Alteration mapping on drill cores using a HySpex SWIR-320m hyperspectral camera: Application to the exploration of an unconformity-related uranium deposit (Saskatchewan, Canada)

In mineral exploration, the search for geophysical, geochemical, and mineralogical pathfinders is of critical importance, and many techniques have been used to detect the presence of mineralization and related host-rock alteration. In the case of unconformity-type uranium deposits that are spatially-linked to unconformities between sedimentary basin and underlying basement rocks, hydrothermal fluid-rock interactions produced extended alteration envelopes which are used to target mineralization and are therefore important guides for uranium exploration. The purpose of this study is to evaluate the utility of hyperspectral mapping of alteration minerals in drill core samples using the HySpex SWIR-320m hyperspectral camera that covers the 1300-2500 nm (SWIR) spectral range. A series of representative samples, including pegmatite, pelitic gneiss, and sandstone, from the area around the Cigar Lake uraniumdeposit (Athabasca Basin, Saskatchewan, Canada) were analyzed by SWIR reflectance spectroscopy and opticalmicroscopy. An algorithm was developed and implemented in the IDL language to determine both the positions and depth of diagnostic absorption bands of various minerals, and to calculate semi-quantitative estimates of mineral content. Subsequent petrographic analysis using optical microscopy validated the hyperspectral mapping methodology. Selected alteration minerals present in the core samples, such as clay minerals and carbonates, were mapped. The pseudo-modal mineralogical composition for each sample was determined. The mineral maps highlight the mineralogy and the main petrographic textures such as foliation, bedding, veins, and the geometry of pervasive alteration. This study offers new perspectives for the use of this method in mineralogical analysis of drill core samples and the characterization of hydrothermal alteration. The proposed mineralogical semi-quantification methodology may be used in other geological contexts and should improve the understanding of the mineralogical alteration distribution around hydrothermal metal deposits. (C) 2016 Elsevier B.V. All rights reserved.