鄂尔多斯及周边地区上地幔三维P波速度结构及其构造意义  

3D P-wave velocity structure beneath Ordos block and its surrounding regions and its tectonic implications

作　　者：王薇 吴建平[1] 蔡妍[1] Wang Wei;Wu Jianping;Cai Yan(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地球物理研究所,中国北京100081

出　　处：《地震学报》2023年第4期628-644,共17页Acta Seismologica Sinica

基　　金：国家自然科学基金(42174117,41774102,41804057)资助.

摘　　要：利用中国地震科学台阵密集流动地震台站和固定地震台站记录的远震P波资料,采用走时层析成像方法反演获得了鄂尔多斯及周边地区上地幔的精细速度结构。结果显示,鄂尔多斯地块下方存在较厚的高速异常,其中西部深度约为180 km,北部约为150 km,中部的局部地区可达300 km,表明鄂尔多斯地块总体上仍保持克拉通特性。鄂尔多斯地块北部相对较薄的岩石圈可能与地幔物质上涌对岩石圈进行了加热和改造有关,其西部岩石圈的减薄可能与青藏高原东北缘上地幔热物质的横向扩展有关。华北克拉通东部地块、中部地块及鄂尔多斯地块东北部的上地幔表现出大范围的低速异常,推测可能与太平洋板块后撤导致的伸展构造背景、滞留板片脱水以及板片前缘局部对流有关。在该地区的伸展背景下,岩石圈或软流圈的熔融物沿着软弱带上涌并形成了包括大同火山在内的火山群。We obtain a high-resolution velocity structure of the upper mantle in the Ordos block and its surrounding regions by travel-time tomography,using the teleseismic P-wave data recorded by dense temporary stations of China Seismic Array and permanent stations.The results show a thick high-velocity anomaly beneath the Ordos block,which extends to a depth of about 180 km in the west,150 km in the north,and up to 300 km in part of the central area,indicating that the Ordos block still maintains craton stability as a whole.The relatively thin lithosphere in the northern Ordos may be related to the heating and modification of the lithosphere by the mantle upwelling,whereas the lithosphere thinning in the western Ordos may be associated with the lateral expansion of the warm upper mantle of northeastern Tibet.The upper mantle of the eastern North China Craton,the central North China Craton and the northeastern Ordos block exhibit broad low-velocity anomalies,which may be related to an extensional tectonic set-ting caused by the rollback of Pacific Plate,the dehydration of the stagnant slab and the local convection at the front edge of the slab.In extensional environments,melts from the litho-sphere or asthenosphere upwelled along the weak zone and formed volcanoes including Datong volcano.

关 键 词：鄂尔多斯地块 上地幔结构 地震层析成像 华北克拉通 地幔上涌 

分 类 号：P315.2[天文地球—地震学]