Lithological Mapping by Correlating Magnetic and Gravity Gradient Airborne Measurements

M. H. Dransfield; M. J. Buckingham; F. J. van Kann

doi:10.1071/EG994025

ISSN: 0812-3985
E-ISSN: 1834-7533

Lithological Mapping by Correlating Magnetic and Gravity Gradient Airborne Measurements
Authors M. H. Dransfield^a, M. J. Buckingham^a and F. J. van Kann^a
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^a Department of PhysicsUniversity of Western Australia, Nedlands, , Western Australia, 6009
Publisher: Australian Society of Exploration Geophysicists
Source: Exploration Geophysics, Volume 25, Issue 1, Mar 1994, p. 25 - 30
DOI: https://doi.org/10.1071/EG994025
- Received: 27 Nov 1992
- Accepted: 25 Mar 1993
- Published online: 01 Mar 1994

Abstract

We report here two new applications of the Poisson relation useful when a joint magnetic and gravity gradient survey has been made. In the first, an apparent susceptibility contrast to density contrast ratio map (which we call the “pseudo-lithology” map) can be estimated. In the second, selected values of the above ratio are used in a “pseudo-magnetic” filter to subtract from the magnetic field measurements the effect of a particular rock type. This would be especially useful as a filter of “geological noise” due perhaps to weathered magnetite products, particularly if the latter had an effect over a large area.

As a test of these techniques we have applied them to a simulated joint airborne survey over a model which we designate “Mini-Elura”, in which the magnetic magnitude and vertical gravity gradient anomalies are not visible above the noise due to surficiai variations.

The computed pseudo-lithology map clearly distinguishes the regions of the map dominated by the alluvium source from those due to the “Mini-Elura” orebody, while the pseudo-magnetic filter does very effectively remove the “noise” due to the alluvium from the magnetic map.

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References

Adams, R.L. and Schmidt, B.L., (1980), ‘Geology of the Elura Zn-Pb-Ag Deposit’, in ‘The Geophysics of the Elura Orebody Cobar, New South Wales’, Emerson, DW. ed., The Australian Society of Exploration Geophysics, Sydney, 1–4.
Baranov, V., (1957), ‘A New Method for Interpretation of Aeromagnetic Maps: Pseudo-gravimetric Anomalies’, Geophysics, 22,359–383.
Blackburn, G., (1980), ‘Gravity and magnetic surveys – Elura orebody’, in ‘The Geophysics of the Elura Orebody Cobar, New South Wales’, Emerson, D.W. ed., The Australian Society of Exploration Geophysics, Sydney, 17–24.
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Emerson, D.W., (1980), ‘The Elura Compendium’, in ‘The Geophysics of the Elura Orebody Cobar, New South Wales’, Emerson, D.W. ed., The Australian Society of Exploration Geophysics, Sydney, v-vi.
Eötvös, Roland von, (1896), ‘Untersuchungen über Gravitation und Erdmagnetismus’, Ann. Physik und Chem. n. f. Leipzig, Band 59, 354–400.
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Gidley, PR. and Stuart, D.C., (1980), ‘Magnetic property studies and magnetic surveys of the Elura prospect, Cobar, N.S.W.’, in ‘The Geophysics of the Elura Orebody Cobar, New South Wales’, Emerson, D.W. ed., The Australian Society of Exploration Geophysics, Sydney, 25–30.
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Article Type: Research Article

Keyword(s): airborne geophysics; Elura; gravity gradients; magnetics; Poisson relation; pseudo-lithology; pseudo-magnetics

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Lithological Mapping by Correlating Magnetic and Gravity Gradient Airborne Measurements

Abstract

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