Semi-brittle deformation of granitoid gouges in shear experiments at elevated pressures and temperatures

详细信息	查看全文 | 推荐本文 |

• 作者：Matej Pec^a ; ^{matej.pec@unibas.ch} ; ^{matej.pec@seznam.cz} ; Holger Stü ; nitz^b ; René ; e Heilbronner^a
• 关键词：Rock deformation ; Microstructures ; Semi-brittle flow ; Brittle-plastic transition ; Fault rocks
• 刊名：Journal of Structural Geology
• 出版年：2012
• 期刊代码：52_01918141
• 类别：ear
• 出版时间：May, 2012
• 卷：38
• 期：Complete
• 页码：200-221
• 文件大小：6085 K

摘要

The physical and chemical processes acting in the 鈥榖rittle-to-plastic鈥?transition are of great interest for a better understanding of fault rheology. We performed a series of experiments on granitoid gouge material under high confining pressures (Pc聽=聽500-1500聽MPa), temperatures (T聽=聽300聽掳C and 500聽掳C) and fast shear strain rates (鈭?.8聽脳聽10^鈭?聽s^鈭?) where the material deforms by semi-brittle flow. Samples deformed at 500聽掳C are systematically weaker than samples deformed at 300聽掳C over the whole examined confining pressure range indicating a non-frictional component of the deformation. All samples develop an S-C鈥?fabrics and deformation localizes in slip zones containing 鈥榓morphous鈥?feldspar material with an intermediate composition (Na, Ca and K-rich). Further, we observe changes in composition of feldspars (enrichment in the albite component) in the highly fragmented - but crystalline - regions with increasing finite shear strain. Our results indicate that mass-transfer processes keep pace with frictional deformation even at high strain rates and together with viscous flow of the 鈥榓morphous鈥?material are responsible for the observed strength difference.