For discrete XRF measurements on dried and ground material a PANalytical Epsilon3-XL XRF spectrometer equipped with a rhodium tube, several filters, and a SSD5 detector was available. A calibration based on certified standard materials (e.g. GBW07309, GBW07316, and MAG-1) was used to quantify elemental counts (cf. Govin et al. 2014).