藏南哲古地区上侏罗统一下白垩统桑秀组火山岩特征及其地质意义

发布时间：2018-05-05 20:19

本文选题：桑秀组 + 火山岩　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：研究区位于青藏高原南部冈底斯—喜马拉雅造山系东北部雅鲁藏布缝合带(YS)与藏南拆离系(STDS)之间的喜马拉雅地块。区内主要发育新特提斯洋盆充填地层,包括上三叠统至下白垩统。该盆地的演化主要受印度板块与欧亚大陆碰撞造山作用影响。本文主要以藏南哲古地区上侏罗统—下白垩统桑秀组为研究对象,重点开展研究对象的野外填图工作,通过对研究区6个图幅野外调查,测制剖面4条,将桑秀组划分为3个段,系统采集样品70件,进行光薄片鉴定、岩石地球化学和地质年代研究。本文使用的大部分地质年代学和岩石地球化学数据为作者本人参加的西藏1:5万哲古、卡珠、邛多江、松多、卡果、让宗幅区域地质矿产调查项目成果。根据桑秀组实测剖面中的岩性组合特征,认为晚侏罗世该区域以滨-浅海陆棚沉积占主导地位。桑秀组中火山岩夹层的锆石协和图和离群性特征指示其结晶年龄为142±1Ma,从而进一步证明桑秀组时代为晚侏罗—早白垩世。根据地球化学特征,认为上侏罗统—下白垩统火山岩,属板内裂谷产物,来源地幔,有地壳物质的混染,岩石类型属于板内碱性玄武岩,是在被动大陆边缘伸展裂谷活动期间形成的。
[Abstract]:The study area is located in the Himalayan block in the south of the Qinghai-Tibet Plateau between YS (YS) and STDS (South Tibet) in the northeast of the Gangdis Himalayan orogenic system. NeoTethys ocean basin is mainly developed in this area, including upper Triassic to lower Cretaceous. The evolution of the basin is mainly influenced by the collision orogeny between the Indian plate and Eurasia. In this paper, the upper Jurassic-Lower Cretaceous Sangxiu formation in the Zeigu area of southern Tibet is taken as the research object, and the field mapping work of the research object is emphasized. Through the field investigation of 6 maps in the study area, 4 sections are measured. The Sangxiu formation was divided into three sections, 70 samples were collected systematically, and the lithochemistry and geochronology were studied. Most of the geochronological and petrogeochemical data used in this paper are the results of the 1: 50 Chegegegu, Kaju, Qiongdujiang, Songduo, Kago, Rengzongzongzongzongzongzongzongzongzongzongzong regional geological and mineral survey project in Tibet. According to the lithologic assemblage characteristics of the Sangxiu formation, it is considered that the shore-shallow shelf deposits dominated the late Jurassic. The zircon consonance diagram and the characteristics of the outliers indicate that the age of crystallization of the volcanic intercalations in the Sangxiu formation is 142 卤1 Ma, which further proves that the age of the Sangxiu formation is late Jurassic-early Cretaceous. According to the geochemical characteristics, the volcanic rocks of the Upper Jurassic-Lower Cretaceous are considered to belong to the products of intraplate rift, the source mantle, the mixed contamination of crustal materials, and the types of rocks belong to the alkaline basalt within the plate. It was formed during the active extension of the rift on the passive continental margin.
【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】：2017
【分类号】：P588.14;P534.5

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