Inversion of TMI Data for Induced and Remanent Magnetization to Target Gold Mineralization in Central Ghana

Traditional susceptibility inversion can be misleading in areas with strong remanent magnetization. We have developed a novel method for simultaneous inversion of the Total Magnetic Intensity (TMI) data into the vectors of induced and remanent magnetizations.

This method incorporates regularization techniques that enforce spatial coherence and geological plausibility, allowing for the retrieval of physically meaningful models even in the presence of strong remanence.

We applied a novel simultaneous inversion method to TMI data acquired over Asankrangwa Gold Belt, central Ghana, to improve gold targeting. The inverse magnetization models were jointly analyzed with the chargeability model produced by 3D inversion of the airborne VTEM survey over the same area. Magnetic lows coinciding with chargeability highs, consistent with hydrothermal alteration zones, were identified within the Mpatasie concession. Bandpass filtering was used to enhance shallow anomalies, and focusing regularization was applied during inversion to recover compact features.

A key result is the recovery of a magnetic low where susceptibility alone suggested a high, emphasizing the value of our method. The coincident magnetic low and chargeability high were interpreted as indicative of sulphide-rich gold mineralization, confirmed by drill results. This integrated geophysical workflow offers a powerful tool for mineral exploration in complex geological environments.