日本地球惑星科学連合2018年大会

講演情報

[EE] Eveningポスター発表

セッション記号 S (固体地球科学) » S-IT 地球内部科学・地球惑星テクトニクス

[S-IT22] 核-マントルの相互作用と共進化

2018年5月22日(火) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:飯塚 毅(東京大学)、渋谷 秀敏(熊本大学大学院先端科学研究部基礎科学部門地球環境科学分野)、土屋 卓久(愛媛大学地球深部ダイナミクス研究センター、共同)、太田 健二(東京工業大学大学院理工学研究科地球惑星科学専攻)

[SIT22-P15] Melting of iron to 290 gigapascals

*新名 良介1,2廣瀬 敬1,2大石 泰生3 (1.東京工業大学地球生命研究所、2.東京大学、3.高輝度光科学研究センター)

キーワード:地球核、鉄、融解、高温高圧

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.