杨五宝, 闫涛, 张永, 卫彦升, 李拯宇. 内蒙古北山造山带小红山TTG岩石锆石U-Pb年龄、地球化学特征及其对百合山构造带性质的制约[J]. 地质通报, 2020, 39(9): 1404-1421.
    引用本文: 杨五宝, 闫涛, 张永, 卫彦升, 李拯宇. 内蒙古北山造山带小红山TTG岩石锆石U-Pb年龄、地球化学特征及其对百合山构造带性质的制约[J]. 地质通报, 2020, 39(9): 1404-1421.
    YANG Wubao, YAN Tao, ZHANG Yong, WEI Yansheng, LI Zhengyu. Zircon U-Pb age and geochemistry of TTG rocks in Xiaohongshan area of the Beishan orogenic belt, Inner Mongolia, and their constraints on the properties of the Baihe Mountain tectonic belt[J]. Geological Bulletin of China, 2020, 39(9): 1404-1421.
    Citation: YANG Wubao, YAN Tao, ZHANG Yong, WEI Yansheng, LI Zhengyu. Zircon U-Pb age and geochemistry of TTG rocks in Xiaohongshan area of the Beishan orogenic belt, Inner Mongolia, and their constraints on the properties of the Baihe Mountain tectonic belt[J]. Geological Bulletin of China, 2020, 39(9): 1404-1421.

    内蒙古北山造山带小红山TTG岩石锆石U-Pb年龄、地球化学特征及其对百合山构造带性质的制约

    Zircon U-Pb age and geochemistry of TTG rocks in Xiaohongshan area of the Beishan orogenic belt, Inner Mongolia, and their constraints on the properties of the Baihe Mountain tectonic belt

    • 摘要: 分布于内蒙北山地区小红山南一带的晚石炭世花岗岩,是由英云闪长岩(T1)、花岗闪长岩(G1)和奥长花岗岩(T2)组成的一套TTG岩石组合。该套组合具有富硅、富钠、低铝的地球化学特征,稀土元素总量偏低,∑REE=27.86×10-6~104.56×10-6,轻稀土元素富集,LREE/HREE值为4.71~22.76,(La/Yb)值为4.78~43.18,δEu为0.62~1.72,稀土元素配分曲线为右倾型,微量元素总体表现为富集大离子亲石元素(LILEs),亏损高场强元素(HFSEs),且具有明显的Nb、P、Ti负异常,Y、Yb含量低。利用LA-ICP-MS锆石U-Pb同位素测定技术,测得该套TTG组合酸性侵入体中花岗闪长岩、英云闪长岩、奥长花岗岩206Pb/238U年龄加权平均值分别为315.6±1.6 Ma、310.8±1.4 Ma、305±1.9 Ma,形成于晚石炭世。研究认为,小红山晚石炭世TTG花岗岩组合具有陆缘弧花岗岩的成因特点,形成于石炭纪百合山弧间洋盆向南侧陆缘消减过程中洋壳俯冲板片的部分熔融,这套与百合山蛇绿岩同期形成的明水陆缘弧的发育,指示了百合山构造带形成于弧盆体系的演化阶段。

       

      Abstract: The Late Carboniferous granites distributed in the south of Xiaohong Mountain in Beishan area of Inner Mongolia are a set of TTG rock combination composed of tonalites(T1), granodiorites(G1)and trondhjemites(T2).This set of TTG combination has the geochemical characteristics of rich silicon, rich sodium, and low aluminum.Meanwhile, the TTG has low total content of REEs(∑REE=27.86×10-6~104.56×10-6), and is enriched in LREEs(LREE/HREE=4.71~22.76, (La/Yb)N=4.78~43.18), with δEu being 0.62~1.72, showing the right-inclined type in chondrite-normalized REE patterns.In addition, the rocks which have the obvious negative anomalies of Nb-P-Ti and the low content of Y-Yb mainly show the enrichment of large ion lithophile elements(LILEs)and the loss of high field-strength elements(HFSEs). LA-ICP-MS zircon U-P dating shows that the 206Pb/238U weighted average age of zircons of tonalites is 315.6±1.6 Ma(MSWD=0.33, n=18), that of granodiorites is 310.8±1.4 Ma(MSWD=0.47, n=25), and that of trondhjemites is 305±1.9 Ma (MSWD=0.79, n=11), suggesting that the rock was formed in Late Carboniferous. Research suggests that the Xiaohong Mountain TTG which has the genetic characteristics of continental marginal arc granite was formed in the partial melting of the subduction plates of the ocean crust in the process of the subduction of Baihe Mountain inter-arc ocean basin to the south continental margin during the Carboniferous period. The development of this set of continental margin arcs which were formed in the same period with Baihe Mountain ophiolite indicates that the Baihe Mountain tectonic belt was formed at the stage of arc-basin system evolution.

       

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