北祁连造山带与贺兰冷裂谷构造边界的探讨

Discussion of the Tectonic Boundary Between North Qilian Orogenic Belt and Helan Cold Rift

北祁连造山带和华北板块西南缘的贺兰冷裂谷在古生代的构造界线位置长期存在不同的认识,其以何种形式穿过贺兰山并向西延伸亦有不同的见解。本文详细分析了祁连造山带及贺兰山早古生代构造沉积演化以及元山子、围沟井晚泥盆世上叠盆地沉积特征,从陆架和陆坡转换地带、上叠盆地基底构造性质及其边界断裂带发育特征等着手,并参考该区的地球物理信息等进行综合研究,确认北祁连造山带与华北板块贺兰冷裂谷的界线位于青铜峡(牛首山)-固原断裂构造线,其在长期构造演化过程中,形成了构造多向性、多期性和多样性等基本特征。该界线在土井子附近穿越贺兰山与内蒙东西向查汗布拉格断裂相连。

Helan cold rift valley is located between north Qilian orogenic belt and southwest margin of North China plate.There also exist different views of the tectonic boundary location in Paleozoic Era,and ways to get across Helan mountain and extend westwards.In the paper,the tectonic-sedimentary evolution of Qilian orogenic belt and Helan mountain in Early Paleozoic and the development characteristics of superposed basin of Yuanshanzi and Weigoujing in Late Devonian are discussed.Based on continental shelf,continental slope transition zones and basal structure of superposed basin and its bordering fault zone and refers to geophysical information in the area,it is determined that the boundary of Helan cold rift between North Qilian orogenic belt and North China Plate is located in Qingtongxia（Niushou mountain）-Guyuan fault belt.In the long tectonic evolution,it is characteristic of multi-directionality,multistage and multiplicity.Near the area of Tujingzi,the boundary passes through Helan mountain and links with the east-west extending Chahanbulage fault in Inner Mongolia.