The modelling provided clear predictions on how BR’s minerals would evolve upon heating under reducing atmosphere. The results are displayed in Fig. 2. Figure 2 - P-T-Log fO2 constraints from thermodynamic modelling using Perple_X for bulk composition of the BR sample (Table 1), at a constant pressure of 1 bar, illustrating phase equilibria under reducing conditions (phase assemblages with H2). Phase assemblages with H2O represent more oxidizing conditions. Legend: Cor, corundum; Geh, gehlenite; Ilm, ilmenite & hematite; Lrn, larnite; Mt, magnetite; Ne, nepheline; Pv, perovskite; Sp, spinel. Figure 2 presents the Perple_X-calculated oxygen fugacity (Log fO₂) versus temperature (T) phase diagram at atmospheric pressure (1 bar), illustrating the stability relationships among the major mineral phases present in the BR. The highlighted vertical band corresponds to the experimental temperature range applied during hydrogen reduction (~1000 ºC), allowing direct comparison between thermodynamic predictions and experimental observations. The diagram shows that under strongly reducing conditions (Log fO₂ ≈ -13 to -25), ferric iron-bearing phases such as hematite and magnetite are thermodynamically unstable and are progressively replaced by reduced iron-bearing phases, including spinel-group minerals and ultimately metallic iron. Magnetite and ilmenite exhibit limited stability fields at intermediate oxygen fugacity but become unstable as fO₂ decreases further under hydrogen-rich conditions, confirming the thermodynamic driving force for iron reduction observed experimentally. Titanium is predicted to preferentially stabilize in perovskite (CaTiO₃), which
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