贵州震旦系陡山沱组磷块岩成磷作用及与新元古代末期氧化事件(NOE)的耦合

贵州地区埃迪卡拉系陡山沱组磷矿床沉积是新元古代晚期全球性成磷事件的典型代表，与气候突变及生命演化等存在密切联系。然而，目前对磷矿床沉积的研究仅局限于成磷机制和磷质来源等问题，而通过同位素地球化学指标研究该矿床成磷过程及与同期古海洋环境的关联研究较为薄弱。本文以贵州省息烽地区陡山沱组磷块岩为研究对象，在野外剖面观察和镜下岩石学特征研究基础上，利用元素分析仪-同位素质谱(EA-IRMS)连续流分析技术精确测得陡山沱组磷块岩的硫酸根硫同位素变化范围为32.7‰~36.9‰(n=32，平均值34.1‰)，比同时期海水的硫同位素值低11‰，两者的差异表明磷块岩中的硫并不全部来自表层海水。理想化早期海洋(>520Ma)化学分带模型指示同时期海水中存在相对亏损³⁴S的H₂S带，结合磷块岩中磷质来源与上升流关系密切的认识，可以认为陡山沱组磷块岩的硫酸根硫同位素组成代表了表层海水和上升流的混合信号。

Phosphogenesis of phosphorite from the Sinian Doushantuo Formation in Guizhou Province and its coupling relation with the Neoproterozoic Oxygenation Event (NOE)

Phosphate deposit of the Ediacaran Doushantuo Formation in Guizhou province is a typical representative of the global phosphorite formation event in the late Neoproterozoic, which is closely related to climate change and evolution of life. However, the current research on the deposition of phosphorus deposits is limited to the mechanism of phosphorus formation and the source of phosphorus, and research on the phosphorus formation process of this deposit and its correlation with the paleo-ocean environment of the same period by isotopic geochemical indicators is relatively weak.In order to determine the sulfur source of phosphorite-associated sulfate.Based on the field section observation and the study of petrological characteristics under the microscope, elemental analyzer-isotope ratio mass spectrometry (EA-IRMS) was used to measure the sulfur isotopic composition of phosphorite-associated sulfate from the Ediacaran Doushantuo Formation. RESULTS: The sulfur isotopic composition of phosphorite-associated sulfate ranged from 32.7‰ to 36.9‰ (n=32, mean=34.1‰), which was 11‰ lower than that of the seawater of the same period, indicating that the phosphorite-associated sulfate was not all from the surface seawater.The idealized early ocean (>520Ma) chemical zoning model indicates that there is a relatively ³⁴S-depleted H₂S zone in the seawater at the same time. Combined with the understanding that the source of phosphorus in the phosphorite is closely related to the upwelling, it can be considered that the sulfur isotopic composition of phosphorite-associated sulfate of the Doushantuo Formation represents the mixed signal of surface seawater and upwelling.