Using the Selector PC application, we studied the process of formation of magnesian skarns at the contact of dolerites with carbonate-salt deposits. The physicochemical parameters of metasomatic processes were estimated by studying the localization of skarn ore shoots and mineral assemblages in the deposits of the Angara-Ilim type. The action of magmatic fluids on the system dolerite-magnesian salt deposits and dolerite-carbonate-salt deposits resulted in zonal columns of infiltration magnesian skarns. The computation was carried out using a dynamic multireservoir model of a flow reactor with a constant temperature gradient and a uniform pressure. We have established that changes in the C/H ratio and Cl content in the fluid source affect the composition of the produced mineral assemblages. Depending on the temperature during the formation of skarns, different mineral assemblages are produced: diopside, enstatite, anorthite, quartz, ilmenite, hercynite, and pyrrhotite at 1040-1010 °C; monticellite, forsterite, magnetite, geikielite, periclase, spinel, calcite, and graphite at 980-740 °C; and calcite, dolomite, phlogopite, halite, and graphite at 710-380 °C. Wollastonite is observed in the rear zone of magnesian skarns. We examined the temperature-dependent sequence of formation of different types of silicates, spinels, and Ti-containing minerals in the metasomatic column. The computation results show that during crystallization, the tholeiitic magma releases a fluid phase with C/H = 0.1-1.0, amounting to 1.5-2.0 wt.%.