Mineralogy and Chemistry of Manganese Nodules from the Southern Part of Carlsberg Ridge

Petrographic study indicates that the nucleus of nodules is generally composed of clay, volcanic glass, basalt fragments, and earlier nodules. Polished sections indicate typical collomorphic globular segregations and partly crystalline oxides of todorokite. Scanning electron micrographs indicate that they are made up of small and large botryoids; and occasional platelets of todorokite, within cavities formed due to post depositional recrystallization. X-ray diffraction patterns do not show any peaks of todorokite due to poor crystallinity, while δ-MnO₂ is seen in all the nodules studied. The nodules analysed show: Mn 15.01-21.40%, Fe 10.07-20.10%, Cu 0.07-0.32%, Ni 0.32-0.57%, Co 0.07-0-21%, and also have a Mn/Fe ratio less than 2. The nodules are of hydrogenetic, secondary origin, source being volcanogenic.