Search

Results:

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)