Sulfur-Deficient Fahlore: Kenoargentotetrahedrite-(Zn) [Ag6]4+(Cu4Zn2)\({\mathbf{S}}{{{\mathbf{b}}}_{{\mathbf{4}}}}{{{\mathbf{S}}}_{{{\mathbf{12}}}}}\)⬜ and Kenoargentotetrahedrite-(Fe) [Ag6]4+(Cu4Fe2)\({\mathbf{S}}{{{\mathbf{b}}}_{{\mathbf{4}}}}{{{\mathbf{S}}}_{{{\mathbf{12}}}}}\)⬜ from the Epithermal Silver-Polymetallic Mangazeyskoye Deposit (Yakutia, Russia)
摘要
For the first time in the ores of the epithermal silver-polymetallic Mangazeyskoye deposit (Yakutia, Russia), sulfur-deficient fahlore (kenoargentotetrahedrite-(Zn) and kenoargentotetrahedrite-(Fe)) is found and described using EPMA and single-crystal X-ray diffraction. Keno-fahlore is found as 5‒7 mm crystals on a quartz druse. One of the crystals is a monomineral kenoargentotetrahedrite-(Zn), the other is a polymineral aggregate composed of early argentotetrahedrite-(Fe)-I and kenoargentotetrahedrite-argentotetrahedrite-(Zn) and late kenoargentotetrahedrite-(Fe)-II, pyrargyrite, and miargyrite. The average composition of the kenoargentotetrahedrite-(Zn) (wt %): Ag 32.80, Cu 13.81, Zn 6.84, Fe 0.12, Sb 25.60, As 0.06, and S 20.39, is calculated on the empirical formula (Ag5.79Cu0.21)Σ6(Cu3.93[Zn1.99Fe0.04]Σ2.03)Σ5.96(Sb4.01As0.02)Σ4.03S12S0.12. The composition of kenoargentotetrahedrite-(Fe) (wt %): Ag 25.39–27.90, Cu 17.55–19.76, Zn 0.80–2.67, Fe 3.70–5.60, Sb 26.04–26.65, As 0.07–0.17, and S 21.37–22.12, is calculated on the empirical formula (Ag4.79–4.29Cu1.21–1.71)Σ6(Cu4.02–3.92[Fe1.82–1.23Zn0.23–0.76]Σ1.97–2.05)Σ5.93–6.00(Sb4.04–3.97As0.02–0.04)Σ3.99–4.06S12S0.25–0.55. The refined unit cell parameters of the kenoargentotetrahedrite-(Zn):