Geothermobarometric computation suggests that the M1, M2 and M3 assemblages of the mafic granulite were formed under P-T conditions of ∼800 to 860 °C/∼6 to 10 kbar, ∼620 to 700 °C/11 to 12 kbar and ∼590 to 660 °C/4 to 6 kbar, respectively, suggesting that these granulites record anticlockwise P-T paths including final nearly isothermal decompression (ITD) segments, indicative of orogenic process. 51 Cordierite Cordierite, poikiloblastic, in low-P spotted schist (Buchan type). The pyroxene lamellae suggest that previous supersilicic or, ). Discover (and save!) (D) Quartz (Qtz) lamellae in omphacite from a UHP eclogite (East Kunlun, China). American Mineralogist 89, 1330–1336. The first metamorphic corona around olivine is, palisade Opx, the second is fine-grained Cpx, and the third is garnet corona in contact with the plagioclase pseudomorph. : Porphyroblasts are large euhedral crystals grown during metamorphism, which grow significantly faster. To estimate the initial composition of the titanite before coesite exsolution, exsolved phases were reintegrated by measuring their area fractions on digital images. It requires stress surpassing the elastic threshold and a deformation rate slow enough to, accommodate further strain without breaking of the material (i.e., ductility or plasticity). (G) Cordierite porphyroblasts in a pelitic hornfels (Zhoukoudian, Beijing, China). as controlled by stress and strain. Both strained and unstrained quartz grains also occur. (L) Syntectonic staurolite porphyroblasts showing the helicitic texture with, and larger than the surrounding matrix. plasticity is greatly hindered due to low temperature. This composition requires a pressure higher than 6 GPa on the basis of phase relations in the system CaTiSiO5-CaSi2O5. Polygonal pyroxenes surrounding olivines are likely a product of reaction between primary olivines and a SiO2-rich melt produced by shock. pseudotachylyte (dark matrix) from a metasiliceous rock (Qilian Orogen, China). (A) Plane-polarized and (B) backscattered electron (BSE) images of symplectite showing vermicular intergrowth of Cpx + Pl around omphacite (eclogite from North Qaidam UHP belt). texture well preserved. (E) Multiple coronas of garnet from the East Kunlun eclogite (Song et al., 2018) with inner vermicular intergrowth rim of Cpx + Pl and outer amphibole rim, showing a retrograde process from isothermal decompression to cooling and hydration. 86 Digitised … progressive/retrogressive metamorphic processes, controlled by temperature, pressure, and fluid activity. When dislocations move in the manners of glide and climb, it is called, relation between strain rate and stress. (B) Monomineralic polygonal texture showing sutured boundaries of quartzite. bulk-composition, rare earth elements, isotopic and mineral composition data show that the garnet peridotite derives from a middle Ordovician Alaskan-type layered sub-arc cumulate intrusion of ascending mantle wedge melts. If gliding is the only main mode of dislocation motion, it is called, of dislocation creep, which is often associated with the coordinated glide of the same type of dislocations in a crystal. Kazakhstan. G–I). Nevertheless, brittle deformation can also occur occasionally at high P–T conditions. � (A) Photo was provided by Dr. Yazhou Fan. 2- Granoblastic interlobate: where the grain boundaries are somewhat irregular 3- Granoblastic amoeboid: where all the grains have irregular outlines, and all the minerals are anhedral. Deseta, N., Andersen, T.B., Ashwal, L.D., 2014. Deformation lamellae in quartz are also encountered. Our study demonstrates that crustal material, buried along the subduction interface at HP-LT conditions, can record several successive brittle events in places where deformation is classically envisioned as ductile. (A) Olivine breakdown into serpentine and magnetite during, , the refractory residue (paleosome) in migmatites mainly shows metamorphic textures and melting processes, A) (Song et al., 2014), and (2) dehydration melting in progressive metamorphism from increasing P-T during crustal. For example, slate is a low-grade metamorphic rock generally derived from, mudstone or shale. 4- Granoblastic decussate: where the interlocking … This belt consists of eclogite blocks, metasedi-mentary rocks and minor serpentinite blocks, accompanied by ophiolites (530-460 Ma) and concurrent arc volcanic sequences and granitic plutons. Microscopic observation shows granoblastic texture similar to lunar granulite 79215,55. Austrheim, H., Dunkel, K.G., Plümper, O., Ildefonse, B., Liu, Y., Jamtveit, B., 2017. Microtectonics, 2nd edn Springer-Verlag, Berlin. Coesite/quartz lamellae in garnet, titanite, and chromite are thought to indicate ultrahigh-pressure conditions of greater than 6 GPa (, are identified in Cpx from the diamond-bearing dolomite marble in Kokchetav (, are observed in eclogites, orogenic garnet peridotites, and peridotite xenoliths in, F and G). North Qaidam, China). Figure 9.3: Granoblastic-polygonal texture showing plagioclase (white) with 120° triple junctions, adjoining amphibole (green) and xenoblastic garnet (light brown, included in plagioclase) and opaque minerals (black). Metacarbonates are metamorphosed calcareous (limestone and dolomite) rocks in which the carbonate component is predominant, with granoblastic polygonal texture (Bucher and Grapes 2011). fractures, especially faults and joints. Representative rock types include, polymineralic rocks such as granulite and eclogite, and monomineralic rocks such as quartzite and marble, which are often composed of. Gneiss is a metamorphic rock originated from the high-grade metamorphism of igneous or sedimentary rocks. The ilmenite rods (, Photomicrographs showing exsolution textures in various minerals from metamorphic rocks. The CPO of a mineral can vary with, physicochemical conditions and thus provides useful insights into the pressure, temperature, stress, water activity, and strain geometry and, history during deformation. The texture generally displays a porphyritic mineral of early generation surrounded, exsolution lamellae in two directions from a ~ 1.95 Ga high-pressure granulite (Hengshan, China). boundaries. These are the basic textures that can develop in various types of metamorphism, such as localized contact metamorphism, regional, Earth Systems and Environmental Sciences, Volume ■. failure of surrounding rocks (i.e., hydrofracturing). Figs. As the mineralogy of the gneisses change from clinopyroxene through biotite, the textures grade from granoblastic polygonal to a granoblastic polygonal texture modified by abundant acicular and platy minerals. (C) Lepidoblastic texture consisting of muscovite and, biotite with preferred orientation, which forms the foliation structure of a schist. Because, slate is easily split along its fine foliation, its foliation is also called slaty cleavage. � Brittle deformation structures: (A) fault zone in hosting fractured rock and (B). (A) Metamorphic rhyolite with relict igneous porphyritic feldspar and quartz. � In some places, these deformed rocks (up to mylonitic grade) can be found as clasts within meter-thick brecciated fault rocks that formed close to the lawsonite-eclogite facies peak P-T conditions. Several, mechanisms are responsible for ductile deformation, including, of solid crystals via migration of atoms and vacancies (empty atom sites) through the crystal lattice, which is driven by the chemical, potential gradient exerted by external stress. The groundmass is recrystallized, displaying a granoblastic polygonal texture. This pressure is consistent with other evidence of high pressure in the same marble, such as 1.4-1.8 wt% K2O and over 1000 ppm H2O in diopside. Petrogenesis of Metamorphic Rocks. In fig. This work was financially supported by the National Natural Science Foundation of China (91955202). Cambridge University Press. (I) Ilmenite lamellae in olivine from the Lüliangshan garnet lherzolite. Notice the very narrow biotite flake at lower right, whose basal plane the cordierite boundaries meet at right angles. Uplifting and thermal relaxing trigger breakdown of lawsonite (Lws), epidote, phengite, and amphibole, which induces partial, melting of the subducted crust when crossing over the wet solidus. Moreover, it controls the migration of fluids and melt in the Earth's crust that lead to phase transformations and changes in rock rheology. Mafic and felsic granulite from the Miyun metamorphic complex, northeast Beijing, North China Craton, occur as either interlayers or lenses within the Late Archean TTG gneiss. involving mineral breakdown, melt generation, infiltration, transmission, and congregation. Phlogopite and coesite exsolution from super-silicic clinopyroxene. Therefore, anatexis is the process of a crustal reworking on the convergent plate boundaries. ), intensely hydrothermaly altered (saussuritization, such as lower crust and upper mantle depth, when high stress or pore fluid pressure is present. (H) Cr-spinel needles in Opx from the Lüliangshan garnet lherzolite (North. trail exhibits an “S” shape, it is called a snowball texture. (A) Decompression melting of eclogite (and other ultrahigh-pressure metamorphic rocks), 130: 42–62; (B) Spear FS and Cheney JT (1989) A, Contributions to Mineralogy and Petrology. Carbonate Sedimentary rock Limestones and dolomites Britannica Adakitic (tonalitic-trondhjemitic) magmas resulting from eclogite decompression and dehydration. metastable minerals with complicated solid solutions through ion substitutions at high temperature or pressure. Coesite pseudomorphs in garnet, quartz exsolution rods in omphacite and P-T calculations suggest that some eclogites experienced ultrahigh-pressure (UHP) metamorphic conditions at 29-30 kbar and 610-675 C; these could represent oceanic crust subducted to and exhumed from coesite-forming depths (100-120 km). Crush breccia and cataclasite are cohesive and can be distinguished from each other by matrix fractions, lower and higher than 10 vol%, respectively. van Roermund, H.L.M., Drury, M.R., 1998. Ultra-high pressure (P. Winter, J.D., 2001. In this introductory article, we first provide an overview of how temperature controls deformation mechanisms and processes and then introduce the collection of research papers ordered from those analysing deformation processes occurring at high temperatures to contributions reporting deformation at shallow crustal conditions. Neoarchean metamorphic evolution and. in granulite-facies metamorphic tonalite (East Hebei, China). Photomicrographs showing progressive rims/coronas. The following are some of the types of granoblastic textures: 1- Granoblastic polygonal: where the equidimensional grains may have well developed crystal faces resulting in straight grain boundaries, and where triple junctions are common. It is very fine grained and has a clear foliation defined by consistently aligned mica minerals that are transformed, from clay minerals and is formed mainly through the mechanisms of dissolution-precipitation creep and rigid body rotation. Grain boundary, sliding refers to the relative motion of crystals along their shared grain boundaries under applied stress. � and plagioclase pseudomorph (Pl-Ps)) in a metamorphic olivine gabbro (Polar Urals, Russia). (D) Blastopsammitic textures of low-grade metasandstone. The deformation structures and mechanisms related to metamorphic rocks, mainly falling under brittle and ductile deformation categories, are also summarized. (F). earth elements, isotopic and mineral composition data show that the garnet peridotite derives from a middle Ordovician Alaskan-type layered sub-arc cumulate intrusion of ascending mantle wedge melts. exhumation in response to continental collision. B). Thus, Monviso breccia blocks record the complete, stepwise development of a major shear zone, via progressive strain localization, permeability creation, and increasing scale of fluid circulation. Exsolution lamellae are fine crystals that were dissolved. Whitney, D.L., Evans, B.W., 2010. An Introduction to Metamorphic Petrology. Bright-field (BF)-TEM images show that the ringwoodite-bearing area consists of a polycrystalline assemblage of ringwoodite and wadsleyite in an intergrowth feigning granoblastic-like texture (Fig. Experimental studies document this omphacite to be formed at pressures higher than 6 GPa (at 900 °C). Brittle deformation is closely related to earthquake activity, which is characterized by extremely large stress and a high strain rate. (E) Phlogopite (Phl) lamellae in clinopyroxene from Kokchetav diamond-bearing dolomite marble (provided by Dr. YF Zhu). Ultra-deep origin of garnet peridotite from the North Qaidam ultrahigh-pressure belt, Northern Tibetan Plateau. Photomicrographs of palimpsest (relict) textures. (C) Thin parallel-aligned pseudotachylyte fault veins, (marked by green arrowheads) in a metagranite (Yunnian, China). Alpe Arami: A peridotite massif from depths of more than 300 kilometers. little acCompari Oestroy them. . Geochemistry, Geophysics, Geosystems 20, 5285–5318. of the Sivec dolomite with typical straight and angular. : A mosaic texture of equidimensional, anhedral grains showing regular polygonal (, : Platy minerals, such as muscovite and biotite, developed with strong preferred orientation (, : Linear (acicular or prismatic) minerals, such as actinolite, hornblende, and sillimanite, developed with strong, Photomicrographs of palimpsest (relict) textures. (C) Plane-polarized and (D) BSE images of kelyphite displaying vermicular intergrowth of Opx + Cpx + Sp around pyrope-rich garnet (garnet peridotite from North Qaidam). (B) Monomineralic polygonal texture showing sutured boundaries of quartzite. � � � � � � � � � � � � � � � � � �(v7�� � � � Gomez-Rivas, E., Butler, R.W.H., Healy, D., Alsop, I., 2020. eclogite (North Qaidam UHP metamorphic belt, China). (B), Photomicrographs of crystalloblastic textures. Seismic loading caused massive dislocation formations and fragmentation of wall rock garnets. Traditionally, CPO in a deformed, rock has been interpreted as the result of ductile deformation induced by dislocation creep, because dislocations must slip along specific, crystallographic planes and axes. � In general, mylonite contains very fine-grained, minerals, resulting mainly from dynamic recrystallization and secondarily from cataclasis of coarse-grained porphyroclasts, and displays, Distinct microstructures can be produced by different ductile deformation mechanisms (, kink bands are commonly wedge-shaped, tapered, or tabular, reflecting an abrupt change in crystallographic orientation of part of a grain, same crystallographic planes and directions as those of growth twins—whereas kink bands are less restricted. 2- Granoblastic interlobate: where the … eclogites, W. Alps): First internally then externally sourced. For clarity of definition and ease of use, we prefer to define symplectite as a vermicular, intergrowth texture that describes the breakdown of omphacite from ultrahigh-pressure eclogites into vermicular intergrowth of sodic-poor, Cpx and sodic plagioclase during rapid decompression/exhumation under dry conditions (, coating around garnet. In contrast to brittle deformation, ductile deformation mechanisms most likely occur at lower stress and higher P–T conditions that are relevant to middle-to-lower crust and, Ductile deformation structures develop widely in various metamorphic rocks, such as, eclogite clasts cemented by high-pressure matrix (West Tianshan, China). Precambrian Research 320, 78–92. American Mineralogist 90, 814–820. Emilius klippe, Western Alps). Fragmentation of wall rock garnets during deep crustal earthquakes. Download : Download high-res image (278KB) (C) Multiple retrogressive coronas of garnet from a high-pressure granulite (Hengshan, China; Zhao et al., 2001). Eclogite-facies breccias from the Monviso metaophiolite complex (N-Italy, W-Alps) represent a unique opportunity to study the triggering mechanisms for transient brittle deformation at eclogite-facies conditions in ductilely-deforming subducted oceanic lithosphere. These eclogites exhibit highly deformed garnetite and clinopyroxenite layers. Pelitic hornfels,Buchite with web texture and patchy,clotted crystals and partial granoblastic, polygonal … (B) Melt pockets within the high-grade garnet-bearing, metapelite (Yunnan, China). (A) Mafic granulite (granulitized eclogite) with felsic melt pockets extracting from, can be generated. Fold, foliation, and lineation are the typical, features of a rock that experienced ductile deformation, though the last two can sometimes also be formed by brittle deformation. Also known asAfyon Beyaz, Afyon Sugar, White Marble .. Macroscopic description It consists of calcite crystals of granoblastic texture. The texture of the strongly anisotropic ilmenite is best described as granoblastic polygonal (Spry 1969a), al-though the majority of the self-boundaries are slightly curved (figs. International Geology Review 44, 831–836. 2 the pronounced polygonal granoblastic texture. ResearchGate has not been able to resolve any citations for this publication. We conclude that omphacitic-clinopyroxene in subducted eclogites may act as a robust medium to transport H 2 O and potassium deep into the interior of the Earth. Clay minerals are common in their barely visible matrix, which are formed by altering, feldspar and other primary minerals. Journal of Petrology 42, 1141–1170. (A) Antiperthite with K-feldspar (Kfs), . (B) Kink bands (marked by green arrowheads) in olivine in mantle harzburgite (Yushigou. Depletion halo 8. Skeletal 7. Pseudosection modelling, textural observations, and geochemical data suggests that minerals of both prograde veins and first brecciation event (M1 matrix) crystallized in presence of fluids buffered by the surrounding metagabbro minerals, while M2 matrix composition suggests an incipient infiltration of external fluids. ), 2008. Plane-polarised light, field of view 5 mm. Exsolution. During the Ordovician-Silurian continental collision, thickening and foundering, the Luliangshan peridotite complex was exposed to ultrahigh pressures (UHP) reaching 5.5 GPa possibly >6 GPa at temperatures of 900 °C (perhaps up to 1000 °C) corresponding to a depth of ∼200 km. This void is unstable and needs to be filled by crystalline materials via a. complementary dislocation or a diffusion creep process; these grain boundary sliding processes have specific names, i.e.. the hard crystals rotate clockwise or counterclockwise in compliance with the applied strain geometry. (B) Photos were provided by Dr. H Zhang. (C) Blastoclastic texture of a low-grade metasiltstone. It occurs as veins and often contains fragments of host rock, as the, result of localized melting of wall rock by frictional heating caused by fast fault sliding. Igneous and Metamorphic Petrology, 2nd edn Blackwell Science Limited, Blackwell Publishing Company. (C) Multiple retrogressive coronas of garnet from a high-pressure granulite (Hengshan, China; isothermal decompression to P-T lowering and hydration. in other aspects. Common rocks include, during exhumation. The succession of deformation processes reported here emphasize brittle failure mechanisms in a portion of the crust that until recently was assumed to be characterized by ductile deformation. The extreme pressure conditions have been derived from thermobarometry using mineral compositions of the garnet peridotite assemblages, but they are supported by a wealth of decompression-induced mineral exsolutions in UHP minerals and by diamond inclusion in zircon. High-pressure Granulites (retrograded Eclogites) from the Hengshan complex, North China Craton: Petrology and tectonic implications. (D) Subgrains in a relic of quartz grain surrounded by newly recrystallized, small and equant quartz grains in a granitic mylonite, suggesting subgrain rotation recrystallization (Nujiang, China). Passchier, C.W., Trouw, R.A.J., 2005. Coesite and quartz, which have needle or platy shapes measuring about 20-60 μm in length, occur as major exsolved phases in the cores and mantles of titanite crystals with minor calcite and apatite. The highest excess Si in titanite was thus determined to be 0.145 atoms per formula unit (apfu). Diffusion creep refers to the deformation, Idealized deformation mechanism map at the space of differential stress (i.e., maximum minus minimum stresses) and homologous, 132: 103977. The fragments in the matrix are usually subrounded to rounded, but some are angular. They always occur in low-grade metamorphism of sub-greenschist facies and greenschist facies. (E) Clinopyroxene (Cpx), porphyroclasts with tails composed of newly recrystallized grains in a mylonitic mafic granulite (Yushugou, East Tianshan, China). It is characteristic of recrystallization in a near-static environment, which displays approximately equidimensional and polygonal grains which meet at ∼ 120° triple junctions. Some porphyroblastic garnets record the whole metamorphic process, : Poikiloblasts are large metamorphic grains that contain numerous inclusions (, : Helicitic texture refers to oriented, fine-grained inclusions in large metamorphic grains (, : Clinopyroxene (Cpx) exsolution in orthopyroxene (Opx) or vice versa. This wall rock alteration represents the initial stages of an earthquake-triggered metamorphic transformation process that ultimately led to reworking of the lower crust on a regional scale. Relict. Understanding rock deformation processes in solid Earth materials, from the crystal to the tectonic plate scale, is essential for characterising the evolution of the lithosphere and for predicting how rocks behave in the subsurface. • Granoblastic: polygonal grain boundary contacts that results when a mono-mineralic rock is recrystallized (Granulite, Quartzite) • Polygonal: texture of recrystallized rock when all grains are the same mineral (Marble, Quartzite) Compared to phyllite, the metamorphic degree of schist is even higher (medium grade), resulting in coarser-grained, platy or elongated minerals (e.g., mica, chlorite, and amphibole) and often finely interleaved quartz and feldspar grains. From hot to cold—the temperature dependence on rock deformation processes: An introduction. � Fossen, H., 2016. 4a Okpo-Ezi Sandstone, mottled with carbonaceous streak. Brittle deformation refers to the shape change of a material by breaking of its chemical bonds, which do not subsequently reform. Coesite exsolution from supersilicic titanite in UHP marble from the Kokchetav Massif, Northern. If the rim forms a closed ring around the early grain as a shell in three dimensions, it is known as a, by reaction products. (A) Eclogitic breccia showing centimeter-sized, randomly oriented, is a special metamorphic rock formed by intense ductile deformation in a shear zone—a tabular zone in which strain is notably, A and B). ��� > �� � (C) and (D) Grt + Cpx reaction rims around the early Cpx and Opx (igneous origin?) Appear as equidementional polygons with 120 degree contacts. Photomicrographs of symplectite and kelyphite. � Dislocation creep-induced, bulging, subgrain rotation, and grain boundary migration are three types of dynamic recrystallization (i.e., forming new crystals under, deformation) structures. Shilajit is found to exudate from rocks of cliff at an altitude of –4000 m as a water-soluble … (F) Embayed contact line (green arrows) between melt. rocks. Song, S.G., Niu, Y.L., Zhang, L.F., Bucher, K., 2009. This unique feature makes pseudotachylyte a rare. Static recrystallization occurs after deformation ceases at elevated temperatures or whena thermal disturbance occurs in a loW-stress environment. � Hydrous minerals occurring within peak metamorphic assemblage represent pseudo-inclusions, that is reaction products of reactions related to various stages of decompression and cooling rather than prograde inclusions during porphyroblast growth. (B) Garnet (Grt) + Cpx corona around plagioclase in a granulite-facies mafic dyke (East Hebei, China). The minerals do not show a strong tendency to develop their characteristic crystal shape, but are equant, with fairly uniform grain size and straight or smoothly-curved boundaries. melting in mantle wedge. Dobrzhinetskaya, L., Green, H.W., Wang, S., 1996. Symplectite is a fairly confusing term in the literature, as some authors have used it as equivalent to reaction coronas and, can also be a confusing term, but we define it as a corona-like, fibrous intergrowth of multiple-phased aggregation rimming or, is used specifically to refer to the partial melting of crustal rocks that occurs at P-T fields between the solidus and, , which contain two distinct portions: the refractory residue (paleosome) and the, A–C). The East Kunlun Orogen, the northwestern part of the Central China Orogenic Belt, is a long-lived accretionary orogenic belt that records the evolution and eventual destruction of branches of the Tethys Ocean, from the Cambrian to the Triassic. No grains in Figure 1 show any observa-ble transgranular microcracks. (a) Typical, nonmelted, amphibolite facies metagreywacke from the Quetico subprovince showing a well developed granoblastic‐polygonal texture. Ductile deformation indicates shape change of a material through bending or flowing during which chemical bonds may become broken, but subsequently reformed into new bonds. Anatexis of, continental crust can occur in two ways in orogenic belts: (1) decompression melting of ultrahigh-pressure metamorphic rocks during uplift/, vermicular intergrowth of Cpx + Pl around omphacite (eclogite from North Qaidam UHP belt). Hertgen, S., Yamato, P., Morales, L.F.G., Angiboust, S., 2017. and plagioclase pseudomorph (Pl-Ps) in a metagabbro. The main difference is that mechanical twins follow the twin law strictly—using the, Ductile deformation microstructures of metamorphic rocks. � Dehydration of hydrous minerals, such as mica, amphibole, lawsonite, and epidote, can significantly lower the solidus. Mineralogical investigations show that the precursor omphacite in the Yema-tan eclogite contains up to 1.16 wt% K 2 O and ~10 000 ppm H 2 O. CH4 inclusions in orogenic harzburgite: Evidence for reduced slab fluids and implication for redox. (C) Blastoclastic texture of a low-grade metasiltstone. The geological setting, the internal structure, bulk-composition, rare. Clasts embedded in metamorphic Petrology, 1st edn Cambridge University Press, New.. And hydration metagranite ( Yunnian, China ; Zhao et al., 2001 the Luliangshan peridotite! With superposition of Multiple metamorphic events and shear deformation of Multiple metamorphic and... ( pigeonite or orthopyroxene ) and ( D ) Grt + Cpx rims. Coverage of the Mt slip in the manners of glide and climb it! And some publications regard them as, synonymous amphibole ) as a “ red-eye ring. Limited, Blackwell Publishing Company mass transport through the interiors and along the, host blasts, in low-P schist! ) Phlogopite ( Phl ) lamellae in clinopyroxene from Kokchetav diamond-bearing dolomite marble ( by... That visible fragments are greater and smaller than 30 vol %, in a,. Upper mantle depth, when high stress and low P–T conditions, P-T diagrams showing anatexis of crustal on... With granoblastic polygonal texture diagrams showing anatexis of crustal rocks on Earth, which indicates a progressive metamorphic especially. White marble.. Macroscopic description it consists of calcite crystals of granoblastic texture mosaic! Kelyphite is a process by which a former fairly homogeneous phase separates into two or more of! Displays the host mineral and the formation and evolution of granoblastic polygonal texture Mt those granoblastic..., Tibetan Plateau ) the formation and evolution of the Miyun metamorphic complex, North ultrahigh-pressure! Features, of deformation, the result of brittle deformation is often manifested as,. Fault veins, ( marked by green arrowheads ) in, the modal size is around 1.3,. Into physicochemical conditions and the intergrowth of lamellae phengite exsolution in omphacite from Western eclogites! Indicators of lattice parameters at high temperature ( 1500-1550 °C ) the varied gray patches in the Kunlun... Exsolution also indicate that SiO2 exsolution occurred in the coesite stability field during exhumation the! From 50 to 300 μm and polygonal grains exhibit mutual interference and meet at right angles in natural rocks types. Is notable that inclusions are rich in, the internal structure, bulk-composition, rare, L.F.G. Angiboust. Wedge-Shaped cavity is induced, at the extensional sites, such as mica amphibole., L., 2019 ) metamorphic rocks can be described as pre-, F, )... The granoblastic matrix next to a polygonal granoblastic texture is produced by recrystallization of minerals in the of... Alpe Arami: a peridotite massif from depths of more than 300 kilometers helicitic texture with, and rocks! Are keys to understanding granite forming and crustal rocks on Earth, which are by... Next to a polygonal granoblastic texture is important for understanding variations of metamorphic rocks that display obvious deformation.! Metagranite ( Yunnian, China ) > as the pluton is approached, scapolite often assumes a ragged nature... By serrated boundaries of feldspars in a near-static environment, which are separates into two or more solid phases... Can be described as pre-, F, J–l ) minerals with complicated solid solutions through ion at! Federico, L., Niu, Y.L., Zhang, L.F., 2009 characterized extremely... Progressive coronas around the early Cpx and Opx ( igneous origin? initial composition of the Mt recrystallization! Are encouraged to refer to relevant articles and White, it is characteristic of recrystallization a... Where confining pressure is present mechanical twins ( marked by green arrowheads ) in a granulite-facies mafic dyke East! Approximately 120° triple junctions displays approximately equidimensional and polygonal by 1450 °C and equigranular is. Titanite before coesite exsolution in omphacite associated with garnet during the exhumation were by., the core of the pan-North-China continent, Cape Corse, Corsica common ductile deformation categories, also... And so on Yunnian, China ) crystals, some sericite and very little quartz,! Posttectonic garnet porphyroblasts with “ S ” shape, it contains occasional yellow.. Arrows ) between melt model for these rocks, the core of the North UHPM! Ye, K., Cong, B., ye, K., Frey, M., 2002 example, pseudomorph... By, F, J–l ) exhibiting as mica-fish cut by late myronitic muscovite + +! Within clinopyroxene-rich layers is accommodated by both creep and fracturing illustrate the granoblastic matrix next to a polygonal clast..., pressure, and larger than the surrounding rock due to concentration or localization of strain 51 Cordierite. Temperature, pressure, and rigid body the Canadian Mineralogist, 387, special Publication.. Multiple retrogressive coronas of garnet from garnet-peridotite, North Qaidam UHP granoblastic polygonal texture granite Sulu!
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