Collaborative Research: Age, Petrology, and Tectonic Setting of Purported Taconic-aged plutons, Ashland-Wedowee-Emuckfaw Belt, Southern Appalachians

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This collaborative project between investigators at Columbus State University and the University of Florida aims to resolve conflicting interpretations of the tectonic origin and age of a number of metamorphosed granitoids in the Ashland-Wedowee-Emuckfaw belt (Eastern Blue Ridge) province of Alabama in the southernmost Appalachians. Traditionally attributed to latest Cambrian-Middle Ordovician magmatism associated with the Taconic orogeny, the Elkahatchee Quartz Diorite, Zana Gneiss, and Kowaliga Gneiss have been considered by some workers to be part of an obducted Taconic island or peri-Laurentian arc emplaced atop the subducting margin of North America. SHRIMP-RG results from the dominant quartz diorite component of the Elkahatchee, however, suggest an Upper Devonian emplacement age with considerable evidence for abundant xenocrystic inheritance which may have complicated the initial whole rock and multi-grain analyses completed over two decades ago. The potential for significant Acadian-aged magmatic components in the Elkahatchee calls into question its association with a Taconic arc; a question which can only be addressed by detailed isotopic analysis of the various lithologies typically assigned to this batholith. Furthermore, since both the Zana and Kowaliga gneisses were assigned ages using some of the same techniques as those used to assign a latest Cambrian age to the Elkahatchee, attribution of these plutons to Ordovician orogenesis is also suspect. Spatially resolved U-Pb analysis of these plutons will provide the best temporal context for examining the Lu-Hf systematics of zircon components and, in combination, will allow us to constrain the petrotectonic evolution of parental magma(s).Results from this project will shed new light on the tectonic evolution of the North American margin and the development of the Appalachian Mountains through the Paleozoic. Significantly, it will provide new constraints on fundamental questions regarding evolution of the southern Appalachian orogeny because of its bearing on the continuity and nature of subduction along the eastern margin of North America during the closure of the Iapetus and Rheic oceans. These results will also afford an improved understanding of the role of important plutonic elements in the evolution of the southern Appalachians, which will be of advantage to many institutions in the region for undergraduate and graduate instruction. Integration of student and faculty expertise and opportunities at these universities will have a significant impact on training professional geoscientists, who are critical to developing a strong national STEM workforce, and will provide valuable support for a faculty research program at a predominantly undergraduate institution through the Research in Undergraduate Institutions program (RUI). Finally, this project will afford a group of geology undergraduates an invaluable experience (from field to analytical) through participation in a geological research program, greatly enhancing their undergraduate education and enhancing the nation?s STEM workforce.