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Zircon megacrysts in alkaline lavas of the Lusatian Volcanic field (Central Europe) – complex magma systems in monogenetic volcanic fields

Zircon megacrysts of gemstone quality hosted at different localities within the Lusatian Volcanic Field. Here two of them, the scoria cone of the basanitic Hofeberg volcano and an alluvial placer Hirschbörnel Creek downstream of the Buchberg trachyte dome, were dated and chemically analysed. The genetic interpretation within their geological context results in two different genetic models: In case of the first locality entrainment of the zircon with primary intergrowth phases in a basanitic melt resulted not only in resorption and reaction zones in the enclosing melt but in recrystallization of the zircon and its intergrown phases. In case of the placer locality the zircon crystals are unresorbed and can be deduced to have been derived from the initial explosive eruption of the highly evolved cupola of the trachytic melt system that is documented by the Buchberg trachytic dome being located upstream. Both, the U/Pb ages and the Hf isotopy of the zircon grains 28.2 ± 1.8 to 32.2 ± 2 Ma and εHf +3.1 to +6.8, respectively, correspond with those of the zircon host rocks. This implicates a cogenetic origin and a complex magma feeding system below the two monogenetic volcanoes.

Details

Author
Jörg Büchner1, Olaf Tietz1, Lothar Viereck2, Axel Gerdes3, Wolfgang Seifert4
Institutionen
1Senckenberg Museum für Naturkunde Görlitz, Germany; 2Institut für Geowissenschaften, FSU Jena, Germany; 3Frankfurt Isotope and Element Research Center (FIERCE), GUF, Germany; 4Lithosphere Dynamics, Deutsches GeoForschungZentrum (GFZ), Potsdam, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/ave1-rs21
Geolocation
Bohemian Massif