Geometry,Kinematics And Dynamic Mechanism Of Complex Folds And Thrust Structure Of Qianzhong Uplift And Peripheral Regions

Qianzhong Uplift is located in the mid-west of Guizhou province, where geologic structures are complicated .In particular, Mesozoic and Cenozoic complicated folds and thrust-nappe tectonics reflect joint region between oceanic and continental tectonics and intra-continental orogeny very well. The researches on them are a key to figure out the tectonics of South China. However, the study on so important tectonic unit is relatively little, and there is not a consistent understanding on its structural attribute. Therefore, this paper focused on Qianzhong Uplift and Peripheral Regions, finely analyzed their structural geometry, kinemetics of complicated multi-stage, muti-level and multi-kind fold-thrust-nappe tectonics. We systematically discussed their dynamic genesis and development. Three conclusions have been made, as follows:1. Analyzing the main fold-systems in Qianzhong uplift and peripheral regions in detail, we separated different folds and their structure features of different geologic time: East-West wide large-scale fold formed in Caledonian movement, but there were no obvious influence of Hercynian and Indosinian movement. However, Yanshan movement which is a revolutionary movement as to Qianzhong uplift and peripheral regions, leading to the present major structures and deformed a series of short-axial fold and different kinds of though-like folds.2. The conclude is educed by a fine analysis of geometry and kinematics of the main arc thrust-nappe structure of north-east trending and north-south trending in Qianzhong uplift and its adjacent areas,that is:The NE-trending arc thrust-nappe structure is formed in the late Yanshanian, broadly with the same period of the NE-trending drape or later.A extensional tectonic movement and a strong compresso-shearing strike-Slip movement are occurred after two main thrust. The thrust-nappe system is a para autochthone for its little thrust distance. The main episode of the NS-trending arc thrust-nappe structure and its movement is formed from early to late Cretaceous, in line with the NS-trending trough-like folds'periods or later, and the local formation is possibly occurred with slight intension thrust after late Cretaceous. A extensional tectonic movement and a strong compresso-shearing strike-Slip movement happened in the research and its contiguous areas which impact on a wider scope after the main episode.The main thrust belts of the NS-trending arc thrust-nappe structure is located in the extrude part of Xuefeng uplift of Kaili south and Sandu north, while the left part is a para autochthone for its little thrust distance.3. The dynamic evolution modle of faults are discussed on the basis of geometry and kinematics analysis in the drape system and faults system of Qianzhong uplift and its adjacent areas. The tectonic-slip in Caledonian episode of Qianzhong uplift and its adjacent areas is related to the nearly NS-trending collided suture, along the vicinity of Shandan area, which is between the Huabei plate and Yangzi plate; the dynamic system of tectonic-slip from late Indosinian and the first episode of Yanshanian is possibly related to the collided convergence between the evolution of Qinlin and Dabieshan orogen of Yangzi plate and the Indosinian plate, which plays a dominant role in collided convergence; the dynamic system of tectonic-slip in the second episode of Yanshanian is related to the sidelong subduction to Yangzi plate between the early Cretaceous Izanagi plate and the Palaeo-pacific plate; the dynamic system of tectonic-slip in the third episode of Yanshanian is related to the strong intension subduction to Yangzi plate owning to the subduction direction and angles of the pacific plate of late Cretaceous were changed from East to West; the dynamic system of tectonic-slip from the late Yanshanian to early Himalayan episode is related to the subduction of pacific plate in early Himalayan episode and the collision of Indosinian plate.