Problems of the Pannonian basin geodynamics

Joint analysis of geological-geophysical data and petrogeochemical characteristics of neotectonic volcanism revealed a close relationship between the neotectonic pattern of the Pannonian basin and deep structure. As shown in this work, main features of the recent deep structure such as the thin crust, hotter lithosphere and lower P wave velocities can be accounted for solely in terms of the model of a mantle floating-up diapir that stretches the lithosphere. Such a tectonic regime is known as synorogenic rifting. The synorogenic rifting model is largely based on the evidence of alkali-basaltic volcanism developing since the beginning of the Pannonian Age (11–10.5 Ma), after the subduction had stopped and the previously widespread calc-alkaline magmatism had localized within the Transcarpathian region. The chemistry of basalts in the Pannonian basin is characterized by concentrations of major, rare and rare-earth elements fully consistent with petrogeochemical features of continental rift basalts. Ultrabasic xenoliths in Pannonian basin basalts belonging to the spinel lherzolite facies also coincide in composition with mantle xenoliths usually present in volcanics of rift zones. The data of this work indicate that evolutionary models of the Pannonian basin based on a passive response of the lithosphere to external factors are invalid. The preliminary results of geodynamic zoning presented in the paper suggest that such processing of the geological-geophysical database is promising, because it enables the identification of individual lithospheric blocks having specific features within a given geostructural province (differing in the relationships between geological-geophysical parameters). This approach provides deeper insights into the nature of the seismic activity in the Pannonian basin that has not been clearly understood as yet.