An interpretation of high-resolution aeromagnetic data over the Manitouwadge greenstone belt, Ontario, Canada.

Abstract

The aim of this study is to interpret aeromagnetic data using 3D techniques. The data consist of eleven high resolution surveys over the Manitouwadge greenstone belt of the Superior Province, Ontario. The interpretation was calibrated to the detailed geological mapping of the area by Zaleski et. al. (1995) The study has three components. First, the data and grid quality were maximized to maintain as much of the high frequency component of the flight line data as possible while minimizing levelling errors and gridding artefacts. Second, a number of 3D interpretation techniques was investigated. Third, the 3D interpretation techniques were applied to the data over the Manitouwadge study area. Grid improvement techniques, particularly micro-levelling and trend reinforcement, were found to be necessary to maximize grid quality. The 3D interpretation techniques used included apparent magnetic susceptibility mapping, analytic signal, horizontal gradient of pseudo-gravity, potential field tilt and Euler deconvolution as well as first and second vertical derivatives. Each method enhances a different component of the total field intensity and complemented each other when interpreted in combination. The apparent susceptibility map combined with the horizontal gradient of pseudo-gravity maxima produced an image that approximates the mapped geology. Calibrating the magnetic interpretation to the known geology allowed the extrapolation of supracrustal rock units into areas of limited geological mapping. The presence of supracrustal units in the engulfing Black Pic tonalitic batholith extends the geological mapping and illustrates regional deformation.