Effects of Lattice Preferred Orientation and Retrogression on Seismic Properties of Eclogite  

作　　者：史锋 王永锋 徐海军 章军锋 

机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences

出　　处：《Journal of Earth Science》2010年第5期569-580,共12页地球科学学刊（英文版）

基　　金：supported by the National Natural Science Foundation of China (Nos. 90714010, 90714005, 40821061, 40702034);the Ministry of Education of China and the State Administration of Foreign Expert Affairs of China (Nos. B07039, 2007B25);National Basic Research Program of China (No. 2009CB825003);the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences

摘　　要：We report here lattice preferred orientations （LPOs） and seismic properties of eclogites from the Sulu （苏鲁） UHP terrane. Our results show strong fabrics in omphacite and amphibole, and approximately random fabrics in garnet with or without strong shape preferred orientations （SPOs）. Dislocation creep is likely to be responsible for the observed omphacite fabrics that vary with geometry and orientation of finite strain ellipsoid. Weak garnet LPOs suggest that garnet did not accommodate plastic strain or was not deformed by dislocation creep with a dominant slip system. The calculated seismic properties of eclogites and their component minerals show a strong correlation with their LPOs. Seismic anisotropies are mostly induced by omphacite component in fresh eclogites and by amphibole component in retrograded eclogites, respectively. Retrogression of omphaeite to amphibole and quartz will increase seismic anisotropies but decreases seismic velocities of eclogite. Garnet component increases the seismic velocities but decreases seismic anisotropies of eciogite. Comparison of the calculated and the measured seismic properties of eclogites suggests that both methods resolve comparable results with some discrepancies. Compositional layering can play a very important role in determining the seismic properties of eclogites in addition to LPO.We report here lattice preferred orientations （LPOs） and seismic properties of eclogites from the Sulu （苏鲁） UHP terrane. Our results show strong fabrics in omphacite and amphibole, and approximately random fabrics in garnet with or without strong shape preferred orientations （SPOs）. Dislocation creep is likely to be responsible for the observed omphacite fabrics that vary with geometry and orientation of finite strain ellipsoid. Weak garnet LPOs suggest that garnet did not accommodate plastic strain or was not deformed by dislocation creep with a dominant slip system. The calculated seismic properties of eclogites and their component minerals show a strong correlation with their LPOs. Seismic anisotropies are mostly induced by omphacite component in fresh eclogites and by amphibole component in retrograded eclogites, respectively. Retrogression of omphaeite to amphibole and quartz will increase seismic anisotropies but decreases seismic velocities of eclogite. Garnet component increases the seismic velocities but decreases seismic anisotropies of eciogite. Comparison of the calculated and the measured seismic properties of eclogites suggests that both methods resolve comparable results with some discrepancies. Compositional layering can play a very important role in determining the seismic properties of eclogites in addition to LPO.

关 键 词：ECLOGITE LPO RETROGRESSION seismic property deformation mechanism. 

分 类 号：P584[天文地球—岩石学]