Melting boundary of Fe‐17%Si up to 5.5 GPa and the timing of core formation

Abstract

Melting of Fe‐17wt%Si has been investigated at temperatures up to 1600°C and pressures up to 5.5 GPa in a cubic anvil press. The melting temperature, TM, was identified with the discontinuity in temperature and pressure dependence of electrical resistance. Two types of electrode materials, Pt and Fe, were used and gave consistent melting results. TM increases with pressure from 1200°C at 1 atm to 1430°C at 5.5 GPa. dTM/dP decreases with pressure and reaches a value of zero at P∼5 GPa. Combined with the thermal profiles of the proto‐Earth, the pressure independence of the melting boundary of Fe‐17%Si at the highest pressures of this study suggests core formation began early in Earth accretion with a substantial liquid metal phase fraction between 30 Ma and 42 Ma.