International Geologiical Congress - Oslo 2008

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EUR-04 Tectonic evolution of the lithosphere from European Precambrian Craton to Alpine system on the base of the deep geophysic

 

EUROBRIDGE revealing Archaean to Devonian geodynamics in the East European Craton

 

Svetlana Bogdanova, Lund University (Sweden)
Marek Grad, Warsaw University (Poland)
Alexander Guterch, Polish Academy of Sciences (Poland)
Tomasz Janik, Polish Academy of Sciences (Poland)
German Karatayev, Academy of Sciences of Belarus (Belarus)
Elena Kozlovskaya, University of Oulu (Finland)
Gediminas Motuza, Vilnius University (Lithuania)
Vitaly Starostenko, Academy of Sciences of Ukraine (Ukraine)
Hans Thybo, Copenhagen University (Denmark)
Jukka Yliniemi, University of Oulu (Finland)
 

 

The EUROBRIDGE (EB'95, 96 and 97) deep seismic refraction profiles traverse c. 1500 km of the East European Craton (EEC) between the Baltic and Ukrainian shields, where the crystalline crust is concealed by the platform cover. EUROBRIDGE crosses two of the most important tectonic features of the EEC. One is the Fennoscandia-Sarmatia suture zone (FSSZ) that separates two Palaeoproterozoic lithospheric plates of different Precambrian evolution, the other the Devonian Pripyat'-Dniepr-Donets Aulacogen (PDDA).
The obtained P- and S-wave images and gravity-seismic modelling of the crust and upper mantle along EUROBRIDGE were integrated with geological data on the crustal evolution in the western EEC (Bogdanova et al. 2006, Mem. Geol. Soc. London, 32). The results show that:
- Juvenile Fennoscandian terranes ranging in age between 2.00 and 1.84 Ga compose a "thick-skinned" stack against NW Sarmatia. Sarmatia comprises various terranes aged between 3.7 and 2.2 Ga, and had an active continental margin at c. 2.0-1.95 Ga. Many of the terrane-bounding faults penetrate the entire crust. Palaeoproterozoic zones of subduction and collision are expressed by Moho offsets and lateral changes of petrophysical properties and compositions in the upper mantle. Final collision took place at c. 1.83-1.80 Ga during the overall assembly of the EEC.
- The FSSZ incorporates Fennoscandian as well as Sarmatian fragmented terranes separated by the detachment Minsk Fault. The seismic structure and composition of the upper lithosphere were mostly defined by postcollisional extension. Important features are a dome of the collisionally stacked crustal layers and wedges beneath the Minsk Fault with associated metamorphic core complex, and the presence of the high velocity lower crust, underlying the FSSZ and adjacent Palaeoproterozoic belts and attendant voluminous magmatism. Particularly, the emplacement of the Korosten AMCG pluton in Sarmatia at 1.80-1.74 Ga caused total rearrangement of the upper lithospheric structure in the area c. 250 km across.
- A similar profound change was caused by the 1.50-1.45 Ga Danopolonian orogeny.
- The Devonian rifting did not thin the crust but reactivated many of the Paleoproterozoic faults; which controlled the position of the listric faults fringing the PDDA Pripyat trough. A major detachment fault is recorded as a SSW-dipping mantle reflector in Sarmatia with a related mantle underplate of low, 8.1 km/s P-wave velocity.

 

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