Ferroan anorthosite

Ferroan anorthosite (FAN) is a pristine coarse-grained igneous rock found in the lunar highlands. FANs have a Ca-rich plagioclase (called anorthite) composition greater than 90 wt%, with many consisting of an anorthite-content of 99 wt%. The first hand sample of FAN, Sample 15415, was discovered at the Apollo 15 landing site, Hadley-Apennine. FANs were also found at the Apollo 16 landing site, the Descartes Highlands. FANs have been used to give insights into the evolution of the early lunar crust. Wood et al. 1970 first proposed that FANs were the result of the flotation of plagioclase crystals in a lunar magma ocean (LMO). However, Wetherill 1975 suggested that FANs formed due to serial magmatism.

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