Rare Earth Elements and Other Critical Metals in Deep Seabed Mineral Deposits: Composition and Implications for Resource Potential

Abstract

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.The surveyed deep-sea mineral deposits include polymetallic nodules, ferromanganese crust, SMS, and deep-sea sediment, and are potential rare earth element (REE) resources (Table 1). Traditionally, Co, Ni, and Mn have been the target metals in nodules and crusts, with less focus on rare earth metals. The majority of REE studies have focused on the origin and genetic environment of ore deposits (e.g., [9][10][11][12] and references therein). Only a few studies have investigated the potential of classical deep-sea mineral deposits as critical metal sources, despite the discovery of seabed mineral deposits almost 50 years ago [3,4,[13][14][15][16]. Critical metals were recently identified as potential seabed resource commodities; however, the extent of critical metal exploitation from seabed deposits remains unclear, because of limited data on resource estimation. This paper discusses the critical metal contents of three conventional seabed mineral resources and a deep-sea sediment resource that is currently being explored by KIOST, and re-evaluates these deposits as potential REE resources. This study examines the resource potential of critical metals of conventional seafloor mineral deposits in Korean tenements and provides a comparison with land-based rare earth metal deposits. The future implications of, and factors relevant to, the critical metal exploitation of seabed mineral deposits are also discussed.

Fractionation Trends and Variability of Rare Earth Elements and Selected Critical Metals in Pelagic Sediment from Abyssal Basin of NE Pacific (Clarion-Clipperton Fracture Zone)

“…According to [10], who analyzed 2000 seafloor sediment samples at 78 Pacific sites, deep-sea muds show high concentrations of REE (2230 ppm maximum), and could constitute a potential source of these elements in the future. Such high REE concentrations in sediments were not confirmed either by the studies of [21], who studied samples from the central North Pacific, or [16], who examined material collected from the southern part of the Korean claim area (KORDI) of the Clarion-Clipperton Fracture Zone (CCFZ). The former research has shown that total REE contents vary from 418 ppm to 810 ppm, with an average of 532 ppm, while the latter recorded a range from 115 ppm to 1115 ppm, with an even lower average of 490 ppm.…”

“…Since the widely cited work of [10], deep-sea sediments have been the subject of numerous studies focused on REE content and resource potential [11][12][13][14][15][16][17][18][19][20]. According to [10], who analyzed 2000 seafloor sediment samples at 78 Pacific sites, deep-sea muds show high concentrations of REE (2230 ppm maximum), and could constitute a potential source of these elements in the future.…”

A Critical Review on Evaluation of the Marine Resources Mining versus the Land-Based Ones for REE

“…The increasing demand for clean energies technologies applied in the permanent magnets and phosphor industries means that REEs such as Nd, Pr and Dy (for permanent magnets) are critical in the international markets, leading to very high prices. The so-called light REEs, such as La and Ce, have broad use as abrasive constituents and naturally have lower prices than HREEs [7,8].…”

Recent Advancements in Metallurgical Processing of Marine Minerals

“…Except for primary metals, rare earth elements are often found in seafloor materials [111,112], enhancing their economic value. However, it is critical to separate REE from base metals, and this might be achieved by SX.…”