Petrology and Geochemistry of Mafic and Ultramafic Rocks from the Northern Bighorn Mountains, Wyoming

摘要

Precambrian intrusive bodies in the northern Bighorn Mountains, Wyoming, were formed during at least two distinct episodes of igneous injection. An older group of metadolerite and metapyroxenite intrusions was emplaced prior to the last regional metamorphism (2.75 b.y. ago) to affect the metasomatic, granitic country rock of the area. A younger group of dolerite and dolerite porphyry dikes has formed since that event. Chemical analyses indicate that both groups of intrusive rocks are of tholeiitic basalt affinity.