Komatiite/koʊˈmɑːtiˌaɪt/ is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava of at least 18 wt% magnesium oxide (MgO).[1] It is classified as a 'picritic rock'. Komatiites have low silicon, potassium and aluminium, and high to extremely high magnesium content. Komatiite was named for its type locality along the Komati River in South Africa,[2] and frequently displays spinifex texture composed of large dendritic plates of olivine and pyroxene.[3]
Komatiites are rare rocks; almost all komatiites were formed during the Archaean Eon (4.03–2.5 billion years ago), with few younger (Proterozoic or Phanerozoic) examples known. This restriction in age is thought to be due to cooling of the mantle, which may have been 100–250 °C (212–482 °F) hotter during the Archaean.[4][5] The early Earth had much higher heat production, due to the residual heat from planetary accretion, as well as the greater abundance of radioactive isotopes, particularly shorter lived ones like uranium 235 which produce more decay heat. Lower temperature mantle melts such as basalt and picrite have essentially replaced komatiites as an eruptive lava on the Earth's surface.
Geographically, komatiites are predominantly restricted in distribution to the Archaean shield areas, and occur with other ultramafic and high-magnesian mafic volcanic rocks in Archaean greenstone belts. The youngest komatiites are from the island of Gorgona on the Caribbean oceanic plateau off the Pacific coast of Colombia, and a rare example of Proterozoic komatiite is found in the Winnipegosis komatiite belt in Manitoba, Canada.
^Le Bas, M. J. 2000. IUGS reclassification of the high-Mg and picritic volcanic rocks. Journal of Petrology, 41(10), 1467–1470. https://doi.org/10.1093/petrology/41.10.1467
^Viljoen, M. J., & Viljoen, R. P. 1969a. Evidence for the existence of a mobile extrusive peridotitic magma from the Komati Formation of the Onvernacht Group. Geological Survey of South Africa, Special Publication, 21, 87 – 112.
^Arndt, N., Lesher, C. M., & Barnes, S. J. 2008. Komatiite. Cambridge: Cambridge University Press.
^Davies, G. F. 1999. Plates, Plumes and Mantle Convection. Cambridge: Cambridge University Press.
^Herzberg, C., Condie, K., & Korenaga, J. 2010. Thermal history of the Earth and its petrological expression. Earth and Planetary Science Letters, 292(1–2), 79–88. https://doi.org/10.1016/j.epsl.2010.01.022
Komatiite /koʊˈmɑːtiˌaɪt/ is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava of at least 18 wt% magnesium...
Widgiemooltha Komatiite is a formation of komatiite in the Yilgarn Craton of Western Australia. The stratigraphy of the Widgiemooltha Komatiite is well known...
komatiite magma and a solid residue very close in composition to Archean lithospheric mantle, but continental shields do not contain enough komatiite...
tectonics, and allowing the production of uncommon igneous rocks such as komatiites that are rarely formed today. The mean heat loss from Earth is 87 mW m−2...
The Winnipegosis komatiite belt is a 150 km (93 mi) long and 30 km (19 mi) wide greenstone belt located in the Lake Winnipegosis area of central Manitoba...
entrail-type pahoehoe lavas on land. Ultramafic magmas, such as picritic basalt, komatiite, and highly magnesian magmas that form boninite, take the composition...
rocks elsewhere in the solar system. Examples include komatiite and picritic basalt. Komatiites can be host to ore deposits of nickel. Ultramafic tuff...
similar to entrail-type pahoehoe lavas on land. Ultramafic lavas, such as komatiite and highly magnesian magmas that form boninite, take the composition and...
diagram of classification. They include picrite, komatiite and meimechite. Picrites and komatiites are somewhat similar chemically (defined as >18% MgO)...
iron-nickel-copper-platinum-group element ore deposit in which the physical processes of komatiite volcanology serve to deposit, concentrate and enrich a Fe-Ni-Cu-(PGE)...
as spinifexes Spinifex, a texture in certain ultramafic lavas such as komatiite Spinifex people, an Aboriginal Australian people, inhabitants of the Spinifex...
hotspot setting. The upwelling magma formed the oceanic plateaus with komatiites and komatiitic basalts in the oceanic crust. After the mantle plume hotspots...
≤45% silica and produce ultramafic lava. Ultramafic flows, also known as komatiites, are very rare; indeed, very few have been erupted at Earth's surface...
ultramafics are typical of many areas of the Archaean cratons, notably the komatiite belts of the Yilgarn Craton in Western Australia. Talc-carbonate ultramafics...
kimberlite is more properly called an ultramafic breccia rather than a tuff. Komatiite tuffs are found, for example, in the greenstone belts of Canada and South...
rocks, with silica (SiO2) contents below 45% are usually classified as komatiites. The word "basalt" is ultimately derived from Late Latin basaltes, a misspelling...
Ultramafic rock is very low in silica, with more than 90% of mafic minerals (komatiite, dunite). This classification is summarized in the following table: The...
Look up komatiite in Wiktionary, the free dictionary. Komati may refer to: Komati caste, is an Indian trading community primarily found in central and...
years ago) age greenstone belts containing a rare volcanic rock called komatiite. The 2,677 million year old Abitibi greenstone belt in Ontario and Quebec...
and augite Kimberlite – Igneous rock which sometimes contains diamonds Komatiite – Magnesium-rich igneous rock Lamproite – Mantle rock expulsed to the...
"Origin and timing of the metasomatic silicification of an early Archaean komatiite sequence, Barberton Mountain Land, South Africa". Precambrian Research...
J., and Dowling S.E., 1990. Physical volcanology of komatiites; A field guide to the komatiites of the Norseman-Wiluna Greenstone Belt, Eastern Goldfields...
nickel-copper-platinum group element deposits, especially those associated with komatiites, their physical volcanology and localization, the geochemistry and petrology...
mafic, igneous, and typically volcanic rocks, e.g. tholeiite, basalt or komatiite, that contain centimeter-scale spherical or globular structures, called...
subdivided into two groups by their dominant ore element: Ni-Cu, found in komatiites, anorthosite complexes, and flood basalts. This also includes the Sudbury...
ISBN 0-471-01488-5. Jarvis, Gary T.; Campbell, Ian H. (December 1983). "Archean komatiites and geotherms: Solution to an apparent contradiction". Geophysical Research...
lavas are commonly of basaltic composition, although pillows formed of komatiite, picrite, boninite, basaltic andesite, andesite, dacite or even rhyolite...