Fig. 4: Formation of the REE distribution patterns in Chang’e-5 basalts.
From: Non-KREEP origin for Chang’e-5 basalts in the Procellarum KREEP Terrane
a, Comparison of REE distribution patterns of Chang’e-5 and Apollo basalts. Apollo (A) and Luna (L) data are from Clive Neal’s Mare Basalt Database (https://www3.nd.edu/~cneal/Lunar-L/). The Apollo 14 groups A, B and C were defined by ref. 42. b, REE modelling of partial melting and fractional crystallization. The blue areas denote the melts produced after 2–3% partial melting of the mantle source (86 PCS + 2% TIRL22; PCS, per cent crystallized solid; TIRL, trapped instantaneous residual liquid) and those followed by 43–78% fractional crystallization. This source composition is calculated based on the source region 87Rb/86Sr and 147Sm/144Nd ratios (Fig. 3). Mineral modes in the source are assumed to be 48% olivine, 23% orthopyroxene, 23% pigeonite, 3% augite and 3% plagioclase. Mineral assemblages of 43–78% crystallization are: 5–10% olivine, 25–59% augite, 2–3% pigeonite and 6–11% plagioclase. Normalization values are from ref. 43. The Chang’e-5 parental melt estimated by the clinopyroxene core with the highest Mg# (sample 406-004, 005) (Extended Data Table 6) requires extensive (43–78%) fractional crystallization after low-degree (2–3%) melting of the mantle source. To match the Chang’e-5 bulk composition, up to 78–88% fractional crystallization is needed. The model parameters are listed in Supplementary Table 3, and details of the batch melting and fractional crystallization model are provided in the Methods.
