潜水したスラブからの超深層のダイヤモンドの極端な酸化還元変数

Fabrizio Nestola¹, Margo E Regier², Robert W Luth²

¹Department of Geosciences, University of Padova, Padova, Italy. fabrizio.nestola@unipd.it.

Nature

|January 4, 2023

まとめ

ダイアモンドインクルージョンを用いて深層マントルのリドックス条件を研究した. 660キロメートルの地震断絶の近くに非常に変動する酸化還元条件が明らかにされ,スラブ脱水と流体分離プロセスと関連しています.

科学分野:

地化学
鉱物物理学
ペトロロジー

背景:

潜水板はマントルに揮発性物質を導入しレドックス・グラデーションを生み出します
深層マントルのリドックス条件は鉱物の安定性と元素の振る舞いに影響を与えます.

研究の目的:

ダイヤモンドインクルージョンを用いて深層マントルのリドックス状態を調査する.
660kmの不連続性に近い極度の酸化還元変異の原因となるプロセスを決定する.

主な方法:

ギニアのカンカンから採取したダイヤモンドの内部の鉱物含有物 (エンスタチット,フェロペリカラーゼ,Mg豊富なオリビン) の分析.
脱水,再水分化,そして流体分化のモデル化.

主要な成果:

インクルージョンは660kmの地震断絶の近くで非常に変動する酸化還元条件下で形成されていることを示しています.
スラブ脱水,リヒドレーション,および流体分離のモデルは,観測された酸化還元グラデーションを説明する.
流体の分断は,Mg末端のリングウッドライトと宿主ダイヤモンドを降ろす極端な条件につながります.

結論:

ダイヤモンドインクルージョンは深いマントル・リドックスに重要な洞察を与えてくれます
トランジションゾーン - マントルの下部境界のスラブ駆動プロセスは,極端な酸化還元変異を生成します.
これらの過程は,ダイヤモンドの形成と地球深層の地化学を理解するために不可欠です.

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