新疆东准噶尔北部岩浆岩岩石地球化学研究

发布时间：2018-07-12 16:19

本文选题：岩浆岩 + 岩石学　；参考：《昆明理工大学》2015年硕士论文

【摘要】：根据全球大地构造板块学说,研究区位于全球大型造山带—乌拉尔—蒙古造山带的中心位置,是全球范围内较典型的造山带,同时也位于西伯利亚陆块和哈萨克斯坦地块的接合部位,而且属于天山—兴安地槽褶皱的一部分。出露地层较全,有下、中泥盆统和下、中石炭统,同时还出露奥陶系,新生界的分布较广。科克库都克、阿克塔斯、克乃特地区位于新疆东准噶尔北部,开展三个地区火山岩、花岗岩的研究对于综合分析地质历史时期东准噶尔北部的大地构造背景具有重要的理论意义。本文通过收集前人的资料和研究成果,运用矿物学、岩石学、地球化学、同位素年代学等学科理论,选取阿克塔斯和科克库都克的火山岩以及克乃特地区的花岗岩进行研究探讨。通过野外和室内的深入研究,本文归纳总结了该区域的岩浆岩岩石学特征、地球化学特征、年代学特征。根据火山岩类的主量元素TAS图解、SiO2-AR图解、A/NK-A/CNK图解和K2O-SiO2图解,同时结合薄片的镜下鉴定结果,分析得出科克库都克、阿克塔斯两个地区火山岩主要以基性-中性为主,进一步确定为准铝质、碱性-钙碱性-高钾钙碱性-钾玄质玄武岩-安山玄武岩-粗面岩-粗面安山岩-粗面英安岩系列。克乃特地区的岩性及原岩主要是钙碱性准铝质-过铝质花岗岩-花岗闪长岩-闪长岩。根据稀土元素球粒陨石配分曲线得知,轻稀土配分曲线相对倾斜、重稀土元素配分曲线比较平缓,基本呈现水平状态。轻重稀土分馏都比较弱,属于弱分异或基本不分异。稀土元素球粒陨石标准化图和微量元素原始地幔标准化蜘蛛网图解均呈右倾的“W”型,元素由左至右,先发散,后集中；岩石相对富集U、Pb,明显正异常；相对亏损Th、Nb、Ce、Pr,明显的负异常,显示出岛弧岩浆的特征。该地区岩浆岩206Pb/238U年龄加权平均值为388.0Ma±6.7Ma、303-397Ma等,表明火山岩形成事件主要在晚古生代的泥盆纪、石炭纪。岛弧岩浆岩来源于俯冲板块滑动过程中产生的流体交代地幔物质而形成的含水的流体,其高场强元素较低,岩浆主要为地幔演化的产物,并含有地壳物质的混染。
[Abstract]:According to the global tectonic plate theory, the study area is located at the center of the large orogenic belt, Ural-Mongolia orogenic belt, and is a typical orogenic belt in the world. It is also located at the junction of the Siberian and Kazakh blocks and is part of the Tianshan-Xingan geosyncline fold. The outcrop strata are relatively complete, there are lower, middle Devonian and Lower Carboniferous, and also the Ordovician, the Cenozoic is widely distributed. The Kirk Kuduk, Aktas, and Kenet regions are located in the northern part of East Junggar, Xinjiang, where volcanic rocks are developed in three areas. The study of granites is of great theoretical significance for the comprehensive analysis of the tectonic setting in the northern part of East Junggar during the geological history. In this paper, by collecting the previous data and research results, we apply the theories of mineralogy, petrology, geochemistry, isotopic chronology, etc. The volcanic rocks of Aktas and Kirk Kuduk and the granite in Knut area are selected to study. In this paper, the petrology, geochemistry and geochronology of magmatic rocks in this area are summarized through field and laboratory studies. According to the principal elements of volcanic rocks, such as TAS diagram, SiO2-AR diagram, A / NK-A / CNK diagram and K _ 2O-SiO _ 2 diagram, combined with the microscopic identification results of the thin sheet, it is concluded that the volcanic rocks in Kirk Kuduk and Aktas are mainly basic-neutral. The series of pseudo-aluminite, alkaline-calc-alkaline-high-potassium-calc-alkaline-kalabinite-anshan basalt-rough andesite-trachyte-trachyte are determined. The lithology and primary rocks of Knite area are mainly calc-alkaline quasi-aluminite peraluminous granite granodiorite diorite. According to the chondrites distribution curve of rare earth elements, the light rare earth distribution curve is relatively inclined, the heavy rare earth element distribution curve is relatively smooth, and the distribution curve of heavy rare earth elements is basically horizontal. Light and heavy rare earth fractionation are relatively weak, belong to weak differentiation or basic non-differentiation. The normalized maps of chondrites and trace elements in the primitive mantle are all "W" type with the elements from left to right, which diverge first and then concentrate, and the rocks are relatively enriched with UPb, which is obviously positive anomaly. The relative depletion of ThnbCe Pris is obviously negative anomaly, which shows the characteristics of island arc magma. The weighted average of 206Pb / 238U age of magmatic rocks in this area is 388.0 卤6.7 Ma, 303-397Ma, which indicates that the formation events of volcanic rocks mainly occurred in late Paleozoic Devonian and Carboniferous. The island arc magmatic rocks are derived from the fluid metasomatism of mantle materials produced during the subduction plate sliding, and the high field strength elements are lower. The magma is mainly the product of mantle evolution and contains the mixed contamination of crustal materials.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.1

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