黔北镇远牛蹄塘组黑色页岩沉积环境与有机质富集关系

The relationship between sedimentary environment and organic matter accumulation in the Niutitang black shale in Zhenyuan,northern Guizhou

通过矿物组分、主量元素、微量元素、碳氧同位素等特征,分析了黔北地区镇远县ZX井牛蹄塘组黑色页岩的岩相类型和不同岩相页岩的沉积环境及其与有机质富集间的关系。结果表明,牛蹄塘组下段以硅质页岩为主,TOC含量4.96%~10.10%;上段以富泥硅质页岩为主,TOC含量1.43%~9.04%。下段硅质页岩沉积于水流停滞的深水陆棚环境,沉积古水体为贫氧的还原状态;上段富泥硅质页岩沉积时期,仍为贫氧的还原环境,但水体滞留程度、还原性较下段硅质页岩沉积期弱。贫氧的还原环境是影响牛蹄塘组黑色页岩有机质富集的主要因素,热液作用和陆源碎屑对牛蹄塘组黑色页岩有机质富集的影响较小。

The mineral composition,major and trace elements,carbon and oxygen isotopes were used to analyze the lithofacies type,as well as sedimentary environments of different lithofacies and their relationship with organic matter accumulation in the Niutitang black shale from the well ZX in Zhenyuan County,northern Guizhou area.The results show that the lower member of Niutitang Formation is mainly composed of siliceous shale with TOC of 4.96 %~10.1%,and the upper member is mainly composed of mud-rich siliceous shale with TOC of 1.43%~9.04%.Even though both siliceous shale and mud-rich siliceous shale were deposited in a reducing environment,the sedimentary environment of siliceous shale was more reductive than that of the mud-rich siliceous shale.In this study area,oxygen-deficient reducing environment has a stronger influence on organic matter enrichment than hydrothermal action and terrigenous detrital content.