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Geoscience ›› 2021, Vol. 35 ›› Issue (05): 1231-1239.DOI: 10.19657/j.geoscience.1000-8527.2020.052

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Zircon U-Pb Age and Geochemical Characteristics of the Granodiorite in Wulanwutai, Inner Mongolia and Its Geological Significance

CHENG Tianshe(), YANG Wenjing, ZHANG Xuebin, WU Rongze, ZHOU Changhong   

  1. Tianjin Institute of Geological Survey, Tianjin 300191, China
  • Received:2019-09-20 Revised:2021-04-09 Online:2021-10-10 Published:2021-11-04

Abstract:

The Wulanwutai granodiorite in Inner Mongolia is located in the middle part of Xilinhot magmatic arc of an arc-basin system, in the middle part of Xingmeng orogen. To discuss its genetic type and tectonic background, 1:50,000 regional geological survey was conducted and the petrology, mineralogy, geochronology and petrochemistry of the granodiorite were studied. The LA-ICP-MS zircon U-Pb age of (384.8±5.1) Ma indicates a Late Devonian granodiorite emplacement. The rocks mainly contain plagioclase, K-feldspar, quartz, biotite, and amphibole, with accessory zircon, ilmenite, apatite, monazite, and magnetite. The mineral contents resemble typical CPG (cordierite-bearing peraluminous granites) in Barbarin granite classification. In addition, the granodiorite is rich in K2O(3.10%-3.94%) and Al2O3(11.70%-12.89%), and is peraluminous (A/CNK=1.16-1.25). The rocks also contain diorite xenolith. Hence, it is considered that the primary magma of the granodiorite may have derived from partial melting of a crust-mantle mixed source, and formed during the continent-continent collision between the Siberian and North China plates.

Key words: Xingmeng orogenic belt, granodiorite, U-Pb dating, Late Devonian, continent-continent collision

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