Neogene–Quaternary magmatism and geodynamics in the Carpathian–Pannonian region: a synthesis

Abstract

In the Carpathian–Pannonian region in Neogene times, westward-dipping subduction in a land-locked basin caused collision of two lithospheric blocks (Alcapa and Tisia) with the southeastern border of the European plate. Calc-alkaline and alkaline magmatism was closely related to subduction, rollback, collision and extension. From the spatial distribution of the magmatic activity, four segments can be defined: Western Segment (magmatism occurring on the Alcapa block), Central Segment (magmatism occurring on both Alcapa and the Tisia blocks), South-Eastern Segment and Interior Segment (both on the Tisia block). Most calc-alkaline magmatism in the region resulted from melting of a heterogeneous asthenospheric mantle source modified by addition of fluids and sediment. Assimilation and fractionation processes at shallow crustal levels occurred in most of the segments, strongly masking the deeper source processes. Long-term subduction, rollback and/or delamination led to contamination of the asthenosphere beneath the Western Segment. Here, large-volume partial melts of the contaminated mantle caused underplating and crustal anatexis, leading to mixing of mantle-derived calc-alkaline magmas with crustal melts. In the Central Segment, calc-alkaline magmas were formed by subduction and rollback, followed by back-arc extension and slab breakoff. A variable mantle source is indicated in the back-arc setting and larger amount of fluid-induced metasomatism, source enrichment and assimilation nearer to the trench. In the Interior Segment, evolution from typical calc-alkaline magmas to adakite-like ones was related to extension due to fast rotations and transtensional tectonics. Here, calc-alkaline magmas formed by decompression melting of a heterogeneous crust–mantle lithosphere, while adakite-like melts resulted from fliud-dominated melting of the lithosphere. Along the South-Eastern Segment, slab breakoff was responsible for the generation of typical calc-alkaline magmas, but in the extreme south of the segment, shallow level tearing of the slab followed breakoff. Strike–slip tectonics allowed the rise of hot asthenosphere and generation of adakite-like magmas, via slab-melting, along the torn edge of the East European Plate. Alkalic basaltic volcanism with an OIB-like asthenosphere source followed the calc-alkaline stage (Western Segment), or was contemporaneous with it (South-Eastern and Interior Segments) mainly in response to local extensional tectonics.