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Interpretation of magnetic anomalies due to relatively-small discrete magnetic bodies
195
INTERPRETATION SMALL DISCRETE
C.B. KIRKPATRICK L.A.
Richardson
OF MAGNETIC ANOMALIES MAGNETIC BODIES
DUE TO RELATIVELY-
and R.L. RICHARDSON
and Assoc.
Pty. Ltd.
(Australia)
The interpretation of magnetic anomalies is greatly facilitated by the assumption that the causative body possesses a simple geometrical shape. Most of the conventional body types used are frequently not realistic and do not provide an adequate match to naturally occurring body shapes. However many bodies can be more satisfactorily matched by the ellipsoidal shaped model (e.g., discrete ironstone bodies, volcanic pipes and lens shaped bodies of magnetic rock). Flexibility in adjusting the shape and depth to the top of the model as well as the dip and strike, make the ellipsoidal model superior to existing models such as the sphere, the prism or the dyke-like body. This paper outlines the mathematical theory of a magnetic interpretation technique that has been applied successfully in Precambrian shield environment for the analysis of magnetic anomalies due to relatively small magnetic bodies. The therory and its application was developed in 1953 by C.B. Kirkpatrick and the late L.A. Richardson and has since been computerized such that profiles and contours of magnetic intensity for ellipsoidal bodies of any geometry and attitude are quickly and economically computer-plotted for direct comparison with field results.
EXPERIENCE WITH TRANSFORMATION TO THE POLE
J.L. CRIBB’ C.S.R.
OF AEROMAGNETIC
DATA
and I.R. VICKERS’
Research
Laboratories,
Rhodes,
N.S. W. (Australia)
Previously hand-contoured aeromagnetic data from an area in Eyre Peninsula, South Australia have been taken and transformed to the pole. This process corrects the asymmetry introduced by the inclination of the earth’s magnetic field. The results show, typically, magnetic anomalies shifted up to about 0.4 km to the magnetic south. To investigate these effects further the same data were transformed to a position where the earth’s field was at 20” I Presently
with C.S.I.R.O.,
Mineral
Physics,
North
Ryde,
N.S.W.,
Australia.
INTERPRETATION SMALL DISCRETE
C.B. KIRKPATRICK L.A.
Richardson
OF MAGNETIC ANOMALIES MAGNETIC BODIES
DUE TO RELATIVELY-
and R.L. RICHARDSON
and Assoc.
Pty. Ltd.
(Australia)
The interpretation of magnetic anomalies is greatly facilitated by the assumption that the causative body possesses a simple geometrical shape. Most of the conventional body types used are frequently not realistic and do not provide an adequate match to naturally occurring body shapes. However many bodies can be more satisfactorily matched by the ellipsoidal shaped model (e.g., discrete ironstone bodies, volcanic pipes and lens shaped bodies of magnetic rock). Flexibility in adjusting the shape and depth to the top of the model as well as the dip and strike, make the ellipsoidal model superior to existing models such as the sphere, the prism or the dyke-like body. This paper outlines the mathematical theory of a magnetic interpretation technique that has been applied successfully in Precambrian shield environment for the analysis of magnetic anomalies due to relatively small magnetic bodies. The therory and its application was developed in 1953 by C.B. Kirkpatrick and the late L.A. Richardson and has since been computerized such that profiles and contours of magnetic intensity for ellipsoidal bodies of any geometry and attitude are quickly and economically computer-plotted for direct comparison with field results.
EXPERIENCE WITH TRANSFORMATION TO THE POLE
J.L. CRIBB’ C.S.R.
OF AEROMAGNETIC
DATA
and I.R. VICKERS’
Research
Laboratories,
Rhodes,
N.S. W. (Australia)
Previously hand-contoured aeromagnetic data from an area in Eyre Peninsula, South Australia have been taken and transformed to the pole. This process corrects the asymmetry introduced by the inclination of the earth’s magnetic field. The results show, typically, magnetic anomalies shifted up to about 0.4 km to the magnetic south. To investigate these effects further the same data were transformed to a position where the earth’s field was at 20” I Presently
with C.S.I.R.O.,
Mineral
Physics,
North
Ryde,
N.S.W.,
Australia.