Petrologic History of Moon Suggested by Petrography, Mineralogy, and Crystallography

Abstract

Opaque mineral compositions indicate that the fugacity of oxygen is approximately 10^-13 (earth basalts, 10^-10). Experiments under reducing conditions suggest that the crystallization range is approximately 1140° to 1070°C. Iron-rich pyroxmangite, fayalite, and hedenbergite occur in microgabbro. Ferropseudobrookite rimmed by ilmenite containing rutile and Cr-spinel lamellae occurs in ferrobasalt. Plagioclase vitrophyres in breccia can explain highland Surveyor VII analysis. We suggest crystal-liquid differentiation of out-gassed convecting moon with growing Fe-rich core, olivine-pyroxene mantle, plagioclase-rich dynamic crust underlain by nonspherical, inversely stratified ferrobasalt. Impact-breaking or convection-thrusting of crust releases fraction rich in Fe and Ti. Scanning electron microscopy of glass balls reveals minute depressions consistent with micrometeorite impact.