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MPN-12 Sederholm symposium on high-grade metamorphism, crustal melting, migmatites and granites
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The petrochemistry characteristic and petrogenesis of peraluminous granite in Tibet
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Zhongli Liao, Chengdu Institute of Geology and Mineral Resources (China)
Xuanxue Mo, China University of Geosciences (China)
Guitang Pan, Chengdu Institute of Geology and Mineral Resources (China)
Dicheng Zhu, Chengdu Institute of Geology and Mineral Resources (China)
Liquan Wang, Chengdu Institute of Geology and Mineral Resources (China)
Zhidan Zhao, China University of Geosciences (China)
Quanru Gen, Chengdu Institute of Geology and Mineral Resources (China)
Xingguo Xiong, Guizhou Academy of Geologic Survey (China)
Guochen Dong, China University of Geosciences (China)
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There are 61 major peraluminous granitic bodies in Tibet (TPGs) along the south of the Bangong Co-Grz-Amdo-Nu Jiang suture, whose lithology include tourmaline granite, muscovite granite, and two-mica granite. The TPGs have SiO2 = 65.7% - 79.52% , K2O + Na2O = 2.20 %-12.51 %, K2O/ Na2O = 0.49-1.04 and A/CNK= 1.04-1.38. Al2O3 gradually decrease and the other oxide disperse along with the increase in SiO2. The rock series is mainly calc-alk series with high Potassium.
It has typical characteristic of strong peraluminous granite. Based on the aluminum saturation index and QAP plots, the peraluminous granites plot is mostly within the continental collision granite (CCG) field, indicating that the peralumious granites in Tibet formed in a continental collisional setting. Ab-Or-Q-H2O phase diagram indicate the pressure of 0.5 - 2 k bar in TPGs, from which it can be deduced the forming temperature was under 700°C.
The TPGs is mainly occurred at the collision stage between two continental crust plates, and the original magma is rooted in the remelting from the upper crust. It is the S-type granite in petrogenesis. The Southern Gandise belt and the Lhagoi Kangri belt have similar characteristics, suggesting that the two belts have the same magma source and the same tectonic setting.
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