were used as the source of metals. These powders were mixed in a the ratio consistent with the composition presented in SI Appendix, Table ; placed in a platinum-rhodium (Pt-Rh) crucible; and heated at 1,000 °C for 1 h for decarboxylation. Thereafter, the temperature was raised to 1,600 °C at the rate of 200 °C h -1 , maintained at that level for 1 h, decreased to 1,450 °C at the rate of 100 °C h - 1 , and maintained at that level for 1 h. During the heating, a gas mixture of H2 and CO2 was flowed to maintain the O2 fugacity at the quartz-fayalite-magnetite (QFM) buffer condition. The sample was then quenched to room temperature, crushed in a quartz mortar, and sieved to obtain the fraction with the particle size smaller than 90 μm.