マントルの超可塑性とその自己生産的な消滅
Takehiko Hiraga1, Tomonori Miyazaki, Miki Tasaka
1Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan. hiraga@eri.u-tokyo.ac.jp
Nature
|December 24, 2010
まとめ
ジオマテリアルには超可塑性があり,故障することなく500%以上変形します. このマントル岩の振る舞いは,粒子の境界が滑り,粒子の成長が大きくなり,マントルの粘度に影響を及ぼします.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- マテリアルサイエンス 材料科学
- ミネラル物理学 ミネラル物理学
背景:
- 超可塑性,つまり固体の材料が大きなプラスチック変形を経験する能力は,金属やセラミクスでよく記録されています.
- 氷床や地球マントルのような地質学的な物質におけるその発生は,長い間推測されてきたが,実験的に確認されていない.
研究 の 目的:
- 地球のマントルに関連する地質物質における超可塑性を実験的に実証し,特徴づけること.
- これらのアナログにおける超プラスチックの流れ中の変形機構および関連する微細構造の進化を調査する.
主な方法:
- 多結晶フォースタイト+ペリクラゼ (9:1) とフォースタイト+エンスタタイト+ダイオプサイド (7:2.5:0.5) の類似体の実験的変形,亜固体条件下.
- 粒子の大きさの進化と変形メカニズム (粒子の境界の滑り) を含む微細構造の変化の分析.
主要な成果:
- ジオマテリアルの類型は,故障なく最大500%の均質な延長を達成し,超可塑性を確認しました.
- 変形はストレスの硬化に伴い,穀物の境界が滑り込み,穀物の成長に起因した.
- 経験的な株-粒の大きさ-粘度関係が確立されました.
結論:
- 地球のマントル,特にシェアゾーンや潜水板における超プラスチックの流れはあり得ると考えられる.
- マントルの超可塑性は,必然的に粒子の成長が大きくなり,粘度が高くなり,最終的に流れが止まります.
- この微細構造の進化は,マントルの動力学とレオロギーに影響を与えます.
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