Hyperspectral remote sensing applied to uranium exploration: A case study at the Mary Kathleen metamorphic-hydrothermal U-REE deposit, NW, Queensland, Australia

- The skarn-hosted U-REE Mary Kathleen (MK) deposit is investigated with HyMap hyperspectral data.
- Metamorphic-hydrothermal and weathered products are seamlessly mapped.
- Zonal alteration includes halos of andradite and pervasive calcite, scapolite, epidote and hornblende.
- Kaolinite, montmorillonite and goethite comprise the surface footprint of the MK mineralization.
- Hyperspectral remote sensing proved as an important complementary tool for U-REE exploration.

The HyMap airborne hyperspectral scanner provides 128 spectral bands between Visible-Near Infrared (VNIR) and Short Wave Infrared (SWIR) wavelengths (0.45-2.5 μm). It transcends any currently operational orbital multispectral sensor (ASTER, WV3, Landsat-8) for mineral mapping in exposed areas. Here we employ HyMap data to study the type and spatial distribution of mineral assemblages in the world-class Mary Kathleen metamorphic-hydrothermal Uranium (U) - Rare Earth Elements (REE) deposit, situated in the Mount Isa Province, Australia. The focus is on Ca-bearing silicates and Fe-rich minerals. Two spectral libraries were built for the task based on publicly available data. The VNIR library comprises goethite and andradite. The SWIR library includes hornblende, epidote, calcite, kaolinite and montmorillonite. Scapolite SWIR spectra were yielded autonomously. These mineral spectra were used as endmembers for HyMap data classification and production of mineral abundance maps. Spectral Angle Mapper (SAM) and Mixture Tuned Matched Filtering (MTMF) were the methods employed for image classification. Results were combined in RGB color composites and enhanced to provide high quality maps of Ca-bearing silicates and other minerals associated with the Ca-skarn hosted U-REE mineralization. The spatial correlation of mineral abundance maps produced here and known exposed surfaces of equivalent minerals in the open pit mine proved plausible. Wallrock alteration halos show characteristic zonal arrangements. Andradite occurs in the outer alteration halo. Selectively pervasive alteration is characterized by calcite, scapolite, epidote and hornblende. These specific mineral types and their distribution in the Mary Kathleen deposit indicate multiple stages of metasomatic processes, resulting in high-temperature and retrograde Ca-bearing silicates associations. In addition, kaolinite, montmorillonite and goethite are the surface footprint of the skarn-hosted U-REE mineralization. HyMap proved to be a solid tool to characterize exposed hydrothermal mineral systems associated to skarns enriched in U and REE, providing the framework for advanced geologic interpretation and conception of a regional exploration model. The occurrence of goethite, kaolinite and montmorillonite and their zonal relationship with the U-REE mineralization, as also mapped here with HyMap, may be also an additional guide for U exploration in the Mount Isa Province, especially if combined with other exploration methods.