东昆仑祁漫塔格阿确礅地区古生代花岗岩成因及大地构造意义

发布时间：2018-03-13 02:18

本文选题：阿确礅地区　切入点：花岗岩　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：祁漫塔格地区位于东昆仑造山带西段,同时也是中央造山带重要组成部分。近年来在东昆仑东段发现一系列的早古生代晚期的高压-超高压岩石,因此如何重新认识东昆仑造山带早古生代的构造演化过程显得尤为重要。花岗岩形成于造山带的不同时期,不同类型的花岗岩包含造山作用阶段的大量地质信息。探讨花岗岩的源岩特征和成因,有助于追索地壳中各种物质含量、造山过程中动力演化及造山过程中壳幔物质交换作用等问题。东昆仑西段祁漫塔格阿确礅地区出露大量花岗质岩体。本文选取奥陶纪、泥盆纪花岗岩作为研究对象,对其开展锆石LA-ICP-MS U-Pb测年和相应的地球化学研究。同时结合前人认识和项目组研究成果,对祁漫塔格阿确礅地区花岗岩的形成时代、岩石成因和大地构造背景方面进行讨论。帕奇通奥陶纪岩体主要由辉石闪长岩和二长花岗岩组成。二者呈涌动式接触关系,同时闪长岩以包体形式产出与二长花岗岩中。其中辉石闪长岩获得年龄为452±2.5Ma,二长花岗岩形成年龄为448±5.4Ma。二者为晚奥陶世岩浆活动的产物。辉石闪长岩和二长花岗岩均表现出类似岛弧I型花岗岩特征。如富集LREE,富集大离子亲石元素(Rb、Ba等),亏损Nb-Ta、Ti等。帕奇通奥陶纪岩体为I型花岗岩,形成于岛弧俯冲消减环境,与祁漫塔格洋盆俯冲相关,代表了俯冲阶段。滩北山岩体的岩石类型包括二长花岗岩和英云闪长岩,其中二长花岗岩和英云闪长岩锆石测年得到384±4.6 Ma、393±4.9Ma,反映侵位时代为中泥盆世。二长花岗岩和英云闪长岩元素研究表明,为准铝质-过铝质的高钾钙碱性,I型花岗岩,为后造山伸展阶段幔源岩浆同化地壳物质的产物。综合区域地质研究结果,祁漫塔格地区在早古生代-晚古生代早期构造演化过程,大致经历三个构造阶段,寒武-奥陶纪洋-陆俯冲阶段,主要以发育大量类似I型弧花岗岩;志留纪-早泥盆世碰撞造山阶段,主要以区域上发育一系列高压-超高压变质岩;泥盆纪造山后伸展阶段,主要以牦牛山组磨拉石建造以及A型花岗岩为标志。
[Abstract]:The Qimantage area is located in the western part of the East Kunlun orogenic belt and is also an important part of the central orogenic belt. In recent years, a series of high-pressure and ultra-high pressure rocks have been discovered in the eastern part of East Kunlun in the late early Paleozoic. Therefore, it is important to re-understand the tectonic evolution of the East Kunlun orogenic belt in the early Paleozoic. The granites were formed in different periods of the orogenic belt. Different types of granites contain a great deal of geological information about the orogenic stage. It is helpful to trace the contents of various materials in the crust by discussing the characteristics and genesis of the source rocks of the granites. Dynamic evolution during orogeny and material exchange between crust and mantle during orogeny. A large number of granitic rocks were exposed in the western Qiman Tagaqog Pier area of East Kunlun. In this paper, Ordovician and Devonian granites are selected as research objects. Zircon LA-ICP-MS U-Pb dating and corresponding geochemical studies have been carried out on it. Combined with previous understanding and project team research results, the formation age of granites in the Qiman Taggoqog block area has been studied. The Pagitong Ordovician rock body is mainly composed of pyroxene diorite and monzomorphic granite. At the same time, diorite was produced in the form of inclusions and in monzomorphic granite. The age of pyroxene diorite was 452 卤2.5 Ma. and the age of formation of dicyanite was 448 卤5.4 Ma. both of them were the product of late Ordovician magmatic activity, and pyroxene diorite and monzomorphic granite were the products of magmatic activity in late Ordovician. All of them show similar characteristics of island-arc I type granites, such as LREE enrichment, large ion lithophile element Rbnba and so on, depleted Nb-Taanti, etc. The Pachitong Ordovician granites are I-type granites, and the Pakitong Ordovician granites are I-type granites. Formed in the subduction environment of island arc and associated with the subduction of the Qimantage ocean basin, it represents the subduction stage. The rock types of the Tandbeishan rock body include monzogranite and dolomite diorite. The zircon dating of the monzogranites and the dolomite shows 384 卤4.6 Ma- 393 卤4.9 Ma. which reflects that the emplacement age is the Middle Devonian. The study of the elements of the monzogranites and the dolomite diorites shows that the quasi-aluminum-peraluminous high-potassium calc-alkaline granites are of the type I. It is the product of mantle magma assimilating crustal material in post-orogenic extensional stage. Based on the results of regional geological studies, Qimantage area experienced three tectonic stages during the early Paleozoic to early late Paleozoic tectonic evolution. The Cambrian-Ordovician ocean-continental subduction stage mainly developed a large number of I-like arc granites; the Silurian early Devonian collisional orogenic stage mainly developed a series of high-pressure and ultra-high pressure metamorphic rocks; the Devonian post-orogenic extension stage, It is mainly marked by the Molashi formation of the Yak Niushan formation and the A-type granite.
【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】：2017
【分类号】：P588.1;P548

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