Lower crustal zircons reveal Neogene metamorphism beneath the Pannonian Basin (Hungary)

Hilary Downes, Andrew Carter, Richard Armstrong, Gabor Dobosi, Antal Embey-Isztin

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Abstract

Neogene alkaline intraplate volcanic deposits in the Pannonian Basin (Hungary) contain many lower crustal granulite-facies xenoliths. U-Pb ages have been determined for zircons separated from a metasedimentary xenolith, using LA-ICPMS and SHRIMP techniques. The zircons show typical metamorphic characteristics and are not related to the hostmagmatism. The oldest age recorded is late Devonian, probably related to Variscan basement lithologies. Several grains yield Mesozoic dates for their cores, which may correspond to periods of orogenic activity. Most of the zircons show young ages, with some being Palaeocene-Eocene, but the majority being younger than 30Ma. The youngest zircons are Pliocene (5.1-4.2 Ma) and coincide with the age of eruptions of the host alkali basalts. Such young zircons, so close to the eruption age, are unusual in lower crustal xenoliths, and imply that the heat flow in the base of the Pannonian Basin was sufficiently high to keep many of them close to their blocking temperature. This suggests that metamorphism is continuing in the lower crust of the region at the present day.

Original languageEnglish
Pages (from-to)223-233
Number of pages11
JournalOpen Geosciences
Volume7
Issue number1
DOIs
Publication statusPublished - Jan 27 2015

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Keywords

  • Pannonian Basin
  • lower crust
  • xenolith
  • zircons

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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