Eruptive pulsing of maar and scoria cone clusters in the West Eifel volcanic field, Germany, during the last glacial maximum revealed by zircon (U-Th)/He dating of crustal xenoliths

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The West Eifel Volcanic Field (Germany) is the type locality of maars, a common volcano type in continental intraplate volcanic fields. Timescales of eruptive recurrence and spatiotemporal clustering of maars and scoria cones are critical to assess controls of melting, magma ascent, and venting in such fields. Here, we overcome limitations of conventional geochronometers to constrain these timescales through zircon (U-Th)/He dating of crustal xenoliths accidentally scavenged during magma ascent. Zircon U-Th-Pb crystallization ages distinguish metaigneous and metasedimentary xenolith provenance from Palaeozoic basement. The absence of pre-eruptive ⁴He in zircon was verified by dating petrologically diverse xenoliths from individual vents, yielding consistent results. Zircon (U-Th)/He eruption ages are: Meerfelder Maar (75 ± 4 ka, all 2σ), Mosenberg (78 ± 9 ka), Emmelberg (48 ± 3 ka), Daun maar group (23 ± 1 ka), Pulvermaar (25 ± 2 ka), Wartgesberg (23 ± 3 ka), Oberwinkler Maar (195 ± 7 ka), and Facher Höhe (25 ± 2 ka). Oberwinkler Maar falls into a previously postulated volcanic hiatus, whereas two volumetrically dominant clusters at c. 25 and 75 ka coincide with deposition of the Central European Eltville and Rocourt tephra markers. The onset of volcanic activity and its peak coinciding with the last glacial maximum correlate with progressive marine regression in the North Sea basin. This contradicts previous models linking volcanic upsurges to interglacial warming and sea level rise. Zircon (U–Th)/He dating of pyrometamorphic crustal xenoliths thus provides a robust chronological framework to improve knowledge about eruptive pulsing in intraplate volcanic fields.