In situ Re–Os geochronology of Re-rich Palaeogene molybdenite by LA-ICP-MS/MS
Date
2025
Authors
Glorie, S.
Thompson, J.
Gilbert, S.
Souders, A.K.
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Journal of Analytical Atomic Spectrometry, 2025; 40(5):1394-1402
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Stijn Glorie, Jay M. Thompson, Sarah E. Gilbert and A. Kate Souders
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Abstract
In situ Re–Os geochronology by LA-ICP-MS/MS was previously demonstrated by reacting Os with CH₄ or N₂O reaction gasses. However, for both reactions, a minor proportion of the Re parent isotope also reacts, potentially leading to significant isobaric interferences of ¹⁸⁷Re on ¹⁸⁷Os, especially for young samples with little radiogenic in-growth. Here we present an interlaboratory comparison and compare three reaction gas mixtures (CH₄ + H₂ + He, N₂O and N2O + He) with the aim to robustly date Palaeogene (66–23 Ma) molybdenite from the Bingham Canyon and Henderson deposits. CH₄ mixed with H₂ gas gives the highest sensitivity, while N₂O and He gas buffer Re reaction. On balance, the analytical method involving N₂O + He reaction gas is most suitable for dating Palaeogene molybdenite, resulting in age precision of 2.6% for Bingham and 5.8% for Henderson. For older, >1 Ga molybdenite, CH₄ + H₂ + He may give comparatively better age precision.
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This journal is © The Royal Society of Chemistry 2025