Dissolution and translocation of residual gold particles under equatorial lateritic conditions

Abstract

Gold mobility under supergene conditions have been the subject of a great number of studies as summarized by Boyle (1979). However, most of these works have demonstrated this mobility by indirect evidences. Thus, for example, Benedetti (1989) reports that trace gold concentrations with an average of 10 −10 to 10 −11 mole / liter have been found around gold deposits in acidic surface waters An other indirect evidence is given by Mann (1984), Freyssinet et al. (1987), Lawrance (1988), Colin et al. (1989), by reporting the occurence of supergene gold crystals in lateritic wheathering profiles. According to Mann (1984), gold mobility in lateritic profiles in the Yilgarn block of Western Australia can be explained by the occurence of high chloride concentrations in the drainage system Thus according to this author and to the experimental studies of Krauskopf (1951) and Cloke and Kelly (1964), gold is complexed by chloride to form auric chloride complex in very acidic, highly oxidizing, chloride-rich conditions. In surficial lateritic environment, however, the acidic surface waters are stronghly diluted and thus the factors which control gold mobility are poorly understood.