吉林中部红帘石片岩的岩石特征及其构造意义

发布时间：2018-06-24 18:31

  本文选题：长春-延吉增生杂岩带 + 红帘石片岩　； 参考：《吉林大学》2016年硕士论文

【摘要】：位于华北板块和西伯利亚板块之间的中国东北及其邻近地区,处于与太平洋板块的叠加部位,同时受古亚洲洋和环太平洋两大构造域的影响,对这一地区大地构造背景的研究具有极高的科学价值。其中,佳木斯-兴凯地块在空间位置上与俄罗斯远东、朝鲜和日本等相邻,在大地构造位置上处于中亚-蒙古构造域与太平洋构造域的叠加部位,可作为研究地体拼贴、两大构造域叠加和转换过程的关键地区。有关佳木斯-兴凯地块与华北地块之间长春-延吉缝合带的闭合时间和大地构造本质仍存在争议。本文以吉林省中部磐石县烟筒山地区的红帘石片岩作为研究对象,通过岩相学,电子探针及锆石U-Pb同位素年代学等研究方法来探讨红帘石片岩的形成温压条件及原岩时代,并结合已有的古生物学资料以及其他年代学资料来探索佳木斯-兴凯板块和华北板块的最终闭合时间及其大地构造背景。野外地质调查显示,岩石经历了强烈变形并具有无层序特点,表示该地区地层可能为构造混杂岩,不具备传统的地层划分和对比意义;红帘石片岩呈构造透镜体状产出于大面积分布的绿片岩中,岩石遭受了强烈的褶曲变形及韧性变形作用。红帘石片岩典型的变质矿物组合为:石英(75%~80%)+多硅白云母(10%)+红帘石(10%)+石榴石(5%)+长石(5%)。其中白云母可以指示岩石压力环境,通过电子探针分析表明,白云母中的Si≥3.305(以氧原子=11为基准),白云母为多硅白云母,为高压变质作用的产物,可证明其经历高压反应改造。本文利用LA-MC-ICP-MS测年技术对红帘石片岩,绿泥石片岩和未变形的长英质岩脉四个岩石样品进行了锆石U-Pb分析,红帘石片岩的年龄数据显示:1)最小年龄为233 Ma,显示原岩年龄为形成与印支期前后;2)峰值为~426Ma,3)峰值为738 Ma的锆石年龄,对应于东北地区的变质结晶基底年龄;4)最大年龄为1800 Ma的锆石年龄,为东北地区存在古老基底的信息。需要指出的是,峰值为233Ma其原岩为三叠系前后,而并不是前人认为的二叠纪或更老。另外,长英质岩脉的年龄数据显示,11粒锆石的加权平均年龄为217±3 Ma(MSWD=0.37),利用该未变形的长英质岩脉可以限定长春-延吉缝合线的下限。本文研究结果表明,具有一系列特征性增生杂岩的长春-延吉缝合带是佳木斯-兴凯地块与华北地块俯冲拼贴形成,并非前人认为的索伦-西拉木伦-长春缝合带的东向延伸,大地构造属性是吉林-黑龙江高压变质带的南缘。吉林-黑龙江高压变质带作为东北地区重要构造单元,记录了古亚洲构造域的结束和古太平洋在晚三叠-早侏罗世西向俯冲开始,标志着太平洋板块俯冲启动。
[Abstract]:Northeast China and its adjacent areas, located between the North China plate and the Siberian plate, are superimposed with the Pacific plate and are also affected by the two tectonic domains of the Paleo-Asian Ocean and the Pacific Rim. The study of tectonic background in this area is of great scientific value. Among them, Jiamusi Xingkai block is adjacent to the Russian far East, Korea and Japan in space, and is located in the superposition of Central Asia Mongolia tectonic domain and Pacific tectonic domain in the geotectonic position, so it can be used as a collage of the study ground. The two major tectonic domains superimpose and transform the key areas. The closing time and tectonic nature of the Changchun-Yanji suture zone between the Jiamusi-Xingkai block and the North China block are still controversial. In this paper, the authors take the red curtain schist in Yanconshan area, Panshi County, central Jilin Province as the object of study. By means of petrography, electron probe and zircon U-Pb isotopic chronology, the forming conditions of the red curtain schist and the age of the original rocks are discussed. The final closure time and tectonic setting of the Jiamusin-Xingkai plate and the North China plate are explored by combining the available paleobiological data and other geochronological data. The field geological survey shows that the rocks have undergone strong deformation and have the characteristics of no sequence, indicating that the strata in this area may be structural melange, without the traditional stratigraphic division and correlation significance. The red curtain schist occurs in a large area of green schist as a structural lens, and the rock is subjected to strong fold deformation and ductile deformation. The typical metamorphic mineral assemblages of red curtain schist are quartz (75%), polysilicon Muscovite (10%), red curtain (10%), garnet (5%) and feldspar (5%). Muscovite can indicate rock pressure environment. Electron probe analysis shows that Muscovite is the product of high pressure metamorphism with Si 鈮，

本文编号：2062516