Geochemistry and Mineralogy of Manganese in the Lower Zone of the Lovozero Rare-Metal Deposit, Kola Peninsula

— The paper presents the first ever data obtained on minerals concentrating Mn in the lower zone (which is not exposed at the surface) of the rare-metal deposit of the Lovozero alkaline massif in the Kola Peninsula. Detailed data are presented on the chemical composition of the pyrophanite, ilmenite, and magnetite. EPMA data indicate that the ilmenite and pyrophanite make up a continuous solid-solution series with Mn concentrations varying from 3.9 to 42.1 wt % MnO. The redox conditions under which the lower zone of the Lovozero intrusion was formed were evaluated based on data on the ilmenite–magnetite assemblage at QFM + 0.68 to QFM + 1.17 at temperatures of 500–550°C and are close to the Ni–NiO buffer. The high contents of Mn minerals and the chemical composition of the rocks highlight a manganoan geochemical specifics of the lower zone of the Lovozero deposit, in which individual Mn minerals occur, such as pyrophanite MnTiO 3 that contains up to 42.1 wt % MnO. Our data are the first ever on such high Mn contents in pyrophanite from Lovozero rocks.