资源环境科技发展态势分析平台

The temporal duration of lunar-evolved magmatism is still poorly constrained. In lunar meteorite Northwest Africa (NWA) 10049, a melt inclusion-bearing zircon fragment provides a new tool to understand the composition and age of the melts from which zircon directly crystallized. The studied zircon-hosted melt inclusions are silica rich and iron poor (e.g., similar to 80-90 wt% SiO2; <0.5 wt% FeO), compositionally similar with immiscible silica-rich melts found in Apollo rocks. Nano-SIMS U-Pb analyses of the zircon yielded a minimum crystallization age of 4,382 +/- 40 Ma, older than the ages for Apollo highly evolved alkali suite lithologies (similar to 3.8-4.33 Ga). Our study shows that the melt inclusion-bearing zircon in NWA 10049 is the oldest microscale evidence for documenting immiscible silica-rich melts in lunar samples, suggesting that lunar-evolved silica-rich melts were prevalent as early as similar to 4.38 Ga. This work implies that there would be a prolonged silicic magmatism occurred on the Moon.

Plain Language Summary Lunar-evolved silica-rich melt is thought to be related to the formation of highly silicic lithologies (e.g., granitic lithologies). These rock types have been observed in Apollo returned samples as lithic clasts and also have been detected by remote-sensing data as silicic domes. The Apollo-evolved lithologies give a wide range of crystallization ages from similar to 3.8-4.33 Ga. However, there is still unclear about the temporal duration of lunar-evolved magmatism and volcanism. In lunar meteorite breccia NWA 10049, a melt inclusions-bearing zircon fragment provides a new tool to understand the composition and age of the melts from which zircon directly crystallized. The studied zircon-hosted melt inclusions are compositionally similar with immiscible silica-rich melts found in Apollo rocks. Nano-SIMS U-Pb analyses of the zircon yielded a minimum crystallization age of similar to 4.38 Ga. This age is older than the ages for Apollo-returned granites (up to 4.33 Ga) and ancient basaltic volcanism (i.e., up to similar to 4.37 Ga), making the studied zircon is the oldest microscale evidence for documenting lunar silicate liquid immiscibility.