Local to regional scale structural controls on mineralisation and the importance of a major lineament in the eastern Mount Isa Inlier, Australia: Review and analysis with autocorrelation and weights of evidence

Abstract

Although major crustal lineaments may play an important role in mineralisation, the relationship between lineaments and mineral deposits can be quite cryptic, and structural controls may vary as a function of scale along lineaments. Major lineaments alone may be of limited use for detailed target generation. The Cloncurry Lineament in the Eastern part of the Mount Isa Inlier is a crustal scale structure defined by potential field-derived ‘worms’. Weights-of-evidence quantifies the association between mineral occurrences and this lineament. Autocorrelation is used to recognise structural controls on mineralisation at different scales, by progressively limiting the lengths of the vectors between mineral occurrence points in the autocorrelation plot. The weights-of-evidence analysis shows that Au, Au–Cu, Cu–Au and Cu deposits have a positive spatial correlation to the Cloncurry Lineament, which suggests it that acted as a primary crustal scale control on the localisation of Cu and Au through focussing mineralisation systems on a broad scale. However, autocorrelation defines a variety of local structural controls, which can be interpreted as shear zones, variably oriented fault sets, en echelon fault arrays, and potentially the orientation of bedding and/or iron formations which localise fluid flow and mineral deposition at finer scales. The results suggest that major lineaments defined by geophysical contrasts can be used in conjunction with techniques of spatial analysis for targeting structurally controlled mineralisation in areas under thin cover adjacent to mineralised terrains such as the Mt Isa Inlier.