIONS OF ZIRCON FROM THE MINERAL KING ROOF PENDANT RHYOLITE UNITS

摘要

Roof pendants engulfed between the granitoid plutons that comprise the Cretaceous Sierra Nevada batholith record the early history of Triassic-to-Jurassic arc volcanism in western North America. This study provides new U-Pb SHRIMP-RG ages of meta-rhyolites from the Mineral King roof pendant, as well as geochemical data, which document an extended and more complex early volcanic history in the southern Sierra Nevada than previous studies have suggested. Additionally, these new ages revise the existing relationship between the rhyolite units within the pendant and suggest that they may not share a common magmatic source. Zircon isotopic and trace element compositions suggest that these rhyolites may record the progressive involvement of continental crust in western North America.