Textures of Igneous Rocks (E)
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Igneous Petrology
Igneous Petrology IGNEOUS PETROLOGY (Practical) SHAREEF AL-HAMED Department of Geology, College of Science, University of Mosul 0 Igneous Petrology Lab. 1 Diagnostic features of igneous minerals under the microscope Felsic minerals 1. Quartz SiO2: anhedral or subhedral, colorless and without pleochroism, without cleavage, low relief, parallel extinction, first order gray interference color, devoid of alteration. 2. Orthoclase KAlSi3O8: subhedral to anhedral, colorless but dusty result alteration to kaolinite and sericite, low relief, carlsbad twinning, first order gray to white interference color, parallel or oblique extinction. 3. Microcline KAlSi3O8: similar to orthoclase but distinguished from it by cross hatch twinning. 4. Sanidine (K, Na)AlSi3O8: similar to orthoclase in most of features (color, relief and interference color) but alteration less than it or devoid of alteration, distinguished by its tabular to elongated euhedral to subhedral crystals and transverse cracks. 5. Plagioclase, Albite NaAlSi3O8 -----Anorthite CaAl2Si2O8: similar to orthoclase in most of features (color, interference color, alteration and sometimes medium relief), tabular to elongate euhedral or subhedral and sometimes anhedral crystals, oblique extinction. Distinguished by its polysynthetic twinning and sometimes zoning. 6. Muscovite KAl3Si3O10(OH)2: colorless or pale color and third to fourth order bright interference color, 1-set cleavage, parallel extinction. 1 Igneous Petrology Mafic minerals 7. Biotite K(Mg, Fe)3(AlSi3O10)(OH)2: brown color and distinct -
Hydrogeologic Applications for Historical Records and Images from Rock Samples Collected at the Nevada National Security Site An
A. 1,461 ft 1,600 ft 2,004.5 ft Lithology interpreted by Richard G. Warren, Comprehensive Volcanic Petrographics, LLC 2,204 ft Figure 3. Representation of rock column derived from lithologic records (A) compared with core samples and thin sections thin-section images (B–E) from the UE-19p borehole. B. Adularia (AA) – Orthoclase (a K-spar polymorph typical of granite), that has formed under hydrothermal rather than magmatic conditions. Image from 2,204 ft at 30 degrees polarization. Acmite (AC) – A Na- and Fe3-rich pyroxene typically found as a Allanite (AL) – An epidote-group mineral containing high contents groundmass phase within devitrified peralkaline rock. Image from of rare-earth elements, found in alkali-calcic volcanic rocks. Image 2,004.5 ft at 90 degrees polarization. from 1,600 ft at 30 degrees polarization. C. Biotite (BT) – A hydrated mafic mineral typical of evolved volcanic rocks. Generally lacking in peralkaline units. Image from 1,461 ft at 90 degrees polarization. Glass (GL) – Typically Ca- and Fe-poor, compositionally at the “granite eutectic” within rhyolitic rocks such as those dominant within the Southwestern Nevada Volcanic Field (SWNVF). Unpolarized image from 1,461 ft. Clinopyroxene (CX) – A Ca-rich pyroxene and anhydrous mafic mineral found in a wide variety of volcanic rocks. Image from 1,461 ft at 30 degrees polarization. D. K-feldspar (KF) – A felsic phenocryst ubiquitous as sanidine within the SWNVF, except absent within the wahmonie Formation. Image from 2,004.5 ft at 30 degrees polarization. Lithic (LI) – A rock fragment incorporated into tuff during eruption, Perrierite/Chevkinite (PE) – A pseudobrookite-group mineral usually from the vent. -
Mineralogy and Petrology of the Santo Tomas-Black Mountain Basalt Field, Potrillo Volcanics, South-Central New Mexico
JERRY M. HOFFER Department of Geological Sciences, The University of Texas at El Paso, El Paso, Texas 79900 Mineralogy and Petrology of the Santo Tomas-Black Mountain Basalt Field, Potrillo Volcanics, South-Central New Mexico ABSTRACT called the Santo Tomas-Black Mountain basalt field (Hoffer, 1969c). The Santo Tomas-Black Mountain basalts The Santo Tomas-Black Mountain basalt were erupted during the Quaternary from field includes four major centers, each with four centers. Six lava flows are present at one or more cones and associated flows Black Mountain, three at Santo Tomas, and (Hoffer, 1969a). From north to south, the one each at Little Black Mountain and San four volcanic centers are Santo Tomas, San Miguel. The basalts are grouped into three Miguel, Little Black Mountain, and Black major types of phenocryst mineralogy: (l) Mountain. The largest volume of lava has plagioclase abundant, (2) olivine abundant, been extruded from the Black Mountain and and (3) both olivine and plagioclase abundant. Santo Tomas centers where six and three All three types are alkali-olivine basalts, individual flows, respectively, have been showing high alkali-silica ratios and total mapped (Hoffer, 1969a). Each of the two alkali content increasing with silica. intervening centers, Little Black Mountain Seven periods of basaltic extrusion among and San Miguel, shows only a single flow. the centers have been established on the No flow from a given center coalesces with basis of field evidence, phenocryst mineralogy, those from neighboring centers, but all ap- and pyroxene-olivine ratios. K-Ar dates show pear to be closely related in time (Kottlowski, the basalts to be less than 0.3 X 106 m.y. -
Module 7 Igneous Rocks IGNEOUS ROCKS
Module 7 Igneous Rocks IGNEOUS ROCKS ▪ Igneous Rocks form by crystallization of molten rock material IGNEOUS ROCKS ▪ Igneous Rocks form by crystallization of molten rock material ▪ Molten rock material below Earth’s surface is called magma ▪ Molten rock material erupted above Earth’s surface is called lava ▪ The name changes because the composition of the molten material changes as it is erupted due to escape of volatile gases Rocks Cycle Consolidation Crystallization Rock Forming Minerals 1200ºC Olivine High Ca-rich Pyroxene Ca-Na-rich Amphibole Intermediate Na-Ca-rich Continuous branch Continuous Discontinuous branch Discontinuous Biotite Na-rich Plagioclase feldspar of liquid increases liquid of 2 Temperature decreases Temperature SiO Low K-feldspar Muscovite Quartz 700ºC BOWEN’S REACTION SERIES Rock Forming Minerals Olivine Ca-rich Pyroxene Ca-Na-rich Amphibole Na-Ca-rich Continuous branch Continuous Discontinuous branch Discontinuous Biotite Na-rich Plagioclase feldspar K-feldspar Muscovite Quartz BOWEN’S REACTION SERIES Rock Forming Minerals High Temperature Mineral Suite Olivine • Isolated Tetrahedra Structure • Iron, magnesium, silicon, oxygen • Bowen’s Discontinuous Series Augite • Single Chain Structure (Pyroxene) • Iron, magnesium, calcium, silicon, aluminium, oxygen • Bowen’s Discontinuos Series Calcium Feldspar • Framework Silicate Structure (Plagioclase) • Calcium, silicon, aluminium, oxygen • Bowen’s Continuous Series Rock Forming Minerals Intermediate Temperature Mineral Suite Hornblende • Double Chain Structure (Amphibole) -
Compositional Zoning of the Bishop Tuff
JOURNAL OF PETROLOGY VOLUME 48 NUMBER 5 PAGES 951^999 2007 doi:10.1093/petrology/egm007 Compositional Zoning of the Bishop Tuff WES HILDRETH1* AND COLIN J. N. WILSON2 1US GEOLOGICAL SURVEY, MS-910, MENLO PARK, CA 94025, USA 2SCHOOL OF GEOGRAPHY, GEOLOGY AND ENVIRONMENTAL SCIENCE, UNIVERSITY OF AUCKLAND, PB 92019 AUCKLAND MAIL CENTRE, AUCKLAND 1142, NEW ZEALAND Downloaded from https://academic.oup.com/petrology/article/48/5/951/1472295 by guest on 29 September 2021 RECEIVED JANUARY 7, 2006; ACCEPTED FEBRUARY 13, 2007 ADVANCE ACCESS PUBLICATION MARCH 29, 2007 Compositional data for 4400 pumice clasts, organized according to and the roofward decline in liquidus temperature of the zoned melt, eruptive sequence, crystal content, and texture, provide new perspec- prevented significant crystallization against the roof, consistent with tives on eruption and pre-eruptive evolution of the4600 km3 of zoned dominance of crystal-poor magma early in the eruption and lack of rhyolitic magma ejected as the BishopTuff during formation of Long any roof-rind fragments among the Bishop ejecta, before or after onset Valley caldera. Proportions and compositions of different pumice of caldera collapse. A model of secular incremental zoning is types are given for each ignimbrite package and for the intercalated advanced wherein numerous batches of crystal-poor melt were plinian pumice-fall layers that erupted synchronously. Although released from a mush zone (many kilometers thick) that floored the withdrawal of the zoned magma was less systematic than previously accumulating rhyolitic melt-rich body. Each batch rose to its own realized, the overall sequence displays trends toward greater propor- appropriate level in the melt-buoyancy gradient, which was self- tions of less evolved pumice, more crystals (0Á5^24 wt %), and sustaining against wholesale convective re-homogenization, while higher FeTi-oxide temperatures (714^8188C). -
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. -
Igneous Rocks
1/26/2011 Igneous rock‐forming environments •Earth’s crust is 4/5 igneous rock. •Every igneous rock begins life as magma. Igneous rock is formed when •As magma migrates toward the surface, some of it chills and molten, or partially molten, hardens underground into various types of igneous rocks. rock solidifies. •Magma that makes it to the surface erupts in either flowing or explosive volcanoes, generating lava or pyroclastic debris. Igneous Rocks (two categories) Pillow Basalt Intrusive Extrusive Magma crystallized slowly within the crust. Lava and Pyroclastic Debris No exposure to the cool atmosphere. Extruded at surface or at very Plutonic –intrusive igneous rock at shallow levels. great depth within crust or mantle. Granite is Intrusive Basalt is Extrusive As magma crystallizes Texture Igneous Rocks a network of interlocking minerals develops. • Igneous Rocks are named on the basis of their Phaneritic texture - with large minerals texture and composition. The composition and (Granite) texture of the resulting Texture of a rock is the size and rock is determined by arrangement of the minerals it these minerals. contains. Composition of a rock is the assemblage of minerals it contains. Large crystals had a long time to crystallize. Therefore, this is an intrusive rock 1 1/26/2011 Texture Texture Texture Vesicular texture – Porphyritic Aphanitic texture - many pits from gas texture - with 2 mineral grains too escape (Basalt) small to see with the distinct grain sizes, unaided eye (Basalt) large and small (Andesite Porphyry) What is the cooling history? Small crystals had a short time to crystallize. Extrusive rock. Therefore, this is an extrusive rock Texture Texture is estimated using visual grain size Composition (depends on crystallization history) Igneous color (gray scale) is used to estimate chemical composition Glassy texture- Felsic Intermediate Mafic without obvious minerals (Obsidian) No crystals. -
GEOLOGIC MAP of the MOUNT ADAMS VOLCANIC FIELD, CASCADE RANGE of SOUTHERN WASHINGTON by Wes Hildreth and Judy Fierstein
U.S. DEPARTMENT OF THE INTERIOR TO ACCOMPANY MAP 1-2460 U.S. GEOLOGICAL SURVEY GEOLOGIC MAP OF THE MOUNT ADAMS VOLCANIC FIELD, CASCADE RANGE OF SOUTHERN WASHINGTON By Wes Hildreth and Judy Fierstein When I climbed Mount Adams {17-18 August 1945] about 1950 m (6400') most of the landscape is mantled I think I found the answer to the question of why men by dense forests and huckleberry thickets. Ten radial stake everything to reach these peaks, yet obtain no glaciers and the summit icecap today cover only about visible reward for their exhaustion... Man's greatest 2.5 percent (16 km2) of the cone, but in latest Pleis experience-the one that brings supreme exultation tocene time (25-11 ka) as much as 80 percent of Mount is spiritual, not physical. It is the catching of some Adams was under ice. The volcano is drained radially vision of the universe and translating it into a poem by numerous tributaries of the Klickitat, White Salmon, or work of art ... Lewis, and Cis pus Rivers (figs. 1, 2), all of which ulti William 0. Douglas mately flow into the Columbia. Most of Mount Adams and a vast area west of it are Of Men and Mountains administered by the U.S. Forest Service, which has long had the dual charge of protecting the Wilderness Area and of providing a network of logging roads almost INTRODUCTION everywhere else. The northeast quadrant of the moun One of the dominating peaks of the Pacific North tain, however, lies within a part of the Yakima Indian west, Mount Adams, stands astride the Cascade crest, Reservation that is open solely to enrolled members of towering 3 km above the surrounding valleys. -
Introduction to Types and Classification of Rocks
Presented at SDG Short Course II on Exploration and Development of Geothermal Resources, organized by UNU-GTP, GDC and KenGen, at Lake Bogoria and Lake Naivasha, Kenya, Nov. 9-29, 2017. Kenya Electricity Generating Co., Ltd. INTRODUCTION TO TYPES AND CLASSIFICATION OF ROCKS Geoffrey Mibei Geothermal Development Company P.O. Box 17700-20100, Nakuru KENYA [email protected] ABSTRACT Generally rocks can be divided into three major types based on the process of their formation. These are; Igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed by the solidification and cooling of magma in volcanic areas, while sedimentary rocks are formed by low temperature accumulation of sediments in tectonic basins and topographical sinks. Metamorphic rocks on the other hand are formed by application of temperature and pressure on pre-existing rocks. Metamorphic rocks therefore form at great depths, but exposed on the surface due to erosion and epirogenic movements. Each of these three rock types can be further classified in terms of; chemistry, how the form and environment of formation. The distributions of these major rock types are critical in regional mapping of natural resources. Igneous is coined from word “ignis” meaning fire and therefore these rocks are good indicators of volcanism and are there associated with geothermal resources and hydrothermal deposits like porphyry copper, and gold etc. sedimentary rocks especially the organic sediments on the other hand are good source rocks and are associated with resources like coal and oil. Sediments are also good proxies for environmental reconstruction, since fossils can be well preserved in these deposits. -
The Origin of Adakites in the Garibaldi Volcanic Complex, Southwestern British Columbia, Canada
The Origin of Adakites in the Garibaldi Volcanic Complex, southwestern British Columbia, Canada A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements For the Degree of Master of Science In Geology University of Regina By Julie Anne Fillmore Regina, Saskatchewan November 2014 Copyright 2014: J.A. Fillmore UNIVERSITY OF REGINA FACULTY OF GRADUATE STUDIES AND RESEARCH SUPERVISORY AND EXAMINING COMMITTEE Julie Anne Fillmore, candidate for the degree of Master of Science in Geology, has presented a thesis titled, The Origin of Adakites in the Garibaldi Volcanic Complex, Southwestern British Columbia, Canada, in an oral examination held on August 22, 2014. The following committee members have found the thesis acceptable in form and content, and that the candidate demonstrated satisfactory knowledge of the subject material. External Examiner: Dr. Martin Beech, Campion College Supervisor: Dr. Ian M. Coulson, Department of Geology Committee Member: Dr. Tsilavo Raharimahefa, Department of Geology Chair of Defense: Dr. Josef Buttigieg, Department of Biology ii Abstract The Garibaldi Volcanic Complex (GVC) is located in southwestern British Columbia, Canada. It comprises two volcanic fields: the Garibaldi Lake Volcanic Field (GLVF) in the north and the Mount Garibaldi Volcanic Field (MGVF) in the south. Petrographical and geochemical studies on volcanic rocks collected from the GVC have determined that they exhibit adakitic characteristics; these intermediate rocks range from basaltic andesite to dacite represented mainly by lava flows, domes and minor pyroclastic material. All the lavas exhibit evidence of magma mixing, which include sieve textured crystals, dehydration reaction textures, differently sized phenocryst populations, xenocrysts and xenoliths. -
Effect of Porphyritic Andesite Int Metamorphism Aureole in Sel
E-ISSN : 2541-5794 P-ISSN :2503-216X Journal of Geoscience, Engineering, Environment, and Technology Vol 5 No 2 2020 RESEARCH ARTICLE Effect of Porphyritic Andesite Intrusion on The Formation of Contact Metamorphism Aureole in Selo Gajah Hill Clastic Limestone, Bojonegoro Regency, East Java, Indonesia Tri Winarno1,*, Jenian Marin1, Wisnu Wijaya Jati1 1Department of Geological Engineering, Diponegoro University, Indonesia Corresponding author : [email protected] Telp :+62 857-4006-6835 Received: Nov 18, 2019, Accepted: Jun 25, 2020. DOI 10.25299/jgeet.2020.5.2.4098 Abstract At Selo Gajah Hill, Jari Village, Gondang Sub-district, Bojonegoro Regency, East Java there are limestone intruded by porphyritic andesite. The intrusion produces contact metamorphisms in the wall rocks. It is very interesting to study the protolith rock, facies of metamorphism and the zonation of contact metamorphism aureole. This research uses field observation method and laboratory analysis i.e. petrographic analysis. Field observation is conducted by doing geological mapping in the Bukit Selo Gajah area and rock sampling for petrographic analysis. Petrographic analysis aims to describe the texture of the rocks and the percentage of minerals, which will be used to determine the protolith rock, metamorphism facies and the determination of contact metamorphism zone. The lithology found in Mount Selo Gajah from oldest to youngest are clastic limestone with intercalation of marl, marl with intercalation of sandstone, porphyritic andesite intrusions, hornfels, and pyroclastic breccia. Metamorphic rocks on Selo Gajah Hill is the product of contact metamorphism of carbonate rock which was intruded by porphyritic andesite intrusion. The metamorphism facies found in the research area are hornblende hornfels and pyroxene hornfels with the protolith rock is carbonate rocks.