内蒙古阿拉善地区北部古生代沉积及其大地构造演化特征

发布时间：2018-05-30 09:57

本文选题：中亚造山带 + 阿拉善北缘　；参考：《中国地质大学(北京)》2016年博士论文

【摘要】：阿拉善及其北缘地区位于中亚造山带中段南缘,处于中朝板块、塔里木板块、西伯利亚板块之间的汇合地带,是天山造山带与兴蒙造山带的交汇部位,是研究中亚造山带构造演化和古亚洲洋最终闭合历史的关键区域。前人对阿拉善及其北缘地区的研究主要集中在构造单元的划分、蛇绿岩以及花岗岩的分析等方面,而对于研究区内沉积地质特征的研究则相对较少,并且对于阿拉善北缘地质演化事件发生的时间也具有很大争议。针对上述问题,本文通过沉积学、古生物学、地球化学和锆石年代学等方法,结合区域地质调查资料和前人岩浆岩等研究成果,对阿拉善北缘地区古生代沉积地质特征进行分析,探讨其构造演化过程,为中亚造山带的研究工作提供基础资料。阿拉善北缘地区发育了三条重要的断裂带:由北至南分别为雅干断裂带、恩格尔乌苏断裂带(蛇绿岩带)和查干础鲁断裂带(蛇绿岩带),以此三条断裂带为界可以将阿拉善北缘划分四个构造带,由北至南分别为雅干构造带、珠斯楞-杭乌拉构造带、沙拉扎山构造带和诺尔公-狼山构造带。其中珠斯楞-杭乌拉构造带和沙拉扎山构造带内保留了相对较多的沉积记录,诺尔公-狼山构造带则发育有大量的岩浆岩,而雅干构造带处于研究区以外。在珠斯楞-杭乌拉构造带内利用生物化石和碎屑锆石年龄(420±3Ma、419.6±3.6Ma),将圆包山组时代从早志留世重新确定为早志留世-中泥盆世;利用火山岩锆石年龄(284Ma)将方山口组的时代重新厘定为晚二叠世;利用古生物化石和碎屑锆石年龄(最新年龄约为299Ma)确定双堡塘组的时代为早二叠世。本带内发育了两套可以反映构造演化过程的沉积组合。第一套组合为中寒武-下奥陶统西双鹰山组(∈2-O1x)、下志留统班定陶勒盖组(S1b)和早志留世-中泥盆纪圆包山组(S1-D2y),此组合代表了多岛洋向活动大陆边缘演化的过程;第二套组合为下二叠统双堡塘组(P1sb)和下二叠统方山口组(P1f),其沉积序列可以反映出完整的弧后盆地演化过程。通过对本带内沉积岩、火山岩的地球化学特征分析以及前人资料,认为杭乌拉地区在古生代经历了两次大洋的开合过程,第一次大洋闭合于晚泥盆-石炭纪,第二次大洋闭合于中二叠世后。在沙拉扎山构造带内利用沉积学、岩石学和地球化学等综合研究方法,重新厘定了“阿木山组”和“本巴图组”的地层层序。其中,“阿木山组”为查干础鲁弧后盆地的产物,其灰岩段形成于晚石炭世-早二叠世早期,火山岩-砂岩段形成于早二叠世晚期,可能延续到中二叠世。通过对在查干础鲁蛇绿岩带中采集的早二叠世放射虫化石和“阿木山组”沉积、地球化学特征的分析,并结合前人年龄研究成果(该蛇绿岩带中辉长岩年龄为275±3 Ma、乌力吉后碰撞型花岗岩年龄为250.8±2.0Ma),认为查干础鲁蛇绿岩带所代表的大洋闭合时间在275Ma和250Ma之间,即查干础鲁缝合带的形成时间为晚二叠世。而“本巴图组”层位低于“阿木山组”,形成于晚石炭世早期,其沉积序列代表了一个稳定大陆边缘向活动大陆边缘转化的过程。在诺尔公-狼山构造带内利用流纹岩中锆石年龄数据(265.6Ma和267.2Ma),认定苏吉火山岩年龄为中二叠世。根据其火山岩地球化学特征和区域构造资料,认为苏吉火山岩形成于大陆弧环境。通过对古生代地层和沉积地质的详细研究,将研究区的沉积与构造演化划分为五个阶段:①中寒武世-早奥陶世,呼和套尔盖洋内弧和沙拉扎山岛弧逐渐形成,此时杭乌拉地区为处于塔里木板块和呼和套尔盖洋内弧之间的多岛洋,大地构造环境相对稳定。②早志留世-中泥盆世,塔里木板块和呼和套尔盖洋内弧之间的大洋向北部呼和套尔盖洋内弧下俯冲,杭乌拉地区结束了早古生代稳定的大陆环境,逐渐转变为活动大陆边缘(位于呼和套尔盖洋内弧南缘)。③晚泥盆世-早石炭世,杭乌拉地区的大洋在此期间闭合。④晚石炭世-早二叠世,沙拉扎山构造带北部活动大陆边缘和查干础鲁弧后盆地逐渐形成,构成了典型的沟-弧-盆体系。杭乌拉地区受呼和套尔盖北部大洋向南的俯冲作用,形成了弧后盆地。⑤中-晚二叠世,研究区内各大洋开始俯冲消减。中二叠世之后,杭乌拉地区的大洋闭合;晚二叠世,查干础鲁蛇绿岩所代表的大洋闭合;晚二叠世晚期,恩格尔乌苏蛇绿岩所代表的大洋闭合。
[Abstract]:Alashan and its northern margin are located in the southern margin of the middle part of the Central Asian orogenic belt, which are located in the confluence zone between the Sino Korean plate, the Tarim plate and the Siberia plate. It is the intersection of the Tianshan orogenic belt and the Xingmeng orogenic belt. It is the key area for the study of the tectonic evolution of the Central Asian orogenic belt and the final closed history of the ancient Asian Ocean. The predecessors had been to Alashan and its predecessors. The northern margin of the study is mainly focused on the division of structural units, the analysis of the ophiolite and the granite, while the study on the sedimentary geological characteristics in the study area is relatively small, and the time of the geological evolution events in the northern margin of Alashan is also very controversial. The study, geochemistry and zircon chronology, combined with the research results of regional geological survey and previous magmatic rocks, analyzed the Paleozoic sedimentary geological characteristics of the northern margin of Alashan and explored its tectonic evolution process, providing basic information for the research work of the Central Asian mountain zone. Three important developments in the northern margin of Alashan have been developed. The fault zone: from north to south, respectively, the jakan fault zone, the Engel Wusu fault zone (ophiolite belt) and Chagan chadu fault zone (ophiolitic belt). By this three fault zones, the northern margin of Alashan can be divided into four tectonic zones, from north to south, respectively, the jakan tectonic belt, the zhusleng hang URA structural belt, the salad Zhan mountain structural belt and Norway. In the Langshan tectonic belt, there are relatively large deposits of sedimentary records in the Pearl - Leng - hang - URA structural belt and the Sarah Zhishan tectonic belt, while the Norman Langshan tectonic belt is developed with a large number of magmatic rocks, while the JYA Jigan tectonic belt is outside the study area. The age of the fossil and detrital zircons in the Pearl - Leng hang tectonic belt (420 +. 419.6) The era of the Yuan Baoshan formation was redefined from Early Silurian to Early Silurian Middle Devonian, and the age of the volcanic zircon age (284Ma) was redefined to the Late Permian, and the age of the paleontological fossils and detrital zircon ages (the latest age of 299Ma) was determined to be the early Permian. The development of this zone was in the development of the early Permian. Two sets of sedimentary assemblages that can reflect the tectonic evolution process, the first set of assemblages are the Middle Cambrian and the lower Ordovician Double Eagle mountain group (2-O1x), the Lower Silurian class Dingtao Le Gu group (S1b) and the Early Silurian - Mian Baoshan Group (S1-D2y). This assemblage represents the evolution of the multi island ocean to the active continental margin; the second sets are the lower two. The sedimentary sequence of the double Fort pond formation (P1sb) and the lower two series of the square Yamaguchi formation (P1f) can reflect the complete evolution process of the back arc basin. Through the analysis of the geochemical characteristics of the sedimentary rocks and volcanic rocks in the present belt and the previous data, it is believed that the region of Hangzhou has experienced two oceanic opening and closing processes in the Palaeozoic, and the first Ocean was closed in the late mud. In the Basin Carboniferous period, the second ocean was closed after the Middle Permian. In the salzhashan tectonic belt, the stratigraphic sequence of the "A Mu mountain formation" and the "Ben Bartle group" was redefined by the comprehensive research methods of sedimentology, petrology and geochemistry. Among them, the "A Mu mountain formation" was the product of the chashanlu back arc basin, and the limestone section was formed late in the late period. Early Permian in the Carboniferous - Early Permian, volcanic rock sandstone segments were formed in the Late Permian Early Permian, possibly extending to the Middle Permian. The geochemical characteristics of the early Permian radiolarian and the "A Mu mountain formation" collected in Chagan chchic ophiolitic belt were analyzed and combined with the research results of the age of the former (the age of gabbro in the ophiolite belt. The age of age is 275 + 3 Ma, and the age of post Uligi collision type granite is 250.8 + 2.0Ma. It is considered that the ocean closure time of the chchinacinu ophiolite belt is between 275Ma and 250Ma, that is, the formation time of chchacinu suture zone is late Permian. The "Ben Bartle group" layer is lower than the "A Mu mountain" formation and formed in the Early Carboniferous. The column represents a process of transformation from a stable continental margin to the active continental margin. In the Norway Langshan tectonic belt, using zircon age data in rhyolite (265.6Ma and 267.2Ma), the Suji volcanic rocks are identified as the Middle Permian. According to their geochemical characteristics and regional tectonic data, the Suji volcanic rocks are considered to be formed in the continent. Arc environment. Through the detailed study of Paleozoic strata and sedimentary geology, the sedimentary and tectonic evolution of the study area are divided into five stages: (1) the Middle Cambrian Early Ordovician, the Huhe and shigai ocean inner arc and the Sarah Zhan island arc gradually formed, and the hang URA region is a multi island between the Tarim plate and the inner arc of the call and the shigai ocean. The tectonic environment of the ocean is relatively stable. (2) the Early Silurian Middle Devonian, the Tarim plate and the inner arc of the inner arc of the inner arc of the Huhh and shigigai ocean, and the subduction of the inner arc of the neigen ocean. The early Paleozoic continental environment was finished in the hang URA region, and gradually transformed into the active continental margin (located in the southern margin of the Huhe and shigai ocean inner arc). In the late Devonian Early Carboniferous period, the ocean in the hang URA region closed during this period. (4) the Late Carboniferous Early Permian, the northern active continental margin of the shagzhan tectonic belt and the Chagan chchidu back basin gradually formed, forming a typical trench arc basin system. After the middle and Late Permian, the ocean in the study area began to subduction. After the Middle Permian, the ocean was closed in the hang URA region; the Late Permian was closed by the Chagan chchidu ophiolite, and the oceanic closure represented by the Engel URU ophiolite in the Late Permian.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P534.4;P548

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