Layered Distribution of Platinum Group Elements in Ferromanganese Nodules from the Cape Basin, Atlantic Ocean

The paper presents data on contents of the platinum group elements (Pt, Ir, Pd, and Ru) and Au in Fe–Mn nodules of different morphology and in their separate layers from the Cape Basin, Atlantic Ocean. The Layer-by-layer analysis of the Fe–Mn nodules and crusts shows that the platinum group elements (PGE) are accumulated in the ferromanganese oxyhydroxide layers relative to the clayey nuclei and the substrate of the crust. Among oxyhydroxide layers, PGE are more significantly concentrated in the hydrogenetic (sedimentation) layers of the nodules than in layers with predominant oxic and suboxic diagenetic material. Gold is demonstrated not to be accumulated in the Fe–Mn nodules. The reason for the predominant accumulation of platinum relative to palladium in nodules is the oxidative sorption on manganese oxyhydroxides suspended in seawater. An increase in the growth rate of the nodules due to the input of diagenetic material from sediments is accompanied by an increase in the Mn/Fe value in the nodules. The increase of Mn/Fe value in nodules is shown to be associated with a decrease in the Pt/Pd ratio, which indicates a dominant role of the hydrogenetic input of PGE to the nodule. The contents of iridium and ruthenium correlate with the contents of platinum and cerium.