大陸の物質が200km以上の深さまで潜り込む可能性
1Laboratory of Lithosphere Tectonic Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing. yekai@hotmail.com
Nature
|October 26, 2000
まとめ
大陸の物質は200km以上の深さで沈み込むことが可能であり,これは石榴石の溶解によって証明されています. この発見は,超大陸の成長とプレートマージンダイナミクスの理解を助けます.
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.
- ミネラロジーは,鉱物学です.
背景:
- 大陸の石層沈殿は,超大陸のサイクルとプレートマージンの進化の鍵です.
- 超高圧 (UHP) 変形岩は,大陸物質が少なくとも120kmの深さに達することを示しています.
- 以前のより深い潜水 (150~300km) の推論は,ガーネット・ペリドータイトからの間接的な証拠に依存していた.
研究 の 目的:
- UHPの変形性地殻岩の大陸沈下の深さを直接追跡するために.
- 深い大陸の沈下に関する信頼できる鉱物学指標を特定する.
- ピロキセンの溶解の予測を,深さ >150 km でガーネットでテストする.
主な方法:
- 中国,スルーUHP変形帯からのエコロギットの分析.
- 石榴石内の鉱物溶液の顕微鏡および化学分析.
- 鉱物化学 (Na2O,八面体Si) を解釈して,圧力-深さの条件を推測する.
主要な成果:
- クリノピロキセン,ルチル,アパタイト溶液の高濃度がガーネットで観察されました.
- これらの溶解を,高圧ピロキセンの固体溶液形成の証拠として解釈した.
- 観測されたNa2Oと八面体Si濃度が200kmを超える潜水深さを示していることが判定されました.
結論:
- 大陸の物質は200km以上の深さまで沈み込むことができます.
- 石榴石の溶解質感は,深い大陸の沈殿の直接的な指標を提供します.
- これは,収束縁の深い地殻のプロセスを理解するための重要なデータを提供します.
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