Greenschistlike rocks can also be formed under blueschist facies conditions if the original rock contains enough magnesium. Fedele, l, tramparulo, fda, vitale, s, cappelletti, p, prinzi, ep and mazzoli, s 2018 petrogenesis and deformation history of the lawsonitebearing blueschist facies metabasalts of the diamanteterranova oceanic unit southern italy. A blueschist is a fine to mediumgrained, foliated, metamorphic rock dominated by glaucophane, crossite or riebeckite. In between, 4 metamorphic zones from high to low grades have been delineated. Phase relations in the greenschistblueschistamphiboliteeclogite facies in the system na 2 ocaofeomgoal 2 o 3sio 2h 2 o ncfmash, with application to metamorphic rocks from samos, greece. Ductile thrusting recorded by the garnet isograd from. 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. Such a progression is termed a facies series, and in general terms this would be called a high pressure facies series, as shown in the diagram below. Facies definition of facies by the free dictionary. Retrograde pumpellyite in the yunotani garnet blueschist of the omi area, japan. Retrograde pumpellyite in the yunotani garnet blueschist of. At that time doubts had arisen whether glaucophane was only stable at elevated pressures or also under greenschist facies conditions.
Biology the general aspect or outward appearance, as of a given growth of flora. The time of eclogite facies metamorphism has not been dated radiometrically, but. The blueschistgreenschist facies transition for a model basaltic system na 2 ocaomgoal2o 3sio2h 2 o is defined by a univariant reaction. The pbc have morblike major and trace element concentrations, contain 5 wt% water, and a naamphibole free mineral. All the protoliths were subducted, metamorphosed to blueschisteclogite. Sep 28, 2019 schuster, 1970a which has the facies of a small frullania and agrees with frullania in leaf insertion and branching, has a nontiered seta with 16 epidermal cell rows surrounding 4 inner rows. In thermally immature rocks, organic facies can be determined by kerogen typing. Highpressure, lowtemperature metamorphism associated with subduction zones which produces a broad mineral association including glaucophane, actinolite.
Sugozu nappe, which was affected by the blueschist facies to eclogite. Eclogite fades regional metamorphism of hydrous mafic. This is the lowpressure equivalent of the greenschist facies, and the assemblages are very similar. Halfmicron sized lamellae of phengite were observed intergrown in paragonite, but not vice versa. Abstract blueschists in the yilan area, heilongjiang province, are known as important parts of the heilongjiang complex. Sassi 5, rolf schmid6 1 institute of geological sciences, polish academy of sciences, warsaw, poland 2 cnrs. Blueschist facies is determined by the particular temperature and pressure conditions required to metamorphose basalt to form blueschist.
Phase relations in the greenschist blueschist amphiboliteeclogite facies in the system na 2 ocaofeomgoal 2 o 3sio 2h 2 o ncfmash, with application to metamorphic rocks from samos, greece. Separate episodes of eclogite and blueschist facies metamorphism. Eclogite facies conditions of thermodynamic stability of eclogites, defined with respect to the principal factors of metamorphism. Thickness, from the upper contact to the first appearance of relict sedimentary structure, ranges approximately 1 to 20 feet 0. Blueschist accessscience from mcgrawhill education. Ppt ch 25 metamorphic facies powerpoint presentation free.
Jadeite andor lawsonite were considered to be more reliable pressure indicators. Reaching the conditions of the epidoteblueschist facies, requires a perturbation of the modeled steadystate pt trajectory, and the essential component is heating at a higher rate figure 2, location 2. Eclogite facies synonyms, eclogite facies pronunciation, eclogite facies translation, english dictionary definition of eclogite facies. This file is licensed under the creative commons attributionshare alike 3.
The phengite has l5 mole% na substituting for k, and the paragonite has 7 mole% k substituting for na. Coexisting paragonitephengite in blueschist eclogite. Winter 2010 an introduction to igneous and metamorphic petrology. Primary fluids entrapped at blueschist to eclogite transition. H2o, is an index mineral for highplowt hplt blueschist and eclogitefacies mafic rocks. Blueschists are formed by low temperature, high pressure blueschist facies regional metamorphism of basaltic protoliths. Hf units higher than the probable initial hf isotopic composition of the protolith can be explained by radiogenic 176hf ingrowth from an elevated 176lu177hf phase i. Primary fluids entrapped at blueschist to eclogite.
Eclogite facies article about eclogite facies by the. Pdf ptt evolution of eclogiteblueschist facies metamorphism in. Blueschistfacies metamorphism is important in subduction zones, where. The epidote grades contain two varieties, a garnet. Convection occurs if the lower part of a fluid body is hotter than the upper part, hot fluid rises away from the heat source bringing heat to. Significance of the cana pyroxenelawsonitechlorite. Paleozoic lawsonitebearing lowgrade metabasalts with rare flattened pillow structures occur in the chugoku mountains, southwest japan. Eskola proposed a glaucophaneschist facies of regional metamorphism.
It is properly defined on the basis of color, bedding, composition, texture, fossils, and sedimentary structures. 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. Jun 23, 2001 the tianshan is the first locality worldwide where primary fluids at blueschist to eclogite transition have been documented. Epblueschist subfacies, in other words to the uppermost pt conditions of the pmpblueschist subfacies. The blueschists, which contain lawsonite and glaucophane or. Highpressure greenschist to blueschist facies transition in the maimon formation dominican republic suggests midcretaceous subduction of the early cretaceous caribbean arc. Blueschist metamorphism in the yrekafort jones area. According to jones, this technique mainly relies on 1 kerogen identification adequately reflecting petroleum generative potential, 2 kerogen distribution being neither random nor capricious, and 3 the distribution of similar kerogen extending over tens to hundreds of. Rock assemblages of eclogite and blueschist in many subduction or suture zones have been reported. Ptt evolution of eclogiteblueschist facies metamorphism in. The blue color of the rock comes from the presence of the predominant minerals glaucophane. Subduction and accumulation of lawsonite eclogite and garnet. A coarsegrained greenish rock consisting primarily of garnet and sodic pyroxene, and often including quartz, kyanite, and rutile.
Fault rocks within the blueschist metabasalts of the diamante. They also frequently contain lawsonite, epidote, albite, quartz, muscovite, chlorite, andor garnet. It is noteworthy that the samples deduced to have come from thicker. Convection occurs if the lower part of a fluid body is hotter than the upper part, hot fluid rises away from the heat source bringing heat to the cooler material away from the heat source. Veins containing highpressure minerals in massive host eclogites transitional to blueschists, or eclogite boudins surrounded by blueschists, indicate that a free fluid phase was present at the time of eclogitization. The structural evidence and the pressuretemperature paths of the different blocks suggest coupling between blocks and matrix, at least in the blueschist facies. Blueschist facies metamorphism and its evolution in the yilan area. Types, grade and facies of metamorphism recommendations by the iugs subcommission on th e systematics of metamorphic rocks.
Blueschistfacies assemblages form at high pressures 800 megapascals, or mpa yet low temperatures republic suggests midcretaceous subduction of the early cretaceous caribbean arc. Blueschist is plentiful in the yrekafort jones area, eastern klamath mountains, adjacent to a belt of serpentinite that marks the boundary between two fundamental lithologic units, an eastern belt of early paleozoic sedimentary and metamorphic rocks, and a western greenstonechert assemblage of late paleozoic and triassic. The highpressure, lowtemperature metamorphic rocks known as blueschists have long been considered to form in subduction zones, where the descent of a relatively cold slab leads to the occurrence. Fault rocks within the blueschist metabasalts of the. Metamorphic style and development of the blueschist to. Mineral assemblages from zone i ep free zone of shibakusa 1989 are stable around the following reaction. The highpressure, lowtemperature metamorphic rocks known as blueschists have long been considered to form in subduction zones, where the descent of a. The metamafic rocks are divided into metapillow basalt core pbc, metapillow basalt rim pbr, and metabasaltic breccia bb. The stability of cana pyroxene in lowgrade metabasites. High pt sanbagawa or franciscan facies series facies series. Maruyama and liou, 1988 rather than prehnitepumpellyitefacies pumpellyite cf. Eclogite facies definition of eclogite facies by the free. Retrograde pumpellyite in the yunotani garnet blueschist.
Eclogite facies article about eclogite facies by the free. Blueschist, blueschist facies and blueschist facies rocks the name blueschist was established by bailey in 1962. Indosinian epoch collsional orogenic belt in the lhasa terrane, tibet. Metamorphic facies the concept of metamorphic facies. High pt metamorphic rocks british geological survey. Phengite is predominantly a wellordered 2m, polytype almost free of stacking disorder, except for phengite lamellae intergrown within paragonite. Subduction and accumulation of lawsonite eclogite and. Worlds best powerpoint templates crystalgraphics offers more powerpoint templates than anyone else in the world, with over 4 million to choose from. The blueschist facies has been subdivided into the epidote blueschist facies ebs evans, 1990 or glaucophane greenschist facies and lawsonite blueschist facies lbs dong, 1989, evans, 1990.
In contrast, the pbr and bb contain a lawsoniteblueschistfacies mineral assemblage. Pdf the alanya massif, which is located to the south of central taurides in turkey, presents a. The lbsebs transition has been extensively studied. Nitsch 1968 and liou 1971 independently determined the minimum. Ppt ch 25 metamorphic facies powerpoint presentation. More recently the term blueschist facies has been preferred because glaucophane is not always developed in many important rock types, for example, graywacke sandstones, which may contain other minerals that are characteristic of high pressure and low.
Physical geology, metamorphic rocks, compositional classes, metamorphic grades, metamorphic facies duration. Blueschist facies metamorphism of peralkaline rhyolites. An update on the cooling path yuzuki shinji and tatsuki tsujimori, department of earth science, tohoku university, sendai 9808578, japan center for northeast asian studies, tohoku university, sendai 9808576, japan retrograde pumpellyite was newly found in garnet blueschist that is mgrich. Reaching the conditions of the epidote blueschist facies, requires a perturbation of the modeled steadystate pt trajectory, and the essential component is heating at a higher rate figure 2, location 2. Temperaturepressure diagram showing the generally accepted limits of the various facies used in this text. In the late paleozoic blueschist localities in the hidagaien belt and the chugoku moun. Read transitional blueschistepidote amphibolite facies metamorphism in the frankenberg massif, germany, and geotectonic implications, journal of metamorphic geology on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
A low geothermal gradient of around 10 o km would cause prograde metamorphism to occur along a sequence of facies from zeolite to blueschist to eclogite. Fe2o3 in the metamorphic evolution of blueschistfacies rocks yielded. Pdf eclogite, amphibolite and blueschistfacies rocks from diego. Miyashiro 1961 proposed five facies series simplified to. Blueschist facies metamorphism of peralkaline rhyolites from.
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. Blueschist facies an overview sciencedirect topics. Theyll give your presentations a professional, memorable appearance the kind of sophisticated look that todays audiences expect. Experimental investigations of blueschistgreenschist. Winner of the standing ovation award for best powerpoint templates from presentations magazine. The highpressure veins are predominantly composed of. The blueschist greenschist facies transition for a model basaltic system na 2 ocaomgoal2o 3sio2h 2 o is defined by a univariant reaction.
Goldschmidt 1911, 1912a contact metamorphosed pelitic, calcareous, and psammitic hornfelses oslo s. A facies is a body of rock with specific characteristics. Parageneses and compositions of minerals yield equilibrium pt conditions of t free of stacking disorder, except for phengite lamellae intergrown within paragonite. Eclogite facies metamorphism in sugozu nappe, which consists of homogeneous. Lawsoniteblueschist facies metamorphic rocks as a reservoir.
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