Table 5.

Monazite SIMS U–Th–Pb data

Sample and spot no.U (ppm)Th (ppm)Th/U1206Pbc2 %Ratios3Age3Disc. %
238U/206Pb±σ (%)207Pb/206Pb±σ (%)207Pb/206Pb±σ
Upernavik Island, sample L1458
Part A, mineral separate, metamorphic
08.1511547531070.0552.0751.20.171030.532567.78.91
05.172645827630.0482.0941.40.170010.452557.77.62
02.147334156990.0052.0731.70.169250.282550.24.80
09.170132556460.0392.1071.40.169160.472549.47.82
03.156245054800.0542.0821.40.168870.512546.58.51
01.173236398500.0242.1081.50.168760.442545.47.42
06.1501564621130.1252.1381.20.16750.822533142
Part B, inclusions in garnet, metamorphic
14.1191846264240.0301.9531.30.182960.352679.95.71
15.158113189350.0161.9641.20.181870.302670.04.91
Part C, inclusions in garnet, metamorphic, used for pooled minimum age
11.2607613281010.0482.11651.20.16810.522538.58.72
12.3182953425290.0952.02731.30.16780.372536.16.1−2
16.1191642995220.0382.15381.70.16670.612525103
11.367458064860.0882.09571.30.16640.512521.88.60
12.1362849372140.0412.06671.20.16620.402520.26.7−1
12.2467354453120.0192.13351.30.16590.302517.05.02
16.266243635660.6622.09921.20.16570.642515110
10.1549547111000.3202.15451.50.16540.602511102
11.488458627660.0872.04341.40.16530.462511.07.8−2
Excluded from pooled age
12.480955352680.0372.10931.30.16920.642550112
11.1596635981072.06611.40.16910.512548.88.50
Little Ramah Bay, sample L1487
Metamorphic
01.1167224721340.491.8411.50.18981.0274117−2
03.111610079870.471.9141.70.18893.92733651
01.268167312481.221.8572.80.18842.0272833−2
09.1863171370.321.9581.80.18791.42724232
08.1781982250.131.8593.60.18681.2271420−2
09.2862698310.351.9131.70.18622.02709330
02.11032487240.601.9971.70.18591.52706243
07.15392641742.022.0212.30.18502.92698494
08.2922666290.712.0051.90.18391.72688293
05.2173198911150.661.9332.30.18381.22687200
07.226214716560.711.9211.40.18341.4268423−1
10.16297311582.001.8952.00.17972.5265042−3
Discordant, outliers
10.262105911711.751.8522.10.17632.5261842−6
04.11148348730.522.1242.70.17543.12610525
02.2852027240.762.0841.80.17481.82604303
Reichel Head, sample L1492
Metamorphic
02.2309933150110.0091.8571.50.189870.412741.06.7−1
04.234892735980.0121.8821.20.189830.392740.76.40
04.4293934681121.8561.40.188930.312732.95.1−2
03.2302835113120.0001.8501.30.188240.302726.95.0−2
02.3329234864111.9371.40.188100.302725.65.02
04.3272533525120.0201.8681.30.188040.452725.17.5−1
04.136952789580.0001.8151.30.187950.302724.34.9−4
03.1254833441130.0191.8611.40.187600.312721.25.2−2
01.1314731700101.8941.50.187160.422717.46.9−1
02.133912827180.0181.8571.50.187010.402716.16.6−2

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

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

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

  • 3 Values corrected for common Pb.