Mineralogy and geochemistry of tellurides, selenides and sulfides from the Zhaishang gold deposit, western Qinling, China: Implications for metallogenic processes

• Published in: Journal of Asian earth sciences 2023-04, Vol.244, p.105536, Article 105536
• Main Authors: Weng, Guoming, Liu, Jiajun, Carranza, Emmanuel John M., Zhai, Degao, Zhang, Fangfang, Wang, Yinhong, Yu, Chao, Zhang, Bin, Liu, Xinhui, Sun, Biao, Ma, Zhenyu
• Format: Article
• Language: English
• Subjects: Mineral chemistry; Ore genesis; Ore-forming fluid; Physicochemical conditions; Zhaishang gold deposit
• ISSN: 1367-9120; 1878-5786
• DOI: 10.1016/j.jseaes.2022.105536

[Display omitted] •The independent selenides coexisting with tellurides and sulfides were discovered for the first time in the Zhaishang gold deposit.•The ore-forming materials leached from the underlying Paleozoic strata, and were affected by Indosinian magmatism.•The mineral paragenetic association shows that the redox conditions have changed from reduction to oxidation during the fluid evolution process.•The sulfur, tellurium and selenium fugacity of hydrothermal fluid of the main metallogenic stage is estimated in this paper. The Zhaishang gold deposit is characterized by Au–Sb–W paragenetic association, hosted in the Middle Devonian strata and Lower Permian strata of the Western Qinling Orogen, Central China; also found in in the mining area is a small carbonatized diorite porphyrite. Besides common sulfides, such as pyrite, arsenopyrite and chalcopyrite, some specific telluride and selenide minerals were found, and especially the first discovery of independent selenides. The assemblage pyrrhotite–arsenianpyrite–arsenopyrite suggests a relatively reducing environment for mineralization during stage II. However, the occurrence of selenides (clausthalite, tiemannite) and sulfates (barite and gypsum) represents a change of redox conditions from reduction to oxidation in stage III. On this basis, combined with the study of fluid inclusions and thermodynamic data, we evaluated the physicochemical conditions of the main metallogenic stages. the sulfur fugacity (log fS2) did not change significantly from stage II to stage III, the selenium fugacity (log fSe2) values were constrained to have been ≤ -13.7 in stage II, ranged from −14.8 to −9.8 in stage III, and the tellurium fugacity (log fTe2) ranged from −14.0 to −11.2 in stage III. Moreover, the He–Ar–Pb isotopic values of sulfides suggest that ore-forming materials were dominantly of stratigraphic source but with important additions of magmatically derived hydrothermal fluid during Indosinian period. Water-rock reaction and ore-forming fluid mixed with magmatically-derived hydrothermal fluid were likely the dominant mechanisms of precipitation. Meanwhile, boiling likely played a certain role in the deposition of selenides and tellurides.