Thermal reduction of molybdite and hematite in water and hydrogen peroxide-bearing solutions: Insights on redox conditions in Hydrothermal Diamond Anvil Cell (HDAC) experiments

► Thermal reduction of MoO3 in H2O and H2O-H2O2 high P-T. ► Characterization of FeFe2O4 with microRaman spectroscopy. ► Determination of fO2 in HDAC experiments in the range 215-620 °C and 6-200 MPa. ► The effect of a noble metal (rhenium) gasket on fO2 in HDAC experiments.