【作者】 李双保； 陆松年； 杨春亮； 李怀坤； 张文治； 王元清；

【Author】 Li Shuangbao Lu Songnian Yang Chunliang Li Huaikun Zhang Wenzhi (Tianjin Institute of Geology and Mineral Resources) Wang Yuanqing (Institute of Geology of the Bureau of Geology and Mineral Resources of Ningxia Province)

【机构】 天津地质矿产研究所； 宁夏地矿局研究所；

【摘要】 本章首次描述了内蒙古阿拉善地区太古宙花岗岩类岩石(阿拉善群),并将其中的一部分划归 TTG 质片麻岩,岩相学特征与辽宁和吉林的片麻岩相当。花岗岩体中的韧性剪切带十分发育,使得识别片麻岩原岩比较困难。TTG 质片麻岩侵入并包裹表壳岩,在镜下可见到许多原始岩浆结晶的结构特征。由于从阿拉善群中剔除了 TTG 质片麻岩,使这套地层的构造格局发生了重大变化。更多还原

【Abstract】 Nobody had described the Archean granitoid rocks of the Alashan region until 1991. Many gray orthogneisses have been included in supracrustal rock series of the Ala- shan Group by many geologists.Through detail field observation,the gneisses have been identified as TTG gneisses(Tonalitic,Trondhjimitic,Granodioritic gneisses)by the authors and their petrographic features can be well compared with those in Liao- ning and Jilin Provinces,North-east China. The paper offers petrographic terminological characteristics of the TTG rocks in the region.The occurence nature of the potassic granites of the Archean,named by predecessors as migmatites,is also mentioned here. The ductile shear zones are so developed in the granitic bodies that it is difficult to identify the protolith of the gray gneisses.The TTG rocks introded in and enve- loped the supracrustal rocks and many petrologic textures of the TTG rocks show ori- ginal magmatic crystalized patterns seen under microscope. Owing to getting rid of the TTG gneisses from the Alashan Group,the structure patterns of the Group has significantly changed. The TTG gneisses occured as ovallifts in Diebusige and Honggueryulin districts, composed of trondhjimitic-tonalitic gneisses and have suffered by granulite facies me- tamorphism,so that it might be the oldest terrane of the region. The gneiss domes of various shapes distributed in the districts of Boluositan Tem- ple, Bijigetai,Dabusu Mountain are composed mainly of TTG complexes. The Archean greenstone belts are distributed in the Bayanwula Mountain,south- west of Jilantai,the Alatanaobao-Chagandugui and the Tikuwula-Saogete districts. They are formed separately and discontiguous linear zones surounding or near the do- mes of the TTG rocks.更多还原