Table 4.

Zircon SIMS U–Th–Pb data

Sample1 spot no.U (ppm)Th (ppm)Th/U2Pb (ppm)206Pbc3 %Ratios4Ages4Disc. %
238U/206Pb±σ (%)207Pb/206Pb±σ (%)206Pb/238U±σ207Pb/206Pb±σ
St Johns Harbour, sample L1412, n5696
Xenocrystic core
20.183530.5995.80.321.2981.50.351480.523683413713.47.81
19.110301950.18666.70.061.9091.00.186090.182715222707.93.00
23.1939880.09602.60.081.8841.00.185760.202744222705.03.3−2
Igneous
05.110333040.29635.20.062.0301.00.169380.182582212551.53.0−1
07.15022490.48319.40.132.0431.00.169320.302568222550.95.0−1
02.17075310.73477.70.122.0211.00.169160.312591222549.35.2−2
22.16812580.37429.50.122.0111.00.169150.242603222549.23.9−3
25.110362670.25638.70.072.0061.00.169040.182607222548.13.1−3
06.17814030.49498.60.082.0421.00.168850.222570212546.33.7−1
27.16742650.38420.80.082.0361.00.168620.232576222544.03.8−2
12.1289770.26175.80.132.0341.10.168520.342578222543.05.7−2
26.15012160.42313.90.112.0471.00.167960.272565222537.44.5−1
Dog Island, sample L1414A, n5546
Igneous
12.3137680.5096.61.8781.30.191710.442752302756.97.10
04.2113750.6683.21.8711.50.191650.452760332756.37.40
12.2107320.3173.61.8471.50.191530.422789342755.36.8−1
02.1138760.58100.41.8491.30.191530.522786302755.38.5−1
03.11701590.96132.41.8641.50.191400.322769342754.35.3−1
09.2119800.6687.01.8821.20.191240.472747262752.97.70
04.11951680.88149.61.8641.50.191220.312769342752.75.1−1
01.3130730.5893.91.8771.50.191020.332753332751.05.40
10.2239750.31163.61.8661.30.191000.342766302750.85.6−1
05.11661560.91127.01.8861.30.190630.372743302747.66.10
06.2153650.42106.90.111.8621.40.190560.412771322747.06.7−1
01.176320.4552.91.8781.60.190500.622752352746100
08.2144580.3998.71.8891.20.190360.462739262745.37.60
04.2322610.17210.00.011.8941.60.189880.342733362741.25.60
08.22651110.42185.30.031.8681.40.189690.472764312739.57.7−1
01.2113530.4980.81.8491.70.189670.67278739273911−2
03.2135590.4594.50.041.8781.80.189090.362752402734.25.8−1
Excluded
10.11921580.79146.21.8571.70.194070.392777382777.06.30
12.4125720.6093.21.8221.60.193530.392820362772.46.5−2
11.234772.3932.81.8921.80.186790.97273540271416−1
10.3134550.4291.41.9061.40.186280.472719302709.67.70
Discordant
07.1918300.03608.70.431.8491.50.21731.72787332961277
Dog Island, sample L1414B, n5541
Igneous and/or xenocrystic
03.253260.4957.20.561.3631.80.339680.443548483661.36.84
05.1162990.66191.80.021.2711.40.339430.263741393660.23.9−3
05.375610.8287.70.381.3241.50.336770.473626413648.27.21
05.282500.6493.40.251.3141.60.336490.533647453646.98.10
01.1158560.36170.60.021.3221.60.335460.493631463642.27.50
06.1220790.39243.60.471.2971.40.334400.353685393637.45.4−2
04.2201670.35214.80.021.3261.30.325020.263622373593.83.9−1
04.1113115261.401389.50.971.3841.30.323730.363506353587.75.53
06.2137490.36143.40.041.3561.60.322740.343561443582.95.21
07.13411890.54366.60.811.3641.80.321590.213546503577.53.31
Discordant
01.219917830.271160.10.662.2701.70.22402.223533330093526
Hebron Fjord, South shore, sample L1453, n5736
Group 1 metamorphic (excluded from minimum pooled age)
54.170140.18349.40.111.7881.20.202760.602864282848.69.7−1
 8.1106270.27472.30.071.8421.20.189670.462796272739.37.6−3
30.1181550.308124.50.061.8521.10.189170.382783252735.06.2−2
25.1100190.19567.01.8601.20.188710.502773282730.98.2−2
 34.197260.27465.30.071.8761.20.188210.592755262726.69.7−1
 64.1101200.20365.81.9111.40.186900.442713312715.17.30
 37.2119290.24778.51.9011.10.186890.472725252715.07.8−1
 26.1100230.21462.50.311.9901.20.186570.562624262712.19.24
Group 1 metamorphic (used for pooled minimum age)
 15.13081130.365208.30.051.9041.00.186330.312721232710.15.1−1
 45.2133360.26387.50.061.9051.10.186330.642720252710100
 57.17471690.225483.40.031.9301.10.186330.182691252710.12.91
 19.15422470.455370.10.051.9191.00.186200.232703232708.93.80
  4.2291970.348197.50.031.8851.00.186180.342743232708.75.6−2
 74.15352110.399362.80.031.9111.30.186180.252714282708.74.10
  4.1107250.24170.50.051.8971.10.186150.462729252708.47.6−1
 41.14911700.348331.00.051.8991.00.186120.242728232708.23.9−1
 69.23841330.361260.30.031.8951.20.186010.232731282707.23.8−1
 21.15222190.423356.30.021.9061.00.185960.222719232706.83.7−1
 41.23281090.331220.80.081.8931.00.185920.292734232706.44.8−1
 45.15781520.255381.00.061.9051.00.185890.262720232706.14.3−1
  3.1119270.23277.80.061.9141.10.185850.462710252705.87.60
 61.15631670.286368.20.141.9351.00.185780.232685232705.13.71
157.2117230.19776.90.041.8881.40.185750.452740312704.97.4−2
 01.13261270.392219.50.141.9211.00.185730.272702232704.74.40
 54.23171040.319212.60.101.9001.10.185710.422726242704.56.9−1
 85.2118300.26077.10.081.9241.30.185640.422698292703.96.90
108.14670.15529.31.9341.40.185530.812686322703131
 34.23251410.449226.40.311.8721.10.185510.462759242702.87.6−3
 78.18161700.223534.10.011.9041.30.185400.282721282701.84.6−1
 20.14781860.385318.70.041.9371.00.185390.242683222701.73.91
 25.2362980.266235.90.191.9291.10.185310.292692232701.04.80
 52.186200.22355.60.071.9241.20.185280.752698262701120
  5.15701480.262376.20.031.9061.00.185280.312719232700.75.1−1
 12.19002970.337607.20.111.8931.00.185200.172734232700.02.8−2
157.1164510.308106.70.021.9551.30.185120.392663282699.36.52
 59.1239840.355160.90.051.9061.10.185060.422719242698.86.9−1
 37.19592530.257627.50.021.9191.00.185010.172704222698.32.80
 22.24692050.430316.70.051.9311.00.185010.242690232698.33.90
 58.1109340.30672.00.031.9201.10.184920.472703252697.57.70
 16.1269880.325177.30.041.9351.10.184910.312685242697.45.01
101.2172520.311114.00.061.9181.30.184870.412704292697.16.70
 49.1130450.33187.50.061.8991.10.184730.482726252695.87.9−1
 23.198210.20765.00.161.8691.20.184720.77276326269613−3
 29.11921090.580135.80.031.8951.10.184700.552732242695.59.1−2
 30.2130350.26985.80.071.9011.10.184620.572724262694.89.4−1
 14.19432000.218623.70.021.8791.00.184500.172750222693.72.7−3
  5.299330.35066.90.041.8911.10.184350.502736252692.48.2−2
147.2187510.273121.00.041.9441.30.184280.342675282691.85.51
 42.1129400.30386.30.161.8901.20.184240.482737272691.47.9−2
 11.1197600.312131.10.051.9061.10.183990.382719252689.26.3−1
Mixed analyses
 53.1250850.318164.30.081.9381.10.183270.352682252682.75.70
 47.18372410.278545.50.031.9331.00.182790.192688222678.43.10
 02.1233570.243143.00.042.0231.00.173680.332589222593.45.40
Group 2 metamorphic (used for pooled maximum age)
108.246110.23227.80.072.0621.40.170950.712549302567121
 51.173220.28344.10.102.0691.20.170880.682542252566111
 11.2171710.419108.60.042.0251.10.170790.402587232565.46.7−1
 48.2115350.29171.60.082.0021.20.170570.522611262563.28.7−2
 31.161160.26637.12.0541.20.170430.822557262562140
 22.1139320.22784.50.112.0301.10.170400.462582242561.57.7−1
101.159120.20734.90.072.0671.40.170270.732544302560121
  3.2101110.10857.90.092.1041.30.169890.532507272556.58.92
 18.1133340.25481.00.062.0331.10.169360.572579232551.39.61
 51.2194820.412120.60.062.0621.10.169180.462549232549.67.70
 29.297280.28058.70.092.0551.10.169090.572556242548.69.40
 09.1139480.35585.60.042.0591.10.168980.442552232547.57.40
147.14180.19224.30.062.0751.50.168950.772536322547131
 32.186120.13549.50.132.0911.20.168820.732519252546121
 78.257110.19334.10.042.0401.40.168190.64257230254011−2
 55.160170.26035.40.482.1081.30.168020.922503272538152
 48.1124310.24374.30.102.0591.10.167700.522552242534.88.8−1
 53.2102120.11460.10.092.0361.20.167600.582575242533.99.7−2
 35.185330.39653.40.072.0341.20.167440.64257725253211−2
 13.296410.42859.60.042.0831.10.167440.552527242532.29.30
Group 2 metamorphic (excluded)
 13.164180.28439.60.132.0201.20.166500.68259226252311−3
 27.185230.26951.60.062.0491.20.166120.612562252519102
 33.172200.27143.40.072.0441.30.166030.88256827251815−2
 60.194260.27455.82.0821.20.165810.552529252515.89.3−1
 63.261150.25136.62.0551.50.165290.63255632251111−2
Little Ramah Bay, sample L1487, n5549
Xenocrystic
 04.1*91230.26101.61.2811.10.361800.323720323757.44.91
Metamorphic
 08.1*59210.3626.61.9061.80.193020.912717412768152
 05.223110.4616.41.8861.60.192160.942743362761151
 09.1*54190.3724.00.041.9311.80.191590.972687422756163
 13.1*59220.3927.00.131.8831.80.19031.02739422745170
 11.1*261830.33119.00.471.8801.20.190200.542753292743.98.90
 07.1*52130.2623.70.201.9021.90.18981.02725432740171
 05.1*59200.3528.00.061.8152.90.189730.87282769274014−4
 03.225110.4517.61.8981.60.18891.02728352733160
 10.1*72140.1932.80.061.8911.70.188720.852739392731140
 03.1*57160.2925.90.141.8981.70.187820.932730402723150
 04.1*63220.3629.20.151.8401.70.186980.89280140271615−4
Igneous
 04.26674120.64768.00.021.3021.10.334940.243673313639.93.7−1
 19.1*1981310.68126.20.171.3471.30.334930.383580383639.85.82
 18.1*373300.08236.10.091.3581.20.332150.263558323627.04.03
 01.1*439410.10279.70.751.3491.20.32580.743576323598111
 02.1*7301430.20472.60.021.3271.10.324340.363623313590.65.5−1
 06.1*495410.09309.81.3711.10.323610.593533313587.19.12
 12.1*350400.12215.40.191.3971.20.321890.323483323578.94.94
 17.1*195900.48117.20.111.4251.30.31541.03436363547154
 16.1*535790.15321.40.021.4291.10.314810.243420313544.73.75
 14.1*693830.12420.50.031.4161.10.313230.383447303536.95.83
 03.1416480.10386.50.081.4381.00.306000.423404273500.96.44
 *314430.14168.60.021.6011.20.264010.343131303270.85.45
 02.12841000.28212.10.331.7491.40.226700.582915343028.99.35
 02.23661420.35273.50.111.7691.00.221690.532888232993.08.64
Discordant
 01.113823210.191017.50.071.7931.00.259960.132857243246.42.015
Little Ramah Bay, sample L1488–89, n5550–n5551
Metamorphic
 07.2254230.09164.30.051.8840.990.192080.302745222760.15.01
 04.2614510.08400.00.031.8631.00.190960.182770232750.52.9−1
 05.1151860.58108.50.251.8811.10.190500.382748242746.56.20
 04.13731280.32245.50.681.9481.10.190350.412671242745.26.73
 02.273530.7353.50.291.9051.20.189440.552720262737.39.11
 05.270450.6347.90.401.9911.40.189330.632624292736105
Little Ramah Bay, sample L1490, n5552
Metamorphic
 03.151170.3335.60.111.8561.20.192920.67277927276711−1
 07.11640.2810.61.8641.80.19231.52768402762240
 01.256180.3338.01.9001.20.190820.602726262749.29.81
06.275280.3851.40.111.8771.10.190810.652753252749110
08.340120.2926.81.8971.50.190320.712730332745121
02.2107470.4475.00.061.8701.10.189220.512762242735.48.3−1
08.2103440.4270.90.381.8981.10.189150.482729242734.87.90
04.21330.249.10.341.8401.80.18911.3279841273422−3
08.168250.3445.30.101.9161.20.189080.572707252734.29.31
04.169250.3747.20.101.8821.20.189000.562747262733.59.2−1
04.250170.3233.60.101.9131.30.187280.702710282718110
07.21030.276.51.8612.20.18721.4277250271724−2
05.21130.257.61.8661.90.18421.4276744269122−3
Reichel Head, sample L1491, n5553
Xenocrystic
07.177310.4288.20.081.2791.20.360380.553725343751.58.4−1
02.1*290740.26200.00.041.2461.20.361560.273801363756.44.1−1
Igneous
02.2*5032380.49334.40.181.2921.10.35400.633702343724101
01.1192970.51226.20.021.2581.20.353400.283771343721.74.22
01.1*137210.1691.80.021.2851.40.35170.953710403714140
03.1*3021590.54206.20.041.2581.20.351150.533776353712.08.1−2
08.1390570.14423.80.041.2761.10.349580.283730313705.24.31
Excluded
03.2*187850.47124.30.051.2941.30.347390.593696383695.68.90
05.1*488990.21313.40.211.3371.10.34570.723600333688.3113
07.1*196810.42123.50.041.3651.30.342900.363544373675.75.55
09.1*1801440.82114.70.021.3491.70.341380.333582513669.05.13
18.1*65190.01413.30.391.3531.10.335010.533568303640.18.23
08.1*710710.10371.70.771.6401.10.282850.273067273378.74.211
Reichel Head, sample L1492, n5547
Detrital
04.1*91420.4753.00.221.4732.80.26592.8334876328243−2
03.1*156840.5686.30.061.5501.90.25781.63212503233251
01.1139500.36122.91.5341.20.25631.03235313224160
02.1*158800.5389.80.071.5101.30.25551.5328436321923−2
02.2204820.41177.70.041.5691.20.253920.263179303209.44.11
05.1114570.4795.61.6391.10.23960.803071273117132
02.1104360.3282.60.071.6701.50.23291.13025363072182
01.2295530.17221.90.031.6971.20.22840.952986303041152
01.1*86370.4542.20.131.7531.60.21632.32916392953372
Metamorphic
04.139020.00247.30.041.8791.00.191100.272750232751.64.50
03.166340.01423.70.011.8640.960.190000.202769222742.13.3−1
04.21144130.01730.20.041.8661.00.188950.142766232733.12.2−1
05.233520.00213.10.051.8711.10.188690.262760252730.84.2−1
06.2588140.02373.80.021.8761.00.187960.192754232724.43.1−1
03.233220.101.9431.00.187320.262677232718.84.32
Reichel Head, sample L1493, n5548
Xenocrystic
03.27321130.14756.00.801.3411.030.346950.173591283693.62.74
Metamorphic grains
04.1524870.16344.40.031.8771.000.189720.202753222739.83.3−1
05.23381330.40229.80.111.9090.960.188620.262715212730.24.21
05.1609980.16391.60.041.9150.980.187190.192708222717.73.10
02.2471580.12306.30.041.8780.950.187110.282752212716.94.6−2
03.2377530.14243.40.231.8951.000.186210.252732222709.04.1−1

Disc. % = (1-(206Pb/238Pb age)/(207Pb/206Pb age))*100

  • 1 sample labels include SIMS data from John deLaeter Centre (*) and NordSIMS (n####).

  • 2 Th/U ratios presented are calculated from measured Th and U oxides.

  • 3 Percentage of common 206Pb in measured 206Pb, calculated from the 204Pb signal assuming a present-day Stacey & Kramers (1975) model terrestial Pb-isotope composition.

  • 4 Values corrected for common Pb.