Geocheminar fall-2016

Secondary alterations in lunar ferroan anorthosites: Implications for the magma ocean hypothesis

Age data, surprisingly far younger than 4.50 Ga, from lunar ferroan anorthosites have been interpreted as key constraints on the hypothesis that the Moon's crust formed mainly by plagioclase flotation over a primordial, global magma ocean. However, various features of apparent secondary origin, such as reverse zoning and Na-poor plagioclase compositions associated with clouds of pyroxene inclusions, imply that the age results should not be directly identified with original igneous crystallization. The magma ocean hypothesis remains viable.