Mapping Mineral Footprints Through Cover Using Surface and Subsurface Mineralogy and Geochemistry

Abstract

Mapping footprints of mineral deposits is often hindered by substantial weathering profiles developed atop buried mineralization. Understanding the mineralogical and geochemical trends in the weathering profile can be crucial for enabling successful exploration, especially when using remote sensing data. Drill core hyperspectral and geochemical data were analyzed in detail to develop a 3D mineralogical/geochemical model that allowed an evaluation of which footprints, associated with gold mineralization in the Bulong area of the Eastern Goldfields (Western Australia), could be discovered at the surface. The combined analysis of hyperspectral and geochemical drill core data also helped to map out clusters of mineral assemblages that are 1) associated with gold, 2) are inversely correlated with gold and/or 3) form a halo in proximity to gold mineralization. White mica was found to be of phengitic composition proximal to gold mineralization, whereas talc-carbonate alteration forms a shell around the mineralized intervals. Phengitic white micas were successfully traced at the surface, indicating potentially new prospective areas. However, due to issues with vegetation and related overlapping absorptions with talc and carbonate, talc-carbonate alteration could not be found in the airborne hyperspectral data. The Bulong case study highlights the need for advancing vegetation un-mixing of remotely sensed hyper-and multispectral imagery. Recent efforts of un-mixing green and dry vegetation on a per pixel basis considerably improved the mapping of single mineralogical components of alteration and background mineral assemblages.