Tertiary subduction and slab break-off model of the Carpathian–Pannonian region

Abstract

This paper illustrates the application of multidisciplinary data analysis to the Carpathian–Pannonian region and presents a new Tertiary development model that incorporates all multidisciplinary parameters. During the Late Cretaceous–Eocene, the future Carpathian orogen was part of the larger Alpine–Carpathian orogen formed by the southeastward subduction (135–55 Ma) of the Penninic Ocean and the ultimate collision (55–40 Ma) of the European and Adriatic continents. The subduction in the Alpine region ended by the slab break-off of the subducting oceanic lithosphere from the continental one and by the related magmatism (43–24 Ma). While the Eocene Alps were under continental collision, the Eocene remnant Carpathian Flysch Basin (rCFB) was still subducting. The Carpathians and eastern parts of the Alps started to occupy the region of the present Carpathians during the Early Miocene. The oceanic plate underlying the rCFB subducted southwestwards, later westwards, while the northeastward and eastward migration velocity of the accreting plate boundary decreased through time. The slower subduction rate caused: a steeper dip of the subducting slab; the beginning of the Eggenburgian (22–19 Ma) and following duration of extension in the orogenic hinterland accompanied by the asthenosphere upwelling; the onset of the crustally derived volcanism above the risen asthenosphere and the younger mantle-derived volcanism, progressively less contaminated by the crustal material, all contemporaneous with a shortening in the Carpathian accretionary wedge. The subduction of the rCFB finally led, at the end of the Early Miocene, to a collision with the continental margin along the westernmost part of the present Carpathian Arc. The subduction roll-back of the subducting slab of the rCFB under the advancing Inner Carpathians, the oblique closure of the basin, the progressive change of the subduction to collision from the west to the east along the Carpathian Arc drove a scissors-like break-off of the subducting oceanic slab along the West Carpathians. The break-off in the East Carpathians was driven by the weight of a subducting oceanic slab and buoyancy of the attached continental slab. The break-off started in the west of the Carpathian Arc in the Early Miocene, ran along the arc to its present position in the bend area between the East and South Carpathians and separated the oceanic slab, that subducted passively under its own weight, from the European continental margin. The lateral propagation rate of the slab tear decreased with time. The break-off-related volcanism was synchronous with the final stages of the collision.