Identifying geological structural complexity using aeromagnetic data: Application to gold exploration

Abstract

Aeromagnetic data can be effectively used for the exploration of gold and other hydrothermal deposits because favorable environments and/or the ore forming process are associated with changes in the amounts of magnetite in the rocks. Archaean lode‐gold deposits are spatially associated with major shear zones and structural control at the deposit scale is usual as crustal breaks act as conduits for mineralizing fluids. Magnetite destructive alteration associated with shear zones results in linear negative anomalies in magnetic data allowing these structures to be mapped. Here we describe automatic image analysis methods applied to aeromagnetic datasets to provide an efficient and non‐subjective means of identifying geologically favourable environments for Archaean lode‐gold deposits. Specifically, areas of structural complexity are sought based on two structural scenarios: the density of structural contacts and the diversity of structure orientations within local neighbourhoods. Our method firstly finds lineaments using texture analysis to examine local magnetic variations and line‐like feature detection to find laterally continuous regions within the texture output. The detected lineaments are then analysed for their spatial associations such as crossings, contacts, and orientation changes to generate two heat maps that highlight structure contact density and structure orientation entropy. An experiment was conducted using an aeromagnetic data from the Goldfields area in Western Australia and the areas identified as structurally complex by the proposed method are highly correlated with the known gold deposits in the area.