Enrichment Characteristics of Critical Metals in Deep-Sea Ferromanganese Crusts and Polymetallic Nodules

Deep-sea ferromanganese crusts and polymetallic nodules are significant deep-sea resources enriched with critical metals such as Co, Ni, and rare earth elements, whose strategic importance continues to rise.This paper reviews the existing literature to clarify the geochemical factors and adsorption mechanisms controlling critical-metal enrichment.Metal accumulation is caused by a combination of macroscale factors such as the growth rate, water depth, and phosphatization.Microscale factors include the electrochemical properties and microstructures of Fe-Mn oxides.The key mechanisms include ion adsorption, which is determined by the surface charge, along with oxidative scavenging, redistribution during phosphatization, and structural incorporation within Mn oxide frameworks.Samples from the Magellan Seamounts show patterns consistent with these processes and exhibit relatively high concentrations of Co, Ni, Y, and Te compared with the reported global averages, potentially indicating significant resources.Future work will utilize synchrotron radiation and transmission electron microscopy to investigate the enrichment processes, focusing on the Magellan crusts as promising targets for sustainable exploration.