KHAAK-SAIR GOLD-SULFIDE-QUARTZ ORE OCCURRENCE (WESTERN TUVA): DATING, PT PARAMETERS, FLUID COMPOSITION, AND ISOTOPES OF S, O AND C

The relevance of the research is caused by the need to determine the age and fluid regime of formation of Khaak-Sair gold-sulfide-quartz ore occurrence in listwanites, characterized by a peculiar ore mineral composition, expressed in the presence of mercurial gold, selenides (fichesserite, naumannite, timannite, claustallite) and tellurides (hessite, Te-bismuthite and coloradoite). The research is aimed to date and examine PT ore-bearing fluid parameters and geochemical peculiarities, and the fluid sources of Khaak-Sair gold-sulfide-quartz ore occurrence in Western Tuva. Methods. 40Ar/39Ar dating was carried out by the method of step heating. The optical studies of ores were performed on Olympus BX41 and P-213M optical microscopes. The mineral composition was detected using MIRA 3 LMU scanning electron microscope with EDU of Oxford Instruments Nanoanalysis Ltd. The temperatures, salt composition, salinities and fluid pressures were obtained from individual fluid inclusions using Linkam TMS-600 stage equipped with Olympus BX 51 optical microscope; the volatile composition of fluid inclusions was examined on Ramanor U-1000 spectrometer with the Horiba DU420E-OE-323 detector, Millennia Pro laser (Spectra-Physics); the bulk volatile composition of the fluid was determined on the Agilent 6890 gas chromatograph, the anions in the water extraction was estimated on the CVET-3000 ion chromatograph, the cation and trace elements were detected by ICP MS (Elan-6100); the sulfur isotope ratios in galena were calculated on Finnigan MAT Delta gas mass-spectrometer in double-entry mode (analysts V.N. Reutsky and M.N. Kolbasova, IGM SB RAS); δ18С and δ18О isotopic ratios in quartz and carbonates were examined on Stable Isotope Ratio Mass Spectrometer Finnigan™ MAT 253 with Finnigan GasBench II sampler and IAEA standards: NBS-18 and NBS-19 (analyst M.N. Pyryaev, IGM SB RAS) and Isoprime with AQS (Akita Quartz Standard, analysts H. Kavarai, O. Matsubaya, University of Akita), respectively. Results. The 40Ar/39Ar dating of synore listwanites is shown 379,4±4,4 million years that corresponds to the Late Devonian. We identified that the ore hosted listwanites were formed due to aqueous Na-K-chloride fluid with salinity of 3,4–6,5 wt. % NaCl eqv and temperatures at least 325–200 °C. Gold-sulfide-quartz veins were formed at P~0,5–0,75 kbar (~1,5–2,3 km) due to CO2-water chloride (Na-K±Fe) fluid containing CH4 with salinity ranged between 4,5 and 37,4 wt. % NaCl eqv. and temperatu