Three compositional varieties of rare-earth element ore

eudialyte-group minerals from the Norra Kärr Alkaline Complex, southern Sweden

Axel S L Sjöqvist*, David H. Cornell, Tom Andersen, Muriel Erambert, Mattias Ek, Magnus Leijd

*Corresponding author for this work

Research output: Contribution to journalArticle

30 Citations (Scopus)
107 Downloads (Pure)

Abstract

Agpaitic nepheline syenites at the Norra Kärr Alkaline Complex, southern Sweden, are rich in zirconium and rare-earth elements (REE), which are mainly accommodated in eudialyte-group minerals (EGM). Norra Kärr hosts three compositionally distinct groups of EGM, which are complex zirconosilicates. Analyses of EGM by electron beam energy-dispersive (SEM-EDS) and wavelength-dispersive (WDS-EMP) X-ray microanalysis are presented and compared, complemented by whole-rock analyses. The SEM-EDS and WDS-EMP methods produce comparable results for most elements. Considering that most SEM instruments have a user-friendly EDS system, it is a useful tool for reconnaissance work in research and especially in exploration-related studies. The EGM evolved markedly from an initial Fe-rich and REE-poor, but HREE-dominated variety, to an intermediate Fe-Mn and HREE-rich one, and to a final Mn- and LREE-rich variety, which occur in rocks classified as lakarpite and grennaite. Based on the Mn/(Fe+Mn) ratios of the EGM, this trend is interpreted as a result of magmatic evolution. The threefold diversity of EGM presented in this work is much broader than has previously been documented.

Original languageEnglish
Pages (from-to)94-120
Number of pages27
JournalMinerals
Volume3
Issue number1
DOIs
Publication statusPublished - 20 Mar 2013

Bibliographical note

Copyright the Author(s) 2013. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • Agpaitic rocks
  • Eudialyte-group minerals
  • Nepheline syenite
  • Norra Kärr Alkaline Complex
  • Rare-earth elements
  • SEM-EDS
  • WDS-EMP

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