Petrogenesis of lunar highlands meteorites: Dhofar 025, Dhofar 081, Dar al Gani 262, and Dar al Gani 400

Abstract

400 clasts and minerals show far stronger FAN affinities than whole rock data suggest, most clasts indicate admixture of ≤12% HMS component based on geochemical modeling. In addition, coexisting plagioclase-pyroxene REE concentration ratios in several clasts were compared to experimentally determined plagioclase-pyroxene REE distribution coefficient ratios. Two Dho 025 clasts have concordant plagioclase-pyroxene profiles, indicating that equilibrium between these minerals has been sustained despite shock metamorphism. One clast has an intermediate FAN-HMS composition.These lunar meteorites appear to represent a type of highland terrain that differs substantially from the KREEP-signatured impact breccias that dominate the lunar database. From remote sensing data, it is inferred that the lunar far side appears to have appropriate geochemical signatures and lithologies to be the source regions for these rocks; although, the near side cannot be completely excluded as a possibility. If these rocks are, indeed, from the far side, their geochemical characteristics may have far-reaching implications for our current scientific understanding of the Moon.

Petrography, mineralogy, and geochemistry of lunar meteorite Sayh al Uhaymir 300

“…15). The Ba concentration (∼50 ppm) of SaU 300 falls within the lower range observed in lunar meteorites and Apollo and Luna samples (Papike et al 1996(Papike et al , 1997Floss et al 1998;Cahill et al 2004) (Fig. 10b).…”

“…Ba and Sr positively correlate with REEs in plagioclase of FAN rocks and lunar highlands meteorites (Papike et al 1997;Floss et al 1998;Cahill et al 2004). The correlation between Ba and Ce is stronger than that of Sr and Ce (Fig.…”

“…Variation in Fo content for olivine in lithic clasts and fragments in SaU 300. (Semenova et al 2000;Anand et al 2002;Nazarov et al 2002;Cahill et al 2004;Takeda et al 2006). These rocks may simply be breccias containing a mixture of both FAN and HMS rocks or represent pristine crustal lithologies (Cahill et al 2004).…”

“…SaU 300 falls at the lower end of the trend. Data are from Koeberl et al (1996), Fagan et al (2003), Korotev et al (2003), Warren (2003), Cahill et al (2004), Cohen et al (2004).…”

“…REE microdistributions in olivine (a), plagioclase (b), pyroxene (c), apatite, and melt glass (d) of SaU 300. FAN and HMS envelopes are adopted from Floss et al (1998), Papike et al (1996, 1997), and Cahill et al (2004. (Cahill et al 2004) and FAN and HMS rocks (Floss et al 1998;Papike et al 1996Papike et al , 1997 …”