华北古元古代末裂解事件——来自内蒙古大青山地区安山岩LA-ICP-MS锆石U-Pb年龄的证据

    Late Paleoproterozoic breakup events of North China: Evidence from LA-ICP-MS zircon U-Pb ages of basaltic andesite from the Daqingshan area in Inner Mongolia

    • 摘要: 在内蒙古大青山地区1∶5 万矿产资源调查中,采用LA-ICP-MS 锆石U-Pb 同位素测年,在一套侏罗纪火山岩中获得锆石U-Pb 年龄加权平均值为1863±10Ma。经野外实测,认为其被上二叠统脑包沟组不整合覆盖。结合岩石主量、稀土和微量元素测试结果进行构造环境分析,认为其为陆内裂谷环境的产物,反映了华北古元古代末—中元古代多期裂谷事件中的一次裂解事件,对华北古元古代末多期裂谷事件的研究具有重要意义,为华北克拉通进入地台型演化的时间提供了重要依据。

       

      Abstract: During the 1∶50000 regional geological survey in Daqingshan area of Inner Mongolia, the authors used LA-ICP-MS zircon U-Th-Pb isotopic dating method and obtained weighted average zircon U-Pb age of 1863±10Ma from the Jurassic volcanic rock. The contact relation is considered to be unconformably covered by Upper Permian Naobaogou Formation, as shown by field survey. According to the major, trace and rare earth elements analytical results of the rock, the basaltic andesite was formed in an intracontinental rift. This was a breakup event between multi -stage rifting in the Late Paleoproterozoic to Neoproterozoic in North China. It is of great significance for studying multi-stage rifting and provides an important basis for the North China Craton (NCC) evolution as a stable platform or para-platform.

       

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