Sulfur isotope exchange between thiophenes and inorganic sulfur compounds under hydrous pyrolysis conditions

•Thermal maturation can enriched model sulfur compounds in 34S up to ∼2‰.•Inorganic sulfur species decrease dramatically the thermal stability of thiophenes.•Benzo- and dibenzo-thiophenes do not exchange isotopes with inorganic sulfur species.•δ34S of BT and DBT are controlled by their relative rates of degradation/formation.•Degradation/formation of BTs and DBTs occur during thermal maturation and TSR.