Misplaced Pages

#817182

29-834: The Mwembeshi Shear Zone lies between the Congo craton to the NW and the Kalahari craton to the SE, to the west (in today's orientation) of the Mozambique Belt , which is on the north and east side of the Kalahari Craton. It was formed during the Pan-African orogeny when "North" and "South" Gondwana were amalgamated along the Kuunga orogeny zone between 580 Ma and 480 Ma. The date of around 550 Ma for

58-686: A large part of central southern Africa, extending from the Kasai region of the DRC into Sudan and Angola . It forms parts of the countries of Gabon , Cameroon , and the Central African Republic . A small portion extends into Zambia as well, where it is called the Bangweulu Block . The Congo Craton and the São Francisco Craton are stable Archaean blocks that formed a coherent landmass until

87-510: A short emplacement interval and resulted in a 3,000–4,000 m (9,800–13,100 ft) thick sequence. Mafic-felsic magma sequences (6,000 m (20,000 ft) thick) on the western edge of the Congo Craton are similar to those of the Paraná and Deccan LIPs, but in the Congo Craton the magma source became shallower with time. There was no geodynamic activity along the western Congo margin during

116-688: Is a stub . You can help Misplaced Pages by expanding it . Congo craton The Congo Craton , covered by the Palaeozoic -to-recent Congo Basin , is an ancient Precambrian craton that with four others (the Kaapvaal , Zimbabwe , Tanzania , and West African cratons) 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 Congo Craton occupies

145-469: Is a hypothetical ancient supercontinent . It was first proposed by John J.W. Rogers and M. Santosh in 2002 and is thought to have existed approximately 2,500 to 1,500 million years ago (Ma), in the Paleoproterozoic era. The assembly of the supercontinent was likely completed during global-scale collisional events from 2,100 to 1,800 Ma. Columbia consisted of proto- cratons that made up

174-597: Is based on the available geological reconstructions of 2.1–1.8 Ga orogens and related Archean cratonic blocks, especially on those reconstructions between South America and west Africa; western Australia and southern Africa; Laurentia and Baltica; Siberia and Laurentia; Laurentia and central Australia; East Antarctica and Laurentia; and North China and India. Of these reconstructions, the fits of Baltica and Siberia with Laurentia; South America with west Africa; and southern Africa with western Australia are also consistent with paleomagnetic data . A new configuration of Columbia

203-401: Is now northern Canada. In the initial configuration of Rogers and Santosh (2002), South Africa, Madagascar , India, Australia, and attached parts of Antarctica are placed adjacent to the western margin of North America, whereas Greenland, Baltica (Northern Europe), and Siberia are positioned adjacent to the northern margin of North America, and South America is placed against West Africa . In

232-758: The Keweenawan Rift in Laurentia (although the latter was located far from the other continental blocks). A series of 1500 Ma dyke swarms also support the close relation between Congo–São Francisco and Siberia: Kuonamka in Siberia and Curaçá and Chapada Diamantina in São Francisco and Angola. These dyke swarms radiate from a mantle plume centre located in what is now north-eastern Siberia. Magmatic events in Congo (Kunene) and Siberia (Chieress) at 1384 Ma also corroborate

261-715: The 1.8–1.7 Ga Ketilidian Belt in Greenland; and the 1.8–1.7 Transscandinavian Igneous Belt, 1.7–1.6 Ga Kongsberggian-Gothian Belt, and 1.5–1.3 Ga Southwest Sweden Granitoid Belt in Baltica. Other cratonic blocks also underwent marginal outgrowth at about the same time. In South America, a 1.8–1.3 Ga accretionary zone occurs along the western margin of the Amazonia Craton, represented by the Rio Negro, Juruena, and Rondonian Belts. In Australia, 1.8–1.5 Ga accretionary magmatic belts, including

290-714: The Arunta, Mount Isa, Georgetown, Coen, and Broken Hill Belts, occur surrounding the southern and eastern margins of the North Australia Craton and the eastern margin of the Gawler Craton . In China, a 1.8–1.4 Ga accretionary magmatic zone, called the Xiong’er belt (Group), extends along the southern margin of the North China Craton. Columbia began to fragment about 1.5–1.35 Ga, associated with continental rifting along

319-491: The Congo-Sao Francisco Craton approached the remainder of southwestern Gondwana from the north, although at the time southwestern Gondwana was oriented about 90 degrees clockwise of today's orientation, and the Congo Craton approached from the east. There was little vertical displacement, but Mwembeshi is a major sinistral transcurrent shear zone. The shear zone accommodates a change in the structural vergence between

SECTION 10

#1733085231818

348-525: The Mesoproterozoic. [REDACTED] Africa [REDACTED] Antarctica [REDACTED] Asia [REDACTED] Australia [REDACTED] Europe [REDACTED] North America [REDACTED] South America [REDACTED] Afro-Eurasia [REDACTED] Americas [REDACTED] Eurasia [REDACTED] Oceania Columbia (supercontinent) Columbia , also known as Nuna or Hudsonland ,

377-645: The Mwembeshi shear zone is based on U-Pb zircon ages of syntectonic granites from the Hook massif and of associated hypabyssal rhyolite. During the amalgamation there was sinistral transpression along the boundary between the Kalahari craton and the Congo and Tanzanian cratons (which had already amalgamated), which is now expressed as the Mwembeshi Shear Zone. The sinistral sense shows that, in modern coordinates,

406-603: The São Francisco–Congo continent. The West Congo Pan-African Belt includes major magmatic events at c. 1000 and 910 Ma. In the Early Neoproterozoic, the western edge of Congo Craton was the location for the initial rifting of Rodinia before its break-up. During the Neoproterozoic, Central Congo or Bas-Congo became a passive margin on which was deposited 4,000 m (13,000 ft) sediments. At

435-735: The Zambezi Belt and the Lufilian Arc. Further to the southwest, the shear zone extends along part at least of the Damaran belt . There are known to be basic connections between geological terranes and mineralization models, so understanding the Mwembeshi Shear Zone is important to understanding where mineral resources may be found in the region. Despite this, as of 1990 there had been relatively little exploration. 15°40′1″S 27°48′0″E  /  15.66694°S 27.80000°E  / -15.66694; 27.80000 This palaeogeography article

464-626: The closeness of these two continents during at least 120 million years. It is possible that the 1110 Ma LIP in Congo–São Francisco, Amazonia, and India was part of a much larger event that also involved West Africa and Kalahari (with a possible but unlikely link to the 1075 Ma Warakurna LIP in Australia). However, while the palaeo-latitudes of India and Kalahari are well constrained, those of Amazonia and Congo–São Francisco are not, making any plate tectonic reconstruction speculative. At

493-417: The cores of the continents of Laurentia , Baltica , Ukrainian Shield , Amazonian Craton , Australia , and possibly Siberia , North China , and Kalaharia as well. The evidence of Columbia's existence is provided by geological and paleomagnetic data. Columbia is estimated to have been approximately 12,900 km (8,000 mi) from north to south at its broadest part. The eastern coast of India

522-481: The end of the Neoproterozoic, Bas-Congo was only affected by the Pan-African orogeny at 566 Ma to a limited extent protected by this passive margin and by the thickness of the craton. At 1000 Ma peralkaline magmatism initiated an early transtensional setting along the western edge of the Congo Craton. An LIP at c. 930–920 Ma was followed by felsic magmatism between c. 920–910 Ma which had

551-628: The events associated with the assembly of Columbia are: Following its final assembly at c. 1.82 Ga, Columbia underwent long-lived (1.82–1.5 Ga), subduction -related growth via accretion at key continental margins, forming at 1.82–1.5 Ga a great magmatic accretionary belt along the present-day southern margin of North America, Greenland, and Baltica. It includes the 1.8–1.7 Ga Yavapai, Central Plains and Makkovikian Belts, 1.7–1.6 Ga Mazatzal and Labradorian Belts, 1.5–1.3 Ga St. Francois and Spavinaw Belts , and 1.3–1.2 Ga Elzevirian Belt in North America;

580-735: The final breakup of the supercontinent at about 1.3–1.2 Ga, marked by the emplacement of the 1.27 Ga Mackenzie and 1.24 Ga Sudbury mafic dyke swarms in North America. Other dyke swarms associated with extensional tectonics and the break-up of Columbia include the Satakunta-Ulvö dyke swarm in Fennoscandia and the Galiwinku dyke swarm in Australia. An area around Georgetown in northern Queensland, Australia , has been suggested to consist of rocks that originally formed part of Nuna 1.7 Ga in what

609-598: The opening of the South Atlantic Ocean during the break-up of Gondwana ( c. 2000–130 Ma). They stabilised during the Transamazonian orogeny and Eburnean Orogeny and have been affected by a long series of orogens since resulting in similar sequences on both blocks. Congo–São Francisco experienced three large igneous province (LIP) events at 1380–1370 Ma, c. 1505 Ma, and c. 1110 Ma. The relative position of Congo–São Francisco within

SECTION 20

#1733085231818

638-683: The opening of the South Atlantic the São Francisco and Congo cratons were connected by a "cratonic" bridge, the Bahia–Gabon Bridge. The most recent orogenic event on this bridge occurred at 2 Ga, so the connection between São Francisco and Congo must have formed during the Palaeoproterozoic. South of this cratonic bridge the Araçuaí–West Congo orogen evolved in the Neoproterozoic in a sea basin made of oceanic crust, an embayment in

667-493: The same year (2002), Zhao et al. proposed an alternative configuration of Columbia, in which the fits of Baltica and Siberia with Laurentia and the fit of South America with West Africa are similar to those of the Rogers and Santosh configuration, whereas the fits of India, East Antarctica, South Africa, and Australia with Laurentia are similar to their corresponding fits in the configuration of Rodinia . This continental configuration

696-871: The supercontinent Nuna/Columbia can be reconstructed because these LIP events also affected other Precambrian continental blocks. Within Nuna the northern part of Siberia was located adjacent to western São Francisco. 1110 Ma dyke swarms in Angola are absent in Siberia but coincide with the Umkondo LIP on the Kalahari Craton and magmatic event in the Bundelkhand Craton in India, the Amazonian Craton in South America, and

725-602: The supercontinent was provided by the relationship between the Columbia region of North America (centered on the state of Washington ) and east India. The naming is not universally accepted. In 1997, P.F. Hoffman proposed the name Nuna (from Inuit "lands bordering the northern oceans") for the Proterozoic core of Laurentia plus Baltica. Because Hoffman published his name earlier than Rogers and Santosh published theirs, there have been calls to use Nuna rather than Columbia , on

754-548: The time for the formation of the supercontinent Gondwana at c. 550  Ma the Congo Craton formed the already amalgamated central African landmass. The southern and eastern margins (modern coordinates) of this landmass was made of the Archaean Angola-Kasai block and Tanzanian Craton. These proto-Congo blocks were deformed in the Palaeoproterozoic Eburnean orogeny but later stabilised. Before

783-680: The western margin of Laurentia (Belt-Purcell Supergroup), eastern India (Mahanadi and the Godavari), southern margin of Baltica (Telemark Supergroup), southeastern margin of Siberia ( Riphean aulacogens ), northwestern margin of South Africa (Kalahari Copper Belt), and northern margin of the North China Block (Zhaertai-Bayan Obo Belt). The fragmentation corresponded with widespread anorogenic magmatic activity, forming anorthosite - mangerite - charnockite - granite suites in North America, Baltica, Amazonia, and North China, and continued until

812-531: Was attached to western North America , with southern Australia against western Canada . In the Paleoproterozoic most of South America was rotated such that the western edge of modern-day Brazil lined up with eastern North America, forming a continental margin that extended into the southern edge of Scandinavia . Columbia was assembled along global-scale 2.1–1.8 Ga collisional orogens and contained almost all of Earth 's continental blocks. Some of

841-423: Was reconstructed by Guiting Hou (2008) based on the reconstruction of giant radiating dike swarms. Another configuration has been suggested by Chaves and Rezende (2019) supported on available paleomagnetic data and fragments of 1.79-1.75 Ga large igneous provinces . Rogers and Santosh proposed the name Columbia for a hypothetical supercontinent preceding Rodinia. They chose the name because critical evidence for

#817182