Optimization of Gold Extraction from Ariab VMS Deposits in the Red Sea Hills, Sudan

Abstract

The Hassaï Cu-Au Volcanogenic Massive Sulphide (VMS) deposits located in the Red Sea Hills were discovered early 1980 by the geologists of the joint venture between Geological and Mineral Resources Department (GMRD) and the French (BRGM). These deposits are belonging to the Neoproterozoic and classified as Siliciclastic type. Two main deposits, Hadal Awatib (HADE) and Hassai (HASS) are potential for Copper, Zinc and Gold extraction. The ore dominant mineralogical assemblage is pyrite, with accessory chalcopyrite and sphalerite. Sequential flotation technique to float Copper first , followed by Zinc Copper and Zinc concentrate in flotation circuit yield a recovery of 82-85% and 65-70% respectively. During Copper rougher flotation, several depressors were used to depress Zinc while floating Copper. The considerable amount of gold (130 tons) in these deposits, made it very necessary to optimize its recovery although as byproduct. Therefore special collectors as Dithiophosphate (F2044) and Monothiophosphate (F2644) were tested. Gold recovery of 35 to 40% and 5 to 10% were obtained within Cu and Zn concentrates. The remaining gold report to flotation tailings, which can be cyanide leached directly to recover 47% of the gold without further preparation. However further preparation as ultrafine grinding or roasting resulted in 57% and 79% recovery of the remaining gold respectively. Variability tests showed that when supergene materials increased in the ore the Zinc recovery and grades are suffering and only Copper and gold can be recovered without complications.