巴颜喀拉山群构造变形特征及物源分析

发布时间：2018-05-21 15:57

本文选题：巴颜喀拉 + 构造变形　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：分布于青藏高原腹地北东部的可可西里—巴颜喀拉三叠纪沉积盆地,其分布范围北以木孜塔格—东昆南—阿尼玛卿断裂带为界,南至西金乌兰—玉树—金沙江断裂带,东以龙门山推覆构造为限,呈现出巨型倒三角形区域。巴颜喀拉盆地除西部和东部部分地区出露二叠系,其他部分地区出露侏罗—第四系外,大部分地区均被巨厚的三叠系所覆盖,其中蕴藏着许多地质信息,从而成为了国内一块神秘的区域,并引起了中外学者的极大关注,被称为“中国的百慕大”。本文以共和-玉树剖面为基础,对巴颜喀拉山群进行了构造变形特征研究,将研究区从南至北划分为三个构造变形分带,分别为紧闭褶皱冲断带、宽缓褶皱冲断带和斜歪倾伏褶皱冲断带。结合野外现象和室内研究分析,识别了3期主要的构造变形:①俯冲挤压变形,以紧闭褶皱和逆冲、走滑断裂为特征,可同区域上中晚三叠世扬子板块与包括柴达木板块在内的华北板块俯冲汇聚事件相配套,并奠定了巴颜喀拉山群主体NWW-SEE向的褶皱-冲断的构造格架;②左行走滑剪切变形,以叠加在早期片理面之倾竖褶皱、劈理化作用为特征,可能为巴颜喀拉地块与扬子板块的NE向斜向俯冲所致;③脆性断裂构造,以发育脆性正断层为特征,可同青藏高原的快速隆升相配套,变形特征上显示一系列的宽缓褶皱被脆性断裂所切断。在此基础之上,进一步分别对各分带的沉积、碎屑成分及古水流、碎屑锆石年龄信息等特征进行了详细的对比,结果显示本区的三个变形分带在层位上、成分变化以及锆石年龄频谱上均显示一定的规律性或者相似性,仅表现在构造外貌上有所不同,因此,我们认为其主要是在同一构造作用下形成的不同构造组合样式。而区域上中晚三叠世扬子板块与包括柴达木板块在内的华北板块俯冲汇聚可能是奠定巴颜喀拉山群主体NWW-SEE向的褶皱—冲断构造格架的主要构造作用,而之后的左行走滑变形以及晚期的断裂构造活动仅仅是对本区构造格架的微调作用。在综合研究前人古水流资料成果的基础上,作者结合砂岩碎屑成分统计分析发现,巴颜喀拉盆地从边缘至盆地中心具蛇绿混杂岩—浊积岩—深海盆地的变化规律。盆地中北部的陆源碎屑物主要来自盆地北部两条造山带:昆仑造山带和秦岭造山带,前者是主要的物质来源,也有来自柴达木板块的部分物源。巴颜喀拉盆地存在发散式古水流,总体方向为北东至南西向,基本上与残留洋盆古水流样式一致。巴颜喀拉盆地在巴颜喀拉山群1段沉积时,为海陆相间的地理格局,到2、3段时,海盆达到最大,沉积中心有向北推移的趋势,4段时,海盆逐渐缩小,呈现出由东向西逐渐消退的趋势,并发育了两个沉积中心。
[Abstract]:The Khoxili-Bayankala Triassic sedimentary basin in the eastern part of the hinterland of the Qinghai-Xizang Plateau is bounded by the Muzitage-East Kunnan-Animachin fault zone in the north, and the Xijin Wu Lan-Yushu-Jinsha River fault zone in the south. To the east, Longmen Mountain nappe structure as the limit, showing a giant inverted triangle area. Except for the Permian in the western and eastern parts of the Bayan Kara basin, and the other parts of the basin, most of them are covered by the extremely thick Triassic system, which contains a lot of geological information. Thus became a mysterious region in China, and attracted great attention of Chinese and foreign scholars, known as "Bermuda of China." Based on the Gong-Yushu section, the structural deformation characteristics of Bayan Kara Mountain Group are studied in this paper. The study area is divided from south to north into three tectonic deformation zones, namely, closed fold thrust zone. Wide gentle fold thrust zone and oblique tilting fold thrust zone. Combined with field phenomena and laboratory analysis, the main tectonic deformation: 1 subduction and compression deformation in three periods are identified, which are characterized by tight fold, thrust and strike-slip faults. It can be matched with the events of subduction and convergence of North China plate, including Qaidam plate, in the Middle and late Triassic of the region, and establishes the fold-thrust tectonic framework of the Bayan Kara Mountain Group in the direction of NWW-SEE direction and the shear deformation of the left strike-slip. Characterized by the dipping vertical fold and cleavage action on the early facies, it may be a brittle fault structure caused by the NE syncline subduction of the Bayan Kara block and the Yangtze plate, which is characterized by the development of the brittle normal fault. It can be matched with the rapid uplift of the Qinghai-Xizang Plateau. The deformation characteristics show that a series of wide and slow folds are cut off by brittle faults. On this basis, the depositional, clastic composition, paleocurrent and age information of zircon in each zone are compared in detail. The results show that the three deformation zones in this area are on the horizon. The composition changes and the zircon age spectrum show certain regularity or similarity, but only show different tectonic appearance. Therefore, we think that they are mainly formed under the same tectonic action of different tectonic combination style. The subduction convergence of the Yangtze plate and the North China plate, including the Qaidam plate, may be the main tectonic framework of the NWW-SEE trending fold thrust tectonic framework in the main body of the Bayan Kara Mountain Group, and the subduction and convergence of the Yangtze plate and the North China plate, including the Qaidam plate, may form the main tectonic framework of the NWW-SEE direction of the Bayan Kara Mountain Group. The subsequent left strike-slip deformation and late fault tectonic activity are only fine-tuned to the tectonic framework in this area. On the basis of synthetically studying the data of paleocurrent, combined with the statistical analysis of sandstone clastic composition, the author found that there are ophiolite, turbidite and deep-sea basins from the margin to the center of the basin in Bayan Kara Basin. The continental clastic material in the central and northern part of the basin mainly comes from two orogenic belts in the northern part of the basin: the Kunlun orogenic belt and the Qinling orogenic belt. The former is the main material source and the other is from the Qaidam plate. There are divergent paleocurrent in Bayankala basin, the general direction is from north east to south west, which is basically consistent with the paleocurrent pattern of residual ocean basin. The Bayankala basin was formed in the first member of the Bayan Kara Group during the deposition of the first member of the Bayan Kara Group. By the time of formation 2 and 3, the basin reached its maximum, and the sedimentary center gradually shrank when the sedimentary center tended to move northward to the fourth member. It shows a trend of fading from east to west, and develops two sedimentary centers.
【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】：2015
【分类号】：P548

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