WIL1A. The Rb-Sr mapping of sample WIL1A probes a white mica aggregate within a highstrain zone running through rather undeformed pegmatite (Fig. ). The formation of the shear zone is most likely related to a regional Devonian-age amphibolite-facies metamorphic event. This is tested by defining one large (4445 pixel) and one small (216 pixel) segments within muscovite (Fig. ). Again, the results obtained with Gaussian and weighted mean approaches yield similar Rb-Sr ages (Table ). However, whereas the large muscovite segment agrees with the anticipated age of the deformation event as constrained by ID-TIMS (Table ), the small muscovite segments appears slightly younger (363 ± 13 Ma). Since the ID-TIMS ages are interpreted to rather represent maximum age estimates for the waning stages of deformation, it is plausible to consider slightly younger in-situ ages in the more extensively deformed highstrain zone probed by the WIL1A mapping.