Search
Results:
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)
Vol. 12 (2009 year), No. 3
Mudruk S.V., Balagansky V.V.
Structural analysis of the Sergovo Palaeoproterozoic Fm of the SE Kola Peninsula (Baltic Shield)
The Kola Peninsula has a block-structure pattern caused by the interaction of main geodynamic processes: continental drift, tectonic activity, and elastic resistance of rocks. The multirange morphotectonic blocks reflected the youngest tectonic structures of the Kola Peninsula and of the mountain massifs Khibiny and Lovozero as the key objects were identified with wide-using morphometric methods. Position location of the blocks’ borders (tectonic zones) and their ranging were recognized by lineament analysis of valleys and tectonic faults presented in relief. The results were checked with aerial photo and satellite images and verified during field-work fixing their geological and landscape features. The discrepancy of the large- and medium-sized geological structures and land forms is established. The low-strength rocks correspond to the highest topographic forms, and the high-strength rocks – to the lowest ones. Geodynamic deformation of the topography surface is reflected in conditional amplitudes of the ascending of different morphotectonic structures. Determined conditional amplitudes are reached 1000 m. From the numerical simulation of stress state of the crust the regularities of stress distribution in the rock massifs depending on relief and lithospheric plate movements have been established. It has been determined the horizontal stresses are concentrated beneath the valley bottoms (beneath the enveloping base surface of relief), and within the uplands they decrease in comparison to applied tectonic stresses. The vertical tectonic stresses are tensile within the uplands and they are compressive beneath the valleys. Combined effect of the gravitation and of the horizontally oriented tectonic forces causes the interrelated lifting and lowering of the blocks – the valley areas are "sinking" and interfluve areas are "floating" relatively to the general rising of the Baltic shield. Stability of the block structures and resistance of natural-engineering systems (mine workings, quarries, etc.) distorted the gravity equilibrium because mining operations depend on tectonic pressing at a depth and expanding at the block lift accompanied with the stress redistribution within rock massifs.
(in Russian, стр.11, fig. 10, tables. 1, ref 18, Adobe PDF, Adobe PDF 0 Kb)
Vol. 15 (2012 year), No. 2
Balagansky V.V., Mudruk S.V., Gorbunov I.A., Raevsky A.B.
Tectonics of detached middle crust in the north-eastern foreland of the Palaeoproterozoic Lapland-Kola collisional orogen, north-eastern Baltic Shield
The Serpovidny Ridge Fold is located in the north-western Keivy Terrane situated in the north-eastern foreland of the Palaeoproterozoic Lapland-Kola Collisional Orogen, north-eastern Baltic Shield. Its isoclinal core is composed of Palaeoproterozoic rift-related rocks and displays sheath-like morphology (8 ? 2 km in size on the surface). Sedimentary structures that indicate the polarity of bedding suggest that this fold is a synformal anticline, with its axial surface dipping northwards. The lower (southern) limb of the fold is strongly thinned (the X/Z ratio up to 25) whereas the upper (northern) limb is almost undeformed. Kinematic indicators suggest that this super-large sheath fold resulted from north-directed movements under amphibolite-facies conditions at the boundary between the middle and lower crust. The core of the Serpovidny Ridge Sheath Fold composed of Palaeoproterozoic rift-related rocks is interpreted as an outlier of a Helvetic-type nappe that came from the Imandra–Varzuga Rift-Belt located ca. 50 km south of the study area. This tectonism is classified as tectonics of detached middle crust in foreland of the Lapland–Kola Collisional Orogen. It seems to be a counterpart of thin-skinned tectonics in foreland of Phanerozoic collisional orogens which operates in the upper crust.
(in English, стр.11, fig. 9, tables. 0, ref 34, Adobe PDF, Adobe PDF 0 Kb)