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Greenschist. Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically 300–450 °C (570–840 °F) and 2–10 kilobars (29,000–145,000 psi). [1] Greenschists commonly have an abundance of green minerals such as chlorite, serpentine, and epidote, and platy ...
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. The name comes from the green hue imparted by the colour of the metamorphic minerals within the mafic rocks: The ...
The Barberton Greenstone Belt is a geologic formation situated on the eastern edge of the Kaapvaal Craton in South Africa. It is known for its gold mineralisation and for its komatiites, an unusual type of ultramafic volcanic rock named after the Komati River that flows through the belt. Some of the oldest exposed rocks on Earth (greater than 3 ...
Basic geological regions of Australia, by age. The large brown region in the lower left of the continent constitutes the Yilgarn Craton. The Yilgarn Craton is a large craton that constitutes a major part of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts.
The craton is a mixture of early Archean (3.0–3.5 Ga) granite greenstone terranes and older tonalitic gneisses (ca. 3.6–3.7 Ga), intruded by a variety of granitic plutons (3.3–3.0 Ga). Subsequent evolution of the Kaapvaal Craton (3.0–2.7 Ga) is thought to be associated with continent–arc collision that caused an overlaying succession ...
The Isua Greenstone Belt, also known as the Isua supracrustal belt since it is composed primarily of supracrustal rocks, is located in southwestern Greenland, in the Isukasia terrane, [1] near the Nuuk capital region. [9] It forms the largest supracrustal enclave in the Itsaq Gneiss Complex, which predominantly comprises 3850 - 3600 million ...
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The West African Craton (WAC) is one of the five cratons of the Precambrian basement rock of Africa that make up the African Plate, the others being the Kalahari craton, Congo craton, Saharan Metacraton and Tanzania Craton. [1] Cratons themselves are tectonically inactive, but can occur near active margins, [2] with the WAC extending across 14 ...