Evidence for Early Mesoproterozoic (and Older?) Crust in the Southern and Central Appalachians of North America

Limited evidence from Sm-Nd TDM model ages, U-Pb ages of xenocrystic zircon, and Pb isotopic data indicates the presence of Paleoproterozoic and Mesoproterozoic crust (2.0-1.3 Ga) in the southern and central Appalachian orogen. This apparently unexposed older crust must underlie much of the Blue Ridge, and it was recycled to produce most of the rocks of the Blue Ridge with ages ≤1.3 Ga. In the eastern Blue Ridge and in blocks to the southeast, there also is a significant juvenile Neoproterozoic source component. Going toward the southeast, the central and eastern Piedmont (Carolina terrane) appears to be underlain by progressively less source component older than 1.0 Ga. Late Proterozoic rocks of the Carolina terrane are derived largely from a juvenile source with a Nd isotopic composition that approaches that of depleted mantle.