Effect of redox conditions on iron metal phase segregation during experimental high-temperature centrifuge modeling of the origin of the Moon’s core

Abstract

The possible origin of the Moon’s metallic core at the precipitation of iron–sulfide phases during the partial melting of ultramafic material under various redox conditions was experimentally modeled by partially melting the model system olivine (85 wt %) + ferrobasalt (10 wt %) + metallic phase Fe₉₅S₅ (wt %) in a high-temperature centrifuge at 1430–1450°C. The oxygen fugacity fO₂ was determined from the composition of the quenched experimental silicate melts (glasses). A decrease in fO₂ is proved to be favorable for the segregation of iron–sulfide melt from the silicate matrix. The metallic phase is most effectively segregated in the form of melt droplets, and these droplets are accumulated in the lower portions of the samples under strongly reduced conditions, at fO₂ ∼ 4.5–5.5 orders of magnitude lower than the iron–wüstite buffer.