地球のマントルの塩素同位体成分
M Bonifacie1, N Jendrzejewski, P Agrinier
1Equipe de Physico-Chimie des Fluides, Géologiques, Institut de Physique du Globe de Paris (IPGP) and Université Paris, Diderot (UPD), CNRS-INSU-Unité Mixte de Recherche (UMR) 7154, 75251 Paris Cedex 05, France. bonifaci@gps.caltech.edu
まとめ
ほとんどの海洋溶岩は塩素汚染を示しており,同位体比 (デルタ37Cl) は海水または塩塩の影響を示している. 汚染されていないマントル源は,地表貯水池よりもデルタ37Cl値が著しく低い.
科学分野:
- 地質化学 地質化学
- 同位体地質学とは,同位体地質学である.
- ペトロロジー・ペトロロジーとは
背景:
- 中洋のベースタルト (MORBs) の塩素 (Cl) 安定同位体組成 (デルタ37Cl) は,マントルのプロセスに関する洞察を提供します.
- Clの源とサイクルの理解は,地球の揮発性の在庫を解読する上で極めて重要です.
研究 の 目的:
- MORBsにおけるCl含量とdelta37Clとの関係を調査する.
- 汚染されていないMORB源マントルのデルタ37Clシグネチャーを決定する.
- 海洋の溶岩における地殻汚染の程度を評価する.
主な方法:
- 塩素の安定同位体組成 (delta37Cl) を22個のMORBサンプルで分析した.
- デルタ37Cl値と大量Cl含有量の相関.
主要な成果:
- MORBsにおけるデルタ37ClとCl含有量との間に正の相関関係がある.
- 高デルタ37Cl,Clに富んだ玄武岩は,海水や塩水などのClに富んだ物質に汚染されています.
- 低デルタ37Cl,Clが少ない玄武岩は,より汚染が少ない,マントル由来マグマを表しています.
結論:
- 海洋の溶岩のほとんどは,もし全部でないとすれば,ある程度汚染されています.
- MORB源のマントルは,地表貯水池 (~0 per mil) に比べて,かなり低いデルタ37Cl (~ -1.6 per mil) を有しています.
- 同位体差は,地球の歴史におけるCl同位体の分割または,遅い37Cl濃縮の揮発性添加を示唆する.
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