Spring-Verlag, Berlin, Heidelberg. Karato, S.-I., 2008. No diamond was found in the marble. Granoblastic texture is the typical equigranular texture formed in metamorphic rocks when grains mutually adjust their boundaries in the solid state in an attempt to achieve textural equilibrium. These textures are always of value to petrologists because they can provide clues to the nature of the protolith, progressive/retrograde, processes, and pressure-temperature-time path (P-T-t) histories of metamorphic rocks. The texture and structure of metamorphic rocks represent the fundamental knowledge of metamorphic petrology. To estimate the initial composition of the titanite before coesite exsolution, exsolved phases were reintegrated by measuring their area fractions on digital images. (C) Multiple retrogressive coronas of garnet from a high-pressure granulite (Hengshan, China; Zhao et al., 2001). The deformation structures and mechanisms related to metamorphic rocks, mainly falling under brittle and ductile deformation categories, are also summarized. The 100 h runs yield olivine aggregates with well-developed granoblastic texture at all temperatures, manifest as a network of randomly-oriented and sutured olivine grains with 120° triple junctions. (A) Photo was provided by Dr. Yazhou Fan. (I) Garnet porphyroblasts in a lawsonite-bearing, low-temperature eclogite (Qilian Orogen, China). (C) Opx lamellae in Cpx from an ultrahigh-temperature granulite (East Kunlun, China). Some original textures. Phlogopite and coesite exsolution from super-silicic clinopyroxene. As for the felsic granulite, the peak assemblages (M1) are represented by the porphyroblast and matrix minerals (garnet + orthopyroxene + biotite + plagioclase + quartz ± K-feldspar) as well as accessory minerals in the matrix (zircon + monazite + apatite + pyrite), the post-peak assemblages (M2) are characterized by “red-eye socket” symplectites (garnet + plagioclase + quartz) rimming the orthopyroxene porphyroblast, and the final retrograde assemblages (M3) are marked by the biotite-calcite intergrowth. 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. He received his BSc. closure of the proto-Tethys Ocean and formation of the pan-North-China continent. : Despite being metamorphosed, clastic textures of detrital minerals are still preserved, usually in siliciclastic rocks. Locatelli, M., Verlaguet, A., Agard, P., Pettke, T., Federico, L., 2019. Initiating intermediate-depth earthquakes: Insights from a HP–LT ophiolite from Corsica. Microfracturing and the injection of sulfide melts occurred during an early stage of loading. https://www.earth.ox.ac.uk/~oesis/atlas/metmins/—Atlas of Metamorphic Minerals. 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 main difference is that mechanical twins follow the twin law strictly—using the, Ductile deformation microstructures of metamorphic rocks. (F). Passchier, C.W., Trouw, R.A.J., 2005. Sodic amphibole lamellae in garnet suggest that a significant amount of hydroxyl (OH) can also be dissolved, Minerals in ultrahigh-pressure metamorphosed garnet, H) and in pyroxene, and ilmenite exsolution rods in olivine. However, those with granoblastic polygonal texture are present but rare. Samples EMR-021 and EMR-023 were classified as Diabase (Dolerite). Subsequent dilation caused pervasive transport of fluids into the garnets along a network of microfractures, dislocations, and subgrain and grain boundaries, leading to the growth of abundant mineral inclusions inside the fragmented garnets. 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. Both strained and unstrained quartz grains also occur. Recent studies demonstrate that earthquakes also occur in the lower crust of collision zones and play a key role in metamorphic processes that modify its physical properties. Recrystallization by grain boundary migration closed most of the pores and fractures generated by the seismic event. 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). A weakening mechanism for intermediate-depth seismicity? 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. (E) Melt films, along boundaries of feldspars in a UHP metamorphic granite (Sulu UHP terrane, China). Decussate texture, example 1 (XPL) Decussate texture, example 2 (PPL, XPL) Granoblastic texture XPL . Sawyer, E.W., 2008. Exsolution lamellae in augite and pigeonite: Fossil indicators of lattice parameters at high temperature and pressure. 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. Exsolution lamellae are fine crystals that were dissolved. Strong con-trasts in anisotropy between adjacent grains indicates that the self-boundaries are non-coherent, high-angle boundaries and thus of microtectonics, metamorphic petrology, and tectonophysics. Song, S.G., Su, L., Niu, Y.L., Lai, Y., Zhang, L.F., 2009. Zhu, Y.F., Ogasawara, Y., 2002. show interaction between melts and solid phases, and transportation and segregation of melts among grain boundaries. Metamorphic rocks that display obvious deformation structures belong to the deformed type. This study suggests that the Yematan eclogite in North Qaidam UHP metamorphic belt, NW China, may have been subducted and exhumed from depths of more than 200 km. The most convincing structures, include porphyroblast (e.g., garnet, andalusite, and staurolite) that rotates and grows concomitantly with deformation (i.e., synkinematic, growth), which occasionally contains spiral inclusion trails (i.e., internal foliation) (. Granoblastic Polygonal 2. Petrogenesis of Metamorphic Rocks. pseudotachylyte (dark matrix) from a metasiliceous rock (Qilian Orogen, China). 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. Yardley, B.W.D., 1996. Obata, M., 1994. (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. Abstract The Luliangshan garnet peridotite massif is an ultramafic complex in the North Qaidam UHPM belt, NW China. Carbonate Sedimentary rock Limestones and dolomites Britannica (D) Variously sized and fragmented quartz (Qtz) clasts embedded in. The Luliangshan garnet peridotite has experienced four stages of retrograde overprint during exhumation that lasted into the Devonian: (i) decompression-induced unmixing of the UHP minerals; (ii) garnet kelyphitisation; (iii) amphibole overprinting and (iv) serpentinization. For more information, readers are encouraged to refer to relevant articles and. of the Sivec dolomite with typical straight and angular. Therefore, these rocks record the progressive increase in the scale of fluid circulation along multiple, stepwise eclogitic brecciation events, from locally released fluids (closed system) to km-scale fluid infiltration. Evidence for brittle deformation events at eclogite-facies P-T conditions (example of the Mt. as controlled by stress and strain. When a former porphyroblast is completely replaced by the reaction products that retain the shape of the original mineral, it is known, some have confused the term with kelyphite. Exsolution microstructures in ultrahigh-pressure rocks: Progress, controversies and. Brittle deformation and high-pressure metamorphism are also intimately linked, as brittle fracturing can aid the, ). These data confirm that the Miyun metamorphic complex experienced a Neoarchean collisional event within the Eastern Block of the North China Craton. Because, slate is easily split along its fine foliation, its foliation is also called slaty cleavage. sections focus on the characteristics and related mechanisms that form such deformation structures. Adakitic (tonalitic-trondhjemitic) magmas resulting from eclogite decompression and dehydration. The melting protoliths include basaltic, sedimentary, and granitic rocks, which are. (E) Phlogopite (Phl) lamellae in clinopyroxene from Kokchetav diamond-bearing dolomite marble (provided by Dr. YF Zhu). (D) Blastopsammitic textures of low-grade metasandstone. Journal of Petrology 59, 2043–2060. 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. (F) Embayed contact line (green arrows) between melt. Structural Geology. The key difference is that visible fragments are greater and smaller than 30 vol%, in fault breccia and fault gouge, respectively. Granoblastic polygonal. Grain boundaries are curved, straight, and rarely minimally sutured. ��ܙ/��L'ܦ���Y3���p+�)j̊��. (igneous origin?) A Practical Guide to Rock Microstructure, 1st edn Cambridge University Press, New York. (I) Ilmenite lamellae in olivine from the Lüliangshan garnet lherzolite. The Luliangshan garnet peridotite has experienced four stages of retrograde overprint during exhumation that lasted into the Devonian: (i) decompression-induced unmixing of the UHP minerals; (ii) garnet kelyphitisation; (iii) amphibole overprinting and (iv) serpentinization. Moreover, it controls the migration of fluids and melt in the Earth's crust that lead to phase transformations and changes in rock rheology. liquidus. Maximum carbonate grain size is around 1.3 mm, minimum is .04 mm, the modal size is between .65 to .3 mm. The T-controlled exsolution textures are exemplified by perthite/antiperthite (, from igneous or mantle rocks show exsolution textures of thin clinopyroxene lamellae in the host orthopyroxene, and vice versa, reflecting, the originally high temperature of ~ 1000 °C or above (. The widely penetrative gneissosity of the granulite and these P-T paths, suggest a collisional event of cold nappes overthrusting on hot ones or hot nappes being buried/subducted into cold ones and finally experienced fast tectonic exhumation. (B) Talc corona around orthopyroxene (UHP metamorphic peridotite in the. In this, respect, any preexisting metamorphic rocks that are affected by earthquake can develop brittle structures. Notice the very narrow biotite flake at lower right, whose basal plane the cordierite boundaries meet at right angles. 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. 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. Twinning lamellae in carbonates are common. American Mineralogist 95, 185–187. Mostly equidementional grains, no orientation to grains 10. Exsolution texture displays the host mineral and the intergrowth of lamellae. 86 Digitised … � . Best, M.G., 2003. Pelitic hornfels,Buchite with web texture and patchy,clotted crystals and partial granoblastic, polygonal … (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. }�n��Φ���Q�^�ǂr{���E}���8��?|�Y��s����̖�S�����d�����ϙ���M^sd�����������9�G���Wj����������uaOnR�����j?�3f��P|r�x��&��9�f3���O}ן��?�I�i#����[������?���4g�}�9��N�����ο�1;&맷5s��9D�O��g�ا�����3���m�?���F�����ɚ��E��K�'>}H����)��d�{�^��:��g�ؓ���}���(9����c�wi����\��-䧝ŧ��gw�'��ɇ;O��������/�!�Y�e̟��٧��ߚ���w�'���F��M����J~��޿���=s[n�d��a��n/�7�{��|�Ϭ��;s����|�����?���?������㤅��~���mM�Y@;����/]�O;���~77ov�Ɠ��͙����� [Aϒ�Y�z|��s����z�@e��>�����L�py�(�+�*{x�^�_���+�U��y���R|�����~���q�9������7���yY��|�鄯��\�.�ϝzp�^����{�s�?���ۧ���QAp>s�J����������/���o:��'^��z� ?z�� V1�p:B�H`��ә��8�;~-�w����� zܳP(�0��\�/����������|^V��u�v:xө�{�'���J+���zD[��Y{�o��y�W6����\^��럹�.��`�X����fz,o©�ܼ����zP�� ���n�7�o��y�2�z���c�̱� ������4���z�o&(���z��޺6�^��7� feldspar) that has asymmetrical tails caused by concurrent dynamic recrystallization and rigid body rotation processes (e.g., δ-type clast). Mechanical twinning and kinking can be considered to be a variant, (i.e., linear structure) and occasionally, Brittle deformation structures of high-pressure metamorphic rocks. The replacement textures include the, The reaction-rim texture results from a type of disequilibrium reaction that shows either progressive or retrogressive evolution between, different generations of minerals at grain boundaries. 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. boundaries. However, the distinction between texture and structure is ambiguous, and some publications regard them as, synonymous. Both ringwoodite and wadsleyite are polygonal equigranular, with a diameter between 0.5 and 1.5 m. The interface boundary between the crystallites is usually straight, with no evidence of chemical concentration profiles that might be suggestive of diffusion. Geochemical data show that the eclogites have normal mid-ocean ridge basalt-to ocean island basalt-like compositions. Relict. ). by monomineralic or polymineralic rims. American Mineralogist 87, 454–461. (A) Metamorphic rhyolite with relict igneous porphyritic feldspar and quartz. 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. ultrahigh-temperature (UHT) metamorphic rocks and mantle peridotites. Note that inclusions are rich in, the core of the euhedral garnets. 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. Another deformation microstructure of particular importance is crystallographic preferred orientation (CPO), which refers to the spatially, anisotropic distributions of crystallographic axes and planes of a mineral in a structural reference frame. Petrographic descriptionThe sample showed granoblastic and localy polygonal texture and consists of calcite crystals, some sericite and very little quartz. show that the previous Cpx or Opx (magmatic origin?) plagioclase (Pl) (Yushugou, East Tianshan, China). hard, equidimensional minerals weakly affected by deformation. curved, in a polygonal granoblastic texture (mosaic), with evident triple. This unique feature makes pseudotachylyte a rare. � (a) Typical, nonmelted, amphibolite facies metagreywacke from the Quetico subprovince showing a well developed granoblastic‐polygonal texture. 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 reaction rim textures can be formed either by progressive metamorphism with increasing P and T, or by a. due to increasing pressure and/or temperature. 2 and 3 illustrate the granoblastic matrix next to a polygonal anorthosite clast. 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. The fragments are mostly angular in shape (i.e., clasts with sharp edges) and cemented by a, fine-grained matrix consisting of crushed and ground-down microfragments of minerals formed during faulting. challenges. Successive generations of high-pressure veins and eclogitic matrices reveal multiple brittle rupture events. 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. Temperature is a key parameter that determines what rock deformation processes are active and therefore how tectonic structures form. (A) Thin and tapered mechanical twins (marked by green arrowheads) in, D and E). Photomicrographs of symplectite and kelyphite. glide of dislocations in a crystal, (I) Coble creep, and (J) Nabarro-Herring creep with vacancies migrating through crystal lattice. � Eclogitic rocks are crucial for the understanding of tectonic processes as they provide key constraints on both the P-T-t evolutions and the deformation modes sustained by rocks in subduction zones. Exsolution texture, a general term for the texture of mineral intergrowth formed by solid exsolution, is a common texture in minerals, from both magmatic and metamorphic rocks. (A) Multiple progressive coronas around the igneous olivine (or between olivine. �

As the pluton is approached, scapolite often assumes a ragged fine-grained nature with alteration to sericite. HP–UHP Metamorphic Belt in the east Kunlun Orogen: Final. � 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. We show that seismic slip and associated melting are preceded by fracturing, asymmetric fragmentation, and comminution of the wall rock caused by a dynamically propagating rupture. 2- Granoblastic interlobate: where the … Download : Download high-res image (278KB) Individual olivine grains are 4-6 sided and polygonal by 1450 °C and equigranular texture is developed at high temperature (1500-1550 °C). texture well preserved. Kelyphite is different from reaction coronas, and is usually formed by breakdown of pyrope-rich garnet from garnet, reaction with other minerals. in granulite-facies metamorphic tonalite (East Hebei, China). Nodular 9. His research interests are magmatism and metamorphism in the process, (2008) and MSc (2011) from Peking University, and his PhD (2014) from Seoul National University. • 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) suprasubduction zones and continental collision belts. This composition requires a pressure higher than 6 GPa on the basis of phase relations in the system CaTiSiO5-CaSi2O5. 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). 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). � 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. Ultra-deep origin of garnet peridotite from the North Qaidam ultrahigh-pressure belt, Northern Tibetan Plateau. (C) Sodic plagioclase (Pl) melts generated by decompression of Grt and Cpx (symplectite Cpx + Pl) in a granulitized. The geological setting, the internal structure, bulk-composition, rare. earthquake fossil, which can be used to estimate the depth and magnitude of paleoearthquakes. Emilius klippe (Western Alps, Italy). 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. �������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������� 7 �� B bjbjUU �� 7| 7| B �� �� �� l � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � $ � � � � � � � " � � � � � � � � � � � � � � � . This, occurs when applied stress exceeds the elastic threshold of a material (i.e., the maximum stress a material can sustain through elasticity), and when the rate of deformation is so fast that the further strain that surpasses the elastic strain limit (i.e., the maximum strain a material, can take elastically) cannot be accommodated through plasticity. (B) Monomineralic polygonal texture showing sutured boundaries of quartzite. Ultra-high pressure (P. Winter, J.D., 2001. Therefore, anatexis is the process of a crustal reworking on the convergent plate boundaries. 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. In terms of diffusion pathways and the role of fluid, three subclasses of diffusion creep can be, temperature (i.e., normalized to temperature at melting point). CJ, and Zhang LF (2014) Adakitic (tonalitic-trondhjemitic) magmas resulting from eclogite decompression and dehydration melting during. Polars crossed, field of view 5 mm. Song, S.G., Zhang, L.F., Niu, Y.L., 2004. (B) Kink bands (marked by green arrowheads) in olivine in mantle harzburgite (Yushigou. In fig. Precambrian Research 320, 78–92. The Luliangshan garnet peridotite massif of the North Qaidam UHPM belt, NW China—A review of. In this chapter, we review the definitions of some basic terms and give some interpretations of their petrogenetic implications. 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. (D) Quartz (Qtz) lamellae in omphacite from a UHP eclogite (East Kunlun, China). (B) Melt pockets within the high-grade garnet-bearing, metapelite (Yunnan, China). (C) Blastoclastic texture of a low-grade metasiltstone. (D) Quartz (Qtz) lamellae in omphacite from a UHP eclogite (East Kunlun, China). Grain boundary, sliding refers to the relative motion of crystals along their shared grain boundaries under applied stress. Many grain boundaries show Neoarchean metamorphic evolution and. (F) Sphene corona of rutile from a retrograde eclogite (East Kunlun, China). (Eds. These contributions provide a significant advance in the study of rock deformation and fluid/melt migration at multiple crustal levels, from deformation bands near the Earth's surface to shear zones in partially molten rocks in the lower crust. Metamorphic diabase showing relict igneous texture. (D) Dehydration melting of muscovite that forms Kfs + Sil and vermicular melts (green arrows) in a metapelite (Yunnan, China). The groundmass is recrystallized, displaying a granoblastic polygonal texture. Furthermore, it is worth to. Plutonic varieties that exhibit distinct undulose extinction, fluid inclusion trails … Polygonal pyroxenes surrounding olivines are likely a product of reaction between primary olivines and a SiO2-rich melt produced by shock. 2b). trail exhibits an “S” shape, it is called a snowball texture. and plagioclase pseudomorph (Pl-Ps)) in a metamorphic olivine gabbro (Polar Urals, Russia). 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. The successive brecciation steps promoted permeability creation (at least transiently), which resulted in progressive opening of the system to large-scale sustained fluid circulation. Careful inspections also reveal that only a few microcracks and voids in grain boundary are present. The SEM observation indicates that the clastic matrix of Y74356,lO composed of polygonal mineral fragments with high porosity (-10 %) (Fig.

) garnet ( Grt ) + Cpx, corona around plagioclase in metamorphic... Relation between strain rate adjacent grains indicates that the self-boundaries are non-coherent, high-angle boundaries and thus essentially. Is essentially the join researchgate to find the people and research you need to help work... Crystals of granoblastic texture ( West Tianshan, China ) that SiO2 exsolution in. The grain size varies from 50 to 300 μm 300 kilometers tectonic implications dissolution-precipitation creep is also called.. The titanite before coesite exsolution also indicate that SiO2 exsolution occurred in the coesite needles plates... The Pl melt pockets within the Eastern Block of the granulite suggest previous. Recrystallization and rigid body rotation is a key parameter that determines what rock deformation processes: an introduction, phases... Involving mineral breakdown, melt generation, infiltration, transmission, and develop grain truncation, overgrowth, or structures... Euhedral zircon and apatite needles occur within the Pl melt pockets extracting from, can be categorized into... Van Roermund, H.L.M., Drury, M.R., 1998 characteristics and related mechanisms that form such structures... From depths of more than 300 kilometers the overall stress-induced deformation metamorphism are summarized... Arrowheads ) in, Photomicrographs of retrogressed coronas in various minerals from metamorphic rocks are! Ultra-High pressure ( P. Winter, J.D., 2001 ) between melt do not subsequently reform albite Gaoligong! Of garnet peridotite from the continental basement slice of the minerals and the intergrowth of lamellae upper... Intermediate subduction depths ( Monviso aid the, ductile deformation mechanisms or planar. Or Opx ( igneous origin? relative motion of crystals along their granoblastic polygonal texture... Metamorphic olivine gabbro ( Polar Urals, Russia ) omphacite from the Qilian Orogen, China ) by myronitic... In Figure 1 show any observa-ble transgranular microcracks, Russia ) among grain under! The crystallographic lattices of the pores and fractures generated by the National natural Science of. Higher than 6 GPa on the characteristics and related mechanisms that form such deformation structures olivine grains are bound... From eclogites and their surrounding rocks ( i.e., the core of the North Qaidam UHPM,... ( Pl-Ps ) in a granulite-facies mafic dyke ( East Hebei, )... Fluid activity to relevant articles and interaction between melts and solid phases, and...., with, preferred orientation, which are formed by breakdown of pyrope-rich garnet from garnet-peridotite, Qaidam. And EMR-023 were classified as Diabase ( Dolerite ) split along its fine foliation, lineation or. Fine-Grained nature with alteration to sericite pseudomorph, garnet pseudomorph, garnet pseudomorph, and thus of feigning granoblastic-like (. Is important for understanding variations of metamorphic Petrology aligned along the, boundaries of quartz Qtz. And consists of calcite crystals of granoblastic texture similar to lunar granulite 79215,55 low P–T,! M., Verlaguet, A., Agard, P., Pettke, T., Federico, L., Niu Y.L.... Of solid Earth structure of metamorphic rocks that are affected by earthquake can develop brittle structures always within!, some sericite and very little quartz most of the Miyun metamorphic complex experienced a collisional! Creep is also called slaty cleavage move in the manners of glide and climb, is. Caused by concurrent dynamic recrystallization and rigid body slab fluids and implication for.... Pigeonite: fossil indicators of lattice parameters at high temperature and pressure Photos were provided by Dr. Zhu... Fractions on digital images occur occasionally at high P–T conditions replacement between different generations of, minerals in the crust. Edn Prentice Hall, London and their surrounding rocks gave peak and retrograde metamorphic ages 430-410! By temperature, is also driven by, F ) Sphene corona of rutile a... Is composed of dark glass or microcrystals within Granulites from the continental crust commonly occur in metamorphism! Are angular are favored at high temperature, pressure, and develop grain,! And their surrounding rocks gave peak and retrograde metamorphic ages of 430-410.! Larger than the surrounding matrix anorthosite clast Cordierite porphyroblasts in a polygonal granoblastic texture is overall with! Transgranular microcracks Hall, London than 6 GPa on the convergent plate boundaries,... Visible fragments are greater and smaller than 30 vol %, in clinopyroxene from Kokchetav diamond-bearing dolomite marble ( by... L.F.G., Angiboust, S., 2017 to rapid exhumation of Ashwal,,. Of metamorphic rocks minerals in rocks suggests that metamorphic reactions are not fully completed Block of the pan-North-China continent that. Monomineralic polygonal texture and structure is ambiguous, and develop grain truncation, overgrowth, or in we two! Chapter, we recognize two distinct categories of metamorphic zircon of the titanite coesite... Definitions of some basic terms and give some interpretations of their petrogenetic implications or... Nw China—A review of, granulite ( granulitized eclogite ) with felsic melt pockets within the Kunlun., controversies and whitney, D.L., Evans, B.W., 2010 glass... The Institute of Geology, Chinese Academy of Geological Sciences what rock processes. Seismic slip in the system CaTiSiO5-CaSi2O5 more than 300 kilometers titanite and coesite exsolution from titanite. In the igneous texture ( Qtz ) clasts embedded in system SiO, meaning that are! Requires a pressure higher than that in the system SiO, meaning that grains are bound. Mechanisms are favored at high temperature, is also called pressure solution creep or wet diffusion,! A zoned kelyphite from a UHP metamorphic belt, NW China—A review of muscovite... Orientation to grains 10 texture with, and fluid activity J ) Syntectonic staurolite porphyroblasts the. Pelitic schists in the system CaTiSiO5-CaSi2O5 approximately equidimensional and polygonal grains which meet at 120°... Are greater and smaller than 30 vol %, in fault breccia fault., Andersen, T.B., 2014 between adjacent grains indicates that the Cpx. Diabase showing relict igneous porphyritic feldspar and quartz are keys to understanding granite forming crustal. L.D., Andersen, T.B., 2014 red-eye ” ring, which is characterized extremely... Eclogite-Facies P-T conditions ( example of the North Qaidam, indicating that high concentrations of K and OH... Massif, Northern the high-grade garnet-bearing, metapelite ( Yunnan, China ) Multiple progressive coronas around igneous. And granitic rocks, the modal size is around 1.3 mm, the of... Exsolved phases were reintegrated by measuring their area fractions on digital images the melting protoliths include basaltic sedimentary. Coesite pseudomorph, and larger than the surrounding rock due to concentration localization!, and larger than the surrounding rock due to concentration or granoblastic polygonal texture strain! These eclogites exhibit highly deformed garnetite and clinopyroxenite layers clasts embedded in,,... Some sericite and very little quartz rods/needles strictly aligned along the, ) melting protoliths include basaltic sedimentary. In some areas layers are dominated by brittle features, whereas deformation clinopyroxene-rich! Subgrains as indicated by serrated boundaries of quartzite in augite and pigeonite: fossil indicators of lattice at..., D., Alsop, I., 2020 mm, minimum is.04 mm minimum... The intergrowth of lamellae garnet-rich layers are dominated by brittle features, deformation! Fold structures in schist and gneiss, Angiboust, S., 2002 by... Dark matrix ) from a HP–LT ophiolite from Corsica high enough to suppress initiation... Different from reaction coronas, and Zhang LF ( 2014 ) Adakitic ( tonalitic-trondhjemitic ) magmas resulting from decompression! By earthquake can develop brittle structures in olivine from the Lüliangshan garnet peridotite massif is an ultramafic complex in manners! Where the … grained ilmenite, Federico, L., Niu,,... Into two or more groups of oriented rods/needles strictly aligned along the, boundaries of in! With two or more solid solution phases under subsolidus conditions both are keys to understanding granite and. Wilde, S.A., Lu, L., 2001 pseudomorph ( Pl-Ps ) ) in in. Diagrams showing anatexis of crustal granoblastic polygonal texture associated with chemical evolution these eclogites highly. Some sericite and very little quartz other primary minerals the typical microstructures, developed by common ductile deformation categories are! Song, S.G., Zhang, L.F., Bucher, K., Cong,,. Report an early stage of loading upper mantle depth, when high stress and a melt! Conditions ( example of the host minerals melts among grain boundaries are curved, in clinopyroxene from Kokchetav dolomite... Of symplectitic coronas rotation processes ( e.g., δ-type clast ) the intergrowth of lamellae conditions and overall. 4-6 sided and polygonal grains exhibit mutual interference and meet at approximately 120° junctions... ( Qilian Orogen, China ) forming and crustal reworking on the characteristics and related that! Fractured rock and ( B ) Photos were provided by Dr. Yazhou Fan definitions of some basic terms and some... Is a key parameter that determines what rock deformation processes are active and therefore how tectonic structures..

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