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Quantification of the phreatomagmatic-to-magmatic eruption style transition of a deeply eroded maar diatreme volcano applying high-resolution field and rock texture analysis

Mátyás Hencz a, Károly Németha,b,c, Tamás Spránitza, Tamás Biród, Dávid Karátsond, Márta Berkesia

  • Affiliations:  a MTA-EPSS FluidsByDepth Lendület Research Group, Institute of Earth Physics and Space Science, Hungarian Research Network (HUN-REN), Sopron, Hungary

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 7

  • Programme No: 3.7.14

  • Theme 3 > Session 7

Abstract

b National Program for Earthquakes and Volcanoes, Geohazard Research Center, Saudi Geological Survey, Jeddah, Saudi Arabia c Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy *d Department of Physical Geography, Institute of Geography and Earth Sciences, ELTE Eötvös Loránd University, Budapest, Hungary * Monogenetic volcanic fields provide critical insights into the complex interactions between magmatic processes, geological settings, and syn-and post-eruptive landscape evolution. This research focuses on the volcanic evolution of Szent György Hill, located within the monogenetic, phreatomagmatic Miocene-Pleistocene Bakony--Balaton Highland Volcanic Field in the Pannonian Basin, Central Europe. Szent György Hill represents a deeply-eroded monogenetic volcano. Field mapping and stratigraphic reconstruction based on mosaic-like outcrops revealed a complex volcanic architecture of the Szent György Hill. Image analysis of pyroclastic rock slab surfaces was used to quantify the relative abundance of different juvenile and lithic components within these pyroclastic samples correlated with their stratigraphy position. The analysis focused on distinguishing components resulted by phreatomagmatic (sideromelane glass) and magmatic (tachylite glass, basaltic clasts) fragmentation processes. The results suggest a temporal shift in eruption style at Szent György Hill from a relatively stable vent location. The initial phreatomagmatism is evidenced by the higher proportion of sideromelane glass in the lower stratigraphic units, which were driven by the interaction of rising magma and external water from syn-eruptive aquifers hosted in a combined Neogene siliciclastic successions and Mesozoic fracture and cavity-controlled, carbonate-dominated substrate. The spatially and temporally changing water supply is likely to have played a crucial role in the evolving eruption dynamics. The underlying siliciclastic sedimentary rocks and carbonate formations provided a combined, partially confined aquifer that influenced the amount and timing of water availability to fuel or suppress phreatomagmatism in the course of the evolving eruption.