ABSTRACT

Mössbauer spectra have been obtained for a limited number of manganese nodules and associated sediments from five areas in the equatorial Pacific high productivity zone and in the S.W. Pacific. The results offer strong evidence that the form of iron in deep-sea manganese nodules is identical and independent of the environment of deposition. Iron occurs in deep-sea nodules as a mixture of α-FeOOH and β-, γ-FeOOH or poorly crystallised Fe oxides. In the associated sediments, iron in the equatorial Pacific sediments appears to be entirely in the ferric state whereas in S.W. Pacific sediments about 15% of the iron is present in the ferrous form. It has not proved possible, using Mössbauer spectra alone, to establish unambiguously whether the iron in the sediments occurs as iron oxidehydroxides or as clay minerals. The data, however, do place boundary conditions on the formation of iron in these sediments.