东昆仑东段沟里地区早古生代火山岩地质特征、形成时代及构造环境研究

发布时间：2018-04-01 06:54

本文选题：沟里地区　切入点：变火山岩　出处：《长安大学》2015年硕士论文

【摘要】：东昆仑造山带具有漫长的演化历史,是一条复合的大陆造山带,其中包括多条重要的构造缝合带。本论文以现代板块构造学理论为指导思想,从地质客观实际出发,主要针对东昆仑造山带东段沟里地区龙洼卡鲁、智玉西侧和山金矿业南侧火山岩进行详细的地质特征、岩石地球化学特征及LA-ICP-MS锆石U-Pb同位素年代学等方面的综合研究,结合区域地质背景对其形成时代、岩石成因、构造环境归属和东昆仑造山带东段早古生代构造演化特征进行探讨,为查明中央造山系和东特提斯构造域早古生代以来的板块构造格局和恢复重建其演化进程提供依据。取得以下主要进展和认识:1、龙洼卡鲁火山岩岩性主体为变基性火山岩(变玄武岩),夹少量变安山岩,变质程度较低。地球化学特征显示龙洼卡鲁变基性火山岩为拉斑玄武岩,兼具岛弧和大洋中脊特征,岩浆来源于富集地幔,变玄武岩主体上为地幔岩部分熔融的结果,形成于由俯冲作用引起弧后盆地构造环境,并获得变玄武岩中锆石U-Pb年龄为442.0±5.4Ma,该年龄为变玄武岩的结晶年龄,表明龙洼卡鲁变玄武岩的形成时代为早志留世初。该结晶年龄限制了变基性火山岩的时代归属,确定了与其相伴生的碳酸盐岩是不同时代的产物。2、确定了智玉西侧变火山岩岩性主要为变玄武岩,变质程度低,达低绿片岩相,地球化学特征显示出亚碱性拉斑玄武岩系列特征。稀土元素和微量元素都表现出与龙洼卡鲁变玄武岩相似的特征,确定为弧后拉张环境的产物。通过岩石组合和构造环境与区域上地层相对比,把该套火山岩归属于纳赤台岩群。3、确定了山金矿业南侧变火山岩岩性为一套变中-中酸性火山岩(变安山岩与变英安岩),变质程度相对较高,部分达高绿片岩相。地球化学特征上,变中-中酸性火山岩表现出LREE富集程度远高于变玄武岩;在微量元素中表现出富集LILE,Nb、Ta等元素的相对亏损,表现出类似岛弧的特征,变中-中酸性岩是属于壳幔混合作用的产物。通过前人获得同位素年龄,结合岩石组合与区域上地层相对比,确定了该套火山岩归属于纳赤台岩群。4、根据沟里地区龙洼卡鲁、智玉西侧及山金矿业南侧火山岩的性质,并结合东昆仑东段区域地质资料,探讨东昆仑地区演化史。东昆仑地区在新元古代末处于裂解阶段,产生大量火山岩;早寒武世早期,东昆仑地区存在着原特提斯洋壳,并在中寒武世,原特提斯洋向北发生俯冲,随着俯冲强度的增大,导致东昆仑地区拉张成弧后小洋盆,出现以清水泉-可可沙-科科可特为代表的蛇绿岩组合,该阶段形成了纳赤台岩群及龙洼卡鲁变火山岩系;中-晚志留世东昆仑地区分别经历了原特提斯洋俯冲造山与碰撞造山;晚志留世-早泥盆世以和勒冈那仁岩体的形成为代表,表明了东昆仑地区开始向较为稳定的陆内构造演化阶段转化。最终以牦牛山组的出现,标志着早古生代原特提斯构造域演化的彻底结束。
[Abstract]:With the evolution history of the East Kunlun orogenic belt, is a composite of the continental orogenic belt, including a number of important tectonic suture zone. This paper takes modern plate tectonics theory as the guiding ideology, from the geological objective reality, mainly to the east of Eastern Kunlun orogenic belt, ditch area south of the Jade Dragon wa Carew, Chi west the mountain and the volcano rock gold mining geological features detailed, comprehensive study of rock geochemistry and LA-ICP-MS zircon U-Pb isotopic chronology and other aspects, combined with the regional geological background of the formation age, petrogenesis, Eastern Early Paleozoic tectonic evolution characteristics of tectonic environment and the East Kunlun orogenic belt, in order to find out since the early Paleozoic Central Orogenic and the eastern Tethys tectonic framework and its evolution process provides the basis for restoration and reconstruction. The following major progress and understanding: 1, dragon wa Carew The main lithology volcano rock metabasic volcano (Xuan Wuyan), with a small amount of variable andesite, lower metamorphic grade. Geochemical characteristics show that the Dragon wa Karoo metabasic volcano tholeiitic Xuan Wuyan, with the characteristics of island arc and oceanic ridge, magma derived from the enriched mantle, the basalt body for partial melting of mantle rocks, formed by subduction caused by back arc basin tectonic environment, and change the zircon U-Pb age of Xuan Wuyan was 442 + 5.4Ma, the age variable crystallization age of Xuan Wuyan, that Xuan Wuyan Carew variable long depression were formed in the Early Silurian. The crystallization age restricted metabasic the age of volcano rock, carbonate rock and determine the associated are the products of different times.2, the Chi jade West variable volcano lithology is mainly Xuan Wuyan, low metamorphic degree, of low greenschist facies, geochemical characteristics show A tholeiitic series. The characteristics of REE and trace elements are shown with the Dragon wa Karoo alteration basalt similar characteristics, determine the product of back arc extensional environment. The rock assemblage and tectonic environment and regional upper layer compared to the volcano rock, red rock group from Taiwan belong to.3, determine on the south side of the mountain of gold industry becomes a volcano rock lithology change - acidic volcano rock (dacite and andesite variable variable), the degree of metamorphism is relatively high, some high greenschist facies. The geochemical characteristics, change in - acidic volcano rock show LREE enrichment degree is much higher than the variable performance of basalt; the enrichment of trace elements in LILE, in Nb, relatively depleted in Ta elements, showing similar characteristics of island arc, in - acid rock is a product which belongs to the crust mantle mixing. Isotope age by predecessors, combined with the rock combination and regional upper layer relative Is to determine the set of volcano rock belongs to Nachitai rock group.4, according to the ditch area dragon wa Carew, nature South and West Mountain volcano rock wisdom jade gold mining industry, and combined with the eastern section of East Kunlun regional geological data, explore the evolution history of the eastern regions of Kunlun. The East Kunlun area in the late Neoproterozoic in cleavage stage, resulting in a large number of volcano rock; Early Cambrian, Eastern Kunlun region exists Dhi Te Tis oceanic crust, and in the Middle Cambrian, proto Tethys northward subduction subduction, with increasing strength, leading to small ocean basin in eastern Kunlun to pull Zhang Chenghu, appeared in the Qingshuiquan - kekesha - Kekekete as the representative of the snake the stage of formation of the ophiolite combination, Nachitai rock group and long depression volcano rocks in the Karoo change; late Silurian in eastern Kunlun area experienced a proto Tethys subduction orogenic collision and orogeny; late Silurian Early Devonian to Gangnaren rock and le The formation indicates that the East Kunlun area began to transform to a relatively stable stage of intra continental tectonic evolution. Finally, the appearance of yyushan formation marks the complete end of the evolution of the early Paleozoic Tethyan tectonic domain.

【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】：P588.14

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