山西沁水盆地东缘太行大断裂构造变形特征及其成因探讨

太行大断裂是山西沁水盆地与太行山隆起的分界,也是华北克拉通内部重要的构造变形带。通过对断层破碎带、断层相关褶皱及共轭节理的野外详细测量,研究了太行大断裂的构造变形特征,探讨其形成的古构造应力场。研究认为,太行大断裂可能经历了3期构造应力作用:(1)印支期在华南、华北板块碰撞的远程效应作用下表现出近N—S向挤压构造应力场。(2)燕山期表现为E—W向至NWW—SEE向挤压构造应力场。(3)喜马拉雅期由NWW—SEE向挤压转换为NE—SW向挤压(或NW—SE向伸展)。太行大断裂由北至南可分为:(1)北段,由3条呈右阶斜列的大型逆断层组成,基岩出露,以逆冲推覆为主。(2)中段,地表出露斜歪褶皱和逆冲断层组合。(3)南段,发育强烈的挤压破碎带,该带中广泛发育构造角砾岩和构造透镜体,构造挤压带内的构造透镜体陡立,显示近水平方向的挤压。

Discussions on structural deformation features and genesis of Taihang Mega Fault,east edge of Qinshui Basin in Shanxi

Taihang Mega Fault,a boundary between Shanxi Qinshui Basin and Taihangshan Mountain belongs to an important internal structural deformation belt in North China Craton.Through detailed field measurement of shattered fault zone,folds related with fault and conjugated joints,the structural deformation characters of Taihang Mega Fault was studied and paleotectonic stress field caused by the structural deformation was discussed.The research showed that there existed three stages of structural deformation during the movement of Taihang Mega Fault:(1) a structural stresst field with nearly N-S strike compression was caused by collision between South China and North China plates during Indosinian;(2) E-W to NWW-SEE strike compression tectonic stress field occurred during Yanshanian;(3) the structural stress field with NWW-SEE compression can be developed to that of NE-SW strike compression during Himalayan.From north to south,Taihang Mega Fault could be divided into north section with emergence of bedrock including three rightstep diagonal large-scale reverse faults.The faults were major thrust-napped structure.Center section was composed of combination of inclined fold and thrust fault.South section was composed of well-developed compressed fracture zone.Tectonic breccia and lens were widely developed in the zone.The nearly horizontal compression showed that the altitude of many tectonic lens were very steep in the compression zone.