The Formation of Highly Positive δ34S Values in Late Devonian Mudstones: Microscale Analysis of Pyrite (δ34S) and Barite (δ34S, δ18O) in the Canol Formation (Selwyn Basin, Canada)

The sulfur isotope composition of pyrite in marine sedimentary rocks is often difficult to interpret due a lack precise isotopic constraints for coeval sulfate. This study examines and barite the Late Devonian Canol Formation (Selwyn Basin, Canada), which provides an archive δ 34 S 18 O values during diagenesis. Scanning electron microscopy (SEM) has been combined with microscale secondary ion mass spectrometry (SIMS) analysis ( n = 1,032) (δ S) O) on samples collected from nine stratigraphic sections Formation. Two paragenetic stages formation have distinguished, both replaced by barium carbonate feldspar. all overlap, between +37.1‰ +67.9‰ (median +45.7‰) +8.8‰ +23.9‰ +20.0‰), respectively. Barite morphologies are consistent precipitation diagenetically modified porewater sulfate (sulfate resupply << depletion) early two generations (Py-1 Py-2) preserve distinct textures end-member records. There large offset seawater framboidal (-29.4‰ -9.3‰), dissimilatory microbial reduction (MSR) Py-2 textural equilibrium generation 2 (Brt-2) records broad range more positive (+9.4‰ + 44.5‰). distinctive highly developed limited conditions around methane transition zone (SMTZ). We propose that combination factors, including low concentrations, MSR, coupled anaerobic oxidation (SR-AOM), led presence other units indicate diagenetic at SMTZ may be general feature Lower Paleozoic basins.