青藏高原东北缘扩展变形范围与深部结构  

Extension range and deep structures of the northeastern Tibetan Plateau

作　　者：刘愿 程斌[1] 杨钊[1] LIU Yuan;CHENG Bin;YANG Zhao(State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069,China;The First Geology Group of Zhejiang Province,Hangzhou 310007,China)

机构地区：[1]大陆动力学国家重点实验室,西北大学地质系,西安710069 [2]浙江省第一地质大队,杭州310007

出　　处：《地球物理学进展》2021年第3期908-922,共15页Progress in Geophysics

基　　金：国家自然科学基金资助项目(41502186);西北大学张国伟院士工作室;陕西省教育厅专项科研计划项目(16JK1753)联合资助。

摘　　要：青藏高原东北缘的隆升和扩展一直是地学界长期关注的重要科学问题,对于研究整个青藏高原的形成演化过程具有非常重要的意义.青藏高原东北缘是高原向北东方向扩展变形的结果,其进一步向北东方向扩展变形的边界范围长期存在较大争议.本文主要收集了近年来前人在青藏高原东北缘及其邻区开展的浅表地质、地壳-上地幔三维结构以及壳-幔变形的相关研究并进行综合分析.前人通过构造热年代学、构造解析等方法的研究,揭示出中-晚新生代以来,海原弧形构造区以及更北端的贺兰构造带—银川地堑发生的强烈构造活动均与高原的隆升、扩展有关,认为高原东北缘向北东方向扩展变形的浅表范围已经越过海原弧形构造区,到达贺兰构造带—银川地堑.深部地球物理探测显示,海原弧形构造区深部结构构造改造过程与青藏高原向北东方向扩展有关.但是其更北端的(贺兰构造带—银川地堑)深部结构构造改造过程是否与青藏高原的扩展有关,目前尚存在一定的争议:重力异常及其大地电磁、部分层析成像、接受函数、地震波各向异性等方法的研究结果揭示,贺兰构造带—银川地堑下方存在大规模代表青藏高原东北缘软流圈的低速异常体、低电阻体,以及其下地壳-上地幔存在NW-SE向的各向异性方向与青藏高原东北缘的快波方向一致,这可能反映其主要是受到青藏高原向北东方向扩展、变形的影响;但是也有研究显示贺兰构造带—银川地堑存在的低速异常体较南部弱,或者规模较小、以及推测贺兰构造带—银川地堑存在中-下地壳NW-SE向的各向异性方向主要是由于存在形变各向异性导致的,认为青藏高原东北缘的边界位于海原断裂带.The uplift and extension of the northeastern Tibetan Plateau are key issues in field of earth science, which is important to research the formation and evolution of the Tibetan Plateau. The northeastern Tibetan Plateau result from the northeastward extension of Tibetan Plateau, but uncertainties remain about northeastward extension range of the Tibet Plateau. This paper mainly collects a large amount of detailed results about the surface geology and obtained results of deep structures(including deep electrical structure, bouguer gravity anomalies, the crustal and upper mantle velocity structure, lithosphere structure and seismic anisotropy)of the northeastern Tibetan Plateau in the recent years and discuss comprehensively about the above characteristics. The results of tectonic thermochronometry and structural features suggest that the strong tectonic activities of Haiyuan arcuate tectonic region and its northern part which are related to the uplift and extension of the northeastern Tibetan Plateau since the Meso-Late Cenozoic. The results show that the surface extension of the northeastern Tibetan Plateau has acrossed the Haiyuan arcuate tectonic region and reached the Helan tectonic belt and Yinchuan graben. In addition, most of deep exploration works also reveal that the deep structure of Haiyuan arcuate tectonic region and its southern part are obviously modified by the extension of the northeastern Tibetan Plateau. However, it is still controversial whether the deep structure of the Helan tectonic belt and Yinchuan graben is the results of the deep extension of the northeastern Tibetan Plateau. Some results of seismic tomography, modeling receiver functions and seismic anisotropy suggest mantle flow from the northeastern Tibetan Plateau to the gap between the Ordos and Alxa blocks. The low-Vp and low-Vs anomalies and low resistance body exist widely in the lower crust and extend to the uppermost mantle in the Helan tectonic belt and Yinchuan graben. The predominant fast velocity direction(NE-SW)of the Helan

关 键 词：青藏高原东北缘 扩展变形范围 浅表地质 深部结构 壳-幔变形 

分 类 号：P315[天文地球—地震学] P541[天文地球—固体地球物理学]