HYPERSPECTRAL IMAGING FOR RARE EARTH ELEMENT EXPLORATION

Rare Earth Elements (REE) are essential for modern technology. Most (97%) of the world’s REE come from the Bayan Obo mine in China. As China modernizes, the Chinese may restrict exports of REE because of their own needs, requiring other developed countries to find additional sources of REE. Because of opposing concentration processes and most REE similar electron valence state (3⁺), REE are widely dispersed on the Earth’s surface. When REE occur in sufficient concentrations in an igneous deposit, there is usually a large disparity between the abundance of Light REE (LREE) and Heavy REE (HREE) with LREE being significantly more abundant than the HREE. LREE vs HREE abundance differences in carbonatites are mainly due to fractionation associated with partial melting of the parent rock. Several REE exhibit pronounced absorption features in the Visible-Near Infrared (VNIR; 400-1000 nm) portion of the electromagnetic spectrum, including Nd, Sm, Dy, and Er; the former two being LREE and the latter two being HREE. Dysprosium (Dy) is especially important as it greatly extends the temperature range and resistance to demagnetization of Nd₂Fe₁₄B magnets. REE absorption features are due to intervalence charge transfer (IVCT). Hyperspectral imaging readily detects these absorption features. JPL’s Airborne Visible Infrared Imaging Spectrometer (AVIRIS) hyperspectral sensor collected imagery over both Mountain Pass, California and the Iron Hill Carbonatite at Powderhorn, Colorado. NASA’s Hyperion sensor collected data over Bayan Obo REE mines. These data were evaluated and preliminary results indicate the feasibility of using hyperspectral imagery to detect the presence of REE from both airborne and satellite sensors.