河套断陷带包头凸起的构造特征  

TECTONIC CHARACTERISTICS OF BAOTOU UPLIFT IN HETAO DEPRESSION ZONE

作　　者：刘志成 高战武 徐伟 袁兆德[2] 王继 王万合 LIU Zhi-cheng;GAO Zhan-wu;XU Wei;WANG Ji;WANG Wan-he(China Earthquake Disaster Prevention Center,Beijing 100029,China;Institute of Geology,China Earthquake Administration,Beijing 100029,China;Xi'an Research Institute of China Coal Technology&Engineering Group,Xi'an 710077,China)

机构地区：[1]中国地震灾害防御中心,北京100029 [2]中国地震局地质研究所,北京100029 [3]中煤科工集团西安研究院,西安710077

出　　处：《地震地质》2019年第5期1105-1122,共18页Seismology and Geology

基　　金：国家重点研发计划项目(2017YFC1500401);中国科学院战略性先导科技专项(XDA2007030204);中国地震局地震科技星火计划项目(XH20074)共同资助

摘　　要：河套断陷带是一个复式断陷盆地,存在2个次级凸起和3个次级凹陷。包头凸起分隔了白彦花凹陷和呼和凹陷,基底为前寒武纪花岗片麻岩,上覆地层为第四系。文中利用浅层地震勘探、活动断裂填图以及跨断层钻孔剖面等手段详细研究了包头凸起的构造特征。浅层地震勘探揭示白彦花凹陷和呼和凹陷都是北深南浅的箕状凹陷,包头凸起是SE陡NW缓、NE宽SW窄的不对称凸起,西沙湾-兴胜断裂和大青山山前断裂分别为凸起的NW和SE边界断裂。凸起的SE边界断裂是全新世活动断裂,属于大青山山前断裂西端的包头段,其在物探剖面上表现为S倾、上陡下缓的铲式断裂,错断了呼和凹陷内的全部沉积地层;断裂在地表沿晚更新世湖积台地南缘展布,构造地貌标志显著。西沙湾-兴胜断裂为隐伏断裂,地震勘探和钻孔联合剖面都揭示该断裂未错断晚更新世湖相地层,为早-中更新世断裂。几何形态、岩性构成和边界断裂等多方面证据均表明包头凸起是大青山隆起的西延,分隔了乌拉山山前断裂和大青山山前断裂,2条断裂构成独立的发震构造。河套断陷带具有复杂的结构形态,许多与其相关的科学问题需要进一步系统研究,解析断陷带的形成与演化过程需要更多地关注断陷带内部的次级构造。The Hetao depression zone,located to the north of Ordos block,is a complex depression basin that consists of two sub-uplifts and three sub-depressions.The depression zone is subject to the regional extensional stress field driven by the Indo-Asian continental collision and the westward subduction of the Pacific Plate.The Baotou uplift that separates the Baiyanhua sub-depression and Huhe sub-depression is mainly composed of Archean gneiss and is overlaid by Quaternary sedimentary strata.The two sub-depressions are bordered by the Wula Mountains and Daqing Mountains to the north,respectively.The bedrock exhumed in Wula Mountains and Daqing Mountains consists mostly of Precambrian granitic gneiss,and the piedmont depressions are infilled by thick Cenozoic strata.The Wulashan piedmont fault and Daqingshan piedmont fault extend along the range front of Wula Mountains and Daqing Mountains,respectively.The subsidence is controlled by the two boundary faults.Previous studies have preliminarily documented the characteristics of the northwest boundary fault of Baotou uplift.Combining shallow seismic exploration,active fault mapping,and geological drilling,this paper presents a detailed study on the tectonic characteristics of the Baotou uplift.The shallow seismic exploration reveals that the Baotou uplift is an asymmetrical wedge with a steep southeast wing and a gentle dipping northwest wing.The Baotou uplift is wider in the northeastern part and narrows down towards the southwest.In seismic profiles,the Baiyanhua subdepression and the Huhe sub-depression manifest as asymmetric dustpan-like depressions with southdipping controlling faults.Baotou uplift is bounded by the Xishawan-Xingsheng Fault to the northwest and Daqingshan piedmont fault to the southeast.The two faults exhibit significant difference in many aspects,such as fault geometry,fault displacement,the latest active time,and so on.The southeast boundary fault of Baotou uplift is the Baotou section of the Daqingshan piedmont fault which is a Holocene active faul

关 键 词：河套断陷带 包头凸起 大青山山前断裂 西沙湾-兴胜断裂 

分 类 号：P315.2[天文地球—地震学]