Rb-Sr age resetting by diffusion and neo/recrystallization in amphibolite-facies metamorphic white mica revealed by micrometer scale LA-ICP-MS/MS mapping

Micrometer-scale (4–8 μm) Rb Sr age mapping was applied to millimeter-sized muscovite from Cambro-Ordovician metapegmatites of the western Bohemian Massif (SE Germany, Erbendorf–Vohenstrauß Zone), overprinted by Devonian amphibolite-facies metamorphism (~380 Ma, >600 °C). These relict magmatic muscovite crystals (ms1) show a wide range of deformation states, from undeformed magmatic “books” to lozenge-shaped, plastically deformed porphyroclasts. Neocrystallized muscovite (ms2) forms along the grain boundaries of white mica fish and within micro-shear zones that are only a few hundred micrometers in width. The ms2 mica uniformly records the ~380 Ma ages displaying sharp age gradients at the interface towards pristine ms1 muscovite, with one case recording a ~ 100 Ma range over