Physical volcanology and geochemistry of the Cambrian Carlton rhyolite in the Fort Sill area, southwestern Oklahoma

Abstract

The Carlton Rhyolite Group was emplaced during Cambrian rifting within the Southern Oklahoma aulacogen. Outcrops occur in the Wichita and Arbuckle Mountains. The largest exposures are in the Fort Sill area in the Wichita Mountains where two rhyolite flows are present. The mostly aphyric Davidson metarhyolite can be traced ~9.25 km along strike. The overlying Fort Sill rhyolite is rich in quartz and alkali feldspar phenocrysts and is the longest flow documented in the Carlton Rhyolite Group. It can be traced ~18.5 km along strike and is inferred to be a remnant of an originally more extensive lava flow, comparable to extrusive units documented from other A-type felsic provinces. A discontinuous unit of volcaniclastic metasedimentary rocks separates the two flows and their margins are partly truncated by intrusive granite. Geochemical data indicate both flows have within-plate, A-type compositions and were derived from separate magma reservoirs or sources.