Details

Autor(en) / Beteiligte

• Li, Jun
• Wu, Qiang
• Li, Jiabo
• Xue, Tao
• Tan, Ye
• Zhou, Xianming
• Zhang, Youjun
• Xiong, Zhengwei
• Gao, Zhipeng
• Sekine, Toshimori

Titel

Shock Melting Curve of Iron: A Consensus on the Temperature at the Earth's Inner Core Boundary

Ist Teil von

• Geophysical research letters, 2020-08, Vol.47 (15), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2020

Link zum Volltext

Quelle

Wiley Online Library Database Model

Beschreibungen/Notizen

• The Earth's core consists of iron as the major component. The melting point of iron at the inner core boundary constrains the thermal structure and solidification of the Earth's core. However, the current estimation of the melting temperature of iron under the core conditions has significant variations. Here, we measured the temperatures of iron shocked up to ~256 GPa using precise pyrometer and velocimeter diagnostics via a two‐stage light‐gas gun. Our results indicated that the melting temperatures of iron at the core‐mantle and inner core boundaries are 4300(250) and 5950(400) K, respectively. These temperatures are significantly lower than some previous shock experiments but are overall consistent with the recent results determined by fast X‐ray diffraction techniques, X‐ray absorption experiments in laser‐heated diamond anvil cells, and by ab initio computations. Our iron melting curve indicates a relatively small Clapeyron slope and supports thermal models for a young inner core. Plain Language Summary Iron is the main constituent of the Earth's core, so its melting characteristics at high pressures are fundamentally crucial for understanding the thermal structure, solidification, and evolution of the core. We determined shock temperatures of melted iron up to ~256 GPa precisely by the use of a time‐resolved quasi‐spectral optical pyrometer. Our results are 1000–2000 K lower than those of some previous shock experiments. Our study reconciles the previous discrepancy in the melting temperatures of iron at pressures of 200–300 GPa and is consistent with theoretical calculations. We conclude that the melting temperature of iron at the Earth's inner core boundary is ~5950(400) K. The present study indicates a relatively gentle melting slope of iron and supports a young inner core age of ~0.565 Gyr inferred from paleomagnetic observations. Key Points The melting temperatures of shocked iron are measured up to ~256 GPa by the time‐resolved pyrometer The melting curves of iron at high pressures agree with each other in dynamic and static experiments and theories The temperature at the inner core boundary is anchored to 5950(400) K based on the melting curve of iron