Late hydrothermal veins exposed in the northern wall of the Novy peeble quarry are studied in a fenitic halo of the western contact of the Ilmenogorsk miaskite complex (South Urals) using scanning electron microscopy, Raman spectroscopy and X-ray diffraction. The veins fill open fractures, the walls of which are covered by feldspar clusters with chlorite-smectite crusts overgrown by calcite, pyrite and ilmenite. The final stage of the hydrothermal process is related to the formation of a zeolite assemblage with harmotome and clinoptilolite-Ca. The pyrite-ilmenite assemblage contains accessory columbite-(Fe), fergusonite-(Y) and syntactic intergrowths of minerals of the polysomatic bastnäsite-synchysite series (hydroxylbastnaesite-(Ce), parisite-(Ce), röntgenite-(Ce)), and hydroxyl analogs of parisite-(Ce), röntgenite-(Ce) and synchysite-(Ce). The Raman spectra of carbonates in vibrational region up to 1800 cm-1 are similar with previously published ones; the main bands are slightly shifted depending on a Ca/∑REE ratio. The assemblage of ilmenite, columbite-(Fe) and fergusonite-(Y) in late hydrothermal veins of the Ilmenogorsk complex is found for the first time.
Keywords: polysomatic series, rare earth fluorocarbonates, harmotome, clinoptilolite, Ilmenogorsk complex, fenite.
Thanks: We are grateful to A.V. Kasatkin for a constructive review, which allowed us to improve the manuscript, and Director of OJSC ZhBI-Service A.N. Komchugov and Chief Engineer G.I. Grebenyuk for their assistance in study of the quarry.
Funding. The analytical work was supported by state contract of the South Urals Federal Research Center of Mineralogy and Geoecology UB RAS (Miass, Russia) no. 125020601683-2. The structures of zeolites were studied in the Center for X-Ray Diffraction Analytical Methos of the Research Park of the St. Petersburg State University (St. Petersburg, Russia) within the project no. 125021702335-5. The Raman studies were supported by the St. Petersburg State University, project no. 124032000029-9.
Conflict of interests. The authors declare that there is no conflict of interest related to the manuscript.
Author contribution. M.A. Rassomakhin – field works, concept development, optical microscopy studies, SEM-EDS studies, writing the manuscript; E.V. Belogub – analytical work, writing the manuscript;
M.S. Avdontceva – analytical work, writing the manuscript; V.N. Bocharov – analytical work, writing the manuscript. All the authors approved the final version of the manuscript prior to publication.
For citation: Rassomakhin M.A., Belogub E.V., Avdontceva M.S., Bocharov V.N. Late hydrothermal mineralization in a fenitic halo of the Ilmenogorsk alkaline complex (South Urals). Mineralogy, 2025, 11(4), 21–38. https://doi.org/10.35597/2313-545X-2025-11-4-2

Received 17.10.2025, revised 17.11.2025 accepted 03.12.2025

Mikhail A. Rassomakhin – South Urals Federal Research Center of Mineralogy and Geoecology UB RAS, Miass, Chelyabinsk region, Russia; miha_rassomahin@mail.ru
Elena V. Belogub –  South Urals Federal Scientific Center of Mineralogy and Geoecology UB RAS, Miass, Chelyabinsk region, Russia; belogub@mineralogy.ru
Margarita S. Avdontceva –   Institute of Earth Sciences, St. Petersburg State University, St. Petersburg, Russia; m.avdontceva@spbu.ru
Vladimir N. Bocharov – St. Petersburg State University, St. Petersburg, Russia; w.bocharow@spbu.ru

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