An attempt has been made to evaluate the applicability of the various experimental sphalerite-galena sulfur isotope fractionation curves as a geothermometer for sulfide ore deposits. Sulfur isotope fractionations for 32 coexisting sphalerite-galena pairs from Providencia, Mexico, and from five other ore deposits are plotted against the filling-temperatures of fluid inclusions in sphalerite.In the temperature range 370 degrees to 200 degrees C, sulfur isotope fractionations plotted according to the filling-temperature data are within + or - 0.3 permil of the experimental curve of Czamanske and Rye (1974). Conversely almost all of the sulfur isotope temperatures based on their curve are within + or - 40 degrees C of the filling temperatures, and the majority are within + or - 20 degrees C. The sulfur isotope temperatures based on the experimental curve of Kajiwara and Krouse (1971) average about 40 degrees C higher than the filling temperatures, and those based on the curve of Grootenboer and Schwarcz (1969) average about 20 degrees C lower.Replicate analyses of individual sphalerite-galena pairs indicate that under the best circumstances an error of + or - 20 degrees C is inherent in the use of the sulfur isotope geothermometer.In the temperature range 200 degrees to 110 degrees C the very large range observed for sulfur isotope fractionations in natural sphalerite-galena pairs suggests that sulfur isotope disequilibrium may occur in low-temperature hydrothermal ore deposits.

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