• FeS 2 and Fe 3 O 4 promoted CH 4 generation from H 2 O-hydrocarbon reaction at 330–450 °C. • δ 13C 1 and δ 2H 1 were evidently affected by the presence of Fe-bearing minerals. • A correlation between H transfer rate constant (k H) and 1000/T for H 2 O-CH 4 was addressed. • Equilibrium H transfer requires < 5 Ma and is available in geological settings with T > 200 °C. Water (H 2 O) and minerals involved organic-inorganic reactions are critical for hydrocarbon evolution in sedimentary basins and deep in the Earth. The mechanism and isotope fractionation for H 2 O-mineral-hydrocarbon interactions remain unclear. In this study, isothermal pyrolysis of 1-methylnaphthalene (1-MNa) involving H 2 O and three Fe-bearing minerals (pyrite–FeS 2 , magnetite–Fe 3 O 4 , and siderite–FeCO 3), was conducted using a gold-tube system at 330–400 °C and a pressure of 50 MPa. It was observed that the presence of FeS 2 and Fe 3 O 4 led to an increase in the yield of hydrocarbon gases (C 1-5). The isomeric ratios (i C 4 / n C 4 and i C 5 / n C 5) were much higher in the presence of Fe-minerals. In addition, 13C of methane (CH 4) in pyrolysis with H 2 O-FeS 2 and H 2 O-Fe 3 O 4 was evidently more depleted than that in pyrolysis with only water. Kinetic calculations and carbon isotope fractionation revealed that FeS 2 and Fe 3 O 4 enhanced the H 2 O-hydrocarbon reaction via either ionic or free radical mechanisms at elevated temperatures. Moreover, the presence of FeS 2 and Fe 3 O 4 promoted hydrogen (H) transfer from H 2 O, causing the enrichment in the 2H of CH 4. Furthermore, we first established a correlation between the H transfer rate constant (k H) and temperature (T): ln k H = −27.545 × 1000/T + 27.077. On this basis, it can be deduced that the time needed for equilibrium H transfer from H 2 O to CH 4 at 200 °C and 400 °C with Fe-bearing minerals is approximately 4.8 Ma and 54.4 d, respectively. [ABSTRACT FROM AUTHOR]