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    福建港里地区变质岩与南园组火山岩地球化学特征及锆石U-Pb年龄对比

    Comparative study on the geochemical features and zircon U-Pb age between the metamorphic rocks and Nanyuan Formation volcanic rocks in the Gangli region, Fujian Province

    • 摘要: 福建港里地区位于长乐—南澳断裂带北段,港里变质岩分布于断裂带南东侧,南园组火山岩分布于断裂带北西侧。港里变质岩与南园组火山岩地球化学特征及锆石U-Pb年龄对比结果表明:(1)港里变质岩和南园组火山岩锆石均属火山碎屑锆石,LA-ICP-MS锆石U-Pb年龄分别为139.7±1.8 Ma和132.7 ±1.2 Ma,均属早白垩世;(2)港里变质岩和南园组火山岩均属钙碱性、钙性岩,低Ba、Nb、Sr,高Pb、Nd,稀土总量普遍较低,具有轻稀土富集、铕中等亏损的稀土配分模式,反映了长乐—南澳断裂带两侧早白垩世中期火山岩的地球化学特征。

       

      Abstract: The Gangli region in Fujian is located in the northern section of the Changle-Nan’ao fault zone, with the Gangli metamorphic rocks in the southeastern side of the Changle-Nanao fault zone and the volcanic rocks of the Nanyuan Formation in its northwestern side. The study conducted comparative analysis on geochemical features and zircon U-Pb ages of the Gangli metamorphic rocks and the Nanyuan Fm. volcanic rocks. The results show that the zircons from both the Gangli metamorphic rocks and the Nanyuan Fm. volcanic rock have concordant ages of 139.7±1.8 Ma and 132.7±1.2 Ma, respectively, suggesting the both are early Cretaceous in age. The both belong to cal-alkaline series, characterized by high SiO2, low Ba, Nb, Sr, and high Pb and Nd, and low total REE content, enrichment in LREE, and medium Eu depletion in REE distribution diagram. This reflects the geochemical features of the middle Cretaceous volcanic rocks on both side of the fault zone.

       

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