内蒙古索伦山缝合带早中二叠世放射虫硅质岩及其地球化学特征

发布时间：2019-06-19 05:27

【摘要】：内蒙古索伦山缝合带长期以来一直是研究华北北缘构造演化历史、认识古亚洲洋演化、确定华北板块与西伯利亚板块拼合时间及其拼合过程等重大地质问题的关键地区,其作为华北板块与西伯利亚板块俯冲消减碰撞造山的最终位置已经被广泛地接受,但是对存在于上述华北和西伯利亚板块之间古亚洲洋的闭合时间及构造演化尚存在比较大的争议。放射虫是喜好大洋环境、营浮游生活的海生单细胞动物,分布十分广泛,具有很好的全球对比意义。由于深海其它门类化石的缺失,放射虫化石往往成为确定蛇绿岩形成时代上限进而探讨其形成环境和地质演化的关键证据之一。迄今只在索伦山缝合带东延部分索伦敖包地区发现放射虫。硅质岩地球化学特征对硅质岩的形成具有很好的指示意义,通过硅质岩主量、微量、稀土元素的分析,可以判断其沉积环境。依托内蒙古索伦山地区六幅1∶50 000区域地质矿产调查项目,对采集于索伦山缝合带蛇绿岩中的硅质岩进行酸处理,对处理出的放射虫化石进行分离与鉴定,共鉴定出放射虫8属15种,其共存时限为早二叠世-中二叠世早期。硅质岩地球化学特征显示其形成环境为大陆边缘和大洋盆地之间且距离大陆边缘较远的沉积环境。表明早二叠世-中二叠世早期索伦山地区的古亚洲洋处于复杂沉积和大洋演化阶段,与现今的太平洋具有相同景观,呈现出多岛洋的地理格局。
[Abstract]:The Solenshan suture belt in Inner Mongolia has long been a key area for studying the tectonic evolution history of the northern margin of North China, understanding the evolution of the ancient Asian oceans, and determining the time and process of convergence between the North China plate and the Siberian plate. It has been widely accepted as the final position of the subduction and collision orogeny between the North China plate and the Siberian plate. However, the closure time and tectonic evolution of the paleo-Asian ocean between the North China and Siberian plates mentioned above are still controversial. Radiolarian is a marine single-celled animal that likes oceanic environment and lives in zooplankton. It is widely distributed and has a good global comparative significance. Due to the lack of other fossils in the deep sea, radiolarian fossils often become one of the key evidence to determine the upper limit of the formation age of ophiolite and to explore its forming environment and geological evolution. So far, radiolarian insects have only been found in the eastern extension of the Solenshan suture zone in the Sauron Aobao area. The geochemical characteristics of siliceous rocks are of great significance to the formation of siliceous rocks. The sedimentary environment can be judged by the analysis of the main quantity, trace and rare earth elements of siliceous rocks. Based on six 1:50 000 regional geological and mineral survey projects in Solunshan area, Inner Mongolia, the siliceous rocks collected from the ophiolite of Solenshan suture zone were treated with acid. The treated radiolarian fossils were isolated and identified. A total of 8 genus and 15 species of radiolarian were identified, and their coexistence time was from early Permian to early Middle Permian. The geochemical characteristics of siliceous rocks show that the formation environment is a sedimentary environment between the continental margin and the oceanic basin and far from the continental margin. It is shown that the ancient Asian ocean in the early Permian to early Middle Permian Solenshan area is in the stage of complex sedimentation and ocean evolution, which has the same landscape as the present Pacific Ocean and presents the geographical pattern of the multi-island ocean.
【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】：P588.244;P534.46

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