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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. 10 (2007 year), No. 1
Bayanova T.B., Yakovlev Yu.N., Guberman D.M., Yakovleva A.K., Skufin P.K.
Isotopic investigations of age of the Archaean rocks from the Kola Superdeep Borehole section, Proterozoic Pechenga structure and its framing.
The results of the study of ore mineralization in the rocks from the three lower volcanic formations in the SG-3 Proterozoic complex and in their near-surface homologues cut by the structural boreholes IX and X have been presented. Sulfide specialization of volcanites from the Majarvi Fm has been found. Oxide specialization of rocks from the Pirttijarvi and Orshoaivi Fms has been confirmed. The distribution, evolution conditions and chemical composition of sulfides and oxides from volcanites have been studied. The main features of development, composition and late alterations of ore minerals could be related to two factors. The composition of sulfide from the Majarvi Fm vulcanite and oxide from the Pirttijarvi and Orshoaivi Fms in the SG-3 section is determined by a "depth factor" that caused a widespread occurrence of mineral solid solutions. Intense development of hematite and transformation of magnetite and ilmenite in volcanites of the Pirttijarvi and Orshoaivi Fms in the SG-3 section are explained by the influence of the regional Luchlompolo fault. High contents of isomorphous admixtures – PGE, Se and Co in sulfides, V, Ti and Mn in oxides that were not observed earlier in the SG-3 section and geoblock as a whole have been established in all major minerals from the formations deep levels.
(in Russian, стр.12, fig. 9, tables. 3, ref 29, Adobe PDF, Adobe PDF 0 Kb)
Vol. 10 (2007 year), No. 2
Yakovlev Yu.N., Skuf'in P.K., Bayanova T.B.
The rhyodacitic porphyry body in the section of the SG-3 Pechenga area (age and ore mineralization)
By geological, geophysical, petrological and isotopic-geochronological data the Archaean complex in the SG-3 section correlates with amphibolite-gneiss complexes of the granite-greenstone area of the Svanvik-Neiden segment located in the Kola-Norwegian block. Plagiogneisses of tonalite-trondhjemite composition, being one of the major components of the SG-3 Archaean complex and the borehole surroundings, include two types. Plagiogneisses of type A are depleted in heavy lanthanoids to a different degree and their ?Nd ranges from +2 to +0.5. Plagiogneisses of type B are rich in HREE, incompatible trace elements and are characterized by negative ?Nd values which is evidence of contamination of the primary melt by the ancient crust material. Amphibolites associated with plagiogneisses are close to tholeiitic basalts of modern oceanic plateaus and Archaean greenstone belts in the trace element composition. By the experimental data, tonalite-trondhjemite melts corresponding to plagiogneisses of types A and B and depleted in heavy lanthanoids to a different degree, formed during metabasic rocks melting at Р ? 10-15 and ? 8 kbar respectively. Model metabasite sources of tonalite-trondhjemite melts that are initial for plagiogneisses of type A are comparable with basalts of modern oceanic plateaus and Archaean basalts of plume origin in the trace element patterns and their indicator ratios. Low Mg# of plagiogneisses excludes the contribution of mantle peridotites in their formation and, hence, does not correlate with subduction oceanic plate. Variations of trace element and isotopic composition of plagiogneisses more likely point to formation of tonalite-trondhjemite melts at different levels of the thickened mafic crust which includes metabasalt material that is heterogeneous in trace element and isotopic composition. The composition peculiarities of amphibolites and model metabasite sources of tonalite-trondhjemite melts suggest that formation of the thickened crust might be caused by accretion of oceanic plateaus.
(in Russian, стр.9, fig. 3, tables. 6, ref 10, Adobe PDF, Adobe PDF 0 Kb)
Vol. 15 (2012 year), No. 2
Mitrofanov F.P., Malitch K.N., Bayanova T.B., Korchagin A.U., Zhirov D.V.
Comparison of East-Scandinavian and Norilsk large plume mafic igneous provinces of PGE ores
The paper is devoted to issues related to the formation of large low-sulfide PGE ore provinces – East-Scandinavian and Norilsk. Basing multidisciplinary data it has been inferred that East-Scandinavian province is being attributed to an intracratonic type without subduction and crust contamination (with Pt-Pd low-sulfide mineralization to predominate). Norilsk province belongs to pericratonic one with PGE – Ci-Ni rich sulfide mineralization to prevail. It has been shown that the main ore provinces PGE metals essentially formed at later stage of existence and initial break-up of supercontinents – predominantly 2.7-2.5 Ga and 1.8-1.7 Ga as a unique case in the Late Paleozoic (Norilsk). For the first time long duration (dozens of Ma) and multistage nature of ore-magmatic system evolution for the East-Scandinavian mafic Large Igneous Province have been demonstrated and this has made it possible to propose it for Norilsk. Comparison of low-sulfide PGE and sulfide Cu-Ni (with PGE) potential of the mafic intrusions is possible using a series of geological, geophysical and geochronological (U-Pb on zircon and baddeleyite, Sm-Nd on rock-forming and sulfides minerals) and isotope geochemical (?Nd(T), TDm, ISr, 3He/4He) indicators.
(in English, стр.15, fig. 8, tables. 1, ref 41, Adobe PDF, Adobe PDF 0 Kb)
Vol. 15 (2012 year), No. 2
Petrovskaya L.S., Bayanova T.B., Petrov V.P.
The Neoarchaean enderbite-granulite complex of the Central Kola block: Stages of evolution (Kola Peninsula)
The paper presents the results of geological-petrological and isotope-geochemical researches of rocks and minerals of the Neoarchaean enderbite-granulite complex (Central Kola block). The results obtained allowed the researchers to determine the sequence of endogenous processes, P-T conditions and duration of the enderbite-granulite complex evolution within 2.73-1.81 Ga. Three stages of metamorphism have been established in gneisses of the Kola Group: (I) – early granulitic (2.73-2.72 Ga); (II) – superimposed amphibolite facies (2.57-2.55 Ga); (III) – retrograde low-temperature amphibolite facies (2.54 Ga). Stages I and II were separated by emplacement of enderbites (2.66 Ga) and formation of cummingtonite-biotite orthogneisses after enderbites (2.64 Ga). Ultrametamorphism in gneisses of the Kola Group was accompanied by injections of anatectic veins of microcline-plagioclase granite with garnet and sillimanite (2.55 Ga). The tectonomagmatic activity in this region culminated by the injection of veined leucogranites (ca. 2.50 Ga) that crosscut gneisses of the Kola Group, enderbite and cummingtonite-biotite orthogneisses. Based on Sm-Nd and Rb-Sr methods, the influence of Paleoproterozoic processes on the granulite-enderbite complex with the alteration of isotopic systems is recorded at 2.50 and 1.81 Ga ago.
(in English, стр.8, fig. 9, tables. 0, ref 19, Adobe PDF, Adobe PDF 0 Kb)