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Abstract <p>The Flechtingen Ignimbrite, a Late Paleozoic volcanic succession in Central Europe, serves as a valuable record of magmatic system evolution and dynamics. Geochemical analyses of bulk rock and fiamme, combined with mineral textures and chemistry, reveal the complex, multi-stage magma reservoir beneath the caldera, characterized by interactions between primitive and evolved magmas. Initially, alkaline and tholeiitic magmas accumulated in the lower crust (~ 1100&#xa0;°C, ~ 10 kbar), later evolving into calc-alkaline and peraluminous silicic magmas, which crystallized garnet, biotite, and monazite at temperatures of ~ 700 to 800&#xa0;°C. Upper crustal silicic magma bodies formed through amalgamation processes, as evidenced by mineral chemistry and fiamme composition. The ignimbrite comprises the monotonous intermediate Steinkuhlenberg member and the monotonous rhyolitic Holzmühlental member, with geochemical heterogeneity reflecting magma mingling and contributions from deep-seated reservoirs. Thermobarometry identifies main magma chambers at 10–16&#xa0;km and 30–40&#xa0;km depths, with garnet stability fields (7–12 kbar) confirming the deep crustal input. Oscillatory zoning in quartz and feldspar reflect small-scale convection and the influence of injected primitive magmas. Ti-rich quartz rims and garnet assemblages suggest underplating of primitive magmas into silicic bodies. The observed enrichment of Y and HREE in rhyolitic fiamme points to significant interactions between crustal assimilation and high-silica rhyolitic magmas, potentially influenced by the extensional tectonic regime. This research enhances the understanding of magmatic differentiation, crustal contamination, and eruption dynamics in Late Paleozoic extensional systems, highlighting the role of prolonged magmatic evolution in forming large, silicic, crystal-rich magma reservoirs during post-Variscan continental rifting.</p> Graphical Abstract <p></p>

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Deciphering the garnet-bearing Flechtingen Ignimbrite, Central Germany: insights into Late Paleozoic magma reservoir dynamics and evolution

  • 期刊论文

  • 发表日期：

    2025年6月28日

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  • Alexander Repstock,
  • Manuela Zeug,
  • Elżbieta Słodczyk,
  • Mandy Zieger-Hofmann,
  • Andrew H. Menzies,
  • Michael Buchwitz,
  • Hripsime Gevorgyan,
  • Johannes Zieger,
  • Christoph Breitkreuz

摘要

Abstract

The Flechtingen Ignimbrite, a Late Paleozoic volcanic succession in Central Europe, serves as a valuable record of magmatic system evolution and dynamics. Geochemical analyses of bulk rock and fiamme, combined with mineral textures and chemistry, reveal the complex, multi-stage magma reservoir beneath the caldera, characterized by interactions between primitive and evolved magmas. Initially, alkaline and tholeiitic magmas accumulated in the lower crust (~ 1100 °C, ~ 10 kbar), later evolving into calc-alkaline and peraluminous silicic magmas, which crystallized garnet, biotite, and monazite at temperatures of ~ 700 to 800 °C. Upper crustal silicic magma bodies formed through amalgamation processes, as evidenced by mineral chemistry and fiamme composition. The ignimbrite comprises the monotonous intermediate Steinkuhlenberg member and the monotonous rhyolitic Holzmühlental member, with geochemical heterogeneity reflecting magma mingling and contributions from deep-seated reservoirs. Thermobarometry identifies main magma chambers at 10–16 km and 30–40 km depths, with garnet stability fields (7–12 kbar) confirming the deep crustal input. Oscillatory zoning in quartz and feldspar reflect small-scale convection and the influence of injected primitive magmas. Ti-rich quartz rims and garnet assemblages suggest underplating of primitive magmas into silicic bodies. The observed enrichment of Y and HREE in rhyolitic fiamme points to significant interactions between crustal assimilation and high-silica rhyolitic magmas, potentially influenced by the extensional tectonic regime. This research enhances the understanding of magmatic differentiation, crustal contamination, and eruption dynamics in Late Paleozoic extensional systems, highlighting the role of prolonged magmatic evolution in forming large, silicic, crystal-rich magma reservoirs during post-Variscan continental rifting.

Graphical Abstract