REE mineralization in alkaline rhyolites of the Pechalninsky ore field (North-East of Russia)

For the first time (by methods Scanning Electron microscopy, X-ray spectral microanalysis and cathodoluminescence method) REE mineralization studies have been conducted in alkaline rhyolites of the Pechalninsky ore field (North-East of Russia), a potentially larger-volume source of HREE. It is shown that in the direction of fluidity, thin interlayers composed of crystalline aggregates of pyroxenes and/or amphiboles impregnated with a silicate substance alternate in the rock, and ribbon-like thin strips and lace separations of Fe, Ti, and Mn hydroxides that have replaced titanomagnetite (relict secretions of which are partially preserved). Microcrystalline aggregates of pyroxenes and/or amphiboles contain the finest inclusions of REE secretions (5–7 microns), the determination of mineral species of the latter is difficult due to the small particle sizes. Scanning electron microscopy (EMF) has determined that these secretions are REE phosphates. Concentrically zonal and radially radiant REE secretions have been revealed in the relics of titanomagnetite crystals. The first ones are represented by silicates enriched with Yt and REE. In them, the content of REE varies unevenly from the center to the edge. Radially radiant aggregates are represented by oxides and/or carbonates containing REE (La, Ce and Nd predominate). The results obtained can be used in the development of enrichment technology.