P–T–X parameters of metamorphogene and hydrothermal fluids, isotopy and age of the Bogunai gold deposit, southern Yenisei Ridge (Russia)

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 °C) and pressures (8.5–9.0 kbar) of minerals of the granulite metamorphic facies are much higher than the crystallization temperatures (220–420 °C) 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 pluton (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%c, 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.

Ore–Bearing Fluids of the Blagodatnoye Gold Deposit (Yenisei Ridge, Russia): Results of Fluid Inclusion and Isotopic Analyses

“…The fraction of mantle helium calculated by the procedure from [39,61] in the fluids from the Blagodatnoye deposit is about 1%. It should be noted that 3 He/ 4 He value of the other deposits of the Yenisei ridge-Sovetskoye, Eldorado, Olimpiada, Gerfed, Panimba and Bogunai-is similar to that of the Blagodatnoye deposit [10,15,[17][18][19][20]. This fact indicates a crustal fluid source for all these deposits.…”

“…The obtained isotope values of sulfur sulfides from the Blagodatnoye deposit ore bodies are considerably heavier than the range of values (δ 34 S = 0 ± 3, ‰), attributed to magmatic sulfur [56][57][58]. Figure 8 shows the composition of sulfur isotopes of sulfides of gold deposits on the Yenisei Ridge: Blagodatnoye, Sovetskoye [10], Eldorado [20], Olimpiada [19], Gerfed [17], Panimba [18] and Bogunai [15]. According to the data obtained, the δ 34 S value varies over a wide range from 0.8 to 21.3‰.…”

“…In these works, data on the temperatures, pressures and salinity of fluids are reported [5][6][7][8][9][10]. Development of Raman spectroscopy and its application to individual fluid inclusions resulted in an increased number of works in which fluid composition is discussed [6,[10][11][12][13][14][15][16][17][18][19].…”

Fluid Components in Cordierite from the Rocks of Epidote-Amphibole Facies of the Muzkol Metamorphic Complex, Tajikistan: Pyrolysis-Free GC-MS Data

“…At present, the non-pyrolysis GC-MS with a shock destruction of the sample in terms of sensitivity (instrumental measurement limits), dynamic ranges, rate, and diversity of determined volatiles has no alternative. GC-MS was used to study the gas phase composition of mineral-forming media in diamonds [109,122,123], minerals of mantle rocks [106,110,124], metamorphic rocks [125,126], hydrothermal minerals from ore deposits [111,127,128], and minerals of sedimentary rocks associated with oil and gas deposits [129,130].…”