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Vol. 1 (1998 year), No. 3

Liferovich R.P., Bayanova T.B., Gogol O.V., Sherstenikova O.G., Delenitsin O.A.
The Genesis of Postcarbonatite Phosphate Mineralization of the Kovdor Phoscorite - Carbonatite Complex

⁸⁷Sr/⁸⁶Sr isotopic ratios were studied in carbonates and phosphates from postcarbonatite hydrothermal mineral assemblages occurring in the phoscorite-carbonatite complex of the Kovdor alkaline-ultrabasic massif. The obtained results compared with those published earlier for the Kovdor carbonatites and phoscorites show that the hydrothermal phosphatic mineralization in cavities of dolomitic carbonatites and phoscorites was formed by juvenile solutions. The latter were not derived from drainaged rock (i.e. from dolomitic carbonatites), but were fluids produced by a magmatic chamber, which was generating phoscorite-carbonatite series during a calcitic stage of formation of the Kovdor complex. The following fact is of interest: mineral-forming solutions, despite being formed in the crust, have a mantle ⁸⁷Sr/⁸⁶Sr ratio, which can be explained by their relation to a mantle-derived carbonatite. Data obtained on Sr isotopic composition of carbonate-fluorapatite, which is a cement-forming mineral in apatite-francolite breccias of the central area of phoscorite-carbonatite complex, suggest an explosive origin for these rocks, followed by significant hydrothermal alteration. The role of exogenic processes in the formation of present-day apatite-francolite breccia composition rises toward the marginal area of the Kovdor phoscorite-carbonatite complex.

(in Russian, стр.8, fig. 1, tables. 1, ref 21, MS Word 95, MS Word 95 85 Kb)

Vol. 3 (2000 year), No. 2

Liferovich R.P., Subbotin V.V., Pakhomovsky Ya.A., Lyalina M.F.
New genetic type of scandium mineralization in the iron-ore complex of the Kovdor massif

Scandium mineralization of a new genetic type has been discovered in the baddeleyite-apatite-magnetite deposit related to the Kovdor alkaline-ultrabasic massif, Kola Peninsula, Russia. It is represented by altered dolomite carbonatites containing a new mineral, juonniite in mineralised caverns. Juonniite occurrences are confined to a linear reactivated fault, which intersects phoscorites and carbonatites. Metasomatism of phoscorites caused almost a two-fold enrichment in Sc in clinohumite-bearing units. Late hydrothermal solutions affected cataclastic clinohumite-bearing phoscorites along the fault zone and the subsequent dissolution of sulphides and Sc-bearing minerals (e.g.: forsterite, baddeleyite, pyrochlore group minerals, etc.) was accompanied by mobilisation of traces of Sc, most likely, in the form of carbonate and sulphate. Fluorapatite-bearing altered dolomite carbonatites with abundant cavities provided the necessary conditions for the precipitation of scandium in the form of a hydrous phosphate, juonniite.

(in Russian, стр.10, fig. 6, tables. 2, ref 24, MS Word 95, MS Word 95 1660 Kb)

Vol. 3 (2000 year), No. 2

Liferovich R.P., Yakovenchuk V.N., Pakhomovsky Ya.A., Bogdanova A.N.
Crandallite group minerals of the Kovdor massif

The crandallite group minerals (CGM) from the hydrothermal assemblages occurring in the carbonatite-phoscorite complex of the Kovdor alkaline-ultrabasic massif have been studied. Goyazite, gorceixite and crandallite occur in low-temperature assemblages in cavities of the dolomitic carbonatites veins; crandallite has been identified also in the crust of weathering and in the carbonate-fluorapatite bearing breccia. The natural evolution of specie-forming cations in the order Sr-Ba-Ca has been shown on the basis of analysis of sequence of the described minerals crystallisation in the hydrothermal assemblages. SEM study has shown that crystalls of the studied phosphates are characterized by similar morphology of faces. Two generations of goyazite have been distinguished. Chemical composition data (microprobe analysis) and IR-spectroscopic data have been presented. Chemically all the described minerals are unique due to the lack of REE admixture. The conclusion about the importance of the CGM as a circumstantial evidence of secondary concentration of scandium and the possibility of scandium phosphates formation during low-temperature stages of hydrothermal mineralization has been made.

(in Russian, стр.10, fig. 5, tables. 2, ref 23, MS Word 95, MS Word 95 1170 Kb)