Pan-African orogeny

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The Pan-African orogeny was a series of major Neoproterozoic orogenic events which related to the formation of the supercontinents Gondwana and Pannotia about 600 million years ago. [1] This orogeny is also known as the Pan-Gondwanan or Saldanian Orogeny. [2] The Pan-African orogeny and the Grenville orogeny are the largest known systems of orogenies on Earth. [3] The sum of the continental crust formed in the Pan-African orogeny and the Grenville orogeny makes the Neoproterozoic the period of Earth's history that has produced most continental crust. [3]

Contents

History and terminology

The term Pan-African was coined by Kennedy 1964 for a tectono-thermal event at about 500 Ma when a series of mobile belts in Africa formed between much older African cratons. At the time, other terms were used for similar orogenic events on other continents, i.e. Brasiliano in South America; Adelaidean in Australia; and Beardmore in Antarctica.

Later, when plate tectonics became generally accepted, the term Pan-African was extended to all of the supercontinent Gondwana. Because the formation of Gondwana encompassed several continents and extended from the Neoproterozoic to the early Palaeozoic, Pan-African could no longer be considered a single orogeny, [4] but rather an orogenic cycle that included the opening and closing of several large oceans and the collisions of several continental blocks. Furthermore, the Pan-African events are contemporaneous with the Cadomian orogeny in Europe and the Baikalian orogeny in Asia, and crust from these areas were probably part of Pannotia (i.e. Gondwana when it first formed) during the Precambrian. [5]

Attempts to correlate the African Pan-African belts with the South American Brasiliano belts on the other side of the Atlantic has in many cases been problematic. [6]

Pan-African belts

West Gondwana with major cratons in brown and Pan-African orogens in grey Cratons West Gondwana and EAO v2.png
West Gondwana with major cratons in brown and Pan-African orogens in grey

Orogenic belts of the Pan-African system include:

Related Research Articles

<span class="mw-page-title-main">Pannotia</span> Hypothesized Neoproterozoic supercontinent from the end of the Precambrian

Pannotia, also known as the Vendian supercontinent, Greater Gondwana, and the Pan-African supercontinent, was a relatively short-lived Neoproterozoic supercontinent that formed at the end of the Precambrian during the Pan-African orogeny, during the Cryogenian period and broke apart 560 Ma with the opening of the Iapetus Ocean, in the late Ediacaran and early Cambrian. Pannotia formed when Laurentia was located adjacent to the two major South American cratons, Amazonia and Río de la Plata. The opening of the Iapetus Ocean separated Laurentia from Baltica, Amazonia, and Río de la Plata. In 2022 the whole concept of Pannotia has been put into question by scientists who argue its existence is not supported by geochronology, "the supposed landmass had begun to break up well before it was fully assembled".

<span class="mw-page-title-main">Atlantica</span> Ancient continent formed during the Proterozoic about 2 billion years ago

Atlantica is an ancient continent that formed during the Proterozoic about 2,000 million years ago from various 2 Ga cratons located in what are now West Africa and eastern South America. The name, introduced by Rogers 1996, was chosen because the parts of the ancient continent are now located on opposite sides of the South Atlantic Ocean.

<span class="mw-page-title-main">Congo Craton</span> Precambrian craton that with four others makes up the modern continent of Africa

The Congo Craton, covered by the Palaeozoic-to-recent Congo Basin, is an ancient Precambrian craton that with four others makes up the modern continent of Africa. These cratons were formed between about 3.6 and 2.0 billion years ago and have been tectonically stable since that time. All of these cratons are bounded by younger fold belts formed between 2.0 billion and 300 million years ago.

The Irumide Belt is a Mesoproterozoic terrane of deformed basement and folded supracrustals, which occurs along the southern margin of an Archaean/Palaeoproterozoic unit called the Bangweulu Block in Zambia. Together with the Damara Belt, it separates the Congo and Kalahari cratons.

<span class="mw-page-title-main">Río de la Plata Craton</span> Medium-sized continental block in Uruguay, eastern Argentina and southern Brazil

The Rio de la Plata Craton (RPC) is a medium-sized continental block found in Uruguay, eastern Argentina and southern Brazil. During its complex and protracted history it interacted with a series other blocks and is therefore considered important for the understanding of the amalgamation of West Gondwana. Two orogenic cycles have been identified in the RPC: a 2000 Ma-old western domain representing the old craton and a 700–500 Ma-old eastern domain assigned to the Brasiliano Cycle. It is one of the five cratons of the South American continent. The other four cratons are: Amazonia, São Francisco, Río Apa and Arequipa–Antofalla.

<span class="mw-page-title-main">Saharan Metacraton</span> Large area of continental crust in the north-central part of Africa

The Saharan Metacraton is a term used by some geologists to describe a large area of continental crust in the north-central part of Africa. Whereas a craton is an old and stable part of the lithosphere, the term "metacraton" is used to describe a craton that has been remobilized during an orogenic event, but where the characteristics of the original craton are still identifiable. The geology of the continent has only been partially explored, and other names have been used to describe the general area that reflect different views of its nature and extent. These include "Nile Craton", "Sahara Congo Craton", "Eastern Saharan Craton" and "Central Saharan Ghost Craton". This last term is because the older rocks are almost completely covered by recent sediments and desert sands, making geological analysis difficult.

<span class="mw-page-title-main">Tuareg Shield</span> Geological formation between the West African craton and the Saharan Metacraton in West Africa

The Tuareg Shield is a geological formation lying between the West African craton and the Saharan Metacraton in West Africa. Named after the Tuareg people, it has complex a geology, reflecting the collision between these cratons and later events. The landmass covers parts of Algeria, Niger and Mali.

<span class="mw-page-title-main">Mozambique Belt</span> Band in the earths crust from East Antarctica through East Africa up to the Arabian-Nubian Shield

The Mozambique Belt is a band in the earth's crust that extends from East Antarctica through East Africa up to the Arabian-Nubian Shield. It formed as a suture between plates during the Pan-African orogeny, when Gondwana was formed.

The Mwembeshi Shear Zone is a ductile shear zone about 550 million years old that extends ENE-WSW across Zambia. In Zambia, it separates the Lufilian Belt to the northwest from the Zambezi Belt to the southeast. It is associated with a sinistral strike slip movement.

<span class="mw-page-title-main">Lufilian Arc</span>

The Kibaran orogeny is a term that has been used for a series of orogenic events, in what is now Africa, that began in the Mesoproterozoic, around 1400 Ma and continued until around 1000 Ma when the supercontinent Rodinia was assembled. The term "Kibaran" has often been used for any orogenic rocks formed during this very extended period. Recently, it has been proposed that the term should be used in a much narrower sense for an event around 1375 Ma and a region in the southeast of the Democratic Republic of the Congo (DRC).

The Zambezi Belt is an area of orogenic deformation in southern Zambia and northern Zimbabwe. It is a segment of a broader belt lying between the Congo Craton and the Kalahari Craton, which also includes the Lufilian Arc and the Damaran Belt. The eastern margin of the belt interacts with the north-south Eastern African orogen.

<span class="mw-page-title-main">East Antarctic Shield</span> Cratonic rock body which makes up most of the continent Antarctica

The East Antarctic Shield or Craton is a cratonic rock body that covers 10.2 million square kilometers or roughly 73% of the continent of Antarctica. The shield is almost entirely buried by the East Antarctic Ice Sheet that has an average thickness of 2200 meters but reaches up to 4700 meters in some locations. East Antarctica is separated from West Antarctica by the 100–300 kilometer wide Transantarctic Mountains, which span nearly 3,500 kilometers from the Weddell Sea to the Ross Sea. The East Antarctic Shield is then divided into an extensive central craton that occupies most of the continental interior and various other marginal cratons that are exposed along the coast.

The Damara orogeny was part of the Pan-African orogeny. The Damara orogeny occurred late in the creation of Gondwana, at the intersection of the Congo and the Kalahari cratons.

<span class="mw-page-title-main">Brasiliano orogeny</span>

Brasiliano orogeny or Brasiliano cycle refers to a series of orogenies of Neoproterozoic age exposed chiefly in Brazil but also in other parts of South America. The Brasiliano orogeny is a regional name for the larger Pan-African/Brasiliano orogeny that extended not only in South America but across most of Gondwana. In a wide sense the Brasiliano orogeny includes also the Pampean orogeny. Almeida et al. coined the term Brasiliano Orogenic Cycle in 1973. The orogeny led to the closure of several oceans and aulacogens including the Adamastor Ocean, the Goianides Ocean, the Puncoviscana Ocean and the Peri-Franciscano Ocean.

The Adamastor Ocean was a "proto-Atlantic" ocean that formed with the break-up of the Rodinia supercontinent c. 780–750 Ma. It separated the Río de la Plata Craton from the Congo Craton. The inversion of the Adamastor Ocean began about 640 Ma with the development of a large back-arc basin along the western margin of the Kalahari Craton, and the ocean closed when Río de la Plata collided with Kalahari about 545 Ma along the sinistral Sierra Ballena Shear Zone. The São Francisco Craton and the Río de la Plata Craton amalgamated 630–620 Ma, closing the Adamastor Ocean on the South American side and forming the Mantiqueira Mountains around 600 Ma.

<span class="mw-page-title-main">Tectonic evolution of the Aravalli Mountains</span> Overview article

The Aravalli Mountain Range is a northeast-southwest trending orogenic belt in the northwest part of India and is part of the Indian Shield that was formed from a series of cratonic collisions. The Aravalli Mountains consist of the Aravalli and Delhi fold belts, and are collectively known as the Aravalli-Delhi orogenic belt. The whole mountain range is about 700 km long. Unlike the much younger Himalayan section nearby, the Aravalli Mountains are believed much older and can be traced back to the Proterozoic Eon. They are arguably the oldest geological feature on Earth. The collision between the Bundelkhand craton and the Marwar craton is believed to be the primary mechanism for the development of the mountain range.

<span class="mw-page-title-main">Owambo Basin</span>

The Owambo Basin is a sedimentary basin located on the Congo Craton in Southern Africa that extends from southern Angola into Namibia and includes the Etosha Pan. It is bound on the southern and western sides by the Damara Belt in Northern Namibia, and by the Cubango River to the East. The northern boundary is scientifically disputed, but is currently mapped by most stratigraphers to include southern Angola with the boundary set at the Kunene River. The Owambo Basin is host to two famous regions: Tsumeb, a major Namibian city and site of a formerly active copper mine with exceptional mineralogical variability producing museum quality rare specimens, and Etosha National Park, the largest protected wildlife sanctuary in Namibia centered around Etosha Pan.

<span class="mw-page-title-main">Central Asian Orogenic Belt</span> Phanerozoic accretionary orogen

The Central Asian Orogenic Belt (CAOB), also called the Altaids, is one of the world's largest Phanerozoic accretionary orogens, and thus a leading laboratory of geologically recent crustal growth. The orogenic belt is bounded by the East European Craton and the North China Craton in the Northwest-Southeast direction, as well as Siberia Craton and Tarim Craton in the Northeast-Southwest direction. It formed by ocean closures during Neoproterozoic to the late Phanerozoic time, from around 750 to 150 Ma. Like many other accretionary orogenic belts, the Central Asian Orogenic Belt consists of a huge amount of magmatic arcs, arc-related basins, accretionary complexes, seamounts, continental fragments and ophiolites. It is also considered a relatively distinctive collisional orogenic belt because widespread subduction-accretion complexes and arc magmatic rocks can be found in the region, but collision-related foreland basins are not common.

References

  1. Glossary.
  2. van Hinsbergen 2011 , p. 148
  3. 1 2 Rino, S.; Kon, Y.; Sato, W.; Maruyama, S.; Santosh, M.; Zhao, D. (2008). "The Grenvillian and Pan-African orogens: World's largest orogenies through geologic time, and their implications on the origin of superplume". Gondwana Research . 14 (1–2): 51–72. doi:10.1016/j.gr.2008.01.001.
  4. Meert 2003
  5. Kröner & Stern 2004 , Introduction, p. 1
  6. Frimmel, Hartwig E. (2010). "Configuration of Pan-African Orogenic Belts in Southwestern Africa". In Gaucher, Claudio; Sial, Alcides; Haverson, Galen (eds.). Neoproterozoic-cambrian tectonics, global change and evolution: a focus on south western Gondwana . Elsevier. pp.  145–151.
  7. Kröner & Stern 2004 , pp. 2–4
  8. Cutten 2002.
  9. Grantham, Maboko & Eglington 2003, p. 417–418.
  10. 1 2 Kröner & Stern 2004 , p. 7
  11. Kröner & Stern 2004 , pp. 7–8
  12. Kröner & Stern 2004 , pp. 8–9
  13. 1 2 Kröner & Stern 2004 , p. 9
  14. 1 2 Kröner & Stern 2004 , pp. 9–10
  15. Kröner & Stern 2004 , p. 10
  16. Kröner & Stern 2004 , pp. 10–11

Sources