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首页> 外文期刊>Journal of Asian earth sciences >Intraplate crustal remelting as the genesis of Jurassic high-K granites in the coastal region of the Guangdong Province, SE China
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Intraplate crustal remelting as the genesis of Jurassic high-K granites in the coastal region of the Guangdong Province, SE China

机译：中国东南部沿海地区侏罗系高钾花岗岩成因的板内地壳重熔

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摘要

The origin and tectonic significance of high-K granites (>3 wt% K_2O at 70 wt% SiO_2), calc-alkaline Ⅰ-type granites in particular, remain controversial. This paper takes granitic plutons distributed in the coastal region of the Guangdong Province of southeastern China as examples to explore the genesis of such rocks. SIMS zircon U-Pb geochronological data show that the granites were emplaced at 166-159 Ma. These granites can be subdivided generally into two groups on the basis of integrated mineralogical, geochem-ical, whole-rock Sr-Nd isotopic and in situ zircon Hf-O isotopic studies. The group A granites (SiO_2 = 64-72 wt%) are characterised by their common occurrence of amphibole (ttitanite) and dominantly metaluminous feature (A/CNK = 0.85-1.03). They are high in K_2O (3.5-7.0 wt%) and K_2O/Na_2O (>1), and have trace element concentrations (e.g., Nb, Y, Zr and Ga) similar to typical I-type granites in the Lachlan Fold Belt, southeastern Australia. Their whole-rock I_(sr) (0.7057-0.7077) and εNd(t) (-6.46 to -3.13) are less evolved than many coeval granites in this region. As in situ zircon Hf-0 isotopes show little evidence of magma mixing, these granites with low zircon δ~(18)O (6.3-7.9‰) and high εHf(t) (-5.9 to -0.2) could have been generated from melting of oxidised high-K basaltic rocks. The group B granites, emplaced to the east of group A granites, are dominantly weakly peraluminous (A/CNK - 1.00-1.05). They have higher SiO_2 (70-76 wt%), less common or absence of amphibole, higher zircon δ~(18)O (6.6-9.0‰) and lower εHf(t) (-11.4 to -5.9) than the group A granites. Zircon Hf-O isotope data reveal that the group B granites contain higher percentage of supracrustal materials than those of the group A, but the variations of major and trace elements do not support an assimilation and fractional crystallization (AFC) model. Instead, the group B granites, with features transitional between typical I-type and S-type granites, were most likely formed in a region where there was physical juxtaposition between infracrustal metaluminous and supracrustal peraluminous source rocks. Thus, granites of both groups represent products of crustal reworking likely due to asthenosphere upwelling and/or underplating and intrusion of mafic magmas. The close association in time and space of these granites with OIB-like basaltic rocks and the secular compositional change of Jurassic basaltic rocks in the region suggest that these rocks probably formed in an intraplate extensional setting resulted from the delamination of a flat-subducted oceanic slab.
机译：高钾花岗岩（在70 wt％SiO_2时> 3 wt％K_2O），特别是钙碱性Ⅰ型花岗岩的起源和构造意义仍存在争议。本文以分布在中国东南沿海地区的花岗质岩体为例，探讨了这类岩体的成因。 SIMS锆石U-Pb年代学数据表明，花岗岩位于166-159 Ma。根据综合的矿物学，地球化学，全岩Sr-Nd同位素和原位锆石Hf-O同位素研究，这些花岗岩大致可分为两类。 A组花岗岩（SiO_2 = 64-72 wt％）的特征是常见的闪石（钛铁矿）和主要的金属特征（A / CNK = 0.85-1.03）。它们的K_2O（3.5-7.0 wt％）和K_2O / Na_2O（> 1）高，并且具有与Lachlan褶皱带中典型的I型花岗岩相似的痕量元素浓度（例如Nb，Y，Zr和Ga），澳大利亚东南部。他们的全岩I_（sr）（0.7057-0.7077）和εNd（t）（-6.46至-3.13）比该地区的许多中世纪花岗岩演化较少。由于原位锆石Hf-0同位素几乎没有岩浆混合的证据，这些锆石δ〜（18）O低（6.3-7.9‰）和高εHf（t）（-5.9至-0.2）的花岗岩可能来自氧化的高K玄武岩融化。 B组花岗岩位于A组花岗岩的东部，主要为弱铝质（A / CNK-1.00-1.05）。与A组相比，它们具有较高的SiO_2（70-76 wt％），较少或不存在闪石，较高的锆石δ〜（18）O（6.6-9.0‰）和较低的εHf（t）（-11.4至-5.9）。花岗岩。锆石Hf-O同位素数据显示，B组花岗岩比A组花岗岩含更高的表壳物质，但主要元素和微量元素的变化不支持同化和分步结晶（AFC）模型。取而代之的是，在典型的I型和S型花岗岩之间过渡的特征的B组花岗岩最有可能形成于在陆壳金属矿床和陆壳金属铝矿源岩之间存在物理并置的区域。因此，这两组花岗岩代表了地壳返工的产物，这可能是由于软流圈上升和/或镁铁质岩浆的底层和侵入造成的。这些花岗岩在时间和空间上与类似OIB的玄武岩的紧密联系以及该地区侏罗纪玄武岩的长期组成变化表明，这些岩石可能形成于板内伸展的环境中，这是由于平板俯冲的海洋板片的分层所致。 。

著录项

  • 来源
    《Journal of Asian earth sciences》 |2013年第25期|280-302|共23页
  • 作者

    Hui-Qing Huang; Xian-Hua Li; Zheng-Xiang Li; Wu-Xian Li;

  • 作者单位

    State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China,ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), Institute for Geoscience Research (TIGeR), Department of Applied Geology, Curtin University, GPO Box U1987,Perth, WA 6845, Australia,School of Environmental and Life Sciences, University of Newcastle, Newcastle, NSW 2308, Australia;

    State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;

    ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), Institute for Geoscience Research (TIGeR), Department of Applied Geology, Curtin University, GPO Box U1987,Perth, WA 6845, Australia;

    State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;

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

    High-K granite; Calc-alkaline; Zircon Hf-O isotopes; Southeastern China;

    机译：高钾花岗岩;钙碱性;锆石Hf-O同位素;中国东南;

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