The Carpathian-Pannonian Region (CPR) hosted some of the largest silicic volcanic
eruptions in Europe during the Early and Middle Miocene, contemporaneously with major
lithospheric thinning of the Pannonian Basin. This was recorded as an ignimbrite flare-up
event from approximately 18.1–14.4 Ma. To gain in-depth perspectives on the eruption
chronology, tephrostratigraphy, and petrogenesis at the onset of CPR silicic volcanism,
we applied a multi-proxy approach to Lower Miocene rhyolitic ignimbrites and pyroclastic
fall deposits from the northern CPR to the Dinaride Lake System. High-precision zircon
U-Pb geochronology distinguished two Lower Miocene groups of volcaniclastic rocks
at ∼18.1 Ma and ∼17.3 Ma. Based on combined tephrostratigraphic signatures we propose
that the ∼18.1 Ma Kalnik and ∼17.3 Ma Eger eruptions produced widespread (intermediate
to) large caldera-forming massive rhyolitic ignimbrites, deposited across northern
and southwestern regions of the CPR. Due to easterly winds that carried volcanic ash
hundreds of kilometers to the southwest, Eger eruption products also reached distal
intra-montane Dinaride lacustrine basins, recorded as pyroclastic fall deposits. Heterogeneous
major and trace elemental compositions of ∼18.1 Ma volcanic glass shards suggest that
the Kalnik eruption was sourced from complex silicic magmatic systems, with simultaneous
tapping of two discrete melt bodies during the eruption. The homogeneous geochemical
composition of ∼17.3 Ma glasses is distinct from the older glasses. Integrated zircon
and bulk glass Nd-Hf isotope compositions have a positive correlation, defining a
regional mantle array, and are more radiogenic in the younger phase of volcanism.
The recorded systematic isotopic change, moving from older more crustal signatures
to younger more juvenile compositions, imply that during the period of lithospheric
thinning of the Pannonian Basin the region underwent more complex variations in the
interaction between metasomatized lithospheric mantle-derived magmas and various crustal
components than previously recognized.
