2.2-billion-year-old KREEP-rich volcanism on the Moon

Abstract

The Moon’s KREEP component—rich in potassium (K), rare earth elements (REE), and phosphorus (P)—is considered a critical heat source sustaining prolonged volcanic activity. However, Chang’e mission samples reveal a lack of KREEP signatures in the sources of mare basalt erupted ∼2.8 and 2.0 billion years ago, raising questions about its contribution to late-stage volcanism. Here, we present geochemical and geochronological analyses of the lunar basaltic meteorite NWA 16286, which crystallized 2201 ± 13 million years ago, representing the youngest known lunar meteorite. Its mantle source shows a high ²³⁸U/²⁰⁴Pb ratio (∼2000) and a low ε_Nd(t) value (–4.3), indicating strong KREEP enrichment and extending the duration of KREEP-related magmatism by ∼800 million years. Compiled isotopic data from lunar basalts reveal three volcanic episodes, each characterized by progressively increasing ²³⁸U/²⁰⁴Pb and decreasing ε_Nd, suggesting episodic mantle convection. We propose that episodic sluggish mantle overturn or plume-driven upwelling triggered initial decompression melting, followed by increasing incorporation of KREEP components into basalt sources during each episode of younger mare volcanism.