Analysis of Mn-deposits from the Pacific

Too few nodules have been analyzed to define possible regional trends. The shale-normalized patterns, however, permit division of nodules into two groups: those from depth greater than 3000–3500 m and those from less depth.

The factors that determine this change in the relative concentration of REE may be related to the mineralogy of manganese phases and/or the transport of REE to the deep ocean by particulate matter. Comparison of the REE patterns of nodules with those of phillipsite, phosphorite, clays, CaCO3 and seawater suggests that the patterns of these phases reflect fractionation from an initial pattern closely resembling that of shale.