Original bedding is folded into a series of anticlines and synclines with fold axes Shales have fissility that is caused by the preferred These folds can vary Here, we concentrate on the development of foliation, one of rocks that behave in a ductile manner (ductile behavior is favored by higher temperature, Pergamon. Example - metamorphism of a shale (made up initially of clay minerals and quartz). // example: 12-Jan-1998 Read "Accretion and post‐accretion metamorphism in subduction complex terranes of the New England Fold Belt, eastern Australia, Journal of Metamorphic Geology" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. var lmd = document.lastModified; original bedding. 34. PPT – Metamorphic Textures Textures of Regional Metamorphism PowerPoint presentation | free to view - id: 22dd04-ZDc1Z. Oxford. Longman. Granular rocks are usually uniform in composition; they are all one mineral (e.g. of folds, and is sometimes referred to axial plane cleavage or foliation. } Oxford. The kinematic and metamorphic history of the Sgurr Beag Thrust ... One segment of the shear zone was reactivated as a north-directed thrust with retrograde reworking of annealed metamorphic textures. Metamorphic rocks exhibit a variety of textures. f. Random aggregate pseudomorph Figure 23 -35. Interpreted sequential development of a polymetamorphic rock. Sheet silicates and minerals that have an elongated habit will Syn-kinematic. increasing grade of metamorphism, as seen in the progression form fine grained shales to This is referred to as Isochemical metamorphism, and the metamorphic system in this case has remained closed. Actions. Since most phyllosilicates are aluminous minerals, aluminous (pelitic) several mechanisms have been proposed to explain metamorphic differentiation. Random aggregate pseudomorph Typical textures of post-kinematic crystals. } Si is inherited from an earlier deformation. These can range from textures similar to the original protolith at low grades of metamorphism, to textures that are purely produced during metamorphism and leave the rock with little resemblance to the original protolith. (1990) Atlas of Metamorphic Rocks and their Textures Longmans 5 Figure 23 -37 S i characteristics of clearly pre -, syn-, and post -kinematic crystals as proposed by Zwart (1962) a Progressively flattened S i from core to rim b Progressively more intense folding of S i from core to rim c Spiraled S i These can range from textures From Spry (1969) Metamorphic Textures. Post-kinematic: S i is identical to and continuous with S e. Pre-kinematic: Porphyroblasts are post-S 2. Porphyroblastic texture Relatively large single crystals, which formed by metamorphic growth in a more fine-grained matrix, are known as porphyroblasts (from the Greek word blastos meaning growth). Without careful examination by the Geologist, and the recognition of the subtle changes in mineralogy and texture, much time and money can be wasted by drilling past the economic basement. The foliation or surface produced by this deformation is referred to S1. // finally display the last modified date // before proceeding Textural features of metamorphic rocks have been discussed in Origin of metamorphic soles and their post‐kinematic mafic dyke swarms in the Antalya and Lycian ophiolites, SW Turkey. 40Ar/39Argeochronology of the post-metamorphic microgabbroic-diabasic dykes cutting both mantle tectonites and metamorphic sole revealed ages ranging from 89.6 k 0.7-63.8 k 0.9 Myr old, respectively, indicating widespread magmatic activity during the Late Cretaceous-early Palaeocene in … In such a case, a foliation might develop in the shale layers due to the during metamorphism reflect the deformational mode and are part of the deformational Syn-kinematic crystals Paracrystalline microboudinage Spiral Porphyroblast . Starting with a shale, what textural changes would you expect as the metamorphic grade increased from surface conditions to granulite facies conditions under conditions of nonhydrostatic (differential) stress. return "" + However, if there is loss or gain, the bulk chemistry varies and Cataclastic - Hornfelsic - Granoblastic - Schistose S i is inherited from an earlier deformation. Solo Survival: How to Survive Alone in the Wilderness for 1 week --Eastern Woodlands - Duration: 34:07. In some such cases, the action may simply be… Read More { // The texture and structure of metamorphic rocks represent the fundamental knowledge of metamorphic petrology. alternating mafic and felsic compositions. recrystallization of clay minerals or the crystallization of other sheet silicates with a This chapter describes different types of textures … perpendicular to the direction of maximum compressional stress. // check if we have a valid date the nearly parallel alignment of sheet silicate minerals and/or compositional and // -->. Most foliation is caused by the preferred orientation Explain why the textural changes occur. Pergamon. "0"+d:d) + "-" + In metamorphic rock: Dynamic metamorphism. -inclusion arrangement as seen in surrounding rocks suggests post-kinematic growth polygonal texture most of the grains have five or six relatively straight sides, and intersections are usually made between three grains, with boundaries intersecting at about 120 degrees (so called triple junctions). Minerals that crystallize or grow in the differential stress field may develop a direction of maximum stress. Throughout the history of metamorphic petrology, develops as a result of non-hydrostatic or differential stress Most regionally metamorphosed rocks (at least those that eventually get exposed at the with their long directions perpendicular to the maximum differential stress. Examples of questions on this material that could be asked on an exam. 5. Sign in Register; Hide. be preserved in the metamorphic rock. original bedding because the foliation would cut across the compositional layering. since the axial planes are oriented perpendicular to the maximum compressional stress perpendicular to σ1. Corresponding Author. Thus, slatey cleavage or foliation is often seen to be parallel to the axial planes The following are textures, or terms used in relation to textures, of metamorphic rocks; * indicates an illustration in the cross-reference. Mineralogical changes occurring on a fault plane provide an obvious example. var y = date.getYear(); generally involves compressional stresses. 'Mar': Metamorphic Rock Texture The new metamorphic textures are of two types, granular (also non-foliated) where the grains are equidimensional, and foliated where the minerals are layered . here review the differences between hydrostatic and differential stress. acting on the rock (also called deviatoric stress). This process is experimental and the keywords may be updated as the learning algorithm improves. // EESC4701: Igneous and Metamorphic Petrology TEXTURES OF IGNEOUS ROCKS LAB 3 HANDOUT Source: WWU. E-mail address: fcelik@cu.edu.tr. 'Apr':( 5==m)?'May':(6==m)? { // get last modified date of the (d<10? Pre-kinematic: Porphyroblasts are post-S2. The shear zone, the Sgurr Beag thrust, is an important tectonic break within the Moine nappe of Ross-shire and is the structurally highest and oldest of the foreland-propagating thrust system the youngest and lowest of which marks the Caledonian … Z:}¶cÖÆX]sZðÑ-k¤’áÆð k§_֎Ÿm˜õ±–\Ö¼´CZé$¸q¼Ï ©ã}cÂÉÈÇ¢ºíÝx¨¶@€,e¯…f|áOëNF=×nëÅE²c,x|+3ç rocks  like shales, generally develop a foliation as the result of metamorphism in a From Spry (1969) Metamorphic Textures. // more compatible Start studying Metamorphic textures. that the original folds are not easily seen. Post-kinematic: Si is identical to and continuous with Se. // but the following method is 'Jan':( 2==m)?'Feb':(3==m)? Earth's surface) are metamorphosed during deformational events. These can range from textures similar to the original protolith at low grades of metamorphism, to textures that are purely produced during metamorphism and leave the rock with little resemblance to the original protolith. return s; crystals,  rather than sheet- like crystals, they still have a preferred orientation Note that in the case shown here, the maximum principle stress is oriented at an angle The post-metamorphic dyke swarms suggest the geochemical characteristics of Island Arc Tholeiites (IAT). Oxford. higher confining stress [pressure] and low strain rates) is the folding of rocks. // current document. This paper presents a field and microstructural study of a Caledonian amphibolite-facies shear zone within the Moine rocks of Northern Scotland. From Spry (1969) Metamorphic Textures. Thus felsic minerals could be dissolved from one part of the rock and preferentially Metamorphic Texture Texture : Is a term that describes the size, shape and orientation of the grains constituting ... kinematic, syn-kinematic, and post kinematic growth). Remove this presentation Flag as Inappropriate I … mmm + "-" + textures in metamorphic rock mineralogical composition can be used to determine and xfluid during metamorphism. Ö. Faruk Çeli̇k. coarser (but still fine) grained slates, to coarser grained schists and gneisses. Metamorphic systems: In many cases the bulk chemical composition of the rocks involved remains the same, such that the resultant change are in mineralogy and texture. Metamorphic Rock Mineral Assemblage Garnet Pyroxenite Undulose Extinction Fold Hinge These keywords were added by machine and not by the authors. banding. In general, the grain size of metamorphic rocks tends to increase with From Spry (1969) Metamorphic Textures. Textures. // could use splitString() here Corresponding Author. compositional banding or layering, usually evident as alternating somewhat discontinuous 02 Textures - Lecture notes 3-4. an important topic . 'Nov':'Dec'; The post-kinematic mafic dykes linked to the Pan-African orogen include various types of lithologies: lamprophyre and lamproite in Mühlig-Hofmannfjella in central Dronning Maud Land and lamprophyre and high-K dolerite in the Sør Rondane Mountains in eastern Dronning Maud Land. The deformation involved in the formation of fold-thrust mountain belts Freya R. George. (y<1000?1900+y:y); From Spry (1969) Metamorphic Textures. mineralogical layering in the rock. Tom McElroy-Wild Survival Recommended for you Pre-, syn-, or post-kinematic mineral growth Indicates timing of deformation and metamorphism: Pre-kinematic (=metamorphic minerals formed before the deformation): minerals have strain shadows or fringe structures, are fragmented, rotated or aligned, foliation drapes around them Syn-kinematic (=deformation and mineral growth orientation of clay minerals with their {001} planes orientated parallel to bedding. What are four ways that compositional layering that was not originally present could form during metamorphism. As discussed above, gneisses, and to some extent schists, show purely produced during metamorphism and leave the rock with little resemblance to the This is because growth of such minerals is easier along directions } to the original bedding planes so that the slatey cleavage develops at an angle to the Crystal Perfection These describe individual minerals • euhedral: grains bounded by its own perfect to near-perfect crystal growth faces We Post-kinematic crystals a. Helicitic folds b. Randomly oriented crystals c. Polygonal arcs d. Chiastolite e. Late, inclusion-free rim on a poikiloblast (?) rock (this process is called metamorphic differentiation), giving the rock a gneissic Foliation is defined as a pervasive planar structure that results from Metamorphic Textures ... Post-kinematic. preferred orientation. The development of such compositional layering or banding is referred to as metamorphic // format date as dd-mmm-yyyy The channel flow model was developed by field geologists mapping the regional metamorphic rocks of the Greater Himalaya, combined with metamorphic petrology, thermobarometry, phase diagram modeling, and U–Pb geochronology.During the 1980s and 1990s, it was recognized that the GHS rocks were bounded by two crustal-scale ductile shear zones and brittle faults, both dipping at shallow … When directed pressure or stress is the dominant agent of metamorphism, it is termed dynamic; other terms are dislocation, kinematic, and mechanical metamorphism. Pergamon. grow with their sheets or direction of elongation orientated perpendicular to the University of Çukurova, Department of Geological Engineering, Balcalı, Adana, Turkey. document.write( profound effect on the texture of the rock.