Аннотация:Paper presents the results of an experimental study on the crystallization of Cr-bearing K-Ba-titanates of the magnetoplumbite group (yimengite and hawthorneite) in the chromite-rutile/ilmenite system in the presence of H2O-CO2-KCO3/BaCO3 fluid at pressures of 3.5 and 5.0 GPa and a temperature of 1200 °C, simulating the formation of these phases during metasomatism of the upper mantle peridotites. The experiments were carried out using two types of the anvil-with-hole high-pressure devices (IEM RAS), i.e. NL-40 (3.5 GPa, 1200°C) and toroidal NL-13T (5.0 GPa, 1200°C). The experiment showed that yimengite and hawthorneite were formed in the entire studied pressure range. In a system with ilmenite, minerals of the magnetoplumbite group are preferably crystallized in comparison to titanates of the hollandite group. Raman spectra of yimengite and hawthorneite are presented. The structure of the yyimengite is refined.Keywords: modal mantle metasomatism, magnetopumbite group, hawthorneite-yimengite solid solution (HAYI), highpressure experiment, aqueous-salt fluid