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Michael Mints, Geological Institute of the Russian Academy of Sciences (Russian Federation)
Irina Philippova, Geological Institute of the Russian Academy of Sciences (Russian Federation)
Arsen Suleimanov, Spetsgeophysica (Russian Federation)
Nadezhda Zamozhniaya, Spetsgeophysica (Russian Federation)
Pavel Babayants, Aerogeophysica (Russian Federation)
Yury Blokh, Aerogeophysica (Russian Federation)
Alexey Trusov, Aerogeophysica (Russian Federation)
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During last decade, data on the Early Precambrian crustal structure and geological history of the East European Craton (EEC) have been significantly supplemented by the new information on the crustal architecture resulted from the Russian system of new reflection seismic geotraverses.
The EEC as a whole should be understood as the Palaeoproterozoic accretionary-collision orogen. The Archaean assemblages irregularly reworked in the Palaeoproterozoic form crustal segments (Archaean cratons that are the fragments of the previous Neoarchaean supercontinent): Kola-Mezen', Karelia, Sarmatia, Volgo-Uralia and Khopior. These segments were divided by the Palaeoproterozoic orogens. The Lapland-Midrussia-Southbaltia intracontinental collision orogen outflanks the Karelia craton and separates it from neighboring Kola-Mezen', Volgo-Uralia and Sarmatia cratons. At seismic sections marginal belts of the orogen appeared as the monoclinally dipping ensembles of tectonic slices that in some cases can be traced down to crust-mantle discontinuity. Axial part of the orogen is built by alternating tectonic slices that form gentle synforms. Tectonic evolution of the orogen started c. 2.5 Ga, the most active period of evolution lasted approximately from 1.95 to 1.75 Ga.
The unique Volgo-Uralia craton is almost entirely formed by the granulite-gneiss complexes originated 2.74-2.59 Ga ago. Two different types of the crustal sections are characteristic for this craton along the Tatseis geotraverse: (1) bowl-shaped Tokmov ovoid, boundaries of which can be traced down to crust-mantle boundary at the depth of c.60 km; (2) three-layer crust beyond Tokmov ovoid. Down to 20 km it is formed by a number of oval synformal structures overthrust one against another. The low-crustal area with thickness of app. 35 km is built by the succession of tectonic slices plunging toward western edge of the profile and penetrating into the mantle. The acoustically transparent area 10-20 km thick replaces boundary between the upper and low crust. It can be traced to the surface of the basement where drill-holes discovered granitoids of Bakalin complex.
New seismic data created a basis for developing 3D models (block-diagrams) of the deep structure of the large crustal segments, Lapland-Kola, Karelia-Belomorian, Midrussia, East-Voronezh and Volgo-Uralia ones. These models demonstrate an image of the tectonically layered crust with predominance of the gently dipping boundaries between main tectonic units and complicated structure of the crust-mantle boundary. Slice-like shape is characteristic for the most of main tectonic units including ?Archaean cratons? that are placed above more ancient and younger complexes as well. The Palaeoproterozoic processes in the internal area of the former Archaean supercontinent play a peculiar role in the Palaeoproterozoic evolution that can be attributed as succession of ?lame attempts? of the disruption of the ancient supercontinent.
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