Age and origin of the Bollsteiner Odenwald

The granitoid protoliths of the gneisses of the Bollsteiner Odenwald, a par t of the Mid German Crystalline Rise, intruded at 405+/-3 Ma. This age was obtained by single zircon Pb-207/Pb-206 evaporation measurements. It is sup ported by: an upper discordia intercept age of 410+/-11 Ma from single zirc on U/Pb data. These granitoids were derived from hybrid magmas according to their geochemical characteristics Inherited zircon grains with apparent ag es of 882 and 1138 Ma further constrain the source heterogeneity. The isoto pe data with Nd model ages for the granitoid gneisses between 1.3 and 1.7 G a also underline the involvement of Proterozoic material into the magma sou rces. Since the geochemical data indicate a subduction zone environment we suggest that the Bollsteiner Odenwald was formed as part of a Silurian/Earl y Devonian magmatic are in an active continental margin. The age data imply that the Bollsteiner Odenwald is closely related to the Spessart and Ruhla Crystalline Complexes but not to the Bergstrasser Odenwald. Therefore the Otzberg zone is considered to be a Variscan suture zone.