Experimental study of the interaction between hemoilmenite and kimberlite melt at a pressure of 2 GPa

The Massadou kimberlite field [3] located in Guinea is characterized by a high concentration of ferrimagnetic (at room temperature) ilmenite in kim berlite with the total content up to 90% in individual bodies (dykes) [10]. Detailed study of these ilmenites demonstrated the presence of a clear rim with the average thickness varying from body to body. The core parts of ilmenites are enriched in the hematite component and depleted in Mg, Ti, and Cr, whereas the rim is represented by picroilmenite paramagnetic at room temperature, which is typical for kimberlite; this min eral is enriched in Mg, Ti, and Cr and depleted in Al and Fe3+ [10]. Such zoned ferrimagnetic ilmenites were later discovered in the kimberlite pipes Dachnaya and Mir (Malo Botuobinskii region, Yakutia) [10]. Ilmenite with such a type of zonation was also found in the Katoka pipe (Angola) and Kundelungu (Zaire) [8, 13]. Because of the low MgO concentration (6 17 mol % Gei) at a high content of trivalent iron, the core parts of zoned ilmenites should be related to solutions of the FeTiO3Fe2O3 series, which form hemoilmenites [FeTiO3]x[Fe2O3]1 x.