Physics of Remote Sensing
Mickaël Germain. Kalifa Goïta.
Field of research
Lithological mapping by modelling radiative transfer in a mining context.
An open pit being mined is used as a planetary regolith analogue for spectral studies. Observations made directly at the site confirm that the pit soil falls within the definition of regolith. The Hapke radiative transfer model, usually used in planetology, can therefore be used for spectral demixing. X-ray diffraction data show significant chemical segregation during fracture leading to a different mineralogy between dust and source rock. The wide distribution of grain sizes encountered in the field requires the calculation of an effective grain size for modelling. Laboratory experiments on mixtures of fine and coarse and coarse grains within and between lithologies show a spectral behaviour that does not seem to correspond to the predictions made by the model. A « shared » grain size function is introduced to report observations. This allows a general improvement in lithological demixes by a factor of two with a reduction in the standard deviation by a factor of more than three. The mineralogical demixing tests highlighted the difficulty of quantifying the relative abundance of minerals because of the high quantity of albite and quartz, semi-transparent minerals in the wavelengths studied. Moreover, the use of pure mineralogical poles taken from spectral libraries is delicate because the variability encountered is so great for the same mineral. Finally, this study proves that rocks, entities composed of different minerals, can be used as pure poles of a mixture of different lithologies.
Poster presentation at the Environment and Mining Symposium in Rouyn-Noranda, 2018. Article in redaction.