Unmixing Of Mineralogical Clay Intimate Mixtures With Laboratory Hyperspectral Images

Mineralogical clays are intimately mixed in soils. Until now, there is not a clear view on which unmixing methods are the most effective in case of intimate mixtures with both clays and with other mineral. A laboratory approach is proposed in order to compare existing linear and nonlinear unmixing approaches in terms of performances. Laboratory images of pure clays of Montmorillonite, Illite and Kaolinite were preprocessed using 6 transformations commonly used in literature (SNV, CR, CWT, Hapke, 1st SGD, Log(1/R)). Prediction of abundances has been performed on non-preprocessed and preprocessed data with 2 linear unmixing methods (FCLS and MESMA) and 2 nonlinear unmixing methods (GBM and MLM). Results show a decrease of unmixing performance due to sample variability, which can be reduced using the appropriate preprocessing. However, no particular advantage has been found on using nonlinear over linear unmixing approaches for clay minerals.