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首页> 外文期刊>Journal of Asian earth sciences >Crustal formation in the Nanling Range, South China Block: Hf isotope evidence of zircons from Phanerozoic granitoids
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Crustal formation in the Nanling Range, South China Block: Hf isotope evidence of zircons from Phanerozoic granitoids

机译：华南地区南岭山脉地壳形成：杂多生代花岗岩中锆石的f同位素证据

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摘要

Granitic rocks are the principle agent of crustal differentiation, therefore their origins yield important information on crustal formation and reworking. An extensive survey of zircon Hf isotopes from granitic rocks in a large region can provide a profile of crustal characteristics that may be further linked to previous crustal evolution. In this study, we measured U-Pb ages and Hf isotope compositions of zircon grains extracted from twenty-five Jurassic, five Triassic and two Ordovician granitic plutons from the Nanling Range, South China Block (SCB). Combined with the published Lu-Hf isotopic data for the granitic rocks in the studied and adjacent areas, three domains with different crustal formation histories have been identified in the southern part of the SCB: eastern side, middle part and western side. The eastern side extends to the coastal area of the SCB, with dominant Hf crustal model ages (T_(DM2)) in zircons falling within the range of 2.2-1.6 Ga. The middle part is partly coincided with the low-Nd model age belt proposed by Chen and Jahn (1998), with zircon Hf T_(DM2) ranging from 1.6 to 1.0 Ga. The western side covers the westernmost Nanling Range and the western end of the Jiangnan orogen, in which the granitoids have zircon Hf T_(DM2) model ages spanning 2.2-1.8 Ga. The Paleo- to Meso-Proterozoic model ages of the Phanerozoic granitoids in the Nanling Range imply a long-term crustal reworking. Zircons from the western and eastern sides have an average ε_(Hf)(155 Ma) at around -10, about 4 epsilon units lower than the middle part (ε_(Hf)(155 Ma) = -6). Hf T_(DM2) histogram from the western Nanling Range is similar to that of the Neoproterozoic granitoids in northern Guangxi Province to the west but much lower to the granites in the middle part to the east. The eastern side has a broader range of Hf model ages in zircons, with the main peak low to ca 1.6 Ga, suggesting the reworking of Mesoproterozoic crust. However, granitoids in the middle part have zircon Hf T_(DM2) ages at 1.6-1.0 Ga, which indicates the incorporation of younger crust materials into the magma sources. The Hf model ages of granitoids, as well as four zircon xenocrysts with ages around 920 Ma within the Mesozoic granitoids in the middle part, indicate that the middle part has similar crustal features with the eastern Jiangnan orogen. We propose that this low T_(DM2) granite belt is probably part of the early Neoproterozoic arc-continent collision belt between different continents (possibly Yangtze and Cathaysia) during the early assembling processes, while the granitoids in the western and eastern sides have similar crustal compositions.
机译：花岗岩是地壳分化的主要推动力，因此它们的成因提供了有关地壳形成和返工的重要信息。对大区域花岗岩岩石中的锆石Hf同位素进行的广泛调查可以提供地壳特征的概况，这可能与以前的地壳演化进一步相关。在这项研究中，我们测量了从华南地区南岭山脉的25个侏罗纪，5个三叠纪和2个奥陶纪花岗岩体中提取的锆石的U-Pb年龄和Hf同位素组成。结合已研究和邻近地区花岗岩岩石的Lu-Hf同位素数据，在南海南部发现了三个地壳形成历史不同的区域：东侧，中部和西侧。东侧延伸到SCB的沿海地区，锆石的主要Hf地壳模型年龄（T_（DM2））在2.2-1.6 Ga范围内。中部部分与低Nd模型年龄带重合。由Chen和Jahn（1998）提出，锆石Hf T_（DM2）的范围为1.6至1.0 Ga。最西侧覆盖最南岭山脉和江南造山带的西端，其中的花岗岩类具有锆石Hf T_（DM2）。 ）的模型年龄跨度为2.2-1.8 Ga。南岭山脉生代花岗岩的古至中元古代模型年龄意味着地壳需要长期返工。西侧和东侧的锆石的平均ε_（Hf）（155 Ma）在-10附近，比中间部分低ε4（ε_（Hf）（155 Ma）= -6）。南岭山脉西部的Hf T_（DM2）直方图与广西北部的新元古代花岗岩相似，但在东部中部的花岗岩较低。东面锆石的Hf模型年龄范围更广，主峰低至约1.6 Ga，表明中元古生代地壳已被重新加工。然而，中部的花岗岩类锆石的Hf T_（DM2）年龄为1.6-1.0 Ga，这表明较年轻的地壳物质已被整合到岩浆源中。花岗岩的Hf模型年龄，以及中部中生代花岗岩中的四个年龄在920 Ma附近的锆石异晶，表明中部的地壳特征与江南造山带相似。我们认为，低T_（DM2）花岗岩带可能是早期组装过程中不同大陆（可能是扬子和华夏）之间新元古代弧-大陆碰撞带的一部分，而东西两侧的花岗岩类则具有相似的地壳成分。

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  • 来源
    《Journal of Asian earth sciences》 |2013年第25期|210-224|共15页
  • 作者

    Xu-Jie Shu; Xiao-Lei Wang; Tao Sun; Wei-Feng Chen; Wei-Zhou Shen;

  • 作者单位

    State Key Laboratory for Mineral Deposits Research, School of Earth Science and Engineering, Nanjing University, Nanjing 210093, China;

    State Key Laboratory for Mineral Deposits Research, School of Earth Science and Engineering, Nanjing University, Nanjing 210093, China,WiscSIMS, Department of Geoscience, University of Wisconsin, 1215 W. Dayton Street, Madison. WI 53706, USA;

    WiscSIMS, Department of Geoscience, University of Wisconsin, 1215 W. Dayton Street, Madison. WI 53706, USA;

    State Key Laboratory for Mineral Deposits Research, School of Earth Science and Engineering, Nanjing University, Nanjing 210093, China;

    State Key Laboratory for Mineral Deposits Research, School of Earth Science and Engineering, Nanjing University, Nanjing 210093, China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    U-Pb age; Hf isotopes; Granitoids; Crustal evolution; Reworking; South China Block;

    机译：U-Pb年龄;f同位素花岗岩地壳演化;返工;华南街区;

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