Abstract:

Interactive inversion of arbitrary shaped three-dimensional body is used to explain complex magnetic body. This approach can be described as follow: the vertical line element method is used to calculate the geological magnetic anomalies, and the visualized technology was used to achieve human-computer interactive inversion. The accuracy affect factors were analyzed through theoretical model: when the number of split sections decrease from 17 to 3, the approximate calculation of the mean square error increased from 0.099 nT to 3.160 nT. The approximate calculation errors will be much smaller when the divided sections number is more. When the divided sections number is fixed, as the center depth increases from 100 meters to 500 meters, the maximum relative error decreased from 39.19% to 7.84%. This indicated that the deeper the center depth, the smaller approximate calculation error gets. Therefore how to divide magnetic body reasonably is the main aspect to improve inversion precision. And two improvement measures are proposed: the model division criterion and potential curve restriction criterion were employed and that can be improved the calculation accuracy. This method is applied in estimating banded iron formation (BIF) of a deposit in Eyre Peninsula, South Australia. The inversion interpreting result is validated by boreholes.

Key words: geophysical prospecting, magnetic abnormity, three-dimensional body, interactive inversion, Eyre Peninsula, banded iron formation