内蒙古白乃庙逆冲推覆构造特征及其地质意义  

Characteristics of Bainaimiao Thrust Belt along Central Inner Mongolia in North China and its Geological Significance

作　　者：周志广[1,2] 张达[1] 谷永昌[3] 王果胜[1] 李红英[1] 於炀森[2] 柳长峰[2] 刘文灿[2] ZHOU Zhiguang;ZHANG Da;GU Yongchang;WANG Guosheng;LI Hongying;YU Yangsen;LIU Changfeng;LIU Wencan(College of Geoscience and Resources, China University of Geosciences (Beijing), Beijing 100083, China;Institute of Geological Survey,China University of Geosciences (Beijing),Beijing 100083,China;Tianjin Center of China Geological Survey,Tianjin 300170,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地质大学(北京)地质调查研究院,北京100083 [3]中国地质调查局天津地质调查中心,天津300170

出　　处：《大地构造与成矿学》2018年第1期1-17,共17页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(41772227);中国地质调查项目(1212011220465;1212011085490;1212011120700;DD20160045-2)联合资助

摘　　要：白乃庙逆冲推覆构造自四子王旗北东的十二台向东经白乃庙、博日和延至化德地区,大致沿北纬42°线东西向延伸超过190 km。它发育于华北克拉通与其北侧的奥陶纪白乃庙岛弧带之间,成为华北克拉通与北缘增生带的构造界线,是一套较为典型的陆缘褶冲带。它表现为华北克拉通北缘的中-新元古界白云鄂博群向北逆冲于白乃庙群及其弧后盆地的上志留统徐尼乌苏组和顶志留统西别河组之上。根据构造变形解析并结合音频大地电磁测深资料(CSAMT),得出白乃庙逆冲推覆构造由一系列分支逆断层组成,并向深部于120~800 m处交汇成主底板断层,构成一套叠瓦式逆冲推覆构造,并发育规模不同的构造窗和飞来峰。根据构造窗与飞来峰之间的距离,提出逆冲位移量大于14 km。通过线理及褶皱枢纽统计,指出白乃庙逆冲推覆构造的逆冲方向为自南向北。依据逆冲岩席中发育的断夹块的叠置关系及构造岩的特征,认为其经历了两个期次的活动。对断裂带内同构造形成的包裹石英透镜体的白云母分别进行了Rb-Sr和Ar-Ar同位素测年,认为白乃庙逆冲推覆构造早期活动于450~410 Ma,是白乃庙岛弧带与华北板块碰撞的构造反映。白乃庙逆冲断层晚期活动于晚二叠世至早三叠世,是古亚洲洋最终闭合的构造表现,亦印证研究区经历了印支期构造运动。The Bainaimiao thrust belt,a typical skinned continental margin thrust sheet,distributes from Xuniwusu to Huade,nearly East-West extending along the42°N with190km in length in the central Inner Mongolia.It is developed between the North China Craton and the Bainaimiao Ordovician island arc.It appears that the Meso–Neoproterozoic Bayan Obo Group developed in the northern margin of the North China Craton(NCC)thrust up northward,and covered the later Silurian Xibiehei Formation deposited in the Bainaimiao arc.Based on the geological mapping and CSAMT bathymetric,it is identified that branches of the thrusts in the sheet pool deeply into a main floor thrust located120?800m at depth.All of the thrusts consist into an imbricate thrust system and double layer structure.The thrust direction of both periods was south to north as indicated by foliation static and lineation orientation.Base on the distance between Windows and the Kilippes in front of the Bainaimiao thrust belt,its displacement is more than14km.According to the spatial characterization of Klippes and horses in the Bainaimiao thrust,two active periods of thrust can be identified.Rb-Sr and Ar-Ar isotope dating of muscovite formed during the thrusting suggests that the early period of thrust took place in450?410Ma,which is possibly related to the subduction of the Paleo-Asian Ocean crust toward the NCC.According to the time of basin sediments controlled by thrusts,the late period is speculated to be in Carboniferous to the Early Permian related to the collision of the Siberian and North China Platform,the close of the Paleo-Asian Oceans,and formation of Central Asian Orogenic Belt.

关 键 词：逆冲岩席 逆冲推覆构造 中亚造山带 华北板块北缘 内蒙古 

分 类 号：P542[天文地球—构造地质学]