Ar-39-Ar-40 and petrologic study of Luna 24 samples 24077,13 and 24077,63

The ferrogabbro 24077,13, with pyroxene and plagioclase major and minor element chemical ranges comparable to the dominant ferrogabbro component in the Luna 24 core, has a Ar-39-Ar-40 temperature release age of 3.33 plus or minus 0.21 billion years. The metaferrobasalt 24077,63 is very fine-grained with a texture and mineralogy consistent with contact metamorphism between superimposed basalt flows or within a single flow. The Ar-39-Ar-40 plateau age of 24077,63 is 3.26 plus or minus 0.4 billion years. The basalt flows in Mare Crisium are about the same age as those of Mare Imbrium and younger than those of Mare Tranquillitatis and Mare Serenitatis.