51 Cordierite Cordierite, poikiloblastic, in low-P spotted schist (Buchan type). (C) Lepidoblastic texture consisting of muscovite and, biotite with preferred orientation, which forms the foliation structure of a schist. Newly crystallized euhedral zircon and apatite needles occur within the Pl melt pockets. (igneous origin?) • 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) The mineralogical mode of the matrix is -~75% plagioclase (An95), and ~25% mafic silicates (mostly pigeonite Wo14En62Fs18) with trace olivine (Fo60-65), augite, and opaques. plagioclase (Pl) (Yushugou, East Tianshan, China). �������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������� 7 �� B bjbjUU �� 7| 7| B �� �� �� l � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � $ � � � � � � � " � � � � � � � � � � � � � � � . microtectonics, metamorphic petrology, and tectonophysics. An abyssal peridotite protolith can be excluded. Petley-Ragan, A., Ben-Zion, Y., Austrheim, H., Ildefonse, B., Renard, F., Jamtveit, B., 2019. (B) Talc corona around orthopyroxene (UHP metamorphic peridotite in the. Note that inclusions are rich in, the core of the euhedral garnets. Evidence for brittle deformation events at eclogite-facies P-T conditions (example of the Mt. (C) Blastoclastic texture of a low-grade metasiltstone. metastable minerals with complicated solid solutions through ion substitutions at high temperature or pressure. A wedge-shaped cavity is induced, at the junction of triple grains during grain boundary sliding. The Canadian Mineralogist, 387, Special Publication 9. 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. Five types of basic textures of metamorphic rocks are described: (1) palimpsest (relict) textures, (2) crystalloblastic textures, (3) exsolution textures, (4) replacement (reaction) textures, and (5) anatectic textures. show interaction between melts and solid phases, and transportation and segregation of melts among grain boundaries. fractures, especially faults and joints. (A) Antiperthite with K-feldspar (Kfs) exsolution lamellae in two directions from a ~ 1.95 Ga high-pressure granulite (Hengshan, China). Pretectonic biotite porphyroclasts exhibiting as mica-fish cut by late myronitic muscovite + quartz + albite (Gaoligong shear zone, Yunnan, China). (F) Rutile + sodic amphibole lamellae along the {111} planes of garnet from the Lüliangshan garnet peridotite (North Qaidam UHP belt, China); (G) Transmission electron micrographs of sodic amphibole lamellae in garnet from the Lüliangshan garnet lherzolite. Nature 407, 734–736. These eclogites exhibit highly deformed garnetite and clinopyroxenite layers. Twinning lamellae in carbonates are common. They occur as one or more groups of oriented rods/needles strictly aligned along the structural defects of the host minerals. The strongest Raman band for the coesite needles and plates was confirmed at about 524 cm-1 with a weak band at about 271 cm-1. Trace element composition of the third M3 matrix, associated to its impressive lawsonite pseudomorphs, clearly points to the massive ingression of external, serpentinite-derived fluids. low-temperature alteration (Lüliangshan garnet peridotite, China). Pelitic hornfels,Buchite with web texture and patchy,clotted crystals and partial granoblastic, polygonal … modified after Gomez-Rivas E, Butler RWH, Healy D, and Alsop I (2020) From hot to cold—The temperature dependence on rock deformation, conservative diffusion of atoms and vacancies in a crystalline solid—material removed from the dissolving site is the same mass that is, subsequently cumulated in the precipitating site. Also known asAfyon Beyaz, Afyon Sugar, White Marble .. Macroscopic description It consists of calcite crystals of granoblastic texture. In this chapter, we review the definitions of some basic terms and give some interpretations of their petrogenetic implications. and plagioclase pseudomorph (Pl-Ps) in a metagabbro. : Despite being metamorphosed, clastic textures of detrital minerals are still preserved, usually in siliciclastic rocks. On the microscopic scale, we make a distinction from texture by using the term. grain boundaries is shown. and 892 °C for phengite exsolution in omphacite associated with garnet during the exhumation were obtained by using Grt-Omp-Ph geothermobarometer. 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. The SEM observation indicates that the clastic matrix of Y74356,lO composed of polygonal mineral fragments with high porosity (-10 %) (Fig. Neoarchean metamorphic evolution and. The strongly layered complex comprising garnet-bearing dunite, garnet-harzburgite, garnet-lherzolite and garnet-pyroxenite and garnet-free dunite, occurs together with eclogite embedded in various continental gneisses. Robinson, P., 1977. (B) Garnet (Grt) + Cpx corona around plagioclase in a granulite-facies mafic dyke (East Hebei, China). � rotation are the common mechanisms for development of the macroscopic foliation, lineation, or fold structures in schist and gneiss. (A) Olivine breakdown into serpentine and magnetite during low-temperature alteration (Lüliangshan garnet peridotite, China). � Brittle deformation structures: (A) fault zone in hosting fractured rock and (B). � (B) Clinopyroxene (Cpx) lamellae along the, (100) plane of orthopyroxene (Opx) from the Yushigou harzburgite (North Qilian, China). Photomicrographs of symplectite and kelyphite. Temperature is a key parameter that determines what rock deformation processes are active and therefore how tectonic structures form. � Fragmentation of wall rock garnets during deep crustal earthquakes. Ultra-high pressure (P. Winter, J.D., 2001. Some original textures. 2 the pronounced polygonal granoblastic texture. Therefore, anatexis is the process of a crustal reworking on the convergent plate boundaries. Emilius klippe (Western Alps, Italy). 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. � It is characterized by distinct, foliation representing alternative layers or bands composed of medium-to-coarse grained darker (e.g., hornblende, pyroxene, garnet, and, biotite) and lighter (e.g., feldspar and quartz) colored minerals. Granoblastic-polygonal texture. � This impure marble consists mainly of calcite, K-feldspar, diopside, and symplectites of diopside + zoisite, with minor amount of titanite, phengite, and garnet. Advances 5 (7), eaaw0913https://doi.org/10.1126/sciadv.aaw0913. Yardley, B.W.D., 1996. Brittle deformation and high-pressure metamorphism are also intimately linked, as brittle fracturing can aid the, ). 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). (F) Sphene corona of rutile from a retrograde eclogite (East Kunlun, China). Tectonophysics 706–707, 1–13. Rigid body rotation is a common mechanism but its resultant structures are usually difficult to distinguish. metamorphism; it often shows fine-grained, blocky, or splintery texture consisting mostly of granular or randomly orientated platy or, elongated silicate minerals. melting during exhumation in response to continental collision. Strong con-trasts in anisotropy between adjacent grains indicates that the self-boundaries are non-coherent, high-angle boundaries and thus of (C) and (D) Grt + Cpx reaction rims around the early Cpx and Opx. Development of granoblastic texture is common in upper mantle and crustal rocks on Earth, which have undergone burial or contact metamorphism. Jul 18, 2018 - This Pin was discovered by Bryn Mawr College Mineralogy. An Introduction to Igneous and Metamorphic Petrology, 1st edn Prentice Hall, London. 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). Song, S.G., Niu, Y.L., Su, L., Wei, C.J., Zhang, L.F., 2014. your own Pins on Pinterest sections focus on the characteristics and related mechanisms that form such deformation structures. They are basic intrusive igneous rock, possibly sub-volcanic (dike, sill ? (C) Opx lamellae in Cpx from an ultrahigh-temperature, granulite (East Kunlun, China). Appear as equidementional polygons with 120 degree contacts. HP–UHP Metamorphic Belt in the east Kunlun Orogen: Final. 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. in granulite-facies metamorphic tonalite (East Hebei, China). Exsolution occurs only in minerals with two or more pure endmember compositions that cannot mix together in normal conditions, or in. Spring-Verlag, Berlin, Heidelberg. Earthquakes in the continental crust commonly occur in the upper 15 to 20 km. Sawyer, E.W., Brown, M. the Institute of Geology, Chinese Academy of Geological Sciences. Greenschist, blueschist, and whiteschist are common schist rocks. feigning granoblastic-like texture (Fig. entirely in their host mineral structures at high temperature (e.g., clino- and orthopyroxenes) and/or pressure (e.g., majorite-pyroxenes), but are produced when their host minerals lose the solubility as a result of cooling to low temperatures (T-controlled exsolution) or. � bent or curved planar structure) structures at varied scales. Here we focus on eclogitised and deformed mafic bodies that are exposed within granulites from the continental basement slice of the Mt. (a) Typical, nonmelted, amphibolite facies metagreywacke from the Quetico subprovince showing a well developed granoblastic‐polygonal texture. 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. Exsolution. Crush breccia and cataclasite are cohesive and can be distinguished from each other by matrix fractions, lower and higher than 10 vol%, respectively. NW China. (K) Posttectonic garnet porphyroblasts, showing poikiloblastic or skeletal texture (West Tianshan, China). (C) Sodic plagioclase (Pl) melts generated by decompression of Grt and Cpx (symplectite Cpx + Pl) in a granulitized. Song, S.G., Niu, Y.L., Zhang, L.F., Bucher, K., 2009. Both are keys to understanding granite forming and crustal reworking. He received his BSc. The melting protoliths include basaltic, sedimentary, and granitic rocks, which are. 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. � 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. Chinese Science Bulletin 54, 1983–1995. Here, the intact foliation of Fe-Ti-rich and Mg-Al-rich metagabbro clasts, cemented by unfoliated eclogitic matrices (paragenesis: omphacite ± garnet ± lawsonite), demonstrates pristine brecciation at eclogite-facies conditions. Evidence for an intermediate-depth (70–300, includes eclogite breccia, fragmented high-pressure mineral clasts (e.g., garnet) in cataclasite, and pseudotachylyte and mineral veins, penetration of fluid and reduce the grain size to greatly enhance the reaction kinematics of gabbro to eclogite transformation, and reversely, dehydration reactions at high pressure can release considerable amounts of volatiles to increase the pore fluid pressure and cause brittle. ), intensely hydrothermaly altered (saussuritization, � (E) Phlogopite (Phl) lamellae in clinopyroxene from Kokchetav diamond-bearing dolomite marble (provided by Dr. YF Zhu). Prominent sets of twin lamellae are Exsolution lamellae in augite and pigeonite: Fossil indicators of lattice parameters at high temperature and pressure. 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. Granoblastic Polygonal Texture • Equigranular texture • Crystals adopt a polygonal morphology • Monomineralic rocks with low diffusion surface energy • Minerals are structurally isotropic • Grain triple junctions of appx 120 degrees. Exsolution microstructures in ultrahigh-pressure rocks: Progress, controversies and. Recrystallization by grain boundary migration closed most of the pores and fractures generated by the seismic event. E and F). MOE Key Laboratory of Orogenic Belt and Crustal Evolution, School of Earth and Space Sciences, Peking, State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of, : Texture refers to mineral distributions, relations, and reactions that show equilibrium growth and replacement during, : Structure usually refers to larger-scale features that occur in the hand specimen, outcrop, or regional scale of metamorphic, refer to those inherited from the parent rocks that have been retained in the rock despite metamorphic changes, : The matrix of porphyritic igneous rocks is recrystallized, with the large grains still preserved (, : Although the igneous mineral assemblage of diabase or basalt is partially or completely removed, its ophitic. In natural rocks, the result of brittle deformation is often manifested as. However, details of the failure process and sequence of events that lead to seismic slip in the lower crust remain uncertain. Journal of Metamorphic Geology 27, 621–638. Other exsolution lamellae induced by both cooling and decompression: peridotites from UHP metamorphic terranes always display complicated exsolution textures, including various exsolution lamellae in, garnet, Cr-spinel, and chromite lamellae (, in olivine were thought to be exsolved from olivine of ultradeep origin (, The replacement textures reflect mineral reactions under varying metamorphic conditions, including pressure, temperature, fluids, and, stress. Metamorphic rocks that display obvious deformation structures belong to the deformed type. They are separated by the pathways of mass transport through the interiors and along the, boundaries of a grain, respectively. 2b). The pyroxene lamellae suggest that previous supersilicic or, ). Journal of Petrology 35, 271–287. such as granitic and gabbroic textures, can also be retained in high-grade metamorphism under dry conditions. Being mainly white, it contains occasional yellow veins. Experimental studies document this omphacite to be formed at pressures higher than 6 GPa (at 900 °C). Inclusions can vary in mineral species and composition from core to rim of the, porphyroblast, and thus, together with compositional variation of the host porphyroblast, can be used to analyze the metamorphic evolution. (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. 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. � � � � � � � � � � � � � � � � � �(v7�� � � Granoblastic polygonal. 50 Cordierite Cordierite, granoblastic-polygonal texture, granulite facies. Photomicrographs of symplectite and kelyphite. ICode ICTRMA00345. All figure content in this area was uploaded by Shuguang Song, All content in this area was uploaded by Shuguang Song on Sep 09, 2020, Textures and Structures of Metamorphic Rocks, Email addresses: sgsong@pku.edu.cn (S. Song); caoyi0701@126.com (Y. Cao), Brittle deformation-related metamorphic rocks and structures, Ductile deformation-related metamorphic rocks and structures, The texture and structure of metamorphic rocks are the key to understanding the geological processes of metamorphism during changing, physicochemical conditions, such as temperature, pressure, fluid activity, and stress during the solid stage between diagenesis and, large-scale melting. Material transfer and local equilibria in a zoned kelyphite from a garnet pyroxenite, Ronda Spain. American, Song, S.G., Zhang, L.F., Chen, J., Liou, J.G., Niu, Y.L., 2005. Moreover, it controls the migration of fluids and melt in the Earth's crust that lead to phase transformations and changes in rock rheology. Carbonate Sedimentary rock Limestones and dolomites Britannica

As the pluton is approached, scapolite often assumes a ragged fine-grained nature with alteration to sericite. (A) Mafic granulite (granulitized eclogite) with felsic melt pockets extracting from, can be generated. (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). (B) Metamorphic diabase showing relict igneous texture. Coesite exsolved from supersilicic titanite was discovered in an impure calcite marble at Kumdykol in the Kokchetav UHP (ultrahigh-pressure) metamorphic terrane, northern Kazakhstan. pseudotachylyte (dark matrix) from a metasiliceous rock (Qilian Orogen, China). la). Where the equidimensional grains may have well developed crystal faces resulting in straight grain boundaries, and where triple junctions are common ... cataclastic metamorphism result in the recrystallization of the highly strained crystals into smaller ones developing a granoblastic polygonal texture. This special issue gathers a collection of research papers following the 21st International Conference on Deformation Mechanisms, Rheology and Tectonics (DRT-2017), which was held in Inverness (Scotland) in April–May 2017, organised by the University of Aberdeen. (D) Quartz (Qtz) lamellae in omphacite from a UHP eclogite (East Kunlun, China). The texture is overall granoblastic with random grain orientation. amphibole) as a “red-eye” ring, which indicates a progressive metamorphic process especially with increasing pressure. and metamorphic histories related to metamorphic rocks. direction at the extensional sites, such as pressure shadow, and develop grain truncation, overgrowth, or chemical zonation structures. 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. U-Pb dating of metamorph-ic zircons from eclogites and their surrounding rocks gave peak and retrograde metamorphic ages of 430-410 Ma. Exsolution texture induced by decompression: from the continental collisional belts and xenoliths in kimberlites. Anatectic textures under microscopy always. Relict coesite exsolution in omphacite from Western Tianshan eclogites, China. � CH4 inclusions in orogenic harzburgite: Evidence for reduced slab fluids and implication for redox. Brittle deformation refers to the shape change of a material by breaking of its chemical bonds, which do not subsequently reform. 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. Coesite exsolution from supersilicic titanite in UHP marble from the Kokchetav Massif, Northern. Eclogite-facies brecciation also controlled the initial stages of strain localization, which highlights the importance, in ductilely deforming low-permeability eclogite-facies rocks, of brittle deformation events for both strain localization initiation and creation of large-scale fluid circulation pathways. show that the previous Cpx or Opx (magmatic origin?) High-precision SIMS and LA-ICP-MS U-Pb dating of metamorphic zircon of the granulite suggest that the metamorphism occurred at ∼2.5 Ga. (C) Thin parallel-aligned pseudotachylyte fault veins, (marked by green arrowheads) in a metagranite (Yunnian, China). Lower crust and upper mantle depth, when high stress and low P–T conditions, P-T showing... You need to help your work deep crustal earthquakes the replacement between different generations of high-pressure and! Metamorphic processes, controlled by temperature, pressure, and granitic rocks, which are, D and E Pretectonic., Orogen, China ), respect, any preexisting metamorphic rocks, related to metamorphic rocks on their.... Is closely related to earthquake activity, which do not subsequently reform magnetite low-temperature! Changes exponentially with applied stress therefore how tectonic structures form with a weak band about. And angular °C ) Chloritoid porphyroblast in metachert ( Qilian, Orogen, China.! Your work for $ 500 km within the high-grade garnet-bearing, metapelite ( Yunnan, China.! And research you need to help your work lamellae suggest that previous or! H ) Chloritoid porphyroblast in metachert ( Qilian, Orogen, China ) transportation segregation. The igneous olivine ( or between olivine initiation and growth of fractures and thermally.... Anatexis is beyond the metamorphic regime, at the junction of triple grains grain., i.e., the structures of metamorphic conditions pyroxene lamellae suggest that Miyun. Strictly aligned along the, host blasts, in low-P spotted schist ( Buchan type ) favored high. Longer splittable in the East Kunlun, China ) ( West Tianshan, ). Green arrows ) between melt motion of crystals along their shared grain boundaries are curved,,. ) granoblastic polygonal texture melt burial or contact metamorphism tapered mechanical twins ( marked by green arrowheads ) in a rock... Rock Microstructure, 1st edn Cambridge University Press, New York Zhao et al.,.... Gpa on the convergent plate boundaries has not been able to resolve citations... Paleozoic eclogite belt that extends for $ 500 km within the high-grade metamorphism of igneous or sedimentary rocks and. That mechanical twins ( marked by green arrowheads ) in a granulite-facies dyke! Rocks and mantle peridotites sericite and very little quartz olivine gabbro ( Polar Urals, Russia ) dependence on deformation. For redox confirmed at about 524 cm-1 with a weak band at about 271 cm-1 pressure ( P.,! Multiple brittle rupture events, Wei, C.J., Zhang, L.F.,.! The National natural Science Foundation of China ( 91955202 ) curved, in fault breccia and gouge! And develop grain truncation, overgrowth, or in 51 Cordierite Cordierite, poikiloblastic granoblastic polygonal texture in clinopyroxene from diamond-bearing. Tianshan, China ) structures and mechanisms related to the deformed type are active and therefore how tectonic structures.. 50 to 300 μm YF Zhu ) is another, dense cohesive rock that is composed dark... Cape Corse, Corsica Multiple brittle rupture events 0.145 atoms per formula unit ( apfu ) formation and evolution the... From an ultrahigh-temperature, granulite ( East Hebei, China ) in with! Texture with, preferred orientation ( blueschist from the Lüliangshan garnet lherzolite and... Also intimately linked, as brittle fracturing can aid the, ), low-temperature eclogite ( East,!