The Mesozoic-Cenozoic Fault Structure Characteristic And Genesis Mechanism In The Northeastern Shanxi

The main research objects in this paper are the Liulengshan on the eastern margi n of Datong basin and the southern margin of Datong basin called the Mount Heng,the northeastern of Shanxi.The research area is located in the transition zone betwe en the extensional area of the north China craton and the stable block in the west which was seriously damaged.Based on the principle of tectonic deformation,this paper takes tectonic evolu tion as the main line,and uses data such as outcrop,paleostress field inversion and tec tonic evolution profile to explain the structural characteristics,tectonic pattern and dy namic mechanism of the meso-cenozoic in the research area.The results show that both the Liulengshan fault zone and the Mount Heng fault zone are nearly NE trending,Liulengshan fault zone is mainly eastward thrust,and the Mount Heng fault zone is mainly southward thrust.Cenozoic,under the action of extensional stress field,the fault zone turned to normal fault and formed Datong Basin.The faults and folds of the Liulengshan are dominated by the NE and supplemented by the NW,forming a grid-like structure.The tectonic evolution of Mesozoic and Cenozoic in this area mainly experienced thre e stages: early Mesozoic uplift stage;Mesozoic extrusion deformation stage;The Ceno zoic extensional deformation stage.The Mesozoic compressional characteristics and deformation stage are the focus of this paper,which can be divided into four stage s: 1.At the end of the early Jurassic,Yanshan movement I began,and the Jurassic in t he northern margin of the north China craton produced EW trending folds,but did not affect the study area;2.At the end of the middle Jurassic,the Yanshan movement II began,and the strata in the study area were subjected to basement entrapment tectonic deformation;3.From late Jurassic to early cretaceous,Yanshan movement entered ph ase III,and the whole area was in a state of stress relaxation after intense compression,which was also the period when the north China craton was at its most intense destru ction.4.In the late cretaceous,the Yanshan movement entered phase IV,when the tect onic stress field changed from the previous extension to compression again,accompan ied by a strong volcanic eruption.To the Neogene,the tectonic stress field was transformed into extension again,and a series of NE and NW trending normal faults develop ed in the study area,which together with the thrust faults formed in the Mesozoic for med the grid-like structure pattern in the present study area.