Multiple Merensky Reef of the Bushveld Complex, South Africa

  • Sofya Chistyakova
  • Rais LatypovEmail author
  • Kirsten Youlton
Original Paper


The Merensky Reef (MR) of the Bushveld Complex is known for containing the lion’s share of the world’s reserves of platinum group elements (PGE). It is commonly described as a single, relatively thin layer (or package) of chromite- and sulphide-bearing orthopyroxenite hosted by almost barren norite and/or anorthosite. Here, we present a drill-core section that contains; however, four separate MR orthopyroxenite layers hosted by mottled anorthosites. Each of these orthopyroxenites is distinguished through occurrence/absence of marginal chromitite seams, grain size, petrographic composition, and PGE abundance. We interpret them as multiple undercutting MR that occurs as sill-like apophyses extending laterally from a pothole margin into the footwall. The undercutting MR is attributed to in situ crystallization within sheet-like melt-filled cavities at potholes margins, which are produced through thermal and/or chemical erosion of the footwall rocks by replenishing magmas. This finding indicates that the MR-forming event involved several distinct pulses of replenishing magmas whose crystallization products were mostly eroded away in the stratiform portions, but remained locally preserved in apophyses within footwall rocks. The mineralized MR formed a few meters below a temporary chamber floor is indicative of strong thermal/compositional convection in the basal layer of the Bushveld’s chamber. The convection was able to deliver large volumes of fresh magma for the scavenging of PGE by sulphide and chromite growing within the sheet-like cavities of the MR potholes.


Merensky Reef Platinum group elements Multiple emplacements Thermal/chemical erosion In situ crystallization Bushveld Complex South Africa 



The research was supported by DST-NRF CIMERA grants to Rais Latypov and Sofya Chistyakova, and by National Research Foundation (NRF) grants to Rais Latypov. Any opinion, finding and conclusion or recommendation expressed in this contribution is that of the authors and the DST-NRF CIMERA and NRF do not accept any liability in this regard. The authors also gratefully acknowledge support from Pilanesberg Platinum Mine for fieldwork undertaken at their open pit and access to drill cores. We would like to specifically thank Jan Van der Merwe, Jan Aucamp and Janus Westraat for allowing us to visit open pits, and much assistance and advice during the field work and sampling of drill cores. We are grateful to Emma Hunt for comments and editing that have significantly improved the manuscript. Official reviews of the paper by F. Roelofse and I. J. Basson and editorial handling by Chris Ballhaus are gratefully acknowledged.

Supplementary material

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Supplementary material 1 (XLSX 36 KB)


  1. Ballhaus C (1988) Potholes of the Merensky reef at Brakspruit shaft, R.P.M.—primary disturbances in the magmatic stratigraphy. Econ Geol 83:1140–1158CrossRefGoogle Scholar
  2. Barnes SJ (1986) The distribution of chromium among orthopyroxene, spinel and silicate liquid at atmospheric pressure. Geochim Cosmochim Acta 50:1889–1909CrossRefGoogle Scholar
  3. Barnes SJ (2007) Cotectic precipitation of olivine and sulfide liquid from komatiite magma, and the origin of komatiite-hosted disseminated nickel sulfide mineralization at Mt Keith and Yakabindie, Western Australia. Econ Geol 102:299–304CrossRefGoogle Scholar
  4. Barrat JA, Zanda B, Moynier F, Bollinger C, Liorzou C, Bayon G (2012) Geochemistry of CI chondrites: major and trace elements, and Cu and Zn isotopes. Geochim Cosmochim Acta 83:79–92CrossRefGoogle Scholar
  5. Boudreau AE (1992) Volatile fluid overpressure in layered intrusions and the formation of potholes. Aust J Earth Sci 39:277–287CrossRefGoogle Scholar
  6. Boudreau AE (2008) Modelling the Merensky reef, Bushveld complex, Republic of South Africa. Contrib Miner Petrol 156:431–437CrossRefGoogle Scholar
  7. Campbell IH (1986) A fluid-dynamic model for the potholes of the Merensky Reef. Econ Geol 81:1118–1125CrossRefGoogle Scholar
  8. Campbell IH (1996) Fluid dynamic processes in basaltic magma chambers. In: Cawthorn RG (ed) Layered intrusions. Elsevier, Oxford, pp 45–76CrossRefGoogle Scholar
  9. Campbell IH, Naldrett AJ, Barnes SJ (1983) A model for the origin of platinum-rich sulphide horizons in the Bushveld and Stillwater complexes. J Petrol 24:133–165CrossRefGoogle Scholar
  10. Carr HW, Groves DI, Cawthorn RG (1994) A GIS based spatial analysis of controls on the distribution of Merensky reef potholes at the Western Platinum Mine, Bushveld Complex, South Africa. S Afr J Geol 97:431–441Google Scholar
  11. Carr HW, Kruger FJ, Groves DI, Cawthorn RG (1999) The petrogenesis of Merensky Reef potholes at the Western Platinum Mine, Bushveld Complex: Sr-isotopic evidence for synmagmatic deformation. Miner Depos 34:335–347CrossRefGoogle Scholar
  12. Cawthorn RG (1999) Platinum-group element mineralization in the Bushveld Complex—a critical reassessment of geochemical models. S Afr J Geol 102(3):268–281Google Scholar
  13. Cawthorn RG (2005a) Pressure fluctuations and the formation of the PGE-rich Merensky and chromitite reefs, Bushveld Complex. Miner Depos 40:231–235CrossRefGoogle Scholar
  14. Cawthorn R (2005b) Contrasting sulphide contents of the Bushveld and Sudbury igneous complexes. Miner Depos 40:1–12CrossRefGoogle Scholar
  15. Cawthorn RG (2011) Geological interpretations from the PGE distribution in the Bushveld Merensky and UG2 chromitite reefs. J South Afr Inst Min Metall 111:67–79Google Scholar
  16. Cawthorn RG (2015) Bushveld Complex. In: Charlier B, Namur O, Latypov R, Tegner C (eds) Layered intrusions. Springer, Dordrecht, pp 517–587CrossRefGoogle Scholar
  17. Cawthorn RG, Eales HV, Walraven F, Uken R, Watkeys MR (2006) The Bushveld Complex. In: Johnson MR, Anhaeusser CR, Thomas RJ (eds) The geology of South Africa. Council for Geoscience, Johannesburg-Pretoria, pp 261–282Google Scholar
  18. Eales HV, Cawthorn RG (1996) The Bushveld Complex. In: Cawthorn RG (ed) Layered intrusions. Elsevier, Oxford, pp 181–229CrossRefGoogle Scholar
  19. Eales HV, Field M, De Klerk WJ, Scoon RN (1988) Regional trends of chemical variation and thermal erosion in the Upper Critical Zone, western Bushveld Complex. Miner Mag 52:63–79CrossRefGoogle Scholar
  20. Fonseca ROC, Campbell IH, O’Neill HSTC, Allen CM (2009) Solubility of Pt in sulphide mattes: Implications for the genesis of PGE-rich horizons in layered intrusions. Geochim Cosmochim Acta 73:5764–5777CrossRefGoogle Scholar
  21. Forien M, Tremblay J, Barnes S-J, Burgisser A, Pagé P (2015) The role of viscous particle segregation in forming chromite layers from slumped crystal slurries: insights from analogue experiments. J Petrol 56:2425–2444CrossRefGoogle Scholar
  22. Gibb FGF, Henderson CMB (1992) Convection and crystal settling in sills. Contrib Miner Petrol 109:538–545CrossRefGoogle Scholar
  23. Godel B (2015) Platinum-group element deposits in layered intrusions: recent advances in the understanding of the ore forming processes. In: Charlier B, Namur O, Latypov R, Tegner C (eds) Layered intrusions. Springer, Dordrecht, pp 379–432CrossRefGoogle Scholar
  24. Golenya F (compiler) (2007) No. 17 Shaft Project. Geology and valuation sub-team report. Bull Geol Dept Impala Platinum Ltd (unpubl), 502, Addendum 1, vol 1, 81 pGoogle Scholar
  25. Hall AL (1932) The bushveld igneous complex. Geol Surv S Afr Memoir 28:560Google Scholar
  26. Hunt EJ, Latypov R, Horváth P (2018) The merensky cyclic unit, bushveld complex, South Africa: reality or myth. Minerals 8:144. CrossRefGoogle Scholar
  27. Huppert HE, Sparks RSJ (1980) The fluid dynamics of a basaltic magma chamber replenished by influx of hot dense ultrabasic magma. Contrib Miner Petrol 75:279–289CrossRefGoogle Scholar
  28. Hutchinson D, Foster J, Prichard H, Gilbert S (2015) Concentration of particulate platinum-group minerals during magma emplacement: a case study from the Merensky Reef, Bushveld Complex. J Petrol 56:113–159CrossRefGoogle Scholar
  29. Jaupart C, Tait S (1995) Dynamic of differentiation in magma reservoirs. J Geophys Res 100:17617–17636CrossRefGoogle Scholar
  30. Kinnaird JA, Kruger FJ, Nex PAM, Cawthorn RG (2002) Chromite formation—a key to understanding processes of platinum enrichment. Trans Inst Min Metall 111:B23–B35Google Scholar
  31. Kruger F (2005) Filling the Bushveld Complex magma chamber: lateral expansion, roof and floor interaction, magmatic unconformities, and the formation of giant chromitite, PGE and Ti-V-magnetitite deposits. Miner Depos 40:451–472CrossRefGoogle Scholar
  32. Latypov RM, Chistyakova SY, Page A, Hornsey R (2015) Field evidence for the in situ crystallization of the Merensky Reef. J Petrol 56:2341–2372CrossRefGoogle Scholar
  33. Latypov RM, Chistyakova SY, Barnes SJ, Hunt EJ (2017a) Origin of platinum deposits in layered intrusions by in situ crystallization: evidence from undercutting Merensky Reef of the Bushveld Complex. J Petrol 58:715–762CrossRefGoogle Scholar
  34. Latypov RM, Chistyakova SY, Mukherjee R (2017b) A novel hypothesis for origin of massive chromitites in the Bushveld Igneous Complex. J Petrol 58:1899–1940CrossRefGoogle Scholar
  35. Latypov RM, Costin G, Chistyakova SY, Hunt EJ, Mukherjee R, Naldrett A (2018) Platinum-bearing chromite layers are caused by pressure reduction during magma ascent. Nat Commun. CrossRefGoogle Scholar
  36. Lee CA (1996) A review of mineralization in the Bushveld Complex and some other layered intrusions. In: Cawthorn RG (ed) Layered intrusions. Elsevier, Oxford, pp 103–145CrossRefGoogle Scholar
  37. Leeb-du Toit A (1986) The impala platinum mines. In: Anhaeusser CR, Maske S (eds) Mineral deposits of Southern Africa. GSSA, Johannesburg, pp 1091–1106Google Scholar
  38. Maier WD, Barnes S-J, Groves DI (2013) The Bushveld Complex, South Africa: formation of platinum–palladium, chrome- and vanadium-rich layers via hydrodynamic sorting of a mobilized cumulate slurry in a large, relatively slowly cooling, subsiding magma chamber. Miner Depos 48:1–56CrossRefGoogle Scholar
  39. Mangan TM, Marsh BD (1992) Solidification front fractionation in phenocryst-free sheet-like magma bodies. J Geol 100:605–620CrossRefGoogle Scholar
  40. Marsh BD (1988) Crystal capture, sorting, and retention in convective magma. GSA Bull 100:1720–1737CrossRefGoogle Scholar
  41. Marsh BD (1989) On convective style and vigor in sheet-like magma chambers. J Petrol 30:479–530CrossRefGoogle Scholar
  42. Martin D, Griffiths RW, Campbell IH (1987) Compositional and thermal convection in magma chambers. Contrib Miner Petrol 96:465–475CrossRefGoogle Scholar
  43. Mathez EA (1995) Magmatic metasomatism and formation of the Merensky Reef, Bushveld Complex. Contrib Miner Petrol 119:277–286CrossRefGoogle Scholar
  44. Mitchell AA, Scoon RN (2007) The Merensky Reef at Winnaarshoek, Eastern Bushveld Complex: a primary magmatic hypothesis based on a wide reef facies. Econ Geol 102:971–1009CrossRefGoogle Scholar
  45. Mondal SK, Mathez EA (2007) Origin of the UG2 chromitite layer, Bushveld Complex. J Petrol 48:495–510CrossRefGoogle Scholar
  46. Morse SA (1986) Convection in aid of adcumulus growth. J Petrol 27:1183–1214CrossRefGoogle Scholar
  47. Mungall JE, Brenan JM (2014) Partitioning of platinum-group elements and Au between sulfide liquid and basalt and the origins of mantle-crust fractionation of the chalcophile elements. Geochim Cosmochim Acta 125:265–289CrossRefGoogle Scholar
  48. Naldrett AJ, Gasparrini EC, Barnes SJ, Von Gruenewaldt G, Sharpe MR (1986) The upper critical zone of the Bushveld Complex and the origin of Merensky-type ores. Econ Geol 81:1105–1117CrossRefGoogle Scholar
  49. Naldrett A, Wilson A, Kinnaird J, Chunnett G (2009) PGE tenor and metal ratios within and below the Merensky Reef, Bushveld Complex: implications for its genesis. J Petrol 50:625–659CrossRefGoogle Scholar
  50. Naldrett A, Kinnaird J, Wilson A, Yudovskaya M, Chunnett G (2011) Genesis of the PGE-enriched Merensky Reef and chromitite seams of the Bushveld Complex. In: Li C, Ripley EM (eds). Revi Econ Geol 17:235–296Google Scholar
  51. Naldrett A, Kinnaird J, Wilson A, Yudovskaya M, Chunnett G (2012) The origin of chromitites and related PGE mineralization in the Bushveld Complex: new mineralogical and petrological constraints. Miner Depos 47:209–232CrossRefGoogle Scholar
  52. Nicholson DM, Mathez E (1991) Petrogenesis of the Merensky Reef in the Rustenburg section of the Bushveld Complex. Contrib Miner Petrol 107:293–309CrossRefGoogle Scholar
  53. Page AS (2006) The Brakspruit pothole, east business area, Rustenburg section. Anglo American Platinum Corporation. Mine Managers Association Presentation Abstracts, Johannesburg, pp 1–32Google Scholar
  54. Roberts MD, Reid DL, Miller JA, Basson IJ, Roberts M, Smith D (2007) The Merensky Cyclic Unit and its impact on footwall cumulates below Normal and Regional Pothole reef types in the Western Bushveld Complex. Miner Depos 42:271–292CrossRefGoogle Scholar
  55. Scoon RN, Teigler B (1994) Platinum-group element mineralization in the Critical Zone of the Western Bushveld Complex: I. Sulphide poor-chromitites below the UG-2. Econ Geol 89:1094–1121CrossRefGoogle Scholar
  56. Smith DS, Basson IJ (2006) Shape and distribution analysis of Merensky Reef potholing, Northam Platinum Mine, Western Bushveld Complex: implications for pothole formation and growth. Miner Depos 41:281–295CrossRefGoogle Scholar
  57. Smith DS, Basson IJ, Reid DL (2003) Normal Reef sub-facies of the Merensky Reef at Northam Platinum Mine, Zwartklip Facies, Western Bushveld Complex, South Africa. Can Mineral 42:243–260CrossRefGoogle Scholar
  58. Vermaak CF (1976) The Merensky Reef—thoughts on its environment and genesis. Econ Geol 71:1270–1298CrossRefGoogle Scholar
  59. Viljoen MJ (1999) The nature and origin of the Merensky Reef of the western Bushveld Complex based on geological facies and geophysical data. S Afr J Sci 95:221–239Google Scholar
  60. Wager LR, Brown GM (1968) Layered Igneous Rocks. Oliver and Boyd, Edinburgh, p 588Google Scholar
  61. Wilson A, Chunnett G (2006) Trace element and platinum group element distributions and the genesis of the Merensky Reef, Western Bushveld Complex, South Africa. J Petrol 47:2369–2403CrossRefGoogle Scholar

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© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.School of GeosciencesUniversity of the WitwatersrandJohannesburgSouth Africa

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