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Origin, Texture, and Classification of Metamorphic Rocks - Teklewold Ayalew
GEOLOGY – Vol. II - Origin, Texture, and Classification of Metamorphic Rocks - Teklewold Ayalew ORIGIN, TEXTURE, AND CLASSIFICATION OF METAMORPHIC ROCKS Teklewold Ayalew Addis Ababa University, Ethiopia Keywords: aluminosilicates, assemblage, fabric, foliation, gneissose banding, index mineral, isograd, lineation, lithosphere, metamorphic facies, metasomatism, orogenic belt, schistosity Contents 1. Introduction 2. Occurrence 2.1. Orogenic Metamorphism 2.2. Contact Metamorphism 2.3. Ocean Floor Metamorphism 3. Classification 4. Minerals of Metamorphic Rocks 5. Metamorphic Facies 5.1. Facies of Very Low Grade 5.2. Greenschist Facies 5.3. Amphibolite Facies 5.4. Granulite Facies 5.5. Hornblende Hornfels Facies 5.6. Pyroxene Hornfels Facies 5.7. Blueschist Facies 5.8. Eclogite Facies 6. Tectonic Setting of Metamorphic Facies 7. Textures 7.1. Layering, Banding, and Fabric Development 8. Kinetics 8.1. Diffusion 8.2. Nucleation 8.3. Crystal Growth AcknowledgmentUNESCO – EOLSS Glossary Bibliography Biographical SketchSAMPLE CHAPTERS Summary Metamorphic rocks are igneous, sedimentary, or other metamorphic rocks whose texture and composition has been changed by metamorphism. Metamorphism occurs as a response to changes in the physical or chemical environment of any pre-existing rock, such as variations in pressure or temperature, strain, or the infiltration of fluids. It involves recrystallization of existing minerals into new grains and/or the appearance of new mineral phases and breakdown of others. Metamorphic processes take place ©Encyclopedia of Life Support Systems (EOLSS) GEOLOGY – Vol. II - Origin, Texture, and Classification of Metamorphic Rocks - Teklewold Ayalew essentially in the solid state. The rock mass does not normally disaggregate and lose coherence entirely; however small amounts of fluids are frequently present and may play an important catalytic role. -
Mineral Mania
The Rock Factory A Pre-Visit Information Guide for Teachers Meets Next Generation Science Standards: 5-PS1-3; MS LS4-1,2; MS ESS1-4; MS-ESS2-1 How does our Earth create so many different types of rocks? Learn about the different processes that form and reform rocks as you identify many types of rocks, minerals and fossils. Students will learn to think like geologists as they move through interactive investigation stations packed with specimens from the Museum’s collections. OBJECTIVES The Rock Cycle: Students will examine the three types of rocks - igneous, metamorphic and sedimentary – and discover the processes that create them. Tracing the connections between shale and slate, limestone and marble, students will discover how the rock cycle changes the very ground beneath our feet! Characteristics of Rocks Students will learn how to observe and identify rocks through their unique characteristics, looking for telling clues such as layering, crystal size, fossils, magnetism, and more. Students will practice their observational skills as they describe the Museum’s unique rock and mineral specimens. Investigation Stations: Students will explore Museum geology specimens up close at investigation stations to answer such questions as: “Why do fossils form only in certain rocks?” “How do rocks form from volcanic eruptions?” “How can I recognize different types of rocks?”. ACTIVITIES Teachers are encouraged to conduct pre-visit and post-visit classroom discussions and activities with their classes to make the most of their experience. Encourage your students to start a classroom rock collection, and create an exhibit with the rocks organized by type – igneous, sedimentary and metamorphic. -
Geologic Boulder Map of Campus Has Been Created As an Educational Educational an As Created Been Has Campus of Map Boulder Geologic The
Adam Larsen, Kevin Ansdell and Tim Prokopiuk Tim and Ansdell Kevin Larsen, Adam What is Geology? Igneous Geo-walk ing of marine creatures when the limestone was deposited. It also contains by edited and Written Geology is the study of the Earth, from the highest mountains to the core of The root of “igneous” is from the Latin word ignis meaning fire. Outlined in red, numerous fossils including gastropods, brachiopods, receptaculita and rugose the planet, and has traditionally been divided into physical geology and his- this path takes you across campus looking at these ancient “fire” rocks, some coral. The best example of these are in the Geology Building where the stone torical geology. Physical geology concentrates on the materials that compose of which may have been formed at great depths in the Earth’s crust. Created was hand-picked for its fossil display. Campus of the Earth and the natural processes that take place within the earth to shape by the cooling of magma or lava, they can widely vary in both grain size and Granite is another common building stone used on campus. When compa- its surface. Historical geology focuses on Earth history from its fiery begin- mineral composition. This walk stops at examples showing this variety to help nies sell granite, they do not use the same classification system as geologists. nings to the present. Geology also explores the interactions between the you understand what the change in circumstances will do to the appearance Granite is sold in many different colours and mineral compositions that a Map Boulder Geologic lithosphere (the solid Earth), the atmosphere, the biosphere (plants, animals of the rock. -
Chapter 1 – Introduction – Review of Rocks and Plate Tectonics Practice Exam and Study Guide
Chapter 1 – Introduction – Review of Rocks and Plate Tectonics Practice Exam and Study Guide To be able to understand the material covered during this course you need to have a basic background in the kinds of rocks making up our planet. This section of the study guide is aimed at helping you gain that background. 1. What are the three major groups of rocks found on planet Earth? Igneous Rocks 2. Which of the following processes is associated with igneous rocks? a. Solid‐state recrystallization b. Weathering and erosion c. Transportation and deposition d. Cooling a silicate liquid to a solid rock e. The accumulation of granitic debris in a moraine 3. If a silicate liquid flows out along the Earth’s surface or seabed, then it is called _______________. 4. If a silicate liquid exists beneath the Earth’s surface or seabed, then it is called _______________. 5. Which of the following terms refer to a body of magma or its solidified equivalent? a. Basalt b. Sandstone c. Gneiss d. Pluton e. Schist 6. If you can see the crystals making up an igneous rock with the naked eye, then the texture is described as a. Pyroclastic b. Phaneritic c. Aphanitic d. Porphyritic e. Aphyric from Perilous Earth: Understanding Processes Behind Natural Disasters, ver. 1.0, June, 2009 by G.H. Girty, Department of Geological Sciences, San Diego State University Page 1 7. In an aphanitic igneous rock can you make out the outlines of individual crystals with the naked eye? Yes or No 8. What type of igneous rock is the most volumetrically important on our planet? Intrusive Igneous Rocks 9. -
Eg, Change Or Extinction of Particular Living Organisms; Field Evidence Or
6.4. Construct explanations from geologic evidence (e.g., change or extinction of particular living organisms; field evidence or representations, including models of geologic cross-sections; sedimentary layering) to identify patterns of Earth’s major historical events (e.g., formation of mountain chains and ocean basins, significant volcanic eruptions, fossilization, folding, faulting, igneous intrusion, erosion). Use the diagram of a geologic cross section below to answer questions #1-2 1. Which rock layer most likely contains the most recently evolved organisms? a. 1 c. 3 b. 2 d. 4 2. Which rock layer represents the oldest rock? a. 1 c. 3 b. 2 d. 4 3. Use the diagram below to answer the question. The diagram shows the fossils in two different sections of rock found on opposite sides of a canyon. Which layer in rock section one is approximately the same age as layer X in rock section 2? a. Layer 1 b. Layer 2 c. Layer 3 d. Layer 4 4. Which statement is true about undisturbed layers of rocks on the side of a mountain? a. The rock layers closest to the ground level have more fossils in them. b. The layers of rock closest to the ground level are older than the layers on top. c. The layers of rocks that are the darkest in color are older than those that are lighter. d. The layers of rocks that are lighter in color are older than those that are darker. 5. The diagram below shows four different rock layers in a hillside. What is the best evidence that one of those rock layers was formed under an ocean. -
Rocks and Geology: General Information
Rocks and Geology: General Information Rocks are the foundation of the earth. Rock provides the firmament beneath our oceans and seas and it covers 28% of the earth's surface that we all call home. When we travel any distance in any given direction, it is impossible not to see the tremendous variety in color, texture, and shape of the rocks around us. Rocks are composed of one or more minerals. Limestone, for example, is composed primarily of the mineral calcite. Granite can be made up of the minerals quartz, orthoclase and plagioclase feldspars, hornblende, and biotite mica. Rocks are classified by their mineral composition as well as the environment in which they were formed. There are three major classifications of rocks: igneous, sedimentary and metamorphic. A question: Which kind of rock came first? Think about it....... The following sections describe the conditions and processes that create the landscape we admire and live on here on "terra firma." IGNEOUS ROCKS The millions of tons of molten rock that poured out of the volcano Paracutin in Mexico, and from the eruption of Mount St. Helens in Washington State illustrate one of the methods of igneous rock formation. Igneous (from fire) rocks are formed when bodies of hot liquid rock called magma located beneath the earth's crust, find their way upward through the crust by way of fissures or faults. If the magma reaches the earth's surface, it forms extrusive igneous rocks or volcanic rocks. If the magma cools before it reaches the surface, it forms bodies of rock called intrusive igneous rocks or plutonic rocks. -
Igneous Rocks and Their Origin
IIggnneeoouuss RRocockkss aanndd ThTheeiirr OOrigrigiinn Chapter 5 Three Types of Rocks • Igneous rocks - Formed from volcanic eruptions - either external or internal • Sedimentary rocks - Formed from erosional processes • Metamorphic rocks - Deforming of rocks above from exposure to high pressure and temperature The Rock Cycle • A rock is composed of grains of one or more minerals • The rock cycle shows how one type of rocky material is transformed into ano ther Igneous Rocks Extrusive igneous rocks form when lava erupts at the surface. Igneous extrusion (lava) The resulting rock is fine-grained or has a glassy texture. Basalt Igneous Rocks Igneous intrusion Intrusive igneous rocks form when magma intrudes into unmelted rock masses. Granite The slow cooling process produces coarsely grained rocks. How do we Know Igneous Rocks Formed at Depth? Torres del Paine, Chile • Mineralogy / Chemistry ? • Grain size (coarse vs fine grained) • Lab expmts require high P & T to form large grains • Outcrops: See intrusions into country rock -Contact/chill zones, baked and metamorphosed • Xenoliths of country rock found in igneous intrusions Igneous Rock Identification • Igneous rock names are based on texture (grain size) and composition • Textural classification – Coarse-grained: Plutonic rocks (gabbro-diorite-granite) cooled slowly at depth – Fine-Grained: Volcanic rocks (basalt-andesite-rhyolite) cooled rapidly at the Earth’s surface • Compositional classification – Mafic rocks (gabbro-basalt) contain dark-colored ferromagnesian minerals, iron rich -
Exploring Origins of Pitted/Vesicular Rocks in Perseverance Valley, Endeavour Crater
50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132) 2327.pdf EXPLORING ORIGINS OF PITTED/VESICULAR ROCKS IN PERSEVERANCE VALLEY, ENDEAVOUR CRATER. A. W. Tait1*, C. Schröder1, W. H Farrand2, J. W. Ashley3, B. A. Cohen4, R. Gellert5, J. Rice6, L. C. Crumpler7, B. Jolliff8, 1Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA, UK ([email protected]), 2Space Science Institute, Boulder, CO, USA, 3Jet Propulsion Laboratory, California In- stitute of Technology, Pasadena, CA, USA, 4NASA Goddard Space Flight Centre, Greenbelt, MD, USA, 5Department of Physics, University of Guelph, Ontario, Canada, 6Planetary Science Institute, Tucson, AZ, USA, 7NM Museum of Natural History & Science, Albuquerque, NM, USA, 8Washington University in St. Louis, MO, USA. Introduction: Since sol 4780, the NASA Mars Ex- ploration Rover (MER) Opportunity has been traversing down Perseverance Valley (PV), a linear, negative-re- lief feature trending perpendicular to the western flank of Endeavour crater. The goal of the current investiga- tion is to understand PVs geomorphology and chemical composition to determine its mode of formation and ap- proximate age. Formation hypotheses include debris or fluid flow, and wind sculpting, all while intersecting possible Noachian lithologies [1]. Rover observations confirms orbital data that there exists a dextral off-set, indicating a structural origin to the valleys formation [2]. This faulting may have allowed for fluids to interact with the rocks [3]. On sol ~5000 Opportunity started to investigate a train of dark pitted/vesicular rocks with an unusual morphology, texture, and composition enriched in Al and Si. Here we describe the rock facies, and ex- plore preliminary formation/alteration hypotheses. -
Towards a Unified Nomenclature in Metamorphic Petrology
8. Amphibolite and Granulite Recommendations by the IUGS Subcommission on the Systematics of Metamorphic Rocks: Web version 01.02.07 1José Coutinho, 2Hans Kräutner, 3Francesco Sassi, 4Rolf Schmid and 5Sisir Sen. 1 J. Coutinho, University of São Paulo, São Paulo, Brazil 2 L M University, Munich, Germany 3 F. Sassi, Department of Mineralogy and Petrography, University of Padova, Italy 4 R. Schmid, ETH-Centre, Zürich, Switzerland 5 S. Sen, Indian Institute of Technology, Kharagpur, India Introduction This paper summarises the results of the discussions by the SCMR, and the response to circulars distributed by the SCMR, which demonstrated the highly variable usage of the terms granulite and amphibolite. It presents those definitions which currently seem to be the most appropriate ones. Some notes are included in order to explain the reasoning behind the suggested definitions. In considering the definitions it is important to remember that some of them are a compromise of highly different, even conflicting, opinions and traditions. The names amphibolite and granulite have been used in geological literature for nearly 200 years: amphibolite since Brongniart (1813), granulite since Weiss (1803). Although Brongniart described amphibolite as a rock composed of amphibole and plagioclase, in those early days the meaning of the term was variable. Only later (e.g. Rosenbusch, 1898) was it fixed as metamorphic rock consisting of hornblende and plagioclase, and of medium to high metamorphic grade. In contrast, the use of the name granulite was highly variable, a position which was further complicated by the introduction of the facies principle (Eskola, 1920, 1952) when the name granulite was proposed for all rocks of the granulite facies. -
A Systematic Nomenclature for Metamorphic Rocks
A systematic nomenclature for metamorphic rocks: 1. HOW TO NAME A METAMORPHIC ROCK Recommendations by the IUGS Subcommission on the Systematics of Metamorphic Rocks: Web version 1/4/04. Rolf Schmid1, Douglas Fettes2, Ben Harte3, Eleutheria Davis4, Jacqueline Desmons5, Hans- Joachim Meyer-Marsilius† and Jaakko Siivola6 1 Institut für Mineralogie und Petrographie, ETH-Centre, CH-8092, Zürich, Switzerland, [email protected] 2 British Geological Survey, Murchison House, West Mains Road, Edinburgh, United Kingdom, [email protected] 3 Grant Institute of Geology, Edinburgh, United Kingdom, [email protected] 4 Patission 339A, 11144 Athens, Greece 5 3, rue de Houdemont 54500, Vandoeuvre-lès-Nancy, France, [email protected] 6 Tasakalliontie 12c, 02760 Espoo, Finland ABSTRACT The usage of some common terms in metamorphic petrology has developed differently in different countries and a range of specialised rock names have been applied locally. The Subcommission on the Systematics of Metamorphic Rocks (SCMR) aims to provide systematic schemes for terminology and rock definitions that are widely acceptable and suitable for international use. This first paper explains the basic classification scheme for common metamorphic rocks proposed by the SCMR, and lays out the general principles which were used by the SCMR when defining terms for metamorphic rocks, their features, conditions of formation and processes. Subsequent papers discuss and present more detailed terminology for particular metamorphic rock groups and processes. The SCMR recognises the very wide usage of some rock names (for example, amphibolite, marble, hornfels) and the existence of many name sets related to specific types of metamorphism (for example, high P/T rocks, migmatites, impactites). -
Landslides and the Weathering of Granitic Rocks
Geological Society of America Reviews in Engineering Geology, Volume III © 1977 7 Landslides and the weathering of granitic rocks PHILIP B. DURGIN Pacific Southwest Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture, Berkeley, California 94701 (stationed at Arcata, California 95521) ABSTRACT decomposition, so they commonly occur as mountainous ero- sional remnants. Nevertheless, granitoids undergo progressive Granitic batholiths around the Pacific Ocean basin provide physical, chemical, and biological weathering that weakens examples of landslide types that characterize progressive stages the rock and prepares it for mass movement. Rainstorms and of weathering. The stages include (1) fresh rock, (2) core- earthquakes then trigger slides at susceptible sites. stones, (3) decomposed granitoid, and (4) saprolite. Fresh The minerals of granitic rock weather according to this granitoid is subject to rockfalls, rockslides, and block glides. sequence: plagioclase feldspar, biotite, potassium feldspar, They are all controlled by factors related to jointing. Smooth muscovite, and quartz. Biotite is a particularly active agent in surfaces of sheeted fresh granite encourage debris avalanches the weathering process of granite. It expands to form hydro- or debris slides in the overlying material. The corestone phase biotite that helps disintegrate the rock into grus (Wahrhaftig, is characterized by unweathered granitic blocks or boulders 1965; Isherwood and Street, 1976). The feldspars break down within decomposed rock. Hazards at this stage are rockfall by hyrolysis and hydration into clays and colloids, which may avalanches and rolling rocks. Decomposed granitoid is rock migrate from the rock. Muscovite and quartz grains weather that has undergone granular disintegration. Its characteristic slowly and usually form the skeleton of saprolite. -
Structure of the Earth
And the ROCK CYCLE Structure of the Earth Compositional (Chemical) Layers Crust: Low density High in silicon (Si) and oxygen (O) Moho: Density boundary between crust and mantle Mantle: Higher density High in Magnesium (Mg) and Iron (Fe) Core: High in Nickel (Ni) and Iron (Fe) Heat Flow in the Earth Heat sources: latent heat from the formation of the Earth Radioactive decay in the core and mantle Temperature in the core: 3000- 5000° C Cooling processes: Convection currents: in outer core and asthenosphere transport heat to the surface Plate tectonics releases heat through the crust (volcanoes) Convection cells in the mantle and core transport heat from the interior of earth to the surface and also return cooler material back into the earth. Mechanical (Physical) Layers of the Earth Lithosphere: Crust and upper, solid part of the mantle; “plates” in plate tectonics Asthenosphere: Partially molten part of mantle; location of convection current that drive plates Outer core: Liquid Inner core: Solid Greatest temperatures, solid due to intense pressure Comparing Compositional Layers to Mechanical Layers Moho What is a Rock? A group of minerals bound together Three major groups: 1) Igneous: Solidified Molten Magma 2) Sedimentary: formed by cementing of sediments. Sediments come from the erosion of other rocks. 3) Metamorphic: Heat and pressure change a rock into something new, without melting. Rock Types Igneous: Solidified molten magma 2 types of Igneous: 1) Extrusive (volcanic) = erupted lava Cools more quickly, so only small crystals form. 2) Intrusive (plutonic) = never erupted magma Cools more slowly within the earth, so larger crystals can form.