Qtz is also present. The dark layered rock in the upper part of the photograph is mylonite formed from Moine Schists. 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. A thin sliver of rock is cut from the sample with a diamond saw and ground optically flat. Thin Section Photos and Videos. Can you see the mylonite fabric in this photo? The brown minerals (in ppl) are likely some type of … Thin Section Microscope Slide of a Mylonite from northern Sardinia. Thin Section Microscope Slide of a Mylonite from northern Sardinia. Originally uploaded in Cutting Edge:Courses:Petrology. 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. This technique has been used to study the Mylonite thin section. 1. 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). Mylonite thin section. Image 33023 is a 900 by 405 pixel JPEG Uploaded: Apr11 12. 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. Thin Section A Mylonite With Idiomorphic Tourmaline Plane Polarized Download Scientific Diagram . Stereographic projection of quartz C-axes from mylonite. Note how the planar, and circular markers change orientation and thickness across the zone. Thin section. Ultra-thin sections. The quartz-feldspar mylonite has a strongly developed lineation defined by granu- lar feldspar strings between larger clasts. Click on the image to make it larger. The Layered Series. Many thanks to the donor for this interesting material. Click on the image to make it larger. XPL image, 2x (Field of view = 7mm). Porphyroclasts are mostly qtz, rusty brown layers are clays produced by shearing. The strain is at its maximum in the central part of the shear zone. Fig.4: Geometric softening due to grain shape and lattice rotation into shear plane. 1st = plane polarized light; 2nd = cross-polarized light. Field of … A thin section of mylonite which was collected from the metamorphic region of Lom, Central Norway. The foliation is defined by thin (< 2 mm) ribbons of quartz, and by slightly T. Huhtelin, in Mineral Deposits of Finland, 2015. This collection consists of the rocks and thin sections used in the Open University modules. Introduction to Petrology by Elizabeth Johnson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted. The quartz grains in this view range in color from white to gray to black, and they form a tight interlocking network. 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 section is overlain by Precambrian Sturt tillite. Thin section. Nov 6, 2018 - Explore Bryn Mawr College Mineralogy's board "Rocks in Thin Section" on Pinterest. In this type of work it’s important to collect oriented rock samples. Relief: Low-Moderate positive Habit/Form: Rare crystals are tabular parallel to (001) with a roughly hexagonal outline. Fig.2: Ideal shear zone. It is hard to know what the protolith was, but based upon the porphyroclasts it was likely an ultramafic or mafic rock. 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). Thin Section Photos and Videos. Proc Iodp 309 312 Site 1256 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. 1st = plane polarized light; 2nd = cross-polarized light. Click on the image to make it larger. Sem Micrographs Of An Etched Thin Section Showing Smectite Kerogen Download Scientific Diagram . The transition is gradual and known as the brittle-plastic transition. Can you identify it also? 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. View Original Image at Full Size. From Passchier (2005). Image to right is of a ductiley deformed quartz-mica mylonite from the Kjeiserhjelmen core complex detachment in the NW part of Spitsbergen, Norway. To finish off the discussion on ductile deformation and deformational fabric development it will be useful to consider further deformation mechanisms at smaller scales. Hopefully you can see porphyroclasts (augens) and mylonite texture in the thin section images below. Plane polarized light. 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. Hopefully you can see porphyroclasts (augens) and mylonite texture in the thin section images below. Mylonite with rotated clasts in plane polarized light. 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. 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. 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. Moine mylonite, Moine Thrust Zone Knockan Crag Outcrop. Fine-grained rocks, particularly those containing minerals of high birefringence, such as calcite, are sometimes prepared as ultra-thin sections. Movie of twin gliding. Kyanite - Al 2 SiO 5 Kyanite was named in 1789 by Abraham Gottlieb Werner from the Greek word "kyanos", meaning "blue". def. At the microscopic scale the banding is not perfectly flat, as it wraps around more resistant crystals. Porphyroclasts are mostly qtz, rusty brown layers are clays produced by shearing. 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. Entire thin section scan. The indentations show positions of former … potassic feldspar-plagioclase mylonite with a platy foliation and a strong stretching lineation. 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. Field of … Thin Section Photos and Videos. It turns out that crystal defects - departures from the ideal lattice structure - are critically important in allowing crystals to deform. All images have two views, in plane- and cross-polarized light. The first set of samples are from the level 3 module 'Understanding the Continents'. Last Modified: 2012-04-11 11:42:26 This area shows a magnificent transition from porphyritic granite to mylonite. Sample A98-KC4. From Jean-Pierre Burg. Photomicrographs Of A Thin Section Of The Bedding Parallel Fault Download Scientific Diagram . The rock has been strongly affected by retrograde metamor- phism as shown by Na-zoisitization. Thin section of mylonite xpl. 1st = plane polarized light; 2nd = cross-polarized light. It's possible to calculate bond strengths in crystals from chemical data. Ductile, micro- (thin section) to macro- (hundreds of meters) scale features are oriented both lineation-parallel (e.g., S-C' fabrics, asymmetric porphyroclasts, shear … A map of each thin section was made using a LEO 1430VP scanning electron microscope. Supplied as a sillimanite mylonite, which mineral it does contain, the most striking minerals are highly pleochroic blue amphibole, with a green hornblende. 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. From Fossen, H. (2016). Commonly found as plates or scales similar to the micas. Commonly the thin layers of granular feldspar wrap under and over the 39 Fig. The stretching lineation is due to elongation of quartz aggregates, and corresponds to the long axes of pressure shadows around feldspar porphyroclasts. 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. There is another structure above and to the left of the blue pencil. The theme of the module is crustal evolution in contrasting environments. Thin Section Photos and Videos. Porphyroclasts are mostly qtz, rusty brown layers are clays produced by shearing. 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. Tabular morphology and the absence of undulatory extinction suggcsts that most of the biotite Mylonites can have many different mineralogical compositions; it is a classification based on the textural appearance of the rock. View Original Image at Full Size. The depth depends on the temperature gradient and the mineralogy of the crust. Hand specimen. Fig.1: Simplfied model of the connection between faults, which normally form in the upper crust, and classic ductile shear zones. The Moine Thrust itself lies between these dark rocks and the white Durness limestone in the centre of the photograph. Many thanks to the donor for this interesting material. 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. Green in ppl is chlorite. Once shearing begins, the mylonitic fabric begins to be developed, which changes the ordering of the mineral phases. This collection consists of the rocks and thin sections used in the Open University modules. 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 students are pointing to one metamorphic feature with their pencils. A thin section of mylonite which was collected from the metamorphic region of Lom, Central Norway. In places has later been silicified (compare unit Jsi).. 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. See more ideas about geology, rock, metamorphic rocks. 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. Last Modified: 2012-04-11 11:42:26 Both the fibrous and traditional forms of sillimanite are common in metamorphosed sedimentary rocks. S-C fabric is visible in the thin section. 1st = plane polarized light; 2nd = cross-polarized light. 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 footwall mylonite is strongly foliated (suggestive of flattening, rather than constriction) and lineated (WSW-trending). Fig.3: Diagrams showing asymmetrical porphyroclasts and other microstructures indicating sense of shear in mylonites. The foliation is defined by thin (< 2 mm) ribbons of quartz, and by slightly flattened feldspar porphyroclasts up to 1 cm in size. Movie of grain boundary migration. Migmatite, Auvergne, France [ Back : Home] Migmatite is a partly molten rock consisting of a solidified liquid (clear color) + a refractory residue (dark color). The brown minerals (in ppl) are likely some type of amphibole. Click on the image to make it larger. 1st = plane polarized light; 2nd = cross-polarized light. Originally uploaded in Cutting Edge:Courses:Petrology. Chlorite #2 thin section (hFOV 2mm) GET 360° LIVE INTERACTION. 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. The vein contains fragments of the host rock as solid inclusions. Over time, this collection should become more orderly and comprehensive, but don't hold your breath. The first set of samples are from the level 3 module 'Understanding the Continents'. Mylonite with rotated clasts in plane polarized light. Plane polarized light. 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). The foliation dips north at a moderate angle, and the stretching lineation plunges towards 290’ at a shallow angle. 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 heterogeneous nature of the … 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. Click on the image to make it larger. Supplied as a sillimanite mylonite, which mineral it does contain, the most striking minerals are highly pleochroic blue amphibole, with a green hornblende. Migmatite: A heterogeneous silicate rock with properties of both igneous and metamorphic rocks. It is hard to know what the protolith was, but based upon the porphyroclasts it was likely an ultramafic or mafic rock. The theme of the module is crustal evolution in contrasting environments. 1st = ppl; 2nd = xpl. From Jean-Pierre Burg. They are seen only in sections parallel to the mineral stretching lineation (XZ plane), sections perpendicular to the lineation showing symmetrical microstructures. At the microscopic scale the banding is not perfectly flat, as it wraps around more resistant crystals. Chlorite PPL properties. 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. Click on the image to make it larger. Many of the illustrations in this section are from a… For granitic rocks it normally occurs in the range of 10-15 km. Image 33023 is a 900 by 405 pixel JPEG Uploaded: Apr11 12. This mylonite is located in the same outcrop as mylonite 1 (mylonite 2 is farther south than mylonite 1). Deformation mechanism maps Behaviour of common minerals VDPM 09.17. Twin Gliding and other mechanisms based on plane defects. It’s possible to learn what goes on in mylonite formation by looking at microscopic thin sections from shear zones. Mylonite is a foliated metamorphic rock that is composed of intensely flattened minerals in a fine-grained streaked matrix. Are the amphiboles prophyroclasts or porphyroblasts? Hopefully you can see porphyroclasts (augens) and mylonite texture in the thin section images below. This mylonite is located in the same outcrop as mylonite 1 (mylonite 2 is farther south than mylonite 1). Thin section of mylonite. Thin Section Photos and Videos Click on the image to make it larger. Mylonites form deep in the crust where temperature and pressure are high enough for the rocks to deform plastically (ductile deformation). Kyanite (also know as disthene) is a mineral, commonly found in aluminium-rich metamorphic rocks. Nevertheless, we see clear evidence for shearing of crystals in deformed rocks. 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. Shown by Na-zoisitization License, except where otherwise noted 405 pixel JPEG uploaded: Apr11 12 time. Ultramafic or mafic rock likely an ultramafic or mafic rock students are pointing to one feature. 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