This study is a petrologic investigation of the high temperature metamorphism and migmatization of mid- crustal pelitic pendants from the southern Sierra Nevada batholith, California. The primary goals are: (1) determine the extent of partial melting of batholith metasedimentary pendants during the large scale plutonism, and (2) quantify the efficiency of two-component mixing between batholith- and pendant-derived melts and the incorporation of pendant melts into large granitoid plutons. This study is designed to test the importance of assimilation of pre-existing shallow crust in the mass budget of the composite batholith. The pelites of the study area underwent extensive high-grade metamorphism and local migmatization in response to the intrusion of large granitoid plutons during the late Cretaceous. The isotopic ratios of Sr, Nd, and O of the batholithic rocks and the compositionally uniform pelite are distinct in the area. Hence, these isotopic ratios will be used as the principal tool in order to: (1) distinguish between batholith-derived and pelite-derived melts, and (2) constrain the mixing between the two in both migmatitic leucosomes and within the batholith. Petrographic studies of mineral and melting reactions within the migmatitic pelite as well as major and trace element chemistry will complement the isotopic data. The significance of crustal hybridization of Cordilleran batholiths with partial melts from metasedimentary host rocks is a controversial topic with important applications to quantifying crustal recycling in Phanerozoic magmatic arcs. This study should put important constraints on the extent and limits of such assimilation and hybridization.
