1887
Volume 45, Issue 4
  • ISSN: 0812-3985
  • E-ISSN: 1834-7533

Abstract

[

The resultant magnetisation vector of a compact magnetic source can be obtained through simultaneous inversion for geometry and magnetisation. The resultant magnetisation vector and induced field vector lie on a plane that intersects the transformed apparent polar wander path to provide estimates for magnetic remanence, susceptibility and age.

,

The remote determination of magnetic remanence in rocks is a method that has largely been ignored because of the ambiguity associated with the estimation of both the Koenigsberger ratio and remanent magnetisation direction. Our research shows that the resultant magnetisation direction can be derived directly through inversion of magnetic data for an isolated magnetic anomaly from a compact magnetic source. The resultant magnetisation direction is a property of the target magnetic rocks and a robust inversion parameter. The departure angle of the resultant magnetisation vector from that of the inducing magnetic field is an important indicator of the existence of remanent magnetisation and the inversion process can detect departures that are not easily detected by visual inspection. This departure angle is called the apparent resultant rotation angle or ARRA.

The induced field vector, remanent magnetisation vector and resultant magnetisation vector lie on the plane of a great circle. We find the intersection of the transformed polar wander vector trace with the great circle plane to obtain one or more possible solutions for the remanent magnetisation vector. Geological deduction will normally allow us to reduce the ambiguity for multiple solutions to obtain the most likely remanent magnetisation direction. Once the remanent magnetisation direction is established, it is then possible to determine the Koenigsberger ratio and magnetic susceptibility for the target.

We illustrate the methodology using survey data over the Black Hill Norite which also has extensive palaeomagnetic data available for comparison with the inversion results. We then apply the remote remanence estimation (RRE) method to a systematic study of a large number of intrusive pipes in the Thomson Orogen, New South Wales. The corrected magnetic susceptibility and remanence properties, spatial distribution and underlying uncertainties are evaluated for their potential use by diamond explorers. The additional information assists with differentiating kimberlites from other intrusive pipes based on age and remanence properties.

]
© 2014 ASEG
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2014-12-01
2026-01-22

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References

  1. Caratori Tontini F. Pedersen L. B. 2008 Interpretating magnetic data using integral moments: Geophysical Journal International 174 815 824 10.1111/j.1365‑246X.2008.03872.x
    https://doi.org/10.1111/j.1365-246X.2008.03872.x [Google Scholar]
  2. Clark D. A. 1997 Magnetic petrophysics and magnetic petrology: aids to geological interpretation of magnetic surveys: AGSO Journal of Australian Geology & Geophysics 17 83 103
    [Google Scholar]
  3. Clark D. A. 2012 New methods for interpretation of magnetic vector and gradient tensor data I: eigenvector analysis and the normalised source strength: Exploration Geophysics 43 267 282 10.1071/EG12020
    https://doi.org/10.1071/EG12020 [Google Scholar]
  4. Clark D. A. 2013 New methods for interpretation of magnetic vector and gradient tensor data II: Application to the Mount Leyshon Anomaly, Queensland: Exploration Geophysics 44 114 127 10.1071/EG12066
    https://doi.org/10.1071/EG12066 [Google Scholar]
  5. Clark D. A. 2014 Methods for determining remanent and total magnetization of magnetic sources – a review: Exploration Geophysics 45 271 304 10.1071/EG14013
    https://doi.org/10.1071/EG14013 [Google Scholar]
  6. Clark D. A. Lackie M. A. 2003 Palaeomagnetism of the Early Permian Mount Leyshon Intrusive Complex and the Tuckers Igneous Complex, North Queensland, Australia: Geophysical Journal International 153 523 547 10.1046/j.1365‑246X.2003.01907.x
    https://doi.org/10.1046/j.1365-246X.2003.01907.x [Google Scholar]
  7. Cordani R. Shukowsky W. 2009 Virtual Pole from magnetic Anomaly (VPMA): a procedure to estimate the age of a rock from its magnetic anomaly only: Journal of Applied Geophysics 69 96 102 10.1016/j.jappgeo.2009.07.001
    https://doi.org/10.1016/j.jappgeo.2009.07.001 [Google Scholar]
  8. Ellis, R. G., de Wet, B., and MacLeod, I. N., 2012, Inversion of magnetic data for remanent and induced sources: ASEG-PESA 22nd International Geophysical Conference and Exhibition, Extended Abstracts, 4 pp.
  9. Foss, C. A., and McKenzie, K. B., 2006, Inversion of anomalies due to remanent magnetization – an example from the Black Hill Norite of South Australia: ASEG AESC2006, Extended Abstracts, 9 pp.
  10. Foss C. A. McKenzie K. B. 2011 Inversion of anomalies due to remanent magnetization: an example from the Black Hill Norite of South Australia: Australian Journal of Earth Sciences 58 391 405 10.1080/08120099.2011.581310
    https://doi.org/10.1080/08120099.2011.581310 [Google Scholar]
  11. Glen, R. A., Saeed, A., Hegarty, R., Percival, I. G., Bodorkos, S., and Griffin, W. L., 2010, Preliminary zircon data and tectonic framework for the Thomson Orogen, northwestern NSW: Geological Survey of NSW, Exploration in the House, Parliament House, Macquarie St., 20 pp., 6 fig.
  12. Grant, F. S., and West, G. F., 1965, Interpretation theory in applied geophysics: McGraw-Hill.
  13. Li Y. Shearer S. Haney M. Dannemiller N. 2010 Comprehensive approaches to the inversion of magnetic data affected by remanent magnetization: Geophysics 75 L1 L11 10.1190/1.3294766
    https://doi.org/10.1190/1.3294766 [Google Scholar]
  14. MacLeod, I. N., and Ellis, R. G., 2013, Magnetic vector inversion, a simple approach to the challenge of varying direction of rock magnetization: ASEG forum on The Application of Remanent Magnetization and Self-Demagnetisation Estimation to Mineral Exploration, Extended Abstracts, 41–46.
  15. McKenzie, K. B., Hillan, D., and Foss, C. A., 2012, An improved search for magnetization direction: ASEG 22nd International Conference and Exhibition, Extended Abstracts, 4 pp.
  16. Medeiros W. E. Silva J. B. 1995 Simultaneous estimation of total magnetization direction and 3-D spatial orientation: Geophysics 60 1365 1377 10.1190/1.1443872
    https://doi.org/10.1190/1.1443872 [Google Scholar]
  17. Merrill, R. T., McElhinny, W., and McFadden, P. L., 1996, The magnetic field of the Earth: Academic Press.
  18. Morris W. Ugalde H. Thompson V. 2007 Magnetic remanence constraints on magnetic inversion models: The Leading Edge 26 960 964 10.1190/1.2769548
    https://doi.org/10.1190/1.2769548 [Google Scholar]
  19. Pratt, D. A., McKenzie, K. B., and White, A. S., 2012, The remote determination of magnetic remanence: ASEG-PESA 22nd International Geophysical Conference and Exhibition, Extended Abstracts, 5 pp.
  20. Rajagopalan S. Clark D. A. Schmidt P. W. 1995 Magnetic mineralogy of the Black Hill Norite and its aeromagnetic and palaeomagnetic implications: Exploration Geophysics 26 215 220 10.1071/EG995215
    https://doi.org/10.1071/EG995215 [Google Scholar]
  21. Schmidt P. W. Clark D. A. 1998 The calculation of magnetic components and moments from TMI: a case study from the Tuckers igneous complex, Queensland: Exploration Geophysics 29 609 614 10.1071/EG998609
    https://doi.org/10.1071/EG998609 [Google Scholar]
  22. Schmidt P. W. Clark D. A. Rajagopalan S. 1993 A historical perspective of the Early Palaeozoic APWP of Gondwana: new results from the Early Ordovician Black Hill Norite of South Australia: Exploration Geophysics 24 257 262 10.1071/EG993257
    https://doi.org/10.1071/EG993257 [Google Scholar]
  23. Smith M. L. Pillans B. J. McQueen K. G. 2009 Paleomagnetic evidence for periods of intense oxidation weathering, McKinnons mine, Cobar, New South Wales: Australian Journal of Earth Sciences 56 201 212 10.1080/08120090802547033
    https://doi.org/10.1080/08120090802547033 [Google Scholar]
  24. Turner, S. P., 1991, Late-orogenic, mantle-derived, bi-modal magmatism in the southern Adelaide Foldbelt, South Australia: Ph.D. thesis, University of Adelaide.
/content/journals/10.1071/EG14031
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Remote remanence estimation (RRE)
Exploration Geophysics 45, 314 (2014); https://doi.org/10.1071/EG14031
/content/journals/10.1071/EG14031
/content/journals/10.1071/EG14031
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  • Article Type: Research Article
Keyword(s): inversion, kimberlite, magnetisation, remanence, resultant, susceptibility.

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