Two contrasting lithologies in off-rift subcontinental lithospheric mantle beneath central Europec-the Krzeniów (SW Poland) case study

Magdalena Matusiak-Malek, Jacek Puziewicz, Theodoros Ntaflos, Michel Gregoire, Mathieu Benoit, Andreas Kluegel

Veröffentlichungen: Beitrag in FachzeitschriftArtikelPeer Reviewed

Abstract

Miocene basanite from Krzeniów (SW Poland, eastern part of Cenozoic Central European Volcanic Province) contains scarce, small (usually <4 cm in diameter) spinel harzburgite and dunite mantle xenoliths. Two groups are defined based on the forsterite (Fo) content in olivine: group A (Fo 90.4-91.7) and group B (Fo 88.0-89.8). Both group A and B rocks are either clinopyroxenefree or clinopyroxene-poor. The group A orthopyroxene (mg# 0.91-0.92) is Al-poor and strongly light rare earth element (LREE) depleted [(La/Lu) N<0.42]. The mg# of group A clinopyroxene varies from 0.92 to 0.94 and is negatively correlated with its Al content. The trace element compositions of clinopyroxene define two patterns: A1, U-shaped [(La/Lu) N=20.23-64.73]; A2, almost linear LREE enriched [(La/Lu) N=11.91-14.00]. The group B orthopyroxene is also Al poor and LREE depleted [(La/Lu) N=0.03-0.04], but its mg# is lower than that in group A orthopyroxene (0.90-0.92).The mg# of group B clinopyroxene (0.90-0.92) is lower than that in group A, whereas theAl content is similar. The REE patterns of group B clinopyroxene mimic those of subgroup A2 [(La/Lu) N=5.64-11.30]. The group A harzburgites and dunites represent spinel-facies lithospheric mantle that underwent metasomatism by CO 2-bearing silicate melts subjected to chromatographic fractionation. Locally carbonatite-silicate immiscible melts were generated. The peridotites in the distal parts of the chromatographic system were little affected by metasomatism and preserve much of their pre-metasomatic, depleted characteristics. The group B rocks are similar to those of group A except for the lower mg# of orthopyroxene and olivine. They were affected by percolating alkaline silicate melt undersaturated in clinopyroxene, which lowered the mg# of the olivine and orthopyroxene ('Fe metasomatism'). The A and B peridotites are representative of the Miocene lithospheric mantle close to the margins of the neighbouring Eger Rift.

OriginalspracheEnglisch
Aufsatznummeregu042
Seiten (von - bis)1799-1828
Seitenumfang30
FachzeitschriftJournal of Petrology
Jahrgang55
Ausgabenummer9
DOIs
PublikationsstatusVeröffentlicht - Sep. 2014

ÖFOS 2012

  • 105105 Geochemie
  • 105120 Petrologie

Schlagwörter

  • MANTLE PERIDOTITES
  • Mantle metasomatism
  • xenolith

Zitationsweisen