Research progress on submarine polymetallic element migration driven by manganese mineral phase transformation during early diagenesis

Manganese oxides in marine sediments are among the most geochemically active minerals. Although they account for less than 1% of the total sediment content, their strong adsorption capacity and redox reactivity play a crucial role in the migration, transformation, and cycling of trace metals. Previous studies have shown that during early diagenesis, manganese oxides undergo complex mineral phase transitions, accompanied by adsorption-desorption and redox reactions. These processes directly influence the forms of trace metals of Co, Ni, Cu, and Zn, and may drive their re-release into pore water and overlying water, which represents an important “bottom-up” flux mechanism in the marine element cycle and offers a new perspective for understanding the imbalance in the global trace metal budget. We systematically reviewed the effects of sediment deposition and early diagenetic processes on the formation and transformation of manganese oxides and examined the mechanisms by which these mineral phase transitions control trace metal migration and isotopic fractionation, focusing on summarizing the forms, adsorption/desorption behaviors, and redistribution patterns of key metals in different manganese oxide minerals. In addition, we evaluated the potential regulatory effects of manganese oxide mineral transformations and benthic fluxes on marine element budgets and furthermore explored the significance of these processes for marine ecosystem functions and global biogeochemical cycles. Despite progress, challenges remain in understanding reaction mechanisms, metal synergistic effects, quantitative constraints, and model applicability. Future research shall integrate multi-scale reaction-transport simulations, isotope tracing, and in-situ observations to comprehensively reveal the diagenetic transformations of manganese oxides and the release processes of trace metals they drive. Such studies will enhance the global marine metal cycle framework and provide theoretical bases for paleoenvironmental reconstruction and resource assessment.