Fluorite-bastnaesite rocks of the Ulan-Ude rare earth occurrence as a new type of carbonatites: Western Transbaikalia, Russia

The aim of the study is to show evidence confirm the magmatic nature of the bastnaesite-fluorite rocks of the Ulan-Ude occurrence that represent a specific type of carbonatites. The minerals have been studied using electron microscopy, thermometry, and analysis of stable isotopes. In many cases, the content of both fluorite and bastnaesite in the studied rocks reaches 50%. The rocks formation time (134.2 ± 2.6 Ma) is close to that of the carbonatites in the Western Transbaikalia province. The temperature of bastnaesite and fluorite formation in the rocks exceeds 500 C. The studied rocks contain phenocrysts of fluorite, bastnaesite, and tetraferriflogopite. Their crystallization began in the intermediate focus. The fine-grain fluorite matrix with small bastnaesite scales was formed in near-to-the-surface conditions and fixed by the hardening of the rocks. The carbonatites feature melt “dryness”, which determines an extremely low occurrence of the hydrothermal processes, changes in the xenoliths and previously formed minerals. The low fluid saturation level is confirmed by the absence of phlogopite water in position A, filled with fluorine only. The carbonatites are characterized by a higher content of sulfates represented by tenardite, glauberite, plumbojarosite, and corkite that are present in the composition of the salt melts released at the later stage of the melt crystallization.

fluorite, bastnaesite, carbonatite, glauberite, plumboyarozite

1. Ripp GS, Izbrodin IA, Lastochkin EI, Rampilov MO, Doroshkevich AG, Chromova EA. A new type of rare metal mineralization in the Western Transbaikalia. Otechestvennaya geologiya. 2018;3:9–21. (In Russ.)

2. Ripp GS, Prokopyev IR, Izbrodin IA, Lastochkin EI, Rampilov MO, Doroshkevich AG., et al. Bastnaesite and fluorite rocks of the Ulan-Ude occurrence (mineral composition, geochemical characteristics, and genesis issues). Geologiya i geofizika. 2019;60(12):1754–1774. (In Russ.) https://doi.org/10.15372/GiG2019122

3. Ripp GS, Doroshkevich AG, Lastochkin EI, Izbrodin IA. Isotope-geochemical features of the rocks in the Oshurkovsky apatite-bearing massif, Western Transbaikalia. Geokhimiya. 2014;4:302–318. (In Russ.) https://doi.org/10.7868/S0016752514020071

4. Demeny A, Sitnikova MA, Karchevsky PI. Stable C and O isotope compositions of carbonatite complexes of the Kola Alkaline Province: phoscoritecarbonatite relationships and source compositions. In: Wall F, Zaitsev AN (eds.). Phoscorites and carbonatites from mantle to mine: the key example of the Kola Alkaline Province. London: Mineralogical Society of Great Britain & Ireland; 2004. p.407–431.

5. Ramdohr P. Ore minerals and their intergrowths. Moscow: Foreign Languages Publishing House; 1962. 1132 p. (In Russ.)

6. Charilaou M, Löffler JF, Gehring AU. Fe-Ti-O exchange at high temperature and thermal hysteresis. Geophysical Journal International. 2011;185(2):647–652. https://doi.org/10.1111/j.1365-246X.2011.04981.x

7. Jackson M, Bowles JA. Curie temperatures of titanomagnetite in ignimbrites: effects of emplacement temperatures, cooling rates, exsolution, and cation ordering. Geochemistry, Geophysics, Geosystems. 2014;15:4343–4368. https://doi.org/10.1002/2014GC005527

8. Andreeva IA, Kovalenko VI, Kononkova NN. Nanocarbonatite melts of the Bolshetagninsk massif, Eastern Sayan. Doklady Akademii nauk. 2006;408(1):78–82. (In Russ.)

9. Korytov FYa, Frolov AA., Bagdasarov YuA. On the temperatures of the formation of the fluoritecontaining carbonatites in the Bolshetagninsky massif. In: Geologiya mestorozhdenii redkikh elementov = Geology of rare element deposits. Iss. 35. Moscow: Nedra; 1972. p.106–108. (In Russ.)

10. Sokolov SV. Fluorite carbonatites of the Bolshetagninsky massif (East Sayan, Russia). In: Geokhimiya magmaticheskikh porod: materialy XXV Vserossiiskogo seminara s uchastiem stran SNG = Geochemistry of Igneous Rocks: Proceedings of the 25th All-Russian Seminar with the CIS participation. Saint Petersburg; 2008. p.144–145. (In Russ.)

11. Santos RV, Dardenne MA, Gouveia de Olivera C. Rare earth elements geochemistry of fluorite from the Mato Preto carbonatite complex, Southern Brasil. Revista Brasilera de Geociências. 1996;26(2):81–86.

12. Williams-Jones AE, Samson IM, Olivo GR. The genesis of hydrothermal fluorite-REE deposits in the Gallinas Mountains, New Mexico. Economic Geology. 2000;95(2):327–342. https://doi.org/10.2113/gsecongeo.95.2.327

13. Nikiforov AV, Öztürk H, Altuncu S, Lebedev VA. Ore-bearing carbonatite-containing complex of Kyzyljaoren: rocks’ formation time and mineral composition (North-West Anatolia, Turkey). Geologiya rudnykh mestorozhdenii. 2014;56(1):41–69. https://doi.org/10.7868/S0016777014010055

14. Viladkar SG. Geology of the carbonatitealkalic diatreme of Amba Dongar Gujarat. Ahmedabad: GMDC Science and Research Centre; 1996. 74 p.

15. Alvin MP, Dunphy JM, Groves DI. Nature and genesis of a carbonatite-associated fluorite deposit at Speewah, East Kimberley region, Western Australia. Mineralogy and Petrology. 2004;80:127–153. https://doi.org/10.1007/s00710-003-0015-3

16. Liu S, Fan HR, Yang KF, Hu FF, Wang KY, Chen F, et. al. Mezoproterozoic and Paleozoic hydrothermal metasomatism in the giant Bayan Obo REE-Nb-Fe deposit: constrains from trace elements and Sr-Nd isotope of fluorite and preliminary thermodynamic calculation. Precambrian Research. 2018;311:228–246. https://doi.org/10.1016/j.precamres.2018.04.021

17. Fang T, Qiu Y, Qiu X. Carbon and oxygen isotopic characteristics of REE-fluorcarbonate minerals and their genetic implications, Bayan Obo deposit, Inner Mongolia, China. Chinese Journal of Geochemistry. 1996;15:82–86. https://doi.org/10.1007/BF03166799

18. Andersson UB, Holtstam D, Broman C. Additional data on the age and origin of the Bastnästype REE deposits, Sweden. Mineral Deposit Research for a High World: 12th SGA Biennial Meeting Conference. 2013;4:1639–1642.

19. Frost RL, Locke AJ, Martens WN. Thermal analysis of beaverite in comparison with plumbojarosite. Journal of Thermal Analysis and Calorimetry. 2008;92:887–892. https://doi.org/10.1007/s10973-007-8702-7

20. Doroshkevich AG, Kobylkina OV, Ripp GS. The role of sulfates in the formation of carbonatites in Western Transbaikalia. Doklady Akademii nauk. 2003;388(4):535–538. (In Russ)