地球の深いマントルのブリッジマニットにおけるカルシウム溶解
Byeongkwan Ko1,2, Eran Greenberg3,4, Vitali Prakapenka3
1School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA. olivine.ko@gmail.com.
Nature
|October 19, 2022
まとめ
カルシウムシリケートペロブスキットは,そのカルシウム成分がブリッジマニットに溶け,単一のペロブスキット領域を形成するので,深い下層マントルに消失します. 鉄と気温の影響による この移行は 地球の深い内部の鉱物学の理解を 変えてしまいます
科学分野:
- 地理学
- 鉱物物理学
- 地球科学
背景:
- 下層マントルは地球の半分以上を占めるので 精密な鉱物学的な理解が必要です
- カルシウムシリケート (CaSiO3) ペロブスキートは下層マントルで3番目に多い鉱物と考えられています.
- ブリッジマニットとフェロペリクラゼは,下層マントルの2つの最も豊富な鉱物です.
研究 の 目的:
- 高圧と高温でブリッジマニットにおけるカルシウムの溶解性を調べる.
- 下層マントルにCaSiO3ペロブスキートが消失する条件を決定する.
- 下層マントルの鉱物学的領域のための新しいモデルを提案する.
主な方法:
- 下層マントルの条件をシミュレートする高圧・高温実験
- ブリッジマニットにおけるカルシウム溶解性の分析
- ミネラル・フェーズ・トランジションの地球物理モデル化
主要な成果:
- ブリッジマニットにおけるカルシウムの溶解性は,40GPaと2,300K以上で著しく増加する.
- CaSiO3ペロブスキートは,地熱に沿って1,800 km以上の深さでブリッジマニットに完全に溶けます.
- 下層マントルの場合,2つのペロブスキート領域 (TPD) から,カルシウム豊富なブリッジマニートの一つのペロブスキート領域 (SPD) への移行が提案されている.
- 鉄はブリッジマニットの溶解性を高める上で重要な役割を果たします.
結論:
- 下層マントルは深度が上がるにつれ TPD から SPD に移行する.
- 温度変動は,TPD-SPD移行の深さに大きく影響する.
- この発見は深層マントルの鉱物学モデルを改訂し,マントルの構成,構造,動態,進化の理解に影響を与えます.
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