上層マントルの謎めいた条紋は,インド南東部のの玄武岩のハフニウムイソトープによって明らかになった
D W Graham1, J Blichert-Toft, C J Russo
1College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA. dgraham@coas.oregonstate.edu
Nature
|March 10, 2006
まとめ
古代の組成線が地球の上層マントルに存在し,インド南東部のの玄武岩でバイモダルのハフニウム同位体分布によって明らかにされています. このマントルの線条は,厚さ約40キロメートルである.
科学分野:
- 地質化学 地質化学
- 地質物理学 地質物理学とは地質物理学です.
- マントルダイナミクス マントルダイナミクス
背景:
- 地球のマントルは,様々なスケールで同位体異質性を示しています.
- マントルのコンベクションとプレートテクトニクスは,この異質性に影響を与えます.
- マントルの構成を理解することは,地球の進化を解読する鍵です.
研究 の 目的:
- インド洋上部マントルの同位体組成を調べるために.
- マントルの異質性の起源と分布を特定する.
- マントルダイナミクスに対する観測された異質性の影響を分析する.
主な方法:
- 東南インド山脊 (SEIR) の中洋山脊玄武岩 (MORB) の分析.
- ベースアルトサンプルにおけるハフニウム (Hf) の同位体分布の測定.
- ストライク特性を決定するための同位体データの統計分析.
主要な成果:
- SEIRの玄武岩でバイモダルのハフニウム同位体分布が観察されました.
- このバイモダリティは,上部マントルに古代の組成線が存在することを示している.
- ストライクの数密度はポアソン分布に従っており,平均厚さは約40kmです.
結論:
- 観測されたストライク分布は,上部マントルがよく動揺したモデルを支えている.
- プレート構造の再生と粘性流は,マントルの異質性を維持する重要なプロセスです.
- 古代の構成構造は,マントルのコンベクションにもかかわらず存続しています.
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