On high-alumina mare basalts

Aluminous mare basalts have been found at several lunar sites, although they are not abundant. A group of crystalline clasts in breccia 14063 are also aluminous mare basalts with higher TiO2, Na2O, Mg/Fe ratio and lower FeO than other aluminous mare basalts. Composition of ilmenite clinopyroxene, and plagioclase confirm that crystallization took place from a melt with high TiO2 and Mg/Fe. A review of ages and siderophile trace-element abundances for aluminous mare basalts, suggests they are not hybrid rocks produced by melting of a mare + terra rock mix, but are pristine igneous melts from the lunar interior. Consideration of rare-earth element abundances indicate the source for aluminous mare basalts is pyroxenitic, with variable clinopyroxene/orthopyroxene ratio, and is not significantly different from the sources(s) of normal mare basalts.