マントル,地殻,炭酸性コンドライトの塩素同位体の均質性
Z D Sharp1, J D Barnes, A J Brearley
1Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA. zsharp@unm.edu
Nature
|April 27, 2007
まとめ
地球の塩素同位体比は,隕石,マントル,地殻に一致しており,異なる太陽星雲の貯水池と惑星の分化に関する以前の理論に異議を唱える. この発見は,塩素の起源と分布に関する私たちの理解を簡素化します.
科学分野:
- 地質化学 地質化学
- 宇宙化学 (コスモケミストリー)
- 同位体地質学とは,同位体地質学である.
背景:
- 塩素 (Cl) は,太陽や隕石の豊富な量と比較して,地球では著しく枯渇しています.
- Cl分布と同位体比を理解することは,これらの枯渇と地球の揮発性在庫の説明の鍵です.
- 以前の研究では,異なる惑星の貯水池で異なる塩素同位体比を示唆した.
研究 の 目的:
- 地球のマントル,地殻,隕石における安定した塩素同位体比 (37Cl/35Cl) を調査する.
- 地殻の堆積物における地質学的年齢とともに同位体変動が存在するかどうかを判断する.
- 地球の形成,微分化,揮発性増殖のモデルを再評価する.
主な方法:
- マススペクトロメトリーを用いた安定した塩素同位体比 (デルタ37Cl) の高精度測定.
- マントルのクセノリト,地殻岩,様々な年齢の堆積物,炭酸性コンドライトを含む多様な地質サンプルを分析する.
主要な成果:
- 37Cl/35Cl比の炭酸コンドライト,地球マントル,地殻の間で有意な差は見つかりませんでした.
- 古代から最近の地殻の堆積物の分析は,地質的な年齢によって体系的な同位体変動がないことを明らかにしました.
- デルタ37Cl値は,地球の歴史を通じて,マントルと地殻の両方において一定のままである.
結論:
- 同位体変動の欠如は,同位体的に異なる塩素の nebular 貯蔵庫の存在を否定する.
- 地球の微分化過程 (核形成を含む) の間における同位素分化は,塩素では無視できる.
- 地殻に,同位素特有の塩素を含有する揮発性物質の重要な後期的な追加はありませんでした.
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