まとめ
地殻下部のキセノリトで発見された原生鉄 (Fe(0) は,地球の深い地殻の環境が減少したことを示唆しています. この発見は,石層から発生する磁気異常の解釈に影響を与えます.
科学分野:
- 地質化学 地質化学
- ミネラロジーは,鉱物学です.
- 地質物理学 地質物理学とは地質物理学です.
背景:
- 下層地殻の粒状クセノライトは,地表の深い過程についての洞察を提供します.
- 固有の鉄 (Fe(0) は,このような地質的な環境ではめったに見つからない.
研究 の 目的:
- 低地殻のゼノリットにおける原生鉄の発生と影響を調査する.
- 大陸の下層地殻と上層マントルの酸化状態を決定する.
主な方法:
- 西アフリカのキンベルライトパイプからのクセノリトの分析.
- 鉄金属の豊富さを定量化するための磁気測定.
- 地熱測定と酸素ジオバロメトリーは,平衡条件を決定する.
主要な成果:
- ネイティブ鉄 (Fe(0) は,ガーネットとイルメナイトの分解産物として特定されています.
- 鉄金属は,体積の0.1%未満を占めています.
- 鉄ウイスタイトと磁石ウイスタイトのバッファの間で均衡が取れた.
結論:
- 観測された鉄ウイスタイトと磁石ウイスタイトのバッファは,大陸下層の酸化状態と枯渇した石層上のマントルの酸化状態を表している可能性があります.
- 鉄磁性原生鉄は,深さ約95kmまで安定しています.
- この発見は,波長の長い静的磁気異常を解釈する上で極めて重要です.
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