Abstract
Gold production in South Africa is projected to continue its decline in future, and prospects for discovery of new high-grade deposits are limited. Many of the mining companies have resorted to mining and processing low-grade and complex gold ores. Such ores are technically challenging to process, which results in low recovery rates, excessive reagent consumption and high operating costs when compared to free-milling gold ores. In the Witwatersrand mines, options of blending low-grade gold ores with high-grade ores exist. Although it is well known that most of the Witwatersrand gold ores are highly amenable to gold cyanidation, not much is known on the leachability of blended ores, especially the effects of mineralogical and metallurgical variability between different gold ores. In this study, we apply a geometallurgical approach to investigate mineralogical and metallurgical factors that influence the leaching of blended ores in a set of bottle shaker and reactor column tests. Three gold-bearing conglomerate units, so-called reefs, i.e., Carbon Leader Reef, Ventersdorp Contact Reef and the Black Reef, all in the Carletonville goldfield, were sampled. The ores were prepared using a terminator jaw crusher followed by vertical spindle pulverizer (20 kg aliquot) and high-pressure grinding rolls (80 kg aliquot). Mineralogical analysis was conducted using a range of complementary tools such as optical microscopy, QEMSCAN and micro–XCT. The results show that Witwatersrand gold ores are amenable to the process of ore blending. Some of the ores, however, contain impervious inert gangue and reactive ore minerals. Leach solution can only access gold locked in impervious gangue minerals through HPGR-induced pores and/or cracks. The optimum ore blending ratio of the bottle shaker experiments (p80 = − 75 μm) comprises 60% Carbon Leader Reef, 20% Ventersdorp Contact Reef and 20% Black Reef and yields 92% recovered Au over a leach period of 40 h. Blended ores with high carbonaceous material (> 1 wt% carbonaceous material, (Black Reef = 36–60%) yield lower recoveries of 60–69% Au). Ore leaching at the mixed-bed reactor column (− 75 μm and − 5.6/+ 4 mm) yields about 70% over a leach period of two weeks. We therefore suggest that the feasibility of ore blending is strongly controlled by the mineralogy of the constituent ores and that a mixed-bed reactor may be a viable alternative method for leaching of the low-grade Witwatersrand gold ores. Material from certain reefs, such as the Black Reef, has synergistic/antagonistic (nonadditive) blending effects. The overall implication of this study is that ore blending ratios, effects of comminution on mineral liberation, an association of gold with other minerals, and gold adsorption behavior will greatly inform future technology choices in the area of geometallurgy.
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References
AngloGold Ashanti. (2017). The mineral resource and ore reserve for AngloGold Ashanti Limited. https://www.anglogoldashanti.com/investors/annual-reports/. Accessed 02 Jan 2019.
Ashley, K. J., & Callow, M. I. (2000). Ore variability: Exercises in geometallurgy. Engineering and Mining Journal,201, 24–28.
Bam, L. C., Miller, J. A., Becker, M., & Basson, I. (2019). X-ray computed tomography: Practical evaluation of beam hardening in iron ore samples. Minerals Engineering,131, 206–215.
Brooy, S. R. (1994). Review of gold extraction from ores. Minerals Engineering,7, 1213–1242.
Bye, A. R. (2011). Case studies demonstrating value from geometallurgy initiatives. In Proceedings of the international geometallurgy conference, Brisbane, Australia, 5–7 September 2011 (pp. 3–90). Melbourne: Australasian Institute of Mining and Metallurgy.
Carrasco, C., Keeney, L., & Walters, S. G. (2016). Development of a novel methodology to characterise preferential grade by size deportment and its operational significance. Minerals Engineering,91, 100–107.
Coetzee, L. L., Theron, S. J., Martin, G. J., Van Der Merwe, J. D., & Stanek, T. (2011). Modern gold deportments and its application to industry. Minerals Engineering,24, 565–575.
Coward, S., & Dowd, P. A. (2015). Geometallurgical models for the quantification of uncertainty in mining project value chains. In Proceedings of the APCOM conference, Fairbanks, AK, USA, 23–27 May 2015 (pp. 360–369). Englewood: Society of Mining Engineers.
Domínguez, A., & Valero, A. (2013). Global gold mining: Is technological learning overcoming the declining in ore grades? Journal of Environmental Accounting and Management,1, 85–101.
Dominy, S. C., Glass, H. J., O’Connor, L., Lam, C. K., Purevgerel, S., & Minnitt, R. C. A. (2018a). Integrating the theory of sampling into underground mine grade control strategies. Minerals,8, 232.
Dominy, S. C., O’Connor, L., Parbhakar-Fox, A., Glass, H. J., & Purevgerel, S. (2018b). Geometallurgy—A route to more resilient mine operations. Minerals,8, 560.
Dunham, S., & Vann, J. (2007). Geometallurgy, geostatistics and project value—does your block model tell you what you need to know? In Project evaluation conference. Melbourne, Vic, 19–20 June 2007 (pp. 189–196). Melbourne.
Dzvinamurungu, T., Viljoen, K. S., Knoper, M. W., & Mulaba-Bafubiandi, A. (2013). Geometallurgical characterisation of Merensky Reef and UG2 at the Marikana Mine, Bushveld Complex. Minerals Engineering,52, 74–81.
Ehrig, K. (2013). Geometallurgy—What do you really need to know from exploration through to production? Proceedings MetPlant 2013 (pp. 28–33). Melbourne: The Australasian Institute of Mining and Metallurgy.
Els, B. G. (1998). The question of alluvial fans in the auriferous Archaean and Proterozoic successions of South Africa. South African Journal of Geology,101, 17–25.
Everard, A. D. (1988). Flat faulting in the Ventersdorp Contact Reef, sub-shaft area, Carletonville goldfield. Elandsrand Gold Mining Company Limited. Company report number 11/173/166.
Frimmel, H. E. (1994). Metamorphism of witwatersrand gold. Exploration and Mining Geology, 3, 357–370.
Frimmel, H. E. (2014). A giant Mesoarchaean crustal gold-enrichment episode: Possible causes and consequences for exploration. Society of Economic Geologists Special Publications,18, 209–234.
Frimmel, H. E. (2018). Episodic concentration of gold to ore grade through Earth’s history. Earth Science Reviews,180, 148–158.
Frimmel, H. E., & Gartz, V. H. (1997). Witwatersrand gold particle chemistry matches model of metamorphosed, hydrothermally altered placer deposits. Mineralium Deposita,32, 523–530.
Frimmel, H. E., Groves, D. I., Kirk, J., Ruiz, J., Chesley, J., & Minter, W. E. L. (2005). The formation and preservation of the Witwatersrand goldfields, the largest gold province in the world. In J. W. Hedenquist, J. F. H. Thomson, & R. J. Goldfarb (Eds.), Economic geology 100th Anniversary volume (pp. 769–797). Littleton: Society of Economic Geologists.
Frimmel, H. E., & Nwaila, G. T. (2020). Geologic evidence of syngenetic gold in the Witwatersrand Goldfields, South Africa. In R.H. Sillitoe, R. Goldfarb, F. Robert, & S. Simmons (Eds.), Geology of the major gold deposits and provinces of the world. Littleton: Society of Economic Geologists, Special Publ., in press.
Fuchs, S. H. J., Williams-Jones, A. E., Jackson, S. E., & Przybylowicz, W. J. (2016). Metal distribution in pyrobitumen of the Carbon Leader Reef, Witwatersrand Supergroup, South Africa: Evidence for liquid hydrocarbon ore fluids. Chemical Geology,426, 45–59.
Gartz, V. H., & Frimmel, H. E. (1999). Complex metasomatism of an Archean placer in the Witwatersrand Basin, South Africa: The Ventersdorp Contact Reef—A hydrothermal aquifer? Economic Geology,94, 689–706.
Ghorbani, Y., Becker, M., Mainza, A., Franzidis, J.-P., & Peterson, J. (2011). Large particle effects in chemical/biochemical heap leach processes—A review. Minerals Engineering,24, 1172–1184.
Ghorbani, Y., Mainza, A. N., Petersen, J., Becker, M., Franzidis, J.-P., & Kalala, J. T. (2013). Investigation of particles with high crack density produced by HPGR and its effect on the redistribution of the particle size fraction. Minerals Engineering,43–44, 44–51.
Ghorbani, Y., Peterson, J., Harrison, S. T. L., Tupikina, O. V., Becker, M., Mainza, A., et al. (2012). An experimental study of the long-term bioleaching of large sphalerite ore particles in a circulating fluid fixed-bed reactor. Hydrometallurgy,129–130, 161–171.
Glass, H. J. (2016). Geometallurgy: Driving innovation in the mine value chain. In Proceedings of the international geometallurgy conference, Perth, Australia, 15–16 June 2016 (pp. 21–28). Melbourne: Australasian Institute of Mining and Metallurgy.
Gumsley, A., Stamsnijder, J., Larsson, E., Söderlund, U., Naeraa, T., de Kock, M. O., & Ernst, R. (2018). The 2789–2782 Ma Klipriviersberg large igneous province: implications for the chronostratigraphy of the Ventersdorp Supergroup and the timing of Witwatersrand gold deposition. In GeoCongress 2018 (p. 133). Geological Society of South Africa (GSSA), Abstract Book.
Guy, B. M. (2012). Pyrite in the Mesoarchaean Witwatersrand Supergroup, South Africa. Ph.D. thesis, University of Johannesburg, Auckland Park (pp. 218–304).
Harmony Gold. (2017). Resources and reserves by operation. https://www.harmony.co.za/component/jdownloads/send/130-2017/. Accessed 02 Jan 2019.
Jackson, J., McFarlane, A., & Olson, H. K. (2011). Geometallurgy—back to the future: Scoping and communicating geomet programs. In Proceedings of the international geometallurgy conference, Burwood, Australia, 5–7 September 2011 (pp. 125–131). Melbourne: Australasian Institute of Mining and Metallurgy.
Jackson, S., Vann, J. E., Coward, S., & Moayer, S. (2014). Scenario-based project evaluation—Full mineral value chain stochastic simulation to evaluate development and operational alternatives. In Proceedings of the international mining geology conference, Adelaide, Australia, 18–20 August 2014 (pp. 1–11). Melbourne: Australasian Institute of Mining and Metallurgy.
Kamo, S. L., Reimold, W. U., Krogh, T. E., & Colliston, W. P. (1996). A 2.023 Ga age for the Vredefort impact event and a first report of shock metamorphosed zircons in pseudotachylitic breccias and granophyre. Earth and Planetary Science Letters,144, 369–387.
Keeney, L. A. (2013). Geometallurgical methodology suitable for resource definition. Society of Economic Geology News,4, 18–19.
Kesler, S. (2007). Mineral Supply and Demand into the 21st Century. In Proceedings for a workshop on deposit modelling, mineral resource assessment, and their role in sustainable development (pp. 55–62).
Kositcin, N., & Krapež, B. (2004). SHRIMP U-Pb detrital zircon geochronology of the Late Archaean Witwatersrand Basin of South Africa: Relation between zircon provenance age spectra and basin evolution. Precambrian Research,129, 141–168.
Lamberg, P. (2011). Particles-the bridge between geology and metallurgy. In: Conference in minerals engineering (p. 1). Luleå.
Letanta, D., Nwaila, G. T., Dohm, C. E., Burnett, M., & Tolmay, L. (2018). Sedimentological characteristics and gold distribution in the Middelvlei Reef, Witwatersrand Supergroup: Implications for estimating gold grade. In Geocongress, 18–20 July 2018 (p. 288). Johannesburg.
Lishchuk, V., Lund, C., & Ghorbani, Y. (2019a). Evaluation and comparison of different machine-learning methods to integrate sparse process data into a spatial model in geometallurgy. Mineral Engineering,134, 156–165.
Lishchuk, V., Lund, C., Koch, P.-H., Gustafsson, M., & Pålsson, B. I. (2019b). Geometallurgical characterization of Leveäniemi iron ore—Unlocking the patterns. Minerals Engineering,131, 325–335.
Lotter, N. O. (2011). Modern process mineralogy: An integrated multi-disciplined approach to flow sheeting. Minerals Engineering,24, 1229–1237.
Lund, C., & Lamberg, P. (2014). Geometallurgy—A tool for better resource efficiency. European Geologist,37, 39–43.
Marsden, J. O., & House, C. I. (2006). The chemistry of gold extractions (2nd ed., pp. 211–212). Littleton: SME.
McCarthy, T. S. (2006). The Witwatersrand supergroup. In M. R. Johnson, C. R. Anhaeusser, & R. J. Thomas (Eds.), The geology of South Africa (pp. 155–186). Johannesburg: Geological Society of South Africa.
McIntosh, K. S. (2004). The systems engineering of automated fire assay laboratories for the analysis of the precious metals. Ph.D. thesis, University of Stellenbosch, Stellenbosch.
McKibben, M. A. (2005). Gold. In R. C. Selley, L. R. M. Cocks, & I. R. Plimer (Eds.), Encyclopaedia of geology (pp. 118–127). Oxford: Elsevier.
McLoughlin, A. C. (2014). Geometallurgical examination of gold, uranium and thorium in the Black Reef Quartzite formation, Gold One International LTD, Springs. M.Sc. thesis, University of Johannesburg, Johannesburg.
Mossman, D. J., Minter, W. E. L., Dutkiewicz, A., Hallbauer, D. K., George, S. C., Hennigh, Q., et al. (2008). The indigenous origin of Witwatersrand “carbon”. Precambrian Research,164, 173–186.
Müller, J., & Frimmel, H. E. (2010). Numerical analysis of historic gold production cycles and implications for future sub-cycles. The Open Geology Journal,4, 29–34.
Neingo, O. N., & Tholana, T. (2016). Trends in productivity in the South African gold mining industry. The Journal of the Southern African Institute of Mining and Metallurgy,116, 283–290.
Nwaila, G. T., Becker, M., Ghorbani, Y., Petersen, J., Reid, D. L., Bam, L. C., De Beer, F. C., & Franzidis, J. -P. (2013). A geometallurgical study of the Witwatersrand gold ore at Carletonville, South Africa. In Australasian institute of mining and metallurgy geometallurgy conference 2013 (pp. 75–83). Brisbane.
Nwaila, G. T., Manzi, M. S. D., Kirk, J., Maselela, H. K., Durrheim, R. J., Rose, D. H., et al. (2018). Recycling of palaeoplacer gold through mechanical and post-depositional mobilisation in the Neoarchaean Black Reef Formation, South Africa. Journal of Geology,127, 137–166.
Prasojo, T. S., Yulianto, A., Hindarto, A., Parinuss, B., & Arifien, A. (2013). Ore blending as mine scheduling strategy to accommodate resources conservation at Pakal Nickel Mine, PT ANTAM (Persero). Tbk. Procedia Earth and Planetary Science,6, 24–29.
Rademan, L., & Groot, D. R. (2012). Cyanidation of reef and surface gold ores. The Journal of the Southern African Institute of Mining and Metallurgy,112, 295–300.
Rees, K. L., & van Deventer, J. J. (2000). Preg-robbing phenomena in the cyanidation of sulphide gold ores. Melbourne: Elsevier.
Sibanye Stillwater. (2017). The mineral resources and mineral reserves report. https://www.sibanyestillwater.com/our-business/southern-africa/gold/resources-reserves. Accessed 02 Jan 2019.
Tauetsile, P., Oraby, E., & Eksteen, J. (2019). Activated carbon adsorption of gold from cyanide-starved glycine solutions containing copper. Part 2: Kinetics. Separation and Purification Technology,211, 290–297.
Tucker, R. F., Viljoen, R. P., & Viljoen, M. J. (2016). A review of the Witwatersrand Basin—The world’s greatest goldfield. Episodes,39, 105–133.
Valenta, R., Clark, A., O’Sullivan, R., & Thomas, J. (2018). Estimating geometallurgical risk in undeveloped complex orebodies. Geometallurgical Modelling 02, Procemin * Geomet. In 5th international seminar on geometallurgy, November 28–30 (pp. 1–7). Santiago.
Van Tonder, E., Deglon, D. A., & Napier-Munn, T. (2010). The effect of ore blends on the mineral processing of platinum ores. Minerals Engineering,23, 621–626.
Vann, J., Jackson, S., Bye, A., Coward, S., Moayer, S., Nicholas, G., & Wolff, R. (2012). Scenario thinking—A powerful tool for strategic planning and evaluation of mining projects and operations. In Proceedings of the project evaluation conference, Melbourne, Australia, 24–25 May 2012 (pp. 5–14). Melbourne: Australasian Institute of Mining and Metallurgy.
Vann, J., Jackson, J., Coward, S., & Dunham, S. (2011). The Geomet Curve—A model for implementation of geometallurgy. In The first AUSIMM international geometallurgy conference/Brisbane, QLD, 5–7-September, 2011 (pp. 35–43). Brisbane.
Vaughan, J. P. (2004). The process mineralogy of gold: The classification of ore types. The Journal of the Minerals, Metals & Materials Society,56, 46–48.
Walters, S. (2008). An overview of new integrated geometallurgical research. In Proceedings of the international congress for applied mineralogy, Brisbane, Australia, 8–10 September 2008 (pp. 79–82). Melbourne: Australasian Institute of Mining and Metallurgy.
WGC (World Gold Council). (2018). Gold demand and supply. https://www.gold.org/about-gold. Accessed 18 Dec 2018.
Williams, S. R. (2013). A historical perspective of the application and success of geometallurgical methodologies. In Proceedings of the international geometallurgy conference, Brisbane, Australia, 30 September–2 October 2013 (pp. 37–47). Melbourne: Australasian Institute of Mining and Metallurgy.
Zeh, A., Ovtcharova, M., Wilson, Al, & Schaltegger, U. (2015). The Bushveld Complex was emplaced and cooled in less than one million years—Results of zirconology, and geotectonic implications. Earth and Planetary Science Letters,418, 103–114.
Zhou, J., Jago, B., & Martin, C. (2004). Establishing the Process Mineralogy of Gold Ores. SGS Minerals—Technical Bulletin, 3, 1–16. https://www.sgsgroup.com.cn/-/media/global/documents/technical-documents/sgs-technical-papers/sgs-min-tp2004-03-process-mineralogy-of-gold-ores.pdf. Accessed 18 Dec 2018.
Acknowledgments
Glen Nwaila thanks CIMERA (Centre of Excellence for Integrated Mineral and Energy Resource Analysis) for funding this research. Various mining companies (Sibanye-Stillwater, Harmony Gold and AngloGold Ashanti) are acknowledged for providing samples. Sibanye-Stillwater is further acknowledged for providing facilities for running experimental work. We thank the University of Cape Town’s Department of Chemical Engineering for providing access to the QEMSCAN, leaching columns schematics and for assisting with analyses. Dr Frikkie De Beer and Mr Lunga Bam of Necsa are acknowledged for providing access to the X-ray tomography facilities.
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Nwaila, G.T., Ghorbani, Y., Becker, M. et al. Geometallurgical Approach for Implications of Ore Blending on Cyanide Leaching and Adsorption Behavior of Witwatersrand Gold Ores, South Africa. Nat Resour Res 29, 1007–1030 (2020). https://doi.org/10.1007/s11053-019-09522-4
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DOI: https://doi.org/10.1007/s11053-019-09522-4