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Y. Fouquet
over 1.5 gm per tonne in crusts at least five centimetres thick. Deposits should of
course have a certain continuity over relatively flat surfaces.
A proper evaluation of the economic potential of these mineral deposits will only
be feasible once field data will be able to determine the parameters required for accurate calculations: geological controls in rich areas, deposit continuity, influence
of substratum on dilution upon pick-up. An important point concerns the study of
seabed roughness, in order to determine the richest, flattest and most continuous
areas in which crust mining would be possible without the crusts being diluted in
too great a volume of sterile substrate. Such cobalt-rich areas are known in the Tuamotu Islands area where crusts form a flat, continuous surface on indurated sediment formations. From a scientific point of view, efforts remain necessary to more
fully understand the rules of distribution, variability in thickness and composition,
and geological and chemical parameters governing the formation of the richest
Fig. 4.6  Map of cobalt concentrations in manganese-rich crusts in the Pacific