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Two small volcanoes, one inside the other: geophysical and drilling investigation of Bažina maar in western Eger Rift
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SYSNO ASEP 0574345 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Two small volcanoes, one inside the other: geophysical and drilling investigation of Bažina maar in western Eger Rift Author(s) Hrubcová, Pavla (GFU-E) ORCID, RID
Fischer, T. (CZ)
Rapprich, V. (CZ)
Valenta, J. (CZ)
Tábořík, P. (CZ)
Mrlina, Jan (GFU-E) ORCID, RID
Dahm, T. (DE)
Vylita, T. (CZ)
Beránek, Roman (GFU-E) ORCID, SAI
Klanica, Radek (GFU-E) RID, ORCID, SAI
Vlček, J. (CZ)
Turjaková, Veronika (GFU-E)Article number e2023EA003009 Source Title Earth and Space Science. - : American Geophysical Union - ISSN 2333-5084
Roč. 10, č. 8 (2023)Number of pages 21 s. Publication form Online - E Language eng - English Country US - United States Keywords drilling ; Eger Rift ; electrical resistivity tomography ; gravity survey ; maar-diatreme volcano ; magnetometry OECD category Volcanology R&D Projects EF16_013/0001800 GA MŠMT - Ministry of Education, Youth and Sports (MEYS) LM2015079 GA MŠMT - Ministry of Education, Youth and Sports (MEYS) Method of publishing Open access Institutional support GFU-E - RVO:67985530 UT WOS 001042207400001 EID SCOPUS 85166746351 DOI https://doi.org/10.1029/2023EA003009 Annotation Maar-diatreme volcanoes are small volcanic structures with a funnel-shaped crater surrounded by a tephra-ring. They are usually formed by the explosive phreatomagmatic eruptions when groundwater comes into the contact with magma. We focus on such a structure in the geodynamically active western Eger Rift (Czech Republic) and present results from multidisciplinary geophysical investigation calibrated by drilling in the newly discovered Pleistocene Bažina maar. We evaluated morphological (LiDAR-based DEM) data and confirmed the existence of a maar-diatreme structure by combined geophysical methods. In the map view, they revealed circular negative gravity anomaly, funnel-shape low-resistivity anomaly, and strong magnetic anomaly. These results allowed for the optimal location of two boreholes in the maar crater, which evinced its contact with country rocks and lithologies of the maar-diatreme filling. The drilling revealed coherent volcanic rocks and volcaniclastic deposits, moreover, it revealed a presence of a pyroclastic cone with the olivine nephelinite feeding conduit. Further investigations disclosed maar structure and subsequent pyroclastic cone(s) with several generations of eruptions and systematic decrease of water influence on the eruption style. Different eruption styles suggest a unique evolution of two volcanoes, one inside the other. The age of the Bažina maar eruption, estimated from the reverse polarity of the detected magnetic anomaly, implies that the effusion and solidification of the lava during the eruption must be older than 0.78 Ma (Pleistocene). This points to an active volcanism in the western Eger Rift in a span of ∼0.5 Ma, where Bažina represents the oldest (maybe opening) phase. Workplace Geophysical Institute Contact Hana Krejzlíková, kniha@ig.cas.cz, Tel.: 267 103 028 Year of Publishing 2024 Electronic address https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023EA003009
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