Petrology and petrogenesis of the Jurassic Eagle Mountain intrusion, southeastern California.

摘要

he 165 Ma Eagle Mountain intrusion is a heterogeneous, enclave-bearing, metaluminous remnant of the Cordilleran Jurassic arc that intrudes Precambrian-Paleozoic metasedimentary rocks in the southeastern Mojave Desert of California. The main phase of the intrusion consists of a microdiorite enclave-bearing host facies of broadly granodioritic composition, a dioritic mixed facies, and a monzogranitic homogeneous facies. The enclaves represent quenched masses of mafic magma. Irregular, late phase leucogranite bodies intrude the main phase.;Mineral equilibria indicate emplacement at 6.5 kilometers depth (1.7 kilobars pressure) and solidus temperatures ranging from 760;The intrusion comprises both juvenile, mantle-derived (;Enclave and host facies magmas were generated from the same source, but ascended different routes before mingling near the level of emplacement. Mixing formed heterogeneous, dioritic mixed facies magma. Crystal fractionation (predominantly plagioclase, orthoclase, and hornblende) and accumulation (predominantly plagioclase, orthoclase, and biotite) expanded the compositional range of the host facies magma. Fractionation of an assemblage rich in plagioclase and hornblende yielded main phase monzogranite, which in turn produced late phase leucogranite by removal of plagioclase