Zircon U-Pb dating,Hf isotope compositions studies of Risong granite,North Gangdese,Tibet
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    Abstract:

    Granite samples from Risong granite of Ritu county-Lameila pass area, Western Tibet, were selected for a detailed geochronological and Hf isotopes study. Petrochemical data showed that Risong granite belongs to calc-alkalic rock series and the vast majority of all samples contain Di in CIPW composition. All samples show in rightly-deviation from the LREE to the HREE with the obviously negative Eu anomaly (δEu=0.42-0.85), and enriched in Rb, Pb, Th and depleted in K, Ba, especially in HFSE (Nb, Ta, Ti). Different from previous studies define its age to late-Cretaceous to Eocene, this article divided the Risong granite into two intrusive of early-Cretaceous and late-Cretaceous. LA-ICPMS U-Pb zircon ages for monzogranite(D1045-2) were 108.4±2.1Ma(MSWD=2.4, n=18), indicating that it were generated in early Cretaceous. Sample of monzogranite (D1045-2) showed positive Hf isotopic initial ratio and variation between 1.49 to 3.86(with 2.50 averages); Sample of quartz diorite (D1045) showed negative Hf isotopic initial ratio and variation between -2.09 to 0.15 (with -0.49 averages). Two samples showed 762.95Ma-884.47Ma (D1045-2), 959.1Ma-1073.49Ma (D1045) of two stage model ages respectively. Zircon Hf isotopic compositions of two samples all showed narrow ranges in Hf isotopic initial ratio and two stage model ages, indicating that the material source magma of granites had homogeneous in Hf isotopic compositions. The characteristics of the zircon U-Pb ages and Hf isotope features, were in accordance with the features of early Cretaceous magmatisms of North Gangdese.The granite were formed by granitic magmatisms during the oceanic crust orogenic subduction, as the magmatic response to the Bangong-Nujiang Tethys evolution.

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Guan Junlei, Geng Quanru, Wang Guozhi, Peng Zhimin, Zhang Zhang, Cong Feng, Li Na.2014. Zircon U-Pb dating,Hf isotope compositions studies of Risong granite,North Gangdese,Tibet[J]. Acta Geologica Sinica,88(1):36-52

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History
  • Received:November 19,2012
  • Revised:April 22,2013
  • Adopted:July 05,2013
  • Online: January 24,2014
  • Published: