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Capacity of imaging spectroscopy for the characterisation of REO, REE bearing minerals & primary REE-deposits


Herrmann,  Sabrina
1.4 Remote Sensing, 1.0 Geodesy, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;
Scientific Technical Report STR, Deutsches GeoForschungsZentrum;

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Herrmann, S. (2019): Capacity of imaging spectroscopy for the characterisation of REO, REE bearing minerals & primary REE-deposits, Master Thesis, (Scientific Technical Report ; 19/08), Potsdam : GFZ German Research Centre for Geosciences, vii, 161 p.

Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_4128900
The spectral characteristics of Rare Earth Elements (REEs) have been poorly researched although the economic interest in these elements is increasing. This study investigates the detection of REEs using remote sensing data. For this purpose the spectral response of each individual REE has been studied with four spectrometers (HySpex (VNIR-1600, SWIR-320m-e), ASD Field Spec 3, Perkin Elmer LAMBDA 950, FTIR Spectrum GX) using a spectral range of 350 to 16000 nm to incorporate different techniques. The relationship between the spectral response and the REE concentration as well as the influence of other materials on the detection of REEs was examined using mixtures of calcium carbonate (the main component of REE ore rocks) and iron (III) oxide (hematite). Finally, characteristic absorption bands have been employed on an EO-1 Hyperion satellite image, covering the REE Mountain Pass mine in California and a HySpex image of a rock sample from Norway (soevite) to evaluate their potential use as REE detectors. The results show that the REEs lanthanum, neodymium, samarium, europium, terbium, dysprosium, holmium, erbium, thulium and ytterbium cause several and differing absorption features in the visible near-infrared (VNIR) and shortwave-infrared (SWIR) region. However, in wavelength ranges between 2500 and 16000 nm no absorption bands distinctive of REEs appeared. In most cases, the concentration of REEs and the absorption depth show a logarithmic relationship for different absorption features. The mixtures of neodymium and iron (III) oxide show that in presence of hematite the absorption features of neodymium are superimposed by those features caused by iron (III) oxide. In comparison to hematite, calcium carbonate has had no influence on the detection of neodymium in the VNIR. The application of characteristic absorption bands on the satellite image shows that the REE signal causes only, if any, very small absorption bands in the spectrum at higher REE concentrations. In the rock sample, however, REEs related absorption bands are detectable and can be seen clearly in the spectrum with a neodymium concentration of around 0.14%. This study shows that imaging spectroscopy serves as a helpful tool for the characterization and detection of REE concentrations in the laboratory and field environment. The detection of REEs via satellite images is limited by the low intensity of the absorption features, despite the high REEs concentration. Nevertheless, the detection of REEs by means of remote sensing is a non-invasive method that saves both money and time for sample preparation, underlining its economic value.