Abstract

Studies of the anorthositic-gabbroic rocks of the Layered Series of the Wichita province, Oklahoma, establish petrologic constraints that suggest the body is an eroded stratiform gabbro complex, originally several kilometres thick, exposed at its approximate midsection. These rocks appear to be genetically unrelated to most of the other igneous rocks of the province. Uplift and erosional removal of several kilometres of upper Layered Series and overburden occurred prior to extrusion of the 500-m.y.-old Carlton Rhyolite and associated Wichita Granite. Time considerations imply a Precambrian age for the Layered Series, the emplacement of which reflects, according to this working hypothesis, a more ancient zone of rifting or crustal weakness, a rejuvenation of which in the Paleozoic evolved as the Southern Oklahoma aulacogen. This association of tholeiitic magmatism with an intracratonic rift system is analogous to the Midcontinent Rift (Duluth gabbro complex) and represents a petrogenesis different from that of the alkaline magmatism commonly found in this tectonic setting.

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