Chalcopyrite-dissolved Cu isotope exchange at hydrothermal conditions: Experimental constraints at 350 °C and 50 MPa

Copper Isotope Fractionation in Archean Hydrothermal Systems: Evidence From the Mesoarchean Carlow Castle Cu‐Co‐Au Deposit

“…Whilst Syverson et al. (2021) note that Δ 65 Cu (chalcopyrite‐Cu(aq)) varies with pH, significant changes in pH are not interpreted to have been critical to ore formation at Carlow Castle and any variations in pH during ore formation are likely to be accounted for within the aforementioned error maxima and minima.…”

“…Additionally, the intensity of such oxidative weathering processes in Archean settings would have been relatively limited in comparison to modern supergene processes and the transient nature of such conditions would preclude the multiple redox cycles necessary to generate significant heavy Cu isotope fractionation in crustal reservoirs (Johnson et al., 2021; Mathur & Fantle, 2015). Similarly, given the physicochemical conditions (minimal H + metasomatism, ∼300°C) of ore formation at Carlow Castle (Fox et al., 2021), it is unlikely that redox changes (oxidation of Cu + to Cu 2+ ) driven by hydrothermal ore‐forming processes would have induced significant heavy Cu isotope fractionation as CuCl 2 − is the predominant stable Cu‐Cl species in solution around 300°C, even under oxidizing conditions (Brugger et al., 2016; W. Liu et al., 2002; Maher et al., 2011; Syverson et al., 2021; Zhu et al., 2002). As such, the monovalent state (Cu + ) dominates Cu speciation both within solution and precipitated sulfide phases under these conditions (Pearce et al., 2006).…”

“…The Cu isotope range of igneous Cu (δ 65 Cu = 0 ± 0.27‰) derived by Ikehata and Hirata (2012) is illustrated as a gray field and the 1 σ error for Δ 65 Cu (chalcopyrite‐Cu(aq)) derived by Syverson et al. (2021) is illustrated as a dashed red line.…”

“…Similarly, given the physicochemical conditions (minimal H + metasomatism, ∼300°C) of ore formation at Carlow Castle (Fox et al, 2021), it is unlikely that redox changes (oxidation of Cu + to Cu 2+ ) driven by hydrothermal ore-forming processes would have induced significant heavy Cu isotope fractionation as CuCl 2 − is the predominant stable Cu-Cl species in solution around 300°C, even under oxidizing conditions (Brugger et al, 2016;W. Liu et al, 2002;Maher et al, 2011;Syverson et al, 2021;Zhu et al, 2002). As such, the monovalent state (Cu + ) dominates Cu speciation both within solution and precipitated sulfide phases under these conditions (Pearce et al, 2006).…”

Copper Isotopic Fractionation During Seafloor Alteration: Insights From Altered Basalts in the Mariana and Yap Trenches

“…In the oceanic crust, copper (Cu), an important metallogenic, redox‐sensitive, fluid‐mobile and chalcophile transition metal element, is mainly hosted by primary sulfides (e.g., chalcopyrite) and typically found in trace amounts in silicate minerals (e.g., olivine; Busigny et al., 2018; Dekov et al., 2013; Wang et al., 2019). Increasing evidence suggests that Cu isotopes provide a diagnostic tool for depicting the contribution of oceanic crust alteration to the global Cu cycle, by many processes such as: Redox reactions (Busigny et al., 2018; Markl et al., 2006; Mathur et al., 2012); mineral dissolution and precipitation (Fernandez & Borrok, 2009; Syverson et al., 2021); adsorption onto minerals and desorption (Liu, Teng et al., 2014; S. A. Liu et al., 2019; Navarrete et al., 2011); equilibrium fractionation between different Cu‐bearing species (e.g., J. Huang et al., 2016) and complexation with organic ligands (Ryan et al., 2014; Sander & Koschinsky, 2011; Stüeken, 2020).…”