Figure 7.

Measured Sm/Nd versus ¹⁴²Nd/¹⁴⁴Nd data for lunar igneous rocks. The best fit line through all the data has a slope of 0.00198 that corresponds to an age of 4352 Ma (103 Ma ¹⁴⁶Sm half-life) to 4416 Ma (68 Ma half-life). On this diagram, a slope of 0.0085 corresponds to the start of Solar System formation (4.567 Ga). Data from Rankenburg et al. [32], Boyet & Carlson [52], Brandon et al. [68], Borg et al. [14] and Borg et al. [61]. Two end member estimates are shown for the bulk-Moon composition, CHUR is the average of ordinary chondrites while EDR is the Early Depleted Reservoir, both defined in Boyet & Carlson [47]. The best fit line to the data passes 9 ppm below the EDR point in ¹⁴²Nd/¹⁴⁴Nd and hence about 9 ppm higher than the CHUR value.