Résultats préliminaires d'une étude sur la dispersion de l'or en milieu latéritique autour de l'indice aurifère de Misséni, au Mali
A study of gold dispersion in laterite above a gold zone is based on 58 analyses of soil samples from two shafts and one trench located in the Misseni gold anomaly area, Mali. The bedrock in this area includes Birrimian volcano-sedimentary rocks (lower Proterozoic). At Misseni, primary gold is associated with disseminated copper and iron sulfides in a silicified shear zone within andesites. The area is dominated by a dry tropical climate, including two contrasting seasons (a short rainy season and a long dry season) and a mean annual rainfall of less than 1500 mm. Misseni area is characterized by low plateaus averaging 350 m in altitude and by a very thick weathered cover (> 35 m) of laterite topped by iron cuirasse. In general, the laterite profiles show, from bottom to top (i) saprolith ("pistache" laterite), variegated and mottled clays, (ii) iron hardpan, (iii) iron cuirasse, and (iv) eluvium. Mineralogical analyses reveal that the laterite is dominated by kaolinite, goethite, quartz, mica, and hemati...