Hallis, L. J.; Greenwood, R. C.; Anand, M. ; Russell, S. S.; Miller, M. F. and Franchi, I. A.
Oxygen isotopic composition of mare-basalts: magma ocean differentiation and source heterogeneity.
In: 72nd Annual Meteoritical Society Meeting, 13-18 Jul 2009, Nancy, France.
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Previous investigations of lunar basalts have demonstrated the heterogeneous nature of mare basalt source regions. Mare basalts are generally classified on the basis of their whole-rock TiO2, Al2O3 and K2O concentrations, abundances and ratios of key trace elements (e.g., Rb, Sr, Sc, Hf and REEs) can also be used for classification. These studies have highlighted the dichotomy between low and high-Ti basalts,with various models proposed to explain the geochemical characteristics and suggest potential source regions. Oxygen isotope studies using laser-assisted fluorination indicate that low-Ti mare basalts have heavier δ18O values than high-Ti basalts. These differences have been interpreted as reflecting source region heterogeneity, established during differentiation of the lunar magma ocean. Here we discuss new high-precision oxygen isotope measurements of a chemically diverse suite of basalt samples from the Apollo 11, 12, 14, 15 and 17 sites. The overall aim of this study is to further investigate mare-basalt genesis, and hence the evolution of the lunar magma ocean.
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