Miocene emplacement and rapid cooling of the Pohorje pluton at the Alpine-Pannonian-Dinaridic junction, Slovenia

L. Fodor, Axel Gerdes, István Dunkl, B. Koroknai, Z. Pécskay, Mirka Trajanova, Péter Horváth, Marko Vrabec, Bogomir Jelen, K. Balogh, Wolfgang Frisch

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

New laser ablation-inductive coupled plasma-mass spectrometry U-Pb analyses on oscillatory-zoned zircon imply Early Miocene crystallization (18.64 ± 0.11 Ma) of the Pohorje pluton at the southeastern margin of the Eastern Alps (northern Slovenia). Inherited zircon cores indicate two crustal sources: a late Variscan magmatic population (∼270-290 Ma), and an early Neoproterozoic one (850-900 Ma) with juvenile Hf isotope composition close to that of depleted mantle. Initial εHf of Miocene zircon points to an additional, more juvenile source component of the Miocene magma, which could be either a juvenile Phanerozoic crust or the Miocene mantle. The new U-Pb isotope age of the Pohorje pluton seriously questions its attribution to the Oligocene age 'Periadriatic' intrusions. The new data imply a temporal coincidence with 19-15 Ma magmatism in the Pannonian Basin system, more specifically in the Styrian Basin. K-Ar mineral- and whole rock ages from the pluton itself and cogenetic shallow intrusive dacitic rocks (∼18-16 Ma), as well as zircon fission track data (17.7-15.6 Ma), gave late Early to early Middle Miocene ages, indicating rapid cooling of the pluton within about 3 Million years. Medium-grade Austroalpine metamorphics north and south of the pluton were reheated and subsequently cooled together. Outcrop- and micro scale structures record deformation of the Pohorje pluton and few related mafic and dacitic dykes under greenschist facies conditions. Part of the solidstate fabrics indicate E-W oriented stretching and vertical thinning, while steeply dipping foliation and NW-SE trending lineation are also present. The E-W oriented lineation is parallel to the direction of subsequent brittle extension, which resulted in normal faulting and tilting of the earlier ductile fabric at around the Early/Middle Miocene boundary; normal faulting was combined with strike-slip faulting. Renewed N-S compression may be related to late Miocene to Quaternary dextral faulting in the area. The documented syn-cooling extensional structures and part of the strike-slip faults can be interpreted as being related to lateral extrusion of the Eastern Alps and/or to back-arc rifting in the Pannonian Basin.

Original languageEnglish
JournalSwiss Journal of Geosciences
Volume101
Issue numberSUPPL. 1
DOIs
Publication statusPublished - 2008

Fingerprint

Faulting
pluton
emplacement
Miocene
Cooling
cooling
Isotopes
faulting
zircon
Rocks
Strike-slip faults
lineation
Laser ablation
Crystallization
Stretching
Minerals
Mass spectrometry
Extrusion
basin
isotope

Keywords

  • Alps
  • Exhumation
  • Geochronology
  • Magmatism
  • Miocene
  • Thermobarometry

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geology
  • Palaeontology
  • Stratigraphy

Cite this

Miocene emplacement and rapid cooling of the Pohorje pluton at the Alpine-Pannonian-Dinaridic junction, Slovenia. / Fodor, L.; Gerdes, Axel; Dunkl, István; Koroknai, B.; Pécskay, Z.; Trajanova, Mirka; Horváth, Péter; Vrabec, Marko; Jelen, Bogomir; Balogh, K.; Frisch, Wolfgang.

In: Swiss Journal of Geosciences, Vol. 101, No. SUPPL. 1, 2008.

Research output: Contribution to journalArticle

Fodor, L. ; Gerdes, Axel ; Dunkl, István ; Koroknai, B. ; Pécskay, Z. ; Trajanova, Mirka ; Horváth, Péter ; Vrabec, Marko ; Jelen, Bogomir ; Balogh, K. ; Frisch, Wolfgang. / Miocene emplacement and rapid cooling of the Pohorje pluton at the Alpine-Pannonian-Dinaridic junction, Slovenia. In: Swiss Journal of Geosciences. 2008 ; Vol. 101, No. SUPPL. 1.
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abstract = "New laser ablation-inductive coupled plasma-mass spectrometry U-Pb analyses on oscillatory-zoned zircon imply Early Miocene crystallization (18.64 ± 0.11 Ma) of the Pohorje pluton at the southeastern margin of the Eastern Alps (northern Slovenia). Inherited zircon cores indicate two crustal sources: a late Variscan magmatic population (∼270-290 Ma), and an early Neoproterozoic one (850-900 Ma) with juvenile Hf isotope composition close to that of depleted mantle. Initial εHf of Miocene zircon points to an additional, more juvenile source component of the Miocene magma, which could be either a juvenile Phanerozoic crust or the Miocene mantle. The new U-Pb isotope age of the Pohorje pluton seriously questions its attribution to the Oligocene age 'Periadriatic' intrusions. The new data imply a temporal coincidence with 19-15 Ma magmatism in the Pannonian Basin system, more specifically in the Styrian Basin. K-Ar mineral- and whole rock ages from the pluton itself and cogenetic shallow intrusive dacitic rocks (∼18-16 Ma), as well as zircon fission track data (17.7-15.6 Ma), gave late Early to early Middle Miocene ages, indicating rapid cooling of the pluton within about 3 Million years. Medium-grade Austroalpine metamorphics north and south of the pluton were reheated and subsequently cooled together. Outcrop- and micro scale structures record deformation of the Pohorje pluton and few related mafic and dacitic dykes under greenschist facies conditions. Part of the solidstate fabrics indicate E-W oriented stretching and vertical thinning, while steeply dipping foliation and NW-SE trending lineation are also present. The E-W oriented lineation is parallel to the direction of subsequent brittle extension, which resulted in normal faulting and tilting of the earlier ductile fabric at around the Early/Middle Miocene boundary; normal faulting was combined with strike-slip faulting. Renewed N-S compression may be related to late Miocene to Quaternary dextral faulting in the area. The documented syn-cooling extensional structures and part of the strike-slip faults can be interpreted as being related to lateral extrusion of the Eastern Alps and/or to back-arc rifting in the Pannonian Basin.",
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AU - Fodor, L.

AU - Gerdes, Axel

AU - Dunkl, István

AU - Koroknai, B.

AU - Pécskay, Z.

AU - Trajanova, Mirka

AU - Horváth, Péter

AU - Vrabec, Marko

AU - Jelen, Bogomir

AU - Balogh, K.

AU - Frisch, Wolfgang

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KW - Alps

KW - Exhumation

KW - Geochronology

KW - Magmatism

KW - Miocene

KW - Thermobarometry

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