Fig. 3: Rb–Sr and Sm–Nd isotopic evolution of lunar materials.
From: Non-KREEP origin for Chang’e-5 basalts in the Procellarum KREEP Terrane
a, 87Rb/86Sr ratios of Chang’e-5 basalt source regions are calculated assuming a single-stage model in which the Moon differentiated at 4.56 Ga with an initial 87Sr/86Sr ratio of 0.69903 (refs. 37,38). The bulk Moon 87Rb/86Sr value is from refs. 38,39. b, The 147Sm/144Nd ratios of the basalt source regions are calculated assuming a two-stage growth model following refs. 20,21. In this model, the Moon followed a chondritic path until differentiation occurred at 4.42 ± 0.07 Ga, represented by the model age of primeval KREEP formation40,41. The Sr and Nd isotopic data of the Chang’e-5 basalts were acquired on plagioclase and merrillite, respectively (Extended Data Tables 3, 4). The initial 87Sr/86Sr and εNd(t) are calculated using 2.03 Ga (ref. 9). The horizontal solid lines in both panels refer to the primordial reservoir. BABI, Basaltic Achondrite Best Initial; CHUR, Chondrite Uniform Reservoir. The Apollo mare basalts and meteorites data are from ref. 21 and references therein.
