Magnetite-apatite-dolomitic rocks of Ust-Chulman (Aldan shield, Russia): Seligdar-type carbonatites?

• Published in: Mineralogy and petrology 2018-04, Vol.112 (2), p.257-266
• Main Authors: Prokopyev, Ilya R., Doroshkevich, Anna G., Redina, Anna A., Obukhov, Andrey V.
• Format: Article
• Language: English
• Subjects: Anhydrite; Apatite; Barite; Carbonates; Chlorides; Composition; Concentrates (ores); Crystals; Earth and Environmental Science; Earth Sciences; Fluid inclusions; Geochemistry; Haematite; Hematite; Hydrothermal solutions; Ilmenite; Inorganic Chemistry; Magma; Magnetite; Mineralization; Mineralogy; Minerals; Monazite; Ores; Rock; Rocks; Rutile; Short Communication; Solid solutions; Solutions; Sulfates; Sulfur trioxide; Sulphate minerals
• ISSN: 0930-0708; 1438-1168
• DOI: 10.1007/s00710-017-0534-y

The Ust-Chulman apatite ore body is situated within the Nimnyrskaya apatite zone at the Aldan shield in Russia. The latest data confirm the carbonatitic origin of the Seligdar apatite deposit (Prokopyev et al. in Ore Geol Rev 81:296–308, 2017). The results of our investigations demonstrate that the magnetite-apatite-dolomitic rocks of the Ust-Chulman are highly similar to Seligdar-type dolomitic carbonatites in terms of the mineralogy and the fluid regime of formation. The ilmenite and spinel mineral phases occur as solid solutions with magnetite, and support the magmatic origin of the Ust-Chulman ores. The chemical composition of REE- and SO 3 -bearing apatite crystals and, specifically, monazite-(Ce) mineralisation and the formation of Nb-rutile, late hydrothermal sulphate minerals (barite, anhydrite) and haematite are typical for carbonatite complexes. The fluid inclusions study revealed similarities to the evolutionary trend of the Seligdar carbonatites that included changes of the hydrothermal solutions from highly concentrated chloride to medium–low concentrated chloride-sulphate and oxidized carbonate-ferrous.