[P-CG23] Shock responses of planetary materials elucidated from meteorites and laboratory experiments

[PCG23-09] Shock-induced melting of iron and the melting temperature at Earth's inner-core boundary revisited

*Youjun Zhang¹, Jun Li², Toshimori Sekine³ (1.Sichuan University, China, 2.Institute of Fluid Physics, China, 3.Center for High Pressure Science and Technology Advanced Research, China)

Keywords:Earth's core, iron, melting temperature, shock compression

Iron is the main constituent of Earth’s core. Its melting temperature at ultrahigh pressures is of fundamental importance for understanding the thermal structure and energetics of the core. In spite of extensive works on the determination of melting temperature by static and shock experiments, it is still debated, especially at the inner-core boundary conditions (~330 GPa). We remeasured the shock temperature of iron by an improved pyrometer up to ~260 GPa, where it was completely melted. The measured temperature in our study is above a thousand kelvins lower than previous measurements [1,2]. The melting temperatures at Hugoniot and partially released states were obtained based on our experiments. Our determined temperature at Earth’s inner-core boundary is consistent with the extrapolations from the laser-heated diamond anvil cells and theoretical computations by ab initio free energy and thermodynamic model [3,4]. Our results support a young inner core.

Refs:
[1]. Bass, J.D., Svendsen, B., and Ahrens, T.J. (1987). High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto, 39, p. 393-402.
[2] Yoo, C.S., Holmes, N.C., Ross, M., Webb, D.J., and Pike, C. (1993) Phys. Rev. Lett., 70(25), 3931-3934.
[3] Dorogokupets, P.I., Dymshits, A.M., Litasov, K.D., and Sokolova, T.S. (2017) Sci. Rep., 7(1), 41863.
[4] Sun, T., Brodholt, J.P., Li, Y., and Vočadlo, L. (2018) Phys. Rev. B, 98(22), 224301.