“…The 40 Ar/ 39 Ar analyses were performed at the University of Leeds (UK) using a doublevacuum, resistance-heated Ta furnace and a modified AEI MS10 mass spectrometer following the procedures described in Guise & Roberts (2002). Approximately 0.02 to 0.06 gram of material was irradiated in high-purity Al foil at the McMaster reactor in Hamilton (Canada; Pidruczny et al 1994) and at the Risø reactor in Roskilde (Denmark) for 10 hours. Samples BGS-1, OC-3, VO-2 and VO-3 were irradiated at the McMaster facility, and the interference correction factors were ( 40 Ar/ 39 Ar) K = 0.02, ( 36 Ar/ 39 Ar) Ca = 0.32 and ( 37 Ar/ 39 Ar) Ca = 1515.…”