内蒙古额济纳旗大扎干敖包花岗岩类研究

发布时间：2018-06-02 08:44

本文选题：内蒙古 + 花岗岩　；参考：《长安大学》2015年硕士论文

【摘要】：内蒙古额济纳旗位于华北板块西部,花岗岩广泛分布,近年来在阿拉善北缘发现了一些花岗岩多形成于晚古生代,这与以往的认识有所不同。本论文在野外地质填图的基础上对阿拉善拐子湖地区大扎干敖包花岗岩类开展了详细的岩石学、年代学、地球化学等综合研究,并探讨了其岩石成因与构造环境。本区花岗质岩石形成年龄在270Ma之间,为二叠纪侵入体,岩性主要为深灰色细粒闪长岩,浅肉红色-灰白色中粒二长花岗岩,灰白色似斑状黑云母花岗岩,肉红色细粒钾长花岗岩。岩体全部为准铝质-弱过铝质,钙碱性-高钾钙碱性系列,不含白云母、堇青石等矿物,暗色矿物主要以黑云母为主,有极其少量的角闪石,表明本区花岗岩主要为I型深熔成因花岗岩,物质来源于地壳物质的熔融,闪长岩物质来源于地幔物质。本区花岗岩类岩浆演化顺序从早到晚依次为926高地浅肉红色中粒二长花岗岩-927.1高地灰白色似斑状黑云母花岗岩-946高地肉红色细粒钾长花岗岩,岩体表现为轻稀土元素、大离子亲石元素(Rb、Th等)富集,重稀土元素、高场强元素(Nb、Ta、Ti、P等)亏损。本区花岗岩类是具有火山弧地球化学特征的后碰撞花岗岩质岩石,在早二叠世,以恩格尔乌苏蛇绿岩为代表的古亚洲洋向南俯冲形成的沟弧盆体系和本区的弧后盆地已经闭合,形成了具有岛弧特征的新增陆壳,在早二叠世,已经进入了后碰撞造山阶段。
[Abstract]:Ejina Banner of Inner Mongolia is located in the western part of North China plate, and granite is widely distributed. In recent years, some granites were found in the northern margin of Alashan, most of which were formed in the late Paleozoic, which is different from previous understanding. On the basis of field geological mapping, detailed petrology, geochronology and geochemistry have been carried out on the granitoids of Dazhagan Aobo in Guizi Lake area, Alashan. The petrogenesis and tectonic environment of the granites have also been discussed. The granitic rocks are mainly dark gray fine-grained diorite, grayish reddish grayish-gray-white monzonitic granites and gray-white porphyry biotite granites, and the granitic rocks are formed at the age of 270Ma and are Permian intrusive bodies, and their lithology is mainly dark gray fine-grained diorite. Meat-red fine-grained potassium feldspar granite. All the rock bodies are quasi-aluminum-weakly peraluminous, calc-alkaline-high-potassium calc-alkaline series, do not contain Muscovite, cordierite and other minerals, dark minerals are mainly biotite, with a very small amount of hornblende, The results show that the granites in this area are mainly type I deep-melt granites with materials derived from the melting of crustal materials and diorite materials from mantle materials. The magmatic evolution sequence of granitic magma in this area is from early to late in the order of grayish white porphyry biotite granitic potash feldspar granitic granites of highlands 926 highlands with light rare earth elements. The heavy rare earth elements and high field strength elements are depleted. Granitoids in this area are post-collisional granite rocks with volcanic arc geochemical characteristics. In the early Permian, the trench arc basin system formed by the subduction of the ancient Asian oceanic ophiolite, represented by the Englesu ophiolite, and the back-arc basin in this area have been closed. The new continental crust with the characteristics of island arc has entered the post-collision orogenic stage in the early Permian.
【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】：P588.121

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