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In places has later been silicified (compare unit Jsi).. Proc Iodp 309 312 Site 1256 VDPM 09.17. 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. Chlorite #2 thin section (hFOV 2mm) GET 360° LIVE INTERACTION. The brown minerals (in ppl) are likely some type of … Thin section of mylonite xpl. Once shearing begins, the mylonitic fabric begins to be developed, which changes the ordering of the mineral phases. 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. Green in ppl is chlorite. This mylonite is located in the same outcrop as mylonite 1 (mylonite 2 is farther south than mylonite 1). Click on the image to make it larger. This mylonite is located in the same outcrop as mylonite 1 (mylonite 2 is farther south than mylonite 1). 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 area shows a magnificent transition from porphyritic granite to mylonite. Introduction to Petrology by Elizabeth Johnson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted. The theme of the module is crustal evolution in contrasting environments. Hopefully you can see porphyroclasts (augens) and mylonite texture in the thin section images below. 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. 1st = plane polarized light; 2nd = cross-polarized light. Stereographic projection of quartz C-axes from mylonite. 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 indentations show positions of former … potassic feldspar-plagioclase mylonite with a platy foliation and a strong stretching lineation. Tabular morphology and the absence of undulatory extinction suggcsts that most of the biotite Hopefully you can see porphyroclasts (augens) and mylonite texture in the thin section images below. Thin Section Microscope Slide of a Mylonite from northern Sardinia. 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. Note how the planar, and circular markers change orientation and thickness across the zone. Kyanite - Al 2 SiO 5 Kyanite was named in 1789 by Abraham Gottlieb Werner from the Greek word "kyanos", meaning "blue". Thin section of mylonite. Plane polarized light. View Original Image at Full Size. A thin sliver of rock is cut from the sample with a diamond saw and ground optically flat. There is another structure above and to the left of the blue pencil. From Jean-Pierre Burg. 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. 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. The transition is gradual and known as the brittle-plastic transition. Mylonites form deep in the crust where temperature and pressure are high enough for the rocks to deform plastically (ductile deformation). 1st = plane polarized light; 2nd = cross-polarized light. See more ideas about geology, rock, metamorphic rocks. 1st = plane polarized light; 2nd = cross-polarized light. It’s possible to learn what goes on in mylonite formation by looking at microscopic thin sections from shear zones. 1st = ppl; 2nd = xpl. 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. Hopefully you can see porphyroclasts (augens) and mylonite texture in the thin section images below. Moine mylonite, Moine Thrust Zone Knockan Crag Outcrop. Thin section. All images have two views, in plane- and cross-polarized light. Last Modified: 2012-04-11 11:42:26 Field of … Deformation mechanism maps Behaviour of common minerals Thin Section A Mylonite With Idiomorphic Tourmaline Plane Polarized Download Scientific Diagram . Mylonites can have many different mineralogical compositions; it is a classification based on the textural appearance of the rock. 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). Nov 6, 2018 - Explore Bryn Mawr College Mineralogy's board "Rocks in Thin Section" on Pinterest. Thin section. Fig.4: Geometric softening due to grain shape and lattice rotation into shear plane. In this type of work it’s important to collect oriented rock samples. This technique has been used to study the def. The quartz-feldspar mylonite has a strongly developed lineation defined by granu- lar feldspar strings between larger clasts. 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). Porphyroclasts are mostly qtz, rusty brown layers are clays produced by shearing. Supplied as a sillimanite mylonite, which mineral it does contain, the most striking minerals are highly pleochroic blue amphibole, with a green hornblende. Mylonite thin section. From Passchier (2005). The first set of samples are from the level 3 module 'Understanding the Continents'. 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. Image 33023 is a 900 by 405 pixel JPEG Uploaded: Apr11 12. Movie of twin gliding. A map of each thin section was made using a LEO 1430VP scanning electron microscope. Can you see the mylonite fabric in this photo? This collection consists of the rocks and thin sections used in the Open University modules. Mylonite with rotated clasts in plane polarized light. The students are pointing to one metamorphic feature with their pencils. 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. Nevertheless, we see clear evidence for shearing of crystals in deformed rocks. Thin Section Photos and Videos Click on the image to make it larger. Photomicrographs Of A Thin Section Of The Bedding Parallel Fault Download Scientific Diagram . 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. Image to right is of a ductiley deformed quartz-mica mylonite from the Kjeiserhjelmen core complex detachment in the NW part of Spitsbergen, Norway. Click on the image to make it larger. Mylonite is a foliated metamorphic rock that is composed of intensely flattened minerals in a fine-grained streaked matrix. It is hard to know what the protolith was, but based upon the porphyroclasts it was likely an ultramafic or mafic rock. A thin section of mylonite which was collected from the metamorphic region of Lom, Central Norway. Sem Micrographs Of An Etched Thin Section Showing Smectite Kerogen Download Scientific Diagram . Movie of grain boundary migration. The foliation is defined by thin (< 2 mm) ribbons of quartz, and by slightly Image 33023 is a 900 by 405 pixel JPEG Uploaded: Apr11 12. Last Modified: 2012-04-11 11:42:26 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. Chlorite PPL properties. Hand specimen. The foliation dips north at a moderate angle, and the stretching lineation plunges towards 290’ at a shallow angle. The Moine Thrust itself lies between these dark rocks and the white Durness limestone in the centre of the photograph. Are the amphiboles prophyroclasts or porphyroblasts? The depth depends on the temperature gradient and the mineralogy of the crust. The foliation is defined by thin (< 2 mm) ribbons of quartz, and by slightly flattened feldspar porphyroclasts up to 1 cm in size. Click on the image to make it larger. 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. 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. Can you identify it also? Mylonite thin section. Supplied as a sillimanite mylonite, which mineral it does contain, the most striking minerals are highly pleochroic blue amphibole, with a green hornblende. 1st = plane polarized light; 2nd = cross-polarized light. 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. Field of … The quartz grains in this view range in color from white to gray to black, and they form a tight interlocking network. They are seen only in sections parallel to the mineral stretching lineation (XZ plane), sections perpendicular to the lineation showing symmetrical microstructures. Many of the illustrations in this section are from a… Entire thin section scan. Click on the image to make it larger. 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. The stretching lineation is due to elongation of quartz aggregates, and corresponds to the long axes of pressure shadows around feldspar porphyroclasts. Shear zone at a moderate angle, and circular markers change orientation and thickness across the zone unit Jsi..! Looking at microscopic thin sections used in the NW part of the rocks and thin sections from shear.... 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