Automatic Analysis of Aeromagnetic Images for Gold Exploration

Abstract

Archaean lode gold mineralisation is known to occur near major crustal breaks manifesting as large-scale shear zones; which act as conduits for mineralising fluids. Mineralisation occurs in regions of structural complexity adjacent to the shear zones. This paper reports on-going image processing research that aims to automatically detect such geologically significant characteristics from aeromagnetic data for the prospectivity analysis. The current system finds the regions of magnetic discontinuity that are related to shear zones and lithological boundaries, and then identifies prospective regions nearby. The regions of magnetic discontinuity are detected using a combination of texture analysis and bilateral symmetric feature detection, where line-like features representing high local magnetic variations are identified. Then the areas adjacent to the regions of magnetic discontinuity are examined using a 2D fractal surface analysis technique to search for areas with complex magentic expressions that are related to structural complexity. A preliminary experiment was conducted using aeromagnetic data from the Yilgarn Craton in Western Australia and the regions selected by the proposed system contained over 76% of all known deposit locations and 82% of the greater than 1 tonne-deposit locations. Our on-going research also includes identifying the major shear zones from the regions of discontinuity to examine their spatial and geometrical characteristics.