ABSTRACT
A study has been made of the Sn-W and sulphide vein mineralization at Cerro Avión and Valdehornillos, south end of the Villar del Ciervo granite (Salamanca, Spain). In this paper we summarize the mineralogical and chemical characteristics of the ore minerals, the processes of hydrotermal alteration, the mineral paragenesis, and the sulphur isotopic ratios of several sulphides. A first mineralization stage resulted in greisenization of the granite and deposition of cassiterite and wolframite, as well as some arsenopyrite disseminated within the greisenized granite. The main mineralization stage formed mostly arsenopyrite, with lesser amounts of other sulphides and bismuth. Scheelite resulted from the transformation of wolframite. Supergenic stage forming scorodite, covellite and iron oxides. Temperatures of formation, as derived from the arsenopyrite and chlorite geothermometers, range from 500 to 450 °C for the first stage, and between 315-250 °C for the main stage. Sulphur isotopes indicate an igneous derivation for the sulphur.
