Phase and Melting Relations of Fe3 C to 300 GPa and Carbon in the Core

Abstract

Carbon is a plausible candidate for a light element in the Earth’s core. Here, we show that Fe3 C melts incongru-ently to form Fe7 C3 and liquid at least up to 200 GPa based on in‐situ X‐ray diffraction measurements and tex-tural observations of the recovered samples, and Fe3 C is stable at least up to 300 GPa at high temperatures. The C content of the liquid coexisting with Fe7 C3 decreases and the Fe‐Fe3 C eutectic composition shifts toward the Fe‐rich direction with increasing pressure. The present result revealed that both Fe3 C and Fe7 C3 are plausible constituents in the inner core.