Geochemical Characteristics and Geological Significance of the Neoproterozoic K-feldspar Granites from the Anshunchang, Shimian Area, Western Yangtze Block
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    Abstract:

    Objectives: Neoproterozoic magmatic rocks are widespread in western margin of the Yangtze block, Petrogenesis of the Neoproterozoic granitic rocks has potential significance to the tectonic evolution of supercontinent Rodinia. Methods: In this paper, we present zircon U-Pb age,and whole-rock major and trace elements,Sr—Nd isotopic compositions of the K-feldspar granites from the Anshunchang, Shimian county. Results: K-feldspar granites zircon U-Pb result show that the crystallization age of 777.3±4.8Ma (MSWD =0.23,2σ), which belongs to Neproterozoic granites. The results indicate that the K-feldspar granites are peraluminous, highK calcalkaline Stype granites, with SiO2 content ranging from 72.64% to 76.27%, A/CNK = 1.06~1.24, K2O/Na2O = 1.40~2.22, σ = 2.08~2.74. The granites are enriched in LREE and depleted in Nb and Ta, with significant negative Eu anomalies (δEu = 018~0.23). The εNd(t) vary from 0.5 to 3.3 (average value =2.1), and TDM=1.19~1.61Ga, suggesting Neoproterozoic crust source region. The Kfeldspar granites have \[n(206Pb)/n(204Pb)\]i=15.4103~17.2707, \[n(207Pb)/n(204Pb)\]i=15.4265~15.5479, and \[n(208Pb)/n(204Pb)\]i =33.3518~35.8641, respectively. Conclusion: In combination with geochemistry, isotopic signatures and the regional geology in the western of the Yangtze block, we argued that Kfeldspar granites from the Anshunchang are peraluminous, highK calcalkaline Stype granites, these Kfeldspar granites were derived from partial melting of the pelite in middle—lower crust. They were formed in an compressive tectonic setting.

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ZHU Yu, LAI Shaocong, ZHAO Shaowei, ZHANG Zezhong, QIN Jiangfeng.2017. Geochemical Characteristics and Geological Significance of the Neoproterozoic K-feldspar Granites from the Anshunchang, Shimian Area, Western Yangtze Block[J]. Geological Review,63(5):1193-1208.

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History
  • Received:December 01,2016
  • Revised:August 05,2017
  • Adopted:
  • Online: September 13,2017
  • Published: