Table 1.

U–Th–Pb isotopic data for zircon analyses

SampleRadiogenic isotope ratiosIsotopic ages
Th/U206Pb* × 10−13 molmol% 206Pb*Pb*/PbcPho (pg)206Pb/204Pb208Pb/206Pb207Pb/206Pb% err207Pb/235U% err206Pb/238U% errcorr. coef.207Pb/206Pb±207Pb/235U±206Pb/238U±
(a)(b)(c)(c)(c)(c)(d)(e)(e)(f)(e)(f)(e)(f)(g)(f)(g)(f)(g)(f)
Comley lb
z10.6940.354198.8026.30.3515360.2160.0599570.2910.8156550.3680.0986660.1380.688601.726.31605.621.68606.660.80
z21.3440.318096.84110.855850.4190.0585780.5340.7199160.6400.0891340.1110.960551.2211.66550.622.72550.470.59
z30.7101.025699.5368.50.4039610.2220.0576570.1490.6605980.2180.0830970.0930.841516.413.26514.980.88514.660.46
z40.7910.695799.12370.5121110.2470.0576400.2670.6597220.3230.0830110.1140.626515.785.87514.441.30514.140.56
z50.9480.350997.59140.717670.2960.0586650.4790.7214080.5660.0891870.1580.644554.4010.46551.502.41550.800.84
z60.5890.571699.11350.4220750.1840.0586370.1960.7245510.2740.0896170.1100.810553.334.28553.351.17553.350.58
z70.5360.565799.27420.3425230.1670.0576400.1810.6634690.2530.0834830.1020.810515.743.97516.731.02516.960.51
z80.4870.302393.4541.752790.1510.0580690.8080.7152340.9240.0893310.2060.638532.0317.70547.853.91551.661.09
Comley ub
z12.3652.328498.84382.2615680.7390.0574300.1750.6500880.2970.0820970.1890.831508.003.85508.531.19508.650.92
z22.0337.931899.601042.6844750.6360.0575020.0980.6512410.1860.0821400.0980.949510.712.15509.240.74508.920.48
z32.2952.372199.48861.0135880.7180.0575390.1390.6519310.2340.0821740.1350.850512.153.06509.670.94509.110.66
z41.8575.520499.842600.72116830.5810.0575520.0970.6519660.1940.0821610.1210.915512.562.13509.690.78509.050.59
z50.7204.754599.741241.0271040.2250.0579810.1030.6848950.3620.0856720.3250.960528.702.26529.731.49529.971.65
z62.4563.275899.863170.39127740.7680.0575180.0960.6516480.1830.0821690.1030.924511.362.12509.490.73509.080.51
z73.0460.692498.13271.099870.9520.0574430.3380.6512530.4140.0822260.1210.714508.597.44509.251.66509.400.59
z82.1090.719298.47280.9212120.6600.0575350.3490.6521450.4110.0822070.1220.616511.987.67509.801.65509.310.60
Cwm Bach 1
z70.7821.054898.38201.4311330.2440.0576270.2470.6661140.3180.0838350.0990.795515.275.42518.351.29519.050.50
z80.7401.587196.1685.284690.2310.0577360.2980.6680740.3720.0839220.1090.755519.446.55519.541.51519.560.54
z90.7731.337398.83271.3115650.2420.0577590.3010.6638660.3640.0833600.1260.633520.326.60516.981.48516.220.63
z110.7022.488799.49621.0536060.2190.0577390.1320.6680580.2240.0839160.1250.864519.522.90519.530.91519.530.62
z120.7692.083898.83272.0515490.2400.0576260.1780.6661140.2610.0838360.1200.810515.253.91518.351.06519.050.60
z130.7180.841398.74250.8814640.2240.0577060.1780.6678900.3790.0839420.1200.618518.307.00519.431.54519.690.60
z140.7870.771197.96161.328990.2460.0577540.3190.6680780.3990.0838960.1040.743520.127.22519.541.62519.410.52
  • (a) z1, z2, etc. are labels for fractions composed of single zircon grains or fragments; all fractions annealed and chemically abraded after Mattinson (2005). (b) Model Th/U ratio calculated from radiogenic 208Pb/206Pb ratio and 207Pb/235U age. (c) Pb* and Pbc represent radiogenic and common Pb, respectively; mol% 206Pb* with respect to radiogenic, blank and initial common Pb. (d) Measured ratio corrected for spike and fractionation only. (e) Corrected for fractionation, spike, and common Pb; up to 1 pg of common Pb was assumed to be procedural blank: 206Pb/204Pb = 18.50 ± 0.50%; 207Pb/204Pb = 15.8 ± 0.5%; 208Pb/204Pb = 38.02 ± 0.75% (all uncertainties 1σ). Excess over blank was assigned to initial common Pb. (f) Errors are 2σ, propagated using the algorithms of Crowley et al. (2007) and Schmitz & Schoene (2007). (g) Calculations are based on the decay constants of Jaffey et al. (1971). 206Pb/238U and 207Pb/206Pb ages corrected for initial disequilibrium in 230Th/238U using Th/U [magma] = 3.