The Kamyshevskii Baykitic deposit of massive Mg-magnetite and apatite-bearing ores is described as an example of the formation of magmatic sill deposits of traps under shallow-depth conditions. The ores are crystallized from an iron-oxide ore liquid separated from a basic melt as a result of its reaction with dolomite in an intermediate chamber. The proposed scheme of isolating free FeO from a melt with an addition of MgO is based on experimental data on iron-free agglomerates and other reduced Fe-rich systems and is supported by thermodynamic calculations of equilibria in the basalt + dolomite + gas multisystem.
