Magnesium isotopic composition of the Moon

摘要: Abstract The Mg isotopic compositions of 47 well-characterized lunar samples, including mare basalts, highland rocks, regolith breccias, and soils were measured to address the behavior isotopes during magmatic differentiation, constrain composition Moon, evaluate degree fractionation between planetary bodies. δ 26 values range from −0.61 ± 0.03‰ 0.02 ± 0.06‰ in 22 −0.34 ± 0.04‰ −0.18 ± 0.06‰ 3 −0.33 ± 0.05‰ −0.14 ± 0.08‰ 7 −0.23 ± 0.05‰ −0.14 ± 0.07‰ 6 soils, −0.41 ± 0.05‰ −0.20 ± 0.09‰ 9 soils. limited variation among bulk breccias indicates negligible isotope by surface processes. By contrast, large low-Ti high-Ti basalts suggests source heterogeneity produced fractional crystallization magma ocean, with ilmenite having lighter than olivine pyroxene. Overall, Moon has a weighted average (δ Mg = −0.26 ± 0.16‰) indistinguishable Earth Mg = −0.25 ± 0.07‰) chondrites Mg = −0.28 ± 0.06‰), suggesting homogeneous distribution solar system lack Moon-forming giant impact.