Figure 11

Representation of the intensities of the 10,780 FTIR/LA-ICP-MS spectra of section #3 presented on Fig. 8 passing a SNR threshold of 500 after double clustering analysis. Spectra were processed by subtraction of the mean and normalization by the standard deviation prior to clustering. The 10,780 spectra were sorted according to a hierarchical cluster analysis shown on top of the figure. The wavenumbers/elements were sorted in 4 clusters by K-means clustering. The dotted line on the left side of the figure indicates the limits of the clusters. The mean spectrum after sorting the wavenumbers/elements by the K-means (“sorted spectrum”) is also presented on the left side of the figure. For the sake of the clarity, the “sorted spectrum” is shown prior to mean subtraction and normalization by standard deviation.