Typomorphic features of niobium rutile from the polymineral occurrence lchetju (the Middle Timan, Russia)
Krasotkina A. O., Machevariani M. M., Korolev N. M., Makeev A. B., Skublov S. G.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2017. V. 146. N 2. P. 88-100
The detail study of rutile and associated minerals in samples of heavy mineral concentrate from the Ichetju polymineral occurrence has been carried out with use of Raman spectroscopy to define mineral phases. The electron microprobe (EDS) analysis has allowed to distinguish varieties of rutile with different contents of Fe and Nb. It is shown that the hydrothermal alteration of the rich-in-niobium rutile (up to 24 wt % Nb2O5) has lead to outflow of niobium with decrease of its content down to formation of the «pure» rutile. This process was accompanied by leaching of iron from the Fe-bearing rutile composing small crossing veinlets in the Nb-bearing one. There were determined two mineral associations: the first one consists of Nb-bearing rutile and columbite; the second includes ilmenite which was replaced by the Fe-bearing rutile and a «pseudorutile». The latter, in its turn, was purified from the iron admixture and transformed into leucoxene in hydrothermal conditions; this is confirmed by transition of the Fe-bearing rutile into anatase.
Key words: rutile, Nb-bearing rutile, ilmenite, «pseudorutile», Ichetju occurrence, Middle Timan.