18 O/ 16 O, 30 Si/ 28 Si, D/H, and 13 C/ 12 C Studies of Lunar Rocks and Minerals

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Abstract
The δ 18O of minerals from lunar gabbros and basalts are: plgioclases +6.06 to +6.33), pyroxenes (+5.70 to +5.95), and ilmenites (+3.85 to +4.12). The uniformity of these results indicates isotopic equilibrium in the mineral assemblages. Estimated plagioclase-ilmenite temperautres range from 1150°C to 1340°C. The bulk 18/ 16O and 30Si/ 28Si ratios of these lunar rocks are identical with ratios of terrestrial basalts, but the lunar glass, breccia, and dust are slightly enriched in the heavier isotopes. The lunar hydrogen (formed from solar wind) has a δ D/H of less than—873 per mil and the value may be even lower, as it is probably contaminated with terrestrial hydrogen. The δ 13C of lunar dust and breccia is unusually high relative to reduced carbon in meteorites or on earth.