Abstract
The San Cristobal tungsten-base metal deposit differs from other quartz-wolframite vein deposits in that it has a major period of base metal mineralization consisting of pyrite, chalcopyrite, sphalerite, and galena. Homogenization temperatures of primary and pseudosecondary inclusions were measured in augelite (260–400°C), quartz (230–350°C) and sphalerite (180–220°C). The δ34S values of H2S in solution in equilibrium with the vein minerals range from 1.6 to 9.0 permil increasing through the paragenesis. The relatively heavy \(\delta ^{34} {\text{S}}_{{\text{H}}_{\text{2}} {\text{S}}} \) values suggest a nonmagmatic source for the sulfur. Evaporitic sulfates are a likely source of heavy sulfur and sedimentary anhydrite is known to occur near the San Cristobal region. In contrast to San Cristobal are three similar quartz-wolframite vein deposits, Pasto Bueno, Panasqueira, and Tungsten Queen. They each have an average δ34S value for sulfides of about 0 permil, suggesting a sulfur of magmatic origin. At San Cristobal an influx of sedimentary sulfur could not only account for the distinctive isotopic signature of the sulfides but also for the presence of the base metal mineralization.
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