Rare earth elements and other critical metals in deep seabed mineral deposits: Composition and implications for resource potential

The critical metal contents of four types of seabed mineral resources, including a deep-sea sediment deposit, are evaluated as potential rare earth element (REE) resources. The deep-sea resources have relatively low total rare earth oxide (TREO) contents, a narrow range of TREO grades (0.049–0.185%), and show characteristics that are consistent with those of land-based ion adsorption REE deposits. The relative REO distributions of the deep-seabed resources are also consistent with those of ion adsorption REE deposits on land. REEs that are not part of a crystal lattice of host minerals within deep-sea mineral deposits are favorable for mining, as there is no requirement for crushing and/or pulverizing during ore processing. Furthermore, low concentrations of Th and U reduce the risk of adverse environmental impacts. Despite the low TREO grades of the deep-seabed mineral deposits, a significant TREO yield from polymetallic nodules and REE-bearing deep-sea sediments from the Korean tenements has been estimated (1 Mt and 8 Mt, respectively). Compared with land-based REE deposits, deep-sea mineral deposits can be considered as low-grade mineral deposits with a large tonnage. The REEs and critical metals from deep-sea mineral deposits are important by-products and co-products of the main commodities (e.g., Co and Ni), and may increase the economic feasibility of their extraction.