Structure Deformation Characteristics And The Exhumation Time Of Xuhuai Arcuate Fold And Thrust Belt

The Dabie-Sulu orogenic belt is formed by the subduction and collision of the South China Block into the North China Block in the Mesozoic.The collision orogenic process is of great significance to the understanding of the continent-continent collision process,but the specific continent-continent collision process has not yet reached a consensus.Previous studies have suggested that the structural evolution of Xuhuai arcuate fold and thrust belt has dynamic relationship with the orogenic process of Dabie-Sulu orogenic belt.The Xuhuai arcuate belt is affected by multi-period tectonic events,and its structural style is relatively complex.However,the Mesozoic deformation characteristics have not been well constrained,and the thrust deformation timing has not been accurately defined.This paper aims to determine the structural deformation characteristics and exhumation time of the Xuhuai arcuate fold and thrust belt,and explore the kinematic relationship between the Xuhuai arcuate fold and thrust belt and the collision orogenic process of the Dabie-Sulu orogenic belt.In this paper,the structural geometry and kinematics of the Xuhuai arcuate fold and thrust belt were studied,and the deformation stages and characteristics of the Xuhuai arcuate belt were clarified with the help of UAV oblique photography technology.3D strata model was established for Chefushan and Xiaoxian outcrops.The Xuhuai arcuate fold and thrust belt north and middle structure deformation characteristic have carried on the detailed analysis,thinking that there are two phases of folds,with the first-generation of nearly E-W-trending upright-oblique-recumbent-overturned folds(f₁)overprinted by the second-generation of NW-protruding arc-shaped upright-oblique folds(f₂).The superposed fold type is Ramsay Type 2.Based on the radiation damage and annealing model,the exhumation time of the Xuhuai arcuate belt was determined by forward and inverse modeling of apatite fission track and zircon(U-Th)/He data.It is concluded that the rapid exhumation time of Xuhuai arcuate fold and thrust belt is no later than 190 Ma,and the thrust and napping time of Xuhuai arcuate fold and thrust belt is limited to the Triassic(ca.245-211 Ma)to 190 Ma.The structural evolution process of the Xuhuai arcuate fold and thrust belt is determined on the basis of identifying the structural deformation characteristics and exhumation time of the Xuhuai arcuate fold and thrust belt.Influenced by the subduction and collisional event of the South China Block to the North China Block,the Xuhuai arcuate fold and thrust belt formed the nearly E-W-trending folds during the Triassic(ca.245-211 Ma).From<245-211Ma to 190 Ma,the NW-protruding arc-shaped folds were formed.Finally,the relationship between the collisional orogeny of the Xuhuai arcuate fold and the Daibie-Sulu orogenic belt is discussed.It is suggested that the stuctural evolution of the Xuhuai arcuate fold and thrust belt is consistent with crustal detachment model and wedging induced continent tearing model.