DOCSLIB.ORG

PLATINUM the PGE Resources of the Great Dyke

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
PLATINUM the PGE Resources of the Great Dyke PLATINUM The PGE resources of the Great Dyke - C Mwatahwa and C Musa 1 Presentation Overview PLATINUM (2/2*,&$/(77,1* 758&785($1'75$7,*5$3+< ,1(5$/2*< • ((),1(5$/2*< • 5(,1(5$/2*< Ò5(6285&(6 ,1,1*Ä52&(66,1* • (() '(17,),&$7,21 • 3(1&$67,1,1* • 1'(5*5281',1,1* • 52&(66,1* 2 Geological Setting PLATINUM 5($7<.(,6$1(/21*$7(/$<(5(' ,17586,21Ì 1758'(',0%$%:($1$5&+$($1 &5$721*5$1,72,'6$1'*5((16721(%(/7 52&.6 03/$&(0(17$*( ÐÓÕÒ ±Ð$ÌÆ,1*$7(ÐÎÎÎËË%Ç :20$,1&+$0%(56:,7+),9( 68%&+$0%(56 0$//(676Ë$985$'21+$68%&+$0%(5Ê //8%&+$0%(56+$9( 5(6285&(6 3 Transverse Section PLATINUM O 2&&856$7 6$0( /,7+2675$7,*5$3+,& 81,7,1$// 68%&+$0%(56 O 76%(+$9,285 )2//2:675(1'2) /$<(5,1*:,7+,1 Ï$1',6 6<00(75,&Ì O ,36$5(6+$//2: 5$1*,1*)520ÏÒ 72Î Stratigraphy PLATINUM $),&81,7$77+(723 2:(5/75$0$),& 6(48(1&(P%52.(1,172 3<52;(1,7($1''81,7( 68&&(66,216 5(6285&(62&&85 1($57+(7232)7+( 8/75$0$),&68&&(66,21Ì 5 Local Stratigraphy PLATINUM • Mafic unit up to 300-1200m thick at axis • Chromite seam at base of mafic unit • Mafic mainly gabbronorite –opx,cpx with plag • Upper P1-plagioclase websterite ±6m thick • Plagioclase websterite underlain by poikilitic plagioclase pyroxenite (so called bronzitite) • MSZ (2-3m)occurs at the top of the plagioclase pyroxenite unit and extends into the base of the websterite • MSZ can be correlated in all subchambers • The S1 Layer=MSZ Mineralogy PLATINUM • 50% of PGEs associated with base metal sulphides(BMS). • Remainder of PGE associated with fine grained bismuthotellurides and arsenides. • Pyrrhotite, Chalcopyrite, pentlandite and pyrite • Pyrrhotite is the dominant BMS • BMS grains are coarse (20-25µm). • Silicate gangue mineralogy made up of pyroxene(dominant), plagioclase, chlorite ,tremolite and talc. PGM distribution PLATINUM PLATINUM MSZ reef Cross section-Shurugwi Subchamber 9 PLATINUM Orebody Morphology PLATINUM Location of PGE resources Location of economic PGE resources 11 Distribution of PGE resources per PLATINUM sub chamber 5% 13% Darwendale subchamber Shurugwi subchamber Wedza subchamber 82% PGE resources= 3.4billion tonnes 12 PLATINUM Distribution of PGE resources 13 PLATINUM Distribution of PGE resources-4E oz 12% 31% Anglo Platinum Zimplats Mimosa ZMDC JVs 4% 53% 4E resources= 411moz inclusive of oxide resources 4E= Pt +Pd+Au+Rh 14 Metal Profiles & Reef Idenfication PLATINUM Reef Identification PLATINUM PLATINUM ,1,1*87 17 PLATINUM 1'(5*5281',1,1* • Mining layout consist of four bords up-dip of the Strike Conveyor and two bords down dip of the Strike Conveyor. • Pillar dimension are 6m by 5m on strike and dip respectively • Bords span is 12m • Strike Conveyor Bord is 8m • Pillar holing is 6m • Total section width is 115 m skin to skin Mining Operations-Underground and Surface PLATINUM Annual 4E production to reach 1,000,000oz by 2013 19 PLATINUM Processing • Unki Concentrator PLATINUM • Thank you.
Load more

Recommended publications
  • F Makwara (PDF)
    CHROMITE GEOLOGY OF ZIMBABWE AND RELATED MINING CHALLENGES PRESENTATION GREAT DYKE : MUTORASHANGA AUGUST 2017 2 WORLD CHROME RESOURCE Estimate World Chromite Resource : +-12 Billion Tonnes • South Africa : 72% of world Resource - Stratiform • Zimbabwe: 12% -Stratiform & podiform • Kazakhstan: 4% - Podiform • Finland : 2% -Podiform • India : 1% -Podiform • Turkey and others : 9% -Largely podiform But Zimbabwe companies producing at full capacity is not in the top 5 producing companies . STRATIFORM & PODIFORM GEOLOGY LOCATION GEOLOGY MAP - ZIMBABWE MASHONALAND CENTRAL MASHONALAND WEST CHIRUMANZU MIDLANDS MASVINGO MBERENGWA 5 LOCATION OF STRATIFORM CHROMITE RESOURCE • Mashonaland Central: North Dyke Tengenenge Impinge Birkdale Mutorashanga • Mashonaland West: Middle Dyke Ngezi Darwendale Maryland Lembe/Mapinga Mutorashanga • Midlands: South Dyke Lalapanzi Mapanzure Bannockburn CSC LOCATION OF PODIFORM CHROMITE RESOURCES • Midlands: Valley Nhema Chirumanzu Mberengwa • Masvingo: Mashava THE GREAT DYKE AND PODIFORMS GEOLOGY • THE GREAT DYKE • Tengenenge to Mberengwa, Location • Stretches for 550km and is 4-11km wide. • PODIFORM • Isolated chrome resources in Shurugwi,Mashava ,Nhema ,Valley, Chirumanzu and Mberengwa • THE DYKE : STRATIFORM • Chromite hosts rocks are :Harzburgite, dunite, serpentinite and pyroxenite Host Rock • PODIFORM • Chromite host rocks are: Serpentinite ,Silicified Talc Carbonate and Talc Carbonate • 10 known seams, The 11 th seam is poorly exposed in the North Dyke • 8cm to 40cm thickness Chrome Seams • Average vertical spacing of seams is 30-40m • Geotechnical Parameters considered fore seams are: Seam Widths, quality, dip, friability, & continuity • Platinum Group Metals Known Minerals in • Chrome the Dyke • Asbestos • Nickel 8 CHROMITE RESOURCES • The dyke intruded as an ultramafic sill ,estimated age 2.7 Ga . STRATIFORM • 11 seams are known to exist on the Great Dyke, but not evenly distributed through out the dyke.
    [Show full text]
  • Mining Within Zimbabwe's Great Dyke: Extent , Impacts & Opportunities
    Mining Within Zimbabwe’s Great Dyke: Extent , Impacts & Opportunities Authors: Gilbert Makore & Veronica Zano Published by: Zimbabwe Environmental Law Association (ZELA) Sponsored by: International Alliance on Natural Resource in Africa (IANRA) Authors: Gilbert Makore and Veronica Zano Editor: Muduso Dhliwayo Copyright: 2012. Zimbabwe Environmental Law Association (ZELA) This publication may be reproduced in whole or in part and in any form for educational or non-profit uses, without special permission from the copyright holder, provided full acknowledgement of the source is made. No use of this publication may be made for resale or other commercial purposes without the prior written permission of ZELA. Year of Publication: 2012 Available from: Zimbabwe Environmental Law Association (ZELA), No. 6 London Derry Road, Eastlea, Harare, Zimbabwe: Tel: 253381; 252093, Email: , Website: www.zela.org Zimbabwe Environmental Law Association International Alliance on Natural Resource in Africa International Alliance on Natural Resources in Africa MINING WITHIN ZIMBABWE’S GREAT DYKE: EXTENT , IMPACTS AND OPPORTUNITIES I Table of Contents Executive Summary: 1 The Great Dyke Mineral Belt: 2 Mining and Mining Development Contribution to Economic Growth: 5 Companies operating in the Great Dyke: 10 Communities along the Great Dyke: 12 Impacts of Mining on the Great Dyke Communities: 14 Recommendations: 19 Conclusion: 20 MINING WITHIN ZIMBABWE’S GREAT DYKE: EXTENT , IMPACTS AND OPPORTUNITIES ii Executive Summary The Great Dyke is a seam of ore-bearing rock that goes from the north to the south of Zimbabwe. The Dyke spans a total length of 550kms and has a maximum width of 11kms. This geological feature represents an important resource for Zimbabwe's national economy and the local communities' livelihoods.
    [Show full text]
  • A Semi-Quantitative Model for the Formation of Great Dyke-Type Platinum Deposits
    A Semi-Quantitative Model for the Formation of Great Dyke-Type Platinum Deposits William P. Meurer1 and Alan E. Boudreau2 1Dept. of Geosciences, Univ. of Houston, 312 Sci. & Res. Bldg. 1, Houston, TX 77204-5007 2Div. Earth Sci., Nicholas School of the Env. and Earth Sci., Box 90227, Duke University, Durham, NC 27708 email: [email protected] The uppermost parts of the ultramafic 2) The PGE-sulfide mineralization is sections of some layered intrusions host significant commonly found below the ultramafic-mafic deposits of the platinum-group elements (PGE). contact. In addition, there are typically significant The type example of this class of PGE deposit is stratigraphic “offsets” between the maximum the Great Dyke of Zimbabwe. The Munni Munni concentrations of the PGE, base metals and sulfur. deposit has a similar occurrence (e.g., Hoatson and 3) At discrete horizons, just below the Keays, 1989). In the Stillwater Complex of ultramafic-mafic boundary, the rocks have higher Montana there are local shows of PGE-sulfide incompatible trace-element concentrations, greater enrichments at the top of the Ultramafic series but modal proportions of interstitial minerals, and more they are not laterally continuous (fig. 1). evolved mineral compositions. These features are These deposits have a number of common interpreted to reflect a marked enrichment in features: crystallized interstitial liquid in these rocks. 1) Each is characterized by a lower A number of investigators have suggested sequence of ultramafic rocks consisting mainly of that these zones are the result of a complex pyroxene and olivine overlain by mafic rocks interplay of extreme fractionation, magma mixing, containing 50 to 60 % plagioclase.
    [Show full text]
  • The Plate Theory for Volcanism
    This article was originally published in Encyclopedia of Geology, second edition published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author’s institution, for non-commercial research and educational use, including without limitation, use in instruction at your institution, sending it to specific colleagues who you know, and providing a copy to your institution’s administrator. All other uses, reproduction and distribution, including without limitation, commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution’s website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: https://www.elsevier.com/about/policies/copyright/permissions Foulger Gillian R. (2021) The Plate Theory for Volcanism. In: Alderton, David; Elias, Scott A. (eds.) Encyclopedia of Geology, 2nd edition. vol. 3, pp. 879-890. United Kingdom: Academic Press. dx.doi.org/10.1016/B978-0-08-102908-4.00105-3 © 2021 Elsevier Ltd. All rights reserved. Author's personal copy The Plate Theory for Volcanism Gillian R Foulger, Department of Earth Sciences, Science Laboratories, Durham University, Durham, United Kingdom © 2021 Elsevier Ltd. All rights reserved. Statement of Plate Theory 879 Background, History, Development and Discussion 879 Lithospheric Extension 880 Melt in the Mantle 881 Studying Intraplate Volcanism 882 Examples 883 Iceland 883 Yellowstone 885 The Hawaii and Emperor Volcano Chains 886 Discussion 888 Summary 888 References 888 Further Reading 889 Statement of Plate Theory The Plate Theory for volcanism proposes that all terrestrially driven volcanism on Earth’s surface, including at unusual areas such as Iceland, Yellowstone and Hawaii, is a consequence of plate tectonics.
    [Show full text]
  • Plate Tectonics on Early Earth? Weighing the Paleomagnetic Evidence
    spe440-12 3rd pages The Geological Society of America Special Paper 440 2008 Plate tectonics on early Earth? Weighing the paleomagnetic evidence David A.D. Evans* Department of Geology & Geophysics, Yale University, New Haven, Connecticut 06520-8109, USA Sergei A. Pisarevsky* School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JW, Scotland, UK ABSTRACT Paleomagnetism is the only quantitative method available to test for lateral motions by tectonic plates across the surface of ancient Earth. Here, we present several analyses of such motions using strict quality criteria from the global paleomagnetic database of pre–800 Ma rocks. Extensive surface motion of cratons can be documented confi dently to older than ca. 2775 Ma, but considering only the most reliable Archean data, we cannot discern differential motion from true polar wander (which can also generate surface motions relative to the geomagnetic reference frame). In order to fi nd evidence for differential motions between pairs of Precambrian cratons, we compared distances between paleomagnetic poles through precisely isochronous intervals for pairs of cra- tons. The existing database yields several such comparisons with ages ranging from ca. 1110 to ca. 2775 Ma. Only one pair of these ages, 1110–1880 Ma, brackets signifi cantly different apparent polar wander path lengths between the same two cratons and thus demonstrates differential surface motions. If slightly less reliable paleomagnetic results are considered, however, the number of comparisons increases dramatically, and an example is illustrated for which a single additional pole could constrain differential cratonic motion into the earliest Paleoproterozoic and late Neoarchean (in the interval 2445–2680 Ma).
    [Show full text]
  • Geological Archive of the Onset of Plate Tectonics
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE Geological archive of the onsetprovided by espace@Curtin of plate tectonics rsta.royalsocietypublishing.org Peter A. Cawood1,2, Chris J. Hawkesworth2,3, Sergei A. Pisarevsky4, Bruno Dhuime3,5, 1 1 Research Fabio A. Capitanio andOliverNebel 1 Cite this article: Cawood PA, Hawkesworth School of Earth, Atmosphere and Environment, Monash University, CJ, Pisarevsky SA, Dhuime B, Capitanio FA, Melbourne, VIC 3800, Australia 2 Nebel O. 2018 Geological archive of the onset Department of Earth Sciences, University of St Andrews, of plate tectonics. Phil.Trans.R.Soc.A376: St Andrews, Fife KY16 9AL, UK 20170405. 3School of Earth Sciences, University of Bristol, Wills Memorial http://dx.doi.org/10.1098/rsta.2017.0405 Building, Queens Road, Bristol BS8 1RJ, UK 4ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS) and Accepted:21June2018 Earth Dynamics Research Group, The Institute for Geoscience Research (TIGeR), Department of Applied Geology, Curtin One contribution of 14 to a discussion meeting University, GPO Box U1987, Perth, WA 6845, Australia issue‘Earthdynamicsandthedevelopmentof 5CNRS-UMR 5243, Géosciences Montpellier, Université de plate tectonics’. Montpellier, Montpellier, France Subject Areas: PAC, 0000-0003-1200-3826;BD,0000-0002-4146-4739; plate tectonics, geochemistry, geology ON, 0000-0002-5068-7117 Keywords: Plate tectonics, involving a globally linked system of lateral motion of rigid surface plates, is a plate tectonics, Archaean, palaeomagnetics, characteristic feature of our planet, but estimates lithosphere, early Earth of how long it has been the modus operandi of lithospheric formation and interactions range from Author for correspondence: the Hadean to the Neoproterozoic.
    [Show full text]
  • The Oxidized Ores of the Main Sulphide Zone, Great Dyke, Zimbabwe: Turning Resources Into Minable Reserves – Mineralogy Is the Key
    The Southern African Institute of Mining and Metallurgy Platinum 2012 T. Oberthür, F. Melcher, P. Buchholz, M. Locmelis THE OXIDIZED ORES OF THE MAIN SULPHIDE ZONE, GREAT DYKE, ZIMBABWE: TURNING RESOURCES INTO MINABLE RESERVES – MINERALOGY IS THE KEY T. Oberthür Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) F. Melcher Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) P. Buchholz Deutsche Rohstoffagentur (DERA) in der Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) M. Locmelis Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS) Abstract The Great Dyke of Zimbabwe constitutes the world’s second largest reserve of platinum group elements (PGE) after the Bushveld Complex in neighbouring South Africa. Within the Great Dyke, economic concentrations of PGE are restricted to sulphide disseminations of the Main Sulphide Zone (MSZ), which are currently mined at the Ngezi, Unki, and Mimosa mines. Near-surface oxidized MSZ ores have a large potential. Their total resources are in the range of ca. 160 – 250 Mt; however, all previous attempts to extract the PGE from this ore type proved uneconomic due to low PGE recoveries (<< 50 per cent) achieved by conventional metallurgical methods. Within the ores of pristine, sulphide-bearing MSZ, the PGE are bimodally distributed. Platinum occurs mainly in the form of discrete platinum group mineral (PGM) grains (mainly bismuthotellurides, sulphides, and arsenides), whereas approximately 80 per cent of the Pd (and some Rh) is hosted in pentlandite. Within the oxidized MSZ ores, the PGE are polymodally distributed. Whereas arsenide- and sulphide-PGMs, making up ca. 25 per cent of the original Pt content of the ore, largely remain stable (relict PGMs), the remaining PGMs are disintegrated.
    [Show full text]
  • A Rheological Investigation of the Behaviour of Two Southern African Platinum Ores ⇑ M
    Minerals Engineering 49 (2013) 92–97 Contents lists available at SciVerse ScienceDirect Minerals Engineering journal homepage: www.elsevier.com/locate/mineng A rheological investigation of the behaviour of two Southern African platinum ores ⇑ M. Becker a, , G. Yorath a, B. Ndlovu a,b, M. Harris a, D. Deglon a, J.-P. Franzidis a a Centre for Minerals Research, Department of Chemical Engineering, University of Cape Town, South Africa b Julius Kruttschnitt Mineral Research Centre, University of Queensland, Australia article info abstract Article history: With the installation of ultrafine grinding on many platinum operations in southern Africa, there were Received 21 February 2013 concerns as to whether this would cause rheologically complex behaviour during the subsequent flota- Accepted 7 May 2013 tion of the ore. Rheologically complex behaviour refers to the non-Newtonian behaviour experienced Available online 5 June 2013 by some suspensions, associated with exponential increases in yield stress and viscosity with increasing solids content. This is attributed to particle size and solids concentration effects, surface chemistry, and Keywords: mineralogy. In this study, the rheological behaviour of two different platinum ores; a western limb UG2 Rheology ore and a Great Dyke platinum ore were investigated and compared with that of single mineral studies of Platinum ores the major gangue minerals of platinum ores (chromite, orthopyroxene, plagioclase and talc). The results Phyllosilicate minerals show that Great Dyke ore is considerably more rheologically complex than UG2 ore. Great Dyke flotation concentrate shows high yield stress and viscosity at low solids concentrations (>20 vol.% solids). Should the ROM ore in a Great Dyke flotation operation suddenly show significant changes in ore mineralogy, the rheological properties of the slurry should be considered since they may be detrimental to the overall performance of the operation (e.g.
    [Show full text]
  • South Africa): Revealing Multiple Events of Dyke Emplacement
    U-Pb baddeleyite dating of intrusions in the south-easternmost Kaapvaal Craton (South Africa): revealing multiple events of dyke emplacement Emilie Larsson Dissertations in Geology at Lund University, Master’s thesis, no 457 (45 hp/ECTS credits) Department of Geology Lund University 2015 U-Pb baddeleyite dating of intrusions in the south-easternmost Kaapvaal Craton (South Africa): revealing multiple events of dyke emplacement Master’s thesis Emilie Larsson Department of Geology Lund University 2015 Contents 1 Introduction ........................................................................................................................................................ 7 2 Regional geology ................................................................................................................................................. 7 2.1 Mafic dyke intrusions 3 Field Geology and Petrography ...................................................................................................................... 10 3.1 SE-trending dykes 3.1.1 SED01 3.1.2 SED02 3.2 Sub-horizontal intrusion (sill) 3.2.1 SED03 3.3 ENE-trending dykes 3.3.1 ENED03 3.3.2 ENED08 3.3.3 ENED09 4 Analytical protocol ........................................................................................................................................... 14 4.1. U / Pb dating of baddeleyite 5 Results ............................................................................................................................................................... 14 5.1
    [Show full text]
  • Mineralogy and Geochemistry of Soils of Ultramafic
    MINERALOGY AND GEOCHEMISTRY OF SOILS OF ULTRAMAFIC ORIGIN FROM THE GREAT DYKE, ZIMBABWE AND GILLESPIE COUNTY, TEXAS A Dissertation by COURAGE BANGIRA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY December 2010 Major Subject: Soil Science Mineralogy and Geochemistry of Soils of Ultramafic Origin from the Great Dyke, Zimbabwe and Gillespie County, Texas Copyright December 2010 Courage Bangira MINERALOGY AND GEOCHEMISTRY OF SOILS OF ULTRAMAFIC ORIGIN FROM THE GREAT DYKE, ZIMBABWE AND GILLESPIE COUNTY, TEXAS A Dissertation by COURAGE BANGIRA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Richard. H. Loeppert Committee Members, Charles T. Hallmark Youjun Deng Alan E. Pepper Head of Department, David D. Baltensperger December 2010 Major Subject: Soil Science iii ABSTRACT Mineralogy and Geochemistry of Soils of Ultramafic Origin from the Great Dyke, Zimbabwe and Gillespie County, Texas. (December 2010) Courage Bangira, B.S., University of Zimbabwe; M.S., Gent University, Belgium Chair of Advisory Committee: Dr. Richard H. Loeppert Although soils developed from ultramafic parent materials have significance to agriculture, ecology and health, their bio-geochemistry is poorly understood. The mineralogical and bio-geochemistry of soils formed from the ultramafic parent materials of the Great Dyke, Zimbabwe and Gillespie County, Texas was investigated. The objectives were to determine the mineralogical and bio-geochemical properties of the soils in order to assess the potential impact and challenges to agriculture, and environmental quality.
    [Show full text]
  • Stratiform Chromite Deposit Model
    Stratiform Chromite Deposit Model Chapter E of Mineral Deposit Models for Resource Assessment Scientific Investigations Report 2010–5070–E U.S. Department of the Interior U.S. Geological Survey COVER: Photograph showing outcropping of the Bushveld LG6 chromitite seam. Photograph courtesy of Klaus J. Schulz, U.S. Geological Survey. Stratiform Chromite Deposit Model By Ruth F. Schulte, Ryan D. Taylor, Nadine M. Piatak, and Robert R. Seal II Chapter E of Mineral Deposit Model for Resource Assessment Scientific Investigations Report 2010–5070–E U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director U.S. Geological Survey, Reston, Virginia: 2012 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Schulte, R.F., Taylor, R.D., Piatak, N.M., and Seal, R.R., II, 2012, Stratiform chromite deposit model, chap. E of Mineral deposit models for resource assessment: U.S.
    [Show full text]
  • Palaeomagnetism, Geochronology and Geochemistry of the Palaeoproterozoic Rabbit Creek and Powder River Dyke Swarms: Implications for Wyoming in Supercraton Superia
    Downloaded from http://sp.lyellcollection.org/ by AJS on May 1, 2016 Palaeomagnetism, geochronology and geochemistry of the Palaeoproterozoic Rabbit Creek and Powder River dyke swarms: implications for Wyoming in supercraton Superia TAYLOR M. KILIAN1*, WOUTER BLEEKER2, KEVIN CHAMBERLAIN3, DAVID A. D. EVANS1 & BRIAN COUSENS4 1Department of Geology and Geophysics, Yale University, 210 Whitney Ave, New Haven, CT 06511, USA 2Geological Survey of Canada, 601 Booth Street, Ottawa, ON, Canada K1A 0E8 3Department of Geology and Geophysics, University of Wyoming, Laramie, WY 82071-3006, USA 4Ottawa–Carleton Geoscience Centre, Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada K1S 5B6 *Corresponding author (e-mail: [email protected]) Abstract: It is likely that Archaean cratons of Laurentia had different palaeogeographic histories prior to their amalgamation. New palaeomagnetic, geochronological and geochemical evidence supports a reconstruction of the Wyoming craton adjacent to the southern margin of the Superior craton at 2.16 Ga, before rifting (c. 2.1–2.0 Ga) and eventual reamalgamation after the Hudsonian Orogeny (c. 1.8 Ga). U–Pb ages (TIMS on baddeleyite) from five dykes yield two groups of ages at c. 2164 and 2155 Ma. The younger group of ages defines the Rabbit Creek swarm at 2161– 2152 Ma and precisely dates its palaeomagnetic pole. Two large and differentiated dykes (.100 m) in the Bighorn and Wind River uplifts are geographically related to the Rabbit Creek swarm but have slightly different orientations and yield slightly older ages at 2171–2157 Ma. These dykes may be parts of a single intrusion (the ‘Great Dyke of Wyoming’) that spans over 200 km between uplifts, possibly representing a different magmatic event.
    [Show full text]