The Rb-Sr data given below are for whole-rock samples from amphibolite metamorphic facies of theLewisian gneiss complex in Scotland (Moorbath et al., 1975), and the Sm-Nd data are for whole-rocksamples from granulite metamorphic facies of the same complex (Hamilton et al., 1979). Do the datayield concordant Rb-Sr and Sm-Nd dates for the complex? If not, suggest a reasonable explanation forthe discordance. Assuming that the complex is of igneous origin, what can you say about the sourceregion for the magma from the initial ratios?

Sample 87Rb/86 Sr 87Sr/86Sr Sample 147Sm/144Nd 143Nd/144Nd

1 0.133 0.7085 1 0.1960 0.512756

2 0.177 0.7090 2 0.2346 0.513518

3 0.086 0.7040 3 0.1707 0.512195

4 0.240 0.7107 4 0.1082 0.511006

5 0.501 0.7211 5 0.0741 0.510376

6 0.594 0.7224 6 0.0875 0.510634

7 0.191 0.7096 7 0.1030 0.510962

8 0.104 0.7049 8 0.0775 0.510501

9 0.400 0.7153 9 0.1127 0.511143

10 1.710 0.7668 10 0.0871 0.510638

11 0.368 0.7152 11 0.0999 0.510902

12 0.049 0.7032

13 0.298 0.7132