It is common in the upper mantle, especially in regions occupied by subducted oceanic plates. Eclogite, any member of a small group of igneous and metamorphic rocks whose composition is similar to that of basalt. Eclogite-rich layers would be intermittent because of low melting points and the temperature-dependency of the relevant phase changes. eclogite facies A set of metamorphic mineral assemblages produced by metamorphism of basic igneous rocks under high-pressure, moderate-temperature conditions and typically characterized by the development of the mineral assemblage pyrope garnet and omphacite (an Na-rich, high-pressure pyroxene).Other rocks of contrasting composition, e.g. Eclogite is one of the important type of rocks. Eclogite-derived melts may be common in the mantle, and contribute to volcanic regions where unusually large volumes of magma are erupted. [4], The eclogite melt may then react with enclosing peridotite to produce pyroxenite, which in turn melts to produce basalt.[5]. Add your answer and earn points. These bodies are generally described as tectonic blocks and their relationship to the Sanbagawa metamorphism is unclear. They are formed when volcanic or metamorphic rocks rich in such mafic minerals are subjected to extremely high pressures and moderate to relatively high temperatures. Plagioclase is not stable in eclogite. Xenoliths of eclogite occur in kimberlite pipes of Africa, Russia, Canada, and elsewhere. The carbon isotopic differences between harzburgitic and eclogitic diamonds supports the hypothesis that those eclogite xenoliths formed from basalt carried down within subduction zones. Eclogites in granulite terranes are known from the Musgrave Block of central Australia where a continental collision took place at 550-530 Ma, resulting in burial of rocks to greater than 45 km (15 kilobars) and rapid (in less than 10 million years[citation needed]) exhumation via thrust faults prevented significant melting. Many investigators believe that eclogite is representative of numerous parts of the upper mantle. Eclogite consists mainly of omphacite and garnet. Eclogite is a rare and important rock because it is formed only by conditions typically found in the mantle or … It is a rare but geologically significant rock type. Instead, basalts can be modelled as having been produced by 1 to 25% partial melting of peridotite, such as harzburgite and lherzolite. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. An unusually dense rock, eclogite can play an important role in driving convection within the solid Earth. Hardness and Strength of Eclogite The physical properties of Eclogite depend on its formation. Known eclogite occurrences in the Sanbagawa metamorphic belt of SW Japan are dominantly in metagabbro bodies which have complex polyphase metamorphic histories. Eclogite, any member of a small group of igneous and metamorphic rocks whose composition is similar to that of basalt. Eclogite definition, a rock consisting of a granular aggregate of green pyroxene and red garnet, often containing kyanite, silvery mica, quartz, and pyrite. A few eclogites also occur in the northwest highlands of Scotland and the Massif Central of France. Eclogites occur with garnet peridotites in Greenland and in other ophiolite complexes. Introduction [2] Crustal rocks metamorphosed at high-pressure (HP) to ultrahigh pressure conditions provide important geody- A. Camacho, B.J. An unusually dense rock, eclogite can play an important role in driving convection within the solid Earth. ... eclogite residues is primarily ‘east-to-west’, and not ‘north-to-south’, as the amphibolite. Posted on 24 October, 2012 by Metageologist. Unreasonably high degrees of partial melting are required to attain basaltic compositions. In the crust, eclogites generally occur as xenoliths (i.e., foreign inclusions) in igneous rocks and as isolated blocks measuring as much as 100 m (328 feet) across in metamorphic rocks. Eclogite forms at pressures greater than those typical of the crust of the Earth. Rocks are rated on the on the Moh's Hardness Scale which rates the rocks on the scale from 1 to 10. Eclogite-facies metamorphic conditions encompass a wide range of pressure–temperature space from deep crustal to mantle depths, reflecting tectonic setting. Eclogites consist primarily of green pyroxene (omphacite) and red garnet (pyrope), with small amounts of various other stable minerals— e.g., rutile. Diamond and coesite occur as trace constituents in some eclogites and record particularly high pressures. Eclogite may completely retrogress to amphibolite or granulite during exhumation. Lawsonite eclogite is known from the U.S. (Franciscan Complex of California; xenoliths in Arizona); Guatemala (Motagua fault zone), Corsica, Australia, the Dominican Republic, Canada (British Columbia), and Turkey. Eclogite is a rare and important rock because it is formed only by conditions typically found in the mantle or the lowermost part of thickened crust. The inclusions had undergone eclogite facies high-pressure metamorphism and amphibolite facies retrogressive metamorphism. It is a rare but geologically significant rock type. Physical properties of rocks play an important role in determining its applications in various fields. Eclogite is a unique metamorphic rock that forms at high pressure and indicates deeply subducted crust or thick continent crust around Moho depth. Let us know if you have suggestions to improve this article (requires login). Removal of the dense lower continen­ tal crust is an important element of … Harzburgitic diamonds typically have titaniferous pyrope, chromian spinel and chromian diopside inclusions, minerals which are not typically found in eclogites. important strategy for establishing control over organic epitaxy. Eclogites are beautiful rocks that form deep within subduction zones. Because eclogite is prone to retrogression during exhumation to the surface, the associated changes in physical properties should be understood. , which emplaced in 191 Ma crust transforms to dense eclogite and delaminates Russia, Canada, and from. Its applications in various fields eclogite xenoliths formed from basalt carried down within subduction zones /ˈɛklədʒaɪt/! 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