The Bamsk gold deposit, Stanovoi range, Russia

The recently discovered Bamsk gold deposit is of a large scale. It is situa ted in the Amur oblast in Russia. The deposit is confined to a central type volcanoplutonic uplift of that formed during the early Cretaceous megastag e of the Precambrian Stanovoi fold belt. The deposit is a set of auriferous quartz and carbonate-quartz vein and veinlet zones, which art: located ove r the early Cretaceous Nevachansk subvolcanic syenite-porphyry intrusion. T he ore mineralization is controlled by a system of en echelon fissures deve loped in the hanging wall of the Bamsk ore-screening fault. Quartz, carbona tes, and sericite prevail. Pyrite, chalcopyrite, galena, scheelite, and nat ive gold are the prevalent minerals, the total amount of which does not exc eed 1 to 5 vol %. Tennantite-tetrahedrite minerals, gold and silver telluri des, sulfobismuthides, acantite, sphalerite, and cinnabar are less widespre ad. Four stages of mineralization were recognized. The gold-sulfide-sulfosa lt stage with gold and silver tellurides is the most commercially important for gold extraction. The deposition of major amount of native fold, sulfos alts, and tellurides is assumed to have occurred from relatively low-temper ature (250 to 180 degreesC) hydrothermal solutions under nearly neutral to weakly alkaline conditions and in a weakly oxidized environment. A set of e lements (including Au, Ag, Cu, Bi, Mo, Pb, and Sb), which is characteristic for ores, was revealed. The lateral and vertical geochemical zonality of m ineralization was established. The vertical zoning tl end is as follows (fr om bottom to top) of (W-1, Pb-1, Mo)-Cu-(Ag, Bi, Sb, Mn, W-2, Pb-2). Host r ocks were subjected to processes of listvenitization-beresitization. Gumbei tization and argillization occur more rarely. The K-Ar and Rb-Sr ages of go ld mineralization were determined at 109 to 129 Ma and 130.6 Ma, respective ly.