柴北缘鱼卡地区折返深俯冲地质体变形期次研究

发布时间：2018-02-14 02:41

本文关键词： 柴北缘超高压变质带鱼卡折返深俯冲地质体变形期次榴辉岩透镜体俯冲期构造构造演化　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：柴北缘超高压变质带经历了古元古代基底形成演化、中-新元古代Rodinia大陆汇聚、早古生代碰撞造山和中-新生代盆山耦合-高原隆升等构造旋回,最引人瞩目的莫过于早古生代的碰撞造山系统,保留了碰撞造山作用过程中形成的高压变质构造带和洋盆封闭留下的蛇绿杂岩残片。本次研究工作中我们将榴辉岩及经历了超高压变质作用的各类片岩(片麻岩)视为一个整体,统称为“折返深俯冲地质体”,通过开展野外地质填图和路线地质调查,查明了(1)折返深俯冲地质体中榴辉岩呈透镜体,似层状产出;(2)折返深俯冲地质体与原地系统的接触关系,表现为早期韧性-脆韧性剪切带接触,后期叠加逆冲推覆作用;(3)产于片麻状花岗岩体分布区的榴辉岩是片麻状花岗岩体之上鱼卡岩群残蚀体或顶垂体中的榴辉岩,并不是片麻状花岗岩体中产榴辉岩。在填图过程中通过对柴北缘鱼卡地区折返深俯冲地质体及其围岩内部构造的几何学、运动学和动力学的综合研究分析,将折返深俯冲地质体的变形划分为以下四个期次:第一期俯冲期构造组合(D1):以塑性递进变形为主要特点,主要构造形迹有似层状展布的榴辉岩透镜体,石榴子石变斑晶保存的俯冲期的面理Sn+1,榴辉岩透镜体的拖尾现象说明本期变形早于峰期变质作用。第二期折返期构造组合(D2):以韧性-脆韧性变形为主要特点,折返早期的构造形迹为折返深俯冲地质体内的斜歪水平褶皱、NW向的多条韧性剪切带和无根钩状褶皱;折返晚期为榴辉岩透镜体内部发育劈理和书斜构造。第三期逆冲推覆构造组合(D3):以中-浅层次的韧脆性变形为主,主要为折返深俯冲地质体与达肯大坂岩群的逆冲推覆带,造成折返深俯冲地质体内部发育多条次级逆冲断层,滩间山岩群形成的一系列小型斜歪倾伏褶皱。第四期重力滑塌构造组合(D4):以脆性变形为主,主要为一些脆性的断裂和破碎带,局部可见重力滑塌构造,是青藏高原隆升后的构造反映。
[Abstract]:The ultrahigh pressure metamorphic belt in the northern margin of Qaidam has undergone the Paleoproterozoic basement formation and evolution, Meso-Neoproterozoic Rodinia continental convergence, early Paleozoic collision orogeny and Mesozoic Cenozoic basin-mountain coupling uplift and other tectonic cycles. The most striking thing is the early Paleozoic collisional orogenic system. The high-pressure metamorphic belts formed during the collision orogeny and the ophiolite fragments left behind by the oceanic basin closure were retained. In this study, eclogite and various schists (gneiss) which have undergone ultrahigh pressure metamorphism have been studied. ) as a whole, Generally referred to as "reentrant deep subduction geological body", through field geological mapping and route geological investigation, the contact relationship between eclogite and in-situ system in the reentrant deep subduction geological body is found out, which is lenticular in eclogite, similar to stratiform production, and reentrant deep subduction geological body. The eclogite, characterized by early ductile ductile shear zone contact and late superimposed thrust nappe, is eclogite in the distribution area of granitic granitic bodies, which is the remnant of Yuka rock group or eclogite in the roof pituitary of the granitic granitic bodies. It is not an eclogite in the granitic granites. In the course of mapping, the geometries, kinematics and dynamics of the geometries, kinematics and dynamics of the deep subduction geological bodies and their surrounding rocks in Yuka area of the northern margin of Qaidam are studied comprehensively. The deformation of the reentrant deep subduction geological body can be divided into the following four stages: the first stage subduction tectonic assemblage D _ (1): eclogite lens, which is mainly characterized by progressive plastic deformation, and the main structural trace is like layered eclogite lens. The metamorphism of pomegranate porphyry preserved in subduction stage and the lag phenomenon of eclogite lens indicate that the deformation in the present period is earlier than the peak metamorphism. The second reentrant tectonic assemblage is characterized by ductile and brittle ductile deformation. The early tectonic trace of the exhumation is a series of ductile shear zones and rootless hook folds of horizontal fold and NW direction in the deep subduction geological body. In the late exhumation period, cleavage and diagonal structure developed in the eclogite lens. The third stage thrust nappe tectonic assemblage is composed of ductile and brittle deformation of middle and shallow layers, and is mainly a thrusting nappe belt between the thrust-thrusting geological body and the Dacendaban rock group. As a result, many secondary thrust faults developed in the reentrant deep subduction geological body, and a series of small oblique tilting folds formed by the interbeach rock group. The gravity collapse tectonic assemblage of the 4th period is characterized by brittle deformation. It is mainly composed of brittle faults and fracture zones, and the local gravity collapse structure is a reflection of the uplift of the Qinghai-Xizang Plateau.
【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

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