内蒙古阿拉善北缘下二叠统双堡塘组地质特征对比及其大地构造意义

发布时间：2018-01-26 02:19

  本文关键词： 内蒙古阿拉善北部 双堡塘组 早二叠世 构造背景　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：研究区位于银根—额济纳旗盆地,为华北板块、塔里木板块、西伯利亚板块以及哈萨克斯坦板块交汇部位,属古亚洲洋中段南缘,是研究古亚洲洋构造域构造演化的重要区域。本文通过沉积学、古生物学、岩石学和地球化学等方法,结合区域地质调查资料和前人研究成果,对阿拉善北缘下二叠统双堡塘组进行了深入研究。研究区古生界以恩格尔乌苏缝合带为界,分为西北部的塔里木—南疆大区和东南部的华北地层大区,下二叠统双堡塘组(P1sb)位于塔里木—南疆大区,主要呈带状分别出露在南部杭乌拉—蒙根乌拉一带和北部哈日敖日布格靠近中蒙边境一带,均为北东东向展布。根据在杭乌拉南部双堡塘组中采集到的大量古生物化石和碎屑锆石U-Pb年龄确定研究区南部双堡塘组时代为早二叠世早期,北部哈日敖日布格一带双堡塘组由于缺少古生物化石证据和年龄数据,本文暂时将其归入双堡塘组。野外研究发现,南北两处双堡塘组在空间展布、岩石组合特征和变质变形程度等方面均存在较大差异,通过对比分析MG和HR两处剖面实测和采样数据,结合室内外研究工作,对两处双堡塘组沉积特征进行了总结和对比,结合砂岩碎屑成分物源分析和地球化学特征对比,认为阿拉善北缘南北两处双堡塘组的物源可能来自于不同大地构造环境。综合岩石组合、沉积构造、古生物化石等证据,认为MG剖面下部为浅海碳酸盐岩台地相向无障壁陆源碎屑海岸相过渡的环境,上部以滨浅海相为主,HR剖面整体表现为滨浅海相为主,逐渐向碳酸盐岩台地过渡的沉积环境。晚石炭—早二叠世,受呼和套尔盖洋内弧北部大洋向南俯冲的影响,研究区南部逐渐形成了完整的沟-弧-盆体系,连续沉积的双堡塘组和方山口组代表了弧后盆地沉积的演化过程;呼和套尔盖洋内弧于早古生代晚期完成洋壳—陆壳的转变,哈日敖日布格一带地层形成于呼和套尔盖洋内弧的北缘。
[Abstract]:The study area is located in Yingen-Ejinaqi basin, which is the intersection of North China plate, Tarim plate, Siberian plate and Kazakstan plate. It is an important area to study the tectonic evolution of the Paleo-Asian oceanic tectonic domain. This paper combines regional geological survey data with previous research results by means of sedimentology, paleontology, petrology and geochemistry. The Lower Permian Shuangboutang formation in the northern margin of Alashan is studied in depth. The Paleozoic in the study area is divided into the northwestern Tarim-South Xinjiang region and the southeastern North China stratigraphic region with the Engelwusu suture belt as the boundary. The lower Permian Shuangboutang formation (P1sb) is located in the Tarim-South Xinjiang area, mainly showing in the southern part of the Hangula-Mongengwula area and in the northern part of Hari Ojbuge near the border between China and Mongolia. According to a large number of paleontological fossils and detrital zircon U-Pb ages collected in the Shuangboutang formation in the southern part of Hangwula, the early early Permian age of the Shuangboutang formation in the southern part of the study area was determined. Due to the lack of paleontological fossil evidence and age data, the Shuangbaotang formation in the northern area of Haribuge area is temporarily classified into the Shuangbaotang formation in this paper. Field studies show that the Shuangbaotang formation in the north and south is distributed in space. There are great differences in rock assemblage characteristics and metamorphic deformation degree. By comparing and analyzing the measured and sampled data of MG and HR sections, combined with indoor and outdoor research work. The sedimentary characteristics of the Shuangbaotang formation are summarized and compared, combined with the source analysis and geochemical characteristics of the sandstone clastic components. It is considered that the provenance of the Shuangboutang formation in the north and south of the northern margin of Alashan may come from different geotectonic environments, comprehensive rock assemblages, sedimentary structures, paleontological fossils, and so on. It is considered that the lower part of MG section is a transition environment from shallow carbonate platform to continental clastic coastal facies without barrier, and the upper section is dominated by shoreline and shallow sea facies. During the late Carboniferous and early Permian, the southern part of the study area gradually formed a complete trench-arc basin system due to the subduction of the northern ocean in the northern arc of Huhu and the Thuergai ocean toward the south. The continuous deposition of Shuangbaotang formation and Fangshankou formation represent the evolution process of back-arc basin. The transition of oceanic crust to continental crust was completed in the late early Paleozoic, and the stratigraphic formation in the area of Hariozibuge was formed in the northern margin of the Huhe Arc.
【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】：P534.46;P548
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本文编号：1464376