西藏冈玛错—日土一带增生杂岩及褶皱冲断带特征

发布时间：2018-05-18 19:08

本文选题：增生杂岩 + 逆冲推覆　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：大洋板块和大陆板块之间发生的运动,是缓慢并且复杂的,在这样的俯冲和碰撞的过程之中,海沟慢慢的向后退,在仰冲板块的前段,会有刮削作用、底侵作用以及前段的剥蚀作用等发生,这些作用使洋壳物质在海沟的内壁发生增生,具体表现出来的是增生楔或者削减杂岩(包括蛇绿混杂岩)的形成、增长(包括垂向和侧向)和岛弧的形成与迁移,从而实现了陆壳的增长。冈玛错增生杂岩位于冈玛错西南的冈玛日附近,以透入性两期变形的浅变质碎屑岩为基质,包含玄武岩、砾岩、基性岩、高压变质岩、大理岩、变质石英砂岩等块体。块体均具有长轴定向的特征,增生杂岩逆冲到康拓组之上,与康托组是逆冲推覆关系。基质常常完整的保存了两期构造的形迹。第一期变形以单剪作用为主,形成典型的单剪构造,如顺层掩卧褶皱,旋转碎斑等。砂岩等刚性块体和基质一同发生第一期单剪变形时,形成了增生杂岩常有的基质—块体结构。第一期变形过程中还伴随有大量流体作用,具体表现为发育较多顺层石英脉,单剪变形形成的块体长轴面倾向稳定,倾向主要为北北西,少量为北西西。第二期变形是在第一期变形基础上的以纯剪作用为主的变形。改造了第一期形成的顺层掩卧褶皱,在软弱的基质中形成了透入性的褶劈理,纵弯褶皱枢纽有北东、北西、西三个优势方位。褶皱轴面则以西倾为主,北倾次之。褶冲带主要由上石炭统展金组、上石炭统擦蒙组、下二叠统曲地组、中—下二叠统吞龙贡巴组、中二叠统龙格组构成,褶冲带碎屑岩与增生杂岩内碎屑岩碎屑岩石类型、沉积相和锆石特征相似,为同一套地质单元遭受不同构造过程而行曾。褶冲带构造样式以逆断层和伴生褶皱为主,发育一期透入性置换面理。这套褶冲带体系是俯冲过程中刮削拼贴的一套地质单元。
[Abstract]:The motion between the ocean plate and the continental plate is slow and complex, and in this process of subduction and collision, the trench slowly recedes, and in the front of the upwelling plate, it scrapes. The underthrust and the erosion of the front member of the trench resulted in the accretion of the oceanic crust material in the inner wall of the trench, which was manifested by the formation of the accretive wedge or the reduction of the complex (including ophiolite melange). Growth (including vertical and lateral) and island arc formation and migration, thus realizing the growth of continental crust. Gangmao accretive complex is located near Gangmai in the southwest of Gangmao. It consists of basalt, conglomerate, basic rock, high-pressure metamorphic rock, marble, metamorphic quartz sandstone and so on. The blocks are characterized by long axis orientation, and the accretive complex thrusts to the Kangtuo formation, which is related to the Kangtuo formation. The matrix often completely preserves the traces of the two-stage structure. The first stage of deformation is dominated by single shear, forming a typical single shear structure, such as bedding cover fold, rotating debris and so on. During the first single shear deformation of sandstone and matrix, the matrix block structure of accretive complex is formed. During the first stage of deformation, there is also a large amount of fluid action, which is characterized by the development of more bedding quartz veins. The long axial plane of the block formed by single shear deformation tends to be stable, mainly north to west, and a little to north west to west. The second stage of deformation is based on the first stage of deformation. The first stage of the bedding covering and lying fold is modified, and the permeable fold cleavage is formed in the weak matrix. The longitudinal bend fold hub has three dominant directions: North, East, North and West. The fold axial surface is mainly inclined to the west, followed by the north. The fold belt is mainly composed of the Upper Carboniferous Zhenjin formation, the Upper Carboniferous Chaimeng formation, the Lower Permian Cambrian formation, the Middle-Lower Permian Tunlong Gongba formation, the Middle Permian Longge formation, and the clastic rocks and accretionary complex types in the fold belt. The sedimentary facies and zircon are similar in character, and they belong to the same set of geological units subjected to different tectonic processes. The tectonic patterns of the fold belt are mainly reverse faults and associated folds, and one stage permeable replacement surface is developed. This pleating system is a set of geological units for scraping and collage during subduction.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P542;P587

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