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. Blueschist accessscience from mcgrawhill education. Facies represent specific temperature pressure regimes. Unlimited viewing of the articlechapter pdf and any associated supplements and figures. Metasomatic formation and petrology of blueschistfacies. Blueschistfacies metamorphism is important in subduction zones, where highpressure, relatively lowtemperature mineral assemblages form. Whereas blueschist epidotes show very high fe content 79. Blueschist, eclogite, paired metamorphic belts, and the. The highpressure, lowtemperature metamorphic rocks known as blueschists have long been considered to form in subduction zones, where the descent of a. Blueschists form only under the unusual conditions of extremely high pressures and relatively low temperatures that are characteristic of subduction zones. Ptt evolution of the cycladic blueschist unit in western.
Eclogite, amphibolite and blueschistfacies rocks from. To clarify the origin of these metamorphic clasts, major and rare earth elements ree, ba, and sr were measured in seven blueschist facies metabasite clasts. 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. Discrete, faultbounded packages of blueschist eclogite facies mafic rocks with minor serpentinite are also present. Syros island is part of the atticcycladic blueschist belt, and mineral assemblages indicate peak metamorphic conditions of at least 1516 kbar and 500c. Thereby, these rocks do not appear blue overall in color.
Types, grade and facies of metamorphism recommendations by the iugs subcommission on th e systematics of metamorphic rocks. The hp event blueschist facies was dated at 358365 ma with the 40 ar 39 ar phengite and rbsr whole rock, phengite, and epidote methods, while a younger age of 345353 ma was determined for the greenschist metamorphic event using the same methods bosse et al. The metabasic rocks, including eclogites, blueschists, and actinolitebearing rocks, are discussed in terms of their. Blueschistfacies metapelites from the malpicatui unit. In central hispaniola 80 km south is a parallel greenschist belt.
Published estimates on the equilibration conditions of blueschistfacies alpine cherts vary widely. Metasomatic formation and petrology of blueschistfacies hybrid rocks from syros greece. A greenschist protolith for blueschist in anglesey, u. Determining the upper and lowerpressure stability of endmember glaucophane places important constraints on the conditions of blueschist metamorphism. Condie, in earth as an evolving planetary system second edition, 2011. The metamorphism on the island of sifnos is characterized by the eocene development of a coherent highpressure blueschist terrane and an early miocene greenschist facies overprint.
Under more typical conditions, this is the greenschist facies, and in a subduction zone it is the blueschist facies. 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. Pdf an oligocene extrusion wedge of blueschistfacies. Metamorphic sole formation, emplacement and blueschist. This explains the scarcity of blueschist preserved from before the neoproterozoic era ma ago when the earths oceanic crust contained more magnesium than todays oceanic crust. Metamorphic style and development of the blueschist. We present the first data on bulkrock major and trace element compositions for a suite of eclogite and blueschist facies rocks from the bantimala complex, indonesia, with the aim of better constraining the protolith origins and nature of the subducted c. The northern part of the cycladic island of sifnos greece is formed by a coherent sequence of interlayered acid and basic metavolcanic rocks and metasediments, which underwent a highpressure blueschist facies metamorphism during the eocene. Facies metamorphism in the active subduction zone beneath the mariana forearc. Metamorphic facies the metamorphic facies are groups of mineral compositions in metamorphic rocks, that are typical for a certain field in pressuretemperature space.
The blueschist facies rocks of the schist belt were exhumed between late jurassic and middle albian time, during the major pulse of contractional deformation in the brooks range orogeny, rather than during. Greenschist facies results from low temperature, moderate pressure metamorphism. Low na m4 values in unaltered actinolitic cores are similar to those in. Sivrihisar massif, lawsonite eclogite occurs as 5cmlong to 3. Petrogenesis of lawsonite and epidote eclogite and. 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. The blueschist unit contains metagraywacke, metashale, metaconglomerate, greenstone, quartz schist, blueschist, and eclogite blocks in a finegrained, schistose matrix which probably recrystallized from a mixture of ultramafic and clayrich, quartzose detritus. 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. Named for equivalent mafic rock type at those conditions. Eclogite facies metamorphism in sugozu nappe, which consists of. Blueschist facies metamorphism is important in subduction zones, where highpressure, relatively lowtemperature mineral assemblages form.
Phase relations in the greenschistblueschistamphibolite. Fe2o3 in the metamorphic evolution of blueschistfacies rocks yielded firstorder. Protolith origin and tectonic setting article pdf available in island arc 224. Blueschist facies an overview sciencedirect topics. Such a scatter is due to the yet insufficient experimental knowledge on the mnsialooh system, including the nearly complete lack of determinations of the influence of other. The island consists mainly of i faultbounded packages of blueschisteclogitefacies mafic. The blueschist facies rocks of the schist belt were exhumed between late jurassic and middle albian time, during the major pulse of contractional deformation in the brooks range orogeny, rather than during late stage extensional collapse or postcontractional isostatic rebound, as suggested by other workers. Ch 25 metamorphic facies 1 ch 25 metamorphic facies 2. Implications for reactions at the slabmantle interface.
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. Ppt ch 25 metamorphic facies powerpoint presentation free. Pdf hydrothermal blueschist facies zircons from the. Blueschistfacies metamorphism is important in subduction zones, where high pressure, relatively lowtemperature. Low na m4 values in unaltered actinolitic cores are similar to those in actinolites formed during seafloor metamorphism. Pdf eclogite, amphibolite and blueschistfacies rocks from diego. Blueschist facies metamorphism, which is associated with high pressure and low temperature subduction zone metamorphism, is usually recognized by the presence of the sodicamphibole glaucophane. The rock contains a relict blueschist assemblage of glaucophane, epidote, and rutile with pervasive retrograde overprint, first under amphibolite, and subsequently, greenschist facies conditions. Geochemistry of eclogite and blueschistfacies rocks from. Blueschist facies and greenschist facies metamorphism occurred during the late ordovician to early silurian. Felsic rocks and pelitic sediments which are subjected to blueschist facies conditions will form different mineral assemblages than metamorphosed basalt. Use these facies if clearly associated with a pluton.
The sivrihisar massif, turkey, is comprised of blueschist and eclogite facies metasedimentary and metabasaltic rocks. Metamorphic style and development of the blueschist to. The acquadolce subunit on the island of elba, italy, records blueschist. Omphacite microstructures as timetemperature indicators of blueschist and eclogitefacies metamorphism. Goldschmidt 1911, 1912a contact metamorphosed pelitic, calcareous, and psammitic hornfelses oslo s.
Blueschist facies article about blueschist facies by the. Amphibolite facies includes calcite marbles, biotite schists and amphibolites. Lawsonite blueschists and lawsonite eclogites as proxies. Geochemistry of eclogite and blueschistfacies rocks from the bantimala complex, south sulawesi, indonesia. Petrology and tectonic setting of blueschist facies metabasites from the emo metamorphics of papua new guinea. 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. Blueschist facies mafic rocks are characterized by the coexistence of sodic amphibole and lawsonite at low. Petrologic and geochemical comparison of the blueschist and.
Blueschistfacies metapelites from the malpicatui unit nw. Structure and metamorphism of blueschist eclogite facies rocks from the ne oman mountains. Revised ages of blueschist metamorphism and the youngest. Petrologic and geochemical comparison of the blueschist. An oligocene extrusion wedge of blueschist facies nappes on evia, aegean sea, greece. Geochemistry of eclogite and blueschist facies rocks from the bantimala complex, south sulawesi, indonesia. Sassi 5, rolf schmid6 1 institute of geological sciences, polish academy of sciences, warsaw, poland 2 cnrs. A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures. The sodic amphibole glaucophane is generally considered as indicative of blueschistfacies metamorphism. The pt stability fields of lawsonite blueschists and lawsonite eclogites represent subfacies of the blueschist and eclogite facies, respectively.
Graduate thesis or dissertation structure and petrography. Blueschistfacies metapelites from the malpicatui unit nw iberian massif. Highpressure greenschist to blueschist facies transition in the maimon formation dominican republic suggests midcretaceous subduction of the early cretaceous caribbean. New evidence of blueschist facies rocks and their geotectonic implication for variscan sutures in the bohemian massif s. Clasts of matrix components and tonalitic plutonic rocks of the ssg melange have been found in exposures of late silurian conglomerate beds in nearby units providing evidence that the ssg was uplifted and eroded by the late silurian. Origin of blueschistfacies clasts in the mariana forearc. Rocks which contain certain minerals can therefore be linked to certain tectonic settings. In the catalina schist terrane, a nappe of blueschist facies melange is overlain by one of isoclinallyfolded greenschist facies rocks.
Peak pressuretemperature conditions were estimated at 10. Early miocene stages of continental collision in the northern apennines. The ages of blueschist facies metamorphism were limited to 750805 ma. Temperaturepressure diagram showing the generally accepted limits of the various facies used in this text. You can make the connection more directly between the metamorphic facies and the types of metamorphism discussed in the previous section by matching up the letters a through e in figure 10. Revised ages of blueschist metamorphism and the youngest prethrusting rocks in the san juan islands, washington. Omphacite microstructures as timetemperature indicators of. Blueschist metamorphism in the yrekafort jones area, klamath. Diagram showing metamorphic facies in pressuretemperature space, with approximately depth marked. Blueschist facies is determined by the particular temperature and pressure conditions required to metamorphose basalt to form blueschist. Eclogiteblueschistfacies rocks from spouthern sifnos. 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. Blueschist metamorphism in the yrekafort jones area.
Metamorphic conditions which create typical greenschist facies assemblages are called the barrovian facies. Worlds best powerpoint templates crystalgraphics offers more powerpoint templates than anyone else in the world, with over 4 million to choose from. In the mariana forearc region, blueschist facies metabasite clasts have been recovered from a serpentinite seamount during ocean drilling program leg 125. Theyll give your presentations a professional, memorable appearance the kind of sophisticated look that todays audiences expect. Geologic trips san francisco and the bay area by ted konigsmark isbn 09661649 geopress. Protolith 25 the blueschist facies is a metamorphic realm of. Eskola proposed a glaucophaneschist facies of regional metamorphism. Hydrothermal blueschist facies zircons from the franciscan complex, california. Eclogiteblueschist relationships as evidenced by mineral equilibria in the highpressure metabasic rocks of sifnos cycladic islands, greece. Highpressure, lowtemperature metamorphism associated with subduction zones which produces a broad mineral association including glaucophane, actinolite. Pdf ptt evolution of eclogiteblueschist facies metamorphism in.
Eclogiteblueschist relationships as evidenced by mineral. Blueschistfacies assemblages form at high pressures 800 megapascals, or mpa yet low temperatures blueschist facies is determined by the particular temperature and pressure conditions required to metamorphose basalt to form blueschist. In general, the mafic rocks have a variety of textures and modes, but most are either finegrained, blueschists with a welldeveloped fabric s approx. Pdf structure and metamorphism of blueschisteclogite.
Metamorphic sole formation, emplacement and blueschist facies. Greenschist facies is determined by the particular temperature and pressure conditions required to metamorphose basalt to form the typical greenschist facies minerals chlorite, actinolite, and albite. Winter 2010 an introduction to igneous and metamorphic petrology. Evolution of the blueschist and greenschist facies rocks. Blueschistfacies metamorphism is important in subduction zones, where highpressure, relatively lowtemperature. Eclogite forms at pressures greater than those typical of the crust of the earth. Blueschist metamorphism in an active subduction zone nature. Winner of the standing ovation award for best powerpoint templates from presentations magazine. Abati abstract the malpicatui unit galicia, nw spain records eclogite and blueschistfacies metamorphism during the onset of the variscan orogeny. 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. Blueschists in major suture zones of china liou 1989.
Metamorphic history of a highgrade blueschist exotic. The blueschists, which contain lawsonite and glaucophane or. At least forty blueschist localities have been described. Rocks which contain certain minerals can therefore be linked to certain tectonic settings, times and. This study documents the metamorphic evolution of the blueschist assemblages, still preserved in the northern parts of the island, and their subsequent transformation into greenschists in the central and southern.
Blueschistfacies metamorphism of manganiferous cherts. The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. Within the pillow basalt there are some thin seams of deep blueschist an inch or so thick. Blueschist facies metamorphism in nordenskiold land of.
Eclogite fades regional metamorphism of hydrous mafic. Eclogite, associated glaucophane and garnetbearing inclusions, serpentinite, micaceous schist and marble, an amphiboliteserpentinitequartz dike complex, and blueschist define a 180kmlong blueschist belt along northern hispaniola. 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. Revised ages of blueschist metamorphism and the youngest pre. New evidence of blueschist facies rocks and their geotectonic. The rock contains a relict blueschist assemblage of glaucophane, epidote, and rutile with pervasive retrograde overprint, first under amphibolite, and subsequently, greenschistfacies conditions. Sugozu nappe, which was affected by the blueschist facies.
Mar 20, 2020 thermodynamic modelling performed for different rock types taking into account the measured fe 2 o 3 contents reveals that sodic amphibole appears at. Lawsonite, blueschist and eclogite formation in the southern. Caroline livermore blunt point stuart point ayala cove simpton point xione point ycamp reynolds zperles beach. Greenschistlike rocks can also be formed under blueschist facies conditions if the original rock contains enough magnesium. Ppt ch 25 metamorphic facies powerpoint presentation. The precise pt conditions for this cool overprint could not be. Importantly, we report here, also for the first time, the observation of a blueschistfacies overprint within the ga unit, visible as blue amphibole rims around hornblende and highersilica phengite rims c. Evolution of the blueschist and greenschist facies rocks of. E h brown, t j lapen, r mark leckie, isabella premoli silva, davide verga, and, b s singer. Petrology and age of precambrian aksu blueschist, nw china. Constraints on the upper pressure stability of blueschist.