【作者】 武国利；

【导师】 胡健民； 施炜；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2009， 硕士

【摘要】 大巴山构造带位于秦岭造山带南部,一直被认为是华北、扬子板块碰撞带前陆逆冲—推覆构造带。本文研究表明,大巴山构造带依据构造变形样式和地层卷入情况,可划分为大巴山冲断-推覆构造带、大巴山前陆构造带(包括基底拆离构造带和盖层滑脱构造带)和大巴山前陆坳陷带。而大巴山前陆构造带,中生代经历了两次明显的叠加变形过程。其中早期变形发生在中-晚三叠世,与华北、扬子的碰撞密切相关,是碰撞造山带的前陆构造带(D1)。在大巴山弧形构造带西段以轴向近东西向的开阔宽缓的台阶式褶皱为特征。而在大巴山弧形构造带中段和东段,通过大比例尺地质构造填图,解析出来一期轴向北东到北北东向褶皱为主的变形。根据叠加变形序列及变形地层时代限定,变形时代很可能也是中三叠世晚期到早侏罗世。大巴山弧形构造带由轴向弧形延伸的线状褶皱与弧形弯曲的逆冲断层组成(D2),根据北大巴山韧性剪切变形带中的同变形云母定年结果161 Ma左右,大巴山地区在这个时间发生过强烈变形.而秭归侏罗纪盆地的沉积充填过程也显示在中晚侏罗世之间,物源和沉积环境发生明显变化,因此,D2期变形时代被确定为晚侏罗世到早白垩世。由于两期变形明显的叠加关系,不可能是递进变形关系,所以大巴山弧形构造带记录了两期不同系统构造变形的叠加,这对研究秦岭造山带的演化,具有重要的意义。更多还原

【Abstract】 The Dabashan Structural belt is a part of south Qinling Mountains, which has been regarded as a foreland thrusting belt of the collisional belt of the north and south China plates. According to tectonic deformation style and involved strata, the Dabashan structural belt can divided into Dabashan nappe-thrust belt, Dabashan foreland structural belt (including Basement Detachment Structural belt and Cover rock Decollement Structural belt) and Dabashan foreland depression belt.The results of the researches show that the Dabashan foreland structural belt has gone through strong superimposed deformation during the Mesozoic. The early deformation (D1) was related to the collision between the north and south China plates and is the foreland thrust belt of the Qinling collisional orogen. It occurred about the middle-late Triassic and the early Jurassic. In the western curvilinear structural belt, the deformation of Dl is of the folds with axis of nearly east to west trending. But both in central and in eastern of the belt, the mapping in lager scale shows that the fold axes of D1 are about nearly south to north. Based on the deformation sequence and the age constraints of the deformed strata, the age of the Dl recognised in the central and eastern curvilinear structural belt also is the late Triassic and the early Jurassic. The Dabashan curvilinear structural belt is composed of linear folds with curvilinear fold hinges and some curvilinear thrust faults (D2). Based on the Ar-Ar ages,161 Ma, of biotites from the ductile shearing zones in the north Dabashan thrust belt, the Dabashan structural belt was gone through a strong deformation. On the other hand, the deposition and filling process of Zigui basin show that the provenance and environment of the basin was changed between the middle and late Jurassic. Therefore, the authors believe that the age of D2 is the late Jurassic to the early Cretaceous. Because of the distinct superimposion of the two phases of deformation, it is impossible that they are progressive. So the Dabashan curvilinear structural belt records two phases of deformation which are formed during different tectonic settings. It is very important for the understanding of the evolution of Qinling orogen.更多还原