Manganese nodules from a wide range of marine environments have been analysed for a series of elements by optical spectrography, atomic absorption spectrophotometry and mass spectrometry to assess the influence of the environment of deposition on the trace element assemblage of nodules and a more detailed assessment has been made of the trace element geochemistry of nodules from area 4C on the flanks of the Carlsberg Ridge in the Indian Ocean. The mineralogical characteristics of the nodules are described and a detailed petrographic and Mass spectrometry (A.E.I. MS7) analysis of three selected specimens presented. Finally, a method is developed for the oxygen isotope analysis of manganese nodules and the application to the problems of paleoclimatology discussed. To investigate the correlation of trace element geochemistry of nodules with depth as suggested by Cronan (1967) and Barnes (1967), a detailed comparison of the trace element geochemistry of nodules from shallow water and deep sea environments was undertaken. The results show a fundamental difference in the trace element assemblage of nodules from continental margin environments compared with those from deep sea and seamount environments. The marked enrichment of Mn and consequent depletion of Fe and trade elements in nodules from continental margin environments indicates the influence of diagenetic remobilisation of manganese in reducing environments on the trace element assemblage of manganese nodules. Variations in the mineralogical characteristics of nodules are attributed to variations in the redox conditions at the sediment-water interface and a correlation between nodule mineralogy and trace element geochemistry becomes apparent. The application of these concepts to the assessment of the paleoenvironmental characteristics of deposition of sedimentary manganese ore bodies is discussed. On the Carlsberg Ridge, the distribution of manganese crusts away from the belt of maximum seismicity along the axis of the mid-Ocean Ridge argues strongly against the influence of submarine vulcanism on nodule formation. A consideration of the ocean floor spreading rate indicate5that the thickness of the manganese crusts on the flanks of the Carlsberg Ridge is related to the length of time the nodule has been in contact with seawater. This suggests that, although submarine vulcanicity may have contributed to the overall mass balance of the oceans, manganese nodules form by the direct precipitation of trace elements from sea water. A consideration of the trace element distribution in a series of sediment cores from the flanks of the Carlsberg Ridge indicates that sediment diagenesis plays only a minor role in influencing the trace element distribution in nodules from this environment. Finally, a discussion of the thermodynamics of nodule precipitation is given and the need for a more detailed assessment of the kinetics of uptake of trace elements in nodules stressed.
From 1983 until 1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions. At the time it was the most extended data compilation on ferromanganese deposits world wide. Initially published in a proprietary format incompatible with present day standards it was jointly decided by AWI and NOAA to transcribe this legacy data into PANGAEA. This transfer is augmented by a careful checking of the original sources when available and the encoding of ancillary information (sample description, method of analysis...) not present in the NOAA-MMS database.
Supplement to: Glasby, Geoffrey P (1970): The geochemistry of manganese nodules and associated pelagic sediments from the Indian Ocean. Ph. D. Dissertation, Imperial College of Science, Technology and Medicine (University of London), London, United Kingdom
