西秦岭北缘断层的多期变形演化及其构造动力学意义  

The multiple deformation of the northern margin fault of the western Qinling and its tectonic dynamic significance

作　　者：常璐璐 郭进京 常西玲 吴彦旺 Chang Lulu;Guo Jinjing;Chang Xiling;Wu Yanwang(School of Geology and Geomatics,Tianjin Chengjian University,Tianjin 300384)

机构地区：[1]天津城建大学,地质与测绘学院,天津300384

出　　处：《地质科学》2022年第2期375-398,共24页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目“西秦岭北缘断裂带新生代构造变形几何学—运动学分析及构造变形演化”(编号:41772215)资助。

摘　　要：西秦岭北缘断层是青藏高原东北缘新生代盆地与西秦岭地块之间的边界断层,其构造变形的几何学—运动学特征和变形历史等研究对于重建青藏高原东北缘新生代以来的构造变形时空动力学过程,限定新生代盆地构造属性,揭示印度板块—欧亚板块碰撞汇聚的远程构造响应和青藏高原东北缘隆升等重大科学问题具有重要地质约束。本文通过对西秦岭北缘新生代盆地南边界F1断层的断层岩类型及分带、构造要素的几何学—运动学特征等较详细的构造解析,辨认出F1断层6期构造变形:第一期为北西西走向、向北倾斜的韧性—韧脆性伸展正断层作用;第二期为北西西走向、向北陡倾或近直立的高角度逆冲断层作用,指示近南北向挤压缩短作用;第三期为走向近南北、向东或向西陡倾的对冲断层作用,指示了近东西向的挤压缩短作用;第四期为北东向右旋和北西向左旋的走滑共轭断层系统,指示了近东西向的挤压作用;第五期为断层面近直立的北东向左旋、北西向右旋的共轭破裂系统,指示了近南北向挤压作用;第六期为断层面近直立的近东西向左旋和近南北向右旋走滑断层构成了几何学—运动学协调的共轭破裂系统,指示了北东向挤压作用。结合西秦岭北缘渐新世—中新世沉积盆地具有断陷盆地沉积序列特征和上新世具有类磨拉石的冲洪积扇粗砾岩特征以及F1断层多期变形对新生代盆地沉积地层的控制和改造作用分析,认为F1断层第一期韧性—脆韧性伸展正断作用始于渐新世,控制了渐新世—中新世伸展断陷盆地沉积;F1断层第二期高角度逆冲缩短变形使得渐新世—中新世断陷盆地封闭、靠近F1断层的底部砾岩层卷入了挤压逆冲断层作用,断层拖曳使地层产状翘起变陡,这期变形持续到上新世冲洪积扇粗砾岩出现;F1断层第三期与第四期虽然都为近东西向挤压,但第�The northern margin fault of the West Qinling is a boundary fault between the Cenozoic basin and the West Qinling block in the northeast margin of Qinghai-Tibet Plateau. Its deformation history and geometric-kinematic characteristics could provide the constraints to the tectonic attributes of Cenozoic basins and spatial-temporal dynamics of crustal uplift and deformation of the northeast margin of the Qinghai-Tibet Plateau which could help understanding the remote tectonic response to the Indian-Eurasian collisional convergence.Based on the detailed structural analysis for the fault rock zoning, the morphology and geometric-kinematic characteristics of various structural elements, and the superposition and cutting relationship between different structural elements of the southern boundary F1 fault in the northern margin of West Qinling, the six phases of structural deformation with different properties and geometric-kinematic characteristics was identified in the F1 fault zone as follows:the first phase is characterized by NWW trending with northward dipping, ductile or ductile brittle extensional normal faulting by north-south tectonic extension;the second phase is characterized by NWW trending with north steep dip, brittle extrusion thrusting by north-south tectonic compression;the third phase is characterized by the north-south strike with west dipping thrust faulting formed by east-west compression;the fourth phase characterized by strike-slipping conjugate fault system with minor oblique thrusting in which NE trending fault is dextral and NW trending is sinistral formed by east-west compression as above;the fifth phase formed a conjugate fault system formed by north-south compression with sinistral NE trending faulting and dextral NW trending faulting, both fault planes is vertical;the sixth phase formed sinistral EW trending strike-slipping fault and NS trending dextral strike-slipping fault which constitute a conjugate fracture system with geometric-kinematic coordination formed by NE-SW compression. On th

关 键 词：西秦岭北缘断层 多期变形 几何学 运动学 动力学 

分 类 号：P542[天文地球—构造地质学]