Three Compositional Varieties of Rare-Earth Element Ore: Eudialyte-Group Minerals from the Norra Kärr Alkaline Complex, Southern Sweden

Minerals

Axel S.L. Sjöqvist²  David H. Cornell²  Tom Andersen¹  Muriel Erambert¹  Mattias Ek² 

[1] Department of Geosciences, University of Oslo, PO Box 1047 Blindern, N-0316 Oslo, Norway; E-Mails:;Department of Earth Sciences, University of Gothenburg, PO Box 460, SE-405 30 Göteborg, Sweden; E-Mails:

关键词: eudialyte-group minerals;    agpaitic rocks;    nepheline syenite;    rare-earth elements;    Norra Kärr Alkaline Complex;    SEM-EDS;    WDS-EMP;   

DOI  :  10.3390/min3010094

来源: mdpi

【 摘 要 】

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.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.