Variscan terrane boundaries in the Odenwald-Spessart basement, Mid-German Crystalline Zone: New evidence from ocean ridge, intraplate and arc-derived metabasaltic rocks

The hitherto unknown differences in the composition and genesis of the various amphibolites in the southern and northern Spessart basement require revision of existing tectonostratigraphic models for the area. Instead of representing one contiguous unit, the various amphibolites are interpreted to belong to two different terranes that became juxtaposed in the Spessart-Odenwald basement. These terranes are separated by a major fault (Otzberg-Michelbach Fault Zone), along which rocks of inferred peri-Gondwana origin, now exposed in the western Odenwald and the northernmost Spessart were thrust onto probable Baltica/Avalonia-derived rocks that are exposed as a tectonic window in the eastern Odenwald and the central and southern Spessart. It is further suggested that the Otzberg-Michelbach Fault Zone is part of the lithospheric-scale Rheic Suture.