Case study of magmatic differentiation trends on the Moon based on lunar meteorite Northwest Africa 773 and comparison with Apollo 15 quartz monzodiorite

Pyroxene and feldspar compositions indicate that most clasts from the Northwest Africa 773 (NWA 773) lunar meteorite breccia crystallized from a common very low-Ti (VLT) mare basalt parental magma on the Moon. An olivine cumulate (OC), with low-Ca and high-Ca pyroxenes and plagioclase feldspar formed during early stages of crystallization, followed by pyroxene gabbro, which is characterized by zoned pyroxene (Fe# = molar Fe/(Fe + Mg) × 100 from ∼35 to 90; Ti# = molar Ti/(Ti + Cr) × 100 from ∼20 to 99) and feldspar (∼An_90-95Ab_05-10 to An_80-85Ab_10-16). Late stage lithologies include alkali-poor symplectite consisting of fayalite, hedenbergitic pyroxene and silica, and alkaline-phase-ferroan clasts characterized by K-rich glass and/or K,Ba-feldspar with fayalite and/or pyroxene. Igneous silica only occurs with the alkaline-phase-ferroan clasts. This sequence of clasts represents stages of magmatic evolution along a ferroan-titanian trend characterized by correlated Fe# and Ti# in pyroxene, and a wide range of increase in Fe# and Ti# prior to crystallization of igneous silica.