The Tectonic Styles And Their Defomation Mechanisms Of Dafang Region In Guizhou Province

Dafang region, located in the west of platform uprise in Northern Guizhou, is a key region of geological structure research in Sichuan-Guizhou region, which has experienced many times of tectonic movement, the structural deformation is very complex, and the structural style is very rich. Seniors carried out the investigation and study on the geological structure of Sichuan-Guizhou region, and had achieved remarkable results. However, the regional geological survey shows that the structural styles of the region need to be further studied. The paper, based on the theory of modern structural geology, fully integrated the theory of the conjunction and compounding of structure, through field geological investigation and indoor data collation and analysis, from aspects of structure geometry, combination feature of structure, conjunction and compounding of structure, regional tectonic stress analysis, and so on, researches the geological structure deformation characteristics, combining with the results of previous studies, and analysis of the regional tectonic style and its formation mechanism.By studying the structural characteristics in the region, the following conclusions are drawn.(1)Compared with the adjacent region, the tectonic deformation is relatively weak in the study region, which belongs to Dafang-Qianxi weak deformation block. There are two main structural components- the NNE and NEE structure and different size of the dome anticline and tectonic basin.(2) The study region can be divided into the NNE trending tectonic zone(I) and the NEE tectonic region(II). The structures belong to a part of the NNE and NEE trending tectonic belt in Sichuan-Guizhou. Most folds are soothing, opening and most of the faults are Strike fault, which are sinistral en echelon arrangement from the north to the south.The deformation of NEE tectonic zone(II) is stronger than that of NNE trending tectonic zone(I), where the main features are the NEE trending normal faults and sinistral strike-slip fault of the tectonic line skew intersection,as well as fold structure in different directions.(3)Fold assemblage in the region is dominated by wild goose form fold and parallel fold. Fault combination patterns include superimposed tile thrust faults, hedge thrust faults, wedge thrust faults, etc. It basically reflects the structural deformation and combination pattern of the region,which is a typical thin-skinned structure.(4)Structural deformation in Dafang region is mainly based on the compounding of structure. Today's NNE and NEE tectonic framework is horizontal compressional stress and left straight torsion tectonic superimposition results during the late Yanshanian and Himalayan, on the basis of the EW trending tectonic zone by N-S horizontal compressional stress in the middle Yanshanian. In addition, the adjacent region has a conjunction structure, which is the E-W horizontal movement in Late Yanshan and the N-S compressional stress from movement between the blocks of the central Guizhou Uplift.(5) The formation of structural styles in the region is related to the four aspects.(1)The tectonic deformation in this region is influenced by the regional tectonic setting.(2)The region is affected by the horizontal compressional stress in different directions during Yanshanian and Himalayan.(3)The superposition and reconstruction of the early stage of the structure, mostly in the compound action of structure deformation, eventually formed the superimposed fold, limiting superimposed and the bending transformation superimposed folds, etc.(4)The region widely developed different hard strata, the fold formation mechanism is dominated by flexural slip fold.(6) The region has experienced many tectonic movements. From nanhua period to Jurassic period, there are more movements of crustal uplift and subsidence. From the late Yanshan to Himalayan period, the tectonic movement is dominated by horizontal extrusion movement.The tectonic stress is N-S compressional stress in the middle of Yanshan. The tectonic stress is E-W compressional stress and sinistral twist stress characteristics at the end of Yanshan and Himalaya. After the tectonic movement, the present tectonic pattern basically had formed.The study basically concludes structure characteristics of the region, clarifies the spatial distribution characteristics of geological structure, analyzes the causes and characteristics of tectonic style and regional stress characteristics. Research results has found out the basic structure of the study region, summarizes the characteristics and formation causes of the combined structure in this region, and analyzes the tectonic deformation period, which have made a new understanding of the structural styles and the forming mechanism of the region. The result has filled the blank of the research of the conjunction and compounding of structure of the study region, and provided a new understanding of the basic geological research in the region.