Original paper

New find of silver tellurosulphides from the Funan gold deposit, East Shandong, China

Gu, Xiang-Ping; Watanabe, Makoto; Hoshino, Kenichi; Shibata, Yasuhiro

Abstract

Two unnamed silver tellurosulphides were discovered in the Funan quartz vein-type gold deposit, East Shandong, China. One is optically isotropic and has the composition Ag8.98Fe1.01Te1.98S4.04 (stoichiometric Ag9FeTe2S4) according to the microprobe analyses of 13 grains. It occurs in close association with galena, chalcopyrite, hessite, cervelleite (?), acanthite and native silver.The second one has the composition Ag16.08Fe1.01Bi0.94Te3.03S7.95 (stoichiometric Ag16FeBiTe3S8) from 3 microprobe analyses of one grain about 5 × 10µm in size and is associated with unnamed Ag9FeTe2S4, acanthite and native silver. Fifteen electron-microprobe analyses of the compounds in the (Ag, Cu)6TeS2-(Ag, Cu)4TeS series, with the generalized formula (Ag12-x, Cux)12(S6-y, Tey)6, 0 ≤ x ≤ 3, 2 ≤ y ≤ 3, reveal a wide range of substitution between Ag and Cu as well as Te and S both in cervelleite-like mineral and a possibly separate phase Ag6TeS2. An unnamed secondary Ag-Au-Cu sulphide, with the composition Ag6.10Au1.06Cu1.86S4.98 (stoichiometric Ag6AuCu2S5) from the microprobe analyses of 6 grains, was observed in association with secondary gold-silver alloy and cerussite replacing primary gold-silver alloy. Microthermometry of fluid inclusions in quartz indicates that the silver tellurosulphides were possibly formed at temperatures around 250°C within the range of LogfTe2 from -17.4 to -13.4 and LogfS2 from -13.6 to -9.0.

Keywords

silver tellurosulphidesag9fete2s4ag16febite3s8ag6tes2cervelleiteag6aucu2s5quartz vein goldchina