GER2B. The timing of the magmatic crystallization and metamorphic (partial) recrystallization of muscovitic mica samples GER2B and WIL1A is well constrained by ID-TIMS analyses. Both are samples of pegmatites that formed at ~485 to 480 Ma and experienced deformation during a secondary metamorphic event at ~382 to 377 Ma. The Rb-Sr age map of sample GER2B (Fig. ) shows the age distribution within a large deformed mica porphyroclast and in newly crystallized syndeformational muscovite (Fig. ). The large mica crystal displays old domains with some degree of parallelism to the mica cleavage (Fig. ). While the oldest domains are restricted to the innermost core, patches of partially reset mica reach out all the way to the interface to neighboring quartz (Fig. ). The elemental maps that have been acquired alongside Rb-Sr isotopes (Fig. ), show a rather similar and homogenous distribution of Al and Fe in deformed and newly formed muscovites. However, the deformed primary mica is clearly depleted in Rb with respect to the newly crystallized mica, with the latter showing a core-rim zonation with higher Rb concentrations observed in their cores (Fig. ). Lithium displays a particularly striking behaviour with concentrations that almost perfectly correlate with the age distribution, i.e. older age domains display higher Li-concentrations (Fig. ). For a more detailed assessment of the element and age distribution we inspected a ~1.3 mm transect across the core region of the large deformed muscovite (Fig. ). In this context, we observe two distinct domains exhibiting partial age reset. One is marked by a noticeable rise in Rb concentration, with an increase of 50-100 µg/g in Rb and a corresponding ~20 µg/g decrease in Li concentration (depicted as blue regions in Fig. ). In contrast, the other domain experiencing age reduction shows a slight decrease in Rb concentration coupled with an increase in Li concentrations. Given that both Rb and Li have a strong affinity for fluids, we propose that the former domain, exhibiting a significant age reset, is a consequence of isotope mobility induced by fluid activity. The latter type of partial age reset, we attribute to isotope mobility occurring during dry diffusion processes.