青藏高原主要地体地壳短缩作用研究现状及存在的问题

    The research progress and problems of the crustal shortening effect of the main terranes in Qinghai-Tibet Plateau, China.

    • 摘要: 在对喜马拉雅、拉萨和羌塘3个地体已有的有关地壳短缩研究成果系统分析的基础上,对3个地体进行了平衡剖面恢复:北羌塘侏罗系短缩率为25.18%,南羌塘短缩率为33.57%;对拉萨地体南段(措勤盆地南部坳褶带)上白垩统恢复得出其短缩率为20.68%,北段中部坳褶带到班公湖-怒江缝合带南缘短缩率为25.3%;地处特提斯喜马拉雅地体东段的郎杰学地体三叠系短缩率达75%,大于前人研究的特提斯喜马拉雅56%~60%的短缩率。通过对比,对3个地体短缩变形的规律进行了分析,认为各地体内部短缩作用并不是一个连续均匀的过程,陆内变形主要是通过稳定地体边界和大型逆冲构造带来吸收的;拉萨地体和羌塘地体新生代内部变形较小。

       

      Abstract: In this paper, based on the systematic collection, analysis and research of the existing data achieved in Himalayas, Lhasa and Qiangtang terranes, we conducted the balanced cross-section study. In the north Qiangtang, the line-balanced cross-section study shows that the Jurassic strata shortened by 25.18%, and the result in south Qiangtang is 33.57%. The balanced cross-section in Lhasa terrane is divided into two sections by central volcanic rocks. The study shows that the Late Cretaceous strata of the south section is shortened by 20.68%, while 25.3% for the north section. The crustal shortening of Triassic Jiangxiong Group of Langjiexue terrane in the eastern part of the Tethyan Himalaya block is up to 75%, higher than previous studies of the Tethyan Himalaya, 56%-60%. After contrasting our research results and the existing data, we analyzed the shortening process and tectonic deformation of the three terranes, and draw the conclusion that the shortening process is not a uniform process in each terrane, and the intraterrane deformation is mainly absorbed by the boundary of the stable blocks, suture zones and large thrust systems. The Cenozoic internal deformation in Qiangtang and Lhasa terranes is not serious.

       

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