PETRO-GEOCHEMISTRY OF SUBVOLCANIC AND EXTRUSIVE FORMATIONS OF THE KEDROVO-KORGONCHIKOVSKY DISTRICT OF THE GORNY ALTAI

The paper provides data on petro-geochemistry, petrology and ore content of subvolcanic and extrusive formations of the Korgon Devonian complex of the Kedrovo-Korgonchikovsky district of the Gorny Altai. Low-alkali rhyodacites, sodium-potassium rhyodacites, trachyrhyodacites, trachyrhyolites and rhyolites are characterized. They are attributed to the aluminous series and mainly to magnesian varieties. Increased gold contents and decreased silver contents are observed in rocks. Ratios of light to heavy lanthanoids show a large range of values – from 2.1 to 26.2 and light ones to medium ones – from 1.94 to 11.8. The tetrad effect of W-type REE fractionation, varying from 0.29 to 0.68 and indicating an abundance of volatile components, including H2O, CO2, S or H2S, was revealed in rocks, that served as the formation of quartzites and argillizites. Volcanites contain signs of mantle formations and contamination by crustal material due to melting of greywackes and amphibolites of the lower crust. The ore content of the district is realized in the formation of promising epithermal gold-silver and copper-molybdenum-gold-porphyry occurrences. The district is thought to be the object of the process manifestation of the fluid mantle-crustal ore genesis during formation of largevolume epithermal gold-silver, copper-molybdenum-gold-porphyry mineralization.