青藏高原北缘阿尔金走滑边界的侧向扩展--甘肃北山晚新生代走滑构造与地壳稳定性分析  

Lateral growth of the Altyn Tagh strike-slip fault at the north margin of the Qinghai-Tibet Plateau:Late Cenozoic strike-slip faults and the crustal stability in the Beishan area, Gansu, China

作　　者：郭召杰[1] 张志诚[1] 张臣[1] 刘畅[1] 张宇[1] 王驹[2] 陈伟明[2] 

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]核工业北京地质研究院,北京100029

出　　处：《地质通报》2008年第10期1678-1686,共9页Geological Bulletin of China

基　　金：国家重点基础研究规划项目(编号:2007CB411305);国家自然科学基金项目(编号:40572123、40672130)资助

摘　　要：对北山地区遥感影像和野外地质特征的分析表明,自阿尔金断裂带向NW方向依次出露三危山-双塔断裂、大泉断裂和红柳河断裂。这些断裂近于平行,且同为左行走滑断裂,具有相似的展布特征,空间走向均为NE40～50°,断裂系末端均发育"树枝状"分支断层,在断层夹块之间形成"多米诺"构造,构成了北山地区主要的构造样式。断层谷地沉积物分析和断层泥ESR年代学测试结果表明,三危山-双塔断裂形成于上新世(N2k),大泉断裂形成于早更新世(1.2～1.5Ma),而北山地区分支断层和次级断层的活动在400ka之后。对北山地区断裂构造几何学和年代学的研究表明,阿尔金断裂系晚新生代以来向NW方向的侧向扩展,是阿尔金走滑边界重要的生长方式。北山地区特殊的走滑构造组合样式,使该地区的构造变形难于在某条断层上聚集能量,而分散在若干条次级断层上的位移量又微乎其微,该地区成为"最稳定的活动区"。Analysis of remote sensing images and field geological features of the Beishan area indicates that the Altyn Tagh fault, Sanweishan-Shuangta fault, Daquan fault and Hongliuhe fault are distributed from southeast to northwest in the Beishan area. The faults are nearly parallel and all left-lateral strike-slip faults. They have similar distribution characteristics and all strike NE40-50°. Secondary dendritic branch faults are developed at the end of the fault system. Granites or blocks intercalated within the branch faults rotate clockwisely, forming ＂Domino＂ structure. It is the main structural style of the Beishan area. Analysis of sediments in fault valleys and ESR. dating of fault gouge show that the Sanweishan-Shuangta fault formed in the late Pliocene, while the Daquan fault in the early Pleistocene （1.5-1.2 Ma）, and that the activities of the branch faults occurred in the late Pleistocene （after 400 ka）. Geometric and chronological studies of faults in the Beishan area indicate that the Altyn Tagh fault has propagated in a NW direction since the Late Cenozoic, which is the important growth manner of the Altyn Tagh strike-slip boundary. The special strike-slip structural association style in the Beishan area caused the structural deformation in the area to accumulate energy in a particular fault with difficulty, while the displacement amounts in several secondary faults negligible. So this area is the most stable seismically active area.

关 键 词：北山地区 阿尔金断裂带 走滑断层 侧向扩展 晚新生代 

分 类 号：P534.6[天文地球—古生物学与地层学] P542.3[天文地球—地质学]