PHASE FORMS OF GOLD AND THEIR INFLUENCE ON RECOVERY IN THE OXIDATION ZONE OF THE ARKHARLY GOLD-SILVER DEPOSIT (KAZAKHSTAN)

The aim of this study is to determine the phase forms of gold in the oxidation zone of the Arkharly deposit and to assess their influence on the efficiency of gold and silver recovery. The main research methods included mineralogical analysis, electron microprobe studies, and technological testing. The study identified and characterized silver halides, established their genetic relationship with gold, and substantiated the role of supergene processes in the redistribution of gold. The Arkharly gold-silver deposit (Kazakhstan) is characterized by a complex composition of ores and a variety of gold occurrence forms, which significantly affect processing efficiency. This paper examines the phase forms of gold in the oxidation zone and their impact on technological recovery indicators. Based on mineralogical, electron microprobe, and technological studies, it was found that gold occurs in various forms: native gold of different fineness, electrum, as well as finely dispersed particles associated with silver minerals. Particular attention is given to silver halides, widely developed in the oxidation zone and forming complex intergrowths with native silver and gold. Textural and structural features of mineral aggregates indicate the redistribution of gold under supergene conditions. The formation of gold-bearing phases is associated with chloride and, presumably, colloidal migration of matter, leading to the formation of zonal structures and inclusions of high-fineness gold. Technological test results showed low efficiency of gravity concentration due to the fine-dispersed nature of gold, and high efficiency of cyanidation and sorption leaching (gold recovery up to 93.5%). A direct relationship between the phase forms of gold and recovery indicators has been established. The obtained results expand the understanding of gold behavior in the oxidation zone and can be used in developing effective technologies for processing complex gold-silver ores.

1. Hedenquist, J.W., Arribas, A., Gonzalez-Urien, E. Exploration for epithermal gold deposits. Reviews in Economic Geology, 13, 245–277 (2000). (in English).

2. Simmons, S.F., White, N.C., John, D.A. Geological characteristics of epithermal precious metal deposits. Economic Geology, 100th Anniversary Volume, 485–522 (2005). (in English).

3. Cooke, D.R., Simmons, S.F. Characteristics and genesis of epithermal gold deposits. SEG Reviews, 13, 221–244 (2000). (in English).

4. Thornber, M.R. Supergene processes in gold deposits. Ore Geology Reviews, 7, 349–364 (1992). (in English).

5. Webster, J.G., Mann, A.W. The influence of climate on the geochemistry of gold. Geochimica et Cosmochimica Acta, 48, 599–614 (1984). (in English).

6. Boyle, R.W. The Geochemistry of Gold and Its Deposits (Geological Survey of Canada, 1979), 584 p. (in English).

7. Zhautikov, T.M. et al. Gold-silver mineralization of Kazakhstan. Geology of Kazakhstan, 212–221 (2008). (in Russian).

8. Rafailovich, M.S., Egorov, S.A., Starova, M.M. et al. On a new type of epithermal gold-silver deposits in Kazakhstan. Geology and Exploration of Subsurface of Kazakhstan, No. 2, 7–12 (1996). (in Russian).

9. Zhautikov, T.M. Volcanic dome structures and their role in ore formation of Southern Jungaria. Proceedings of the National Academy of Sciences of the Republic of Kazakhstan. Geological Series, No. 4, 21–34 (2003). (in Russian).

10. Skrinnik, L., Gadeev, R., Umarbekova, Z., Tretyakov, A. Collisional and orogenic granitoids of Kazakhstan. SGEM 2020 Proceedings, 51–66 (2020). https://doi.org/10.5593/SGEM2020/1.1/S01.006. (in English).

11. Umarbekova, Z.T. et al. The role of hydrothermal eruptions in gold mineralization at the Arkharly epithermal gold-silver deposit. SGEM 2025 Proceedings, 97–100 (2025). https://doi.org/10.5593/sgem2025/1.1/s01.13. (in English).

12. Zhautikov, T.M. Regularities of Placement and Principles of Prediction of Gold Mineralization in Kazakhstan (Almaty, 1987), 448 p. PhD Thesis. (in Russian).

13. Corbett, G.J., Leach, T.M. Southwest Pacific Rim Gold-Copper Systems: Structure, Alteration and Mineralization (SEG, 1998). (in English).

14. Grebenchikov, A.M. Mineralogical and Geochemical Features of Near-Surface Gold Deposits of the Late Paleozoic Volcanic Belt of Kazakhstan (Moscow, 1976), 24 p. PhD Abstract. (in Russian).

15. Zhautikov, T.M. et al. Gold and silver of the hypergene zone of gold and gold-bearing deposits of Kazakhstan. Bulletin of NAS RK. Geological and Technical Sciences Series, No. 3, 15–33 (2011). (in Russian).

16. Umarbekova, Z.T. et al. Silver halides in the hypergene zone of the Arkharly gold deposit as indicators of formation in dry and hot climate (Dzungar Alatau, Kazakhstan). International Journal of Engineering Research and Technology, 13 (1) (2020). Available at: http://www.irphouse.com. (in English).

17. Umarbekova, Z.T. et al. The halides of silver in the hypergene zone of the Arkharly gold-silver deposit (South Dzhungaria). News of NAS RK. Series of Geology and Technical Sciences, 2(428), 242–250 (2018). (in English).

18. Reich, M., Kesler, S.E., Utsunomiya, S. Solubility of gold in arsenian pyrite. Geochimica et Cosmochimica Acta, 69, 2781–2796 (2005). (in English).

19. Palenik, C.S., Utsunomiya, S., Reich, M. “Invisible” gold revealed. American Mineralogist, 89, 1359–1366 (2004). (in English).

20. Saunders, J.A. Colloidal transport of gold. Economic Geology, 85, 171–181 (1990). (in English).

21. Marsden, J., House, I. The Chemistry of Gold Extraction, 2nd ed. (SME, 2006), 651 p. (in English).

22. Adams, M.D. (Ed.). Advances in Gold Ore Processing (Elsevier, 2005), 1076 p. (in English).