Neogene evolution of the Carpatho-Pannonian region: an interplay of subduction and back-arc diapiric uprise in the mantle

Abstract

Abstract. Geodynamic evolution of the Carpathian arc and Pannonian basin during the Neogene times is presented as a set of palinspastic reconstructions. The structural evolution is modeled in terms of a coupled system of: (1) Alpine (Atype) subduction and compressive orogene belt development owing to compression by the Adriatic microplate, (2) lateral extrusion of Alcapa lithosphere from the Alpine collision assisted by transform faults, (3) Carpathian gravity driven (Btype) subduction of oceanic or suboceanic lithosphere underlying former flysch basins and (4) back arc extension associated with the diapiric uprise of asthenospheric mantle.The variable timing of accretionary prism and back arc basin evolution in the Western Carpathians, the NW part of the Eastern Carpathians, and the SE part of the Eastern Carpathians confirms that the final Tertiary evolution of the Carpathian arc and Pannonian basin was not a uniform process. Rather, it took place successively in three segments, reflecting gravity driven subductions compensated by return asthenospheric flows (involving the back-arc diapiric uprise of asthenospheric mantle). The observed low subduction rate implies obstacles to the compensating asthenosphere flow, perhaps represented by confining thick lithosphere at the NW and SE sides of the arc. This segmentation may arise from a gravity driven process allowing asthenospheric side flow to take place speeding up the gravity driven overturn (subduction). Structural evolution as well as the timing and spatial distribution of the arc-type (subduction-related) andesite volcanics suggests that subduction halted because the subducting plate became nearly vertical, followed closely by the detachment of the sinking lithosphere slab from the continental margin. Late stage alkali basalt volcanic rocks imply that during the final stage of back arc basin evolution the related diapiric uprise of asthenospheric mantle incorporated unmetasomatized mantle material, brought possibly into the area of the diapiric uprise by compensating athenosheric mantle counterflows.Correspondence to: J. Lexa (lexa@gssr.sk)

Structure and tectonic evolution of the NE segment of the Polish-Ukrainian Carpathians during the Late Cenozoic: subsurface cross-sections and palinspastic models

“…subsidence) including original uplifts in the basement which separate the West Carpathian subbasins (Książkiewicz 1965). Convergence of the continental plates of the lithosphere was compensated in the collision zone by diapiric uprise of the mantle (Konečný et al 2002).…”

“…As distinct from the uplifted Małopolska Block beneath the Western Outer Carpathians, the western part of the Eastern Outer Carpathians is superimposed on the Transcarpathian Depression in the basement, which separated the Western Carpathian and Transylvanian mantle diapirs (Naumenko 1984). The influence of the advanced subduction of the basement in that part of the Outer Carpathians is manifested by the occurrence of Neogene volcanics in the hinterland, accompanied by a detached and sunken lithospheric slab (Konečný et al 2002). The differentiation of the evolution from NW to SE of the central-outer belt of the Outer Carpathians during the Late Tertiary (34-12 Ma) is reflected by the large variation of measured parameters (Table 1) The parameters above are different from the ones determined by balancing of one traverse with a different subsurface interpretation and conceptual kinematic model (Behrmann et al 2000;Gągała et al 2012).…”

“…The arc of the Outer Carpathians, created by thrusting and folding, overlies faulted segments of the European Platform lithosphere, bounded to the SW by the collision zone with altered, thinned lithosphere of a mantle diapir (Konečný et al 2002). The lithosphere underlies the Carpathian Internides and back-arc basins, and that zone is identified with zero values of the Wiese vector (Jankowski et al 1979).…”

“…The new representation of the evolution of the NE segment of the Outer Carpathians can be supported by interpretations of the tectonics of the slope of the subducted European Platform, which are based on seismic tomography and thermal modelling (Konečný et al 2002), and magnetotelluric sounding (Kuśmierek 2010).…”

“…According to Konečný et al (2002), at the contact between the Western and Eastern Carpathians, that slope was offset by an oblique, SW-NE-trending deep-seated fracture which separated the Małopolska Block (Massif) from the basement of the Transcarpathian Depression. Within that depression, no deep well drilled in the Ukrainian Carpathians reached the platform basement under the Skole Nappe (Zayats 2013).…”