地殻の形成と,後方弧の山脊の下でのマントルの急速な移行を対比する
Robert A Dunn1, Fernando Martinez
1Department of Geology and Geophysics, University of Hawaii, Honolulu, Hawaii 96822, USA. dunn@soest.hawaii.edu
Nature
|January 14, 2011
まとめ
バック・アーク・盆地の広がりは,海底の地殻の性質の急激な変化を明らかにし,漸進的な進化モデルに挑戦しています. これは,潜水地帯の近くで,マントルの動的上昇過程が起きていることを示唆している.
科学分野:
- 地質学 地質学 地質学
- 地質物理学 地質物理学とは地質物理学です.
- テクトニクス (地質学) とは
背景:
- バックアーク盆地は,リフトと海底の広がりを通じて,潜水地帯の後ろに形成されます.
- 広がる山脊の溶岩は,潜水の影響から離れるにつれて徐々に変化することが予想されます.
- 既存のモデルは,広がる山脊に沿って地殻の性質の漸進的な変化を予測しています.
研究 の 目的:
- 東部ラウの拡散センターにおける地殻の特性変化の性質を調査する.
- 岩層が火山の弧から移動するにつれて,地殻の性質の変化が漸進的または突然であるかどうかを判断する.
主な方法:
- 海底の形態学の分析.
- 上層地殻の地震速度の測定.
- 重力の異常と静止状態の解釈.
主要な成果:
- 海底の形状,地震速度の急激な変化 (20%以上の増加),地殻の厚さ (1.9km以上の薄め) が観察されました.
- これらの変化は,山頂軸と火山のフロントの最小の分離 (わずか5km) で発生しました.
- 地殻の特性の横断と縦断の変動は,有意で突然であった.
結論:
- この発見は,漸進的な地殻の進化を予測するモデルと矛盾している.
- 急激な変化は,ダイナミックな上流ゾーンが水豊富なマントルを捕獲し,その後放出することで,引き寄せられたマントルの急速な進化を示唆しています.
- このダイナミックなプロセスは,マントルのの角の近くの海中山脊の典型的な,安定した,広い三角形の上流地域を形成することを困難にします.
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