Distribution and Controls on Silver Mineralization in the Hackett River Main Zone, Nunavut, Canada: An Ag- and Pb-enriched Archean Volcanogenic Massive Sulfide Deposit

Constraints on the behavior of trace elements in the actively-forming TAG deposit, Mid-Atlantic Ridge, based on LA-ICP-MS analyses of pyrite

“…This is similar to the behavior of Sn observed in many ancient seafloor massive sulfide deposits (e.g. Huston et al, 1995;Hannington et al, 1999a;Grant et al, 2015). Although Bi is present at very low concentrations, it was detected in high-temperature Py I cores and chalcopyrite from the base of the mound.…”

“…The ablation profiles of Co, Se, Te, Mo, Ge, In, and Sn are all smooth, indicating that they are present mainly as substitutions in the mineral lattice (e.g., Co and Sn for Fe; In for Cu: Huston et al, 1995). Most of the Ag and As is also hosted in solid solution in chalcopyrite (e.g., Ag for Cu; As for Fe : Cabri, 1992;Huston et al, 1995;Grant et al, 2015;George et al, 2016).…”

“…Silver may be transported both as chloride and bisulfide complexes depending on the temperature, redox conditions and availability of ligands (Seward, 1976;Gammons and Seward, 1996). In seafloor hydrothermal systems, Ag is mainly transported as a chloride complex (AgCl 2 − ) at high temperatures, similar to Cu, In, and Sn, and as a bisulfide complex [(Ag(HS) 2 − ] at low temperatures (e.g., Hannington, 1993;Huston et al, 1996;Grant et al, 2015), spanning the full range of mineralization temperatures documented at TAG. Lower-temperature and more oxidized conditions (e.g., in the TAG-2 area at the top of the mound) favor the precipitation of Ag in micro-inclusions of sulfosalts or galena in Py II, Py V, and marcasite, whereas higher-temperature and more reduced conditions favor incorporation in chalcopyrite by lattice substitution (Huston et al, 1996;Grant et al, 2015).…”

“…In seafloor hydrothermal systems, Ag is mainly transported as a chloride complex (AgCl 2 − ) at high temperatures, similar to Cu, In, and Sn, and as a bisulfide complex [(Ag(HS) 2 − ] at low temperatures (e.g., Hannington, 1993;Huston et al, 1996;Grant et al, 2015), spanning the full range of mineralization temperatures documented at TAG. Lower-temperature and more oxidized conditions (e.g., in the TAG-2 area at the top of the mound) favor the precipitation of Ag in micro-inclusions of sulfosalts or galena in Py II, Py V, and marcasite, whereas higher-temperature and more reduced conditions favor incorporation in chalcopyrite by lattice substitution (Huston et al, 1996;Grant et al, 2015). The presence of up to 4.5 ppm Au in pyrite from the TAG 2 area mainly reflects low-temperature transport under weakly acidic to acidic pHs and destabilization of AuHS 0 complexes by mixing and cooling (Williams-Jones and .…”

Enrichment of precious metals associated with chalcopyrite inclusions in sphalerite and pyrite

“…Arsenic-induced defects have been proposed to facilitate the incorporation of Au in arsenian pyrite (Gopon et al, 2019;Zhang et al, 2022), with substitution of Au 1+ for Fe 2+ (Merkulova et al, 2019;Filimonova et al, 2020;Meng et al, 2022). Galena can host significant quantities of Ag 1+ , through the following coupled substitutions of Ag 1+ + Sb 3+ ⇔ 2Pb 2+ or Ag 1+ + Bi 3+ ⇔ 2Pb 2+ (Lueth et al, 2000;Chutas et al, 2008;Grant et al, 2015). Silver(I) can enter the chalcopyrite structure via a co-substitution mechanism: (x + 2y)(Ge, Sn) 4+ + x(Zn, Pb) 2+ + y(Cu, Ag) 1+ ⇔ (2x + 3y)Fe 3+ (Belissont et al, 2019) and can also be incorporated into the sphalerite structure through limited coupled substitutions via 2Ag 1+ + Sn 4+ ⇔ 3Zn 2+ (Cook et al, 2009) or Ag 1+ + Cu 1+ + Sn 4+ ⇔ 3Zn 2+ (Pring et al, 2020).…”