柴达木盆地新生代走滑构造特征及成因演化

The Characteristics and Genetic Evolution of the Cenozoic Strike-slip Structure in Qaidam Basin

柴达木盆地是青藏高原北部最大的中、新生代山间盆地,为阿尔金山、祁连山和昆仑山所围绕,形成“三山一盆”的构造格局,具有复杂的盆山关系。通过柴达木盆地西部地区地震资料精细构造解释,首次发现跃进二号东构造下部干柴沟组构造为正花状构造,而其上部干柴沟组、油砂山组、狮子沟组、七个泉组构造为负花状构造。构造演化剖面分析表明,走滑构造发育经历了七个泉组沉积末期强烈的压扭构造作用,发育了正花状构造样式,而至柴达木组沉积的前期构造由经历了强烈的张扭构造作用,发育了负花状构造,且叠加在早期正花状构造之上,使得浅层层序主要发育正断层,两期走滑断裂作用叠加产生了现今复杂的负反转走滑断裂带。而柴达木盆地北部地区也有相同的构造特征,由此可推断柴达木盆地是受阿尔金走滑断裂影响的斜向压扭构造,非走滑断裂主干位移带内的拉分盆地。因此,系统分析柴达木盆地地区构造发育演化对于深入认识复杂的盆山关系具有重要的意义。

The Qaidam Basin is the largest Mesozoic-Cenozoic intermountain basin in the north of Qinghai-Tibet Plateau.Surrounded by Aljin,Qilian,and Kunlun Mountains,a tectonic pattern of“Three Mountains and One Basin”is formed in a complex mutual relationship among basin and mountains.Based on fine structural interpretation of seismic data in the western part of the Qaidam Basin,apositive flower-like structure was discovered in the lower part(the Lower Ganchaigou Formation)of the YuejinNo.2 East Structure,and a negative flower-like structure was found in the upper part(the Upper Ganchaigou,Youshashan,Shizigou,and Qigequan Formations).Analysis in tectonic evolution reveales a strike-slip tectonic evolution,from a strong compressive-shear setting in positive flower tectonic pattern during the formation of the top Qigequan Formation to a strong transtensional tectonic setting during the sedimentation of lower Qaidam group sedimentary structure by experienced,develops a negative flower structure,and superimposes over early positive flower structure,and makes the shallow layers of main development normal fault.Nowdays,two phase of the superposition of strike-slip faulting produced complex negative inversion of strike-slip fault zone.The northern part of the Qaidam Basin also has the same structural characteristics,so it can be inferred that the Qaidam Basin is an oblique compression-torsional structure affected by the Aljinstrike-slip fault and a pull-apart basin within the main displacement zone of the non-strike-slip fault.Therefore,analysis of the tectonic development and evolution in the Qaidam Basin is very important to gain a deeper understanding of the complex relationship between basin and mountain.