甘肃敦煌盆地侏罗纪原型盆地性质与沉积环境演化

Jurassic depositional environmental evolution and prototype basin in Dunhuang Basin,Gansu Province

为研究敦煌盆地侏罗纪原型盆地性质及沉积环境演化,本文利用地震资料、航磁资料、野外地质考察资料、同位素定量测年数据,基于前人在阿尔金断裂系构造理论成果,对敦煌盆地基底岩性组成、深部动力学背景、盆地发育时限和盆地性质做了系统研究,认为敦煌盆地与塔里木盆地、柴达木盆地、酒泉盆地的前侏罗纪基底组成不相同,是一个相对独立的盆地。敦煌地块的南部边界为红柳沟—拉配泉断裂,西部边界为民丰—且末断裂带,阿尔金主断裂为敦煌盆地的东部边界。三危山断裂是分割敦煌盆地南北凹陷的控凹断裂,民丰—且末断裂、红柳沟—拉配泉断裂、阿尔金主断裂是控盆断裂。青藏高原南缘的北向超深俯冲、北缘陆内南向的浅俯冲、深部地幔羽结构等多元驱动机制导致敦煌地块显生宙以来大部分时间处于隆升剥蚀状态,很少接受沉积,至侏罗纪塌陷形成敦煌湖盆。敦煌盆地在三叠纪和晚侏罗世—早白垩世青藏高原两次重大的碰撞造山之间的松弛拉张期形成了侏罗纪沉积盆地。敦煌盆地发育经历3个阶段:早侏罗世填平补齐阶段,中侏罗世断陷阶段和晚侏罗世坳陷阶段,其中中侏罗世断陷阶段为主成盆期。

Objective:To study the Jurassic depositional environmental evolution and the prototype basin in the Dunhuang Basin,NW China.Methods:The paper used seismic data,aeromagnetic data,field geological survey data,and isotope quantitative dating data,based on the results obtained by predecessors in the structural theory of the Altyn fault system,the Dunhuang Basin’s basement lithological composition,deep dynamic background,basin development time limit and the nature of the basin has been systematically studied.Results:It is believed that the Dunhuang Basin,Tarim Basin,Qaidam Basin,and the Jiuquan Basin have different pre-Jurassic basement lithological composition.The Jurassic basin is a relatively independent basin.The southern boundary of the Dunhuang block is the Hongliugou—Lapeiquan fault,the western boundary is the Minfeng—Qiemo fault,and the Altyn main fault is the eastern boundary of the Dunhuang Basin.The Sanweishan fault is a basin-controlling fault that separates the north and south sags of the Dunhuang Basin.The Minfeng—Qiemo fault,Hongliugou—Lapeiquan fault,and Altyn main fault are basin-controlling faults.The multiple driving mechanisms such as the northward ultra-deep subduction of the southern margin of the Qinghai—Xizang(Tibetan)Plateau,the shallow intracontinental southward subduction of the northern margin,and the deep mantle plume structure have caused the Dunhuang block to be a state of uplift and denudation for most of the time since the Phanerozoic,and it rarely accepts deposition.It was not until the Jurassic collapsed that the Dunhuang Basin was formed.The Dunhuang Basin was a Jurassic sedimentary basin,which resulted from the stress relaxation between two northward collision of the Qinghai—Xizang(Tibet)Plateau between the Triassic and the Late Jurassic—Early Cretaceous.Conclusion:The Jurassic Dunhuang Basin is a relatively independent basin,the evolution of the Dunhuang Basin has undergone 3 stages:the Early Jurassic filling stage,the Middle Jurassic rift stage and the Late Jurassic depression stage,and the Middle Jurassic rift stage is the main basin-forming stage.