Differentiation of a very thick magma body and implications for the source regions of mare basalts

Mass-balance calculations indicate that the molten layer originally covering the moon may have been several hundred kilometers deep. The solidification of this magma ocean involved some unusual effects resulting from the large-pressure differential in the thick magma layer. The sunken cumulates from this differentiation would be more iron-rich, less refractory, and would contain more incompatible elements than would be expected in simple isobaric fractional crystallization and crystal sinking models of magma differentiation. These lower cumulates can have the mineralogical and chemical properties of the source regions of the low-Ti mare basalts.