Earth Science Frontiers ›› 2019, Vol. 26 ›› Issue (2): 264-280.DOI: 10.13745/j.esf.sf.2018.9.6

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Superposed folding since the Permian on both sides of the Xar Moron Suture, southeastern Inner Mongolia: implications for syn- and post-collision geodynamic process

ZHANG Yuqing, ZHANG Changhou, HOU Liyu, ZHANG Yipeng, HUANG Yingzhu, CHEN Hanlin, CHANG Lizhong   

  1. 1. School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China
    2. School of Earth Sciences, Zhejiang University, Hangzhou 310027, China
    3. Guangdong Key Laboratory of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China
    4. Research Center for the Structures in Oil & Gas Bearing Basins, Ministry of Education, Hangzhou 310027, China
    5. Geology and Mineral Exploration Institute of Inner Mongolia, Hohhot 010010, China
  • Received:2018-02-23 Revised:2018-06-07 Online:2019-03-30 Published:2019-03-30
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Abstract: Multi-scale fold interference patterns developed in the Permian strata on both sides of the Xar Moron fault, southeastern Inner Mongolia. These superimposed folds and the deformation within the Jurassic strata recorded multiple tectonic events in the research area since the Permian. Research on these deformations is crucial for a better understanding of the tectonic evolution from the Paleo-Asian system to the Paleo-Pacific system along the northern margin of the North China Block. In this study, we employed detailed field mapping to decipher the geometry of these superimposed structures and their evolution. Folds distributed in the Permian strata are characterized by sinuous axial trace with southeast verging. Folds in the Mesozoic strata, however, are trending southeast with northwest verging. Three tectonic deformation phases were identified in this research: (D1) East-northeast trending folds in the Permian strata implying a north-northwest-south-southeast compression from the end of the Permian to the Middle Triassic; (D2) Regional shear events during the Late Triassic resulting in the formation of the Type2a and Type1d fold interference patterns proposed by simon, 2004; and (D3) Northwest-verging folds within the Middle Jurassic strata thought to be developed under a northwest-southeast compression during the Late Jurassic. Furthermore, D3 deformation led to fold tightening within the Permian strata. We interpret these three deformation phases (D1, D2, D3) as the consequences of the final closure of the Paleo-Asian Ocean and collisional orogeny, the east-northeast extrusion of blocks between the dextral strike-slip of the Xar Moron fault in northern China and the sinistral strike-slip East Gobi Fault in southeastern Mongolia, and the westward subduction of the Paleo-Pacific oceanic plate under the Eurasian plate, respectively.

 

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