Origin of amphibole megacrysts in the Pliocene-Pleistocene basalts of the Carpathian-Pannonian region

A. Demény, Torsten W. Vennemann, Z. Homonnay, Andy Milton, Antal Embey-Isztin, G. Nagy

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Major and trace element compositions, stable H and O isotope compositions and Fe3+ contents of amphibole megacrysts of Pliocene-Pleistocene alkaline basalts have been investigated to obtain information on the origin of mantle fluids beneath the Carpathian-Pannonian region. The megacrysts have been regarded as igneous cumulates formed in the mantle and brought to the surface by the basaltic magma. The studied amphiboles have oxygen isotope compositions (5.4±0.2 ‰, 1 σ), supporting their primary mantle origin. Even within the small δ18O variation observed, correlations with major and trace elements are detected. The negative δ18O-MgO and the positive δ18O-La /Sm(N) correlations are interpreted to have resulted from varying degrees of partial melting. The halogen (F, Cl) contents are very low (2 = 0.84) can be related to the Mg-Cl avoidance in the amphibole structure. The relationships between water contents, H isotope compositions and Fe3+ contents of the amphibole megacrysts revealed degassing. Selected undegassed amphibole megacrysts show a wide δD range from -80 to -20 ‰. The low δD value is characteristic of the normal mantle, whereas the high δD values may indicate the influence of fluids released from subducted oceanic crust. The chemical and isotopic evidence collectively suggest that formation of the amphibole megacrysts is related to fluid metasomatism, whereas direct melt addition is insignificant.

Original languageEnglish
Pages (from-to)179-189
Number of pages11
JournalGeologica Carpathica
Volume56
Issue number2
Publication statusPublished - Apr 2005

Fingerprint

amphibole
Pliocene
basalt
Pleistocene
mantle
fluid
trace element
isotope
halogen
cumulate
degassing
metasomatism
oceanic crust
partial melting
oxygen isotope
water content
magma
melt

Keywords

  • Amphibole megacrysts
  • Carpathian-Pannonian region
  • Degassing
  • Mantle metasomatism
  • Stable isotopes
  • Trace elements

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Origin of amphibole megacrysts in the Pliocene-Pleistocene basalts of the Carpathian-Pannonian region. / Demény, A.; Vennemann, Torsten W.; Homonnay, Z.; Milton, Andy; Embey-Isztin, Antal; Nagy, G.

In: Geologica Carpathica, Vol. 56, No. 2, 04.2005, p. 179-189.

Research output: Contribution to journalArticle

Demény, A. ; Vennemann, Torsten W. ; Homonnay, Z. ; Milton, Andy ; Embey-Isztin, Antal ; Nagy, G. / Origin of amphibole megacrysts in the Pliocene-Pleistocene basalts of the Carpathian-Pannonian region. In: Geologica Carpathica. 2005 ; Vol. 56, No. 2. pp. 179-189.
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