DOCSLIB.ORG

Lecture 2 Classification of Igneous Rocks

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Lecture 2 Classification of Igneous Rocks Lecture 2 Classification of Igneous Rocks Friday, January 28th, 2005 Classification of Igneous Rocks Figure 2-1a. Method #1 for plotting a point with the components: 70% X, 20% Y, and 10% Z on triangular diagrams. An Introduction to Igneous and Metamorphic Petrology, John Winter, Prentice Hall. 1 Classification of Igneous Rocks Ratio of Y to Z = 100Y(Y + Z) = 100*20(20 + 10) = 67 Figure 2-1b. Method #2 for plotting a point with the components: 70% X, 20% Y, and 10% Z on triangular diagrams. An Introduction to Igneous and Metamorphic Petrology, John Winter, Prentice Hall. Q (a) The rock must contain a total of at least 10% of the minerals below. Quartzolite Renormalize to 100% 90 90 Quartz-rich Granitoid Classification of 60 60 Tonalite Granite Grano- Igneous Rocks diorite Alkali Feldspar Granite Alkali Fs. 20 20 Qtz. Diorite/ Quartz Syenite Quartz Quartz Quartz Qtz. Gabbro Foids are feldspathoids Alkali Fs. Syenite Monzonite Monzodiorite 5 5 Diorite/Gabbro/ Syenite Syenite Monzodiorite such as nepheline and 10 35 Monzonite 65 90 Anorthosite A (Foid)-bearing (Foid)-bearing (Foid)-bearing P leucite Syenite Monzonite Monzodiorite 10 10 (Foid)-bearing Diorite/Gabbro (Foid)-bearing (Foid) Syenite Alkali Fs. Syenite (Foid) (Foid) Monzosyenite Monzodiorite (Foid) Gabbro Figure 2-2. A classification of the phaneritic igneous 60 60 rocks. a. Phaneritic rocks with more than 10% (quartz + (Foid)olites feldspar + feldspathoids). After IUGS. F 2 Let’s try an example Modal analysis of a rock gives the following mineral proportions Quartz = 26.9 K-feldspar = 23.7 Plagioclase = 39.8 Biotite = 5.3 Hornblende = 4.3 Re-summing Qtz = 29.8 Kspar = 26.2 Plag = 44.0 100P/(P + A) = 63 Rock is a granite! How about another? Modal analysis of a rock gives the following mineral proportions Quartz = 8.5 K-feldspar = 5.1 Plagioclase = 59.6 Biotite = 16.1 Hornblende = 10.9 Re-summing Qtz = 11.6 Kspar = 7.0 Plag = 81.4 100P/(P + A) = 92 Rock could be Qtz diorite or Qtz gabbro 3 Classification of Igneous Rocks Plagioclase Anorthosite Figure 2-2. A classification of the phaneritic 90 igneous rocks. b. Gabbroic rocks. c. Ultramafic rocks. After IUGS. Troctolite Olivine Gabbro Olivine Dunite gabbro 90 Wehrlite Peridotites Plagioclase-bearing ultramafic rocks Lherzolite Pyroxene Olivine Harzburgite (b) 40 Orthopyroxenite Olivine Websterite Pyroxenites 10 Websterite (c) 10 Clinopyroxenite Orthopyroxene Clinopyroxene Q Classification of Igneous Rocks 60 60 Rhyolite Dacite 20 20 Trachyte Latite Andesite/Basalt 35 65 A (foid)-bearing (foid)-bearing (foid)-bearing P Trachyte Latite Andesite/Basalt 10 10 Phonolite Tephrite Figure 2-3. A classification and nomenclature of volcanic rocks. After IUGS. 60 60 (Foid)ites F 4 Classification of Igneous Rocks Alkaline -alkaline or calc Tholeiitic Figure 2-4. A chemical classification of volcanics based on total alkalis vs. silica. After Le Bas et al. (1986) J. Petrol., 27, 745-750. Oxford University Press. An actual example from the Hawaii Scientific Drilling Project The dashed line separates alkalic from tholeiitic basalts Total alkali = SiO2 x 0.37 + 14.43 5 We can calculate an alkalinity index from the previous equation. It measures how far a sample plots above or below the alkali – tholeiite line. In other words, how alkaline or tholeiitic it is. Alkalinity Index = (Na2O + K2O) – (SiO2 x 0.37 + 14.43) This example shows the alkalinity index with depth in rocks from the Hawaii Scientific Drilling Project Classification of Igneous Rocks Figure 2-5. Classification of the pyroclastic rocks. a. Based on type of material. After Pettijohn (1975) Sedimentary Rocks, Harper & Row, and Schmid (1981) Geology, 9, 40-43. b. Based on the size of the material. After Fisher (1966) Earth Sci. Rev., 1, 287-298. 6 Some Useful Textural Terms ● Grain Size – determined by cooling rate of a magma (also influenced by volatile content). Fine < 1 mm Medium 1 – 5 mm Course > 5 mm ● Aphanitic – a rock that is so fine-grained that individual minerals cannot be distinguished without a microscope. ● Phaneritic – all essential minerals are clearly visible ● Porphyritic – a rock containing large phenocrysts in a finer grained groundmass ● Grain Shapes euhedral – grains with well-developed crystal faces subhedral – grains with a few well-developed crystal faces anhedral – grains that have no distinct shape 7.
Load more

Recommended publications
  • Ophiolite in Southeast Asia
    Ophiolite in Southeast Asia CHARLES S. HUTCHISON Department of Geology, University of Malaya, Kuala Lumpur, Malaysia ABSTRACT semblages are classified into definite ophiolite, tentatively identified ophiolite, and associations that have previously been named No fewer than 20 belts of mafic-ultramafic assemblages have ophiolite but that are not. Each of the ophiolite or other been named "ophiolite" in the complex Southeast Asia region of mafic-ultramafic associations is listed in Table 1, with brief reasons Sundaland. Fewer than half of these can be confidently classified as for its classification, particularly in regard to the petrography of the ophiolite. The only well-documented complete ophiolite, with con- rock suite and the nature of its sedimentary envelope. The basis for tinuous conformable sections from mantle harzburgite through identification (or rejection) of these rock associations as ophiolite is gabbro to spilite, occurs in northeast Borneo and the neighboring discussed in the following section. Philippine Islands. It contains a record of oceanic lithospheric his- tory from Jurassic to Tertiary and has a Miocene emplacement age. OPHIOLITE FORMATION All other ophiolite belts of the region are either incomplete or dis- membered. The Sundaland region probably has examples of several The oceanic lithosphere, with its thin oceanic crust formed along types of emplacement mechanism and emplacement ages ranging the spreading axes of divergent plate junctures, is thought to be from early Paleozoic to Cenozoic. Key words: Sundaland, plate consumed at arc-trench systems of convergent plate junctures (Fig. tectonics. 2). Minor subtractions of crustal and mantle material from de- scending slabs of oceanic lithosphere are thought to be added to INTRODUCTION belts of mélange, and imbricate slices are caught in crustal subduc- tion zones at the trenches (Dickinson, 1972).
    [Show full text]
  • Depleted Spinel Harzburgite Xenoliths in Tertiary Dykes from East Greenland: Restites from High Degree Melting
    Earth and Planetary Science Letters 154Ž. 1998 221±235 Depleted spinel harzburgite xenoliths in Tertiary dykes from East Greenland: Restites from high degree melting Stefan Bernstein a,), Peter B. Kelemen b,1, C. Kent Brooks a,c,2 a Danish Lithosphere Centre, éster Voldgade 10, DK-1350 Copenhagen K, Denmark b Woods Hole Oceanographic Institution, Woods Hole, City, MA 02543, USA c Geological Institute, UniÕersity of Copenhagen, éster Voldgade 10, DK-1350 Copenhagen K, Denmark Received 28 April 1997; revised 19 September 1997; accepted 4 October 1997 Abstract A new collection of mantle xenoliths in Tertiary dykes from the Wiedemann Fjord area in Southeast Greenland shows that this part of the central Greenland craton is underlain by highly depleted peridotites. The samples are mostly spinel harzburgites with highly forsteritic olivinesŽ. Fo87± 94 , average Fo 92.7 . This, together with unusually high modal olivine contentsŽ. 70±)95% , places the Wiedemann harzburgites in a unique compositional field. Relative to depleted Kaapvaal harzburgites with comparable Fo in olivine, the Wiedemann samples have considerably lower bulk SiO2 Ž average 42.6 wt% versus 44±49 wt%. Spinel compositions are similar to those in other sub-cratonic harzburgites. Pyroxene equilibrium temperatures average 8508C, which is above an Archaean cratonic geotherm at an inferred pressure of 1±2 GPa, but low enough so that it is unlikely that the xenoliths represent residual peridotites created during Tertiary magmatism. Among mantle samples, the Wiedemann harzburgites are, in terms of their bulk composition, most similar to harzburgites from the ophiolites of Papua New GuineaŽ. PNG and New Caledonia Ž.
    [Show full text]
  • Nonexplosive and Explosive Magma/Wet-Sediment Interaction
    Journal of Volcanology and Geothermal Research 181 (2009) 155–172 Contents lists available at ScienceDirect Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores Nonexplosive and explosive magma/wet-sediment interaction during emplacement of Eocene intrusions into Cretaceous to Eocene strata, Trans-Pecos igneous province, West Texas Kenneth S. Befus a,⁎, Richard E. Hanson a, Daniel P. Miggins b, John A. Breyer a, Arthur B. Busbey a a Department of Geology, Texas Christian University, Box 298830, Fort Worth, TX 76129, USA b U.S. Geological Survey, Denver Federal Center, Box 25046, Denver, CO 80225, USA article info abstract Article history: Eocene intrusion of alkaline basaltic to trachyandesitic magmas into unlithified, Upper Cretaceous Received 16 June 2008 (Maastrichtian) to Eocene fluvial strata in part of the Trans-Pecos igneous province in West Texas produced Accepted 22 December 2008 an array of features recording both nonexplosive and explosive magma/wet-sediment interaction. Intrusive Available online 13 January 2009 complexes with 40Ar/39Ar dates of ~47–46 Ma consist of coherent basalt, peperite, and disrupted sediment. Two of the complexes cutting Cretaceous strata contain masses of conglomerate derived from Eocene fluvial Keywords: deposits that, at the onset of intrusive activity, would have been N400–500 m above the present level of phreatomagmatism peperite exposure. These intrusive complexes are inferred to be remnants of diatremes that fed maar volcanoes during diatreme an early stage of magmatism in this part of the Trans-Pecos province. Disrupted Cretaceous strata along Trans-Pecos Texas diatreme margins record collapse of conduit walls during and after subsurface phreatomagmatic explosions.
    [Show full text]
  • Tom Abstraktow 6B-Ost Ver Publ.Pdf
    Cover photo: A euhedral, oscillatory zoned, primary monazite has been altered at the rims and along cracks to an allanite-apatite-xenotime assemblage. The host mineral is feldspar. Granite, Strzegom Massif. Workshop on accessory minerals, University of Warsaw, September 2014 Editors of Volume Bogusław BAGIŃSKI, Oliwia GRAFKA Witold MATYSZCZAK, Ray MACDONALD Institute of Geochemistry, Mineralogy and Petrology, University of Warsaw Al. Żwirki i Wigury 93, 02-089 Warszawa [email protected] Language correction: Ray MACDONALD Institute of Geochemistry, Mineralogy and Petrology, University of Warsaw Al. Żwirki i Wigury 93, 02-089 Warszawa [email protected] 1 Organizing committee: Bogusław BAGIŃSKI Ray MACDONALD Michał RUSZKOWSKI Financial support: Workshop on accessory minerals was financially supported by the Polish Ministry of Science and Higher Education subvention and research grant No N N307634040, Faculty of Geology University of Warsaw and PIG-PIB. 2 Workshop on accessory minerals, University of Warsaw, September 2014 Preface The progress made over the past two decades in our understanding of accessory minerals containing HFSE has been remarkable. Even when “fresh-minted”, minerals such as monazite, xenotime, allanite and zircon are compositionally and structurally complex. The complexity increases many times during low-temperature alteration processes, such as interaction with hydrothermal fluids and weathering. Progress has, of course, been expedited by the introduction of a range of exciting new technologies, especially in structure determinations. On re-reading the excellent 2002 review of accessory mineral research by Poitrasson et al., one is struck by how far the subject area has advanced in 12 years. We felt that this was an opportune time to bring together a group of Earth scientists with special expertise in accessory minerals to outline their current research interests, to share ideas and to consider productive future research directions.
    [Show full text]
  • The Alkaline Volcanic Rocks of Craters of the Moon National Monument, Idaho and the Columbia Hills of Gusev Crater, Mars Details
    The alkaline volcanic rocks of Craters of the Moon National Monument, Idaho and the Columbia Hills of Gusev Crater, Mars Details Meeting 2016 Fall Meeting Section Planetary Sciences Session Terrestrial Analogs for Planetary Processes: Oceans, Volcanoes, Impacts, and Dunes I Identifier P31E-01 Authors Haberle, C W*, Mars Space Flight Facility, Arizona State University, Tempe, AZ, United States Hughes, S S, Idaho State University, Idaho Falls, ID, United States Kobs-Nawotniak, S E, Department of Geosciences, Idaho State University, Idaho Falls, ID, United States Christensen, P R, Arizona State University, Tempe, AZ, United States Index Sediment transport [4558] Terms Atmospheres [5405] Titan [6281] Venus [6295] Abstract Idaho's Eastern Snake River Plain (ESRP) is host to extensive expressions of basaltic volcanism dominated by non evolved olivine tholeiites (NEOT) with localized occurrences of evolved lavas. Craters of the Moon National Monument (COTM) is a polygenetic lava field comprised of more than 60 lava flows emplaced during 8 eruptive periods spanning the last 15 kyrs. The most recent eruptive period (period A; 2500-2000 yr B.P.) produced flows with total alkali vs. silica classifications spanning basalt to trachyte. Coeval with the emplacement of the COTM period A volcanic pile was the emplacement of the Wapi and Kings Bowl NEOT 70 km SSE of COTM along the Great Rift. Previous investigations have determined a genetic link between these two compositionally distinct volcanic centers where COTM compositions can be generated from NEOT melts through complex ascent paths and variable degrees of fractionation and assimilation of lower-middle crustal materials. The Mars Exploration Rover, Spirit, conducted a robotic investigation of Gusev crater from 2004-2010.
    [Show full text]
  • Open-File Report 2005-1235
    Prepared in cooperation with the Idaho Geological Survey and the Montana Bureau of Mines and Geology Spatial databases for the geology of the Northern Rocky Mountains - Idaho, Montana, and Washington By Michael L. Zientek, Pamela Dunlap Derkey, Robert J. Miller, J. Douglas Causey, Arthur A. Bookstrom, Mary H. Carlson, Gregory N. Green, Thomas P. Frost, David E. Boleneus, Karl V. Evans, Bradley S. Van Gosen, Anna B. Wilson, Jeremy C. Larsen, Helen Z. Kayser, William N. Kelley, and Kenneth C. Assmus Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government Open-File Report 2005-1235 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey P. Patrick Leahy, Acting Director U.S. Geological Survey, Reston, Virginia 2005 For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report. Contents Abstract .......................................................................................................................................................... 1 Introduction
    [Show full text]
  • Global Variations in Abyssal Peridotite Compositions
    Lithos 248–251 (2016) 193–219 Contents lists available at ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos Invited review article Global variations in abyssal peridotite compositions Jessica M. Warren Dept. of Geological Sciences, University of Delaware, Penny Hall, Newark, DE 19716, USA article info abstract Article history: Abyssal peridotites are ultramafic rocks collected from mid-ocean ridges that are the residues of adiabatic decom- Received 28 March 2015 pression melting. Their compositions provide information on the degree of melting and melt–rock interaction Accepted 24 December 2015 involved in the formation of oceanic lithosphere, as well as providing constraints on pre-existing mantle hetero- Available online 9 January 2016 geneities. This review presents a compilation of abyssal peridotite geochemical data (modes, mineral major elements, and clinopyroxene trace elements) for N1200 samples from 53 localities on 6 major ridge systems. Keywords: fi fi Abyssal peridotite On the basis of composition and petrography, peridotites are classi ed into one of ve lithological groups: (1) re- Mid-ocean ridge sidual peridotite, (2) dunite, (3) gabbro-veined and/or plagioclase-bearing peridotite, (4) pyroxenite-veined Partial melting peridotite, and (5) other types of melt-added peridotite. Almost a third of abyssal peridotites are veined, indicat- Melt–rock interaction ing that the oceanic lithospheric mantle is more fertile, on average, than estimates based on residual peridotites Mantle geochemistry alone imply. All veins appear to have formed recently during melt transport beneath the ridge, though some py- Pyroxenite roxenites may be derived from melting of recycled oceanic crust. A limited number of samples are available at intermediate and fast spreading rates, with samples from the East Pacific Rise indicating high degrees of melting.
    [Show full text]
  • Geomorphology of the Bushveld Complex
    Cademo Lab. Xeo16xico de Laxe Coruña. 1997. Vol. 22, pp. 209-227 Geomorphology of the Bushveld Complex Geomorfología del Complejo de Bushveld LAGEAT,Y. This paper deals wich che differenc relacion becween scruccure and lichology in che geomorphology of che Bushveld Complexo The final resules demonscrace chac, even so differenc scale ofsize, widerfor che epirogenic-cecconic movements and smaller for che lichology, che cwo faccors need co be considered for a beccer underscanding ofche landscape evolucion ofche area. Key words: ulerabasic and basic rocks, Bushveld Complex, scruccural geomorphology, lichological differences. LAGEAT, Y. (Universicé Blaise Pascaland UPRES-A 6042 (CNRS). Clermont-Ferrand (France) 210 Lageat, Y. CAD. LAB. XEOL. LAXE 22 (997) INTRODUCTION subdued topography. So, being concerned with the relationships between scenery and In spiteofthestrong emphasisonclimatic structure, the study wil1 consider two topics in French geomorphology since the different but complementary topics: fifties, research dealing with structural differential erosion and regional evolution landforms developed in crystalline shields ofa shield area (Y. LAGEAT, 1989). pioneered by the late Professor P. Birot has been upheld. In numerous regional monographs, widely distributed between GEOLOGICAL POTENTIAL theArcticCircleand theTropicofCapricorn, special attention has been devoted to the A presentation of the geology of the relationships between landforms and Bushveld Complex is essential to any geological structure, with the purpose to understanding of its surface morphology. distinguish between the direct control of Ranging in composition from ultrabasic ro recent faulting and the response of acid, it outcrops largely within a region contrasting rock units todifferential erosiono covered bya characteristicvegetation termed This ambiguity may be easily overcome in «Bushveld».
    [Show full text]
  • Earth Science Chapter 6
    Chapter6 Rocks Chapter Outline 1 ● Rocks and the Rock Cycle Three Major Types of Rock The Rock Cycle Properties of Rocks 2 ● Igneous Rock The Formation of Magma Textures of Igneous Rocks Composition of Igneous Rocks Intrusive Igneous Rock Extrusive Igneous Rock 3 ● Sedimentary Rock Formation of Sedimentary Rocks Chemical Sedimentary Rock Organic Sedimentary Rock Clastic Sedimentary Rock Characteristics of Clastic Sediments Sedimentary Rock Features 4 ● Metamorphic Rock Formation of Metamorphic Rocks Why It Matters Classification of The hundreds of different types of Metamorphic Rocks rocks on Earth can be classified into three main types: igneous, sedimentary, and metamorphic. This formation in Arizona is made of sedimentary rock. When you know the type of rock, you know something about how that rock formed. 132 Chapter 6 hq10sena_rxscho.indd 1 3/25/09 4:10:29 PM Inquiry Lab Sedimentary Sandwich 15 min Use slices of different types of bread to model Questions to Get You Started layers of different types of sediment deposits. Next, 1. Make a labeled diagram showing the rock layers in put your model in a plastic bag. Place a weight on the sample you observed. top of the bag to simulate the process of 2. Which factors might affect the thickness of a rock compacting sediment into rock. Then, use an empty layer in a real rock formation? film canister to obtain a core sample of the sedimentary sandwich. Trade samples with another 3. Your model has layers of different types of rocks. group and observe the other group’s sample. In a real formation, what might changes in Identify the different layers of rock and determine if rock type indicate about the rock layers are the same thickness or if some are formation’s geological history? thicker than others.
    [Show full text]
  • The Nain Anorthosite Project, Labrador: Field
    THE NAIN ANORTHOSITE PROJECT, LABRADOR: FIELD REPORT 1971 S. A. MORSE I EDITOR R. V. PITS I ULAK CONTRIBUTION NO. 9 GEOLOGY DEPARTMENT UNIVERSITY OF MASSACHUSETTS AMHERST, MASSACHUSETTS L THE NAIN ANORTHOSITE PROJECT, LABRADOR: FIElD REPORT 1971 S. A. Morse, Editor Final Report under NSF Grants GA-21386 and GA-27134 to Franklin and Marshall College: "Evolution of Anorthosite and Related Crustal Rocks in Coastal Labrador", and "Facility for Crustal Studies in Coastal Labrador." S. A. Morse, Principal Investigator (now at U.Mass/Amherst) Dirk de Waard, Syracuse Associate Investigators E. P. Wheeler 2nd, Cornell Other contributors: Research Assistants: J. H. Berg, U. Mass/Amherst C. D. Brauer, Vassar G. A. Plananaky, Harvard F. Finley, Syracuse C. C. Rubins, Syracuse T. H. Folkomer, Franklin & Marshall B.G.J. Upton, Edinburgh D. Russell, Syracuse Charles Woodward, Syracuse J. A. Speer, Virginia Polytechnic Contribution No. 9 Amherst, Massachusetts Geology Department December, 1971 Uni~ersity of Massachusetts L I - CONTENTS INTRODUCTION •••••••••.•••••.•••••••••• ......................... 1 GEOLOGIC~ REPORT. • • • • • • • . • • . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 9 General Statement ••••••• 9 Collateral Studies •• 12 Eastern Con tact Zone . .....................................•.... 15 Country rocks of the anorthosite massif and anorthosite contacts in the Ford Harbour Region (de Waard) ••••••••••••••••••••• 15 Intrusive contact relations in the outer is lands (Wlleele r) ....................................
    [Show full text]
  • Petrography and Engineering Properties of Igneous Rocks
    ENGINEERil~G MONOGRAPHS No. I United States Department of the Interior BUREAU OF RECLAMATION PETROGRAPIIY AND ENGINEERING· PROPER11ES OF IGNEOUS ROCKS hy Rit~bard C. 1\lielenz Denver, Colorado October 1948 95 cents (R.evised September 1961) United States Department of the Interior STEWART L. UDALL, Secretacy Bureau of Reclamation FLOYD E. DOMINY, Commissioner G~T BLOODGOOD, Assistant Commissioner and Chief Engineer Engineering Monograph No. 1 PETROGRAPHY AND ENGINEERING PROPERTIRES ·OF IGNEOUS RO<;:KS by Richard C. Mielenz Revised 1959. by William Y. Holland Head. Petrographic Laboratory Section Chemical Engineering Laboratory Branch Commissioner's Office. Denver Technical Infortnation Branch Denver Federal Center Denver, Colorado ENGINEERING MONOGRAPHS are published in limited editions for the technical staff of the Bureau of Reclamation and interested technical circles in Government and private agencies. Their purpose is to record devel­ opments, innovations, .and progress in the engineering and scientific techniques and practices that are employed in the planning, design, construction, and operation of Rec­ lamation structures and equipment. Copies 'may be obtained from the Bureau of Recla- · mation, Denver Federal Center, Denver, Colon.do, and Washington, D. C. Excavation and concreting of altered zones in rhyolite dike in the spillway foundation. Davis Damsite. Arizona-Nevada. Fl'ontispiece CONTENTS Page Introduction . 1 General Basis of Classification of Rocks . 1 Relation of the Petrographic Character to the Engineering Properties of Rocks . 3 Engineering J?roperties of Igneous Rocks ................................ :. 4 Plutonic Rocks . 4 Hypabyssal Rocks . 6 Volcanic Rocks..... 7 Application of Petrography to Engineering Problems of the Bureau of Reclamation . 8 A Mineralogic and Textural Classification of Igneous Rocks .
    [Show full text]
  • 62237 Troctolitic Anorthosite 62.4 Grams
    62237 Troctolitic Anorthosite 62.4 grams Figure 1: Photo of 62237. NASA S72-41797 (B&W), NASA S72-38959 (color). Cube is 1 cm. Introduction 62237 and 62236 are chalky white rocks that were Warren and Wasson (1977) concluded that 62237 is collected together along with 62235 and incidental soil, “chemically pristine”, because it was lacking in from the rim of Buster Crater, station 2, Apollo 16 meteoritic siderophiles. (figure 2), where they were found half buried in the regolith (Sutton 1981). The mineral chemistry of these 62237 has been crushed to form a cataclastic texture, rocks is similar and indicates that they belong to the but, in places, the original coarse-grained igneous suite of lunar plutonic rocks termed ferroan anorthosite texture can be discerned by relic clasts (figure 3). (James 1980). Mineralogy Olivine: Olivine (Fo ) crystals up to 3 mm in size Petrography 59-61 Dymek et al. (1975) concluded that 62237 was a slowly are reported in 62237 by Dymek et al. (1975). Warren cooled plutonic lunar rock (figure 1). The mineralogy and Wasson (1977) and Bersch et al. (1991) also of 62237 is that of a ferroan anorthosite with fairly provided analyses of olivine in 62237. Dymek et al. abundant (~20%) mafic minerals (figure 5). noted that olivine in 62237 was extremely depleted in Ca. Lunar Sample Compendium C Meyer 2011 Figure 2: Location of 62237. Pyroxene: Dymek et al. (1975) and Bersch et al. (1991) determined the composition of pyroxene in 62237 (figure 4). Plagioclase: Plagioclase in 62237 is An95-99 and contains only small amount of minor elements (Dymek et al.
    [Show full text]