Contributions to Mineralogy and Petrology

, Volume 147, Issue 5, pp 549–564

U-Pb columbite-tantalite chronology of rare-element pegmatites using TIMS and Laser Ablation-Multi Collector-ICP-MS


    • Dept. of Earth SciencesThe Open University
    • Geological Survey of Canada
  • G. L. Foster
    • NERC Isotope Geosciences Laboratory
    • Department of GeologyLeicester University
  • R. L. Romer
    • GeoForschungsZentrum Potsdam
  • A. G. Tindle
    • Dept. of Earth SciencesThe Open University
  • S. P. Kelley
    • Dept. of Earth SciencesThe Open University
  • S. R. Noble
    • NERC Isotope Geosciences Laboratory
  • M. Horstwood
    • NERC Isotope Geosciences Laboratory
  • F. W. Breaks
    • Ontario Geological Survey
Original Paper

DOI: 10.1007/s00410-003-0538-y

Cite this article as:
Smith, S.R., Foster, G.L., Romer, R.L. et al. Contrib Mineral Petrol (2004) 147: 549. doi:10.1007/s00410-003-0538-y


U-Pb isotopic analyses using TIMS and Laser Ablation-Multi Collector-ICP-MS were carried out on columbite-tantalite minerals from three suites of rare-element (Li, Cs, Ta) pegmatites in the Superior Province of Canada. Conventional TIMS analyses of these columbite-tantalite crystals produce scattered data and reverse discordance even after HF leaching of the grains prior to dissolution, possibly reflecting the incomplete removal of the open-system metamict segments during sample preparation. LA-MC-ICP-MS analyses of unleached, primary columbite free from inclusions and alteration give consistent and precise (<0.5%) Pb-Pb ages, demonstrating the utility of this approach. However, normal and reverse discordance is also observed in U-Pb data from LA-MC-ICP-MS analyses. This discordance represents either U-Pb mobilisation during recent weathering, sample preparation and/or an analytical artefact originating from variable elemental fractionation between U and Pb during ablation and ionisation that itself may have its origin in the contrasting metamictization of the dated columbite and the monazite standard used. Best age estimates of columbite from pegmatites in the Superior Province are; 2670±5 Ma for the Pakeagama Lake pegmatite, 2644±7 Ma for the Separation Rapids group, and 2665±8 Ma for the Mavis Lake group. The ages broadly show that the rare-element pegmatites are temporally synchronous with adjacent peraluminous granites.

Copyright information

© Springer-Verlag 2004