【作者】 路孝平；

【导师】 吴福元；

【作者基本信息】 吉林大学 ， 矿物学、岩石学、矿床学， 2004， 博士

【摘要】 近十年里，随着全球1.8 Ga -2.1Ga造山事件研究，“Columbia”超大陆被越来越多的科学家识别和承认，许多地质学家对其拼合和裂解进行研究并取得了重要进展，而我国的华北板块的基底构造在近几年研究中取得的重要进展是提出该板块基底可分为东部陆块、西部陆块和位于二者之间的中部造山带，东、西部陆块在1.85 Ga沿中部造山带拼合，导致华北克拉通最终拼合。华北板块北缘东段，郯庐断裂带以东的辽吉地区，北部跨龙岗陆块，并与兴蒙造山带相邻，南部属辽南陆块和朝鲜的狼林陆块（因朝鲜的狼林陆块资料较少，在此不做详细讨论），区内广泛发育一套古元古代变质岩石，在辽东地区多称辽河群，在吉南地区称集安岩群和老岭群，并且有大面积的古元古代花岗岩侵位，该套变质岩的层序、构造背景、时代格架等问题多年来一直没有得到解决，各家存在重大分歧。通化地区是该套古元古代变质岩出露较为齐全的典型地区，本文选择了该地区的古元古代变质岩进行同位素年代学研究。 研究区内分布有大面积的古元古代变质岩，包括变质火山岩，变质沉积岩和古元古代花岗岩，尽管上世纪30年代就有人进行地质研究，但直到70年代才有较系统的区域地质资料，80年代以后，先后有天津地矿所、长春地质学院、沈阳地矿所、吉林地矿局等多单位、多人对其进行深入的研究工作，提出了多种理论和认识，同时形成了“百家争鸣”之势。近年来，随着国内外古元古代变质岩研究工作的深入开展，尤其华北板块的古元古代变质岩研究取得了重大进展，明显显示出本研究区古元古代变质岩研究的薄弱，许多重大基础地质问题亟待解决：1）古元古代变质岩原始的沉积层序和沉积基底问题；2）古元古代花岗岩形成的精确时代、成因、构造背景、形成机制等问题；3）变质作用时代问题；4）古元古代地壳演化问题。而解决上述问题的关键是建立正确的古元古代构造岩浆事件年代学格架，为古元古代地壳演化提供正确的时代依据。 <WP=160>本论文选择了通化地区，在充分了解和掌握前人资料和研究成果的基础上，通过详实的地质填图工作后，系统采集了岩石样品，针对不同的岩石单位，运用不同的实验方法进行了高精度的同位素年龄测定，实验技术方法选择了TIMS、SHRIMP、LA-ICPMS等，获得一批高精度的同位素年龄数据，结合锆石形态特征、透射光反射光特征和阴极发光图像特征，详细研究锆石结构后，精确定出研究区的构造岩浆事件年代学格架如下：早期2.19Ga-2.16Ga形成张裂性构造环境的赤柏松镁铁-超镁铁岩和钱桌沟岩体角闪正长花岗岩；晚期1.87Ga-1.85Ga发生造山作用，形成大规模的清河岩体、卧龙泉岩体和双岔岩体等花岗岩岩体，并同时发生变质作用；二者间期，发生火山活动并同时沉积了集安岩群和老岭群碎屑岩；1.83Ga 的矿洞沟正长岩侵位。花岗岩的地质、地球化学特征显示：早期的赤柏松镁铁-超镁铁岩具有较高的铂族元素，而钱桌沟岩体正长花岗岩具有“A”型花岗岩特征，二者均形成于拉伸环境中；晚期的清河岩体石英闪长岩和卧龙泉岩体二长花岗岩具有“I” 型花岗岩特征、双岔岩体巨斑状花岗岩具有“S”型花岗岩特征；而矿洞沟岩体为“A”型正长岩。结合辽南陆块和龙岗陆块的太古宙地质体的差异，可初步确定郯庐断裂以东的华北板块东段前寒武纪基底是由南部的辽南陆块（包括朝鲜的狼林陆块）和北部的龙岗陆块两个彼此独立的块体组成，并在1.85Ga时期拼合而成，而辽吉地区古元古代光华岩群、集安岩群和老岭群发生的变质作用及1.83Ga-1.87Ga的花岗岩侵位则是该拼合造山作用的产物。而早期的钱桌沟岩体（辽吉花岗岩）和赤柏松镁铁-超镁铁岩则与该造山作用无关，是该造山作用前由热地幔柱活动引发的岩石圈伸展作用的产物。通过上述研究分析可以得出通化地区原厘定的古元古代裂谷系沉积产物形成环境实际可划分出两种不同的构造环境，其一是2.18Ga-2.16Ga产生于古元古代伸展环境的钱桌沟岩体（辽吉花岗岩）和赤柏松镁铁-超镁铁岩，地球动力学背景是热地幔柱，并且，钱桌沟岩体（辽吉花岗岩）构成了古元古代沉积岩的基底；其二是沉积于钱桌沟岩体（辽吉花岗岩）之上的集安岩群和老岭群及光华岩群等发生的变质作用和侵位于1.83Ga-1.87Ga的花岗岩，是古元古代造山带产物，该古元古代造山作用与华北板块的东西地块对接是同时代的，也是华北板块对全球“Columbia” 超大陆的响应。更多还原

【Abstract】 In the recent decade, with the advance of the global orogenic event at 2.1-1.8Ga, the Columbia super-continent has become more and more well-recognized and known. Many geologists have studied its amalgamation and breakup and obtained important advances. While, the advance on the basemental tectonic of North China Craton (NCC) is that the basement of the NCC could be divided into Eastern Block, Western Block and the Central Orogenic Belt between the two blocks. At about 1.85Ga, the collision between the Eastern and Western Blocks along the Central Orogenic Belt, leading to the ultimate amalgamtion and cratonization of the NCC.Liaoji Area, located to the east of the Tanlu Fault zone in the eastern NCC, includes the Longgang terrain in the north which is adjacent to Xing-Meng orogenic belt, Liaonan and Rangnim Blocks in the south. The Rangnim Block will not be discussed because of a few data. Paleoproterozoic metamorphic rocks, named as “Liaohe Group” in the Liaodong and “Ji’an Group and Laoling Group” in the Jinan area, are widespread throughout the area with emplacement of Paleoproterozoic granitic plutons. However, there are still controversial on the stratigraphy, tectonic setting and geochronologic frame of the metamorphic rock. In this paper, we present the geochronology of the Paleoproterozoic metamorphic rocks from a typical area-The Tonghua area, to resolve the problem. Paleoproterozoic metamorphic rocks are widespread in the studied area, including metamorphic volcanics, metamorphic sedimentary rocks and Paleoproterozoic granites. Although studying had been done since 1830’s, there was not systematic geology material untill 1970’s. Since 1980’s, the Institute of Geology and Mineral of Tianjin, Changchun <WP=162>College of Geology, Shenyang Institute of Geology and Mineral Resources, Jilin Bureau of Geology and Mineral and other units, as well as some scholars, had studied thoroughly, and proposed different theories and thoughts. Recently, with adavance of the study of Paleoproterozoic metamorphic rocks all over the world, especially the important development of Paleoproterozoic metamorphic rocks of NCC, it obviously shows flaws of study on the Tonghua area. Many basic geological problems about Paleoproterozoic metamorphic rocks in the Tonghua area need to be resolved urgently, including: 1) the primary sedimentary sequence and sedimentary besement of Paleoproterozoic metamorphic rocks; 2) the precise dating, petrogenesis, tectonic setting, petrological progress of Paleoproterozoic granites; 3) the geochronology of metamorphism; 4) the crustal evolution during Paleoproterozoic. Geochronological frame of Paleoproterozoic tectonic-magmatic event is fundamental to answer the above questions and provides new evidence to understand the Paleoproterozoic crustal evolution. On the basis of previous data and study and detailed geologic mapping, we collected samples systemically and then dated the different rocks using TIMS, SHRIMP and LA-ICPMS. The shape characteristics of the zircons, the photos of the transmitted light and the reflected light, and the characteristics of the cathode luminescence image, give the detailed structure of the zircon. The results give the geochronological frame of tectonic-magmatic event as below. In early stage (2.18Ga-2.16Ga), mafic-ultramafic rock of Chibaisong pluton and syenite-granite of Qianzhuogou pluton emplaced in an extensional setting. In late stage (1.87Ga-1.85Ga), large scale of granitic plutons, such as Qinghe pluton, Wolongquan pluton and Shuangcha plutons, emplaced in an orogenic setting with regional metamorphism. Between the two stages, volcanic activities happened simultaneously and formed the Ji’an Group and Laoling Group fragmentary rocks deposited. In the last stage, the Kuangtonggou syenite pluton emplaced at about 1.83Ga. Geological and geochemical features of granites show that the early mafic-ultramafic rocks of Chibaisong pluton have high platinum group element contents, while Qianzhuogou syenites and granites have similar characteristics to A-typ更多还原