The Sarmatian crustal segment: Precambrian correlation between the Voronezh Massif and the Ukrainian Shield across the Dniepr-Donets Aulacogen

Sarmatia is the southernmost crustal segment of the East European Precambrian Craton. The Phanerozoic Dniepr-Donets Aulacogen (DDA) subdivides it into unequal halves, the Ukrainian Shield in the south and the Voronezh Massif in the north. Correlation between the Ukrainian Shield and the Voronezh Massif is reviewed, the overall structure and age-province subdivision of Sarmatia are assessed, and constraints are imposed on displacement along the DDA. It is shown that differences in the trends of the principal basement structures, highlighted by magnetic anomalies outlining Palaeoproterozoic banded iron formations, are a consequence of the heterogeneous structure of the Archaean-Palaeoproterozoic basement rather than the kinematics of the opening of the DDA. Only minor right-lateral displacement along the DDA has occurred. The main crustal units of the Ukrainian Shield, i.e. the Azov, Middle Dniepr and Ingul-Ingulets Blocks, correlate excellently with the Oskol, Sumy and Sevsk Blocks of the Voronezh Massif, which allows the definition of three coherent Oskol-Azov, Sumy-Dniepr and Sevsk-Ingulets crustal domains. Presently available radiometric datings show that these three domains all have Archaean crustal ages of 3.65-3.0, 3.2-3.1 and 3.1-2.8 Ga, respectively. The inter-domain boundaries appear largely to have existed already in the Archaean, but were subsequently masked by Palaeoproterozoic deformation and overlain by Proterozoic cover and nappe piles. Amongst the three crustal domains of central and eastern Sarmatia, the Oskol-Azov and Sevsk-Ingulets ones have been reworked substantially in the Palaeoproterozoic, while the Sumy-Dniepr Domain acted as a stable cratonic unit, although apparently rotating anti-clockwise between 2.3 and 2.1 Ga ago. The Palaeoproterozoic banded iron belts of Sarmatia can be subdivided into the cratonic-margin Krivoy Rog type and the interior, intra-domain Oskol type. The former outline the cratonic Sumy-Dniepr Domain, while the latter associate with NW-SE continental rifting that followed Archaean zones of weakness inside the Oskol-Azov Domain. The Bryansk Block in the northwestern part of the Voronezh Massif is a part of the large Bryansk-Bragin Granulite Domain which was formed between ca. 2.2 and 2.1 Ga ago, and extends into the northwestern Ukrainian Shield. In the east, the Lipetsk-Losev Volcanic Belt and the East Voronezh turbidite-schist province follow the boundary between the Sarmatian and Volgo-Uralian crustal segments. Together, these two crustal units appear to represent a Palaeoproterozoic orogenic environment, ca. 2.1-2.0 Ga in age.