15:30 〜 16:30
[S22-P-01] Cenozoic rifting and crustal dynamics controlled by Variscan paleoplate boundaries in the mantle lithosphere
Studies of seismic anisotropy with the use of teleseismic data recorded during the last two decades at dense networks of temporary and permanent stations provided basis for modelling large-scale fabric of the lithosphere–asthenosphere system of Variscan massifs in Europe. Inferences from differently oriented seismic anisotropy image the massifs as mosaics of different microplates that roughly correspond to mapped crustal tectonic units. The mantle lithosphere preserves fossil olivine fabrics of individual domains of the massifs formed before their assembly. Changes of the anisotropy orientation related to boundaries of the tectonic units document rigidity of their mantle lithosphere and a long memory of the coherent olivine fabrics (Babuska and Plomerova, Gondwana Res. 2013). A distinct mantle boundary between the Saxothuringian (ST) unit in the north and the Tepla–Barrandian (TB) and Moldanubian (MD) units in the south, in case of the Bohemian Massif (BM) in central Europe, witnessed a Saxothuringian oceanic subduction followed by a continental collision of the microplates. The suture resulting from the ST/TB collision served as a major Variscan exhumation channel of the HP–UHP rocks. Also the central part of the Cenozoic Eger Rift with a characteristic graben structure developed above this mantle suture. Unlike the HP–UHP rocks exhumed along the ST/TB suture, the Late Cretaceous and Cenozoic volcanic products within the BM follow the broader rim of the ST mantle lithosphere that extends outside of the ST/TB suture (Plomerova et al., G-Cubed 2016). We suggest that younger tectonic and volcanic processes imprinted in the crust are often related to rejuvenated paleo-boundaries in the uppermost mantle. The deep boundaries of the mantle lithosphere domains can be sharp or diffused, depending on how well the microplates were welded into the continental plates.