MINE WASTE IDENTIFICATION AND CHARACTERIZATION USING AIRBORNE AND UNCREWED AERIAL SYSTEMS RADIOMETRIC GEOPHYSICAL SURVEYING

Mine waste, historically overlooked in the broader context of mining operations, may hold potential as a source of critical minerals essential for advanced technologies and clean energy applications. With increasing demand for these resources, it is important to explore innovative methods for their extraction and characterization. Airborne radiometric survey data, a.k.a. gamma-ray spectrometry for K, Th, and U, can function like “remote geochemistry,” allowing quick characterization of surficial or shallow (< 1 m depth) features, even in the presence of vegetation. Recent airborne surveys have shown how these data can be applied to mine waste studies. Here, we show new airborne radiometric data collected using both a fixed wing airplane and an uncrewed airborne system (UAS, i.e. “drone”) through the Earth Mapping Resources Initiative can be used to characterize mining waste. For example, a fixed-wing airborne magnetic and radiometric survey was conducted over the central Florida phosphate mining district to support studies of industrial minerals. These data show locally elevated K, U, and Th over mine waste stacks and some remediated areas. Geochemical analyses of samples from these stacks are in progress, with specific interest in rare earth elements.

For fixed-wing surveys, the data footprint is several hundred meters due to flying heights of 90-100 m. Determining local variability within mine waste targets requires even higher resolution data that can only be obtained from measurements taken at a lower ground clearance. The USGS has acquired a radiometric sensor designed to be flown on a UAS ~1-3 m above the ground. We present results of UAS radiometric data collection over two mine waste sites in SW New Mexico: 1) Black Hawk Mine – mined for Ag but with high grade native Ni, and Co arsenides that are associated with carbonate veins and local uraninite, and 2) Copper Flat Mine – a small copper porphyry deposit with waste areas that appear as local radiometric highs in a fixed-wing radiometric survey. We use co-located geochemical data to ground truth our UAS measurements and demonstrate the increase in resolution by comparing our UAS data with recent fixed-wing airborne radiometric survey data.