Manifestación de greisen relacionada a la mineralización de wolframio de la Mina San Martín, Río Negro

Abstract

“Greisen Manifestation Related to Wolframium Mineralization at the San Martin Mine, Rio Negro”. A new locality with greisen alteration was found associated to the Permian granite and tungsten mineralization of the San Martin mine, Patagonian Massif. The greisen consists of muscovite-quartz and minor amounts of apatite, tourmaline and scarce crystals of topaz and zircon. It is found on the walls of the quartz veins within the host gran - ite. The greisenized rock shows an increase in Si, P, Sn, Hf, Zr and rare earths related to the original rock. The mica is classified as muscovite 2M1. Fluid inclusion studies reveal that the fluids have temperatures of trapping of 460 º C and low salinities (4 wt% NaCl equivalent). The calculated isotopic d 18 O values between 11 and 13 ‰ and d D between -32 and -34 ‰ on muscovite, suggest that the greisen was formed from magmatic waters with little involve - ment of metamorphic waters. The greisen is related to unevolved Paleozoic, metaluminous, I type granites with associated W mineralizations in the Northpatagonian Massif. The San Martin mine greisen differs in mineralogy and geochemistry, from greisens of Sierras Pam - peanas Occidentales which are associated to highly evolved S and A type Paleozoic granites with tungsten-tin mineralization.