The mineralogy of manganese nodules from a range of marine environments

The mineralogy of 45 managanese nodules from a range of marine environments is described. 10 Å manganite is shown to be the principal mineralogical phase in 9 nodules from shallow-water, continental-margin environments, whereas δ MnO₂ is the principal mineralogical phase in 35 nodules from the Carlsberg Ridge, Indian Ocean. The phase relationships appear to be controlled by the redox characteristics of the sedimentary environment rather than the kinetics of nucleation or mineralogical ageing phenomena. The present data give no evidence to support the influence of submarine volcanism on nodule mineralogy.