M.E. Williamson | Geology Reports

USGS1981

Mineralogy and composition of concentric layers within a manganese nodule from the North Pacific Ocean

The minor-element composition of concentric layers within a single ferromanganese nodule from the eastern North Pacific exhibits strong correlations with Fe and Mn contents but appears to be independent of pronounced mineralogic variations. On the basis of these correlations, the elemental composition of individual layers apparently is controlled by the relative contribution of two sources: seawater, and interstitial water of associated sediment. In contrast, the mineralogy of the nodule, consisting of birnessite in the outer few layers and todorokite in the inner layers, is considered to be a function of nodule diagenesis.

Marine Geology↗

USGS1977

Composition of Pacific Ocean ferromanganese nodules

Bulk composition of ferromanganese nodules from the pelagic environment of the Pacific Ocean is apparently related to nodule-growth rate, sediment-accumulation rate, and biologic productivity in the overlying seawater. Nodules with a high Mn Fe "> MnFe ratio and high Ni and Cu concentrations tend to occur in areas where primary productivity in the surface layer of the ocean is high and the sediment-accumulation rate low. Nodules with a low Mn Fe "> MnFe ratio and low Ni and Cu concentrations occur in areas either where sediment-accumulation rate is high or biologic productivity is low. They may have a Mn Fe "> MnFe ratio as low as one and accrete at rates as low as 1 mm 10 6 yrs "> 1mm106yrs . Nodules with a larger Mn Fe "> MnFe ratio apparently have growth rates that are greater by as much as a factor of 10.

Marine Geology↗