A metamorphic rock composed chiefly of amphibole and plagioclase feldspar and having little or no quartz. This is the reason why most names of individual meta morphic facies are derived from mineral assemblages of this rock group. Thickness, from the upper contact to the first appearance of relict sedimentary structure, ranges approximately 1 to 20 feet 0. Partial melting of metavolcanics in amphibolite facies. Rocks which contain certain minerals can therefore be linked to certain tectonic settings, times and. Metamorphism of mafic rocks first evident in the greenschist facies, which correlates with the chlorite and biotite zones of associated pelitic rocks. A significant proportion of gold production from the archean yilgarn craton in western australia has come from lode and veinstyle deposits hosted in amphibolite and granulite facies metamorphic rocks rather than in greenschist facies terranes, which are the normal hosts of such deposits in. Amphibolite facies definition of amphibolite facies by. For sale by the books and openfile reports section u. These were formed during a first metamorphic event m1a which is characterized by a.
The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. Angular particles, green to grey colored, ranging in size from pebbles to boulders. Basic rocks metamorphosed to the eclogite facies are eclogites, containing the green sodic pyroxene called omphacite and garnet. This facies grades into the greenschist facies under less intense metamorphic conditions and. The aim of the scmr was to define amphibolite and granulite in accordance. This file is licensed under the creative commons attributionshare alike 3. Melting studies of basaltic materials have been restricted to equilibrium studies conducted with rock powders. On the other hand, coals that sharply overlie nonrooted faciesparticularly higher energy sandstone and conglomerate facieswere eroded and transported from a nearby peatforming environment and are genetically related to underlying sediments mccabe, 1984.
If the file has been modified from its original state, some details such as the timestamp may not fully reflect those of the original file. Phase equilibrium modelling suggests that melts from the metamorphic rocks have implications with the. Gold deposits in amphibolite and granulite facies terranes. Epidoteamphibolite facies, one of the major divisions of the mineralfacies classification of metamorphic rocks, the rocks of which form under moderate temperature and pressure conditions 250400 c 500750 f and up to 4 kilobars 1 kilobar equals about 15,000 pounds per square inch. The metatexites are characterized by centimetrescale segregation of melt into leucosomes to form stromatic migmatite. Late neoproterozoic amphibolitefacies metamorphism of a pre. Amphibolite facies article about amphibolite facies by. A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures. Metamorphic field gradients as rocks are pushed deeper into the earth as a result of tectonism, they will encounter four stages during which temperature and pressure change in the rock in different ways. Pdf variscan amphibolitefacies rocks from the kurtoglu. Amphibolite facies synonyms, amphibolite facies pronunciation, amphibolite facies translation, english dictionary definition of amphibolite facies. The regional amphibolite facies retrograde overprint, which has been widely documented by previous studies e.
Geological survey, federal center, box 25425, denver, co 80225. The hornblende is, green to yellow green to light brown. Layered facies described as alternating layers of lightcolored biotitequartzplagioclase gneiss and amphibolite. In higher pressure facies series it is not well known whether metavolcanic rocks dehydrate. Sassi, department of mineralogy and petrography, university of padova, italy. In lower pressure facies series, metavolcanics will be represented by granulites rich in orthopyroxene when dehydration occurs at much lower temperatures than melting. In this study, laser ablationinductively coupled plasmamass spectrometry laicpms analyses of pyrite and pyrrhotite, along with. Typical minerals include chlorite, albite, actinolite, epidote, quartz, and possibly calcite, biotite, or stilpnomelane.
It can be produced through the metamorphism of mafic igneous rocks such as basalt and gabbro, or from the metamorphism of clayrich sedimentary rocks such as marl or graywacke. This facies series is called the hornfels facies series or the contact facies series. Abstract upper amphibolite facies felsic gneiss from broken hill records the metatexite to schlieren diatexite to massive diatexite transition in a single rock type over a scale of tens to hundreds of metres. Amphibolite facies an overview sciencedirect topics. Late neoproterozoic amphibolitefacies metamorphism of a. Partial melting of metavolcanics in amphibolite facies regional. Sassi 5, rolf schmid6 1 institute of geological sciences, polish academy of sciences, warsaw, poland 2 cnrs. Amphibolite facies definition of amphibolite facies by the. Where possible, the greenschistfacies and the epidoteamphibolite and amphibolitefacies groups are divided into three facies. The luusika bouguer anomaly source is placed within the alutaguse domain, which is characterized by amphibolite facies rocks that pass towards granulite facies rocks bogdanova et al. An older metamorphic suite comprises arcrelated, granulitefacies assemblages less than 5 kbar and 860 to 920c dated at ca.
Massive facies described as a granodiorite gneiss with a uniform texture, grain size, and color. The names amphibolite and granulite have been used in geological literature for nearly 200 years. Amphibolitefaciestogranulitefacies reactions in experimentally deformedo unpowdered amphibolite bru. Ansrucr reactions in mafic amphibolite marking the transition from amphibolite to granulite. Group comprises a series of metasedimentary rocks of the amphibolite facies with. The concept was first defined in 1914 by a finnish petrologist, pentti eelis eskola, as any rock of a. Less intense temperatures and pressures form rocks of the. Amphibolite facies, one of the major divisions of the mineralfacies classification of metamorphic rocks, the rocks of which formed under conditions of moderate to high temperatures 500 c, or about 950 f, maximum and pressures. Amphibolite facies is a result of continuing burial and thermal heating after greenschist facies is exceeded. The suite includes eclogite, amphibolite, clinopyroxenite, garnet websterite, granulite, and spinel peridotite nealey and sheridan 1989. Rocks which contain certain minerals can therefore be linked to certain tectonic settings.
Partial melting of amphibolitefacies cummingtonite and biotitebearing metavolcanics compared to metapelitic compositions. Seven rbsr mineral isochron ages date amphibolite facies fluid infiltration at 414. Background pioneered by goldschmidt 1911, 1912 from study of contact metamorphosed pelitic, calcareous, and psammitic hornfelses. The estimated pt conditions are in favor of their metamorphism under epidote amphibolite 550. Late neoproterozoic amphibolitefacies metamorphism of a precaledonian basement block in southwest wedel jarlsberg land, spitsbergen. Garnet group minerals from the amphibolite facies metamorphic. Pdf amphibolite facies and granulitefacies metamorphism in the. The metamorphic paragenesis of hornblende plus plagioclase in basic rocks is the basis for the original definition of this facies. Amphibolite and granulite recommendations by the iugs subcommission on the systematics of metamorphic rocks. Metamorphic devolatilization of basalts across the. The effects of amphibolite facies metamorphism on the.
This file contains additional information such as exif metadata which may have been added by the digital camera, scanner, or software program used to create or digitize it. Rocks of prehnitepumpellyite, greenschist and epidote amphibolite facies occurring at depths of 96000 m in the kola superdeep borehole section have a common origin and, in general, they do not differ much from the rocks selected at the outcrops elsewhere in the pechenga complex glebovitsky, 1973. Amphibolite definition of amphibolite by the free dictionary. 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. Contains shiny black biotite plates and distinctive magnetite grains.
Amphibolite is a rock of convergent plate boundaries where heat and pressure cause regional metamorphism. Samples from beaverdam creek are well foliated, schistose to gneissic rocks composed primarily of quartz, plagioclase, epidote, and hornblende, typical of the epidote amphibolite facies. Amphibolite and granulite british geological survey. Phase equilibrium modelling of the amphibolite facies metamorphism in the yelapa1 chimo metamorphic complex, mexico 2 3 fabia. Although brongniart described amphibolite as a rock composed of amphibole and plagioclase, in those early days the meaning of the term was variable.
Durmishaj2 1faculty of science, university of sarajevo, bosnia and herzegovina 2faculty mining and metallurgy, department of mineral deposits, mitrovica, kosovo. Metamorphic rock metamorphic rock metamorphic facies. Download figure caption and tables supplementary material. Nov 11, 2012 metamorphic facies the metamorphic facies are groups of mineral compositions in metamorphic rocks, that are typical for a certain field in pressuretemperature space. A younger, overprinting, collisionrelated metamorphic suite comprises amphibolitefacies assemblages 7. The geology of 700 km of highgrade metamorphic rocks from doubtful sound, new zealand, is described. The trace element composition of pyrite has been used to explore for hydrothermal ore deposits and to understand oreforming processes. Pdf we present new geochronological, geochemical, and petrological data of metapelitic and metabasitic rocks of the krone metammorphic terrane, which. In higher pressure facies series it is not well known whether metavolcanic rocks dehydrate or melt at temperatures lower or similar to that of metapelites. Media in category amphibolite the following 58 files are in this category, out of 58 total. The lowermost zone of the amphibolite facies is the hornblendeactinolite zone, which forms a 3. Xenocrysts of pyroxene, amphibole, plagioclase and quartz are common in the latite tyner 1984, and have been interpreted as originating in the lower crust to upper mantle. Types, grade and facies of metamorphism recommendations by the iugs subcommission on th e systematics of metamorphic rocks. Phase equilibrium modelling of the amphibolite facies.
Douglass1 prepared in cooperation with state of alaska department of natural resources, division of geological and geophysical surveys open file report 9129. Metamorpic facies metamorphic facies concept introduced. New london consists of a layered facies and a massive facies. Metamorphic facies the metamorphic facies are groups of mineral compositions in metamorphic rocks, that are typical for a certain field in pressuretemperature space. Mineral chemistry and geothermometry of amphibole and. Metamorphic facies the concept of metamorphic facies. Amphibolite facies article about amphibolite facies by the. Amphibolite facies togranulite facies reactions in experimentally deformedo unpowdered amphibolite bru. Metamorphic facies series q q q traverse upgrade through a metamorphic terrane should cross through a sequence of zones and facies that reflect the pt gradient of metamorphism within the terrane led miyashiro 1961, 1973 to introduce concept of metamorphic facies series for progressive sequences myashiro initially proposed five facies series.
Rocks of prehnitepumpellyite, greenschist and epidoteamphibolite facies occurring at depths of 96000 m in the kola superdeep borehole section have a common origin and, in general, they do not differ much from the rocks selected at the outcrops elsewhere in the pechenga complex glebovitsky, 1973. Highgrade metamorphism of upper amphibolite facies and strong deformation has obliterated all primary features. The effects of amphibolite facies metamorphism on the trace. Paleoproterozoic amphibolite facies retrogression and. However, the effects of metamorphism on the trace element distribution in pyrite have received relatively limited attention. Albiteepidote hornfels facies z likely to be recognized only in the outermost parts of thermal aureoles in country rocks originally of very low metamorphic grade. The granulite and hornfels facies were named after the textures of the rocks, with hornfels being the. Rocks in most archean gneiss belts are metamorphosed at the amphibolite facies. This is the lowpressure equivalent of the greenschist facies, and the assemblages are very similar.
This file contains representative major element compositions wt. Metamorphic facies q q q q concept introduced by eskola 1915 to describe sets of repeatedly associated metamorphic mineral assemblages that reflect metamorphism of different rock types under the same, restricted range of pt conditions. The isb experienced multiple episodes of amphibolitefacies metamorphism that reached. Geology of the granulite and amphibolite facies gneisses of doubtful. Metamorphic facies map of southeastern alaska distribution, facies, and ages of regionally metamorphosed rocks by cynthia ouselbacon, david a. Prismatic crystals elongated along 001 or 100, perhaps the largest of any species, to 50 m and,500 t. Basic rocks metamorphosed to the amphibolite facies are amphibolites, containing mostly hornblende and plagioclase. The rocks have complex structural and metamorphic histories. The namegiving rock is amphibolite, a dense and dark green to black rock generated by metamorphism under moderate temperature ca.
Less intense temperatures and pressures form rocks of the epidoteamphibolite facies, and more intense temperatures and pressures form rocks of the granulite facies. These are the first experiments ofthis type at high pressure using unpowdered rock and the first using unpowdered mafic rock. Further burial and metamorphic compression but little extra heat will lead to eclogite facies metamorphism. The pt conditions in the peak and retrograde stages are constrained to 78 kbar and c. Which metamorphic facies can be found in e a greenschist b. Where possible, the greenschist facies and the epidotearnphibolite and arnphibolite facies groups are divided into three facies series based on pressure. Most parts of the central block is built up of amphibolite facies rocks. Show full abstract amphibolite facies and they record two major orogenic periods.
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