The purpose of this research was to examine paleoenvironments, hydrothermal activity, and seawater restriction of the lower Cambrian Niutitang Formation shale gas reservoir in the eastern Xuefeng uplift and to determine factors affecting organic matter (OM) enrichment. In the studied borehole Xiangan 1 well in western Hunan Province, the Niutitang Formation can be subdivided into the Niu1, Niu2, and Niu3 Members based on geological and geochemical features, including trace element enrichment, lithology, and fossil content. Total organic carbon values of the Niutitang Formation are variable, averaging 1.5 wt. % in the Niu1 Member, 12.7 wt. % in the Niu2 Member, and 5.1 wt. % in the Niu3 Member. Paleoclimatic changes were responsible for changes in biota, which impacted patterns of OM enrichment. Climate proxy (chemical index of alteration) and productivity proxies (biogenic Ba, Cu/Al, and Ni/Al) consistently indicate higher paleoproductivity in the Niu2 Member. The Niu1 and Niu2 Members may be affected by hydrothermal events, whereas hydrothermal activity was absent during deposition of the Niu3 Member. Hydrothermal activity may provide nutrients and silica but may also enhance the reducing condition of the water column. In addition, hydrothermal events may have possibly influenced biological survival in the different environments, which in turn increased their reproduction within the early Cambrian ocean and affected OM production. Redox proxies (Mo and U enrichment factors) imply that the Niu1, Niu2, and Niu3 Members were deposited in suboxic, euxinic, and ferruginous environments, respectively. Redox conditions, strongly restricted water environments, and hydrothermal events were conducive to OM enrichment during the early Cambrian.

中文翻译：

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华南下寒武统牛蹄塘页岩有机质富集的沉积环境及热液控制

本研究的目的是研究雪峰隆起东部下寒武统牛蹄塘组页岩气藏的古环境、热液活动和海水限制，并确定影响有机质（OM）富集的因素。在研究的湘西湘安1井钻孔中，根据微量元素富集、岩性、化石含量等地质地球化学特征，可将牛蹄塘组划分为牛1段、牛2段和牛3段。牛蹄塘组的总有机碳值是可变的，平均为 1.5 wt。% 在 Niu1 成员中，12.7 wt。% 在 Niu2 成员中，和 5.1 wt。% 在 Niu3 会员中。古气候变化是造成生物群变化的原因，这影响了 OM 富集的模式。气候代表（蚀变的化学指数）和生产力代表（生物成因 Ba、Cu/Al 和 Ni/Al）一致表明牛二段较高的古生产力。牛一、牛二段可能受到热液事件的影响，而牛三段沉积期间不存在热液活动。水热活动可以提供养分和二氧化硅，但也可以增强水柱的还原条件。此外，热液事件可能影响了不同环境中的生物生存，进而增加了它们在寒武纪早期海洋中的繁殖并影响了有机质的产生。氧化还原代理（Mo 和 U 富集因子）意味着 Niu1、Niu2 和 Niu3 成员分别沉积在低氧、富氧和铁质环境中。氧化还原条件，