西昆仑西段布伦阔勒岩群变质变形研究

发布时间：2018-04-04 20:13

本文选题：西昆仑造山带　切入点：布伦阔勒岩群　出处：《成都理工大学》2017年硕士论文

【摘要】：西昆仑造山带位于青藏高原西北边缘,是中央造山带的重要组成部分,具多旋回碰撞造山特征,是连接泛亚和特提斯构造域重要的构造界线。位于西昆仑造山带内的布伦阔勒岩群,构造变形和变质异常复杂,记录了不同期次、不同性质的变质变形事件。本文选取布伦阔勒岩群代表性的剖面进行研究。岩石学及岩相学研究表明,布伦阔勒岩群主要由片岩类、片麻岩类构成,其次为变粒岩、糜棱岩及大理岩。本文主要针对片岩和片麻岩进行地球化学分析测试,主量元素、稀土元素、微量元素特征及地层产状表明:布伦阔勒岩群片岩类岩石总体应为副变质岩,原岩可能为泥质岩、泥质砂岩、粉砂岩;不含角闪石的片麻岩原岩可能为砂质岩或杂砂岩;含角闪石的片麻岩类,其原岩主体可能为杂砂岩,局部可能夹杂少量火山碎屑沉积岩。根据矿物共生组合及其之间的相互关系,作者发现研究区布伦阔勒岩群从早到晚至少经历了四期变质作用。第一期(M1)为绿片岩相-角闪岩相区域动力热流变质作用,主要形成递增变质带;第二期(M2)为绿片岩相动力变质作用,形成糜棱岩;第三期(M3)为气液交代变质作用,表现为伟晶岩脉两侧地层中黑云母被交代形成毛发状散乱排列的矽线石,锆石LAICPMS U-Pb年龄显示作用时间为燕山早期(179±1.4Ma);第四期(M4)为绿片岩相退变质作用,表现为无向的低温矿物组合取代高温矿物组合。研究区布伦阔勒岩群至少经历了四期变形作用。第一期(D1)为区域变形作用,主要形成区域性片理和片麻理;第二期(D2)为顺层挤压变形作用,主要形成褶皱;第三期(D3)为韧性走滑变形作用,形成小韧性剪切带和糜棱岩;第四期(D4)是冲断推覆变形作用,形成逆冲推覆构造。通过变质变形综合分析,布伦阔勒岩群具以下变质变形关系:区域动力热流变质作用(M1)与区域变形作用(D1)是同变质变形作用;之后叠加顺层挤压变形(D2),仅发生变形未发生变质;随后发生动力变质(M2),同时发生韧性走滑变形(D3),二者是同变质变形;之后叠加冲断推覆变形(D4),仅发生变形未发生变质;晚期发生气液交代变质作用(M3),仅发生变质为发生变形;最晚期发生退变质作用(M4),仅发生变质为发生变形。
[Abstract]:The West Kunlun orogenic belt is located on the northwest margin of the Qinghai-Xizang Plateau. It is an important part of the central orogenic belt with the characteristics of polycyclic collision orogeny and is an important tectonic boundary connecting the pan-Asian and Tethys tectonic domains.The brunkolitic group located in the West Kunlun orogenic belt is characterized by complex structural deformation and metamorphism, which records the metamorphic events of different stages and different properties.In this paper, the representative section of Blunkole rock group is selected to study.The petrological and petrographic studies show that the Bloenkole group is mainly composed of schist, gneiss, metamorphic rock, mylonite and marble.The geochemical analysis and test of schist and gneiss are carried out in this paper. The main elements, rare earth elements, trace element characteristics and stratigraphic occurrence indicate that the schist rocks of the Brunkaule group should generally be parametamorphic rocks, and the primary rocks may be argillaceous rocks.Argillaceous sandstone, siltstone, gneiss without hornblende may be sandy rock or complex sandstone, gneiss containing amphibole may be mainly composed of complex sandstone, and a small amount of pyroclastic sedimentary rock may be mixed locally.Based on the mineral symbiotic assemblages and their interrelationships, the authors found that the brunkolian rock group in the study area has undergone at least four metamorphic periods from early to late.The first stage is the regional dynamic heat flow metamorphism of the greenschist facies and amphibolite facies, and the second stage is the progressive metamorphism zone, the second stage is the greenschist facies dynamic metamorphism to form mylonite, the third stage is the gas-liquid metasomatic metamorphism.It is characterized by the metasomatism of biotite in both sides of the pegmatite vein to form hairlike and scattered sillimanite. The LAICPMS U-Pb age of zircon shows that the time of action is 179 卤1.4 Mai in the early Yanshanian period, and the fourth stage is the retrograde metamorphism of greenschist facies, the fourth stage of which is the retrograde metamorphism of greenschist facies.The undirected low temperature mineral assemblage replaces the high temperature mineral combination.The study area has undergone at least four stages of deformation.The first stage is regional deformation, which mainly forms regional lithology and schism, the second stage is bedding extrusion deformation, and the third stage is ductile strike-slip deformation, forming small ductile shear zone and mylonite, the second stage is bedding extrusion deformation, the third stage is ductile strike-slip deformation, and the third stage is ductile strike-slip deformation, forming small ductile shear zone and mylonite.The fourth stage (D 4) is the deformation of thrust nappe, forming thrust nappe structure.According to the comprehensive analysis of metamorphic deformation, there are the following metamorphic deformation relationships in the Blungoule rock group: regional dynamic heat flow metamorphism (M _ 1) and regional deformation (D _ 1) are the same metamorphic deformation, and then superimposed bedding compression deformation (D _ 2), only the deformation does not occur metamorphism;The dynamic metamorphism of M _ (2) and ductile strike-slip deformation (D _ (3)) occurred, which were the same metamorphic deformation, then superimposed nappe deformation (D _ (4)) occurred only without metamorphism, and the late stage of gas-liquid metasomatic metamorphism (M _ (3)) occurred only metamorphism.Retrograde metamorphism occurred in the late stage, and only metamorphism occurred as deformation.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P542;P588.3

【参考文献】