The abundance of organic matter in shales, which has a direct effect on the hydrocarbon generation potential of shales, is an important organic geochemical parameter for evaluating shale gas reservoirs. The total organic carbon content (TOC content) in shale is controlled by the abundance of original sedimentary organic matter. Therefore, it is very important to study the mechanism of organic matter enrichment in shale. In this paper, the Lower Cambrian marine shales from the Lower Yangtze region are selected as the research subject, most of which originate from a typical area well called Well JXY1. The degree of pyritization (DOP) is used to characterize the redox environment of the water body, while the P/Al ratio is used to analyze the biological productivity of paleoseawater. The paleosalinity of seawater is calculated via carbon and oxygen isotope analysis. In addition, the early Cambrian hydrothermal activities were studied by using core description; Si, Al, Fe, and Mn elemental analysis; and oxygen isotope calculations. The results show that during the early Cambrian Wangyinpu sedimentary period, the seawater was an anaerobic water body with H2S, and the oxygen concentration was approximately 0 mL/L. In the middle stages of the Wangyinpu sedimentary period, the water body had the strongest reducibility and the highest biological productivity. Moreover, the paleoocean in this period between the Yangtze plate and the Cathaysian plate was greatly affected by hydrothermal activities, with temperatures ranging from 90°C to 120°C. Active hydrothermal activities promoted high biological productivity and an anaerobic environment, both of which were conducive to the preservation and enrichment of organic matter, resulting in extremely high TOC content in the Wangyinpu shales (from 6.5% to approximately 16%).

中文翻译：

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华南下扬子地区早寒武世海相页岩有机质富集机制研究——以JXY1井为例

页岩有机质丰度直接影响页岩生烃潜力，是评价页岩气藏的重要有机地球化学参数。页岩中总有机碳含量（TOC 含量）受原始沉积有机质丰度控制。因此，研究页岩有机质富集机制具有十分重要的意义。本文选取下扬子地区的下寒武统海相页岩作为研究对象，其中大部分来源于典型地区JXY1井。黄铁矿化程度（DOP）用于表征水体的氧化还原环境，而P/Al比用于分析古海水的生物生产力。海水的古盐度是通过碳和氧同位素分析计算出来的。此外，利用岩心描述研究了早寒武世热液活动；Si、Al、Fe和Mn元素分析；和氧同位素计算。结果表明，早寒武世王银铺沉积期，海水为含H2S的厌氧水体，氧浓度约为0 mL/L。王银铺沉积中期，水体还原性最强，生物生产力最高。此外，在扬子板块和华夏板块之间这段时期的古海洋受热液活动的影响很大，温度在90°C到120°C之间。