Forearc tectonics and volcanism during the Devonian–Carboniferous evolution of the North Patagonian segment, southern Chile (41,3°S)

Late Paleozoic to early Mesozoic subduction complexes formed during the evolution of southwestern Gondwana and extensively crop out along Chilean continental margin. Recent findings in northern Patagonia (40°–43°S) revealed that accretionary processes were active since Devonian when enhanced lithosphere stretching forearc led formation Chaitenia island arc. The extension crust consecutively developed a backarc basin, which culminated compressive episode re-amalgamated arc with This produced intermediate grade metamorphism sedimentary rocks throughout extension. To constrain tectonic these processes, we combined petrology, structural analysis, whole-rock geochemical, isotopic tracing (Sr-Nd-Pb) data thermodynamic modelling. Two petro-tectonic domains are here defined. Western Coastal Range Domain is composed Carboniferous Permian metapsammopelitic rocks, mainly schists metasedimentary protolith exhibiting penetrative northeast southwest dipping main foliation associated basal accretion. Eastern comprised by garnet micaschists, metabasalts, metarhyolites, metasandstones. unit folded three ductile structures: first related rootless isoclinal folds, second kilometric scale west-verging tight third cylindrical folds. volcanic this domain middle alkaline metarhyolites metabasalts enriched-MORB normal-MORB affinities. Trace element composition suggests through shallow melting an extensional setting over supra-subduction zone. Nd Pb isotope point mantle source change for basaltic melts from EM1-like DM-like interpreted reflect embryonic mature system. calculated P–T micaschists follows: 1) clockwise IP–IT prograde Barrovian path, 2) isobaric thermal increase at ∼7 kbar 540°C, 3) adiabatic decompression. Finally, after metamorphism, uplifted thrusting probably occurred late Permian.