Open Research Online The Open University’s repository of research publications and other research outputs Carbon Chemistry Of Giant Impacts Thesis How to cite: Abbott, Jennifer Ileana (2000). Carbon Chemistry Of Giant Impacts. PhD thesis The Open University. For guidance on citations see FAQs. c 2000 The Author Version: Version of Record Link(s) to article on publisher’s website: http://dx.doi.org/doi:10.21954/ou.ro.00004a66 Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online’s data policy on reuse of materials please consult the policies page. oro.open.ac.uk ##1111111111111111I Il 1111111 Carbon chemistry of giant impacts. by Jennifer kana Abbott BSc. Hons. (Ct Andrews University) 1993 MCc. (The University of Leeds) 1995 A the(i\ wbniitied for the degree of Doctor of Philosophy September I999 Planetu). Sciences Research Institute The Open University ABSTRACT. Impact diamonds were found in several inipactites from the Ries crater. Geriiiaiiy including fallout and fallback (crater fill) suevites. a glass bomb, impact melt i-ock and shocked gneiss. These diamonds formed two distinct grain size populations: 50-300 pii apographitic. platy aggregates with surface ornamentation and etching that \vere observed using optical and scanning electron microscopy and 5-20 pm diaiiionds which displayed two different inorphologies identified using traiisinission electron microscopy and selected area electron diffraction. These 5-20 pm grains comprised apographitic. platy gi-nins with stacking faults, etching and graphite intergrowths together with elongate skeletal grains with prefemd orientations to the individual crystallites. Thermal annealing of stacking fa~ilisand surface features was also detected. Stepped combustion coiiibined with static mass spectrometry to give carbon isotopic analysis of iiidividunl diamonds. graphite and acid-residues indicate that the priinai-y carbon source is graphite. This graphite was found to be %depleted with i-cspcct to similar samples firom the Popigai impact crater. The admixture of presumably carbonate derived carbonaceous material is wzyxteù to account for the "C-enriched 6°C coinpositions encountered in whole-i-ock we\.ites known to include carbonate melts. 011the busis of moiphology. iiineralogicnl associations. diamoncVgraphite ratios aiid carbon isotopic compositions three possible formation mechanisms for impact dimionds are suzgested: fast. high temperature conversion of graphite following the pissage of the shock wave, a vapour phase condensation or growth within substrate iiiiiicrnls 01- an orientated stress field and the incomplete translomiation of a mixture of aiiiorphous and ralhe graphite. Further niore exotic mechanisms such as iiitcriiiediary carbyne phases cannot be discounted. linpact diamonds, 1-5 pni in size. were also identified in suevite residues and a hlack matrix lithic breccia from the Gardnos impact crater. Norway. The carbon isotopic Jennifer i Abbott ABSTRACT conipositions are in agreement with previous measurements of whole rock saiiiplcs with ;i riiiall "C-cnriched component probably representing diamond. Jennifer I Abhott ABSTRACT ~~ ACKNOWLEDGEMENTS. Firstly I would like to thank Colin Pillinger and Ian Gilmour for their supervision. lain Gilinour foi- discussions and critical reviews of this thesis. In addition for managing to \cimunge drinks off iiie at OU summer xhools. I would also like to thank Rob Hough who contributed his iiine and effort reading through and cornmeriting on this the\¡\. Thanks go to PPARC for funding this research Grciteftil thanks to D. Stöffler, B. French and S. Vishneviky who provided the samples wiihoul u-hich this study could not have existed. 'Tliuiiks go to J~idyPilliiiger for sorting out various problems and necessary supplies Huge tlianks go to Jenny Gibson and Michelle Higgins for training me io use the various carbon stable isotope inass spectroineters and especially teaching nie how to dcai with their occasional quirks. Thanks also to Ia11 Wright, Frachi and Sasha for fixing ihe various little quirks. Criitcf~ilappreciation and thanks iiiust bc extended to Naoiiii Williariis for all her help with ihc SEM. cathodoluminescence, TEM and dark room facilities. most especially in iiiigiiing a teinperainental TEM. In addition to Gordon Inilach who must have been heinused hy iiiy grateful excitement at finding an operational dark rooin. To iiiy tlatmates for the last two years Nicky Siinpson and Julia Hadley thanks for putting LIPwith iiie and all those late night discussions and panics. Thanks go to a11 the staff and regular habitués of the Cellar bar for riot mentioning deadlines. Most of all thanks to my parents for their constaiit support and encouragement over the 1;isi 28 years. I wont evenmake you read it. Thanks to my sister for providing wine and distnictiiig nephews and Colin ror catching the lobsters. Jennifer i Abbott ACKNOWLEDGEMENTS LIST OF CONTENTS. Abstract Acknowledgements List of contents. i List of figures. vii List of tables. xi List of equations. xii Abbreviations. xiii CHAPTER 1. INTRODUCTION AND BACKGROUND. 1 I, i. Lunar and terrestrial cratering record. 2 1.2. Asteroids and comets. 5 1.3. Experimental cratering. 7 i .4. Atmospheric effects of impacts. 7 1.5. Shock metarnoiphisin. 8 1.5.1. General shock effects. 10 1.6. Classification of impactites (with reference to the Ries crater). Il I .6.1. Proximal impactites. 12 1.6.2. Distal impactites 15 1.7. Carbon. 18 1.7.1. Diamonds in meteorites. 18 I .7.2. Diamonds associated with impacts. 20 1.7.3. Graphite associated with impacts. 21 I .7.4. Fullerenes and soot associated with impacts. 22 I .7.5. Carbynes associated with impacts. 24 1.8. Impact diamond occurrences and characteristics. 25 I .9. Stable carbon isotopes. 28 I. 10. Suggested formational mechanisms. 30 1. I i, Objectives. 33 CHAPTER 2. PETROGRAPHIC DESCRIPTIONS AND EXPERIMENTAL TECHNIQUES. 35 2. i, introduction. 35 2.2. Ries crater sample descriptions. 36 2.2.1. Ötting quarry, fallout suevite (OQS). 31 2.2.2. Ötting quarry, glass bomb (OQGB). 40 Jennifer I Abbott LIST OF CONTENTS i 2.2.3. Seelbronn quarry (Aufhausen), fallout suevite (SBS). 41 2.2.4. Auhmüle quany, Bunte breccia (BB). 41 2.2.5. Polsingen quarry, impact melt breccia (PIMR). 42 2.2.6. Itzingen quarry, granite (ITZ). 43 2.3. Nördlingen 1973 drill core. 44 2.3. I. Brecciated crystalline basement 1059, 10-25111 depth. 45 2.3.2. Suevite 494, 64-86 m depth. 45 2.3.3. Suevite 384,07-14 m depth. 46 2.3.4. Suevite 343, 20 m depth. 47 2.4. Gardnos and Lappajärvi impact craters. 48 2.4.1. Gardnos impact structure. 48 2.4.2. LappajarVi impact crater. 49 2.5. Sample crushing and preparation. 50 2.6. Acid demineralisation. 50 2.6. I. Conventional acid demineralisation 51 2.6.2. Microwave assisted dissolution. 53 2.6.3. High pressure bombs. 54 2.6.4. Additional sample preparation techniques. 54 2.7. Carbon stable isotopic analyses. 55 2.7.1. Whole-rock bulk carbon isotopic analyses 55 2.7.2. Stepped combustion carbon analyses. 56 2.8. Optical and electron microscopy. 57 2.X. I. Petrolo&l microscope. 58 2.8.2. Scanning electron microscope (SEM). 59 2.8.3. Transmission electron microscope (TEM) 62 CHAPTER 3. IMPACT DIAMONDS IN THE RIES CRATER I. REGIONAL AND LITHOLOGICAL DISTRIBUTIONS IN FALLOUT IMPACTITES. 65 3. I. Introduction. 65 3.2. Regional and general geology of the Ries crater. 67 3.2. I. Moldavite tektites. 68 3.2.2. Bunte Breccia (lithic impact breccia). 69 3.2.3. Suevite (polymict impact breccia with glass). 69 3.3. Occurrence and distribution of diamond and graphite in impact produced rocks of the Ries crater. 70 3.4. Morphological characteristics of impact diamonds and graphite from the Ries crater 71 ~~~~ ~ ____ .. Jennifer i Ahbott LIST OF CONTENTS 11 3.4. I. Layered grains. 74 3.4.2. Linear orientation features. 78 3.4.3. Pitting and etching features. 79 3.4.4. Skeletal grains. 87 3.4.5. Polycrystalline grains. 93 3.4.6. Diamonds/graphite intergrowths. 95 3.4.7. Stacking faults. 96 3.4.8. Twinning. IO0 3.4.9. Summary of diamond occurrence, structures and morphology. 101 3.5. Shock features in zircon. I o3 3.5. I. Sample preparation and results. 103 3.6. Stable isotopic composition of carbon in Ries impact rocks. I O6 3.6.1.ötting quariy suevite samples. 108 3.6.2. Seelbronn quarry suevite samples. 109 3.7. Carbon stable isotopic compositions of residues 110 3.7. I .Stcpped combustion residue analyses 111 3.7.2. Graphite carbon stable isotopic compositions. 113 3.7.3. Diamond carhon stable isotopic compositions. 117 3.7.4. Silicon carbide. I I8 1.8. Sunimary and discussion. 120 3.8. I. Morphology and structures 120 3.8.2. Carbon stable isotopes.. i 24 3.8.3. Mcclianisms for transformation. 127 CHAPTER 4. IMPACT DIAMONDS IN THE RIES CRATER AREA 11. AN INVESTIGATION OF THE N~RDLINGEN1973 DRILL COKE. 129 4. I. Introduction. 129 4. I. I. Lithology of Nördlingen 1973 core. 130 4.1.2. Shock metamorphism in Nördlingen core 1973. 131 4. I .3. Structure and geophysical properties of Nördlingen core 1973. 133 4.2. Hand specimen descriptions. 135 4.3. Occurrence and distribution of impact diamonds and graphite in impact produced rocks and shocked basement material. 136 4.4. Morphological characteristics of diamonds and graphite in impact pi-oduced rocks and shocked basement material. 137 4.4. I. Layering. 138 4.4.2. Stacking faults. 141 4.4.3. Etching. 144 ... Jennifcr I Abhott LIST OF CONTENTS 111 4.4.4. Skeletal stnictures. i45 4.4.5. Twinning. i46 4.4.6. Sumnmy of' diamond occurrence, structures and morphology. 148 4.4.7. Comparison of the distribution and frequency of stmctural and morphological features from a variety of Ries crater impactites.