Tectonic response of overriding plate to the continental deep subduction:Insights from the Jiao-Liao area
The exhumation of ultra-high-pressure metamorphic rocks largely reforms the geometry of the orogenic belt related to continent deep subduction,making it difficult to identify the contractional structures formed during plate convergence.The overriding plate,due to being less influenced by exhumation,is key to understanding the plate convergence.This work focuses on the deformations of the overriding North China block when the South China block deeply subducted beneath the North China block,takes the Jiao-Liao area as the target,carries out the structural analysis,and combines previous results,to understand the tectonic response of the overriding plate.Then,we correlate the deformation events recorded in the subducted and overriding plates to understand the tectonic evolution of the Sulu orogenic belt and its geodynamics.Our study shows that the North China block(overriding plate)experienced Triassic NE-SW contractional tectonics related to the continental collision between the South China block and the North China block:NE-directed thrusting and SW-directed back-thrusting.The first contractional structure is characterized by Early to Middle Triassic top-to-the-NE ductile shearing in the Laixi unit,Jiaobei massif,and Middle to Late Triassic top-to-the-NE ductile shearing,NE-directed folding and thrusting in the Changshan Island and Lüshun-Dalian-Jinzhou area,Liaodong massif.From south to north,the ductile deformation evolves to the brittle-ductile one,and it seems that the deformation timing becomes younger.The second contractional structure is manifested by Late Triassic top-to-the-SW ductile shearing in the Linsishan unit,Jiaobei massif,and SW-directed back-thrusting in the Liaodong massif.Combined with the tectonics events developed in the Sulu orogenic belt,our new structural results allow us to build a three-stage evolution model for the continental collision between the South China block and the North China block.Our model also highlights that the flat-slab subduction of the South China block may account for the large-scale contractional tectonics developed in the overriding North China block.In addition,the NE-SW trending convergence of the South China block and North China block,while NW-SE post-orogenic exhumation,characterized the tectonic framework of the Sulu orogenic belt.
Continental deep subductionOverriding plateTriassic NE-SW contractional tectonicsStructural analysisSulu orogenic belt
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