MUSCOVITE-GARNET GRANITES IN THE MOJAVE DESERT - RELATION TO CRUSTAL STRUCTURE OF THE CRETACEOUS ARC

A previously undocumented belt of Upper Cretaceous,primary muscovite- and garnet-bearing granites is exposed within the Mesozoic batholith o f the central and western Mojave Desert of California. This granite be lt occurs more than 140 km west of the better known Cordilleran interi or belt of primary muscovite-bearing granitoids, and the central and w estern Mojave granites are derived from much different sources, possib ly Pelona-Orocopia-Rand schists or similar rocks. Anatexis of Pelona-O rocopia-Rand schists to produce these granites would require emplaceme nt of the schists prior to the Late Cretaceous-early Tertiary, the mos t widely accepted time of schist emplacement. The granite belt may als o correlate with similar rocks in the southernmost Sierra Nevada and e astern Salinia. The distinctive isotopic and petrologic character of t he granite belt reflects differences in crustal structure between the Mojave-southern Sierra Nevada and the central Sierra Nevada portions o f the Cretaceous continental margin batholith, Possible correlation of this belt with rocks in eastern Salinia also places further limits on the pre-early Tertiary position of Salinia.