The state of knowledge and possibilities to extract strategic raw materials from the ocean polymetallic deposits

The paper presents the characteristics of types, occurrence and distribution of the ocean polymetallic deposits: polymetallic nodules, cobalt-rich ferromanganese crusts, seafloor massive sulphides and metalliferous clays. Possibility of extraction of critical raw materials (for the EU) and strategic raw materials (according the OECD report) from the ocean polymetallic deposits is indicated. Polymetallic nodules are the most recognized type of ocean polymetallic deposits, abundant mostly in abyssal basins at the depths of3500-6000 m b.s.l. The most important practical metals from the polymetallic nodules are: Fe, Mn (280 000-320 000 ppm), Ni (11 000-14 000 ppm), Co (2100 ppm), Cu (9500-13 000 ppm), Mo and rare earth elements (REE). Cobalt-rich ferromanganese crusts, which are laminatedferromanganese clusters occurring at a depth interval between 400-4000 m b.s.l., can have a prospective significance for the extraction of critical raw materials. They are found on the seamounts where seafloor currents have swept the rocky bottom clear of sediment. They contain large amounts of metals: Mn, Co, Ti, Pt, Te, Mo and Zr. The key factor determining the profitability of the crust mining will be cobalt extraction. However, profitability may increase if nickel, tellurium or REE would be recovered at the same time. The analyses show that the seafloor massive sulphides would be of great importance, as they are the potential source of gold, platinum, silver, copper, zinc and lead. Extraction ofthese deposits is associated with the smallest area ofexploitation and depth ofoccurrence (between 1500-3700 m b.s.l.) which can significantly facilitate commencing of mining operations. Their commercial extraction could begin in the next few years, provided a high concentration of gold and metals in the location near the coast, and a depth below 2000 m b.s.l. Metalliferous clays, which are the deposits enriched in manganese oxides or hydroxides and sulphides or iron, could become an important prospective source of rare earth elements. This is confirmed by a study in two regions: eastern South and central North Pacific. Prospective possibilities of mining the ocean polymetallic deposits increased due to a high concentration ofMn, Ni, Cu, Co, Pt and REE (La, Ce, Nd, Yb, Eu). REE recovery particularly increases the economic value of these deposits. Mining of the ocean polymetallic deposits would meet many technological difficulties and should be preceded by detailed environmental studies