辽西地区构造系统的形成与东北亚区域构造演化

Formation of structural systems in western Liaoning and regional tectonic evolution of northeastern Asia

燕山造山带东部辽西地区的构造填图、地质研究 ,以及中生代火山 沉积岩系的同位素资料 ,提供了东北亚和燕山板内造山带的演化历史。华北板块北部燕山 辽西地区自中元古宙至古生代 ,与整个华北克拉通一起 ,接受相同的地台盖层沉积 ,其沉积历史完全相同。在中晚三叠世之后 ,该区沉积了中生代火山碎屑岩和陆相沉积岩 ,并发生强烈的构造变形 ,这才有别于华北克拉通的其它稳定区。同位素资料表明 ,兴隆沟期火山岩、蓝旗期火山岩和义县期火山岩形成时间分别为 2 0 0 - 170Ma、170 - 155Ma、14 0 - 10 0Ma。按构造成因和系统的指导思想 ,将该区构造归并成 3种构造系统 ,即逆冲推覆构造系、正滑断裂系和走滑断裂系。这 3种断裂系统的发育顺序是 :逆冲推覆构造形成于早白垩世中期 (相当于义县组、九佛堂组之间的界面 ) ;正滑断裂构造系是九佛堂组和阜新组的同沉积构造 ;走滑断裂构造系形成最晚 ,为晚白垩世形成的构造。其中早期逆冲推覆构造起了主导作用 ,奠定了本区构造格局的基本格架 ,晚期构造的叠加并未从根本上改变已有的构造格局。三叠纪到早白垩世期间 ,在欧亚板块向南挤压和古太平洋板块向北西方向的挤压作用下 ,于早白垩世中期形成本区的逆冲推覆构造 ;早白垩世晚期受古亚洲大陆区域扩张的影响 ,形成?

Recent structural mapping,geologic study in western Liaoning,the eastern part of Yanshanian orogenic belt,and geochronologic data of Mesozoic volcanic sedimentary rocks have revealed the evolutionary history of the Yanshanian intraplate orogenic belt of the northeastern Asia.From Middle proterozoic to Paleozoic time the Yanshan western Liaoning,the northern part of North China plate was characterized by the same platform sedimentary cover and the same sedimentary history with the North China craton as a whole.Since Middle Late Triassic the sedimentation of volcanic pyroclastic and continental sedimentary rocks and the strong deformation of the above rocks occurred in the study area which was distinct from other stable areas of North China craton.Geochronologic data show that the formetion ages of volcanic rocks of the Xinglonggou,Lanqi and Yixian Formations are 200-170Ma,170-155Ma,and 140-100Ma respectively. Based on the ideas of the genesis and system of structures,the structures in the study area can be divided into three generation systems,i.e.the thrust nappe system,the normal slipping system and the strike slipping system.The three structural systems were developed in the following order.The thrust nappe structural system was formed in the middle of Early Cretaceous (corresponding to the time boundary between Yixian and Jiufutang Formations).The normal slipping structural system represented the syn sedimentary structures of Jiufutang and Fuxing Formations.The strike slipping structural system was formed the latest,in Late Cretaceous.Of the above structural systems the early thrust nappe system is the predominant,and constitutes the basic structural framework of the study area.The superimposition of later structural systems have not changed the existing structural framework.During the period from Triassic to Cretaceous,under the southward compression of Euro Asian plate and the northwestward compression of paleo Pacific plate,the thrust nappe structures appeared in the middle of Early Cretaceous.While by the effect of the regional extension of paleo Asian continent in the late period of Early Cretaceous the normal slipping system in western Liaoning was formed.The formation of NNE trending strike slipping fault system was originated from the reactivation of Tan Lu giant fault.