コマタイト は,アルカイア 時代 の 深い の 貯水 池 を 示し て い ます
Alexander V Sobolev1,2, Evgeny V Asafov2, Andrey A Gurenko3
1Université Grenoble Alpes, Institute Science de la Terre (ISTerre), CNRS, F-38041 Grenoble, France.
Nature
|April 1, 2016
まとめ
古代のコマタイトは高温で噴火し そのマグマには 0.6%の水が含まれていたことが 新しい研究で示されています これは地球の初期の歴史における 羽根の起源と深層マントルの水分化を支持しています
科学分野:
- 地化学
- ペトロロジー
- 初期の地球環境
背景:
- 古代のコマタイトは 極度のマントルの溶け方を示す 超マフィカルな溶岩です
- コマタイトの水分含有量,噴火温度および起源モデル (羽根対潜水) に関する不確実性があります.
研究 の 目的:
- アーカイアンコマタイトの親溶液の組成と結晶温度を直接推定する.
- コマタイトの水分含有量とそのマントルプロセスへの影響に関する議論を解決する.
主な方法:
- マグネシアンオリビンの溶融中の水,揮発性,主要および微量元素の分析.
- 溶融の進化と源の特性を地化学的にモデル化する.
主要な成果:
- 27億年前のアビティビ・コマチートの親溶液は30%のMgO,0.6%のH2Oを含み,不適合な元素で枯渇していた.
- 結晶化は,減少条件下で1530°Cで開始され,小分結晶化と小規模な地殻同化を経由して進化した.
- 高いH2O/Ce比は,マントルの移行地帯から水分物質の引き寄せを示唆しています.
結論:
- コマタイトの組成と低酸素の流動性は,沈殿と矛盾しており,羽根の起源を支持しています.
- 結果は高アルカイアンマントルの温度を確認し,地球の歴史の初期に深い水性マントルの貯水池を示唆しています.
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