内蒙古阿拉善巴音诺尔公一带二叠纪侵入岩地质特征

发布时间：2018-06-10 14:07

本文选题：阿拉善地区 + 二叠纪　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：阿拉善地块北缘晚古生代岩浆活动非常强烈,其成因研究对分析华北板块与塔里木板块的碰撞演化过程具有重要的意义。研究区位于内蒙古西部,大地构造位置为华北板块西北缘,本文主要对内蒙古阿拉善左旗巴音诺尔公一带出露的早二叠世侵入岩进行研究,通过收集和研究前人资料,在野外观察的基础上,对岩石学,岩石化学和年代学进行研究,讨论其形成时代和大地构造环境。研究区早二叠世岩浆活动以辉长岩、花岗闪长岩、二长花岗岩和正长花岗岩为主,本文主要研究早二叠世花岗闪长岩、二长花岗岩和正长花岗岩。从岩石的化学特征上上看,研究区巴音诺尔公一带的花岗闪长岩、二长花岗岩和正长花岗岩均属高钾钙碱性系列。同时富集轻稀土和大离子Rb、Th、K等亲石元素,亏损Nb、Ta、Sr、Ti等高场强元素,这些地球化学特征显示早二叠世华北板块北缘处于古亚洲洋的俯冲作用之下。其中对花岗闪长岩样品进行进行LA-ICP-MS锆石U-Pb法测年,获得的加权平均年龄为278.1±1.2 Ma;二长花岗岩的加权平均年龄范围为277.84±0.9 Ma;正长花岗岩的加权平均年龄范围值在289.53±0.74 Ma;以上测年数据表明研究区主要岩体形成时代为早二叠世。从岩石的地球化学特征上看,岩石的A/CNK值平均小于1.1,岩石中常见黑云母、磁铁矿,角闪石,矿物组合中出现q、or、ab、an、c、hy的CIPW标准矿物组合形式,这些特点反映了研究区花岗岩I型花岗岩的特征。从地质资料可知,阿拉善北部地区幔源岩浆强烈参与了二叠纪的岩浆活动,这一时期该地区可能形成于俯冲作用下的岩浆弧。构造环境判别图解也显示研究区花岗岩从总体上讲形成与俯冲作用过程有关,是幔源和壳源混合源的。
[Abstract]:The late Paleozoic magmatic activity in the northern margin of the Alashan massif is very strong. Its genetic study is of great significance to the analysis of the collision and evolution process of the North China plate and the Tarim plate. The study area is located in the western Inner Mongolia and the geodetic tectonic position is the northwest margin of the North China plate. This paper is mainly exposed to the Inner Mongolia Alashan Left Banner. The early Permian intrusive rocks were studied. On the basis of the collection and study of previous data, the petrology, petrochemistry and chronology were studied on the basis of field observation. The formation age and tectonic environment were discussed. The early Permian Magmatism in the study area was mainly gabbro, granodiorite, two granitic and syenite. The early Permian granodiorite, two long granite and syenite are mainly studied. From the chemical characteristics of the rocks, the granite diorite, the two long granite and the syenite are all high potassium calc alkaline series in the study area, and the rich rare earth and the Rb, Th, K and other feldspar elements are enriched, and the loss of Nb, Ta, Sr, Ti and so on is high. These geochemical characteristics show that the northern margin of the North China plate in the early Permian is under the subduction of the ancient Asian Ocean. Among them, the LA-ICP-MS zircon U-Pb dating of the granodiorite samples was carried out with a weighted average age of 278.1 + 1.2 Ma, and the average age range of the two granitic granite was 277.84 + 0.9 Ma; The weighted average age range of the granites is 289.53 + 0.74 Ma, and the above dating data indicates that the main rock mass in the study area is early Permian. From the geochemical characteristics of the rock, the A/CNK value of the rock is less than 1.1, and the common biotite, magnetite, hornblende, and mineral assemblage in the rock appear Q, or, AB, an, C, hy. These characteristics reflect the characteristics of granite I granite in the study area. From geological data, the mantle derived magma in northern Alashan has been strongly involved in the Permian magmatic activity. This area may be formed in the subduction of magma arc in this period. It is said that the formation is related to the process of subduction, and is the mixed source of mantle source and crust source.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.12

【共引文献】