Phase equilibria of HP–UHP mica-schists in Jiangling, Eastern Dabieshan orogen  

作　　者：Hang Chu Chunjing Wei Shangguo Su 

机构地区：[1]MOE Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China [2]China University of Geosciences, Beijing 100083, China

出　　处：《Progress in Natural Science:Materials International》2009年第8期973-982,共10页自然科学进展·国际材料（英文版）

基　　金：supported by National Natu-ral Science Foundation of China (Grant No. 40525006).

摘　　要：The HP-UHP metamorphic terrane of Jiangling, eastern Dabieshan comprises extensively distributed granitic gneisses, mica-schists and numerous eclogite blocks. The mica-schists generally contain garnet, phengitic muscovite, biotite, plagioclase, quartz, rutile and a small amount of epidote and hornblende. Study on petrography and phases equilibria in the NCKMnFMASH system indicates that the present mineral assemblages in mica-schists are not in equilibrium. The earlier stage of mineral assemblage represented by garnet and phengite reflects a HP-UHP condition. The garnet compositions and the phengite Si contents give a PT condition of 580-600 ~C at 2.62.8 GPa. The garnet zonation records an earlier progressive metamorphic process which may be associated with the appearance of glaucophane, jadeite and lawsonite. The later stage of mineral assemblage characterized by the presence of biotite and plagioclase reflects a PT condition of 620-635 ~C at 0.9-1.1 GPa, belonging to the HP amphibolite facies. The main mineral assemblage in mica- schists from the Jiangling region has recorded a complete HP-UHP metamorphic process. 2009 National Natural Science Foundation of China and Chinese Academy of Sciences. Published by Elsevier Limited and Science in China Press, All rights reserved.The HP–UHP metamorphic terrane of Jiangling, eastern Dabieshan comprises extensively distributed granitic gneisses, mica-schists and numerous eclogite blocks. The mica-schists generally contain garnet, phengitic muscovite, biotite, plagioclase, quartz, rutile and a small amount of epidote and hornblende. Study on petrography and phases equilibria in the NCKMnFMASH system indicates that the present mineral assemblages in mica-schists are not in equilibrium. The earlier stage of mineral assemblage represented by garnet and phengite reflects a HP–UHP condition. The garnet compositions and the phengite Si contents give a PT condition of 580–600 °C at 2.6–2.8 GPa. The garnet zonation records an earlier progressive metamorphic process which may be associated with the appearance of glaucophane, jadeite and lawsonite. The later stage of mineral assemblage characterized by the presence of biotite and plagioclase reflects a PT condition of 620–635 °C at 0.9–1.1 GPa, belonging to the HP amphibolite facies. The main mineral assemblage in micaschists from the Jiangling region has recorded a complete HP–UHP metamorphic process.

关 键 词：HP-UHP metamorphism Phase equilibria Mica-schist DABIESHAN 

分 类 号：P578.959[天文地球—矿物学] TE257.1[天文地球—地质学]