Platinum Group Elements in Ferromanganese Crusts of the Atlantic Ocean: Forms and Sources of Matter

The behavior of platinum group elements (PGE = Pt, Pd, Ru, Ir) in separate layers of ferromanganese crusts of the Atlantic Ocean is considered. The studied crusts, in addition to the hydrogenous source of the matter (crusts from the Bathymetrists Seamounts), formed under the variable influence of hydrothermal (MAR, station 2176) and halmyrolytic sources of matter (Angola Basin, station 2179). It was found that during the evolution of the crusts, the content of hydrogenous elements (Co, Ce) increases and the mass fraction of PGE (Pt, Ir, Pd) decreases. The most probable reason for this enrichment is the release of platinum into seawater as a result of halmyrolysis of the underlying volcanic rocks at an early stage of crust formation. The study of the forms of PGE (adsorbed and native) using hydrochloric acid leachates showed the absence of notable amounts of native platinum in the lower layers of crusts enriched in it. Consequently, PGE are present in the ore phase of crusts in oxidized form independently of the source of material input and cannot passively accumulate in the form of intermetallic compounds during weathering of substrate volcanic rocks.