AN ASSESSMENT OF THE TECTONIC HISTORY OF THE SOUTHERN APPALACHIANS BY INTEGRATING U-PB GEOCHRONOLOGY AND ELEMENTAL RATIOS OF ZIRCONS FROM THE BLUE RIDGE, PIEDMONT, AND COASTAL PLAIN

Despite serving as a prototypical example of continental collision and supercontinent formation, a comprehensive chronology of deformation, metamorphism and magmatism in the Appalachian mountains remains elusive. Whereas Appalachian orogenesis has often been viewed as the result of a series of discrete tectonic episodes, the growing database of Appalachian tectonics may support more continuous and/or diachronous models. Here we use variations in U-Pb ages and elemental ratios from southern Appalachian zircons collected from in situ crystalline rocks and the detritus eroded from them to better constrain the integrated history of southern Appalachian tectonics. U/Th data coupled with U-Pb ages from zircons in and derived from the southern Appalachians indicate substantial Devonian metamorphism and minimal Carboniferous-Permian and Ordovician metamorphism. These data support less episodic tectonic models, and suggest peak metamorphism occurred during the Acadian phase of the orogeny. U-Pb detrital-zircon ages from Mesozoic-Cenozoic sediments and sedimentary rocks derived from the southern Appalachians indicate dominant periods of magmatism during the Silurian and Carboniferous periods.