A review of the Famatinian Ordovician magmatism in southern South America: evidence of lithosphere reworking and continental subduction in the early proto-Andean margin of Gondwana

摘要

Along the proto-Pacific margin of Gondwana, from Venezuela to northeastern Patagonia, the Early-Middle Ordovician Famatinian orogeny was the first orogenic event following assembly of the supercontinent. Previous isotope studies of the igneous and (meta-)sedimentary rocks of southwestern Gondwana yield ambiguous implications for the role of juvenile mantle addition during the early crustal growth at the supercontinental margin. To interpret the geological and tectonic evolution of the orogen and the magma sources in different episodes we look at evidence from a large area of southern South America, including the 700 x 600 km type sector of the orogen in the Sierras Pampeanas (27 degrees-33 degrees S), the Precordillera, and northeastern Patagonia. Previous geological, geochemical and geochronological results are reviewed together with new U-Pb SHRIMP crystallization ages, Hf-177/Hf-176 and O-18/O-16 data for dated zircon, and whole-rock Sr and Nd isotope compositions.