マントルダイヤモンドのとして,超高温溶解の残留物
Carl Walsh1, Balz S Kamber2, Emma L Tomlinson3
1School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, Queensland, Australia.
Nature
|March 16, 2023
まとめ
古代大陸の強さは 浅いプロセスではなく 熱い溶融によるものです 新しいモデルでは 200kmの深さで クラトンの根やマグネシウムオリビンが 溶け出ていることが示されています
科学分野:
- 地化学
- ペトロロジー
- 地力学
背景:
- 古代のクレートンは 深く 冷たく 硬く 根はダイヤモンドの安定地帯に 広がっています
- クラトンの強さは,溶融の抽出により,冷たく硬い石層に導かれます.
- 現存するモデルでは 浅い融解に続く 深い根の形成が提案されていますが この研究はこれを否定しています
研究 の 目的:
- クラトン形成の熱力学と地化学的条件を調査する
- マグネシウムオリビンを生成する 融解プロセスをモデル化します
- グリーンストーンベルトのような地表の地質学的特徴と クラトンの根の組成を調和させるため
主な方法:
- 高温溶解の熱力学および地化学モデリング
- マントルの融解の閉鎖システムとオープンシステムのモデリング.
- クラトン根とダイヤモンドインクルージョンの鉱物組成の分析
主要な成果:
- 深層溶解 (約) 非常に高い温度 (≥1,800°C) で,クラトンマントルの鉱物組成を成功裏に再現します.
- モデル化されたコマタイトは,表面のグリーンストーンベルトの観測と一致して,アルミニウム濃縮とTi濃縮の形態に進化した.
- Ti- 欠乏したコマチートの少なさは,開かれたシステムでの相互作用が,進んだ閉じたシステムでの融解よりもより有意であったことを示唆している.
結論:
- クラトニックの根は おそらく 深い,超高温の融解によって形成され 浅い融解モデルに挑戦しています
- より深い液体と耐火性マントルの融解を含むオープンシステムプロセスはクレートン形成に不可欠です.
- ダイヤモンドの形成は,超高温の融解と古代の熱帯の影響で,クラトニックの根を縮小させる条件に関連している可能性があります.
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