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The Late Paleozoic ignimbrite flare-up of central Europe: Following magma source and pathways by mineralogical and geochemical constraints

A swarm of devastating caldera-forming eruptions (>VEI 6) blanketed the Permo-Carboniferous of central Europe with voluminous pyroclastic deposits within a long-lasting period of 50 Myrs. Although of different tectonic setting, the pyroclastic record of this ignimbrite flare-up is similar to the Cenozoic deposits in the western USA, ranging from crystal-poor rhyolitic Snake River-type and compositionally zoned tuffs to crystal-rich monotonous intermediates and rhyolites.

Combined textural and chemical analysis data on whole rock, juvenile fragments (fiamme, glass shards), and mineral phases were acquired to unravel the origin and lithospheric evolution of the magma reservoirs. Two different geochemical suites can be distinguished: (I) a diopside- and (II) a corundum-normative. Examples of the diopside-normative suite are the caldera systems of Wurzen and the Wendland, as well as the vitrophyric Planitz Ignimbrite. Although all pyroclastic deposits show corundum-normative compositions; solely, the magma system of the Flechtingen Ignimbrite crystallizes almandine-garnet in a deep-seated magma chamber. In general, thermobarometric estimations suggest an interplay of hydrous near-solidus granitic systems penetrated by anhydrous SiO2-rich superheated magmas. These systems can be tracked down to depths of 25 to 40 km (7-12 kbars) and provide insights into the post-Variscan rift-related magmatic activity.

Details

Author
Alexander Repstock1, Elżbieta Słodczyk2, Manuela Zeug3, Andrew Menzies4
Institutionen
1Section of Geological Survey and Geophysics, Saxon State Office for Environment, Agriculture and Geology, Dresden, Germany; 2Institute of Geological Sciences, University of Wrocław, Wrocław, Poland; 3Department for Geology, Landesamt für Geologie und Bergwesen Sachsen-Anhalt, Halle, Germany; 4Bruker Nano Analytics GmbH, Berlin, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/3jkg-7q07