Palinspastic reconstruction of the Grenville terrane in the Blue Ridge Geologic Province,southern and central Appalachians,U.S.A

Examinations of Grenville massifs in the Blue Ridge Geologic Province of Virginia and North Carolina indicate that the country rocks (～ 1100–1450 Ma) are layered gneisses that were metamorphosed during Grenville orogenesis (～ 1000–1100 Ma) to amphibolite to granulite facies and intruded by plutonic suites. Subsequently, the Grenville terrane was intruded by a suite of peralkaline granitic plutons (～ 700 Ma) and progressively overlapped westward by Upper Precambrian to Cambrian sedimentary and volcanic rocks. Following deposition of Upper Precambrian and Palaeozoic rocks, the Blue Ridge Geologic Province was subjected to Taconic metamorphism (～ 450–480 Ma) which generally increased in intensity southeastward from greenschist (chlorite grade) to upper amphibolite (sillimanite grade) facies. Large-scale late Devonian thrusting (～ 350 Ma) along the Fries fault system and the Brevard zone-Yadkin fault system produced the present day distribution of juxtaposed Grenville massifs and Palaeozoic metamorphic zones in the Blue Ridge Geologic Province. Palinspastic restoration of the Taconic metamorphic zones to their pre-late Devonian relative positions yields an ～ 50 km displacement on the Fries fault system near the Grandfather Mountain window and and an ～ 80 km displacement on the Smith River allochthon farther east. Restoration of the Grenville massifs to this same palinspastic base shows that Grenville metamorphic grade decreased southeastward from the deeper granulite facies (opx + gar) to the shallower granulite facies (opx ± amp) to amphibolite facies.