Enhanced detection of gossans using hyperspectral data: Example from the Cape Smith Belt of northern Quebec, Canada

Abstract

Owing to the links between gossans and mineral deposits, detecting gossans by remote sensing means is essential for mineral exploration. In northern regions, gossans can develop as thin oxidized surfaces, named thin gossans, that can be covered with lichens. This study investigates the effects of spectral mixing between such gossans with lichens and their rock substrates using laboratory spectroscopic data obtained from samples collected in the Cape Smith Belt of Canada. These observations are then scaled up to the airborne hyperspectral data obtained from the same area. Our laboratory results indicate that the presence of lichens on gossans induces a general spectral shift towards shorter wavelengths of the iron absorption typical of gossan spectra. The opposite shift is observed due to the influence of the rock substrates. These effects can thus impede classification of gossans based on the interpretation of iron oxide mineralogy from spectra. Our airborne spectral results suggest that thin gossans can be detected and discriminated from thick gossans, and further broken down into several classes according to their host rock substrates. The ability to define distinct classes of thin gossans is significant since the association of these gossans with specific rock substrates can be exploited for exploration. The ability to distinguish thin and thick gossans alone can contribute to mineral exploration since it can be either the former or the latter group of gossans that acts as an ore deposit vector.