U–Pb analyses of zircon in a metarhyolite (AF94-DD2) from the Delaney Dome Formation (modified from Friedrich 1998)

ConcentrationErrors 2-s (%)Age (Ma)d
FractionWeight (μg)U (ppm)Pb (ppm)206Pba/204Pb208Pb/206Pbb206Pb/238Uc% err207Pb/235Uc% err207Pb/206Pbc% err206Pb/238U207Pb/235U207Pb/206Pbcorr. coef.Pbe (pg)Pba/Pbe

a Radiogenic Pb.

b Measured ratio corrected for spike and fractionation only. Mass fractionation correction of 0.15%/amu ± 0.04%/amu was applied to single collector Daly analyses and 0.12%/amu ± 0.04% for dynamic Faraday–Daly analyses.

c Corrected for fractionation, spike, blank, and initial common Pb.

d Age calculations are based on the decay constants of Steiger & Jäger (1977).

e Total common Pb in analysis. Total procedural blank for Pb ranged from 0.65–3.7 pg and < 1.0 pg for U. Blank isotopic composition: 206Pb/204Pb = 19.10 ± 0.1, 207Pb/204Pb =15.71 ± 0.1,208Pb/204Pb = 38.65 ± 0.1.

All errors are reported as 2σ. Number of zircons in each fraction shown in parentheses after fraction name. Sample weights are estimated using a video monitor with gridded screen and are known to within 40%. Common Pb corrections were calculated using the model of Stacy & Kramers (1975) and the interpreted age of the sample.