The sequence of formation of pyrochlore crystals of various morphology and composition is considered in an aggregate with ilmenite and feldspar of nepheline-feldspar pegmatite at Mt. Dolgaya (Vish-nevye Mountains, South Urals): altered yellowish green «uranium pyrochlore» with a UO3 content of 7.62– 42.44 wt. % in different parts of the crystal, and also fuorocalciopyrochlore, fersmite, and associated minerals. The alteration of «uranpyrochlore» includes fersmitization and silicifcation in contrast to relatively late fuo-rocalciopyrochlore and fersmite. The compositions and Raman spectra of altered «uranpyrochlore» and later fuorocalciopyrochlore are given.
Keywords: titanoniobates, «uranpyrochlore», fuorocalciopyrochlore, fersmite, formation sequence, Vishnevye Mountains, Southern Urals.

Received 06.08.2021, accepted 19.04.2022

V.I. Popova, South Urals Federal Research Center of Mineralogy and Geoecology UB RAS, Institute of Mineralogy Miass, Chelyabinsk region, 456317 Russia; popov@mineralogy.ru

V.A. Popov, South Urals Federal Research Center of Mineralogy and Geoecology UB RAS, Institute of Mineralogy Miass, Chelyabinsk region, 456317 Russia;

I.A. Blinov, South Urals Federal Research Center of Mineralogy and Geoecology UB RAS, Institute of Mineralogy Miass, Chelyabinsk region, 456317 Russia;

V.A. Kotlyarov, South Urals Federal Research Center of Mineralogy and Geoecology UB RAS, Institute of Mineralogy Miass, Chelyabinsk region, 456317 Russia;

S.M. Lebedeva, South Urals Federal Research Center of Mineralogy and Geoecology UB RAS, Institute of Mineralogy Miass, Chelyabinsk region, 456317 Russia

1. Bonstedt-Kupletskaya E.M. (1951) [Mineralogy of alkali pegmatites of the Vishnevy Mountains]. Moscow, AN SSSR, 176 p. (in Russian)
2. Chesnokov B.V. (1960) [Comparative characteristics of physical properties of crystalline and metamict pyrochlore of the Vishnevy Mountains]. Materialy po geologii i poleznym iskopaemym Urala. Trudy SGI [Materials on Geology and Exploration of the Urals. Proceedings of the Sverdlovsk Mining Institute], 37, 183–191. (in Russian)
3. Es’kova E.M., Zhabin A.G., Muchitdinov G.N. (1964) [Mineralogy and geochemistry of rare elements of the Vishnevy Mountains]. Moscow, Nauka, 319 p. (in Russian)
4. Gaydukova V.S., Sidorenko G.A. (1983) [Stability and phase transformations of pyrochlore]. Novye dannye o mineralakh SSSR. Trudy Mineralogicheskogo muzeya [New data on minerals of USSR. Proceedings of the Mineralogical Museum], 31, 31 –41. (in Russian)
5. Ivanov A.A., Borovsky I.B., Jarosch N.A. (1944) [Nb-bearing minerals of the Vishnevy Mountains in the Urals]. Trudy gorno-geologicheskogo Institutа UFAN SSSR [Proceedings of the Mining and Geological Institute UB AN UdSSR], 5, 1–18. (in Russian)
6. Levin V.Ja., Ronenson B.M., Samkov V.S., Levina I.A., Sergeev N.S., Kiselev A.P. (1997) [Alkali-carbonatite complexes of the Urals].Ekaterinburg, Urals Geological Committee, 274 p.
7. Nedosekova I.L., Belyatsky B.V. (2012) Age and substance sources of the Ilmeno-Vishnevogorsky alkaline complex (South Urals): Rb-Sr, Sm-Nd, U-Pb and Lu-Hf isotope data. Doklady Earth Sciences, 446, 1071–1076.
8. Nedosekova I.L., Koroteev V.A., Bayanova T.B., Serov P.A., Popova V.I., Chervyakovskaya M.V. (2020) [Age of pyrochlore carbonatites from the Ilmeno-Vishnev-ogorsky alkaline complex, South Urals: insights from Rb-Sr and Sm-Nd isotope data]. Litosfera [Litosphere], 20(4), 486–498. (in Russian)
9. Popova V.I., Popov V.A., Blinov I.A., Kotlyarov V.A. (2018) [New data on pyrochlore of alkali pegmatites and ore zones of the Vishnevye Mountains (Southern Urals)]. Mineralogiya [Mineralogy], 4(3), 46–60. (in Russian)