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Geoscience ›› 2021, Vol. 35 ›› Issue (05): 1218-1230.DOI: 10.19657/j.geoscience.1000-8527.2021.050

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Geochronology, Geochemistry, and Tectonic Significance of the Hailasituowula A-type Granites in Sunitezuoqi, Inner Mongolia

SUN Xiaodong1(), CHEN Haiyun2, YU Guangning1   

  1. 1. No.9 Institute of Geology and Mineral Resources Development of Inner Mongolia, Xilin Hot, Inner Mongolia 026000, China
    2. Northwest Engineering Co.Ltd., Xi’an, Shaanxi 710065, China
  • Received:2020-06-08 Revised:2021-08-31 Online:2021-10-10 Published:2021-11-04

Abstract:

The Hailasituwula arfvedsonite-aegitite augite-alkali granite is distributed in southern Chagan’aobao, Sunitezuoqi of Inner Mongolia, an important component of the Erlian-Hegenshan tectonic belt. Through chronological and geochemical studies on it, to explore regional tectonic evolution, LA-ICP-MS zircon U-Pb dating yielded (285.4±1.1) Ma, belonging to the Early Permian, This geochemical study shows that the rocks are featured by being metaluminous, and have relatively high SiO2(76.12%-80.10%) and alkalis (K2O+Na2O=7.62%-9.19%), but low MgO (0.06%-0.10%) and CaO (0.11%-0.20%). The Alkaline index (AI) is 0.98-1.04, and the rocks belong to the alkaline series. The total REE contents of the rocks are relatively low, and the LREEs and HREEs are obviously fractionated. Negative Eu anomalies are distinct (δEu=0.37-0.51), which are coeval with the regional post-orogenic extension. The results indicate that the Erlian-Hegenshan tectonic belt may have entered the post-orogenic stage in the Early Permian.

Key words: Inner Mongolia, A-type granite, Permian, tectonic setting

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