Seismic anisotropy and deformation patterns in upper mantle xenoliths from the central Carpathian–Pannonian region: Asthenospheric flow as a driving force for Cenozoic extension and extrusion?

Abstract

We review deformation fabrics in mantle xenoliths from the central part of the Carpathian–Pannonian Region (CPR) and, in combination with seismic shear wave splitting data, attempt to define patterns of upper mantle anisotropy. Our interpretations from both lines of evidence support a model for east–west oriented asthenospheric flow, decoupled (at least in part) from the overlying lithosphere. Mantle flow fields resulting from Tertiary indentation of Europe by the Adria micro-plate and the resulting Alpine orogen may thus have been an important factor in driving the eastward extrusion of lithospheric blocks in the CPR accompanied by lithospheric extension, rapid ‘rollback’ of the Carpathian subduction system, and its diachronous collision with the European craton. According to this model, eastward asthenospheric flow would add significantly to the effects of slab rollback and gravitational instability. Thus, opening of the Pannonian Basin, rather than being exclusively driven by ‘slab pull’ and gravitational instability, could have been resulted, at least in part, from mantle flow associated with the Adria–European collision and ensuing Alpine orogeny. Such models have also been proposed for analogous geodynamic scenarios such as the western and eastern Mediterranean, and western and southwestern Pacific regions, offering a potential generic model for back-arc basin opening.