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    北祁连山东段新元古代火山岩的年代学证据

    Chronological evidence of Neoproterozoic volcanic rocks in the eastern segment of the North Qilian Mountains

    • 摘要: 提要:在1∶5万石门川幅、老龙湾幅区域地质调查时发现,北祁连山东段上吊吊坡地区存在一套不同于下奥陶统阴沟群的火山岩,经全岩样品Sm-Nd同位素测定,获得Sm-Nd等时线年龄为(723±25.0)Ma, 表明其形成时代为新元古代。地球化学特征表明该套火山岩形成于岛弧环境,说明当时北祁连东段仍处于洋壳俯冲挤压环境。

       

      Abstract: Abstract: According to the geological survey of 1:50000 Shimenchuan Sheet and Laolongwan Sheet, volcanic rocks different from those in the Early Ordovician Yingou Goup have been found in the Shandiaodiaopo area, Jingtai County in the eastern segment of the North Qilian Mountains. Sm-Nd isochron dating of the volcanic rocks shows that they formed during the Neoproterozoic, about 723 million years ago. REE and trace element and trace element geochemical characteristics suggest that a compressional environment resulting from subduction of oceanic crust occurred there at that time.

       

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