Tectonic scheme of the Siberian platform. East Siberian platform

The SIBERIAN PLATFORM is one of the large, relatively stable sections of the continental earth's crust, belonging to the number of ancient (pre-Riphean) platforms, occupies the middle part of North Asia. Siberian platform is limitedzones of deep faults - marginal seams, well-defined gravitational steps, and has a polygonal outline. The modern boundaries of the platform took shape in the Mesozoic and Cenozoic and are well expressed in the relief. The western boundary of the platform coincides with the valley of the Yenisei River, the northern one - with the southern margin of the Byrranga mountains, the eastern one - with the lower reaches of the Lena River (Verkhoyansk marginal trough), in the southeast - with the southern tip of the Dzhugdzhur ridge; in the south, the boundary runs along the faults along the southern margin of the Stanovoy and Yablonovy ridges; then, going around from the north along a complex system of faults in Transbaikalia and the Baikal region, it descends to the southern tip of Lake Baikal; the southwestern boundary of the platform extends along the Main East Sayan Fault.

On the platform, the Early Precambrian, mainly Archean, basement and platform cover (Riphean-Anthropogenic) stand out. Among the main structural elements of the platform stand out: the Aldan Shield and the Leno-Yenisei Plate, within which the foundation is exposed on the Anabar massif, Olenyok and Sharyzhalgai uplifts. The western part of the plate is occupied by the Tungusskaya, and the eastern part by the Vilyui syneclise. In the south there is the Angara-Lena trough, separated from the Nyu depression by the Peledui uplift.

The foundation of the platform is sharply dissected and composed of highly metamorphosed Archean rocks, which have latitudinal strikes in the western half and north-northwest strikes in the eastern half. The weaker metamorphosed strata of the Lower Proterozoic (Udokan Group) are preserved in separate depressions and grabens, lie gently and are formations of the protoplatform cover.

A typical platform cover begins to form from the Riphean time and 7 complexes are distinguished in its composition. The Riphean complex is represented by carbonate-terrigenous, red-variegated rocks 4000-5000 m thick, filling aulacogenes and gentle depressions. The Vendian-Cambrian complex is composed of shallow-water terrigenous and terrigenous-carbonate deposits, and in the Angara-Lena trough - and salt-bearing (lower - middle Cambrian) strata, 3000 m. m. The Devonian-Lower Carboniferous complex is limited; in the south, the Devonian is represented by continental red-colored strata with traps, in the north - by variegated carbonate-terrigenous deposits; in the Vilyui syneclise - a thick trap stratum and salt-bearing deposits, 5000-6000 m. - tuff and upper - lava parts (undifferentiated tholeiitic basalts); all deposits are intruded by dikes, stocks, and basalt sills; in the Devonian, Triassic and Cretaceous, kimberlite explosion pipes are formed in the northeast of the platform. The Upper Triassic - Cretaceous complex is composed of continental and less often marine sandy-clayey coal-bearing deposits, 4500 m, distributed only on the outskirts of the platform. The Cenozoic complex is developed locally and is represented by continental deposits, weathering crusts, and glacial formations. The Paleogene Popigai astrobleme is known in the Anabar massif.

The Siberian Platform is characterized by intense magmatism, which manifested itself in the Early Proterozoic, Riphean - Early Cambrian, Middle Paleozoic, Upper Paleozoic - Triassic and Late Mesozoic. Trap magmatism absolutely dominates in volume (more than 1 million km3).

The Siberian platform is rich in minerals. Large deposits iron ore are located on the Aldan shield, in the Angara-Ilim iron ore basin. Copper-nickel sulfide deposits are associated with traps in the Norilsk ore region, and cuprous sandstones are developed in the Udokan series on the Aldan Shield. Diamonds are confined to kimberlite pipes. Large deposits of coal are known on the Siberian platform (the Lena coal basin, the Tunguska coal basin, the Irkutsk coal basin, the Kansko-Achinsk coal basin, the South Yakutsk coal basin), deposits of rock and potassium salt, gypsum, phosphorites, manganese and gold ores, graphite, mica ( phlogopite), fluorite and other minerals. Mountain Encyclopedia

Geological history

1. During the Archean and the beginning of the Proterozoic, most of the basement of the East Siberian Platform was formed.
2. At the end of the Proterozoic (Vend) and the beginning of the Paleozoic, the platform was periodically covered by a shallow sea, resulting in the formation of a thick sedimentary cover.
3. At the end of the Paleozoic, the Ural Ocean closed, the crust of the West Siberian Plain consolidated, and it, together with the East Siberian and East European platforms, formed a single continent.
4. In the Devonian, an outbreak of kimberlite magmatism.
5. A powerful outbreak of trap magmatism occurred at the Permian–Triassic boundary.
6. In the Mesozoic, some parts of the platform were covered by epicontinental seas.
7. At the boundary of the Cretaceous and Paleogene, rifting and a new outbreak of magmatism, including carbonatite and kimberlite, took place on the platform. Russian Wikipedia

To the essence of the concept

The concept of "Siberian platform" was first introduced into the geological literature by A. A. Borisyak in 1923. Since then, the Siberian platform has been understood as a vast region of Eastern Siberia with a two-story tectonic structure. This is a segment of the earth's crust, relatively stable from the Riphean to the Cenozoic, limited by folded structures of the Late Proterozoic, Paleozoic and Mesozoic age. The lower structural stage - the basement is composed of Early Precambrian predominantly crystalline rocks, the upper (sheath) - non-metamorphosed relatively weakly dislocated sedimentary and volcanogenic-sedimentary strata with age from Riphean to Cenozoic. The area of ​​the Siberian platform in the modern erosion section is over 4 million square kilometers.

Hydrography

The Siberian platform is located between the rivers Yenisei in the west and the Lena with a tributary Aldan in the east. These mighty rivers flow in a submeridional direction and flow into the marginal seas of the Arctic Ocean. The Yenisei flows into the Kara Sea, the Lena into the Laptev Sea. Their tributaries cross the territory of the Siberian Platform mainly in the sublatitudinal direction. The main tributaries of the Yenisei (from south to north): Angara or Upper Tunguska, Podkamennaya Tunguska, Lower Tunguska and Kureika. All of them are right tributaries of the Yenisei. The main right tributaries of the Lena River (from south to north): Kirenga, Vitim, Olekma and Aldan; left tributaries (from south to north): Kuta, Vilyui. In the north of the platform, in addition, the Olenek, Anabar and Khatanga rivers flow into the Laptev Sea (from east to west).

Orography

The relief of the platform is very diverse. Most of its territory is occupied by the Central Siberian Plateau. Against the background of the general high standing of the surface of the platform, separate more elevated areas stand out, which are called plateaus. In its northwest there is the Putoransky (Putorana Plateau), in the northeast - the Anabarsky, in the west - the Tungussky and Zaangarsky, in the southwest - the Angarasky, in the south - the Leno-Angarasky and Prilensky plateau. From the south, the platform is surrounded by mountain structures, the uplift of which also involves its marginal parts (from east to west): the Al-Dano-Stanovoe and Baikal-Patom highlands, the mountains of the Western Baikal region and the Eastern Sayan, the uplift of the Yenisei Ridge. From the north, the Central Siberian Plateau is surrounded by lowlands: West Siberian in the west and northwest, North Siberian in the north and Central Yakut in the northeast. The last two occupy part of the territory of the Siberian platform. To the east of the Central Yakut lowland lies the Verkhoyansk Range, to the north of the North Siberian Lowland there is the sea, and on the Taimyr Peninsula the Byrranga Range. Buldygerov, p.5

Sources

1. Buldygerov V.V. Geological structure of the Irkutsk region. Irkutsk. 2007
2. Mountain Encyclopedia. In 5 vols. M. "Soviet encyclopedia. 1984-1991
3. Russian Wikipedia

Recently, in a television program dedicated to the relief and climate of Siberia, I heard such a phrase as "the shield of the Siberian platform." I thought about what kind of shield it is, how it looks, and how many of them exist within this platform. The attraction of additional sources of information helped to expand my geographical knowledge.

Location of the Siberian Platform

Before dealing with the shields, I wanted to learn more about the Siberian platform, its location and features. It turns out that she has ancient origin and belongs to the number of the earliest blocks of the continental crust of the planet. The platform is part of the Eurasian Plate. In relation to the modern geographical location, we can say that it is located within Russian Federation. From north to south, it practically pierces the entire territory of the country, and from west to east it stretches from the Yenisei to the Lena.

Anabar and Aldan shields

What is a platform shield? This is the place where its foundation comes to the surface. The rest of the platform basement at that time is covered with a kind of cover of igneous rocks. On the territory of the Siberian platform there are two shields - Aldan and Anabar. In a thesis presentation, the Aldan shield can be described as follows:

• occupies the southeastern part of the platform;
• in relief terms, it practically coincides with the highlands of the same name;
• is the location of the only deposit on the planet used in jewelry and having a high cost of the mineral charoite (Lilac stone in the south of Yakutia).

As for the Anabar shield, its originality can be briefly described as follows:

• has a less extensive size compared to the Aldan shield;
• localized in the north of the platform within the Yakut part of the Central Siberian Plateau;
• in terms of relief, it is compatible with the Anabar plateau, maximum height which is equal to 905 m;
• contains traces of ancient glaciation;
• is the location of deposits of such minerals as magnetites and apatites.

The Siberian platform is bounded by deep fault zones - marginal sutures, well-defined gravity steps, and has a polygonal outline. The modern boundaries of the platform took shape in the Mesozoic and Cenozoic and are well expressed in the relief. The western boundary of the platform coincides with the valley of the Yenisei River, the northern one with the southern margin of the Byrranga Mountains, the eastern one with the lower reaches of the Lena River (Verkhoyansk marginal trough), in the southeast with the southern tip of the Dzhugdzhur Ridge; in the south, the boundary runs along the faults along the southern margin of the Stanovoy and Yablonovy ridges; then, going around from the north along a complex system of faults in Transbaikalia and the Baikal region, it descends to the southern tip of Lake Baikal; the southwestern boundary of the platform extends along the Main East Sayan Fault.

On the platform stands out mainly the foundation and the platform cover (-). Among the main structural elements of the platform stand out: Aldan shield and Leno-Yenisei plate, within which the foundation is exposed on the Anabar massif, Olenyok and Sharyzhalgay uplifts. The western part of the plate is occupied by the Tungusskaya, and the eastern part by the Vilyui syneclise. In the south there is the Angara-Lena trough, separated from the Nyu depression by the Peledui uplift.

The foundation of the platform is sharply dissected and composed of highly metamorphosed Archean rocks, which have latitudinal strikes in the western half and north-northwest strikes in the eastern half. Weaker metamorphosed strata of the Lower Proterozoic (Udokan series) are preserved in separate depressions and grabens, lie gently and are formations of the protoplatform cover.

A typical platform cover begins to form from the Riphean time and 7 complexes are distinguished in its composition. The Riphean complex is represented by carbonate-terrigenous, red-variegated rocks 4000-5000 m thick, filling aulacogenes and gentle depressions. The Vendian-Cambrian complex is composed of shallow-water terrigenous and terrigenous-carbonate deposits, and in the Angara-Lena trough - and saline (lower - middle Cambrian) strata, 3000 m. The Ordovician-Silurian complex is represented by variegated terrigenous rocks, as well as limestones and dolomites, 1000- 1500 m. The Devonian-Lower Carboniferous complex is limited; in the south, the Devonian is represented by continental red-colored strata with traps, in the north - by variegated carbonate-terrigenous deposits; in the Vilyui syneclise - a thick trap stratum and salt-bearing deposits, 5000-6000 m. - tuff and upper - lava parts (undifferentiated tholeiitic basalts); all deposits are intruded by dikes, stocks and sills of basalts; in the Devonian, Triassic and Cretaceous, kimberlite explosion pipes form in the northeast of the platform. The Upper Triassic-Cretaceous complex is composed of continental and less often marine sandy-clayey coal-bearing deposits, 4500 m, distributed only on the outskirts of the platform. The Cenozoic complex is developed locally and is represented by continental deposits, weathering crusts, and glacial formations. The Paleogene Popigai astrobleme is known in the Anabar massif.

The Siberian platform is characterized by intense magmatism, manifested in the early Proterozoic, Riphean - early Cambrian, Middle, Upper Paleozoic - Triassic and late. Trap magmatism absolutely dominates in volume (more than 1 million km3).

The Siberian platform is rich

6.1. general characteristics

Siberian platform - the second ancient platform in Russia. It covers an area of ​​4.4 million square meters. km, which is 26% of the territory of the Russian Federation.

The platform is located between the rivers Yenisei - in the west and Lena - in the east.

In contrast to the East European, the Siberian platform has a predominantly mid-mountain relief with absolute elevations of 1,000-1,500 m. Aldan Highlands, Stanovoy and Dzhugdzhur ridges. Along the territory of the Siberian platform, in addition to the above, the rivers Nizhnyaya and Podkamennaya Tunguska, Angara, Vitim, Olekma, Aldan, belonging to the basin of the Arctic Ocean, flow.

The boundaries of the platform are: in the west and south - the structures of the Ural-Mongolian belt, in the east - the structures of the Pacific belt, in the north - the Yenisei-Khatanga trough, which separates the Siberian platform from the folded structures of Taimyr.

6.2. Main structural elements

The Siberian platform has a two-tiered structure.

The lower tier is the Archean-Early Proterozoic foundation, the upper tier is the cover. In contrast to the East European Platform, where the formation of the cover began in the Early Riphean, the cover complex on the Siberian Platform began to form in the second half of the Early Proterozoic. Areas of development of the platform cover meets Central Siberian (Leno-Yenisei) plate.

The foundation on the Siberian platform lies at depths from 0 to (according to geophysical data) 10-12 km.

Shields correspond to the exits of the foundation to the surface. There are two shields on the platform: in its northern part - Anabar shield and Olenek uplift, in the southeastern part - Aldan (Aldano-Stanovoy) shield.

The following structures are located within the Central Siberian (Lena-Yenisei) Plate.

On the frame of the Anabar shield and the Olenek uplift is located Anabar anteclise, on the frame of the Aldan shield - Aldan anteclise; in the western part of the platform is Yenisei anteclise, in the southwestern Angara-Lena anteclise. The anteclises are predominantly composed of Riphean and Early Paleozoic complexes.

Between the Anabar and Yenisei anteclises located Tunguska syneclise, composed of Late Paleozoic-Mesozoic formations, including Permian-Triassic trap complexes that are unique in terms of distribution area and volume. Between the Anabar and Aldan anteclises is located Leno-Vilyui syneclise, performed mainly by Mesozoic sedimentary strata. Located in the northeastern part of the platform Pre-Verkhoyansk trough, also composed of Mesozoic sedimentary strata and occupying a transitional position to the Verkhoyansk-Chukotka folded region of the Pacific belt.

A diagram of the main structures of the Siberian platform is shown in Fig. 5.

Rice. 5. Scheme of the main structures of the Siberian Platform

1. Late Jurassic-Early Cretaceous foredeep. 2. Jurassic-Cretaceous syneclises and superimposed depressions. 3. Permo-Triassic trap complexes. 4. Early Paleozoic anteclises. 5. Ledges of the crystalline basement. 6. Boundaries of the main structures. 7. Local grabens and horsts.

8. Astroblems. 9. Folded platform frame. 10. Faults. Roman numerals indicate: I - Aldan shield (Ia - Aldan block, Ib - Stanovoi block), II - Aldan anteclise, III - Angara-Lena anteclise, IV - Yenisei anteclise, V - Anabar anteclise, VI - Anabar shield, VII - Olenek uplift, VIII - Tunguska syneclise, IX - Lena-Vilyui syneclise, X - Cis-Verkhoyansk trough.

6.3. Foundation structure

The foundation of the platform is formed by Archean and Early Proterozoic complexes of deeply metamorphosed rocks, and it is represented on the Aldan (Aldan-Stanovoi), Anabar shields and the Olenek uplift.

Aldan (Aldano-Stanovoy) shield. It is located in the southeastern part of the platform, where it has tectonic junctions with the structures of the Ural-Mongolian belt.

Aldan (Aldano-Stanovoy) shield according to its features geological structure is divided into two blocks: northern - Aldan and southern - Stanovoy, separated by a large fault. The differences between these two blocks are that Paleozoic and Mesozoic granitoids are widespread in the Stanovoi block, reflecting its tectonic-magmatic activation associated with magmatism that accompanied the formation of the Pacific belt.

archaeus(AR). Archean metamorphic formations of the Aldan block ( Aldan complex) are conditionally divided into three parts. In the lower part there are ferruginous quartzites, high-alumina crystalline schists, biotite-garnet and garnet-sillimanite granulites. Within this part of the section, there are bodies of crystal-bearing pegmatites, as well as iron ore deposits of the ferruginous quartzite formation. In the middle part - amphibole, biotite-amphibole, hypersthene gneisses, marble; at the top, biotite, hypersthene, and garnet-biotite gneisses. The Aldan complex contains two groups of intrusive rocks of different ages: 1) Archean granite-gneisses, which form large concordant bodies with gradual transitions to host rocks; 2) Early Proterozoic leucocratic granites, represented by small bodies with tearing contacts.

In the Stanovoi block, Archean formations ( deadlift series) are represented by biotite, two-mica, epidote-biotite, amphibole gneisses, and amphibolites. These formations are broken large quantity granites of the Archean, Early Proterozoic, as well as Paleozoic and Mesozoic ages.

The total thickness of the Archean metamorphic formations is at least 10 km.

Lower Proterozoic (PR 1). The Early Proterozoic formations include garnet-hypersthene, hypersthene-amphibole-diopside, biotite, garnet-biotite, etc. gneisses, schists, marbles, calciphyres. The thickness of these formations is estimated at no less than 12 9 km. Large arrays of anorthosites, gabbro-anorthosites of the same age are represented here.

Anabar shield and Olenek uplift. In these structures located in the northern part of the platform, Archean(AR) metamorphites are arranged as follows. In their lower part, two-pyroxene, amphibole-pyroxene plagiogneisses, amphibolites, and quartzites occur; higher are leucocratic hypersthene gneisses and biotite gneisses; even higher - garnet and garnet-biotite gneisses, calciphyres, diopside rocks; the section ends with biotite-amphibole gneisses, amphibolites, and quartzites. In the development fields of these formations, Archean and Early Proterozoic intrusive massifs of charnockites (hypersthene granites), granodiorites, alaskites, and migmatites occur.

6.4. Case structure

As noted above, the beginning of the formation of the platform cover on the Siberian Platform dates back to the second half of the Early Proterozoic. This period includes education udokan series, which is a protoplatform cover in the western part of the Aldan Shield. The Udokan series, about 12 km thick, has a three-membered structure. In its lower part there are biotite-graphite shales, carbonaceous phyllites, quartzites, in the middle part - marbled dolomites and dolomitic limestones, in the upper part - red-colored cross-bedded sandstones, to which the Udokan deposit of copper sandstones, unique in scale, is confined.

On the Central Siberian Plate, seven structural-stratigraphic complexes (from bottom to top) are distinguished in the structure of the platform cover: Riphean, Vendian-Cambrian, Ordovician-Silurian, Devonian-Lower Carboniferous, Middle Carboniferous-Middle Triassic, Jurassic-Cretaceous and Cenozoic.

An important feature of the structure of the cover of the Siberian Platform, which distinguishes it from the East European one, is the wide participation of igneous complexes of different ages in it (Fig. 6).

Rice. 6. Scheme of distribution of igneous complexes of different ages

on the Siberian platform

1-2 - Jurassic-Cretaceous: 1 - granitoids and syenites ( a), felsic and intermediate volcanics ( b),

2 – alkaline gabbroids and syenites; 3-6 - Late Paleozoic-Triassic: 3 - alkaline-ultrabasic formation (a- kimberlite pipes, b– arrays of alkaline-ultrabasic composition); 4-6 - trap formation (4 - intrusions, 5 - lavas, 6 - tuffs); 7-8 - Middle Paleozoic: 7 - trap formation ( a- intrusions b– volcanics), 8 – alkaline-ultrabasic formation, kimberlites; 9 - Late Proterozoic-Early Cambrian traps, intrusions of ultrabasic and alkaline rocks; 10 - platform boundaries.

Riphean complex.

Distributed on the frames of the Aldan, Anabar shields and the Olenek uplift.

Lower Riphean(R1). At the base of the sediments of this age lie gray and red-colored quartz and quartz-feldspar sandstones, sometimes containing glauconite, and gravelites. Dolomites lie above. The total thickness is about 1.5 km.

Middle Riphean(R2). It is represented by three times repeating rhythms, in the lower parts of which quartz-glauconite sandstones, siltstones and mudstones occur, and in the upper parts - limestones and dolomites. The total thickness is about 3 km.

Upper Riphean(R3). It is represented mainly by a stratum of dolomites with a thickness of about 700 m.

Sedimentation on the platform was accompanied by intrusion of dikes, sills, and stocks of trap-type gabbrodolerites, as well as small intrusions of alkaline-ultrabasic composition.

Vendian-Cambrian complex.

Wend(V). It is distributed mainly in anteclises. In the section of the Vendian deposits, as a rule, dolomites and argillaceous limestones, underlain by sandstones, sometimes red-colored, predominate. The thickness of these deposits in different parts of the platform varies within 1–2 km.

Cambrian(Є ). In general, the Cambrian is characterized by carbonate-sulphate-halogen deposits.

Lower and Middle Cambrian ( Є 1-2) is represented by a sequence of alternating limestones, dolomites, anhydrites, clays, rock and potash salts. Power up to 2 km.

For the Upper Cambrian ( Є 3) are characterized by predominantly massive dolomites, in some places facies replaced by red-colored cross-bedded sandstones. The thickness is about 500 m.

Ordovician-Silurian complex.

Ordovician(O) is represented by all three divisions.

In the sediment Lower Ordovician(O 1) are sandstones and siltstones in the lower parts of the section, passing higher into dolomites and limestones. In places, the section is completely represented by carbonate strata. Power up to 1 km.

TO Middle Ordovician (O2) include terrigenous-carbonate deposits composed of sandstones, siltstones, calcareous sandstones, marls containing phosphorite concretions and phosphorite pebbles. In places, the section contains dolomites and gypsum. Power up to 300 m.

Upper Ordovician(O 3) is represented by red sandstones, mudstones with gypsum interlayers, facies replaced by limestones and marls. Power up to 300 m.

deposits Silurian(S) are characterized by the predominant carbonate composition of the sediments.

Lower Silurian(S1) is represented by a 100-150-meter limestone stratum underlain by dark gray shale. In some places, limestone facies are replaced by gypsum-dolomite strata.

Upper Silurian(S2) up to 300 m thick is composed in the lower part of the section of dolomites, marls and limestones with interlayers of gypsum, and in the upper part of the gypsum-clayey-dolomite sequence.

Devonian-Lower Carboniferous complex.

This complex is limited in distribution. A feature of this complex is that at this age level, intense trap magmatism began to appear on the Siberian platform, which reached its maximum development in the Middle Carboniferous-Middle Triassic time.

Devonian(D). Common, as a rule, on the frames of syneclise.

Lower Devonian(D1). The deposits of this time are represented by variegated carbonate siltstones and mudstones with limestone interbeds up to 100 m thick.

Middle Devonian(D2). This level includes carbonate-saline deposits, which include clayey and bituminous limestones, dolomites, gypsums, anhydrites, horizons alternating in section and along strike. rock salt.

TO Upper Devonian(D3) include mudstones, gypsum, anhydrites - in the lower part of the section, dolomites and limestones - in the middle part and dolomites, gypsum, anhydrites with layers of rock salt - in the upper part. Power up to 750 m.

Education Lower Carboniferous(C1) have a complex and variegated lithofacies composition. For the Tournaisian stage ( C 1 t) are characterized by limestones replaced laterally by strata of alternating sandstones and basaltic lavas. As part of the Visean ( C 1v) and Serpukhov ( C1s) stages are dominated by terrigenous-carbonate deposits (sandstones, siltstones, limestones). Thickness 100-900 m.

In the Devonian-Early Carboniferous time, magmatism of basic and alkaline-ultrabasic composition was widely manifested on the territory of the Siberian Platform. In section D 1 and D 2, there are powerful flows and covers of basaltic lavas of the trap type. Numerous dikes, sills, stocks of dolerites and gabbrodolerites are associated with them. The dikes are up to 20 m thick and 160 km long.

Alkaline-ultrabasic intrusions (alkaline pyroxenites, peridotites) are accompanied by dike and tubular bodies of kimberlites containing minerals associated with diamonds (pyrope, picroilmenite, etc.)

Middle Carboniferous-Middle Triassic (Tunguska) complex. These are predominantly continental formations that make up the Tunguska syneclise, covering an area of ​​about 1.5 million square kilometers, which is almost 25% of the area of ​​the entire Siberian platform.

In the section of this complex, three strata are distinguished: the lower one is productive (C 2 -P), the middle one is tuffaceous (T 1, in some places descending into P 2), the upper one is lava (T 1-2).

Middle Carboniferous-Permian(C2-P). The formations of this stratigraphic interval are identified as a productive stratum.

Deposits C 2 and C 3 are composed of mudstones, siltstones, sandstones with layers and lenses of coals, which are of industrial importance in some places. Power up to 400 m.

The Permian deposits are also coal-bearing. They are represented by alternating mudstones, siltstones, conglomerates, gravelstones with coal seams reaching a thickness of 70 m. In a number of places in the section of Permian deposits, covers of basaltic lavas and horizons of their tuffs occur. The thickness of the Permian formations is 600-800 m.

Lower-Middle Triassic(T 1-2). This stratigraphic interval is represented mainly by tuffs and basaltic lavas containing interlayers, horizons, beds of tuff siltstones, tuff mudstones, tuff sandstones, and, in places, limestones and even anhydrites. The thickness of the formations of this interval reaches 2 km.

Permo-Triassic(R-T) trap magmatism forms the bulk of the Tunguska syneclise. This magmatism is realized in the form of thick (2.5-3 km) accumulations of basalts, their tuffs and accompanying intrusions, occupying a volume of about 1 million km3. This igneous complex is dominated by lavas and intrusions, which occupy about 80% of the entire section, while tuff material accounts for only 20%. Basalts often have amygdaloidal textures. As a result of synvolcanic hydrothermal activity, the tonsils are often filled with calcite, including water-transparent Icelandic spar, often of industrial importance. The intrusions are mainly represented by dolerites and gabbrodolerites, which form stocks, sills, dikes, saucer- and funnel-shaped bodies. Dikes often form close swarms, stretching for 400–500 km, with individual dikes up to 100 m thick. Most of the intrusions are undifferentiated. In the case of differentiated (chamber) intrusions, they show a certain zoning expressed as follows: picrite dolerites are found in the lower parts of the chambers, olivine dolerites in the middle parts, and leucocratic and quartz dolerites and gabbrodolerites and even granodiorites in the upper parts. The deposits of copper-nickel ores of the Norilsk region are confined to the picrite dolerites of the lower parts of the chambers. Dolerite intrusions have a metamorphosing contact effect on host rocks. In particular, when dolerites cross coal seams, graphite deposits are formed in the contact zone (Kureiskoye and other deposits).

Triassic(T)alkaline ultramafic magmatism manifested mainly in the northern part of the platform, between the Anabar shield and the Olenek uplift. The area of ​​this magmatism is known in the geological literature as the Meimecha-Kotui alkaline-ultrabasic province. (The name is given by the Meimecha and Kotui rivers).

The stratum of alkaline ultrabasic rocks, at least 1000 m thick, is composed of lavas of nepheline basalts, their tuffs, trachybasalts, hawaiites, augitites, and meimechites. They are of Early-Middle Triassic age, and facies notice, and in some places overlap the trap complex. Lavas are associated with intrusive rocks in the form of dikes and sills of nepheline dolerites and meimechites. Complex multiphase differentiated intrusions up to hundreds of square kilometers in size are also known. The early phases of these intrusions are represented by pyroxenites, olivinites, peridotites, and the late phases by ijolites and melteigites, with which carbonatites are associated. An indispensable element of alkaline ultrabasic magmatism are kimberlite pipes with an area of ​​up to 3.5-5 thousand square meters. km, as well as kimberlite dikes up to several meters thick and a few kilometers long. About 300 kimberlite pipes are known on the platform, about half of which are diamondiferous. Among the kimberlite pipes, there are not only Triassic, but also Jurassic and Devonian-Early Carboniferous, which are of industrial importance.

On the slopes of the Olenek uplift, marine terrigenous deposits of the Triassic occur, which are not associated with the Tunguska complex. They are represented by sandstones, siltstones, mudstones, and tuffites, containing locally small horizons of marls. Such an association is characteristic of the entire section of Triassic deposits, from the Lower to the Upper Triassic inclusive. The thickness of these deposits reaches 800-1000 m.

Jurassic-Cretaceous Complex.

It is distributed mainly on the outskirts of the platform, within syneclises and troughs.

Yura(J). Jurassic deposits, which are predominantly continental in nature, are represented on the platform by all three divisions.

The generalized section of the Jurassic deposits is as follows.

Lower Jurassic (J1) is represented by conglomerates, polymictic sandstones, clays, locally interbedded with limestones and siderites, and brown coal. Power up to 470 m.

Middle Jurassic (J2) is composed of sandstones and clays up to 150-200 m thick.

Upper Jurassic (J3) is represented mainly by siltstones and sandstones with seams of coking coal, reaching a thickness of 25 meters, and therefore of industrial importance (the Neryungri deposit in the South Yakutsk coal basin). Power up to 1.5 km.

Cretaceous deposits(TO), formed by essentially terrigenous rocks, in principle inherit the areas of Jurassic deposits.

Lower Cretaceous(K 1) is present in both marine and continental facies. Marine deposits (clays, siltstones) are confined to the northern margin of the platform, where they are overlain by continental coal deposits. In the Leno-Vilyui syneclise, the Lower Cretaceous deposits are exclusively continental, coal-bearing, containing up to 35 coal seams with a working thickness of up to 5 m, which are developed at the Lenskoye deposits. coal basin. The thickness of the Lower Cretaceous deposits reaches 1.8 km.

Upper Cretaceous(K 2) is distributed only in the Lena-Vilyui syneclise, where it reaches a thickness of 450-1,000 m, and here quartz sands, sandstones, clays.

In the Jurassic and Cretaceous, the Siberian Platform, mainly in its southeastern part, experienced intense magmatic activity. It is realized in the form of dolerite dikes (up to 100 km long and up to 250 m thick) (continuing Permian-Triassic trap magmatism), intrusions of kimberlites, syenites, nepheline syenites, granites, granodiorite-porphyries.

Cenozoic complex.

Paleogene(P)and Neogene(N) deposits are limited. Their most complete section is presented in the Lena-Vilyui syneclise. Here, the Lower Paleogene (Paleocene) is represented by quartz and quartz-feldspar sands up to 380 m thick, the Middle Paleogene (Eocene) is absent, the Upper Paleogene (Oligocene) is sands, clays, lignites up to 30 m thick, the Lower Neogene (Miocene N 1) - these are ferruginous sands (up to 120 m thick). The section ends with Pliocene-Quaternary (N 2 -Q) sands, pebbles and clays. All these deposits have a continental genesis - these are lacustrine, deluvial, alluvial, deluvial-proluvial accumulations.

Quaternary (Q) sediments (sands, pebbles, clays) are also continental formations, and they are represented by all genetic types - alluvial, eluvial, proluvial, deluvial, glacial, fluvioglacial.

6.5. Minerals

The Siberian platform is rich in various minerals located both in its basement and in the mantle. These include fuel and energy raw materials, ferrous, non-ferrous, rare, noble metals, non-metallic minerals.

Minerals in the foundation of the platform

Black metals.

In the metamorphic formations AR 2 of the Aldan shield, deposits of the formation of ferruginous quartzites are localized Charo-Tokkinsky iron ore region (on the border of the Republic of Sakha-Yakutia with the Irkutsk and Chita regions). This area covers an area of ​​about 1.5 thousand square kilometers. The largest explored object in this area is Tarynnakh deposit with iron ore reserves of about 1.3 billion tons. The total iron ore reserves of the region are estimated at 16 billion tons with an average iron content in the ore of 27%. Magnetite, cummingtonite-magnetite and pyroxene-amphibole-magnetite mineral types of ores stand out in the deposits.

In the Early Proterozoic layered array of gabbro-anorthosites, Chineiskoe deposit of disseminated titanomagnetite and ilmenite-titanomagnetite ores. The main ore minerals are titanomagnetite and ilmenite. The average contents are: Fe - 25.6%, TiO 2 - 4.9%, V 2 O 5 - 0.34%, platinum and palladium are present in the ores in quantities of about 100 mg / t.

Minerals in the platform cover

Hydrocarbon raw materials. There are two oil and gas bearing provinces (OGP) on the platform – Leno-Tungusskaya and Leno-Vilyuiskaya.

Leno-Tungusskaya oil and gas field covers an area of ​​2.8 million square meters. km, covering most platform cover structures. It revealed 20 different-scale deposits. The carbonate and terrigenous deposits of the Upper Riphean and Vendian-Lower Cambrian are productive, located at depths of 1.5-3.5 km. The most famous is Markovskoe field.

Leno-Vilyui oil and gas field confined to the Lena-Vilyui syneclise and Predverkhoyansk trough, occupies an area of ​​280 thousand square meters. km. It revealed 8 different-scale predominantly gas fields, the most famous of which are Ust-Vilyuiskoye and Sredne-Vilyuiskoye. The deposits of the Upper Permian, Lower Triassic, Lower and Upper Jurassic, established at depths of 1-4 km, are productive.

The fields of these oil and gas fields are the main source of raw materials for the oil and gas pipeline under construction Eastern Siberia- Pacific Ocean.

solid fuel. The following major coal-bearing basins are represented on the platform: Lena, South Yakutsk, Irkutsk.

Lensky coal-bearing basin covers an area of ​​about 600 thousand square meters. km, being confined to the Leno-Vilyui syneclise and Predverkhoyansk trough. Terrigenous deposits of the Jurassic, Cretaceous and Neogene are coal-bearing. The coals are brown and stone. Explored reserves of coal amount to 3.2 billion tons. The total geological resources of coals in this basin amount to almost 1.7 trillion tons, of which 945 billion tons fall to the share of brown coals. This basin contains 10% of the estimated world coal resources and 25% of the coal resources of the former USSR.

South Yakutsk the coal-bearing basin covers an area of ​​25 thousand sq. km. The terrigenous deposits of the Upper Jurassic and Upper Cretaceous are coal-bearing. Explored coal reserves are about 5.4 billion tons. Coals are predominantly stone. The most famous is the deposit Neryungri, on the basis of which the city of the same name was created.

Irkutsk the coal-bearing basin occupies an area of ​​37 thousand sq. km. The terrigenous Jurassic deposits are coal-bearing. Explored coal reserves are 7.5 billion tons, including hard coal - 5.2 billion tons, brown - 2.3 billion tons. The most famous is Cheremkhovskoye field.

Black metals.

Angaro-Ilimsky the iron ore basin is confined to the southeastern edge of the Siberian platform. The deposits of this basin, the most famous of which is Korshunovskoye, are represented by skarn-magnetite ores. They are formed at the contacts of tubular bodies of Permian-Triassic gabbrodolerites (trap complex) intruding terrigenous-carbonate deposits of the Cambrian and Ordovician. The main ore mineral is magnetite. The total reserves of the basin are estimated at 2 billion tons of ore with an iron content of 26-35%.

Angaro-Katskaya A group of iron ore deposits is confined to the Permo-Triassic Tunguska trap complex, and in their type, conditions of formation and composition of ores, they are largely similar to the objects of the Angara-Ilim basin. The total reserves of iron ores are estimated at almost 550 million tons with an average iron content of 33%.

The tectogenesis of the whole of North Asia is determined by the Siberian platform, which occupies a vast territory between the Yenisei and the Lena.

In the south, the platform extends to the latitude of the southern shore of Lake Baikal, in the southeast - to the Stanovoy Ridge and the coast Sea of ​​Okhotsk, in the north, the edge of the platform lies at the latitude of the Khatanga mouth.

Over the entire vast area, the Siberian Platform is covered by a thick sedimentary cover. Its crystalline foundation protrudes within the Anabar massif and the Aldan Shield. The most important feature of the platform is its folded framing of consecutive zones of Baikal, Caledonian, Hercynian, and Mesozoic folding.

According to modern concepts (Tectonics of Eurasia, 1966), the crystalline basement of the Siberian Platform has a heterogeneous structure and consists of heterogeneous blocks formed in the pre-platform and platform periods (Bulina and Spizharsky, 1967). Older paleoblocks are preserved sections of folded systems that make up the base of the platform. The systems also include median massifs, structural-facies zones, anticlinoria and synclinoria, etc. With further division of these structural elements into small parts, neoblocks were formed, which formed from the Middle Proterozoic to the Early Triassic. Blocks of different nature are separated by faults. The regularities of the structure of the crystalline basement of this platform can, however, be interpreted in another historical and geological context. The main structural elements of the Siberian platform are the Anabar and Aldan Precambrian crystalline shields, as well as its Precambrian folded frame - the Stanovoy Range, the Eastern Sayan and the Yenisei Ridge.

The Siberian platform is one of the most striking examples of the successive growth of the continental crust at the expense of the oceanic one. In the northeast of the mainland, folded formations fill the entire space between the platform and the Pacific Ocean, and are located between the Siberian platform and the crystalline massifs of Central and South Asia. A wide zone of Baikalids separates the Anabar and Aldan shields. The Angara-Lena trough, which extends in a northeasterly direction, is connected with it. On its continuation, the Vilyui syneclise is located and further - the Lena-Vilyui Mesozoic trough (Mikhailov and Filatov, 1967).

Precambrian deposits take part in the structure of the crystalline basement of the Siberian Platform. On the Anabar Shield, the most ancient Early Archean formations are represented by volcanogenic-magmatic rocks of basic composition (Tugarinov and Voitkevich, 1966). Late Archean formations are characterized by the predominance of biotite-amphibole gneisses and the appearance of carbonate rocks containing intrusions of alkaline granitoids and charnockites. The eroded surface of the Archean group of sediments is overlain by Proterozoic (Sinian) sandstones, gravelstones, limestones, and dolomites, which are 1500 million years old.

Upper Archean deposits compose the Olenek crystalline massif, located 300 km east of Anabar. The age of the biotite granites exposed there, like those of the Anabar, is 2100 Ma (Tugarinov and Voitkevich, 1966).

The metamorphic strata of the Anabar Shield are collected in simple large folds extending north westbound and complicated by secondary folding and faults.

Located in the southeastern part of the Siberian Platform, the Aldan shield extends in the north to the middle reaches of the Aldan, in the east to the upper reaches of the river. Uchur, in the south - to the Stanovoy Range and in the west - to the Olekma Valley. Further to the west, Precambrian structures are found in the Baikal Highlands and the Eastern Sayan Mountains. The southern and western folded margins of the shield, including the Stanovoi Ridge and the Olekminsky zone, are correlated with the Karelian folding (Tectonics of Eurasia, 1966). The central part of the Aldan shield is composed of metamorphic rocks subdivided into three series with a total thickness of 20,000 m. Their geochemical features are determined by the predominance of silica and alumina in the lower series, iron-magnesian silicates in the middle series, and carbonate compounds in the upper series. The entire Aldan section can be divided into two complexes: the lower one, associated with rocks of the basic composition, and the upper one, with a predominance of carbonate strata. The age of the rocks of the Aldan complex is 2800-1900 Ma (Tugarinov, Voitkevich, 1966).

The metamorphic strata of the Aldan massif form large simple folds extending in the northwestern, submeridional direction. According to A. A. Paturaev and I. Ya. Bogatykh (1967), these structures form a complex system of echelon-shaped folds, are characterized by great complexity and the presence of subordinate folded structures of various orders. Numerous faults create a fold-block structure of the shield. Crushing zones and faults extend in the same direction as folding. There are a number of stages in their formation. The development of the platform basement ended in the Precambrian.

In the post-Cambrian time, the Siberian Platform was an arena of intense volcanism and sedimentation. In the Late Paleozoic and Early Mesozoic, significant subsidence in the southwest of the platform led to the formation of the Tunguska syneclise. Large structures are the Vilyui and Khatanga syneclises, the Irkutsk, Rybinsk, and Kansk-Yenisei troughs. The Angara-Lena trough, as noted, divides the Siberian platform into two independent parts. These troughs served as basins for the accumulation of platform cover, the formation of which began as early as the Late Proterozoic.

The thickness of the sedimentary cover on the Siberian platform is not the same. It is most significant within the Vilyuisky trough - about 3500 m, in the Tunguska syneclise - less and on the slopes of the platform is insignificant. The total thickness of sedimentary deposits is about 7000 m.

Sediments from the Cambrian to Quaternary systems take part in the structure of the sedimentary cover of the Siberian Platform, of which especially great importance in the structure of the relief they have Cambrian, Carboniferous, Permian and Triassic. The Cambrian system is composed of red sandy-argillaceous salt-bearing and carbonate rocks. Salt is being developed in a number of regions. In most cases, the Cambrian deposits lie quietly and form separate domes. In the Angara-Lena trough, the Cambrian and Silurian formations are collected into linear folds that make up the Prilensk fold zone.

Ordovician deposits are common on the margins of crystalline massifs and in the Angara-Lena trough. They are represented by shallow marine formations, which include a lot of limestone. Limestones are also found in the Silurian deposits. Devonian rocks fill the Rybinsk depression and lie on the outskirts of the Tunguska syneclise. The latter is characterized by carboniferous strata of the Carboniferous.

The Permian and Triassic deposits on the Siberian Platform include a thick volcanogenic sequence, in which traps are especially distinguished. They form dikes, veins, thick sheet-like deposits and covers in the north of the platform. Jurassic deposits are concentrated in the depressions of the Khatanga, Irkutsk, Kansk-Yenisei, Vilyui, and others. Tertiary deposits are widespread in the lower part of the Vilyui. Marine Quaternary formations of boreal transgression are known in the Khatanga and Lena depressions. During the maximum phase of glaciation, the Siberian platform was covered with continental ice. The features of the distribution of the sedimentary platform cover and its composition determine the main features of the relief of many regions of this country.

The Siberian platform is the main structural part of the tectonosphere, which determines the main features of the structure of Northeast Asia. The crystalline foundation of the platform consists of separate parts different ages and structures connected at different times by sedimentary formations of predominantly geosynclinal origin.

Structures of different ages differ primarily in the composition and degree of metamorphism of the rocks that compose them. Structural-geomorphological analysis of the platform basement gives grounds to see a multi-island structure in its paleotectonics. There are two independent (Anabar and Aldan) centers of build-up of the Siberian Platform until the Late Proterozoic, which developed in parallel. In the era of Baikal folding, they were combined into one massif. The seam connecting the Anabar and Aldan shields runs in the direction of the Angara-Lena trough, filled with Cambrian, Silurian, and in the northeast and southwest - Jurassic deposits. A relic of the most ancient Angara-Lena geosyncline is, perhaps, the Baikal depression, pressed against the outskirts of the Aldan massif. Its location in a tectonically active zone can explain its long existence.

The Anabar massif is the oldest center of formation of the continental crust in North Asia. It occupied a central place in the early Archean island system, stretching in a northeasterly direction. In addition to the Anabar shield, this system included, in separate links, the buried massifs Igarka, Nizhneoleneksky, and Lyakhovsky, separated by troughs, subsequently filled with geosynclinal deposits. In the northwest, the Khatanga geosynclinal trough separated the paleotectonic system of the Anabar Islands from the Taimyr one, which formed later. The strike of Taimyr structures is generally northeast. The same strike can be traced on Bolshevik Island, which, according to structural and geomorphological features, apparently belongs to the island system of Novaya Zemlya. The latter is separated from the Taimyr system by the Kara Sea trough, which is a relic of the Paleozoic interisland basin.

The anticlinorium of Taimyr is composed of Precambrian metamorphological deposits, including numerous small Paleozoic intrusions (Tectonics of Eurasia, 1966). In Taimyr, rocks of the trap formation are known. Sandy-argillaceous, often flyschoid deposits take part in the structure of the trough. They are collected in steep linear folds. On the southeastern edge of the Khatanga trough, Jurassic and Cretaceous deposits are common, forming gentle cuestas. To the west, younger formations are developed. Calm landforms are associated with them.

The Taimyr fold country is a polystructural formation. It developed around individual massifs or islands of the outer (in relation to the Anabar shield) system from the Proterozoic to the Permian. According to the features of paleotectonics and geographical location, the structure is a marginal part of the Siberian platform, according to the time of formation, it is a Hercynian subplatform.

The Aldan Shield was a key part of the Precambrian complex island system stretching in a northeasterly direction from Baikal to Chukotka. The inner part of this system was the Aldan massif proper. On its outer side, there was an island arc, which included massifs of the Stanovoy Ridge and the Seimkan Mountains. A system of islands adjoined it, stretching in a northwesterly direction. Its main constituent parts were the Kolyma and Omolon massifs. To the north, in general, almost in a latitudinal southeast direction, the Chukchi paleotectonic island system of Northeast Asia stretched, passing into Alaska in North America. It includes the massifs Uelen, Wrangel Island, etc.

The Chukchi paleotectonic island system is the structural boundary between the basins of the Arctic and Pacific Oceans, outlined in the Precambrian.

The depressions between the paleotectonic island arcs of Northeast Asia served for a long time as basins for the accumulation of geosynclinal deposits. The latter are dominated by volcanogenic formations. Dislocated sedimentary strata determine the modern geomorphological appearance of this country.

The tectonic relief of the Siberian Platform has a long history of development. Structural, accumulative and denudation forms naturally combine here. All these complexes are determined to some extent by the lithological composition of relief-forming rocks. The surface of the platform is characterized by the Central Siberian in the north and the Aldan plateau in the south. They correspond to the Anabar and Aldan shields. The plateau delimits the Leno-Vilyui alluvial lowland, which occupies a trough and adjacent parts of the shields.

In the northwest, the Anabar shield is adjacent to the North Siberian accumulative lowland, which is located within the Khatanga trough. Further to the west rises the Taimyr Highlands. The Byrranga mountains stand out in its relief. Their structure is dominated by sandstones and traps, the massifs and rocks of which give the relief of the mountains a uniform severity.

The structural topography of the southern part of the Siberian Platform is much more complex. Throughout its length from the Sea of ​​Okhotsk to Lake Baikal, it is bordered by mountain ranges and highlands. They are characterized by a folded-block structure. General feature their topography - the ancient leveling surface - is also the top surface. Located at different heights, it serves as an indicator of the amplitude of movements that occurred after its formation. The magnitude of vertical displacements of blocks in many cases is measured in thousands of meters.

The mountainous structures of the southern part of the platform are separated by significant intermountain depressions made by younger sediments compared to the rocks that form the ridges. Their relief is flat, accumulative. In some places, it becomes more complicated depending on the lithological composition of the rocks.

The ancient structural relief of the considered part of the Siberian Platform is the relief of the Stanovoi Range, the Patom Upland, the Vitim Plateau, the Eastern Sayan Mountains, Eastern Tuva, etc. The Stanovoi Range extends eastward from the middle reaches of the Olekma for 700 km. Further, its continuation is the Dzhugdzhur ridge. In the orography of the Stanovoy Range, two or three parallel ridges are distinguished, elongated in the direction of the strike of the ridge. Its structure is dominated by gneisses and shales of Precambrian age, containing intrusions of various igneous rocks. In some places, strata of sedimentary rocks of the Cambrian and Jurassic systems occur.

The relief of the Stanovoy Ridge is characterized by wide rounded ridges and individual dome-shaped mountain peaks. In the highest parts of the mountains, rocky bald mountains and stone placers predominate. Their foothills are covered with talus and covered with deluvial-proluvial covers. The upper reaches of the rivers here have wide and flat valleys. Down the slope, the valleys deepen and become narrow. Glacigenic landforms are common in the western part of the range. Such common features relief are also characteristic of the Baikal mountainous country.