Isotopic peculiarities of regional alkaline metasomatites of Pre-Cambrian

Distribution of O18 and C13 was studied in sodium-carbonate metasomatites and ore zones of Pre-Cambrian ultrametamorphic complex of gneisses, migmatites and granites that were transformed in dislocation zones into albitites containing silicates, oxides and titanates of uranium. The studies showed that the solutions that caused alkaline metasomatosis were isotopically, and maybe even chemically, similar to those participating in regional metamorphism, ultrametamorphism and granitization. Isotopically light surface hydrosphere waters were of primary importance in determining the isotopic composition of the rocks, the temperature and mineral composition of the latter governing the limits of the effect. Uranium metallizations related to the carbonate stage of alkaline metasomatosis. It is suggested that albitized zone calcites are remobilized proto-sedimentary carbonates. The pattern of carbonate isotopic content evolution during albitization indicated active participation of carbonate ion and CO2 in alkaline metasomatosis while inverse relationship between deltaC13 and deltaO18 on one hand and albitization degree on the other demonstrates that carbonate isotopic composition was formed at a temperature below 130 deg C. This temperature is the upper limit for albitization, carbonatization and uranium metallization processes. Uranium-bearing solutions originated from rock masses that accumulated uranium during sediment formation. Uranium mobilization via oxidation to