When it comes to mining sulphide minerals, the focus is usually fixed on a single or a few valuable elements. Copper from chalcopyrite and bornite, zinc from sphalerite, and lead from galena are the primary considerations. However, these minerals are often associated with a broad range of trace elements, which can make up valuable by-products to ease the financial burden of running and operating a mine. In this article, we delve into the trace elements commonly found in the sulphide minerals pyrite, sphalerite, galena, bornite, and chalcopyrite.
Pyrite (FeS2), known throughout as “fool’s gold”, is the most common sulphide mineral in the world. When compared to the minerals bornite, chalcopyrite, sphalerite and galena, pyrite will be the preferred host of the elements As, Co, Ni, Au, Se and Te. As arsenic will readily substitute with Fe to form arsenopyrite (FeAsS), it is no surprise that pyrite will contain abundant (>1000 ppm) concentrations of As. Interestingly, the concentration of As in pyrite has direct implications for the concentration of Au and Te (Wu et al., 2021; Large and Maslennikov, 2020; Reich et al., 2005). Gold can be hosted in pyrite in the form of native Au nanoparticles, nanoparticles of Au-bearing tellurides, or as a solid solution phase of which often directly correlates with the abundances of As (Reich et al., 2005). In a similar fashion, Se and Te will directly substitute for S, and are generally enriched in Carlin-type deposits (Keith et al., 2018; Chouinard et al., 2005). Cobalt and Ni will both readily substitute for Fe (Co, Ni ↔ Fe) in the pyrite lattice (Paul F, 1945). When there is copious amounts of Co and Ni available, the incorporation of these elements form the minerals cattierite (CoS2) and Vaesite (NiS2), which mimic the crystal lattice of pyrite (Paul F, 1945). These minerals are of particular importance for current cobalt mining, and are critical for the mass production of EV technology (Crundwell et al., 2020).
Sphalerite (ZnFeS) is possibly the most well characterised mineral in the world with regards to its trace element composition. Literally hundreds of peer review studies have been published that are dedicated to assessing the trace element composition of this mineral (Zhao et al., 2023; Frenzel et al., 2016; Cook et al., 2009). Of particular importance for this article, sphalerite will readily incorporate the elements Cd, In, Ge and Ga. Sphalerite with out a doubt is the chief host of Cd, which is often extracted as a by-product from Zn-Pb deposits (Schwartz, 2000). Cadmium will readily substitute for Zn and is typically present in concentrations 0.2-1wt%, however extreme enrichments of ~13.2wt% have been documented at the Baisoara Fe (Zn-Pb) skarn deposit (Cook et al., 2009). Interestingly, the abundance of In, Ge and Ga in sphalerite correlate with deposit type and the formation temperature of sphalerite (Zhao et al., 2023; Frenzel et al., 2016). Indium is generally enriched in sphalerite from high-temperature deposits with a magmatic-hydrothermal affinity (Zhao et al., 2023; Bauer et al., 2019). Typically, In will undergo coupled substitution with Cu in order to replace zinc (In + Cu ↔ 2Zn) (Cook et al., 2009). In almost opposing fashion, Ge and Ga are concentrated in sphalerite from low-temperature (<150°C) ore deposits with no obvious magmatic-hydrothermal affinity (Bauer et al., 2019; Frenzel et al., 2016). Germanium and gallium substitute into the sphalerite lattice by replacing Zn coupled with various amounts of Ag, Cu and Tl (Ag, Cu, Tl + Ge, Ga ↔ 2Zn) (Cook et al., 2009). Interestingly, if sphalerite is exposed to deformation and metamorphism, Ge can be released from the sphalerite lattace to form micro-scale Ge-bearing minerals, such as briartite (Fougerouse et al., 2023; Cugerone et al., 2019).
Galena (PbS) is one of the more understudied minerals, with only a few published articles focused on assessing the trace element composition of this mineral (George et al., 2015). Trace elements that are considered important within galena include Ag, Bi, Sb and Tl (George et al., 2015). In most circumstances, the concentration of Ag and Sb in galena range from 10 ppm to <1.5 wt% (George et al., 2015). While Bi is typically <1 wt% in most galena, extreme values >10 wt% of Bi have been documented in the Lamo skarn Zn-Cu deposit, which is termed bismuthoan galena (Xilin, 1990). The elements Ag, Bi and Sb all play an important role in how they are substituted into galena. The most important substitution mechanism for Bi and Sb is coupled substitution alongside Ag for Pb (Ag+(Bi,Sb) ↔ 2Pb) . Relative to sphalerite and chalcopyrite, galena is the preferred host of Tl, with concentrations ranging from 1 to >100 ppm (George et al., 2015). Much like Ag, the Tl ion will substitute into the galena lattice through coupling with Bi and Sb (Tl + (Bi,Sb) ↔ 2Pb) (George et al., 2015).
Bornite (Cu5FeS4) is another mineral that hasn’t received as much attention as deserved, with only a few studies assessing the trace element composition of this mineral (Cook et al., 2011). From the limited studies available, bornite appears to be an important carrier of the trace elements Ag, Bi, Se and Te. Silver and Bi are typically present in the highest concentrations, ranging from 70-8000 ppm & 134-17500 ppm respectively (Cook et al., 2011). Both of these elements are interpreted to be incorporated into the galena lattice through solid solution with Cu (Bi, Sb ↔ Cu) to form Bi and Sb nanoparticles (Cook et al., 2011). Both Se and Te may be present in bornite with concentrations >1000 ppm (Cook et al., 2011). These elements are heterogeneously distributed throughout the bornite, and are interpreted to reflect the presence of micron-scale inclusions of selenide and telluride minerals (Cook et al., 2011).
Chalcopyrite (CuFeS2) is the most common Cu-sulphide in the world and is present throughout a wide range of ore deposits. When co-crystallising with other sulphide minerals, such as galena, sphalerite and chalcopyrite, is often the least preferred host of all aforementioned trace elements (Cave et al., 2020; George et al., 2016). Because of this, chalcopyrite is often termed a “garbage” mineral, and will accommodate whatever trace elements are not incorporated into the other co-crystallising minerals. Rarely are the concentration of trace elements (Mn, Co, Ga, Se, Ag, Cd, In, Sn, Sb & Tl) in chalcopyrite surpass a few hundred ppm (George et al., 2018). There is a single exception to this rule, which is indium. In some circumstances, such as magmatic Ni-Cu-PGE deposits, chalcopyrite is it the preferred host of In, containing higher concentrations relative to the minerals pyrrhotite, pentlandite and pyrite (Mansur et al., 2021). In sediment-hosted massive sulphide (SMHS) deposits, chalcopyrite is the secondary host of In behind sphalerite, but elevated concentrations (>100 ppm) can still be observed (Cave et al., 2020).
In summary, this article provides a concise evaluation of the prevalent trace elements present in pyrite, sphalerite, galena, bornite, and chalcopyrite. The trace element composition and its selective distribution among these minerals hold crucial importance in determining the feasibility of extracting these trace elements from such minerals in the future.
References:
Bauer, M.E., Burisch, M., Ostendorf, J., Krause, J., Frenzel, M., Seifert, T., Gutzmer, J., 2019. Trace element geochemistry of sphalerite in contrasting hydrothermal fluid systems of the Freiberg district, Germany: insights from LA-ICP-MS analysis, near-infrared light microthermometry of sphalerite-hosted fluid inclusions, and sulfur isotope geochemi. Miner. Depos. 54, 237–262.
Cave, B., Lilly, R., Barovich, K., 2020. Textural and geochemical analysis of chalcopyrite, galena and sphalerite across the Mount Isa Cu to Pb-Zn transition: Implications for a zoned Cu-Pb-Zn system. Ore Geol. Rev. 103647.
Chouinard, A., Paquette, J., Williams-Jones, A.E., 2005. Crystallographic controls on trace-element incorporation in auriferous pyrite from the Pascua epithermal high-sulfidation deposit, Chile–Argentina. Can. Mineral. 43, 951–963.
Cook, N.J., Ciobanu, C.L., Danyushevsky, L. V, Gilbert, S., 2011. Minor and trace elements in bornite and associated Cu–(Fe)-sulfides: A LA-ICP-MS studyBornite mineral chemistry. Geochim. Cosmochim. Acta 75, 6473–6496.
Cook, N.J., Ciobanu, C.L., Pring, A., Skinner, W., Shimizu, M., Danyushevsky, L., Saini-Eidukat, B., Melcher, F., 2009. Trace and minor elements in sphalerite: A LA-ICPMS study. Geochim. Cosmochim. Acta 73, 4761–4791.
Crundwell, F.K., Du Preez, N.B., Knights, B.D.H., 2020. Production of cobalt from copper-cobalt ores on the African Copperbelt–An overview. Miner. Eng. 156, 106450.
Cugerone, A., Cenki-Tok, B., Oliot, E., Muñoz, M., Barou, F., Motto-Ros, V., Le Goff, E., 2019. Redistribution of germanium during dynamic recrystallization of sphalerite. Geology.
Fougerouse, D., Cugerone, A., Reddy, S.M., Luo, K., Motto-Ros, V., 2023. Nanoscale distribution of Ge in Cu-rich sphalerite. Geochim. Cosmochim. Acta 346, 223–230.
Frenzel, M., Hirsch, T., Gutzmer, J., 2016. Gallium, germanium, indium, and other trace and minor elements in sphalerite as a function of deposit type—A meta-analysis. Ore Geol. Rev. 76, 52–78.
George, L., Cook, N.J., Ciobanu, C.L., Wade, B.P., 2015. Trace and minor elements in galena: A reconnaissance LA-ICP-MS study. Am. Mineral. 100, 548–569.
George, L.L., Cook, N.J., Ciobanu, C.L., 2016. Partitioning of trace elements in co-crystallized sphalerite–galena–chalcopyrite hydrothermal ores. Ore Geol. Rev. 77, 97–116.
George, L.L., Cook, N.J., Crowe, B.B.P., Ciobanu, C.L., 2018. Trace elements in hydrothermal chalcopyrite. Mineral. Mag. 82, 59–88.
Keith, M., Smith, D.J., Jenkin, G.R.T., Holwell, D.A., Dye, M.D., 2018. A review of Te and Se systematics in hydrothermal pyrite from precious metal deposits: Insights into ore-forming processes. Ore Geol. Rev. 96, 269–282.
Large, R.R., Maslennikov, V. V, 2020. Invisible gold paragenesis and geochemistry in pyrite from orogenic and sediment-hosted gold deposits. Minerals 10, 339.
Mansur, E.T., Barnes, S.-J., Duran, C.J., 2021. An overview of chalcophile element contents of pyrrhotite, pentlandite, chalcopyrite, and pyrite from magmatic Ni-Cu-PGE sulfide deposits. Miner. Depos. 56, 179–204.
Paul F, K., 1945. Cattierite and vaesite: new Co-Ni minerals from the Belgian Congo. Am. Mineral. J. Earth Planet. Mater. 30, 483–497.
Reich, M., Kesler, S.E., Utsunomiya, S., Palenik, C.S., Chryssoulis, S.L., Ewing, R.C., 2005. Solubility of gold in arsenian pyrite. Geochim. Cosmochim. Acta 69, 2781–2796.
Schwartz, M.O., 2000. Cadmium in zinc deposits: economic geology of a polluting element. Int. Geol. Rev. 42, 445–469.
Wu, Y.-F., Evans, K., Hu, S.-Y., Fougerouse, D., Zhou, M.-F., Fisher, L.A., Guagliardo, P., Li, J.-W., 2021. Decoupling of Au and As during rapid pyrite crystallization. Geology 49, 827–831.
Xilin, L., 1990. Bismuthoan galena—A new variety of galena. Chinese J. geochemistry 9, 378–384.
Zhao, H., Shao, Y., Zhang, Y., Cao, G., Zhao, L., Zheng, X., 2023. Big data mining on trace element geochemistry of sphalerite. J. Geochemical Explor. 107254.