再论贺兰山南部北西向构造成因

贺兰山南部分布着多个方向的构造,其中最明显地是一系列的北西向构造,目前这些构造的相 互关系以及形成机制还没有得到合理地解释,争论很大;野外构造研究表明,贺兰山南部北西向构造的 形成与青铜峡固原断裂活动有密切的关系,是该断裂由走滑运动向挤压运动转换时的派生构造;从另 一角度也说明,在中新生代由青铜峡固原断裂所限定的地块(卫宁北山)向东运动,而这些北西向构造 的形成主要发生在新生代。由于卫宁北山向东运动的动力来源于青藏高原,因此,贺兰山南部北西向构 造的形成与青藏高原的演化有密切的联系。所以,作为中国重要地质界限的南北向构造———贺兰山已 经被青藏高原的构造活动所叠加。

Rediscussion of the mechanism of the northwest trending structures in the southern part of Helan Mountains

There are several sets of structures in the southern part of Helan Mountains, which are mostly trending north- west. However the mechanism of these structures have not been recognized clearly yet, there are many disputations. Based on the study of the field, we find that it is the movement of the Qingtongxia-Guyuan fault that led to the formation of these northwest trending structures. In other words, all these northwest trending structures were developed in the site where the movement of fault changed from strike-slip to thrust; furthermore, it also means that in the Cenozoic the block limited by Qingtongxia-Guyuan fault was moving eastwards, and the northwest trending structures were developed in the Cenozoic, so there may be close relationships between the formation the northwest trending structures and the evolution of the Qinghai- Tibet Plateau.