Au– Ag– Te Mineralization of the Low‐Sulfidation Epithermal Aginskoe Deposit, Central Kamchatka, Russia

• Published in: Resource Geology
• Main Authors: Andreeva, Elena D., Matsueda, Hiroharu, Okrugin, Victor M., Takahashi, Ryohei, Ono, Shuji
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2013
• Subjects: Kamchatka
• Online Access: http://dx.doi.org/10.1111/rge.12013; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Frge.12013; https://onlinelibrary.wiley.com/doi/pdf/10.1111/rge.12013

Abstract Mineralogic studies of major ore minerals and fluid inclusion analysis in gangue quartz were carried out for the for the two largest veins, the A ginskoe and S urprise, in the L ate M iocene A ginskoe A u– A g– T e deposit in central K amchatka, R ussia. The veins consist of quartz–adularia–calcite gangue, which are hosted by L ate M iocene andesitic and basaltic rocks of the A lnei F ormation. The major ore minerals in these veins are native gold, altaite, petzite, hessite, calaverite, sphalerite, and chalcopyrite. Minor and trace minerals are pyrite, galena, and acanthine. Primary gold occurs as free grains, inclusions in sulfides, and constituent in tellurides. Secondary gold is present in form of native mustard gold that usually occur in F e‐hydroxides and accumulates on the decomposed primary A u‐bearing tellurides such as calaverite, krennerite, and sylvanite. K–Ar dating on vein adularia yielded age of mineralization 7.1–6.9 M a. Mineralization of the deposit is divided into barren massive quartz (stage I ), A u– A g– T e mineralization occurring in quartz‐adularia‐clays banded ore ( S tage II ), intensive brecciation ( S tage III ), post‐ore coarse amethyst ( S tage IV ), carbonate ( S tage V ), and supergene stages ( S tage VI ). In the supergene stage various secondary minerals, including rare bilibinskite, bogdanovite, bessmertnovite metallic alloys, secondary gold, and various oxides, formed under intensely oxidized conditions. Despite heavy oxidation of the ores in the deposit, T e and S fugacities are estimated as S tage II tellurides precipitated at the log f T e 2 values −9 and at log f S 2 −13 based on the chemical compositions of hypogene tellurides and sphalerite. Homogenization temperature of fluid inclusions in quartz broadly ranges from 200 to 300° C . Ore texture, fluid inclusions, gangue, and vein mineral assemblages indicate that the A ginskoe deposit is a low‐sulfidation (quartz–adularia–sericite) vein system.