High-precision analysis of multiple sulfur isotopes using NanoSIMS

We report here data of multiple sulfur isotopes (32S, 33S, and 34S) measured by NanoSIMS 50L ion microprobe in Fe–Ni–Cu standards, and pyrite grains recovered from the Neoarchean Abitibi Supracrustal Terrain, Canada. Careful attention to instrument tuning, sample preparation and sample stage positioning results in highly precise and accurate data for 32S–33S–34S similar to that of larger radius SIMS instruments. Our results using a multi-Faraday collection system demonstrate that the NanoSIMS 50L instrument is capable of high-precision measurements of multiple isotopes of sulfur capable of resolving mass-independent variations in 33S (∆33S) on the order of 0.4‰ (2σ) with improvements possible with higher S count rates. Pyrite grains from the Abitibi Supracrustal terrane have a large range of δ34S values between −9.6 and +6.3‰, and corresponding ∆33S values between −0.8 and +1.5‰, consistent with other datasets from Neoarchean sedimentary rocks. The new data indicate the incorporation of atmospheric sulfur affected by mass-independent fractionation (MIF) of 33S into the Neoarchean marine sulfur cycle and point to subsequent sulfate reducing microorganisms at that time. •High-precision analyses of multiple sulfur isotopes are by SIMS are reported.•The NanoSIMS 50L can resolve mass-dependent isotope variations to ±0.8‰ (2σ).•Mass-independent isotope anomalies in 33S can be measured to ±0.4‰ (2σ).•Analysis of pyrite from the Neoarchaen Abitibi Supracrustal Terrain is reported.•The data show the influence of atmospheric sulfur in the Archean sulfur cycle.