Geochemistry of re and trace elements in ferromanganese nodules and their genesis

Trace and RE element geochemistry and genesis have been studied with respect to ferromanganese nodules from the sediments of the Pacific, Atlantic and Indian oceans.

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Geochemical characteristics of major and trace elements The essential composition is Mn and Fe in nodules with 17.88-28.64% of H₂O. Besides δ-MnO₂ and Fe₂O₃, there are hydrous Mn and Fe oxides such as Mn(OH)₄, Fe(OH)₃, MnO₂·nH₂O and Fe₂O₃·nH₂O in the nodules. Fe and Mn are presented in higher valences such as Fe³⁺ and Mn⁴⁺. The Fe²⁺ was not found by chemical analysis and EPR in ferromanganese nodules, but Mn²⁺ was. These nodules contain by weight 1-2 percent of the oxides of nickel (Ni), copper (Cu), and cobalt (Co). The Ba/Sr ratio of the nodules, is usually over 2. It is considered that foraminifera cannot be the material source of the nodule, because foraminifera with calcite structure usually contain a great deat of Sr but almost no Ba.