75-12 New Geochemical data for Rhyolites and Diabase intrusions in the Wichita Mountains, Southern Oklahoma Aulacogen

Session: Mineralogy, Geochemistry, Petrology, and Volcanology Student Session (Posters)

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Abstract:

The late Ediacaran to Cambrian Southern Oklahoma Aulacogen (SOA) records extensive bimodal magmatic activity associated with the opening of the southern Iapetus Ocean. The igneous rocks crop out in the Wichita and Arbuckle Mountains and consist of the Carlton Rhyolite Group, Wichita granites, gabbros, widespread diabase intrusions, and extensive subsurface basalt flows.

The rhyolites form the uppermost portion of the igneous rift fill and provide insight into the distribution, and petrogenesis of felsic volcanic activity in the region. The diabases contain information about mantle source regions and the evolution of mafic magmas in the crust during rifting.

Here, we present complete major and trace element data for 30 rhyolites and diabases in the Wichita Mountains that have not been analysed previously, or for which trace element data are incomplete.

On standard discrimination diagrams, our diabase data mostly fall within available data for diabases in the SOA. Almost all our samples show similar REE patterns, with slight Eu anomalies in some cases and moderate LREE enrichment similar to enriched MORB. Two samples, however, show higher total REE contents but similar overall E-MORB-type patterns. One of the samples comes from the eastern Wichitas, and the other comes from much further to the west. This suggests that two types of diabase with somewhat different petrogenetic histories occur in the Wichita Mountains.

Rhyolite samples show strong LREE enrichment, negative Eu anomalies, and high HFSE concentrations, supporting an origin from high-temperature, A-type magmas. Our data show strong geochemical similarities to other rhyolites previously analysed in the SOA. One of our rhyolite samples comes from a dike intruding Wichita granite. Most of our rhyolites come from lava flows that predate intrusion of the granites. This dike shows similar trace element contents to the other rhyolites, indicating a similar petrogenetic history in spite of the time difference.

Another analysed rhyolite dike is located at the base of the thickest rhyolite flow in the Wichita Mountains and shows strong geochemical similarities to it. This suggests that the dike served as a feeder for the overlying flow. This is the only known example of a feeder dike associated with any of the rhyolite flows in the SOA.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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