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    蚌埠隆起区五河杂岩的形成时代:锆石LA-ICP-MS U-Pb定年证据

    Age of the Wuhe complex in the Bengbu uplift:evidence from LA-ICP-MS zircon U-Pb dating

    • 摘要: 提要:本文对蚌埠隆起区五河杂岩中的石榴斜长辉石岩进行了锆石LA-ICP-MS U-Pb定年研究。采自凤阳独山石榴斜长辉石岩中锆石的阴极发光图像显示出3种结构特征,一种为均匀吸收的自形锆石;另一种为内部结构清晰,具有典型核边结构的锆石;第三种为具有典型生长环带的自形锆石。对锆石吸收程度不同部位测定的U-Pb定年结果表明,207Pb/206Pb年龄介于(17 83±8) Ma~(1 895±8) Ma,49个测点的加权平均年龄为(1 833±8) Ma。这一结果表明,蚌埠隆起区五河杂岩的形成时代为古元古代。这与华北克拉通中央造山带的形成时间及胶东高压麻粒岩相变质作用的时间相吻合,进而暗示五河杂岩应属于华北克拉通的基底。

       

      Abstract: Abstract:This paper reports the LA-ICP-MS zircon U-Pb dating results of garnet-plagioclase pyroxenite in the Wuhe complex in the Bengbu uplift. The cathodoluminescence (CL) images of zircons from the garnet-plagioclase pyroxenite show three textural types of zircon, i. e.:euhedral zircon of homogeneous absorption, zircons with a distinct internal structure and typical core-rim structure and euhedral zircons with typical growth zones. The zircon U-Pb dating of spots with different intensities of zircon absorption indicates that their 207Pb/206Pb ages range from 1783±8 to 1895±8 Ma and that the weighted mean age of 49 analyzed spots is 1833±8Ma. This result suggests that the Wuhe complex was formed in the Paleoproterozoic, which is in agreement with the age of formation of the central orogenic belt of the North China craton and the age of high-pressure granulite-facies metamorphism in Jiaodong, and further implies that the Wuhe complex should belong to the basement of the North China craton.

       

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