Tantalum-niobium mineralization of the Taikeu ore cluster, the Polar Urals

Abstract

The Taikeu ore cluster comprises four tantalum-bearing ore deposits: Taikeu, Ust-Mramorny, Longotyugan, and Neudachny. Their ores are related to microcline-albite and less frequent quartz-albite-mica (phengite) metasomatic rocks replacing granites. The major ore minerals belong to the fergusonite and pyrochlore groups (mainly plumbopyrochlore). The compositional evolution of these minerals is considered in detail. High-Yb fergusonite containing up to 22-27 wt % Yb 2 O 3 was established in the ore cluster for the first time. Its formula is ({Yb 0.30 Er 0.15 Dy 0.05 Lu 0.04 Tm 0.04 …} 0.61 Y 0.39 )[Nb 0.99 Ta 0.01 ]O 3.96 . The density of this mineral determined by microvolumetric method is 6.47 ± 0.06 g/cm 3 . Fergusonite evolves from high-Yb to low-Yb varieties, with relatively small variations in Er and Dy. It is suggested that this fractionation trend is caused by high solubility of Yb 2+ complexes (primarily, fluoride complexes) in aqueous fluid during albitization. The chemical composition of the pyrochlore-group minerals evolves as follows: Na+Ca U+Th Pb. Plumbopyrochlore was formed at the late metasomatic stage of tantalum-niobium mineralization. The characteristic features of this stage are a high oxidation potential, on the one hand, and a low activity of sulfide sulfur, on the other hand.

Rare earth element geochemistry of columbite-group minerals: LA-ICP-MS data

“…The CGM may also represent secondary alteration phases replacing other tantaloniobates (e.g. Baldwin et al, 2005;De Vito et al, 2006;Vasil'ev et al, 2009). In LCT-family pegmatites, Č erný (1997) described a general trend of progressive REE depletion of a differentiating pegmatitic melt by precipitation of minerals incorporating REE (e.g.…”

The Origin of the Natural Water Chemical Composition in the Permafrost Region of the Eastern Slope of the Polar Urals

“…The Polar Urals is a region of northern Russia on which great hopes are pinned for the development and renewal of the mineral resource base of the Russian Federation [1][2][3]. This remote region has not been studied well, particularly with respect to hydrogeochemical aspects.…”