TECTONOSTRATIGRAPHIC RELATIONSHIPS THAT DEFINE A FUNDAMENTAL APPALACHIAN TERRANE BOUNDARY WITHIN THE CENTRAL BLUE RIDGE OF NORTH GEORGIA

Recent detailed geologic mapping WNW of Dahlonega, GA has led to significant progress in the understanding of the Allatoona/Hayesville/Gossan Lead fault and terrane boundary within the central Blue Ridge of North Georgia. The Hayesville/Soque River and Allatoona faults separate three distinct tectonostratigraphic assemblages in this area; the Coweeta Group (CG), Great Smoky Group (GSG), and Dahlonega Gold Belt (DGB). The DGB here contains metasandstone, pelitic schist, and abundant mafic rocks of the Otto Formation and the Sally Free Mafic Complex (SFMC), while the GSG contains metasandstone and pelitic schist with abundant calc-silicate. The abundance of calc-silicate and apparent lack of mafic rocks in the GSG versus the apparent lack of calc-silicate and presence of abundant mafic rocks in the DGB support the delineation of the Allatoona fault (DGB over GSG). The Hayesville/Soque River thrust sheet, containing rocks of the CG, is bounded to the northwest by the Hayesville fault (CG over GSG) and to the southeast by Hayesville-Soque River fault (CG over DGB). Delineation of the Hayesville and Soque River faults here suggests that they are equivalent, and that the area immediately WNW of Dahlonega marks the southwestern terminus of the Hayesville/Soque River thrust sheet (as previously suggested by Nelson). Inequigranular, biotite-dominant (over trace muscovite), often migmatitic metasandstone and schist of the Coleman River Formation (CG) versus two-mica, nonmigmatitic, often equigranular metasandstone and schist of the GSG and Otto Formation constitute the principal criteria for the delineation of the Hayesville/Soque River fault. The Allatoona fault, which represents the southwest continuation of the terrane boundary, is truncated by the Hayesville/Soque River fault approximately 10 km west of Dahlonega. Observed field relationships combined with modal analysis (of all lithologic units); XRF whole-rock chemical analysis of mafics within the CG, Otto Formation, and SFMC; and a U-Pb SHRIMP zircon age date of a felsic gneiss within the SFMC provide additional crucial information concerning similarities and differences of these three distinct tectonostratigraphic assemblages.