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Mobility of gold and silver in lateritic weathering profiles; some observations from Western Australia
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1984
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EngineeringGeomorphologyAgcl ComplexChemistryMineral ProcessingEarth ScienceGeophysicsLateritic Weathering ProfilesWestern AustraliaLow PhCorrosionWeatheringGeographyGeologyAcid Chloride SolutionsOre FormationEconomic GeologyGeochemistryOre GenesisPetrologyMineral Geochemistry
Experimental evidence suggests that very acid chloride solutions generated in lateritic profiles by ferrolysis (oxidation and hydrolysis of iron) are responsible for the dissolution of gold and silver. Au is subsequently reprecipitated by reduction of the AuCl 4 (super -) ion with Fe (super +2) . Reduction of the AgCl complex does not similarly occur because of the relative redox potentials of Fe (super +2) /Fe (super +3) and Ag/AgCl . Thus chemical refinement of gold occurs during lateritization. The development of low pH and the redistribution of gold and silver in lateritic weathering profiles appear to be more common over granitic and gneissic basement and may be inhibited by the presence of carbonate in the weathering zone of basic rock sequences.--Modified journal abstract.