Abstract

The Precambrian rocks of the Wichita Mountains compose a stratiform complex in which alumina-poor red granophyre, with related granite and granophyric rhyolite, overlies gabbro and anorthosite. The complex is the upper part of a huge gabbroic lopolith, formed under conditions of tectonic quiet or tension. Zircon age determinations indicate that the granophyres are about 640 million years old, and the complex may correlate with the Keweenawan of the Lake Superior region.

The very different complex of the Arbuckle Mountains is composed mostly of aluminarich granite to quartz diorite and probably represents part of a composite batholith formed in an orogenic belt. Two zircon determinations of the age of a granite average 940 million years and indicate correlation with the granitic rocks of central Texas.

The granophyric rhyolites of the Timbered Hills area of the Arbuckle Mountains and the numerous diabase dikes cutting the Arbuckle granitic rocks are probably related to the rocks of the Wichita Mountains, but the plutonic rocks of the two areas are unrelated.

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