Geochemistry on manganese nodules from the Southern Ocean

Mn/Fe and todorokite/delta-MnO2 ratios decrease southeasterly from the Southwestern Pacific Basin to the Drake passage-Scotia Sea. Relative to Mn, the greatest enrichments of Co, Ti, V, Zn, Mo and Sn occur in Drake Passage-Scotia Sea nodules, while Ni and Cu are most enriched in the Southwestern Pacific Basin.

Manganese mineralogy is directly related to the Mn/Fe ratio, so that todorokite rather than delta-MnO2 predominates when high manganese vs iron contents are found. Trace metal contents are also related to mineralogy, with high values of Ni, Cu, Zn and Sn, and low values of Co, Ti, V and Mo associated with high todorokite contents. Nodules having indistinct zeolitits/vesiculite nuclei tend to have Mn/Fe and todorokite/delta-MnO2 ratios significantly higher than average for the region in which they are found, whereas ferromanganese oxide fragments dredged from submarine rock surfaces usually have Mn/Fe and todorokite/delta-MnO2 ratios lower than regional average.