新林—塔源一带蛇绿混杂岩带特征及其大地构造意义

发布时间：2018-02-04 16:41

本文关键词： 新林蛇绿混杂岩大地构造大兴安岭　出处：《吉林大学》2016年硕士论文　论文类型：学位论文

【摘要】：新林-塔源蛇绿混杂岩带位于大兴安岭北部地区,大地构造位置属于中亚造山带东段,曾被认为是额尔古纳地块和兴安地块的碰撞缝合带。但最近研究表明兴安地块是否存在前寒武纪基底有一定争议。本次调查工作,在野外调查的基础上,收集前人资料开展综合研究工作,认为该带为板块碰撞或弧陆碰撞缝合区,物质成分复杂,构造运动强烈,它们由不同时代、不同来源的岩块和基质构成。区内倭勒根岩群和蛇绿岩为该带的重要组成部分。通过在倭勒根岩群获得的变砂岩碎屑锆石LA-ICP-MS U-Pb同位素最小峰值年龄453.2±6.4 Ma、454.7±3.0 Ma,粉砂质板岩碎屑锆石LA-ICP-MS U-Pb同位素最小峰值年龄480.3±3.0 Ma,安山质凝灰岩锆石LA-ICP-MS U-Pb同位素结晶年龄430±4.6 Ma,将其初步厘定为下奥陶-下志留统;依据野外实际调查工作,通过岩石地球化学、同位素地质学研究,提出塔源西柯多蒂河东上游二辉橄榄岩属于新林蛇绿岩带的组成部分。确认多宝山岛弧西北侧存在一条北东向展布的晚奥陶—中志留世镁铁质岩浆岩带,空间展布上与新林蛇绿岩相重叠,同位素年龄为443-432 Ma。将新林蛇绿岩的形成时代初步厘定为晚奥陶—中志留世。研究确认新林蛇绿岩构造岩石组合具有层序性蛇绿岩和构造冷侵位的成因特征,地球化学特征属E-MORB,为富集型扩张洋脊残片。综合多宝山岛弧的时空展布特征,提出塔源-新林蛇绿岩带形成的构造环境为弧后盆地的认识。
[Abstract]:The Xinlin-Tayuan ophiolite melange belt is located in the northern part of the Daxingan Mountains and belongs to the eastern part of the Central Asian orogenic belt. It was considered to be the collisional suture zone between the Erguna and Xingan massif. But recent studies have shown that the existence of Precambrian basement in the Xingan massif is controversial. This investigation is based on the field investigation. It is considered that the belt is a suture area of plate collision or arc land collision with complex material composition and strong tectonic movement. The Wulergen group and ophiolite are important components of the zone. Zircon zircon from metamorphic sandstone obtained from the Wulergen rock group is an important part of the zone. The minimum peak age of U-Pb isotope is 453.2 卤6.4 Ma. The minimum peak age of LA-ICP-MS U-Pb isotope of silty slate is 480.3 卤3.0 Ma. The zircon LA-ICP-MS U-Pb isotopic crystallization age of Anshan tuff is 430 卤4.6 Ma, which is preliminarily classified as Lower Ordovic-Lower Silurian; According to the field investigation work, through the rock geochemistry, isotopic geology research. It is suggested that the lherzolite is part of the Xilin ophiolite belt in the upper reaches of the East Cordotti River in the west of Tawanyuan. It is confirmed that there is a late Ordovician magmatic belt on the northwest side of the island arc of Dobaoshan. The spatial distribution overlaps with the Xinlin ophiolite. Isotopic age 443-432. Ma. the forming age of Xinlin ophiolite is preliminarily determined as late Ordovic-Middle Silurian. It is confirmed that the tectonic rock assemblage of Xinlin ophiolite has the genetic characteristics of sequence ophiolite and tectonic cold emplacement. The geochemical characteristics of E-MORBs are enriched extensional ridge fragments. Based on the spatial and temporal distribution of the island arc in Dobaoshan, it is suggested that the tectonic environment formed in the Tayuan-Xinlin ophiolite belt is a back-arc basin.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P587;P548

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