Petrography and mineralogy of new lunar meteorite MIL090036

MIL090036 is a previously unknown meteorite(a feldspathic lunar breccia) that was discovered in Antarctica. The detailed petrography and mineralogy of this meteorite forms the subject of this paper. It has a typical clastic texture that consists of various types of rock debris(e.g. anorthosite, gabbroic anorthosite, gabbro, regolith breccia, troctolite, microporphyritic crystalline impact melt and compound clasts), mineral crystal fragments(e.g. pyroxenes, plagioclase, olivine and ilmenite) and feldspathic glass clasts. The fine-grained recrystallized minerals and mineral clasts are cemented together in a glassy groundmass. The anorthite content of plagioclase in the gabbro(An81-83) and anorthosite(An88-93) both have relatively low calcium content compared to those from other breccias(An90-98). The pyroxene composition(Fs12-35 Wo3-44 En22-79) in the rock debris, crystal mineral clasts and anorthositic glass clasts are relatively iron-deficient compared to those from gabbro debris with melt glass(Fs37-65 Wo10-29 En21-49) and groundmass(Fs18-69 Wo3-45 En14-50). In contrast, the pyroxene grains in the gabbroic anorthosite display a narrow compositional range(Fs24-27 Wo7-14 En59-69). Olivine grains in mineral fragments and the groundmass have a wider compositional range(Fo57-79) than those in the rock debris(Fo67-77). The Fe/Mn ratio in olivine is in the range of 47 to 83(average 76) and 76 to 112(average 73) in pyroxenes, and hence classify within the lunar field. The characteristics of texture, mineral assemblage and compositions suggest that MIL090036 possibly originated from a region beyond that of the Apollo and Luna samples. Further study of MIL090036 is therefore likely to lead to a better understanding of the geological processes on the Moon and the chemical composition of the lunar crust.