Formation And Evolution And Its Structural Modeling Of Hala’alate Thrust Nappe At The Northwestern Margin Of Junggar Basin

The Northwestern margin of Junggar Basin is the important part of theCentral Asian orogenic belt. It underwent multiple structure movements, such asHercynian, Indosinian, Yanshan and Himalayan movement. The characteristics ofthis region are that the geological structure is very complicated and unconformitiesphenomenon are widely developmental. Due to its complex geological features,volcano rock development and lack of Seismic processing technique, althoughmany geological experts have made lots of research in this area, there are stillmany controversies in the aspects of its structure character and evolution.According to the previous studies of this area and the theory of Sedimentology,Petroleum Geology, Structural Geology, Seismic Geology and Fault-related foldtheoretic, combining the outcrops of Hala’alate Mountain, two dimensionalseismic data and well data, we select the Hala’alate Mountain and its southern area,Wu-Xia fault belt, as the research objects, doing the research on its structurecharacter and evolution. Through the above research, we get:1. This area is mainly controlled by reverse faults, the faults system can bedivided into two structure system. The upside of upper faults system disappearedin the Jurassic layer, with its attitude from gentle to steep, the lower part isconverged at the decollement in the bottom of Permian. The upside of lower faultssystem, which developed in the Carboniferous or Devonian, disappeared at theunconformity between the Carboniferous and Permian, the lower part is convergedat the decollement in the Carboniferous or Devonian.2. There are many unconformities in this region, such as P1j/C, P2/P1,P2w/P2x, T/P, J/T, J1b/J1s, J1s/J2-3and K/J et al. The P1j/C and T/J are moreobvious, contacting with high angular unconformity. These unconformitiesphenomenon indicate that the research area underwent multi-falling and uplift,which made the overlap and erosion developed widely.3. The formation of Hala’alate Mountain and Wu-Xia fault belt is the result of multi-structure activities, its structure character different from north to south, fromeast to west. There is small-scale thrust in late carboniferous. The main thrustingmovement begins after the middle Permian and strengthened during the end ofPermian to the beginning of Triassic and gradually becomes stable after that. Theclimax of thrusting period is during the end of Triassic to the early of Jurassic. Inthe period of Yanshan-Himalayan adjustment, the structure movement of thisregion is almost stagnant.4. The anticlines in Wu-Xia fault belt region experienced two large-scalesuperimposition of structure deformation. The first stage is that this region waspressed by the force from NW to SE, which formed these gentle folds during themiddle to the late of Permian. The second stage is that the orogeny of Hala’alatemade the deposition of Permian system at the southern of Hala’alate nappe foldedstrongly during the end of Triassic to the early of Jurassic. Finally these anticlines,such as Wu’erhe anticline, Fengcheng anticline and Xiazijie anticline, wereformed.