Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

A method for in-situ analysis of trace-element contents in magmatic sulfides has been developed using laser ablation microprobe-inductively coupled plasma-quadrupole mass spectrometry, along with a hexapol collision cell (LA-HEX-ICP-QMS). Analysis of Ru, Rh, Pc1 in sulfide minerals using LA-ICP-MS analysis is hampered due to molecular argide interferences. By filling the hexapol with a gas mixture (7% H2 in He) interferences are reduced by ~7-25 times, with only 20-50% reduction in sensitivity. Gas blanks are also reduced and therefore detection limits are not compromised. The use of the hexapol collision cell allows for a simple LA-ICP-MS analysis routine and is suitable for most types of sulfides. By selecting interference free isotopes, the method significantly reduces or eliminates the requirement for external corrections. The technique is particularly effective at resolving real trace-element variations within each individual analysis which may otherwise be masked by changnng argide molecule formation. Detection limits for PGE range from ~20 ppb for Ru and Rh to <5 ppb for Pt and Ir using 40-80 µm spot sizes.