Inversion of magnetic data for remanent and induced sources

Abstract

Magnetic field data are of fundamental importance in many areas of geophysical exploration with 3D voxel inversion being a common aid to their interpretation. In the majority of voxel based inversions it is assumed that the magnetic response arises entirely from magnetic induction. However, in the last decade, several studies have found that remanent magnetization is far more prevalent than previously thought. Our experience with numerous minerals exploration projects confirms that the presence of non-induced magnetization is the rule rather than the exception in base metal exploration. In this work we show that failure to accomodate for remanent magnetization in 3D voxel-based inversion can lead to misleading interpretations. We present a technique we call Magnetization Vector Inversion (MVI), which incorporates both remanent and induced magnetization without prior knowledge of the direction or strength of remanent magnetization. We demonstrate our inversion using model studies and field data. Successful application to numerous minerals exploration surveys confirms that incorporating remanent magnetization is essential for the correct interpretation of magnetic field data.