Rocks which contain certain minerals can therefore be linked to certain tectonic settings, times and. Metamorphic events also vary spatially and temporally, and have been dated at 1190 to 1160 ma, 1080 to 1020 ma and 1010 to 990 ma in different parts of the province e. Polymetamorphism is a metamorphism resulting from more than one metamorphic event fig. An unusually dense rock, eclogite can play an important role in driving convection within the solid earth the fresh rock can be striking in appearance, with red to pink garnet almandinepyrope in a green matrix of sodiumrich pyroxene.
Granulite facies mpht the granulite facies is the highest grade of metamorphism at medium pressure. Granulite facies metamorphism occurs at temperatures of approximately 500 to 700 and pressures of 870 kbar. Greenschist, amphibolite, granulite facies origin of granulite facies rocks is complex and controversial. A characteristic mineral for this facies and the pyroxene hornblende facies is orthopyroxene. Nov 11, 2012 granulite facies mpht the granulite facies is the highest grade of metamorphism at medium pressure. The granulite and hornfels facies were named after the textures of the rocks, with hornfels being the rocks commonly found in contact metamorphic aureoles high temperature, low pressure environments and granulites being coarse grained rocks with a granulitic texture and. Trap falls formation may be equivalent in part to golden hill schist gray to silvery, partly rusty weathering, mediumgrained generally well layered schist, composed of quartz, sodic plagioclase, biotite, muscovite, and garnet, locally with sillimanite or kyanite, interlayered with twomica gneiss and granulite and with amphibolite. The calculations presented here of coh fluid composition for conditions of granulite facies metamorphism show that oxygen fugacity f o 2 estimates from many terranes are sufficiently low. At the upper limit of the facies, migmatite formation may occur. Mar 27, 2017 metamorphic facies is not obvious in a given field specimen. Metamorphic rocks, minerals, grade, and facies lucky sci.
Metamorphic facies is not obvious in a given field specimen. Most metamorphic terranes, especially in the internal parts of continents, are composed of greenschist, amphibolite, and granulite facies rocks, including migmatites at the high metamorphic grades. Use these facies if clearly associated with a pluton. Although the carbonate minerals category accounts for a substantial fraction in these samples and the samples may not be suitable for use in ternary diagrams, important knowledge about the composition of the frame.
Greenschist, amphibolite, granulite facies 2 granulites are dry rocks dont melt due to lack of available water granulite facies terranes represent deeply buried and dehydrated roots of the continental crust fluid inclusions in granulite facies rocks of s. This paper studies magnetic properties and composition of granulitefacies rocks of both the neogene and archean continental lower crust in the neogene xenolithbearing hannuoba alkaline basalt and the exposed lower crustal section in the archean huaian terrain wayaokou manjinggou profile, the northern north china craton. Wikipedia has a good list of the minerals possible in each facies. The diagrams presented here show that melt loss at a given temperature has a significant influence on both uptemperature and downtemperature stable mineral assemblages. 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. Texture, composition, and age variations in monazite from. The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. Gold distribution in archeanprecambrian granulite facies terrains from bahia state, brazil, is investigated by means of flameless a. Metamorphism of pelitic rocks metapelites springerlink. The composition range of common mafic rocks is shaded. As the chart below shows, certain facies are associated. Winter 2001 an introduction to igneous and metamorphic petrology. Consequently, a reinvestigation of the temperature and pressure conditions during regional metamorphism was undertaken.
Norway are co 2rich, whereas those in the amphibolite facies rocks are h. Bhattacharya a, sen sk 1986 granulite metamorphism, fluid buffering and dehydration melting in the madras charnockites and metapelites. Granulite facies article about granulite facies by the. Amphibolite facies to granulite facies reactions in experimentally deformedo unpowdered amphibolite bru. Granulite facies definition of granulite facies by the. Granulite definition of granulite by merriamwebster. The preservation of granulite facies mineral assemblages is an important feature in understanding highgrade processes in the middle to lower continental crust.
Crustal structure and tectonics of the northern part of the. The role of water activity, however, complicates characterization of the amphibolitegranulite facies transition. A pelitic or calcareous rock will develop very different mineral assemblages from a metabasalt, yet the same facies names apply. Granulite facies definition of granulite facies by the free. There seems now to be a broader recognition of the variety of pt paths and tectonic settings to be found in granulitefacies terrains. Ansrucr reactions in mafic amphibolite marking the transition from amphibolite to granulite. 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. Types and facies of metamorphismmetamorphism is the process that engages the structural and compositional changes that took place during solid rock information as imposed by physical and chemical elements whereby the change is subjected at nearearths exterior zone of weathering and diagenesis 200oc, 300 mpa. Most xenoliths found are pyroxeneplagioclase orthogneisses, although quartzo. Garnet smnd ages from granulite facies fabrics near the northeastern margin of the malaspina pluton constrain the timing for initiation of crustal extension.
There seems now to be a broader recognition of the variety of pt paths and tectonic settings to be found in granulite facies terrains. One might suppose that the middle crust in the sg3 area can be represented by rocks similar in age and composition of the protoliths to the sg3 archaean complex but metamorphosed under conditions of hightemperature amphibolite and granulite facies. The granulite and hornfels facies were named after the textures of the rocks, with hornfels being the rocks commonly found in contact metamorphic aureoles high temperature, low pressure environments and granulites being coarse grained rocks with a granulitic texture and being generally free of hydrous minerals. Metamorphic facies defined and explained thoughtco. Monometamorphism is a metamorphism resulting from one metamorphic event fig. Granulite facies complexes how is granulite facies. Texture, composition, and age variations in monazite from the lower amphibolite to the granulite facies, longstaff bluff formation, baffin island, canada september 2009 the canadian mineralogist. Petromagnetic properties of granulitefacies rocks from.
Sedimentary facies and sediment composition changes 115 cm, and 159960c25x2, 41. The trace element compositions of samples from exposed granulite facies terrains and 17 granulitic lower crustal xenoliths were determined using an inductively coupled plasma. Thus, one can refer to a greenschist facies pelitic schist, an amphibolite facies calcsilicate rock, or a. Learn vocabulary, terms, and more with flashcards, games, and other study tools.
The aim of the scmr was to define amphibolite and granulite in accordance with its general. Geochemistry of gold in archean granulite facies terrains. Geochemistry of exposed granulite facies terrains and. That mineral suite is taken as a sign of the pressure and temperature that made it. Melt loss and the preservation of granulite facies mineral. Franz, in reference module in earth systems and environmental sciences, 2015. Granulite facies metamorphic rocks principally occur in the following broad types of setting. A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures. Granulite article about granulite by the free dictionary. You may make use of these photographs for bona fide educational purposes. The buchan facies series of regional metamorphism is characterized by the presence of andalusite, and sometimes cordierite, in intermediate grade mineral assemblages indicating that the conditions of metamorphism were at lower pressure and along a higher metamorphic field gradient than that recorded in barrovian facies series metamorphic rocks. Amphibolitefaciestogranulitefacies reactions in experimentally deformedo unpowdered amphibolite bru. Metamorphic facies represent specific pressure and temperature conditions.
Types and facies of metamorphism essay example graduateway. Such basement complexes are often of relatively uniform grade, but also may show some variation towards. Recognizing iocg alteration facies at granulite facies in. Crustal structure and tectonics of the northern part of. Each facies has several mineral assemblages unique to that facies. Pdf constraints on granulite genesis from carbon isotope. Granulite definition is a granular metamorphic rock consisting mainly of feldspar and quartz. Main types of metamorphism regional metamorphism is a type of metamorphism which occu rs over an area of wide extent, that is, affecting a large rock vo lume, and is associated with largescale tectonic processes, such. Granulite facies synonyms, granulite facies pronunciation, granulite facies translation, english dictionary definition of granulite facies. Eclogite forms at pressures greater than those typical of the crust of the earth. Granulite facies character of rocks studied by bugge in the arendal region has here been partially overprinted by later metamorphism and granitisation.
A metamorphic rock consisting of similarly sized, interlocking minerals, especially feldspar, quartz, and garnet, and lacking the layering and foliation. Geochemistry of exposed granulite facies terrains and lower. Texture, composition, and age variations in monazite from the. Sassi, department of mineralogy and petrography, university of padova, italy. Garnet growth in mediumpressure granulite facies metapelites. Amphibolite and granulite recommendations by the iugs subcommission on the systematics of metamorphic rocks. Ppt ch 25 metamorphic facies powerpoint presentation. Changes in mineralogy depends very much on protolith, however, production of pyroxene, microcline and sapphirine are most characteristic. Recognizing iocg alteration facies at granulite facies in the. Granulite gallery petrological features of granulites, charnockites and migmatites.
Granulite facies is a highgrade metamorphic facies associated with orogenic regional metamorphism. To sum up, a metamorphic facies is the set of minerals found in a rock of a given composition. Crustal structure and tectonics of the northern part of the southern granulite terrane, india v. An unusually dense rock, eclogite can play an important role in driving convection within the solid earth.
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