Stratigraphy and tectonic setting for the Ordovician VMS deposit in La Colorada mine (Argentinian Puna)

Abstract

Understanding seaflor massive sulfie mineralizations that have been modifid by deformation and metamorphism requires knowledge of their volcanic substrate, their base and precious metals contents and theirgeological setting. The massive sulfie ores of La Colorada mine (La Colorada-Limeca District, Salta province,NW Argentina) are hosted by a volcano-sedimentary sequence of Ordovician age with a complex history ofsuperposing magmatism, hydrothermal alteration and metamorphism. La Colorada Mine is located 68 km N ofSan Antonio de Los Cobres, in the town of Cobres (La Poma department), at an average altitude of 3900 m a.s.l.Previous works described the La Colorada massive sulfies either as Sedex or as VMS-type. In this study, based onthe cores from three drill holes in the mine area, we present petrographic and geochemical data of the host rocksand the sulfie ores and discuss them in the context of the lithostratigraphic sequence of the site. The studied orelevels consist of massive sulfies, with the metal association Fe?Cu?Pb?Zn. The sulfie mineral assemblage isdominated by pyrrhotite and pyrite, accompanied by sphalerite, galena, chalcopyrite, and minor amounts ofarsenopyrite associated with Au/Ag-sulfosalts. The geochemical information about the ore lenses suggestsclassifying the deposit into the Au-rich volcanic massive sulfie (VMS) typology, with a Zn-rich lens, in a pelitemafi subtype, while the geochemical data on interlayered volcanic rocks point towards a back-arc setting, inagreement with the regional geotectonic reconstructions of the Easter basin of Northern Puna.