Mineralogical and lithological unmixing with radiative transfer modelling in the open-pit context of Mine Canadian Malartic

• Published in: Journal of quantitative spectroscopy & radiative transfer 2020-01, Vol.241, p.106707, Article 106707
• Main Authors: Clabaut, Étienne, Germain, Mickaël, Goïta, Kalifa, Morisset, Caroline-Emmanuelle, Plante, Benoît, Tessier, Christian, Lemelin, Myriam, Hébert, Ronan, Siebels, Kevin
• Format: Article
• Language: English
• Subjects: Earth Sciences; Grain Size; Hapke's Model; Lithological/Mineralogical Unmixing; Mine Canadian Malartic; Porosity; Radiative Transfer; Sciences of the Universe
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/j.jqsrt.2019.106707

•An open-pit mine can be seen as a regolith.•A mineralogical segregation occurs during the crushing/sieving process.•RMSEs are not discriminant to retrieve minerals relative abundances.•Considering lithologies as pure endmembers is a valid assumption. In this study, Hapke's radiative transfer model is used to verify the feasibility of retrieving the composition and grain-size of the ground in an open-pit mine, seen as a regolith. Such a tool could be useful for dust surveys and thus preventing potential environmental risks such as acid mine drainage. As the true compositional endmembers of the medium are not retrieved but rather chosen from spectral libraries and the range of grain sizes (a few to hundreds of micrometers) and porosities (0.22 to 0.52 for the filling factor) vary greatly in an open-pit mine, we show that the mineralogical unmixing results are not reliable. Too many combinations of different relative abundances, grain sizes and porosities lead to fits between modelled and measured spectra under 0.3% in reflectance. To tackle this issue, we explore a lithological unmixing approach. Considering lithologies as endmembers, as opposed to considering minerals, reduces the variability in the solutions as fewer endmembers are used. The results show that the studied samples with multi-component grains behave spectrally as expected for mono-mineral grains. With no root mean square errors higher than 5%, the relative abundances retrieved are sufficiently precise to consider mapping lithologies with this method. [Display omitted]