Polymetallic VMS deposits of the Andes Fueguinos (southernmost Argentina): Preliminary report

The polymetallic volcanic-hosted massive sulphide deposits of the Andes Fueguios occur in a highly deformed but coherent stratigraphic succession of Late Jurassic metavolcanic and metasedimentary rocks. Local stratigraphy consists of porphyries along with rhyolitic lava, acidic tuff, breccias, conglomerates, radiolarian lutites and basaltic rocks: Mineralization occurs as massive stratiform, massive replacement and sulphide stringer veins. Sulphides are typically massive, fine-grained, layered and locally brecciated andconsists of pyrite and sphalerite, with lesser pyrrhotite, chalcopyrite, galena, tetrahedrite-freibergite, bourmonite, cobaltite and arsenopyrite. Styles of hydrothermal alteration identified in the host rocks include proximal silicification and more distal chloritization, sericitization and, in places, carbonatization. Future research will be focused on identifying the salient physico-chemical controls on the mineralization process and their implications for volcanic-hosted massive sulphide exploration in the district.