Kalahari craton
Encyclopedia
The Kalahari craton is a craton
, an old and stable part of the continental lithosphere with thick crust and deep lithospheric roots extending up to a few hundred kilometers into the Earth's mantle
, that occupies a large portion of South Africa
and consists of the Kaapvaal, the Zimbabwe craton
, the Limpopo belt
, and the Namaqua Belt.
, Limpopo
, Mpumalanga
, and North West provinces
, previously known as the Transvaal
, that consists of granite
s, gneiss
es, and migmatite
s that are ~3.4 Ga. Within this granitic basement
are a number of greenstone belt
s where the rocks have been less highly metamorphosed
and contain many primary features. These rocks comprise the Swaziland system. They form a thick pile of volcanics and chert
s, which pass up into turbidite
s and sandstone
s. The ancient basement became stabilised around 3.0 Ga, and was then covered by a thick sequence of shallow-water sediment
s, lava
s, and igneous intrusion
s.
Additional crust
was formed and reworked along all of the craton’s margins at 1.4–1.0 Ga. To the north, the Damara-Lufilian-Zambezi Fold Belt separates the Congo craton
to the north with the Kalahari. Central Zambia exhibits the largest number of Precambrian
eclogite
occurrences in Africa. These eclogites and the associated gabbro
s are interpreted as relics of a fossil subducted
slab that marks a suture zone between the Congo craton
to the north and the Kalahari.
The Zambezi Belt and the Lufilian Arc are part of the Pan-African orogenic system that crosscuts southern Africa, separating the Congo and Kalahari cratons and their respective Paleo- and Mesoproterozoic units. These Pan-African belts were formed during the assembly of the Gondwana
supercontinent
. Eclogite facies metamorphism
occurred at ca. 600 Ma, whereas peak metamorphism during the subsequent continental collision occurred around 530 Ma ago, with metamorphic P–T conditions reaching the high pressure amphibolite facies. The Zambezi Belt crosscuts and thus divides the Meso-proterozoic parts of Zambia into the Irumide Belt and the Choma-Kalomo Block. The junction of the Neoproterozoic belts and the Mesoproterozoic parts is marked by a 200 km long and up to 40 km wide zone containing lenses of eclogite, metagabbro, gabbro and rare ultramafic rocks. The eclogite-bearing zone is located in the interior of the Zambezi Belt, and runs parallel to strike
. The eclogites and associated mafic rocks form isolated hills of 10 to 100 metres in diameter.
Pan-African belts along the northern and eastern craton margins are associated in one area with a 1.4 Ga ophiolite/arc terrane
. The orthogneisses
form part of an extensive region north of the Kalahari craton and east of the Congo craton that includes large amounts of 1.15–1.0 Ga arc-type rocks containing juvenile crustal components. This region may represent one of the main convergent zones active during Rodinia
assembly, although its original relations are obscured by intense Pan-African overprinting. Along the southern margin, the Namaqua–Natal–Maud belt underwent arc magma
tism, terrane
accretion
, polyphase amphibolite- to granulite
-grade contractional/transpression
al deformation, and late-syntectonic granite intrusion at 1.38–1.0 Ga. A largely buried orogen along the western margin records amphibolite-grade deformation and granitoid pluton
ism at 1.35–1.2 Ga and is inferred to connect with the Namaqua belt to the south. 1.1–1.0 Ga granitoid orthogneisses within Widespread intraplate magmatism affected much of the Kalahari craton at 1.1 Ga and is inferred to record impact of a mantle plume inboard of the Namaqua–Natal–Maud belt.
The Limpopo Belt
separates the Rhodesian province to the north from the Transvaal province to the south. The Limppoo Belt also joins the Zimbabwe craton
to the north with the Kaapvaal craton
to the south. The belt is composed of a granitic basement with narrow greenstone belts. Within the greenstone belts, the sequence consists of basic volcanics, covered by greywacke
s, shale
s, and conglomerate
s.
studies showed that the Umkondo sills in eastern Zimbabwe correlated with similar mafic intrusions in Botswana and South Africa. It was therefore suggested that the Umkondo igneous province is present over a large part of the Kalahari craton, and also a detached fragment now located in East Antarctica. New paleomagnetic data are in excellent agreement with this. The great majority of the sites have the same polarity suggesting that the dolerites were emplaced during a limited time span, consistent with the geochronology. The pole position places the Kalahari craton off southeast Laurentia within the Rodinia supercontinent. In Laurentia, there is widespread within-plate magmatism coeval with the Umkondo event, raising the possibility that the two igneous provinces were linked within Rodinia.
The Kalahari craton probably converged with southwestern Laurentia
between 1060 and 1030 Ma to become part of the Rodinia supercontinent
by 1000 Ma. In Rodinia, the Kalahari craton lay near East Antarctica with the Namaqua–Natal orogenic belt facing outboard and away from the Laurentian craton. The Kalahari and Congo cratons probably collided during the assembly of Rodinia, however they could have also been just juxtaposed during the assembly of Gondwana (550–500 Ma) at the end of the Neoproterozoic
. In the former case, the transcontinental, ~550 Ma Damaran-Lufilian-Zambezi orogen separating the two cratons would represent a Himalayan-style collisional belt formed by the consumption of a wide ocean. In the later case it may have been a closure of narrow Neoproterozoic basins that developed across previously assembled parts of Rodinia. A third view is that there was a convergence between the Kalahari craton and a composite Congo-Laurentia craton during the assembly of Rodinia, generating the Kibaran-Grenvillian-Llano belts. This orogenic belt system extends for over 3000 km and is over 400 km wide in Africa and is the result of the convergence of Paleoproterozoic
/Archaean cratonic blocks forming the Congo craton
to the north and a mosaic including the Kalahari, Bangweulu, Tanzania and West-Nilian cratons (hereafter called the Kalahari craton) to the south.
The arc on the flank of Madagascar collided with the African margin at ~640 Ma, and remained attached to the African margin when Madagascar rifted during Gondwana breakup. This ~640 event has been considered to date the collision of India, Madagascar, parts of eastern Antarctica and Kalahari cratons (IMSLEK terranes) with the Congo-Tanzania Craton and Arabian Nubian Shield.
system is the world's most productive source of gold
. Gold ores
occur in fracture systems in the greenstone belt
s. The Transvaal system contains important iron ores, and the Bushveld igneous complex
contains platinum
, chromium
, titanium
-iron, and tin
ores.
Manganese
of high-grade is mined in the large Kalahari manganese field from hydrothermal enrichments in stratabound deposits that formed approximately 2.1 Ga.
s (9,600 kg)) produces more than the combined Central African cratons (37 million carats (7400 kg)) and the West African craton (2.1 million carats (420 kg)). The difference is even more pronounced in value terms where the Kalahari craton (approximately US$5.1 billion) is clearly ahead of the Central African (US$2.2 billion) and West African cratons (US$0.34 billion). The dominance of the Southern African Craton is largely due to the excellent infrastructure, favourable climate and stable political and socio-economic regime, which have ensured continuous exploration and mining activities for the past century. The Kasai craton extends over the border into Angola
where 77 diamond kimberlites have been discovered. Eleven others have been found in the less explored DRC
section of the craton.
Craton
A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
, an old and stable part of the continental lithosphere with thick crust and deep lithospheric roots extending up to a few hundred kilometers into the Earth's mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
, that occupies a large portion of South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
and consists of the Kaapvaal, the Zimbabwe craton
Zimbabwe craton
The Zimbabwe craton is an area in Southern Africa of ancient continental crust and an example of Early Archaean lithology dating back to 3.5 billion years ago in the southern African nation of Zimbabwe. Late Archean metamorphism joined the Southern Marginal Zone of the Kaapvaal craton to the...
, the Limpopo belt
Limpopo Belt
The Limpopo Belt is located in South Africa and Zimbabwe, runs E-NE, and joins the Kaapvaal craton to the south with the Zimbabwe craton to the north. The belt is of high-grade metamorphic rocks that have undergone a long cycle of metamorphism and deformation that ended 2.0 billion years ago, after...
, and the Namaqua Belt.
Geology
Kalahari craton has formed a stable unit for the past 2.3 billion years (2.3 Ga). As such, it contains some of the oldest known rocks and microfossils in the world. The oldest rocks are in the GautengGauteng
Gauteng is one of the nine provinces of South Africa. It was formed from part of the old Transvaal Province after South Africa's first all-race elections on 27 April 1994...
, Limpopo
Limpopo
Limpopo is the northernmost province of South Africa. The capital is Polokwane, formerly named Pietersburg. The province was formed from the northern region of Transvaal Province in 1994, and initially named Northern Transvaal...
, Mpumalanga
Mpumalanga
Mpumalanga , is a province of South Africa. The name means east or literally "the place where the sun rises" in Swazi, Xhosa, Ndebele and Zulu. Mpumalanga lies in eastern South Africa, north of KwaZulu-Natal and bordering Swaziland and Mozambique. It constitutes 6.5% of South Africa's land area...
, and North West provinces
North West (South African province)
North West is a province of South Africa. Its capital is Mafikeng. The province is located to the west of the major population centre of Gauteng.-History:...
, previously known as the Transvaal
Transvaal Province
Transvaal Province was a province of the Union of South Africa from 1910 to 1961, and of its successor, the Republic of South Africa, from 1961 until the end of apartheid in 1994 when a new constitution subdivided it.-History:...
, that consists of granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
s, gneiss
Gneiss
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...
es, and migmatite
Migmatite
Migmatite is a rock at the frontier between igneous and metamorphic rocks. They can also be known as diatexite.Migmatites form under extreme temperature conditions during prograde metamorphism, where partial melting occurs in pre-existing rocks. Migmatites are not crystallized from a totally...
s that are ~3.4 Ga. Within this granitic basement
Basement (geology)
In geology, the terms basement and crystalline basement are used to define the rocks below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin...
are a number of greenstone belt
Greenstone belt
Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archaean and Proterozoic cratons between granite and gneiss bodies....
s where the rocks have been less highly metamorphosed
Metamorphism
Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...
and contain many primary features. These rocks comprise the Swaziland system. They form a thick pile of volcanics and chert
Chert
Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...
s, which pass up into turbidite
Turbidite
Turbidite geological formations have their origins in turbidity current deposits, which are deposits from a form of underwater avalanche that are responsible for distributing vast amounts of clastic sediment into the deep ocean.-The ideal turbidite sequence:...
s and sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
s. The ancient basement became stabilised around 3.0 Ga, and was then covered by a thick sequence of shallow-water sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s, lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
s, and igneous intrusion
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
s.
Additional crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
was formed and reworked along all of the craton’s margins at 1.4–1.0 Ga. To the north, the Damara-Lufilian-Zambezi Fold Belt separates the Congo craton
Congo craton
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...
to the north with the Kalahari. Central Zambia exhibits the largest number of Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
eclogite
Eclogite
Eclogite is a mafic metamorphic rock. Eclogite is of special interest for at least two reasons. First, it forms at pressures greater than those typical of the crust of the Earth...
occurrences in Africa. These eclogites and the associated gabbro
Gabbro
Gabbro refers to a large group of dark, coarse-grained, intrusive mafic igneous rocks chemically equivalent to basalt. The rocks are plutonic, formed when molten magma is trapped beneath the Earth's surface and cools into a crystalline mass....
s are interpreted as relics of a fossil subducted
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
slab that marks a suture zone between the Congo craton
Congo craton
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...
to the north and the Kalahari.
The Zambezi Belt and the Lufilian Arc are part of the Pan-African orogenic system that crosscuts southern Africa, separating the Congo and Kalahari cratons and their respective Paleo- and Mesoproterozoic units. These Pan-African belts were formed during the assembly of the Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
. Eclogite facies metamorphism
Metamorphism
Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...
occurred at ca. 600 Ma, whereas peak metamorphism during the subsequent continental collision occurred around 530 Ma ago, with metamorphic P–T conditions reaching the high pressure amphibolite facies. The Zambezi Belt crosscuts and thus divides the Meso-proterozoic parts of Zambia into the Irumide Belt and the Choma-Kalomo Block. The junction of the Neoproterozoic belts and the Mesoproterozoic parts is marked by a 200 km long and up to 40 km wide zone containing lenses of eclogite, metagabbro, gabbro and rare ultramafic rocks. The eclogite-bearing zone is located in the interior of the Zambezi Belt, and runs parallel to strike
Strike and dip
Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault, or other planar feature is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented...
. The eclogites and associated mafic rocks form isolated hills of 10 to 100 metres in diameter.
Pan-African belts along the northern and eastern craton margins are associated in one area with a 1.4 Ga ophiolite/arc terrane
Terrane
A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...
. The orthogneisses
Gneiss
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...
form part of an extensive region north of the Kalahari craton and east of the Congo craton that includes large amounts of 1.15–1.0 Ga arc-type rocks containing juvenile crustal components. This region may represent one of the main convergent zones active during Rodinia
Rodinia
In geology, Rodinia is the name of a supercontinent, a continent which contained most or all of Earth's landmass. According to plate tectonic reconstructions, Rodinia existed between 1.1 billion and 750 million years ago, in the Neoproterozoic era...
assembly, although its original relations are obscured by intense Pan-African overprinting. Along the southern margin, the Namaqua–Natal–Maud belt underwent arc magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
tism, terrane
Terrane
A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...
accretion
Accretion (geology)
Accretion is a process by which material is added to a tectonic plate or a landmass. This material may be sediment, volcanic arcs, seamounts or other igneous features.-Description:...
, polyphase amphibolite- to granulite
Granulite
Granulites are medium to coarse–grained metamorphic rocks that have experienced high temperature metamorphism, composed mainly of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure...
-grade contractional/transpression
Transpression
Transpression is a geological term used to describe a region of the Earth's crust that experiences strike-slip shear and a component of shortening, resulting in oblique shear. Transpression typically occurs at a regional scale, such as plate boundaries that have an oblique convergence. More...
al deformation, and late-syntectonic granite intrusion at 1.38–1.0 Ga. A largely buried orogen along the western margin records amphibolite-grade deformation and granitoid pluton
Pluton
A pluton in geology is a body of intrusive igneous rock that crystallized from magma slowly cooling below the surface of the Earth. Plutons include batholiths, dikes, sills, laccoliths, lopoliths, and other igneous bodies...
ism at 1.35–1.2 Ga and is inferred to connect with the Namaqua belt to the south. 1.1–1.0 Ga granitoid orthogneisses within Widespread intraplate magmatism affected much of the Kalahari craton at 1.1 Ga and is inferred to record impact of a mantle plume inboard of the Namaqua–Natal–Maud belt.
The Limpopo Belt
Limpopo Belt
The Limpopo Belt is located in South Africa and Zimbabwe, runs E-NE, and joins the Kaapvaal craton to the south with the Zimbabwe craton to the north. The belt is of high-grade metamorphic rocks that have undergone a long cycle of metamorphism and deformation that ended 2.0 billion years ago, after...
separates the Rhodesian province to the north from the Transvaal province to the south. The Limppoo Belt also joins the Zimbabwe craton
Zimbabwe craton
The Zimbabwe craton is an area in Southern Africa of ancient continental crust and an example of Early Archaean lithology dating back to 3.5 billion years ago in the southern African nation of Zimbabwe. Late Archean metamorphism joined the Southern Marginal Zone of the Kaapvaal craton to the...
to the north with the Kaapvaal craton
Kaapvaal craton
The Kaapvaal craton , along with the Pilbara craton of Western Australia, are the only remaining areas of pristine 3.6-2.5 Ga crust on Earth...
to the south. The belt is composed of a granitic basement with narrow greenstone belts. Within the greenstone belts, the sequence consists of basic volcanics, covered by greywacke
Greywacke
Greywacke or Graywacke is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lithic fragments set in a compact, clay-fine matrix. It is a texturally immature sedimentary rock generally found...
s, shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
s, and conglomerate
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
s.
Kalahari craton with Laurentia, Rodinia, and Gondwana
Early paleomagneticPaleomagnetism
Paleomagnetism is the study of the record of the Earth's magnetic field in rocks. Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form. This record provides information on the past behavior of Earth's magnetic field and the past location of...
studies showed that the Umkondo sills in eastern Zimbabwe correlated with similar mafic intrusions in Botswana and South Africa. It was therefore suggested that the Umkondo igneous province is present over a large part of the Kalahari craton, and also a detached fragment now located in East Antarctica. New paleomagnetic data are in excellent agreement with this. The great majority of the sites have the same polarity suggesting that the dolerites were emplaced during a limited time span, consistent with the geochronology. The pole position places the Kalahari craton off southeast Laurentia within the Rodinia supercontinent. In Laurentia, there is widespread within-plate magmatism coeval with the Umkondo event, raising the possibility that the two igneous provinces were linked within Rodinia.
The Kalahari craton probably converged with southwestern Laurentia
Laurentia
Laurentia is a large area of continental craton, which forms the ancient geological core of the North American continent...
between 1060 and 1030 Ma to become part of the Rodinia supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
by 1000 Ma. In Rodinia, the Kalahari craton lay near East Antarctica with the Namaqua–Natal orogenic belt facing outboard and away from the Laurentian craton. The Kalahari and Congo cratons probably collided during the assembly of Rodinia, however they could have also been just juxtaposed during the assembly of Gondwana (550–500 Ma) at the end of the Neoproterozoic
Neoproterozoic
The Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods...
. In the former case, the transcontinental, ~550 Ma Damaran-Lufilian-Zambezi orogen separating the two cratons would represent a Himalayan-style collisional belt formed by the consumption of a wide ocean. In the later case it may have been a closure of narrow Neoproterozoic basins that developed across previously assembled parts of Rodinia. A third view is that there was a convergence between the Kalahari craton and a composite Congo-Laurentia craton during the assembly of Rodinia, generating the Kibaran-Grenvillian-Llano belts. This orogenic belt system extends for over 3000 km and is over 400 km wide in Africa and is the result of the convergence of Paleoproterozoic
Paleoproterozoic
The Paleoproterozoic is the first of the three sub-divisions of the Proterozoic occurring between . This is when the continents first stabilized...
/Archaean cratonic blocks forming the Congo craton
Congo craton
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...
to the north and a mosaic including the Kalahari, Bangweulu, Tanzania and West-Nilian cratons (hereafter called the Kalahari craton) to the south.
The arc on the flank of Madagascar collided with the African margin at ~640 Ma, and remained attached to the African margin when Madagascar rifted during Gondwana breakup. This ~640 event has been considered to date the collision of India, Madagascar, parts of eastern Antarctica and Kalahari cratons (IMSLEK terranes) with the Congo-Tanzania Craton and Arabian Nubian Shield.
Metals
The WitwatersrandWitwatersrand
The Witwatersrand is a low, sedimentary range of hills, at an elevation of 1700–1800 metres above sea-level, which runs in an east-west direction through Gauteng in South Africa. The word in Afrikaans means "the ridge of white waters". Geologically it is complex, but the principal formations...
system is the world's most productive source of gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
. Gold ores
Gold mining
Gold mining is the removal of gold from the ground. There are several techniques and processes by which gold may be extracted from the earth.-History:...
occur in fracture systems in the greenstone belt
Greenstone belt
Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archaean and Proterozoic cratons between granite and gneiss bodies....
s. The Transvaal system contains important iron ores, and the Bushveld igneous complex
Bushveld igneous complex
The Bushveld Igneous Complex is a large layered igneous intrusion within the Earth's crust which has been tilted and eroded and now outcrops around what appears to be the edge of a great geological basin, the Transvaal Basin. Located in South Africa, the BIC contains some of the richest ore...
contains platinum
Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
, chromium
Chromium
Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
, titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
-iron, and tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
ores.
Manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
of high-grade is mined in the large Kalahari manganese field from hydrothermal enrichments in stratabound deposits that formed approximately 2.1 Ga.
Diamonds
Diamond mining from the Kalahari craton has been extensive. Based on current annual output the Southern African Kalahari craton (approximately 48 million caratCarat (mass)
The carat is a unit of mass equal to 200 mg and is used for measuring gemstones and pearls.The current definition, sometimes known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures, and soon afterward in many countries around the world...
s (9,600 kg)) produces more than the combined Central African cratons (37 million carats (7400 kg)) and the West African craton (2.1 million carats (420 kg)). The difference is even more pronounced in value terms where the Kalahari craton (approximately US$5.1 billion) is clearly ahead of the Central African (US$2.2 billion) and West African cratons (US$0.34 billion). The dominance of the Southern African Craton is largely due to the excellent infrastructure, favourable climate and stable political and socio-economic regime, which have ensured continuous exploration and mining activities for the past century. The Kasai craton extends over the border into Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
where 77 diamond kimberlites have been discovered. Eleven others have been found in the less explored DRC
Democratic Republic of the Congo
The Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...
section of the craton.
See also
- Kaapval craton
- Zimbabwe cratonZimbabwe cratonThe Zimbabwe craton is an area in Southern Africa of ancient continental crust and an example of Early Archaean lithology dating back to 3.5 billion years ago in the southern African nation of Zimbabwe. Late Archean metamorphism joined the Southern Marginal Zone of the Kaapvaal craton to the...
- Copperbelt ProvinceCopperbelt ProvinceCopperbelt Province in Zambia covers the mineral-rich Copperbelt, and farming and bush areas to the south. It was the backbone of the Northern Rhodesian economy during British colonial rule and fuelled the hopes of the immediate post-independence period, but its economic importance was severely...
- Limpopo BeltLimpopo BeltThe Limpopo Belt is located in South Africa and Zimbabwe, runs E-NE, and joins the Kaapvaal craton to the south with the Zimbabwe craton to the north. The belt is of high-grade metamorphic rocks that have undergone a long cycle of metamorphism and deformation that ended 2.0 billion years ago, after...
- South AfricaSouth AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...