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The authors have studied melt-fluid and fluid inclusions in quartz and fluorite of sideritic and ankerite-calcitic carbonatites of the Karasug ore field, as well as melt inclusions in apatite from granosyenites. The content of salt and fluid components in brine-melt inclusions was evaluated on the basis of the thermodynamic data, the calculations of volumes and densities of the solid phases, a solution of about 50% concentration, and the gas phase of the inclusions, as well as the results of the LA-ICP-MS analysis. The content of salt phases, the solution, and the gas phase amounted to 85–70, 10–25, and about 5% of the inclusion substance, respectively. The total percentage of salt and fluid components (H2O and CO2) amounted to 90–80 and 10–20 wt %, respectively. The fraction of a carbonate constituent in the inclusions was as high as 45–50% and over in ankerite-calcite carbonatites and about 15 wt % in sideritic carbonatites. The 117.2 ± 1.3 Ma age of these carbonatites by 40Ar/39Ar, along with other datings for this area, shows that their formation was associated with a manifestation of the Cretaceous alkaline-mafic magmatism (117–120 Ma). The presented model of the formation of carbonatites is in agreement with the sequence of the development of magmatic processes and mineralization in this area. The model is also confirmed by the results of the studies of melt and fluid inclusions in minerals.

Based on study of fluid and melt inclusions in minerals from igneous rocks and associated ore-metasomatic objects, we consider the formation conditions of oxidized fluids produced at the final stages of differentiation of alkali-basic, alkaline, lamproitic, and some granitoid melts. These fluids are characterized by wide variations in composition, concentrations, and physicochemical parameters (P, T, Eh, pH, etc.) and are of sulfate-chloride, sulfate-carbonate, sulfate-fluoride, fluoride-sulfate, essentially sulfate, and other types. The specific composition of these magmatogene fluids showing a high extractive power favors the effective removal of ore-forming elements (Fe, Mn, Co, N, Ag, Cu, Pb, Zn, Mo, W, Bi, U, REE, etc.) from melt and their trapping from the host rocks. The set of these elements is determined by P-T-X-parameters, conditions of fluid separation from melts, composition of fluid-generating magmas, and geochemical composition and metal-bearing capacity of rocks through which the fluids migrate. These factors significantly determine the metallogeny of alkaline, alkali-basic, and some granitoid complexes and associated mineralization.