Abstract The deposit belongs to the type of aposerpentinite gold-bearing serpentine veins and is localized in the thrust zone of NW dipping, separating the Dzhabyk‒Karagay anticlinorium and the Sukhtelinsky synclinorium. Mineralization is controlled by the thrust zone of NW dipping and tension cracks mainly of SEE dipping, caused by the dynamic impact of the Dzhabyk granitoid massif during its formation. Ores are represented by poor sulfide sheared and brecciated talc-carbonate rocks. Ore talc-carbonate metasomatism is manifested in the sequential replacement of serpentinites by talc and carbonates (breunnerite, magnesite) and ends with the formation of veinlet dolomite, talc, and antigorite. Ore minerals are represented by disseminated small particles of native gold, sulfides, and sulfoarsenides of Cu, Fe, Ni, and Co (pentlandite, chalcopyrite, violarite, ulmanite, millerite, and gersdorffite‒cobaltite), as well as sulfoarsenides of Ir (irarsite) and Pt (platarsite). The sulfur content in the ores is no more than 0.02 wt %. Native gold grains (the Au‒Ag solid solution with a fineness of more than 910‰) are enclosed in serpentine, chlorite, talc, and less often carbonate; they are often confined to shear cracks in metasomatites. Serpentinites at a distance from the deposit are specialized in Ni, Co, and Cr. In addition, talc-carbonate rocks are found to have higher contents of granitophile elements (W, Sn, Rb, Cs, and U) as compared with serpentinites. Antigorite veinlets contain Ni, Sb, and Ta; talc veinlets, Ag; and dolomite veinlets, Mn, Sr, Ba, REE, Pb, Mo, Bi, and Cd. The thermocryometric study of fluid inclusions in carbonates has shown that talc-carbonate metasomatites were formed in the temperature range of 400‒200°C from fluids belonging to the H2O‒NaCl, H2O‒NaCl‒NaHCO3 and H2O‒NaCl (MgCl2) salt systems of low salinity (2.6‒5.3 wt % equiv. NaCl). Interpretation of the results of the oxygen and carbon isotope composition of carbonates (δ18O and δ13C, respectively, 19.2‒24.2‰ and ‒7.3‒8.5‰), as well as oxygen and hydrogen of serpentine, talc, and chlorite (δ18O = 12.5…18.2‰, δD = ‒50.6…‒68.0‰), has demonstrated a metamorphic origin of the fluid. This fluid was formed as a result of the interaction of juvenile water with volcanogenic-sedimentary rocks enclosing the ultramafic massif. Participation of water released during the replacement of serpentine and talc by carbonates, as well as magmatic fluid genetically related to the Dzhabyk granitoid massif, is allowed. It is assumed that Cu, Fe, Ni, Co, Au, Pt, and Ir in the ores were extracted from ultrabasic rocks by a carbon dioxide fluid, and the increased contents of granitophile elements (W, Sn, Rb, Cs, U, etc.) are related to the magmatic fluid influx.

Kirovskoe Gold Deposit in Talc-Carbonate Rocks (South Urals): Mineralogy, Geochemistry, Physicochemical Conditions of Formation, and Genesis

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发表日期：

2025年8月1日

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V. V. Murzin,
A. Yu. Kisin

摘要

Abstract

The deposit belongs to the type of aposerpentinite gold-bearing serpentine veins and is localized in the thrust zone of NW dipping, separating the Dzhabyk‒Karagay anticlinorium and the Sukhtelinsky synclinorium. Mineralization is controlled by the thrust zone of NW dipping and tension cracks mainly of SEE dipping, caused by the dynamic impact of the Dzhabyk granitoid massif during its formation. Ores are represented by poor sulfide sheared and brecciated talc-carbonate rocks. Ore talc-carbonate metasomatism is manifested in the sequential replacement of serpentinites by talc and carbonates (breunnerite, magnesite) and ends with the formation of veinlet dolomite, talc, and antigorite. Ore minerals are represented by disseminated small particles of native gold, sulfides, and sulfoarsenides of Cu, Fe, Ni, and Co (pentlandite, chalcopyrite, violarite, ulmanite, millerite, and gersdorffite‒cobaltite), as well as sulfoarsenides of Ir (irarsite) and Pt (platarsite). The sulfur content in the ores is no more than 0.02 wt %. Native gold grains (the Au‒Ag solid solution with a fineness of more than 910‰) are enclosed in serpentine, chlorite, talc, and less often carbonate; they are often confined to shear cracks in metasomatites. Serpentinites at a distance from the deposit are specialized in Ni, Co, and Cr. In addition, talc-carbonate rocks are found to have higher contents of granitophile elements (W, Sn, Rb, Cs, and U) as compared with serpentinites. Antigorite veinlets contain Ni, Sb, and Ta; talc veinlets, Ag; and dolomite veinlets, Mn, Sr, Ba, REE, Pb, Mo, Bi, and Cd. The thermocryometric study of fluid inclusions in carbonates has shown that talc-carbonate metasomatites were formed in the temperature range of 400‒200°C from fluids belonging to the H₂O‒NaCl, H₂O‒NaCl‒NaHCO₃ and H₂O‒NaCl (MgCl₂) salt systems of low salinity (2.6‒5.3 wt % equiv. NaCl). Interpretation of the results of the oxygen and carbon isotope composition of carbonates (δ¹⁸O and δ¹³C, respectively, 19.2‒24.2‰ and ‒7.3‒8.5‰), as well as oxygen and hydrogen of serpentine, talc, and chlorite (δ¹⁸O = 12.5…18.2‰, δD = ‒50.6…‒68.0‰), has demonstrated a metamorphic origin of the fluid. This fluid was formed as a result of the interaction of juvenile water with volcanogenic-sedimentary rocks enclosing the ultramafic massif. Participation of water released during the replacement of serpentine and talc by carbonates, as well as magmatic fluid genetically related to the Dzhabyk granitoid massif, is allowed. It is assumed that Cu, Fe, Ni, Co, Au, Pt, and Ir in the ores were extracted from ultrabasic rocks by a carbon dioxide fluid, and the increased contents of granitophile elements (W, Sn, Rb, Cs, U, etc.) are related to the magmatic fluid influx.