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 εHf_(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 εHf_(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. [Copyright &y& Elsevier]