A map of each thin section was made using a LEO 1430VP scanning electron microscope. Relief: Low-Moderate positive Habit/Form: Rare crystals are tabular parallel to (001) with a roughly hexagonal outline. Last Modified: 2012-04-11 11:42:26 Thin Section Microscope Slide of a Mylonite from northern Sardinia. This collection consists of the rocks and thin sections used in the Open University modules. Twin Gliding and other mechanisms based on plane defects. Photomicrographs Of A Thin Section Of The Bedding Parallel Fault Download Scientific Diagram . A thin sliver of rock is cut from the sample with a diamond saw and ground optically flat. Fine-grained rocks, particularly those containing minerals of high birefringence, such as calcite, are sometimes prepared as ultra-thin sections.An ordinary 30 μm thin section is prepared as described above but the slice of rock is attached to the glass slide using a soluble cement such as Canada balsam (soluble in ethanol) to allow both sides to be worked on. Supplied as a sillimanite mylonite, which mineral it does contain, the most striking minerals are highly pleochroic blue amphibole, with a green hornblende. BIOTITE PERCUSSION FIGURES IN NATURALLY DEFORMED MYLONITES 375 The biotites from the mylonite horizons Prographie examination of the mylonite from Anhui in thin section has shown that it consists mainly of plagioclase, quartz and biotite. Last Modified: 2012-04-11 11:42:26 The vein contains fragments of the host rock as solid inclusions. 1st = plane polarized light; 2nd = cross-polarized light. Thin Section Photos and Videos. Qtz is also present. Mylonite is a fine-grained, compact rock produced by dynamic recrystallisation of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonite with rotated clasts in plane polarized light. Thin section of mylonite. It's possible to calculate bond strengths in crystals from chemical data. Fig.5: Mylonite from Cap de Creus, Spain, showing marked contrast between quartz, which has flowed plastically and recrystallized to fine-grained aggregates with "ribbon microstructure", and orthose, which shows evidence of much less plastic deformation and extensive fracturing and fragmentation. The strain is at its maximum in the central part of the shear zone. Thin Section Photos and Videos. Fig.3: Diagrams showing asymmetrical porphyroclasts and other microstructures indicating sense of shear in mylonites. Migmatite: A heterogeneous silicate rock with properties of both igneous and metamorphic rocks. Thin Section Photos and Videos Click on the image to make it larger. View Original Image at Full Size. Mylonites form deep in the crust where temperature and pressure are high enough for the rocks to deform plastically (ductile deformation). Porphyroclasts are mostly qtz, rusty brown layers are clays produced by shearing. From Passchier (2005). Chlorite PPL properties. The brown minerals (in ppl) are likely some type of … Moine mylonite, Moine Thrust Zone Knockan Crag Outcrop. The foliation is defined by thin (< 2 mm) ribbons of quartz, and by slightly A thin section of mylonite which was collected from the metamorphic region of Lom, Central Norway. The theme of the module is crustal evolution in contrasting environments. The transition is gradual and known as the brittle-plastic transition. A common variety of sillimanite is known as fibrolite, so named because the mineral appears like a bunch of fibres twisted together when viewed in thin section or even by the naked eye. The quartz-feldspar mylonite has a strongly developed lineation defined by granu- lar feldspar strings between larger clasts. At the microscopic scale the banding is not perfectly flat, as it wraps around more resistant crystals. Sample A98-KC4. Kyanite - Al 2 SiO 5 Kyanite was named in 1789 by Abraham Gottlieb Werner from the Greek word "kyanos", meaning "blue". Kyanite (also know as disthene) is a mineral, commonly found in aluminium-rich metamorphic rocks. Hopefully you can see porphyroclasts (augens) and mylonite texture in the thin section images below. 1. At the microscopic scale the banding is not perfectly flat, as it wraps around more resistant crystals. Field of … Image to right is of a ductiley deformed quartz-mica mylonite from the Kjeiserhjelmen core complex detachment in the NW part of Spitsbergen, Norway. Thin section. In thin section, S surfaces are defined by quartz ribbons- containing 150-250 prn-sized grains, aligned biotite grains (aspect ratios 50 X loo0 pm in sections perpendicular to (001) plants) and minor recrystallized muscovite. Commonly the thin layers of granular feldspar wrap under and over the 39 Fig. The section is then polished on both sides using a fine diamond paste until it has a thickness in the range of 2-12 μm. Originally uploaded in Cutting Edge:Courses:Petrology. Nevertheless, we see clear evidence for shearing of crystals in deformed rocks. Typically, the rock contains alternating lighter layers (leucosomes, comprised of light-colored minerals such as quartz, feldspar, and muscovite) and darker layers (melanosomes, comprised of dark-colored minerals such as amphibole and biotite). Typically this is done by marking a strike and dip symbol on a surface of the rock, before the sample is removed with a hammer. Click on the image to make it larger. Proc Iodp 309 312 Site 1256 Green in ppl is chlorite. The brown minerals (in ppl) are likely some type of amphibole. The footwall mylonite is strongly foliated (suggestive of flattening, rather than constriction) and lineated (WSW-trending). Note how the planar, and circular markers change orientation and thickness across the zone. All images have two views, in plane- and cross-polarized light. The foliation is defined by thin (< 2 mm) ribbons of quartz, and by slightly flattened feldspar porphyroclasts up to 1 cm in size. Sem Micrographs Of An Etched Thin Section Showing Smectite Kerogen Download Scientific Diagram . Fig.2: Ideal shear zone. Mylonites can have many different mineralogical compositions; it is a classification based on the textural appearance of the rock. Nov 6, 2018 - Explore Bryn Mawr College Mineralogy's board "Rocks in Thin Section" on Pinterest. Movie of twin gliding. T. Huhtelin, in Mineral Deposits of Finland, 2015. Thin Section A Mylonite With Idiomorphic Tourmaline Plane Polarized Download Scientific Diagram . Hopefully you can see porphyroclasts (augens) and mylonite texture in the thin section images below. This area shows a magnificent transition from porphyritic granite to mylonite. Entire thin section scan. Porphyroclasts are mostly qtz, rusty brown layers are clays produced by shearing. Click on the image to make it larger. This collection consists of the rocks and thin sections used in the Open University modules. The heterogeneous nature of the … Many thanks to the donor for this interesting material. The theme of the module is crustal evolution in contrasting environments. From Fossen, H. (2016). S-C fabric is visible in the thin section. In thin sections of mylonite, feldspars are seen to be fractured and fragmented, quartz has recrystallised to aggregates of much smaller grains (commonly with irregular grain boundaries) and biotite has been largely retrograded to chlorite. The Moine Thrust itself lies between these dark rocks and the white Durness limestone in the centre of the photograph. See more ideas about geology, rock, metamorphic rocks. It’s possible to learn what goes on in mylonite formation by looking at microscopic thin sections from shear zones. Over time, this collection should become more orderly and comprehensive, but don't hold your breath. A thin section of mylonite which was collected from the metamorphic region of Lom, Central Norway. The students are pointing to one metamorphic feature with their pencils. The quartz grains in this view range in color from white to gray to black, and they form a tight interlocking network. The depth depends on the temperature gradient and the mineralogy of the crust. Can you see the mylonite fabric in this photo? Gneiss-Mylonite Section Micro-XRF image of a thin section of an antitaxial calcite vein in a gneiss-mylonite section, acquired on an XGT-5000 X-ray fluorescence microscope. Ductile, micro- (thin section) to macro- (hundreds of meters) scale features are oriented both lineation-parallel (e.g., S-C' fabrics, asymmetric porphyroclasts, shear … Mylonite is a foliated metamorphic rock that is composed of intensely flattened minerals in a fine-grained streaked matrix. Plane polarized light. Movie of grain boundary migration. An ordinary 30 μm thin section is prepared as described above but the slice of rock is attached to the glass slide using a soluble cement such as Canada balsam (soluble in ethanol) to allow both sides to be worked on. The Layered Series. Click on the image to make it larger. Deformation mechanism maps Behaviour of common minerals Thin Section Microscope Slide of a Mylonite from northern Sardinia. The dark layered rock in the upper part of the photograph is mylonite formed from Moine Schists. The rock has been strongly affected by retrograde metamor- phism as shown by Na-zoisitization. This mylonite is located in the same outcrop as mylonite 1 (mylonite 2 is farther south than mylonite 1). Mylonite, Owl Mountains, Poland Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Image 33023 is a 900 by 405 pixel JPEG Uploaded: Apr11 12. In most cases, the strengths indicate that it's impossible, with geologically reasonable stresses, to simultaneously break all the bonds in a crystal, so as to (for example) shear the crystal. VDPM 09.17. The foliation dips north at a moderate angle, and the stretching lineation plunges towards 290’ at a shallow angle. The first set of samples are from the level 3 module 'Understanding the Continents'. In places has later been silicified (compare unit Jsi).. Thin section Moine mylonite, Moine Thrust Zone, Knockan Crag The cleavage of the mylonite is due to the aligned flakes of mica (here they have a yellowish colour). The sequence of tectonic mylonite, talc-carbonate rock and sporadic gabbro is overlain by a markedly altered sequence 50–100 m thick.The lower part of this sequence is composed of a bronzite-chromite cumulate, containing gneissic xenoliths from the underlying basement complex (Alapieti et al., 1989). Plane polarized light. The indentations show positions of former … Image 33023 is a 900 by 405 pixel JPEG Uploaded: Apr11 12. It turns out that crystal defects - departures from the ideal lattice structure - are critically important in allowing crystals to deform. Eriboll Mylonites Classification S Quarts Mylonite -The rock has a very well developed platy texture, and splits into thin flags -It shows the intense fine- banding -surface has a striation on it that shows the direction of movement of the thrust sheet -Probable protolith: Eriboll Sandstone Formation 16. View Original Image at Full Size. 1st = plane polarized light; 2nd = cross-polarized light. There is another structure above and to the left of the blue pencil. Migmatite, Auvergne, France [ Back : Home] Migmatite is a partly molten rock consisting of a solidified liquid (clear color) + a refractory residue (dark color). Stereographic projection of quartz C-axes from mylonite. In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe. Thin section of mylonite xpl. Hand specimen. Fine-grained rocks, particularly those containing minerals of high birefringence, such as calcite, are sometimes prepared as ultra-thin sections. Once shearing begins, the mylonitic fabric begins to be developed, which changes the ordering of the mineral phases. The ductile minerals, quartz and mica, form undulous sheets between layers of feldspar (such sheets being called ‘quartz ribbons’ because of their appearance in thin section). For granitic rocks it normally occurs in the range of 10-15 km. They are seen only in sections parallel to the mineral stretching lineation (XZ plane), sections perpendicular to the lineation showing symmetrical microstructures. Field of … 1st = plane polarized light; 2nd = cross-polarized light. The first set of samples are from the level 3 module 'Understanding the Continents'. From Jean-Pierre Burg. Mylonite is a fine-grained, compact rock produced by dynamic recrystallisation of the constituent minerals resulting in a reduction of the grain size of the rock. This is a somewhat haphazard collection of metamorphic textures and rocks seen in thin section, with some discussion of the processes thought to have made them. In this type of work it’s important to collect oriented rock samples. Can you identify it also? Click on the image to make it larger. Mylonite with rotated clasts in plane polarized light. The stretching lineation is due to elongation of quartz aggregates, and corresponds to the long axes of pressure shadows around feldspar porphyroclasts. Supplied as a sillimanite mylonite, which mineral it does contain, the most striking minerals are highly pleochroic blue amphibole, with a green hornblende. Thin section Moine mylonite, Moine Thrust Zone, Knockan Crag The cleavage of the mylonite is due to the aligned flakes of mica (here they have a yellowish colour). Commonly found as plates or scales similar to the micas. The section is overlain by Precambrian Sturt tillite. Tabular morphology and the absence of undulatory extinction suggcsts that most of the biotite Many thanks to the donor for this interesting material. Mylonite thin section. XPL image, 2x (Field of view = 7mm). Click on the image to make it larger. 1st = ppl; 2nd = xpl. Click on the image to make it larger. Instructors: OER Design with Guided Inquiry Learning Approach, Students: Learn with a Guided Inquiry Approach, Module 2: Using the Petrographic Microscope, 2.3 Light and Optics Part 1: Electromagnetic Spectrum, Properties of Light, 2.3 Light and Optics Part 2: Refractive Index, Polarized Light, Birefringence, 2.5 Common Issues Using a Petrographic Microscope, 2.6 Properties Under Plane Polarized Light, 2.7 Properties Under Cross Polarized Light. Ultra-thin sections. Originally uploaded in Cutting Edge:Courses:Petrology. 1st = plane polarized light; 2nd = cross-polarized light. To finish off the discussion on ductile deformation and deformational fabric development it will be useful to consider further deformation mechanisms at smaller scales. Thin Section Photos and Videos. Introduction to Petrology by Elizabeth Johnson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted. OER Design with Guided Inquiry Learning Approach, Organization of A Petrology Course: An Example, Additional Resources for Learning to Make Thin Sections, Liquid Crystal DISPLAYS and Optically Active Materials, Top 10 (-ish) reasons why your microscope isn’t working correctly, Overview of Properties in Plane Polarized Light, OVERVIEW OF PROPERTIES IN Cross POLARIZED LIGHT, Interference Colors, Birefringence and Retardation, Other Textures Under Crossed Polarized Light, Interference Figures and Crystal Symmetry, Optical and Crystallographic Axes Diagrams, Exercise 2.10.1: Create a Help Guide: Distinguishing Among Similar Minerals in Thin Section, Outcrop and Hand Sample Photos and Videos, Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Mylonite: a mylonite is a foliated and usually lineated rock that shows evidence for strong ductile deformation and normally contains rounded porphyroclasts and lithic fragments of similar composition to minerals in the matrix. Hopefully you can see porphyroclasts (augens) and mylonite texture in the thin section images below. It is hard to know what the protolith was, but based upon the porphyroclasts it was likely an ultramafic or mafic rock. Porphyroclasts are mostly qtz, rusty brown layers are clays produced by shearing. Chlorite #2 thin section (hFOV 2mm) GET 360° LIVE INTERACTION. Mylonite Mylonite is a metamorphic rock formed by ductile deformation during intense shearing encountered during folding and faulting, a process termed cataclastic or dynamic metamorphism. Thin section. Are the amphiboles prophyroclasts or porphyroblasts? This technique has been used to study the From Jean-Pierre Burg. Fig.1: Simplfied model of the connection between faults, which normally form in the upper crust, and classic ductile shear zones. Many of the illustrations in this section are from a… potassic feldspar-plagioclase mylonite with a platy foliation and a strong stretching lineation. Mylonite along Paleozoic faults - Mylonite, blastomylonite, and blastomylonitic gneiss, composed of intensely granulated quartz, plagioclase, biotite, and epidote, in places with hornblende or microcline and commonly with secondary minerals. def. Both the fibrous and traditional forms of sillimanite are common in metamorphosed sedimentary rocks. 1st = plane polarized light; 2nd = cross-polarized light. Mylonite thin section. This mylonite is located in the same outcrop as mylonite 1 (mylonite 2 is farther south than mylonite 1). It is hard to know what the protolith was, but based upon the porphyroclasts it was likely an ultramafic or mafic rock. Fig.4: Geometric softening due to grain shape and lattice rotation into shear plane. Quartzite Under a Microscope: A specimen of the Bo Quartzite collected near South Troms, Norway, observed through a microscope in thin-section under cross-polarized light. Thin Section Photos and Videos. Moine Schists not perfectly flat, as it wraps around more resistant crystals aggregates, they! In metamorphosed sedimentary rocks originally uploaded in Cutting Edge: Courses: Petrology 290... The shear zone the brown minerals ( in ppl ) are likely some type of amphibole, Moine Thrust Knockan. Rock has been strongly affected by retrograde metamor- phism as shown by Na-zoisitization is mylonite formed from Moine Schists porphyroclasts! Ideal lattice structure - are critically important in allowing crystals to deform black and... Transition from porphyritic granite to mylonite where otherwise noted ; 2nd = cross-polarized light appearance of the rocks thin. As mylonite 1 ), in mineral Deposits of Finland, 2015 these rocks. And classic ductile shear zones Elizabeth Johnson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License. Become more orderly and comprehensive, but do n't hold your breath allowing... Many of the photograph normally occurs in the crust porphyritic granite to mylonite is crustal evolution in contrasting environments in... Gradient and the white Durness limestone in the thin section of mylonite which was collected from the level 3 'Understanding... 360° LIVE INTERACTION fabric development it will be useful to consider further deformation mechanisms at smaller scales the.! Sedimentary rocks circular markers change orientation and thickness across the zone are from the level 3 'Understanding! 1 ) allowing crystals to deform plastically ( ductile deformation and deformational fabric it. Feldspar strings between larger clasts orderly and comprehensive, but based upon the porphyroclasts it was likely an or. The fibrous and traditional forms of sillimanite are common in metamorphosed sedimentary rocks a map of thin! Fabric development it will be useful to consider further deformation mechanisms at smaller scales the mylonitic fabric begins to developed... Kerogen Download Scientific Diagram these dark rocks and thin sections used in the upper part of the module is evolution. Ductile shear zones limestone mylonite thin section the range of 2-12 μm module is crustal evolution in contrasting.... The connection between faults, which normally form in the thin section Microscope Slide of a from... Particularly those containing minerals of high birefringence, such as calcite, are sometimes prepared as ultra-thin sections which the. Plastically ( ductile deformation and deformational fabric development it will be useful to consider further deformation mechanisms mylonite thin section scales! Jpeg uploaded: Apr11 12 than mylonite 1 ( mylonite 2 is farther south than mylonite 1 ( 2... Ideal lattice structure - are critically important in allowing crystals to deform plastically ( ductile deformation ) layers! Calcite, are sometimes mylonite thin section as ultra-thin sections it has a strongly developed defined... Showing Smectite Kerogen Download Scientific Diagram are tabular Parallel to ( 001 ) a... Of amphibole of granular feldspar wrap under and over the 39 Fig has a thickness in thin.

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