The Gold Mineralization of the Baranyevskoe Au-Ag Epithermal Deposit in Central Kamchatka

Abstract

The Baranyevskoe Au-Ag epithermal deposit of low-sulfidation (LS) type is located on the Kamchatka Peninsula in the Neogene-Quaternary Central Kamchatka Volcanic Belt, where Au-bearing quartz veins are usually accompanied by veinlet stockworks. Two economic associations are typical of the Baranyevskoe deposit. The first corresponds to gold-pyrite-quartz association with low-grade native gold (521–738‱) intergrown with pyrite. Some accessory Au-Ag minerals within the early association were also identified: acanthite AgS2, hessite AgTe2, lenaite Ag(Fe,Cu)S2, petzite Ag3AuTe2, utenbogardite Ag3AuS2 and unnamed Ag-Sb-As sulfosalts. The former Au-Ag minerals were most likely formed in the temperature range of 320–330 °C based on the study of arsenopyrite thermometers and fluid inclusions. The second, a gold-sulfosalt-quartz association, includes high-grade native gold (883-941‱) in intergrowth with chalcopyrite. Cuprous phases (bornite, chalcocite, heerite, native copper, Cu-Zn solid solutions), Bi-rich sulfosalts (aikinite PbCuBiS3, emplectite CuBiS2, witticenite Cu3BiS3), stannoidite Cu8Fe3Sn2S12, mawsonite Cu6Fe2SnS8), Au-bearing galena, Te-free and Bi-rich tetrahedrite-tennantite represent this association. Fluid inclusions in gold-sulfosalt-quartz association are characterized by homogenization temperature ranging from 226 to 298 °C, and salinity from 0.4 to 1.2 wt. % NaCl eq.

Keywords

• Baranyevskoe deposit
• LS epithermal deposit
• gold-pyrite-quartz association
• gold-sulfosalt-quartz association
• Kamchatka Peninsula