新疆阿尔泰喀纳斯地区早古生代火山岩地质特征及构造意义

发布时间：2018-03-02 23:16

本文选题：火山岩　切入点：地球化学　出处：《新疆大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文着重从岩石学、地球化学角度对喀纳斯地区早古生代火山岩进行系统的讨论,同时对火山岩的分布组合、形成环境及形成时代进行了探讨和全面认识。借助地球化学数据的分析和对比研究为该区古生代地质演化研究提供重要的依据。喀纳斯地区发育一套火山-沉积地层东锡勒克组,由于缺少可靠的年龄和地球化学数据,使其形成时代及地球动力学背景长期存在争议。为探讨这一问题,本次工作选择区内火山岩作为研究对象,对糜棱岩化英安岩进行锆石LA-ICPMS U-Pb同位素定年,得到两个样品的~(206)U/~(238)Pb年龄分别为445.4±3.1Ma和445.7±3.7Ma,代表火山岩结晶年龄为晚奥陶世。这表明东锡勒克组地层形成于晚奥陶世。火山岩SiO_2含量为53.99%~71.04%,具有富铝(Al_2O_3=13.83%~16.27%),贫镁(MgO=1.09%~3.53%),K_2O介于1.11%~3.83%之间,平均为2.84%,属于高钾质火山岩系列的特征。轻稀土富集,Eu负异常(δEu=0.65~0.82);岩石地球化学研究表明,火山岩富集大离子亲石元素(Rb、Th、Ce)和亏损高场强元素(K、Nb、Ta),具有岛弧火山岩特征。结合区域资料及本文成果,笔者认为,该套火山岩形成于活动大陆边缘洋壳俯冲消减后期同碰撞的环境。晚奥陶世末古亚洲洋由南向北向西伯利亚板块之下俯冲形成具有活动大陆边缘弧性质的喀纳斯地区晚奥陶世火山岩。
[Abstract]:In this paper, the early Paleozoic volcanic rocks in Kanas area are systematically discussed from the viewpoint of petrology and geochemistry, and the distribution and assemblage of volcanic rocks are also discussed. The formation environment and age of formation are discussed and fully understood. The analysis and comparative study of geochemical data provide an important basis for the study of Paleozoic geological evolution. A set of volcanic-sedimentary development in Kanas area. Formation of East Sirk formation, Due to the lack of reliable age and geochemical data, the age of formation and geodynamic background have been disputed for a long time. In order to study this problem, volcanic rocks in this area are selected as the research objects. Zircon LA-ICPMS U-Pb isotopic dating of mylonitic dolomite is carried out. The two samples were obtained at the ages of 445.4 卤3.1 Ma and 445.7 卤3.7 Ma, respectively, representing the crystallization age of the volcanic rocks in the late Ordovician. This indicates that the formation of the East Silerk formation was formed in the late Ordovician. The SiO_2 content of the volcanic rocks is 53.990.74, and the SiO_2 content of the volcanic rocks is 53.990.The SiO_2 content of the volcanic rocks is 53.9971.04, and the Al2O3-rich Al _ 2O _ 2O _ (13.83N) is 16.2727, and the MgO1.093.53K _ 2O is between 1.113.83% and 1.113.83%. The average value is 2.84, which belongs to the characteristics of high-potassium volcanic rock series. LREE is enriched with negative EU anomaly (未 EU _ (0.65) ~ 0.82 ~ (g)). Volcanic rocks are rich in large ion lithophile elements RbSe (Th) and depleted elements of high field strength (KNB) Taan, which are characterized by island arc volcanic rocks. In combination with regional data and the results of this paper, the authors believe that, The volcanic rocks were formed in the colliding environment during the late subduction and subduction of the active continental margin oceanic crust. The late Ordovician Paleo-Asian Ocean subducted from south to north to Siberia plate to form Kanas with active continental margin arc. Late Ordovician volcanic rocks in the region.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P588.14

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