兰州大学机构库 >地质科学与矿产资源学院
西宁盆地新生代地层碎屑锆石U-Pb年代学及其地质意义
Alternative TitleDETRITAL ZIRCON U-Pb GEOCHRONOLOGY OF THE XINING BASIN AND ITS GEOLOGICAL IMPLICATIONS IN CENOZOIC
姚丽洁
Thesis Advisor宋春晖
2019-05-20
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Degree Discipline矿物学、岩石学、矿床学
Keyword青藏高原东北缘 西宁盆地 碎屑锆石U-Pb年代学 物源分析 构造隆升
Abstract新生代印度板块和欧亚板块的碰撞导致了喜马拉雅造山带的形成,使得喜马拉雅造山带以北近2000千米的区域隆升变形,形成了世界屋脊——青藏高原。青藏高原隆升对亚洲内陆构造-地貌格局和气候造成了很大的影响,因此 ,青藏高原隆升和扩展机制及其对全球变化的影响一直是国内外地学研究热点问题之一。随着新生代印度板块和欧亚板块的持续碰撞,青藏高原北缘构造变形及地貌演化强烈,发育了多个造山带和菱形盆地,是研究青藏高原隆升和高原扩展机制的理想地区。沉积盆地和造山带是大陆地貌的两个基本构造单元,两者是在统一地球动力学背景和构造框架下不可分割的耦合过程和正负构造单元,沉积盆地中的陆源碎屑沉积物不仅记录了盆地的沉积演化信息,也记录了周围造山带的构造隆升信息。本文选择青藏高原东北缘西宁盆地为研究区域,在前人研究基础上,根据盆-山耦合关系,主要通过对盆地新生代地层进行不同层位碎屑锆石U-Pb年代学研究,结合盆地新生代地层的沉积特征、古水流特征和砾石成分特征,探讨了西宁盆地新生代物源变化及区域构造演化过程,主要有以下认识:西宁盆地新生代沉积物碎屑锆石U-Pb年龄主要发生了五次变化:41Ma以前碎屑锆石U-Pb年龄分布以200-300Ma为主要年龄峰,400-550Ma为次要年龄峰;41->31Ma碎屑锆石U-Pb年龄分布以400-550Ma为主要年龄峰,200-300Ma和1000-2000Ma为次要年龄峰;31->22Ma 碎屑锆石U-Pb年龄在前期基础上,突然出现700-1000Ma组分并成为主要年龄峰;22->12Ma碎屑锆石U-Pb年龄以200-300 Ma和400-550Ma为主要年龄峰,1000-2000Ma为次要年龄峰;12->3.6Ma碎屑锆石U-Pb年龄以1000-2000Ma为主要年龄峰;~3.6Ma碎屑锆石U-Pb年龄以400-550Ma为主要年龄峰,200-300Ma为次要年龄峰。西宁盆地新生代物源在始新世早中期(52->41Ma)主要为东昆仑造山带,始新世晚期-渐新世晚期(41->22Ma)主要物源转变为祁连造山带。中新世早中期(22->12Ma)以中祁连造山带为主要物源,拉脊山开始抬升并成为盆地物源之一;中新世晚期-上新世早期(12->3.6Ma)主要物源来自盆地北缘祁连山前寒武系;早上新世以来(~3.6Ma)盆地湟水最高阶地沉积物的主要物源为北祁连造山带古生代地层。新生代早期印度板块与欧亚板块碰撞后应力就传递到了青藏高原东北缘,导致东昆仑造山带隆升剥蚀与西宁盆地凹陷开始接受沉积;始新世晚期(~41Ma)阿尔金断裂发生强烈走滑运动使中祁连造山带初始隆升,随后在35-31Ma加速隆升;中新世早期(~22Ma)青藏高原东北缘发生一次广泛地构造运动,拉脊山开始逐步隆升成为分割西宁盆地与贵德盆地分水岭;中新世晚期以来(<12Ma)青藏高原东北缘阶段性强烈构造活动,使西宁盆地周围山体快速隆升。~3.6Ma西宁盆地迅速抬升遭受剥蚀,古湟水河开始长期逐步切割盆地并形成一系列阶地,这与青藏运动A幕发生时间基本一致。
Other AbstractThe collision between India and Asia led to the formation of the Himalayan orogeic belt at the Early Cenozoic. The area of nearly 2,000 kilometers north of the Himalayan orogenic belt is uplifted and deformed. The uplift of the Tibetan Plateau during the Cenozoic had a great impact on the tectonic-geomorphica pattern and climate of Asian inland. Therefore, the study on the mechanism of the uplift and expansion of the Tibetan Plateau has become international research hotspots. With the continuous convergence between India and Asia, the tectonic deformation and geomorphology of the northeastern margin of the Tibetan Plateau are strongly evolved. It is a unique geomorphic tectonic pattern formed by a series of mountains and the Cenozoic basins sandwiched between them is an idea area for studying the Tibetan Plateau's uplift, mechanism and the distal effects of India-Asian collision. Basins and orogenic belts are the two basic tectonic units of continental geomorphology. They are inseparable coupling processes and tectonic framework under unified geodynamic background. In the basin, sediments eroded from the nearby mountains and transported by the rivers can record precise information on the unroofing history of the ranges. In this paper, the Xining Basin in the northeastern margin of the Tibetan Plateau is selected as the research object. Based on the previous studies, we will use the basin-mountain coupling relationship with the characteristics of the zircon U-Pb age distribution in different layers of the Cenozoic strata to analyze the provenance of the Xining Basin(including stratigraphic sedimentary facies analysis, paleocurrent analysis, gravel composition analysis). Mainly obtained the following understanding: 1. There are five major changes in the zircon U-Pb age of the Cenozoic sediments in the Xining Basin: the detrital zircon U-Pb age populations before 41Ma is 200-300Ma as the main age peak, and 400-550Ma is the secondary age peak; 41->31Ma detrital zircon U-Pb age distribution with 400-550Ma as the main age peak, 200-300Ma and 1000-2000Ma as the secondary age peak; 31->22Ma detrital zircon U-Pb age on the basis of the previous, the 700-1000Ma group suddenly appeared and became the main age peak; the 22->12Ma detrital zircon U-Pb age was 200-300 Ma and 400-550Ma as the main age peak, and 1000-2000Ma was the secondary age peak; 12->3.6Ma detrital zircon U-Pb age with 1000-2000Ma as the main age peak; since ~3.6Ma the detrital zircon U-Pb age with 400-550Ma as the main age peak, 200-300Ma as the secondary age peak. 2. The main source in the Early-Middle Eocene (52->41Ma) of Xining Basin was the East Kunlun Orogenic Belt, and the main source in the late Eocene-late Oligocene (41->22Ma) was transformed into the Qilian orogenic belt. In the early and middle Miocene (22->12Ma), the Central Qilian orogenic belt was the main source, and the Laji Shan began to uplift and became one of the basin sources. The main source of the Late Miocene-Pliocene (12->3.6Ma) came from the Precambrian of the Qilian orogenic belt in the northern margin of the basin. Since the early Pleistocene (~3.6Ma) the main source of sediments in the Huangshui terraces is the Paleozoic strata of the Qilian orogenic belt. 3. After the collision between the Indian and Eurasian in the Cenozoic, the stress was transmitted to the northeastern margin of the Tibet Plateau, which led to the uplift and erosion of the Eastern Kunlun orogenic belt and the sedimentation of the Xining Basin depression. The late Eocene (~41Ma) Altun fault occurred the strong strike-slip movement caused the Central Qilian orogenic belt initially uplifted, and then accelerated uplifting at 35-31 Ma. In the early Miocene (~22Ma), a extensive tectonic movement occurred in the northeastern margin of the Tibet Plateau, and the Laji Shan began to gradually uplift and became the watershed of the Xining Basin and the Guide Basin; since the late Miocene (<12Ma), the strong tectonic activity of the northeastern margin of the Tibet Plateau has caused the mountains around Xining Basin to rise rapidly, ~3.6Ma the basin was uplifted and denuded and the Huangshui River began to form.
Pages74
URL查看原文
Language中文
Document Type学位论文
Identifierhttp://ir.lzu.edu.cn/handle/262010/338437
Collection地质科学与矿产资源学院
Affiliation地质科学与矿产资源学院
First Author AffilicationSchool of Earth Sciences
Recommended Citation
GB/T 7714
姚丽洁. 西宁盆地新生代地层碎屑锆石U-Pb年代学及其地质意义[D]. 兰州. 兰州大学,2019.
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