辽宁省北镇市石墨矿地质地球化学特征及原岩恢复

发布时间：2018-06-04 04:26

本文选题：辽宁北镇石墨 + 碳质板岩　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：北镇地区位于华北地台燕山台陷带的辽西台陷,医巫闾山背斜的东翼,东部与下辽河盆地相接,受东西向要路沟—锦西壳断裂、锦州—哈尔套壳断裂及韧性剪切带的控制。区内可见构造以断裂构造和背斜褶皱为主。地层由太古界建平群大营子组、瓦子峪组,中元古界长城系大红峪组、高于庄组以及新生界第四系地层组成。岩浆岩主要为已经变质的太古代火山岩和中生代火山岩。该地区出露的岩石以碳质板岩,局部大理岩和受花岗岩岩浆作用的过渡性板岩为主,属于区域变质岩里的低级变质岩系列。由于研究区受到不同程度的变质及变形作用,单靠野外岩石组合和岩石学特点来确认北镇地区变质岩系的原岩建造是比较困难。因此,本文选择了部分有代表性样品进行分析。通过分析该地区全岩数据百分含量特点;计算关键元素对的比值、DF值、尼格里特征值,并做相关图解判别原岩类型,通过F1—F2碎屑岩物源判别函数图,ω(La)/ω(Th)-ω(Hf)/10-6物源属性判别图等构造判别图来分析原岩的物源及构造背景。最后,综合以上方法得出如下结论:1.辽宁省北镇地区的岩石类型主要碳质板岩、大理岩等,主要矿物为云母类和长石类,在镜下矿物可见明显的定向排列,说明在一定时期内收到挤压或伸展运动的影响。2.根据北镇地区的岩石化学成分特征及有关数据,推测该地区的原岩为沉积岩或中酸性火山岩3.锆石SHRIMP分析显示年龄集中在古元古代和下侏罗统,说明他们与古元古代的古老变质岩基底有关,反映了该地区石墨沉积变质的过程。4.根据北镇地区地球化学数据及原岩恢复相关图解,判断研究区为副变质岩,即原岩为沉积岩,以粘土岩、泥质砂岩、长石质砂岩为主;物源成分以长英质、石英质岩石为主,并含有火成物源及古老再循环沉积物。研究区变质岩虽然形成于被动大陆边缘环境,但是物源继承了更早期活动大陆边缘和岛弧盆地的地化信息,说明该地区是从活动大陆岛弧到被动陆缘逐步演化的。
[Abstract]:The Beizhen area is located in the western Liaoning platform of the Yanshan platform depression belt of the North China platform, the eastern wing of the Yiwulushan anticline, which is connected with the Lower Liaohe Basin in the east, and is controlled by the east-west Yuzhou-Jinxi crust fault, the Jinzhou-Hal crust fault and the ductile shear zone. Fault structures and anticline folds dominate the visible structures in the area. The strata are composed of the Daiying formation, the Waziyu formation, the middle Proterozoic the Great Wall system and the Dahongyu formation of the Jianping Group of the Archean, higher than that of the Zhuang formation and the Quaternary formation of the Cenozoic. Magmatic rocks are mainly metamorphic Archean volcanic rocks and Mesozoic volcanic rocks. The exposed rocks in this area are mainly carbonaceous slate, local marble and transitional slate with granitic magmatism, which belong to the low grade metamorphic series of regional metamorphic rocks. Due to the metamorphism and deformation in the study area, it is difficult to confirm the original rock formation of metamorphic rock series in Beizhen area by relying solely on the field rock assemblages and petrological characteristics. Therefore, some representative samples are selected for analysis in this paper. By analyzing the percentage content characteristics of the whole rock data in this area, calculating the ratio of key element pairs, DF value and Nigri characteristic value, and making relevant diagrams to distinguish the original rock types, The provenance and tectonic background of the original rock are analyzed by using the source discriminant function diagram of F1-F2 clastic rock and the structural discriminant map of the provenance properties of 蠅 -Lao- / 蠅 -Hf- / 10-6 provenance. Finally, combined with the above method, the following conclusion is drawn: 1. The rock types in Beizhen area of Liaoning Province are mainly carbonaceous slate, marble and so on. The main minerals are mica and feldspar. According to the characteristics of rock chemical composition and related data in Beizhen area, it is inferred that the primary rock in this area is sedimentary rock or intermediate acid volcanic rock. Zircon SHRIMP analysis shows that the ages are concentrated in Paleoproterozoic and Lower Jurassic, indicating that they are related to the basement of ancient metamorphic rocks in Gu Yuan, which reflects the process of graphite depositional metamorphism in this area .4. According to the geochemical data of Beizhen area and the related diagrams of the restoration of the original rocks, it is judged that the study area is metamorphic, that is, the primary rocks are sedimentary rocks, mainly clay rocks, argillaceous sandstones, feldspathic sandstone, and feldspathic and quartz rocks. And contains pyrogenic material sources and ancient recycled sediments. Although metamorphic rocks were formed in the passive continental margin environment, the provenance inherited the geochemistry information of the earlier active continental margin and island arc basin, indicating that the area evolved from active continental island arc to passive continental margin.
【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】：2015
【分类号】：P619.252

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