CONICET | Buscador de Institutos y Recursos Humanos

By means of facial, stratigraphic, petrographic, geochemical andgeochronological studies we characterize the Garamilla Formation, cropping outin the western Nordpatagonian Massif.The studies of these volcanic rocks reveal an Early Jurassic volcanic episodeformed by three volcanic units that change from normal calc-alkaline to high-Kcalc-alkaline series. Other geochemical features reveal a progressive changefrom an initial subduction-related volcanism to one intraplate-related volcanism.This volcanic episode is temporally and geochemically equivalent to thosevolcanic units located in half-grabens in several areas of the Neuquén Basin.The volcanic units were erupted into different structural designs. A portion of itsdepocenter was interpreted as a transtensional half-graben, whereas the otherexhibits a trapdoor structure. The lineament trends that bound the volcanicsystem were also recognized in western Nordpatagonian Massif, and wereassigned to the Gondwanide Orogeny.