Hydrothermal activity drives paleoenvironmental change and manganese mineralization in South China during the Neoproterozoic interglacial

Highlights • Pronounced Hg anomalies in the lower Datangpo Formation has been determined. • Hydrothermal activity provided Mn and coupled with the paleoclimate evolution. • Episodic cold events were identified within the interglacial, reflecting an unstable paleoclimate. • A complete paleo-oceanic redox evolution with obvious salinity stratification has been reconstructed. The co-evolution of hydrothermal activities, paleoclimate, and marine environments during Neoproterozoic glacial–interglacial cycles is crucial for understanding the biological activity on Earth’s history. The Central Hunan region, governed by graben–horst tectonics, may exhibit sedimentary and geochemical patterns distinct from the broader Nanhua Basin. However, this potential heterogeneity has remained poorly constrained. Based on high-resolution inorganic geochemical analyses of drill cores, this study reconstructs the spatiotemporal evolution of interglacial hydrothermal activity, climate variability, salinity, and redox conditions in the Nanhua Basin. The results show that the lower Datangpo Formation exhibits pronounced Hg anomalies, suggesting that hydrothermal input provided an important material source for manganese mineralization. The sedimentary record also identifies multiple intermittent cooling events, highlighting pronounced climatic instability during interglacial periods. During the early stage of Datangpo deposition, the paleo-ocean was characterized by low salinity and weak seawater restriction. As terrigenous input increased and evaporation intensified under warming conditions, salinity progressively increased and transformed into a saline environment, exhibiting a distribution pattern of rising salinity from shallow to deep waters areas. Furthermore, multiple redox proxies indicate a stepwise rise in dissolved oxygen concentrations in the paleo-ocean, consistent with the evolution of paleoclimate and salinity. In summary, episodic hydrothermal activities and paleogeographic configuration jointly regulated the coupled fluctuations of paleoclimate, seawater salinity, and redox condition during the interglacial intervals. These findings offer essential geochemical evidence for understanding the marine environmental evolution in the Nanhua basin.