⁴⁰Ar/³⁹Ar Geochronology of Chang’E-5 and Chang’E-6 Basalts

Understanding the history of lunar volcanism is fundamental to reconstructing the Moon's thermal and chemical evolution. Although lunar mare basalts cover only ~17% of the surface, they archive extensive magmatic activity. Precise eruption ages and durations, coupled with geochemical data, are critical for modeling the flux, scale, and mantle sources of lunar volcanism. China's lunar exploration program has recently returned samples from the nearside (Chang’E-5, CE-5, 2021) and farside (Chang’E-6, CE-6, 2024). High-precision dating of these basalts can define volcanic episodes at each site and test for possible asymmetries in volcanic history between the two hemispheres. While in-situ U–Pb dating offers high precision, its high closure temperature limits its sensitivity to later isotopic resetting by impacts. The ⁴⁰Ar/³⁹Ar system, with its lower closure temperature and greater thermal sensitivity, is better suited for resolving fine-scale thermal histories. We present comprehensive ⁴⁰Ar/³⁹Ar geochronology on basaltic clasts from CE-5 and CE-6 samples. Therefore, we conducted comprehensive ⁴⁰Ar/³⁹Ar geochronological analyses on basaltic clasts from the CE-5 and CE-6 samples. Our preliminary results, integrated with petrography and μCT data, yield eruption ages of ~2021 Ma for CE-5 basalts and ~2792 Ma for CE-6 Low Ti basalt. These ages refine the volcanic timeline at each landing site.