Diagenetic mobilization of manganese in Peru Basin sediments

The Mn contents and sedimentation rates of two cores from different areas of the Peru Basin have been determined. The southern core is associated with Mn nodules of conventional slow accretion rates (~ mm/10⁶ yr) while the northern one accompanies nodules with very high growth rates (~10² mm/10⁶ yr). The depletion of Mn observed within the top 40 cm of the cores is interpreted as resulting from a diagenetic remobilization of Mn⁺² due to the oxidative characteristics of the sedimentary column. In both cores, the calculated flux of Mn provided by the sediment is higher than the total Mn recovered in the overlying nodules. This indicates that the Mn content of the Peru Basin nodules can be supplied by diagenetic processes from the sediment, not only for the slowly growing nodules but also for the extremely fast growing concretions found in the north of the basin.