A PETROGRAPHIC ANALYSIS OF THE COLD SPRINGS BRECCIA (WICHITA MTS., OKLAHOMA): NEW APPROACHES TO AN OLD PROBLEM

Early Cambrian igneous rocks in the magmatically bimodal Southern Oklahoma Aulacogen are well exposed around the Wichita Mts of SW Oklahoma. Outcrops of the Cold Springs Breccia (CSB) beautifully record a strong episode of felsic and mafic components interacting. Previous studies have examined the CSB with varying results but a definitive petrogenetic model has yet to be produced. Mafic and felsic magmas clearly co-existed at this site, consistent with recent U-Pb zircon ages for Wichita igneous complex gabbros and granites on the regional scale and interbedded mafic and felsic lavas. What is the relationship of Wichita mafic and felsic magmatism and can we gain hints about these relationships by studying the CSB? Does the CSB represent a region of incipient melting or magma unmixing? Insights on the relationship between mafic and felsic igneous activity may be gained by studying the mineralogical, geochemical, and isotopic characteristics of the CSB. Can we relate CSB mafic components to any Wichita Mt. gabbros (e.g., anhydrous vs. hydrous) and/or CSB felsic component to Wichita granites (e.g., Quanah, Mt. Scott, Reformatory)? New imaging techniques allow for more detailed petrographic study than previously possible. Careful petrographic study will be followed by electron microprobe analyses of mineral phases that will allow us to find how it relates to the other members of this magmatic suite for a more thorough understanding of the Southern Oklahoma Aulacogen and rift-related magmatism.