Leading Research Institute of Chemical Technology, Moscow, Russia:

E. P. Bugrieva, Head of the Geology and Mineralogy Division, e-mail: otdel-a@vniiht.ru
V. I. Dyakin, Lead Researcher at the Geology and Mineralogy Division, Candidate of Geology & Mineralogy Sciences
А. К. Selivanovskiy, Head of the Laboratory for Rare, Rare Earth and Radioactive Elements, Candidate of Chemical Sciences
Yu. M. Trubakov, Deputy Director for Research – Head of the Department of Comprehensive Processing of Rare Metal and Radioactive Ores and Man-Made Materials

This paper looks at the possibility to extract easily recoverable forms (ERF) of rare earth elements from the Tomtor ores. The method developed for estimating the amount of easily recoverable REMs contained in clay and the so-called ionic ores does not solve the issue of their recovery from high-grade phosphate rare earth/niobium ores. Due to the presence of ERFs in the Tomtor ores and considering the design high cost of hydrometallurgical processing selective mining is shown to be a cost-effective solution. This technique implies separation of rare-earth ores with low concentrations of niobium and further recovery of easily recoverable REMs through in-situ heap leaching. This way the amount of conveyed ore will be reduced bringing down the cost of rare earth concentrate. At the first stage, it is necessary to identify rare earth ores with low and off-balance concentrations of niobium and determine their locations and amounts. The second stage involves small-scale testing (mapping) of identified ores and pilot laboratory studies using a method developed by the Leading Research Institute of Chemical Technology. If the laboratory studies prove to deliver positive results, tests are to be conducted with group laboratory samples (which are 1-2 t samples) with the purpose of developing a simpler process to produce rare earth concentrate.

1. Tolstov A. V., Tyan O. A. The geology and mineralization of the Tomtor body. Yakutsk : YaNTs SO RAN, 1999. 164 p.
2. Pakhomov A. A., Danilov Yu. G., Grigoriev V. P. Problems and prospects of development of Tomtor niobium — rare earth deposits. Eurasian Mining. 2015. No. 2. pp. 44–47. DOI: 10.17580/em.2015.02.11.
3. Bykhovskiy L. Z., Arkhipova N. A. Strategic rare metal supply in Russia: Current state and future prospects. Gornyi Zhurnal. 2017. No. 7. pp. 4–10. DOI: 10.17580/gzh.2017.07.01.
4. Erlich E. Zoning of REE Mineralization of the Udzha Region,Republic of Sakha (Yakutia). Doklady Earth Sciences. 2018. Vol. 483, Iss. 1. pp. 1485–1486.
5. Kuzmin V. I., Flett D. S., Kuzmina V. N., Zhizhaev A. M., Gudkova N. V. et al. The composition, chemical properties, and processing of the unique niobium–rare earth ores of the Tomtor deposit. Chemical Papers. 2019. Vol. 73. pp. 1437–1446.
6. Mitchell R. H. Primary and secondary niobium mineral deposits associated with carbonatites. Ore Geology Reviews. 2015. Vol. 64. pp. 626–641.
7. Kravchenko S. M., Zamanskiy D. Zh., Fedorenko V. A. The geochemistry and genesis of carbonites in the Tomtor body. Geokhimiya. 2003. No. 6. pp. 608–622.
8. Delitsyn L. M., Melentiev G. B., Tolstov A. V., Magazina L. A., Samonov A. E. et al. The technological issues of Tomtor and their solution. Redkie zemli. 2015. No. 2. pp. 164–179.
9. Melentiev G. B., Delitsyn L. M., Lebedev G. G. et al. The prospects of pyrochemical treatment of phosphate materials containing rare metals. Rare elements in non-conventional raw materials and their potential production as a by-product : Research papers. Moscow : IMGRE, 1987. pp. 18–31.
10. Zolotov Yu. A., Kholkin A. I., Pashkov G. L., Kuzmin V. I. et al. Hydrometallurgical processing of non-conventional raw materials containing rare and non-ferrous metals. Moscow : FORUM, 2010. 180 p.
11. Tolstov A. V. The problems of estimating and mining niobium/rare earth ores of the Tomtor deposit. Proceedings of the 14^th International Meeting on Geology of Placer Deposits and Residual Soils. Novosibirsk : Apelsin LLC, 2010. pp. 656–660.
12. Tolstov A. V. The Tomtor body: The largest of the “rare”. Nauka i tekhnika v Yakutii. 2011. No. 2. pp. 16–23.
13. Lapin A. V. Geological and geochemical model of the one-of-a-kind rare metal deposit of Tomtor. Prognozirovanie i otsenka mineralnykh resursov. 1999. No. 10. pp. 16–28.
14. Sleptsov A. P., Tomashev A. V., Rylov D. A., Tolstov A. V. New features of the method used for estimating the complex ore reserves of the Tomtor deposit. Geology and Mineral Resources of Russia’s North-East: Proceedings of the 7^th Russian National Conference marking the 60^th anniversary of the Institute of Diamond and Precious Metal Geology at the Siberian Branch of the Russian Academy of Sciences. 2017. pp. 575–581.
15. Sleptsov A. P., Tolstov A. V., Baranov L. N. Mineral resources of the Tomtor ore field reconsidered. Geology and Mineral Resources of Russia’s North-East: Proceedings of the 6^th Russian National Conference. 2016. pp. 271–275.
16. Tolstov A. V. The geochemistry of thorium and uranium from the Tomtor body. Regional geochemical operations as the basis for estimating the ore and oil-and-gas content of a territory : Conference proceedings. 2015. pp. 31–33.
17. Tarkhanov A. V. Unique rare earth/yttrium anomalies. Rare metals: The mineral base, development, production, consumption: Proceedings of the 1^st Russian National Conference. Moscow, 2011. pp. 132–133.
18. Tolstov A. V., Konoplev A. D., Kuzmin V. I. Tomtor: The mineral base, assessment and development prospects. Rare metals: The mineral base, development, production, consumption: Proceedings of the 1^st Russian National Conference. Moscow, 2011. pp. 158–163.
19. Pokhilenko N. P., Kryukov V. A., Tolstov A. V., Samsonov N. Yu. Tomtor as a priority investment project aimed at ensuring Russia’s security in terms of rare earth elements. EKO. 2014. No. 2. pp. 22–35.
20. Yatsenko V. A. Niobium/rare earth ore of the Tomtor deposit: Analysis of priority transportation routes to reach potential concentrators. Interekspo Geo-Sibir. 2016. Vol. 3, No. 1. pp. 26–30.