REE Mineralization in Alkaline Rhyolites of the Pechalninskii Ore Field (Northeast Russia)

For the first time by the method of scanning electron microscopy, REE mineralization studies are conducted in alkaline rhyolites of the Pechalninskii ore field (Northeast Russia), a potentially large-volume source of HREEs. It is shown using the methods of electron microprobe analysis and cathodoluminescence that microcrystalline aggregates of pyroxenes and/or amphiboles in alkaline rhyolites contain the finest inclusions of REE segregations (5–7 µm). Using SEM, it is determined that the largest segregation is cerium phosphate. Concentrically zonal and radial-fibrous REE segregations are revealed in the relics of titanomagnetite crystals by EDS. The first ones are represented by silicates enriched with Y and REEs and the content of each REE varies regularly from the center to the edge. The radial-fibrous aggregates are represented by oxides and/or carbonates containing REEs (La, Ce, and Nd predominate). The results obtained can be used in the development of enrichment technology.