Mineralogical and Chemical Investigations of the Amguid Crater (Algeria): Is There Evidence on an Impact Origin?

Total Page:16

File Type:pdf, Size:1020Kb

Mineralogical and Chemical Investigations of the Amguid Crater (Algeria): Is There Evidence on an Impact Origin? geosciences Article Mineralogical and Chemical Investigations of the Amguid Crater (Algeria): Is there Evidence on an Impact Origin? Gian Paolo Sighinolfi 1, Maurizio Barbieri 2,* , Daniele Brunelli 1 and Romano Serra 3 1 Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, 41125 Modena, Italy; giampaolo.sighinolfi@unimore.it (G.P.S.); [email protected] (D.B.) 2 Dipartimento di Scienze della Terra, Università la Sapienza, 00185 Roma, Italy 3 Dipartimento di Fisica e Astronomia, Università di Bologna, 40126 Bologna, Italy; [email protected] * Correspondence: [email protected] Received: 14 December 2019; Accepted: 16 March 2020; Published: 18 March 2020 Abstract: Mineralogical and chemical investigations were carried out on intra-craterial bedrocks (Lower Devonian sandstone) and regolithic residual soil deposits present around the Amguid structure, to discuss the hypothesis of its formation through a relatively recent (about 0.1 Ma) impact event. Observations with an optical microscope on intra-craterial rocks do not unequivocally confirm the presence of impact correlated microscopic planar deformation features (PDFs) in quartz crystals. Field observations, and optical and instrumental analysis (Raman spectroscopy) on rocks and soils (including different granulometric fractions) do not provide any incontrovertible pieces of evidence of high energy impact effects or products of impact (e.g., high pressure—temperature phases, partially or totally melted materials, etc.) either in target rocks or in soils. A series of selected main and trace elements (Al, Fe, Mg, Ni, Co and Cu) were analysed on rocks and soils to evaluate the presence in these materials of extraterrestrial sources. Comparative chemical data on rocks and soils suggest that these last are significantly enriched in Fe-poor Mg-rich materials, and in Co, Ni and Cu, in the order. A large number of EDAX-SEM analyses on separated soil magnetic particles indicate an abnormally high presence of Al-free Mg-rich sub-spherical or drop-like silicate particles, showing very similar bulk chemistries compatible with forsterite olivine. Some particles were found associated with a Ni-rich iron metal phase, and this association suggests a specific extraterrestrial origin for them. Electron microscope analysis made on a large number of soil magnetic particles indicates that 98% of them are terrestrial phases (almandine garnet, tourmaline and Fe-oxides, in abundance order), whereas, only a few grains are of questionable origin. One of the Mg-rich silicate particles was found to be a forsterite (Mg = 0.86) Mn-rich (MnO: 0.23%) Cr-free olivine, almost surely of extraterrestrial sources. Electron microprobe analysis of three soil particles allowed identification of uncommon Cr-rich (Cr2O3 about 8%) spinels, poorly compatible with an origin from terrestrial sources, and in particular from local source rocks. We propose a specific extraterrestrial origin for sub-spherical olivine particles characterised by quite similar magnesian character. Excluding any derivation of these particles from interplanetary dust, two other possible extraterrestrial sources should be considered for them, i.e., either normal micrometeorite fluxes or strongly un-equilibrated, or the Vigarano type Carbonaceous (CV) chondrite meteorite material. In this case, further studies will confirm an impact origin for Amguid, as such magnesian olivine components found in soils might represent the only remnants of a vaporised projectile of ordinary non-equilibrated meteoritic composition. Keywords: impact crater; chemical data; rocks; soil; instrumental analysis. Geosciences 2020, 10, 107; doi:10.3390/geosciences10030107 www.mdpi.com/journal/geosciences Geosciences 2020, 10, 107 2 of 15 Geosciences 2019, 9, x FOR PEER REVIEW 2 of 15 1. Introduction Europeans discovered the circular structure known as the Amguid crater (26°05’17” N, 04°23’49” Europeans discovered the circular structure known as the Amguid crater (26 05 17 N, 04 23 49 E, Figure 1) in 1948 and it was confirmed from an aircraft in 1954. Jean‐Philippe◦ le0 Franc00 made◦ 0 the00 E, Figure1) in 1948 and it was confirmed from an aircraft in 1954. Jean-Philippe le Franc made the first first scientific description of it in 1969 [1]. One of the best‐preserved impact craters on Earth—the scientific description of it in 1969 [1]. One of the best-preserved impact craters on Earth—the Amguid Amguid crater in Algeria—is also one of the hardest to access crater in Algeria—is also one of the hardest to access (https://www.wondermondo.com/amguid-crater/): (https://www.wondermondo.com/amguid-crater/): FigureFigure 1.1. AmguidAmguid crater,crater, Algeria.Algeria. OwingOwing toto thethe toughtough accessibility,accessibility, relativelyrelatively fewfew visitorsvisitors havehave reachedreached thethe areaarea soso far.far. Hence,Hence, relativelyrelatively fewfew scientificscientific studiesstudies werewere publishedpublished afterafter itsits discovery.discovery. TheThe originorigin ofof thethe structurestructure isis correlatedcorrelated to to an an impact impact event event proposed proposed by Lambert by Lambert et al. [et1 ].al. The [1]. theory The oftheory an impact of an event impact is assumed event is byassumed some macroscopic by some macroscopic structural structural and morphological and morphological features of features the exposed of the crater exposed rocks crater and rocks evidence and inevidence them of in microscopic them of microscopic planar deformation planar deformation features (PDFs) features in mineral (PDFs) phases in mineral (quartz) phases present (quartz) in the possiblepresent in target the possible rocks, correlated target rocks, to shock correlated metamorphic to shock e ffmetamorphicects [1]. effects [1]. DuringDuring anan ItalianItalian expeditionexpedition mademade inin FebruaryFebruary 2011,2011, aa seriesseries ofof “in“in situ”situ” observationsobservations werewere dedicateddedicated toto findingfinding evidenceevidence ofof thethe possiblepossible impactimpact event.event. To thisthis aim,aim, wewe alsoalso collectedcollected aa setset ofof materials,materials, includingincluding substratesubstrate intra-craterintra‐crater rocksrocks andand soilsoil samplessamples fromfrom thethe surrounding surrounding area. area. ThisThis studystudy aimedaimed toto ascertainascertain thethe impactimpact originorigin ofof thethe structurestructure and,and, byby thethe meansmeans ofof mineralogicalmineralogical andand chemicalchemical datadata onon thethe collectedcollected materials,materials, shedshed lightlight onon thethe possiblepossible modemode ofof impactimpact andand naturenature ofof thethe impactorimpactor [[2].2]. 2.2. GeneralGeneral InformationInformation onon thethe AmguidAmguid StructureStructure TheThe morphologicalmorphological andand structuralstructural featuresfeatures ofof thethe AmguidAmguid structurestructure werewere describeddescribed inin detaildetail byby LambertLambert etet al.al. [[1].1]. TheThe 550550 mm [[3]3] crater crater is is formed formed in in Lower Lower Devonian Devonian sandstones. sandstones. ItIt hashas anan elevatedelevated rim of up to 65 m [3,4]. The bottom of the crater (observation on February 2011) is partially filled by very bright, and fine‐grained eolian silts and sands (Figure 2), and in part, is covered by detrital materials composed of fall‐back breccias, also containing a fine‐grained component. The near‐perfect Geosciences 2020, 10, 107 3 of 15 rim of up to 65 m [3,4]. The bottom of the crater (observation on February 2011) is partially filled Geosciencesby very 2019 bright,, 9, x FOR and PEER fine-grained REVIEW eolian silts and sands (Figure2), and in part, is covered by detrital3 of 15 materials composed of fall-back breccias, also containing a fine-grained component. The near-perfect preservationpreservation state state of of the the crater crater led led Lambert Lambert et et al. al. [1] [1 ]to to estimate estimate a a presumed presumed age age of of 0.1 0.1 Ma, although in in reality, itit isis probablyprobably less.less. FigureFigure 2. Image 2. Image of the of the Amguid Amguid structure structure (intra (intra-crater‐crater soils soils location). location). ThereThere are are a series a series of of distinct distinct sandstone sandstone bed bed outcrops outcrops on on the internal wallswalls ofof thethe crater, crater, with with a a dip dipthat that becomes becomes progressively progressively steeper steeper in the in upperthe upper parts parts of the of walls. the Accordingwalls. According to Belhai to and Belhai Sahoui and [ 4], Sahouithe upturned [4], the upturned sandstones sandstones and overturned and overturned strata observed strata at observed the North-North-West-West at the North‐North‐ (NNWW)West‐West and (NNWW)South-South-East and South (SSE)‐South parts‐East of (SSE) the elevated parts of rim the are elevated consistent rim with are macroscopic consistent with impact macroscopic deformation impactfeatures. deformation According features. to Lambert According et al. [1 to], furtherLambert evidence et al. [1], for further an impact evidence origin for of an Amguid impact isorigin provided of Amguidby up tois provided three sets by of PDFup to textures three sets in quartzof PDF crystals textures from in quartz intra-crater crystals rocks. from intra‐crater rocks. 3. Foundations3. Foundations of ofthe the Present Present Investigations Investigations and and Studied Studied Materials Materials TheThe complete complete absence absence
Recommended publications
  • Pantasma: Evidence for a Pleistocene Circa 14 Km Diameter Impact Crater in Nicaragua
    Meteoritics & Planetary Science 1–22 (2019) doi: 10.1111/maps.13244 Pantasma: Evidence for a Pleistocene circa 14 km diameter impact crater in Nicaragua P. ROCHETTE 1*, R. ALACß 2, P. BECK3, G. BROCARD2, A. J. CAVOSIE 4, V. DEBAILLE5, B. DEVOUARD1, F. JOURDAN4, B. MOUGEL 6,11, F. MOUSTARD1, F. MOYNIER6, S. NOMADE7, G. R. OSINSKI 8, B. REYNARD9, and J. CORNEC10 1Aix-Marseille Univ., CNRS, INRA, IRD, Coll. France, CEREGE, 13545 Aix-en-Provence, France 2Basin Genesis Hub, School of Geosciences, University of Sydney, Sydney, Australia 3Univ Grenoble Alpes, CNRS, IPAG, UMR 5274, 38041 Grenoble, France 4Space Science and Technology Centre and The Institute for Geoscience Research (TIGeR), School of Earth and Planetary Science, Curtin University, Perth, Western Australia, Australia 5Laboratoire G-Time, Universite Libre de Bruxelles, Brussels, Belgium 6Institut de Physique du Globe de Paris, Universite Sorbonne Paris Cite, CNRS UMR 7154, Paris, France 7LSCE, CEA, CNRS UVSQ et Universite´de Paris Saclay, 91190 Gif sur Yvette, France 8Centre for Planetary Science and Exploration and Department of Earth Science, University of Western Ontario, London, Canada 9University of Lyon, ENS de Lyon, Universite´Claude Bernard Lyon 1, CNRS, UMR 5276 LGL-TPE*, 69007 Lyon, France 10Geologist, Denver, USA 11Present address: Centro de geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro *Corresponding author. E-mail: [email protected] (Received 07 March 2017; revision accepted 15 December 2018) Abstract–The circa 14 km diameter Pantasma circular structure in Oligocene volcanic rocks in Nicaragua is here studied for the first time to understand its origin. Geomorphology, field mapping, and petrographic and geochemical investigations all are consistent with an impact origin for the Pantasma structure.
    [Show full text]
  • The Tennessee Meteorite Impact Sites and Changing Perspectives on Impact Cratering
    UNIVERSITY OF SOUTHERN QUEENSLAND THE TENNESSEE METEORITE IMPACT SITES AND CHANGING PERSPECTIVES ON IMPACT CRATERING A dissertation submitted by Janaruth Harling Ford B.A. Cum Laude (Vanderbilt University), M. Astron. (University of Western Sydney) For the award of Doctor of Philosophy 2015 ABSTRACT Terrestrial impact structures offer astronomers and geologists opportunities to study the impact cratering process. Tennessee has four structures of interest. Information gained over the last century and a half concerning these sites is scattered throughout astronomical, geological and other specialized scientific journals, books, and literature, some of which are elusive. Gathering and compiling this widely- spread information into one historical document benefits the scientific community in general. The Wells Creek Structure is a proven impact site, and has been referred to as the ‘syntype’ cryptoexplosion structure for the United State. It was the first impact structure in the United States in which shatter cones were identified and was probably the subject of the first detailed geological report on a cryptoexplosive structure in the United States. The Wells Creek Structure displays bilateral symmetry, and three smaller ‘craters’ lie to the north of the main Wells Creek structure along its axis of symmetry. The question remains as to whether or not these structures have a common origin with the Wells Creek structure. The Flynn Creek Structure, another proven impact site, was first mentioned as a site of disturbance in Safford’s 1869 report on the geology of Tennessee. It has been noted as the terrestrial feature that bears the closest resemblance to a typical lunar crater, even though it is the probable result of a shallow marine impact.
    [Show full text]
  • Geology, Published Online on 5 January 2011 As Doi:10.1130/G31624.1
    Geology, published online on 5 January 2011 as doi:10.1130/G31624.1 Geology Kamil Crater (Egypt): Ground truth for small-scale meteorite impacts on Earth L. Folco, M. Di Martino, A. El Barkooky, M. D'Orazio, A. Lethy, S. Urbini, I. Nicolosi, M. Hafez, C. Cordier, M. van Ginneken, A. Zeoli, A.M. Radwan, S. El Khrepy, M. El Gabry, M. Gomaa, A.A. Barakat, R. Serra and M. El Sharkawi Geology published online 5 January 2011; doi: 10.1130/G31624.1 Email alerting services click www.gsapubs.org/cgi/alerts to receive free e-mail alerts when new articles cite this article Subscribe click www.gsapubs.org/subscriptions/ to subscribe to Geology Permission request click http://www.geosociety.org/pubs/copyrt.htm#gsa to contact GSA Copyright not claimed on content prepared wholly by U.S. government employees within scope of their employment. Individual scientists are hereby granted permission, without fees or further requests to GSA, to use a single figure, a single table, and/or a brief paragraph of text in subsequent works and to make unlimited copies of items in GSA's journals for noncommercial use in classrooms to further education and science. This file may not be posted to any Web site, but authors may post the abstracts only of their articles on their own or their organization's Web site providing the posting includes a reference to the article's full citation. GSA provides this and other forums for the presentation of diverse opinions and positions by scientists worldwide, regardless of their race, citizenship, gender, religion, or political viewpoint.
    [Show full text]
  • A METEORITE IMPACT CRATER in CENTRAL TIBET? M. Schmieder1,2, E
    75th Annual Meteoritical Society Meeting (2012) 5006.pdf A METEORITE IMPACT CRATER IN CENTRAL TIBET? M. Schmieder1,2, E. Tohver1, F. Jourdan2 and A. Bevan3, 1University of Western Australia, Crawley, Australia, [email protected], 2Curtin University, Perth, Australia, 3Western Australian Museum, Perth, Australia. Introduction: Only a few impact structures have been recognized in Central Asia to date. Apart from the recent discovery of the Xiuyan impact structure in eastern China [1], no meteorite craters are known in this part of Asia. Satellite images reveal a distinct crater-like depression on a fluvial plain on the Tibetan Plateau, ~630 km NW of the Tibetan capital of Lhasa. Remote Sensing and Geology: An apparently well-preserved crater 27 m in diameter (31°59'39"N, 85°9'14"E) is located on the active fluvial plain of the Shialzu River, at ~4,550 m above sea level. The recent fluvial sediments overlie Cretaceous (Aptian-Albian) limestones of the northern Lhasa Terrane [2]. The ‘Shialzu crater’ exhibits a simple bowl shape and a slightly polygonal outline (Fig. 1A-B). The crater rim seemingly consists of smaller, up to meter-sized, cliffs of disrupted rocks and slump blocks. A man-made structure resembling a stone paddock and a local vehicle track lie 400 m south of the crater; a cluster of circular pingos and pingo scars lies ~2-3 km to the southwest. Fig. 1: Satellite images of the ‘Shialzu crater’ on the Tibetan Plateau (A: 18/03/2004; B: 29/12/2005; mapabc.com images implemented in Google Earth) and two simple impact craters of similar appearance on an alluvial plain on Mars (C; HiRISE image ESP_020323_2050_RED).
    [Show full text]
  • Evidence for Subsolidus Quartz-Coesite Transformation in Impact Ejecta from the Australasian Tektite Strewn field
    Available online at www.sciencedirect.com ScienceDirect Geochimica et Cosmochimica Acta 264 (2019) 105–117 www.elsevier.com/locate/gca Evidence for subsolidus quartz-coesite transformation in impact ejecta from the Australasian tektite strewn field Fabrizio Campanale a,b,⇑, Enrico Mugnaioli b, Luigi Folco a, Mauro Gemmi b Martin R. Lee c, Luke Daly c,e,f, Billy P. Glass d a Dipartimento di Scienze della Terra, Universita` di Pisa, V. S. Maria 53, 56126 Pisa, Italy b Center for Nanotechnology Innovation@NEST, Istituto Italiano di Tecnologia (IIT), Piazza San Silvestro 12, 56127 Pisa, Italy c Department of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK d Department of Geosciences, University of Delaware, Newark, DE, USA e Australian Centre for Microscopy and Microanalysis, University of Sydney, Sydney 2006, NSW, Australia f Space Science and Technology Centre, School of Earth and Planetary Science, Curtin University, Bentley, 6102 WA, Australia Received 1 April 2019; accepted in revised form 11 August 2019; Available online 21 August 2019 Abstract Coesite, a high-pressure silica polymorph, is a diagnostic indicator of impact cratering in quartz-bearing target rocks. The formation mechanism of coesite during hypervelocity impacts has been debated since its discovery in impact rocks in the 1960s. Electron diffraction analysis coupled with scanning electron microscopy and Raman spectroscopy of shocked silica grains from the Australasian tektite/microtektite strewn field reveals fine-grained intergrowths of coesite plus quartz bearing planar deformation features (PDFs).À Quartz and euhedral microcrystalline coesite are in direct contact, showing a recurrent pseudo iso-orientation, with the ½111* vector of quartz near parallel to the [0 1 0]* vector of coesite.
    [Show full text]
  • Meteorite Times Magazine
    Meteorite Times Magazine Contents Paul Harris Featured Articles Accretion Desk by Martin Horejsi Jim’s Fragments by Jim Tobin Meteorite Market Trends by Michael Blood Bob’s Findings by Robert Verish Micro Visions by John Kashuba Norm’s Tektite Teasers by Norm Lehrman Mr. Monning’s Collection by Anne Black IMCA Insights by The IMCA Team Meteorite of the Month by Editor Tektite of the Month by Editor Terms Of Use Materials contained in and linked to from this website do not necessarily reflect the views or opinions of The Meteorite Exchange, Inc., nor those of any person connected therewith. In no event shall The Meteorite Exchange, Inc. be responsible for, nor liable for, exposure to any such material in any form by any person or persons, whether written, graphic, audio or otherwise, presented on this or by any other website, web page or other cyber location linked to from this website. The Meteorite Exchange, Inc. does not endorse, edit nor hold any copyright interest in any material found on any website, web page or other cyber location linked to from this website. The Meteorite Exchange, Inc. shall not be held liable for any misinformation by any author, dealer and or seller. In no event will The Meteorite Exchange, Inc. be liable for any damages, including any loss of profits, lost savings, or any other commercial damage, including but not limited to special, consequential, or other damages arising out of this service. © Copyright 2002–2015 The Meteorite Exchange, Inc. All rights reserved. No reproduction of copyrighted material is allowed by any means without prior written permission of the copyright owner.
    [Show full text]
  • Minimeteorites from the Transantarctic Mountains
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Earth-prints The Kamil Crater in Egypt Luigi Folco1, Mario Di Martino2, Ahmed El Barkooky3, Massimo D'Orazio4, Ahmed Lethy5, Stefano Urbini6, Iacopo Nicolosi6, Mahfooz Hafez5, Carole Cordier1, Matthias van Ginneken1, Antonio Zeoli1, Ali M. Radwan5, Sami El Khrepy5, Mohamed El Gabry5, Mahomoud Gomaa5, Aly A. Barakat7, Romano Serra8, Mohamed El Sharkawi3 1 Museo Nazionale dell'Antartide Università di Siena, Via Laterina 8, 53100, Siena, Italy. 2 Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Torino, 10025 Pino Torinese, Italy. 3 Department of Geology, Faculty of Sciences, Cairo University, Giza, Egypt. 4 Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126 Pisa, Italy. 5 National Research Institute of Astronomy and Geophysics, Helwan, Egypt. 6 Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Roma, Italy. 7 Egyptian Mineral Resources Authority, 3 Salah Salem Road, Abassiya, Cairo, Egypt. 8 Dipartimento di Fisica, Università di Bologna, Via Irnerio 46, 40126 Bologna, Italy. Abstract. We report on the discovery in southern Egypt of an impact crater 45 m in diameter with a pristine rayed structure. Such pristine structures have been previously observed only on atmosphereless rocky or icy planetary bodies in the Solar System. This feature and the association with an iron meteorite impactor and shock metamorphism provides a unique picture of small-scale hypervelocity impacts on the Earth's crust. Contrary to current geophysical models, ground data indicate that iron meteorites with masses of the order of tens of tons can penetrate the atmosphere without significant fragmentation.
    [Show full text]
  • Shatter Cones in Hypervelocity Impact Experiments: Structure, Formation and Comparison to Natural Impact Craters
    Shatter cones in hypervelocity impact experiments: Structure, formation and comparison to natural impact craters DISSERTATION Zur Erlangung des akademischen Grades “doctor rerum naturalium“ (Dr. rer. nat.) Der Fakultät für Umwelt und natürliche Ressourcen Der Albert-Ludwigs-Universität Freiburg i. Brsg. vorgelegt von Jakob Wilk Geb. in Berlin, Pankow Freiburg im Breisgau 2017 Dekan: Prof. Dr. Tim Freytag Erstbetreuer/Referent: Prof. Dr. Thomas Kenkmann Korreferent: Prof. Dr. Alex Deutsch Zweitbetreuer: Prof. Dr. Stefan Hergarten Tag der Disputation: ABSTRACT Impact processes have dominated the formation and development of planetary bodies in our solar system. The study of impact crater formation provides deeper knowledge of early Earth’s history and enables us to understand a surface process profoundly shaping the surface of most rocky planetary bodies. The highly dynamic process of impact cratering causes a series of characteristic effects in the targeted rocks, which are referred to as shock metamorphic effects. These shock effects provide a valuable tool to analyze impact craters and their formation. Shatter cones are diagnostic for shock metamorphism. They are the only macroscopic effect caused by shock, thus, being unambiguously identifiable in the field, provide a valuable tool to find and verify impact structures. Over the last decades, hypervelocity impact experiments and shock recovery experiments fundamentally enhanced our understanding of impact cratering, by controlled laboratory conditions. With this technique, e.g., microscopic effects were calibrated to corresponding shock pressures, or the effect of target properties on the cratering process was extensively studied. However, in only few experiments shatter cones were found and analyzed. Thus, the conditions of shatter cone formation remained unclear.
    [Show full text]
  • An Unusual Occurrence of Coesite at the Lonar Crater, India
    Meteoritics & Planetary Science 52, Nr 1, 147–163 (2017) doi: 10.1111/maps.12745 An unusual occurrence of coesite at the Lonar crater, India 1* 1 2 1 3 Steven J. JARET , Brian L. PHILLIPS , David T. KING JR , Tim D. GLOTCH , Zia RAHMAN , and Shawn P. WRIGHT4 1Department of Geosciences, Stony Brook University, Stony Brook, New York 11794–2100, USA 2Department of Geosciences, Auburn University, Auburn, Alabama 36849, USA 3Jacobs—NASA Johnson Space Center, Houston, Texas 77058, USA 4Planetary Science Institute, Tucson, Arizona 85719, USA *Corresponding author. E-mail: [email protected] (Received 18 March 2016; revision accepted 06 September 2016) Abstract–Coesite has been identified within ejected blocks of shocked basalt at Lonar crater, India. This is the first report of coesite from the Lonar crater. Coesite occurs within SiO2 glass as distinct ~30 lm spherical aggregates of “granular coesite” identifiable both with optical petrography and with micro-Raman spectroscopy. The coesite+glass occurs only within former silica amygdules, which is also the first report of high-pressure polymorphs forming from a shocked secondary mineral. Detailed petrography and NMR spectroscopy suggest that the coesite crystallized directly from a localized SiO2 melt, as the result of complex interactions between the shock wave and these vesicle fillings. INTRODUCTION Although there is no direct observation of nonshock stishovite in nature, a possible post-stishovite phase may High-Pressure SiO2 Phases be a large component of subducting slabs and the core- mantle boundary (Lakshtanov et al. 2007), and Silica (SiO2) polymorphs are some of the simplest stishovite likely occurs in the deep mantle if basaltic minerals in terms of elemental chemistry, yet they are slabs survive to depth.
    [Show full text]
  • Shock Metamorphism and Impact Melting at Kamil Crater, Egypt
    Università di Pisa Dipartimento di Scienze della Terra Scuola di Dottorato in Scienze di Base “Galileo Galilei” Programma in Scienze della Terra XXVII Ciclo SSD GEO/07 SHOCK METAMORPHISM AND IMPACT MELTING AT KAMIL CRATER, EGYPT PhD Student Advisor Prof. Massimo D’Orazio Agnese Fazio Co-advisor Dott. Luigi Folco Anno Accademico 2013-2014 Ricorda: “Quando stai per rinunciare, quando senti che la vita è stata troppo dura con te, ricordati chi sei. Ricorda il tuo sogno”. (Il Delfino - S. Bambarén) TABLE OF CONTENTS ABSTRACT 7 RIASSUNTO 9 PREFACE 11 1. INTRODUCTION 13 1.1. IMPACT CRATERING AS A TERRESTRIAL GEOLOGICAL PROCESS 13 1.2. IMPACT CRATERING STAGES 17 1.3. SHOCK METAMORPHISM 21 1.3.1. Quartz 24 1.3.2. Deformation in other minerals 28 1.3.3. Selective and localized melting 29 1.4. IMPACT MELTING 31 1.5. SHOCK EFFECTS IN QUARTZ-BEARING ROCKS: CRYSTALLINE VS. SEDIMENTARY TARGETS 34 1.6. REFERENCES 37 2. SHOCK METAMORPHISM AND IMPACT MELTING IN SMALL IMPACT CRATERS ON EARTH: EVIDENCE FROM KAMIL CRATER, EGYPT 41 3. TARGET-PROJECTILE INTERACTION DURING IMPACT MELTING AT KAMIL CRATER, EGYPT 89 4. MICROSCOPIC IMPACTOR DEBRIS IN THE SOIL AROUND KAMIL CRATER (EGYPT): INVENTORY, DISTRIBUTION, TOTAL MASS AND IMPLICATIONS FOR THE IMPACT SCENARIO 131 5. CONCLUSIONS 161 6. FUTURE WORK 165 6.1. COMBINED MICRO-RAMAN AND TEM STUDY OF HIGH-PRESSURE PHASES FROM KAMIL CRATER (EGYPT): IMPLICATIONS FOR THEIR FORMATION IN SMALL IMPACT CRATERS ON EARTH 165 6.2. LIQUID IMMISCIBILITY FEATURES IN IMPACT MELTS 165 6.3. REFERENCES 166 APPENDIX I. USE OF THE UNIVERSAL STAGE (U-STAGE) FOR INDEXING PLANAR DEFORMATION FEATURES IN QUARTZ 169 APPENDIX II.
    [Show full text]
  • Small Simple Impact Craters
    Small simple impact craters Amelia Carolina Sparavigna Dipartimento di Fisica, Politecnico di Torino C.so Duca degli Abruzzi 24, Torino, Italy Abstract The paper discusses some examples of image processing applied to improve optical satellite imagery of small craters (Kamil, Veevers, Haviland). The examples show that image processing can be quite useful for further in-situ researches, because the resultant imagery helps to have a better picture of the crater shape and of the distribution of debris about it. The paper is also disclosing an interesting underwater structure, with shape and size of a small crater, located on the coast-line of Sudan. Key-words : Image processing, Satellite maps, Craters, Underwater craters. The term Crater ( κρατηρ) in Greek means the bowl used to mix wine and water during symposia. This term passed to describe volcanic and impact depressions found on the surface of Earth or other rocky planets. A simple impact crater, created by the collision of a relatively small body with the surface of the planet, has a landform with roughly circular outline and a raised rim, when diameter is small, that is, the form of a bowl. Small impact events are producing simple craters. Here we consider as small craters, those with a diameter less than 100 m. These structures are common and detectable on the rocky bodies of the Solar System. Easy to observe, these craters remain well-preserved on the lunar surface, providing a record of the rate of impacts and of the distribution of bullet sizes: to deduce a similar curve from impacts over Earth’s surface is complicated [1].
    [Show full text]
  • Remote Sensing of Impact Craters 195
    THIRTEEN Remote s ensing of i mpact c raters Shawn P. Wright * , Livio L. Tornabene † and Michael S. Ramsey ‡ * Institute of Meteoritics, MSC03 2050, University of New Mexico, Albuquerque, NM 87131, USA † Centre for Planetary Science and Exploration, Department of Earth Sciences Western University, 1151 Richmond Street, London, ON, N6A 5B7, Canada ‡ Department of Geology and Planetary Science, University of Pittsburgh, 4107 O ’ Hara Street, Pittsburgh, PA 15260 - 3332, USA 13.1 Introduction themes, followed by two case studies that utilize one or more of these aspects to solve a geological problem about an impact site. As discussed throughout this book, impact cratering is a funda- mental geological process that has shaped and modifi ed the surfaces of planets throughout geological time (see summary in 13.2 Background Chapter 1 ). However, the low frequency of meteorite impacts during the recent past and the ongoing active geological processes An early and ongoing goal involving remote sensing of terrestrial on Earth offer rare opportunities to examine pristine impact sites, impact craters has been to simply discover new impact craters which are common on the surfaces of other terrestrial planets. solely from remote - sensing data (Garvin et al ., 1992 ; Koeberl, With the exception of a few robotic and manned space explora- 2004 ; Folco et al ., 2010, 2011 ) or fi nd spectral differences between tion missions, the analysis of orbital data has been the primary shocked rocks and their protoliths (D ’ Aria and Garvin, 1988 ; method for studying impact craters in a variety of settings and Garvin et al ., 1992 ; Johnson et al ., 2002, 2007 ; Wright et al ., 2011 ).
    [Show full text]