Fig. 4

BSE images (a, c, e, g) of maps 1, 2, 3 and 4, respectively (indicated in Fig. 3). High-resolution non-confocal SR-XRF scans displayed as RGB images showing the K-line intensities of Ca (R), Fe (G), and S (B) (b, 250 nm step size), Ca (R), Fe (G), and Cr (B) (d and h, 100 nm step size) and Ca (R), Fe (G), and Mn (B) (f, 200 nm step size). Red/white crosses mark the points, where confocal point analyses were performed, the results of which are shown in Tables 2 and 3. Due to difficult sample positioning, there is a slight misalignment between the BSE and SR-XRF images