Alpine low-T prograde metamorphism in the post-Variscan basement of the Great Plain, Tisza Unit (Pannonian Basin, Hungary)

P. Arkai, K. Balogh, A. Berczi-Makk

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Abstract

Traditionally, the Tisza Unit in the Pannonian Basin has been considered a very stable, refractory crustal block or microplate, the pre-Tertiary basement of which escaped Alpine prograde metamorphism. After describing sporadic occurrences of Alpine metamorphism from the Mesozoic (Arkai 1990; Balogh et al. 1990; Arkai et al. 1998), a systematic regional study applying microstructural, mineral paragenetic, illite and chlorite crystallinity, white K-mica geobarometric and K-Ar isotope geochronological methods was carried out on the post-Variscan (mainly Mesozoic) part of the pre-Tertiary basement of the Great Plain (Tisza Unit). New data prove that prograde metamorphism affected considerable parts of the post-Variscan basement beneath the overthrusted polymetamorphic Variscan - pre-Variscan (?) formations, or in a disrupted, allochthonous tectonic position along the main Alpine thrust zones. The regional metamorphism was of an orogenic (dynamothermal) type. Its grade culminated in the epizone (greenschist facies chlorite zone) in the easternmost part (Sarand area). In addition, anchizonal rocks have also been described from various parts of the basement. The age of the ca. 200-350 °C prograde, medium, transitional low-medium pressure-type metamorphism is Cretaceous. Thus, the Tisza Unit formed an organic part of the Mediterranean orogenic belt, also from the point of view of regional metamorphism.

Original languageEnglish
Pages (from-to)43-63
Number of pages21
JournalActa Geologica Hungarica
Volume43
Issue number1
Publication statusPublished - Jan 1 2000

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Keywords

  • Alpine metamorphism
  • Chlorite crystallinity
  • Hungary
  • Illite crystallinity
  • Isotope geochronology
  • K-Ar dating
  • Low-T metamorphism
  • Pannonian Basin
  • Tisza Unit

ASJC Scopus subject areas

  • Geology

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