These features suggest that the Archean and Paleoproterozoic rocks had undergone the same tectono-metamorphic event in the Paleoproterozoic Era because the low-grade metamorphic Mesoproterozoic unconformably overlies on the Archean and the Paleoproterozoic rocks (Xijiang BGMR, 1993). Shaded area represents P–T paths for slab surface from Arcay et al. The bluest, most schistose blueschist—like this example—is made from sodium-rich mafic rocks like basalt and gabbro. It is interpreted as the remnant of a Paleozoic accretionary complex formed after subduction and exhumation of oceanic crust and its sedimentary cover (Bernard-Griffiths et al., 1986; El Korh et al., 2009). At these conditions, the H2O content of the rock was estimated to be around 6 wt.% (Schmidt and Poli, 2014). n. A bluish schist that forms under conditions of high pressure and low temperature and often contains the mineral glaucophane. In addition to low-to-medium temperature (LT–MT) eclogites in various units, this massif is characterized by the presence of a high number of HT eclogites and ultrahigh-temperature (UHT) UHP garnet peridotites and garnet pyroxenites that occur within HP felsic granulites and migmatites. These are close to the BS nearby in the Oman that are 5–10 Ma older than those in the Zagros. 650 °C), resulting in the formation of migmatites. The HP peak metamorphic conditions were estimated to be 1.6–2.5 GPa and 550–600°C in eclogites, and 1.7–2.3 GPa, 450–525°C in blueschist facies metabasites from the eastern part of the island using THERIAK-DOMINO (El Korh et al., 2009). Blueschist facies is determined by the particular temperature and pressure conditions required to metamorphose basalt to form blueschist. At pressures exceeding the stability of amphibole, other hydrates exist that can account for transport of water into greater depth. Earth and Planetary Science Letters 163: 361–379.) 5 by Agard, P., Omrani, J., Jolivet, L., Whitechurch, H., Vrielynck, B., Spakman, W., Wortel, R., 2011. Felsic rocks and pelitic sediments which are subjected to blueschist facies conditions will form different mineral assemblages than metamorphosed basalt. Also, several new high-pressure hydrous minerals have been identified in these assemblages, indicating that some water is recycled into the mantle and that not all water is lost by dehydration to the mantle wedge. [To convert lithostatic pressures of kilobar to approximate depths of kilometer, multiply the kilobar by the density of overlying rocks (e.g., 7 kbar multiplied by ∼3 = ∼21 km)]. Eclogites and blueschist facies rocks are frequent in the eastern part of the island, whereas greenschist facies rocks are dominant in the western part (Figure 9.1). Exhumation to midcrustal depths less than 15–20 km occurred at rates on the order of 1–2 mm/year before 80 Ma; Paleocene–Eocene (60–40 Ma) slab break-off led to successive magmatic arcs with lateral extension within the upper plate being general from the first in the SSZ, the second in Kermanshah, and finally the Urumieh–Dokhtar arc; and. Geological map showing the spatial distribution of Precambrian rocks in the Tarim Block. Copyright © 2020 Elsevier B.V. or its licensors or contributors. Thus in order for blueschist facies assemblages to be seen at the Earth's surface, the rock must be exhumed swiftly enough to prevent total thermal equilibration of the rocks which are under blueschist facies conditions with the typical geothermal gradient. Metamorphism along a medium P/T-gradient leads to only a few metamorphic minerals, such as almandine-rich garnet at lower amphibolite facies conditions – and partial melting takes place at the temperatures of the granite minimum in H2O-saturated conditions (ca. and at oxygen fugacity of approximately Ni-NiO buffer. [2], In Minoan Crete blueschist and greenschist was used as to pave floors of streets and courtyards between 1650 and 1600 BC. Find out information about blueschist facies. Another possibility is that blueschists are thrust upward during later collisional tectonics. Glaucophane and lawsonite, both of which have a bluish color, are common minerals in this setting. Lawsonite (11 wt.% H2O) has a maximum abundance of 25 vol.% at the onset of blueschist-facies metamorphism and decreases to ∼10 vol.% at the amphibole-out reaction. For the chemographic presentation of mineral assemblages, the AKF-system is applied (Figure 9). There are a variety of Blueschist Uses and the Blueschist Reserves are found in many countries around the world. Blueschist often has a lepidoblastic, nematoblastic or schistose rock microstructure defined primarily by chlorite, phengitic white mica, glaucophane, and other minerals with an elongate or platy shape. The name “blueschist” derives from the fact that at this metamorphic grade, rocks of ordinary basaltic composition are often bluish because they contain the sodium-bearing blue amphiboles glaucophane or crossite rather than the calcium-bearing green or black amphiboles actinolite or hornblende, which are developed in the more common greenschist- or amphibolite-facies metamorphism. Garnet peridotites are less common in the Massif Central, and garnet pyroxenites are known from the Iberian and Armorican Massifs. Blueschist-facies metamorphism is important in subduction zones, where high-pressure, relatively low-temperature mineral assemblages form. Afifé El Korh, ... Alexey Ulianov, in Ultrahigh-Pressure Metamorphism, 2011. The contribution of the mafic, basaltic, and gabbroic, part of the slab to the transport and release of fluids during subduction, has been extensively investigated both at H2O-saturated conditions, that is, in the presence of water (Forneris and Holloway, 2003; Litasov and Ohtani, 2005; Okamoto and Maruyama, 2004; Pawley and Holloway, 1993; Poli, 1993; Poli and Schmidt, 1995; Schmidt and Poli, 1998), in the presence of a CO2 fluid (Molina and Poli, 2000; Yaxley and Green, 1994), and with variable C–O–H fluids (Poli et al., 2009). For the chemographic presentation of quartzo-feldspathic rocks, the AKF-system is applied. Although the stability of lawsonite is shifted by only 30–80 °C, this difference is relevant as the reaction has a slope parallel to most P–T paths, and small temperature differences control whether the rock is dry or volatiles are present in the rock. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL: https://www.sciencedirect.com/science/article/pii/B9780123852274000080, URL: https://www.sciencedirect.com/science/article/pii/B9780128150481000056, URL: https://www.sciencedirect.com/science/article/pii/B9780123851444000084, URL: https://www.sciencedirect.com/science/article/pii/B0080437516030346, URL: https://www.sciencedirect.com/science/article/pii/B9780124095489090497, URL: https://www.sciencedirect.com/science/article/pii/B9780128128725500015, URL: https://www.sciencedirect.com/science/article/pii/B9780123851444000114, URL: https://www.sciencedirect.com/science/article/pii/B978044453802400052X, Earth as an Evolving Planetary System (Second Edition), Tectonic and Structural Framework of the Zagros Fold-Thrust Belt, Developments in Structural Geology and Tectonics. Blueschist and Eclogite Facies • The blueschist facies is characterized in metabasites by the presence of a sodic blue amphibole stable only at high pressures (notably glaucophane, but some solution of crossite or riebeckite is possible) • The association of glaucophane + lawsonite is diagnostic. Lawsonite and zoisite dominate the higher-pressure regime down to more than 200 km depths (Okamoto and Maruyama, 1999; Ono, 1998; Poli and Schmidt, 1998; Schmidt and Poli, 1998), although other minor phases can also be stable, for example, Mg chloritoid, talc, and phengite. From Fig. Explanation of blueschist facies Well-exposed blueschists also occur in Greece, Turkey, Japan, New Zealand and New Caledonia. The Ile de Groix corresponds to the emerged part of an HP–LT metamorphic Hercynian blueschist–eclogite unit, located off the southern coast of Brittany (Audren & Lefort, 1977). 60 relations. As a serpentinized cold corner has a much lower viscosity than anhydrous mantle, the serpentinized cold corner may develop a counter-convection cell and stagnate in its corner, whereas the rest of the mantle wedge undergoes large-scale convection (examples of cold corner counter-flow are found in Davies and Stevenson, 1992). Blueschists and other high-pressure subduction zone rocks are thought to be exhumed rapidly by flow and/or faulting in accretionary wedges or the upper parts of subducted crust, or may return to the Earth's surface in part owing to buoyancy if the metabasaltic rocks are associated with low-density continental crust (marble, metapelite, and other rocks of continental margins). 1.3). The metamorphic basement of the Tarim Block is mainly composed of Archean to Early Neoproterozoic metamorphosed strata and magmatic rocks and it mainly crops out in four areas surrounding the orogenic belts of the basin, i.e. The name facies was first used for specific sedimentary environments in sedimentary rocks by Swiss geologist Amanz Gressly in 1838. Schmidt, S. Poli, in Treatise on Geochemistry, 2003. Beyond depths of ∼15 km the oceanic crust enters into the blueschist facies in which the major hydrous minerals are chlorite, sodium-rich, calcium-poor amphiboles (glaucophane to barroisite), phengite (white mica), lawsonite or zoisite, and paragonite (e.g., Sorensen, 1986). Blueschist facies is determined by the particular temperature and pressure conditions required to metamorphose basalt to form blueschist. 5.1). Experimental results on mixed fluid (C–O–H) MORB compositions suggest however that, as CO2 strongly fractionates into carbonates leaving a coexistent H2O-rich fluid, amphibole stability is not significantly affected. The fraction of Fe3+/Fetot is generally highest at the onset of subduction-zone metamorphism and decreases with increasing grade. click for more detailed Chinese translation, definition, pronunciation and example sentences. The HP event (blueschist facies) was dated at 358–365 Ma with the 40Ar/39Ar (phengite) and Rb–Sr (whole rock, phengite, and epidote) methods, while a younger age of 345–353 Ma was determined for the greenschist metamorphic event using the same methods (Bosse et al., 2005). The streak of Blueschist is white to grey. Available data (Figure 10) report that at 700–750 °C, amphibole is stable up to a pressure of about 2.5 GPa. blueschist facies - Free definition results from over 1700 online dictionaries lawsonite-blueschist facies translation in English-French dictionary. (2007) with different water weakening effects: straight line represents a model reference for a ‘dry’ rock; dashed line refers to a moderate rock strength reduction due to water; narrow dashed line refers to a relevant strength reduction. In the assemblage K-feldspar–biotite–muscovite–quartz, the phengite content of muscovite expressed as Si per formula unit decreases with temperature but increases with pressure due to substitution of the Tschermak-molecule Mg+ 1Si+ 1Al− 1Al− 1. The AKF chemographic projections show the significant mineral assemblages at different metamorphic grades. Welsh history in ruins; Often remote and hard to find, a number of wild and weathered ruins still remain around Wales waiting to be found. Blueschist mineralogy varies by rock composition, but the classic equilibrium assemblages of blueschist facies are: Blueschist facies generally is considered to form under pressures of >0.6 GPa, equivalent to depth of burial in excess of 15–18 km, and at temperatures of between 200 and 500 °C. Eclogites are common in all massifs, but blueschists and blueschist facies rocks are exposed in the Iberian, Armorican, and Bohemian Massifs. Grain size is rarely coarse, as mineral growth is retarded by the swiftness of the rock's metamorphic trajectory and perhaps more importantly, the low temperatures of metamorphism and in many cases the anhydrous state of the basalts. Otherwise, incipient metamorphism is demonstrated by phengitic muscovite, chlorite ± stilpnomelane. The high dehydration rates in conjunction with a—close to the trench—thin mantle wedge should lead to rapid, full serpentinization of the cold corner (i.e., within 0.8–3.0 Ma) if fluids pass pervasively through the mantle wedge (see also Gerya et al., 2002). blueschist facies in Chinese : :蓝片岩相…. Metamorphic rock - Metamorphic rock - Zeolite facies: In the zeolite facies, sediments and volcanic debris show the first major response to burial. Greenschist facies refers to the low to medium metamorphic facies corresponding to temperatures of about 300–500°C and pressures of 3–20 kbar (crustal depths of 8–50 km). The subducting slab probably began to tear locally at depth from ∼10 Ma to the present. Some authors have proposed that the metamorphic zonation is related to a gradient with P–T conditions varying continuously from west to east and where the metamorphic domains are separated by “isograds” (Triboulet, 1974; Carpenter, 1976; Quinquis, 1980; Djro et al., 1989; Schulz et al., 2001). Earth and Planetary Science Letters 443, 48–58. Most of the Zagros BS were formed during convergence at conditions near 11 kbar and 520–530°C. We use cookies to help provide and enhance our service and tailor content and ads. Laser probe 40Ar-39Ar radiometric age constraints on phengite yield cooling ages between 95 and 85 Ma, with a scatter of up to 115 Ma. This formation and evolution were closely related to the assembly and breakup of the supercontinents of Columbia (Nuna) and Rodinia (Lu et al., 2008; Zhang et al., 2012). Zagros blueschists: episodic under-plating and long-lived cooling of a subduction zone. The first event (D1) corresponds to the progressive deformation responsible for the blueschist facies foliation S1. Stilpnomelane is only stable in lower greenschist- and blueschist-facies conditions whereas muscovite remains stable up to about 650–700 °C, then breaking down to K-feldspar, quartz, and an Al2SiO5-modification. (2005) proposed a new model suggesting that the high-grade rocks were extruded from the lower crust by crustal-scale buckling in the orogenic root in the Moldanubian Zone. Blueschist facies Blueschist facies is determined by the particular Temperature-Pressure conditions required to metamorphose basalt to form blueschist. The difference to the ACF-projection is the consideration of K instead of Ca. In the Qulukatage Complex, these Neoarchean and Paleoproterozoic rocks underwent two metamorphic events at 1.9–1.8 Ga and 1.1–1.0 Ga, which are considered as having been related to the assembly of the Columbia and Rodinia supercontinents, respectively (Shu et al., 2011; Zhang et al., 2012). (2005, 2006, 2011) divided the history of the closure of Neo-Tethys in Iran into three main phases: Figure 5.4. Two main phases of deformation were described according to the metamorphic history (Quinquis, 1980; Quinquis & Choukroune, 1981). Detrital zircons from an albitic micaschist were dated using the U–Pb method and provided an age of 399±62 Ma, interpreted as the maximum age for the HP–LT event (Peucat & Cogné, 1977; Peucat, 1986). From the Oligocene onward (∼30–0 Ma): As ocean closure migrated to the SW, like the closure of a zip fastener, it led to the progressive migration of deformation to the SW with successive topographic buildup of the SSZ (20–15 Ma) the High Zagros (∼12–8 Ma), and the still actively advancing simply folded belt (5–0 Ma). In most places, the Archean rocks outcrop as stripes or lenses with variable dimensions that are tectonically enclosed within the Paleoproterozoic paragneiss; both of them generally show foliations that are concurrent to each other (Zhang et al., 2012). Blueschist facies is determined by the particular Temperature-Pressure conditions required to metamorphose basalt to form blueschist. However, their lithology and quantity, as well as the metamorphic characteristics of their surrounding rocks, vary when we compare the eastern sector of the belt (the Bohemian Massif, Schwarzwald, and Vosges) with the western sector (the Iberian and Armorican Massifs and the French Massif Central). A discontinuous oceanic suture with ophiolites and eclogites of MORB affinity begins in the Galician and continues through the Ligerian or southern Brittany, the French Massif Central to the northwest along the boundary between the Saxothuringian and Moldanubian Zones. 1 in Angibousta, S., Agardb, P., Glodnya, J., Omranic, J., Onckena, O., 2016. Figure 4. These rocks were likely quarried in Agia Pelagia on the north coast of central Crete.[3]. The presence of eclogites within the Monotonous and Varied Units suggests that the Moldanubian Zone was, during the Variscan orogeny, part of an accretionary wedge into which the HP/UHP were tectonically emplaced. Blueschist Facies synonyms, Blueschist Facies pronunciation, Blueschist Facies translation, English dictionary definition of Blueschist Facies. Again feldspar, quartz, and H2O are used as projection phases. Neoarchean to Paleoproterozoic rocks in the Tarim Block mostly outcrop along its eastern and northern margins which are mainly exposed in the Quruqtagh and Dunhuang complexes, and include the Neoarchean tonalitic granitic rocks and the Paleoproterozoic amphibolite to granulite facies paragneiss, most of which were emplaced in the period 2.60–2.50 Ga (Lu, 1992; Long et al., 2010, 2011; Shu et al., 2011; Zhao and Gawood, 2012; Zhang et al., 2012). Most felsic granulite derived from granite (Janoušek et al., 2004), and their present mineral assemblages show maximum pressures of 2.0–2.3 GPa (Rötzler et al., 2004; Vrána et al., 2006; O’Brien, 2008). The HP–LT metamorphic rocks consist of about 20% metabasite lithologies, varying from a few centimeters to meter-scale lenses to layers of several tens of meters, intercalated with 80% metapelites (Audren et al., 1993; Bosse et al., 2002; Ballèvre et al., 2003). Analogous with these sedimentary facies a number of metamorphic facies were proposed in 1921 by Finnish petrologist Pentti Eelis Eskola. In the broad sense of the definition of blueschist facies, the highest‐grade part of the Northern Shimanto belt belongs to the blueschist facies. The HP rocks are integral to all crustal massifs of the European Variscan Belt. This assertion is arguably wrong because the earliest oceanic crust would have contained more magnesium than today's crust and, therefore, would have formed greenschist-like rocks at blueschist facies. However, granitoids often remain in a dry state preventing the rock from complete metamorphosis. By continuing you agree to the use of cookies. High-pressure rocks of the blueschist and/or eclogite facies were metamorphosed at a low geothermal gradient, that is., small increase in temperature with depth (Figure 1). The facies is named after the schistose character of the rocks and the blue minerals glaucophane and lawsonite. Figure 9. The chemical composition of quartzo-feldspathic rocks plot in the lower Al-poor part of the triangle and therefore these lithologies contain only few and not diagnostic assemblages. The Tarim Block has experienced several stages of tectonic evolution since its formation, and the previous geochronological data from the TTG (Trondhjemite-Tonalite-Granodiorite) and other rocks from the Quruqtagh, Altyn-Tagh and Tiekelike areas suggest that the Tarim Block was mainly built up in several tectonic episodes at 2.65–2.45 Ga, 2.0–1.8 Ga and 1.1–0.9 Ga (Hu et al., 2000; Lu and Yuan, 2003; Zhu et al., 2008; Lu et al., 2008). However, the chemical composition of muscovite changes significantly with T and particularily with P and may be used as a geobarometer. The hydrated oceanic crust loses up to two-third of the entire water content before the breakdown of amphibole through numerous dehydration reactions. In the Moldanubian Zone of the Bohemian Massif, these rocks (HP felsic granulites, garnet peridotites, and HT eclogites) are part of the Gföhl Unit, which has also been considered to be a nappe overlaying the amphibolite facies Monotonous and Varied Units (Tollmann, 1982; Matte et al., 1990). In basic rocks of the eastern part of the island, Ballèvre et al. In general, blueschist-facies rocks are stable in subduction … A similar model is accepted for pyroxenites in the Iberian Massif (Santos et al., 2002). This is a 'low temperature, high pressure' prograde metamorphic path and is also known as the Franciscan facies series, after the west coast of the United States where these rocks are exposed. The HP/UHP metamorphic rocks usually occur as part of nappe stacks overlaying amphibolite-to-greenschist facies units, or they form lenses and boudins in amphibolite facies rocks (paragneisses, orthogneisses, and amphibolite–ophiolite complexes). Anhydrous minerals typically comprise 5–25 vol.% (e.g., Thurston, 1985; Okay, 1980) at 5–10 km depth and some 100 °C, grow in volume to ∼50 vol.% just before the amphibole-out reaction, and increase to >70 vol.% at pressures beyond amphibole stability. In many cases, they occur adjacent to greenschist-amphibolite facies metasediments that may contain relics of blueschist/eclogite facies metamorphism. In quartzofeldspathic rocks, which have undergone eclogite-facies metamorphism, plagioclase is usually replaced by jadeite, zoisite, and quartz and biotite by garnet and phengite. Long-lived (150- to 35-Ma) subduction beneath Iran into BS facies at depths of 35–50 km was followed by a brief phase of exhumation before 80 Ma that raised them to depths of less than 15–20 km (Fig. Blueschist facies - Rock Library Glossary, Imperial College London, A metavolcanic rock that forms by the metamorphism of basalt and rocks with similar composition, "Emergence of blueschists on Earth linked to secular changes in oceanic crust composition", "Types of schist used in buildings of Minoan Crete", https://en.wikipedia.org/w/index.php?title=Blueschist&oldid=992930150, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License, This page was last edited on 7 December 2020, at 21:42. As a result, the bulk composition exerts a fundamental role on phase stabilities, and therefore, experiments performed in certain tholeiitic compositions cannot be simply extrapolated to the wide range of compositions known to exist in basaltic oceanic crust. P. Fumagalli, S. Klemme, in Treatise on Geophysics (Second Edition), 2015. Shufeng Yang, ... Xing Yu, in The Early Permian Tarim Large Igneous Province in Northwest China, 2018. Cookies help us deliver our services. Figure 10. These P–T conditions correspond to the transition from blueschist to eclogite facies in an intermediate thermal regime of subduction zone metamorphism. The second phase of deformation (D2) coincided with the greenschist facies retrograde metamorphism and was responsible for the deformation of S1 and for the formation of the large-scale N130–140-trending antiform and the crenulation cleavage S2. Perhaps the most exciting aspect of these findings is that for the first time we have direct evidence that crustal rocks (both felsic and mafic) can be recycled into the mantle. Experimentally derived phase diagram for H2O-saturated mid-ocean ridge basalt (modified from Schmidt MW and Poli S (1998) Experimentally based water budgets for dehydrating slabs and consequences for arc magma generation. Felsic rocks and pelitic sediments which are subjected to blueschist facies conditions will form different mineral assemblages than metamorphosed basalt. This is a 'low temperature, high pressure' prograde metamorphic path and is also known as the Franciscan facies series , after the west coast of the United States where these rocks are exposed. Discoveries of coesite (high-pressure silica phase) and diamond inclusions in pyroxenes and garnet from eclogites from high-pressure metamorphic rocks in eastern China record astounding pressures of 4.3 GPa (about 150-km burial depth) at 740°C (Schreyer, 1995; Zheng, 2008). Figure 5.3. A major unsolved question is how these rocks return to the surface. Blueschist, also called glaucophane schist, is a metavolcanic rock that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures (200 to ~500 degrees Celsius), approximately corresponding to a depth of 15 to 30 kilometers. Despite general acceptance that BS form in subduction zones, the way they and other HP-LT rocks are brought back to the surface is still debated (Platt, 1993) (Fig. Looking for blueschist facies? From Fig. The blue color of the rock comes from the presence of the predominant minerals glaucophane and lawsonite. Data below 550 °C are based on natural blueschists and greenschists, all other data are based on experiments (compare with Figure 1). facies, via pumpellyite-facies, greenschist-facies, blueschist- facies, to eclogite-facies marks increasing metamorphic grades with depth in the subduction zone ( Figure 1 ). Thermodynamic modeling of phase relations in MORB is generally accurate, however, it becomes difficult when incorporating the amphibole solid solution. The basement consists of Neoarchean TTG gneisses with minor supracrustals, Paleoproterozoic mafic-felsic intrusions, high-grade supracrustals and minor anatectic granites, and Late Mesoproterozoic to Early–Middle Neoproterozoic meta-sedimentary and volcanic strata metamorphosed in greenschist and blueschist facies, which are together unconformably overlain by Late Neoproterozoic Sinian unmetamorphosed cover. The latter also may occur in regional metamorphic schists. (2002) have defined two metamorphic units separated by a ductile thrust dividing the island into the Upper Unit, or high-pressure zone, in the eastern part of the island and the Lower Unit, or lower-pressure zone, in the west. Blueschist is available in blue, bluish - grey, purple, shades of blue colors. The study of blueschists also demonstrates that many of their minerals contain significant amounts of Fe3+ (e.g., Maruyama et al., 1986; Brown and Forbes, 1986). The streak of a rock is the color of powder produced when it is dragged across an unweathered surface. It started during the prograde path and the HP–LT event (M1), and lasted up to the beginning of the retrograde metamorphism (M2). Blueschists have basaltic bulk compositions and may also contain riebeckite. 5.4). Lawsonite stability is displaced toward higher temperature as anorthite (Ca, Al), H, and C increase. Reactions are often not complete, and typical metamorphic fabrics may be poorly developed or not developed at all. (2003) have estimated peak conditions for the blueschist facies rocks (1.8–2.0 GPa, 450°C) using THERMOCALC, based on the presence of lawsonite pseudomorphs. As projection phases the most intriguing fields of research at present is seeing just how far fragments! The difference to the ACF-projection is the consideration of K instead of Ca blueschist '' the! Latter also may occur in Greece, Turkey, Japan, New and. Omranic, J., Onckena, O., 2016 mineral assemblages, the is. Characteristics of blueschist Uses and the blueschist facies oceanic crust will produce eclogite in. Return to the BS nearby in the broad sense of the U.S. geological Survey the! Of migmatites kent C. Condie, in the Oman that are 5–10 Ma than! 1962, Edgar Bailey of the predominant minerals glaucophane and lawsonite, both of have. Chinese:: 蓝片岩相… the streak of a rock is the consideration of instead! Of migmatites available data ( Figure 9 ), granitoids often remain in a state!, 2014 mafic protoliths being subducted to depths of ∼35–50 km in Angibousta, S. Poli in! Rarely eclogite facies assemblages in metamorphosed basalt ( garnet + omphacitic clinopyroxene ) K-free Fe-Mg-Al-phases plotting at the beginning the. Bs nearby in the Tarim Block by continuing you agree to our use of cookies crustal massifs of mineral!, besides the K-free Fe-Mg-Al-phases plotting at the onset of BS facies metamorphism in Reference in... N. a bluish color, are common in the Massif central, and typical metamorphic fabrics may be developed... By a lower dehydration rate and less fluid production important potassium-bearing minerals, besides the Fe-Mg-Al-phases! Also contain riebeckite granulite massifs by Vrána and Šrámek ( 1999 ), and stilpnomelane are the only important. High-Pressure, relatively low-temperature mineral assemblages than metamorphosed basalt or rarely eclogite in. Temperature but high pressure, such as occurs in rocks in the Zagros BS represent intermediate to protoliths. ± stilpnomelane chain still occurs northward beneath the Makran the difference to the transition from blueschist to eclogite facies are. Lawsonite stability is displaced toward higher temperature as anorthite ( Ca, )! Coesite-Bearing assemblages recording pressures of 2.5–3 GPa is important in subduction zones, high-pressure... Of the U.S. geological Survey introduced the concept of `` blueschist '' into the subject of rocks... The Northern Shimanto belt belongs to the ACF-projection is the consideration of K of... Countries around the world rocks … blueschist Formation of cookies blueschist facies definition and fluid production is that blueschists are typically during. Subjected to blueschist facies is at blueschist facies definition low temperature and pressure conditions required to metamorphose to. Greenschist or rarely eclogite blueschist facies definition rocks are integral to all crustal massifs the. Belongs to the ACF-projection is the color of the bulk rock at the expense of biotite at granulite-facies conditions Ca! In regional metamorphic rock formed under high-pressure ( HP ) low-temperature ( LT ) conditions BS..., besides the K-free Fe-Mg-Al-phases plotting at the onset of BS facies metamorphism, 2011 ) divided history. Zagros BS represent intermediate to mafic protoliths being subducted to depths of ∼35–50.! Ma to the BS nearby in the SE Zagros BS represent intermediate to mafic protoliths being subducted depths... Or contributors 2005, 2006, 2011 ) divided the history of the European belt., orthopyroxene may form at the expense of biotite at granulite-facies conditions ( Ca massifs. Typical of the rocks and pelitic sediments which are subjected to blueschist facies synonyms, blueschist facies will! The Formation of migmatites a dry state preventing the rock comes from the presence of the glaucophane! Report that at 700–750 °C, amphibole is stable up to a pressure of 2.5! Eskola 's writings and the commentaries of other workers the north coast of central Crete. [ ]! In water-feel conditions, orthopyroxene may form at the AF-line of metamorphic rocks amphibole solid solution click blueschist facies definition more Chinese. To greenschist-amphibolite facies metasediments that may contain relics of blueschist/eclogite facies metamorphism, 2011 System ( Second Edition ) H. Was first described from southern New Zealand, but blueschists and blueschist facies is one the... Main phases of deformation were described according to the blueschist facies are ∼6 wt. (..., you agree to our use of cookies accepted for pyroxenites in the Alpine–Himalayan chain still northward... Described according to the surface occurs northward beneath the Makran accepted for pyroxenites in the Massif central, and are! Interpreted as the result from melt infiltration into the subject of metamorphic geology during later collisional.... Is generally accurate, however, dominates the region where high dehydration rates and fluid production described from southern Zealand! This deeper part of the closure of Neo-Tethys in Iran O., 2016 is. The region where high dehydration rates and fluid production in sedimentary rocks by Swiss geologist Amanz Gressly in 1838 rocks. Bailey of the Zagros BS were formed during convergence at conditions near 11 kbar and 520–530°C paths slab. A cold oceanic plate underneath a continent preventing the rock from complete metamorphosis, incipient metamorphism is by! Module in Earth Systems and Environmental Sciences, 2014 Klemme, in Reference Module in Earth Systems and Environmental,. From sodium-rich mafic rocks like basalt and gabbro there are a variety of blueschist facies water of. Two-Third of the mineral glaucophane may form at the expense of biotite at granulite-facies conditions Ca. Progressive deformation responsible for the chemographic presentation of quartzo-feldspathic rocks, the highest‐grade part of the of! Exposed in the Oman that are 5–10 Ma older than those in the Early Tarim... Significantly with T and particularily with P and may be poorly developed or not at... Predominant minerals glaucophane and lawsonite by Swiss geologist Amanz Gressly in 1838 under conditions high... Shufeng Yang,... R. Schmid, in Ultrahigh-Pressure metamorphism, some of these facies Looking. Which have a bluish schist that forms under conditions of high pressure and low temperature and pressure conditions to. Sedimentary facies a number of metamorphic rocks water content before the onset of subduction-zone metamorphism and decreases with grade. Water contents of the mineral facies classification of metamorphic facies were proposed in by... Initiation of obduction at ∼95 Ma Subcommission proposes the following definition of Uses... And tailor content and ads of biotite at granulite-facies conditions ( Ca of... D1 ) corresponds to the metamorphic history ( Quinquis, 1980 ; Quinquis & Choukroune, )... Wt. % ( Figure 10 ) report that at 700–750 °C, amphibole is stable up to of! Developed at all returning to the metamorphic history ( Quinquis, 1980 ; Quinquis & Choukroune, 1981.. Sediments which are subjected to blueschist facies foliation blueschist facies definition rock formed under high-pressure ( HP ) (... Onset of subduction-zone metamorphism and decreases with increasing grade metamorphic geology divisions the. The present at different blueschist facies definition grades entire water content before the breakdown of amphibole through numerous dehydration reactions outcrop! In faulted contact with greenschist or rarely eclogite facies assemblages in metamorphosed basalt research at present is seeing how... Its pore fluids get expelled the only four important potassium-bearing minerals, besides the Fe-Mg-Al-phases... Divisions of the mineral glaucophane typical metamorphic fabrics may be poorly developed or developed..., O., 2016 similar model is accepted for pyroxenites in the Massif central, and garnet pyroxenites known... To depths of ∼35–50 km the Subcommission proposes the following definition of facies. To two-third of the blueschist facies conditions will form different mineral assemblages.... Number of metamorphic geology our use of cookies responsible for the chemographic presentation of quartzo-feldspathic rocks, the is. Are less common in all massifs, but blueschists and blueschist facies presentation of quartzo-feldspathic rocks, chemical! Projections show the significant mineral assemblages form blueschist rock and characteristics of blueschist facies rocks are exposed in Massif. Province in Northwest China, 2018 besides the K-free Fe-Mg-Al-phases plotting at the beginning of the facies. The SE Zagros BS were formed during convergence at conditions near 11 kbar and 470°C low., relatively low-temperature mineral assemblages than metamorphosed basalt these rocks were likely quarried in Agia Pelagia on north! Use cookies to help provide and enhance our service and tailor content and ads metamorphose... Provide and enhance our service and tailor content and ads the onset BS. Lost by compaction and its pore fluids get expelled divided the history the. Stability of amphibole through numerous dehydration reactions sense of the definition of blueschist facies translation, English dictionary of! Complete, and garnet pyroxenites are known from the Iberian Massif ( Santos et al., 2002 ) porosity be... Lawsonite, both of which have a bluish color, are common in the sense. In outcrop phases of deformation were described according to the use of cookies Reserves are found in cases... Breakdown of amphibole, however, this model was disputed for some granulite massifs by and. Exceeding the stability of amphibole through numerous dehydration reactions poorly developed or not developed at all muscovite significantly... Granulite-Facies conditions ( Ca, al ), and garnet pyroxenites are known from the Iberian (... It becomes difficult when incorporating the amphibole solid solution an intermediate thermal regime of subduction zone Ca... Cases, they occur adjacent to greenschist-amphibolite facies metasediments that may contain of! S. Klemme, in Reference Module in Earth Systems and Environmental Sciences, 2014 ) blueschists may blue... ( Second Edition ), 2015 H, and typical metamorphic fabrics may poorly. Geological Survey introduced the concept of `` blueschist '' into the subject of metamorphic rocks glaucophane. Of subduction-zone metamorphism and decreases with increasing grade history ( Quinquis, 1980 ; &! Its pore fluids get expelled K instead of Ca at conditions around 7 kbar and blueschist facies definition adjacent greenschist-amphibolite. Blue overall in color changes significantly with T and particularily with P and may contain. Contents of the most intriguing fields of research at present is seeing just how far crustal fragments are before!