Geochemistry of lithium in marine ferromanganese oxide deposits

We have measured lithium content of marine ferromanganese oxide deposits of different origins and conducted a sequence of selective dissolution experiments on them. There is more lithium in diagenetic and transitional marine ferromanganese nodules than in hydrogenic ferromanganese crusts. Lithium in diagenetic and transitional nodules is in the 10 Å-manganate phase rather than in the lithiophorite or other phases, as shown by the sequential selective dissolution results. The different contents of lithium in the different generic types of marine ferromanganese oxide deposits are attributed to the varying mineralogy. Ten Å manganates, the main minerals in diagenetic and transitional marine ferromanganese nodules, can incorporate significant amounts of lithium because of their distinct structure and can be regarded as an important scavenger of lithium in the oceans. The diagenetic and transitional marine ferromanganese nodules may play a role in the mass balance of lithium in the oceans. On the other hand, it appears that lithium is present in hydrogenic marine ferromanganese crusts in an aluminosilicate phase rather than in other phases such as vernadite (δ-MnO2) or ferric oxide/hydroxide. Vernadite (δ-MnO2) and ferric oxide/hydroxide adsorb very small amounts of lithium in the oceans.