40Ar/39Ar dating of Apollo 12 regolith: Implications for the age of Copernicus and the source of nonmare materials

Argon Stable Isotope Concentrations in Lunar Regolith

“…Basically, the same ratio is observed in the Earth atmosphere, meteorites and lunar regolith samples of various ages, from zero up to 4.5 Ga (Levine et al, 2007;Berra et al, 2006). This is the evidence of the homogeneity of the presolar nebula from which all the bodies in the Solar System were formed.…”

Apollo 12 revisited

“…We also synthesize some disparate observations of the immediate post-mission work and cast them in a modern context. We have reported preliminary or incomplete results of this study in several abstracts (Korotev and Rockow, 1995;Korotev et al, 2000Korotev et al, , 2002Jolliff et al, 2000bJolliff et al, , 2005Zeigler et al, 2006a;Seddio et al, 2009aSeddio et al, ,b, 2010 and one paper (Barra et al, 2006). AT APOLLO 12 (1971) Meyer et al (1971) recognized four textural types of KREEP in the Apollo 12 regolith: "(1) yellow-brown glasses, which grade into (2) breccias with glass matrices exhibiting flow textures and (3) rocks of orthopyroxene-plagioclase-potassium feldspar-whitlockite [RE-merrillite] assemblage, which grades into (4) light-colored, brecciated, and welded fragments of (3)."…”

“…The lithic fragments discussed here are the same suite that we described briefly in Barra et al (2006). We present a more complete description and discussion here.…”

The geochemistry and provenance of Apollo 16 mafic glasses

“…However, these craters are all relatively small (<100 km) and very distant (>1000 km), which makes it unlikely that they deposited a significant amount of material at the Apollo 16 site. Furthermore, the Ar-Ar systematics of suspected Copernicus ejecta (both glass and lithic fragments) at the Apollo 12 site have been reset (or at least disturbed; Eberhardt et al, 1973;Alexander et al, 1976;Barra et al, 2006), which is not the case for the basaltic andesite glasses of Zellner et al (2005). Another possible source crater is the lower Imbrium crater Arzachel (18°S, 2°E; Wilhelms, 1987).…”