EUROPROBE News 9
EUROBRIDGE
Palaeoproterozoic Accretion of Sarmatia
and Fennoscandia
by Svetlana Bogdanova (Lund) and
Eurobridge colleagues
EUROBRIDGE research of the East-European Craton
(EEC) is providing surprising new insights into Palaeoproterozoic processes of continental
collision and crustal accretion. The EEC is composed by three major segments Fennoscandia,
Sarmatia and Volgo-Uralia, each with complex Archaean and Palaeoproterozoic histories,
that were assembled as part of a megacontinent in the late Palaeoproterozoic (c. 1.85-1.80
Ga). EUROBRIDGE studies are concentrated on a broad transect in the southwestern part of
the craton, extending from the Palaeoproterozoic crust of the Fennoscandian Shield to the
Archaean of the Ukraine, spanning the boundary between Sarmatia and Fennoscandia. Based on
geophysical and geochemical studies, particularly of isotopic-age and provenance, it has
been shown that this part of the craton is a remarkable assemblage of Palaeoproterozoic
terranes, with arcuate belts of lower crustal rocks thrust together with upper crustal
units. Archaean components, thought previously to dominate this part of the EEC, are
apparently absent. The suture zone between Fennoscandia and Sarmatia separates terranes
with fundamentally different Archaean and Palaeoproterozoic histories.
The EEC in the Baltic States, the Republic of
Belarus and the Ukraine is largely covered by Neoproterozoic and Phanerozoic rift-related
and platform successions. Knowledge of the underlying crystalline basement is primarily
derived from analyses of drillcores and geophysical data. Over 6000 drillholes in the
research transect provide both the unique opportunity and the challenge to decipher the
Proterozoic and earlier history. New seismic experiments, complementary to the existing
potential field data, are providing insight into the deeper lithosphere.
EUROBRIDGE is carrying out a wide range of
interdisciplinary studies to better understand the Palaeoproterozoic and Archaean crustal
evolution, in particular, the processes involved in the accretion of vast volumes of
juvenile Palaeoproterozoic crust. The research centers on:
The deep structure of the southwestern EEC. This is
being investigated by a DSS (refraction and wide angle reflection) transect extending for
over 1500 km from the exposed crust of southwestern Fennoscandia to the Ukrainian Shield.
Complementary potential field data are being acquired.
Investigations of the structure and P-T conditions
of the various terranes, in combination with isotope dating of crust-forming processes,
with a focus on the Palaeoproterozoic terranes and the collision zone between Fennoscandia
and Sarmatia.
Analysis of the Riphean and Phanerozoic structural
histories, particularly of the Volhyn-Orsha depression and the Pripyat Trough, to better
understand the influence of Palaeoproterozoic rheology on the younger structural
evolution.
Studies of lower crustal and upper mantle
xenoliths, some diamondiferous.
Comparison with other parts of the EEC and other
cratons, particularly with those in North America, Greenland, South America and Siberia.
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