Detection of apatite in ferroan anorthosite indicative of a volatile-rich early lunar crust

Determination of the systematics of volatile elements (for example, H, Cl, S) of the early Moon is one of the main objectives of lunar science. This has been hindered by the lack of the main volatile-bearing mineral, apatite, in ferroan anorthosites (FANs), which are thought to represent the primary products of the lunar magma ocean and the earliest lunar crust. Due to the absence of apatite, plagioclase and bulk samples of the FAN suite have been previously utilized for the studies of volatiles in samples representing the earliest-formed lunar crust. Here we provide evidence of apatite in a FAN clast in the lunar meteorite Arabian Peninsula 007. We report that Arabian Peninsula 007 has an ancient age, comparable to those of Apollo FAN samples, with lighter hydrogen (delta D = -45 parts per thousand) and heavier chlorine (delta 37Cl = +44 parts per thousand) isotopic compositions than FAN bulk and plagioclase data. These results suggest that the early lunar crust was significantly more volatile rich than previously thought. This Article provides evidence for apatite in a ferroan anorthosite clast in a lunar meteorite, allowing direct measurement of the volatile systematics of the primary products of the lunar magma ocean and the earliest lunar crust.