Widespread Involvement of Low‐Abundance <scp>KREEP</scp> in the Mantle of Chang'e‐5 and Its Surrounding Units

ABSTRACT The return of the young Chang'e‐5 (CE‐5) samples provide new insights into the lunar thermal evolution. In this study, we present a new type of exotic low‐Ti basalt in CE‐5 breccia, which has a magmatic equigranular texture with low Ti content and high Mg bulk composition and minerals. Low rare earth elements (REEs) imply that the clast was probably derived from a primitive source, which may originate from western ancient mare unit. Based on fractional crystallisation modelling, the exotic basalt source is considered as low‐Ti high‐Al, opposing the source of CE‐5 basalts. Our partial melting and REE modelling further imply that the addition of 8% plagioclase and only 1% KREEP contributes to the formation of this specific magma source. This low degree of KREEP involvement in mantle sources may be widespread in Chang'e‐5 terrane and its surrounding units, playing an important role in prolonging lunar magmatism.