Eclogite piece with a garnet (red) and omphacite (greyish-green) groundmass. The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives Omphacite is a member of the Pyroxene group of Silicate minerals with formula ( Ca, Na)( Mg, Fe 2+ Al The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or Crystals are embedded The sky-blue crystals are kyanite. Kyanite, whose name derives from the Greek word kyanos, meaning blue is a typically blue Silicate Mineral, commonly found in Aluminium -rich Some white quartz is seen too, it was probably once coesite. Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Coesite is a form ( polymorph) of Silicon dioxide Si[[oxygen O]]2 that is formed when very high pressure (2&ndash3 Gigapascals and A few gold-white phengite mica minerals can be seen at the top. Phengite is a series name for dioctahedral Micas of composition K(AlMg2(OH2(SiAl4O10 similar to Muscovite but with addition The word "mica" is thought to be derived from the Latin word la micare, "glitteren" in reference to the brilliant appearance of this mineral (especially Coin of 1 euro (2,3 cm) for scale. 1 Euro coins (€1 or 1€ are made of two Alloys the inner part of Cupronickel, the outer part of nickel Brass. A centimetre ( American spelling: centimeter, symbol cm) is a unit of Length in the Metric system, equal to one hundredth

Eclogite

Eclogite (pronounced /ˈɛklədʒaɪt/) is a coarse-grained mafic (basaltic in composition) metamorphic rock. Mafic is an adjective describing a Silicate mineral or rock that is rich in magnesium and iron the term was derived by contracting "magnesium" and "ferric" Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change 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. In Geology, a crust is the outermost solid shell of a planet or moon EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Second, being unusually dense rock, eclogite can play an important role in driving convection within the solid Earth. Convection in the most general terms refers to the movement of molecules within Fluids (i

The fresh rock can be striking in appearance, with red to pink garnet (almandine-pyrope) in a green matrix of sodium-rich pyroxene (omphacite). In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 The pyroxenes are a group of important rock-forming Silicate minerals found in many Igneous and metamorphic rocks. Omphacite is a member of the Pyroxene group of Silicate minerals with formula ( Ca, Na)( Mg, Fe 2+ Al Accessory minerals include kyanite, rutile, quartz, lawsonite, coesite, amphibole, phengite, paragonite, zoisite, dolomite, corundum, and, rarely, diamond. Kyanite, whose name derives from the Greek word kyanos, meaning blue is a typically blue Silicate Mineral, commonly found in Aluminium -rich Rutile is a Mineral composed primarily of Titanium dioxide, Ti[[oxygen O]]2 Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Lawsonite is a hydrous calcium aluminium sorosilicate mineral with formula CaAl2Si2O7(OH2·H2O Coesite is a form ( polymorph) of Silicon dioxide Si[[oxygen O]]2 that is formed when very high pressure (2&ndash3 Gigapascals and Amphibole (pronounced amfi-bowl defines an important group of generally dark-colored rock-forming inosilicate Minerals composed of double chain SiO4 Phengite is a series name for dioctahedral Micas of composition K(AlMg2(OH2(SiAl4O10 similar to Muscovite but with addition Paragonite, also known as Natron-Glimmer, Paragonit or Paragonita, is a Mineral, related to Muscovite. This article is about the mineral named zoisite For the Sailor Moon character see Shitennou. Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed Corundum (from Tamil kurundam குருந்தம் or kuruvindam குருவிந்தம் is a Crystalline form of In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in Plagioclase is not stable in eclogites. Plagioclase is a very important series of tectosilicate Minerals within the Feldspar family Glaucophane and titanite (sphene) form in eclogite as pressures decrease during exhumation of the rocks, or may be earlier formed minerals that did not entirely react away. Glaucophane is a Mineral belonging to the Amphibole group chemical formula Na 2( Mg, Fe)3 Al 2 Titanite or sphene is a Calcium Titanium nesosilicate Mineral, Ca[[titanium Ti]] Si[[oxygen O]]5

Origins

Eclogite typically results from high-pressure metamorphism of mafic igneous rock (typically basalt or gabbro) as it plunges into the mantle in a subduction zone. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. Gabbro (ˈɡæbrəʊ is a dark coarse-grained intrusive Igneous rock chemically equivalent to Basalt. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided In Geology, a subduction zone is an area on Earth where two tectonic plates meet and move towards one another with one sliding underneath the other Such eclogites are generally formed from precursor mineral assemblages typical of blueschist metamorphism. Blueschist (ˈbluːʃɪst is a rock that forms by the Metamorphism of Basalt and rocks with similar composition at high Pressures and low Eclogite can also form from magmas that crystallize and cool within the mantle or lower crust of continents. Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet

Eclogite facies

Eclogite facies is determined by the temperature and pressure conditions required to metamorphose basaltic rocks to an eclogite assemblage. The term " Facies " can also refer to distinctive Facial expressions associated with conditions such as Williams syndrome. The typical eclogite mineral assemblage is garnet (pyrope to almandine) plus clinopyroxene (omphacite).

Eclogites record pressures in excess of 1. 2 GPa (45 km depth) at >400–1000 °C and usually in excess of 600-650 °C. This is extremely high pressure, medium to high temperature metamorphism. Diamond and coesite occur as trace constituents in some eclogites and record particularly high pressures. In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in Coesite is a form ( polymorph) of Silicon dioxide Si[[oxygen O]]2 that is formed when very high pressure (2&ndash3 Gigapascals and In fact, ultrahigh-pressure (UHP) metamorphism has been defined as metamorphism within the eclogite facies but at pressures greater than those of the quartz-coesite transition (the two minerals have the same composition -- silica). Some UHP rocks appear to record burial at depths greater than 150 km.

Eclogites containing lawsonite (a hydrous calcium-aluminium silicate) are very rarely exposed at the Earth's surface, although they are predicted from experiments to form during normal subduction of oceanic crust at depths between ~ 45-300 kilometers. Lawsonite is a hydrous calcium aluminium sorosilicate mineral with formula CaAl2Si2O7(OH2·H2O Oceanic crust is the part of Earth's Lithosphere that surfaces in the Ocean basins The rarity of lawsonite eclogites therefore does not reflect unusual formation conditions but unusual exhumation processes. Examples of lawsonite eclogite are 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 the highest pressure metamorphic facies and is usually only the result of advancement from blueschist metamorphic conditions. Blueschist (ˈbluːʃɪst is a rock that forms by the Metamorphism of Basalt and rocks with similar composition at high Pressures and low

Importance of eclogite

Photomicrograph of a thin section of eclogite from Turkey. Historic definition The name facies was first used for specific Sedimentary environments in Sedimentary rocks by Swiss geologist Amanz The prehnite-pumpellyite facies is a metamorphic facies typical of subseafloor alteration of the Oceanic crust around Mid-ocean ridge spreading centres Zeolite facies describes the mineral assemblage resulting from the pressure and temperature conditions of low-grade Metamorphism. Greenschist - also known as greenstone - is a general field petrologic term applied to metamorphic and/or altered Mafic Volcanic rock Blueschist (ˈbluːʃɪst is a rock that forms by the Metamorphism of Basalt and rocks with similar composition at high Pressures and low Amphibolite (æmˈfɪbəlaɪt is the name given to a rock consisting mainly of hornblende Amphibole, the use of the term being restricted however to Metamorphic Granulites are fine to medium–grained Metamorphic rocks that have experienced high Temperatures of metamorphism composed mainly of Feldspars sometimes associated Green omphacite (+ late chlorite) + pink garnet + blue glaucophane + colorless phengite.

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 continental crust. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided

Eclogites are helpful in elucidating patterns and processes of plate tectonics because many represent oceanic crust that has been subducted to depths in excess of 35 km and then returned to the surface. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere Oceanic crust is the part of Earth's Lithosphere that surfaces in the Ocean basins

Eclogite that is brought to shallow conditions is unstable, and retrograde metamorphism often occurs: secondary amphibole and plagioclase may form reaction rims on the primary pyroxene, and titanite may form rims about rutile. Amphibole (pronounced amfi-bowl defines an important group of generally dark-colored rock-forming inosilicate Minerals composed of double chain SiO4 Plagioclase is a very important series of tectosilicate Minerals within the Feldspar family Eclogite may completely retrogress to amphibolite or granulite during exhumation. In some retrogressed eclogites and accompanying more silica-rich rocks, UHP (ultrahigh-pressure) metamorphism has been recognized only because of the preservation of coesite and/or diamond inclusions within trace minerals such as zircon and titanite.

Xenoliths of eclogite occur in the kimberlite pipes of the diamond mines of Africa, Russia, Canada, and elsewhere. This article concerns the geologic term for other uses see Xenolith (disambiguation A xenolith ( Greek: 'foreign rock' is a rock Kimberlite is a type of potassic Volcanic rock best known for sometimes containing Diamonds It is named after the town of Kimberley in South Africa In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in 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 >45km (15 kilobars) and rapid (in less than 10 million years!) exhumation via thrust faults prevented significant melting. For a topic outline on this subject see List of basic Australia topics. A thrust fault is a type of fault, or break in the Earth's crust with resulting movement of each side against the other in which a lower stratigraphic position is pushed up Felsic rocks in these terranes contain sillimanite, kyanite, coesite, orthoclase and pyroxene, and are rare, peculiar rocks formed by an unusual tectonic event. Sillimanite also called Bucholzite is an alumino-silicate Mineral with the Chemical formula Al2SiO5 Kyanite, whose name derives from the Greek word kyanos, meaning blue is a typically blue Silicate Mineral, commonly found in Aluminium -rich Coesite is a form ( polymorph) of Silicon dioxide Si[[oxygen O]]2 that is formed when very high pressure (2&ndash3 Gigapascals and Physical properties Orthoclase crystallizes in the Monoclinic crystal system The pyroxenes are a group of important rock-forming Silicate minerals found in many Igneous and metamorphic rocks.

Eclogite and basalt petrogenesis

Peridotite is the dominant rock type of the upper mantle, not eclogite, as established by seismic and petrologic evidence. Likewise, peridotite is a much more important source rock of common magmas.

Melting of eclogite to produce basalt is generally not supported in modern petrology. Unreasonably high degrees of partial melting are required to attain basaltic compositions. Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet To get a basalt from melting an eclogite (ie; a rock with basalt composition) it has to undergo 100% partial melting. Instead, basalts can be modelled as having been produced by 1 to 25% partial melting of peridotite, such as harzburgite and lherzolite. A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. The Ultramafic rock harzburgite, is a variety of Peridotite consisting mostly of the two Minerals Olivine and low- Calcium (Ca Lherzolite is a type of Ultramafic Igneous rock. It is a coarse grained rock consisting of 40 to 90% Olivine along with significant Orthopyroxene However, some andesite-like rocks could be produced from partial melting of eclogite; for instance, an unusual rock type called adakite (first described from Adak Island in the Aleutians) has been proposed to be a product of partial melting of eclogite. Likewise, partial melting of eclogite has been modeled to produce granodiorite-like granitic melts. Granodiorite (ˌgrænəˈdaɪəraɪt/ /ˌgreɪn- is an intrusive Igneous rock similar to Granite, but contains more Plagioclase than Potassium feldspar

Basalt is generally created as a partial melt of peridotite at between 20-120km depth. Eclogite is more dense than the surrounding asthenosphere. Unless the eclogite is created in very young oceanic crust, it is cool at the time of initial subduction and so is usually carried down to great depths without melting. If that subducted eclogite is subsequently carried upwards during mantle convection together with peridotite, then it would melt by decompression melting (see discussion in igneous rock) at lower temperature than the accompanying peridotite. Mantle convection is the slow creeping motion of Earth's rocky mantle in response to perpetual gravitationally unstable variations in its density Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Eclogite-derived melts may therefore be part of the melt contribution derived from mantle plumes. A mantle plume is an upwelling of abnormally hot rock within the Earth's mantle.

Eclogite melting creates granite; Nature 425, 605-609 (9 October 2003)

Eclogite diamonds

Many diamonds from eclogite xenoliths have a ¹³C:¹²C isotope ratio different from that typical of diamonds from peridotite xenoliths. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. The carbon isotopic differences between harzburgitic and eclogitic diamonds supports the hypothesis that those eclogite xenoliths formed from basalt carried down within subduction zones.

Eclogite diamonds are also typically higher in nitrogen, and will have a different suite of mineral inclusions than harzburgitic diamonds. Harzburgitic diamonds typically have titaniferous pyrope, chromian spinel and Cr-diopside inclusions, minerals which are not typically found in eclogites. This article is about the mineral For the bird sometimes placed in the monotypic genus Pyrope see Fire-eyed Diucon. The spinels are any of a class of Minerals of general formulation XY2 O 4 which Crystallize in the cubic (isometric Diopside is a Monoclinic Pyroxene Mineral with composition MgCaSi2O6

Distribution

Eclogites occur with garnet peridotites in Greenland and in other ophiolite complexes. A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. Greenland (Kalaallit Nunaat meaning "Land of the Greenlanders" Grønland is a self-governing Danish Province located between the An Ophiolite is a section of the Earth's Oceanic crust and the underlying upper mantle that has been uplifted or emplaced to be exposed within Continental Examples are known in Saxony, Bavaria, Carinthia, Norway and Newfoundland. The Free State of Saxony (Freistaat Sachsen ˈzaksən Swobodny Stat Sakska is the easternmost federal state of Germany. Bavaria ( German:, with an area of 70553 Km² (27241 square miles and almost 12 Carinthia (Kärnten Koroška is the southernmost Austrian state or Land. Norway ( Norwegian: Norge ( Bokmål) or Noreg ( Nynorsk) officially the Kingdom of Norway, is a Constitutional Newfoundland — ˈn(jufənˌlænd (Terre-Neuve Talamh an Éisc — is a large island 15 km off the east coast of A few eclogites also occur in the north-west highlands of Scotland and the Massif Central of France. Scotland ( Gaelic: Alba) is a Country in northwest Europethat occupies the northern third of the island of Great Britain. This article is about the country For a topic outline on this subject see List of basic France topics. Glaucophane-eclogites occur in Italy and the Pennine Alps. Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest The Pennine Alps (also Valais Alps) are a Mountain range in the western part of the Alps. Transitional Granulite-Eclogite facies granitoid, felsic volcanics, mafic rocks and granulites occur in the Musgrave Block of the Petermann Orogeny, central Australia. The Petermann Orogeny was an intra Continental event that affected basement rocks of the northern Musgrave Province and Proterozoic Sediments of

References

• Blatt, Harvey and Robert Tracy, 1995, Petrology: igneous, sedimentary, and metamorphic, Freeman, ISBN 0-7167-2438-3
• Camacho, A. , Hensen, B. J. , Armstrong, R. , Isotopic test of a thermally driven intraplate orogenic model, Australia', Geology, 30, pp. 887-890
• The Petermann Orogeny, Central Australia
• Rapp, Robert P., Shimizu Nobumichi, and Marc D. Norman. Growth of early continental crust by partial melting of eclogite. Nature 425, 605-609 (9 October 2003)

External links

• Mantle eclogites
• Eclogite sample
• Eclogite melting in production of Archaean TTG granitoids