鉄硫化物の分離によって,地球マントルから高度にシドロフィールな元素が剥がれた
David C Rubie1, Vera Laurenz2, Seth A Jacobson3
1Bayerisches Geoinstitut, Bayreuth, Germany. dave.rubie@uni-bayreuth.de.
まとめ
地球の核形成の過程で,高サイドロフィール元素 (HSEs) が枯渇した. HSE濃度とマントルの超コンドリート比率は,遅い増殖ではなく",ハデアンマット"相によって説明される.
科学分野:
- 地化学
- 惑星科学
- 地球科学
背景:
- 高度 siderophile 元素 (HSEs) は,地球の大量シリケートマントルで枯渇していますが,ほぼコンドリート的な豊富さを示しています.
- 従来の理論では,これはコア形成の剥離と遅い蓄積補充に起因する.
研究 の 目的:
- コア形成中の金属シリケート均衡と分離がHSEマントルの濃度に与える影響を調査する.
- HSEの豊富性を確立する際に遅い増殖と初期のプロセスの貢献を再評価する.
主な方法:
- コア形成に関連する高圧での金属シリケート均衡のモデル化.
- 硫化鉄の液体 ("ハデアンマット") の溶解中のHSEの振る舞いを分析する.
主要な成果:
- 高圧での金属シリケート均衡は,以前の仮定に反して,低い分割係数によるHSEマントルの濃度を増大させた.
- 冷却中のマグマ海洋からの"ハデアンマット"の分離は,遅い蓄積前にHSEを効果的に剥がした.
- このプロセスは,観測された超コンドリートパラジウム/イリジウムとルテニウム/イリジウムの比率を説明する.
結論:
- 初期の地球過程,特に"ハデアンマット"分離は,HSEの枯渇とマントルの特定の同位体比の主要な要因である.
- HSEの濃度決定における遅い増殖の役割は,以前考えられていたより少ない.
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