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

Abstract

The δ ^(18)O 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)/^(16)O and ^(30)Si/^(28)Si 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 ^(13)C of lunar dust and breccia is unusually high relative to reduced carbon in meteorites or on earth.

Additional details