Melting relationships in the Fe-Fe3S system up to the outer core conditions

In situ X-ray diffraction experiments in the Fe-Fe3S system were performed up to 175 GPa and 3500 K using a laser-heated diamond anvil cell to investigate melting relationships in the system. Partial melting in the Fe-Fe3S system was observed based on the disappearance of X-ray diffraction peaks of solid Fe3S and texture observation of the recovered samples. The melting relationship of the Fe-Fe3S system as a function of pressure is evaluated based on Kraut-Kennedy law. Our results of melting relationships suggest that the temperature at the inner core boundary is between 4700(160) and 4930(330) K if sulfur is the only light element in the Earth's core. Assuming the adiabatic temperature gradient in the outer core, the temperature at the core-mantle boundary is estimated to be in the range of 3600-3770 K. The present temperature profile of the core is consistent with the core-mantle boundary temperature that can explain the core heat flux to maintain the core dynamo and the seismic structure at the base of the lower mantle.

► Melting relation in Fe-Fe3S system was investigated to 182 GPa based on in situ XRD. ► TICB was estimated based on the melting curve. ► TCMB was estimated by assuming the adiabatic temperature gradient in the outer core. ► A recovered sample from 123 GPa was observed by FE-SEM. ► A dendritic texure was observed.