Geodynamic evolution of the early Paleozoic Western Gondwana margin 14°–17°S reflected by the detritus of the Devonian and Ordovician basins of southern Peru and northern Bolivia

Abstract

We present results of a combined study of in situ U-Pb and Lu-Hf analyses on detrital zircons of Ordovician to Devonian sandstone successions of the Eastern Cordillera of Peru and Bolivia, as well as of the Altiplano and Coastal Cordillera of Peru (14°-17°S). We use our data to constrain the provenance and tectonic evolution of this part of the Gondwana margin in the early Paleozoic. The zircon-age composition is very variable in the different locations. Sandstones of the Eastern Cordillera have a dominant input of Brazilian-age zircons (0.7-0.5Ga) with two prominent peaks at around 0.52- 0.58Ga and 0.61-0.67Ga. A prevailing eastern source (Brazilian Shield, Amazonian Craton) is inferred. In contrast, sandstones from the Coastal Cordillera and Altiplano have major inputs of Famatinian (0.5-0.4Ga), Grenvillian (1.2-0.9Ga) and occasionally zircons of 1.85-1.75Ga crystallisation ages. Here, a dominant provenance from the Arequipa Massif is likely. Zircons preserving a juvenile component with eHf(t) values range from about +12 to +6 are limited to crystallisation ages between 1.45 and 1.0 Ga. All younger grains have lower eHf(t) values consistent with recycling of old crust without juvenile additions during the Neoproterozoic. Brazilian-age zircons of an Amazonian craton provenance and Famatinian-age zircons of an Arequipa Massif provenance have similar Hf model ages suggesting their derivation from the same evolved crust. © 2010 International Association for Gondwana Research.