青海共和盆地下—中三叠统物源分析

发布时间：2018-05-07 22:21

本文选题：共和盆地 + 古流向分析　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：对于青海省东部共和盆地的研究,不仅能揭示出在早—中三叠世时期共和盆地的盆地属性,对恢复当时该地区的古地理面貌,对研究盆地及其周缘的构造演化也有着非常重要的意义。本文利用典型的物源分析对共和盆地的物源进行研究,然后根据地层特征结合物源性质来揭示共和盆地的盆地属性。首先,根据文献资料和野外考察发现盆地内东部和西部早—中三叠世的沉积物具有不同特征,地层序列也与弧后盆地地层相似,其火山岩的组成也与弧后盆地类似;然后根据古流向研究确定物源来自于西部、东北部以及南部;从迪金森三角图解法确定物源来自于再旋回造山带以及岩浆弧物源区,与弧后盆地的沉积物源相同;通过地球化学方法得到物源区母岩的构造背景分别是活动大陆边缘以及大陆岛弧,显示其物源为火山及陆源物质;然后通过重矿物分析方法再次确定物源来自于三个方向,即东昆仑、南祁连、阿尼玛卿山。最后根据以上结果,共和盆地物源主要有东北方的祁连造山带和西方的东昆仑岩浆弧,还有南部的阿尼玛卿山(在此时期阿尼玛卿山已经隆起),东昆仑此时期处于火山活跃时期,东北部的祁连造山带为盆地的陆相物源供给区,盆地周围并无广阔的大洋在当时。西部火山相,东部陆相,古地理位置又恰好位于火山弧后与造山带浅海之间,再根据盆地内地层充填序列发现其为典型的弧后盆地沉积特征,所以确定共和盆地在早—中三叠世时期为一弧后盆地。
[Abstract]:The study of the Gonghe Basin in eastern Qinghai Province can not only reveal the basin attributes of the Gonghe Basin during the early and Middle Triassic, but also restore the paleogeographic features of the area at that time. It is also of great significance to study the tectonic evolution of the basin and its periphery. In this paper, the provenance of Gonghe basin is studied by means of typical provenance analysis, and then the basin attributes of Gonghe basin are revealed according to stratigraphic characteristics and provenance properties. Firstly, according to the literature and field investigation, it is found that the sediments of the eastern and western part of the basin have different characteristics, the stratigraphic sequence is similar to that of the back-arc basin, and the composition of the volcanic rocks is similar to that of the back-arc basin. According to the study of paleodirection, the source is from the west, the northeast and the south, and from the Dickinson triangle diagram, the source comes from the re-cycle orogenic belt and the source of magmatic arc, which is the same as the sediment source of the back-arc basin. The tectonic setting of the parent rocks in the source area is obtained by geochemical method, which shows that the active continental margin and the continental island arc are the source of volcanic and continental source materials, and the source is determined from three directions by the method of heavy mineral analysis. That is, East Kunlun, South Qilian, the Animaqing Mountains. Finally, according to the above results, the provenance of the Gonghe Basin mainly consists of the Qilian orogenic belt in the northeast and the eastern Kunlun magmatic arc in the west. There are also the Animaqing Mountains in the south (the Animaqing Mountains have been uplifted in this period, the East Kunlun is in the period of volcanic activity, the Qilian orogenic belt in the northeast is the continental material supply area of the basin, and there is no broad ocean around the basin at that time. The western volcanic facies, the eastern continental facies and the paleogeographic location are located between the volcanic arc and the shallow sea of the orogenic belt. According to the filling sequence of the interior layer of the basin, it is found to be a typical sedimentary feature of the back-arc basin. Therefore, the Gonghe basin was determined to be a back-arc basin during the early-Middle Triassic.
【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】：P534.51

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