LA-ICP-MS Zircon U-Pb Geochronology and Geochemical Characteristics of the Tasikuola Granite in Western Junggar,Xinjiang and Its Geological Significance
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Earth Science & Resources College of Chang’an University,Xi’an,,Earth Science & Resources College of Chang’an University,Xi’an;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits, MLR, Xi’an, shaanxi, 710054,Earth Science & Resources College of Chang’an University,Xi’an;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits, MLR, Xi’an, shaanxi, 710054,Earth Science & Resources College of Chang’an University,Xi’an,Northwest Bureau of China Metallurgical Geology, Xi’an, shaanxi,Earth Science & Resources College of Chang’an University,Xi’an

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    Abstract:

    The Late Carboniferous tectonic setting of the West Junggar region, Xinjiang is still in big controversy, which, to a great extent, restricts the deep insight into the tectonic evolution. Taking the Tasikuola granite in southern Miaoergou of West Junggar as the research object, this study carried out a detailed field geological survey, LA-ICP-MS zircon U-Pb isotopic dating and geochemical analysis to investigate its petrogenic age, petrogenesis and tectonic setting. The results show that the Tasikuola granite consists mainly of granodiorite with massive mafic microgranular enclaves (MMEs). Zircon UPb dating yields an age of 314.9±1.9 Ma for the granodiorite, defining an early Late Carboniferous magmatic event. Petrographic and geochemical features show that the Tasikuola granodiorite belongs to calalkaline series metaluminous to weakly peraluminous Itype granite and is characterized by medium silicon (SiO2=64.41%~66.48%) and aluminum (Al2O3=15.66%~16.45%), but low magnesium (MgO=1.61%~1.86%) and calcium (CaO=3.04%~3.26%), with A/CNK ratios ranging from 0.92 to 1.05. The granodiorites are enriched in large ion lithophile elements (LILEs: eg, Rb and K) and high field strength elements (HFSEs: eg, Zr and Hf) but strongly depleted in Nb, Ta, Ti, P and HREEs, with slightly negative Eu anomalies (δEu=0.32~0.68, 0.61 in average), which show significant similarities with Xiaerpu and Buerkesitai magma mixing granites occurred in southern West Junggar in emplacement age, geochemical characteristics and petrogenesis. Combined with regional geological background and magmatic evolution, it can be concluded that the Tasikuola granites formed in a subductionrelated island arc setting in early Late Carboniferous. They were most likely derived from partial melting of basalticdominated basic rocks in the lower crust, which were induced by underplating of the mafic magma melted by overlying mantle wedge that had been metasomatized by fluids in subduction belt, with magma mixing between mantle and crustalderived melts in the deep crust to some extent.

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DUAN Fenghao, LI Yongjun, WANG Ran, ZHI Qian, CHAO Wendi, MA Yonglin.2018. LA-ICP-MS Zircon U-Pb Geochronology and Geochemical Characteristics of the Tasikuola Granite in Western Junggar, Xinjiang and Its Geological Significance[J]. Acta Geologica Sinica,92(7):1401-1417

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History
  • Received:April 09,2017
  • Revised:April 17,2018
  • Adopted:November 18,2017
  • Online: July 13,2018
  • Published: