APOLLO 12 ROPY GLASSES REVISITED

We analyzed ropy glasses from Apollo 12 soils 12032 and 12033 by a var iety of techniques including SEM/EDX, electron microprobe analysis, IN AA, and Ar-39-Ar-40 age dating. The ropy glasses have KREEP-like compo sitions different from those of local Apollo 12 mare soils; it is like ly that the ropy glasses are of exotic origin. Mixing calculations ind icate that the ropy glasses formed from a liquid enriched in KREEP and that the ropy glass liquid also contained a significant amount of mar e material. The presence of solar Ar and a trace of regolith-derived g lass within the ropy glasses are evidence that the ropy glasses contai n a small regolith component. Anorthosite and crystalline breecia (KRE EP) clasts occur in some ropy glasses. We also found within these glas ses clasts of felsite (fine-grained granitic fragments) very similar i n texture and composition to the larger Apollo 12 felsites, which have a Ar-39-Ar-40 degassing age of 800 +/- 15 Ma (Bogard et al., 1992). M easurements of Ar-39-Ar-40 in 12032 ropy glass indicate that it was de gassed at the same time as the large felsite although the ropy glass w as not completely degassed. The ropy glasses and felsites, therefore, probably came from the same source. Most early investigators suggested that the Apollo 12 ropy glasses were part of the ejecta deposited at the Apollo 12 site from the copernicus impact. Our new data reinforce this model. If these copy glasses are froin Copernicus, they provide n ew clues to the nature of the target material at the Copernicus site, a part of the Moon that has not been sampled directly.