Structural Features And Tectonic Evolution In Dafang Area,Guizhou Province

Dafang area located in the northwest of guizhou province,belongs to the Middle Guizhou Upheaval.The structure in the area is affected by many tectonic movements,the structure type is complete and the style is complex.Since Mesozoic,the plate mosaic and ocean-land subduction formed complex fault and fold system,Especially since the collision between the Yangtze plate and the Southern China plate in Mesozoic,the tectonic evolution of the region is closely related to the tectonic evolution of the Yangtze Southern China plate.In this paper,author combined with modern structural geology,plate tectonic theory,by means of field geological survey,indoor structure analysis,combining previous data,to study the geometry and kinematics,and stress field and tectonic evolution of the paleo tectonic,obtaining the following understanding:1,The structural features in the study area is NNE and NEE,Roughly along the "Shuchang – jichang-Linquan" for the sector,most of the structures in the northern are NNE trending,with a larger scale,the folds are open,developed more structural dome.The northern are NEE trending,the arrangement is compact,the scale is not large,developed structural basin.2,The folds in the study area are mostly formed by bending and folding,and the depth is limited,it is typical thin skinned structure.Faults are mostly reverse faults,and imbricate fan faults are more common,Therefore,the tectonic system in this area should be formed by thrust nappe.3,The formation of the structural pattern in this area is mainly controlled by three factors,First,it is controlled by the regional geological structure background,and its overall tectonic trend is the same as that of the central Guizhou Upheaval and its adjacent areas;The second is that the area has experienced many times and many kinds of tectonic movement,and the tectonic composite joint action is more obvious in this area;The last is that the structure is also affected by the competence of mixing of the rock,and folds along the Permian Longtan Formation mudstone and siltstone.4,In the middle period of Yanshan,a series of near EW trending folds formed in the study area due to the N-S compressive stress.Late stage Yanshan to Early stage of Xishan,the study area is mainly influenced by the Pacific plate and the Qinghai Tibet Plateau,A series of NNE trending folds and faults were formed and superimposed on the early NEE trending folds,The later tectonic movement in the area further compressed existence tectonic system.