Geochemically, ALHA81005 has all the attributes expected of a regolith sample from the lunar highlands. Most important is its Fe/Mn ratio (77), within uncertainty the same as the mean lunar ratio. There are significant differences, however, in comparison to previously sampled lunar regoliths. The closest precedents are the Apollo-16 and Luna-20 regoliths, particularly the latter, but ALHA81005 has lower contents of Na, Ti, and incompatible elements. Feldspathic granulitic breccias such as 72559, which texturally resemble the most abundant type of clast in ALHA81005, are also similar compositionally. From its low KREEP and Na contents we infer ALHA81005 originated well away from the K, Th, and U-rich region near the center of the nearside, at least as far away as the eastern limb. |