Structural deformation features of Jurassic Sewa Formation in the southern Qiangtang terrane of Tibet and its tectonic significance
Cui Yuliang1, Wang Genhou2, Lang Xinxin2,3, Li Dian2
1. Beijing Institute of Exploration Engineering, Beijing 100083;
2. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083； 3. Inner Mongolia No.10 Institute of Geology and Mineral Exploration and Development， Chifeng， Inner Mongolia 024005
The evolution of the Bangong Co—Nujiang ocean has attracted much more attention all the time. There are many different opinions about its subduction polarity， and most of the predecessors discussed it from petrology， geochemistry and other aspects， while lack of the researches of tectonic deformation. In this paper， guided by the structural analysis theory， the works such as field mapping at a large scale and tectonic measured section are done to study the structural style and deformation phases of the Sewa Formation in the research area. Comprehensive studies showed that the Jurassic Sewa Formation of the two areas both develops tight three—level complex fold and superimposed gentle—open fold in late period. The earlier fold axis and slaty cleavage are nearly E—W trending， which is product of S—N trending compression. In Renacuo region， there is angular unconformity between the Early Cretaceous volcanic rock of Meiriqiecuo Formation and Jurassic Sewa Formation which has deformed， and tight fold tectonic style of Sewa Formation didn’t form in volcanic rock of Meiriqiecuo Formation， which can infer tight fold formed before the Early Cretaceous. Combined with tectonic background in the study area， we can infer that early tight three—level complex fold of Jurassic Sewa Formation is the product of northward subduction of Bangong Co—Nujiang ocean in the study area， and the superimposed gentle—open fold at late stage is related to the collision between Southern Qiangtang block and Lhasa block.
Cui Yuliang,Wang Genhou,Lang Xinxin et al. Structural deformation features of Jurassic Sewa Formation in the southern Qiangtang terrane of Tibet and its tectonic significance
[J]. Chinese Journal of Geology, 2016, 51(3): 748-762.