Volatile chemical speciation in terms of outgassed mole fraction vs. oxygen fugacity of the mantle. The x-axis indicates the oxygen fugacity range in logarithmic units relative to the IW buffer. For reference (in log units), buffers QIF = IW-1, QFM = IW+3.8, and NiNiO = IW+4.2 approximately (Wood et al. 1990). From top to bottom: BOM, active MO phase, EOM and a steam-atmosphere phase that are characterized by different initial H/C between hydrogen and carbon. The corresponding input values of the initial volume mixing ratio of volatiles, surface pressures P_s, and temperatures T_s (Nikolaou et al. 2019) for the speciation model are indicated at the top of each panel.