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Apollo 12 ropy glasses revisited
Author(s) -
Wentworth S. J.,
McKay D. S.,
Lindstrom D. J.,
Basu A.,
Martinez R. R.,
Bogard D. D.,
Garrison D. H.
Publication year - 1994
Publication title -
meteoritics
Language(s) - English
Resource type - Journals
eISSN - 1945-5100
pISSN - 0026-1114
DOI - 10.1111/j.1945-5100.1994.tb00596.x
Subject(s) - regolith , anorthosite , lunar soil , geology , breccia , meteorite , mineralogy , geology of the moon , impact crater , geochemistry , astrobiology , basalt , plagioclase , physics , paleontology , quartz
— We analyzed ropy glasses from Apollo 12 soils 12032 and 12033 by a variety of techniques including SEM/EDX, electron microprobe analysis, INAA, and 39 Ar‐ 40 Ar age dating. The ropy glasses have KREEP‐like compositions different from those of local Apollo 12 mare soils; it is likely that the ropy glasses are of exotic origin. Mixing calculations indicate that the ropy glasses formed from a liquid enriched in KREEP and that the ropy glass liquid also contained a significant amount of mare material. The presence of solar Ar and a trace of regolith‐derived glass within the ropy glasses are evidence that the ropy glasses contain a small regolith component Anorthosite and crystalline breccia (KREEP) clasts occur in some ropy glasses. We also found within these glasses clasts of felsite (fine‐grained granitic fragments) very similar in texture and composition to the larger Apollo 12 felsites, which have a 39 Ar‐ 40 Ar degassing age of 800 ± 15 Ma (Bogard et al , 1992). Measurements of 39 Ar‐ 40 Ar in 12032 ropy glass indicate that it was degassed at the same time as the large felsite although the ropy glass was 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 ropy glasses are from Copernicus, they provide new clues to the nature of the target material at the Copernicus she, a part of the Moon that has not been sampled directly.