コンドリート隕石と地上の蓄積におけるハロゲン
Patricia L Clay1, Ray Burgess1, Henner Busemann2
1School of Earth and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK.
Nature
|December 1, 2017
まとめ
新しい研究により,隕石に含まれる重型ハロゲン (塩素,ブロミン,ヨウ素) の量は,これまで考えられていたよりもかなり低いことが明らかになりました. この発見は地球の理解に影響を与えます
科学分野:
- 地化学
- 惑星科学
- 宇宙化学
背景:
- 重いハロゲン (塩素,ブロミン,ヨウ素) を含む揮発性元素は,地球の形成と分化を理解するために不可欠です.
- 重いハロゲンは,蓄積過程の貴重なトレーサですが,通常は少量に見られます.
- ノーブルガスのプロキシ同位体は,重いハロゲン濃度を決定するための高感度方法を提供します.
研究 の 目的:
- 様々な隕石の塩素 (Cl),ブロミン (Br),ヨウ素 (I) の豊富さを正確に定量化する.
- 地球上のハロゲン埋蔵と 原始的な隕石の埋蔵を比較する
- 地球上のハロゲン発送,保持,分布を制御するプロセスを調査する.
主な方法:
- 炭酸,エンスタチット,ルムルティ,および通常のコンドライトの重ハロゲン濃度の分析
- 研究した隕石におけるBr/ClとI/Clの比率の決定.
- 隕石のハロゲンデータと大量のシリケート地球の推定値の比較
主要な成果:
- Cl,Br,I のコンドライトの濃度は,以前から認められた値よりそれぞれ6x,9x,および15-37x低い.
- 隕石におけるBr/ClとI/Clの比率は,大量のシリケート地球上の推定値と一致している.
- 地球のマントルのハロゲンの枯渇は,同様に揮発性のあるリトファイルの元素を反映しています.
結論:
- 地球の現在のハロゲン予算は 後期増殖だけでは説明できません
- 重いハロゲンの有意な部分 (80-90%) は地球の表面貯水池に存在する.
- 地上ハロゲン濃度について説明するには,初期の地球分化と後期増殖とマントルの脱ガスとともに,ハロゲン豊富な液体の効率的な抽出が必要である.
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