高级检索

    青藏高原羌塘中部蜈蚣山花岗片麻岩锆石U-Pb定年——泛非与印支事件的年代学记录

    Zircon U-Pb dating of granitic gneiss in Wugong Mountain area, central Qiangtang, Qinghai-Tibet Plateau: age records of Pan-African movement and Indo-China movement

    • 摘要: 提要:羌塘盆地位于青藏高原北部,是研究青藏高原古特提斯洋演化及冈瓦纳大陆与欧亚大陆界线的关键区域,其基底的时代和性质直接决定了羌南—保山板块的大地构造属性和冈瓦纳大陆的范围。笔者通过对羌塘中部蜈蚣山花岗片麻岩捕虏体的锆石LA-ICP-MS U-Pb定年,确定该花岗片麻岩形成于晚三叠世(209.1±2.8 Ma),是冈瓦纳大陆与欧亚大陆汇聚事件的物质记录,与羌塘中部已有的研究结果相一致;同时还在花岗片麻岩中发现了冈瓦纳大陆泛非运动晚期(464.5±4.8 Ma)的年龄记录,是羌塘地区首次发现泛非运动的物质记录,并且该年龄可以与滇西怒江、保山以及印度板块内部和喜马拉雅造山带中发育的大量早古生代花岗质岩石相对比,表明羌南—保山板块与印度大陆具有很好的亲缘性。以上研究成果为探讨羌塘地区的基底属性和确定冈瓦纳大陆与欧亚大陆碰撞的时限提供了新的证据。

       

      Abstract: Abstract:Qiangtang basin located in northern Tibetan plateau is a key area in studying the evolution of the Paleo-Tethys Ocean and the boundary of Gondwana and Eurasia, and the age and properties of its basement directly determine the tectonic attribute of southern Qiangtang plate and the range of Gondwana. In this paper, LA-ICP-MS U-Pb dating was carried out for zircons from granitic gneiss inclusions (xenoliths) in Wugong Mountain area, central Qiangtang. The dating results show that granitic gneiss inclusions were formed in late Triassic (209.1±2.8Ma). This age is consistent with the existing research results of the convergence events of Gondwana and Eurasia in central Qiangtang, so the granitic gneiss inclusions are material records of the convergence events of Gondwana and Eurasia. Moreover, the dating results also indicate that granitic gneiss inclusions contain a age record of the end of Pan-African period (464.5±4.8Ma), which is the first age of Pan-African movement found in Qiangtang area, and this age can be compared with ages of large amounts of early Paleozoic granitic rocks in Nujiang area and Baoshan area in western Yunnan, internal Indian plate and Himalayan orogenic belt, suggesting that southern Qiangtang plate has good affinity to Indian plate. All the results obtained by the authors can provide fresh evidence for the study of the properties of Qiangtang basement and the age of the convergence events of Gondwana and Eurasia.

       

    /

    返回文章
    返回