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1 IRD UMR 161 and CEREGE UMR 6635, BP A5, 98848 Noumea, New Caledonia
2 UNC, BP 4477, 98847 Noumea, New Caledonia
3 Falconbridge, 9 Rue dAusterlitz, BP MGA 8, 98802 Noumea, New Caledonia
4 School of Earth and Geographical Sciences, UWA, 35 Stirling Highway, Crawley, WA 6009, Australia
* E-mail address of corresponding author: nicolas.perrier{at}noumea.ird.nc
Evidence for fire affecting the solubility of metals in Fe oxide-rich Oxisols of the Koniambo Massif of New Caledonia is presented. Acid-dissolution studies showed that Ni, Al and Cr are substituted for Fe in the structure of the Fe oxides. Thermal dehydroxylation of goethite under oxidizing conditions led to the formation of hematite and to the migration of some of these metals towards the surface of hematite crystals as indicated by their enhanced release during the early stage of dissolution. Dehydroxylation of goethite under reducing conditions led to the formation of hematite and maghemite. Nickel and Al were released preferentially during the early stages of dissolution whereas Cr was not released preferentially and may be uniformly incorporated within maghemite and hematite crystals. These results have significance to the mineral-processing industry, to geochemical exploration and to the availability of these metals to plants growing on burnt soils.
Key Words: Goethite Maghemite Hematite Dehydroxylation Acid Dissolution Lateritic Ore New Caledonia
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