Shale Gas Research Institute, Petro China Southwest Oil & Gas field Company
Sichuan Key Laboratory of Shale Gas Evaluation and Exploitation
National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing)
College of Geosciences, China University of Petroleum (Beijing)
Institute of Unconventional Petroleum Science and Technology, China University of Petroleum (Beijing)

海相页岩中硅质矿物含量及成因往往与有机质丰度和可改造性存在密切关系。为揭示研究区二叠系海相页岩硅质矿物赋存特征及物质来源,对野外露头和钻井样品开展了系统的岩石学与元素地球化学分析,利用岩石薄片、扫描电镜、能谱分析、主量元素、微量元素等对吴家坪组-大隆组页岩中的石英赋存特征和成因进行深入解剖,认为:①硅质矿物主要包括4种赋存状态,即碎屑石英、石英胶结物、硅质生屑及石英脉体,硅质矿物来源为火山喷发-陆源物质输入、生物成因、深部热液成因三类;②硅质页岩主要沉积于拉张性海槽地堑区,吴三段及其他层段的Al、Ti和Th的含量低于上地壳,且吴一、二段和大隆组的碎屑石英为陆源输入成因,Al-Fe-Mn和Zn-Ni-Co三角图中吴家坪组-大隆组页岩样品落在生物成因和热液成因区,表明石英胶结物和石英脉体为生物及热液成因,且硅质矿物及水体营养化与有机质富集具有耦合关系。

The content and genesis of siliceous minerals in marine shales are often closely related to the abundance and transformability of organic matter. To elucidate the occurrence characteristics and sources of siliceous minerals in the Permian marine shales of the study area, this paper carried out a systematic petrological and elemental geochemical analysis on field outcrop samples and drilling samples. The occurrence characteristics and origin of quartz in the shales of Wujiaping-Dalong Formation were deeply dissected by means of thin section of rock, scanning electron microscopy, energy spectrum analysis, principal and trace elements. The conclusions are as follows: ①There are four main types of siliceous minerals: clastic quartz, quartz cement, siliceous bioclasts, and quartz veins; the origins of these siliceous minerals can be classified into three categories: volcanic eruption and terrigenous input, biological origin, and deep hydrothermal origin. ② The siliceous shales are primarily deposited in the extensional trough graben areas; the content of Al, Ti and Th in the Wu member is lower than that of the upper crust, and the detrital quartz of Wu member, Wu member and Dalong Formation is of terrigenous input origin; the Al-Fe-Mn and Zn-Ni-Co triangle diagrams show that the shale samples of the Wujiaping-Dalong Formation fall in the biogenic and hydrothermal origin areas, indicating that the quartz cements and quartz veins are mainly biogenic and hydrothermal; the development of siliceous minerals has a strong correlation with aqueous nutrient enrichment and organic matter accumulation.

国家自然科学基金项目(42072151);中国石油天然气集团有限公司科技项目(2023ZZ21-04);中国石油西南油气田公司科研项目(20230304-08)