Conference Proceedings

Matrix effects in Pb/U measurements during LA-ICP-MS analysis of the mineral apatite

Jay Thompson, Sebastien Meffre, Roland Maas, Vadim Kamenetsky, Maya Kamenetsky, Karsten Goemann, Kathy Ehrig, Leonid Danyushevsky

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY | ROYAL SOC CHEMISTRY | Published : 2016

Abstract

U-Pb ages of several apatite reference materials, acquired by LA-ICP-MS over a 3.5 year period using the Otter Lake apatite as a primary standard, show systematic offsets (up to 3%) from reference ages obtained by isotope dilution mass spectrometry. The offsets are well outside known analytical errors from counting statistics, uncertainty in common Pb corrections or excess 206Pb in high-Th/U materials. The age offsets also do not correlate strongly with the concentrations of F, Cl, REE, Th and U, with accumulated radiation dose or with the depth of ablation pits. We suggest that the observed age offsets are related to elemental fractionation at the ablation site, but their direction and magn..

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University of Melbourne Researchers

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Funding Acknowledgements

The authors would like to thank David Chew for providing most of the apatite samples used in this study. Funding for this project came from the Australian Research Council (ARC) Linkage Grant titled: "The supergiant Olympic Dam U-Cu-Au-REE ore deposit: towards a new genetic model". We would also like to thank the reviewers for their helpful comments.