Isotope studies and their implication for metamorphic processes in the Kuiseb Formation of the southern Damara Orogen, Namibia

The pTt-path of the Khomas Trough was examined by correlating individual metamorphic products produced at different stages of the metamorphic development. On the basis of a cooling model a mineral age was interpreted as the time where, at a certain closure temperature, Sr isotope diffusion became restricted to single grains. Rb-Sr analyses on minerals and whole rock samples from metasediments of the Kuiseb Formation of differing metamorphic grade were concentrated on. A thin slab technique was applied to samples showing a distinct sedimentary layering or metamorphic banding which were cut into slabs of mm- to cm-scale parallel to their compositional layering and analyzed as whole rock samples. Mineral fractions were also separated from individual slabs. U-Pb analyses on metamorphic monazites, which represent independent and isolated isotopic systems, were chosen to standardize Rb-Sr data. 6 refs., 1 fig