DOCSLIB.ORG

Open Kosei.Pdf

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

The Pennsylvania State University The Graduate School Department of Geosciences GEOCHEMISTRY OF ARCHEAN–PALEOPROTEROZOIC BLACK SHALES: THE EARLY EVOLUTION OF THE ATMOSPHERE, OCEANS, AND BIOSPHERE A Thesis in Geosciences by Kosei Yamaguchi Copyright 2002 Kosei Yamaguchi Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy May 2002 We approve the thesis of Kosei Yamaguchi Date of Signature ____________________________________ _______________________ Hiroshi Ohmoto Professor of Geochemistry Thesis Advisor Chair of Committee ____________________________________ _______________________ Michael A. Arthur Professor of Geosciences ____________________________________ _______________________ Lee R. Kump Professor of Geosciences ____________________________________ _______________________ Raymond G. Najjar Associate Professor of Meteorology ____________________________________ _______________________ Peter Deines Professor of Geochemistry Associate Head for Graduate Program and Research in Geosciences iii ABSTRACT When did the Earth's surface environment become oxic? The timing and mechanism of the rise of atmospheric pO2 level in the early Precambrian have been long debated but no consensus has been reached. The oxygenation of the atmosphere and oceans has significant impacts on the evolution of the biosphere and the geochemical cycles of redox-sensitive elements. In order to constrain the evolution of the atmosphere, oceans, biosphere, and geochemical cycles of elements, a systematic and multidisciplinary study of inorganic geochemistry and stable isotope geochemistry was conducted using Archean– Paleoproterozoic black shales, graywackes, and red shales. The samples were collected from unweathered drillcores of the Swaziland Supergroup (3.25 Ga Sheba Formation of Fig Tree Group), the Witwatersrand Supergroup (2.96 Ga Parktown Formation of the West Rand Group), the Ventersdorp Supergroup (2.71 Ga Rietgat Formation of the Platberg Group), and the Transvaal Supergroup (2.64 Ga Black Reef Formation of the Wolkberg Group, 2.56 Ga Oak Tree Formation of the Chuniespoort Group, 2.22 Ga Timeball Hill Formation of the Pretoria Group, and ~2.2 Ga Mapedi Formation of the Olifantshoek Group) in South Africa and the Mt. Bruce Supergroup (2.72 Ga Pillingini Tuff Formation and 2.69 Ga Jeerinah and Lewin Shale Formations of the Fortescue Group and >2.60 Ga Marra Mamba Iron Formation, 2.60 Ga Wittenoom and Carawine Dolomite Formations of the Hamersley Group) in Australia. The above objective was pursued from an array of inter-related studies: (1) the systematics of organic C - pyrite S - ferric Fe - ferrous Fe - P contents and stable isotopes of organic C and pyrite S; (2) the Mo geochemistry; (3) the N isotope geochemistry; and (4) the U-Th geochemistry. For comparison, data from modern sediments and Phanerozoic sedimentary rocks were complied from the literature. Based on these data, the geochemical iv cycles of C, S, N, Fe, P, Mo, and U in the Archean–Paleoproterozoic surface environments were compared with those of Phanerozoic through modern environments. From (1), I suggest that the contents and stable isotopic compositions of organic C and pyrite S in sediments have been primarily controlled by redox / biological processes in diverse sedimentary redox environments involving oxygenic photosynthesis, aerobic recycling of organic matter, bacterial sulfate reduction, and methanogenesis throughout geologic time. Iron has been oxidized during weathering and reduced during diagenesis, and the P-mediated redox stabilization of the atmosphere and oceans has been operating throughout geologic time. The geochemical cycles of C-S-Fe-P-O would have been essentially the same as today, and they were already in full operation at least 3.25 Ga ago. From (2), based on the kinetics of metal sulfide dissolution, I suggest that Mo- bearing minerals were quantitatively oxidized during weathering and transported to the -6 oceans if the pO2 was higher than 10 atm, i.e., >0.0005 % PAL (present atmospheric level). The dissolved Mo was fixed by organic matter and S in locally anoxic environments. The geochemical cycle of Mo during the Archean–Paleoproterozoic time was essentially the same as today. From (3), I suggest that the microbially mediated redox cycling of N involving biological N2-fixation, nitrification, denitrification, and ammonification was already in operation during the Archean, based on the characteristics of the N isotopic compositions of organic-bound N and clay-bound N observed in marine sediments throughout the geologic ages. High Fe content and a positive correlation between Mo and Corg contents of the shales support (although is not an evidence for) the operation of enzymes (FeMo cofactor) responsible for microbial N2-fixation (nitrogenase) and denitrification (dinitrogenase and dinitrogenase-reductase) in the Archean oceans. From (4), I suggest that the continental weathering flux of U in the Archean was probably the same as today because of the enhanced weathering rate of U-bearing silicate v minerals (feldspars) under a high pCO2 atmosphere. The weathering of uraninite is considered to be minor in the total continental weathering flux of U. Generally low U contents of the Archean-Paleoproterozoic shales (< 10 ppm) are explained by extensive submarine hydrothermal activity at mid-oceanic ridges as a major sink for the oceanic U and the lack of significant enrichment of organic matter in the shales. The sedimentary enrichment of U by organic matter and the secular increase of the Th/U ratios suggests an importance of the decoupling of U and Th and tectonic recycling of U throughout geologic time. The geochemical cycle of U in the Archean–Paleoproterozoic surface environments was essentially the same as it is today. The most important discovery of this study is the early development of the present day redox environments, microbial activity, and geochemical cycles of redox-sensitive elements in the Archean. In the Archean, N2-fixers, photosynthesizers, nitrifyers, denitrifyers, sulfate-reducers, and methane-producing / consuming microorganisms had already formed complex ecosystems, like those of today, in the globally oxic world where the atmosphere and the oceans were oxic with local anoxic environments such as mid-depth O2-minimum zone and anoxic / euxinic basins. This study has implications for the early evolution of an oxic atmosphere, oxic oceans, and complex microbial biosphere not only on the Earth but also on the other Earth-like planets distributed in the universe. Such astrobiological implications expand the possibilities for the discovery of extraterrestrial biosignatures in future space missions. vi TABLE OF CONTENTS LIST OF FIGURES....................................................................................................xvi LIST OF TABLES ....................................................................................................xxiii ACKNOWLEDGMENTS.........................................................................................xxv Chapter 1 General introduction: Evolution of the atmosphere and biosphere in the early Precambrian.....................................................................1 1-1. Introduction .....................................................................................................1 1-2. Evolution of the atmosphere in the early Precambrian......................................2 1-2-1. Prebiotic atmosphere...............................................................................2 1-2-2. Emergence of life....................................................................................3 1-2-3. Rise of oxygen........................................................................................4 1-2-3-1. Source and sink of atmospheric O2....................................................4 1-2-3-2. Controversy over the rise of atmospheric O2......................................5 1-2-3-3. Geological evidence bearing information on the atmospheric O2........6 Prevailing view: Low O2 level before 2.2 Ga................................6 Emerging view: High O2 level since ~3.8 Ga...............................7 1-3. Evolution of the biosphere in the early Precambrian ........................................9 1-3-1. Chemofossils of possible photosynthesizers at 3.8 Ga...........................9 1-3-2. Microfossils and stromatolites at 3.5 Ga...............................................10 1-3-3. Sulfate-reducing bacteria at 3.5 ~ 3.4 Ga..............................................10 1-3-4. Nitrogen-metabolizing bacteria at 3.5 G................................................11 1-3-5. Thermophilic microfossils at 3.2 Ga.....................................................11 1-3-6. Organic biomarkers for cyanobacteria, methanotrophic bacteria, and eukaryotes at 2.7 Ga ..........................................................................11 1-3-7. Methanogens and methanotrophs at 2.7 Ga..........................................12 1-3-8. Life on land at 2.6 Ga ...........................................................................12 1-3-10. Eukaryotic megafossils at 2.1 Ga..........................................................12 vii 1-4. Evolution of the continental crust in the early Precambrian............................12 1-5. Evolution of the geochemical cycles of redox-sensitive elements (C, S, N, Fe, P, Mo, and U) .........................................................................13 1-5-1. Geochemical cycles
Recommended publications
  • South African Palaeo-Scientists the Names Listed Below Are Just Some of South Africa’S Excellent Researchers Who Are Working Towards Understanding Our African Origins

    South African Palaeo-Scientists the Names Listed Below Are Just Some of South Africa’S Excellent Researchers Who Are Working Towards Understanding Our African Origins

    2010 African Origins Research MAP_Layout 1 2010/04/15 11:02 AM Page 1 South African Palaeo-scientists The names listed below are just some of South Africa’s excellent researchers who are working towards understanding our African origins. UNIVERSITY OF CAPE TOWN (UCT) Dr Thalassa Matthews analyses the Dr Job Kibii focuses PALAEOBIOLOGICAL RESEARCH thousands of tiny teeth and bones of fossil on how fossil hominid Professor Anusuya Chinsamy-Turan is one microfauna to reconstruct palaeoenviron- and non-hominid of only a few specialists in the world who mental and climatic changes on the west faunal communities coast over the last 5 million years. changed over time and African Origins Research studies the microscopic structure of bones of dinosaurs, pterosaurs and mammal-like uses this to reconstruct reptiles in order to interpret various aspects ALBANY MUSEUM, past palaeoenviron- of the biology of extinct animals. GRAHAMSTOWN ments and palaeo- A summary of current research into fossils of animals, plants and early hominids from the beginning of life on Earth to the Middle Stone Age PERMIAN AGE PLANTS ecology. THE HOFMEYR SKULL Dr Rose Prevec studies the “No other country in the world can boast the oldest evidence of life on Earth extending back more than 3 billion years, the oldest multi-cellular animals, the oldest land-living plants, Professor Alan Morris described the Glossopteris flora of South Africa (the PAST HUMAN BEHAVIOUR Hofmeyer skull, a prehistoric, fossilized ancient forests that formed our coal Professor Chris Henshilwood directs the most distant ancestors of dinosaurs, the most complete record of the more than 80 million year ancestry of mammals, and, together with several other African countries, a most remarkable human skull about 36 000 years old deposits) and their end-Permian excavations at Blombos Cave where that corroborates genetic evidence that extinction.
  • Volcanology and Mineral Deposits

    Volcanology and Mineral Deposits

    THESE TERMS GOVERN YOUR USE OF THIS DOCUMENT Your use of this Ontario Geological Survey document (the “Content”) is governed by the terms set out on this page (“Terms of Use”). By downloading this Content, you (the “User”) have accepted, and have agreed to be bound by, the Terms of Use. Content: This Content is offered by the Province of Ontario’s Ministry of Northern Development and Mines (MNDM) as a public service, on an “as-is” basis. Recommendations and statements of opinion expressed in the Content are those of the author or authors and are not to be construed as statement of government policy. You are solely responsible for your use of the Content. You should not rely on the Content for legal advice nor as authoritative in your particular circumstances. Users should verify the accuracy and applicability of any Content before acting on it. MNDM does not guarantee, or make any warranty express or implied, that the Content is current, accurate, complete or reliable. MNDM is not responsible for any damage however caused, which results, directly or indirectly, from your use of the Content. MNDM assumes no legal liability or responsibility for the Content whatsoever. Links to Other Web Sites: This Content may contain links, to Web sites that are not operated by MNDM. Linked Web sites may not be available in French. MNDM neither endorses nor assumes any responsibility for the safety, accuracy or availability of linked Web sites or the information contained on them. The linked Web sites, their operation and content are the responsibility of the person or entity for which they were created or maintained (the “Owner”).
  • Geochemical Heterogeneity Within Mid-Ocean Ridge Lava £Ows: Insights Into Eruption, Emplacement and Global Variations in Magma Generation

    Geochemical Heterogeneity Within Mid-Ocean Ridge Lava £Ows: Insights Into Eruption, Emplacement and Global Variations in Magma Generation

    Earth and Planetary Science Letters 188 (2001) 349^367 www.elsevier.com/locate/epsl Geochemical heterogeneity within mid-ocean ridge lava £ows: insights into eruption, emplacement and global variations in magma generation K.H. Rubin a;*, M.C. Smith a, E.C. Bergmanis a, M.R. Per¢t b, J.M. Sinton a, R. Batiza a;c a b c Received 5 September 2000; accepted 28 March 2001 Abstract Compositional heterogeneity in mid-ocean ridge (MOR) lava flows is a powerful yet presently under-utilized volcanological and petrological tracer. Here, it is demonstrated that variations in pre- and syn-eruptive magmatic conditions throughout the global ridge system can be constrained with intra-flow compositional heterogeneity among 10 discrete MOR flows. Geographical distribution of chemical heterogeneity within flows is also used along with mapped physical features to help decipher the range of conditions that apply to seafloor eruptions (i.e. inferred vent locations and whether there were single or multiple eruptive episodes). Although low-pressure equilibrium fractional crystallization can account for much of the observed intra-flow compositional heterogeneity, some cases require multiple parent magmas and/or more complex crystallization conditions. Globally, the extent of within-flow compositional heterogeneity is well correlated (positively) with estimated erupted volume for flows from the northern East Pacific Rise (EPR), and the Mid Atlantic, Juan de Fuca and Gorda Ridges; however, some lavas from the superfast spreading southern EPR fall below this trend. Compositional heterogeneity is also inversely correlated with spreading rate. The more homogeneous compositions of lavas from faster spreading ridges likely reflect the relative thermal stability and longevity of sub-ridge crustal magma bodies, and possibly higher eruption frequencies.
  • U–Pb Zircon (SHRIMP) Ages for the Lebombo Rhyolites, South Africa

    U–Pb Zircon (SHRIMP) Ages for the Lebombo Rhyolites, South Africa

    Journal of the Geological Society, London, Vol. 161, 2004, pp. 547–550. Printed in Great Britain. 2000) and the ages corroborate and further strengthen the SPECIAL chronology of the Lebombo stratigraphy. The rapid eruption of the Karoo succession is thought to have been responsible for trigger- U–Pb zircon (SHRIMP) ing the early Toarcian extinction event (Hesselbo et al. 2000). Geological setting. The Karoo Supergroup succession along the ages for the Lebombo Lebombo monocline is highlighted in Figure 1. The oldest phase of Karoo volcanism is marked by the Mashikiri nephelinites, rhyolites, South Africa: which unconformably overlie Jurassic Clarens Formation sand- stones (Fig. 2). The nephelinites have been dated at 182.1 Æ refining the duration of 1.6 Ma (40Ar/39Ar plateau age; Duncan et al. 1997) and form a lava succession up to 170 m thick (Bristow 1984). These rocks Karoo volcanism are confined to the northern part of the Lebombo rift and are absent along the central and southern sections. The nephelinites T. R. RILEY1,I.L.MILLAR2, are conformably overlain by picrites and picritic basalts of the 3 1 Letaba Formation, although in the southern Lebombo the picrites M. K. WATKEYS ,M.L.CURTIS, directly overlie the Clarens Formation. The picrites overlap in 1 3 P. T. LEAT , M. B. KLAUSEN & age (182.7 Æ 0.8 Ma; Duncan et al. 1997) with the Mashikiri C. M. FANNING4 nephelinites and are believed to form a succession up to 4 km in thickness. 1British Antarctic Survey, High Cross, Madingley Road, The Letaba Formation picrites are in turn overlain by a major Cambridge, CB3 0ET, UK (e-mail: [email protected]) succession (4–5 km thick) of low-MgO basalts, termed the Sabie 2British Antarctic Survey c/o NERC Isotope Geosciences River Basalt Formation (Cleverly & Bristow 1979).
  • Meso-Archaean and Palaeo-Proterozoic Sedimentary Sequence Stratigraphy of the Kaapvaal Craton

    Meso-Archaean and Palaeo-Proterozoic Sedimentary Sequence Stratigraphy of the Kaapvaal Craton

    Marine and Petroleum Geology 33 (2012) 92e116 Contents lists available at SciVerse ScienceDirect Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo Meso-Archaean and Palaeo-Proterozoic sedimentary sequence stratigraphy of the Kaapvaal Craton Adam J. Bumby a,*, Patrick G. Eriksson a, Octavian Catuneanu b, David R. Nelson c, Martin J. Rigby a,1 a Department of Geology, University of Pretoria, Pretoria 0002, South Africa b Department of Earth and Atmospheric Sciences, University of Alberta, Canada c SIMS Laboratory, School of Natural Sciences, University of Western Sydney, Hawkesbury Campus, Richmond, NSW 2753, Australia article info abstract Article history: The Kaapvaal Craton hosts a number of Precambrian sedimentary successions which were deposited Received 31 August 2010 between 3105 Ma (Dominion Group) and 1700 Ma (Waterberg Group) Although younger Precambrian Received in revised form sedimentary sequences outcrop within southern Africa, they are restricted either to the margins of the 27 September 2011 Kaapvaal Craton, or are underlain by orogenic belts off the edge of the craton. The basins considered in Accepted 30 September 2011 this work are those which host the Witwatersrand and Pongola, Ventersdorp, Transvaal and Waterberg Available online 8 October 2011 strata. Many of these basins can be considered to have formed as a response to reactivation along lineaments, which had initially formed by accretion processes during the amalgamation of the craton Keywords: Kaapvaal during the Mid-Archaean. Faulting along these lineaments controlled sedimentation either directly by Witwatersrand controlling the basin margins, or indirectly by controlling the sediment source areas. Other basins are Ventersdorp likely to be more controlled by thermal affects associated with mantle plumes.
  • Desktop Palaeontological Heritage Impact

    Desktop Palaeontological Heritage Impact

    DESKTOP PALAEONTOLOGICAL HERITAGE IMPACT ASSESSEMENT REPORT ON THE SITES OF SEVEN PROPOSED SITES OF WIDENING OF THE N4 HIGHWAY (NAMED WB1, WB3, WB4, WB5, WB7, EB1 AND EB3) TO BE LOCATED BETWEEN WATERVAL BOVEN AND NELSPRUIT, MPUMALANGA PROVINCE 7 February 2016 Prepared for: Prism Environmental Management Services (Pty) Ltd On behalf of: Postal address: SANRAL P.O. Box 13755 Hatfield 0028 South Africa Cell: +27 (0) 79 626 9976 Faxs:+27 (0) 86 678 5358 E-mail: [email protected] DESKTOP PALAEONTOLOGICAL HERITAGE IMPACT ASSESSEMENT REPORT ON THE SITES OF SEVEN PROPOSED SITES OF WIDENING OF THE N4 HIGHWAY (NAMED WB1, WB3, WB4, WB5, WB7, EB1 AND EB3) TO BE LOCATED BETWEEN WATERVAL BOVEN AND NELSPRUIT, MPUMALANGA PROVINCE Prepared for: Prism Environmental Management Service (Pty) Ltd On Behalf of: SANRAL Prepared By: Prof B.D. Millsteed 2 Desktop Palaeontological Impact Assessment Report – on seven sites of proposed widening of the N4 Highway between Waterval Boven and Nelspruit, Mpumalanga Province. EXECUTIVE SUMMARY The South African National Roads Agency SOC Ltd (SANRAL) is proposing upgrades by widening certain sections of the existing National N4 Toll Route between eMgwenya (Waterval Boven) and Mbombela (Nelspruit), Mpumalanga. As part of continual upgrading of this road corridor between Pretoria in the west and Maputo, Mozambique in the east; a need has arisen to introduce extensions to existing passing lanes whilst new passing lanes are also required. SANRAL has an implementing agent and concessionaire for the National N4 Toll Route existing between Pretoria and Maputo known as “Trans African Concessions” (TracN4) – a concessionaire established during the mid-90’s specifically for the management of the N4 corridor between South Africa and Mozambique.
  • South Africa's Coalfields — a 2014 Perspective

    South Africa's Coalfields — a 2014 Perspective

    International Journal of Coal Geology 132 (2014) 170–254 Contents lists available at ScienceDirect International Journal of Coal Geology journal homepage: www.elsevier.com/locate/ijcoalgeo South Africa's coalfields — A 2014 perspective P. John Hancox a,⁎,AnnetteE.Götzb,c a University of the Witwatersrand, School of Geosciences and Evolutionary Studies Institute, Private Bag 3, 2050 Wits, South Africa b University of Pretoria, Department of Geology, Private Bag X20, Hatfield, 0028 Pretoria, South Africa c Kazan Federal University, 18 Kremlyovskaya St., Kazan 420008, Republic of Tatarstan, Russian Federation article info abstract Article history: For well over a century and a half coal has played a vital role in South Africa's economy and currently bituminous Received 7 April 2014 coal is the primary energy source for domestic electricity generation, as well as being the feedstock for the Received in revised form 22 June 2014 production of a substantial percentage of the country's liquid fuels. It furthermore provides a considerable source Accepted 22 June 2014 of foreign revenue from exports. Available online 28 June 2014 Based on geographic considerations, and variations in the sedimentation, origin, formation, distribution and quality of the coals, 19 coalfields are generally recognised in South Africa. This paper provides an updated review Keywords: Gondwana coal of their exploration and exploitation histories, general geology, coal seam nomenclature and coal qualities. With- Permian in the various coalfields autocyclic variability is the norm rather than the exception, whereas allocyclic variability Triassic is much less so, and allows for the correlation of genetically related sequences. During the mid-Jurassic break up Coalfield of Gondwana most of the coal-bearing successions were intruded by dolerite.
  • The Geology of the Middle Precambrian Rove Formation in Northeastern Minnesota

    The Geology of the Middle Precambrian Rove Formation in Northeastern Minnesota

    MINNESOTA GEOLOGICAL SURVEY 5 P -7 Special Publication Series The Geology of the Middle Precambrian Rove Formation in northeastern Minnesota G. B. Morey UNIVERSITY OF MINNESOTA MINNEAPOLIS • 1969 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I THE GEOLOGY OF THE MIDDLE PRECAMBRIAN ROVE FORMATION IN NORTHEASTERN MINNESOTA by G. B. Morey CONTENTS Page Abstract ........................................... 1 Introduction. 3 Location and scope of study. 3 Acknowledgements .. 3 Regional geology . 5 Structural geology . 8 Rock nomenclature . 8 Stratigraphy . .. 11 Introduction . .. 11 Nomenclature and correlation. .. 11 Type section . .. 11 Thickness . .. .. 14 Lower argillite unit. .. 16 Definition, distribution, and thickness. .. 16 Lithologic character . .. 16 Limestones. .. 17 Concretions. .. 17 Transition unit . .. 17 Definition, distribution, and thickness. .. 17 Lithologic character . .. 19 Thin-bedded graywacke unit . .. 19 Definition, distribution, and thickness. .. 19 Lithologic character. .. 20 Concretions ... .. 20 Sedimentary structures. .. 22 Internal bedding structures. .. 22 Structureless bedding . .. 23 Laminated bedding . .. 23 Graded bedding. .. 23 Cross-bedding . .. 25 Convolute bedding. .. 26 Internal bedding sequences . .. 26 Post-deposition soft sediment deformation structures. .. 27 Bed pull-aparts . .. 27 Clastic dikes . .. 27 Load pockets .. .. 28 Flame structures . .. 28 Overfolds . .. 28 Microfaults. .. 28 Ripple marks .................................. 28 Sole marks . .. 28 Groove casts . .. 30 Flute casts .
  • Sampling and Estimation of Diamond Content in Kimberlite Based on Microdiamonds Johannes Ferreira

    Sampling and Estimation of Diamond Content in Kimberlite Based on Microdiamonds Johannes Ferreira

    Sampling and estimation of diamond content in kimberlite based on microdiamonds Johannes Ferreira To cite this version: Johannes Ferreira. Sampling and estimation of diamond content in kimberlite based on micro- diamonds. Other. Ecole Nationale Supérieure des Mines de Paris, 2013. English. NNT : 2013ENMP0078. pastel-00982337 HAL Id: pastel-00982337 https://pastel.archives-ouvertes.fr/pastel-00982337 Submitted on 23 Apr 2014 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. N°: 2009 ENAM XXXX École doctorale n° 398: Géosciences et Ressources Naturelles Doctorat ParisTech T H È S E pour obtenir le grade de docteur délivré par l’École nationale supérieure des mines de Paris Spécialité “ Géostatistique ” présentée et soutenue publiquement par Johannes FERREIRA le 12 décembre 2013 Sampling and Estimation of Diamond Content in Kimberlite based on Microdiamonds Echantillonnage des gisements kimberlitiques à partir de microdiamants. Application à l’estimation des ressources récupérables Directeur de thèse : Christian LANTUÉJOUL Jury T M. Xavier EMERY, Professeur, Université du Chili, Santiago (Chili) Président Mme Christina DOHM, Professeur, Université du Witwatersrand, Johannesburg (Afrique du Sud) Rapporteur H M. Jean-Jacques ROYER, Ingénieur, HDR, E.N.S. Géologie de Nancy Rapporteur M.
  • Sequence Stratigraphic Development of the Neoarchean Transvaal Carbonate Platform, Kaapvaal Craton, South Africa Dawn Y

    Sequence Stratigraphic Development of the Neoarchean Transvaal Carbonate Platform, Kaapvaal Craton, South Africa Dawn Y

    DAWN Y. SUMNER AND NICOLAS J. BEUKES 11 Sequence Stratigraphic Development of the Neoarchean Transvaal carbonate platform, Kaapvaal Craton, South Africa Dawn Y. Sumner Department of Geology, University of California 1 Shields Ave, Davis, CA 95616 USA e-mail: [email protected] Nicolas J. Beukes Department of Geology, University of Johannesburg P.O. Box 524, Auckland Park, 2000 South Africa e-mail: [email protected] © 2006 March Geological Society of South Africa ABSTRACT The ~2.67 to ~2.46 Ga lower Transvaal Supergroup, South Africa, consists of a mixed siliciclastic-carbonate ramp that grades upward into an extensive carbonate platform, overlain by deep subtidal banded iron-formation. It is composed of 14 third-order sequences that develop from a mixed siliciclastic-carbonate ramp to a steepened margin followed by a rimmed margin that separated lagoonal environments from the open ocean. Drowning of the platform coincided with deposition of banded iron-formation across the Kaapvaal Craton. The geometry and stacking of these sequences are consistent with more recent patterns of carbonate accumulation, demonstrating that Neoarchean carbonate accumulation responded to subsidence, sea level change, and carbonate production similarly to Proterozoic and Phanerozoic platforms. The similarity of carbonate platform geometry through time, even with significant changes in dominant biota, demonstrates that rimmed margins are localized primarily by physiochemical conditions rather than growth dynamics of specific organisms. Stratigraphic patterns during deposition of the Schmidtsdrift and Campbellrand-Malmani subgroups are most consistent with variable thinning of the Kaapvaal Craton during extrusion of the ~2.7 Ga Ventersdorp lavas. Although depositional patterns are consistent with rifting of the western margin of the Kaapvaal Craton during this time, a rift-to-drift transition is not required to explain subsidence.

  • Pillow Basalts from the Mount Ada Basalt, Warrawoona Group, Pilbara Craton: Implications for the Initiation of Granite-Greenstone Terrains D

    Goldschmidt2015 Abstracts Pillow basalts from the Mount Ada basalt, Warrawoona group, Pilbara Craton: Implications for the initiation of granite-greenstone terrains D. T. MURPHY1*, J. TROFIMOVS1, R. A. HEPPLE1, D. WIEMER1, A. I. S. KEMP2 AND A. H. HICKMAN3 1Earth, Environmental and Biological Sciences, Queensland University of Technology, 4001, Australia (correspondence: [email protected]) 2School of Earth and Environment, The University of Western Australia, 6009, Australia 3Department of Mines and Petroleum, Western Australia The Pilbara Craton represents the archetypal Archean granite-greenstone terrain in which mafic volcanic dominated supercrustals are intruded by granitic domes. This crustal morphology reflects distinct tectonic settings that formed in a hotter early Earth. The ambient temperature in the Paleoarchean mantle is estimated to be 1600oC [1] and corresponds with the liquidus temperature of Barberton komatiites [2]. In the Paleoarchean mantle a pyrolite composition at depths of less than 100 km is expected to melt and generate ultramafic magmas. Here we present volcanology, petrology and geochemistry data of well-preserved basaltic lavas ascribed to the Mount Ada Basalt, Warrawoona Group from the Doolena Gap Greenstone Belt. The Mount Ada Basalt was coeval with the Callina plutonic event that marks the initiation of dome formation in the Pilbara Craton [3]. The Doolena Gap sequence is exclusively pillow basalts with MgO < 10%. Isotopically the basalts are indistinguishable from contemporary non-chondritic Bulk Earth (εNd, 1.0 ± 0.2 and εHf, 2.3 ± 0.2). Here we address the implications of Paleoarchean basalts with MgO% < 10 derived from melting of a source indistinguishable from non-chondritic Bulk Silicate Earth to the initiation and subsequent evolution of the Pilbara Craton.
  • Thomas Spring Thesis (PDF 7MB)

    Thomas Spring Thesis (PDF 7MB)

    RECONSTRUCTION OF THE PHYSICAL VOLCANOLOGICAL PROCESSES AND PETROGENESIS OF THE 3.5GA WARRAWOONA GROUP PILLOW BASALT OF THE WARRALONG GREENSTONE BELT, PILBARA CRATON WESTERN AUSTRALIA Thomas Frederick David Spring Bachelor of Applied Science (Geology) Submitted in fulfilment of the requirements for the degree of Master of Applied Science (Geoscience) School of Earth, Environment and Biological Science Faculty of Science and Engineering Queensland University of Technology 2017 Abstract The formation of Earth’s continental crust initiated in the early Archean and has continued to the present day. In the early Archean, the Earth was substantially hotter than the present day leading to dramatically different tectonic processes. Early Archean tectonic processes have to be inferred from the rare well-preserved remnants of Archean crust. Models for the formation of Archean crust include large scale mantle melting associated with mantle plumes to generate thick basaltic to ultramafic crust. This crust than undergoes partial melting and internal differentiation to more felsic compositions. The Pilbara craton provides an ideal area for research into the Archean crust, with some of Earth oldest crust being preserved in relatively low strain and low metamorphosed greenstone belts. The volcanic cycles preserved in the greenstone belts of the Paleoarchean East Pilbara Terrane of the Pilbara craton represent the type example of plume-derived volcanism in the early Earth. Here I investigate the lithostratigraphy, volcanology and depositional environment of a volcanic and sedimentary succession ascribed to the Warrawoona group of the East Pilbara Supergroup from the Eastern Warralong Greenstone belt of the East Pilbara Terrane. In addition, I investigate the petrogenesis of well-preserved basaltic samples from the pillow basalt sequence ascribed to the Mt Ada Basalts in the study area.