Shape and origin of the East-Alpine slab constrained by the ALPASS teleseismic model

• Published in: Tectonophysics Vol. 510; no. 1; pp. 195 - 206
• Main Authors: Mitterbauer, Ulrike, Behm, Michael, Brückl, Ewald, Lippitsch, Regina, Guterch, Alexander, Keller, G. Randy, Koslovskaya, Elena, Rumpfhuber, Eva-Maria, Šumanovac, Franjo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-09-2011
• Subjects: Alps; Anomalies; Discontinuity; Eastern Alps; Extrusion; Lithosphere; Mantle; Pannonian fragment; Slabs; Stations; Subduction; Teleseismic tomography; Upper mantle structure; ANE, Europe; Teleseismic tomography; Pannonian fragment; Upper mantle structure; Extrusion; Eastern Alps; Subduction
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2011.07.001

During the last two decades teleseismic studies yielded valuable information on the structure of the upper mantle below the Alpine–Mediterranean area. Subducted oceanic lithosphere forms a broad anomaly resting on but not penetrating the 670
km discontinuity. More shallow slabs imaged below the Alpine arc are interpreted as subducted continental lower lithosphere. Substantial advances in our understanding of past and active tectonic processes have been achieved due to these results. However, important issues like the polarity of subduction under the Eastern Alps and the slab geometry at the transition to the Pannonian realm are still under debate. The ALPASS teleseismic experiment was designed to address these open questions.
Teleseismic waveforms from 80 earthquakes recorded at 75 temporary and 79 permanent stations were collected during 2005 and 2006. From these data, a tomographic image of the upper mantle was generated between 60
km and 500
km depth. Crustal corrections, additional station terms, and ray bending caused by the velocity perturbations were considered. A steeply to vertically dipping “shallow slab” below the Eastern Alps is clearly resolved down to a depth of ~
250
km. It is interpreted as European lower lithosphere detached from the crust and subducted during post-collision convergence between Adria and Europe. Below the Pannonian realm low velocities or high mantle temperatures prevail down to ~
300
km depth, consistent with the concept of a Pannonian lithospheric fragment, which underwent strike–slip deformation relative to the European plate and extension during the post-collision phase of the Alpine orogeny. Between 350
km and 400
km depth, a “deep slab” extends from below the central Eastern Alps to under the Pannonian realm. It is interpreted as subducted lithosphere of the Alpine Tethys. At greater depth, there is a continuous transition to the high velocity anomaly above the 670
km discontinuity.
► Slab of European continental lower lithosphere below the central Eastern Alps. ► High temperatures down to 300
km depth at the transition to the Pannonian basin. ► Close relation between upper mantle and Moho structure. ► Remnants of the Penninic Ocean at greater depth (350–450
km).