| Longmen Mountain tectonic belt is located in the northwestern margin of the Sichuan Basin and also it is an important tectonic belt in southwestern tectonic belt of China.It is the western barrier of the Sichuan Basin in landscape, In structure,it is not only the boundary zone between the Sichuan Basin and the western tectonic zone,but also the boundaty zone of eastern and western-the north west of the Longmen Mounta-ins is theSongpan-Ganzi fold belt, southeastis the foreland basin. Geographic ally, the Dujiangyan and the Anxian put the Longmen Mountains into three parts: the north, the middle, the south. The south of Dujiangyan to Tianquan wecalled the south, Dujiangyan to Anxian we called the middle,and the north of Anxian to Guangyuan we called the north.From it,s northwest to southeast,there are three main faults which we called Maoxian-Wenchuan fault, Yingxiu-Beichuan fault, Pengguan- Anxian fault. Tangwangzhai area that we studied is located in the north of Longmen Mountain tectonic belt, a large syncline in easten Yingxiu –Beichuan fault.Affected by tectonic units such as Yangtze Platform, North China Plate, Songpan-Ganzi fold belt, the Longmen Mountain tectonic belt has experienced a complex structural dynamics in the geological history, also, there are many complicat-es structural compositions and the great Transformation based on the structures which were formed previously from the tectonic movement in later stage. Due to that, the characteristic of multiphasic congruence has been showcased in Longmen Mount-ain tectonic belt. For the study of the Longmen Mountain tectonic belt, many geological seniors have repeatedly involved in this area, a lot and in-depth of research work have been done to it’s geometry, material composition, deformation characteris-tics, genetic mechanism and evolutionary, these findings deepen our standing of the Longmen Mountain, guiding the oil and gas exploratinon in Longmen Mountain tectonic belt and the western Sichuan forland basin. And also, we achieved a good economic results.Different sizes klippen structural which distributed in Longmen Mountain tectonic belt has always been a hot issue to geologist. Tangwangzhai syncline area is one of the most eye-catching of the northern of the Longmen Mountain tectonic belt. On it’s research, different geologist put forward their own views:some people think it is the napples formed in Indosinian movement, some people also believe that it is the results of former thrusting and later gravitygliding. In this article,ac coding to the field work in Tangwangzhai syncline area and the indoor structural-physics simulated experiment,investigated he genetic mechanism of structural dynamics, based on structural geometry, structural dynamics and other geological disciplines.Through the field investigation we found that: the two wings(the northwest wing and the southeast wing) developed very asymmetric. There are significant differences on the strata exposed cases and the geological structure.The northwest wing strara exposed full, thick, it’s form is monoclinic. The southeast wing thickness and small, even missing, a series of tectonic compression developed, such as reverse folds, fault-related folds and so on, and the reverse faults are the main reason of thinning.The structural-physics simulated experiment is a very effective means of reaser-ch in the structural geology. It’s essence is the geometric deformation method,by using a variety of analog materials, such as: quartz sand, gypsum, clay, silica to creat a geological model to simulate the structural form and the rock properties.and by loading an external power to simulate the tectonodynamic background. During the experiment, observe the deformation characteristics of each model simulation, record the experiment data, and put the result and the actual geological section into comparison, in order to verificate the proposed theoretical perspectives. Based on the results of previous studies on Tangwangzhai syncline, and the harvest of field geological survey, three different power sources structural-physics simulated experiment have been designed:(1) vertical uplift;(2) uniaxial way squeeze;(3) vertical uplift superimposed uniaxial way squeeze. The results show that: in the vertical uplift superimposed uniaxial unidirectional extrusion power source, the simulation results has a high similarity with the actual field geological section.The Structural dynamics genetic mechanism of Tangwangzhai syncline is closely related to the tectonic evolution of the entire Longmen Mountain tectonic belt. By summarizes the results of previous studies on Tangwangzhai syncline, comprehensive the field geological survey and indoor construction physics simulation, Tangwangzhai syncline must be formed in the effects of the differences uplift between Sichuan Basin and Songpan-Ganzi Plateau, and after that recreated by the Yanshan movement and the Himalayan movement. |
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