东昆仑东段南坡闹仓坚沟组地质特征、物源属性与构造演化
发布时间：2018-11-04 18:47
【摘要】：沉积盆地和造山带为大陆地壳上最为重要的构造单元,二者之间的耦合关系是大陆动力学研究的热点。盆地沉积碎屑物则是盆地沉积和构造演化的直接证据,更反映了物源区和沉积盆地的有机联系,因此通过研究盆地沉积碎屑物,进而恢复沉积盆地的沉积环境以及源区构造背景。本文以分布于东昆仑东段南坡的中三叠统闹仓坚沟组沉积地层为研究对象,以沉积岩石学、碎屑组分统计分析、岩石地球化学及碎屑锆石同位素年代学等方法相结合,综合研究闹仓坚沟组沉积特征,分析物源及其构造属性,在此基础上结合前人研究成果,建立恢复东昆仑地区晚古生代—早中生代古特提斯洋的构造演化过程。主要获得以下进展和成果:1、根据地层岩石组合与沉积环境的差异,将闹仓坚沟组由下到上划分为上下两个亚组,8个段。其中下亚组(一段—四段)主要为一套碎屑岩夹碳酸盐岩组合,表现为浅海陆源碎屑陆棚沉积环境;上亚组(五段—八段)主要为一套碳酸盐岩夹碎屑岩组合,表现为浅海碳酸盐岩台地沉积环境。说明此时弧前盆地有趋于填满的势头,沉积层序上表现为水深变浅。结合前人古生物资料、碎屑锆石年龄信息,晚三叠世科科鄂阿龙岩体的侵入及不整合接触面(上覆中三叠统希里可特组与闹仓坚沟组呈微角度不整合接触,上覆上三叠统八宝山组与闹仓坚沟组呈角度不整合接触)四个方面,确定闹仓坚沟组地层时代为中三叠世(T2)。2、闹仓坚沟组砂岩岩相学特征显示为近源沉积;Dickinson三角图解显示闹仓坚沟组沉积地层的物质来源比较复杂,主要为碰撞造山带和再旋回造山带,少数来自于岩浆弧;砂岩地球化学显示闹仓坚沟组沉积地层的物源区构造背景为大陆岛弧。综合认为闹仓坚沟组物源区构造背景为大陆岛弧。3、通过对闹仓坚沟组碎屑锆石U-Pb年龄研究表明,样品11072/15碎屑锆石年龄值主要有(226~324Ma、372~576Ma、749~936Ma、1010~1092Ma)4个年龄组。闹仓坚沟组下亚组第二段LA-ICP-MS锆石U-Pb年龄信息证明闹仓坚沟组沉积地层的物源主要为东昆仑地区原特提斯洋和古特提斯洋演化所形成的岩浆弧以及与其相配套的沉积地层。结合区域资料和上述分析结果认为闹仓坚沟组物源区主要为晚海西—早印支期安第斯型陆缘弧,加里东期岩浆弧次之。4、综合前人研究成果及区域构造岩浆演化事件,将东昆仑南缘晚古生代—早中生代构造演化过程划分为4个阶段:(1)晚泥盆世—中二叠世古特提斯洋壳形成及扩张阶段;(2)晚二叠世-中三叠世古特提斯洋壳俯冲消减与陆缘弧发育阶段;(3)中三叠世末古特提斯洋闭合与碰撞造山阶段;(4)晚三叠世碰撞造山后伸展与侏罗纪叠加改造阶段。
[Abstract]:Sedimentary basins and orogenic belts are the most important tectonic units in continental crust. The sedimentary clastic material of the basin is the direct evidence of the sedimentary and tectonic evolution of the basin, which reflects the organic relation between the source region and the sedimentary basin. Therefore, by studying the sedimentary clastic material of the basin, Then the sedimentary environment and source tectonic setting of the sedimentary basin are restored. In this paper, the sedimentary strata of the middle Triassic Naocangjianggou formation on the south slope of the eastern part of East Kunlun are studied. The methods of sedimentary petrology, statistical analysis of clastic components, geochemistry of rocks and isotopic chronology of detrital zircon are combined. Based on the comprehensive study of the sedimentary characteristics of the Nocangjianggou formation and the analysis of the provenance and its tectonic attributes, the tectonic evolution of the late Paleozoic to early Mesozoic PaleoTethys in the East Kunlun region was established on the basis of previous research results. The main achievements are as follows: 1. According to the difference of stratigraphic rock assemblage and sedimentary environment, the Noucangjiangjianggou formation is divided into two subgroups from the bottom to the top and eight sections. The lower sub-formation (member 1-4) is mainly composed of a set of clastic rock intercalated carbonate rock assemblages, which is characterized by the sedimentary environment of shallow-sea continental clastic shelf. The upper sub-formation (Wuduan-8th formation) is mainly composed of carbonate rock clastic rock assemblage, which is characterized by shallow sea carbonate platform sedimentary environment. The results show that the front arc basin tends to be filled, and the sedimentary sequence is shallow. Based on previous paleontological data and age information of clastic zircon, the intrusive and unconformities of the late Triassic Keke Oallon intrusions and unconformities (the upper and middle Triassic Silicot formation and the Nocangjian Gou formation are in micro-angle unconformable contact with each other). The upper Triassic Babaoshan formation and the Naocang Jiangou formation are in contact with each other at an angle unconformity). The stratigraphic epoch of the Nocangjianggou formation is determined to be the middle Triassic (T2). 2. The lithofacies characteristics of the sandstone of the Nocangjianggou formation are shown to be near source deposits. The Dickinson triangulation shows that the material source of the sedimentary strata of the Nao Cangjian Gou formation is complex, mainly composed of collisional orogenic belt and recirculation orogenic belt, and a few come from magmatic arc. The sandstone geochemistry shows that the source of the sedimentary strata of the Nao Cang Jian Gou formation is continental island arc. It is considered that the tectonic setting of the provenance of the Naocang Jianguo formation is continental island arc. The U-Pb age of the clastic zircon of the Nocangjianggou formation is studied. The results show that the age of 11072 / 15 detrital zircon is mainly in four age groups: (226U 324Ma-372MN 7496Ma) 936Ma (101092Ma). The LA-ICP-MS zircon U-Pb age information of the second member of the lower subformation of the Noucangjinggou formation proves that the sedimentary strata of the Naocang Jiangou formation are mainly derived from magmatic arcs formed by the evolution of the original Tethys and paleoTethys oceans in the East Kunlun region and the relationship between the The associated sedimentary strata. Based on the regional data and the above analysis results, it is concluded that the provenance of the Nocangjianggou formation is mainly a late Hercynian-early Indosinian Andean marginal arc, followed by the Caledonian magmatic arc. 4. The results of previous studies and the regional tectonic magmatic evolution events are synthesised. The late Paleozoic to early Mesozoic tectonic evolution processes in the southern margin of East Kunlun were divided into four stages: (1) the late Devonian to the Middle Permian Paleo-Tethys oceanic crust formation and extension; (2) the late Permian-Middle Triassic PaleoTethys ocean crust subduction and continental margin arc development stage, (3) the late Middle Triassic PaleoTethys ocean closure and collision orogenic stage; (4) the late Triassic post-collision orogenic extension and Jurassic superimposition.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P548
本文编号：2310818
[Abstract]:Sedimentary basins and orogenic belts are the most important tectonic units in continental crust. The sedimentary clastic material of the basin is the direct evidence of the sedimentary and tectonic evolution of the basin, which reflects the organic relation between the source region and the sedimentary basin. Therefore, by studying the sedimentary clastic material of the basin, Then the sedimentary environment and source tectonic setting of the sedimentary basin are restored. In this paper, the sedimentary strata of the middle Triassic Naocangjianggou formation on the south slope of the eastern part of East Kunlun are studied. The methods of sedimentary petrology, statistical analysis of clastic components, geochemistry of rocks and isotopic chronology of detrital zircon are combined. Based on the comprehensive study of the sedimentary characteristics of the Nocangjianggou formation and the analysis of the provenance and its tectonic attributes, the tectonic evolution of the late Paleozoic to early Mesozoic PaleoTethys in the East Kunlun region was established on the basis of previous research results. The main achievements are as follows: 1. According to the difference of stratigraphic rock assemblage and sedimentary environment, the Noucangjiangjianggou formation is divided into two subgroups from the bottom to the top and eight sections. The lower sub-formation (member 1-4) is mainly composed of a set of clastic rock intercalated carbonate rock assemblages, which is characterized by the sedimentary environment of shallow-sea continental clastic shelf. The upper sub-formation (Wuduan-8th formation) is mainly composed of carbonate rock clastic rock assemblage, which is characterized by shallow sea carbonate platform sedimentary environment. The results show that the front arc basin tends to be filled, and the sedimentary sequence is shallow. Based on previous paleontological data and age information of clastic zircon, the intrusive and unconformities of the late Triassic Keke Oallon intrusions and unconformities (the upper and middle Triassic Silicot formation and the Nocangjian Gou formation are in micro-angle unconformable contact with each other). The upper Triassic Babaoshan formation and the Naocang Jiangou formation are in contact with each other at an angle unconformity). The stratigraphic epoch of the Nocangjianggou formation is determined to be the middle Triassic (T2). 2. The lithofacies characteristics of the sandstone of the Nocangjianggou formation are shown to be near source deposits. The Dickinson triangulation shows that the material source of the sedimentary strata of the Nao Cangjian Gou formation is complex, mainly composed of collisional orogenic belt and recirculation orogenic belt, and a few come from magmatic arc. The sandstone geochemistry shows that the source of the sedimentary strata of the Nao Cang Jian Gou formation is continental island arc. It is considered that the tectonic setting of the provenance of the Naocang Jianguo formation is continental island arc. The U-Pb age of the clastic zircon of the Nocangjianggou formation is studied. The results show that the age of 11072 / 15 detrital zircon is mainly in four age groups: (226U 324Ma-372MN 7496Ma) 936Ma (101092Ma). The LA-ICP-MS zircon U-Pb age information of the second member of the lower subformation of the Noucangjinggou formation proves that the sedimentary strata of the Naocang Jiangou formation are mainly derived from magmatic arcs formed by the evolution of the original Tethys and paleoTethys oceans in the East Kunlun region and the relationship between the The associated sedimentary strata. Based on the regional data and the above analysis results, it is concluded that the provenance of the Nocangjianggou formation is mainly a late Hercynian-early Indosinian Andean marginal arc, followed by the Caledonian magmatic arc. 4. The results of previous studies and the regional tectonic magmatic evolution events are synthesised. The late Paleozoic to early Mesozoic tectonic evolution processes in the southern margin of East Kunlun were divided into four stages: (1) the late Devonian to the Middle Permian Paleo-Tethys oceanic crust formation and extension; (2) the late Permian-Middle Triassic PaleoTethys ocean crust subduction and continental margin arc development stage, (3) the late Middle Triassic PaleoTethys ocean closure and collision orogenic stage; (4) the late Triassic post-collision orogenic extension and Jurassic superimposition.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P548
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