Heath(1981)による〔『Ferromanganese nodules of the deep sea』(736p)から〕


 Pelagic ferromanganese nodules are abundant at the sea floor in areas where oxidized sediments are accumulating at rates of less than about 7 m per million years. Foraging benthic organisms are believed to keep nodules at the sea floor for periods of hundreds of thousands to millions of years. Such benthic activity has yet to be observed, however.
Economically attractive concentrations of Cu and Ni are found only on the fringes of the Pacific equatorial zone of high surface biological productivity. Existing data suggest that the surface biota extract transition metals from seawater and deliver them to the sea floor in large particles, such as fecal pellets. Oxic and suboxic diagenesis of the biogenic debris frees the metals to enter the sediments or nodules, or to escape to the bottom waters of the ocean. The relative roles of inorganic reactions, bacterial activity (both in releasing and fixing transition metals), and nodule mineralogy in controlling nodule compositions still are controversial and currently are areas of active research. Cu and Ni are less abundant in nodules beneath the most productive surface waters because of dilution by manganese released from underlying, organic-rich, reduced sediments.
 Assuming that legal-social-political questions surrounding the commercial exploitation of deep-sea nodules can be resolved by the United Nations Law of the Sea and subsequent negotiations, it appears that 8 to 60 mine sites, each containing about 70 million tons of recoverable nodules with more than about 1.8 percent Cu + Ni and having surface concentrations in excess of 5 kg per square meter, are available in the Clarion-Clipperton region of the eastern equatorial North Pacific. Development of the first of these sites should be far advanced by the end of this century.』



Regional distribution
Local distribution
Buried nodules
Surface textures
Attached organisms
Internal structure
Growth rates
Elemental composition
Sources of metals
Concentration mechanisms
Relationship between composition and abundance
Unresolved problems
Economic potential
Environmental consequences of nodule mining
Legal-political considerations