Minerals Report - International Seabed Authority

Manganese, manganophile elements (e.g. cobalt, nickel, cadmium,
molybdenum), and the iron oxyhydroxide phase generally decrease, whereas
detrital phase-related elements (silicon, aluminium, iron, yttrium) increase
with increasing latitude (94). The intensification of the OMZ in the equatorial
zone of high bio productivity allows for greater amounts of manganese to
remain in solution in seawater and slower growth rates of crusts. The
increase in iron, silicon, aluminium, and yttrium to the north is partly due to
increased supply of detritus by the trade winds. The same trends in
manganese and manganophile elements should occur with longitude
(increasing to the east) in the equatorial region because regional bio
productivity increases in that direction. However, a paucity of seamounts
exists between Hawaii and North America, so that trend cannot be confirmed
Pacific-wide; regardless, the trend is generally poorly developed regionally
(e.g., 95). Contents of manganophile elements in California continental
margin crusts are diluted by detrital and biogenic inputs, which ameliorates
the increased δ-MnO2-related elements expected to occur there. The residual
biogenic phase elements generally increase with proximity to the equatorial
zone of high bio productivity and in the eastern Pacific, where productivity is
yet higher (96).
Manganese, manganophile elements, and CFA-related elements
decrease, whereas iron, copper, and detrital-related elements increase with
increasing water depth of occurrence of crusts (97). Cobalt and other
manganophile elements are enriched more than manganese is in shallow
water (98). Those relationships have been explained by the increased
dissolved manganese in the OMZ (about 300-1500 m water depths; Fig. 2) and
an increased supply of detrital phases at greater water depths, which
contributed iron, aluminium, and silicon.
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