First geochemical and geochronological characterization of Late Cretaceous mesosilicic magmatism in Gastre, Northern Patagonia, and its tectonic relation to other coeval volcanic rocks in the region

Abstract

This work characterizes Late Cretaceous calc-alkaline volcanic rocks in Gastre, Northern Patagonia, Argentina. These newly found porphyritic rocks bear an 40Ar–39Ar amphibole age of ∼ 74–76 Ma, a subduction-type geochemical signature and a deep, garnet-bearing source. Extruded in a stage of low magmatic activity in the Northern Patagonian Andes (∼ 41–44° S), they could represent an eastward migration of the Late Cretaceous magmatic arc that was associated with a regional compressive deformational stage in the South American margin.