Deeply exhumed impact structures: A case study of the Vredefort structure, South Africa

  • R. L. Gibson
  • W. U. Reimold
Part of the Lecture Notes in Earth Sciences book series (LNEARTH, volume 91)


The main evidence in the Vredefort Dome and surrounding parts of the Witwatersrand Basin is presented, which indicates that this terrain represents the deeply exhumed root zone of a large, 2023 ± 4 Ma, complex impact structure. Shock metamorphic features such as impact melt, shatter cones, high-pressure quartz polymorphs and shock microdeformation features are restricted to the Vredefort Dome, which constitutes the central uplift of the impact structure. High strain rate brittle deformation features, including pseudotachylites and clastic breccias, are found over a larger radial distance of at least 100 km from the center of the structure. Low-temperature (∼300 °C) hydrothermal effects occur up to a similar radial distance but, in the central uplift, metamorphic mineral parageneses overprinting the shock and brittle deformation features in pelites indicate a strong radially-inward increase in temperature to between 700 and 900 °C. Pressure estimates of 0.2–0.3 GPa obtained from these mineral parageneses indicate that the Vredefort structure has been eroded by between 7 and 10 km. The original depth of burial of these rocks after the impact and their elevated temperatures explain the anomalous appearance and restricted distribution of many of the shock features compared to other, less eroded, structures. The metamorphism and hydrothermal activity are attributed to the combined effects of exhumation of deep (hot) crustal levels by the cratering event and formation of the central uplift, and shock heating, possibly with a minor component of heating caused by an overlying impact melt volume. The structural, shock and thermal impact-related features in the Vredefort Dome and Witwatersrand Basin provide a case study that should assist in the identification of other deeply exhumed impact structures.


Impact Structure Central Uplift Witwatersrand Basin Transvaal Supergroup Sudbury Structure 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Akaogi M, Navrotsky A (1984) The quartz-coesite-stishovite transformations: New calorimetric measurements and calculation of phase diagrams. J Phys Earth Plan Int 36: 124–134Google Scholar
  2. Allsopp HL, Fitch FJ, Miller JA, Reimold WU (1991) 40Ar/39Ar stepheating age determinations relevant to the formation of the Vredefort Dome, South Africa. S Afr J Sci 87: 431–442Google Scholar
  3. Armstrong, RA, Compston W, Retief EA, Williams LS, Welke HJ (1991) Zircon ion microprobe studies bearing on the age and evolution of the Witwatersrand basin. Precambr Res 53: 243–266Google Scholar
  4. Ashley AJ, Gibson RL, Koeberl C, Reimold WU, Greshake A (1999) A new type of melt rock and first evidence of shock deformation in plagioclase from the Vredefort impact structure, South Africa. Meteor Planet Sci 34 (Suppl): A9–A10Google Scholar
  5. Bohor BF, Betterton WJ, Krogh TE (1993) Impact-shocked zircon: discussion of shock-induced textures reflecting increasing degrees of shock metamorphism. Earth Plan Sci Lett 119: 419–424Google Scholar
  6. Brink MC, Waander FC, Bisschoff AA (1997) Vredefort: A model for the anatomy of an astrobleme. Tectonophys 270: 83–114Google Scholar
  7. Carter NL (1965) Basal quartz deformation lamellae — a criterion for recognition of impactites. Am J Sci 263: 786–806Google Scholar
  8. Deutsch A, Grieve RAF, Avermann M, Bischoff L, Brockmeyer P, Buhl D, Lakomy R, Müller-Mohr V, Ostermann M, Stöffler D (1995) The Sudbury Structure (Ontario, Canada): a tectonically deformed multi-ring impact basin. Geol Rdsch 84: 697–709Google Scholar
  9. Dietz RS (1961) Vredefort Ring structure: meteorite impact scar? J Geol 69: 499–516Google Scholar
  10. Dressler BO (1984) The effects of the Sudbury event and the intrusion of the Sudbury Igneous Complex on the footwall rocks of the Sudbury Structure. In: Pye EG, Naldrett AJ, Giblin PE (eds) The geology and ore deposits of the Sudbury Structure. Ontario Geol Survey, Sudbury, Spec Vol 1, pp 97–136Google Scholar
  11. Durrheim RB, Nicolaysen LO, Corner B (1991) A deep seismic reflection profile across the Archean-Proterozoic Witwatersrand Basin, South Africa. Am Geophys Union Geodyn Ser 22: 213–224Google Scholar
  12. Fletcher P, Reimold WU (1989) Some notes and speculations on the pseudotachylites in the Witwatersrand basin and the Vredefort dome. S Afr J Geol 92: 223–234Google Scholar
  13. French BM (1998) Traces of Catastrophe: A handbook of shock-metamorphic effects in terrestrial meteorite impact structures. LPI Contribution No. 954, Lunar and Planetary Institute, Houston. 120 ppGoogle Scholar
  14. French BM, Nielsen RL (1968) Vredefort Bronzite Granophyre: chemical evidence for origin as a meteorite impact melt. Tectonophys 171: 119–138Google Scholar
  15. French BM, Orth CJ, Quintana LR (1989) Iridium in the Vredefort Bronzite Granophyre: impact melting and limits on a possible extraterrestrial component. Proc 19th Lunar Planet Sci Conft, Cambridge Univ. Press, pp 733–744Google Scholar
  16. Fricke A, Medenbach O, Schreyer W (1990) Fluid inclusions, planar elements and pseudotachylites in the basement rocks of the Vredefort structure, South Africa. Tectonophys 171: 169–183Google Scholar
  17. Frimmel HE (1997) Chlorite thermometry in the Witwatersrand Basin: Constraints on the Paleoproterozoic geotherm in the Kaapvaal Craton, South Africa. J Geol 105: 601–615Google Scholar
  18. Geology Forum (1997) Discussion of paper by Sharpton VL and Dressler BO (1996) New constraints on the Slate Islands impact structure: Comments and Reply. Geology 26: 666–669Google Scholar
  19. Gibson RL, Armstrong RA, Reimold WU (1997b) The age and thermal evolution of the Vredefort impact structure: a single-grain U-Pb zircon study: Geochim Cosmochim Acta 61: 1531–1540Google Scholar
  20. Gibson RL, Reimold WU, Wallmach T (1997a) Origin of pseudotachylite in the lower Witwatersrand Supergroup, Vredefort Dome (South Africa): Constraints from metamorphic studies. Tectonophys 283: 241–262Google Scholar
  21. Gibson RL, Reimold WU, Stevens G (1998) Thermal-metamorphic signature of an impact event in the Vredefort Dome, South Africa. Geology 26: 787–790Google Scholar
  22. Gibson RL, Courtnage PM, Charlesworth EG (1999) Bedding-parallel shearing and related deformation in the lower Transvaal Supergroup north of the Johannesburg Dome, South Africa. S Afr J Geol 102, in press (Editors: available in November 1999) Google Scholar
  23. Grieve RAF (1987) Terrestrial impact structures. Ann Rev Earth Plan Sci 15: 245–270Google Scholar
  24. Grieve RAF (1998) Extraterrestrial impacts on earth: the evidence and the consequences. In: Grady MM, Hutchison R, McCall GJH, Rothery DA (eds) Meteorites: Flux with Time and Impact Effects. Geol Soc, London, Spec Publ 140, pp 105–131Google Scholar
  25. Grieve RAF, Coderre JM, Robertson PB, Alexopoulos J (1990) Microscopic planar deformation features in quartz of the Vredefort structure: Anomalous but still suggestive of an impact origin. Tectonophys 171: 185–200Google Scholar
  26. Hargraves RB (1961) Shatter cones in the rocks of the Vredefort Ring. Trans Geol Soc S Afr 64: 147–154Google Scholar
  27. Hart RJ, Andreoli MAG, Reimold WU, Tredoux M (1991) Aspects of the dynamic and thermal metamorphic history of the Vredefort cryptoexplosion structure: implications for its origin. Tectonophys 192: 313–331Google Scholar
  28. Henkel H, Reimold WU (1998) Integrated geophysical modelling of a giant, complex impact structure: anatomy of the Vredefort Structure, South Africa. Tectonophys 287: 1–20Google Scholar
  29. Huffman AR, Reimold WU (1996) Experimental constraints on shock-induced microstructures in naturally deformed silicates. Tectonophys (N.L. Carter Vol) 256: 165–217Google Scholar
  30. Kamo SL, Reimold WU, Krogh TE, Colliston WP (1996) A 2.023 Ga age for the Vredefort impact event and a first report of shock metamorphosed zircons in pseudotachylitic breccias and Granophyre. Earth Planet Sci Lett 144: 369–388Google Scholar
  31. Killick AM (1992) Pseudotachylytes of the West Rand Goldfield, Witwatersrand Basin, South Africa. Unpubl PhD thesis, Rand Afrikaans Univ, Johannesburg, 273 ppGoogle Scholar
  32. Koeberl C, Reimold WU, Shirey SB (1996) A Re-Os isotope study of the Vredefort granophyre: Clues to the origin of the Vredefort structure, South Africa. Geology 24: 913–916Google Scholar
  33. Krogh TE, Davis DW, Corfu F (1984) Precise U-Pb zircon and baddeleyite ages of the Sudbury Structure. In: Pye EG, Naldrett AJ, Giblin PE (eds) The geology and ore deposits of the Sudbury Structure: Ontario Geol Survey, Sudbury, Spec Vol 1, pp 431–446Google Scholar
  34. Leroux H, Reimold WU, Doukhan JC (1994) A TEM investigation of shock metamorphism in quartz from the Vredefort dome, South Africa. Tectonophys 230: 223–239Google Scholar
  35. Leroux H, Reimold WU, Koeberl C, Hornemann U (1999) Experimental shock deformation in zircon: a transmission electron microscopic study. Earth Plan Sci Lett 169: 291–301Google Scholar
  36. Martini JEJ (1978) Coesite and stishovite in the Vredefort Dome, South Africa. Nature 272: 715–717Google Scholar
  37. Martini JEJ (1991) The nature, distribution and genesis of the coesite and stishovite associated with pseudotachylite of the Vredefort Dome, South Africa. Earth Planet Sci Lett 103: 285–300Google Scholar
  38. Martini JEJ (1992) The metamorphic history of the Vredefort dome at approximately 2 Ga as revealed by coesite-stishovite-bearing pseudotachylites. J Metam Geol 10: 517–527Google Scholar
  39. McCarthy TS, Charlesworth EG, Stanistreet IG (1986). Post-Transvaal structural features of the northern portion of the Witwatersrand Basin. Trans Geol Soc S Afr 89: 311–324Google Scholar
  40. McCarville P, Crossey LJ (1996) Post-impact hydrothermal alteration of the Manson impact structure, In: Koeberl C, Anderson RR (eds) The Manson Impact Structure, Iowa: Anatomy of an Impact Crater. Geol Soc Amer, Boulder, CO, Spec Pap 302, pp 347–376Google Scholar
  41. Melosh HJ (1989) Impact Cratering: A geologic process. Oxford Mon Geol Geophys 11, 245 ppGoogle Scholar
  42. Melosh HJ, Ivanov B (1999) Impact crater collapse. Ann Rev Earth Planet Sci 27: 385–415.Google Scholar
  43. Morgan J, Warner M (1999) Chicxulub: The third dimension of a multi-ring impact basin. Geology 27: 407–410.Google Scholar
  44. Moser DE, (1997) Dating the shock wave and thermal imprint of the giant Vredefort impact, South Africa. Geology 25: 7–10Google Scholar
  45. Nicolaysen LO, Reimold WU (1999) Vredefort shatter cones revisited. J Geophys Res 104: 4911–4930Google Scholar
  46. Raikes SA, Ahrens TS (1979) Post-shock temperatures in minerals. Geophys J R Astron Soc 58: 717–747Google Scholar
  47. Reimold WU (1991) The geochemistry of pseudotachylites from the Vredefort dome, South Africa. N Jahrb Mineral Abh 162: 151–184Google Scholar
  48. Reimold WU (1995) Pseudotachylite — Generation by friction melting and shock brecciation? — A review and discussion. Earth-Science Rev 39: 247–264Google Scholar
  49. Reimold WU (1998) Exogenic and endogenic breccias: a discussion of major problematics. Earth-Science Rev 43: 25–47Google Scholar
  50. Reimold WU, Colliston WP, (1994) Pseudotachylites of the Vredefort Dome and the surrounding Witwatersrand Basin, South Africa. In: Dressler BO, Grieve RAF, Sharpton VL (eds) Large Meteorite Impacts and Planetary Evolution. Geol Soc Amer, Boulder, CO, Spec Pap 293, pp 177–196Google Scholar
  51. Reimold WU, Gibson RL (1996) Geology and evolution of the Vredefort Impact Structure, South Africa. J Afr Earth Sci 23: 125–162Google Scholar
  52. Reimold WU, Reid AM, Horsch M, Durrheim RJ (1990) The ‘Bronzite'-Granophyre from the Vredefort Structure — a detailed analytical study and reflections on the origin of one of Vredefort's enigmas. Proc 20th Lunar Planet Sci Conf Lunar Planet Inst, Houston, pp 433–450Google Scholar
  53. Reimold WU, Colliston WP, Wallmach T (1992) Comment on “Nature, provenance and distribution of coesite and stishovite in the Vredefort structure” by JEJ Martini. Earth Plan Sci Lett 112: 213–217Google Scholar
  54. Reimold WU, Koeberl C, Fletcher P, Killick AM, Wilson JD (1999) Pseudotachylitic breccias from fault zones in the Witwatersrand Basin, South Africa: Evidence of autometasomatism and post-brecciation alteration processes. Miner Petrol 66: 25–53Google Scholar
  55. Roddy DJ, Davis LK (1977) Shatter cones formed in large-scale experimental explosion craters. In: Roddy DJ Pepin RO, Merrill RB (eds) Impact and Explosion Cratering. Pergamon Press, New York, pp 715–750Google Scholar
  56. Rondot J (1994) Recognition of eroded astroblemes. Earth-Science Rev 35: 331–365Google Scholar
  57. Schreyer W (1983) Metamorphism and fluid inclusions in the basement of the Vredefort Dome, South Africa: guidelines to the origin of the structure. J Petrol 24: 26–47Google Scholar
  58. Schreyer W, Abraham K (1978) Symplectitic cordierite-orthopyroxene-garnet assemblages as products of contact metamorphism of pre-existing basement granulites in the Vredefort structure, South Africa. Contrib Mineral Petrol 68: 53–62Google Scholar
  59. Sharpton VL, Marin LE, Carney C, Lee S, Ryder G., Schuraytz BC, Sikora P, Spudis PD (1996a) A model of the Chicxulub impact basin based on evaluation of geophysical data, well logs and drill core samples. In: Sharpton VL, Ward PD (eds), Global catastrophes in Earth history: An interdisciplinary conference on impacts, volcanism, and mass mortality. Geol Soc Amer, Boulder, CO, Spec Pap 247, pp 55–74Google Scholar
  60. Sharpton VL, Dressler BO, Herrick RR, Schnieders B, Scott J (1996b) New constraints on the Slate Islands impact structure, Ontario, Canada. Geology 24: 851–854Google Scholar
  61. Simpson C (1978) The structure of the rim synclinorium of the Vredefort Dome. Trans Geol Soc S Afr 81: 115–121Google Scholar
  62. Snyder DB, Hobbs RW (1999) Ringed structural zones with deep roots formed by the Chicxulub impact. J Geophys Res 104: 10743–10755Google Scholar
  63. Spray JG (1995) Pseudotachylyte controversy: Fact or friction? Geology 23: 1119–1122Google Scholar
  64. Spray JG (1997) Superfaults. Geology 25: 579–582Google Scholar
  65. Spray JG, Kelley SP, Reimold WU (1995) Laser-probe 40Ar-39Ar dating of pseudotachylytes and the age of the Vredefort impact event. Meteoritics 30: 335–343Google Scholar
  66. Stepto D (1990) The geology and gravity field in the central core of the Vredefort structure. Tectonophys 171: 75–103Google Scholar
  67. Stevens G, Gibson RL, Droop GTR (1997) Mid-crustal granulite facies metamorphism in the Central Kaapvaal Craton: The Bushveld Complex connection. Precambr Res 61: 113–132Google Scholar
  68. Stöffler D, Langenhorst F (1994) Shock metamorphism of quartz in nature and experiment: I. Basic observation and theory. Meteoritics 29: 155–181Google Scholar
  69. Therriault AM, Reimold WU, Reid AM (1996) The Vredefort granophyre: Part 1. Field studies. S Afr J Geol 99: 1–21Google Scholar
  70. Therriault AM, Reimold WU, Reid AM (1997a) Geochemistry and impact origin of the Vredefort Granophyre. S Afr J Geol 100: 115–122Google Scholar
  71. Therriault AM, Grieve RF, Reimold WU (1997b) Original size of the Vredefort Structure: implications for the geological evolution of the Witwatersrand Basin. Meteor Planet Sci 32: 71–77Google Scholar
  72. Trieloff M, Reimold WU, Kunz J, Boer RH, Jessberger EK (1994) 40Ar-39Ar thermochronology of pseudotachylites at the Ventersdorp Contact Reef, Witwatersrand Basin. S Afr J Geol 97: 365–384Google Scholar
  73. Walraven F (1997) Geochronology of the Rooiberg Group, Transvaal Supergroup, South Africa. Econ Geol Res Unit Inf Circ 316, Univ of the Witwatersrand, Johannesburg, 27 ppGoogle Scholar
  74. Walraven F, Elsenbroek JH (1991) Geochronology of the Schurwedraai Alkali Granite and associated nepheline syenite and implications for the origin of the Vredefort Structure. S Afr J Geol 94: 228–235Google Scholar
  75. Walraven F, Armstrong RA, Kruger FJ (1990) A chronostratigraphic framework for the north-central Kaapvaal Craton, the Bushveld Complex and the Vredefort structure. Tectonophys 171: 23–48Google Scholar
  76. White JC (1993) Shock-induced melting and silica polymorph formation, Vredefort Structure, South Africa. In: Boland JN, FitzGerald JG (eds) Defects and Processes in the Solid State: Geoscience Applications. The McLaren Volume. Elsevier Sci Publ, Amsterdam, pp 69–84Google Scholar
  77. Wilshire HG (1971) Pseudotachylite from the Vredefort Ring, South Africa. J Geol 79: 195–206Google Scholar
  78. Zhao B, Caluer N, Robb LJ, Zwingmann H, Toulkeridis T, Meyer FM (1999) K-Ar dating of white micas from the Ventersdorp Contact Reef of the Witwatersrand Bsin, South Africa: Timing of post-depositional alteration. Miner Petrol 66: 149–170Google Scholar

Copyright information

© Springer-Verlag 2000

Authors and Affiliations

  • R. L. Gibson
    • 1
  • W. U. Reimold
    • 1
  1. 1.Department of GeologyUniversity of the WitwatersrandJohannesburgSouth Africa

Personalised recommendations