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UCLA Meteorite Gallery Lecture Series

Title: Discovering Lost Lunar Magmas Using Apollo Zircons
Lecturer: Dr. Melanie Barboni, Arizona State University

An accessible record of the processes leading to the origin and early evolution of the Earth-Moon system, and thus of the formation of the rocky planets of the inner solar system, is best preserved in those precious rocks brought back from the surface of the Moon half a century ago. Indeed, Lunar magmatic rocks not only recorded critical information about planetary differentiation, they also recorded the tempo of meteorite impacts in the early inner solar system. Lunar zircons found within Apollo samples record over 500 Ma (from 4.4 to 3.9 Ga) of the Moon's magmatic history and are thought to have crystallized during one of the two situations described above (primary differentiation of the Moon or in later impact events).

However, identifying which zircon derives from the crystallization of the Lunar Magma Ocean, and which crystallized in subsequent impact melts is not straight forward. This is because most lunar rocks record a mixture of these primary and secondary processes, preserving chemical signatures inherited from early magmatism and potentially overprinted by secondary impact heating. In this talk, I will present old and new geochemical tools applied to Lunar zircons that, used together, have the potential to decipher the complex magmatic history of the Moon and re-discover lunar magmas that got lost along the tumultuous history of our shiny neighbor.