Gold mass balance in lateritic profiles from savanna and rain forest zones
French Guiana ; Geochemistry ; Gold ; Laterite ; Mali ; Mineralization ; Palaeoclimate ; Pedogenesis ; Savanna ; Tropical rain forest ; Tropical zone ; Weathering
In this paper, the gold behavior in laterites was compared under a tropical contrasted climate in Banankoro, South Mali, and under an equatorial climate in Yaou, French Guiana. Gold distribution was studied in detail in terms of pedologic horizons
, and mass balance calculations of gold were applied to both sites in order to evaluate the extent of gold mobility for each type of weathered profile.
At Posse, primary gold mineralization occurs near the base of a sequence of metamorphosed volcanic and volcaniclastic rocks. During the Velhas geomorphological cycle (Oligocene to Lower Pleistocene) the region experienced extensive lateritization
. The observed gold distribution in the weathering profile has arisen through saprolitization during the Velhas cycle, then leaching, compaction and downward (and limited lateral) transport of gold during pedogenesis. The climatic and geomorphological history
of central Brazil has led to the formation of a low grade supergene gold orebody in the weathering profile at Posse.