A concentric-zonal texture of mineral aggregate observed in alkali pegmatite of the Vishnevye Mountains was formed as a result of melt-fuid crystallization in a closed system. At the frst stage, rare large monazite crystals were crystallized creating wave concentration felds. Allanite-(Ce), bastnäsite-(Ce), chevkinite-(Ce), thoroaeschinite, apatite-(CaF), zircon, calcite and other minerals crystallized in the end of the monazite growth. Feldspars (syntactic intergrowths of albite with K-feldspar) were dominant in the fnal stage of crystallization. The change in the composition of melt-fuid (magma) from phosphate-silicate to silicate is atypical.

Figures 5. Table 1. References 5.

Key words: monazite-(Ce), rare metal and rare-earth minerals, alkali pegmatites, dissipative textures, Vishnevye Mountains, South Ural.

V.A. Popov, Institute of Mineralogy UB RAS, Miass, Chelyabinsk district, 456317, Russia; popov@mineralogy.ru

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