Fig. 1: The FeO-Fe2O3 region of the equilibrium phase diagram22.
The crystalline regions are in white, the single-phase liquid regions in grey and two liquid region in blue. Dashed lines are oxygen isobars labelled with log10 p(O2) (atm.). Circles and diamonds represent measurement conditions in this study and the star is the data point from Waseda et al.10. Our measurements in O2 gas are plotted to the right of the 100 = 1 atm. O2 line, because equation 12 of ref. 35 used to calculate Fe3+/ΣFe differs slightly from the most recent phase diagram22 (see uncertainty discussion and Supplementary Fig. S9). For measurements taken in the most reducing gas mixture (99CO:1CO2) the dome boundary between the oxide liquid and mixed metal + oxide region was used to determine the sample compositions (pink triangles).
