タルク含有サーペンチナイトとサンアンドレアス断層の爬行部分
Diane E Moore1, Michael J Rymer
1US Geological Survey, 345 Middlefield Road, Mail Stop 977, Menlo Park, California 94025, USA. dmoore@usgs.gov
Nature
|August 19, 2007
まとめ
サンアンドレアス断層のサーペンチナイトで発見されたタルクは,断層の滑り方を説明する可能性があることを示唆しています. この発見は,弱い断層の行動と蛇形鉱物の高い強さの間の不一致を解決する.
科学分野:
- 地質学 地質学 地質学
- テクトニクス (地質学) とは
- ミネラロジーは,鉱物学です.
背景:
- カリフォルニア州中部のサンアンドレアス断層 (SAF) は,年当たり28ミリメートル (mm/yr) までの大幅な滑りを見せている.
- サーペンチナイトはしばしば,この弱い断層の行動の原因として引用されていますが,サーペンチン鉱物は,観測と矛盾する摩擦力を有しています.
- 以前の研究は,強い地殻の設定に埋め込まれた弱い欠陥を示していた.
研究 の 目的:
- SAF沿いのサーペンチナイトの鉱物学的組成を調査する.
- この断層の低シア強度と安定したクリープに起因するメカニズムを特定する.
- サーペンチナイトの存在と,観察された断層の弱さとの調和を図るため.
主な方法:
- サンアンドレアス断層深層観測所 (SAFOD) のメインホールのサーペンチナイト断層の分析.
- 岩石サンプルを顕微鏡および鉱物学的に検査する.
- 地質的な文脈に基づく鉱物形成過程の推論.
主要な成果:
- SAFからのサーペンチナイトサンプルの中にタルクを発見した.
- タルクは,サーペンタインとシリカが豊富な熱水流体との反応によって形成されると推測されています.
- タルクは,断層線に沿って切断された蛇形岩に含まれています.
結論:
- タルクは,SAFの低い切断強度と一致する高温での摩擦特性を持っています.
- タルクの安定した滑り方は,観測された断層の滑り方と一致しています.
- タルクは,サンアンドレアス断層の断層のクリープにサーペンチナイトの存在を結びつける重要な鉱物かもしれません.
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