理塘地区断裂构造变形及演化

发布时间：2018-10-24 18:01

【摘要】：理塘地区断裂构造位于三江特提斯造山带东缘,松潘-甘孜造山带西南缘,扬子板块西侧,是中国大陆地壳中三江特提斯造山带与松潘—甘孜造山带的重要组成部分。理塘地区位于青藏高原东缘,此处断裂构造的几何学、运动学、动力学研究对于三江特提斯造山带、松潘-甘孜造山带乃至扬子板块的形成及演化具有重要意义。理塘地区断裂构造从平面几何展布上看可以划分为主要由3个方向的断裂组成,分别是南北向(S-N)断裂、北西-南东(NW-SE)向断裂和北东-南西(NE-SW)向断裂。本文应用构造解析方法对理塘地区露头尺度的断裂构造几何形态进行了观测、对断裂构造的运动学与动力学方面解析并对本区内断裂构造变形期次和区域构造演化进行了初步探讨。本文认为自印支期以来,理塘地区断裂构造变形次数至少可达6次。早在印支晚幕初期发生了NW-SE方向的碰撞挤压,在此期应力作用下,形成了NW向的劈理,本文将此次碰撞挤压作用作为研究区内的第一期构造变形。第二期最大主应力方向为NE-SW,发生在印支晚幕晚期。在此期应力作用下,形成了断层面倾向为NE、SW的断层。这些断层带内后期填充了大量石英脉。第三期应力性质为拉张,最小主应力方向为NNE-SSW,在燕山中晚期此应力作用下,以前形成的走向为NW的断层被拉伸、扩大(此时石英脉形成)。第四期应力方向为E-W,在喜马拉雅运动中期此期应力作用下,对以前期次形成的断层、节理以及断层内的石英脉不同程度错动,并形成本期次NE走向的断层。第五期应力方向为NE-SW,在上更新世早期此期应力作用下,再次对以前期次形成的断层、节理以及断层内的脉体不同程度错度,并且强化NW走向的断层。第六期应力方向性质不明,形成时间最晚,约为早更新世。特征断层多窄小(2-3cm),带内充填大量断层泥和碎粒,且无石英脉充填。正是多方向多期次的区域应力造就了如今地质构造复杂的理塘地区断裂构造。
[Abstract]:The fault structure in Litang area is located in the eastern margin of the Sanjiang Tethys orogenic belt, the southwest margin of the Songpan-Ganzi orogenic belt and the west side of the Yangtze plate. It is an important part of the middle Sanjiang Tethys orogenic belt and the Songpan-Ganzi orogenic belt in the Chinese mainland. The Litang area is located in the eastern margin of the Qinghai-Tibet Plateau. The study of the geometry, kinematics and dynamics of the fault structures is of great significance for the formation and evolution of the Sanjiang Tethys orogenic belt, the Songpan-Ganzi orogenic belt and even the Yangtze plate. The fault structure in Litang area can be divided into three main faults from the plane geometry, namely, S-N fault, NW-SE fault and NE-SW fault. In this paper, the structural geometry of outcrop scale faults in Litang area has been observed by means of structural analysis method. The kinematics and dynamics of fault structures are analyzed and the deformation stages and regional tectonic evolution of faults in this area are preliminarily discussed. Since the Indosinian period, it is believed that the times of tectonic deformation of the Litang area can reach at least 6 times since the Indosinian period. The collision extrusion in the direction of NW-SE occurred early in the late curtain of Indosinian. Under the stress of this period, the cleavage of NW direction was formed. In this paper, the collision extrusion is regarded as the first tectonic deformation in the study area. The second phase of the maximum principal stress direction of NE-SW, occurred in the late Indosinian late curtain. Under the stress of this period, faults tend to be NE,SW on the break plane. A large number of quartz veins were filled in these fault zones late in the period. The third stage of the stress is tensional and the direction of the minimum principal stress is NNE-SSW,. Under the action of this stress in the middle and late Yanshanian period, the faults formed in the direction of NW have been stretched and expanded (at this time, quartz veins are formed). The stress direction of the fourth phase is E-W. Under the action of the stress in the middle period of Himalayan movement, the faults, joints and quartz veins formed in the early stage of the Himalayan movement are staggered to different degrees, and the faults of the current sub-NE strike are formed. The fifth stress direction is that NE-SW, under the action of early Pliocene stress, reacts on the faults, joints and veins in the early stage of the early Pliocene, and reinforces the faults along the NW strike. The direction of the sixth stage stress is unknown, and the formation time is the latest, about the early Pleistocene. The characteristic faults are multi-narrow (2-3cm), the belt is filled with a large number of fault gouges and fragments, and no quartz veins are filled. It is the multi-direction and multi-stage regional stress that leads to the fault structure in Litang area which has complicated geological structure.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P542.3

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