Russian Journal of Earth Sciences
Vol. 4, No. 5, October 2002
Problems of the Pannonian Basin Geodynamics
A. F. Grachev and V. A. Nikolaev
Abstract
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
therecent 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.