Nov 01, 2012 the granulitefacies, metabasite layers tonalitic composition are orthopyroxenebearing whereas the metapelite layers represent sillimanitebearing restites. Discovery of granulitefacies metamorphic rocks in the ji. Part of the advances in physical geochemistry book series physical geoche, volume 5. In the granulite facies area, two distinct rock types occur. Pdf trace element partitioning in the granulite facies. The most common mineral assemblage of granulite facies consists of antiperthitic plagioclase, alkali feldspar containing up to 50% albite and al 2 o 3 rich pyroxenes. Reactions in mafic amphibolite marking the transition from amphibolite to granulite facies were investigated by hydrostatically heating and deforming solid cylinders of an.
South uist wikipedia other rock types found are charnockites, granite gneiss, khondalites, leptynites, metamorphic gneisses with detached occurrences of crystalline limestone, iron ore, dolerites and anorthosites. Charnockitic metagranodiorite and metatonalite are magnesian in composition and show calcalkalic to alkalicalcic affinities. The magnetic properties and fabric of granulite facies. Granulite facies amphibole pargasite in the olivine gabbro is distinguished from the amphibolite facies. The third stage is characterized by a continued increase in pyrope in the garnet rim, suggesting decompression with slight heating from the peak pressure to reach the peak. Mount hay is comprised primarily of mafic granulite plus lesser amounts of charnockitic, porphyroclastic, and quartzofeldspathic granulite.
This will promote limited degrees of partial fusion and the formation of granulitic migmatites, but will not produce mobile granitoid magma. Granulite facies relics are found in the early paleozoic kyanitebearing melanocratic metagabbro from the fuko pass metacumulate mass of the oeyama belt, southwestern japan. Co 2 is extracted from scapolite without fractionating carbon isotopes by reaction with phosphoric acid at 25 or 75c. Abstract carbon isotope compositions of scapolite from granulite facies gneisses and lower crustal xenoliths document the composition and constrain the source of carbon in scapolite from the lower crust.
The hightemperature ht conditions characteristic of this facies are indicated by the presence of orthopyroxene, whilst the upper pressure boundary with the eclogite facies corresponds to. Geochronological constraints on granulite formation in. Modelling the partial melting of metasediments in a lowpressure. Although granulite facies rocks are present in zones of orogenesis ranging in age from 300 to 3,000 m. Pdf extraction and carbon isotope analysis of co2 from. In such rocks abundant mesoperthitic kfeldspar testifies to the former presence of high temperature. Crustal granulite facies metamorphism is indicated by twopyroxene metagabbroic bodies and twopyroxene metasedimentary paragneiss. Some show granulite facies metamorphism, but most are the slightly lower temperature amphibolite facies. Geochemical characteristics of granulite and constraining the. Association of canada, montreal, guide book, fieldtrip a2, 52p. Geochemical characteristics of granulite facies rocks in.
In various memoirs and books turner used the doubtful sound pyroxene assemblages as examples of his almandinediopsidehornblende subfacies 1948, hornblende granulite facies 1958, and amphibolite granulite transition facies 1968. Progressive metamorphism of mafic rocks from greenschist to. The island of sri lanka is located to the southeast of india and is formed predominantly of precambrian rocks that occur in several major terrains. Granulites by name but eclogite facies by formation. The granulite facies assemblage consists of relict alrich clinopyroxene up to 8.
The amphibolite facies precursor minerals green diamonds were replaced by pairs of intergrown granulite facies minerals red squares. Granulite facies, one of the major divisions of the mineral facies classification of metamorphic rocks, the rocks of which formed under the most intense temperaturepressure conditions usually found in regional metamorphism. Granulite facies paragneisses from the middle segment of the mogok metamorphic belt, central myanmar march 2017 journal of mineralogical and petrological sciences 1121. Magnetic fabric of these variably deformed, deep crustal rocks provide insights into the deformation. A metamorphic rock consisting of similarly sized, interlocking minerals, especially feldspar, quartz, and garnet, and lacking the layering and foliation. Discovery of granulitefacies metamorphic rocks in the jian.
In both granitoids and gabbros, amphibole and biotite are late magmatic minerals. Outcrops of eclogitefacies rocks showing a granulite facies overprint are. They are medium to coarsegrained and mainly composed of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure. A series of reactions to account for the development of the coronas is proposed using measured mineral compositions. The granulite facies is characterized by the following mineral assemblages. Granulites are massive medium to coarsegrained highgrade metamorphic rocks of the granulite facies formed under high temperature and moderate pressure. Rocks of the granulite facies of metamorphism occupy a central role in. The facies distinction was controlled by wholerock composition, whereby mafic components recrystallized to eclogite and dioritic components recrystallized to granulite.
Fyfe, turner and verhoogen 1958 have subdivided this facies into the hornblendegranulite and pyroxenegranulite subfacies. Granulitefacies overprint in garnet peridotites and kyanite. As a metamorphic facies, characterized by the dehydration of hydrous minerals, granulitic rocks include mafic 68 wt. The minerals found in the rocks of the granulite facies include pyroxene, biotite, garnet, calcium plagioclase, and quartz or olivine. Carbonate rocks have a different composition than a basalt lava, the minerals that. A lowpressure greenschist to granulitefacies regional aureole of c. Abstract gneisses of tonalitetrondhjemitegranodiorite ttg composition, typical rocks found in archaean terrains all over the world, also occur in the taihua highgrade terrain of the lushan area, central china. Heier this volume has pointed out the presence of carbon dioxide rich fluid inclusions in granulite facies minerals. Melt composition is more dependent on the rock composition than the variation in water.
The geothermometer applied to the garnetbiotite, garnetcordierite and garnetorthopyroxene pairs gave a t of approx 730oc, while the garnetorthopyroxeneplagioclasequartz geobarometer gave p of approx. At the upper limit of the facies, migmatite formation may occur. The other instances of highgrade, granulitefacies metamorphic rocks so far. Pressure granulite facies overprinting during the exhumation. Whereas felsic to mafic granulites with an average intermediate major element composition are typically observed in old exposed lower crustal. Therefore, when considering the prograde history of a granulite. Pdf granulite facies metamorphism and the rheology of the. Although it is virtually omnipresent, it has yet not attracted the attention in geochronology that it could have, mostly due to a frustrating high. Granulite to amphibolitefacies metamorphism and penetrative. The granulite facies, partial melting and the archaean crust. The granulites are typically characterized by a granoblastic texture and a large amount of quartz and feldspar or quartz and pyroxene with a. Jun 01, 2009 fayalite granitoids are mediumgrained and are composed of fayalite, ferich clinopyroxene, ferich edenite, quartz, plagioclase, annite, potassic feldspar and ilmenite.
Granulite news newspapers books scholar jstor march 2012 learn how and when to remove this template message. Towards the upper limits of the granulite facies request pdf. Geothermobarometric data from garnet amphibolite and granulite facies metagabbro within the ophiolitic suite yielded pressure and temperature conditions of 57 kb and 650750 c. The upper plate is shaded in green, the lower plate in pink, the metamorphic core in blue, and post1. Fluids of granulite facies metamorphism springerlink. Geochemistry of exposed granulite facies terrains and lower. The potential role of fluids during regional granulitefacies. Pdf granulite facies metamorphism and the rheology of. This definition of granulite was used by eskola barth et al. Outcrops of eclogitefacies rocks showing a granulitefacies overprint are. We applied this scheme to 414 granulites of mafic, intermediate and aluminous bulk compositions.
Upb rutile dating in granulitefacies rocks by laicpms. Metamorphic grade increases toward the igneous complex. Small quantities of h 2 orich fluid may be present at the onset of granulite facies conditions. This metamorphism is attributed to crustal thickening related to overriding of the cabo delgado nappe.
It is believed that the granulite facies, introduced by eskola 1939, originates through a further rise in temperature after the field of the highesttemperature subfacies of the almandineamphibolite facies has been traversed. Late neoproterozoic granulite facies metamorphism in the. This suggests another possible factor to be considered in granulite formation. Granulite facies rocks make up the lower continental crust, and its lithologies are considered to be represented by varying proportions of granulite facies xenoliths and terrains. The granulites are typically characterized by a granoblastic texture and a large amount of quartz and feldspar or quartz and pyroxene with a variable proportion of garnets. Metamorphic p t evolution and geological implications cai, jia liu, fulai. Pt conditions of granulitefacies rocks from the hidaka. Due to the strong overprinting at subsequent granulite. Geochemistry and single zircon geochronology of archaean. Uht metamorphism forms the highertemperature part of the granulite facies, which itself spans metamorphic conditions of 318 kbar and 7001100 c fig. Transition between amphibolite and granulite facies is defined by these reaction isograds.
Geology of the granulite and amphibolite facies gneisses of. According to turner and verhoogen, the granulite facies comprises temperatures between 700800c. The most common mineral assemblage of granulite facies consists of antiperthitic plagioclase, alkali feldspar containing up to 50% albite and al 2 o 3rich pyroxenes. The greenschistamphibolite facies boundary line 2, in figure 5 is characterized in mafic rocks by. Plagioclase in the granulites has compositions between labradorite and anorthite. Review paper highpressure granulites of the bohemian. The granulite grade metamorphic terrains of southern india form an integral part of east gondwana. Review paper highpressure granulites of the bohemian massif. Rocks of the granulite facies of metamorphism occupy a central role in discussions of petrogenesis of the crust.
A sample of granulite facies metamorphic rock of felsic composition, with garnet porphyroblasts. Granulites and palaeoproterozoic lower crust of the. Geochemical characteristics of granulite and constraining. The hightemperature ht conditions characteristic of this facies are indicated by the presence of orthopyroxene, whilst the upper pressure boundary with the eclogite facies corresponds to the breakdown of plagioclase. Although granulite facies rocks are sporadically exposed in younger terrains. Detail information on the granulite world of stones. Granulite facies synonyms, granulite facies pronunciation, granulite facies translation, english dictionary definition of granulite facies. Their petrology, geochemistry and single zircon geochronology suggests that they are. A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under. Granulites may be produced in either fluidpresent or fluidabsent metamorphism.
Our findings suggest that granulites are much hotter than. A pelitic or calcareous rock will develop very different mineral assemblages from a metabasalt, yet the same facies names apply. Granulite facies migmatites 750 900c, 5 6 kbar from the namaqualand metamorphic complex, south africa, contain complex zoned monazite in both palaeosome and neosome domains. The amphibolite facies occurs in the east, and increases to granulite facies in the west figure l. Because granulite facies metamorphism typically occurs at temperatures higher than the h 2 osaturated melting curve for intermediate composition rocks, it has generally been assumed that any. Metamorphic evolution and petrogenesis of garnetcorundum. Granulite is a highgrade metamorphic rock in which femgsilicates are dominantly hydroxylfree. Granulite facies are documented by grtopxcpxplbearing mafic granulites and charnockitic gneisses, reporting p 0. Major lithotectonic domains are written in upper case black and constituent. Such differences suggest that the compositions of pl2 and pl4 are largely dependent on the.
The separate granulite metamorphic facies was defined on the basis of mineral assemblages in basic rocks. Lithos 124 2011 viiix contents lists available at sciencedirect lithos j o u r n a l h o m e p a g e. Backscatter electron imaging, compositional mapping and spot analysis using both eds and wds electron microprobe techniques reveal several chemicallydistinct. Rutile is a common accessory phase in several metamorphic rock types mafic, pelitic and felsic protoliths. Features of the amphibolite granulite facies boundary line 3, in figure 5 and the lower limit of the greenschist facies line 1, in figure 5 have been briefly discussed. Uht metamorphism was originally defined in the mid 1990s as granulite facies crustal metamorphism at peak conditions of greater than 900 c for pressures in the range 7 kbar. Granulite facies relics in the early paleozoic kyanite. Discovery of granulitefacies metamorphic rocks in the jian area, northeastern jiaoliaoji belt, north china craton.
Geochemical characteristics of granulite facies rocks in the. Geochemistry of exposed granulite facies terrains and. Granulites are a class of highgrade metamorphic rocks of the granulite facies that have. The type area for this model is the adirondack highlands of upstate new york, where much of the terrain consisted of preorogenic pyroxenebearing igneous rocks and their highgrade thermal aureoles, subsequently metamorphosed to give grenville age ma granulite facies assemblages. The prevailing rock types in these blocks are igneous enderbites, tonalitictrondhjemiticgranodioritic migmatites and mafic granulites. Thus, partial yields of co 2 from scapolite are sufficient for accurate. Pdf granulite facies paragneisses from the middle segment. Igneous and metamorphic activity spanned over one billion years of earth history, from 1.
Thus, one can refer to a greenschist facies pelitic schist, an amphibolite facies calcsilicate rock, or a. Granulite facies in rocks of basaltic composition, the granulite facies is an anhydrous facies that results from progressive dehydration of amphibolites. Granulite facies metamorphism of metabasic and intermediate. Almost all wellstudied examples are precambrian, which has suggested to many workers that metamorphic temperature regimes operating in the remote geological past were higher than are characteristic of more recent metamorphism. Fluidpresent granulites can be formed by relatively lowt dehydration reactions, in the presence of a fluid dominated by a species other than h 2 o e.
These rocks underwent highamphibolite to granulite facies metamorphism and intense deformation. A classic work of turners was the book he published in 1948 titled. The d values derived in this study are broadly similar to magmatic partition coefficients for intermediate melt compositions. Mafic dykes as monitors of hp granulite facies metamorphism in the. The trace element compositions of samples from exposed granulite facies terrains and 17 granulitic lower crustal xenoliths were determined using an inductively coupled plasma. The present paper gives an account of the petrology of the pyroxene granulite facies rocks of the central high mountain tract of jotunheimen. Granulitefacies metamorphism of the palaeoproterozoic. The lower pt limits of the granulite facies are thought to be around 0. In summary, combining the published age of the hp granulite facies metamorphic event 179 ma with our new results from zircon and rutile, we propose that the 177 ma zircon age could represent the timing of hp granulite facies overprinting stage, while the rutile lower intercept age of 168 ma could reflect the timing of the later stage of. Bucher, in encyclopedia of geology, 2005 the metamorphic facies scheme, additional aspects and facies boundaries. Archean lower crustal granulites are exposed as faultbounded blocks in the varpaisjarvi area, central finland. Pdf granulite facies amphibole and biotite equilibria. Granulite facies definition of granulite facies by the. The geochronologic data distribution in these terrains show granulite facies events at ca.
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