Tracing widespread Early Miocene ignimbrite eruptions and petrogenesis at the onset of the Carpathian-Pannonian Region silicic volcanism

Brlek, M and Richard Tapster, S and Schindlbeck-Belo, J and Gaynor, S P and Kutterolf, S and Hauff, F and Georgiev, S V and Trinajstic, N and Suica, S and Brcic, V and Wang, K-L and Lee, H-Y and Beier, C and Abersteiner, A B and Misur, I and Petcheva, I and Kukoc, D and Németh, B and Trajanova, Mirka and Balen, D and Guillong, Marcel and Szymanowski, D and Lukács, Réka (2023) Tracing widespread Early Miocene ignimbrite eruptions and petrogenesis at the onset of the Carpathian-Pannonian Region silicic volcanism. GONDWANA RESEARCH (116). pp. 40-60. ISSN 1342-937X

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Abstract

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 mas- sive 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 M a 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 metasoma- tized lithospheric mantle-derived magmas and various crustal components than previously recognized.

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