Unraveling the Mineral Components in Lunar Highlands Materials

The ferroan anorthosite suite (FAS) is thought to contain material representing the very first lunar crust. As such, the FAS serves as the only direct sampling of the lunar magma ocean (LMO) available for study. Understanding the history of this ancient suite is paramount to furthering our knowledge of the evolution of the Moon and the early solar system as a whole. Recent geochronologic studies of this suite, however, challenge our conventional understanding of lunar evolution through necessitating a protracted active LMO beyond which most thermal models can account. In an attempt to investigate this outstanding issue in lunar geology, this study aims to better characterize six FAS samples with reported Sm-Nd crystallization ages on a mineral scale resolution via implementing a variety of in-situ analysis techniques. We then compare these results to five models of LMO evolution to determine likely provenance for the individual minerals in each sample. The results of this study reveal individual FAS members to be largely heterogeneous in nature containing material both consistent and inconsistent with an LMO source. In addition to this, individual samples also contain material representative of crystallization out of separate stages of LMO evolution. As such, we prescribe caution to any interpretation to the ages of this suite within the context of the lunar geologic history and propose investigating a non-chondritic initial LMO depleted in the light rare earth elements (LREE).