Provenance of a late Proterozoic–early Cambrian basin, Sierras de Córdoba, Argentina

Abstract

Abstract Detrital zircons in metasedimentary rocks of Cambrian or older age in the Sierras de Cordoba provide information on sources of continental detritus on the western paleo-margin of Gondwana. Analysis of single zircon grains indicates dominant populations of Neoproterozoic (∼600–700 Ma) and Mesoproterozoic (950–1050 Ma) age, and a limited presence of Paleoproterozoic (∼1900 Ma) zircon. Additional constraints on provenance are provided by the Pb isotopic compositions of peraluminous granites derived from the metasedimentary section. These compositions fall within the distinctive 207 Pb -rich Gondwana provinces and therefore appear to rule out a Laurentian source such as the Argentine Precordillera. We interpret the sources of the Neoproterozoic and Paleoproterozoic zircons to be Gondwanan, most likely derived from the cratonic regions of South America and/or the once contiguous cratons of southwestern Africa. The Mesoproterozoic population constitutes more than half the analyzed grains and could be derived from ∼1.0 Ga rocks exposed along the western margin of the Amazon craton (e.g. Sunsas belt, Colombian Andes) and/or its rifted equivalents (e.g. Arequipa Massif). We conclude that the metasedimentary rocks in the Sierras de Cordoba and related rocks to the north in the Puncoviscana Formation developed marginal to Gondwana when much of the locally exposed crust was composed of Mesoproterozoic rocks, although these rocks are now sparingly exposed. The most likely sources for Mesoproterozoic sediment are the Arequipa–Antofalla terrane, the Borborema Province and the Kalahari craton, all of which were proximal to the Sierras Pampeanas in late Neoproterozoic reconstructions. Additional constraints on the relative paleogeographic locations of the Arequipa–Antofalla terrane, the Kalahari craton and the Puncoviscana trough in the late Neoproterozoic are needed to distinguish among these potential sources.