Manganese nodules diagenetic formed

Perhaps the most comprehensive explanation of the role of hydrogenetic and diagenetic processes on manganese nodule accretion has been presented by Dymondetal (1984). On their classification, hydrogenous deposition involves the direct precipitation or accumulation of colloidal metals oxides from seawater. Strictly, this involves deposition of manganese oxides on surfaces in contact with seawater such as involved in the formation of manganese crusts. In practice, manganese nodules formed on red clays have charac-... 

A limited amount of work has been done on the dating of shallow-water nodules, which, because of diagenetic remobihzation of manganese within the sediment column, generally form more rapidly than deep-ocean deposits. Unlike deep-water nodules, the rapidly growing shallow-water nodules do not contain excess °Th or Pa but instead contain, initially, quantities of °Th and Pa that are less than their equilibrium... 

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