Home – Home – Jornals – Russian Geology and Geophysics 2015 number 6

Fluid inclusions in quartz, sulfides from quartz veins, and quartz, garnet, plagioclase, and orthoclase from granulites of the Bogunai gold deposit located in the granulites of the Angara-Kan block of the Yenisei Ridge were studied by thermobarometry, gas chromatography, chromato-mass-spectrometry, Raman spectroscopy, and mass spectrometry with inductively coupled plasma. The formation temperatures (850-950 ºC) and pressures (8.5–9.0 kbar) of minerals of the granulite metamorphic facies are much higher than the crystallization temperatures (220–420 ºC) and pressures (0.1–1.6 kbar) of gold-quartz veins of the Bogunai deposit. These veins formed with the participation of H₂O–CO₂–hydrocarbon fluids with a salt (predominantly MgCl₂) concentration of 2–19 wt.% NaCl equiv. The gas phase of fluid inclusions from quartz, pyrite, chalcopyrite, galena, and sphalerite contains not only H₂O, CO₂, CH₄, and N2 but also the first found compounds of sulfur (CS₂, O₂S, COS, C₂H₆S₂) and nitrogen (C₃H₇N, C₃H₇NO, C₄H₈N₂O) and numerous hydrocarbons of different classes (paraffins, arenes, naphthenes, alcohols, aldehydes, ketones, carbonic acids, and furans). The age of the Krasnoyarsk mineralized zone, one of the sites of the Bogunai deposit, is 466 ± 3.2-461.6 ± 3.1 Ma, which is almost 1400 Ma younger than the age of granulite metamorphism and 255 Ma younger than the age of diaphthoresis but is close to the age of the Lower Kan granitoid massif (455.7 ± 3.4 Ma). The sulfur isotope ratios (δ₃₄S) of sulfides (pyrite, chalcopyrite, sphalerite, and galena) are close to the mantle values, 0.8 to 3.5‰, and are in the range of the granitoid values, which indicates the crustal source of the fluid sulfur. Gold of the Bogunai deposit accumulated with the participation of H₂O–CO₂–hydrocarbon fluids generated both in deep-fault zones and in granitoid intrusions.