ROLE OF CARBON DIOXIDE IN ROCK-FORMING OF THE CARBONATITE COMPLEXES

摘要

The paper analyzes effect of carbon dioxide upon generation of carbonatized alkali-silicate magmas in the mantle, their evolution, and petrographic composition of carbonatite-bearing complexes CO_2 takes its role in appearance of carbonatite melts due to crystallization differentiation or liquation of mother alkaline magma. Analytical data show variable and, in the whole, rather low CO_2 mole fraction in fluids being in equilibrium with the carbonatite melt: no greater than several M/kg H_2O, up to 30 M/kg H_2O in separate samples only. Progressive increase of the X_(CO_2) in microinclusions has been revealed within consequent generations of carbonates and apatites in carbonatites of Kola peninsula (from 0.03 to 0.12 and 0.17 to 0.29, respectively). Increase of the CO_2: H_2O ratio is well correlating with consequence in appearance of different mineral types of carbonatites, with their different parageneses of carbonates and typical silicates. Participation of CO_2 in the heterogenization of mineral-forming systems (liquation of melts, stratifying of fluids) enabled the concentration in carbonatites of phosphorus, rare and rare-earth elements.