Composition of fluid Inclusions in quartz from rocks of the Beregovoe site,Litsa uranium-ore area, Kola Region

Kaulina Т. V., Avedisyan А. А., Ryabukha M. А., Il’chenko V. L.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2020. V. 149. N 3. P. 111-125

https://doi.org/10.31857/S086960552003003X

Language: Russian

Abstact

Water-salt and gas composition of fluid inclusions in quartz was studied for rocks from the Beregovoe locality of the Litsa uranium ore area, where several uranium occurrences of 1.8 and 0.4 Ga have been found. The composition of fluid inclusions was studied by microthermometry and Raman spectroscopy methods. Ore-bearing fluid is represented by MgCl₂–H₂O and CaCl₂–H₂O solutions of medium and high salinity (7–21 wt % NaCl equiv.). The formation of these fluids was most likely associated with magmatic sources and post-magmatic hydrothermal activity in the range of 1.85–1.75 Ga. After 1.75 Ga, the composition of fluid manifested in inclusions from feldspar-quartz veins evolves to predominantly NaCl–KCl composition. The study suggests that the formation of uranium ore occurrences in the Beregovoe area occurred at temperature of 100–250 °C and pressure of 0.5–0.9 kbar (in shallow conditions), apparently in substantially aqueous system with a gas phase presented by methane and nitrogen, or by CO₂ with an admixture of nitrogen and methane.

Keywords: fluid inclusions, hydrothermal uranium mineralization, Litsa area, Kola region