ORE-BEARING METASOMATITES ASSOCIATED WITH LITHIUM-FLUORIC GRANITES OF THE SEVERNY MASSIF (CHAUN-CHUKOTKA)

The facies composition and stages of formation of hydrothermal-metasomatic units spatially associated with lithium-fluoric granites of the Severny massif in Chaun-Chukotka were studied based on large-scale geological mapping, as well as petrographic, mineralogical and geochemical data. The identification of zwitters of the Severny massif - quartz-topaz-zinnwaldite greisens accompanying Li-F granites and bearing rare-metal (Nb, REE, Y, Li, Bi, Sn, W) mineralization is justified. The bulk of zwitter mineralization is distributed within the massif in the form of moderate alterations in biotite leucogranites. Facies diversity of tourmalinite metasomatites was established. Muscovite-quartz-tourmaline, albite-tourmaline-quartz, chlorite-muscovite-tourmaline, and adularia-tourmaline metasomatic facies with tourmaline of three types were identified. A scheme of facies division of ore-bearing metasomatites was developed and a sequence of stages of their formation was proposed: 1) albitites, 2) zwitters, 3) tourmalinites, 4) chloritites, and 5) argillizites. The zwitter-tourmalinite metasomatic complex of the massif is characterized by spatial conjugation with and zonal arrangement relative to intrusions of Li-F granites, orderly nature of formation and geochemical evolution, common accessory and ore mineralization of metasomatites and veins. Ore mineralization potential of the Severny massif is associated with tourmalinite, argillizites, and zwitters. Tourmalinite make up tin deposits. Industrial uranium mineralization is associated with argillizites. A predictive assessment of bodies of zwitters, tourmalinite, and chloritites for yttrium-rare-earth and complex rare-metal mineralization is required.