Table 1. 

U–Pb analytical results for monazite and initial Pb isotopic composition for cogenetic K-feldspar

Fraction*Weight (mg)U (ppm)Pbrad (ppm)206Pb/204Pb†Rad. Pb (atomic %)‡Atomic ratios‡Apparent ages (Ma)
206Pb207Pb208Pb206Pb/238UError 2σ (%)207Pb/235UError 2σ (%)207Pb/206PbError 2σ (%)206Pb/238U207Pb/235U207Pb/206Pb
BOC-01, aplitic vein
1, large, (2) gr, ab0.0116850920121231.81.766.60.049370.20.35460.30.052100.2310.6308.2289.8
2, medium, (6) gr, ab0.008598298461126.61.472.00.050550.60.36560.60.052460.3317.9316.4305.4
3, medium, (8) gr, ab0.017422394982619.01.080.10.049200.60.35330.70.052090.4309.6307.2289.2
4, medium, (6) gr, ab0.011533398851823.41.275.30.050170.80.36621.60.052941.4315.6316.8326.2
5, small, (14) gr, ab0.025643794568927.81.470.70.047240.70.33680.90.051720.2297.6294.8272.8
6, small, (18) gr, ab0.0795978867268228.11.570.50.047050.80.33951.00.052340.08296.4296.8300.4
7, small, (10) gr0.06232303258335040.52.157.30.047300.90.34491.20.052900.07297.9300.9324.5
8, K-fsp:§ 206Pb/204Pb=18.285; 207Pb/204Pb=15.718; 208Pb/204Pb=38.481
TGD-01, leucogranitic vein
9, medium, op incl, (10) gr0.058199181572855952.22.745.10.047710.60.34540.60.052510.07300.4301.3307.8
10, medium, (6) gr0.028234661779564255.52.941.60.048800.70.35320.70.052490.08307.2307.1306.6
11, large, (2) gr0.033375262258930568.43.628.00.047800.90.34620.90.052530.06301.0301.8308.3
12, medium, (4) gr0.018346192291830164.43.432.30.049430.50.35780.50.052490.07311.0310.5306.8
13, K-fsp:§ 206Pb/204Pb=18.586; 207Pb/204Pb=15.888; 208Pb/204Pb=38.944
TGD-02, mylonitic orthogneiss
14, medium, (13) gr0.1205532971719424.21.374.60.049030.60.35340.60.052270.08308.6307.3297.1
15, small, op incl, (10) gr0.09459311007514825.01.373.70.049090.50.35470.50.052390.07308.9308.2302.6
16, medium, (7) gr0.08858181006983624.81.373.90.049571.10.36011.10.052690.08311.8312.3315.4
17, medium, op incl, (5) gr0.03957131062320823.11.275.70.049650.40.35940.40.052500.1312.4311.8307.2
18, small, op incl, (6) gr0.026581695562725.71.472.90.048791.00.35821.50.053241.1307.1310.9339.1
19, K-fsp:§ 206Pb/204Pb=19.035; 207Pb/204Pb=16.121; 208Pb/204Pb=39.311
TGD-05, orthogneiss
20, small, op incl, (16) gr0.12456801130980828.91.669.50.066590.70.50950.70.055500.06415.6418.1432.2
21, medium, (13) gr0.05562991167374130.51.767.80.065390.50.49550.50.054960.1408.3408.6410.4
22, medium, (8) gr0.04955001112199828.11.670.30.065750.40.49890.40.055030.09410.5410.9413.2
23, small, op incl, (12) gr0.06149661060463728.11.670.40.069220.50.53020.50.055550.09431.4431.9434.5
24, small, (3) gr0.00953401015100031.31.767.00.068740.40.52290.50.055170.2428.6427.1419.1
25, small, (7) gr, ab0.01540561022234024.31.474.30.070770.40.54430.50.055780.1440.8441.2443.7
26, small, (8) gr, ab0.01141681265135720.31.178.60.071260.30.54250.40.055220.2443.7440.1421
27, small, (7) gr, ab0.01356921291127025.81.472.80.067580.60.51130.60.054870.2421.6419.3406.9
28, small, (11) gr, ab0.029138135476223.41.375.30.069400.40.52560.50.054930.2432.6428.9409.3
29, K-fsp:§ 206Pb/204Pb=18.217; 207Pb/204Pb=15.886; 208Pb/204Pb=38.833
TGD-06, leucogranite of Grime
30, large, op incl, (2) gr0.010530752685568381.64.314.10.047950.70.34950.70.052860.1301.9304.3322.8
31, small, op incl, (5) gr0.003370282109201477.34.118.60.051130.40.37480.50.053160.2321.5323.2335.4
TGD-11, leucogranite dyke of Grime
32, medium, (7) gr0.028272941395318469.53.627.00.041230.60.29100.80.051200.05260.4259.4249.7
33, medium, (12) gr0.083328881094372474.53.821.70.028780.60.20360.80.051310.08182.9188.2254.7
34,, medium, (6) gr0.046223631040294665.43.331.30.035290.50.24750.70.050870.05223.6224.6234.9
35, small, (20) gr0.025231231138270266.93.429.70.038220.60.26650.80.050580.05241.8239.9221.8
36, K-fsp:§ 206Pb/204Pb=18.455; 207Pb/204Pb=15.886; 208Pb/204Pb=38.830
TGD-10, fine-grained paragneiss
37, small, (26) gr0.1325372803722729.21.569.30.050490.80.36701.00.052720.1317.6317.4316.6
38, large, (16) gr0.1235876849717630.01.668.50.050030.50.36350.40.052700.05314.7314.8315.8
39, medium, (20) gr0.1376723934910931.41.767.00.050411.20.36671.40.052760.2317.0317.2318.4
40, small, (30) gr0.1906745950652431.11.667.30.050600.80.36881.00.052860.1318.2318.8322.8
41, K-fsp:§ 206Pb/204Pb=18.183; 207Pb/204Pb=15.787; 208Pb/204Pb=38.687
TGD-08, Rouet granite
42, large, op incl, (4) gr0.0723103611227421.21.177.70.048250.50.34670.50.052110.09303.8302.2290.2
43, medium, op incl, (7) gr0.0406644952307128.51.570.00.047190.80.33730.80.051830.08297.3295.1277.8
44, medium, op incl, (4) gr0.050451485155622.11.276.70.048120.50.35550.60.053590.4302.9308.9353.7
45, large, op incl, (3) gr0.011393566664825.11.373.50.049140.40.35940.50.053040.2309.3311.7330.5
46, medium, op incl, (3) gr0.0096398898105329.71.668.70.048260.60.34910.60.052460.2303.8304305.6
47, large, (4) gr, ab0.0173922758163621.61.177.30.048250.30.34490.40.051850.2303.8300.9278.7
48, K-fsp:§ 206Pb/204Pb=18.230; 207Pb/204Pb=15.675; 208Pb/204Pb=38.614
  • *Small, grains <100 μm in length; medium, grains 100–150 μm in length; large, grains >150 μm in length; ab, air abraded; K-fsp, potassium feldspar; op incl, opaque inclusion; numbers in parentheses are numbers of grains (gr) per fraction.

  • †Measured ratio, corrected for mass discrimination (0.10 ± 0.05%/a.m.u.) and isotopic tracer contribution.

  • ‡Ratio corrected for mass discrimination, isotopic tracer contribution, 60 pg of Pb blank, 1 pg of U blank, and initial common lead determined in leached K-feldspar from the same rock sample. Rad. Pb, radiogenic lead.

  • §Initial common Pb determined in leached K-feldspar from the same rock sample; corrected for mass discrimination (0.10 ± 0.05%/a.m.u.; Pb blank is negligible).