Tectonic elements of the territory of Belarus. Tectonic structure of Belarus The largest positive tectonic structure of Belarus
The territory of Belarus is located in the western part of the East European platform. Here, a crystalline basement of Archean-Middle Proterozoic age and a sedimentary cover are distinguished, which includes deposits from the Upper Proterozoic to Quaternary. They are subdivided into a number of structural complexes. The main ones are Gothic (foundation), Early Baikal, Late Baikal, Caledonian, Hercynian, Cimmerian and Alpine.
Geosynclinal (folded) Basement complexes on the territory of Belarus are characterized by intrusive rocks of different composition, with a high degree of metamorphism.
Igneous rocks represented by granites, diorites, gabbro and their effusive counterparts
Among complexly dislocated and metamorphosed rocks gneisses, crystalline schists, and quartzites are widespread.
Forms of folding sedimentary cover appear in the form of brachyanticlines, ridges, domes, and other forms of folds, complicated by faults, and within the Pryatsky trough - salt tectonics.
Crystal Foundation on the territory of the republic, it occurs at various depths - from the first tens to 5000 m. It comes to the surface in the southernmost part of the republic (Glushkovichi village, Lelchitsky district).
According to the depths of the foundation on the territory of Belarus, the following structural and tectonic elements are distinguished: the Belarusian anteclise, the Ukrainian shield, the Voronezh anteclise, the Polesskaya, Bragin-Loevskaya, Zhlobinskaya, Latvian saddles, the Pripyat and Dnieper-Donetsk troughs, Podlyassko-Brest and Orsha depressions, the Baltic syneclise, the Mikashevichsko-Zhitkovichi ledge and the Lukovo-Ratnovsky horst.
Belarusian anteclise located in the northwestern part of Belarus and in adjacent regions of Poland, Lithuania, Latvia on an area of 300x220 km. In the adjacent part of the anteclise (Central Belarusian massif, Ivatsevichi ledge), the sedimentary sequence is represented by Upper Proterozoic deposits (mainly the Vendian complex), which is overlain by Mesozoic and sometimes Cenozoic. Cambrian, Ordovician and Silurian deposits are developed in the northwest of the Central Belarusian massif, Vendian deposits in the south. In the sedimentary cover, mainly Upper Proterozoic, Cambrian, Ordovician and Silurian deposits are developed, as well as Evonian. On the territory of the Vileika buried ledge, Vendian and Middle Devonian deposits are continuous, and in the northwest, Cambrian, Ordovician and Silurian. Riphean, Vendian and Middle Devonian deposits are known on the Bobruisk buried ledge.
Voronezh anteclise enters the territory of Belarus with its western part. It highlights the Surazhsky and Gremyachsky ledges and the Klintsovsky graben separating them. Riphean, Vendian and Devonian deposits are developed, which are buried under the Mesozoic.
Baltic syneclise, is located on the territory of the Baltic States, Russia, Poland, Denmark, partly Sweden and, in a small area, enters the NW of Belarus with its southern wing. It is represented by Cambrian, Ordovician and Silurian deposits.
Pripyat trough located on the south-east of Belarus. The area is 180x130 km. The depth of the foundation is from 1500 to 6000 m. It is divided into numerous structures: steps, horsts, grabens, buried ledges. Upper Proterozoic deposits are widespread in the southwestern and central parts. Devonian deposits are continuous, and Carboniferous and Permian-Triassic deposits are widespread over a large area.
Dnieper-Donets trough the main part of the finds on the territory of Ukraine, a small part adjoins the Pripyat trough. The depth of the foundation is up to 7000-8000 m or more.
Podlasie-Brest depression located in the south-western part of Belarus and in adjacent regions of Poland. The area is 140x130 km. The crystalline foundation lies at a depth of 1200-1500 m and up to 6000 m in Poland. It is overlain by the Vendian volcanic series, and in the eastern regions by the Belarusian series. The deposits of the Cambrian, Ordovician, Silurian, Jurassic, Paleogene, Neogene and Anthropogen occur above the volcanogenic strata. The Permian and Triassic appear in the NW regions, and the Carboniferous in the southernmost regions. The main stage in the formation of the depression is the Silurian.
In the south-east, the Podlyassko-Brest depression is bounded by the Lukovsky-Ratnovsky horst, located in the north-west of Ukraine. Its area is 350x20-30 km. It separates the Russian plate from the Volyn-Azov. Orsha depression occupies a significant north-east part of Belarus on an area of 300x200 km. The depth of the basement reaches 1800 m. In the sedimentary strata, sediments of the Upper Precambrian, Devonian and Anthropogenic are distinguished here. In the southern regions, in addition, Jurassic, Cretaceous, Paleogene and Neogene appear.
Ukrainian shield enters Belarus only in its northern part. It lies shallow and only in the area of vil. Glushkovichi comes to the surface.
Braginsko-Loevskaya saddle separates the Pripyat and Dnieper-Donetsk troughs. The basement depth is 500-2000 m. The platform cover is composed of Devonian and younger sediments.
Polissya saddle connects the Belarusian massif with the Ukrainian shield and separates the Pripyat trough and the Podlasie-Brest depression. Its area is 120x95 km. The crystalline basement here lies at a depth of 300-500 to 800-1000 m. Upper Precambrian, Cretaceous, Paleogene, Neogene and Quaternary deposits.
Zhlobin saddle separates the Orsha depression from the Pripyat trough and stretches in the NW direction for 110 km, with a width of 25-50 km. The foundation lies at a depth of 400-700 m and is overlain by Upper Precambrian, Devonian, Jurassic, Cretaceous, Paleogene, Neogene and Anthropogenic deposits.
Latvian saddle 120x95 km in size separates the Baltic and Moscow syneclises - and connects the Belarusian anteclise with the Baltic Shield. In a small area, it enters the northern part of Belarus. The foundation here lies at depths of 500-700 m and is overlain by deposits of the Upper Precambrian, Ordovician, Devonian, and Anthropogenic.
When conducting tectonic zoning of any territory, geologists are guided simultaneously by several criteria, the most important of which are:
- 1) the depth of the crystalline foundation;
- 2) thickness of the sedimentary cover.
Structures of I, II, III and other lower orders are distinguished in the system of tectonic zoning of the territory of Belarus.
Figure 1 - Tectonic zoning of the territory of Belarus
Tectonic structures of the first order within Belarus are: 1) Russian plate; 2) Azov-Podolsk plate; 3) Ukrainian shield.
I. The Russian plate lies at the base of most of the country's territory and consists of individual anticlises, syneclises, troughs, depressions, saddles, faults, horsts, and grabens.
Anteclise - a fold of rock layers facing upwards. As a rule, the most ancient rocks are located in the core of the anticlise. Syneclise - a gentle (concave) deflection of the layers of the earth's crust within the platforms, which has predominantly irregular rounded outlines. The slope of the layers on the wings is measured in fractions of a degree. Deflection - a negative tectonic structure of a platform of increased mobility of a linearly elongated shape with a large thickness of the platform cover deposits, limited by faults. Depression - a large rounded depression of the earth's surface, which is predominantly of tectonic origin, characterized by a large thickness of the sedimentary cover. Saddle - a transitional tectonic platform structure with an average thickness of platform cover deposits, which separates two positive (or negative) tectonic structures. Fault - displacement of rock blocks relative to each other along a vertical or inclined surface of a tectonic rupture. As a result of the fault, horsts and grabens are formed (fault tectonics). Horst - a section of the earth's crust raised along fault lines. Graben - a section of the earth's crust lowered along fault lines.
The Belarusian anticlise occupies the western and central regions of Belarus. Its most elevated part is formed by the Central Belarusian massif.
Within the Babovnyansky ledge, crystalline rocks lie directly under the Quaternary deposits. Relatively elevated blocks of the crystalline basement correspond to the Vileika, Mazursky and Bobruisk buried ledges.
The Vileika buried ledge and the Central Belarusian massif are separated by the Volozhinsky graben.
The eastern part of Belarus is occupied by the slope part of the Voronezh anticlise, whose private structures include the Surazhsky and Gromyatsky buried ledges, separated by the Klintsovsky graben.
The Zhlobin saddle separates the Belorussian and Voronezh anticlises and has an asymmetric structure. Its northern slope is quite gentle, and the southern one is a system of stepped faults.
The Belarusian anticlise in the north borders on the Baltic syneclise. In the east, the Orsha depression adjoins it.
Within the Baltic syneclise, the basement plunges to a depth of 500 m. Its eastern edge is limited by powerful faults with an amplitude of up to 300 m. The Neman graben is a particular structure of the Baltic syneclise.
The Orsha depression is huge and is characterized by a significant subsidence of the basement surface towards the northeast. The depression has rather steep edges and a flat bottom. In the central part of this structure there is the Central Orsha horst with an amplitude of about 200 - 300 m, which separates the Vitebsk and Mogilev troughs.
A trough is a kind of flat, bowl-shaped synclinal folds.
The Podlasie-Brest depression is located in the southwestern part of Belarus, partially capturing the territory of neighboring Poland. Within its limits, the basement surface descends from east to west up to 8 km (the territory of neighboring Poland). From the north and south, the depression is bounded by faults with an amplitude of up to 300 m. In the east of the Podlasie-Brest depression, there are separate brachiosynclines (“brachio” - short, disproportionate) with an amplitude of about 50–80 m. Their diameter does not exceed 5 km.
The Polessky saddle separates the Podlasie-Brest depression from the Pripyat trough. The surface of the foundation within the Polessky saddle is characterized by absolute heights from -20 to -500 m.
The Mikoshevichi-Zhitkovichi ledge has an insignificant width (about 10 km). From the south, it is limited by a system of deep faults with an amplitude of 1 to 3 km. Within this ledge, crystalline rocks occur at a depth of only about 10 - 30 m, repeatedly overlain by Neogene and Quaternary deposits. This structure is divided by a system of powerful faults into three horsts: 1) Zhitkovichi horst; 2) Mikosevic horst; 3) Ozernitsky horst.
The Pripyat trough stretches from west to east for about 300 km, and from north to south - for 140-150 km. The boundaries of the Pripyat trough are stepped faults with an amplitude of 2 - 4 km. The Pripyat trough is characterized by extremely complex fold-fault tectonics. Here, separate tectonic steps, horsts and grabens are distinguished, which, like the trough as a whole, were formed as a result of block movements along fault lines. The Rechitsko-Shatilkova and Malodushinsko-Krasnoslobodskaya blocks are located in the northern part of the trough. The Rechitsko-Shatilkovo block is about 240 km long and 10–25 km wide.
The Narovlyansky horst is located in the southern part of the Pripyat trough, stretching for 150 km in length and about 6 km in width. The absolute marks of the foundation within this tectonic structure range from - 1.8 to - 4.0 km.
In the section of the platform cover of the Pripyat trough, there are huge (up to 4 km) strata of potash and rock salt deposits, which determines a certain specificity of tectonic processes and relief formation.
The Braginsko-Loevsky saddle separates the Pripyat trough from the Dnieper-Donets trough. It is formed by the Braginsky buried ledge and the Loevsky saddle. Within the Bragin buried ledge (length 45 - 50 km), the foundation descends from south to north to a depth of about - 1,500 m. This structure is limited by faults up to 3 km deep. Faults also limit the Loevskaya saddle, which stretches for 50 - 60 km with a width of 30 - 40 km. In its axial part, the foundation surface is at a depth of about 1,500 m.
The Dnieper-Donetsk trough enters the territory of Belarus with its western tip. The internal structure of this trough generally resembles the structure of the Pripyat trough. The boundaries of the Dnieper-Donetsk trough are faults of the sublatitudinal direction.
The northernmost part of Belarus belongs to the Latvian saddle, which separates the Baltic syneclise and the Orsha depression. In the central part of the saddle, crystalline rocks lie at elevations of about -700 m. In the east, they go to a depth of about 1,400 m, and from the side of the Belarusian anticlise they rise to 500 m.
The Velizh saddle belongs to the structures of the Moscow syneclise and is characterized by the depth of the crystalline basement from - 1,300 m to - 400 m.
II. The Azov-Podolsk plate occupies the extreme southwestern part of Belarus. Particular structures of this plate are the Lukovsky-Ratnovsky horst and the Volyn monocline.
Monocline - a type of occurrence of rock layers with the same slope in one direction.
Lukovsko-Ratnovsky horst stretches in the latitudinal direction for 350 - 400 km and has a width of approximately 13 - 40 km. This tectonic structure has a block structure and is limited by faults with an amplitude of 100 (in the east) to 1,000 m (in the west).
Volyn monocline characterized by a steady subsidence of the basement to the southwest to a depth of about 3 km. Against the background of monoclinal subsidence, several troughs and uplifts stand out.
III. The Ukrainian shield occupies the extreme southern part of the territory of Belarus. Near the village of Glushkovichi, Lelchitsky district (Gomel region), the rocks of the crystalline basement come to the surface. A particular structure of the Ukrainian shield is the Ovruch graben-syncline, limited by deep faults and extending for 110 km in length and about 20 km in width.
The crystalline basement is an ancient mountain system that formed in the Archean and Proterozoic eras. The largest tectonic structures on the territory of Belarus are the Russian plate, the Volyn-Azov plate, the Ukrainian shield. Depending on the depth of the foundation, they are divided into: positive, negative and transitive. Positive tectonic structures include anteclises and shields. Anteclise- this is one of the tectonic structures of the platform, a gentle, dome-shaped elevation of the earth's crust. Shield– platform element within which the crystalline foundation comes to the surface. The largest tectonic structure is the Belarusian anteclise (it occupies the northwestern and central part). The east of the country is occupied by the eastern slopes of another positive structure of the B-E platform, the Voronezh anteclise. In the very south, the Ukrainian shield enters the territory. Smaller positive structures are also distinguished. Negative tectonic structures are represented dips and dips. The most ancient is the Orsha depression. Another negative structure is the Brest depression, in the southwest of the country. The Pripyat trough is located in the southeast of Belarus, the youngest tectonic structure formed in the Devonian. Allocate transitional tectonic structures - saddles is a platform structure that separates two positive and negative tectonic structures. These include - Latvian, Zhlobinskaya, Polesskaya, Braginsko-Loevskaya.
The territory is characterized by a flat relief. Lowlands occupy 30% of the territory (from 80 to 150 meters high). About half of the territory is occupied by plains with a height of 150 to 200 meters. Hills 200-345 meters high. Uplands are confined to the rise of the crystalline basement - Minsk, Novogrudskaya, Oshmyanskaya, etc. Negative and transitional structures correspond to lowlands. Within the Pripyat trough are located - Polesskaya lowland, within the Latvian saddle - Polotsk. Vitebsk and Orsha uplands within the Orsha depression (reverse relief). And etc.
Methods for mapping various phenomena on thematic physical and geographical maps (method of areas, qualitative and quantitative background, methods of isolines, icons, diagrams).
Way of areas:
The method of areas (from the Latin word "area" area, space) is used to highlight on the map areas of continuous (for example, glaciation) or scattered distribution (for example, rice growing area). In most cases, this method shows the distribution of plants, animals, minerals, agricultural land, etc. In the legend, the conventional sign of the range is usually explained by the words "region (region) of distribution ...."
The range of phenomena that can be displayed by the area method is very large. The only condition for each of these objects is the non-ubiquity of its distribution for the entire territory displayed on the map, since in the latter case the area coincides with the entire area of the map and this method of mapping loses its meaning. The presence of this condition determines the fundamental difference between the methods of qualitative background and areas, although they are very similar in technical execution. The area method is used mainly for the qualitative characterization of the mapped territory, although the area can also be distinguished by quantitative characteristics (for example, an area where the average population density is more than 20 people per km²).
Areas are absolute, outside of which this phenomenon does not occur, and relative, within which this phenomenon has certain properties (for example, the area of industrial development of coal within the area of its occurrence). The relative area is narrower - it shows the places of the greatest concentration of the phenomenon. The ranges are divided into exact and schematic ones depending on the use of real (reliable) or imaginary boundaries. If the mapping object has precise boundaries, then the area will be accurate. Schematic areas are characterized by an approximate display of the phenomenon, when there is no exact data on its location, or for this phenomenon, the uncertainty of boundaries in nature is characteristic.
Graphically, the possibilities of depicting areas are diverse: it is a solid or dotted line of various patterns and colors, coloring or colored shading, geometric or visual icons, or even an inscription.
Ranges can sometimes be accompanied by quantitative indicators, such as the relative density of an animal or bird range, or the average intensity of an event in a range.
The area method is widely used on zoogeographic, geobotanical (animal and plant areola) and other maps of nature, as well as on socio-economic maps that display, for example, areas where certain agricultural crops are grown. Often it is used as an additional method. For example, on an economic map, zones of agricultural specialization are shown using a qualitative background method and, additionally, against the background of coloring areas using special signs, places of cultivation of individual crops (sugar beet, tobacco, etc.) or areas of the most developed horticulture are displayed. Areas can generalize the iconic way. For example, separate icons of deposits of any mineral can be combined into a pool of this mineral.
Qualitative and quantitative background:
Similar information.
When conducting tectonic zoning of any territory, scientists are guided simultaneously by several criteria, the most important of which are invariably:
depth of the crystalline foundation,
thickness of the sedimentary cover.
Structures of I, II, III and other (lower) orders are distinguished in the system of tectonic zoning of the territory of Belarus.
Tectonic structures of the first order within Belarus are the Russian plate, the Azov-Podolsk plate and the Ukrainian shield.
I. The Russian plate lies at the base of most of the country's territory and consists of individual anticlises, syneclises, troughs, horsts, grabens, and saddles.
The Belarusian anticlise occupies the western and central regions of Belarus. Its most elevated part is formed by the Central Belarusian massif.
In the aisles of the Babovnyansky ledge, crystalline rocks lie directly under the Pliocene - Anthropogenic strata. Relatively elevated blocks of the crystalline basement correspond to the Vileika, Mazursky and Bobruisk buried ledges. The Vileika buried ledge and the Central Belarusian massif are separated by the Volozhin graben.
The western part of Belarus is occupied by the slope part of the Voronezh anticlise. The structures of the Voronezh anticlise include the Surazhsky and Gromyatsky buried ledges, which are separated by the Klintsovsky graben.
The Zhlobin saddle separates the Belorussian and Voronezh anticlises and has an asymmetric structure: its northern slope is quite gentle, and the southern slope is a system of stepped faults.
The Belarusian anticlise in the north borders on the Baltic syneclise; in the east, the Orsha depression adjoins it.
Synekliza - (from the Greek syn - together and enklisis - inclination) - an extensive (up to several hundred km in diameter) gentle deflection of the layers of the earth's crust within the platforms, which has predominantly irregular rounded outlines; the slope of the layers on the wings is measured in fractions of a degree.
Within the Baltic syneclise, the basement plunges to a depth of up to 500 m. Its eastern side is limited by powerful faults with an amplitude of up to 300 m. The Neman graben is a particular structure of the Baltic syneclise.
The Orsha depression is huge and is characterized by a significant subsidence of the basement surface in the northeast direction from -800 m to -1700 m. The depression has rather steep edges and a flat bottom. In the central part of this tectonic structure there is the Central Orsha horst with an amplitude of 200-300 m, which separates the Vitebsk and Mogilev troughs.
A trough is a kind of flat, bowl-shaped synclinal folds.
In the southwestern part of Belarus there is the Podlasie-Brest depression, which partially covers the territory of neighboring Poland. Within its limits, the basement surface descends from east to west from - 650 m to - 8 km. From the north and south, the depression is bounded by faults with an amplitude of up to 300 m. In the east of the Podlasie-Brest depression, there are separate brachiosynclines (“brachio” - short, disproportionate) with an amplitude of about 50-80 m, their diameter does not exceed 5 km.
The Polessky saddle separates the Podlasie-Brest depression from the Pripyat trough. The surface of the foundation within the Polessky saddle is characterized by absolute heights from -20 to -500 m. Its width is about 10 km. From the south, this protrusion is limited by a system of faults with an amplitude of 1 to 3 km. Within the Mikashevichi-Zhitkovichi ledge, crystalline rocks occur at a depth of 10 - 30 m and are overlain by Neogene-Anthropogenic deposits. This structure is divided by a system of powerful faults into three horsts:
Zhitkovichsky,
Mikoshevichsky,
Ozernitsky.
The Pripyat trough stretches from west to east for about 300 km, and from north to south - for 140-150 km. The boundaries of the Pripyat trough are a system of stepped faults with an amplitude of 2 - 4 km. The Pripyat trough is characterized by extremely complex fold-block tectonics. Here, tectonic steps, horsts, grabens are distinguished, which, like the trough itself as a whole, were formed as a result of block movements on fault lines. In the northern part of the trough, there are the Rechitsko-Shatilkova and Malodushinsko-Krasnoslobodskaya blocks. The Rechitsko-Shatilkovsky block is about 240 km long and about 10-25 km wide.
The Narovlyansky horst stretches for 150 km and has a width of about 6 km. The absolute marks of the foundation within this tectonic structure range from - 1.8 to - 4.0 km.
In the section of the platform cover of the Pripyat trough, there are huge (up to 4 km) strata of potash and rock salt deposits, which determines a certain specificity of tectonic processes and relief formation.
The Braginsko-Loevsky saddle separates the Pripyat trough from the Dnieper-Donets trough. It is formed by the Braginsky buried ledge and the Loevsky saddle. Within the Bragin buried ledge (length 45 - 50 km), the foundation descends from south to north to a depth of 300 - 1500 m. This structure is limited by faults with an amplitude of up to 3 km. Faults also limit the Loevskaya saddle, which stretches for 50-60 km with a width of 30-40 km. In its axial part, the foundation surface is at a depth of 1500 m.
The Dnieper-Donetsk trough enters the territory of Belarus with its western edge. Its internal structure is generally similar to that of the Pripyat trough. The boundaries of the Dnieper-Donetsk trough are faults of the sublatitudinal direction.
The northernmost part of Belarus belongs to the Latvian saddle, which separates the Baltic syneclise and the Orsha depression. In the central part of the saddle, crystalline rocks lie at elevations of about - 700 m, in the east they go to a depth of about - 1400 m, and from the side of the Belarusian anticlise they rise to - 500 m.
The Velizh saddle belongs to the structures of the Moscow syneclise and is characterized by the depth of the crystalline basement from - 1300 m to - 1400 m.
II. The Azov-Podolsk plate occupies the extreme southwestern part of Belarus. Private tectonic structures of this plate are the Lukovsky-Ratnovsky horst and the Volyn monocline.
Monocline - a type of occurrence of rock layers with the same slope in one direction.
Lukovsko-Ratnovsky horst stretches in the latitudinal direction for 350-400 km and has a width of approximately 13-40 km. This tectonic structure has a block structure and is limited by faults with an amplitude of 100 (in the east) to 1000 m (in the west).
Volyn monocline is characterized by a gradual steady lowering of the foundation to the southwest from 0 to 3 km. Against the background of monoclinal subsidence, several troughs and uplifts stand out with absolute heights from 1.0 to -1.6 km.
III. The Ukrainian shield occupies the extreme southern part of the territory of Belarus. Near the village of Glushkovichi, Lelchitsy district, the rocks of the crystalline basement come to the surface. The Ovruch graben-syncline stands out as a particular structure of the Ukrainian Shield, which is limited by deep faults and extends for 110 km with a width of 5–20 km.
Tectonic setting of Belarus. There is still no single point of view on the structure of the foundation of the East European Platform. With the accumulation of actual geological and geophysical materials and changes in views on the Precambrian history of the Earth's development, the ideas about the structure of the foundation of the East European Platform also changed, which can be clearly seen from the maps of the foundation of the East European Platform on three editions of the International Tectonic Map of Europe, the Map of Precambrian Tectonics continents and others, as well as numerous publications on this topic.
Currently, the most popular scheme of the structure of the basement of the East European Platform is the scheme of S.V. Bogdanova, who identified three major segments in the basement of the East European Platform: Fennoscandinavian, Sarmatian and Volga-Ural, separated by suture zones (see Fig. 3.6) . In her opinion, the latter were inherited by the main Riphean-Early Vendian aulacogenes (Volyn-Orsha-Kresttsovsky, Central Russian, Pachelmsky). The Volga-Ural and Sarmatian segments are composed mainly of the Archean crust, the Fennoscandinavian - mainly of the Early Proterozoic complex
There is a largely alternative point of view on the structure of the foundation of the East European Platform. Analyzing the spatial distribution of the Early Precambrian structural-material complexes of the East European Platform, N.V. Aksamentova came to the conclusion that one of the most characteristic features of the structure of the crystalline basement of the East European Platform is the submeridional orientation of the main structural elements and their mostly symmetrical arrangement: the most ancient granulite and gneiss-amphibolite complexes prevail in the western Baltic-Belarusian-Western Ukrainian geostructural region and in the eastern - Volga-Ural. They are separated by the younger Late Archean-Early Proterozoic granite-greenstone Karelian-Kursk-Krivoy Rog superbelt. Within its boundaries, the most complete and thick sections of Upper Archean and Lower Proterozoic deposits are developed, while in the regions adjacent to the west and east, complexes synchronous in age are either completely absent or distributed over a limited area.
The main difference between the western geostructural region and the eastern one is that in the first of them, the basement at the end of the early-late Proterozoic underwent significant reworking, in connection with which most of the isotope age figures are at the level of 1900-1700 million years, obtained for rocks independently on their composition and actual age.
It is still a controversial question whether the mechanism of plate tectonics was already in operation in the early Proterozoic. In this regard, very convincing data were obtained from the seismic profile BABEL (“Baltic and Bothien echoes from the Lithosphere” - The Babel Project (1992). segment: the more ancient Archean White Sea-Karelian and the younger, mainly Early Proterozoic Baltic-Belarusian.
On the northwestern margin of the Sarmatian segment, according to drilling materials and other geological and geophysical data, the Osnitsko-Mikashevichsky volcano-plutonic belt is distinguished, which stretches as a strip 100-150 km wide, NE-trending from the northwestern corner of the Ukrainian shield and the Teisseira- Tornkvist through the southern part of Belarus and further beyond its borders to the Bryansk, Smolensk and Kaluga regions of Russia, with a total length of more than 650 km. It is limited by deep faults - Stokhodsko-Mogilev in the northwest and Perzhansko-Surazh in the southeast. Most of the belt is overlain by Riphean and Lower Vendian deposits of the Volyn-Orsha trough.
The Osnitsko-Mikashevichi belt is a unique tectonic element of the foundation of the East European Platform. The belt is composed of the youngest igneous complexes, different in composition and conditions of formation, which have not undergone significant regional metamorphism. The belt is discordantly superimposed on older polymetamorphic complexes of the Archean-Early Proterozoic basement. Within the belt, formations are distinguished, the successive change of which from metagabbro-diabase with an age of 2100-2000 Ma to subalkaline gabbro-dolerite (1700 Ma) reflects a long (about 400 million years) and multi-stage history of the development of the belt. N.V. Aksamentova considers the belt to be an intracontinental structure formed as a result of the collision of continental blocks.
S.V. Bogdanova and her colleagues attribute this belt to a boundary structure - a marginal-continental volcanic-plutonic belt, which arose at the edge of the Archean Sarmatian continent as a result of subduction of the oceanic crust. It is unlikely that a volcano-plutonic belt of such a rank could have arisen without the participation of the process of subduction of the oceanic crust under the marginal region of the vast Sarmatian continent. By the time of 1.85 Ga, the continental crust of Fennoscandia had already been formed and subduction was replaced by the collision of the continental segments of Sarmatia and Fennoscandia, the final connection of which into a common basement block occurred about 1.7 Ga ago.
At the junction of these segments, the Central Belarusian (Smolevichsko-Drogichinskaya, according to I.V. Naidenkov) zone was formed, located between the Stokhodsko-Mogilev and Korelichi faults. This zone is a Belarusian segment of a longer - over 600 km (up to the Teisseira-Tornquist zone) Fennoscandinavian-Sarmatian suture zone. The Central Belarusian zone has a very complex structure: it consists of a series of wedge-shaped blocks of metamorphic and igneous complexes of different ages broken by differently oriented faults. A narrow strip of the so-called Rudmyanskaya series stretches along the western edge of the zone (rocks of granulite facies: amphibolite gneisses, calciphyres, schists, pyroxenoliths, marbles, etc.), further - rocks of the Okolovo series (gneiss-shale complex). According to the geological, petrological and geochemical features, the rocks of both strata belong to the island-arc association. Among the igneous formations, the most remarkable are the rocks of the Rusino complex (diabases, metadiabases, metagabbrodiabases, gabbroids, hornblendites), which are close in geochemical characteristics to the ophiolite associations of the ocean floor. On the surface of the Moho, the Central Belarusian zone is generally characterized by an uplift linearly elongated in the northeast direction, which occurs in the center of the zone corresponding to the Minsk granulite massif at depths of about 48 km, and at its southwestern and northeastern extremities - at depths 50-55 km.
The formation of the substance and structure of the earth's crust proceeded along the zone unequally: in some areas, the rocks in the approach zone were subjected to deformations such as bending of the layers, in others they cracked and collapsed under the influence of horizontal pressures, faults were formed, along which, as a result of magmatism processes, rocks of various types were introduced into the upper crust. composition, in the third, deformations manifested themselves in the form of thrusts. All this diversity of the picture of the stress-strain state of the earth's crust of the Central Belarusian zone gave grounds to propose a geological model for the formation of this zone as a suture along which the subduction of the oceanic crust under the Sarmatian continent took place, and then the collision of Fennoscandia and Sarmatia. It is possible that in the late Devonian the formation of a gently sloping transcrustal detachment (detachment) took place along the subduction zone, which in the southern part of the Pripyat paleorift crosses the Moho surface and plunges into the upper mantle.
Thus, according to modern tectonic concepts, a unique geological event took place on the territory of Belarus in the Precambrian - a collision of three large geosegment plates - Sarmatian, Fennoscandian and Volga-Ural, which now form the East European craton. The collision zone is clearly expressed by the Central Belarusian suture zone and the Vitebsk granulite massif. A deep study of this tectonic phenomenon practically began in the 90s of the last century, when complex geological and geophysical studies were carried out along the Varena-Nesvizh-Vystupovichi profile within the framework of the EUROBRIDGE international project.
To date, based on a comprehensive interpretation of geophysical data, the tectonic picture of the earth's crust on the territory of Belarus can be represented by the Lithuanian-Belarusian geoblock, bounded in the north and south by sublatitudinal fault belts, respectively, Polotsk-Kurzeme and Pripyat-Brest. The central part of this geoblock is represented by the Central Belarusian suture zone of northeast strike and the Vitebsk massif of submeridional strike. There are geophysical data that give grounds to assume that in the process of formation of such an architecture of the crystalline basement of Belarus along the Polotsk-Kurzeme and Pripyat-Brest lineaments, a horizontal shift of the Lithuanian-Belarusian block took place in the Late Proterozoic.
An analysis of the tectonic and geophysical picture of the territory of Belarus shows that, due to the above conditions for the formation of the earth's crust, the structure and geodynamics of the formation of the lithosphere in the Belarusian region is specific, anomalous in relation to the adjacent areas of the East European craton.
The confinement to the territory of Belarus of the junction zone of the three largest segments of the earth's crust of the East European craton - Fennoscandinavian, Sarmatian and Volga-Ural - is a favorable prerequisite for the formation of ore-controlling and ore-concentrating zones. And above all in the junction zone of Fennoscandia and Sarmatia.
Fault tectonics. Features of the tectonic development of the territory of Belarus determined the pattern of faults in the basement and in the platform cover. Let us consider the leading deep faults in the consolidated crust of Belarus.
In the Geological Dictionary (1973, pp. 175-176), deep faults are defined as “zones of mobile articulation of large blocks of the earth's crust and the underlying part of the upper mantle, with a length of up to many hundreds and thousands of kilometers with a width sometimes reaching several tens of kilometers. The duration of the development and existence of deep faults is very significant and is measured in periods and eras ... On the surface, deep fault zones are manifested by a thickening of subparallel faults that form complex systems - deep fault belts. Sometimes thrusts occur in zones of deep faults and integumentary and scaly structures appear. Magmatism plays a particularly important role in the development of deep faults. The most characteristic are belts of basic and ultrabasic rocks and serpentinites developed along them. Intrusions of granitoids and volcanic eruptions are often associated with deep faults. Deep faults of ancient platforms usually belong to the closed (blind) type and break only the foundation, manifesting themselves in the platform cover in strengthening platform folded dislocations (swells, placanticlines, flexures). Deep faults of activated platforms manifest themselves in the formation of aulacogens, grabens, and rift systems.”
Many researchers divide deep faults into those penetrating into the upper mantle, and into crustal ones, damping within the earth's crust. According to the depth of their penetration, superdeep faults are distinguished, which originate in the D layer of the mantle, i.e. at a depth of 400-700 km; mid-depth faults that cross the asthenosphere and reach a depth of 100-300 km; subcrustal (through-crustal) deep faults that penetrate into the upper mantle and can reach the roof of the asthenosphere. Crustal faults are divided into two types: upper crustal - those faults that are developed only in the sedimentary cover and granite-metamorphic layer; deep crustal - faults penetrating down to the bottom of the earth's crust.
According to the kinematics, deep faults are divided into deep faults, reverse faults, thrusts, and expansions.
Understanding faults as geological bodies, they are considered as zones of dislocation metamorphism and as zones of geochemical changes in ore concentrations or the placement of magmatic bodies.
Deep faults have three main properties: large extent, significant depth of occurrence, duration and multi-phase development, often with a change in the sign of movement along the fault. In addition, as a rule, deep faults separate large blocks (blocks) of the crust, which are significantly different in history and mode of movement.
Many faults are quite confidently manifested in geophysical fields. Significant cracking, discontinuity of the "fault-body" in the process of tectonic activity leads to deconsolidation of the material of the fault zone, to the dispersion of magnetic minerals. Therefore, strip negative gravitational and magnetic anomalies of a linear nature are often observed above the fault. The possible manifestation of intrusive activity in the marginal fault zones causes narrow linearly elongated positive or negative strip gravity and magnetic anomalies along the fault sides. In the absence of near-edge intrusive bodies, the fault zone is expressed by sharp gravitational steps and strip magnetic anomalies. Chains of magmatic bodies create a system of localized gravitational and magnetic anomalies linearly sustained along the strike of the fault.
High fracturing and watering of the "fault-body" determine favorable conditions for high conductivity of electric current: over such faults, band anomalies of conductivity are observed, associated with a decrease in the electrical resistivity of rocks in the "fault-body".
In a wave seismic field, faults are manifested by a violation of the correlation of waves from the seismic interfaces of media, the appearance of diffracted waves, loss of reflections, a shift in the phases of the in-phase axes in time, anomalously abrupt attenuation of refracted waves occurs, and complex interference phenomena occur. The manifestation of faults in the seismic section is characterized by a lateral change in the velocities of seismic waves, a change in the pattern of reflecting areas (their number and angles of inclination), a sharp vertical shift or even the disappearance of seismic interfaces and, above all, the Moho boundary, the appearance of layers with anomalous seismic characteristics and etc.
According to mainly geophysics data for the territory of Belarus, a map of faults in the consolidated lithosphere of the territory of Belarus was compiled (Fig. 3.10), which have a variety of directions, rank, depth, size, kinematics, etc.
As can be seen from Fig. 3.10, several systems of faults of the consolidated crust are distinguished on the territory of Belarus, differing not only in spatial orientation, but also in the time of initiation and duration of development. Faults of submeridional, northeastern, northwestern and sublatitudinal strikes prevail in the basement of Belarus.
Faults of submeridional direction
It is clearly seen in the diagram of the distribution of faults in the lithosphere of Belarus that the faults of this direction fit into two separated systems: north-north-east and north-north-west, manifested, respectively, in the Fennoscandian and Sarmatian segments of the East European craton. In a narrow strip between these two megablocks, which corresponds to the Central Belarusian suture zone, most of the faults also have submeridional strikes, but still tend to strike structures in the Fennoscandian segment.
Faults of the north-north-west direction are identified mainly in the Vitebsk granulite block in the north-east of Belarus.
Faults of the northeast direction
Faults in this direction can be divided into two groups: the northeastern plan proper and the northeast sublatitudinal plan.
The first group is the faults that are predominantly developed in the Central Belarusian zone and arose in the process of formation of this suture zone in the Early Proterozoic time.
This group of faults mainly occupies a secant position with respect to the structures of granulite areas and is closely related to the formation of the Central Belarusian suture zone at the junction of the Fennoscandinavian and Sarmatian crustal segments.
The second group - faults of northeast-sublatitudinal strike. They are developed mainly in the southern and southeastern parts of Belarus and are associated mainly with the Osnitsko-Mikashevichi magmatic belt.
Faults of northwestern strike on the territory of Belarus are grouped into several zones. Each of these zones is a system of closely spaced discontinuous faults of the fault-slip type with a length from a few tens of kilometers to 150-180 km. The width of the zones ranges from a few kilometers to 50–70 km, with a total length of up to 500 km or more.
The longest is the Berestovetsky fault, stretching from the northern slope of the Ukrainian shield in the direction of Stolin-Ivatsevichi-Volkovysk-Grodno and further outside Belarus up to the Curonian Lagoon. From the southeast, through the central regions of Belarus in the northwest direction, the Oshmyany fault zone is traced.
Faults of sublatitudinal direction
are quite widely represented on the territory of Belarus, although with varying degrees of severity in geophysical fields. According to geological and geophysical features, almost all sublatitudinal disturbances can be combined into three large zones: Polotsk-Kurzeme, Central and Pripyat-Brest. The first and last of these zones isolate a block of geophysical homogeneity in the center of Belarus (Belarusian-Lithuanian tectonic megablock). The structure of the gravitational and magnetic fields, it differs sharply from the regions of the north and south
The Polotsk-Kurzeme fault belt is limited by extended marginal faults: in the north - Liepaja-Lokhnov, and in the south - Neman-Polotsk. Within the intended limits, the fault belt stretches in the latitudinal direction from the coast of the Baltic Sea almost 800 km to the east with a width of 120-180 km. The Polotsk-Kurzem belt can be considered as an extensional structure that formed simultaneously with the entire system of Riphean rift structures of the East European Platform, which were laid down in the junction of the Fennoscandian, Sarmatian, and Volga-Ural segments of the earth's crust. In this system, the Polotsk-Kurzeme belt is a western continuation of the grabens of the sublatitudinal Moscow-Gzhatsk and Tver branches of the grabens of the paleorift system.
In the center of Belarus there is a latitudinal Central system of close discontinuities. It is planned in the area from the northern regions of Poland and further through Grodno-Novogrudok-Smilovichi goes to the Krichevsky and South Krichevsky faults in the east of Belarus. The central system is fixed in a strip about 30-50 km wide by a series of rare discontinuous disjunctives with a relatively small extent. To the west, in northern Poland, this system is controlled by rapakivi massifs, gabbro-anorthosites, the Elk subalkaline massif, and carbonatite bodies, which are characteristic of rejuvenation zones. Crossing the basement structures, the faults of this system break and shift the uneven-aged complexes of the Precambrian basement. This indicates activation processes that occurred along this zone, but within a much wider band.
The Pripyat-Brest sublatitudinal fault system is long-lived and active over many stages of geological history. It stretches along the northern slope of the Ukrainian shield and is considered within the boundaries of the Northern and Southern marginal faults of the Pripyat graben, the Lyakhovichi fault zone in the north, and latitudinal faults that form the Ratnovsky horst in the south. The Polessye latitudinal fault, located south of the Pripyat graben, should be included in the same system.
As can be seen, the consolidated lithosphere of Belarus is broken up by numerous faults of different ages of very different lengths, directions, penetration depths, listricity, horizontal and vertical amplitudes, kinematics, etc. At the same time, analyzing all this variety of faults, one can outline their certain ordering according to hierarchy, direction, and other features. They fix geoblocks with sharp changes in the lateral heterogeneity of the layers of the earth's crust and the entire consolidated lithosphere. The largest fault zones and faults generally coincide with the boundaries of those various geophysical types of the earth's crust in Belarus (Fig. 3.5). This indicates that the selected blocks of the continental lithosphere of Belarus have their own types of the earth's crust and consolidated lithosphere and show their clear large fractal discreteness. A more detailed analysis can also show a more fractional fractality of these crustal blocks.
Rice. 3.10.
according to geophysical data
1 - deep mantle faults, limiting blocks of the earth's crust with different geophysical types; 2 - deep mantle faults; 3 - crustal intrablock deep faults; 4 - local feathering faults; 5 - marginal deep faults of the Pripyat trough; 6 - names of leading faults; 7 - geophysical types of the earth's crust; 8 - the name of the faults: 1-Vladimir-Volynsky, 2-Lutsky, 3-Braginsky, 4-Beshenkovichisky, 5-Volozhinsky, 6-Ivenetsky, 7-Skidelsky, 8-Shchuchinsky, 9-Pruzhansky, 10-Kozlovshchinsky, 11-Kossovsky , 12-Dyatlovsky, 13-Ostrovetsky, 14-Borisovsky, 15-Zaslavlsky, 16-Begomsky, 17-Yachnensky, 18-Kokhanovsky, 19-Smolensky, 20-Gorynsky, 21-Nagornovsky, 22-Simanovichsky, 23-Krichevsky, 24 -South-Krichevsky, 25-Krasnoslobodsky, 26-North-Western, 27-Central, 28-Teterevsky, 29-Loevsky, 30-Berestovetsky, 31-Oshmyansky, 32-Naliboksky, 33-Dobryansky, 34-Zhlobinsky, 35-Lepelsky , 36-Lyakhovichsky, 37-Orekhovsky, 38-Vitebsky, 39-Bogushevsky, 40-Svislochsky, 41-Polessky, 42-Lubashevsky-Rudensky.
The scheme was compiled by R.G. Garetsky, G.I. Karataev, I.V. Dankevich., Yu.V. Belov based on the materials of I.K. Pashkevich, R.A. Apirubite, I.V. Dankevich, G.I. Emelyanov, G.I. based on the interpretation of the anomalous gravitational and magnetic fields according to well-known criteria, using literary sources of different years and, above all, the “Tectonic Map of Belarus and adjacent territories” at a scale of 1:1000000 edited by R.G. Garetsky (1974), and the “Geological map of the crystalline basement Belarus and Adjacent Territories" scale 1:1000000 by N.V. Aksamentova and I.V. Naidenkov (1990). Editor R.G.Garetsky.
earth core crust deep
