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Perspectives on the Early Miocene silicic volcanism of the Carpathian-Pannonian Region

The Carpathian-Pannonian Region (CPR) hosted some of the largest silicic volcanic eruptions in Europe during the Early and Middle Miocene contemporaneously with the major lithospheric thinning of the rift Pannonian Basin, which was recorded as an ignimbrite flare-up event from ~18.1 Ma to ~14.4 Ma. In order 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 on the Lower Miocene rhyolitic ignimbrites and volcaniclastic deposits ranging from the northern CPR to the Dinaride Lake System. High-precision zircon geochronology indicates there were two discrete pulses of volcanic activity at ~18.1 Ma and ~17.3 Ma. Based on combined tephrostratigraphic signatures, we propose that large 18.1 Ma Kalnik and 17.3 Ma Eger eruption events produced far- traveled, massive rhyolitic ignimbrites, which were deposited across northern and southwestern regions of the CPR. Due to easterly winds which carried volcanic ash hundreds of kilometers to the southwest, Eger eruption products also reached distal intra- montane Dinaridic lacustrine basins. Both events therefore capture important marker horizons in basin stratigraphy. Integrated zircon and bulk glass Nd-Hf isotope compositions have a positive correlation, defining a regional mantle array. A systematic isotopic change was recorded, moving from more crustal signatures in older eruptive events towards more juvenile compositions through time. This implies variations in the interaction between metasomatized lithospheric mantle-derived magmas and various crustal melts with time. It is likely that CPR eruptions also contributed significant protolith material for subsequent Dinaridic karst bauxites in the region. By combining our new volcanic data set with high- precision zircon petrochronology from these bauxites, it is possible to refine models of transport of weathered material and provide a glimpse into CPR magmatic evolution during Early Miocene lithospheric thinning. Finally, these geochronology data from the bauxites help constrain broader Miocene environmental processes by constraining the timing of bauxitization in paleo mid-latitude Europe, providing continental paleoclimate data, and provide significant insight into the Miocene Climatic Optimum.

CA-ID-TIMS geochronology ; Volcanic glass chemistry ; Hf and Nd isotope tracers ; Tephrostratigraphy ; Petrogenesis ; Bauxites ; Miocene Climatic Optimum ; Source-to-sink

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