The problems of origin and types of sources of the Ilmeno-Vishnevogorsk complex are considered. The Vishnevogorsk, Potanino, Buldym, and Ilmeny deposits of Nb and REE have been investigated. Geochemical evolution and isotopic characteristics of the Ilmeno-Vishnevogorsk alcaline-carbonatite complex prove the role of silicate-carbonate liquid immiscibility and fluids in origin of carbonatites. Isotopic data testify about derivation of alkaline rocks and carbonatites of the Vishnevogorsk massif from depleted mantle (DM) and carbonatites of the Buldym massif - from a deep mantle source of EMI type.