Gold-bearing mineral assemblages of Cu-ore deposits in the Altai-Sayan folded area

The high gold potential of Cu-ore (Cu-skarn, porphyry Cu-Mo, and pyrite-polymetallic) deposits widespread in the Altai-Sayan folded area is shown. The ore formation processes at these deposits included multistage mineralization with the gradually decreasing temperature of ore-forming solutions. At the early high-temperature stages, mainly the profile ores (often, of zonal structure) of the deposits were produced. Their mineral composition is closely related to the composition of the corresponding ore-magmatic system and is regularly repeated in ore objects of different sizes and ages. At the final stages, low-temperature mineral assemblages formed, which often have a similar set of ore and vein minerals. A distinctive feature of these assemblages is the presence of Ag, Pb, and Au tellurides, Bi minerals, native bismuth, and Hg-containing minerals. Gold in the minerals is of varying fineness; the main trace elements in it are Ag and Hg. The low-temperature mineral assemblages are close to ores of epithermal deposits (including Carlin-type ones) developed in the same areas. These ores might be the products of the final-stage evolution of the ore-magmatic systems.