特提斯喜马拉雅东段中生代大陆边缘裂谷盆地的背景与样式

发布时间：2018-07-04 17:45

本文选题：特提斯喜马拉雅 + 中生代　；参考：《成都理工大学》2017年硕士论文

【摘要】：特提斯喜马拉雅东段的中生代沉积记录对认识特提斯构造演化具有重要意义。本文对特提斯喜马拉雅东段洛扎-隆子一带的中生代裂谷盆地进行了初步研究。研究区裂谷盆地的发育时限为晚三叠世到早白垩世,经历了晚三叠世-中侏罗世和晚侏罗世-早白垩世两个扩展过程,其西南边界可能位于打隆-洛扎-曲卓木一带。研究区的盆地充填过程可分为两个阶段,第一阶段为初始陆缘裂谷盆地阶段,包括涅如组大陆斜坡相复理石序列、日当组陆棚边缘盆地相序列、陆热组浅海陆棚序列;第二阶段为以强烈的火山喷发活动为特色的陆缘裂谷盆地阶段,主要包括了遮拉组火山-细碎屑浅海沉积序列、维美组滨海—三角洲相沉积序列和桑秀组火山-细碎屑沉积序列。物源分析表明,从涅如组到维美组,它们均以450-650Ma和750-1000Ma的优势年龄为特征,显示了强烈的印度亲缘性,但是区域上的涅如组存在拉萨物源区。维美组铬尖晶石以低Al2O3(0.50%-20.82%)、高Cr#(0.51-0.99)和Fe2+/Fe3+比值(2.14-41.27)、以及具有变化的TiO2含量(0.00%~1.95%)为特征,母岩可能为特提斯喜马拉雅石炭二叠纪地层。通过沉积充填序列和物源对比分析,本文认为涅如组和朗杰学群是两套不同的地层单元,并进一步提出在晚三叠世末期班公湖怒江洋向南俯冲于拉萨地体之下引起的板片回转导致拉萨地体与印度北缘之间发生弧后裂谷作用,由于裂谷很狭窄,以至于拉萨地体能同时为朗杰学群和涅如组提供物源,只是朗杰学群接收了更多的拉萨物源供给,而涅如组具有更多的印度物源亲缘性。早侏罗世初期,俯冲板片进一步回转导致拉萨地体开始向北漂移和新特提斯弧后洋盆开始扩张,此时,印度北缘成为研究区侏罗系地层的唯一物源区。
[Abstract]:Mesozoic sedimentary records in the eastern part of the Tethys Himalayas play an important role in understanding the tectonic evolution of Tethys. The Mesozoic rift basin in the eastern part of the Tethys Himalayas is studied in this paper. The development time of rift basin in the study area is from late Triassic to early Cretaceous, and it has undergone two extension processes: late Triassic-Middle Jurassic and late Jurassic-early Cretaceous. The southwestern boundary of rift basin may be located in the area of Dalon-Luoza-Quzomu. The filling process of the basin in the study area can be divided into two stages. The first stage is the initial continental margin rift basin stage, which includes the sequence of continental slope facies of the Neiru formation, the sequence of the shelf margin basin facies of the Ridang formation, and the sequence of the shallow sea shelf of the continental heat formation. The second stage is the continental margin rift basin stage characterized by strong volcanic eruptive activity, which mainly includes the Jura formation volcanic-fine clastic shallow sea sedimentary sequence. The littoral-delta facies sedimentary sequence and the volcanic-fine clastic sedimentary sequence of the Sangxiu formation in the Weimei formation. The provenance analysis shows that the dominant ages of 450-650 Ma and 750-1000 Ma are the dominant ages from the Neru formation to the Weimei formation, showing strong Indian kinship, but there is a provenance in Lhasa in the Nelu formation. The chrome spinel of the Weimei formation is characterized by low Al _ 2O _ 3 (0.50-20.82%), high Cr # (0.51-0.99) and Fe _ 2 / Fe _ 3 ratios (2.14-41.27), and a variable TIO _ 2 content (0.000.95%). The parent rock may be Tethyan Himalayan Carboniferous Permian formation. Based on the analysis of sedimentary filling sequence and provenance correlation, it is considered that the Nelu formation and the Namgyai group are two different sets of stratigraphic units. Furthermore, it is proposed that the plate rotation caused by the subduction of the Nujiang River in Bangong Lake south under the Lhasa terrane at the end of the late Triassic led to a backarc rift between the Lhasa terrane and the northern margin of India, which is very narrow. The physical ability of Lhasa provides both Namgyai and Neru groups with material resources, but the Namgyai group receives more supplies of Lhasa material sources, and Nelu Group has more affinity of Indian provenances. In the early Jurassic, the subduction plate further turned to cause the Lhasa terrane to drift northward and the Neo-Tethys back-arc ocean basin to begin to expand. At this time, the northern margin of India became the only source of Jurassic strata in the study area.
【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

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