THE CRATERVILLE UNIT, A DISTINCT BODY ASSOCIATED WITH THE QUANAH GRANITE PLUTON IN THE WICHITA MOUNTAINS, OKLAHOMA

The Wichita Mountains in southwestern Oklahoma expose roughly a dozen Cambrian granite plutons emplaced as part of the Southern Oklahoma Aulacogen. The Quanah Granite comprises one of the youngest plutons. It is a relatively coarse-grained alkali feldspar granite that uniquely contains arfvedsonite in addition to Fe-Ti oxides. Although marked with ostensibly autogenic pegmatitic dikes and pods, its mapped pluton boundaries contain several anomalous granite intrusions with texture and composition more difficult to relate to the host granite. The largest of these comprises a portion of the mountains on and adjacent to Ft. Sill; its western portion crosses Oklahoma Highway 115 near Quanah Mountain. We refer to this distinct body as the Craterville unit.

The rock is distinct in texture and mineral composition. Like the Quanah Granite, it can be relatively coarse grained, it contains miarolitic cavities and hematite staining, and it weathers into boulders and grus, forming relatively steep topography. Unlike the Quanah, it contains sparse to abundant granophyre, a texture typically found in the region's other granites. Optical and SEM petrography, as well as XRPD, reveals hematite ± chlorite to be its only mafic minerals.

Due to its differences and its size, we postulate that the Craterville unit is a separate mappable body, resolvable at the 1:100 000 scale. Based on initial reconnaissance, we estimate the Craterville unit to have at least 8 km² of exposed surface area. Its documented contacts are somewhat enigmatic, but its southern edge appears to intrude the Cache Granite. At this time, its petrological and chronological relationship with the Quanah Granite or other bodies remains undefined.