PB ISOTOPES AS A CORRELATION TOOL TO CONSTRAIN RODINIA RECONSTRUCTION

Whole-rock Pb isotopic signatures of Proterozoic rocks appear to be coherent across large belts of Precambrian cratons, but may differ from one craton to another. As such, whole-rock Pb isotopic data could be a valuable correlation tool for reconstructing the Meso-Neoproterozoic supercontinent, Rodinia, by establishing or testing links between transferred terranes and potential “parent cratons”. In previous studies Pb isotopic data corroborated independent evidence that links the Paleozoic cover and Mesoproterozoic basement of the Argentine Precordillera Terrane with southeastern Laurentia, supported previously proposed correlation of southwestern Scotland with Labrador and Greenland and were used in conjunction with U/Pb geochronology to refute correlation of northeastern Laurentia and the Arequipa-Antofalla Basement of proto-Andean Amazonia within Rodinia.

Combining whole rock Pb and geochronologic data, we identify an alternate position for Amazonia within Rodinia. Pb isotopic compositions from juvenile ca. 1.3-1.0 Ga rocks from the Grenville Province of the United States are similar everywhere inboard of the Appalachian orogen, suggesting derivation from a common source reservoir. The signature of Grenvillian basement of the central and southern Appalachians is anomalous with respect to that of eastern Laurentia, but indistinguishable from that of Mesoproterozoic Amazonia. We propose that the Grenvillian basement of the central and southern Appalachians may be an allochthonous block of the ca. 1.3-1.0 Ga Sunsás Province of Amazonia that was transferred to eastern Laurentia as a result of collision between western Amazonia and southeastern Laurentia during amalgamation of Rodinia.