TERTIARY SUBDUCTION AND SLAB BREAK-OFF MODEL OF THE CARPATHIAN-PANNONIAN REGION

This paper illustrates the application of multidisciplinary data analy sis to the Carpathian-Pannonian region and presents a new Tertiary dev elopment model that incorporates all multidisciplinary parameters. Dur ing the Late Cretaceous-Eocene, the future Carpathian orogen was part of the larger Alpine-Carpathian orogen formed by the southeastward sub duction (135-55 Ma) of the Penninic Ocean and the ultimate collision ( 55-40 Ma) of the European and Adriatic continents. The subduction in t he 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 E ocene remnant Carpathian Flysch Basin (rCFB) was still subducting. The Carpathians and eastern parts of the Alps started to occupy the regio n of the present Carpathians during the Early Miocene. The oceanic pla te underlying the rCFB subducted southwestwards, later westwards, whil e the northeastward and eastward migration velocity of the accreting p late boundary decreased through time. The slower subduction rate cause d: a steeper dip of the subducting slab; the beginning of the Eggenbur gian (22-19 Ma) and following duration of extension in the orogenic hi nterland accompanied by the asthenosphere upwelling; the onset of the crustally derived volcanism above the risen asthenosphere and the youn ger mantle-derived volcanism, progressively less contaminated by the c rustal material, all contemporaneous with a shortening in the Carpathi an accretionary wedge. The subduction of the rCFB finally led, at the end of the Early Miocene, to a collision with the continental margin a long the westernmost part of the present Carpathian Are. The subductio n roll-back of the subducting slab of the rCFB under the advancing inn er Carpathians, the oblique closure of the basin, the progressive chan ge of the subduction to collision from the west to the east along the Carpathian Are drove a scissors-like break-off of the subducting ocean ic slab along the West Carpathians. The break-off in the East Carpathi ans was driven by the weight of a subducting oceanic slab and buoyancy of the attached continental slab. The break-off started in the west o f the Carpathian Are in the Early Miocene, ran along the are to its pr esent position in the bend area between the East and South Carpathians and separated the oceanic slab, that subducted passively under its ow n weight, from the European continental margin. The lateral propagatio n rate of the slab tear decreased with time. The break-off-related vol canism was synchronous with the final stages of the collision. (C) 199 8 Elsevier Science B.V. All rights reserved.