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|Title:||Dynamics of exhumation and deformation of HP-UHP orogens in double subduction-collision systems: numerical modeling and implications for the Western Dabie Orogen|
|Citation:||Earth-Science Reviews, 2018; 182:68-84|
|Liming Dai, Sanzhong Li, Zhong-Hai Li, Ian Somerville, Yanhui Suo, Xiaochun Liu, Taras Gerya, M. Santosh|
|Abstract:||The dynamics of formation and exhumation of high-pressure (HP) and ultra-high pressure (UHP) metamorphic orogens in double subduction-collision zones remain enigmatic. Here we employ two-dimensional thermo-mechanical numerical models to gain insights on the exhumation of HP-UHP metamorphic rocks, as well as their deformation during the collision of a micro-continent with pro- and retro-continental margins along two subduction zones. A three-stage collisional process with different convergence velocities is tested. In the initial collisional stage, a fold-and-thrust belt and locally rootless superimposed folds are developed in the micro-continent and subduction channel, respectively. In the second (exhumation) stage of HP-UHP rocks, a faster convergence model results in upwelling of the asthenosphere, which further leads to a detachment between the crust and lithospheric mantle of the micro-continent. A slower convergence model results in rapid exhumation of HP-UHP rocks along the north subduction channel and a typical piggy-back thrusting structure in the micro-continent. A non-convergence model produces a slab tear-off, leading to the rebound of residual lithosphere of the micro-continent. In the third and final stage, a series of back and ramp thrusts are formed in the micro-continent with the pro-continent re-subducted. Based on an analogy of our numerical results with the Western Dabie Orogen (WDO), we suggest that: (1) slab tear-off results in a rebound of residual lithosphere, which controls the two-stage syn-collisional exhumation process of HP-UHP rocks in the WDO; and (2) in contrast to the single subduction-collision system, the exhumation range of the partially molten rocks with lower viscosity and density is restricted to a specific region of the micro-continent by the Mianlue and Shangdan subduction zones, which generated the complex deformation features in the WDO.|
|Keywords:||Double subduction-collision system; numerical models; exhumation of HP-UHP rocks; multi-stage deformation; Western Dabie Orogen|
|Rights:||© 2018 Elsevier B.V. All rights reserved.|
|Appears in Collections:||Geology & Geophysics publications|
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