Experimental and petrological investigations into the origin of the lunar Chang'e 5 basalts

Haupt, CP; Renggli, CJ; Klaver, M; Steenstra, ES; Berndt, J; Rohrbach, A; Klemme, S

Abstract

The origin of young Chang’e 5 (CE5) lunar basalts is highly debated. We present results from high-pressure, hightemperature (P-T) phase equilibria experiments, and from petrological modeling, to constrain the depth and temperature of the source of these unique mare basalts. The experimental results indicate that the CE5 basalts could have formed either by melting clinopyroxene and Fe–Ti oxide-rich cumulates in the shallow lunar mantle, or by extreme fractional crystallization of a hot Mg-rich parental melt. Our findings corroborate the local preservation of significant heat (of at least 1200 ◦C) in the lunar mantle that is needed to generate basaltic melts of CE5 compositions at 2 Ga. We argue that the CE5 basalts are most likely formed by melting of Fe and Ti-rich cumulates in the shallow lunar mantle as extreme fractional crystallization of olivine and plagioclase from picritic parental melts requires too high temperatures in the lunar mantle (> 1500 ◦C) at ~2 Ga.