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Russian Geology and Geophysics

2015 year, number 6

P-T-X PARAMETERS OF METAMORPHOGENE AND HYDROTHERMAL FLUIDS, ISOTOPY AND AGE OF THE BOGUNAI GOLD DEPOSIT, SOUTHERN YENISEI RIDGE (Russia)

M.A. Ryabukha1, N.A. Gibsher1, A.A. Tomilenko1, T.A. Bulbak1, M.O. Khomenko1, A.M. Sazonov2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Institute of Mining, Geology, and Geotechnologies of Siberian Federal University, pr. Svobodnyi 79, Krasnoyarsk, 660041, Russia
Keywords: Quartz, sulfides, gold, ore-forming fluid, hydrocarbons, δ34S, Ar-Ar age

Abstract

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 (8.59.0 kbar) of minerals of the granulite metamorphic facies are much higher than the crystallization temperatures (220420 ºC) and pressures (0.11.6 kbar) of gold-quartz veins of the Bogunai deposit. These veins formed with the participation of H2OCO2hydrocarbon fluids with a salt (predominantly MgCl2) concentration of 219 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 H2OCO2hydrocarbon fluids generated both in deep-fault zones and in granitoid intrusions.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.05.007