The molecular and sulfur isotope distribution of volatile compounds in natural gases and condensates from Alberta, Canada

•Volatile organic S compounds (VOSC) in natural gases analyzed for S isotopes.•VOSC in the gas samples are 34S enriched by 3–4‰ relative to their associated H2S.•δ34S of alkylthiophenes in one of the gas samples suggests mixing of gas and oil.•Condensates in the area show similar δ34S values of VOSC to the natural gases.•The likely source of H2S in all the studied reservoirs is the Charlie Lake anhydrite.