ИСТИНА

Kekura is the largest gold deposit in the Stadukhino gold district located 50 km south away from Bilibino, Western Chukchi Peninsula, Russia. It is spatially related to the shallowly eroded Late Cretaceous granodiorite pluton that intrudes Lower Triassic deformed terrigenous sequence enriched in organic matter. Gold-bearing quartz veins and lenses occur within the pluton and near-contact country rocks. Three types of alteration were recognized at the deposit: propylitic, dolomite-quartz-sericite and argillic. Greenish fine-grained propylite is composed of quartz, oligoclase, actinolite, clinochlore, and carbonate. The most abundant whitish dolomite-quartz-sericite rock is altered and contains relict biotite, K-Na feldspar, oligoclase, newly formed muscovite, dolomite and quartz. This alteration is occasionally cut by veinlets with tourmaline, which in turn are cut by carbonate veinlets. Carbonate pods are found in the altered rock. Relict REE phosphates, apatite, and rutile are accessory minerals. The presence of argillic alteration is marked by illite that replaces muscovite in dolomite-quartz-sericite rock.