MINERALOGICAL AND GEOCHEMICAL FEATURES AND CONDITIONS OF BARSUCHY GOLD-SULFIDE-QUARTZ DEPOSIT FORMATION (NORTH-EASTERN TUVA)

Gold ore objects in skarns are widespread in geological structures of the Eastern Tuva, but their estimation is considerable difficult due to poor information about mineralogical, geochemical and petrographic peculiarities of ores. The study of the genesis and conditions of gold deposits formation, which are located in skarns, is one of the fundamental scientific disciplines in geological science. The aim of the study is to examine the mineralogical and geochemical peculiarities and conditions of ore formation of the Barsuchy deposit in North-Eastern Tuva. Methods: field work, detailed mineralogical study of ore mineralization using Tescan Vega 3 SBU scanning electron microscope with EMF Oxford Instruments X-act. PT conditions of mineral associations' formation are determined by fluid inclusion study as well as using geofugometers and mineral paragenesis. Results. The authors have manifested that the gold mineralization of the Barsuchy deposit is post-skamed and has a hydrothermal genesis forming a vein-disseminated mineralization of stockwork-type in quartz-diorites, contact (hornfels, skarns) and hydrothermal-metasomatic formations. Near-ore processes are expressed in beresitization and listwanitization of quartz-diorites, skarns and carbonate rocks. The native gold was formed during two stages. According to the composition of the productive mineral associations, Barsuchy deposit is related to a gold-pyrrhotite-pyrite-chalcopyrite type with the AuTe2 calaverite, petzite, hessite and minerals of the tellurobismuthite-tellurantimony series. The gold-quartz-sulfide mineralization is formed due to aqueous fluids with Na and K chlorides containing CO2 and CH4 with a salinity of 1-10,5 wt. % NaCI-eq. accompanied with Redox-potential changes and the variations of f S-2 , f Se-2, f Te-2 and temperature fall of the ore-bearing fluid (the first productive stage is 360-280 degrees C, the second one - 320-240 degrees C). According to mineralogical and geochemical features, Barsuchy deposit belongs to gold-sulfide-quartz formation (with less than 5 % sulfides) and is close to Au-Bi geochemical type of deposits.