Geology of Niger

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The geology of Niger comprises very ancient igneous and metamorphic crystalline basement rocks in the west, more than 2.2 billion years old formed in the late Archean and Proterozoic eons of the Precambrian. The Volta Basin, Air Massif and the Iullemeden Basin began to form in the Neoproterozoic and Paleozoic, along with numerous ring complexes, as the region experienced events such as glaciation and the Pan-African orogeny. Today, Niger has extensive mineral resources due to complex mineralization and laterite weathering including uranium, molybdenum, iron, coal, silver, nickel, cobalt and other resources.

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Stratigraphy, Tectonics & Geologic History

The oldest rocks in Niger, along the border with Burkina Faso and northern Ghana predate the 2.2 billion year old Proterozoic Birimian rocks common in much of West Africa. The pre-Birimian crystalline basement rocks include gneiss and migmatite metamorphosed to amphibolite grade in the sequence of metamorphic facies. The Liptako region, in the west has amphibolite, chlorite-schist, meta-andesite, meta-arkose, micaceous quartzites and garnet gneiss which are younger. These rocks formed after a granite-gneiss complex in the area, but before the mudstones, tuff, quartzite, conglomerate and greywacke of the Amarasinde and Bellekoire beds. These Upper Birimian Supergroup rocks are intruded by younger granites.

The Air Massif began to form in the Precambrian. More than half of the basement rock in the massif is metamorphic, including the Edoukel mesozonal micaschist, Azanguerene gneiss, Tafourfouzete letpynite[ check spelling ] and possible ophiolite of the Aouzeueur formation. [1]

Neoproterozoic (1 billion-539 million years ago)

The Volta Basin syncline along the border with Burkina Faso contains Neoproterozoic rocks, with the oldest rocks near the edge of the basin. After the 50 percent of basement rocks that are metamorphic, the rest of the rocks in the Air Massif Renatt type and Dabaga type granite, which formed during the Pan-African orogeny mountain building event 600 million years ago. [2]

Paleozoic (539-251 million years ago)

During the Cambrian as multi-cellular life became commonplace, anorogenic magmatism formed ring complexes, that now comprise 30 different massifs in the Niger-Nigerian Younger Granite Province. The oldest, Cambrian massifs formed in the north.

Throughout the Paleozoic ring complexes with significant variety in structure and rock type formed in the Air Massif. In fact, the Air Massif has the largest ring-dike in the world, with a diameter of 65 kilometers. Geologists subdivide the different ring complexes into three different types. The Taghouaji-type has plutonic alkaline rocks and may have peralluminous granites while the Goudai-type is mainly acid volcanic rocks. The Ofoud-type is the most varied, encompassing gabbros, granites and anorthosite.

The Iullemeden Basin at Tamesna began to form in the Paleozoic. The center of the basin was uplifted by the Hercynian orogeny to form the Hoggar Mountains. Sedimentary rocks from the Paleozoic, thicken toward the mountains and to the south. East of Tamesna, Cambrian and Ordovician sedimentary rocks are up to 500 meters thick and include conglomerates and sandstones. There is an unconformity between these deposits and glacial sediments, associated with the widespread glaciation and global cooling of the Ordovician-Silurian extinction event. In ascending order, glacial deposits are overlain by Early Silurian graptolite shales, Devonian sandstones and shales and Early Carboniferous deltaic sandstones.

A coal bearing layer, likely tied to a marine transgression is overlain by shales and limestones, which contain coral and conodont fossils. [3]

Mesozoic-Cenozoic (251-66 million years ago)

A marine transgression in the Cenomanian, during the late Mesozoic topped off the Iulllemeden Basin with marine sedimentary rocks, often on top of Early Cretaceous terrestrial sedimentary rocks. The region remained flooded well into the Cenozoic, throughout the Paleocene, before drying out and shifting from marine sediment deposition to continental sediments. [3]

Hydrogeology

Hydrogeology in Niger is poorly researched. The Eocene Continental Terminal is an unconfined sandstone aquifer. [4]

Natural resource geology

Mined uranium is Niger's biggest export, but mining remains a relatively small part of GDP. The country also has gold and coal and deposits of tin and phosphate were mined in the past. Uranium is extracted from two concessions at Arlit and Akouta, more than 200 kilometers northwest of Agadez, with estimated reserves of 200,000 tons. Low global demand for uranium has driven down production for more than 30 years since 1986. There may be other reserves at Imouraren, Afasto Ouest, Abkorum-Azelik, Afasto Est, Tassa N'Taghalgue and Teguida N'Tessoun, with uranium concentrations ranging between 0.22 and 0.45 percent. Molybdenum is often produced as a byproduct of uranium mining. Niger also has vein-type copper deposits, with malachite and chalcopyrite associated with molybdenum, lithium and silver—or zinc and lead in the Proche-Tenere District. Native copper, chrysocolla and cuprite are found in sediments in the Agadez region.

Relatively low-grade coal formed in a small basin at Anou-Araren, with estimated reserves of 10 megatons. Because of its poor quality, it is mainly used to provide electricity for uranium mines. The Iullemeden Basin contains lignite and small amounts of petroleum. The Liptako area in the northeast is the terminus of the West African gold belt, which extends from the Atlantic in Ghana. It hosts gold in the Birimian greenstones of Tera-Gasso and Gorouel belts. The gold belt actually extends further east, past the Niger River, but is largely concealed by younger sediments and sedimentary rocks. Gold mineralization also occurs in shear-related quartz veins. Some gold has been freed from sulfides in these veins by laterite weathering due to heavy rainfall in the last 2.5 million years of the Quaternary. Silver mineralization occurs where greenstones and granite intrusions meet, in the same quartz veins that host gold and sulfides. The silver is typically mineralized within sphalerite, chalcopyrite, arsenopyrite, pyrite or covellite. One hundred thirty five kilometers south of Niamey, is the Tapoa phosphate deposit Neoproterozoic and Cambrian sedimentary rocks of the Volta Group. The Tahoua deposit, 375 kilometers northeast of the capital contains nodular apatite in Paleocene and Eocene sediments. The Tidekelt region has up to 25 million tons of salt brines, with a yield of 70 percent sodium chloride.

There are some indications of platinum in the Makalondi District, south of Liptako, associated with chromite lenses in gabbros, anorthosite and chloritoschists. Ophiolites in the Abuzegueur overthurst[ check spelling ], in the Air region also show potential for platinum mineralization and may also have chromite, nickel and cobalt. The Fantio deposit in the Liptako area has heavily weathered ultra-mafic rocks, with 0.8 percent nickel, totaling up to as much as 200,000 tons. Makalondi, also in Liptako, hosts chromium concentrations of 5.1 to 17.4 percent.

Iron is common in Niger, in rocks from the Precambrian through the Cenozoic, although the Cenozoic rocks of the Termit-Agadem and Ader-Doutchi regions have the highest iron concentrations, at up to 55 percent. Pegmatite hosted, granite and sedimentary deposits of tin were mined commercially from 1984 until 1991 in the Air Massif. Today, only small scale artisanal mining continues. [5]

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Geology of the Republic of the Congo

The geology of the Republic of the Congo, also known as Congo-Brazzaville, to differentiate from the Democratic Republic of the Congo, formerly Zaire, includes extensive igneous and metamorphic basement rock, some up to two billion years old and sedimentary rocks formed within the past 250 million years. Much of the country's geology is hidden by sediments formed in the past 2.5 million years of the Quaternary.

The geology of Liberia is largely extremely ancient rock formed between 3.5 billion and 539 million years ago in the Archean and the Neoproterozoic, with some rocks from the past 145 million years near the coast. The country has rich iron resources as well as some diamonds, gold and other minerals in ancient sediment formations weathered to higher concentrations by tropical rainfall.

Geology of Ghana

The geology of Ghana is primarily very ancient crystalline basement rock, volcanic belts and sedimentary basins, affected by periods of igneous activity and two major orogeny mountain building events. Aside from modern sediments and some rocks formed within the past 541 million years of the Phanerozoic Eon, along the coast, many of the rocks in Ghana formed close to one billion years ago or older leading to five different types of gold deposit formation, which gave the region its former name Gold Coast.

Geology of the Democratic Republic of the Congo

The geology of the Democratic Republic of the Congo is extremely old, on the order of several billion years for many rocks. The country spans the Congo Craton: a stable section of ancient continental crust, deformed and influenced by several different mountain building orogeny events, sedimentation, volcanism and the geologically recent effects of the East Africa Rift System in the east. The country's complicated tectonic past have yielded large deposits of gold, diamonds, coltan and other valuable minerals.

The geology of Malawi formed on extremely ancient crystalline basement rock, which was metamorphosed and intruded by igneous rocks during several orogeny mountain building events in the past one billion years. The rocks of the Karoo Supergroup and newer sedimentary units deposited across much of Malawi in the last 251 million years, in connection with a large rift basin on the supercontinent Gondwana and the more recent rifting that has created the East African Rift, which holds Lake Malawi. The country has extensive mineral reserves, many of them poorly understand or not exploited, including coal, vermiculite, rare earth elements and bauxite.

The geology of Mauritania is built on more than two billion year old Archean crystalline basement rock in the Reguibat Shield of the West African Craton, a section of ancient and stable continental crust. Mobile belts and the large Taoudeni Basin formed and filled with sediments in the connection with the Pan-African orogeny mountain building event 600 million years ago and a subsequent orogeny created the Mauritanide Belt. In the last 251 million years, Mauritania has accumulated additional sedimentary rocks during periods of marine transgression and sea level retreat. The arid country is 50% covered in sand dunes and has extensive mineral resources, although iron plays the most important role in the economy.

Geology of Namibia

The geology of Namibia encompasses rocks of Paleoproterozoic, Mesoproterozoic and Neoproterozoic and Paleozoic to Cenozoic age. About 46% of the countryʼs surface are bedrock exposure, while the remainder is covered by the young overburden sediments of the Kalahari and Namib deserts.

Geology of Tanzania

The geology of Tanzania began to form in the Precambrian, in the Archean and Proterozoic eons, in some cases more than 2.5 billion years ago. Igneous and metamorphic crystalline basement rock forms the Archean Tanzania Craton, which is surrounded by the Proterozoic Ubendian belt, Mozambique Belt and Karagwe-Ankole Belt. The region experienced downwarping of the crust during the Paleozoic and Mesozoic, as the massive Karoo Supergroup deposited. Within the past 100 million years, Tanzania has experienced marine sedimentary rock deposition along the coast and rift formation inland, which has produced large rift lakes. Tanzania has extensive, but poorly explored and exploited natural resources, including coal, gold, diamonds, graphite and clays.

The geology of Uganda extends back to the Archean and Proterozoic eons of the Precambrian, and much of the country is underlain by gneiss, argillite and other metamorphic rocks that are sometimes over 2.5 billion years old. Sedimentary rocks and new igneous and metamorphic units formed throughout the Proterozoic and the region was partially affected by the Pan-African orogeny and Snowball Earth events. Through the Mesozoic and Cenozoic, ancient basement rock has weathered into water-bearing saprolite and the region has experienced periods of volcanism and rift valley formation. The East Africa Rift gives rise to thick, more geologically recent sediment sequences and the country's numerous lakes. Uganda has extensive natural resources, particularly gold.

Geology of Zambia

The geological history of Zambia begins in the Proterozoic eon of the Precambrian. The igneous and metamorphic basement rocks tend to be highly metamorphosed and may have formed earlier in the Archean, but heat and pressure has destroyed evidence of earlier conditions. Major sedimentary and metamorphic groups formed in the mid-Proterozoic, followed by a series of glaciations in the Neoproterozoic and much of the Paleozoic which deposited glacial conglomerate as well as other sediments to form the Katanga Supergroup and rift-related Karoo Supergroup. Basalt eruptions blanketed the Karoo Supergroup in the Mesozoic and Zambia shifted to coal and sandstone formation. Geologically recent windblown sands from the Kalahari Desert and alluvial deposits near rivers play an important role in the modern surficial geology of Zambia. The country has extensive natural resources, particularly copper, but also cobalt, emeralds, other gemstones, uranium and coal.

Geology of South Sudan

The geology of South Sudan is founded on Precambrian igneous and metamorphic rocks, that cover 40 percent of the country's surface and underlie other rock units. The region was affected by the Pan-African orogeny in the Neoproterozoic and extensional tectonics in the Mesozoic that deposited very thick oil-bearing sedimentary sequences in rift basins. Younger basalts, sandstones and sediments formed in the last 66 million years of the Cenozoic. The discovery of oil in 1975 was a major factor in the Second Sudanese Civil War, leading up to independence in 2011. The country also has gold, copper, cobalt, zinc, iron, marble, limestone and dolomite.

The geology of Morocco formed beginning up to two billion years ago, in the Paleoproterozoic and potentially even earlier. It was affected by the Pan-African orogeny, although the later Hercynian orogeny produced fewer changes and left the Maseta Domain, a large area of remnant Paleozoic massifs. During the Paleozoic, extensive sedimentary deposits preserved marine fossils. Throughout the Mesozoic, the rifting apart of Pangaea to form the Atlantic Ocean created basins and fault blocks, which were blanketed in terrestrial and marine sediments—particularly as a major marine transgression flooded much of the region. In the Cenozoic, a microcontinent covered in sedimentary rocks from the Triassic and Cretaceous collided with northern Morocco, forming the Rif region. Morocco has extensive phosphate and salt reserves, as well as resources such as lead, zinc, copper and silver.

Geology of Senegal

The geology of Senegal formed beginning more than two billion years ago. The Archean greenschist Birimian rocks common throughout West Africa are the oldest in the country, intruded by Proterozoic granites. Basins formed in the interior during the Paleozoic and filled with sedimentary rocks, including tillite from a glaciation. With the rifting apart of the supercontinent Pangaea in the Mesozoic, the large Senegal Basin filled with thick sequences of marine and terrestrial sediments. Sea levels declined in the Eocene forming large phosphate deposits. Senegal is blanketed in thick layers of terrestrial sediments formed in the Quaternary. The country has extensive natural resources, including gold, diamonds, and iron.

Geology of Sudan

The geology of Sudan formed primarily in the Precambrian, as igneous and metamorphic crystalline basement rock. Ancient terranes and inliers were intruded with granites, granitoids as well as volcanic rocks. Units of all types were deformed, reactivated, intruded and metamorphosed during the Proterozoic Pan-African orogeny. Dramatic sheet flow erosion prevented almost any sedimentary rocks from forming during the Paleozoic and Mesozoic. From the Mesozoic into the Cenozoic the formation of the Red Sea depression and complex faulting led to massive sediment deposition in some locations and regional volcanism. Sudan has petroleum, chromite, salt, gold, limestone and other natural resources.

The geology of Nigeria formed beginning in the Archean and Proterozoic eons of the Precambrian. The country forms the Nigerian Province and more than half of its surface is igneous and metamorphic crystalline basement rock from the Precambrian. Between 2.9 billion and 500 million years ago, Nigeria was affected by three major orogeny mountain-building events and related igneous intrusions. Following the Pan-African orogeny, in the Cambrian at the time that multi-cellular life proliferated, Nigeria began to experience regional sedimentation and witnessed new igneous intrusions. By the Cretaceous period of the late Mesozoic, massive sedimentation was underway in different basins, due to a large marine transgression. By the Eocene, in the Cenozoic, the region returned to terrestrial conditions.

The geology of Arizona began to form in the Precambrian. Igneous and metamorphic crystalline basement rock may have been much older, but was overwritten during the Yavapai and Mazatzal orogenies in the Proterozoic. The Grenville orogeny to the east caused Arizona to fill with sediments, shedding into a shallow sea. Limestone formed in the sea was metamorphosed by mafic intrusions. The Great Unconformity is a famous gap in the stratigraphic record, as Arizona experienced 900 million years of terrestrial conditions, except in isolated basins. The region oscillated between terrestrial and shallow ocean conditions during the Paleozoic as multi-cellular life became common and three major orogenies to the east shed sediments before North America became part of the supercontinent Pangaea. The breakup of Pangaea was accompanied by the subduction of the Farallon Plate, which drove volcanism during the Nevadan orogeny and the Sevier orogeny in the Mesozoic, which covered much of Arizona in volcanic debris and sediments. The Mid-Tertiary ignimbrite flare-up created smaller mountain ranges with extensive ash and lava in the Cenozoic, followed by the sinking of the Farallon slab in the mantle throughout the past 14 million years, which has created the Basin and Range Province. Arizona has extensive mineralization in veins, due to hydrothermal fluids and is notable for copper-gold porphyry, lead, zinc, rare minerals formed from copper enrichment and evaporites among other resources.

Geology of Sweden

The geology of Sweden is the regional study of rocks, minerals, tectonics, natural resources and groundwater in the country. The oldest rocks in Sweden date to more than 2.5 billion years ago in the Precambrian. Complex orogeny mountain building events and other tectonic occurrences built up extensive metamorphic crystalline basement rock that often contains valuable metal deposits throughout much of the country. Metamorphism continued into the Paleozoic after the Snowball Earth glaciation as the continent Baltica collided with an island arc and then the continent Laurentia. Sedimentary rocks are most common in southern Sweden with thick sequences from the last 250 million years underlying Malmö and older marine sedimentary rocks forming the surface of Gotland.

Geology of North Macedonia

The geology of North Macedonia includes the study of rocks dating to the Precambrian and a wide array of volcanic, sedimentary and metamorphic rocks formed in the last 539 million years.

The geology of South Korea includes rocks dating to the Archean and two large massifs of metamorphic rock as the crystalline basement, overlain by thick sedimentary sequences, younger metamorphic rocks and volcanic deposits. Although extent is small, Geology is diverse, and There are diverse rocks which is formed during long-time from Precambrian to Cenozoic Era in Korea Peninsula.

References

  1. ↑ Schlüter, Thomas (2008). Geological Atlas of Africa. Springer. p. 190.
  2. ↑ Schlüter 2008, p. 190.
  3. 1 2 Schlüter 2008, p. 192.
  4. ↑ Favreau; et al. (2009). "Estimating specific yield and transmissivity with magnetic resonance sounding in an unconfined sandstone aquifer (Niger)". Hydrogeology Journal. 17 (7): 1805–1815. Bibcode:2009HydJ...17.1805B. doi:10.1007/s10040-009-0447-x. S2CID   129592122.
  5. ↑ Schlüter 2008, pp. 192–193.
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