As it cooled, it crystallized first magnesian olivine and then pyroxene, followed by Ca-rich feldspar after about 80% of total crystallization. By this model, a hot early Moon was mostly or entirely molten. suggested that this crust formed very early in lunar history, by crystallization of material rich in Ca-rich feldspar from a global magma ocean. Remote sensing and geological studies have shown that most of the Moon is covered by a crust of anorthositic rock. These observations may support other models of crust formation on the Moon or suggest that there are complexities in the lunar magma ocean scenario to allow for multiple generations of anorthosite formation. Compositional and isotopic data from other authors also suggest that lunar anorthosites are chemically heterogeneous and have a wide range of ages. Comparisons of our data with other lunar meteorites and Apollo samples suggest that there is notable heterogeneity in the trace element abundances of lunar anorthosites, suggesting these samples did not all crystallize from a common magma source. Calculations of the melt in equilibrium with anorthite show that it apparently crystallized from a magma that was unfractionated with respect to rare earth elements and ranged in abundance from 8 to 80×CI. Every plagioclase exhibited a positive Eu-anomaly, with Eu abundances of up to approximately 20×CI. The rare earth elements were present in abundances of approximately 0.1 to approximately 10× chondritic (CI) abundance. Rare earth and other element abundances have been measured in situ in relict anorthosite clasts from two feldspathic lunar meteorites: Dhofar 908 and Dhofar 081. We are undertaking a study of the geochemical characteristics of anorthosites from lunar meteorites to test this model. By this model, the Moon was initially largely molten and the anorthositic crust that now covers much of the lunar surface directly crystallized from this enormous magma source. The lunar magma ocean model is a well-established theory of the early evolution of the Moon.
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