Early Jurassic tectonomagmatic stages in the western North Patagonian Region, Argentina: insights from the Comallo volcanic sedimentary complex

The Comallo volcanic sedimentary Complex in the western North Patagonian Region begins with the development and collapse of Plinian-type eruptive columns of rhyolitic and dacitic composition associated to vent at approximately 192 Ma. Synchronous deposits are originating in alluvial and lagoon environments. The & sigma;Hf(t) values obtained in zircon grains indicate possible derivation by melting Paleoproterozoic and Mesoproterozoic crust. Upwards in the sequence appears basaltic and andesitic lava flows, as well as pyroclastic deposits produced during the eruptions. This volcanism is related to sustained pyroclastic fountains with a U-Pb zircon age of 185 Ma. The volcanic rocks were possibly derived from Paleoproterozoic, Mesoproterozoic, and Neoproterozoic crust affected by juvenile magmas in volcanic-arc environments. Chemical and isotopic variations are mainly due to changes in the local and regional tectonic conditions, the thickness of the continental crust, as well as the dip and age of the subducted oceanic crust.

Automated summary

The Comallo volcanic sedimentary Complex in the western North Patagonian Region is formed by the development and collapse of Plinian-type eruptive columns of rhyolitic and dacitic composition. The synchronous deposits are found in alluvial and lagoon environments. The derived zircon grains indicate the possibility of melting Paleoproterozoic and Mesoproterozoic crust. Basaltic and andesitic lava flows and pyroclastic deposits appear in the upward sequence, which are related to sustained pyroclastic fountains with a U-Pb zircon age of 185 Ma. The volcanic rocks are possibly derived from Paleoproterozoic, Mesoproterozoic, and Neoproterozoic crust affected by juvenile magmas in volcanic-arc environments. Chemical and isotopic variations are mainly caused by changes in the local and regional tectonic conditions, the thickness of the continental crust, as well as the dip and age of the subducted oceanic crust.