RF/PHI ANALYSIS ON THE KOWALIGA GNEISS: IMPLICATIONS FOR THE BREVARD ZONE IN THE EASTERN BLUE RIDGE OF ALABAMA

The Middle-Upper Ordovician Kowaliga gneiss lies on the northwestern flank of the Brevard fault zone in the Ashland-Wedowee-Emuckfaw belt of the eastern Blue Ridge composite terrane in the southern Appalachians of Alabama. Intruding interlayered amphibolites and schists of the Emuckfaw Group near the structural and stratigraphic top of the eastern Blue Ridge, the Kowaliga gneiss is a batholith-scale composite pluton affected by Carboniferous (ca. 330 ma) regional middle-upper amphibolite facies metamorphism. Kyanite-sillimanite zone metamorphic conditions and associated regional deformation have produced ductilely-deformed feldspar throughout the Alabama eastern Blue Ridge. Although traditionally used on quartz grains in metasedimentary rocks (e.g. metaconglomerate), Rf/phi analysis of deformed feldspars in orthogneiss has been shown to be an effective tool for quantifying strain in metaigneous rocks where P-T conditions resulted in ductile deformation of feldspar. These ductilely-deformed feldspars record regional deformation, partitioning of strain within ductile shear zones, and have been used as strain markers in kinematic studies within the region. Regional Rf/phi studies from the eastern Blue Ridge in Alabama suggest a general increase in strain from northwest to southeast, towards the Brevard fault zone. In this study, we focus on a detailed Rf/phi transect across the Kowaliga gneiss in order to test the assumptions and results of these earlier studies and quantify strain gradients in proximity to the Brevard fault zone.