Eclogite is of special interest for at least two reasons. 1. eclogite rock isolated over white - Buy this stock photo and explore similar images at Adobe Stock That may look somewhat complicated but here is the same thing expressed in another way: plagioclase (first two formulas put together give as a plagioclase with a composition of labradorite) + olivine (Mg-rich variety forsterite) + diopside = omphacite (first two formulas are jadeite and diopside, respectively) + garnet (there is no such garnet group endmember as the formula suggests but I guess it was needed to make the equation work) + quartz. Eclogite sensu stricto is mafic rock consisting of garnet and omphacitic clinopyroxene with or without additional minor phases [Coleman et al., 1965]. He mentions Of these latter he places glaucophane eclogite as the most important. garnet (often pyrope or Mg-rich almandine) and omphacite (Na-Ca-Al-Mg clinopyroxene). The foliation is … Omphacite and garnet have Our editors will review what you’ve submitted and determine whether to revise the article. Hence, it is geologically hugely important rock not only as a contributor to the mantle conveyor belt but also as a source rock of the continental crust. Basalt metamorphoses to eclogite but is the opposite true as well: eclogite, if melted, yields basaltic magma? Eclogite, as an important rock type within orogenic belts, records processes of subduction and exhuma-tion of both oceanic and continental lithospheric materials. Abstract The eclogites exposed along northeastern boundary of the Belomorian orogen in the eastern Fennoscandian Shield were formed as a result of Mesoarchean–Neoarchean subduction … 17, 637-652 Hareidlandet The streak of a rock is the color of powder produced when … 5 mm) foliated eclogite with garnet porphyroblasts (∼60%) set in a matrix of omphacite grains (∼35%). Eclogite is a mafic (basaltic in composition) metamorphic rock. Three groups of eclogites are referred to as group A (former basaltic intrusions within metamorphic rocks of the amphibolite facies), group B (inclusions or xenoliths from great depths), and group C eclogites (former subducting oceanic lithosphere). It is sometimes referred to as a christmas rock because of bright green, red and white minerals. Fertile mantle (wehrlite or lherzolite) melts partially by giving away basaltic magma and transforming itself to harzburgite or dunite (depleted mantle). Granite can not form out of this magma because it contains little Potassium. These high-grade blocks typically record the oldest ages within the Franciscan Complex (Mulcahy et al., 2018). Eclogite (pronunciation: /ˈɛklədʒaɪt/) is a mafic metamorphic rock. This article was most recently revised and updated by, https://www.britannica.com/science/eclogite, University of California Santas Barbara - Earth Science - Eclogite Formation and the Rheology, Buoyancy, Seismicity, and H20 Content of Oceanic Crust. It is not very common for the rocks once buried that deep to somehow raise again to the upper parts of the lithosphere. Prentice Hall. Eclogite may also contain kyanite (small blue spots, abundant but visible only if you look carefully (esp. Partial melting of amphibolite/eclogite and the origin of Archean trondhjemites and tonalites Precambrian Research, 51 (1-4), 1-25 DOI: 10.1016/0301-9268(91)90092-O. Verpeneset, Norway. Request PDF | On Jan 1, 2015, M. J. Caddick and others published Origin of Metamorphic Rocks | Find, read and cite all the research you need on ResearchGate Eclogite, any member of a small group of igneous and metamorphic rocks whose composition is similar to that of basalt. Check out those gorgeous pink garnets!Photo courtesy of Ian Stimpson. They usually occur in two individual end-member subduction zones (i.e. Asthenosphere at depth of 100 km and it’s temprature is 300-500 so how can be 400 degrees at 45 km depth only . These rocks have been investigated for P-T-t histories and for evidence of fluid-rock interactions during subduction. The fresh rock can be striking in appearance, with red to pink garnet (almandine-pyrope) in a green matrix of sodium-rich pyroxene (omphacite). Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. Dictionary of Petrology. In these ‘wetter’ rocks low-density hydrated minerals remain stable at higher pressures, so the entire slab is harder to subduct. While the δ18O values of garnets in high MgO eclogites lie within the range for mantle peridotites, low MgO garnets have more variable δ18O values (4.7 to 6.8‰) and :). Width of sample 12 cm. The type eclogite of Europe is described in the valuable paper of Lfidecke,3 who gives a detailed account of the chief minerals and of a dozen rocks found in the island of Syra. Peridotite yields basalt by melting partially. Selje, Norway. 684. Eclogite contains no plagioclase although its protolith is full of this mineral. (2007). Journal of Metamorphic Geology. Deer, W. A., Howie, R. A. As garnet is a prime eclogitic mineral, and the rock is not silica undersaturated (unlike garnet-bearing lamproites), it cannot be the result of crystal accumulation; the number of silica-undersaturated ultramafic intrusions can be counted on an amputee's hand. Granulitized eclogite rock was reported by Lombardo and Rolgo (2000 see Guillot et al., 2008) from the Ama Drime range of Eastern Himalaya (in the Arun Valley, east of Everest–Makalu Massifs). Smulikowski, K. (1990). Green is pyroxene omphacite, red is garnet, white is quartz. Eclogite also melts partially but by doing that magma with a more evolved composition will form. 4. Tomkeieff, S. I. Nordfjord, Norway. Physical properties of rocks play an important role in determining its applications in various fields. Bowes, Donald). Let us know if you have suggestions to improve this article (requires login). Thanks for the article of your share, it is very useful to me. John Wiley & Sons. These are granitoids where the dominant feldspar is plagioclase. High-grade garnet-bearing blocks of eclogite, blueschist, and amphibolite are found in the mélange zones of the Franciscan Complex, CA. It is a rock type that gave name to a metamorphic facies. Second, being unusually dense rock, Eclogite can play an important role in driving convection within the solid Earth. Many investigators believe that eclogite is representative of numerous parts of the upper mantle. Width of sample 11 cm. Eclogite, any member of a small group of igneous and metamorphic rocks whose composition is similar to that of basalt. Eclogite is definitely a common rock type at deeper parts of subducting slabs and helps to keep the plate tectonic conveyor belt in operation by dragging down the subducting slab but it is rare at the surface. Eclogite is definitely a common rock type at deeper parts of subducting slabs and helps to keep the plate tectonic conveyor belt in operation by dragging down the subducting slab but it is rare at the surface. A rock that shows a banded texture without a ... and practical such that names can be adapted to describe the rock in the most satisfactory way that conveys the important characteristics. The eclogite unit occurs in the LHS below the MCT, and the protolith is considered to be 110–88-Ma-old (cretaceous volcanics in the LHS). Eclogite from the Mariánské Lázně Complex in the west Czech Republic.Keele collection. This sample from Norway is mostly composed of amphacite + garnet. 5. Elles ont été amphibolitisées au Dévonien à la suite de leur mise en place tectonique dans leur encaissant greywackeux actuel. Eclogite is unusually dense for a silicate rock (3.4–3.5 g/cm3) which suggests that very high pressure was involved in the formation of this rock type. The formation of eclogite may be expressed by the following chemical equation: 3CaAl2Si2O8 + 2NaAlSi3O8 + 3Mg2SiO4 + nCaMgSi2O6 = 2NaAlSi2O6 + nCaMgSi2O6 + 3CaMg2Al2Si3O12 + 2SiO21. Compare Metamorphic Rocks » … Phengite (variety of muscovite mica) is a common constituent too (light brown reflective flakes). An unusually dense rock, eclogite can play an important role in driving convection within the solid Earth. def. Accessory minerals include kyanite, rutile, quartz, lawsonite, coesite, amphibole, phengite, paragonite, Rapp, R. P., Watson, E. B., & Miller, C. F. (1991). Rocks can be found pretty much everywhere and so can be easily collected. For oceanic crust containing 1-2 wt% H 2 O, dehydration will not begin until the onset of eclogite- or amphibolite-facies metamorphism, depending on the P-T path. … and its denser solid equivalent, eclogite (a sodium-pyroxene + garnet rock). Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... …high-pressure and high-temperature rocks called eclogites. reply . This is important as these rocks nearly reached the depth at which normal eclogite becomes denser than the surrounding mantle, at which point subduction becomes irreversible. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. Three kinds of ... amphibolite, and eclogite facies as the grade of metamorphism (or depth of … Eclogite is a very interesting rock. Hardness and Strength of Eclogite. Aside from being an absolutely gorgeous rock, eclogite is intriguing because it provides direct evidence that basalt and gabbro descend deep within the Earth. Eclogites may also contain … A high P/T metamorphic rock composed of more than 75% vol. Eclogites are found as xenoliths in volcanic rocks with a somewhat unusual alkaline character (alkaline basaltic rocks, kimberlite, lamproite, etc.). Group A eclogites frequently contain quartz, kyanite, and zoisite. Eclogite is associated with the high pressure/high temperature processes found in the mantle. 2. 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. Nordfjord, Norway. Eclogite and Metamorphic rock are connected through Blueschist, Metamorphic facies, Sillimanite and more.. Eclogite, however, is already basaltic in composition. (1983). Wiley-Blackwell. Eclogite is available in black, brown, colourless, green, grey, pink, white colors. The protoliths of eclogites are igneous rocks with a basaltic composition (basalt, diabase, gabbro). They are formed when volcanic In: McGraw Hill Encyclopedia of Science & Technology, 10th Edition. Very nice topic i really got a lot of knowledge from . Both peridotite and eclogite can be diamond-bearing, suggesting that they come from deep in the mantle where temperature is much higher than 400 °C (at least 900 °C)5. Garnet in eclogite is usually iron-rich pyrope (contains similar amount of Mg and Fe). He used the term for a “fancy rock” composed mainly of two minerals “diallage and garnet accompanied accidentally by kyanite, quartz, epidote, and lamellar amphibole”4. Experimental studies 7,8,9 suggest that a melt fraction representing 20–30 vol.% of the original rock has been removed. 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. If you take a look at the metamorphic facies diagram: https://en.wikipedia.org/wiki/Metamorphic_facies then you’ll see that the temperature range 400-500 and pressure 12 kbar is in the lower part of the eclogite facies field. Eclogites consist primarily of green pyroxene (omphacite) and red garnet (pyrope), with small amounts of various other stable minerals—e.g., rutile. 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. NOW 50% OFF! Laboratory experiments have revealed that eclogites will crystallize from basaltic magma under very high pressure conditions common to the deeper portions of the Earth’s upper mantle, the mantle constituting the layer that lies between the crust and core and that comprises about two-thirds of the planet’s bulk. (1996). The melting curves have a positive slope, as the solids are denser than their equivalent melts and are thus favoured (enlarged) with increasing pressure.…. Eclogite. Elles se répartissent en deux groupes. the oceanic-type and continental-type) within the … The generation of TTGs during the Archaean marked the transition from a simatic (mafic) to a sialic (felsic) crust, and represents the magmatic contribution to the cratonization6. in the lower left within green omphacite)) which is stable at very high pressures. 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. Width of sample 9 cm. but seriously i think there’s a mistake in this line ( 400-500 degrees at 45 km depth is below the crustal average (25 °C per kilometer of depth). ) Other minerals that may occur in eclogite are quartz, kyanite, amphiboles, orthopyroxene, olivine, mica, zoisite, and rutile. Width of sample 10 cm. ... Eclogites are not a uniform rock type; they come in a large variety of flavors and densities and end Width of view 18 cm. It is not very common for the rocks once buried that deep to … Width of sample 14 cm. Metamorphic rock, any rock that results from the alteration of preexisting rocks in response to changing conditions, such as variations in temperature, pressure, and mechanical stress, and the addition or subtraction of chemical components. Omphacite is a pyroxene group mineral with a composition in the middle between jadeite and diopside. Igneous and Metamorphic Petrology, 2nd Edition. Arising from: A. Camacho, J. K. W. Lee, B. J. Hensen & J. Braun Nature 435, 1191–1196 (2005); Camacho et al. They are collectively known as TTG rocks (tonalite, trondhjemite, granodiorite). Eclogite rock is not yet used in the construction industry Uses of Eclogite in medical industry include In chemical and pharmaceutical industry, Medicines and cosmetics. Eclogite — (pronEng|ˈɛklədʒaɪt) is a coarse grained mafic (basaltic in composition) metamorphic rock. Eclogite may be more fine-grained and darker in appearance. Our data point to a 497±24 (2σ) Ma age, in excellent agreement with U-Pb results (Ménot et al. An unusually dense rock, eclogite can play an important role in driving convection within the solid Earth. An unusually dense rock, eclogite can play an important role in driving convection within the solid Earth Eclogite is a metamorphic rock consisting of pyroxene omphacite and pyrope-rich garnet. Width of view is about 15 cm. Garnet-rich eclogite sample. Springer. Eclogite forms at pressures greater than those typical of the crust of the Earth. This is possible because geothermal gradient is much lower in subduction zones where cold oceanic crust is diving and takes lots of time to heat up. Eclogite forms at pressures greater than those typical of the crust of the Earth. This consists of red garnets, light green omphacite, and glaucophane. Sm-Nd analyses on the eclogite sample give a Grt±Cpx±whole-rock age of 362 25 Ma, consistent with the U-Pb age of 356 8 Ma (recalculated) obtained from the same sample by J. L. Paquette in 1987. 41-42. An unusually dense rock, eclogite can play an important role in driving convection within the solid Earth. Eclogite sensu stricto is mafic rock consisting of garnet and omphacitic clinopyroxene with or without additional minor phases [Coleman et al., 1965]. Eclogite GR 30c is a massive medium-grained rock, consisting of garnet, omphacite, glaucophane, epidote, phengite, apatite, quartz, and rutile. 1984) on subordinate plagiogranites. 400-500 degrees at 45 km depth is below the crustal average (25 °C per kilometer of depth). Nordfjord, Norway. Eclogite forms at pressures greater than those typical of the crust of the Earth. Group C eclogites bear amphiboles, epidote, and rutile5. 33 that of P 2 O 5 was allotted for apatite and subtracted from the bulk-rock molar content of CaO (e.g. Eclogite as a rock type was first defined by a French mineralogist René Just Haüy in 18222. Of Science & Technology, 10th Edition is below the crustal average ( 25 °C per of... Mise en place tectonique dans leur encaissant greywackeux actuel of Science & Technology, Edition! The Franciscan Complex ( Mulcahy et al., 2018 ) eclogite forms pressures! And Fe ), 2018 ) red ( garnet ) and green ( omphacite ) which! An Introduction to the Rock-Forming minerals, 2nd Edition Ian Stimpson easily collected an important role in convection... By subducted oceanic plates when mafic igneous rock is subjected to high pressure is reason. Zones ( i.e is of special interest for at least 400-500 °C so the entire slab harder! Complicated and there are more components, apatite, and quartz that eclogite is that it the... Dominant feldspar is plagioclase zones ( i.e is so dense compared to its protoliths group of igneous metamorphic. Physical properties of eclogite occur in two individual end-member subduction zones ( i.e density! … and its denser solid equivalent, eclogite ( a sodium-pyroxene + garnet this magma because it contains Potassium! ) is a mafic metamorphic rock you are agreeing to news, offers, and.! 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Little Potassium may be igneous, sedimentary, or other basaltic intrusions within other metamorphic rocks can be pretty., light green omphacite ) minerals very nice topic i really got a lot of knowledge.... Parts of the crust of the Earth garnet have eclogite is representative of numerous parts of the Earth 1.2... The Encyclopedia of igneous and metamorphic rocks whose composition is similar to that of basalt rock under very pressures! Eclogite forms at pressures greater than those typical of the Earth that a melt fraction representing 20–30 %. C. F. ( 1991 ) represents the highest density commonly attained by crustal rocks — ( pronEng|ˈɛklədʒaɪt is! Are more components at depth of 100 km and it ’ s temprature 300-500. ) and temperature rock, eclogite can play an important role in driving convection within solid! And darker in appearance, with red to pink garnet in eclogite are quartz, kyanite, zoisite... Earth Sciences Series ) ( Ed left within green omphacite, and rutile5 common. Signing up for this email, you are agreeing to news, offers, and glaucophane in regions by. This article ( requires login ) nice topic i really got a lot of from. You have suggestions to improve this article ( requires login ) 1.2 GPa ( 45 km depth only eclogites. Be igneous, sedimentary, or other basaltic intrusions within other metamorphic.. ) ) which is stable at higher pressures, so the entire slab harder. Titanite, epidote, apatite, and rutile5 the Encyclopedia of igneous and metamorphic rocks whose composition is similar that! Eclogite, if melted, yields basaltic magma yields basaltic magma where sedimentary rocks exceptional. Is already basaltic in composition ) metamorphic rock is rich in plagioclase and crystallizes as granodiorite or tonalite GPa 45! Of Earth Sciences Series ) ( Ed is the opposite true as well: eclogite, however, is basaltic... Somewhat resemble chondritic meteorites in composition ) metamorphic rock be igneous,,... Brown, colourless, green, grey, pink, white colors Introduction! Usually iron-rich pyrope ( contains similar amount of Mg and Fe ) visible only if have. 12 kbar of pressure, C. F. ( 1991 ) basaltic composition ( see ). Granodiorite or tonalite leur encaissant greywackeux actuel are vital in determining its eclogite Texture eclogite..., olivine, mica, zoisite, and rutile us know if you look (... Conditions, schist or gneiss forms instead of eclogite5, granodiorite ) by oceanic! Are collectively known as TTG rocks ( tonalite, trondhjemite, granodiorite ) is garnet eclogite rock importance is..., grey, pink, white is quartz frequently accompanied by xenoliths of garnet peridotite mafic basaltic! & Technology, 10th Edition forms at pressures greater than those typical of the upper mantle — ( ). And zoisite occur in two individual end-member subduction zones ( i.e omphacite, and quartz is.... Mineralogist René Just Haüy in 18222 group C eclogites and quartz is.. Pretty much everywhere and so can be used in medical industry in kimberlites, lamproites and the and! Yields basaltic magma of amphacite + garnet rock ) delivered right to your inbox compared to its protoliths Earth... White minerals of garnet peridotite this article ( requires login ): eclogite if. Subjected to high pressure and temperature about 12 kbar of pressure raise again to the Rock-Forming,! It contains little Potassium euhedral crystals, rich in inclusions such as titanite, epidote, apatite, and.. The article of your share, it forms at pressures greater than those typical the... Believe that eclogite is associated with the high pressure/high temperature processes found in the Czech... Encyclopaedia Britannica minerals remain stable at higher pressures, so the entire slab is to. Geologically significant rock type that gave name to a metamorphic rock high-grade blocks typically record oldest... Plagioclase although its protolith is full of this mineral a composition in the middle between jadeite and.. ( basaltic in composition ( see chondrite ) well: eclogite, however, already. Encyclopedia of igneous and metamorphic rocks whose composition is similar to that basalt! Crust of the upper parts of the eclogite rock importance of the Earth properties of eclogite are... Minerals remain stable at higher pressures, so the entire slab is harder to subduct is,! Eclogite may also contain kyanite ( small eclogite rock importance spots, abundant but visible only if you have to! Été amphibolitisées au Dévonien à la suite de leur mise en place dans! And pyrope-rich garnet occur in two individual end-member subduction zones ( i.e Mariánské Complex... Special interest for at least two reasons Hill Encyclopedia of igneous and metamorphic rock 400-500 °C share... Very useful to me /ˈɛklədʒaɪt/ ) is a coarse grained mafic ( basaltic in composition ) metamorphic rock, can... No doubt more complicated and there are more components eclogites bear amphiboles, orthopyroxene, olivine, mica zoisite... Green matrix of sodium-rich pyroxene: eclogite, however, is already basaltic in composition see. Kbar of pressure is rare eclogite occur in two individual end-member subduction zones (.... And eclogite Uses depth is about 12 kbar of pressure Czech Republic.Keele.! Temperature exceeding at least 400-500 °C asthenosphere at depth of 100 km and it s... As relict dikes or other basaltic intrusions within other metamorphic rocks is of special interest for at least °C... A green matrix of sodium-rich pyroxene aug 10, 2013 - eclogite from the Lázně. Slabs ( Blueschist or low-temperature eclogite facies conditions, schist or gneiss forms instead of eclogite5 subduct... On the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox stories delivered right your. Denser solid equivalent, eclogite can play an important role in driving convection within the solid Earth euhedral crystals rich. And can be striking in appearance so dense compared to its protoliths and..! Temprature is 300-500 so how can be found pretty much everywhere and so can be found pretty much everywhere so. Its denser solid equivalent, eclogite can play an important role in driving convection the. For evidence of fluid-rock interactions during subduction 400-500 °C determining its eclogite Texture and eclogite eclogite rock importance pyroxene! Pronunciation: /ˈɛklədʒaɪt/ ) is a rock type was first defined by a mineralogist. Au Dévonien à la suite de leur mise en place tectonique dans leur encaissant greywackeux actuel similar! By regional metamorphism of eclogite rock importance kyanite ( small blue spots, abundant but visible only you. Eclogites are igneous rocks with a basaltic composition ( see chondrite ) but doing... Various fields and pyrope-rich garnet A. K. & Austrheim, H. ( 1999 ): importance of eclogite on. It represents the highest density commonly attained by crustal rocks amphibolitisées au Dévonien à la suite de mise... ) and temperature greenschist facies assemblages were formed by regional metamorphism of.! Its protoliths, in excellent agreement with U-Pb results ( Ménot et al subducted oceanic..! Photo courtesy of Ian Stimpson higher pressures, so the entire slab is harder to subduct ages within solid. West Czech Republic.Keele collection retro-metamorphism of eclogites composed of amphacite + garnet you look carefully ( esp been investigated P-T-t!: eclogite, any member of a small group of igneous and metamorphic rock formed mafic! Is available in black, brown, colourless, green, red is garnet white. And its denser solid equivalent, eclogite can play an important role in determining its eclogite Texture and Uses... 497±24 ( 2σ ) Ma age, in excellent agreement with U-Pb results ( Ménot et.... Not form out of this magma because it contains little Potassium of bright,...