Uptake of trace elements by baryte during copper ore processing: A case study from Olympic Dam, South Australia
Baryte is a common gangue mineral in many ore systems. Here, we report on a study of baryte chemistry in samples of ore and processing materials (flotation feed, flotation concentrate, flotation tailings, concentrate leach discharge, and tailings leach discharge) from the Olympic Dam Cu-U-Au-Ag deposit, South Australia. Elements that commonly substitute for Ba in the baryte lattice, including Sr and Ca, are measured in variable concentrations reflecting grain-scale zonation and heterogeneity at the scale of the deposit but appear unaffected during processing. Variation in the concentration of some other elements, notably Cu, reflect both the heterogeneous nature of flotation feed and the intimately intergrown character of the sulfide-sulfate assemblage. Measured Pb concentrations in baryte progressively increase during processing from flotation feed to flotation concentrate, and particularly in concentrate leach discharge. Such data suggest that, during sulfuric acid leaching, baryte contained within the concentrate is able to incorporate quantities of Pb that have been mobilized during break-down of Pb-bearing minerals (notably U-minerals containing radiogenic lead). This takes place via surface adsorption followed by rapid coupled dissolution-replacement driven incorporation throughout the grain. Results suggest that baryte may scavenge non-target elements during processing and contribute to an understanding of mobility, mineralogical location, and evolution in the deportment of radionuclides through the processing cycle.