Lead Isotope Characteristics of the Mindyak Gold Deposit, Southern Urals: Evidence for the Source of Metals

The isotopic composition of Pb in pyrite of the Mindyak orogenic gold deposit located in the Main Ural Fault Zone, the Southern Urals, has been studied by the high-precision MC-ICP-MS method. Orebodies at the deposit are composed of early pyrite and late polysulfide–carbonate–quartz mineral assemblages. The orebodies are localized in olistostrome with carbonaceous clayey-cherty cement. Pyrites from early and late mineral assemblages are close in Pb isotope ratios. For early pyrite 206 Pb/ 204 Pb = 18.250–18.336, 207 Pb/ 204 Pb = 15.645–15.653, 208 Pb/ 204 Pb = 38.179–38.461; while for late pyrite 206 Pb/ 204 Pb = 18.102–18.378, 207 Pb/ 204 Pb = 15.635–15.646, 208 Pb/ 204 Pb = 38.149–38.320. The model parameters μ 2 ( 238 U/ 204 Pb = 9.91 ± 2), ω 2 ( 232 Th/ 204 Pb = 38.5 ± 4), and 232 Th/ 238 U = 3.88 ± 3 indicate that an upper crustal Pb source played a leading role in ore formation. Carbonaceous shale as an olistostrome cement and syngenetic sulfide mineralization are considered to be the main Pb sources of both early and late mineral assemblages. An additional recept in apparently magmatic lead is suggested for the late veinlet mineralization. The involvement of lead from several sources in ore formation is consistent with the genetic model, which assumes a two-stage formation of orebodies at the Mindyak deposit.