Range in isotopic composition is small, with a mean close to that for meteorite sulfur, suggesting a magmatic hydrothermal origin and derivation from a deep-seated source, perhaps within the mantle. Pyrite samples show the entire range of compositions, from S-32/S-34 ratios of 22.151 to 22.306. Vein pyrite is richer in S-34 than disseminated pyrite. Sulfide minerals of individual samples show increasing mean S32/S34 ratios in the sequence molybdenite-pyrite-chalocopyrite-bornite. Weak zonation is shown by progressive depletion of S-34 outward from the central zone of the district.

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