Oxygen isotopic composition of mare-basalts: magma ocean differentiation and source heterogeneity

Hallis, L. J.; Greenwood, R. C.; Anand, M.; Russell, S. S.; Miller, M. F. and Franchi, I. A. (2009). Oxygen isotopic composition of mare-basalts: magma ocean differentiation and source heterogeneity. In: 72nd Annual Meteoritical Society Meeting, 13-18 Jul 2009, Nancy, France.

URL: http://www.lpi.usra.edu/meetings/metsoc2009/pdf/53...

Abstract

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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