Authors / CoAuthors
Exon, N.F. | Raven, M.D. | DeCarlo, E.
Abstract
In 1992, ferromanganese nodules and crusts on the sea bed of the Christmas Island region south of Java (~10?S) were investigated. The region consists of flat plains covered in red clay, abyssal hills, volcanic ridges and isolated sea mounts. Ferromanganese nodules were sought at 28 free-fall grab stations in water depths of 4700-5900 m, and were recovered from 23 deployments at nine stations. Nodules were most commonly recovered near the base of seamounts. Nodules are small and not very abundant; some are rough and others smooth. They are of low grade, averaging 9.6 % Fe, 19.7% Mn, 0.51% Ni, 0.49% Cu and 0.12% Co. The majority contain vernadite as the dominant Mn-bearing phase, with birnessite and jacobsite very commonly present, and todorokite commonly present. The nodules are dominantly hydrogenetic. Ferromanganese crusts were recovered from eight dredge hauls on the flanks of five of nine dredged seamounts, in water depths of 1450-3700 m. The crusts were laid down in several phases and are up to 10 cm thick, with estimated average deposition rates of 1-1.5 mm/m.y.. Significant compositional variations occur in one thick crust examined in detail. The crusts are generally of low grade, averaging 13.9% Fe, 16.2% Mn, 0.35% Ni, 0.11% Cu and 0.44% Co. The majority contain vernadite as the dominant Mn-bearing phase, with birnessite and jacobsite common, and todorokite sometimes present. The crusts are also dominantly hydrogenetic. The highest Co grades are ~0.8% in the shallowest water depths, suggesting that any future exploration should be conducted in depths of about 500-1500 m, near the oxygen minimum zone.
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nonGeographicDataset
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38693
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- External PublicationAbstract
- ( Theme )
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- marine
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2002-01-08T00:00:00
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