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The Siberian Platform, occupying the entire Central Siberian Plateau, is located in the interfluve of the Yenisei and Lena from Taimyr in the north to the Baikal Highlands and the Eastern Sayan Mountains in the south. The Siberian platform is composed of an Archean - Early Proterozoic foundation and sedimentary cover, where the main role is played by widespread Paleozoic and Precambrian deposits. Unlike the East European Platform, the Siberian Platform is characterized by a more complex geological structure associated with a wide distribution of faults, the presence of powerful trap intrusions and pronounced lithological-facial heterogeneity of Lower Paleozoic, Vendian and Riphean deposits.
The Siberian platform has Ar-Chaean-Early Proterozoic crystalline. The section of the Upper Proterozoic-Phanerozoic cover contains shallow-marine terrigenous and carbonate sediments, rock and potassium salts, continental coal-bearing series, and a trap complex. In the center of the platform there is a strip of kimberlite pipes; plutons of basic and alkaline rocks are developed in the north and southeast. The foundation of the Sino-Korean platform (Sino-Korean) is formed by Archean and Lower Proterozoic complexes.
The Siberian platform has a two-tier structure. The lower structural stage is composed of complexly dislocated and highly metamorphosed formations of Archean and Early Proterozoic ages, forming the foundation of the platform. They emerge on the day surface on the Aldan and Anabar shields and in the Angara-Kan part of the Yenisei Ridge. The upper structural stage is composed of rocks from Late Proterozoic to Quaternary age. It is divided into a number of floors corresponding to certain stages of sedimentation and - formation of tectonic structures.
The Siberian platform occupies a huge area, and the permafrost conditions here are also varied. In general, for the territory, the average annual temperature of rocks under natural conditions and when they are disturbed varies from 4 in the southwest to -9 in the northeast. Khety) in natural conditions, the average annual temperature of the rocks varies from - 6 5 for areas with moss cover and minimal snow accumulation to - 4 for areas with turf cover and maximum snow accumulation. The destruction of the moss-peat cover leads to an increase in the average annual temperature of the rocks from - 2 with maximum snow accumulation to - 6 with compacted snow cover. Disturbance of surface conditions increases the range of changes in the average annual temperature of rocks.
The Siberian platform is a type of ancient platform. Formations of all geological systems participate in its structure. Heavily metamorphosed rocks of the Archean and Lower Proterozoic form a crystalline basement, which is exposed on the surface of the Anabar and Aldan shields, and in the internal field of the platform is buried under a cover of sediments with a thickness of up to 10 - 20 km in sinecli.
The Precambrian Siberian Platform occupies the space between the Yenisei and Lena rivers. Its boundaries are deep faults that separate the platform in the west from the Hercynian West Siberian plate, in the east from the mesozoids of Northeast Eurasia, in the south from the activated regions of the Mongol-Okhotsk belt. In the north, the border is drawn conditionally within the shelf north of the islands of the Severnaya Zemlya archipelago.
Siberian platform, since the volume of drilling and seismic exploration here was insignificant, and other research methods were ineffective due to the complex geological structure due to the presence of a thick trap cover, evaporites and a developed network of faults. A fundamental assessment of the possible industrial oil and gas content of Lower Paleozoic and Precambrian deposits became possible thanks to the discovery in 1973 of the first oil and gas field in the Kuyumba basin, which is now being explored.
The Cambro-Ordovician-Silurian deposits of the Siberian platform are characterized by a predominantly carbonate composition. Taking into account the universally developed fractures of the basement deposits (G.P. Sverchkov, V.L. Dsdoev, G.B. Ostryi, etc.), as well as the phenomenon of formation of secondary porosity inherent in carbonate rocks, the reservoir properties of deposits of this age in general can be considered favorable for formation of oil and gas accumulations.
Siberian platform and is confined to the stage of the same name.
The Siberian platform, complicating the Sobinsko-Tete - Ra megaswell of the Katanga saddle, separates the Baykitskaya and Nepa-Botuobinskaya anteclises.
S-3 of the Siberian platform - Dokl.
The territory of the Siberian Platform is rich in hydropower resources, the development of which predetermined the development of hydraulic engineering construction in the east of the country from this region. Here in the 60s the following were built: the Irkutsk hydroelectric station - the firstborn of the Angara-Yenisei cascade; largest in the world Bratsk hydroelectric power station, which created the largest reservoir with a capacity of 169 billion m3; first on Far North high rock-fill dam of the Vilyuiskaya hydroelectric power station; Mamakanskaya HPP, and in 1970 the first units of the northernmost Ust-Khantayskaya HPP were launched.
Considering the Siberian platform, one cannot fail to mention explosion tubes - peculiar structures formed as a result of the breakthrough of magmatic melts onto the surface. Associated with the explosion pipes are primary diamond deposits, as well as small occurrences of oil, gas, semi-liquid and solid bitumen.
In the Siberian platform, the East Siberian megaprovince is distinguished, which includes the Leno-Tunguska, Leno-Vi-Lyu and Yenisei-Anabar oil and gas provinces.
6.1. general characteristics
The Siberian platform is 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 Yenisei rivers in the west and Lena rivers in the east.
Unlike the East European Platform, the Siberian Platform has predominantly mid-mountain relief with absolute elevations of 1,000-1,500 m. In the central part of the platform there is the Central Siberian Plateau, in the southeast - the Aldan Highlands, the Stanovoy and Dzhugdzhur ridges. Along the territory of the Siberian Platform, in addition to those named, flow the rivers Nizhnyaya and Podkamennaya Tunguska, Angara, Vitim, Olekma, Aldan, which belong to the Arctic Ocean basin.
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, separating the Siberian platform from the folded structures of Taimyr.
6.2. Main structural elements
The Siberian platform has a two-tier structure.
The lower tier is the Archean-Early Proterozoic foundation, the upper tier is the cover. Unlike the East European Platform, where the formation of the cover began in the Early Riphean, on the Siberian Platform the cover complex began to form in the second half of the Early Proterozoic. The areas of development of the platform case are responsible 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 – Aldansky (Aldano-Stanovoi) shield.
The following structures are located within the Central Siberian (Leno-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. Anteclises are composed predominantly of Riphean and Early Paleozoic complexes.
Between the Anabar and Yenisei anteclises Tunguska syneclise is located, composed of Late Paleozoic-Mesozoic formations, including Permian-Triassic trap complexes that are unique in their distribution area and volume. Between the Anabar and Aldan anteclises there is Leno-Vilyui syneclise, made mainly of Mesozoic sedimentary strata. In the northeastern part of the platform is located Pre-Verkhoyansk trough, also composed of Mesozoic sedimentary strata and occupying a transitional position to the Verkhoyansk-Chukchi folded region of the Pacific belt.
A diagram of the main structures of the Siberian Platform is shown in Fig. 5.
Rice. 5. Diagram of the main structures of the Siberian Platform
1. Late Jurassic-Early Cretaceous marginal trough. 2. Jurassic-Cretaceous syneclises and superimposed depressions. 3. Permo-Triassic trap complexes. 4. Early Paleozoic anteclises. 5. Protrusions of the crystalline foundation. 6. Boundaries of main structures. 7. Local grabens and horsts.
8. Astroblemes. 9. Folded frame of the platform. 10. Rifts. Roman numerals indicate: I – Aldan shield (Ia – Aldan block, Ib – Stanovoy block), II – Aldan anteclise, III – Angara-Lena anteclise, IV – Yenisei anteclise, V – Anabar anteclise, VI – Anabar shield, VII – Olenek uplift, VIII – Tunguska syneclise, IX – Leno-Vilyui syneclise, X – Pre-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-Stanovoy), Anabar shields and the Olenek uplift.
Aldan (Aldan-Stanovoy) shield. It is located in the southeastern part of the platform, where it has tectonic connections with the structures of the Ural-Mongolian belt.
The Aldan (Aldan-Stanovoi) shield, according to the peculiarities of its geological structure, is divided into two blocks: the northern - Aldan and southern - Stanovoi, separated by a large fault. The differences between these two blocks are that Paleozoic and Mesozoic granitoids are widespread in the Stanovoy block, reflecting its tectono-magmatic activation associated with magmatism that accompanied the formation of the Pacific belt.
Archaea(AR). Metamorphic formations of the Archean Aldan block ( Aldan complex) are conventionally divided into three parts. The lower part contains 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 there are amphibole, biotite-amphibole, hypersthene gneisses, marbles; in the upper part there are biotite, hypersthene and garnet-biotite gneisses. The Aldan complex contains two groups of intrusive rocks of different ages: 1) Archean granite-gneisses, forming large consonant bodies with gradual transitions to the host rocks; 2) Early Proterozoic leucocratic granites, represented by small bodies with discontinuous contacts.
In the Stanovoy block, Archean formations ( deadlift series) are represented by biotite, two-mica, epidote-biotite, amphibole gneisses, and amphibolites. These formations are intruded by a large number of granites of Archean, Early Proterozoic, as well as Paleozoic and Mesozoic ages.
The total thickness of 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, crystalline schists, marbles, calciphyres. The thickness of these formations is estimated to be no less than 12 9 km. Large massifs of anorthosites and 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 in the following way. In their lower part lie two-pyroxene, amphibole-pyroxene plagiogneisses, amphibolites, and quartzites; 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 fields of development of these formations lie Archean and Early Proterozoic intrusive massifs of charnockites (hypersthene granites), granodiorites, alaskites, and migmatites.
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. Education dates back to this time 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 lie biotite-graphite schists, carbonaceous phyllites, quartzites, in the middle part - marbleized dolomites and dolomitized limestones, in the upper part - red cross-bedded sandstones, to which the Udokan deposit of cuprous sandstones, unique in scale, is confined.
On the Middle Siberian Plate, in the structure of the platform cover, seven structural-stratigraphic complexes are identified (from bottom to top): 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 Platform, is the widespread participation of igneous complexes of different ages in it (Fig. 6).
Rice. 6. Scheme of location of igneous complexes of different ages
on the Siberian platform
1-2 – Jurassic-Cretaceous: 1 – granitoids and syenites ( A), volcanics of felsic and intermediate composition ( b),
2 – alkaline gabbroids and syenites; 3-6 – Late Paleozoic-Triassic: 3 – alkaline-ultrabasic formation (A– kimberlite pipes, b– massifs 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 and Anabar shields and the Olenek uplift.
Lower Riphean(R 1). At the base of deposits of this age lie gray and red quartz and quartz-feldspathic sandstones, sometimes containing glauconite, and gravelites. Dolomites lie above. The total thickness is about 1.5 km.
Middle Riphean(R 2). It is represented by threefold 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(R 3). It is represented mainly by a dolomite sequence with a thickness of about 700 m.
Sedimentation on the platform was accompanied by the intrusion of dikes, sills and stocks of trap-type gabbrodolerites, as well as small intrusions of alkaline-ultrabasic composition.
Vendian-Cambrian complex.
Vend(V). Distributed mainly in anteclises. The section of Vendian deposits, as a rule, is dominated by dolomites and clayey limestones, underlain by sandstones, sometimes red-colored. 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-sulfate-halogen deposits.
Lower and Middle Cambrian ( Є 1-2) is represented by a sequence of alternating limestones, dolomites, anhydrites, clays, rock and potassium salts. Power up to 2 km.
For the Upper Cambrian ( Є 3) are characterized by predominantly massive dolomites, in places replaced by red cross-bedded sandstones. Thickness is about 500 m.
Ordovician-Silurian complex.
Ordovician(O) is represented by all three departments.
As part of sediments Lower Ordovician(O 1) sandstones and siltstones are represented in the lower parts of the section, passing higher into dolomites and limestones. In some places the section is entirely 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 nodules and phosphorite pebbles. In some 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, faciesally replaced by limestones and marls. Power up to 300 m.
Sediments Silurian(S) are characterized by a predominant carbonate composition of sediments.
Lower Silurian(S 1) is represented by a 100-150-meter thickness of limestone, underlain by dark gray shales. In some places, limestones are faciesally replaced by gypsum-dolomite strata.
Upper Silurian(S 2) up to 300 m thick is composed of dolomites, marls and limestones with gypsum layers in the lower part of the section, and gypsum-clay-dolomite strata in the upper part.
Devonian-Lower Carboniferous complex.
This complex has a limited distribution. The peculiarity of this complex is that at this age level, intense trap magmatism began to appear on the Siberian Platform, which received its maximum development in the Middle Carboniferous-Middle Triassic time.
Devonian(D). Common, as a rule, on the frames of syneclises.
Lower Devonian(D 1). Sediments of this time are represented by variegated carbonate siltstones and mudstones with limestone interlayers up to 100 m thick.
Middle Devonian(D 2). This level includes carbonate-salt deposits, which include clayey and bituminous limestones, dolomites, gypsum, anhydrites, and rock salt horizons alternating in section and along strike.
TO Upper Devonian(D 3)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(C 1) have a complex and variegated lithologic-facies composition. For the Tournaisian Stage ( C 1 t) are characterized by limestones, replaced laterally by a thickness of alternating sandstones and basaltic lavas. As part of the Visean ( C 1 v) and Serpukhov ( C 1 s) tiers are dominated by terrigenous-carbonate deposits (sandstones, siltstones, limestones). Thickness 100-900 m.
In Devonian-Early Carboniferous times, mafic and alkaline-ultrabasic magmatism widely manifested itself on the territory of the Siberian Platform. Sections D 1 and D 2 contain powerful flows and covers of trap-type basaltic lavas. Numerous dikes, sills, dolerite and gabbrodolerite stocks are associated with them. The thickness of the dikes reaches 20 m, and their length is 160 km.
Alkaline-ultrabasic intrusions (alkaline pyroxenites, peridotites) are accompanied by dyke- and pipe-shaped kimberlite bodies containing diamond satellite minerals (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 sq. km, 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 places descending into P 2), the upper one is lava (T 1-2).
Middle Carboniferous-Permian(C2-P). Formations of this stratigraphic interval are identified as productive strata.
Sediments C 2 and C 3 are composed of mudstones, siltstones, sandstones with layers and lenses of coals, which in some places are of industrial importance. Power up to 400 m.
Permian deposits are also carboniferous. They are represented by alternating mudstones, siltstones, conglomerates, gravelites with coal seams reaching a thickness of 70 m. In a number of places, the section of Permian sediments contains covers of basaltic lavas and horizons of their tuffs. 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, layers of tuffaceous siltstones, tuffaceous mudstones, tuffaceous sandstones, and in some places limestones and even anhydrites. The thickness of the formations of this interval reaches 2 km.
Permo-Triassic(R-T) trap magmatism composes the main volume 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 km 3. This igneous complex is sharply dominated by lavas and intrusions, occupying about 80% of the entire section; tuff material accounts for only 20%. Basalts often have almond-like textures. As a result of synvolcanic hydrothermal activity, amygdalae are often filled with calcite, including water-transparent Iceland spar, often of industrial importance. Intrusions are represented mainly by dolerites and gabbrodolerites, composing stocks, sills, dikes, saucer- and funnel-shaped bodies. Dikes often form close swarms, stretching for 400-500 km, with the thickness of individual dikes up to 100 m. Most intrusions are undifferentiated. In the case of differentiated (chamber) intrusions, they exhibit a certain zoning, expressed as follows: in the lower parts of the chambers there are picritic dolerites, in the middle parts - olivine dolerites, in the upper parts - leucocratic and quartz dolerites and gabbrodolerites and even granodiorites. Deposits of copper-nickel ores in the Norilsk region are confined to the picrite dolerites of the lower parts of the chambers. Dolerite intrusions have a metamorphosing contact effect on the host rocks. In particular, when dolerites cross coal layers, 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 after the Meimecha and Kotui rivers).
The thickness of alkaline ultrabasic rocks, at least 1000 m thick, is composed of lavas of nepheline basalts, their tuffs, trachybasalts, Hawaiiites, augitites, and meimechites. They are of Early-Middle Triassic age, and faciesly mark, and in places overlie, the trap complex. Intrusive rocks in the form of dikes and sills of nepheline dolerites and meimechites are associated with lavas. 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, and peridotites; the later phases are represented 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 diamond-bearing. 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 lie marine terrigenous sediments of the Triassic, not associated with the Tunguska complex. They are represented by sandstones, siltstones, mudstones, tuffites, locally containing small horizons of marls. This association is characteristic of the entire section of Triassic deposits - from the Lower Triassic to the Upper Triassic inclusive. The thickness of these deposits reaches 800-1000 m.
Jurassic-Cretaceous complex.
Distributed mainly on the outskirts of the platform, within syneclises and troughs.
Yura(J). Jurassic sediments, which are predominantly continental in nature, are represented on the platform by all three departments.
The generalized section of Jurassic deposits is as follows.
Lower Jurassic (J 1) is represented by conglomerates, polymictic sandstones, clays, and in places with interlayers of limestone and siderites and brown coals. Thickness up to 470 m.
Middle Jurassic (J 2) is composed of sandstones and clays up to 150-200 m thick.
Upper Jurassic (J 3) is represented mainly by siltstones and sandstones with layers of coking coals reaching 25 meters in thickness, and therefore of industrial importance (Neryungrinskoye 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 represented in both marine and continental facies. Marine sediments (clays, siltstones) are confined to the northern edge of the platform, where they are overlain by continental coal-bearing sediments. In the Lena-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 in the deposits of the Lena 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, and clays participate in its composition.
In Jurassic and Cretaceous times, intense magmatic activity occurred on the Siberian Platform, mainly in its southeastern part. It is realized in the form of dolerite dikes up to 100 km long and up to 250 m thick (continuing Permo-Triassic trap magmatism), intrusions of kimberlites, syenites, nepheline syenites, granites, and granodiorite porphyries.
Cenozoic complex.
Paleogene(P)and Neogene(N) deposits are limited in distribution. Their most complete section is presented in the Leno-Vilyui syneclise. Here, the Lower Paleogene (Paleocene) is represented by quartz and quartz-feldspathic 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) is 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 are of continental origin - these are lacustrine, deluvial, alluvial, and 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 a variety of minerals located both in its foundation and in its cover. These include fuel and energy raw materials, ferrous, non-ferrous, rare, precious metals, non-metallic minerals.
Minerals in the platform foundation
Black metals.
In the AR 2 metamorphic formations of the Aldan shield, deposits of the ferruginous quartzite formation are localized Charo-Tokkinskogo iron ore region (on the border of the Republic of Sakha-Yakutia with Irkutsk and Chita regions). This area covers an area of about 1.5 thousand sq. km. The largest explored object in this area is Tarynnakhskoe deposit with iron ore reserves of about 1.3 billion tons. General reserves Iron ore in the region is estimated at 16 billion tons with an average iron content of 27% in the ore. Magnetite, cummingtonite-magnetite and pyroxene-amphibole-magnetite mineral types of ores are distinguished at the deposits.
Localized in the Early Proterozoic layered gabbro-anorthosite massif Chineiskoe deposit of disseminated titanomagnetite and ilmenite-titanium magnetite ores. The main ore minerals are titanomagnetite and ilmenite. Average contents are: Fe - 25.6%, TiO 2 - 4.9%, V 2 O 5 - 0.34%, the ores contain platinum and palladium in quantities of about 100 mg/t.
Minerals in the platform cover
Hydrocarbon raw materials. There are two oil and gas provinces (OGP) on the platform – Leno-Tunguska and Leno-Vilyui.
Leno-Tunguska oil and gas field occupies an area of 2.8 million square meters. km, covering most of the structures of the platform cover. It has identified 20 deposits of different sizes. Carbonate and terrigenous sediments of the Upper Riphean and Vendian-Lower Cambrian, located at depths of 1.5-3.5 km, are productive. The most famous is Markovskoe field.
Leno-Vilyuiskaya oil and gas field confined to the Lena-Vilyui syneclise and the Pre-Verkhoyansk trough, occupies an area of 280 thousand square meters. km. It identified 8 different-scale predominantly gas fields, the most famous of which are Ust-Vilyuiskoe And Sredne-Vilyuiskoe. The deposits of the Upper Permian, Lower Triassic, Lower and Upper Jurassic, found at depths of 1-4 km, are productive.
The deposits of these petroleum gas fields are the main source of raw materials for the Eastern Siberia – Pacific Ocean oil and gas pipeline under construction.
Solid fuel . The following most important coal-bearing basins are represented on the platform: Lensky, South Yakutsky, Irkutsk.
Lensky The coal-bearing basin occupies an area of about 600 thousand square meters. km, being confined to the Leno-Vilyui syneclise and the Pre-Verkhoyansk trough. The terrigenous deposits of the Jurassic, Cretaceous and Neogene are coal-bearing. Brown and stone coals. Explored coal reserves amount to 3.2 billion tons. The total geological resources of coal in this basin amount to almost 1.7 trillion tons, of which brown coal accounts for 945 billion tons. This basin contains 10% of the world's estimated coal resources and 25% of the coal resources of the former USSR.
South Yakutsk The coal-bearing basin occupies an area of 25 thousand sq. km. The terrigenous deposits of the Upper Jurassic and Upper Cretaceous are coal-bearing. Explored coal reserves amount to about 5.4 billion tons. The 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 covers an area of 37 thousand sq. km. The terrigenous Jurassic deposits are carbon-bearing. Explored coal reserves amount to 7.5 billion tons, including hard coal - 5.2 billion tons, brown coal - 2.3 billion tons. The most famous is Cheremkhovskoe 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 are Korshunovskoe, are represented by skarn-magnetite ores. They are formed at the contacts of tube-shaped bodies of gabbrodolerites (trap complex) of Permian-Triassic age, cutting through 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 iron group ore deposits is confined to the trap Tunguska complex of Permo-Triassic age, and in their type, conditions of formation and composition of ores, they are largely similar to the objects of the Angara-Ilim basin. Total iron ore reserves are estimated at almost 550 million tons with an average iron content of 33%.
The Siberian platform is limited by zones of deep faults - marginal sutures, well-defined gravitational steps, and has polygonal outlines. The modern boundaries of the platform took shape in the Mesozoic and Cenozoic and are well expressed in relief. Western border the platform coincides with the valley of the Yenisei River, the northern one - with the southern edge of the Byrranga Mountains, the eastern one - with the lower reaches of the Lena River (Verkhoyansk regional trough), in the southeast - with the southern end of the Dzhugdzhur ridge; in the south the border runs along faults along southern outskirts Stanovoy and Yablonovy ridges; then, bending around from the north along a complex fault system of Transbaikalia and Pribaikalia, it descends to the southern tip of Lake Baikal; the southwestern border of the platform extends along the Main East Sayan Fault.
The platform is mainly distinguished by the foundation and the platform cover (-). Among the main structural elements of the platform, the following stand out: Aldan shield and Lena-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 Tunguska, and the eastern by the Vilyui syneclise. In the south there is the Angara-Lena trough, separated from the Nyu depression by the Peleduy uplift.
The foundation of the platform is sharply dissected and composed of highly metamorphosed Archean rocks, which have latitudinal trends in the western half and north-northwest trends in the eastern half. Weakly metamorphosed strata of the Lower Proterozoic (Udokan series) are preserved in individual depressions and grabens, lie flat and are formations of the protoplatform cover.
A typical platform cover begins to form from the Riphean time and includes 7 complexes. The Riphean complex is represented by carbonate-terrigenous, red-variegated rocks with a thickness of 4000-5000 m, filling aulacogens 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. 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 of limited distribution; 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 sequence and salt-bearing deposits, 5000-6000 m. The Middle Carboniferous - Middle Triassic complex is developed in the Tunguska syneclise and is represented by the Middle Carboniferous - Permian coal-bearing strata up to 1000 m thick and the Triassic volcanogenic strata (3000-4000 m), subdivided into the lower - tuff and upper - lava parts (undifferentiated tholeiitic basalts); all deposits are intruded by basalt dikes, stocks and 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 commonly 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 sediments, weathering crusts and glacial formations. The Paleogene Popigai astrobleme is known on the Anabar massif.
The Siberian platform is characterized by intense magmatism, which manifested itself in the Early Proterozoic, Riphean - Early Cambrian, Middle, Upper Paleozoic - Triassic and Late. Trap magmatism absolutely dominates in volume (more than 1 million km 3).
The Siberian platform is rich
OLWest Siberian Plain- the plain is located in northern Asia, occupies the entire western part of Siberia from the Ural Mountains in the west to the Central Siberian Plateau in the east. In the north it is limited by the coast of the Kara Sea, in the south it extends to the Kazakh small hills, in the southeast the West Siberian Plain, gradually rising, gives way to the foothills of Altai, Salair, Kuznetsk Altai and Mountain Shoria. The plain has the shape of a trapezoid tapering towards the north: the distance from its southern border to the northern reaches almost 2500 km, the width is from 800 to 1900 km, and the area is only 2.7 million km².
The West Siberian Plain is the most populated and developed (especially in the south) part of Siberia. Within its borders are the Tyumen, Kurgan, Omsk, Novosibirsk and Tomsk regions, the Yamalo-Nenets and Khanty-Mansi Autonomous Okrugs, the eastern regions of the Sverdlovsk and Chelyabinsk regions, a significant part of the Altai Territory, the western regions of the Krasnoyarsk Territory (about 1/7 of the area of Russia). In the Kazakh part, within its boundaries there are areas of the North Kazakhstan, Akmola, Pavlodar, Kustanai and East Kazakhstan regions of Kazakhstan.
Relief and geological structure
The surface of the West Siberian Lowland is flat with a fairly insignificant difference in elevation. However, the relief of the plain is quite diverse. The lowest areas of the plain (50-100 m) are located mainly in the central (Kondinskaya and Sredneobskaya lowlands) and northern (Nizhneobskaya, Nadymskaya and Purskaya lowlands) parts. Along the western, southern and eastern outskirts stretch low (up to 200-250 m) hills: North Sosvinskaya and Turinskaya, Ishim Plain, Priobskoye and Chulym-Yenisei Plateau, Ket-Tymskaya, Verkhnetazovskaya and Lower Yenisei uplands. A clearly defined strip of hills is formed in the inner part of the plain by the Siberian Uvals (average height - 140-150 m), stretching from the west from the Ob to the east to the Yenisei, and the Vasyugan Plain parallel to them.
The relief of the plain is largely determined by its geological structure. At the base of the West Siberian Plain lies the Epihercynian West Siberian Plate, the foundation of which is composed of intensely dislocated Paleozoic sediments. The formation of the West Siberian plate began in the Upper Jurassic, when, as a result of breaking off, destruction and degeneration, a huge area between the Urals and the Siberian platform subsided, and a huge sedimentation basin arose. During its development, the West Siberian Plate was repeatedly captured by marine transgressions. At the end of the Lower Oligocene, the sea left the West Siberian plate, and it turned into a huge lacustrine-alluvial plain. In the middle and late Oligocene and Neogene, the northern part of the plate experienced uplift, which gave way to subsidence in Quaternary time. The general course of development of the plate with the subsidence of colossal spaces resembles an incomplete process of oceanization. This feature of the slab is emphasized by the phenomenal development of wetlands.
Individual geological structures, despite the thick layer of sediments, are reflected in the relief of the plain: for example, the Verkhnetazovskaya and Lyulimvor hills correspond to gentle anticlinal uplifts, and the Barabinskaya and Kondinskaya lowlands are confined to the syneclises of the foundation of the plate. However, in Western Siberia, discordant (inversion) morphostructures are also common. These include, for example, the Vasyugan Plain, formed on the site of a gently sloping syneclise, and the Chulym-Yenisei Plateau, located in the zone of basement deflection.
The mantle of loose sediment contains horizons of groundwater - fresh and mineralized (including brine), and hot (up to 100-150°C) water is also found. There are industrial deposits of oil and natural gas (West Siberian oil and gas basin). In the area of the Khanty-Mansi syneclise, Krasnoselsky, Salym and Surgut regions, in the layers of the Bazhenov formation at a depth of 2 km, there are the largest shale oil reserves in Russia.
Climate
West Siberian Plain. Flood of the Taz and Ob rivers. July 2002
The West Siberian Plain is characterized by a harsh, fairly continental climate. Its large extent from north to south determines a clearly defined climate zonation and significant differences in climatic conditions in the northern and southern parts of Western Siberia. On continental climate Western Siberia is also significantly influenced by the proximity of the Arctic Ocean. The flat terrain facilitates the exchange of air masses between its northern and southern regions.
During the cold period, within the plain there is an interaction between an area of relatively high atmospheric pressure, located over the southern part of the plain, and an area of low pressure, which in the first half of winter stretches in the form of a trough of the Icelandic pressure minimum over the Kara Sea and the northern peninsulas. In winter, continental air masses of temperate latitudes predominate, which come from Eastern Siberia or are formed locally as a result of cooling of the air over the plain.
Cyclones often pass through the border zone of areas of high and low pressure. Therefore, in winter the weather in the coastal provinces is very unstable; On the coast of Yamal and the Gydan Peninsula, strong winds occur, the speed of which reaches 35-40 m/sec. The temperature here is even slightly higher than in neighboring forest-tundra provinces, located between 66 and 69° N. w. However, further south, winter temperatures gradually rise again. In general, winter is characterized by stable low temperatures, there are few thaws. Minimum temperatures throughout Western Siberia are almost the same. Even near the southern border of the country, in Barnaul, there are frosts down to −50…−52°. Spring is short, dry and relatively cold; April, even in the forest-swamp zone, is not yet quite a spring month.
In the warm season, low pressure is established over Western Siberia, and an area of higher pressure forms over the Arctic Ocean. high pressure. In connection with this summer, weak northern or northeastern winds predominate and the role of westerly air transport noticeably increases. In May there is a rapid increase in temperatures, but often, when arctic air masses invade, there are returns of cold weather and frosts. The warmest month is July, average temperature of which - from 3.6° on Bely Island to 21-22° in the Pavlodar area. The absolute maximum temperature is from 21° in the north (Bely Island) to 44° in the extreme southern regions (Rubtsovsk). High summer temperatures in the southern half of Western Siberia are explained by the arrival of heated continental air from the south - from Kazakhstan and Central Asia. Autumn comes late.
Duration of snow cover in northern regions reaches 240-270 days, and in the south - 160-170 days. The thickness of the snow cover in the tundra and steppe zones in February is 20-40 cm, in the forest-swamp zone - from 50-60 cm in the west to 70-100 cm in the eastern Yenisei regions.
The harsh climate of the northern regions of Western Siberia contributes to soil freezing and widespread permafrost. On the Yamal, Tazovsky and Gydansky peninsulas, permafrost is found everywhere. In these areas of continuous (merged) distribution, the thickness of the frozen layer is very significant (up to 300-600 m), and its temperatures are low (in watershed areas - 4. -9°, in valleys -2. -8°). To the south, within the northern taiga to a latitude of approximately 64°, permafrost occurs in the form of isolated islands interspersed with taliks. Its power decreases, temperatures rise to 0.5–1°, and the depth of summer thawing also increases, especially in areas composed of mineral rocks.
Hydrography
The territory of the plain is located within the large West Siberian artesian basin, in which hydrogeologists distinguish several second-order basins: Tobolsk, Irtysh, Kulunda-Barnaul, Chulym, Ob, etc. In connection with high power a cover of loose sediments consisting of alternating permeable (sands, sandstones) and water-resistant rocks, artesian basins are characterized by a significant number of aquifers associated with formations of different ages - Jurassic, Cretaceous, Paleogene and Quaternary. The quality of groundwater in these horizons is very different. In most cases, artesian waters of deep horizons are more mineralized than those lying closer to the surface.
More than 2,000 rivers flow on the territory of the West Siberian Plain, the total length of which exceeds 250 thousand km. These rivers carry about 1,200 km³ of water into the Kara Sea annually - 5 times more than the Volga. The density of the river network is not very large and varies in different places depending on the topography and climatic features: in the Tavda basin it reaches 350 km, and in the Barabinsk forest-steppe - only 29 km per 1000 km². Some southern regions of the country with a total area of more than 445 thousand km² belong to areas of closed drainage and are distinguished by an abundance of drainless lakes.
The main sources of nutrition for most rivers are melted snow waters and summer-autumn rains. In accordance with the nature of the food sources, the runoff is uneven over the seasons: approximately 70-80% of its annual amount occurs in spring and summer. Especially a lot of water flows down during the spring flood, when the level of large rivers rises by 7-12 m (in the lower reaches of the Yenisei even up to 15-18 m). For a long time (in the south - five, and in the north - eight months), Western Siberian rivers are frozen. Therefore, no more than 10% of the annual runoff occurs in the winter months.
The rivers of Western Siberia, including the largest ones - the Ob, Irtysh and Yenisei, are characterized by slight slopes and low flow speeds. For example, the fall of the Ob riverbed in the area from Novosibirsk to the mouth over a distance of 3000 km is only 90 m, and its flow speed does not exceed 0.5 m/sec.
On West Siberian Plain There are about one million lakes, the total area of which is more than 100 thousand km². Based on the origin of the basins, they are divided into several groups: those occupying the primary unevenness of the flat terrain; thermokarst; moraine-glacial; lakes river valleys, which in turn are divided into floodplain and oxbow. Peculiar lakes - “fogs” - are found in the Ural part of the plain. They are located in wide valleys, overflow in the spring, sharply reducing their size in the summer, and by autumn many disappear altogether. In the southern regions, lakes are often filled with salt water. The West Siberian Lowland holds the world record for the number of swamps per unit area (the area of the wetland is about 800 thousand square kilometers). The reasons for this phenomenon are the following factors: excess moisture, flat topography, permafrost and the ability of the peat available here to large quantities, hold a significant mass of water.
Natural areas
The large extent from north to south contributes to a pronounced latitudinal zonality in the distribution of soils and vegetation cover. Within the country there are gradually replacing one another tundra, forest-tundra, forest-swamp, forest-steppe, steppe and semi-desert (in the extreme south) zones. In all zones, lakes and swamps occupy fairly large areas. Typical zonal landscapes are located on dissected and better drained upland and riverine areas. In poorly drained inter-river spaces, drainage from which is difficult, and the soils are usually very wet, swamp landscapes predominate in the northern provinces, and landscapes formed under the influence of saline soils in the south. groundwater
Siberian platform
The Siberian (Central Siberian) platform covers a vast area between the Lena and Yenisei rivers. Its border for the most part determined by deep faults. In the east it stands out most confidently and practically coincides with the Lena Valley, then to the south it almost reaches the coast of the Sea of Okhotsk (Uda Bay) and sharply turns west - southwest to Chita. From here the border goes to the southern tip of the lake. Baikal, then to the west and northwest to the Yenisei, along the valley of which it rises up to the mouth of the river and again sharply turns east to the Khatanga Bay and the mouth of the Lena.
Speaking about Siberia, you involuntarily recall the words of M.V. Lomonosov that “...wealth Russian Siberia will grow." Even then, the brilliant scientist understood how rich this region was. However, for many centuries, Siberia was a remote taiga region, where the only trade was hunting for fur-bearing animals. In 1670, the Amsterdam bookseller Etienne Roger, who visited Siberia, wrote : “Siberia is a vast unexplored space, stretching to the Wall of China. Those traveling to Siberia spend six years on this journey, being forced to stop in some places in winter and in others in summer. Furs, which cannot be found anywhere else, are the main trade item of the local inhabitants. Instead of bread, which is not available here, they eat dried fish. For as long as six to seven weeks, divided into groups, they go hunting on sleighs, dressed in three or four layers of skins.”
The industrial development of Siberia began only in the 19th century. But only after the Great October Revolution socialist revolution and especially in our days it has begun to be carried out on a large scale. Recently, the French publicist P. Rondier, who visited this “bear corner”, noted: “Nothing stands still here, everything moves, boils, rapidly rushes forward... Vast, boundless, rich, promising and eternally seething land... And those who know nothing about it do not know the future of our planet!”
Despite the desire of geologists to unravel as fully as possible the secrets of the structure of the subsoil of the Siberian platform and explore the riches hidden there, the knowledge of this territory is still very small. As of January 1, 1978, more than 2.2 million meters of deep wells had been drilled here. However, drilling density, i.e. the ratio of the total volume of available wells to the area of the region, averages only 0.64 m/km 2, which is almost 17 times lower than the average density deep drilling on the Soviet Union. Moreover, the drilling volume is concentrated in central regions platforms and wells are located mainly along river arteries. In most of the territory, only a few wells have been drilled and the drilling density ranges from 0.001-0.08 m/km 2 . In the central and northern regions of the Tunguska Lowland there are no wells at all.
Geophysical research has been carried out on a larger scale within the Siberian Platform. The area is covered by magnetic and gravimetric surveys. Electrical prospecting and seismic surveys were carried out in a number of places. Areal seismic exploration, which allows for sufficient detailed probing of the subsoil structure, was carried out on less than one fifth of the territory.
Summing up the consideration of the level of knowledge of the subsoil of the Siberian platform, it can be noted that more than half of its area is not covered even by regional geological and geophysical work. Nevertheless, researchers of this inaccessible region have already lifted the curtain on some of its geological secrets and are determined to continue the assault on the subsoil.
The foundation is a mystery
For now, many regions of Siberia are fraught with many mysteries. One of them is the foundation of the platform. It emerges on the daytime surface in the north (Anabar ledge) and in the south (Aldan shield), and is also exposed along the periphery in the regions of Transbaikalia and along the Yenisei. The foundation is most well studied in the region of the Aldan Shield, where it is composed of crystalline rocks of the Archean and Lower Proterozoic. The Archean group includes three complexes (from bottom to top): Iengra, Timpton and Dzheltulinsky, formed mainly by gneisses with lenses of ferruginous ores and marbles. This sequence is overlain by the Lower Proterozoic Olekma complex, consisting of crystalline schists and gneisses. Metamorphic basement rocks are intruded by powerful intrusions of granites, dunites and gabbros. Elsewhere, the basement of the Siberian Platform has a similar composition.
Along the southern and western peripheries of the platform (Transbaikalia, the middle and lower reaches of the Yenisei), the basement also includes younger Proterozoic rocks, represented by crystalline schists, quartzites, conglomerates with interlayers of effusive igneous rocks. There are also granite intrusions (Barguzin complex).
The basement of the Siberian Platform, like the basement of the East European Platform, consists of several large polygonal blocks with a consolidation age from Archean to Late Proterozoic. This feature of the tectonic structure of the foundation was noted by the first platform researchers N.S. Shatsky and A.D. Arkhangelsky: “According to our ideas, the foundation of the Siberian plate consists of elements of different ages, namely, two ancient granite-gneiss blocks - the North Siberian (Anabar. - V.G.) and Aldan and from much younger folded structures of the Precambrian era that encircle the Archean massifs."
Taking into account modern data, the regional structure of the foundation of the Siberian Platform is determined by five main geoblocks: Anabar, Aldan, Vilyui, Tunguska and Baikal.
The Anabar geoblock extends from the Lena delta south to northern tip lake Baikal. It is composed of highly metamorphosed Archean complexes. The magnetic and gravimetric fields of the geoblock are characterized by linear anomalies of a northwestern strike.
The Aldan geoblock is located in the southeast of the Siberian Platform. It is formed by deeply metamorphosed, mainly Archean formations, crushed into linear folds of northwestern strike. The magnetic and gravimetric fields of the geoblock are variable, predominantly with a northwestern orientation of the anomalies.
Between the Anabar and Aldan Archean geoblocks extends the Vilyui geoblock, presumably of Early Proterozoic consolidation age. Within its boundaries, the orientation of the anomalies of the magnetic and gravimetric fields changes sharply from northwestern to sublatitudinal.
The Tunguska geoblock corresponds to the western part of the Siberian Platform. The structure of its foundation is the most debatable. The magnetic and gravimetric fields are obscured by the influence of traps, which distorts the picture internal structure foundation. Presumably, the age of stabilization of the Tunguska geoblock is considered Early Proterozoic, although some scientists (P.N. Kropotkin, B.M. Valyaev, R.A. Gafarov and others) are inclined to consider it Archean.
The youngest (Late Proterozoic) Baikal geoblock of the Siberian Platform basement extends in a relatively narrow strip in the south, southwest and west of the platform. It includes the Baikal folded zone, the Eastern Sayan, the Yenisei Ridge and the Turukhansk-Norilsk ridge. Here, the Upper Proterozoic deposits are highly dislocated and cut through by granite intrusions.
What is the mystery of the foundation of the Siberian platform? It is not that it has still been studied very little, but that even the initial steps in understanding it have brought a lot of unexpected, if not sensational. Thus, in the south of the Aldan shield several years ago, geologists discovered relics of the ancient earth’s crust, formed 4-4.5 billion years ago, when the planet was at the lunar stage of its development. To make it clearer to the reader what it is, let’s make a short excursion into the past of the Earth.
At the very early stage of its formation, our planet experienced a development that was completely unusual in modern times. It had no atmosphere, no hydrosphere, no crust. There was a core and a mantle. Under the influence internal heat, released by the decay processes of radioactive elements, the upper part of the mantle began to melt. At the same time, differentiation of the substance occurred, light components sublimed upward, forming “seas” of molten basaltic lava. When the primary rocks of the mantle melted, vapors of various gases and water were released from them, which ultimately led to the formation of the hydrosphere and atmosphere. True, their chemical composition was completely different from what it is now. The landscape of our planet at that time was probably very similar to the panorama of the Moon or Mars. Scientists have long assumed such a possibility of events on Earth, but there were no facts. Back in 1922, Academician A.P. Pavlov expressed an original hypothesis that the Earth and the Moon once developed in the same way. But the Moon, having exhausted its internal energy, has stopped developing, retaining to this day its face, formed several billion years ago. The earth has moved on and has changed beyond recognition since then. What facts did A.P. Pavlov have? Virtually none, mostly the intuition of a scientist and the imagination of a geologist. "Imagination more important than knowledge..." - these words belong to the brilliant scientist A. Einstein, and the great G. Lorca wrote: “For me, imagination is synonymous with the ability to discover...” Our example is clear proof of this.
It seemed that man would never penetrate the secrets of the ancient existence of our planet. And here is an unexpected find: rocks of the Sutam series in the south of the Aldan shield. Why are they unusual? Firstly, its composition. These are very specific shales, eclogite-like rocks, gabbronorites and gabbro-anorthosites. The formation of these rocks, as researchers have established, occurred at very high pressures of 1000-1200 MPa and temperatures of 700-800 °C. Chemical and mineral composition point to them family connection with basalts of the Moon. Secondly, the age of the series is 4.5-4.58 billion years. Geologists have never known such ancient rocks. Thirdly, a peculiar tectonics: the dominance of negative rounded structures such as bowls, consisting of a chaotic accumulation of ring, oval, looped negative forms, separated by narrow ridge-like uplifts (Fig. 8). E.V. Pavlovsky, one of the leading scientists of our country, who studied these unusual rocks, concludes: “The ancient age of the rocks of the Sutam series, the proximity of their composition to lunar basalts, the dominance of negative unoriented structures give grounds for classifying the series as those formations that arose in during the lunar stage of Earth's life." Later, by analogy with the Siberian platform, they began to identify the remains of the lunar crust on the Kola Peninsula, in Africa (Southern Rhodesia). By analyzing space images, geologists have found buried remains of the lunar crust and mysterious ring structures in closed areas of platforms.
Nuclear nuclei were also discovered in the body of the foundation of the Siberian platform, reflecting the next post-lunar stage of the development of the Earth *. The presence of such nuclei can be noted within the same Aldan shield. The absolute age of the domes is 3.3 billion years. This clears up one of the oldest pages in the chronicle of our planet; the study of the foundation of the Siberian Platform played a significant role in this.
* (Not all geologists agree with the idea of the existence of lunar and nuclear stages of the Earth's development. Some (Ch.B. Borukaev and others) are inclined to explain the presence of cup-shaped structures of the Sutam complex and nuclear nuclei by other reasons.)
The internal structure of the foundation of the platform in question is the same as that of the East European one. Here there are mainly anticlinoria and synclinoria, expressed in the terrain by relatively low mountain ranges.
Structure of the sedimentary cover
The sedimentary cover is developed over most of the Siberian Platform. It is characteristic that Upper Proterozoic complexes directly overlie the crystalline basement. The power of the cover changes sharply from 0 to 10.0 km. It consists of deposits of the Upper Proterozoic (Riphean), Paleozoic, Mesozoic and Cenozoic.
Riphean deposits, represented by red sandstones, conglomerates, interlayers of bituminous limestones and oil shale, begin the sedimentary cover everywhere, with the exception of the young Baikal block, where they are part of the basement. It is characteristic that Riphean formations, as a rule, are present in aulacogens and do not extend beyond the boundaries of these graben-like troughs of the basement. Vendian deposits (Yudoma Formation) are more widely developed in space; they are composed of clastic rocks and dolomites.
Paleozoic sediments cover the foundation in a continuous cloak. Based on their lithology, they are divided into two strata: the lower one, predominantly carbonate, and the upper one, predominantly clastic. The lower sequence includes rocks of the Cambrian, Ordovician and Silurian systems. These are limestones, marls, dolomites up to 4-4.5 km thick. A distinctive feature of the Lower Paleozoic deposits is the presence in their composition of a thick Cambrian salt-bearing strata, which can be traced from the Yenisei Ridge in the west to the Lena flow in the east and from Lake. Baikal in the south to Norilsk in the north. Here is how academician A.L. Yanshin characterizes these unique rocks: “The thickness of the salt-bearing deposits in the basin reaches 3 km. Its area is approaching 2 million square kilometers, and the mass of salt accumulated in it, according to modern estimates, is at least 5 .85*10 5 km 3".
The upper Paleozoic strata includes Devonian, Carboniferous and Permian sediments. Devonian formations are developed to a limited extent in space (mainly in the north-west); they are composed of clastic rocks of continental origin with interlayers of lagoonal sediments and volcanic tuffs.
The deposits of the Carboniferous and Permian systems of the Paleozoic group, together with the sediments of the Triassic system of the Mesozoic, form a very unique sequence, found in our country only on the Siberian Platform. It is distinguished under the name of the Tunguska series, since it is present mainly in the west of the platform within the Tunguska syneclise. The uniqueness of the series lies in the fact that it is all “stuffed” with layers of basalts. A “layer cake” was formed, consisting of alternating layers of sandstones, mudstones, coal, basalts, volcanic tuffs, and tuff conglomerates. The upper part of the series is covered by lava flows of basaltic, diabase, and porphyritic composition. The lava layers created stepped forms in the relief, reminiscent of a staircase (trap), and therefore the entire complex of deposits was called the trap formation. The formation of the traps occurred at the end of the Paleozoic - the beginning of the Mesozoic, when basaltic lava penetrated from the depths of the platform to the surface along “revived” deep faults. At the same time, diamond-bearing explosion tubes (diatremes) were also formed. This unusual activation of faults in Siberia is associated with the global activity of the internal forces of the Earth, which laid the foundation for the split and “spreading” of the previously unified supercontinents Gondwana (southern hemisphere) and Laurasia (northern hemisphere).
The total thickness of the Tunguska series deposits is several kilometers, and the area covered by it is more than 500,000 thousand km 2. It must be said that the traps greatly complicate the study of the deep structure of the platform. After all, most often research is carried out using seismic exploration methods, and the elastic waves sent deep into the earth’s crust are reflected from the basalt layers and return “in disorder” without reaching the required depth. Extra information “confuses the maps” and does not make it possible to clarify the tectonic structure of the deeper subsoil.
Mesozoic deposits of the Siberian Platform (except for the Triassic) are very limitedly developed. Jurassic sediments are known in the east (Vilyui syneclise) and in small spots in the west (Irkutsk, Kan, Rybinsk depressions), Cretaceous - only in the east (Vilyui syneclise). They are represented by sandstones, clays of coastal-marine and continental origin. Interlayers of hard coal, often of industrial importance, are found in large quantities. The total thickness of Mesozoic deposits sometimes exceeds 3-4 km.
Cenozoic rocks are found only in the intermontane graben-like depressions of Transbaikalia: these are weathering crusts (Paleogene) and red-colored conglomerates (Neogene), the thickness of the latter sometimes reaches 2 km. Quaternary sediments are represented by alluvial, glacial, lake-marsh formations, and sometimes peat layers.
Various geostructural elements take part in the tectonic structure of the Siberian Platform: a shield and a plate; massifs, anteclises and syneclises; arches, zones of uplifts, shafts, depressions, troughs, etc. Large convex (positive) structural elements are concentrated mainly on the periphery of the platform, and concave (negative) structures are in its central regions (Fig. 9).
The most significant platform elevation is the Aldan Shield, which we have already mentioned. Let us add that its structure, in addition to anticlinoria and synclinorium, is also complicated by the Ulkan and Bilyakchan aulacogens and superimposed Mesozoic depressions, which form the South Yakut strip of depressions of sublatitudinal strike (Chulman trough, Gonom and Tokyo depressions). The depressions have a graben-like nature and probably owe their origin to the activity of a deep fault that became active in the Mesozoic era. The shield also includes the Berezovskaya depression, located in its northwestern part and filled with sediments of the Riphean, Lower Paleozoic and Jurassic.
The Baikal folded region continues the mountain frame of the Siberian Platform to the southwest of the Aldan Shield. It is located between the lake. Baikal and the Aldan shield, including the Vitim and Patom highlands. In the composition of the region, the external and internal zones, consisting of anticlinoria and synclinorium. The zones are separated by the Baikal anticlinorium, which stretches along the southeastern coast of the lake of the same name.
In the Cenozoic era, the Baikal folded region experienced an intensification of block movements along deep faults, which led to the formation of graben-like depressions. One of them, the largest in size, is occupied by the waters of the lake. Baikal. The resulting depressions are filled with a thick layer of Cenozoic sediments. Neogene-anthropogenic deposits alone account for up to 1.2 km. Tectonic nature of the lake. Baikal was previously proven solely by external signs; steep banks, outcrops of frozen basaltic lavas, characteristic geophysical anomalies. In 1977, Baikal researchers made an attempt to directly study the underwater geology of the lake. It turned out that the slopes of the depression have a stepped structure. They are formed by a system of parallel faults that divide the sides of the lake into separate tectonic plates. Some faults are expressed in the bottom topography as narrow underwater canyons. The slopes of the lake are composed of basalt rocks that rose to the surface along cracks in the earth's crust.
Active movements along faults, which at one time led to the formation of the lake graben. Baikal, continue in our time. This area belongs to earthquake-prone areas. There have even been cases of catastrophic earthquakes. One of them occurred in 1861 with the epicenter in the center of the lake. In one night, the Sagan steppe with an area of 230 km 2, located near the Selenga delta, sank (G. E. Ryabukhin, 1940).
To the southwest, south and northwest of the Baikal region extends the East Sayan folded zone, which is also part of the Baikal geoblock of the basement of the Siberian Platform. Pre-Riphean and Riphean complexes of this zone are folded into northwest-trending folds, which are grouped into the Proterosayan and Khamar-Daban anticlinoriums. Within the East Sayan zone there is a graben-shaped Rybinsk depression, formed in the Mesozoic era and superimposed on an ancient foundation.
The Yenisei shield (ridge) limits the internal sagging areas of the platform from the west. This is an area of Early Baikalian folding, where basement formations, crushed into box folds, anticlinoria and synclinorium, are widely developed on the surface.
The Turukhansk-Norilsk ridge continues to the north the strip of Baikal folded platform structures. The ridge is elongated in the submeridional direction and consists of two horst-shaped projections of the basement, the slopes of which are limited by deep faults.
The indicated geostructural elements (Aldan shield, Baikal folded region, Eastern Sayan, Yenisei Ridge and Turukhansk-Norilsk ridge) form an external arc-shaped frame of the Siberian platform, encircling its internal regions from the south and west. The rest of the platform is characterized by the subsidence of a basement of different ages and the widespread development of sedimentary cover. This internal submerged part of the platform is distinguished as the Central Siberian (Lena-Yenisei, according to N. S. Shatsky) plate. The relief of the slab foundation is extremely complex, which is explained by the manifestation of multi-amplitude and multi-directional tectonic movements, which determined the features of the formation of geostructural elements. The plate includes the Anabar massif, the Nepa-Botuobinsk and Baikit anteclises, the Tunguska, Sayan-Yenisei and Vilyuisk syneclises, the Angara-Lena trough, the Pre-Verkhoyansk foredeep and other smaller-scale structural elements.
The Anabar massif is one of the largest positive geostructural elements of the plate. Its boundaries are deep faults. As part of the massif, one can distinguish the Anabarsky ledge (shield) and the Oleneksky ledge (arch), delimited by the Sukhansky trough, as well as the Munsky arch and the Morkokinsky mega-swell, separated by the Markhinsky trough. The structures of the Anabar massif are poorly studied. They are developed within the distribution of Cambro-Silurian deposits and form gentle arches, megaswells or swells separated by troughs. The dip angles of the layers do not exceed several degrees. Some shafts are confined to flexural bends of the cover and are associated with deep faults in the basement.
The Nepa-Botuobinskaya anteclise is located between the Tunguska and Vilyuiskaya syneclises and the Angara-Lena trough. The study of the geological structure of the anteclise is almost just beginning. It consists of a number of arched uplifts (Nepsky, Syuldyukarsky, Mirnensky, Peleduysky, Chonsky arches), separated by depressions and troughs. The depth of the foundation is 2-2.5 km.
Geophysical research in recent years has made it possible to identify another large uplift located in the west of the platform near the Yenisei Ridge - the Baikit anteclise. Its dimensions are 1000 km X 400 km. The foundation is covered by a three-kilometer layer of sediment. The structure of the anteclise has not yet been studied, and the structure itself, despite its impressive size, became known to geologists only relatively recently.
The Tunguska syneclise - the largest structure of the Siberian platform (1500 km X 700 km) - is a huge depression of submeridional strike, open to the north. In the west it is limited by the Turukhansk-Norilsk ridge and the Baikit anteclise, in the south by the Nepa-Botuobinsk anteclise, and in the east by the Anabar massif. The boundaries are tectonic in nature. The Tunguska syneclise is filled with a thick (up to 10 km) thickness of sedimentary volcanic rocks. On the surface it is covered by continental rocks of the Tunguska series. The layers are inclined from the sides of the syneclise to its center at an angle of up to 3°.
The syneclise consists of several depressions, of which the largest are Kureiskaya and East Tunguska. The depressions and swells are complicated by local uplifts with the dip angle of the wings usually 3-5° and with amplitudes up to 150-200 m. The folds, as a rule, have a simple structure (flat arches and gentle wings). In general, the syneclise is characterized by a number of structural features unique to it: a flat bottom surrounded by relatively steep sides, which are complicated by flexures and faults; significant role of igneous products in the structure of the section. This gave rise to a number of scientists, in particular M.V. Muratov, to single out the Tunguska syneclise as special kind platform structures, which he called amphiclises.
To the north of the Tunguska syneclise is the Yenisei-Khatanga trough, elongated in the sublatitudinal direction. The structure of the deflection has not been studied. It has been established that it is filled with a thick layer of sediments of Paleozoic and Mesozoic age. The earth's crust within its boundaries is thinner than is usually the case on platforms: its thickness is 27-30 km.
The Vilyui syneclise is located in the southeastern part of the Siberian Platform. The total thickness of the cover here reaches 8.0 km. Central part The syneclise is occupied by the Ura aulacogen of northeastern strike, probably composed of Riphean rocks. Syneclise developed most actively in Mesozoic time (starting from the Jurassic). Its composition includes a number of depressions (Lindenskaya, Lunkhinskaya, Ygyattinskaya, Kempendyaiskaya) and swell-like uplifts separating them (Suntarskoye, Khapchagayskoye, Namaninskoye). In some depressions (Kempendyayskaya) rock salt strata are known, apparently of Cambrian age. The salt forms domes here with wing angles of up to 40-60°, heavily broken by disturbances. In relief, salt domes are expressed as small hills up to 120 m high.
The Sayano-Yenisei (Biryusa) syneclise is located between the Yenisei Ridge, Nepa-Botuobinskaya and Baikitskaya anteclises. Its boundaries are deep faults. It is made mainly of Paleozoic deposits. The thickness of the cover within its limits reaches 8.0 km. The syneclise includes the Dolgomostovskaya, Murskaya, Kanskaya and Tushamskaya depressions, separated by the Chunsky, Bratsky and Pushkinsky (Pushkinsko-Zakharovsky) swells. The foundation is most deeply immersed in the Kansk graben-shaped depression, which is filled with coal-bearing Jurassic deposits.
The Pre-Verkhoyansk foredeep of Mesozoic age stretches along the entire eastern periphery of the Siberian Platform for a distance of 1200 km with a width of up to 120 km. It separates the Precambrian Siberian Platform from the Verkhoyansk-Kolyma Mesozoic region.
Between the Central Siberian plate and the Baikal folded region there is the Angara-Lena trough, which extends for 1500 km. The trough is filled with Riphean and Lower Paleozoic sediments; in the south, within the Irkutsk superimposed depression, Jurassic rocks appear. The Cambrian formations contain a salt-bearing sequence up to 1.5 km thick, which divides the sedimentary cover into sub-salt (Riphean) and post-salt (Lower Paleozoic) complexes.
Gold, diamonds and their connection with faults
In the depths of the Siberian platform, deposits of oil and gas, iron, coal, copper, nickel, gold, platinum and a number of other useful and people need fossils. Some underground storerooms have been developed for a long time, others have been discovered recently, and others are still being sought by geologists and geophysicists. Perhaps the greatest glory of Siberia was brought by the noble yellow metal, which has been mined on an industrial scale in the taiga wilds of the region for more than 100 years.
Primary gold deposits are known here in the form of quartz-gold-bearing veins in ancient granites of the Aldan Shield, Anabar Massif, Yenisei Ridge, and Transbaikalia. Placer gold deposits are much more widespread in the floodplains of the Lena, Aldan, Yenisei, Bodaibo and other rivers. Their development is carried out by dredging or quarrying methods, and, despite severe frosts, all year round. In winter, a stream of hot steam melts the river ice, which prevents the washing of the bottom sand. And the dredge itself, during operation, continuously spews out hot water, which does not allow the ice hole to linger.
An interesting pattern emerges in the spatial distribution of bedrock gold deposits: they are usually associated with deep crustal faults. This is most clearly observed in the well-exposed and, accordingly, more studied areas of Transbaikalia and the Aldan Shield.
As you know, Transbaikalia is a relatively young geoblock of the platform. At the platform stage of development (i.e., the last 700-600 million years), it experienced predominantly upward vertical movements along faults that form orthogonal and diagonal systems. The degree of expression of faults within its various structural zones is not the same. In the Lensky gold mining region, sublatitudinal discontinuities are clearly visible. Gold-bearing nodes (Kropotkinsky, Artemovsky, etc.) are confined to the intersection of these zones with weakly expressed faults of northwestern strike. In the Mamsky region, gold ore occurrences gravitate toward a deep fault of northeastern orientation, which is clearly outlined by a series of ultrabasic intrusions. The Patom Highlands are dominated by northwest-trending faults. In general, for the regions of Transbaikalia, it is this direction of faults that is of decisive importance. Faults of sublatitudinal and northeastern directions are less clearly expressed, and gold-bearing veins within them are found only at the places of their intersection with faults of northwestern strike.
A significant role in the distribution of mineralization in Transbaikalia is played not only by the large deep faults themselves, but, above all, by the small faults associated with them. The structure of the Irokindinsko-Kindikan ore field is indicative in this regard (Fig. 10). The main ore-controlling structure here, according to many geologists, is the Kilyansky fault, called the Irokindinsky fault within the ore field. Most of the productive veins are located in faults with a northeastern trend, and a smaller part - in faults with a northwestern direction. Almost all the veins are associated with fractures associated with the main fault; only isolated ore bodies were discovered directly in the zone of the fault itself. All veins dip northwest or southwest at an angle of 30-45°. The ruptures are characterized by the predominance of reverse-slip or normal-slip displacements, which caused the cracks to open slightly. The shapes of ore bodies are controlled by the bends of the fractures and the places of their intersections. The confinement of gold mineralization to the intersections of regional faults of similar directions is also noted for the areas of Pre-Baikal and Eastern Sayan.
In the south of the Siberian Platform, within the Aldan Shield, there is a large elongated horst that formed in Early Proterozoic times - the Stanovoy Range. Within its central part, gold mineralization is known, formed in the Mesozoic era. At this time, the constituent blocks of the Stanovoy Range “came to life” again, and experienced multidirectional movement in the vertical direction along the faults that bound them. In the Early Cretaceous, there was an intensification of volcanic activity, accompanied by gold mineralization, and in the Late Cretaceous there was a new outbreak of volcanism and the formation of gold, mercury, antimony, and arsenic.
The largest fault of the Stanovoy Range, which controls ore formation, is the Apsakan zone of ancient origin of sublatitudinal orientation, which is intersected by faults in the northeastern direction. Together, these systems form the Apsakan gold-bearing cluster here (Fig. 11). The localization of ore bodies is observed along the entire fault zone, but the richest ores are found at the intersection of it with the northeastern faults. Here the fracturing of rocks sharply increases, and the cracks, according to experts, served as the channels through which ore-containing solutions moved.
The ore-controlling role of faults affects not only the formation of gold deposits. Studying the patterns of distribution of ore deposits in Transbaikalia, a number of scientists, in particular D.I. Gorgievsky, N., A. Fogelman and others, came to the conclusion that deposits of polymetallic ores and non-ferrous metal ores (molybdenum, tungsten, lead, zinc, tin, arsenic, etc.) tend to the intersection points of latitudinal and diagonal faults. Moreover, as these researchers note, ore-containing faults are characterized by a duration of development.
In addition to Transbaikalia, deposits of non-ferrous metals have been identified in the lower reaches of the Yenisei (copper, nickel, etc.). Here, sulfide mineralization has been established in an intrusive body of ultramafic composition. The intrusion is confined to a large deep fault that borders the Siberian platform from the west. There are also platinum deposits here. The Norilsk Mining and Metallurgical Combine was created on the basis of this storeroom. Copper deposits are also known in the Olekmo-Vitim interfluve (for example, Udokan).
An interesting fact: despite the fact that the Siberian platform has been studied much less geologically than the East European one, a larger number of deposits of precious and non-ferrous metals have been discovered here. Does this mean that the subsoil of Siberia is much richer than the subsoil of the European part of the country? Such a conclusion cannot be drawn. And that's why. In areas of the Siberian Platform, basement rocks are exposed to the surface much more often. Here the area of their outcrops is 3 times larger than on the East European Platform. But the overwhelming majority of ores were formed in geosynclines, where the sublimation of deep substance into the upper horizons of the crust was especially active. That is why ore accumulations are located in geosynclinal formations that form the foundations of platforms. Abroad, for example, outcrops of the foundations of ancient platforms provide about two-thirds of the production of iron ores, three-quarters of gold and platinum, nine-tenths of nickel, cobalt and uranium, almost all of the production of thorium, beryllium, tantalum, niobium and zirconium, about a third of manganese production , more than a quarter of copper and chromium.
If gold and other precious and non-ferrous metals have long been the glory of Siberia, then diamond mining here is a relatively new business. The first diamond was found in Yakutia in riverbed deposits in 1948, and the first kimberlite pipe was discovered in 1954. Diamond-bearing kimberlite pipes are oval-shaped tubular bodies with a diameter of up to 500 m, filled with brecciated rock (kimberlite). The tubes extend almost vertically into the depths. Their formation is associated with a sudden breakthrough of ultrabasic magma from the depths through narrow cracks or channels. In this case, so-called explosion tubes (diatrems) are formed. Under the conditions of enormous pressure and high temperatures, carbon crystallizes and diamonds form. The most famous explosion tubes are Mir, Aikhal, etc.
As we already know, unusually active magmatic processes engulfed the Siberian platform at the end of the Paleozoic - the beginning of the Mesozoic, when the Tunguska series of deposits was formed. At the same time, the formation of diamond-bearing explosion pipes associated with deep fault zones also occurred. Geologists began to use this connection as a search feature. For example, space research in Yakutia has identified submeridional faults. Some of them are associated with kimberlite fields. Within one of these fields, industrial diamond-bearing pipes are known, producing stones of rare beauty. Recently, on the eve of the 60th anniversary of the October Revolution, in the Udachnaya tube, not far from the village. Mirny, they found a diamond of 120 carats (1 carat = 0.2 g). They called it “60th anniversary of the Great October Revolution”.
Oil, gas and coal
Combustible raw materials are extremely necessary for the harmonious development of industry in Eastern Siberia. By the beginning of 1978, 22 oil and gas fields had been discovered here and encouraging signs of these minerals had been obtained in 25 areas. However, the total identified reserves of “black gold” are still very small. According to experts, they amount to only 2.7% for gas and 0.1% for oil of those predicted reserves that are scientifically substantiated by geologists. This means that major discoveries are yet to come. Therefore, in recent years, the scope of oil and gas exploration work here has expanded significantly. So far, deposits are known within the Vilyui syneclise, the Angara-Lena trough and the Nepa-Botuobinsk anteclise.
The first gas reservoir within the Vilyui syneclise was discovered in 1956 in Cretaceous deposits. Now a group of deposits has already been identified here - Srednevilyuyskoye, Nedzhelinskoye, Sobokhainskoye and others. Gas deposits have also been established in the adjacent areas of the Pre-Verkhoyansk Foredeep. The deposits here are confined to terrigenous rocks of the Mesozoic and Upper Permian and are associated with anticlinal folds. Their depth is 1-2.5 km, and in the central regions of the syneclise up to 3-3.5 km.
In the Angara-Lena Trough, oil and gas deposits are contained in Lower Cambrian and Vendian sediments. Productive horizons are established in the sub-salt terrigenous complex, in the inter-salt and supra-salt terrigenous-carbonate complexes. The average depth of productive horizons is 2.5 km. The deposits are confined to local uplifts; lithologically limited deposits are also known. In this area, the Markovskoye, Krivolukskoye, Ilimskoye, Yuzhno-Ustkutskoye and other deposits have now been identified. The most studied is the Markovskoye deposit, located near the village of Markovo, Ust-Kut district, Irkutsk region. Here, in 1962, an oil gusher was obtained from Lower Cambrian sandstones from a depth of 2164 m. The initial flow rate of the well reached 1000 m 3 /day. Markov oil is the first Cambrian oil in the Soviet Union.
IN Lately industrial gas inflows were obtained within the Nepa-Botuobinskaya anteclise (Nepsky arch), which, undoubtedly, will be a new, most interesting region of the Siberian Platform in terms of oil and gas potential. So far, the gas deposits discovered here cannot be classified as significant. The largest of them, the Srednebotuobinskoye field, contains a gas deposit with dimensions of 55 km X 18 km and a height of about 20 m. Well flow rates reach 720 thousand m 3 / day. The deposit is confined to sandstones of Vendian age. Another thing is striking: wherever wells are drilled within the Nepa-Botuobinskaya anteclise, they, as a rule, reveal Cambrian, Vendian and Riphean rocks saturated with droplet-liquid oil (data from A.V. Ovcharenko, V.E. Bakin, 1979). This means that the subsoil of the area is enriched with “black gold”.
The Krasnoyarsk Territory (the region of the Tunguska syneclise) is characterized by certain potential opportunities. Scientists have long been in favor of prospecting for oil and gas here. And in 1977, the first fountains of gas and oil were obtained from the pre-salt deposits of the Mota Formation (Vendian). Productive wells were drilled east of the Yenisei Ridge and near the village. Vanavara on Podkamennaya Tunguska. Industrial deposits of oil and gas in Lower Cambrian sediments have been identified in the Kuyumbinskaya area. Let's hope that these are just the first signs.
There are many unusual things in Siberia. There were some surprises for the gas workers as well. In Yakutia, researchers for the first time encountered the property of natural flammable gas to be in the earth's crust in a solid state. Now experts are deciding how to develop such deposits and evaluate their reserves. In the future, solid gas can become an important source of blue fuel.
Coal is of great importance for the development of industry in the central and eastern regions of Siberia. Its deposits are quite widespread in the depths of the platform, and the total reserves amount to 68% of the all-Union reserves of brown and hard coals. In most cases, productive formations occur in Jurassic and Lower Cretaceous rocks. The largest within the Siberian Platform, the Lena coal basin occupies the territory of the Vilyui syneclise and the Pre-Verkhoyansk foredeep. Its total area is 400,000 km 2, and coal reserves in 1955 were estimated at 2647 billion tons. Over the past 20 years, geologists have explored new coal deposits here, and now it is one of the richest basins in the world. Productive formations are confined to Cretaceous and Jurassic deposits, their thickness reaches 5-8 m.
The Tunguska coal basin is somewhat inferior to the Lensky one; its reserves in 1955 were estimated at 1744 billion tons. Productive horizons are associated with the Upper Paleozoic deposits of the Tunguska series. In places where there is a breakthrough productive strata The coal is graphitized by trap dikes. The Kansk-Achinsk coal basin is located in the southwest of the Siberian platform. The layers of combustible stone are confined to the Jurassic sequence, which fills graben-like depressions (Irkutsk, Kansk, Rybinsk). The total reserves of coal, mainly brown, reach 1220 billion tons. Now, on the basis of this basin, the Kansk-Achinsk energy complex is being formed at an accelerated pace. The time is not far off when thermal power plants and other energy-intensive industries will grow here.
Other riches of the Siberian subsoil
We have not yet said anything about deposits of iron, bauxite, mineral salts, and numerous types of nonmetallic raw materials, which Siberia is so rich in.
Iron on the Siberian Platform has been discovered and is being explored in five iron ore basins: Angaro-Ilimsky, Sredneangarsky, Angaro-Katsky, Angaro-Pitsky and South Aldansky. Ores of hydrothermal, sedimentary and metamorphic origin are confined to Proterozoic and Lower Paleozoic deposits. The iron content in the ores is up to 45%, its total reserves are estimated at over 4 billion tons. In the western part of Transbaikalia, magnetite ore deposits have been established in the Iron Ridge mountain range. Similar deposits of ferruginous quartzites are known in Eastern Sayan, on the Yenisei Ridge.
Bauxite deposits are developed within the Yenisei Ridge. The deposits here are confined to loose Paleogene deposits, filling karst depressions in the carbonate rocks of the Cretaceous and Cambrian. Bauxite deposits were established in the Buryat Autonomous Soviet Socialist Republic in the Lower Cambrian.
Mica deposits (mainly muscovite and phlogopite) have been identified along the northwestern edge of the Baikal folded region, the eastern slope of the Eastern Sayn (deposits Bukachanskoye, Akukanskoye, Slyudyanskoye, Biryusinskoye, Yeniseiskoye, etc.)
Iceland spar, used in the optical industry, is confined to trap intrusions of the Upper Paleozoic. Its deposits were discovered in the Krasnoyarsk Territory.
Rock salt of Early Cambrian age, the reserves of which are practically inexhaustible, is currently being developed only in the Irkutsk region (Irkutsk salt-bearing basin), where several powerful productive strata are located close to the surface.
Other non-metallic mineral resources of the Siberian Platform include graphite (Noginskoye deposit), magnesite (Talskoye and Kardakinskoye deposits on the Yenisei Ridge), phosphorite (Iliktinskoye deposit in Western Transbaikalia), corundum (Chainitskoye deposit in the Stanovoy Range), kaolin and rock crystal (Irkutsk deposit in the Aldan basin), semi-precious stones, in particular lapis lazuli (Transbaikalia).
The Siberian subsoil is also rich in amazingly beautiful facing materials, primarily marble. Unique deposits of it have been discovered in the southeast Novosibirsk region. Along with white, gray and cherry-red marble, a rare variety of bright green color was discovered here. This is the only deposit of green marble on the territory of our country. In terms of its qualities, it is not inferior to the famous Italian one, which is very highly valued on the world market. The deposit's reserves amount to more than 1.5 million m3. Siberian marble will find its first use in finishing Novosibirsk metro stations.
Finally, it is necessary to say about mineral and thermal springs, which are still practically not used. Only in the lake area. Baikal scientists from the Institute of the Earth's Crust of the Siberian Branch of the USSR Academy of Sciences discovered more than 300 outlets underground water with a high content of mineral salts. 23 sources have medicinal properties. Mineral waters of deep origin, they made their way to the surface of the Earth along the faults that outline the lake. Hot springs with water temperatures up to +60 °C were also found here. Similar thermal springs have been identified in the valleys of the rivers Upper Angara, Chara, Olekma, Byssa, Bureya and their tributaries.
Underground storerooms along the BAM route
As you can see, the Siberian subsoil contains considerable wealth, but many treasures are still waiting in the wings. The exploration of these natural reserves is primarily hampered by difficult climatic conditions. But the development of the national economy of our country urgently requires the active involvement of Siberian deposits in industrial production, and in an extremely short time. One of the decisive steps taken in the development of the riches of Siberia is the construction Baikal-Amur Mainline(Fig. 12). The creation of this route will dramatically increase production in all surrounding areas, and the area of these lands is considerable. According to experts, it is 3.5 times larger than the territory of France. The active development of the Kodaro-Udokan copper ore province, the Kansk-Achinsk coal basin, underground oil and gas reserves of Yakutia will begin, the thermal and mineral waters of Baikal will find use, etc.
The construction of BAM is a school of courage and civic maturity for thousands of young enthusiasts who have to overcome great difficulties - bitter frosts in winter and heat in summer, vileness, and disorderly life. Quite unexpectedly, it turned out that the gentle mountain ranges along which the highway will run are avalanche dangerous. Only in the area of the river. Naminga experiences up to 250 avalanches per year. Before the route comes here, it is necessary to find effective ways to combat “snow death”.
For now there is only one way - preventive release of avalanches using mortar shots.
According to experts, the cost of BAM is quite an impressive figure. Naturally, the question arises: are the depths of this region rich enough, which the highway is designed to awaken? How many pantries has nature prepared along the route? The BAM passes through one of the most geologically complex parts of our country. Research in these areas has been ongoing for a long time. A geological survey of the area adjacent to the highway has already been carried out. The work was carried out by a large team of geologists under the leadership of Corresponding Member of the USSR Academy of Sciences, A.I. Krasny. Deposits of tungsten, molybdenum, titanium, tin, fluorite, manganese, polymetals, iron, lead, zinc, copper, apatite, phosphates, precious and ornamental stones, and building materials have been discovered. The range of minerals, as we see, is quite large.
The greatest fame of the Baikal-Amur Mainline was probably brought by Udokan copper. In its middle part, the route passes through the picturesque Char Valley, surrounded by the Udokan and Kodar mountain ranges, individual peaks of which rise more than 3 km. The ore of the Udokan Range is very diverse in composition and contains many valuable impurities. Geologists have not yet fully completed exploration of the Udokan subsoil, but the significance of this deposit has now been determined. The adits dig into the ridge for more than 1.5 km - and there is copper everywhere. Even the famous hostess copper mountain Compared to Udokan, she would look like a poor relative. In the valley itself, deposits of iron, coking coal, and building materials have been discovered. Near Char, a deposit of a previously unknown pink-violet mineral was found, which was called charoite.
Specialists associate great prospects with the development of unique igneous rocks of alkaline composition of the Synnyr massif. From these synnyrites it is possible to obtain alumina - a raw material for the production of aluminum, valuable potash fertilizers, potash and other useful substances.
In the north of Buryatia, 18 km from the steel main, the Molodezhnoe asbestos deposit was discovered. The mineral lies literally on the surface, so it can be extracted using the cheapest quarry method. This pantry is rare: asbestos has a very high content of textile fibers, the length of which reaches 12 mm.
The list of underground storage facilities along the Baikal-Amur Mainline can be continued, but what has been said is enough to conclude that capital investments in the construction of the route will more than pay off. Those who will develop the subsoil here are faced with the task of making the most rational, comprehensive use of these resources. Geologists are now not only searching for and exploring new deposits, but also compiling a catalog of all underground treasures that can be used in national economy. Using the example of Siberia, and in particular the example of the BAM, it became obvious that almost all types of mineral raw materials are complex and require a unified development system, i.e., when exploiting the main type of mineral, deposits of associated raw materials must also be involved in development. In the first years of Soviet power, fifteen to twenty useful elements were extracted from ores, in 1950 - forty-three, in 1960 - already sixty-six, and in the 70s - seventy-four. With integrated development of deposits, the costs of obtaining raw materials are reduced and the economic profitability of this process increases. One of the real ways of comprehensive exploitation of subsoil is the creation of territorial-industrial complexes. This is a new, more progressive form of production organization, designed to make maximum use of natural reserves. In the area of the BAM highway, the Udokan territorial-industrial complex will be created, which will include a mining and processing plant, a copper smelter, the city of Udokan and other objects.