准噶尔盆地永进地区及天山北缘中段齐古组沉积物源分析

SEDIMENT PROVENANCE ANALYSIS OF THE QIGU FORMATION IN YONGJIN AREA AND THE MIDDLE PART OF THE NORTHERN MARGIN.OF TIANSHAN MOUNTAIN,JUNGGAR BASIN

准噶尔盆地是我国重要的含油气盆地,也是研究中亚造山带的天然实验室,盆地内物源体系一直是前人研究的热点。近年来随着勘探程度的加深,在准噶尔盆地永进地区西山窑组地层中单独划分出了齐古组地层,因此永进地区齐古组地层的物源研究还比较薄弱。为解决该问题,本次研究以永进地区齐古组钻井岩心为研究对象,同时选取研究观点相对统一的天山北缘中段露头剖面进行对比研究,以期使结论更加充分。通过岩石学(样品40件)、重矿物(样品22件)及主微量元素分析方法(样品7件)对其进行物源分析。经主微量元素与重矿物组成特征方法分析认为永进地区的源区母岩岩性为中-酸性岩,天山北缘中段为中-酸性岩浆岩+变质岩组合;岩石碎屑组分显示永进地区的源区构造背景为火山岛弧,而天山北缘中段为火山岛弧+再旋回造山带背景;古流向与ZTR指数指示永进地区物源方向来自北西向,天山北缘中段来自南东方向,微量元素均一化蛛网图、稀土元素标准化分配模式图和Q型聚类分析结果也显示物源区不同。综合以上分析认为永进地区物源区为扎伊尔山,且车-莫古隆起可能提供了一定的物源;天山北缘中段物源区为北天山和中天山。

The Junggar Basin,located in the Central Asian orogenic belt,is an important oil-gas-bearing basin,and the provenance system of sediments in the basin has been a hot research topic.In recent years,with the deepening of exploration,Qigu Formation has been separated from Xishanyao Formation in Yongjin area of Junggar Basin,but the provenance research of this newly established formation is still weak.To solve this problem,in this paper,the drilling core of Qigu Formation in Yongjin area is taken as the research object.Meanwhile,the outcrop profile in the middle part of the north margin of Tianshan Mountains with relatively unified research views is selected for comparative study,with a view of making the conclusions more adequate.The provenance analysis is carried out by petrology(40 samples),heavy minerals(22 samples),as well as main and trace elements analysis(7 samples).Based on the analysis of the composition characteristics of major elements,trace elements and heavy minerals in the Qigu Formation,it is recognized that the parent rock in the Yongjin area is intermediate-acid rock,while in the middle part of the north margin of Tianshan Mountains,the parent rock is a combination of intermediate-acid magmatic rock and metamorphic rock.The rock clastic components show that the tectonic background of Yongjin area is volcanic island arc,while the middle part of north margin of Tianshan Mountains is volcanic island arc plus recycle orogenic belt background.Analysis of paleo-flow direction and ZTR index indicates that the provenance direction of Yongjin area is from the northwest region,and the middle part of the northern margin of Tianshan Mountains is from the southeast region.The results of uniform spider map of trace elements,standardized distribution pattern diagram of rare earth elements and Q-type cluster analysis also show the deposition of these two areas have different provenance.It is considered that the provenance of Yongjin area is Mount Zaire,and the Che-Mo uplift may provide a certain provenance.The provenance area in the middle part of the north margin of the Tianshan Mountains is North Tianshan Mountain and Middle Tianshan Mountain.