Spinel lherzolite xenoliths from the Premier kimberlite (Kaapvaal craton, South Africa)

nature and evolution of the shallow upper mantle beneath the Bushveld complex

Michel Grégoire*, C. Tinguely, D. R. Bell, A. P. le Roex

*Corresponding author for this work

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Coarse-grained, granular spinel lherzolites xenoliths from the Premier kimberlite show evidence of melt extraction and metasomatic enrichment, documenting a complex history for the shallow mantle beneath the Bushveld complex. Compositions of orthopyroxene, clinopyroxene and spinel indicate equilibration within the spinel-peridotite facies of the upper mantle, at depths from 80 to 100 km and temperatures from 720 to 850 °C. Bulk compositions have lower Mg-number [atomic 100 Mg/(Mg + Fe*)] than previously studied spinel peridotites from Premier, and have higher Mg/Si than low-temperature coarse grained garnet lherzolites, suggesting shallower melting conditions or metasomatic enrichment. Clinopyroxene in one sample is highly LREE-depleted indicating very minor modification of a residue of ∼20% melt extraction, whereas the calculated REE pattern for a melt in equilibrium with a mildly LREE-depleted sample is similar to MORB or late Archean basalt, possibly related to the Bushveld Complex. Bulk and mineral compositions suggest minimal refertilization by silicate melts in four out of six samples, but REE patterns indicate introduction of a LIL-enriched component that may be related to kimberlite.

Original languageEnglish
Pages (from-to)185-205
Number of pages21
JournalLithos
Volume84
Issue number3-4
DOIs
Publication statusPublished - Oct 2005
Externally publishedYes

    Fingerprint

Keywords

  • Bushveld
  • Kaapvaal craton
  • Mantle metasomatism
  • Mantle xenoliths
  • Spinel lherzolites
  • Trace elements

Cite this