Alpine prograde and retrograde metamorphism in an overthrusted part of the basement, Great Plain, Pannonian Basin, eastern Hungary

Péter Árkai, Anikó Bérczi-Makk, Dénes Hajdu

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As proved by a hydrocarbon exploratory borehole, a pre-Alpine polymetamorphic complex was thrusted over a low-temperature prograde metamorphic Mesozoic sequence in a Neogene depression of the Pannonian Basin, eastern Hungary. The detectable first, prograde, medium thermal gradient amphibolite facies event was followed by a retrograde, medium thermal gradient amphibolite facies event was followed by a retrograde metamorphism connected to a mylonite formation in the overthrusted complex. The polymetamorphic history of this gneiss-mica schist-amphibolite complex has also been recorded by the changes in chemistry of amphibole, white K-mica, and plagioclase. The footwall Mesozoic parautochthon is built up by an upper sub-unit (dolomitic-fine clastic), a middle (calcareous-fine clastic) and a lower one (calcareous-basic to intermediate volcanoclastic). On the basis of phyllosilicate crystallinity and vitrinite reflectance data, the metamorphic grade of the upper part corresponds to the low-temperature part of the anchizone and that of the middle and lower parts to the epizone, having been very close to the boundary between the epizone and anchizone. The maturity parameters of the basin-filling Neogene formations refer only to diagenetic conditions, indicating non-equilibrium conditions. The Neogene (<5 Ma) burial has had no detectable effects on the metamorphic conditions of the basement units, which had already occupied their present tectonic position during their post-metamorphic uplift (cooling) in the Upper Cretaceous. The retrograde metamorphism in the polymetamorphic nappe and the low-temperature prograde metamorphism in the Mesozoic parautochthon proved to be of Eo-Alpine (Cretaceous) age, and was older than the overthrusting. The tectonic (shearing) strain connected to the overthrusting influenced the structural state of phyllosilicates in a rather irregular way, both in the hanging wall and the footwall units.

Original languageEnglish
Pages (from-to)179-210
Number of pages32
JournalActa Geologica Hungarica
Issue number2
Publication statusPublished - Jan 1 1998


ASJC Scopus subject areas

  • Geology

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