Structural control on the development of an anomalous concentration of calderas in the Neuquén Andes: Pino Hachado volcanic complex (38°30´S-71°W)

Abstract

One of the most important concentrations of volcanic complexes in the entire Southern Andes, developed during the last 5 Ma, is present at 38°30´S next to the drainage divide. These volcanic features, formed calderas and domic complexes which have been amalgamated in a volcanic plateau of 50 x 50 kilometers. Its origin is associated with young activity of one of the branches of the northern intra-arc Liquiñe-Ofqui fault system, as widespread Plio-Quaternary faulting is developed east of the volcanic arc. Moreover, quadrangular geometries in the volcanic complexes, as well as widespread linear controls in fissural monogenetic fields, suggest that additional mechanisms, linked to basement structure, have defined the emplacement of such big volumes of magmas. Aeromagnetic data constitute a first approach to determine basement segmentation active in the region during ancient phases of crustal attenuation. Therefore, final geometry and distribution of the Pino Hachado volcanic complex (38°30´S-71°W), eventhough related to Plio-Quaternary tectonics at the arc zone, are deeply influenced by basement structure.