Mineral Characterization of Gold Ore Occurrences in the Khaptasynnakh Ore Zone, Anabar Shield, Far East Region, Russia

Mineral characterization of gold-bearing metasomatites in the Khaptasynnakh ore zone of the Anabar Shield is provided in detail. The following ore formation sequence of mineral associations in the Khaptasynnakh zone was found: pyrite and pyrrhotite → gersdorffite and molybdenite → chalcopyrite, sphalerite, and galena → bornite and chalcocite → tellurides, native gold, stibnite, cinnabar, and native bismuth. Native gold is characterized by varying fineness (550 to 926‰) and Cu impurity (up to 7.87%) values. Most often, it forms symplectite intergrowths with Au telluride–calaverite. Native gold and Au tellurides showed inclusions of chalcocite, bornite, altaite, tellurobismuthite, rickardite, petzite, and clausthalite. A two-stage formation process of the examined gold is suggested: Low-fineness gold was introduced into the system during early potassium metasomatism, while higher-fineness gold related to silica metasomatism resulted from its additional mobilization by fluid during late-stage formation. The low-temperature gold–telluride association observed in the mineral paragenesis of ore-bearing rocks, as well as its inclusions in native gold, suggests epithermal gold–telluride mineralization. Mineral inclusions examined in placer gold validate a genetic relation between the examined ores and gold placers in the Khaptasynnakh ore zone.