【摘要】 通过对白云鄂博及周边地区地质和构造形迹的系统调研 ,综合分析了白云鄂博地区的古板块构造单元、白云鄂博群的沉积构造背景以及白云鄂博地区的构造组合特征。白云鄂博群可以划分为三个沉积组合 ,它们分别代表中元古代、晚元古代和早古生代白云鄂博地区由陆内裂谷向陆缘裂谷转化到活动大陆边缘裂谷的沉积过程。白云鄂博地区以白银角拉克 -宽沟断裂为界 ,南北两侧存在重大地质差异。断裂南侧的该群岩石不整合覆盖在相当于五台群的色尔腾山群之上 ,是在华北陆壳基底上发展起来的陆缘沉积。局部碳酸盐岩和页岩层位在加里东期遭受了强烈的地幔流体改造 ,形成大规模稀土矿化 ;在海西期又遭受了强烈的区域变质改造。断裂北侧的白云鄂博群以发育蛇绿混杂岩 -叠瓦状冲断层 -紧闭同斜褶皱为特征 ,具有古板块俯冲形成的加积杂岩特征。在此基础上 ,对白云鄂博地区的古板块构造演化动力学过程进行了初步总结。更多还原

【Abstract】 Regional geology and tectonic characteristics were investigated for Bayan Obo and surrounding areas in northern Inner Mongolia. The results place constraints on paleoplate tectonic units , the tectono sedimentary settings of Bayan Obo Group and the features of tectonic assemblages in this region. The Bayan Obo Group can be divided into three sedimentary associations which represent the transition processes of sedimentary environments within rift basins from interior continent at Mesoproterozoic to continetal margin at Neoproterozoic, and to active continental margin at Early Paleozoic. There are important differences in geology and tectonics between southern and northern regions along Bayanjiaolake-Kuanggou Fault as a boundary. The rocks in the southern region uncomformably overlies the rocks of Seertengshan Formation in Wutai Group and thus the sedimentary rocks of continental margin are developed on the continental basement of North China. Some strata of carbonate and shale underwent intensive metasomatism of mantle derived fluid at Early Paleozoic, forming a large scale REE mineralization. Regional metamorphism overprinted both metasomatic and unmetasomatic strata again at Late Paleozoic. The Bayan Obo Group in the northern region is characterized by development of ophiolite mélange, imbricate thrust and tightly synclinal fold, corresponding to accretionary complex scrapped off during plate subduction. A preliminary scheme is presented to outline the geodynamic processes of tectonic evolution associated with plate subduction in Bayan Obo Region.更多还原