Minerals Report - International Seabed Authority

averaging 2kg/m 2 . These contain elemental concentrations and densities on
the seafloor of up to 10 wt. % manganese but with less than 1 kg/m 2 , up to
1 wt.% copper with less than 10g/m 2 , up to 4000 ppm cobalt with a
maximum of 10 mg/m 2 , and 0.5 wt. % nickel with less than 0.025 kg/m 2 .
The combined nickel and copper concentration is up to 2 wt. %.
Because of a number of factors including depth of water and
sedimentation rates, the pattern of nodule distribution seen to the north of
the equator is not found in to the south (Halbach,1983).
Table 2. Average abundance of Mn, Fe, Ni, Co and Cu in manganese nodules and
crusts from different environments (in weight per cent) (after Cronan 1977).
Seamounts
Plateaux
Active
ridge
Other
ridge
Continental
margin
Marginal
seamounts
Nodules densities of up to 8 kg/m 2 are found in the Pacific
southern equatorial belt at the edge of the calcareous zone between 180°E
and 220°E. However, occurrences are infrequent throughout much of the
area. An exception is an area between the East Pacific Rise and South
America densities of up to 6kg/m 2 are reported.
Manganese nodules with up to 2 wt. % of combined nickel and
copper and up to 4000 ppm cobalt contents are found in an area in the
Indian Ocean (Figures 1, 15, 17, 19) that extends from 10°S to 25°S and
70°E to 86°E, but have concentration of less than 1 kg/m 2 (Frazer and
Wilson, 1980).
INTERNATIONAL SEABED AUTHORITY 704
Abyssal
plains
Mn 14.62 17.17 15.15 19.74 38.69 15.65 16.78
Fe 15.81 11.81 19.15 20.08 1.34 19.32 17.27
Ni 0.351 0.641 0.306 0.336 0.121 0.296 0.540
Co 1.15 0.347 0.400 0.570 0.011 0.419 0.256
Cu 0.058 0.087 0.081 0.052 0 082 0.078 0.370
Mn/Fe 0.92 1.53 0.80 0.98 28.8 0.81 0.97
Depth 1872 945 2870 1678 3547 1694 4460