东昆仑南缘布青山可可尔塔地区花岗岩地质特征及构造属性研究

发布时间：2018-06-25 23:18

本文选题：东昆仑 + 布青山构造混杂岩带　；参考：《长安大学》2015年硕士论文

【摘要】：阿尼玛卿—布青山构造带位于东昆仑造山带、西秦岭造山带、巴颜喀拉造山带交接地区,是研究中国大陆构造及其大陆动力学的关键地区。本文选择东昆仑南缘布青山构造混杂岩带中的可可尔塔地区花岗岩体作为研究对象,通过详细的野外地质调查、构造地质学、岩石学、岩石地球化学及同位素年代学等方面的研究,并以板块构造学说、大陆动力学的最新成果及理论为指导思想,结合前人研究资料对可可尔塔地区花岗岩的形成时代、构造环境及布青山地区早古生代的构造演化进行探索,得出以下认识:1.可可尔塔南浅灰色中细粒似斑状黑云母花岗闪长岩侵位于中元古界苦海岩群(Pt2K)之中,地球化学特征显示铝饱和指数A/CNK值介于1.01~1.09之间,为弱过铝质高钾钙碱性系列I型花岗岩;稀土元素总量偏低,轻稀土富集,具较弱的Eu负异常,与岛弧钙碱性岩浆系列相似,岩体形成于与俯冲有关的岛弧环境或陆弧环境。利用LA-ICP-MS锆石U-Pb定年,结果表明:可可尔塔南中细粒似斑状黑云母花岗闪长岩的成岩年龄为422.5±1.2Ma(MSWD=0.53),为晚志留世。2.可可尔塔北浅灰-灰白色细粒黑云母花岗闪长岩侵位于中元古界苦海岩群(Pt2K)之中。地球化学特征显示,铝饱和指数A/CNK值介于1.05~1.09之间,平均1.07,为弱过铝质中钾钙碱性系列I型花岗岩;岩石地球化学特征显示其源区为加厚下地壳的玄武质岩石熔融形成,且其受到地幔楔的混染。利用LA-ICP-MS锆石U-Pb定年,结果表明:可可尔塔北细粒黑云母花岗闪长岩的成岩年龄为403±2Ma(MSWD=2.2),为早泥盆世,形成于碰撞向后碰撞过渡的构造环境。3.禾日沟贡玛浅灰色中细粒块状花岗闪长岩出露于二叠纪马尔争组(P1-2m)地层之中,与两侧地层呈断层接触关系。地球化学特征显示为中钾钙碱性系列,铝饱和指数A/CNK值为1.084,为弱过铝质I型花岗岩;岩石地球化学特征表明其岩浆为加厚下地壳富Na基性玄武质岩石熔融形成,并受到地幔楔的混染。利用LA-ICP-MS锆石U-Pb定年,结果显示,禾日沟贡玛中细粒块状花岗闪长岩的成岩年龄为398±2Ma(MSWD=2.2),为早泥盆世,形成于碰撞向后碰撞过渡的构造环境。综合研究表明禾日沟贡玛中细粒块状花岗闪长岩与可可尔塔北细粒黑云母花岗闪长岩具有相似的岩石学和地球化学特征,其形成时代基本一致,可能代表同一期次的构造岩浆事件,形成的构造环境一致。4.东昆仑南缘地区存在早古生代的洋-陆转换,晚志留世-早泥盆世是该区的主造山时期。可可尔塔地区花岗岩体的形成可能与东昆仑地区早古生代洋-陆转化及陆-陆碰撞造山作用相关。
[Abstract]:The Animaching-Buqingshan tectonic belt is located at the junction of the East Kunlun orogenic belt, the West Qinling orogenic belt and the Bayankala orogenic belt, which is the key area for the study of continental tectonics and continental dynamics in China. In this paper, the granitic body of the Keerta area in Buqingshan tectonic melange belt in the southern margin of East Kunlun is selected as the research object. Through detailed field geological survey, structural geology, petrology, Rock geochemistry and isotopic chronology, with plate tectonics, the latest achievements and theories of continental dynamics as the guiding ideology, combined with previous research data, to study the formation age of granites in the Kerta area, The tectonic environment and the early Paleozoic tectonic evolution in Buqingshan area were explored. Calcareous granodiorite intrusions in the Mesoproterozoic Kuhai Group (Pt2K) are located in calcareous granodiorite transgression of grayish gray-grained medium grain-like granodiorite in Cooltanan. The geochemical characteristics show that the Al saturation index A / CNK is between 1.01and 1.09, and is a weakly peraluminous high-potassium calc-alkaline series I-type granite. The total amount of rare earth elements is low, the LREE is enriched, with weak EU negative anomaly, similar to the island arc calc-alkaline magma series, and the rock body is formed in the subduction-related island arc environment or continental arc environment. Using LA-ICP-MS zircon U-Pb dating, the results show that the diagenetic age of the granodiorite is 422.5 卤1.2 Ma (MSWD0. 53), which is the late Silurian. The granodiorite intrusion of caltabean granodiorite is located in the Middle Proterozoic Kuhai Group (Pt2K). The geochemical characteristics show that the Al saturation index (A / CNK) is between 1.05 and 1.09, with an average value of 1.07, which is a weakly peraluminous medium potassium calc-alkaline series I-type granite, and the petrogeochemical characteristics indicate that the source area is the melting formation of Black Tortoise rocks in the thickened lower crust. And it is mixed by mantle wedge. Using LA-ICP-MS zircon U-Pb dating, the results show that the diagenetic age of the granodiorite is 403 卤2Ma (MSWDU 2.2), which was formed in the tectonic environment of collision to collision transition. The grain-grained granodiorite of Gongma in Heligou is exposed to the Permian Marjean formation (P1-2m) and is in contact with both sides of the formation. The geochemical characteristics show that it is a medium potassium calc-alkaline series, and the Al saturation index A / CNK is 1.084, which is a weakly peraluminous I-type granite. The geochemical characteristics of the rocks indicate that the magma is formed by melting of the thickened lower crust, which is rich in Na basic-type Black Tortoise rocks. And by the mantle wedge mixed dye. Using LA-ICP-MS zircon U-Pb dating, the results show that the diagenetic age of fine-grained granodiorite in Gongma is 398 卤2Ma (MSWD2. 2), which is an early Devonian and formed in the tectonic environment of collision to collision transition. The comprehensive study shows that the granodiorite and the granodiorite in the medium and fine grained granodiorite of Heligou Gongma have similar petrological and geochemical characteristics, and their formation age is basically the same. It is possible that the tectonic magma events of the same period are formed in the same tectonic environment. 4. The early Paleozoic ocean-land transition occurred in the southern margin of East Kunlun, and the late Silurian and early Devonian were the main orogenic periods. The formation of granitic bodies in the Keerta area may be related to the early Paleozoic ocean-land transformation and land- continent collision orogeny in the East Kunlun area.
【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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