Abstract

Recent advances in magnetic surveying have focused on achieving higher levels of instrument sensitivity and better definition of the morphology of the magnetic field through the use of measured magnetic field gradients. Images derived from these high-resolution magnetic surveys are widely used as a direct proxy for geologic mapping, especially in areas of limited surface exposure. Commonly, this involves the application of skeletonization (e.g., multiscale edges, or “worms”), Euler, and/or wavelet-based processing routines to generate estimates of the location, and morphology of the edges of anomalous source bodies. The primary assumption for all of these image- (map-) based data processing routines is that the observed magnetic data set provides an unbiased representation of the magnetic mineral variation in the surface and subsurface geology. This assumption may be valid when the observed magnetic anomalies are greater than 5000 nT and the topography is relatively flat, but it is certainly not valid when the observed anomalies are less than 100 nT and topographic variations exceed 100 m. Indeed, in some situations, topographic variations of less than 20 m can lead to geologically erroneous conclusions derived from ground magnetic surveys.

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