Origin, Texture, and Classification of Metamorphic Rocks - Teklewold Ayalew
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Geology of the Berne Quadrangle Black Hills South Dakota
Geology of the Berne Quadrangle Black Hills South Dakota GEOLOGICAL SURVEY PROFESSIONAL PAPER 297-F Prepared partly on behalf of the U.S. Atomic Energy Commission Geology of the Berne Quadrangle Black Hills South Dakota By JACK A. REDDEN PEGMATITES AND OTHER PRECAMBRIAN ROCKS IN THE SOUTHERN BLACK HILLS GEOLOGICAL SURVEY PROFESSIONAL PAPER 297-F Prepared partly on behalf of the U.S. Atomic Energy Commission UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1968 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 CONTENTS Page Page Abstract._ _-------------_-___________-_____________ 343 Pegmatites Continued Introduction.______________________________________ 344 Mineralogy __ _____________-___-___-_-------_--- 378 Previous work__________________________________ 345 Origin.- --___-____-_-_-_---------------------_ 380 Fieldwork and acknowledgments._-_-_--__________ 345 Paleozoic and younger rocks. ________________________ 381 Geologic setting____--__-______________________ ____ 345 Deadwood Formation, __________________________ 381 Metamorphic rocks_________________________________ 347 Englewood Formation.. _ __________--____-_-__--_ 381 Stratigraphic units west of Grand Junction fault___- 347 Pahasapa Limestone- _______-_____.__-----_-- - 381 Vanderlehr Formation.._____________________ 347 Quaternary and Recent deposits. _________________ 382 Biotite-plagioclase gneiss.________________ -
Tectonic Interleaving Along the Main Central Thrust, Sikkim Himalaya
research-articleResearch ArticleXXX10.1144/jgs2013-064C. M. Mottram et al.Tectonic Interleaving Along the Mct 2014 Journal of the Geological Society, London, Vol. 171, 2014, pp. 255 –268. http://dx.doi.org/10.1144/jgs2013-064 Published Online First on January 14, 2014 © 2014 The Authors Tectonic interleaving along the Main Central Thrust, Sikkim Himalaya CATHERINE M. MOTTRAM1*, T. W. ARGLES1, N. B. W. HARRIS1, R. R. PARRISH2,3, M. S. A. HORSTWOOD3, C. J. WARREN1 & S. GUPTA4 1Department of Environment, Earth and Ecosystems, Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR), The Open University, Walton Hall, Milton Keynes MK7 6AA, UK 2Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK 3NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK 4Department of Geology & Geophysics, I.I.T., Kharagpur—721 302, India *Corresponding author (e-mail: [email protected]) Abstract: Geochemical and geochronological analyses provide quantitative evidence about the origin, devel- opment and motion along ductile faults, where kinematic structures have been overprinted. The Main Central Thrust is a key structure in the Himalaya that accommodated substantial amounts of the India–Asia conver- gence. This structure juxtaposes two isotopically distinct rock packages across a zone of ductile deformation. Structural analysis, whole-rock Nd isotopes, and U–Pb zircon geochronology reveal that the hanging wall is characterized by detrital zircon peaks at c. 800–1000 Ma, 1500–1700 Ma and 2300–2500 Ma and an εNd(0) signature of –18.3 to –12.1, and is intruded by c. 800 Ma and c. -
Metamorphic Field Gradients Across the Himachal Himalaya
TECTONICS, VOL. 32, 540–557, doi:10.1002/tect.20020, 2013 Metamorphic field gradients across the Himachal Himalaya, northwest India: Implications for the emplacement of the Himalayan crystalline core Remington M. Leger,1,2 A. Alexander G. Webb,1 Darrell J. Henry,1 John A. Craig,1 and Prashant Dubey3 Received 28 August 2012; revised 23 January 2013; accepted 3 February 2013; published 31 May 2013. [1] New constraints on pressures and temperatures experienced by rocks of the Himachal Himalaya are presented in order to test models for the emplacement of the Himalayan crystalline core here. A variety of methods were employed: petrographic analysis referenced to a petrogenetic grid, exchange and net-transfer thermobarometry, Ti-in-biotite thermometry, and analysis of quartz recrystallization textures. Rocks along three transects (the northern Beas, Pabbar, and southern Beas transects) were investigated. Results reveal spatially coherent metamorphic field gradients across amphibolite-grade and migmatitic metamorphic rocks. Along the northern Beas transect, rocks record peak temperatures of ~650–780C at low elevations to the north of ~3210’ N; rocks in other structural positions along this transect record peak temperatures of <640C that decrease with increasing structural elevation. Rocks of the Pabbar transect dominantly record ~650–700C peak temperatures to the east of ~7755’ E and ~450–620C peak temperatures farther west. Peak temperatures of ~450–600C along the southern Beas transect record a right-way-up metamorphic field gradient. Results are integrated with literature data to determine a metamorphic isograd map of the Himachal Himalaya. This map is compared to metamorphic isograd map pattern predictions of different models for Himalayan crystalline core emplacement. -
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. -
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). -
Metamorphic Rocks
Metamorphic Rocks Geology 200 Geology for Environmental Scientists Regionally metamorphosed rocks shot through with migmatite dikes. Black Canyon of the Gunnison, Colorado Metamorphic rocks from Greenland, 3.8 Ga (billion years old) Major Concepts • Metamorphic rocks can be formed from any rock type: igneous, sedimentary, or existing metamorphic rocks. • Involves recrystallization in the solid state, often with little change in overall chemical composition. • Driving forces are changes in temperature, pressure, and pore fluids. • New minerals and new textures are formed. Major Concepts • During metamorphism platy minerals grow in the direction of least stress producing foliation. • Rocks with only one, non-platy, mineral produce nonfoliated rocks such as quartzite or marble. • Two types of metamorphism: contact and regional. Metamorphism of a Granite to a Gneiss Asbestos, a metamorphic amphibole mineral. The fibrous crystals grow parallel to least stress. Two major types of metamorphism -- contact and regional Major Concepts • Foliated rocks - slate, phyllite, schist, gneiss, mylonite • Non-foliated rocks - quartzite, marble, hornfels, greenstone, granulite • Mineral zones are used to recognize metamorphic facies produced by systematic pressure and temperature changes. Origin of Metamorphic Rocks • Below 200oC rocks remain unchanged. • As temperature rises, crystal lattices are broken down and reformed with different combinations of atoms. New minerals are formed. • The mineral composition of a rock provides a key to the temperature of formation (Fig. 6.5) Fig. 6.5. Different minerals of the same composition, Al2SiO5, are stable at different temperatures and pressures. Where does the heat come from? • Hot magma ranges from 700-12000C. Causes contact metamorphism. • Deep burial - temperature increases 15-300C for every kilometer of depth in the crust. -
Relationship Between Rock Type, Metamorphic Grade
Canadian Mineralogist Vol. 25, pp. 485-498(1987) RELATIONSHIPBETWEEN ROCK TYPE, METAMORPHIC GRADE, AND FLUID- PHASECOMPOSITION IN THE GRENVILLESUPERGROUP, LIMERICKTOWNSHIP, ONTARIO P. JAMES LgANDERSON Depaftmentof Geologyand GeologicalEngineering, Colorado School of Mines, Goldm, Colorado8M01, U.S.A. JAMES L. MUNOZ Depafimentof GeologicalSciences, University of Colorado,Boulder, Colorado80309-0250, U.S.A, ABSTRACT entre535 et 550'C dansles marbres et 402et 543"Cou plus dans les lithologies pauvres en carbonate. La valerir de The srudy area in Limerick Township in the southern X(CO) seraitentre 0,45 et 0.55 dansles marbreset moins Grenville Province consistsof a sequenceof late Proterozoic de 0. l0 dansles milieux pauvresen carbonate.La relatlon metabasalts,noncalcareous and calcareousquartzofeld- entre degr€de m6tamorphismeet lithologie refldte la dimi spatlfc granofels,and marblesintruded by two gabbro com- nution du X(CO) du marbre vers les unit€s moins riches plexes.During the Grenville Orogeny,metamorphism of en calcaire.Cette relation pourrait 6tre attribude l) d un marble producedassemblages that are below the titanite, tamponnageinterne de la phasefluide par lesr6actions iso- actinolite - calcite,and hornblende- K-feldsparisograds, gradiquesi des valeurs 6levdesde X(CO) dans les mar- but above the hornblende - K-feldspar isograd in the bres et des valeurs inf6rieures dans les unit6s pauvres en quartzofeldspathicunits and amphibolitss. Calcite-dolomite carbonate, ou 2) d un tamponnagedes fluides i desvaleurs and two-feldspargeothennometry, and calculationof the faibles de X(CO) par les r€actionsisogradiques suite i displacementof intersectingequilibria due to solid-solution, l'infiltration de fluides aqueux au travers des unit€s pau- bracket equilibrium temperaturesbetween 535 and 550'C vres ou sanscarbonate. -
Metamorphic Rocks -- Rocks That Change by Cindy Grigg
Metamorphic Rocks -- Rocks that Change By Cindy Grigg 1 Rocks can be put into three main groups. They are grouped by how the rocks formed. Metamorphic (met-uh-MOR-fic) rocks are changed by the heat and pressure inside Earth. "Metamorphic" comes from a Greek word that means "change of form." Metamorphic rocks can be formed from other metamorphic rocks. They can form from sedimentary and igneous rocks, too. 2 The temperature deep inside the Earth is much hotter than temperatures near or on the surface. The weight of tons of land and rocks on top presses down on the rocks underneath. This pressure, along with heat, causes the rocks inside the Earth to go through a physical or chemical change. Movement of Earth's plates causes pressure on rocky material under the surface, resulting in folding. Water can dissolve and redeposit minerals. This can also cause a change in rocks. Minerals react with each other at high heat. Atoms rearrange, and new minerals are created from old ones. Grains in rocks are pressed and made more compact. Rocks morph into other kinds of rocks. 3 Some metamorphic rocks are slate, schist, gneiss, marble, and quartzite. Sandstone is a sedimentary rock. It is made of grains of sand pressed together. Sandstone is fairly soft. It crumbles easily. When sandstone changes into the metamorphic rock quartzite, is becomes one of the hardest rocks. 4 The sedimentary rock shale changes into slate. The mineral grains in shale change directions because of the heat and pressure. Slate, a metamorphic rock, can be changed by continued heat and pressure into a rock called schist. -
Vein Assemblages and Metamorphism in Dutchess County, New York ABSTRACT Others, 1972) and Shows the Study Area
ROSEMARY J. VIDALE Department of Geology and Geophysics, State University of New York at Binghamton, Binghamton, New York 13901 Vein Assemblages and Metamorphism in Dutchess County, New York ABSTRACT others, 1972) and shows the study area. The Stuyvesant Falls, Mount Merino, Indian major geologic mapping of this area was River, and Austin Glen). Carbonate-rich Mineral assemblages of fissure veins in done by Barth (1936) and by Balk (1936) layers occur locally in pelitic rocks of both pelitic rocks are a consistent function of with significant additions by Fisher and autochthon and allochthon and are espe- metamorphic grade within a 1,700 km2 area others (1972). cially abundant near the base of the in and near Dutchess County, New York. The principal geologic units are the Walloomsac. The following vein assemblages are ob- Precambrian gneisses of the Hudson and Figure 2 shows metamorphic isograds in served with increasing grade: quartz and Housatonic Highlands; autochthonous this region. They were first mapped by Barth quartz-calcite up to just above the staurolite lower Paleozoic units, including Cambrian (1936, p. 777-779 and Plate 1) but have isograd, with limited occurrence of quariz- quartzite (Poughquag), Cambrian- been remapped (Vidale, in prep.). Barth's albite below the biotite isograd; quartz and Ordovician carbonate rock (Wappinger, isograds correspond accurately to first quartz-plagioclase (An20 to An50) from tie Stockbridge, and In wood), and Ordovician megascopic appearance of index minerals. staurolite isograde up to the sillimanite- pelitic rock (Walloomsac); and allochtho- Detailed thin-section examination of rocks orthoclase isograd; and quartz, quartz- nous Cambrian-Ordovician pelitic units with appropriate bulk chemical composi- plagioclase, and quartz-plagioclase- (Everett, Nassau, Germantown, Elizaville, tion for the first occurrence of index orthoclase above the sillimanite-orthoclase isograd. -
A Sillimanite Gneiss Dome in the Yukon Crystalline Terrane, East-Central Alaska: Petrography and Garnet- Biotite Geothermometry
PROPERTY OF DUG,r c LiiiRARYyw A Sillimanite Gneiss Dome in the Yukon Crystalline Terrane, East-Central Alaska: Petrography and Garnet- Biotite Geothermometry By CYNTHIA DUSEL-BACON and HELEN L. FOSTER SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 1170-E Petrographic, geothermometric, and structural data are used to support the hypothesis that a 600-km* area of pelitic metamorphic rocks is a gneiss dome -- -- UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1983 UNITED STATES DEPARTMENT OF THE INTERIOR JAMES G. WATT, Secretary GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Dusel-Bacon. Cynthia. A sillimanite gneiss dome in the Yukon crystalline terrane, eastcentral Alaska. (Shorter contributions to general geology) (Geological Survey Professional Paper 1170-E) Bibliography Supt. of Docs. no.: 1 19.412: 1170-E 1. Gneiss--Alaska. 2. Intrusions (Geology)-Alaska. I. Foster, Helen Laura. 1919- . 11. Title. Ill. Series. IV. Series: United States: Geological Survey. Professional Paper 1170-E. QE475.G55D87 1983 552'.4 83-60003 1 For sale by the Distribution Branch, U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 42304 CONTENTS Page Abstract .............................................................................................................................................................. El Introduction ..................................................................................................................................................... -
Week of May 4 – May 10
Week of May 4 – May 10 Read the definition and description of the sedimentary rocks in the article titled “Pictures of Sedimentary Rocks” Complete the worksheets: “How are sedimentary rocks are formed” “How are sedimentary rocks classified” Pictures of Sedimentary Rocks Photos of Common Clastic, Chemical, and Organic Sedimentary Rock Types. Article by: Hobart M. King, Ph.D., RPG Breccia is a clastic sedimentary rock that is composed of large (over two-millimeter diameter) angular fragments. The spaces between the large fragments can be filled with a matrix of smaller particles or a mineral cement which binds the rock together. The specimen shown above is about two inches (five centimeters) across. What Are Sedimentary Rocks? Sedimentary rocks are formed by the accumulation of sediments. There are three basic types of sedimentary rocks. Clastic sedimentary rocks such as breccia, conglomerate, sandstone, siltstone, and shale are formed from mechanical weathering debris. Chemical sedimentary rocks, such as rock salt, iron ore, chert, flint, some dolomites, and some limestones, form when dissolved materials precipitate from solution. Organic sedimentary rocks such as coal, some dolomites, and some limestones, form from the accumulation of plant or animal debris. Photos and brief descriptions of some common sedimentary rock types are shown on this page. Coal is an organic sedimentary rock that forms mainly from plant debris. The plant debris usually accumulates in a swamp environment. Coal is combustible and is often mined for use as a fuel. The specimen shown above is about two inches (five centimeters) across. Chert is a microcrystalline or cryptocrystalline sedimentary rock material composed of silicon dioxide (SiO2).