摘要
四川盆地五峰组中下部黑色页岩具有高总有机碳(total organic carbon,TOC)、高硅质含量、低黏土含量的特征,且硅质放射虫大量发育,通常认为其沉积水体深度较大,应超过上覆龙一_(1)亚段。对涪陵地区五峰组黑色页岩段与龙一_(1)亚段放射性元素含量特征开展了分析与对比,其中U含量、Th/U以及计算得到的平均相对水深,显示五峰组黑色页岩沉积时期其水体深度稍大于龙一_(1)亚段上部但小于龙一_(1)亚段下部,最大水深没有超过龙一_(1)亚段。同时五峰组黑色页岩Th、K含量反应的陆源碎屑注入量小于整个龙一_(1)亚段。涪陵地区五峰组闭塞的水体条件、较强的还原环境和较少的陆源碎屑注入量,加之温暖、湿润的气候条件,藻类和硅质生物发育和保存的适合程度超过了水深更大的龙一_(1)亚段下部,从而形成了与其相当甚至略高的TOC和硅质矿物含量。通过对四川盆地不同地区五峰组黑色页岩放射线元素含量特征分析,明确了中下部具有全盆地水体逐渐加深,陆源碎屑注入量逐渐减少的沉积环境变化特征,但不同地区的变化趋势并不完全一致。结合放射性元素、岩性、区域构造运动和微观构造变形特征,认为五峰组沉积时期扬子地台受到华夏板块的进一步挤压,在不均衡挠曲作用之下,不同地区发生差异化沉降-抬升作用,且幅度不尽相同,造成不同地区水体深度、陆源碎屑注入量不同,从而形成五峰组黑色页岩空间上和时间上的演化差异。
The black shale of Wufeng Formation in Sichuan Basin is characterized by high total organic carbon(TOC),high siliceous content and low clay content,and a large number of siliceous radiolarians are developed.It is generally considered that its sedimentary water depth is large and should exceed the overlying Longmaxi^(1)_(1) sub member.The content characteristics of radioactive elements in Wufeng Formation-Longmaxi^(1)_(1) sub section in Fuling area were analyzed and compared.The U content,Th/U and the calculated average relative water depth show that the water depth of Wufeng Formation during the deposition period is slightly greater than the upper part of Longmaxi^(1)_(1) sub section,but less than the lower part of Longmaxi^(1)_(1) sub section,and the maximum water depth does not exceed Longmaxi^(1)_(1) sub section.At the same time,the injection amount of terrigenous clasts reflected by the content of Th and K in Wufeng Formation is less than that of the whole Longmaxi^(1)_(1) sub member.Due to the blocked water conditions,strong reduction environment and less injection of terrigenous debris of Wufeng Formation in Fuling area,coupled with warm and humid climate conditions,the suitability for the development and preservation of algae and siliceous organisms exceeds the lower part of Longmaxi^(1)_(1) sub member with greater water depth,resulting in equivalent or even slightly higher TOC and siliceous mineral content.Through the analysis of the content characteristics of radioactive elements in shale of Wufeng Formation in different areas of Sichuan Basin,it is clear that the sedimentary environment changes with the gradual deepening of water and the gradual reduction of terrigenous clastic injection in the whole basin,but the change trends in different areas are not completely consistent.Combined with the characteristics of radioactive elements,lithology,regional tectonic movement and microstructural deformation,it is considered that the Yangtze platform is further compressed by the Cathaysian plate during the depo
作者
边瑞康
刘忠宝
张培先
杜伟
刘珠江
聂海宽
乔辉
BIAN Rui-kang;LIU Zhong-bao;ZHANG Pei-xian;DU Wei;LIU Zhu-jiang;NIE Hai-kuan;QIAO Hui(State Key Laboratory of Shale Oil&Gas Enrichment Mechanisms and Effective Development,Beijing 102206,China;Key Laboratory of Shale Oil and Gas Exploration&Production,SINOPEC,Beijing 102206,China;Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 102206,China;Exploration and Production Research Institute of East China Oil&Gas Company,SINOPEC,Nanjing 210019,China;SINOPEC Exploration Company,Chengdu 610041,China)
出处
《科学技术与工程》
北大核心
2022年第28期12339-12348,共10页
Science Technology and Engineering
基金
国家科技重大专项(2017ZX05036004)。
关键词
五峰组
放射性元素
黑色页岩
地质意义
四川盆地
Wufeng Formation
radioactive element
black shale
geological significance
Sichuan Basin
