Résumé
We have developed in-situ analysis protocols on the SHRIMP-SI for accurate and precise measurements of the four isotopes of sulfur. Charge-mode detection of the low abundance (super 36) S isotope has proven to be a major advantage on the determination of Delta (super 36) S. Typical internal precision for Delta (super 36) S measurement is 0.2 ppm (sigma ) with reproducibility typically better than 0.5 ppm (95% confidence limits). This has allowed us to fully resolve the biogeochemical fractionation (BGF; Delta (super 36) S/Delta (super 33) S of approx. - 7) from the Archean atmospheric fractionation (AAF; Delta (super 36) S/Delta (super 33) S of approx. -1). Coupled with delta (super 34) S, the high precision analysis of Delta (super 33) S and Delta (super 36) S have been used to trace the atmospheric sulfur chemistry in the Archean and Paleo-Proterozoic as well as biological and abiological sulfur fractionation in the Phanerozoic. Archean sulfides samples show large fractionations in Delta (super 33) S and Delta (super 36) S as have previously been observed. Proterozoic sulfides samples show large fractionations in delta (super 34) S, but thus far we have seen no anomalies in Delta (super 33) S and Delta (super 36) S. The isotopic record in Phanerozoic sedimentary sulfides and in sulfide-bearing ore deposits show sulfur isotope variations that reflect distinct sources of sulfur and mechanisms of sulfide deposition and ore genesis.