Physical Modeling Of Xu-Huai Arc Structure On The Southeastern Margin Of North China Block

The collision between the North China block and the South China block,and the activity of the Tan-Lu fault zone have led to the development of a unique curved structure in the Xu-Huai area,which is convex in the northwest direction on the plane,with complex deformation and obvious tectonic differences.Due to the significance of the continental dynamics and tectonic evolution process,and the proven rich mineral resources,it has attracted wide attention.With the study of the Xu-Huai arc structure,the research area has more abundant field data,but the understanding of the causes and evolution process of the arc structure is still insufficient.This paper will take into account the results of previous research,combine the field geological survey,divide the tectonic activity period,and use the physics modeling to study the mechanism of the arc structure,aiming to better understand the evolution process of the arc structure,providing a reference for mineral resources surveys.Mainly achieved the following understanding:(1)Xu-Huai arc structure is obviously different in the space.It has the characteristics of east-west zoning and north-south segmenting.A series of thrusts,inclined folds and overturned folds are developed in the arc,and back thrust are rare.Through field geological survey,the study area has experienced at least two stages of tectonic stress field,namely the Indosinman-Yanshan early NW-SE compression and the Yanshanian late NNE-SSW compression,but the overall structure is affected by NW-SE compression.(2)The physical modeling experiment of the section shows that there is ductile decollement in the Xu-Huai area.The difference between the eastern and western structural styles is controlled by two sets of main control decollement,namely Qingbaikou decollement and Cambrian decollement is bounded by Huang-Cang Valley anticline,the west is thrust nappe belt,the main control decollement is shallow,the tectonic deformation is strong,the faults and folds are densely developed,and the thrust is dominant.Characteristics ofhigh-angle thrust faults and imbricated thrust;in the East decollement belt,the main controlling decollement is deep,the faults and folds are sparsely developed,and inclined folds are mainly developed.(3)Plane physical modeling show that lateral extrusion is the main controlling factor for the formation of Xu-Huai arc structure,the lateral extrusion of the Su-Lu UHP metamorphic belt.The zone is divided into the northern,middle and southern sections by the Su-Bei fault and the Waste Yellow River fault.The north and the south section develops brachy folds,thrusts and a small number of back thrust,while the middle section is stronger than the north-south side,which is dominated by linear folds,high-angle thrusts and imbricated thrusts.