African-Arabian platform. Arabian platform Alpine fold structures

The platforms of the Gondwanan group include the South American, Hindustan, African-Arabian, Australian and Antarctic. It is assumed that in the Paleozoic they formed a supercontinent - Gondwana, subsequently separated by oceanic depressions.

3.2.1. The South American platform - occupies most of the continent of the same name and is the western fragment of the Gondwana mainland destroyed in the Mesozoic. It borders on the west with the Andean sector of the Pacific mobile belt, which has retained tectonic and magmatic activity since the Late Proterozoic. Based on the age of the basement, the South American Platform is divided into parts: the western one is Early Precambrian and the eastern one is Late Precambrian.

The foundation of the western part, within the so-called. The Amazonian craton was consolidated in the trans-Amazonian phase of folding (1.9-1.8 billion). It emerges on the surface on the Guiana and Central Brazilian shields, where it is formed by a combination of the Gurian gneiss complex (>3.0 Ga) and granite–greenstone complexes of the Takuy (2.6–1.8 Ga) tectonomagmatic cycles. The shields are separated by the latitudinal Paleozoic-Mesozoic Amazonian trough. On the Guiana Shield, the basement is overlapped in places by a cover of protoplatform deposits of the Roraima Formation (1.8–1.7 Ga). On the Central Brazilian Shield, the early platform complex is represented by the Lower Riphean volcanic-plutonic and terrigenous-volcanic sequences occurring in wide troughs.

East foundation. parts of the South American platform - the so-called. The East Brazilian Craton consists of a system of submeridian zones of Late Proterozoic folding separated by ancient massifs. The western zones are formed by sedimentary and volcanic-sedimentary complexes of the Urushan (1.4-1.0 Ga) and Brazilian (1.0-0.6 Ga) tectonic development cycles, among which are massifs of deeply metamorphosed Early Precambrian rocks. Two large median massifs stand out: San Francisco and Goias, the base of which is composed of Archean and Lower Proterozoic rocks. Archaean in these massifs is represented by metavolcanogenic-sedimentary, metasedimentary greenstone complexes. belts (2.7-2.5 billion years) and older migmatite-gneisses with late Archean granites separating them. The largest Early Precambrian block, the San Francisco massif, is covered over a large area by a cover of Riphean platform formations of the syneclise of the same name. The eastern part of the craton - the Atlantic zone is composed of Archean and Lower Proterozoic granulites, which underwent deep tectonic-magmatic processing and isotopic "rejuvenation" during the Brazilian phase of diastrophism. Late Proterozoic metasediments are of subordinate importance in their structure; ophiolites are present in the La Plata zone.

The final consolidation of the basement of the South American Platform occurred in the Cambrian. At the same time (the end of the Brazilian cycle, about 650 Ma), the foundation of the platform was divided into a system of blocks by submeridional and sublatitudinal faults. Apparently, the splitting of the Amazonian craton into the Guianan and Central Brazilian shields with the formation of aulacogen, which later turned into the latitudinal Amazonian syneclise, was apparently associated with late Brazilian movements.

The platform cover (Silurian - Cenozoic) accumulated in several isolated negative structures. The basement is deeply buried in the Amazonian syneclise, which crosses the platform from west to east. It opens to the west, to the Andes and to the east, to the Atlantic Ocean, and the thickness of the cover sharply increases in the pericratonic parts of the syneclise.

The syneclises of Paranaiba (Maragnano), Parana and located to the west - Chaco are meridional oriented. The thickness of the cover is usually about 5 km. In the section, shallow-water terrigenous-carbonate formations of the Silurian-Devonian, glacial terrigenous deposits of the Middle-Upper Carboniferous, marine terrigenous (below) and red-colored continental deposits of the Permian and Triassic are isolated.

Usually, the Mesozoic-Cenozoic complex, lying unconformably, begins with continental, often volcanic deposits of the Upper Jurassic - Lower Cretaceous. Volcanic trap complexes are especially widely represented in the Parana syneclise, where their thickness exceeds 1.5 km. Upper Cretaceous - Cenozoic complexes are common in the marginal perioceanic troughs, as well as near the Andes. In the section of the Pre-Andean trough, there are marine (Cretaceous-Paleogene), as well as thick continental strata (Cenozoic).

Numerous massifs of basic alkaline and alkaline-ultrabasic rocks (Jurassic - Eocene) are known in the platform complex.

Rice. 7. Scheme of the structural elements of South America.

1-2 - protrusions of the platform foundation: 1 - Archean complexes, 2 - Archean-Proterozoic complexes. Platform cover: 3 - Proterozoic,

4 - Paleozoic-Mesozoic, 5 - Mesozoic-Cenozoic; 6 - zones of Mesozoic trap magmatism. 7 - Precambrian and Paleozoic folded complexes;

8 - Neogene-Quaternary foredeep; 9 - areas of Neogene-Quaternary volcanism and intermontane depressions; 10 - folded structures of the Pacific belt. Shields, arrays: 1 - Guianan, II - Central Brazilian, III - East Brazilian, IY - Sierra Pampa; syneclises, deflections: 1 - Amazonian, 2 - Maragnano (Paranaiba), 3 - Sao Francisco, 4 - Paranas, 5 - Chaco Pampas

4.2.2. Hindustan platform occupies the Hindustan Peninsula. It has the appearance of an irregular rhombus, bounded on the north side by the folded structures of the Suleiman Mountains, Kirtkhara, the Himalayas, the Arakan Mountains and their forward troughs, and on the south by the depressions of the Indian Ocean.

The foundation of the platform is exposed in its southern half - on the South Indian Shield, which forms the Hindustan Peninsula and in the arches of platform uplifts in the north of the platform - within the Vindian Plate, where Archean gneisses compose a significant part of the Bandelkand dome. Most of the basement was consolidated in the Archean. In the Precambrian structure of the shield, the granite-greenstone region of the Baster craton, which occupies the central part of the peninsula, and the East Ghat and West Ghat granulite belts framing it, stretching along the margins of the peninsula, stand out.

In the structure of the Baster craton, tonalite-trondhjemite “peninsular gneisses” (3.3–3.2 Ga) are of primary importance, containing inclusions of amphibolites, paragneisses, and quartzites, rocks of younger volcanic-sedimentary complexes. The latter form in the northwestern part of the craton, south of the Deccan Plateau, greenstone belts of two generations: the smaller Sargur belts (3.2–3.15 Ga) and the larger Dharvar belts (3.1–2.6 Ga). The belts have a NW-SSE direction and are spatially separated. In the Dharvar belts, two volcanogenic-sedimentary strata (groups) have been distinguished: the lower Bababudan and the upper Chitradurga. The “gneisses of the peninsula” to the east of the greenstone belts are intruded by batholiths of late tectonic granites with an age of 2.5–2.4 billion years. Tonalite-trondhjemite gneisses with fragments of younger rocks also appear in the Singbum Dome, Shillong and Bijanar uplifts.

The West Gat and East Gat belts are composed of gneisses of the metamorphic granulite facies (protolith age ≈ 3.4 Ga) and other rocks of the Katazon, which experienced a long history of structural metamorphic transformations up to 0.5 Ga ago. The boundary of 1.7 - 1.8 Ma is especially important, when the East Ghat belt was pushed over the Kudapakh syneclise, composed of the Lower Proterozoic. The belts articulate in the south of the peninsula and are separated from the Archean granite-greenstone area by large thrusts falling under them. The metamorphic complexes of Sri Lanka belong to the Western Ghat belt.

The Archean "pre-Darvarian" migmatite-gneiss basement of the northern part of the platform is dissected by two belts of Early Proterozoic folding. The Delhi-Aravalli belt is larger, stretching in the NE-SW direction, mostly under the platform cover to the north of the river. Normada and Son. In the older Aravalli system of this belt, a stratum of paraschists with subordinate marbles, metabasites, and ultrabasic bodies is distinguished. The rocks are intruded by granites with an age of 2.15-1.8 billion years. The younger Delian system is composed of psammite-pelites, conglomerates, gravelstones, mostly with the rhythmic nature of their alternation. The rocks are altered under conditions of greenschist and amphibolite facies. The formation of the belt ended with the intrusion of granites (1.7-1.6 Ga).

The smaller Satpur belt of Early Proterozoic folding is located in the northeast of the platform. In the Satpura Range, it is composed of metaterrigenous turbidites containing rocks of the ophiolite association and overlying Early Riphean molassoids. There is an idea that the Aravalli-Delhi and Satpur belts are segments of a larger belt framing the north of the Archean complexes of the South Indian Shield.

The platform cover in the northern part of the platform begins with clastic formations of the Riphean (the so-called Vindian system), filling the Vindian and Kuddapah syneclises. On the northern outskirts of the platform (Salt Ridge) are known salt-bearing, red-colored and carbonate deposits of the Vendian-Cambrian, which are overlain by glacial formations of the Upper Carboniferous-Lower Permian, shallow Upper Permian, and continental deposits of the Triassic-Lower Jurassic. The marine shallow-water terrigenous-carbonate deposits of the Sind-Punjab trough lie above. The upper part of the Lower and Middle Paleozoic is absent on the platform.

Relatively widespread rocks of the Upper Paleozoic-Lower Mesozoic (Gondwana series) with a thickness of about 6 km, filling the Late Paleozoic aulacogenes (rifts), the main of which is the Normada-Son-Damodar. The Gondwana Series includes Upper Carboniferous-Lower Permian glacial deposits, Upper Permian parallic coal-bearing sequence, Lower-Middle Triassic variegated formations, Upper Triassic-Middle Jurassic coal-bearing formations, and Upper Jurassic-Lower Cretaceous variegated volcanogenic stratum with traps.

The formation of rift structures on the platform continued in the Mesozoic and Cenozoic (West Bengal rift, etc.). In the Mesozoic - Paleogene, the Sind-Punjab trough developed along the northwestern margin of the platform adjacent to the Balochistan system, where a thickness (4-5 km) of terrigenous and carbonate deposits of the Jurassic - Paleogene accumulated. In the Late Cretaceous-Paleocene, active trap magmatism occurred in the western part of the South Indian Shield, and the Deccan syneclise formed. In the Eocene, the Cambay Rift was formed northeast of the Deccan Plateau. It is assumed that the Hindustan Peninsula became part of the Asian continent at the end of the Eocene. The Neogene-Quaternary orogeny in the Alpine-Himalayan region contributed to the widespread occurrence of thick Neogene-Quaternary molasse complexes around the platform, which experienced significant deformations on the inner sides of the marginal troughs.

Rice. 8. Structural elements of the Hindustan platform. (According to V.E. Khain, with changes).

1 - Archean granite-gneiss and granite-greenstone complexes; 2 - Archean granite-gneiss complex of the Eastern Ghats, reworked in the Early Proterozoic;

3 - Lower Proterozoic complexes of the Aravali system; 4 – Mesozoic-Cenozoic cover; 5 - Upper Cretaceous and Paleogene traps; 6 - Gondwana series in grabens, 7 - Upper Proterozoic sheath complex; (8) Neogene-Quaternary molasses of foredeeps; 9 - Alpine folded platform framing systems; 10 - the largest thrusts; 11 - faults. Numbers in circles: Late Proterozoic syneclises: 1 - Vindian, 2 - Kuddapakh; Late Paleozoic-Early Mesozoic aulacogenes: 3 - Godavari, 4 - Mahanadi,

5-Normada-Sleep; late Mesozoic structures: 6 - Kanbei aulacogen,

9- Sind-Punjabi, 10 - West Bengal; blocks and foundation elevations:

11 - Bandelkand massif, 12 - Shillong massif, 13 - Darwar block

4.2.3. African-Arabian platform- the largest among the platforms of the Gondwana group, reflects all the features of their structure. It occupies most of the African continent, the Arabian Peninsula and continues on the island of Madagascar (Fig. 9). From the northwest it is bounded by the Paleozoic folded structures of the Maghreb, from the northeast - by the Alpine Pre-Zagros (Mesopotamian) marginal foredeep. In the south, a zone of early Cimmerian structures of the Cape Mountains stands out. From the west, east, northeast, the deep-water depressions of the South are adjacent to the platform. Atlantic, Indian Ocean, Mediterranean.

In the north of the platform, within the Sahara Plate, the basement is exposed in large massifs (Regimbat, Tuareg, Nubian-Arabian, Leono-Liberian, etc.), separating individual depressions on the plate. In the south, the basement massifs merge into two continuous meridional bands separated by a trough zone: the Congo, Okovango, Kalahari and Karru

The Precambrian foundation of the platform consists of isometric blocks - folding areas (protocratons), and belts - Archean, early and late Proterozoic. In its basement, the Southern and Northern tectonic provinces differ in age. The boundary between them runs somewhat north of the equator, parallel to the Precambrian belt systems and Mesozoic rifts, with which the Bangui magnetic anomaly coincides in the west.

The dominant role in the structure of the Southern tectonic province is played by the Archean granite-greenstone regions of cratons (Zimbabwean, Tanzanian Kaapwal in South Africa, Kalahari, Congo). Of less importance here are cratons with granite-gneiss basements of the Early Proterozoic (South Angola, Bangweulu). Between the cratons and along their periphery there are folding belts of different ages: the Archean granulite Limpopo (between the Kaapwal and Zimbabwean), Early Proterozoic (Case between the Kaapwal and Kalahari, Lomagundi - in the western frame of the Zimbabwean craton, Bugando-Toro - along the northern edge of the Tanzanian craton, Otoue - along the northwestern edge of the Congo), Middle Riphean (Kibarsky - between Tanzanian and Congo, Namaqua-Natal - along the southern framing of Kaapvalsky), Pan-African (700-600 million years) (granulite East African with Madagascar - along the eastern framing of the Kaapval, Zimbabwean and Tanzanian cratons, the Domar craton between the Congo and Kalahari cratons, the Atlantic one in the western framing of the Kalahari, South Angol and Congo cratons).

Of particular interest is the Kaapvaal protocraton, within which there is a Late Archean-Early Proterozoic protoplatform cover, which includes five thick volcanogenic-terrigenous complexes (3.0-1.8 Ga). The section of the upper complexes contains siliceous and carbonate rocks. Metamorphism usually does not exceed the greenschist stage. The protoplatform cover includes large mafic intrusive massifs (Bushveld and others), large dike swarms, and alkaline intrusions (2.0–1.4 Ga).

The basement section of the Archean protocratons contains the most ancient gneisses and granitoids from tonalite to trondhjemite composition with an age of about 3.5 Ga, as well as rock complexes typical of greenstone belts.

The basement of the western part of the Northern Tectonic Province from the Mauritian Mountains to the Hogar Highlands was consolidated in the Archean (Liberia, Sierra Leone, northeast Mauritania) and in the Early Proterozoic (Guinea, Mali, Côte d'Ivoire, Ghana, Burkina Faso, western Nigeria , southwestern Algeria, southern Morocco). Granite-greenstone complexes of the Archean and Early Proterozoic appear in two shields - Guinean in the south and Regibad in the north, separated by the Taoudeni syneclise. In general, this ancient stable region stands out as the West African Craton. The latter is framed on all sides by the Pan-African folding belts (700-600 million years): Rockell in the southwest, Mauritanian in the west, Anti-Atlas in the north and Atakor in the southwest. Pan-African structures form the foundation from the Hogar Highlands to the Persian Gulf. The vast area of the Pan-African basement is a young craton, which can be conventionally called the Arabian-North African. In its basement, according to the type and age of the metamorphic strata, granite-greenstone associations of the Late Proterozoic are distinguished, similar to the Archean and Early Proterozoic ancient cratons and areas in which the Early Proterozoic complexes underwent Pan-African tectonic-magmatic reworking. In the Southern tectonic province, on ancient blocks, the cover of platform deposits begins from the Lower Precambrian. From the Upper Archean and Lower Proterozoic on the Kaapval craton, the Lower Proterozoic - on the Congo cratons, and the Zimbabwean, Upper Proterozoic on the Kalahari and Tanzanian cratons.

The Lower-Middle Paleozoic cover (Cambrian - Devonian) is known in the northwest of the Sahara and on the Arabian plates. These are relatively shallow-water terrigenous and carbonate deposits, with tillites in the Ordovician (northwest Africa), evaporites in the Cambrian (southern Arabia). In the north of the plates, shallow-water formations of the Silurian are most widespread. The central and southern parts of the platform were uplifted in the Early - Middle Paleozoic.

A new stage in the formation of the cover complex began in the Late Paleozoic. In the north, the cover continued to form in two latitudinal zones - the North Sahara and South Sahara (Sahel), separated by a band of uplifts - massifs (Regimbad, Akhagar, Tibesti, etc.). Massifs and transverse meridiananal block uplifts in the north of the continent divide the latitudinal zones of subsidence into separate depressions - Tindouf syneclise, Western Sahara, East Sahara, East Libyan, Lower Nile, Muzruk and others - in the northern strip and Taoudeni, Senegalese, Mali- Nigerian, Chad, Kufra, Upper Nile and others - in the south. In the Late Paleozoic, sedimentation in the north of the platform decreased, and in the cover of the listed syneclises, the Lower-Middle Paleozoic and younger Mesozoic strata are predominant.

In the south of the platform, the Upper Paleozoic cover formed in a submeridional subsidence zone formed by a chain of depressions (Kongo, Okovango, Kalahari, and Karru). Upper Paleozoic - Lower Mesozoic deposits are made by graben-like structures superimposed on the Upper Proterozoic cover (Congo syneclise) or crystalline basement. In some places it begins with glacial deposits of the Upper Carboniferous, sometimes with continental red-colored sediments of the Permian.

The complex of Upper Paleozoic - Lower Mesozoic sediments (Karoo superseries) is most fully represented in the Karoo syneclise, where it includes four series with a total thickness of up to 8-9 km. The lower terrigenous series with tillites, sometimes overlying glacial landforms, belongs to the Upper Carboniferous. The Lower Permian terrigenous sequence includes limestone, coal, and iron ore beds. Dolerite dikes are confined to it. The overlying red-colored sediments of the Upper Permian - Lower Triassic contain known locations of reptiles and amphibians. The upper series in the lower part is composed of variegated sandstones and clays, which are overlain by unconformably occurring covers of Lower Jurassic basalts.

The southern syneclises were finally formed in the Mesozoic; The section of the cover is dominated by terrigenous sequences.

From the side of the Atlantic and Indian oceans, the African-Arabian platform is framed by pericontinental troughs that began to develop in the rift mode at different times: from the Late Carboniferous (Namibia, South Africa, Madagascar), Permian (Mozambique, Tanzania, Kenya, Senegal, Mauritania), Late Jurassic , Neocom (Angola, Guinea, Sierra Leone, Liberia), Apta (Cote d'Ivoire-Ghana, Gabon, Equatorial Guinea), Alba (Cameroon, Nigeria). Mesozoic rifting led to the separation of the Chad and Benue grabens. In the Mesozoic (Jurassic, Cretaceous), along the edges of the platform, coinciding with the boundaries of the modern continent, there was a separation of grabens - zones of stepped subsidence along the Atlantic coast (Western Sahara, Mauritanian-Senegalese, Guinean and other troughs), as well as along the coast of the Indian Ocean (Somali , Kenyan, Mozambique troughs) with a cover of Upper Mesozoic marine sediments. Particularly active in the Mesozoic was the northern part of the platform, adjacent to the structures of the Mediterranean belt.

The latest stage of development is characterized by the formation of the giant East African rift system. From the beginning of the Neogene, the northeastern part of the platform became part of the Asian continent due to the formation of the Red Sea Rift.

On the African-Arabian platform, epicratonic magmatism formations of different ages are widely represented: Archaean (Pretoria, Pongola, Ventersdorp volcanics of the Kaapval craton, Great dike on the Zimbabwe craton), Early Proterozoic (Bushveld complex of the Kaapval craton, mafic rocks on the Zimbabwe craton and Shiu shield of the Congo craton), Riphean (basites on the Tanzanian craton, alkaline granites on the Tuareg and Arabian-Nubian shield, pegmatites of the East African folding belt), Paleozoic (alkaline complexes of the Air Plateau in Niger, Red Sea Mountains of Sudan), Mesozoic (traps of the Kaapwal and West African cratons, alkaline granitoids Jurassic of the Jos Plateau of Nigeria, Cretaceous kimberlites on ancient cratons), Cenozoic (alkaline basalts and their differentiates on shield uplifts of the Pan-African basement).

Rice. 9. Structural elements of the African-Arabian platform:

1 - ledges of the Precambrian basement; 2-3 - cover: 2 - Paleozoic-Cenozoic,

3 - predominantly Upper Paleozoic-Mesozoic; 4 - zones of recent volcanism and rifting; 5 - folded frame - Mediterranean belt. Shields, arrays: 1- Regimbat, II - Akhagar, III - Nubian-Arabian, IY - Leono-Liberian and Dahomey, Y - Cameroonian, YI - Central African, YII - Western Congolese, YIII - Rhodesian, IY - Tanganyika, Zimbabwe, etc. ; large syneclises, depressions, deflections 1 - Karru, .2 - Kalahari, 3 - Okovango, 4 - Congo, 5 - Chad, 6 - Mali-Nigerian, 7 - Taudeni, 8 - Somali, 9 - Senegalese, 10 - Mozambican, 11 - Nigerian, 12 - Benue, 13 - Upper Nile

4.2.4. Australian platform(Fig. 12). occupies the main western part of the continent of the same name . From the west and south, it is bounded by the deep-water basins of the Indian Ocean, from the east by the Paleozoic folded structures of the Tasmanian folded system, from the north by the deep-water trench of the Sulawesi Sea and the folded structures of the eastern part of New Guinea. The shelf Timor and Arafura Seas, as well as the Gulf of Carpentaria, belong to the areas of modern accumulation of the cover of the northern margin of the platform.

Basement outcrops form massifs separated by areas covered by mantle (Yukla, Canning, Kimberley syneclises, etc.). Two large massifs (Pilbara and Yilgarn) are located in the western part of the platform; in the central part is the Musgrave massif, and in the southeast - Gawler. The basement was exposed along the southern framing of the Kimberley syneclise and also in the northeast of the platform. Three provinces can be distinguished in the Australian platform based on the age of the basement: Western - Archean, Central - Early Proterozoic and Eastern - Late Proterozoic. Foundation Zap. The province is exposed in two shields, the larger southern Yilgarn and Pilbara. The Precambrian structure of the Pilbara consists of two zones of Archean folding: a large granite-greenstone area (3.0-2.76 Ga) and a granulite-gneiss area (3.63 Ga). The first area consists of a tonalite-granodiorite complex and narrow greenstone belts of three generations located in it (3.5-3.3; 3.2-3.15; 3.15-2.9 Ga). Here, radiometric methods were used to diagnose complexes of an older crustal substrate (3.72–3.53 Ga) that experienced melting and asynchronous, differentiated ascent with the formation of granite-gneiss domes. In the second area, Early Archean gneisses are combined with younger metasediments. The folded structures of both regions are mostly oriented in the submeridional direction.

Upper Archean and Lower Proterozoic granite-greenstone associations and Lower Archean gneiss complexes separating them protrude at the southern margin of the platform in the Goler Shield. The structures of the supracrustal complexes are oriented sublatitudinally.

The foundation of the largest Central Province consists of a combination of different-sized blocks of the Archean substrate (in particular, Kimberley) and the folding belts of the second half of the Early Proterozoic (2.2-1.7 billion years) located between them. The blocks are overlain by platform deposits of the Upper Proterozoic and Phanerozoic. Granulites of the second half of the Early Proterozoic, granitized to varying degrees, are exposed in the uplifts of southwestern Australia (Albania-Fraser belt) and in the center of the mainland. Granulites underwent tectonic-magmatic reworking and isotopic "rejuvenation" in the Late Proterozoic. In general, much less metamorphosed, mainly metasedimentary rocks, are composed of early complexes of coeval folding belts identified in the basement of the northern part of the Central Province. The same type and coeval Capricorn belt is located in the basement of the Australian Platform between the Yelgarn and Pilbara shields. In most of the northern belts, the rocks of the second half of the Early Proterozoic are altered mainly under the conditions of the greenschist facies (in some places up to the amphibolite facies), intruded by syntectonic granites, which in some places take part in the structure of dome structures. In the Eastern Province, the basement of the Australian Platform is formed by almost exclusively folded sandy-clayey strata of the Late Proterozoic: Lower (Mount Isa Belt) and Upper Riphean (Adelaide Belt).

The oldest protoplatform deposits (2.8–2.4 Ga) are distributed on the southern slope of the Pilbara Shield. They perform the Hamersley syneclise. Its section contains basalts, jaspilites, and red flowers. The deposits are crumpled into folds and separated by granite-gneiss domes. The protoplatform lower Proterozoic (2000-1769 Ma) also overlaps the Archean Kimberley block.

The cover of the platform begins with the Upper Proterozoic, the base of which is rejuvenated from the northwest to the southeast and east. A system of rifts also formed in the Riphean, in particular the Amadies Rift, which separated the Musgrave and Aranta shields. The cover complex in most aulacogenes begins with the Upper Riphean. In general, the accumulation of the platform complex on different blocks of the basement began at different times, however, active platform subsidence in the east has been noted since the Late Riphean due to the subsidence of the Adelaide fold system and the Amadies latitudinal aulacogen transverse to it. In the Early Paleozoic, the trough was localized in areas adjacent to the Adelaide system and the Amadeus trough. In the Middle Paleozoic, most of the platform was uplifted. The Late Paleozoic stage of the cover formation is marked by residual troughs in the Canning and Officer syneclises and the formation of extended rift structures along the western edge of the continent. The Late Carboniferous-Early Permian is the epoch of glaciation in Australia with a general high standing of the platform.

Rice. 12. The main tectonic structures of Australia. (Tectonics of continents..., 1988).

1-5 - platform cover: 1 - Permian - Cenozoic, 2 - Lower Paleozoic,

3 - Upper Riphean, 4 - Lower Riphean, 5 - Archean-Lower Proterozoic;

6-10 - folded areas with the age of orogeny and cratonization, Ma: 6 - 570-230,

7 - 900-650, 8 - 1900-900, 9 - 2000-1400, 10 - >2500

The Mesozoic-Paleogene stage is the time of the final formation of the modern structure of the platform. Its central part was uplifted, but the edges of the continent were involved in subsidence. At the end of the Cretaceous and Paleogene, the Australian and Antarctic continents separated.

4.2.5. Antarctic platform - occupies east. half of the continent of the same name, in connection with which it is also called the East Antarctic Platform. The main territory is covered with a thick ice sheet. Included in the Gondwanan group of platforms. In the west, it borders on the folded structures of the Transantarctic system, which serve as a continuation of the structures of the Andes. In the northeast and southeast, the Antarctic platform is cut off by depressions of the Atlantic and Indian oceans. Along the western boundary of the platform, a linear structure can be traced - the ridge of the Transanlantic Mountains with outcrops of shale-graywacke flysch of the Upper Proterozoic - Cambrian, intruded by granitoids. The folded structures of this complex (Rossids) were formed at the Cambrian-Ordovician boundary. Apparently, the Rosside structures should be attributed to the Pacific belt, since they underlie the younger structures of West Antarctica, known in the literature as the Antarctica.

The basement of the Antarctic Platform is composed mainly of highly metamorphosed Archean complexes. The Lower Proterozoic strata are part of a latitudinally oriented zone composed of metabasites, green shales, and jaspilites (Prince Charles Mountains, western Queen Maud Land). At the end of the Precambrian and the beginning of the Paleozoic, tectono-thermal activation with the intrusion of granitoids is noted on the Antarctic platform. The Paleozoic cover includes the Silurian-Devonian, the Upper Paleozoic, and the Jurassic. In its section, along with shallow-water terrigenous and carbonate rocks, plateau basalts (Lower Jurassic) and thick coal-bearing series (Permian) are known.

In the south - the African Plate, in the west, the border with the African Plate is the Red Sea Rift and the Dead Sea Rift, in the north, the Arabian Plate is joined by a convergent boundary with the Anatolian and Eurasian plates.

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An excerpt characterizing the Arabian platform

Naturally, this could not calm down the already rather excited guys. Someone ran to call an ambulance, and someone clumsily tried to help me somehow, only complicating an already unpleasant situation for me. Then I tried to concentrate again and thought that the bleeding should stop. And began to wait patiently. To everyone's surprise, in just a minute nothing was seeping through my fingers! I asked our boys to help me get up. Fortunately, my neighbor, Romas, was there, who usually never contradicted me in anything. I asked him to help me get up. He said that if I stood up, then the blood would probably “flow like a river” again. I took my hands away from the cut... and what was our surprise when we saw that there was no more blood at all! It looked very unusual - the wound was large and open, but almost completely dry.
When the ambulance finally arrived, the doctor who examined me could not understand what had happened and why I was not bleeding with such a deep wound. What he didn't know was that not only did I not bleed, but I also didn't feel any pain at all! I saw the wound with my own eyes and, according to all the laws of nature, I should have felt a wild pain ... which, oddly enough, in this case was not at all. I was taken to the hospital and prepared to be stitched up.
When I said that I did not want anesthesia, the doctor looked at me as if I were a quiet lunatic and prepared to give an anesthetic injection. Then I told him that I would scream ... This time he looked at me very carefully and, nodding his head, began to sew up. It was very strange to watch how my flesh was pierced with a long needle, and I, instead of something very painful and unpleasant, felt only a slight “mosquito” bite. The doctor watched me all the time and asked several times if everything was all right with me. I answered yes. Then he asked if this always happens to me? I said no, just now.

Mesopotamian trough.

Alpine folded structures.

Middle and Near East

This is the territory of the Arabian Peninsula, Iran and the Asian part of Turkey.

In tectonic terms, it is located within the ancient African-Arabian platform in the Alpine folded belt (including the junction zone of the platform and the folded belt) and the Mesopotamian trough.

They include the city of Taurus, the Zagross and Elburs ranges, the Central Iranian Plateau, and the South Caspian Depression.

It is located between the Arabian Platform in the SW and the folded structures in the NE. On the southeast of its continuation is the Persian Gulf. N N and NE the trough is limited by a system of overthrusts, along which the Alpine folded structures are pushed onto the lower folded wall of the trough. It is filled with Сm-Q deposits, thickness 11-12 km.

It occupies vast areas to the west and southwest of the Mesopotamian trough. A significant part of the platform is occupied by the Arabian-Nubian shield, its slopes and the marginal part or plate, which is complicated by a number of both positive and negative structural elements. In general, the slab, according to Pz and Mz deposits, is a monoclinal step, immersed in the sowing. and NE direction. Among the elements of the plate, the Palmyra folded zone stands out - this is the area of arch-block dislocations of the eastern coast of the Mediterranean Sea.

Within the Middle and Near East, there are: the basin of the Persian Gulf, Adan, Central Iranian (Dashte Kevid). In addition, along the on the outskirts of the Gulf of Aden, the Aden NGB stands out, and within Yemen, the Shabwa NGB. And finally, in the Middle and Near East, the southern outskirts of the South Caspian, Karakum (Murghab depression) stand out.

In the Aden basin, 2 deposits are known in limestones of the Miocene-Oligocene and Eocene.

In the small basin of Shabva there are 8 deposits with deposits in subsalt deposits J 2 .

In addition, on Wed. and B. East, more than 10 depressions are known, which are considered as VNGB. All of them are located in the Alpine belt and are poorly studied.

The main and most important is the laterally heterogeneous basin of the Persian Gulf. Its area is 1100 x 1300 km. Since 1902, more than 300 oil and gas fields have been discovered, of which more than 10 have reserves from 1 to 10 billion tons and 40 deposits with reserves from 100 million tons to 1 billion tons. Productive: Miocene, Paleogene, Cretaceous, Jura , Triassic and Permian. Reservoirs - carbonate deposits predominate, there are also terrigenous ones.

It is located on the territory of Turkey, Syria, Iraq, Iran, Saudi Arabia, Kuwait, Qatar, Bahrain, UAE and is confined to a common buried area of the earth's crust in the junction zone of the ancient platform with the Alpine folded belt.

The limits of the basin are: to the SW - Arav.-Nub. shield, in the south - the Hadramaut plateau, in the west - the Palmyrid zone, the Jordanian and Aleps uplifts, in the N, NE and E - Alpine folded structures. Production in 1999 - 974 million tons.

(Saudi Arabia - 372, Kuwait - 64, Iran - 173, UAE - more than 100 million tons, Iraq - 132, Oman - 45, Syria - 26, Yemen - 20),

reserves of 93 billion tons of oil, about 53 trillion. m 3 gas.

Tectonic elements of the basin

The largest part is within the Arabian Plate. In the north, it adjoins the Cis-Taurian system of dislocations, in the NE, the Mesopotamian trough, and in the east, the Oman trough. The extreme NE element of the basin is the Outer Zone of the Zagros Anticlinorium.

Arabian Plate complicated by a series of ups and downs. The most important in terms of n/g are the following: The Central Arabian uplift, its eastern part near the coast of the Persian Gulf, is called the Gaza structural terrace. To the northwest of this uplift is the Basra-Kuwait depression, and to the east and southeast of the Rub-al-Khali syneclise. The thickness of the sedimentary cover in the syneclise is about 8 km, in the basin about 7 km, and on the Central Arabian uplift about 5 km.

The most submerged part of the Rub-El-Khali syneclise, the Basra-Kuwait depression, is part of the East Arabian pericratonic trough, which continues further to the northwest.

The next major element of the basin is the Mesopotamian Foredeep. It stretches across the entire pool. It has an asymmetric structure, filled with sedimentary deposits. Power up to 10-12 km.

The outer Zagros zone is an area of development of large linear folds that strike NW and are disturbed.

There are two main o/g regions in the basin. One region of the Arabian Plate, it includes the outer sides of the Mesopotamian and Pre-Doman troughs.

The second is the folded wall of the Mesopotamian trough, which includes both the outer zone of the Zagross and the zone of Pre-Taurian dislocations.

N/g region of the Arabian Plate. The deposits are concentrated in its SE region and extreme NE regions.

SE region of the n/g region of the Arabian Plate. The section is characterized by: Up to R ex. - sandstones, clays. In Cm - salt, P-J 1 - terr.-carb. thickness more than 1000 m, Ј 2 - Ј 3 - clay-carb., carb. and salt, M - 1300 m. Berrias - evaporites - 400 m. Neokom - terr.-carb. - 1100 m. Apt - carb. – 100 m. Turon – maastri-clay-carb.-1100 m. carb. with clays and evaporites. М = 850 m, N – territories, marls, evaporites М = 550 m.

In this area, the following areas are distinguished from SE to NW:

SE, Gaza, Basra-Kuwait and possibly S. Oman on the SE side of the Rub-al-Khali syneclise.

SE region - part of it on land, part in the water area (Iran, Qatar, UAE). Deposits here are dominated by anticlinal type. On land, their formation is controlled by the movements of F blocks and, to a lesser extent, by salt tectonics. The latter is more clearly manifested in the eastern part and in the water area. The structures here are more complex and often broken.

Productive on land are Aptian limestones, in the east also Cenomanian and R sandstones. On land, gas and oil deposits dominate, with oil predominating. The giant deposits here are Murban-Bab, Murban-Bu-Gaza (600 and 500 million tons). In the water area there are oil fields with a gas cap and are productive here: limestone, dolomites, Ј 3 (St. Arab.) and Aptian limestone. Large deposits of Umm-Shaif (300), Idd-El-Shargi, Maidan - Makhzan (280 million tons), etc.

The area has been known since 1953, but is still promising.

Gaza region (Saudi Arabia, Kuwait, Qatar, Bahrain). Part of it is on land, and the NE part is in the water area (Iran, Kuwait, etc.).

It occupies a structural terrace. Gaza and its underwater continuation. The n/g zones are confined to large swells of submeridial strike. Oil fields of the anticline type predominate, the structures are formed mainly due to the movements of the foundation blocks.

Productivity changes from S to N. On land - J 3 (Arab.) - basic, less Neocomian limestone, deposits - news from R.

In the water area - limestones of the Upper Oligocene - Lower Miocene, K 2, Neocomian and Albian sandstones.

Most of the deposits are in Saudi Arabia. Several fields in Qatar, Bahrain, Kuwait, Iran.

Many deposits are gigantic, with reserves ranging from 100 to 200 million tons (Fadili, Zuluf, and others). A number of deposits have reserves of 1-1.5 billion tons (Berry, Harsanid, Manifa, Katif). Abqaik - 1.7 billion and finally Javar - 11.4 (beginning).

The last deposit is confined to the En-Nala swell (240x20 km). The field combines 7 closed uplifts. For all under and separating saddles, a single deposit was established in J 3 - limestones. Tire Ј 3 - anhydrites. Operated since 1948. 322 wells Annual production is more than 100 million tons.

In recent years, a number of deposits have been discovered in the extreme western part of the Gaza region (Kureis, Kirdi, etc.), where the deposits of Ј 3 and Ј 2 are productive and the reserves of this group are commensurate with Javar.

In the water area, the swells have a NNE strike. There are a number of large deposits here: Safaniya-Khafji (4.1 billion K 1 and K 2) - Kuwait-Saudi Arabia, Kirus, Dirius (Iran), Esfandiar - Lulu (several billion tons).

The Basra-Kuwait region is located in the basin of the same name (Kuwait, Iraq). Here, the n/g zones are united by gently sloping uplifts that have arisen due to the movements of F blocks. The deposits are dominated by oil deposits. The main productive horizons are the Barremian (Zubair), Alba (Burgan) and Cenomanian (Vara) peninsulas. Of less importance are the Neocomian and Cenomanian.

There are 5 giant deposits here: Rumaila, Zubair (Iraq) - 2.7 and 1 billion tons. Kuwaiti Vafra, Raudatain - Sabriya (2 billion) and Great Burgan (10.7).

The last deposit is confined to a vast uplift, elongated in the sublatitudinal direction. It consists of three Burgan brachyanticlines (40x14) and two smaller Magwa and Ahmadi.

The field is complicated by low-amplitude faults. Arched deposits in Albian, Cenomanian sandstones. 4 layers. Gives about 40 million tons per year.

NE part of the n/g region of the Arabian Plate. The Iraqi-Syrian region stands out here. The thickness of the sedimentary cover here is about 7 km. Pz - 3 km, T-Y-K - carb. rocks with clays and evaporites. Power - 1.9 km. Paleocene - n. Eocene mudstones with sandstones and izv. Thickness 500 m. Eocene - n. Miocene - known - 1.1 km. Wed Miocene - Pliocene - Terr. complexes with marls and limestones. Power - 1.0 km.

The n/g zones unite platform uplifts, sometimes slightly disturbed. Arched traps, lime collectors and dolomites. The southern part of the region experienced uplift in the last stages. The deposits here are small. In the Miocene, oil is heavy. In the north, carbs are productive. T 3, J 1 and K 2. Latest major. The largest deposits are Suedia (180 million tons) and G/K Djibissa (Miocene, K 2 , T).

So: for the region of the Arabian Plate, it is typical: more than 90% of the explored reserves at a depth of 1-3 km. Little gas. Productive mainly Mz ex., especially J 3 and K 1 -K 2 .

Folded n/g region of Cis-Taurian dislocations of the inner side of the Mesopotamian trough and the outer Zagross zone (Iran, Iraq, Turkey, and Syria). There are 4 main regions: Predtaursky, Kurdistan and Iraqi-Iranian and South Iranian.

Predtaursky (Turkey). The section here is close to the Iraqi-Syrian region, but the thickness is large up to 9 km. and more widely developed carbonate rocks in Pz, K, and 1. The n/g zones here are anticlinal, the folds are asymmetric and broken. Oil fields, less often gas and oil. Productive limestones are K 1 -K 2 and n. Paleogene. Deposits (several tens) are small - Selmo, Bati-Raman (50-20 million tons).

Kurdistan (Kirkuk) SW Iraq. The most ancient deposits - Ј 3 - carb. and evaporites more than 1 km, K - records, marls - 1.0 km, 1 - marls - 100 m, Eocene - n. Miocene - news - 500 m, avg. Miocene - Fars Formation - 1.8 km below the evaporite stratum, above sandy-clayey red deposits.

Pliocene - St. Bakhtiari - red-colored rough material 0.6 km.

Productive: Alb-Cenomanian, Campanian-Maastrichtian limestones, cf. Eocene - c. Oligocene, sometimes N. Miocene.

The largest deposits cf. Eocene - c. Oligocene

Zones n/g strike NW, anticlinal folds have a two-storey structure. Pre-Middle Miocene deposits form simple folds with a wide arch and not very steep limbs. Younger strata of the Miocene, Pliocene above the arches of the slope. dissected by overthrusts, along which the tectonic strata are shifted to the SW.

The most significant deposits are Kirkuk (3 billion tons), Bai-Gassan and Jambur.

Kirkuk (100x5 km), 3 uplifts, 3 deposits. The upper one is Eocene-N.Miocene, the middle one is Campanian-Maastrichtian and the lower one is Albian-Cenomanian.

Iraqi-Iranian region(Bushir-Akhvaz) about 20 n/g deposits. The section is close to Kurdistan. J 3 - limestone and evaporites with a thickness of more than 1.0 km. K 1 -K 2 - news, marls about 3 km. Paleocene - cf. Oligocene - limes, marls, clays - 2.7 km. In the Oligocene - n. Miocene (St. Asmari) - reef artifacts - 0.8 km. Wed upper Miocene - St. Fars - more than 2 km. Pliocene St. Bakhtiari - 3.5 km.

There's a lot of power here. Large thickness of the Miocene-Pliocene.

The main productive complex is the Asmari and K 2 suite. Tires are evaporites and clayey marls.

The n/g zones are anticlinal, the folds have a two-storied structure. Simple to Middle Miocene and complex at the top. The degree of complexity of the structure of the upper part of the structures increases towards the NE. In this direction, the degree of disharmony between carb. Mz - n. Miocene rocks and territories. - top floor.

The first deposit was discovered in 1908 at Mesjid-i-Suleiman. The next in 1920 and later. The largest deposits in Iran. Agha-Jari (1.9), Gai-Saran (2.1), Marun (2.2), Ahvaz (2.4) and others.

Oil fields were discovered in K 2 in the northeast of the Iraqi-Iranian region in the outer zone of Zagrom.

And finally, in the south of the inner side of the Mesopotamian trough, a number of giant gas fields (Kangan, Pars, Dalan, etc.) were discovered confined to linear folds with deposits in limestones and dolomites P at a depth of about 3 km. (In some deposits, the reserves are estimated at more than 8 trillion m 3 - Kangan). It is possible that these deposits form an independent region (S.Iransky).

More than 15 billion tons have already been extracted from the bowels of the Persian Gulf basin. The reserves are, according to various estimates, 93 billion (2001) and 53 trillion. m 3. Annual production has already exceeded 1 billion tons, although now it is artificially reduced (974 million tons).

The abundance of accumulated hydrocarbons in the depths of the basin is explained by the following reasons:

1) from Cm until the early Miocene, a steady subsidence occurred (the thickness of the sedimentary cover is more than 10 km), a significant part of the deposits passed the middle stage of catagenesis.

2) In the section there are good collectors and tires.

3) Arched traps are widely developed, slightly disturbed. Big sizes.

4) The basin is characterized by hydrogeological closure.

This provided very favorable past and present conditions for the generation, accumulation and preservation of deposits.

Mesopotamian trough.

Alpine folded structures.

Middle and Near East

This is the territory of the Arabian Peninsula, Iran and the Asian part of Turkey.

In tectonic terms, it is located within the ancient African-Arabian platform in the Alpine folded belt (including the junction zone of the platform and the folded belt) and the Mesopotamian trough.

Οʜᴎ include ᴦ. Taurus, the Zagross and Elburs ranges, the Central Iranian Plateau and the South Caspian Depression.

It occupies vast areas to the west and southwest of the Mesopotamian trough. A significant part of the platform is occupied by the Arabian-Nubian shield, its slopes and the marginal part or plate, which is complicated by a number of both positive and negative structural elements. In general, the slab, according to Pz and Mz deposits, is a monoclinal step, immersed in the sowing. and NE direction. Among the elements of the plate, the Palmyra folded zone stands out - ϶ᴛᴏ the area of arch-block dislocations of the eastern coast of the Mediterranean Sea.

Within the Middle and Near East, there are: the basin of the Persian Gulf, Adan, Central Iranian (Dashte Kevid). However, along the north on the outskirts of the Gulf of Aden, the Aden NGB stands out, and within Yemen, the Shabwa NGB. And finally, in the Middle and Near East, the southern outskirts of the South Caspian, Karakum (Murghab depression) stand out.

In the Aden basin, 2 deposits are known in limestones of the Miocene-Oligocene and Eocene.

In the small basin of Shabva there are 8 deposits with deposits in subsalt deposits J 2 .

However, on Wed. and B. East, more than 10 depressions are known, which are considered as VNGB. All of them are located in the Alpine belt and are poorly studied.

(Saudi Arabia - 372, Kuwait - 64, Iran - 173, UAE - more than 100 million tons, Iraq - 132, Oman - 45, Syria - 26, Yemen - 20),

reserves of 93 billion tons of oil, about 53 trillion. m 3 gas.

Tectonic elements of the basin

Arabian Plate complicated by a series of ups and downs. The most important from the point of view of n/g are the following: The Central Arabian uplift, its eastern part near the coast of the Persian Gulf, is usually called the structural terrace of Gaza. To the northwest of this uplift is the Basra-Kuwait depression, and to the east and southeast of the Rub-el-Khali syn-clise. The thickness of the sedimentary cover in the syneclise is about 8 km, in the depression about 7 km, and on the Central Arabian uplift about 5 km.

The most submerged part of the Rub-El-Khali syneclise, the Basra-Kuwait depression, is part of the East Arabian pericratonic trough, which continues further to the northwest.

The next major element of the basin is the Mesopotamian Foredeep. It stretches across the entire pool. It has an asymmetric structure, filled with sedimentary deposits. Power up to 10-12 km.

Outer zone Zagros - represents the area of development of large linear folds with a NW strike, disturbed.

There are two basic n/g regions in the basin. One region of the Arabian Plate, it includes the outer sides of the Mesopotamian and Pre-Doman troughs.

The second is the folded wall of the Mesopotamian trough, which includes both the outer zone of the Zagross and the zone of Pre-Taurian dislocations.

N/g region of the Arabian Plate. The deposits are concentrated in its SE region and extreme NE regions.

In this area, the following areas are distinguished from SE to NW:

SE, Gaza, Basra-Kuwait and possibly South Oman on the SE side of the Rub al-Khali syn-clise.

Productive on land are the Aptian limestones, in the east also Cenomanian and R sandstones. On land, gas and oil deposits dominate, with oil predominating. The giant deposits here are Murban-Bab, Murban-Bu-Gaza (600 and 500 million tons). In the water area there are oil fields with a gas cap and are productive here: limestone, dolomites, Ј 3 (St. Arab.) and Aptian limestone. Large deposits of Umm-Shaif (300), Idd-El-Shargi, Maidan - Makhzan (280 million tons), etc.

The area has been known since 1953, but is still promising.

Gaza region (Saudi Arabia, Kuwait, Qatar, Bahrain). Part of it is on land, and the NE part is in the water area (Iran, Kuwait, etc.).

Productivity changes from S to N. On land - J 3 (Arab.) - basic, less Neocomian limestone, deposits - news from R.

In the water area - limestones of the Upper Oligocene - Lower Miocene, K 2, Neocomian and Albian sandstones.

Most of the deposits are in Saudi Arabia. Several fields in Qatar, Bahrain, Kuwait, Iran.

The last deposit is confined to the En-Nala swell (240x20 km). The field combines 7 closed uplifts. At all under. and separating saddles, a single deposit was established in J 3 - limestones. Tire Ј 3 - anhydrites. Operated since 1948. 322 wells Annual production is more than 100 million tons.

The Basra-Kuwait region is located in the depression of the same name (Kuwait, Iraq). Here, the n/g zones are united by gently sloping uplifts that have arisen due to the movements of F blocks. The deposits are dominated by oil deposits. The main productive horizons are the Barremian (Zubair), Alba (Burgan) and Cenomanian (Vara) peninsulas. Of less importance are the Neocomian and Cenomanian.

There are 5 giant deposits here: Rumaila, Zubair (Iraq) - 2.7 and 1 billion tons. Kuwaiti Vafra, Raudatain - Sabriya (2 billion) and Great Burgan (10.7).

The last deposit is confined to a vast uplift, elongated in the sublatitudinal direction. It consists of three Burgan brachyanticlines (40x14) and two smaller Magwa and Ahmadi.

The field is complicated by low-amplitude faults. Arched deposits in Albian, Cenomanian sandstones. 4 layers. Gives about 40 million tons per year.

So: for the n / g region of the Arabian Plate is typical: more than 90% of the explored reserves at a depth of 1-3 km. Little gas. Productive mainly Mz ex., especially J 3 and K 1 -K 2 .

Folded n/g region of Cis-Taurian dislocations of the inner side of the Mesopotamian trough and the outer Zagross zone (Iran, Iraq, Turkey, and Syria). There are 4 base regions: Predtaursky, Kurdistan and Iraqi-Iranian and South Iranian.

Pliocene - St. Bakhtiari - red-colored rough material 0.6 km.

Productive: Albian-Cenomanian, Campanian-Maastrichtian limestones cf. Eocene - c. Oligocene, sometimes N. Miocene.

The largest deposits cf. Eocene - c. Oligocene

The most significant deposits are Kirkuk (3 billion tons), Bai-Gassan and Jambur.

Kirkuk (100x5 km), 3 uplifts, 3 deposits. The upper one is Eocene-N.Miocene, the middle one is Campanian-Maastrichtian and the lower one is Albian-Cenomanian.

There's a lot of power here. Large thickness of the Miocene-Pliocene.

The main productive complex is the Asmari and K 2 suite. Tires are evaporites and clayey marls.

The first deposit was discovered in 1908 at Mesjid-i-Suleiman. The next in 1920 and later. The largest deposits in Iran. Agha-Jari (1.9), Gai-Saran (2.1), Marun (2.2), Ahvaz (2.4) and others.

Oil fields were discovered in K 2 in the northeast of the Iraqi-Iranian region in the outer zone of Zagrom.

And finally, in the south of the inner side of the Mesopotamian trough, a number of giant gas fields were discovered (Kangan, Pars, Dalan, etc.) confined to linear folds with deposits in limestones and dolomites P at a depth of about 3 km. (In some deposits, the reserves are estimated at more than 8 trillion m 3 - Kangan). It is possible that these deposits form an independent region (S.Iransky).

More than 15 billion tons have already been extracted from the bowels of the Persian Gulf basin. The reserves are, according to various estimates, 93 billion (2001 ᴦ.) and 53 trillion. m 3. Annual production has already exceeded 1 billion tons, although now it is artificially reduced (974 million tons).

The abundance of accumulated hydrocarbons in the depths of the basin is explained by the following reasons:

2) In the section there are good collectors and tires.

3) Arched traps are widely developed, slightly disturbed. Big sizes.

4) The basin is characterized by hydrogeological closure.

This provided very favorable past and present conditions for the generation, accumulation and preservation of deposits.

The African-Arabian platform and the shield of the same name cover the territory of almost the entire African continent, except for relatively small areas in the northwest and extreme south, represented by fold zones; the Arabian Peninsula and about. Madagascar, which are geologically related to it. The total area of the African-Arabian platform is about 30 million km2.

In the southern part of the continent, signs of the most ancient stage of the origin of the African platform, its nuclear stage (3.5-3 billion years) have been established. The stage of granitization (3.0-2.5 billion years) of primary greenstone formations of the nuclear stage - the formation of huge fields of granite-gneisses and migmatites - has been distinguished.

In North Africa, a thick sedimentary cover is developed, from under which only, in some places, ancient granitized rocks of nuclear structures protrude.

The mineral wealth of the African Shield is varied and plentiful; Africa ranks first in the world in the production of gold (60% of the production of capitalist countries), diamonds (95% of production), cobalt (80% of production), platinum and palladium (50% of production), one of the leading places in the production of uranium, tantalum, niobium, beryllium, lithium, germanium, zirconium, cesium, rare earth elements and many other minerals.

According to geographical features and geological structure, four large regions are distinguished: North Africa, Central Africa, South Africa, East Africa with about. Madagascar.

Northern Africa (Western Sahara, ARE), as well as Saudi Arabia, are covered with a sedimentary cover of Riphean and younger deposits, from under which massifs of the Precambrian folded basement protrude in places: the Regibat shield, the Tuareg shield and a number of smaller ones. The most ancient Precambrian series here - Suggaria - is represented by gneisses, amphibolites, charnockites, quartzites, migmatized granites. Above unconformity, Faruziy lies - conglomerates, shales, phyllites, rhyolites and andesites.

In West Africa, the most ancient is the Dagomian formation, composed of crystalline schists, gneisses, migmatites, charnockites (this formation is comparable to the Suggar of the Sahara.) The Birrimia series (2200 million years) unconformably overlies the Birrimia series (2200 million years) - quartzites, slates, volcanogens, and even higher unconformably Tarquius (1950 Ma) - basal conglomerates, sandstones and quartzites with horizons of gold-bearing conglomerates.

Central Africa (mainly Zaire). The most ancient rocks are represented by gneisses and shales of the West Nile and Bomu formations (3500-3200 Ma). Overlying is the Banzyville Formation composed of sheared quartzites, chlorite schists, and phyllites. In the southern part of Zaire, the most ancient formations are the base of the Kasai shield (up to 3300 Ma) and the Kalundwe formations (2650 Ma) composed of gneisses, migmatites, quartzites, and itabirites.

Above these ancient complexes, the Kibara-Urundi group (850-1150 Ma) is located sharply unconformably, with which large pegmatite deposits of tin, tantalum, niobium, lithium, beryllium, etc. are associated. which are widely developed and of great metallogenic significance are the deposits of the Katanga group (520-630 Ma). The latter are represented by conglomerates, sandstones, quartzites, shales and dolomites, which are ore-bearing for copper deposits of world importance in the province of Katanga (Zaire) and Zambia, as well as for industrial concentrations of cobalt, zinc, lead, cadmium, germanium, selenium and uranium. The total thickness of the deposits of the Katanga group is 4-6 km.

South Africa (Namibia, South Africa, Southern Rhodesia, etc.) In Southern Rhodesia, three Precambrian rock systems are distinguished (from bottom to top): 1) Sebakviyskaya (3390 million years) - ferruginous quartzites, magnesian rocks, marbles, granulites and granite-gneisses; 2) Bulavayskaya (2850 Ma) - conglomerates, basalts, dacites, quartzites, jaspers, ultrabasic intrusions; 3) Shamvai (2650 million years) - conglomerates, sandstones, graywackes, phyllites.

In the Republic of South Africa, the oldest complex of Swaziland (3500 million years) lies at the base of the Precambrian; above it are rocks of the Witwatersrand system (according to Schuber - 2540 million years) - conglomerates, sandstones, quartzites. The famous gold and uranium-bearing conglomerates are confined to it.

Above lies the Transvaal system of slates, quartzites and dolomites, cut through by the intrusion of the Bushveld complex (1950 Ma).

Among the dolomites of this suite are deposits of lead and zinc, vanadium and fluorite.

In Namibia and the Republic of South Africa (Namaqualand), significant areas are occupied by the younger strata of Damara (800-1000 Ma) and Otavi (760 Ma). These deposits, composed of quartzites, shales, dolomites, are ore-bearing. The Damara system is intruded by granites, with which rare-metal pegmatites (with beryl, lepidolite, etc.) of an absolute age of 800 million years are associated; the dolomites of the Otavi system contain the copper-lead-zinc deposit rich in germanium, Tsumeb, and a number of vanadium deposits (Abenab-West and others).

The youngest, crowning the section of the Precambrian of South Africa, is the Waterberg system (630 Ma), composed of clastic material and basic lava flows.

Madagascar island. The most ancient on the island are the rocks of the Andrey system, composed of paragneisses, marbles, pyroxenites, charno whales. Above is the Graphite system with abundant graphite in leptinites, gneisses, shales, and migmatites. The absolute age of monazite was determined at 2430 Ma. After a significant break, deposits of the Vogibori system formed - gneisses, shales, marbles. Fields of rare-metal pegmatites with beryl and rare earths are confined to the Vogibori system. The age of the system is 2170 million years, and the pegmatites are much younger - 485 million years.

The Tsipolino series (1050-1125 million years) lies on the metamorphic basement with angular unconformity - marbles, schists, quartzites, dissected by veins of copper-lead ores.

The eastern part of the African continent is characterized by a completely different tectonic development and is a Riphean folded zone formed in a trough that covered the southwestern part of Saudi Arabia, the eastern part of the ARE, northeastern Sudan, northeastern Ethiopia and northern Somalia. This belt is composed of volcanogenic and clastic formations intruded by synorogenic (1000 Ma) and postorogenic (480-600 Ma) granitoids. In the south, this belt is linked to the "Mozambique belt" and the western part of about. Madagascar, where granitoids with an absolute age of 480-650 Ma are also known. This whole zone is a part of the Proterozoic basement of the platform reactivated by the Riphean movements.

African platform. The zone of the Central African graben and the East African zone of rift valleys, which are associated with intrusions of nepheline syenites and the largest deposits of carbonatites associated with them, developed in the period from the Precambrian and Lower Paleozoic to the Tertiary time inclusive, due to the periodic rejuvenation of ancient faults and repeated intrusion intrusions

On the African continent, granitoid intrusions are very widely developed, among which there are "ancient" granites that are part of the Precambrian basement, and "young" granites of the Lower Cambrian and younger, formed in activated zones. Many rare-metal pegmatite fields with beryllium, tantalum-columbite, and lithium minerals are associated with "ancient" granites.

All intrusions of "young" granites are confined to two tectonic zones of the Upper Riphean reactivation. The first zone runs from Northern Nigeria north to Western Sahara, the second extends from ARE along the Red Sea coast and further south along the Indian Ocean. For "young" granites (435-540 million years - Lower Cambrian?), the development of ring structures and a concentric structure, increased alkalinity, the presence of columbite and cassiterite mineralization in them (in Nigeria, Central Sahara, ARE, Sudan, Ethiopia, Somalia, Saudi Arabia, Malagasy Republic). The absolute age of these granites ranges from 435-540 million years (Lower Cambrian?). with granitoids. Madagascar (485 million years) pegmatites are associated with practically interesting mineralization of uranium, thorium, beryllium, niobium, tantalum and rare earths.

In southern, central, and eastern Africa, intrusions of alkaline rocks are widely developed, which are also characterized by a ring structure and connection with the platform stage of the development of the continent. Within the Bushveld igneous complex, with its variety of rocks from ultramafic to felsic and alkaline, the latter are the youngest and are associated with the post-Waterberg alkaline intrusion phase. Deposits of carbonatites are associated with the Spitz-Kop alkaline complex (age younger than Karru and pre-Cretaceous).

In Namibia, East Africa and the eastern part of the Republic of Zaire, in Uganda and Kenya, ultrabasic alkaline intrusions are known, which are often accompanied by carbonatites; the time of their formation from the Karoo to the Paleogene. Alkaline complexes with carbonatites have a linear arrangement and tend to zones of large faults - rifts.

Among the deposits of the African Shield, the following main groups stand out.

1. Deposits among granitoid massifs.

2. Rare-metal granite pegmatites.

3. Carbonatite deposits.

4. Deposits associated with basic and ultrabasic intrusions.

5. Metamorphogenic deposits of iron, manganese and gold-uranium ores.

6. Stratiform deposits of copper, cobalt, uranium, lead and zinc in the rocks of the platform cover.

7. Diamond deposits associated with kimberlites.

The first group of deposits among granitoid massifs includes columbite-bearing granites of Northern Nigeria. Except columbite granites

The second group includes numerous rare-metal granitic pegmatites of Africa, which are grouped into a number of belts.

African carbonatite deposits are associated with ultrabasic-alkaline complexes and are of great interest as sources of niobium, zirconium, and rare earths. One of the features of carbonatite deposits in Africa is their large age range - from Precambrian to Paleogene - and gravitation to the zone of the Great African Rifts.

The largest number of carbonatite deposits is located in Zaire, Rwanda, Uganda, Kenya, Tanzania, Rhodesia and Zambia. The largest deposits are Luesh (Kivu Province, Zaire) - a pyrochlore deposit of the Barreiro de Arasha type in Brazil and Karonga in Burundi - a bastnasite deposit similar to Mountain Pas in California, USA.

Among the alkaline and carbonatite complexes of Africa, three groups of different age are distinguished: 1) intruded after the Lower Precambrian and before the Karoo; 2) introduced after Karoo and before the Paleogene; 3) Paleogene and modern complexes.

Deposits associated with basic and ultrabasic complexes are known in South Africa and Southern Rhodesia, where they are confined to the Bushveld complex and the Great Dike. Huge concentrations of proper magmatic ores of chromite (Selukwe in Southern Rhodesia, Bushveld group in South Africa) and segregation deposits of copper-nickel sulfide ores with an admixture of cobalt, platinum and palladium, confined to the Merensky horizon (bronzitites and anorthosites ) Bushveld lopolit (Rustenburg region, etc.). In terms of the extraction of chromite, these deposits occupy one of the leading places in the world, and in terms of the scale of extraction of platinum and palladium (total 10 tons per year) they are first among the capitalist countries.

The next, very important group of ore deposits in Africa belongs to the metamorphogenic type and includes the largest concentrations of iron ores such as ferruginous quartzites (in the Transvaal), manganese ores (Nsuta in Ghana, Postmasburg in South Africa) and gold-uranium-bearing conglomerates (Witwater strand and Ghana). Of particular importance is the Witwatersrand deposit in South Africa, which has been developed for more than a hundred years and currently produces annually more than 700 tons of gold (half of the world production of capitalist countries) and up to 4-5 thousand tons of uranium at grades of 10-11 g/t, respectively. and 0.01%. In addition to gold and uranium, the Witwatersrand conglomerates also contain monazite, zircon, xenotime, iridosmine, rutile, cirtholite, and diamonds. The source of material for the Witwatersrand conglomerates was probably Katarchean rocks, among which gold-bearing quartz veins and uranium-bearing pegmatites occurred. The sedimentary rocks of the Katanga (Upper Riphean) group in the Republic of Zaire and Zambia are associated with copper deposits of world importance, as well as industrial concentrations of cobalt, zinc, lead, cadmium, germanium, uranium and selenium.

In the Katanga group, three systems are distinguished (from bottom to top): Roan, the Great Conglomerate, and the Mwashiya and Kundelungu series. Copper-cobalt mineralization is confined to the Roan system, represented by sandstones and dolomites; lead-zinc mineralization with germanium is associated with Kundelungu carbonate rocks. The age of the rocks of the Katanga group is 520-630 million years; all the granites of the area are older, and only the mafic gabbro sills and dikes are younger than the deposits of the Roan system.

The deposits are confined to certain horizons of the Roan system and are represented by stratiform bodies of copper sulfides scattered in sandstones and dolomite shales; cobalt sulfides are of secondary importance, sometimes an admixture of uranium, nickel and tellurium, in other cases - cadmium; selenium and germanium (in the form of rennerite). Similar deposits are also known in the Republic of the Congo and in Namibia, in the Otavi mountains.

The most interesting is the Tsumeb copper-polymetallic deposit, whose ores are a source of significant germanium mining (it is present in the form of germanite and rennyrite). The ore body is lenticular and occurs among dolomites. There are disagreements on the issue of the genesis of the deposits of the copper belt of Katanga - Zambia and the Tsumeb deposit. For a long time, these deposits were considered as hydrothermal, associated with a hypothetical granite chamber, but at present, there are more and more supporters of the syngenetic accumulation of metals in terrigenous and carbonate facies, with their subsequent redistribution and redeposition in the form of epigenetic, sometimes massive ore bodies.

The last group of the most interesting deposits in Africa are numerous primary and alluvial diamond deposits. According to the geological age and conditions of diamond manifestation, four provinces are distinguished: Kimberlite in South Africa with kimberlite pipes and primary deposits, the age of which is 51-55 million years; Lubilashskaya in Zaire with diamonds in sandstones and conglomerates of the Triassic and rich alluvial placers; Birrimskaya in Ghana with diamonds in Proterozoic conglomerates; Wit-Watersrand with single diamonds in Archean conglomerates. The first two provinces are of great industrial importance. The annual production of diamonds in Africa has exceeded 20-25 million carats (4-5 tons) in recent years.

hindostan shield

The Hindustan shield is located on the territory of the Asian peninsula of the same name and covers an area of more than 3 million km 2, including the states of India, Pakistan and Bangladesh; Fr. belongs to the Hindustan shield. Sri Lanka.

The Hindustan peninsula is a plateau composed of rocks of an ancient crystalline shield, partially covered by covers of basalt (Dean basalts).

The Indian shield during the entire Precambrian and Paleozoic was an integral part of the huge southern continent of Gondwana, which also included Africa, the Arabian Peninsula, South America, Western Australia and, probably, Antarctica - hence the elements of great similarity in the geological structure and metallogeny of these areas.

In the Precambrian of the Indian Shield, researchers distinguish two groups of rocks: Archean and younger - Proterozoic (Purana). The Archean group, in turn, is subdivided into the oldest system of granite-gneisses and charnockites of the Lower Archean and the Darvar system of crystalline schists, quartzites and layered hornfelses of the Upper Archean.

In South India and on about. Sri Lanka has widely developed hypersthene granites-charnockites of the Lower Archean age with pegmatites containing monazite, zircon, ilmenite and other valuable minerals, which are also scattered as accessory minerals among charnockites. The destruction of charno-whales and associated pegmatites has led to the formation of rich coastal marine placers, which are mined mainly for monazite.

The rocks of the Darwar system are widespread in the province of Mysore, the southern parts of the provinces of Bombay and Madras; also developed in Nagpur, Bihar, in the range. Aravalli and Assam mountain ranges. The Darvar system is characterized by rich and varied mineralization: iron, manganese, gold, copper, lead, uranium, pegmatites with beryl, tantalum-columbite, and lithium minerals. The age of the rocks of the Darwar system, according to a few definitions, is set within the range of 2450-2300 million years.

A series of Proterozoic rocks (Purana) rests sharply unconformably on the Archean rocks. The lower part of the section is composed of sandstones and shales, limestones, sills of basic rocks (large deposits of asbestos and barite are associated with the latter), ferruginous quartzites with hematite deposits. All these rocks are intruded by basalt dikes, which are considered as parent rocks in relation to secondary diamond deposits (in the conglomerates of the Golconda mines).

The upper part is represented by a suite of quartzites and shales with intercalations of limestone containing deposits of lead ores; at the very top there are interlayers of hematite shales, in some places with industrial deposits of iron ore.

The youngest sequence of the Precambrian of India is the Vindia sedimentary suite, developed on the northern margin of the shield - in the Vindia Mountains. The formation is composed of limestones, shales, sandstones and conglomerates. In the Kornul region, this suite is dominated by diamondiferous rocks - dark ferruginous or feldspar coarse-grained sandstones and Banagapalli conglomerates.

The largest metamorphic deposits of rich iron and manganese ores are located within the Hindustan shield. Iron ores, represented by ferruginous quartzites and deposits of massive hematite or magnetite ores subordinate to them, occur among the rocks of the Darwar system and partly of the Kuddapah system. The most famous are exploited on a large scale deposits of high-quality hematite ores of the Singbhum and Mayurbhanj regions - the raw material base of the ferrous metallurgy of India.

The manganese deposits of India, also of metamorphogenic genesis, are associated with the gondite suite of the Darwar system. Gondites are sedimentary rocks rich in manganese, subsequently metamorphosed into spessartine-rhodonite rock. The processes of ancient weathering of the latter resulted in the concentration of manganese in the form of rich brownite-psylomelane deposits. Large deposits of this type are being developed in the Balagat, Bandara, Nagpur regions (central provinces), as well as in the states of Bihar and Orissa.

The deposits of non-ferrous metals in India are of comparatively little importance. Copper ores are confined to the rocks of the Darwar system and are developed in the district of Singbhum, where they are represented by veins or stockworks of copper sulfides. Lead-zinc ores are known in Madras, Rajasthan and Bihar, where they are subordinated to limestones or crystalline schists of the Vindic system.

Of great economic importance are bauxite deposits in India, which belong to the type of aluminous laterites that arose in connection with the weathering of basalt covers. The largest deposits are located in the central states, in the regions of Balaghat and Jabalpur.

India is one of the countries that over the past hundred years have produced a small but stable gold production - annually 10 tons. ,5 m, in bulges up to 10 m with a gold grade of 5-50 g/t (average 14-16 g/t). Developments have now reached a depth of 4 km - these are the deepest mines in the world.

Indian diamonds are of great interest. Diamond deposits are known in the Eastern Deccan, Hyderabad, in the central states and further north to the Windy Ridge. At present, the main development of diamonds is carried out in the vicinity of the city of Panna, where kimberlite pipes are installed, and in the interfluve of Mahanadi - Godavari, and in ancient times the mines of Golconda in Madras were known. Diamonds are mined from vindium conglomerates and from modern alluvium, partly from recently discovered primary deposits, and the annual production does not exceed 2-3 thousand carats.

Of the well-known diamonds mined in India, one can name Pitt (410 carats), Great Mogul (280 carats), Orlov (193 carats), Kuinur (186 carats). Indian diamonds are for the most part perfectly clean and transparent. There are also red, green, blue and black diamonds of exceptional beauty.

The primary sources of diamonds are considered to be igneous rocks of the Kuddapah system (Upper Proterozoic or blue) - the main olivine-bearing dikes and sills and alkaline rocks, pyroxenites and picrites of the Daly system. In the area of the city of Panna, diamond-bearing kimberlite pipes of the Riphean age have been found, but there are also younger ones.

Among other precious stones, the extraction of rubies and sapphires from the Precambrian marbles of the Mogok region in Burma (rubies) and gneisses and pegmatites of Kashmir (sapphires) is of some importance. Beryl and its precious varieties - emerald and aquamarine - are associated with pegmatites that cut through the crystalline rocks of the Lower Archean.