Earth Science Frontiers ›› 2018, Vol. 25 ›› Issue (6): 136-151.DOI: 10.13745/j.esf.sf.2018.11.9

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Petrogenesis of the monzonitic granite of the Qinmalong District, Nanmulin County, Tibet, China.

WEI Qirong,ZHAO Shan,WANG Jian,ZHANG Min,XU Huan,OU Bo,XU Changjun,JIN Lei   

  1. Faculty of Earth Resources, China University of Geosciences(Wuhan), Wuhan 430074, China
  • Received:2018-07-19 Revised:2018-09-02 Online:2018-11-30 Published:2018-11-30
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Abstract: In this paper, we performed comprehensive analyses on the monzonitic granite outcropped in the Qinmalong District, Nanmulin County, Tibet including field geological survey, petrology, LA-ICP-MS zircon U-Pb dating, elemental and Lu-Hf isotope geochemistry. The results showed that the monzonitic granite from the Qinmalong District belongs to the A-type granite and formed in the Paleogene (E1). The LA-ICP-MS zircon U-Pb age of the granite was 62.0±0.5 to 63.0±0.5 Ma. The weakly peraluminous monzonitic granite formed in high temperature (the saturation temperature of zircon was 745805 ℃, averaged at 766 ℃) and belongs to the high-potassium-calcium-alkaline series. It was enriched in SiO2 (72.6%74.97%), Na2O (2.86%3.59%) and K2O (4.12%5.25%) but depleted in CaO (0.72%1.39%) and MgO (0.26%0.36%). In addition, the granite had high FeOT/MgO value (7.2610.30) and obvious negative Eu anomalies (Eu/Eu*=0.400.70), depleted in Ba, Sr, P and Ti but enriched in Rb, Th, K, Zr and Hf element. The εHf(t) value was -4.7-1.8. The cursts two-stage Hf model age (tDM2) was 1.11.3 Ga. Our study indicates that the A-type granite originates from partial melting of the crustal materials in the Gangdese basement and formed in a tectonic setting of localized stretching in arc environment in response to the subduction and collision between the Indian and Eurasian Plates in the Paleogene.


Key words: monzonitic granite of Qinmalong District, zircon U-Pb dating, element and Lu-Hf isotope geochemistry, petrogenesis, Gangdese

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