Abstract
We 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. Liquid-liquid immiscibility was observed 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 O-rich liquid core, although oxygen cannot be a single core light element. We estimated the range of possible liquid core compositions in Fe-O-Si-C-S and found that the upper bounds for silicon and carbon concentrations are constrained by the crystallization of dense inner core at the ICB.
Acknowledgments
We thank K. Yonemitsu for help in sample analyses with FIB, EDS, and EPMA. Comments from three anonymous reviewers helped improve this paper substantially.
Funding
This work was supported by the JSPS grant no. 16H06285 to K.H., G.M., N.C., and G.F. acknowledge funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation program (ERC Planet Dive, grant agreement no. 670787).
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