Earth, Planets and Space

, Volume 56, Issue 2, pp 125–137 | Cite as

Variations in the thickness of the crust of the Kaapvaal craton, and mantle structure below southern Africa

  • C. Wright
  • M. T. O. Kwadiba
  • R. E. Simon
  • E. M. Kgaswane
  • T. K. Nguuri
Open Access


Estimates of crustal thicknesses using Pn times and receiver functions agree well for the southern part of the Kaapvaal craton, but not for the northern region. The average crustal thicknesses determined from Pn times for the northern and southern regions of the craton were 50.52 ± 0.88 km and 38.07 ± 0.85 km respectively, with corresponding estimates from receiver functions of 43.58 ± 0.57 km and 37.58 ± 0.70 km. The lower values of crustal thicknesses for receiver functions in the north are attributed to variations in composition and metamorphic grade in an underplated, mafic lower crust, resulting in a crust-mantle boundary that yields weak P-to-SV conversions. P and S wavespeeds in the uppermost mantle of the central regions of the Kaapvaal craton are high and uniform with average values of 8.35 and 4.81 km/s respectively, indicating the presence of depleted magnesium-rich peridotite. The presence of a low wavespeed zone for S waves in the upper mantle between depths of 210 and about 345 km that is not observed for P waves was inferred outside the Kaapvaal craton. The 410 km discontinuity shows similar characteristics to that in other continental regions, but occurs slightly deeper at 420 km. There is no evidence for a discontinuity near 520 km depth. The 660 km discontinuity also appears to be slightly deeper than average (668 km), and is poorly defined for P waves, but clear for S waves.

Key words

Gondwanaland Kaapvaal craton crust and mantle structure 


  1. Ammon, C. J., The isolation of receiver effects from teleseismic P wave-forms, Bull. Seism. Soc. Am., 81, 2504–2510, 1991.Google Scholar
  2. Ben-Ismail, W., G. Barruol, and D. Mainprice, The Kaapvaal craton seismic anisotropy: petrophysical analyses of upper mantle kimberlite nodules, Geophys. Res. Lett., 28, 2497–2500, 2001.CrossRefGoogle Scholar
  3. Bloch, S., A. L. Hales, and M. Landisman, Velocities in the crust and upper mantle of southern Africa from multi-mode surface wave dispersion, Bull. Seism. Soc. Am., 59, 1599–1629, 1969.Google Scholar
  4. Brudzinski, M. R., W.-P. Chen, R. L. Nowack, and B.-S. Huang, Variations of P wave speeds in the mantle transition zone beneath the northern Philippine Sea, J. Geophys. Res., 102, 11,815–11,827, 1997.CrossRefGoogle Scholar
  5. Carlson, R. W., T. L. Grove, M. J. de Wit, and J. J. Gurney, Program to study crust and mantle of the Archean craton in southern Africa, Eos, Trans. Am. Geophys. Union, 77(29), 273, 277, 1996.CrossRefGoogle Scholar
  6. Chapman, C. H., A new method for computing synthetic seismograms, Geophys. J. R. Astron. Soc, 54, 481–518, 1978.CrossRefGoogle Scholar
  7. Cichowicz, A. and R. W. E. Green, Tomographic study of upper mantle structure of the South African continent, using waveform inversion, Phys. Earth Planet. Inter, 72, 276–285, 1992.CrossRefGoogle Scholar
  8. De Wit, M. J., C. Roering, R. J. Hart, R. A. Armstrong, C. E. J. Ronde, R. W. E. Green, M. Tredoux, E. Peberdy, and R. A. Hart, Formation of an Archaean continent, Nature, 357, 553–562, 1992.CrossRefGoogle Scholar
  9. Dey, S. C., B. L. N. Kennett, J. R. Bowman, and A. Goody, Variations in upper mantle structure under northern Australia, Geophys. J. Int., 114, 304–310, 1993.CrossRefGoogle Scholar
  10. Durrheim, R. J., Seismic refraction investigations of the Kaapvaal craton, S. African Geophys. Rev., 2, 29–35, 1998.Google Scholar
  11. Durrheim, R. J. and R. W. E. Green, A seismic refraction investigation of the Archaean Kaapvaal craton, South Africa, using mine tremors as the energy source, Geophys. J. Int., 108, 812–832, 1992.CrossRefGoogle Scholar
  12. Eales, H. V., A first introduction to the geology of the Bushveld complex, and those aspects of South African geology that relate to it, in Popular Geoscience Series 2, Council for Geoscience, 84 pp., Pretoria, South Africa, 2001.Google Scholar
  13. Flanagan, M. P. and P. M. Shearer, Global mapping of topography on transition zone velocity discontinuities by stacking SS precursors, J. Geophys. Res., 103, 2673–2692, 1998.CrossRefGoogle Scholar
  14. Freybourger, M., J. B. Gaherty, T. H. Jordan, and coKaapvaal Seismic Group, Structure of the Kaapvaal craton from surface waves, Geophys. Res. Lett., 28, 2489–2492, 2001.CrossRefGoogle Scholar
  15. Gane, P. G., A. L. Hales, and H. O. Oliver, A seismic investigation of the Witwatersrand earth tremors, Bull. Seismol. Soc. Am., 36, 49–80, 1946.Google Scholar
  16. Graham, G. (ed.), Seismological Bulletins (produced monthly), Council for Geoscience, Pretoria, South Africa, April-December issues, 1997.Google Scholar
  17. Graham, G. (ed.), Seismological Bulletins (produced quarterly), Council for Geoscience, Pretoria, South Africa, January–March, April=2-June, July–September and October–December issues, 1998.Google Scholar
  18. Graham, G. (ed.), Seismological Bulletins (produced quarterly). Council for Geoscience, Pretoria, South Africa, January–March and April–June issues, 1999.Google Scholar
  19. Hales, A. L. and I. S. Sacks, Evidence for an intermediate layer from crustal structure studies in the Eastern Transvaal, Geophys. J. R. Astron. Soc, 2, 15–33, 1959.CrossRefGoogle Scholar
  20. Hurich, C. A., S. J. Deemer, and A. Indares, Compositional and metamorphic controls on velocity and reflectivity in the continental crust: An example from the Grenville Province of eastern Québec, J. Geophys. Res., 106, 665–682, 2001.CrossRefGoogle Scholar
  21. James, D. E., M. J. Fouch, J. C. VanDecar, S. van der Lee, and coKaapvaal Seismic Group, Tectospheric structure beneath southern Africa, Geophys. Res. Lett., 28, 2485–2488, 2001.CrossRefGoogle Scholar
  22. Kaiho, K. and B. L. N. Kennett, Three-dimensional seismic structure beneath the Australian region from refracted wave observations, Geophys. J. Int., 142, 651–668, 2000.CrossRefGoogle Scholar
  23. Kennett, B. L. N. (ed.), IASPEI 1991 Seismological Tables, 167 pp., Research School of Earth Sciences, Australian National University, Canberra, Australia, 1991.Google Scholar
  24. Kennett, B. L. N., O. Gudmundsson, and C. Tong, The upper mantle S and P velocity structure beneath northern Australia from broad-band observations, Phys. Earth Planet. Int., 86, 85–98, 1994.CrossRefGoogle Scholar
  25. Kgaswane, E. M., C. Wright, M. T. O. Kwadiba, S. J. Webb, and R. G. McRae-Samuel, A new look at South African seismicity using a temporary network of seismometers, S. Afr. J. Sci., 98, 377–384, 2002.Google Scholar
  26. Kwadiba, M. T. O. G., C. Wright, E. M. Kgaswane, R. E. Simon, and T. K. Nguuri, Pn arrivals and lateral variations of Moho geometry beneath the Kaapvaal craton, Lithos Special issue: The Slave-Kaapvaal Workshop: A Tale of Two Cratons, edited by A. G. Jones, R. W. Carlson, and H. Grutter, 71, 393–411, 2003.Google Scholar
  27. Nguuri, T. K., J. Gore, D. E. James, S. J. Webb, C. Wright, T. G. Zengeni, O. Gwavava, J. A. Snoke, and coKaapvaal Seismic Group, Crustal structure beneath southern Africa and its implications for the formation and evolution of the Kaapvaal and Zimbabwe cratons, Geophys. Res. Lett., 28, 2501–2504, 2001.CrossRefGoogle Scholar
  28. Qiu, X., K. Priestley, and D. McKenzie, Average lithospheric structure of southern Africa, Geophys. J. Int., 127, 563–587, 1996.CrossRefGoogle Scholar
  29. Ringwood, A. E., Role of the transition zone and 660 km discontinuity in mantle dynamics, Phys. Earth Planet. Int., 86, 5–24, 1994.CrossRefGoogle Scholar
  30. Rudnick, R. L. and D. W Fountain, Nature and composition of the continental crust: a lower crustal perspective, Rev. Geophys., 33, 267–309, 1995.CrossRefGoogle Scholar
  31. Ryberg, T., F. Wenzel, A. V. Egorkin, and L. Solodilov, Properties of the mantle transition zone in northern Eurasia, J. Geophys. Res., 103, 811–822, 1998.CrossRefGoogle Scholar
  32. Schimmel, M. and H. Paulssen, Noise reduction and detection of weak, oherent signals through phase-weighted stacks, Geophys. J. Int., 130, 497–505, 1997.CrossRefGoogle Scholar
  33. Silver, P. G., S. S. Gao, K. H. Liu, and cothe Kaapvaal Seismic Group, Mantle deformation beneath southern Africa, Geophys. Res. Lett., 28, 2493–2496, 2001.CrossRefGoogle Scholar
  34. Simon, R. E., The structure of the upper mantle, transition zone and upper-most lower mantle beneath southern Africa from broad-band seismology, Ph.D. thesis, 152 pp., University of the Witwatersrand, Johannesburg, 2003.Google Scholar
  35. Simon, R. E., C. Wright, E. M. Kgaswane, and M. T. O. Kwadiba, The P wavespeed structure below and around the Kaapvaal craton to depths of 800 km, from traveltime and waveforms of local and regional earthquakes and mining-induced tremors, Geophys. J. Int., 151, 132–145, 2002.CrossRefGoogle Scholar
  36. Simon, R. E., C. Wright, M. T. O. Kwadiba, and E. M. Kgaswane, Mantle structure and composition to 800 km depth beneath southern Africa and surrounding oceans from broad-band body waves, Lithos Special issue: The Slave-Kaapvaal Workshop: A Tale of Two Cratons, edited by A. G. Jones, R. W. Carlson, and H. Grutter, 71, 353–367, 2003.Google Scholar
  37. Stankiewicz, J., S. Chevrot, R. D. van der Hilst, and M. J. de Wit, Crustal thickness, discontinuity depth, and upper mantle structure beneath southern Africa: constraints from body wave conversions, Phys. Earth Planet. Int., 130, 235–251, 2002.CrossRefGoogle Scholar
  38. Walck, M. C., The P wave upper mantle structure beneath an active spreading centre: the Gulf of California, Geophys. J. R. Astr. Soc., 76, 697–723, 1984.CrossRefGoogle Scholar
  39. Weidner, D. J. and Y. Wang, Phase transformations: implications for mantle structure, in Earth’s Deep Interior. Mineral Physics and Tomography from the Atomic to the Global Scale, edited by S. Karato, A. M. Forte, R. C. Liebermann, G. Masters, and L. Stixrude, pp. 215–235, Geophysical Monograph 117, American Geophysical Union, Washington, D.C., 2000.CrossRefGoogle Scholar
  40. Willmore, P. L. and A. M. Bancroft, The time-term approach to refraction seismology, Geophys. J. R. Astron. Soc., 3, 419–432, 1960.CrossRefGoogle Scholar
  41. Willmore, P. L., A. L. Hales, and P. G. Gane, A seismic investigation of crustal structure in the western Transvaal, Bull. Seismol. Soc. Am., 42, 53–80, 1952.Google Scholar
  42. Wright, C., M. T. O. Kwadiba, E. M. Kgaswane, and R. E. Simon, The structure of the crust and upper mantle to depths of 320 km beneath the Kaapvaal craton, from P wave arrivals generated by regional earthquakes and mining-induced tremors, J. Afr. Earth Sci., 35, 477–488, 2002.CrossRefGoogle Scholar
  43. Wright, C., E. M. Kgaswane, M. T. O. Kwadiba, R. E. Simon, T. K. Nguuri, and R. McRae-Samuel, South African seismicity, April 1997-April 1999, and regional variations in the crust and uppermost mantle of the Kaapvaal craton, Lithos Special issue: The Slave-Kaapvaal Workshop: A Tale of Two Cratons, edited by A. G. Jones, R. W. Carlson, and H. Grutter, 71, 369–392, 2003.Google Scholar
  44. Zhao, D., A. Hasegawa, and S. Horiuchi, Tomographic imaging of P and S wave velocity structure beneath northeastern Japan, J. Geophys. Res., 97, 19909–19928, 1992.CrossRefGoogle Scholar
  45. Zhao, M., C. A. Langston, and A. A. Nyblade, Upper mantle velocity structure beneath southern Africa from modeling regional seismic data, J. Geophys. Res., 104, 4783–4794, 1999.CrossRefGoogle Scholar

Copyright information

© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2004

Authors and Affiliations

  • C. Wright
    • 1
  • M. T. O. Kwadiba
    • 1
    • 2
  • R. E. Simon
    • 1
  • E. M. Kgaswane
    • 1
  • T. K. Nguuri
    • 1
  1. 1.Bernard Price Institute of Geophysical Research, School of GeosciencesUniversity of the WitwatersrandWitsSouth Africa
  2. 2.Department of Geological SurveyLobatseBotswana

Personalised recommendations