Internal geology and emplacement processes of Kimberlites, Case Study from the Tsabong Kimberlite Field, Botswana Mpho Ndebele Geosciences, master's level (120 credits) 2020 Luleå University of Technology Department of Civil, Environmental and Natural Resources Engineering Table of Contents Introduction ........................................................................................................................................... 6 Aims and Objectives .......................................................................................................................... 7 Background ........................................................................................................................................ 7 Regional Geology of Southern Africa .............................................................................................. 7 Kapvaal Craton ................................................................................................................................ 8 Zimbabwe Craton ............................................................................................................................ 9 Limpopo mobile belt ....................................................................................................................... 9 Tsabong local Geology ...................................................................................................................... 9 Tsabong stratigraphy ...................................................................................................................... 11 Dwyka Group ................................................................................................................................. 12 Malogong Formation ..................................................................................................................... 12 Khuis Formation ............................................................................................................................ 13 Middlepits Formation .................................................................................................................... 13 Ecca Group ..................................................................................................................................... 13 Kobe Formation ............................................................................................................................. 13 Otshe Formation ........................................................................................................................... 13 Botswana Kimberlites ..................................................................................................................... 13 Botswana Kimberlite Fields ........................................................................................................... 14 Orapa Kimberlite Field ................................................................................................................... 15 Jwaneng Kimberlite Field .............................................................................................................. 15 Tsabong Kimberlite Field ............................................................................................................... 16 Kimberlite Pipe Classes .................................................................................................................. 17 Class 1 ............................................................................................................................................ 17 Class 2 ............................................................................................................................................ 17 Class 1 (Classical Southern African Kimberlites) ........................................................................ 18 Kimberlite Emplacement Models .................................................................................................. 19 Hydrovolcanic (Phreatomagmatic) Model .................................................................................... 20 Magmatic (Bottom up embryonic) model ..................................................................................... 20 Application of Geophysical Methods in Kimberlite Exploration ................................................ 21 Magnetic Susceptibility of Kimberlites ......................................................................................... 22 Factors Affecting Kimberlite Magnetic Susceptibility (Local Scale) .......................................... 22 Kimberlite Contamination (Country rock assimilation) ................................................................. 22 Post Emplacement and Hydrothermal Alteration ......................................................................... 22 Kimberlite Weathering .................................................................................................................. 23 1 | P a g e Kimberlite Reintrusion................................................................................................................... 24 Methodology ........................................................................................................................................ 25 Sampling ........................................................................................................................................... 26 Petrography ..................................................................................................................................... 26 Section modelling ............................................................................................................................. 26 Terminology and classification ....................................................................................................... 26 Updated kimberlite terminology and classification ...................................................................... 27 Kimberlite Textures ........................................................................................................................ 28 Volcaniclastic Kimberlite (VK) ........................................................................................................ 28 Resedimented volcaniclastic kimberlite (RVK) .............................................................................. 28 Pyroclastic Kimberlite (PK) ............................................................................................................ 29 Tuffistic kimberlite breccia (TKB) or Tuffistic kimberlite ............................................................... 29 Hypabassal kimberlite (HK) ........................................................................................................... 29 DeBeers internal kimberlite nomenclature and classification ..................................................... 29 1) Resedimented volcaniclastic kimberlite ................................................................................ 29 2) Pyroclastic kimberlite ............................................................................................................ 30 Clast size and shape analysis .......................................................................................................... 30 Magmaclasts analysis ...................................................................................................................... 31 Magnetic susceptibility measurements .......................................................................................... 31 Onsite data acquisition procedure ................................................................................................ 31 Data visualization (Downhole magnetic susceptibility variations) .............................................. 31 Results .................................................................................................................................................. 32 Macroscopic Observations.............................................................................................................. 32 Microscopic Observations .............................................................................................................. 32 RVKA-Resedimented volcaniclastic kimberlite A ....................................................................... 32 Macroscopic Analysis .................................................................................................................... 32 Microscopic analysis ...................................................................................................................... 34 퐑퐕퐊퐁풎-Resedimented volcaniclastic kimberlite B (matrix supported) .................................... 35 Macroscopic Observations ............................................................................................................ 35 퐑퐕퐊퐁푪-Resedimented volcaniclastic kimberlite B (Clast supported) ....................................... 37 Macroscopic analysis ..................................................................................................................... 37 Microscopic analysis........................................................................................................................ 38 퐑퐕퐊퐁풎-Resedimented volcaniclastic kimberlite B (matrix supported) ...................................... 38 퐑퐕퐊퐁푪-Resedimented volcaniclastic kimberlite B (Clast supported) ......................................... 39 Pyroclastic Kimberlite 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