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Incipient charnockite formation in the Trivandrum Block, southern India: Evidence from melt-related reaction textures and phase equilibria modelling

文献类型：期刊论文

作者Wang, Yuquan3,4,5; Zhai, Mingguo2,3; He, Hailong5; George, P. M.1; Sajeev, K.6; Jiao, Shujuan4,5; Liu, Bo7; Guo, Jinghui3,4,5
刊名LITHOS
出版日期2021
卷号380页码:17
ISSN号0024-4937
关键词Incipient charnockite Trivandrum Block Reaction texture Phase equilibria modelling Garnet Southern India
DOI10.1016/j.lithos.2020.105825
英文摘要The formation of incipient charnockite is significant for understanding the deep crustal process, which, however, remains under broad controversy. Patches of incipient charnockite occur ubiquitously in garnet-biotite gneiss in southern India. Here, we present new textural observations, geochemical analyses and phase equilibria modelling on the incipient charnockite and its garnet-biotite gneiss host from the Irinrayam quarry in the Trivandrum Block, with the aim to provide some new insights into the petrogenesis of incipient charnockite. Both rock types have similar bulk compositions which are characterized by high SiO2 (c. 70 wt%) and K2O (5.5-6.2 wt%), and low K/Rb (c. 150). Both rock types share similar peak mineral assemblage of garnet, K-feldspar, plagioclase, quartz, ilmenite and biotite except for the presence of orthopyroxene in the incipient charnockite. Phase equilibria modelling and thermobarometers reveal that these rocks record similar peak P-T conditions (870-900 degrees C, 6.2-7.2 kbar) followed by extensive cooling. Nonetheless, temperature versus mole H2O (T-M(H2O)) pseudosections show that orthopyroxene-bearing mineral assemblage is stable at lower M(H2O) than that without orthopyroxene. The post-peak cooling stage is characterized by fine-grained secondary garnet + quartz biotite +/- feldspar symplectite in the incipient charnockite, but by simple biotite + quartz symplectite in the garnet-biotite gneiss. The garnet-bearing symplectite overgrows around peak ferromagnesian minerals in the incipient charnockite, corresponding to the increase of garnet proportion with the consumption of anatectic melt in the phase equilibria modelling. Garnet in the symplectite is extremely depleted in heavy rare earth elements (HREEs), which might be inherited from the anatectic melt and other reactants. These phase equilibria modelling and garnet REE results suggest that the garnet-bearing symplectite is a melt-related retrograde texture. The appearance of anhydrous garnet during cooling indicates that the system of the incipient charnockite, especially the anatectic melt itself, is more anhydrous than that of the garnet-biotite gneiss. Simple process of fluid-absent melting and melt loss was likely insufficient to dehydrate the melt itself, and we propose that the infiltration of low-water-activity fluid is likely a significant process to reduce the water activity of the whole petrogenetic system, leading to the incipient charnockite formation in this area. (c) 2020 Elsevier B.V. All rights reserved.
WOS关键词KERALA KHONDALITE BELT ; HIGH-GRADE METAMORPHISM ; P-T CONDITIONS ; GARNET THERMOMETER ; MINERAL EQUILIBRIA ; HIGH-TEMPERATURE ; GRANULITE BLOCK ; CONSTRAINTS ; DEHYDRATION ; EVOLUTION
资助项目National Natural Science Foundation of China[41530208] ; National Natural Science Foundation of China[41602203] ; Chinese Academy of Sciences[QYZDY-SSWDQc017] ; Chinese Academy of Sciences[XDB18030205]
WOS研究方向Geochemistry & Geophysics ; Mineralogy
语种英语
出版者ELSEVIER
WOS记录号WOS:000612259900002
资助机构National Natural Science Foundation of China ; National Natural Science Foundation of China ; Chinese Academy of Sciences ; Chinese Academy of Sciences ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Chinese Academy of Sciences ; Chinese Academy of Sciences ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Chinese Academy of Sciences ; Chinese Academy of Sciences ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Chinese Academy of Sciences ; Chinese Academy of Sciences
源URL[http://ir.iggcas.ac.cn/handle/132A11/100066]  
专题地质与地球物理研究所_岩石圈演化国家重点实验室
通讯作者Zhai, Mingguo; He, Hailong
作者单位1.Northwest Univ, Dept Geol, State Key Lab Continental Dynam, Xian 710069, Peoples R China
2.Chinese Acad Sci, Key Lab Computat Geodynam, Beijing 100049, Peoples R China
3.Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing 100049, Peoples R China
4.Chinese Acad Sci, Innovat Acad Earth Sci, Beijing 100029, Peoples R China
5.Chinese Acad Sci, State Key Lab Lithospher Evolut, Inst Geol & Geophys, Beijing 100029, Peoples R China
6.Indian Inst Sci, Ctr Earth Sci, Bengaluru 560012, India
7.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China
推荐引用方式
GB/T 7714		 Wang, Yuquan,Zhai, Mingguo,He, Hailong,et al. Incipient charnockite formation in the Trivandrum Block, southern India: Evidence from melt-related reaction textures and phase equilibria modelling[J]. LITHOS,2021,380:17.
APA Wang, Yuquan.,Zhai, Mingguo.,He, Hailong.,George, P. M..,Sajeev, K..,...&Guo, Jinghui.(2021).Incipient charnockite formation in the Trivandrum Block, southern India: Evidence from melt-related reaction textures and phase equilibria modelling.LITHOS,380,17.
MLA Wang, Yuquan,et al."Incipient charnockite formation in the Trivandrum Block, southern India: Evidence from melt-related reaction textures and phase equilibria modelling".LITHOS 380(2021):17.

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来源：地质与地球物理研究所

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