Inversion of anomalies due to remanent magnetisation: an example from the Black Hill Norite of South Australia

Abstract

There has been a recent renewal of interest in estimation of magnetisation direction for improved magnetic field interpretation. In this study we review practical issues of recovering magnetisation direction using magnetic moments of the causative body. We also investigate the recovery of magnetisation directly from multi-stage inversion of magnetic field data. We apply these methods to the well-studied magnetic anomalies over the Black Hill Norite of South Australia. Both magnetic moment analysis and inversion recover consistent magnetisation directions, and these can be used in further studies to estimate geological structure. The magnetisation directions agree closely with measured remanent magnetisation directions. This implies that the anomalies are principally due to the remanence of a high Koenigsberger ratio (Q).

KEY WORDS:

• magnetic
• moment
• anomaly
• remanent
• magnetisation
• inversion

Acknowledgements

We thank PIRSA for supply of the magnetic data for this study. The magnetic moment analysis used was coded by Blair McKenzie and Tony White based on algorithms by Schmidt and Clark. All model computations used ModelVision.