About the event
Kenta Oka, Ph.D. graduate student from the University of Tokyo (visiting Prof. Choong-Shik Yoo’s laboratory, Institute for Shock Physics)
Melting in the Fe-FeO system to 204 GPa: Implications for oxygen in Earth’s core
Constraining the composition of the Earth’s core is essential for understanding Earth’s accretion process, core formation, and the sustainment of Earth’s magnetic field. The liquid-outer and solid-inner core are primarily made of iron but probably contain ‘light’ elements such as hydrogen, carbon, oxygen, silicon, and sulfur because the core’s density is smaller than that of pure iron. Melting phase relation (e.g., a eutectic composition) in the iron-light element(s) system at high pressures strongly constrains the core composition. In this study, I performed melting experiments on Fe-O alloys up to 204 GPa and 3500 K in a diamond anvil cell (DAC) and determined the liquidus phase relations in the Fe-FeO system based on textural and chemical characterizations of recovered samples. I observed liquid-liquid immiscibility up to 29 GPa. Oxygen concentration in eutectic liquid increased from >8 wt% O at 44 GPa to 13 wt% at 204 GPa and is extrapolated to be about 15 wt% at the inner core boundary (ICB) conditions. These results support an oxygen-rich liquid core, although oxygen cannot be a single core light element.