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Vol. 1 (1998 year), No. 3

Balagansky V.V., Timmerman M.Ya., Kislitsyn R.V., Dayly J.S., Balashov Yu.A., Gannibal L.F., Sherstenikova O.G., Ryunenen G.I.
The Isotope Age of the Kolvitsa Belt and the Umba Granulite Terrane (South-East of the Lapland Granulite Belt), the Kola Peninsula

The Lapland Granulite Belt (LGB) in the northern Baltic Shield is interpreted to have resulted from plate tectonic processes in the Palaeoproterozoic. The Kolvitsa Belt and the tectonically overlying metasedimentary Umba Granulite Terrane (UGT) are thought to be isolated fragments of the LGB in the Kola Peninsula. U-Pb (on zircon) and Rb-Sr (whole rock) ages, as well as Sm-Nd and Rb-Sr data presented in the paper indicate that the Kandalaksha metabasalt sequence, the Por’ya Guba mafic to intermediate granulite complex, the Kolvitsa massif of gabbro-anorthosites and its dyke complex are related to a single volcano-plutonic suite, which was developing 2.43-2.47 Ga ago at an initial stage of the earliest Palaeoproterozoic rifting of a Neoarchaean craton. Values of initial 143Nd/144Nd and 87Sr/86Sr ratios in rocks of this Kolvitsa suite coincide with those of 2.44-2.50 Ga old layered mafic intrusions in the Baltic Shield. In contrast with the Kolvitsa suite, the deposition of sedimentary protoliths of garnet-quartz-feldspar granulites and garnet, sillimanite and cordierite gneisses of the UGT was occurring ca. 2.0-2.1 Ga ago as suggested by model depleted mantle ages of 2.1-2.4 Ga and age data available on the granulite metamorphism (1.91 Ga). The sedimentary protoliths of the Umba paragranulites were derived largely from Palaeoproterozoic juvenile material, which permits to interprete the depositional environment as an island arc setting.

(in Russian, стр.14, fig. 5, tables. 3, ref 44, MS Word 95, MS Word 95 1420 Kb)

Vol. 3 (2000 year), No. 2

Kislitsyn R.V., Balagansky V.V., Manttari I., Gannibal L.F., Pozhilenko V.I.
U-Pb zircon age from gabbronorites and gabbroanorthosites of the Voche-Lambina study area, the Kola Peninsula

The Voche-Lambina study area is located within the Voche-Lambina Shear Zone (VLSZ), which is a part of a shear zone system that separates the Belomorian and Central-Kola Terranes. The emplacement of gabbronorite and gabbroanorthosite of the Main Fault Zone is connected to the initiation of the VLSZ. An upper intercept age of magmatic zircons from the gabbronorite is 2491В±13 Ma, which we interpret as the time of the initiation of the VLSZ. An upper intercept age of metamorphic zircons from the gabbroanorthosite is 2403В±7 Ma. This age dates the first shearing and metamorphic reworking, which took place simultaneously with those of the Main Ridge Gabbro-Anorthosite Massif (2406В±3 Ma). The isotopic dates obtained suggest that the VLSZ originated at the initial Palaeoproterozoic rifting 2.4-2.5 Ga ago. From published data, the Kolvitsa Shear Zone originated at the same time span; thus, the VLSZ and the Kolvitsa Shear Zone are components of one Palaeoproterozoic system of shear zones.

(in Russian, стр.8, fig. 3, tables. 1, ref 40, MS Word 95, MS Word 95 171 Kb)