Chang’e-6 farside anorthosites indicate hemispherically comparable magma ocean solidification

Abstract

Abstract Ferroan anorthosites (FANs) reflect the nature of the Moon’s crust formed during the late-stage lunar magma ocean (LMO). Remote sensing suggests a hemispheric dichotomy in crustal composition, with the farside anorthositic highlands being more magnesian than the nearside. Lacking direct compositional and chronological constraints from farside anorthosites, whether this crustal dichotomy reflects asynchronous LMO solidification or post-LMO crustal reworking remains uncertain. Here we present an integrated petrological, geochemical, and geochronological study of farside anorthosite clasts returned by the Chang’e-6 mission. These clasts exhibit both mineralogical and compositional similarity with nearside Apollo FANs, supporting a comparable LMO-derived primary crust on both hemispheres. A zircon-bearing anorthosite domain contains recrystallised plagioclase enriched in rare earth elements (REE), thorium, and phosphorus, suggesting thermal reworking and metasomatism by a KREEP (potassium, REE, and phosphorus)-rich magma. High-precision lead-lead dating of zircon constrains this reworking event to 4,410 ± 8 Ma, establishing a local lower bound for farside LMO solidification. These findings establish a critical chronological benchmark for farside LMO solidification and offer direct evidence of a comparable primary crust across the Moon, constraining the origin of the crustal dichotomy to post-LMO reworking.