Some regions within the Rb-Sr map display anomalously low ages, in particular around a larger K-feldspar crystal, which is identified by the quantitative chemical mapping (Fig. , doi:10.5281/zenodo.8245448). This is interpreted as an artefact from mixed K-Fsp/mica analyses, for which mica-based matrix correction does not correctly account for the Rb/Sr fractionation behavior of K-feldspar.