原特提斯北界东段构造演化与拼合方式

发布时间：2018-11-29 08:34

【摘要】：原特提斯洋是从Rodinia超大陆裂解到加里东末期发育于滇缅泰/保山微陆块以北、塔里木-华北陆块以南的一个近东西向古大洋，洋内存在华北、扬子、华夏、柴达木、中祁连、印支、北秦岭等诸多陆块/微陆块。但是对原特提斯洋的边界、不同陆块/微陆块的属性及洋-陆格局等尚不清楚。因此，本文主要以北秦岭-桐柏造山带北缘为研究对象，利用精细的野外构造几何学和运动学解析及LA-ICPMS、40Ar/39Ar测年等方法，结合已有的火成岩大地构造、沉积岩大地构造、岩石地球化学、同位素年代学、岩相古地理等诸多研究资料，进行集成创新，以厘定原特提斯洋的北界东段；确定原特提斯北部东段陆块/微陆块的属性、拼合时序及方式，建立洋-陆格局；探讨其构造演化过程，为Pangea超大陆的全球陆块重建打下坚实基础。 1.通过对古洛南-栾川断裂带两侧的沉积地层、碎屑锆石年龄谱、岩浆活动、构造变形变质等方面进行大地构造对比，得到作为被动陆缘的华北地块南缘和早古生代作为活动陆缘的北秦岭两者的地质特征具有天壤之别，厘定原特提斯北界东段边界为古洛南-栾川断裂。 2.构造变形幕次及特征：基于详细的构造解析及地质年代学资料，本文将早古生代研究区的构造变形划分为三幕。第一幕变形以发育区域上透入性的片理及向南倾的逆冲断层为主；第二幕变形主要表现为以近北西向的紧闭褶皱为主；第三幕变形以近北西西向的宽缓褶皱为主要特征。 3．拼合时序及方式：540Ma，宽坪洋向南俯冲，之后俯冲极性发生反转，460Ma，商丹洋开始向北俯冲，450Ma，北秦岭岛弧与华北地块南缘发生弧陆碰撞。 4.北秦岭-桐柏造山带北缘及其邻区的构造单元可划分为如下的大地构造分区及演化历程，自北向南依次是华北地块南缘新元古代-早古生代为被动大陆边缘；宽坪群为近岛架的火山裂谷-大洋盆地，碎屑物质主要来源于北秦岭；二郎坪群为宽坪大洋向南俯冲的弧前盆地，后期转变成为岛弧或弧后盆地；秦岭群为一古老的独立微陆块，于早古生代转变为大陆岛弧，且末期向北与华北地块碰撞拼贴为一体；商丹洋为独立的大洋盆地或者可能是宽坪大洋向南俯冲形成的弧后盆地；龟山杂岩和南湾复理石属晚古生代商丹洋向北发生俯冲产生的弧前增生楔体系及构造混杂岩带，但南秦岭及扬子北缘早古生代均为被动陆缘。
[Abstract]:The original Tethys ocean developed from the Rodinia supercontinent to the end of Caledonian, north of Yunnan, Myanmar, Thailand / Baoshan microcontinent, and south of Tarim to North China block. There are North China, Yangtze, Cathaysia, Chaidamu and Middle Qilian in the ocean. Indosinian, North Qinling and many other land blocks / microcontinental blocks. However, it is not clear about the boundary of the original Tethys ocean, the attributes of different land blocks / microblocks and the ocean-land pattern. Therefore, in this paper, the northern margin of Qinling to Tongbai orogenic belt is taken as the research object, and the detailed methods of structural geometry, kinematics and LA-ICPMS,40Ar/39Ar dating are used to combine with the existing igneous geotectonics. Sedimentary geotectonics, geochemistry, isotopic geochronology, lithofacies and paleogeography, and so on, have been integrated and innovated to determine the eastern segment of the northern boundary of the original Tethys Ocean. The attributes of the continental blocks / microblocks in the eastern segment of the northern part of the former Tethys are determined, the sequence and pattern of the assemblage are combined, the ocean-continental pattern is established, and the tectonic evolution process is discussed, which lays a solid foundation for the reconstruction of the global land blocks of the Pangea supercontinent. 1. The geotectonic correlation of sedimentary strata, zircon age spectrum, magmatic activity, tectonic deformation and metamorphism on both sides of the Paleo-Luonan-Luanchuan fault zone is carried out. The geological characteristics of the southern margin of the North China block as a passive continental margin and the North Qinling Mountains as the active margin of the early Paleozoic are different from each other, and the eastern boundary of the northern boundary of the original Tethys is determined to be the Palonan-Luanchuan fault. 2. Tectonic deformation episodes and characteristics: based on detailed tectonic analysis and geochronological data, the tectonic deformation of the early Paleozoic study area is divided into three acts in this paper. The deformation of the first act is mainly characterized by the permeable lithology of the developing region and the thrusting fault trending to the south, the deformation of the second act is mainly characterized by the closed fold near the north-west direction, and the deformation of the third act is characterized by the wide and gentle fold in the near NW direction. 3.The sequence and mode of assemblage are as follows: 540Ma. the Kuanping Ocean subducts south, then the subduction polarity reverses, 460Ma. the Shangdan Ocean subducts northward, 450 Ma. the arc-land collision occurs between the northern Qinling island arc and the southern margin of the North China block. 4. The tectonic units in the northern margin of the North Qinling-Tongbai orogenic belt and its adjacent areas can be divided into the following tectonic divisions and evolution processes. The southern margin of the North China Block is the Neoproterozoic to the early Paleozoic as the passive continental margin from north to south. The Kuanping Group is a volcanic rift oceanic basin near the island frame, and the clastic material is mainly derived from the North Qinling Mountains, while the Erlangping Group is a front arc basin of the Kuanping Ocean subducting to the south, and is transformed into an island arc or a back-arc basin in the latter stage. The Qinling Group is an ancient independent microcontinental block, which was transformed into a continental island arc in the early Paleozoic and collided with the North China block in the late stage, and the Shangdan Ocean is an independent oceanic basin or possibly a back-arc basin formed by the subduction of the Kuanping Ocean to the south. The Qiushan complex and the Nanwan flysch belong to the late Paleozoic Shangdan Ocean subduction northward system of accretive wedge system and tectonic melange belt, but the South Qinling Mountains and the northern margin of Yangtze are all passive continental margin in early Paleozoic.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P736.22

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