The Study Of E-W Direction Secondary Folds In The Central Guizhou Fault Zone

The properties of central Guizhou fault zone is a regional strike-slip fault,which is the boundary of Central Guizhou Uplift and Southern Guizhou Depr ession. The previous research of the central Guizhou fault zone focused on th e sedimentary mechanism of Central Guizhou Uplift and Southern Guizhou De pression. The analysis of structural deformation, tectonic evolution and stress st ate about that fault is relatively insufficient,and the study of the related E-W direction secondary folds is limited. This paper has a detailed field research on the central Guizhou fault zone, focused on structural geometry, tectonic chro nology and stress analysis, have a conclusion about the structural deformation, stress state and tectonic evolution on this fault.The field geological investigation and the existing research mate-rials show that the fault zone striking whole present NEE, some area consists of severa l parallel to the main fault branch faults both ends connected to the main fault formed a typical “braids structure” of strike-slip faults. Fault zone is a strikeslip fault with characteristics of trust, there are six kinds of structural elements in a ty-pical Riedel shear system, the lateral we can find the R?P?R?shear-s and T tension fracture, the en echelon arrangement of R shears and folds in Riedel experiment can be used as shear sense criteria to deduce the overall m ovement sense along the basement fault. According to the relationship betweenR,P shears and main strike-slip fault judged the main fault is a left lateral str ike-slip fault.Along the fault zones has two secondary folds which axial consistent with the strike of the fault, such as Wudang anticline and Jiling anticline. These secondary fold axial direction perpendicular to the Jura-type fold that develop ment in the Trait Sag, these two kind of fold is involved in the same stratu m. This relationship reflects the tectonic stress field is mutual contradiction. A ccording to the secondary fold output is small and distribution characteristics i s strictly controlled by the fault zone, combining with the petrofabric analysis,it is concluded the stress state of the fault zone. Author thought that these se condary folds may be formed in the process of the fault activity, is strike-slip related folds. As many observation post in the fault show up strike-slip and thrust properties, prove the fault in these areas in transpression background, th e east-west direction fold may be caused by the compress component.By petrofabrics analysis,in the Wudang fault has at least two stages shear stress, the main direction is NE-SW and NW-SE.According to the tectonic chronology analysis of experimental data, comb ining previous research data indicates that the main activities of the fault is concentrated in Hercynian,Indo-Chinese epoch, Yanshan epoch, and Pleistocene epoch in the Quaternary period. The Quaternary period 136Ka-322 Ka may be the last time for the fault activity.