Phase equilibria of HP–UHP mica-schists in Jiangling, Eastern Dabieshan orogen
Phase equilibria of HP–UHP mica-schists in Jiangling, Eastern Dabieshan orogen
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DOI：
10.1016/j.pnsc.2008.12.004
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发表时间：
2009-08
期刊：
影响因子：
--
通讯作者：
H. Chu;C. Wei;S. Su
中科院分区：
文献类型：
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作者：
H. Chu;C. Wei;S. Su
大别山东部江陵高压-超高压变质杂岩体由广泛分布的花岗质片麻岩、云母片岩和大量榴辉岩块组成。云母片岩一般含石榴石、多晶白云母、黑云母、斜长石、石英、金红石及少量绿帘石和角闪石。对NCKMnFMASH系统的岩相学和相平衡研究表明，云母片岩中的矿物组合不平衡。早期以石榴子石和多硅白云母为代表的矿物组合反映了高压-超高压条件。石榴石成分和多硅白云母Si含量给出了在2.6-2.8GPa下580-600°C的PT条件。石榴子石分带记录了一个较早的渐进变质过程，可能与蓝闪石、硬玉和硬柱石的出现有关。后期以黑云母和斜长石为特征的矿物组合反映了620-635°C，0.9-1.1GPa的PT条件，属于HP角闪岩相。江陵地区云母片岩中的主要矿物组合记录了一次完整的高压-超高压变质过程。
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 2.6–2.8GPa. 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 0.9–1.1GPa, 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.