The source and thermal driver of young (<3.0 Ga) lunar volcanism.

The thermal mechanism that drives the prolonged volcanism on the Moon, especially after the major pulse of Imbrian-aged eruptions, remains unknown. Here, we present a petrological and geochemical study of two types of young farside mare basalts, the ~2.8-billion year (Ga) low-Ti and ~2.9-Ga very-low-Ti basalts, collected during the Chang'e-6 mission. The results of our study show that these basalts have pyroxenitic sources and originate from a depth of ~60 to 80 kilometers and ~120 kilometers, respectively. The depth of their source that became progressively shallower over time, combined with thermal modeling results, suggests that magmatic underplating beneath the ilmenite-bearing cumulate (IBC) that escaped the mantle overturn phase could be a thermal driver for the young lunar magmatism. Global remote-sensing investigations further reveal different TiO contents between young basalts from each side of the Moon, attributable to asymmetric composition and thickness of the IBC in the uppermost mantle.