The physicochemical dynamics of carbonatization of the rocks of lithospheric mantle beneath the Siberian Platform

Software modeling flow multireservoir systems was used to study the dynamics of carbonatization of lithospheric mantle with flows of magmatic fluids directed from a chamber in the upper mantle to the permeable zone, which dissects continental lithosphere. It has been shown that the region of physicochemical conditions of carbonatization in depleted mantle rocks corresponds to the narrow range of the compositions of hypothetical fluids. If the total content of the fluid is ~ 4 wt.% and the contents of SiO2 and Ca are 0.5-0.1 moles, (1) the ratio of the molar fractions of Si to Ca is less than unity; (2) the ratios of molar fractions in the C-H-O system are 1:2:3 or 2:1:2; (3) -8 < log pO2 < -11; and (4) CO2 content in the fluid is higher than H2O content by a factor of 1.5-2, and chlorine significantly dominates over fluorine. If the content of the fluid phase is lower and this phase has a lower major-element content by an order of magnitude, the carbonatization becomes stronger as Ca content decreases.