DOCSLIB.ORG

Petrology, Zircon and Monazite Geochronology

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Petrology, Zircon and Monazite Geochronology Eburnian, Kibaran and Pan-African metamorphic events in the Ubendian belt of Tanzania: Petrology, zircon and monazite geochronology Dissertation zur Erlangung des Doktorgrades an der Mathematisch{Naturwissenschaftlichen Fakult¨at der Christian{Albrechts{Universit¨at zu Kiel vorgelegt von Nelson Boniface Kiel 2009 Eburnian, Kibaran and Pan-African metamorphic events in the Ubendian belt of Tanzania: Petrology, zircon and monazite geochronology Dissertation zur Erlangung des Doktorgrades an der Mathematisch{Naturwissenschaftlichen Fakult¨at der Christian{Albrechts{Universit¨at zu Kiel vorgelegt von Nelson Boniface Kiel 2009 Gedruckt mit Unterst¨utzungdes Deutschen Akademischen Austauschdienstes Referent: Prof. Dr. Volker Schenk Korreferentin: Prof. Dr. Astrid Holzheid Tag der m¨undlichen Pr¨ufung: 29. Januar 2009 Zum Druck genehmigt: Der Dekan Erkl¨arung Hiermit erkl¨areich, Nelson Boniface, dass die vorgelegte Abhandlung, abgesehen von der Beratung durch meinen akademischen Lehrer Professor Dr. Volker Schenk, nach Inhalt und Form meine Arbeit ist und ausschließlich unter Verwendung der angegebenen Hilfsmittel entstanden ist. Des Weiteren erkl¨areich, dass ich weder diese noch eine ¨ahnliche Arbeit an dieser oder einer anderen Hochschule im Rahmen eines Pr¨ufungsverfahrens vorgelegt oder ver¨offentlicht habe. Kiel, den ................................ ....................................... vi Acknowledgment I am greatly indebted to my academic advisor Prof. Dr. Volker Schenk who planned this project. His supervision, advices, guidances and constructive criticism are lifeblood of my achievement. Our relationship was not strictly academic, he always treated me as a good friend, I immensely value this! It was a great honor to get the financial support for the project from DAAD (Deutscher Akademischer Austausch Dienst) and the DFG (Deutsche Forschungsgemeinschaft). The permits to research in the Ubendian belt, issued by the Mpanda district commissioner (2004) and by the director for Tanzania geological survey, Dodoma (2006) are appreciated. Many thanks to Prof. Dr. Astrid Holzheid for her enthusiastic participations in seminars and for always giving positive recommendations and constructive comments. A lot of thanks to Prof. Abdul Mruma of the geological survey of Tanzania for the guidance in the field during a second field trip in 2006. It was much easier with him to locate useful outcrops. Special thanks go to my lovely wife Flora Stephano and to our wonderful kids, Kennedy and Elizabeth, for patience and prayers. The kids missed very much the paternal care as most of the time I was away. I highly appreciate the contributions of Dr. Peter Appel in dating monazite, discussing the results and the guides on how to use Electron Probe Microanalyser (EPMA). Thanks to Dr. Timm John for his guides in handling samples with acids in a clean geochemical laboratory. A lot of thanks to Dr. Peter Raase as he was available whenever I need help to read thin sections. Dr. S¨onke Brandt is appreciated for reading chapter four and giving constructive comments. My colleagues, Dr. Niels J¨ons,Dr. Denny Loose, Dr. Fran¸coisvan der Straaten and Dr. Christoph Beier who pursued doctoral degrees during my stay in Kiel were academically co-operative and not to mention the social activities we did together. By sharing with me whatever they knew facilitated my world of using many computer programs like LATEX and others. The contributions of the technical stuffs of the Petrology division were of significant importance. Mrs. Barbara Mader apart from being helpful in the EPMA laboratory always provided social help at any time of need. Mr. Andreas Fehler prepared all the thin sections I needed on time. Mrs. Astrid Weinkauf helped me a lot in preparing glass disks for XRF and ICP-MS. I wish to thank the ICP-MS laboratory team at the University of Kiel. Dr. Dieter Garbe- Sch¨onberg made useful comments whenever I approached him, Mrs. Petra Fiedler and viii Mrs. Ulrike Westernstr¨oerwere always available to help me to use the ICP-MS laboratories in a proper way. Many thanks to a team of technical staffs of the SHRIMP laboratory in St. Petersburg, Russia. Just to name few of them; A. Larionov, I. Paderin, S. Presniakov and N. Rodionov were very kind and co-operative. Other members in our institute of geosciences provided me with academic or social support in one way or another. Dr. Ralf Halama, Dr. Petra Herms, Dr. Wolf-Achim Kahl, Dr. Philip Kegler, Mrs. Maike Zakrotzky and Ms. Katja Beier. Last but not least thanks to Mr. Nambunga, now a retired driver from the University of Dar es Salaam, for driving our car during a field trip in the Ubendian belt in 2004. Contents Declaration v Acknowledgment vi Einf¨uhrungund Zusammenfassung xvii Introduction and outline of the thesis xix 1 Paleoproterozoic and Neoproterozoic sutures in the Ubendian belt 1 Abstract . 1 1.1 Introduction . 2 1.2 Geological settings . 2 1.3 Analytical techniques . 4 1.4 Metamorphic events . 4 1.4.1 Ubende terrane . 4 1.4.2 Ufipa terrane . 5 1.4.3 Wakole and Katuma terranes . 6 1.4.4 Mbozi terrane . 6 1.5 Discussion and conclusions . 9 1.6 Acknowledgment . 10 References . 10 2 Paleoproterozoic eclogites of the Ubendian belt 13 Abstract . 13 2.1 Introduction . 13 2.2 Geological settings . 15 2.3 Analytical techniques . 17 2.4 Petrology, geochemistry and geochronology of eclogites . 19 2.4.1 Petrography and mineral chemistry . 19 2.4.2 P-T conditions . 22 2.4.3 Geochemistry . 25 2.4.4 U-Pb SHRIMP zircon ages . 29 2.5 Geochronology of metapelites and mafic granulites . 32 2.5.1 Sample localities . 33 x Contents 2.5.2 U-Pb SHRIMP zircon ages . 34 2.5.3 Th-U-total Pb CHIME monazite ages . 37 2.6 Conclusions . 45 2.6.1 Paleoproterozoic subduction of oceanic crust . 45 2.6.2 Relationships between subduction and regional metamorphism . 45 2.6.3 Kibaran and Pan-African orogenic impacts in the Ubendian belt . 46 2.7 Acknowledgment . 46 References . 46 3 Kibaran age metamorphism in NW Ubendian belt of Tanzania 53 Abstract . 53 3.1 Introduction . 53 3.2 Geological settings . 54 3.3 Analytical techniques . 56 3.4 Petrography and mineral chemistry . 57 3.4.1 Wakole terrane . 57 3.4.2 Ubende terrane . 58 3.5 Mineral reactions . 59 3.6 Geothermobarometry . 62 3.7 U-Pb SHRIMP zircon dating . 64 3.7.1 Zircon textures and U-Th contents . 64 3.7.2 Zircon ages . 64 3.8 Th-U-total Pb monazite dating . 66 3.8.1 Monazite composition and textures . 66 3.8.2 Monazite isochron ages . 68 3.9 Discussion and conclusions . 71 3.10 Acknowledgment . 72 References . 72 4 Neoproterozoic eclogites in the Ubendian belt 77 Abstract . 77 4.1 Introduction . 78 4.2 Analytical techniques . 79 4.3 Geological setting . 79 4.4 Petrography and mineral chemistry . 83 4.4.1 Kyanite-free eclogites . 83 4.4.2 Kyanite-bearing eclogites . 83 4.5 Mineral reaction history . 86 4.5.1 Kyanite-free eclogites . 86 4.5.2 Kyanite-bearing eclogites . 86 4.6 Geothermobarometry . 93 4.7 Geochemistry of kyanite-free eclogites . 96 4.8 Geochronology . 100 Contents xi 4.8.1 Textures and U-Th-Pb compositions of zircons . 100 4.8.2 Results of the U-Pb dating . 101 4.9 Discussion . 103 4.9.1 Geochronological and geochemical results . 103 4.9.2 Neoproterozoic eclogite formation in the Ubendian belt and geody- namic consequences . 103 4.10 Conclusions . 105 4.11 Acknowledgment . 106 References . 106 Curriculum vitae 111 xii Contents List of Figures 1.1 Locations of Kibaran orogenic system in southern Africa . 3 1.2 REE patterns of the Eclogites . 5 1.3 Monazite BSE images for the Ubendian belt metapelites . 7 1.4 Simplified geological map of central Gondwana with Pan-African sutures and eclogites . 10 2.1 The 2.1-1.8 Ga collisional orogens of the World . 14 2.2 Location of the Ubendian belt . 15 2.3 Textures of mylonitic eclogites of the Ubende terrane . 19 2.4 Grt and Cpx composition of the Ubende terrane eclogites. 20 2.5 BSE image of rutile and calculated temperatures . 22 2.6 P-T conditions in mylonitic eclogites . 24 2.7 Classification of mylonitic eclogites on magma discrimination diagrams . 25 2.8 REE and trace element patterns of the Ubende terrane eclogites . 26 2.9 Plot of Nb=La vs (La=Sm)N for Ubende terrane eclogites . 26 2.10 Zircon textures, Ubende terrane eclogites . 29 2.11 Concordia diagrams with U-Pb zircon ages of eclogites . 30 2.12 Map of the Ubendian belt showing ages distribution . 32 2.13 Textures of zircon of metapelites and mafic granulites . 35 2.14 Concordia diagrams with U-Pb zircon ages of metapelites and mafic granulite 36 2.15 Textures in monazite showing ages in cores and rims . 38 2.16 Monazite composition, Ufipa terrane . 39 2.17 Monazite isochron ages . 40 2.18 Textures in monazite showing ages in cores and rims . 41 2.19 Monazite composition sample T21-1-04 . 42 2.20 Monazite isochron ages, Mbozi terrane . ..
Load more

Recommended publications
  • Back Matter (PDF)
    Index Page numbers in italic refer to tables, and those in bold to figures. accretionary orogens, defined 23 Namaqua-Natal Orogen 435-8 Africa, East SW Angola and NW Botswana 442 Congo-Sat Francisco Craton 4, 5, 35, 45-6, 49, 64 Umkondo Igneous Province 438-9 palaeomagnetic poles at 1100-700 Ma 37 Pan-African orogenic belts (650-450 Ma) 442-50 East African(-Antarctic) Orogen Damara-Lufilian Arc-Zambezi Belt 3, 435, accretion and deformation, Arabian-Nubian Shield 442-50 (ANS) 327-61 Katangan basaltic rocks 443,446 continuation of East Antarctic Orogen 263 Mwembeshi Shear Zone 442 E/W Gondwana suture 263-5 Neoproterozoic basin evolution and seafloor evolution 357-8 spreading 445-6 extensional collapse in DML 271-87 orogenesis 446-51 deformations 283-5 Ubendian and Kibaran Belts 445 Heimefront Shear Zone, DML 208,251, 252-3, within-plate magmatism and basin initiation 443-5 284, 415,417 Zambezi Belt 27,415 structural section, Neoproterozoic deformation, Zambezi Orogen 3, 5 Madagascar 365-72 Zambezi-Damara Belt 65, 67, 442-50 see also Arabian-Nubian Shield (ANS); Zimbabwe Belt, ophiolites 27 Mozambique Belt Zimbabwe Craton 427,433 Mozambique Belt evolution 60-1,291, 401-25 Zimbabwe-Kapvaal-Grunehogna Craton 42, 208, 250, carbonates 405.6 272-3 Dronning Mand Land 62-3 see also Pan-African eclogites and ophiolites 406-7 Africa, West 40-1 isotopic data Amazonia-Rio de la Plata megacraton 2-3, 40-1 crystallization and metamorphic ages 407-11 Birimian Orogen 24 Sm-Nd (T DM) 411-14 A1-Jifn Basin see Najd Fault System lithologies 402-7 Albany-Fraser-Wilkes
    [Show full text]
  • Pan-African Orogeny 1
    Encyclopedia 0f Geology (2004), vol. 1, Elsevier, Amsterdam AFRICA/Pan-African Orogeny 1 Contents Pan-African Orogeny North African Phanerozoic Rift Valley Within the Pan-African domains, two broad types of Pan-African Orogeny orogenic or mobile belts can be distinguished. One type consists predominantly of Neoproterozoic supracrustal and magmatic assemblages, many of juvenile (mantle- A Kröner, Universität Mainz, Mainz, Germany R J Stern, University of Texas-Dallas, Richardson derived) origin, with structural and metamorphic his- TX, USA tories that are similar to those in Phanerozoic collision and accretion belts. These belts expose upper to middle O 2005, Elsevier Ltd. All Rights Reserved. crustal levels and contain diagnostic features such as ophiolites, subduction- or collision-related granitoids, lntroduction island-arc or passive continental margin assemblages as well as exotic terranes that permit reconstruction of The term 'Pan-African' was coined by WQ Kennedy in their evolution in Phanerozoic-style plate tectonic scen- 1964 on the basis of an assessment of available Rb-Sr arios. Such belts include the Arabian-Nubian shield of and K-Ar ages in Africa. The Pan-African was inter- Arabia and north-east Africa (Figure 2), the Damara- preted as a tectono-thermal event, some 500 Ma ago, Kaoko-Gariep Belt and Lufilian Arc of south-central during which a number of mobile belts formed, sur- and south-western Africa, the West Congo Belt of rounding older cratons. The concept was then extended Angola and Congo Republic, the Trans-Sahara Belt of to the Gondwana continents (Figure 1) although West Africa, and the Rokelide and Mauretanian belts regional names were proposed such as Brasiliano along the western Part of the West African Craton for South America, Adelaidean for Australia, and (Figure 1).
    [Show full text]
  • A Review of the Neoproterozoic to Cambrian Tectonic Evolution
    Accepted Manuscript Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution H. Fritz, M. Abdelsalam, K.A. Ali, B. Bingen, A.S. Collins, A.R. Fowler, W. Ghebreab, C.A. Hauzenberger, P.R. Johnson, T.M. Kusky, P. Macey, S. Muhongo, R.J. Stern, G. Viola PII: S1464-343X(13)00104-0 DOI: http://dx.doi.org/10.1016/j.jafrearsci.2013.06.004 Reference: AES 1867 To appear in: African Earth Sciences Received Date: 8 May 2012 Revised Date: 16 June 2013 Accepted Date: 21 June 2013 Please cite this article as: Fritz, H., Abdelsalam, M., Ali, K.A., Bingen, B., Collins, A.S., Fowler, A.R., Ghebreab, W., Hauzenberger, C.A., Johnson, P.R., Kusky, T.M., Macey, P., Muhongo, S., Stern, R.J., Viola, G., Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution, African Earth Sciences (2013), doi: http://dx.doi.org/10.1016/j.jafrearsci.2013.06.004 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1 Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian 2 tectonic evolution 3 H.
    [Show full text]
  • Lecture Notes in Earth Sciences 40 Editors: S
    Lecture Notes in Earth Sciences 40 Editors: S. Bhattacharji, Brooklyn G. M. Friedman, Troy H. J. Neugebauer, Bonn A. Seilacher, Tuebingen Sunday W. Petters Regional Geology of Africa Springer-Verlag Berlin Heidelberg NewYork London Paris Tokyo Hong Kong Barcelona Budapest Author Sunday W. Petters Department of Geology University of Calabar Calabar, Nigeria "For all Lecture Notes in Earth Sciences published till now please see final page of the book" ISBN 3-540-54528-X Springer-Verlag Berlin Heidelberg New York ISBN 0-387-54528-X Springer-Verlag New York Berlin Heidelberg This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. @ Springer-Verlag Berlin Heidelberg 1991 Printed in Germany Typesetting: Camera ready by author Printing and binding: Druckhaus Beltz, Hemsbach/Bergstr. 32/3140-543210 - Printed on acid-free paper Dedicated to: Wissenschaftskolleg zu Berlin - Institute for Advanced Study - Preface This book represents the first attempt in three decades to marshall out available information on the regional geology of Africa for advanced un- dergraduates and beginning graduate students. Geologic education in African universities is severely hampered by the lack of a textbook on African regional geology.
    [Show full text]
  • A Detrital Record of the Nile River and Its Catchment
    Downloaded from http://jgs.lyellcollection.org/ by guest on September 26, 2021 Research article Journal of the Geological Society Published online December 7, 2016 https://doi.org/10.1144/jgs2016-075 | Vol. 174 | 2017 | pp. 301–317 A detrital record of the Nile River and its catchment Laura Fielding1, Yani Najman1*, Ian Millar2, Peter Butterworth3, Sergio Ando4, Marta Padoan4, Dan Barfod5 & Ben Kneller6 1 Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK 2 NIGL, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK 3 BP Egypt, 14 Road 252, Al Maadi, Cairo, Egypt 4 DISAT, University of Milano-Bicocca, Piazza della Scienza, 4 20126 Milano, Italy 5 SUERC, Rankine Ave, Scottish Enterprise Technology Park, East Kilbride, G75 0QF, UK 6 University of Aberdeen, Aberdeen AB24 3FX, UK *Correspondence: [email protected] Abstract: This research uses analyses from Nile catchment rivers, wadis, dunes and bedrocks to constrain the geological history of NE Africa and document influences on the composition of sediment reaching the Nile delta. Our data show evolution of the North African crust, highlighting phases in the development of the Arabian–Nubian Shield and amalgamation of Gondwana in Neoproterozoic times. The Saharan Metacraton and Congo Craton in Uganda have a common history of crustal growth, with new crust formation at 3.0 – 3.5 Ga, and crustal melting at c. 2.7 Ga. The Hammamat Formation of the Arabian– Nubian Shield is locally derived and has a maximum depositional age of 635 Ma. By contrast, Phanerozoic sedimentary rocks are derived from more distant sources. The fine-grained (mud) bulk signature of the modern Nile is dominated by input from the Ethiopian Highlands, transported by the Blue Nile and Atbara rivers.
    [Show full text]
  • A Detrital Record of the Nile River and Its Catchment
    Research article Journal of the Geological Society Published online December 7, 2016 https://doi.org/10.1144/jgs2016-075 | Vol. 174 | 2017 | pp. 301–317 A detrital record of the Nile River and its catchment Laura Fielding1, Yani Najman1*, Ian Millar2, Peter Butterworth3, Sergio Ando4, Marta Padoan4, Dan Barfod5 & Ben Kneller6 1 Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK 2 NIGL, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK 3 BP Egypt, 14 Road 252, Al Maadi, Cairo, Egypt 4 DISAT, University of Milano-Bicocca, Piazza della Scienza, 4 20126 Milano, Italy 5 SUERC, Rankine Ave, Scottish Enterprise Technology Park, East Kilbride, G75 0QF, UK 6 University of Aberdeen, Aberdeen AB24 3FX, UK *Correspondence: [email protected] Abstract: This research uses analyses from Nile catchment rivers, wadis, dunes and bedrocks to constrain the geological history of NE Africa and document influences on the composition of sediment reaching the Nile delta. Our data show evolution of the North African crust, highlighting phases in the development of the Arabian–Nubian Shield and amalgamation of Gondwana in Neoproterozoic times. The Saharan Metacraton and Congo Craton in Uganda have a common history of crustal growth, with new crust formation at 3.0 – 3.5 Ga, and crustal melting at c. 2.7 Ga. The Hammamat Formation of the Arabian– Nubian Shield is locally derived and has a maximum depositional age of 635 Ma. By contrast, Phanerozoic sedimentary rocks are derived from more distant sources. The fine-grained (mud) bulk signature of the modern Nile is dominated by input from the Ethiopian Highlands, transported by the Blue Nile and Atbara rivers.
    [Show full text]
  • Supercontinent Reconstruction the Palaeomagnetically Viable, Long
    Geological Society, London, Special Publications The palaeomagnetically viable, long-lived and all-inclusive Rodinia supercontinent reconstruction David A. D. Evans Geological Society, London, Special Publications 2009; v. 327; p. 371-404 doi:10.1144/SP327.16 Email alerting click here to receive free email alerts when new articles cite this service article Permission click here to seek permission to re-use all or part of this article request Subscribe click here to subscribe to Geological Society, London, Special Publications or the Lyell Collection Notes Downloaded by on 21 December 2009 © 2009 Geological Society of London The palaeomagnetically viable, long-lived and all-inclusive Rodinia supercontinent reconstruction DAVID A. D. EVANS Department of Geology & Geophysics, Yale University, New Haven, CT 06520-8109, USA (e-mail: [email protected]) Abstract: Palaeomagnetic apparent polar wander (APW) paths from the world’s cratons at 1300–700 Ma can constrain the palaeogeographic possibilities for a long-lived and all-inclusive Rodinia supercontinent. Laurentia’s APW path is the most complete and forms the basis for super- position by other cratons’ APW paths to identify possible durations of those cratons’ inclusion in Rodinia, and also to generate reconstructions that are constrained both in latitude and longitude relative to Laurentia. Baltica reconstructs adjacent to the SE margin of Greenland, in a standard and geographically ‘upright’ position, between c. 1050 and 600 Ma. Australia reconstructs adja- cent to the pre-Caspian margin of Baltica, geographically ‘inverted’ such that cratonic portions of Queensland are juxtaposed with that margin via collision at c. 1100 Ma. Arctic North America reconstructs opposite to the CONgo þ Sa˜o Francisco craton at its DAmaride–Lufilian margin (the ‘ANACONDA’ fit) throughout the interval 1235–755 Ma according to palaeomag- netic poles of those ages from both cratons, and the reconstruction was probably established during the c.
    [Show full text]
  • Re-Imagining and Re-Imaging the Development of the East African Rift
    Thematic set: Tectonics and petroleum systems of East Africa Petroleum Geoscience Published Online First https://doi.org/10.1144/petgeo2017-036 Re-imagining and re-imaging the development of the East African Rift P. G. Purcell P&R Geological Consultants Pty Ltd, 141 Hastings Street, Scarborough, WA 6019, Australia P.G.P., 0000-0001-5006-5863 [email protected] Abstract: The East African Rift (EAR) has fascinated and challenged the geological imagination since its discovery nearly a century ago. A new series of images showing the sequential development of faulting and volcanism along the Rift from 45 Ma to present offers a regional overview of that development. The EAR is the latest phase of the extensive Phanerozoic rifting of the East African continental plate, interwoven with the lithospheric fabrics knitted together during its complex Proterozoic past. South of 5° S, the EAR variously follows or cuts across the Karoo rift trends; north of 5° S, it is almost totally within new or reworked Neoproterozoic terranes, while the Karoo rifts are almost totally outside them. The compilations raise several aspects of rift development seemingly in need of re-imagining, including tight-fit reconstructions of the Gulf of Aden, and the projection of Mesozoic rifts from Yemen to Somalia. Overall, the rifting process does not accord well with a mechanistic paradigm and is better imagined within the Prigoginian paradigm, which accepts instability and disorder within natural processes such as mantle plumes. The structural complexity of Afar and its non-alignment with magnetic anomalies suggests that the seafloor spreading process is, in its beginnings at least, more chaos than order.
    [Show full text]
  • An Overview of Nickel Mineralisation in Africa with Emphasis on the Mesoproterozoic East African Nickel Belt (EANB)
    319 An overview of nickel mineralisation in Africa with emphasis on the Mesoproterozoic East African Nickel Belt (EANB) D. M. Evans1, J. P. P. M. Hunt2, and J. R. Simmonds3 1 Carrog Consulting, 21 rue Jean de la Bruyère, 78000 Versailles, France. E-mail: [email protected] 2 Council for Geoscience, Private Bag X112, Pretoria 0001, South Africa 3 Nyiici Pty Ltd, 64 McKenzie Street, Wembley WA 6014, Australia DOI: 10.18814/epiiugs/2016/v39i2/95780 Nickel production in Africa takes place principally they remain undeveloped due to their distance to the coast in Botswana, South Africa and Zimbabwe, with much of and a lack of transport and energy infrastructure. The the South African and Zimbabwean production being a Kabanga sulphide deposit now comprises a total mineral by-product of platinum-group element mining in the resource of 58 million tonnes grading 2.6% nickel. The Bushveld Complex and Great Dyke. Several large nickel Musongati laterite deposit comprises an overall resource deposits have been discovered elsewhere in Africa but of 122 million tonnes with a grade of 1.4% nickel. until recently, their development has been hindered by political risk and limitations in energy and transport Introduction and geological setting infrastructure. Most of the continent is significantly of nickel deposits underexplored with respect to base metals, including the area covered by the East African Nickel Belt (EANB). The vast majority of nickel deposits worldwide are hosted by or related to rocks of mafic to ultramafic composition, either as products The known nickel deposits of the EANB all occur in of crystallization from primitive mantle melts (picritic and tholeiitic mafic-ultramafic intrusive rocks of the Mesoproterozoic- basalt or komatiitic magma) or, tectonically-emplaced slices of upper age Kibaran igneous event.
    [Show full text]
  • Palaeoproterozoic Eclogite Formation in Tanzania: a Structural, Geochronological, Thermochronological and Metamorphic Study of the Usagaran and Ubende Orogenic Belts
    Palaeoproterozoic eclogite formation in Tanzania: a structural, geochronological, thermochronological and metamorphic study of the Usagaran and Ubende orogenic belts. Rachael A. Brick Geology & Geophysics School of Earth & Environmental Science University of Adelaide Submitted – 8th April, 2011 TABLE OF CONTENTS Abstract i. Acknowledgements iii. Declaration v Chapter 1 - Tectonic settings of Palaeoproterozoic eclogites 1.1 1.1 Introduction 1.1.1 Eclogite or not eclogite, what is the difference? 1.1.2 Problems in dating eclogites 1.1.3 Precambrian plate tectonics 1.1.4 Problems of P-T determination 1.2 1.2. Eclogite types and their tectonic settings 1.3 1.3 Tectonic scenarios for Palaeoproterozoic eclogite-hosting orogens 1.3.1 Tanzania 1.3.1.1 Usagaran Orogen 1.3.1.2 Ubende Orogen 1.3.2 Snowbird tectonic zone, Canada 1.4 1.3.3 Lapland Granulite Belt 1.5 1.3.4 North China Craton 1.3.5 Sare Sang, Afghanistan 1.3.6 Archaean Eclogites and high-P rocks 1.3.6.1 Belomorian Eclogites 1.3.6.2 Barberton granitoid-greenstone terrane 1.4. Discussion 1.6 1.5. Scope of this project 1.7 Chapter 2 - Characterising the crustal evolution of the Tanzanian Craton using LA-ICPMS U-Pb and Lu-Hf 2.1 analyses of detrital zircon 2.1 Introduction 2.2 Geology and geochronology of the Tanzanian Craton 2.3 Samples and analytical techniques 2.2 2.3.1 Sampling strategy 2.3.2 Sample preparation 2.3 2.3.3 Analytical technique – LA-ICPMS U-Th-Pb geochronology 2.3.4 Analytical technique – LA-MC-ICPMS Hf isotope analysis 2.4 Results 2.4 2.4.1 TC2 – Zira River, Mbeya district 2.4.2 TC3 – Durumo River, Singida district 2.4.3 TC4 – Malagarasi River, Uvinza township 2.5 2.4.4 Albsong-05 2.5 Discussion 2.5.1 The significance of concordant Archaean U-Pb ages 2.5.2 The significance of Archaean Lu-Hf data 2.7 2.5.3 Post-Archaean crustal evolution of the Tanzanian Craton 2.6 Conclusions 2.8 Chapter 3 - 40Ar/39Ar Thermochronology and U-Pb geochronology of the eclogite-hosting Ubende Belt, 3.1 Tanzania 3.1 Introduction 3.2.
    [Show full text]
  • New Insights Into the Crust and Lithospheric Mantle Structure of Africa from Elevation, Geoid, and Thermal Analysis
    New insights into the crust and lithospheric mantle structure of Africa from elevation, geoid, and thermal analysis Jan Globig(1), Manel Fernàndez(1), Montserrat Torne(1), Jaume Vergés(1), Alexandra Robert(2) and Claudio Faccenna(3) (1) Institute of Earth Sciences Jaume Almera, ICTJA-CSIC, Group of Dynamics of the Lithosphere (G.D.L.), Barcelona, Spain (2) Géosciences Environnement Toulouse, Observatoire Midi-Pyrénées, France (3) University Roma TRE, Dept. of Geological Sciences, Italy Key points: 1) We present 10 min resolution crust and lithosphere maps of Africa constrained by a compilation of seismic Moho data and tomography models. 2) Our maps cover large areas of Africa where no data are available showing 76% fit with seismic data after excluding the Afar plume region. 3) Misfits with seismic data in the Afar region are discussed in terms of residual topography related to sublithospheric processes. Abstract 1. Introduction 2. Tectonic Background 3. Data 4. Method and model parameters 5. Results This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/2016JB012972 © 2016 American Geophysical Union. All rights reserved. 6. Discussion 7. Conclusion Appendix References Acknowledgments Abstract We present new crust and lithosphere thickness maps of the African mainland based on integrated modeling of elevation and geoid data and thermal analysis. The approach assumes local isostasy, thermal steady-state, and linear density increase with depth in the crust and temperature-dependent density in the lithospheric mantle.
    [Show full text]
  • Victoria Continental Microplate Dynamics Controlled by the Lithospheric Strength Distribution of the East African Rift ✉ Anne Glerum 1 , Sascha Brune 1,2, D
    ARTICLE https://doi.org/10.1038/s41467-020-16176-x OPEN Victoria continental microplate dynamics controlled by the lithospheric strength distribution of the East African Rift ✉ Anne Glerum 1 , Sascha Brune 1,2, D. Sarah Stamps 3 & Manfred R. Strecker2 The Victoria microplate between the Eastern and Western Branches of the East African Rift System is one of the largest continental microplates on Earth. In striking contrast to its 1234567890():,; neighboring plates, Victoria rotates counterclockwise with respect to Nubia. The underlying cause of this distinctive rotation has remained elusive so far. Using 3D numerical models, we investigate the role of pre-existing lithospheric heterogeneities in continental microplate rotation. We find that Victoria’s rotation is primarily controlled by the distribution of rheo- logically stronger zones that transmit the drag of the major plates to the microplate and of the mechanically weaker mobile belts surrounding Victoria that facilitate rotation. Our models reproduce Victoria’s GPS-derived counterclockwise rotation as well as key complexities of the regional tectonic stress field. These results reconcile competing ideas on the opening of the rift system by highlighting differences in orientation of the far-field divergence, local extension, and the minimum horizontal stress. 1 Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences, Potsdam, Germany. 2 University of Potsdam, Potsdam-Golm, Germany. ✉ 3 Virginia Tech, Blacksburg, VA, USA. email: [email protected] NATURE COMMUNICATIONS | (2020) 11:2881 | https://doi.org/10.1038/s41467-020-16176-x | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-020-16176-x he East African Rift System (EARS) is the largest Cenozoic continental blocks like Victoria.
    [Show full text]