贺兰山和银川盆地的岩石圈结构和断裂特征——深地震反射剖面结果

发布时间：2018-03-03 01:19

本文选题：华北克拉通　切入点：深地震反射剖面　出处：《中国科学:地球科学》2017年02期 　论文类型：期刊论文

【摘要】：位于南北构造带北段的贺兰山和银川盆地是华北克拉通西部的一个板内构造变形带和活动构造带,有着复杂的形成和演化历史,对该区复杂的地质构造和现代地震活动有着重要的控制作用.2014年初,跨银川盆地和贺兰山完成的长度135km的深地震反射剖面揭示了该区的岩石圈层结构和断裂的深浅构造特征.研究结果表明,沿剖面莫霍面埋深自东向西逐渐加深,地壳厚度40~48km,且不同构造部位的地壳反射结构图像、速度分布、壳内界面形态和莫霍面起伏存在着明显差异.深地震反射剖面揭示,贺兰山两侧有着不同的断裂构造特征,在贺兰山东侧,黄河断裂、贺兰山东麓断裂以及银川盆地内的多条隐伏断裂均为第四纪以来仍在活动的正断层,控制了银川盆地的新生代沉积,在剖面上呈"负花状"构造展布;在贺兰山西侧,巴彦浩特断裂和贺兰山西麓断裂在剖面上表现为东倾的逆冲断层,使得贺兰山隆起区的中生代地层发生褶皱、冲断和结构变形;地壳深断裂位于银川盆地的西侧,该断裂倾角陡直,向下错断中-下地壳和莫霍面,向上可能与两组上地壳断裂相联系;这套不同时期形成的走滑、逆冲和正断并存的深浅断裂系统是该区盆山耦合、地壳结构变形和壳幔结构变化的构造条件.深地震反射剖面揭示的另外一个重要现象是,在贺兰山和银川盆地之下还存在有一组强能量的上地幔反射波组(UMR),其界面深度约为82~92km,暗示该区上地幔中存在有速度跃变层或速度间断面,反映了该区上地幔结构的纵向不均匀性.探测结果为进一步分析研究华北克拉通西部复杂的深部结构、不同地块的结构差异和深浅构造关系等提供了地震学证据.
[Abstract]:Located in the northern section of the North South tectonic belt of Helan mountains and the Yinchuan basin is a plate in the western North China Craton tectonic deformation zone and tectonic zone, has a complex formation and evolution history of the geologic structure complex and modern seismic activity plays an important role in.2014 control at the beginning of the deep seismic reflection profile cross Yinchuan basin and Helan mountain to complete the length of 135km reveals the depth of structural features of rock layer structure and fracture in this area. The results show that the Moho depth along the profile from the east to the west gradually deepened, the crustal thickness 40~48km, crustal reflection images, and the velocity distribution in different tectonic positions, there are significant differences in the shell the interface morphology and Moho surface. Deep seismic reflection profiles revealed that Helan has a mountain on both sides of faults with different characteristics in Helan, Shandong side, Helan the Yellow River fault, Shandong piedmont fault and Yinchuan Basin A plurality of buried faults in Quaternary are still active normal faults, control of the Yinchuan basin in the Cenozoic sediments showed a negative flower structure distribution in the section in Helan; Shanxi side, BAYANHOT fault and Helan Shanxi Lu fracture of an East dipping thrust fault in the section, the Helan the mountain uplift area of Mesozoic strata occurrence of folds, thrust and structural deformation; deep crustal faults in the Yinchuan basin on the west side, the steep dip angle of fault, fault - down in the lower crust and the Moho, to contact with two groups of upper crust may fracture phase; slip form this set of different periods, the inverse depth of fracture the system is broken and coexistence is the basin mountain coupling deformation of crustal structure and tectonic conditions of crust mantle structures change. Another important phenomenon revealed by deep seismic reflection profile, under the Helan mountain and Yinchuan basin is still a strong group The upper mantle reflection wave group (UMR), the interface depth is about 82~92km, suggesting that the upper mantle of this area exists in the speed or velocity discontinuity of thermocline, the upper mantle of this area reflects the vertical inhomogeneity of the structure. The detection results for further analysis of the deep structure of western North China Craton complex, structural differences the different plots and the depth of structural relationship provides the Seismological Evidence.

【作者单位】：中国地震局地球物理勘探中心;
【基金】：国家自然科学基金项目(批准号:91214205) 地震行业科研专项项目(编号:201408023)资助
【分类号】：P542;P315.2

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