MINERALOGY OF TITANOMAGNETITE-PEROVSKITE ORES FROM THE AFRIKANDA MASSIF, KOLA PENINSULA, RUSSIA

Sokolov S. V.

Fedorovsky All-Russia Scientific-Research Institute of Mineral Resources (VIMS), Moscow, Russia

The considered titanomagnetite-perovskite deposit is confined to the Afrikanda Massif, which is made up of olivine and pyroxene ultramafic rocks, calcite-amphibole-pyroxene rocks, and alkaline pegmatites. Iron-titanium mineralization is accumulated in the ore varieties of pyroxenites, olivinites, and pyroxene-nepheline pegmatites.

Ore sample from this deposit was studied by mineralogical, optical-petrographic, X-ray diffraction, and various chemical methods. The investigation of sections, polished sections, and more than 150 samples showed that it differs in qualitative and quantitative mineral composition from the above-mentioned types of ores and shows the predominance of perovskite over titanomagnetite (65% and 8%, respectively). Ore minerals are ubiquitously associated with following minerals (in order of decreasing abundance): Fe-pargasite, calcite, titanite, diopside, and micas of biotite-phlogopite series.

Based on the chemical analyses (wt. %), the major components of the ore sample are TiO₂ 37.3, CaO 27.5, FeO 11.0, which are involved into perovskite, titanomagnetite, and titanite. A significant prevalence of Ti over Fe is related to the high content of perovskite and the presence of titanite. In addition, the ore has high SiO₂ content (9.9%) caused by the wide abundance of silicates and aluminosilicates. Note also that the studied sample is characterized by the elevated concentrations of Nb (0.99%), Ta (0.038%), as well as high contents of REE_Ce (3.8%).

Thus, based on mineral composition, the studied sample is classed as silicate-titanomagnetite-perovskite ore type. Individual ore varieties are distinguished additionally by the elevated contents of amphibole, calcite, or titanite.