The cordierite- to spinel-cataclasite transition: Structure of the lunar crust

Abstract

Of the plutonic pristine highlands rocks, which are commonly the norites, troctolites (±spinel), and anorthosites, only the spinel- and cordierite-cataclasites (olivine + plagioclase + high alumina orthopyroxene ± spinel ± cordierite) exhibit phase changes and considerable variations in their mineral chemistry at depths appropriate to the lunar stratigraphic column. These have been calibrated by experiment in the system MgO-Al2OrSiO2 and applied to the natural lunar spinel- and cordierite-cataclasites by solution thermodynamics.