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Kaolinites, Laterites and Bauxites |
CRA Exploration Pty Ltd, P.O. Box 175, Belmont, W. Australia 6104
Institute of Geological Sciences, Keyworth, Nottingham NG12 5GG
Institute of Geological Sciences, Murchison House, West Mains Road, Edinburgh EH9 3LA
Detailed mapping and limited geochemical sampling of a Lower Pliocene trachyandesite-sediment-tuff sequence reveals two juxtaposed but distinct kaolinised sequences caused by tropical weathering and hydrothermal activity. The stratigraphy and sequence of alteration in the lower Taungni section is difficult to establish. The kaolinised rocks are characterized by high lead and arsenic content and contain large irregular masses of silica. Kaolinisation resulted either directly from metalliferous hydrothermal activity or from acidic fluids released by oxidation of sulphides. The upper, well-bedded Kyauktaga section shows regular redistribution of silica resembling that of the silcrete profile and vertical base metal zoning attributable to groundwater movement.