Northern ancestry for the Goochland terrane as a displaced fragment of Laurentia

Abstract

The ancestral position of the Goochland terrane, an isolated block containing Mesoproterozoic crust in the Appalachian Piedmont of eastern Virginia, during Grenvillian orogenesis has direct bearing on the breakup of Rodinia. Ages, lithology, geochemistry, and Pb and Nd isotope compositions of the Montpelier Anorthosite and State Farm Gneiss of the Goochland terrane allow correlation with the Grenvillian Roseland Anorthosite and associated igneous suites of the Blue Ridge farther west in Virginia. In contrast, extensive metapelites, which underwent Devonian metamorphism and intrusion, and amphibolites of the Goochland terrane lack equivalents in the Blue Ridge. Dextral slip faults, which bound the Goochland terrane, as well as dextral faults farther north, suggest large-scale translation prior to late Paleozoic reaccretion. Ages of extension-related A-type granitoids within the Virginia Blue Ridge (735-680 Ma) suggest physical separation from compositionally similar granitoids in the Goochland terrane (630-588 Ma), Reading Prong (602 Ma), and Manhattan Prong (563 Ma). Pre-Iapetan restoration of the Goochland terrane northeastward of the Blue Ridge and outboard of the Reading Prong accounts for its affinities to the Blue Ridge (unique anorthosites), Manhattan Prong (abundant amphibolites), and Reading Prong (ca. 600 Ma magmatism). Thus similar to the translation of Madagascar out of Africa, the Goochland terrane was rifted from Laurentia, marooned in oceanic crust, and then dextrally translated southward ∼500 km prior to late Paleozoic reaccretion. Documentation of large-scale dextral translation of eastern Laurentia relative to its fragments and other cratons during the Neoproterozoic and Paleozoic may assist in locating far-traveled pieces of the Grenville orogen for reconstruction of Rodinia.