Parbhakar-Fox, Anita1; Degeling, Helen2; Lisitsin, Vlad2
1 W.H.Bryan Mining and Geology Research Centre, Sustainable Minerals Institute, 40 Isles Road, Indooroopilly, Queensland, Australia, 4068, 2 Geological Survey of Queensland, Department of Natural Resources, Mines and Energy, Level 4, 1 William Street, Brisbane, Queensland, Australia, 4002
The global response to climate change, initiated by the Paris Agreement, has been to encourage transition to low-carbon economies. Technologies such as electric vehicles, low-emission power sources and products for the medical and defence sectors are required to support this. The manufacture of these products requires resources of ‘new economy metals’ including cobalt, tungsten, rare earth elements (REEs), indium, gallium and germanium. Traditionally, these metals were considered unwanted by-products of base metal and precious metal mining operations, and consequently are concentrated in mine waste.
Mine waste reprocessing is a business proposition that is increasingly being adopted in many countries, with at least 75 active projects, including one in Queensland at the Century Mine. Whilst the concept of remediating sites through removing and reprocessing mine waste is being considered to extend the life-of-mine at operational mines and to rehabilitate abandoned and legacy wastes, these materials are mineralogically heterogeneous thus, a ‘one approach-fits all’ will not optimise value-recovery or indeed, guarantee that the waste is environmentally de-risked. Further, as these wastes are surficially deposited in different climatic zones, metal cycling can be a more dynamic process in for example, sub-tropical to tropical climates than when comparison to temperate or Mediterranean climates. Thus, geochemical processes, as related to mineralogy, must be studied at each.
This research focusses on secondary prospectivity in Queensland, where there are at least 40 significant metalliferous mining operations producing mine waste streams containing unknown quantities of new economy metals. Additionally, there are 120 state-managed abandoned mines. Many of these sites contain reactive sulphide-rich mine waste with associated acid and metalliferous drainage risks. The ongoing management of these sites is costly, but their potential new economy metal content – as yet uncharacterised – presents a unique opportunity to economically rehabilitate these sites through reprocessing waste.
In this research, the new economy metal fertility of reactive mine waste (tailings, waste rock, spent heap leach) at nine sites (Capricorn Copper, New Century, Osborne, Selwyn, Lady Annie, Wolfram Camp, Baal Gammon, Mt Oxide, Pindora) was examined. For each site, geometallurgical assessments were undertaken using bulk geochemical, mineralogical (X-ray diffractometry, mineral liberation analysis) and mineral chemistry (LA-ICPMS) tools. Integration of these data allowed for a first-pass assessment of metal fertility. In terms of Co, the greatest tenor was reported at Osborne (TSF 1= 856 ppm; TSF 2= 582 ppm- data from Chinova Resources) and is refractory in pyrite. Waste rock at Capricorn Copper was also endowed (273 ppm; n=20) and associated with Mn and Fe oxides, but the sampled tailings were less endowed (63 ppm; n=79) however, only the upper 1.5 m was sampled and it is postulated that grade will increase with depth. Several waste rock samples from Baal Gammon reported > 500 ppm indium (93 ppm; n=41) in chalcopyrite whilst at Pindora, REE’s were endowed in iron oxides contained in heap leach (n=17) and waste rock (n=8) (e.g., Ce- 200 ppm and 1,374 ppm respectively, La 123 ppm and 884 ppm respectively). Detailed investigations for critical metal recovery at these four sites is ongoing.
Anita is a Senior Research Fellow in Geometallurgy and Applied Geochemistry. Anita’s research is focussed on mine waste characterisation to improve mine planning and waste management practices where she has worked with mining industry, METS sector and government stakeholders.