Apollo 12 feldspathic basalts 12031, 12038 and 12072 - Petrology, comparison and interpretations

摘要: Modal and chemical data indicate that 12072, 12038, 12031, the Apollo 12 feldspathic basalts, form a well-defined group which cannot be related to other rock types. 12072 contains phenocrysts of olivine pigeonite microphenocrysts Cr-spinel set in fine-grained, variolitic groundmass. 12038 is medium-grained, equigranular basalt with texture indicating it was multiply saturated. 12031 coarse-grained granular graphic intergrowths pyroxene plagioclase; also Petrologic observations, as well bulk chemistry, are consistent interpretation could derived from through fractionation Cr-spinel, olivine, pigeonite, observed phenocryst assemblage. however, more less three times much Ca-phosphate minerals, one-fifth troilite, sodic plagioclase than 12072. These differences must have come separate igneous body. Consideration compositions indicates neither nor been or ilmenite basalts by crystal--liquid fractionation. The general petrologic similarities between suggests they were produced either same more » similar source regions. petrologically chemically unique, probably exotic landing site. « less