46 EUROPE/East European Craton anomaly that marks an important iron-ore province At about the time that these rock belts were formed, an ancient platform cover began to be deposited The largest sedimentary basin was in the Sevsk-Ingulets (Kirovograd) domain In north-western Sarmatia, some Palaeoproterozoic volcanic rocks, e.g those in the Teterev Belt, have mantle-related geochemical signatures and probably represent island arcs The most conspicuous complexes of juvenile igneous rocks, however, are found in the East Voronezh belts in eastern Sarmatia, where an approximately 2.1 Ga volcanic arc and back-arc sedimentary basins with numerous ultramafic and mafic intrusions occur Together with numerous granitoid intrusions of the same age along the edge of the Archaean Oskol–Azov Block, these indicate the presence of an ocean–continent interface At this time Sarmatia was assembled and its dominant north–south-trending suture zones were created These have crustal roots approximately 60 km deep Along the north-western margin of Sarmatia, the Early Palaeoproterozoic north–south fabric is truncated by several wide north-east-trending belts of Late Palaeoproterozoic rocks These are the Osnitsk–Mikashevichi Igneous Belt, the Central Belarus Belt, and the Vitebsk granulite domain (Figure 11), all of which were formed between 2.0 Ga and 1.9 Ga, a top south-eastwards dipping subduction zones or zones of arc collision In particular, the presence of the extensive Osnitsk– Mikashevichi Igneous Belt suggests the existence at around 2.0 Ga of a unified Sarmatia, complete with a coherent north-western to northern margin The Osnitsk–Mikashvichi Igneous Belt is 200–250 km wide and comprises volcanic, hypabyssal, and dominantly plutonic igneous rocks The volcanic and dyke rocks are metabasalts and dolerites, meta-andesites, and meta-keratophyres, all metamorphosed in various ranges of the amphibolite facies Granodiorites and granites with subordinate gabbros and diorites form large batholithic plutons, which are only weakly deformed and metamorphosed The metavolcanics and minor interbedded metasedimentary rocks occupy small areas within the plutons or form septa between them A striking feature in Sarmatia is the occurrence of several large plutons of gabbro-anorthosites and rapakivi granites of 1.80–1.72 Ga age that are rich in titanium and other ore deposits Traditionally, these intracratonic plutons have been considered to be anorogenic, but recent discussion tends to connect them with zones of preceding plate collision New seismic results indicate that the anorthosite–rapakivi magmatism strongly influenced the composition of both the crust and the upper mantle In the Devonian, the formation of the Dniepr– Donets Aulacogen subdivided the Sarmatian crustal segment into two parts The southern part contains the Ukrainian Shield, and the northern part contains the Voronezh Massif However, no significant displacement along the aulacogen can have taken place, since the terrains on each side correlate excellently Volgo-Uralia The crystalline crust of Volgo-Uralia is mostly Neoarchaean, the highest depleted-mantle Nd model ages being approximately 3.1 Ga This crust is completely buried beneath a Phanerozoic, mostly Devonian to Triassic, sedimentary cover The only exception is the Taratash complex (Figure 12), where a basement slice was brought up to the Earth’s surface by thrusting connected with the Uralide Orogeny Under the Phanerozoic cover, however, there are numerous Meso- to Neoproterozoic aulacogens and troughs filled with 2–10 km thick sedimentary rocks intercalated with rare volcanics Proterozoic rifting substantially complicated the margins of Volgo-Uralia and penetrated deeply into its interior Because of the extensive cover, information on the crystalline crust is mostly derived from geophysics and from thousands of drill cores, which are particularly numerous because of the high oil and gas potential of the region Volgo-Uralia in general is a realm of high magnetization and dense upper crust A characteristic feature of its magnetic field is the presence of numerous, in part very large (300 km and more), circular to oval concentric anomalies separated by wide belts of more or less linear anomaly patterns Traditionally, such patterns have been explained by assuming that the non-linear nearly isometric anomalies represent stable Archaean massifs, while the linear zones relate to Palaeoproterozoic mobile belts In Volgo-Uralia, however, this interpretation is at complete variance with the presently available geological information, which demonstrates that the circular anomalies represent Palaeoproterozoic domal, relatively uplifted, structures In contrast, the linear belts consist of relatively well-preserved Archaean rocks These are 3.0–2.7 Ga old and comprise metasedimentary and subordinate metaigneous granulites, these two types mostly forming separate belts In addition, there are also greenstone sequences with komatiitic volcanics Associated with the Archaean belts are zones of strong shearing and mylonitization defining fold–thrust structures and generally trending north-east–south-west to east–west Most of the domes in the Volga–Kama megablock (Figure 12) are made up of Archaean granulites reworked during the Palaeoproterozoic In their