Characterisation and Metallurgical Response of Gold Ores from Transition Zones in Ashanti Belt Zone of Ghana

Abstract

The complex and variable mineralogical compositions of transitional gold ore zones pose significant metallurgical challenges. Using a multi-technique analytical approach that integrates geological, mineralogical, and metallurgical data, this study characterises gold ores from transitional zones within Ghana's Ashanti Belt. XRD, light microscopy, XRF, Raman spectroscopy, sulphur and carbon speciation, preg-robbing index (PRI) tests, and diagnostic leaching studies were performed on six representative samples from three mining companies. The results show that the ores, which are mainly rich in quartz and sericite, have variable sulphide (0.11-0.94%) and organic carbon (0.13-2.11%) contents, which significantly affect the cyanidation performance. Raman spectroscopy revealed different levels of carbon maturity, while optical microscopy verified the presence of pyrite and arsenopyrite. Diagnostic leaching showed highly variable gold deportment: gold was distributed among free-milling phases, sulphides, carbonaceous materials (CM), and residual fines. Samples with higher sulphide and organic carbon contents demonstrated strong preg-robbing behaviour and poor cyanide leach recoveries (34-40%), while those with lower contents achieved recoveries of 75-77%. The study highlights the pronounced intra- and inter-sample variability across the transitional zone ores, underlining the inadequacy of conventional processing approaches. It concludes that a geometallurgical framework anchored in integrated multi-technique characterisation is essential for optimising gold recovery and guiding efficient, domain-specific processing strategies for transitional gold ore deposits.