Abstract

The core of the Wichita Mountains of Oklahoma is a layered igneous intrusive mass composed of plagioclase cumulates, predominantly anorthosite, with some olivine-bearing anorthosite, gabbro, and olivine gabbro. Some chemical trends in the rocks indicate that cryptic layering is present but is the reverse of that found in most mafic layered intrusions. The anomalous position of highly calcic plagioclase near the top of the intrusion, inferred from field relations, coupled with possible reverse cryptic layering suggests a separation of anorthosite by flotation or rafting of plagioclase.

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