Geology, Geochronology, Geochemistry, and Pb-Isotopic Compositions of ProterozoicRocks, Poachie Region, West-Central Arizona: A Study of the East Boundary of Proterozoice Mojave Crustal Province

摘要

Plutonic rocks dominate the Proterozoic geology of the Poachie region, west-central Arizona, and are about equally divided between Early and Middle Proterozoic age. Plutons are separated by screens and contain inclusions of amphibolite-facies metamorphosed sedimentary rocks and metamorphosed felsic and mafic volcanic rocks. Early Proterozoic plutonic rocks range in composition from gabbro to granite; gabbro forms only small intrusions, whereas granodiorite and granite from large plutons or plutonic suites. Middle Proterozoic plutonic rocks are mostly granite but range in composition from granite to mafic granodiorite. Textures of plutonic rocks of both ages range from coarse grained and polyphyritic to fine grained. The Early Proterozoic rocks are variably foliated. The older ones commonly but not everywhere have a well-developed foliation; the younger ones have an apparently tectonic foliation only in local zones. The Middle Proterozoic rocks commonly have a well-developed flow foliation.