西藏荣玛乡擦蒙岩组变质砂岩物源分析及地质意义

发布时间：2018-04-17 13:11

本文选题：荣玛乡 + 增生杂岩　；参考：《中国地质大学(北京)》2016年硕士论文

【摘要】：研究区位于西藏地区荣玛乡,地处南羌塘腹地。研究区增生杂岩是一套整体无序局部有序的非史密斯地层。本文重点对雪水河岩群中的擦蒙岩组的变质砂岩展开重点研究,并主要对擦蒙岩组的物源性质及其形成的大地构造环境做出探讨。为探究擦蒙岩组的物源区性质,笔者通过野外实地调查和典型剖面的测制,采集大量的样品进行测试分析,并根据测试数据展开物源区的分析和验证工作。本文分别从岩相学、年代学、碎屑锆石骨架成分和地球化学方面展开物源分析工作。碎屑锆石的形态分析和年代学研究,说明研究区沉积盖层至少接受了来自早古生代地层的物质。擦蒙岩组中大量年龄记录了泛非构造热事件年龄,这表明碎屑物质来自于冈瓦纳大陆变质基底,这一结论支持了羌南地块属冈瓦纳大陆的认识。对变质砂岩骨架矿物成分所应用的Dickinson三角图解显示擦蒙岩组物源区为大陆板块、岩浆岛弧和再旋回造山带的混和物源。根据砂岩的地球化学元素数据,通过进行多种构造判别图解的图解综合分析,显示出荣玛乡地区擦蒙岩组物源区构造类型主要是被动大陆边缘构造背景。综合研究表明,擦蒙岩组物源区经历泛非期构造岩浆热事件,在二叠纪之前,该地区进入古特提斯洋俯冲期,海底扇沉积的雪水河岩群砂板岩充当了混杂岩的基质,早古生代地层及高压变质岩(蓝片岩、榴辉岩等)均以块体的形式混杂进入砂板岩基质中。到二叠纪-晚三叠世,古特提斯洋处于消减碰撞期,在该地区形成典型增生杂岩。
[Abstract]:The research area is located in Rongma Township of Tibet region, located in the hinterland of South Qiangtang.The accretive complex in the study area is a set of unordered non-Smith strata.This paper focuses on the study of metamorphic sandstone of the Chao Mengyan formation in the Xueshuihe rock group, and mainly discusses the provenance properties and the tectonic environment of the formation.In order to investigate the source region of the mengyan formation, the author collected a large number of samples for test and analysis through field investigation and typical profile measurement, and carried out the analysis and verification of the source area according to the test data.In this paper, provenance analysis is carried out in lithofacies, geochronology, detrital zircon skeleton composition and geochemistry.The morphological analysis and chronological study of the detrital zircons indicate that the sedimentary caprocks in the study area have at least accepted materials from the early Paleozoic strata.A large number of ages of Pan-African tectonic thermal events have been recorded in the mengyan formation, which indicates that the clastic material originates from the metamorphic basement of Gondwana continent, which supports the understanding that the southern Qiang massif belongs to Gondwana continent.The Dickinson triangulation for the mineral composition of metamorphic sandstone skeleton shows that the source of the eraser rocks is the continental plate, the magmatic island arc and the recirculation orogenic belt.Based on the geochemical element data of sandstone, through the comprehensive analysis of various tectonic discriminant diagrams, it is shown that the tectonic types of the source area of the mengyan formation in Rongmaxiang area are mainly passive continental margin tectonic background.A comprehensive study shows that the source region of the ergite formation experienced a pan-African tectonic magmatic thermal event. Before the Permian, the area entered the PaleoTethys subduction period, and the slate of Xueshui River group deposited by the submarine fan acted as the matrix of the melange.Early Paleozoic strata and high-pressure metamorphic rocks (blueschist, eclogite, etc.) are mixed into the slate matrix in the form of blocks.From Permian to late Triassic, the PaleoTethys ocean was in the subduction collision period and formed typical accretive complex in this area.
【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】：2016
【分类号】：P588.3

【相似文献】