The paper investigates trace elements and crystal-rich fluid inclusions in spodumene from rare-metal pegmatites of the Kolmozero lithium deposit in the Kola region, Russia. The main lithium mineral in the pegmatites is spodumene, which occurs in three generations, designated as Spd-I, Spd-II and Spd-III. Iron, Na and Mn are the most typical element impurities in spodumene. The Fe/Mn ratio is 7.1 in Spd-I, 12.3 in Spd-II and 13.2 in Spd-III. Spd-II contains fluid and crystal-rich fluid inclusions. The crystal-rich fluid inclusions in Spd-II originally trapped CO₂-bearing aqueous fluids with dissolved alkali carbonates. The crystal-rich fluid inclusions contain zabuyelite (Li₂CO₃) and cristobalite (SiO₂) as solid phases, which have not been reported previously from the Kolmozero rare-metal pegmatites. These minerals are assumed to have resulted from a reaction between a CO₂-bearing aqueous fluid and host Spd-II and are not related to the mineral-forming system of pegmatites.

This study utilizes LA-ICP-MS-determined minor and trace element contents of megacrystic blocky K-feldspar to reveal the chemical variability and fractionation degree of albite-spodumene and barren feldspar pegmatites of the Kolmozero lithium deposit in the Kola region, Russia. K-feldspar from albite-spodumene pegmatite is represented by two generations: early microcline-I and late microcline-II. Rb, Cs, Li, and Tl are the most typical impurity elements in K-feldspar that replace K in its crystal lattice. Microcline-II differs from microcline-I: (i) relatively high contents of Rb (6520 and 4490 ppm, respectively), Cs (146 and 91 ppm), and Li (86 and 68 ppm), Tl (34 and 28 ppm); and (ii) low contents of Ba (13 and 29 ppm), Sr (8 and 24 ppm), and Pb (14 and 26 ppm). K-feldspar from feldspar pegmatites of the Kolmozero pegmatite field differs from those in the Kolmozero Li deposit in (i) low contents of Rb, Cs, Li, Tl, and an orthoclase component; and (ii) high contents of Sr, Ba, Pb, and an albite component. K/Sr, K/Ba, Rb/Ba, and Rb/Sr element ratios increase, while K/Rb, K/Cs, K/Tl, and K/Li element ratios decrease in K-feldspar, from feldspar pegmatites to albite-spodumene pegmatites. These trends reflect different fractionation degrees of pegmatite evolution. The implications of the detected trace element variations in K-feldspar are discussed in respect of tracing the rare element enrichments in pegmatite systems. A model is proposed for the formation of the Kolmozero pegmatites by differentiation from a hypothetical parental granite, rather than by anatexis of the host rock.

Beryl is both an accessory and a rock-forming mineral in pegmatites that contain beryl, making it a major source of Be. Beryl-bearing pegmatites of the Shongui deposit, located in the Kola province of the Northeastern Fennoscandian Shield, hold beryl with a yellowish-greenish color. An investigation into the chemical composition of this beryl from pegmatite dike No. 7 has been performed for the first time via the secondary ion mass spectrometry (SIMS) technique, and the chemical composition of the beryl-bearing pegmatites has been analyzed for the first time by the inductively coupled plasma mass spectrometry (ICP-MS) method. These pegmatites have high concentrations (ppm) of Be (11.8), Li (30.9), Rb (482), Nb (50.3), Ta (14.6), Cs (66.8), and Mn (283) and low concentrations of Sr, Y, Ba, rare earth elements (REE), Zr, and Th. In the Shongui pegmatite field, concentrations of Be, Li, Rb, Cs, Nb, Ta, and Mn increase from barren to beryl-bearing pegmatites, whereas concentrations of Ba, Sr, Y, and REE decline. Rb/Ba, Rb/Sr, and Zr/Hf ratios, showing the fractionation degree, change from the barren to beryl-bearing pegmatites: Rb/Ba and Rb/Sr increase from 111 and 0.46 to 1365 and 8.06, respectively, and Zr/Hf decreases from 18.9 to 14.5. The chemical composition of beryl from the Shongui deposit is unique. This mineral has a concentration of 25,300 ppm of alkalis (Li, Cs, K, Rb, Na) and the average Li, Ce, and Na content is 4430, 5000, and 15,400 ppm, respectively. According to its chemical composition, the Shongui beryl belongs to the Li-Cs-Na type, a type that is not recognized in the available classifications. It is supposed that this beryl was mainly crystallized in the magmatic stage rather than in any hydrothermal and metasomatic stages. Two beryl groups have been distinguished in beryl-bearing pegmatite dike No. 7: beryl from the intermediate zone (Brl-I) and beryl from the core zone (Brl-II). These beryls are concluded to have crystallized in the following order: Brl-I and then Brl-II. Compared with Brl-I, Brl-II is depleted in Cs, Na, Cl, and H₂O and is enriched in Fe and Mn. The Fe/Mn ratio varies from 9.18 to 16.50 in these beryls and their yellowish-greenish shades are thought to be driven by a large amount of Fe compared to Mn.

In this paper we present textural and compositional data for columbite group minerals (CGMs) and associated Nb-Ta-Sn oxides from lithium-beryllium-tantalum pegmatite deposits of the Kolmozero–Voronja belt, NW Russia, with the aim of deciphering these characteristics for minerals from deposits with different mineral signatures and lithium ore grade. Minerals from four deposits, including two of world-class (Kolmozero and Polmostundra), are examined. The main controlling factors for CGM compositional ranges are the diversity and rate of magmatic fractionation, hydrothermal overprint and mineral paragenesis, following the specific geochemical signature of the different pegmatite deposits. CGM from Kolmozero include several mineral species (columbite-(Fe), columbite-(Mn), tantalite-(Fe), and tantalite-(Mn)), showing large compositional variations, mainly controlled by Nb-Ta fractionation (Ta/(Ta + Nb) = 0.16–0.70; Mn/(Mn + Fe) = 0.45–0.63). Textural patterns are various (oscillatory, homogeneous, and patchy); spongy domains and overgrowing Ta-rich rims are also observed somewhere. This indicates the involvement of numerous magmatic and hydrothermal processes. The Polmostundra CGMs are represented by columbite-(Fe) with Ta/(Ta + Nb), ranging from 0.05 to 0.39; some crystals are homogenous, and others present normal, oscillatory, mottled and reverse-zoning patterns. The Okhmylk CGMs are irregular normal, patchy and homogeneous columbite-(Fe) and columbite-(Mn), with Ta/(Ta + Nb) = 0.09–0.24 and Mn/(Mn + Fe) = 0.29–0.92, indicating the suppressed magmatic fractionation and iron drop due to precipitation of Fe minerals. Columbite-(Fe) and columbite-(Mn) from the Be-Ta Shongui deposit are less evolved, with Ta/(Ta + Nb) = 0.07–0.23 and Mn/(Mn + Fe) = 0.31–0.55. The minerals are characterized by progressive normal, oscillatory, homogeneous and irregular reverse patterns. Associated pyrochlore minerals occur both as early magmatic (Kolmozero) and late hydrothermal (Polmostundra, Okhmylk). Cassiterite is found only in the Okhmylk dykes, and is apparently of hydrothermal origin. CGM from Li pegmatites have impurities of Ti (0.01–0.05 apfu) and W (up to 0.02 apfu), whereas CGM from Be pegmatites contains elevated Ti (up to 0.09 apfu). The mineral system analysis presented here is relevant for exploration.

The Archean Complex homologs of the Kola superdeep borehole (SG-3) were identified in the northern part of the White Sea mobile belt. Tonalite-trondhjemite-granodiorite gneisses of the Voche-Lambina test site and metavolcanic dacite-rhyodacite rocks of the borehole SG-3 were formed at the stages of 2.97–2.82, ∼2.81, and 2.78–2.79 Ga. The Sm-Nd model ages of the studied rocks do not exceed 3.1 Ga, and their positive ɛNd(t) values vary from +0.5 to +3.34. They are characterized by Mg# = 0.20−0.44, similar concentrations (HFSE) of Zr, Nb, Y, and also Rb, Cr, and Ni, and sharply differentiated spectra of the REE distribution (Ce/Sm = 3.2−5.8; Gd/Yb = 2.6−7.1). Primary melts were formed in balance with garnetamphibole restite under P ≥ 15−16 kbar.

The paper presents data on morphology and chemical composition of spodumene from rare-metal pegmatites of the Kolmozerskoe lithium deposit. Spodumene is the main rock-forming mineral (~ 20 %) and the major Li-bearing mineral in pegmatites. There are three generations of spodumene, and the intraphase heterogeneity of spodumenes of the first and second generations has been detected in the study for the first time. This heterogeneity is appearing in the presence of spots and zones differing by chemical composition — with high and low Fe/Mn ratio: 10.75—17.57 and 4.63—9.80, respectively. Any heterogeneity has not been revealed in the third generation spodumene. The second generation spodumene is the most widespread there, and the Li 2 O content in it varies from 7.11 to 8.08 wt %. As the common distinctive feature, the Kolmozerskoe deposit spodumenes have elevated contents of iron and rubidium in their chemical composition.