1887
Volume 26, Issue 2-3
  • ISSN: 0812-3985
  • E-ISSN: 1834-7533

Abstract

Aeromagnetic surveying carried out in the Abminga area by Mines and Energy South Australia (MESA) and published in 1993 identified several groups of isolated magnetic anomalies which have a strong prima facie resemblance to kimberlite or lamproite diatreme fields. Aeromagnetic anomalies produced by diatremes are characterised as being generally of low amplitude, isolated, compact, di-polar, of short strike length and indicative of a shallow source.

This paper compares data flown for diamond explorer Caldera Resources NL at 100 metre line spacing with the published 400 metre line spaced data. Modelling of several of the anomalies using an inversion algorithm gives very good fits to shallow pipe-like bodies with appreciable depth extent. Conventional field exploration techniques such as loaming have not been successful but floaters of ultramafic rocks collected at 3 anomaly sites have been petrographically identified as extremely weathered kimberlites. Chromite grains recovered from these carry up to 59% CrzCX Diamonds have not yet been recovered but active exploration is in progress.

It is concluded that while most of the magnetic anomalies were successfully identified from the 400 metre line spaced data, useful modelling can only be done using more detailed data. Although positive identification of the source of these magnetic anomalies is still awaited they constitute some very intriguing exploration targets.

© 1995 ASEG
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1995-06-01
2026-01-15

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References

  1. Borner, J. E., 1994, Various petrographic reports for Caldera Resources NL: unpublished.
  2. Jenke, G. and Cowan, D. R., 1994, Geophysical Signature of the Ellendale Lamproite Pipes, Western Australia, in Geoph. Signatures of W. A. Min. Deposits, Geol. and Geophs. Dept. Univ. of W. A., and Aust. Soc. Explor. Geoph., Eds. Dentith M.C., Frankombe K.E., Ho S.E., Shepherd J.M., Groves D.I., and Trench A., 403-414.
  3. Kelly, P. R., 1994, Determination of Uranium Concentration in Individual Zircon Grains using Fission Track Analysis: Geotrack Report 513, unpublished.
  4. Kresten, P. 1973, Kimberlitic Zircons: Proceedings of the First International Kimberlite Conference 191-194.
  5. Maboko, M. A. H., 1992, Geochronological Evidence for a Juxtaposition of Two Proterozoic Metamorphic Terrains in the Musgrave Ranges, Central Australia: Aust. Journal of Earth Sciences Vol. 39; 457-471.
  6. Macnae, J. C, 1979, Kimberlites and Exploration Geophysics: Geophysics, vol 44, pp 1395-1415.
  7. Major, R. B. & C. H. H. Conor, 1993, Musgrave Block, The Geology of South Australia Vol.1. The Precambrian. MESA Bull 54, 156-167.
  8. Middleton, D. D. 1994, Various Geological reports prepared for Caldera Resources NL: unpublished.
  9. Pooley, G. 1994, Various Reports for Caldera Resources NL: unpublished.
  10. Robson, H. R. 1984, Final Report EL 1187: Stockdale Prospecting Ltd, Gem JV, unpublished.
  11. Smith, C. B., W. J. Atkinson and E. W. J. Tyler. 1993, Diamond Exploration in Western Australia, Northern Territory and South Australia, in Aspects of the Discovery of Some Important Mineral Deposits in Australia: Mono. Series 17, Aus. I.M.M. Melbourne, 429-454.
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  • Article Type: Research Article
Keyword(s): Aeromagnetic anomalies; diamond exploration; kimberlite rocks; magnetic modelling

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