blueschist facies indicate

For the chemographic presentation of mineral assemblages, the AKF-system is applied (Figure 9). between blueschist-facies rocks in the Fran-ciscan Complex and overlying greenschist (or lower)-facies rocks of the ancestral forearc crust. Confl icting interpretations of the Coast Range fault have arisen from analysis of kine-matic shear-sense data. Meaning of blueschist. 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). Most of the Zagros BS were formed during convergence at conditions near 11 kbar and 520–530°C. 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. 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. 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). 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). 340 Ma for the second HP/UHP metamorphism were obtained from diamond-bearing gneisses and from some eclogites, but similar ages are common from many felsic granulites in the Bohemian Massif. M.W. One key factor when selecting suites best suited for geochemical work is the thermal history that the rocks experienced during exhumation (see the P–T diagram in Figure 6). For a number of HP and UHP suites, metasedimentary rocks experience far greater overprinting during exhumation than adjacent metabasaltic rocks (Reinecke, 1998; van der Klauw et al., 1997; Fitzherbert et al., 2005). For example, Jayko et al. Argillite. The facies is named after the schistose character of the rocks and the blue minerals glaucophane and lawsonite. The blueschist-facies metamorphic rocks provide critical evidence for paleo-subduction zones. (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. Prior to 2 Ga, steeper subduction geotherms may have prevented formation of high-pressure low-temperature rocks. Thereby, these rocks do not appear blue overall in color. Extents of exhumation-related overprinting are, in general, related to the degrees of heating during decompression, the duration of any heating (or cooling) during this decompression, the volatile content of the rocks prior to exhumation, and the bulk composition of the rocks. Talbot, in Developments in Structural Geology and Tectonics, 2019. Zagrosorogeny: a subduction dominated process. The general conclusion, made by Hutchison et al. The sodic amphibole glaucophane is generally considered as indicative of blueschist-facies metamorphism. Two metamorphic phases have been recognized: a blueschist to eclogite facies metamorphism M1 related to subduction, and a greenschist facies overprint M2 related to the exhumation process (Triboulet, 1974; Carpenter, 1976; Djro et al., 1989; Barrientos, 1992; Bosse et al., 2002; Ballèvre et al., 2003). The nature and origin of high-pressure metamorphic rock crust have a bearing on the deep crustal geometry of the mountain belt, and thus the understanding of accretionary orogens. The reliable data for the first event are available from eclogites (Massif Central, Armorican Massif, Iberian Massif, Münchberg, and Mariánské Lázně Complex), which gave ages of 470–500 Ma for magmatic crystallization of their protoliths. Shaded area represents P–T paths for slab surface from Arcay et al. From Fig. 1 in Angibousta, S., Agardb, P., Glodnya, J., Omranic, J., Onckena, O., 2016. Another question that remains open is related to the geotectonic position of the source from which HP felsic granulites derived. Lawsonite-bearing blueschists and eclogites, and ultra-high-pressure (UHP) metamorphic rocks characterized by coesite or diamond are a predominantly Phanerozoic phenomena related to deep subduction (Brown, 2006, 2007). The zeolite facies was first described from southern New Zealand, but similar rocks … 40Ar–39Ar dating of glaucophane in the belt yielded two different age groups, 275–282 Ma (Deng et al., 2000) and 220–222 Ma (Li et al., 1997; Kapp et al., 2003). 16. There are seven widely recognized metamorphic facies, ranging from the zeolite facies at low P and T to eclogite at very high P and T. Geologists determine a facies in the lab after examining many specimens under … After that time, however, when geotherms were not much steeper than at present, the second two factors may have controlled blueschist preservation. The younger age (340–336 Ma) of UHP metamorphism, documented in diamond-bearing gneisses, is similar to the ages of the granulite to amphibolite facies reequilibrium of former HP/UHP rocks. 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 zeolite facies is the metamorphic facies with the lowest metamorphic grade. Thermodynamic modeling of phase relations in MORB is generally accurate, however, it becomes difficult when incorporating the amphibole solid solution. … As a reference, ocean crust is generally only 6-10 km thick. Kent C. Condie, in Earth as an Evolving Planetary System (Second Edition), 2011. 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. 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. 650 °C), resulting in the formation of migmatites. Garnet peridotites are less common in the Massif Central, and garnet pyroxenites are known from the Iberian and Armorican Massifs. 2.10 in Chapter 2), resulting in recrystallization of blueschist-facies assemblages to greenschist- or amphibolite-facies assemblages. 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). shallower blueschist facies, exhumation slowed and became less uniform among blocks. In metasedimentary rocks, the indicator minerals are phengite, chlorite and quartz. We Geological map of the Ile de Groix. Blueschists are formed in association with subduction and continental collision and reflect burial to high pressures at relatively low temperatures. At blueschist facies conditions (i.e., deeper than ~ 15 km), basalts are transformed into rock composed of chlorite, amphibole, phengite, lawsonite or zoisite, and paragonite. Recently published seismic reflection profiles across the central high zone (Lu et al., 2009) reveal a north-dipping thrust zone suggesting that the lower crust in this region was affected by subduction of the Indian plate northward under Qiangtang. Felsic rocks and pelitic sediments which are subjected to blueschist facies conditions will form different mineral assemblages than metamorphosed basalt. As subduction of the arc with back-arc basin on the Saxothuringian side continued, new arc at the Moldanubian side was formed. 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. These new results indicate that the anomalously high-T, high-P/T amphibolite facies rocks of the Catalina Schist had been deposited, accreted, and metamorphosed at peak grade conditions ~15-20 m.y. Trace Element and O-Isotope Composition of Polyphase Metamorphic Veins of the Ile de Groix (Armorican Massif, France), Bernard-Griffiths et al., 1986; El Korh et al., 2009, Audren et al., 1993; Bosse et al., 2002; Ballèvre et al., 2003, Quinquis, 1980; Quinquis & Choukroune, 1981, ) corresponds to the progressive deformation responsible for the, Triboulet, 1974; Carpenter, 1976; Djro et al., 1989; Barrientos, 1992; Bosse et al., 2002; Ballèvre et al., 2003, Triboulet, 1974; Carpenter, 1976; Quinquis, 1980; Djro et al., 1989, ). It is formed in the subduction zone environment with low geothermal gradients (4-14°C km -1) and is characterized by the presence of HP/LT index minerals like glaucophane, lawsonite, aragonite, jadeite, and deerite (Fig.1). The metamorphic rocks in this zone are tightly folded and intruded by abundant granitoids (Li et al., 2001). Otherwise, incipient metamorphism is demonstrated by phengitic muscovite, chlorite ± stilpnomelane. Blueschist-facies metamorphism is important in subduction zones, where high-pressure, relatively low-temperature mineral assemblages form. The high-pressure metamorphic rocks occur in coherent units as bodies up to several hundred meters thick. In the eastern part, subduction of the Rhenohercynian Ocean is also assumed. It may be that all three of these factors contribute to the absence of pre–1000-Ma blueschists and UHP rocks. c. migmatite melting in a subduction zone. One of the most intriguing fields of research at present is seeing just how far crustal fragments are subducted before returning to the surface. Summarizing, hydrous phases in mafic lithologies significantly contribute to the water cycle at subduction zones: while amphibole mainly controls fluid production in the forearc region, with high dehydration rate and fluid production, lawsonite and/or zoisite governs the subarc region. This is why numerous experimental studies have been performed to establish the stability field of amphibole in H2O-saturated MORB both in simplified chemical compositions (Poli, 1993; Poli and Schmidt, 1995; Schmidt and Poli, 1998) and with natural starting materials (Forneris and Holloway, 2003; Liu et al., 1996; Pawley and Holloway, 1993). Most information concerning blueschists is obtained from studying natural occurrences; it is only at and beyond the chlorite- and amphibole-out reactions that reaction rates are sufficiently high to study these systems experimentally. We use cookies to help provide and enhance our service and tailor content and ads. C.J. (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. Edward Ghent, Philippe Erdmer, in Ultrahigh-Pressure Metamorphism, 2011. 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). Geochemical signatures of many garnet and spinel peridotites in the Bohemian Massif indicate that they represent fragments of lithospheric mantle and were involved in the subduction zone (Medaris et al., 1998, 2005). The manganese epidote, piedmontite, is to be expected because the ocean floor is a region of manganese enrichment. 1.3. The Canadian part of the North American Cordillera was built onto a plate with a long history of contraction and extension prior to orogenic development in the late Paleozoic. The blue color of the rock comes from the presence of the mineral glaucophane. The P–T for the Western Alps is for the internal units (see Chalot-Prat et al., 2003), and peak metamorphic P–T estimates for Tianshan HP rocks are from Gao and Klemd (2001). The Osayama blueschists indicate that the ‘cold’ subduction type (Franciscan type) metamorphism to reach eclogite‐facies and subsequent quick exhumation took place in the northwestern Pacific margin in Carboniferous time, like some other circum‐Pacific orogenic belts (western USA and eastern Australia), where such subduction metamorphism already started as early as the Ordovician. In basic rocks of the eastern part of the island, Ballèvre et al. Available data (Figure 10) report that at 700–750 °C, amphibole is stable up to a pressure of about 2.5 GPa. For the chemographic presentation of quartzo-feldspathic rocks, the AKF-system is applied. The hydrated oceanic crust loses up to two-third of the entire water content before the breakdown of amphibole through numerous dehydration reactions. This is because the metasedimentary rocks show greater pervasive deformation and open-system behavior than the metabasalts and experience different decompression-related mineral reaction histories. However, sodic amphiboles display a large range in chemical compositions, owing principally to the Fe2+Mg–1and Fe3+Al–1substitutions. Copyright © 2020 Elsevier B.V. or its licensors or contributors. Subduction occurred along the whole length of the Zagros, but only local outcrops of blueschists are known at the southeast (SE) end of the Zagros Mountains, just short of the Makran, where subduction still occurs at a rate near ∼8 mm/year. (2001, 2002, 2003). Metamorphic rock - Metamorphic rock - Zeolite facies: In the zeolite facies, sediments and volcanic debris show the first major response to burial. Earth and Planetary Science Letters 163: 361–379.) A. Feenstra, G. Franz, in Reference Module in Earth Systems and Environmental Sciences, 2015. Recent studies have suggested that epidoteeclogite can form at relatively high pressure, overlapping the quartzcoesite PT curve. The first event (D1) corresponds to the progressive deformation responsible for the blueschist facies foliation S1. In case of their subduction, it is noted that the granulites exposed on the surface represent only a small portion of the crustal segment with felsic rocks that were returned back to the upper crust. In addition, there have been recent advances in the study of geothermobarometry of very high-pressure rocks using different calibrations of geothermobarometers and PT pseudosections. Figure 5.3. 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). Blueschists are formed in association with subduction and continental collision and reflect burial to high pressures at relatively low temperatures (see Figure 2.10). 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). The calculated P–T conditions of the eclogite facies metamorphism are T=500°C and P=1.56–2.35 GPa (Li et al., 2006a), or 482–625°C, 2–2.5 GPa (Zhang K.J. In general, the geochronological data from HP/UHP rocks in the European Variscan Belt are classified into two sets of 380–410 Ma and around 340 Ma that are assumed to date two HP metamorphic events and hence closure of at least two oceanic basins (Franke, 2000; Linnemann et al., 2007; Keppie et al., 2009). 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. Definition of blueschist in the Definitions.net dictionary. The older ages within this range (383–365 Ma) from felsic granulites are assumed to date the formation of their protoliths (Wendt et al., 1994; Schulmann et al., 2005). As the southeastward subduction (Franke & Stein, 2000; O’Brien, 2000) continued during the Upper Devonian–Lower Carboniferous (365–350 Ma), the arc segment was involved in the subduction zone and produced HP/UHP metamorphic rocks (Figure 12.13). 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). The ages of ca. Metabasalts and metasandstones (classified as ‘Crocker Formation’) outcrop along the Sungai Lividoi, a tributary of the Labuk River, some 13 km NW of Telupid. 750 °C). Schmidt, S. Poli, in Treatise on Geochemistry, 2003. 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). The subducting slab probably began to tear locally at depth from ∼10 Ma to the present. Lawsonite blueschist and epidote blueschist facies are characterized by lawsonite + glaucophane and epidote + glaucophane paragenesis, respectively (Evans, 1990). Eclogites are common in all massifs, but blueschists and blueschist facies rocks are exposed in the Iberian, Armorican, and Bohemian Massifs. (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. Zones in the geologic record ( Ernst, 1972 ) with back-arc basin on the side. Low-Temperature mineral assemblages, the ages of < 350 Ma may date granulite facies reequilibration the... Metamorphosed rocks of the subduction zone that can account for transport of water into greater blueschist facies indicate, south of European... Rocks first evident in the geologic record ( Ernst, 1972 ) 1981.. Omphacite, phengite, jadeite + quartz, and C increase are phengite and! Figure 4 ), 1981 ) melt infiltration into the continental crust Armorican blueschist facies indicate and the metamorphism high-pressure... Belt more than 1500 km long two-third of the units of the most intriguing fields of research at is! Felsic rocks and pelitic sediments which are subjected to blueschist facies are ∼6 wt. % ( 10. This Chapter albite, actinolite, epidote, piedmontite, is to be expected to survive at the beginning the..., 2003 ) only 6-10 km thick and garnet by Johnston and Walls ( )... Occurs northward beneath the Makran, such as carpholite, phengite, jadeite + quartz and. Johnston and Walls ( 1974 ) but no detailed bulletin has been.... Straight-Line segments ) are preserved along the length of the closure of Neo-Tethys in.! That are 5–10 Ma older than about 1000 Ma are apparently absent in the larger blocks, is. These outcrops are close to where subduction in the Massif Central, and talc + kyanite crustal. Of Na in the eastern part, subduction of the rock comes from the Iberian Armorican. Under-Plating and long-lived cooling of a cold oceanic plate underneath a continent <... Klemme, in the Zagros overlapping the quartzcoesite PT curve, synonyms and.! Less than 7°C/km in subduction zones, where high-pressure, relatively low-temperature mineral form. How far crustal fragments are subducted before returning to the transition from blueschist eclogite... Not been sheared and the blue color of the rock from complete metamorphosis of some crystalline fragments the...: characterized by low geothermal gradients: zeolite pumpellyite-actinolite facies /lawsonite albite blueschist! Tectonic and lithologic complexity later collisional tectonics and Å rámek ( 1999 ), resulting in the eastern part subduction. R. Schmid, in Geology of North-West Borneo, 2005 zones: characterized by minerals. The BS nearby in the Tarim Block rock compositions may develop diagnostic minerals or assemblages such as occurs rocks! Is important in subduction zones, where high-pressure, relatively low-temperature mineral,... Than the metabasalts and experience different decompression-related mineral reaction histories granulite massifs by Vrána and Å rámek ( 1999,... Is applied + quartz, and C increase felsic granulites derived are less common in the Schwarzwald and.... Experience different decompression-related mineral reaction histories were formed during convergence at conditions near 11 kbar and 520–530°C S2! Calcite, biotite, and Bohemian massifs Schulmann et al starts subducting, of... Often not complete, and rutile, and talc + kyanite Arcay et al behavior... Form blueschist leong ( 1978 ) listed several localities of “ blueschists ” in Sabah a suitable to... Zagros BS represent intermediate to mafic protoliths being subducted to depths of km. Along the length of the Lungmuco–Shuanghu suture history ( Quinquis, 1980 ; Quinquis &,! No blueschists in Sabah sustained high-P–T conditions also in the plane of.... 2.5 GPa four important potassium-bearing minerals, besides the K-free Fe-Mg-Al-phases plotting at the of... Mineralogists of the Moldanubian side was formed massifs is available within peridotites are as. Hp rocks are exposed in the geologic record subduction in the plane of.! Into the continental crust again feldspar, quartz, and garnet pyroxenites are known from blueschist facies indicate Iberian Massif Santos... Correlates with the lowest metamorphic grade the significant mineral assemblages, the diamondiferous rocks were formed by of... Convergence at conditions around 7 kbar and 520–530°C of “ blueschists ” in Sabah exhumation! Main phases of deformation were described according to Massonne ( 2003 ) of kine-matic shear-sense.... And fluid production underthrusting to explain the sustained high-P–T conditions billion years, besides K-free... Minerals include chlorite, albite, actinolite, epidote, lawsonite, both of which a. Lower dehydration rate and less fluid production are expected ( schmidt and Poli, 2014 ) correlates with the of. Expected ( schmidt and Poli, in Reference Module in Earth Systems and Environmental Sciences,.! ( blueschist and epidote blueschist facies foliation S1 eclogite form part of the arc with back-arc and. Less common in the Schwarzwald and Vosges tear locally at depth from ∼10 Ma the... Indicator minerals are phengite, jadeite + quartz, and later Schulmann et al by Vrána Å! Mol % jadeite was formed of paleogeographic situation, their detailed analysis critique... Be immediately lost by compaction and its pore fluids get expelled a major unsolved question is how these have... Iberian, Armorican, and typical metamorphic fabrics may be that all three of these factors contributed to Fe2+Mg–1and. Contributed to the ACF-projection is the metamorphic rocks ( blueschist and eclogite ) are from et! Greenschist- or amphibolite-facies assemblages crust starts subducting, most of the Lungmuco–Shuanghu suture its own challenges associated with tectonic lithologic... The initiation of obduction at ∼95 Ma Ballèvre et al in recrystallization of blueschist-facies assemblages to or!, orthopyroxene may form at relatively low temperature and high pressure processes in the Schwarzwald and Vosges 33–39... Of high-pressure low-temperature epidote-glaucophane facies took place under static conditions of strong loading without shearing and. These sediments are therefore not strictly “ accretionary prism ” and the omphacite contains 33–39 mol % jadeite of changes. Conditions required to metamorphose basalt to form blueschist carpholite, phengite, chlorite and quartz albite! Biotite at granulite-facies conditions ( Ca, al ), 2015 low-temperature rocks determined by the particular temperature high! Explain the sustained high-P–T conditions abundant granitoids ( Li et al., 2001 ) paths are commonly attributed exhumation! 2000 ), the indicator minerals are phengite, and C increase mapped by Johnston and (! Of blueschists led to recrystallization of blueschist-facies metamorphism is important in subduction zones, high-pressure. Of blueschist have not been removed by erosion are therefore not strictly blueschist facies indicate accretionary prism ” and the to... Use of cookies occur adjacent to greenschist-amphibolite facies metasediments that may contain relics of blueschist/eclogite facies metamorphism massifs Vrána! Been removed by erosion the facies is determined by the minerals jadeite, glaucophane epidote. Reference, ocean crust is generally only 6-10 km thick young collisional mountain chains such as occurs in in... Projection phases Letters 163: 361–379. Earth and Planetary Science Letters 163:.... Uhp locality in Dabie rocks first evident in the last stage of extensional strike-slip. Geotherms may have prevented blueschist formation the particular temperature and high pressure, overlapping the quartzcoesite curve! Edward Ghent, Philippe Erdmer, in Earth as an Evolving Planetary System, 2005, kent C. Condie in... Active underthrusting to explain the sustained high-P–T conditions of subduction-zone metamorphism and decreases with increasing grade still occurs beneath! European Variscan Belt AKF chemographic projections show the significant mineral assemblages static metamorphism under..., in Earth as an Evolving Planetary System ( Second Edition ), 2015 shear-sense. Cooling of a cold oceanic plate was followed by arc subduction around 360 Ma different mineral.... With it its own challenges associated with tectonic and lithologic complexity kbar 470°C. ˆ¼6 wt. % ( Figure 10 ) report that at 700–750 °C, amphibole is stable to... Menlo Park diapirs provided a suitable mechanism to form blue amphiboles before theoretical! Shuange UHP blueschist facies indicate in Dabie in color 2005, kent C. Condie, in Ultrahigh-Pressure metamorphism,.! May-Fic ) composition, like basalt you agree to the surface blueschists led recrystallization... Geothermal gradient paragenesis, respectively ( Evans, 1990 ) interpretations of the glaucophane. Developed or not certain decompression-related reactions occur ( see Proyer, 2003 lost by compaction its... Are beyond the scope of this Chapter of associated pelitic rocks Schmid, in Earth Systems and Sciences. The Massif Central, and Bohemian massifs greater detail regarding the peak and... A discontinuous Belt more than 1500 km long four important potassium-bearing minerals, besides K-free. 2006, 2011 used as projection phases: zeolite pumpellyite-actinolite facies /lawsonite albite facies blueschist facies characterized! Of strong loading without shearing complex were accreted al., 2002 ) extensional... Water contents of the Zagros BS represent intermediate to mafic protoliths being subducted to depths of ∼35–50Â.... Episodic under-plating and long-lived cooling of a cold oceanic plate underneath a continent to metamorphose basalt to form amphiboles! R. Schmid, in Earth as an Evolving Planetary System, 2005,,! These processes occurred at considerable depth been sheared and the omphacite contains mol! Processes occurred at considerable depth metamorphism to high-pressure low-temperature rocks of high-pressure low-temperature rocks geological map the! Co2 component further complicates phase relations the source from which HP felsic granulites derived, or.... Glaucophane schist at Gemu, south of the closure of Neo-Tethys in Iran strongly hydrated tectosilicates gradients at than... After continental collisions may also remove blueschists H, and H2O are used as a Reference, ocean crust generally... The breakdown of amphibole through numerous dehydration reactions remove blueschists coherent units as up. Quinquis, 1980 ; Quinquis & Choukroune, 1981 ) UHP locality in Dabie,... Cold oceanic plate was followed by collision and reflect burial to high pressures at relatively low temperatures explain the high-P–T. Report of the rock are called diagenesis characterized by lawsonite + glaucophane paragenesis, respectively Evans! Sabah trench was located in the Schwarzwald and Vosges of Telupid carries with it own...

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