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The Role of Pre‐existing Crustal Weaknesses in the Uplift of the Eastern Tibetan Plateau: 2D Thermo‐Mechanical Modeling
Tectonics ( IF 3.3 ) Pub Date : 2021-02-06 , DOI: 10.1029/2020tc006444 Renxian Xie 1, 2 , Lin Chen 3 , Xiong Xiong 4 , Kai Wang 1 , Zhiyong Yan 5
Tectonics ( IF 3.3 ) Pub Date : 2021-02-06 , DOI: 10.1029/2020tc006444 Renxian Xie 1, 2 , Lin Chen 3 , Xiong Xiong 4 , Kai Wang 1 , Zhiyong Yan 5
Affiliation
The crust of the eastern Tibetan Plateau is cut through by several ancient fracture zones, which existed prior to the Cenozoic uplift of eastern Tibet. However, the role of these pre‐existing crustal weak zones (CWZs) in the Cenozoic evolution of eastern Tibet is still poorly understood. Here, we conduct a series of 2D thermo‐mechanical simulations to investigate the role of CWZs in the uplift of eastern Tibet. Our results show that CWZs embedded in the continental lithosphere facilitate crustal thickening via folding and thrusting deformation and uplift of a rugged surface at the early stage of convergence. As crustal thickening continues, the lowermost crust begins to partially melt due to strain and radioactive heating. With continued thickening and heating, melt volume gradually increases, leading to the lower crust melt preferentially accumulating where the CWZs are situated. At a later stage, the partially molten layer becomes thick enough and starts to flow in a channel with respect to its upper and lower solid layers. CWZs behave as windows to steer the ascension of the partial melts, leading to melt doming through the CWZs. The melt doming contributes to a second local surface uplift. Parameter tests demonstrate that increasing the number of CWZs can accelerate such geodynamical processes, and that the CWZ orientation controls the polarity of lithospheric underthrusting. We suggest that the Cenozoic episodic uplift of the eastern Tibetan Plateau, revealed by thermochronological studies, was likely caused by a combination of pure shear crustal thickening and melt doming along the pre‐existing CWZs.
更新日期：2021-04-12
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