Hydrothermal activity plays a critical role in ancient oceanic environments, organic matter accumulation, and metallic ore deposit formation. During the Early Cambrian, the development of hydrothermal systems in the southern Anhui Province of the Lower Yangtze Block has long attracted geological attention. This study focuses on the Lower Cambrian black shales of the Hongtaocun (HTC) section in the southern Anhui Province, employing major- and trace-element analyses, rare earth element (REE) geochemistry, and field-emission scanning electron microscopy (FE-SEM) observations to identify evidence for Early Cambrian hydrothermal activity on the Yangtze Platform and its controls on mineralization. Our results demonstrate that major-element proxies classify the HTC samples as biogenic, but this classification is demonstrably incorrect given the mineralogical and REE evidence, which highlights the limitations of major-element discrimination alone. Hyalophane (Hy) occurrence records Ba-rich hydrothermal fluids, while positive Eu anomalies in the REE patterns further corroborate hydrothermal influence. We, therefore, emphasize that major-element chemistry alone is insufficient to reliably identify hydrothermal processes. These findings substantially advance the discrimination criteria for ancient seafloor hydrothermal activity.
Huang et al. (Thu,) studied this question.