Elsevier Encyclopedia of Geology

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The Belomorian typically features extensive belts of

mafic metavolcanics, continental-margin turbidites,

and TTG-type granitoids, all arranged in large folded

thrust sheets overriding the edge of the Karelian Pro-

tocraton. Thrusting here occurred at about 2.70–

2.65 Ga, when the different terranes and crustal prov-

inces – except possibly the western Archaean pro-

vince – collided and merged to form a Neoarchaean

continent. Concomitantly, parts of the Karelian pro-

vince underwent high-grade metamorphism and mig-

matite formation. Along its boundary with the

Belomorian Belt, 2.7 Ga eclogites are present. Ex-

humation and cooling then followed. Cratonization

became complete at around 2.5 Ga.

Between 2.5 Ga and 2.0 Ga, Archaean Fennoscan-

dia underwent extension, rifting, and even breakup,

leading to the opening of small oceanic basins. Inter-

mittently there was strong dominantly mafic but also

komatiitic igneous activity. Most conspicuous are

large greenstone rifts and belts, which tend to follow

the boundaries between the different Archaean

terranes. Ophiolites with ages of about 1.96 Ga

occur in places.

The latter half of the Palaeoproterozoic was a

period of intense orogenic activity across most of

Fennoscandia. In the north, the Lapland–Kola colli-

sional orogeny at about 1.96–1.85 Ga welded to-

gether the crustal units that constitute the present

Archaean domain. Some of these appear to have

been parts of a Neoarchaean continent that was

broken up in the Early Palaeoproterozoic. In the

case of other crustal units, an exotic provenance has

been suggested. Altogether, the Lapland–Kola Oro-

gen is a tectonic collage of reworked Late Archaean

terranes and intervening belts of Palaeoproterozoic

juvenile crust and turbidites (Figure 10). Prominent

among the latter is the Lapland Granulite Belt, made

famous by Eskola’s work on the facies of metamorph-

ism. Arc magmatism has been dated at 1.96 Ga;

southwards thrusting and collision occurred at

1.91–1.90 Ga, while post-collisional magmatism, ex-

humation, and cooling lasted until 1.85 Ga.

To the south-west of the Archaean domain, the

Proterozoic crust of central Fennoscandia was also

created around and soon after 1.90 Ga in a series of

orogenic events collectively named the Svecofennian

Orogeny. Initial subduction between about 1.93 Ga

and 1.91 Ga appears to have been towards the present

south-west, creating a primitive volcanic arc, but

soon its direction reversed to plunge beneath the

Archaean Protocraton in the north-east.

In simplified outline, the Svecofennian Orogen con-

sists of two volcanic belts and an intervening turbidite

basin (the Bothnian Basin). In south central Finland

there is a very large complex of granitoid plutons. The

northern volcanic belt follows the edge of the

Archaean Protocraton in Scandinavia but then swings

south-eastwards to western and southern Finland,

skirting the complex of granites. The southern belt

extends between southernmost Finland and south cen-

tral Sweden. Continuations of these terranes beyond

Lake Ladoga into Russia are conceivable (Figure 9).

The ages of volcanism in the two belts overlap

within the 1.90–1.88 Ga bracket; dominantly TTG-

type plutonism lasted until about 1.87 Ga. The pres-

sure–temperature ratios of Svecofennian metamorph-

ism were mostly low to moderate, which attests to the

absence of continent–continent collision. Between

them, the two volcanic belts house the majority of

the renowned Finnish and Swedish sulphide and

iron ores. By 1.85 Ga, the Svecofennian Orogen had

been consolidated; however, 1.86–1.84 Ga plutons of

granitoids occur locally at its south-western margin

and along some major intra-orogenic province

boundaries.

Figure 5 The south-western margin of the East European

Craton in the Neoproterozoic. The ruled area shows the Meso-

to Neoproterozoic Volyn–Orsha Aulacogen, which is filled by

mostly terrigenous sedimentary rocks. In the vicinity of the

Trans-European Suture Zone, however, the approximately

550 Ma Volynian flood basalts (blue markings) form a large

outcrop set in Vendian and Early Cambrian sedimentary rocks

(the sand-coloured areas). The basalts fill a basin that trends

across the Aulacogen and runs roughly parallel to the Trans-

European Suture Zone. This indicates that the south-western

margin of the craton was passive at the end of the Neoproterozoic.

ß Svetlana Bogdanova.

40 EUROPE/East European Craton

Subsequently, granitic magmatism associated with

metamorphism and migmatite formation but lacking

connection with mafic rocks took place at various

sites and times within the 1.84–1.78 Ga bracket.

Current interpretation sees this as a response to com-

pression and thickening of the Svecofennian crust,

largely caused by orogeny outside the limits of the

Svecofennian domain.

After 1.85 Ga, growth of new crust continued to-

wards the south and the west, outwards from the

cratonized Svecofennian territory. Several accretion-

ary orogenic events at around 1.84–1.83 Ga and

1.81–1.78 Ga, and again during the Gothian Orogeny

at 1.71–1.67 Ga, have been distinguished in a belt

that stretches from Lithuania across southern and

western Sweden to central Norway. Outside the limits

of Svecofennian crust, the granitoid rocks are TTG-

type calc-alkaline, whereas within a marginal western

zone of the Svecofennian Orogen the 1.84–1.67 Ga

Figure 6 The patterns of the Meso- to Neoproterozoic rifts and aulacogens beneath the sedimentary cover of the Russian Platform

conform well with the three-segment fundamental structure of the East European Craton. Thus, the Volyn–Orsha, central Russian, and

Pachelma rifts follow the Palaeoproterozoic sutures between Fennoscandia, Sarmatia, and Volgo-Uralia. The Mezen rifts in the north

align with the Lapland–Kola collisional orogen and delimit the Timanides, while Volgo-Uralia is completely surrounded by troughs,

aulacogens, and the Peri-Caspian Basin. ß Svetlana Bogdanova.

Figure 7 The Mesoproterozoic (Riphean) cover sequence in

the western foreland of the southern Urals was folded in the

Palaeozoic. The sequence is approximately 1500 m thick. Its

components are interbedded conglomerates, sandstones, silt-

stones, pelites, limestones, and dolostones, with numerous de-

posits of siderite ore. The picture shows rocks of the Bakal

Formation in the Irkutskan siderite pit. ß Svetlana Bogdanova.

EUROPE/East European Craton 41

Figure 8 Major crustal provinces of the East European Craton. Apart from Palaeoproterozoic domal structures and some sedimentary and igneous rocks, Volgo-Uralia is almost

completely Archaean. Sarmatia, in contrast, comprises several large Archaean protocratonic units that were cemented together mostly during the Palaeoproterozoic. In Fennoscandia,

Archaean crust is concentrated in the north-eastern part, where it forms a separate domain. Sarmatia and Fennoscandia contain relics of approximately 3.7–3.5 Ga crust, while Volgo-Uralia

is wholly Neoarchaean. Another important difference is that the dominant 2.2–2.0 Ga Palaeoproterozoic crust in Sarmatia is substantially older than the 1.92–1.85 Ga crust of central

Fennoscandia. Thus, the age patterns and structural arrangements in each of the three crustal segments are distinct. They are also largely discordant at the segment boundaries. The

boundary between Sarmatia and Volgo-Uralia is marked by belts of reworked Archaean crust, while the boundary between Fennoscandia and the other two crustal segments is different in

its north-eastern, largely Archaean, and south-western, dominantly Proterozoic, parts. In the north-east, the 200 km wide Central Russian Belt is built up of elongated wedged blocks derived

from the adjacent crustal segments, whereas in the south-west, beneath the Neoproterozoic Volyn–Orsha Aulacogen, there are various Palaeoproterozoic terranes ranging from

continental-margin types to outboard volcanic arcs. These were stacked atop each other between about 1.8 Ga and 1.7 Ga. ß Svetlana Bogdanova.

42 EUROPE/East European Craton

Figure 9 The major crustal provinces of Fennoscandia reflect the subdivision of that crustal segment into largely separate Archaean

and Proterozoic parts. The master story of the Archaean part appears to have been the formation of a Mesoarchaean Protocraton in

Karelia followed by a Neoarchaean continent. The latter was broken up in the Early Palaeoproterozoic but then brought together again

during the Lapland–Kola collisional Orogeny. In that process, Archaean terranes exotic to Fennoscandia may also have participated.

Essentially coeval with the Palaeoproterozoic Lapland–Kola collision in the present north was the first stage of the accretionary

formation of Proterozoic crust in the rest of the Fennoscandian crustal segment. In the present west, this process continued

episodically until about 1.55–1.50 Ga, apparently without involving major collisions of continental crustal units. In the south-west,

continental collision is indicated for the period between 1.5 Ga and 1.4 Ga, when interaction with a different craton – possibly Proto-

Amazonia – appears to have led to the Danopolonian Orogeny. The subsequent Sveconorwegian orogenic process, between about

1.1 Ga and 0.95 Ga, was pronouncedly collisional and approximately coeval with the Grenvillian Orogeny in Laurentia and the

assembly of the Supercontinent Rodinia. Along the south-eastern margin of Fennoscandia, the wide Baltic–Belarus belts of stacked

inboard and outboard terranes mark the Late Palaeoproterozoic (

ca. 1.8–1.7 Ga) collision zone with Sarmatia. Here, the West

Lithuanian Belt and its continuation into south-eastern Poland differ sharply from the adjacent East Lithuanian and Belarus–Podlasie

belts in terms of both the direction of the tectonic grain and the age of crustal formation. In western Lithuania, the crust is nearly coeval

with that in south-western Sweden. Mz, Mylonite Zone. ß Svetlana Bogdanova.

EUROPE/East European Craton 43

magmatism was bimodal mafic to granitic and

commonly alkali-calcic. As a cumulative result of

the different igneous episodes, the large north–south

trending Transscandinavian Igneous Belt was formed

within the western margin (Figure 9). The Baltic–

Belarus belts, some of them with a Palaeoproterozoic

evolution similar to that of the Svecofennian in the

Baltic Shield, characterize the south-western part

of Fennoscandia; they are, however, overlain by

phanerozoic sedimentary cover (Figure 3A).

During the Mesoproterozoic, renewed Orogeny

between 1.6 Ga and 1.5 Ga created new crust in west-

ernmost Sweden and southern Norway (the Kongsber-

gian event), etc. In contrast, orogenic events around

1.5–1.4 Ga (the Danopolonian Orogeny) and between

1.1 Ga and 0.9 Ga (the Sveconorwegian Orogeny) were

largely collisional. The Sveconorwegian Orogeny

involved only limited creation of new crust in south-

western Norway but fairly voluminous granitic mag-

matism and granulitic to eclogitic metamorphism

with migmatization in many places. Some of the

metamorphic assemblages indicate pressures between

1 GPa and 1.5 GPa. High-grade granulitic rocks

accompanied by charnockite, and numerous large

granite bodies were also formed at around 1.4 Ga.

During both these events, major more-or-less north–

south-trending faults, thrusts, and suture zones were

developed in most of southern Scandinavia.

According to some hypotheses, all of southern

Norway and western Sweden west of the so-called

‘Mylonite Zone’ (Figure 9) constitute terranes exotic

to Fennoscandia, which were accreted to the East

European Craton during the Sveconorwegian

Orogeny.

Figure 10 (A) Tectonics of the Lapland–Kola collisional belt in the Kola Peninsula. (Map supplied by the Secretariat of the

EUROPROBE Programme). (B) Cross-section showing the juxtaposition of various Archaean terranes (the Karelian, Belomorian,

Murmansk, and Central Kola–Keivy) with the Palaeoproterozoic Imandra–Varzuga volcanic belt and the Umba Granulite Terrane. Map

and cross-section by courtesy of the Secretariat of the EUROPROBE Programme.

44 EUROPE/East European Craton

At about 1.64–1.62 Ga, and again at 1.57 Ga,

around 1.5 Ga, and 0.93 Ga, numerous large intru-

sions of rapakivi granites and associated charnocki-

tic, mangeritic, and anorthositic rocks penetrated the

Fennoscandian crustal segment. Extensive swarms of

mafic dykes and sheets were formed throughout the

Proterozoic, with maxima at 2.45–2.1 Ga, 1.6–

1.5 Ga, and 1.3–1.2 Ga and 0.97–0.95 Ga. Some of

these may be the results of superplume events in the

Earth’s mantle. In addition there are plugs and

plutons of alkaline and carbonatitic rocks (see Igne-

ous Rocks: Carbonatites), some of which are Precam-

brian and others Phanerozoic in age. Alkaline

magmatism was particularly voluminous in the Kola

Peninsula and along rifts such as the Permian Oslo

Graben in Norway. Other intrusions formed isolated

minor plugs.

Sarmatia

The Sarmatian segment is built up of several Ar-

chaean crustal provinces with ages ranging between

3.7 Ga and 2.7 Ga (Figure 11). Belts of Palaeoproter-

ozoic crust intervene between some of these, but

accretion and welding appear to have commenced in

the Archaean.

The oldest crustal units are the Palaeo- to

Mesoarchaean Podolian Block in the extreme south-

west and the Oskol (Kursk-)–Azov Block in the east.

Ages of 3.65–3.60 Ga have been obtained from

ultramafic and tonalitic rocks, while major TTG in-

trusions are 3.4–3.3 Ga old. Both the Podolian Block

and the Oskol–Azov Block represent one-time lower

crust but have evolved through several events of

high-grade granulitic metamorphism and multiphase

magmatism in the Archaean and Palaeoproterozoic.

The Sumy–Dniepr gneiss–granite–greenstone ter-

rane is generally somewhat younger. It was formed

mainly between 3.2 Ga and 3.1 Ga and is characterized

by numerous belts of principally mafic metavolcanic

and sedimentary rocks. These contain basal sequences

of komatiites, komatiitic basalts, and tholeiites, reach-

ing thicknesses of 4–5 km. Atop the mafic volcanics rest

calc-alkaline felsic volcanic rocks, tuffites, immature

sandy metasediments, and banded iron formations

with quartzites. These belts were metamorphosed and

deformed concomitantly with the development of

domal structures containing juvenile TTG-type grani-

toids and felsic gneisses with granulites. The alteration

processes were related either to rifting and the opening

of a Mesoarchaean ocean or to the evolution of a pre-

existing oceanic basin of Palaeo- to Mesoarchaean age.

In the Palaeoproterozoic, between about 2.6 Ga

and 2.3 Ga, major belts of supracrustal rocks contain-

ing numerous banded iron formations were formed.

Some of these outline the margins of Archaean

terranes, while others appear to be controlled by

rifts in the interior parts of the Oskol–Azov Block.

The latter are the cause of the strong Kursk magnetic

Figure 11 The processes that shaped the internal structure of Sarmatia were the docking of the older Archaean Oskol–Azov and the

younger Archaean Sumy–Dniepr crustal blocks and, during the Proterozoic, the accretion of the Podolian Block to the evolving main

mass of the Sarmatian crustal segment. The latter process was coeval with the generation of mantle-derived juvenile Proterozoic crust

elsewhere in Sarmatia. Directly related to the assembly of the East European Craton were the formation of the East Voronezh belts

along the developing boundary between Sarmatia and Volgo-Uralia about 2.1–2.0 Ga ago and the formation of the continental-margin

Osnitsk–Mikashevichi Igneous Belt and the outboard Central Belarus Belt at around 2.0 Ga. These two belts faced the ocean basin that

was consumed during the collision of united Volgo-Uralia and Sarmatia (i.e. ‘Volgo-Sarmatia’) with Fennoscandia. ß Svetlana

Bogdanova.

EUROPE/East European Craton 45

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 de-

posited. The largest sedimentary basin was in the

Sevsk-Ingulets (Kirovograd) domain.

In north-western Sarmatia, some Palaeoprotero-

zoic 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 ultrama-

fic and mafic intrusions occur. Together with numer-

ous granitoid intrusions of the same age along the

edge of the Archaean Oskol–Azov Block, these indi-

cate 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 trun-

cated by several wide north-east-trending belts of

Late Palaeoproterozoic rocks. These are the

Osnitsk–Mikashevichi Igneous Belt, the Central Bela-

rus 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 dom-

inantly plutonic igneous rocks. The volcanic and dyke

rocks are metabasalts and dolerites, meta-andesites,

and meta-keratophyres, all metamorphosed in vari-

ous 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 dis-

placement 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 com-

pletely buried beneath a Phanerozoic, mostly Devon-

ian to Triassic, sedimentary cover. The only exception

is the Taratash complex (Figure 12), where a base-

ment 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-Ura-

lia 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 magnetiza-

tion 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 concen-

tric 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 Palaeoproter-

ozoic mobile belts. In Volgo-Uralia, however, this inter-

pretation 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 Ar-

chaean rocks. These are 3.0–2.7 Ga old and comprise

metasedimentary and subordinate metaigneous granu-

lites, 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

46 EUROPE/East European Craton

central parts are Palaeoproterozoic granite and gneiss

complexes. In contrast, the very large circular struc-

ture in the Middle Volga megablock has Palaeo-

proterozoic rocks and Palaeoproterozoic reworking

on its flanks, while north-east–south-west striking

Archaean granulites similar to those outside the

dome occupy the centre.

All the domes feature radial and ring-shaped faults

related to the deformation of the Archaean crust and

associated with rare Palaeoproterozoic metasedimen-

tary and metavolcanic rocks. The domes were formed

between 2.3 and 2.0 Ga and may be related to the

nearly coeval collision of Volgo-Uralia with Sarmatia.

Along that collision zone and in the north-east of

Volgo-Uralia there are large areas of Palaeoprotero-

zoic turbiditic and metapelitic mica schists, silts,

sandstones, and carbonaceous shales formed on the

shelf margins of the crustal segment.

The Archaean and Palaeoproterozoic rocks of

Volgo-Uralia are cut by numerous mafic dykes and

sills, which were intruded during several stages of

Meso- to Neoproterozoic rifting.

The Proterozoic fault systems of Volgo-Uralia

strongly influenced the formation and structure of

the sedimentary cover and the locations of the major

Palaeozoic oil and gas resources.

Assembly of the East European Craton

The assembly of the East European Craton can be

followed from palaeomagnetic data, isotopic ages,

and analyses of rock formation and igneous activity

at the margins of the three involved crustal segments

(Figure 13).

First to collide were Volgo-Uralia and Sarmatia.

The collision occurred at 2.1–2.05 Ga, when Volgo-

Uralia was thrust onto Sarmatia. Geophysically, the

suture can be followed for 30 km beneath Volgo-

Uralia. At the Earth’s surface, the junction zone con-

tains extensive shelf deposits on the Volgo-Uralian

Figure 12 The specifics of Volgo-Uralia were largely determined by the development of Palaeoproterozoic domal structures in the

Neoarchaean continental crust. At about 2.1–2.0 Ga, the marginal belt facing Sarmatia was formed. This belt is composed of

Palaeoproterozoic sedimentary commonly flysh-like rocks, which suggest the one-time existence of a passive margin. Subsequent

Mesoproterozoic rifting and the formation of troughs, aulacogens, and basins influenced the structure of Volgo-Uralia more than that of

the other two East European crustal segments. The Peri-Caspian Basin is unique in the East European Craton in having a relatively

shallow Moho and a great thickness of sedimentary cover. ß Svetlana Bogdanova.

EUROPE/East European Craton 47

side, while the so-called East Voronezh belts mark the

edge of Sarmatia.

The south-westernmost belt represents a volcanic

island arc, while the north-eastern belts preserve

back-arc volcanic rocks and turbidites. Voluminous

granitic magmatism occurred particularly in Volgo-

Uralia. During the Mesoproterozoic, the Pachelma

Aulacogen developed along the Sarmatia–Volgo-

Uralia junction.

After that collision, it was several hundred million

years before the combined Sarmatia and Volgo-Uralia

(‘Volgo-Sarmatia’) approached Fennoscandia. Mean-

while, accretionary crustal growth occurred separ-

ately along the edges of both Fennoscandia and

Sarmatia. At approximately 2.0 Ga, subduction of

oceanic crust beneath the presently north-western

edge of Volgo-Sarmatia commenced. This process

eventually consumed all the oceanic crust between

the protocraton and Fennoscandia. Within the

continental margin of Sarmatia, the Osnitsk–

Mikashevichi Belt began to develop, while the

Central Belarus island arcs were formed outboard.

Further west, the Middle Lithuanian Suture Zone,

separating east–west trending rocks of the West

Lithuanian Terrane from a belt of north-north-east-

striking rocks in eastern Lithuania, was created. It

may either coincide with the actual Fennoscandia–

Sarmatia suture or be one of several components

within a swarm of intersegment terrane boundaries.

Palaeomagnetic data indicate that the colliding seg-

ments were still at least 2000 km apart between

1.80 Ga and 1.75 Ga.

The Palaeoproterozoic suture between Fennoscan-

dia and Volgo-Sarmatia became the site where the

Volyn–Orsha and central Russian systems of aulaco-

gens, rifts and troughs, and sedimentary basins

were developed in the Late Mesoproterozoic and

Early Neoproterozoic.

Elsevier Encyclopedia of Geology - vol I A-E

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