Geochronology and Geochemistry of Late Carboniferous Jinggesitai Alkaline Granites, Inner Mongolia: Petrogenesis and Implications for Tectonic Evolution
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Tianjin institute of Geology and Mineral resources

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    Abstract:

    In this paper, we present zircon U-Pb dating, in-situ Hf isotopic analysis, whole rock Nd isotopic and geochemical data of the late Carboniferous alkaline granites from Jinggesitai region, central part of the Xingmeng Orogenic Belt. Zircon U-Pb dating give weighted average age of 301.3±1.5Ma (n=21, MSWD=1.3), indicating that this intrusion was formed in late carboniferous. These rocks show the characterics of high silica (75.16~76.96%), alkali(K2O=4.61~5.04%,Na2O=3.98~4.24%) contents,low CaO (0.08~0.25%), MgO (0.07~0.1%), FeOt (1.05~2.05%) contents, respectively, but with high FeOt/MgO ratios (12.85~29.66), which are similar with typical A-type granite. Trace elemental data of these rocks show enrichment of Rb, Th, U, K, Zr, Hf, but strong depletion of Sr, Ba, P, Ti. Total REE contents are moderate (ΣREE=70.19~193.93×10-6) with obvious fractionation between LREE and HREE((La/Yb) Nrange from 3.85 to 11.55) and strong negative Eu abnormity (δEu range from 0.03~0.07). Furthermore, these rocks have positive zircon εHf(t) and whole rock εNd(t) values, with two stage Hf and Nd model ages of Neoproterozoic, indicating the source of Jinggesitai alkaline granites of juvenile crust from mantle in Neoproterozoic. These geochemical and NdHf isotopic signatures argue for derivation from partial melting of juvenile crust by depression and heating of upwelling asthenosphere in a extensional setting, demonstrating late Post-Orogenic tectonic regime of Erlian-Dongwuqi region in 301Ma.

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WANG Shuqing, HU Xiaojia, ZHAO Hualei, XIN Houtian, YANG Zeli, LIU Wengang, HE Li.2017. Geochronology and Geochemistry of Late Carboniferous Jinggesitai Alkaline Granites, Inner Mongolia: Petrogenesis and Implications for Tectonic Evolution[J]. Acta Geologica Sinica,91(7):1467-1482

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History
  • Received:March 10,2016
  • Revised:June 24,2016
  • Adopted:November 13,2016
  • Online: July 11,2017
  • Published: