Abstract

Largest carbonate-hosted lead-zinc deposit known in the Mississippian Windsor Group. The orebody consists of: stratiform, disseminated sulfides as open-space fillings in primary and secondary pores of the dolomite and fault-controlled veinlike bodies of high-grade, massive sphalerite and galena. Four main stages of evolution. Microthermometry of fluid inclusions yields the following mean homogenization temperatures: sphalerite, 215 degrees C; ore-stage calcite, 173 degrees C; postore calcite, 142 degrees C; fluorite, 142 degrees C; and barite, 137 degrees C. Pressure corrections should be minimal for these temperatures. No evidence of boiling was observed in the inclusions. Salinity determinations from the ice-melting temperatures of inclusions in postore fluorite and calcite yield a value of ca. 20.4 equivalent wt percent NaCl for the hydrothermal fluid during the waning stages of mineralization. Isotopic analyses indicate that anhydrite and gypsum in the overlying evaporites and barite within the orebody are enriched in heavy sulfur (delta 34 S = 13.1-16.5 per mil), suggesting a Mississippian seawater source. Ore-stage sphalerite, galena, and chalcopyrite probably derived their sulfur (delta 34 S = 8.0-13.65 per mil) from sulfates or possibly a homogenized basement source. Postore marcasite and pyrite are characterized by light, probably biogenic, sulfur (delta 34 S = -9.7 to -46 per mil). Both disseminated and massive ores are probably the result of the same mineralizing episode involving deeply convecting brines.--Modified journal abstract.

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