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Palaeomagnetism of the Vredefort meteorite crater and implications for craters on Mars


Magnetic surveys of the martian surface have revealed significantly lower magnetic field intensities over the gigantic impact craters Hellas and Argyre than over surrounding regions1. The reduced fields are commonly attributed to pressure demagnetization caused by shock waves generated during meteorite impact2,3, in the absence of a significant ambient magnetic field. Lower than average magnetic field intensities are also observed above the Vredefort meteorite crater in South Africa, yet here we show that the rocks in this crater possess much higher magnetic intensities than equivalent lithologies found elsewhere on Earth. We find that palaeomagnetic directions of these strongly magnetized rocks are randomly oriented, with vector directions changing over centimetre length scales. Moreover, the magnetite grains contributing to the magnetic remanence crystallized during impact, which directly relates the randomization and intensification to the impact event. The strong and randomly oriented magnetization vectors effectively cancel out when summed over the whole crater. Seen from high altitudes, as for martian craters, the magnetic field appears much lower than that of neighbouring terranes, implying that magnetic anomalies of meteorite craters cannot be used as evidence for the absence of the planet's internally generated magnetic field at the time of impact.

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Figure 1
Figure 2: Representative demagnetization diagrams of Vredefort rocks.
Figure 3: Equal area stereonet plots of the magnetic measurements.
Figure 4: Comparison of the angular distance between minimum anisotropy of magnetic susceptibility (AMS) axes and magnetization component directions between two samples.


  1. Acuña, M. H. et al. Global distribution of crustal magnetization discovered by the Mars Global Surveyor MAG/ER experiment. Science 284, 790–793 (1999)

    ADS  Article  PubMed  Google Scholar 

  2. Hood, L. L., Richmond, N. C., Pierazzo, E. & Rochette, P. Distribution of crustal magnetic fields on Mars: Shock effects of basin-forming impacts. Geophys. Res. Lett. 30, 1281, doi:10.1029/2002GL016657 (2003)

    ADS  Article  Google Scholar 

  3. Mohit, P. S. & Arkani-Hamed, J. Impact demagnetization of the Martian crust. Icarus 168, 305–317 (2004)

    ADS  Article  Google Scholar 

  4. Moser, D. E. Dating the shock wave and thermal imprint of the giant Vredefort impact, South Africa. Geology 25, 7–10 (1997)

    ADS  CAS  Article  Google Scholar 

  5. Stöffler, D. & Langenhorst, F. Shock metamorphism of quartz in nature and experiment: I. Basic observation and theory. Meteoritics 29, 155–181 (1994)

    ADS  Article  Google Scholar 

  6. Grieve, R. A. F., Langenhorst, F. & Stöffler, D. Shock metamorphism of quartz in nature and experiment: II. Significance in geoscience. Meteoritics 31, 6–35 (1996)

    CAS  Article  Google Scholar 

  7. Cloete, M. et al. Characterization of magnetite particles in shocked quartz by means of electron- and magnetic force microscopy: Vredefort, South Africa. Contrib. Mineral. Petrol. 137, 232–245 (1999)

    ADS  CAS  Article  Google Scholar 

  8. Hart, R. J., Hargraves, R. B., Andreoli, M. A. G., Tredoux, M. & Doucouré, C. M. Magnetic anomaly near the center of the Vredefort structure: implications for impact-related magnetic signatures. Geology 23, 277–280 (1995)

    ADS  Article  Google Scholar 

  9. Hart, R. J. et al. ‘Super magnetic’ rocks generated by shock metamorphism from the center of the Vredefort impact structure, South Africa. S. Afr. J. Geol. 103, 151–155 (2000)

    Article  Google Scholar 

  10. Hargraves, R. B. Paleomagnetic evidence relevant to the origin of the Vredefort ring. J. Geol. 78, 253–263 (1970)

    ADS  Article  Google Scholar 

  11. Jackson, G. M. Paleomagnetic Study and Magnetic Modeling of the Vredefort Dome. Thesis, Univ. Witwatersrand (1982)

    Google Scholar 

  12. Hargraves, R. B. & Roy, D. W. Paleomagnetism of anorthosite in and around the Charlevoix cryptoexplosion structure, Quebec. Can. J. Earth Sci. 11, 854–859 (1974)

    ADS  Article  Google Scholar 

  13. Halls, H. C. Shock-induced remanent magnetization in late Precambrian rocks from Lake Superior. Nature 255, 692–695 (1975)

    ADS  Article  Google Scholar 

  14. Clark, D. A. & Emerson, D. W. Notes on rock magnetic characteristics in applied geophysical studies. Exp. Geophys. 22, 547–555 (1991)

    Article  Google Scholar 

  15. Gilder, S. & McNulty, B. Tectonic exhumation and tilting of the Mount Givens pluton, central Sierra Nevada, California. Geology 27, 919–922 (1999)

    ADS  Article  Google Scholar 

  16. Wennerström, M. & Airo, M. L. Magnetic fabric and emplacement of the post-collisional Pomovaara Granite Complex in northern Fennoscandia. Lithos 45, 131–145 (1998)

    ADS  Article  Google Scholar 

  17. Crawford, D. A. & Schultz, P. H. Laboratory observations of impact-generated magnetic fields. Nature 336, 50–52 (1988)

    ADS  Article  Google Scholar 

  18. Crawford, D. A. & Schultz, P. H. Electromagnetic properties of impact-generated plasma, vapor and debris. Int. J. Impact Eng. 23, 169–180 (1999)

    Article  Google Scholar 

  19. Turtle, E. P. & Pierazzo, E. Constraints on the size of the Vredefort impact crater from numerical modeling. Meteorit. Planet. Sci. 33, 483–490 (1998)

    ADS  CAS  Article  Google Scholar 

  20. Gilder, S. A., LeGoff, M., Chervin, J. C. & Peyronneau, J. Magnetic properties of single and multi-domain magnetite under pressures from 0 to 6 GPa. Geophys. Res. Lett. 31, L10612, doi:10.1029/2004GL019844 (2004)

    ADS  Article  Google Scholar 

  21. Samara, G. & Giardini, A. Effect of pressure on the Néel temperature of magnetite. Phys. Rev. 186, 577–580 (1969)

    ADS  CAS  Article  Google Scholar 

  22. Schult, A. Effect of pressure on the Curie temperature of titanomagnetites [(1 - x)·Fe3O4–x·TiFe2O4]. Earth Planet. Sci. Lett. 10, 81–86 (1970)

    ADS  CAS  Article  Google Scholar 

  23. Turcott, D. L. & Schubert, G. Geodynamics (Wiley & Sons, New York, 1982)

    Google Scholar 

  24. Grieve, R. A. F. & Pilkington, M. The signature of terrestrial impacts. J. Austr. Geol. Geophys. 16, 399–420 (1996)

    Google Scholar 

  25. Nel, L. T. Geological Map of the Country Around Vredefort. Scale 1:63360 (Union of S. Afr., Dept Mines and Ind., Geol. Surv., Pretoria, 1927)

    Google Scholar 

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We thank A. Galdeano, G. Hulot, M. Cloete, M. Le Goff, Y. Gallet and G. Plenier for discussions and comments. This work was supported by the French Ministries of Foreign Affairs and Education and Research, INSU and the South African National Research Foundation.

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Correspondence to Stuart A. Gilder.

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Carporzen, L., Gilder, S. & Hart, R. Palaeomagnetism of the Vredefort meteorite crater and implications for craters on Mars. Nature 435, 198–201 (2005).

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