Comparisons of Mineralogy of Lunar Meteorites Possibly from the Farside and The Kaguya Remote Sensing Data to Reconstruct the Earliest Anorthositic Crust of the Moon

Ohtake et al. [1] observed by the Kaguya multiband imager and spectral profiler anorthosites composed of nearly pure anorthite (PAN) at numerous locations in the farside highlands. Based on the Th map made by the GRS group of the Kaguya mission, Kobayashi et al. [2] showed that the lowest Th region in the lunar farside occurs near the equatorial region and noted that the regions well correspond to the lunar highest region and the thickest crust region recently measured by Kaguya mission [3,4]. Such remote sensing data have been interpreted in terms of mineralogical studies of lunar meteorites of the Dhofar 489 group [5,6] (e.g., Dhofar 489, 908, and 307) and Yamato (Y-) 86032 [7], all possibly from the farside highlands. Although the presence of magnesian anorthosites in the Dhofar 489 group has been reported, we have not encountered large clast clearly identifiable as PAN. In this study, we investigated mineralogy and textures of large clasts of nearly pure anorthosites recognized in Dhofar 911 and the d2 clast in Dhofar 489 [8]. The d2 clast is the largest white anorthosite clast in Dhofar 489, but its mineralogy has not been investigated at that time. The low bulk FeO concentrations suggests that the d2 clast may be the pure anorthosite with very low abundance of mafic silicates. In conjunction with all data of the Dhofar 489 group including Dhofar 489, 908, 309 and 307, we propose a model of formation of the farside crust.