Japan Geoscience Union Meeting 2018

Presentation information

[EE] Poster

S (Solid Earth Sciences) » S-IT Science of the Earth's Interior & Tectonophysics

[S-IT22] Interaction and Coevolution of the Core and Mantle in the Earth and Planets

Tue. May 22, 2018 10:45 AM - 12:15 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Tsuyoshi Iizuka(University of Tokyo), Hidetoshi Shibuya(Department of Earth and Environmental Sciences, Faculty of Advanced Science and Technology, Kumamoto University), Taku Tsuchiya(愛媛大学地球深部ダイナミクス研究センター, 共同), Kenji Ohta(Department of Earth and Planetary Sciences, Tokyo Institute of Technology)

[SIT22-P15] Melting of iron to 290 gigapascals

*Ryosuke Sinmyo1,2, Kei Hirose1,2, Yasuo Ohishi3 (1.Earth-Life Science Institute, Tokyo Institute of Technology, 2.The University of Tokyo, 3.Japan Synchrotron Radiation Research Institute)

Keywords:Earth's core, iron, melting, high-pressure and -temperature

The Earth’s core is composed mainly of iron. Since liquid core coexists with solid core at the inner core boundary (ICB), the melting point of iron at 330 gigapascals offers a key constraint on core temperatures. However, previous results using a laser-heated diamond-anvil cell (DAC) have been largely inconsistent with each other, likely because of an intrinsic large temperature gradient and its temporal fluctuation. Here we employed an internal-resistance-heated DAC and determined the melting temperature of pure iron up to 290 gigapascals, the highest ever in static compression experiments. A small extrapolation indicates a melting point of 5500 ± 80 kelvin at the ICB, about 500–1000 degrees lower than earlier shock-compression data. It suggests the upper bound for the temperature at the core–mantle boundary (CMB) to be 3760 ± 180 K. Such present-day CMB temperature combined with the recently-proposed nominal core cooling rate suggests that the lowermost mantle was no longer globally molten, at least in the early Proterozoic Eon, consistent with the recycling of subducted crustal materials originally formed more than 1.5 Gyr ago.