Amphibole-bearing assemblages as indicators of microdomain-scale equilibrium conditions in metabasites: An example from Alpine ophiolites of the Meliata Unit, NE Hungary

P. Horváth, P. Árkai

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The polymetamorphic evolution of metamorphosed Mesozoic ophiolitic rocks in NE Hungary was studied by microtextural and mineral chemical analyses of metagabbros and metabasalts. Both rock types preserved their original textures remarkably well. By contrast, magmatic minerals (especially clinopyroxene) were preserved only in the metagabbros. The original magmatic whole-rock and mineral chemical features had a strong influence on the formation and preservation of the various metamorphic assemblages as testified by the chemically different amphiboles (and other major minerals) formed in various microdomains. The calculated metamorphic P-T conditions are in part different for metabasalts and metagabbros. These results are in accordance with the observed petrographic features, among which the sequence of crystallisation of Na-amphibole and actinolite in the two rock types is most characteristic. Crystallisation of actinolite is followed by Na-amphibole in metabasalts, while Na-amphibole formed first in the metagabbros. Overall equilibrium conditions were not attained throughout the NE Hungarian Mesozoic ophiolite unit during Alpine metamorphic evolution. Additionally, various disequilibrium metamorphic assemblages with several generations of chemically complex amphiboles were formed even on the thin section scale. Various P-T paths during the tectonic evolution of the accretionary wedge were experienced by parts of the dismembered ophiolite sequence, which originally formed a coherent unit, and were brought back into close spatial relationship only during the post-metamorphic exhumation processes.

Original languageEnglish
Pages (from-to)233-258
Number of pages26
JournalMineralogy and Petrology
Volume84
Issue number3-4
DOIs
Publication statusPublished - Jul 2005

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Bearings (structural)
Amphibole Asbestos
Hungary
metabasite
amphiboles
amphibole
metabasalt
Minerals
Rocks
minerals
rocks
mineral
Crystallization
ophiolite
rock
crystallization
P-T conditions
accretionary prism
Tectonics
thin section

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

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title = "Amphibole-bearing assemblages as indicators of microdomain-scale equilibrium conditions in metabasites: An example from Alpine ophiolites of the Meliata Unit, NE Hungary",
abstract = "The polymetamorphic evolution of metamorphosed Mesozoic ophiolitic rocks in NE Hungary was studied by microtextural and mineral chemical analyses of metagabbros and metabasalts. Both rock types preserved their original textures remarkably well. By contrast, magmatic minerals (especially clinopyroxene) were preserved only in the metagabbros. The original magmatic whole-rock and mineral chemical features had a strong influence on the formation and preservation of the various metamorphic assemblages as testified by the chemically different amphiboles (and other major minerals) formed in various microdomains. The calculated metamorphic P-T conditions are in part different for metabasalts and metagabbros. These results are in accordance with the observed petrographic features, among which the sequence of crystallisation of Na-amphibole and actinolite in the two rock types is most characteristic. Crystallisation of actinolite is followed by Na-amphibole in metabasalts, while Na-amphibole formed first in the metagabbros. Overall equilibrium conditions were not attained throughout the NE Hungarian Mesozoic ophiolite unit during Alpine metamorphic evolution. Additionally, various disequilibrium metamorphic assemblages with several generations of chemically complex amphiboles were formed even on the thin section scale. Various P-T paths during the tectonic evolution of the accretionary wedge were experienced by parts of the dismembered ophiolite sequence, which originally formed a coherent unit, and were brought back into close spatial relationship only during the post-metamorphic exhumation processes.",
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