The University of Arizona

Petrogenesis of lunar mare basalt meteorite Miller Range 05035

Y. LIU, C. FLOSS, J. M. D. DAY, E. HILL, L. A. TAYLOR

Abstract


Miller Range (MIL) 05035 is a low-Ti mare basalt that consists predominantly of pyroxene (62.3 vol%) and plagioclase (26.4 vol%). Pyroxenes are strongly shocked and complexly zoned from augite (Wo33) and pigeonite (Wo17) cores with Mg# = 50-54 to hedenbergite rims. Coexisting pyroxene core compositions reflect crystallization temperatures of 1000 to 1100 °C. Plagioclase has been completely converted to maskelynite with signs of recrystallization. Maskelynite is relatively uniform in composition (An94Ab6An91Ab9), except at contacts with late-stage mesostasis areas (elevated K contents, An82Ab15Or3). Symplectites (intergrowth of Fe-augite, fayalite, and silica) of different textures and bulk compositions in MIL 05035 suggest formation by decomposition of ferro-pyroxene during shock-induced heating, which is supported by the total maskelynitization of plagioclase, melt pockets, and the presence of a relict pyroxferroite grain. Petrography and mineral chemistry imply that crystallization of MIL 05035 occurred in the sequence of Fe-poor pyroxenes (Mg# = 50-54), followed by plagioclase and Fe-rich pyroxenes (Mg# = 20-50), and finally hedenbergite, Fe-Ti oxides, and minor late-stage phases. Petrography, bulk chemistry, mineral compositions, and the age of MIL 05035 suggest it is possibly source craterpaired with Asuka (A-) 881757 and Yamato (Y-) 793169, and may also be launch-paired with Meteorite Hills (MET) 01210. MIL 05035 represents an old (~3.8-3.9 Ga), incompatible element-depleted low-Ti basalt that was not sampled during the Apollo or Luna missions. The light-REE depleted nature and lack of Eu anomalies for this meteorite are consistent with an origin distant from the Procellarum KREEP Terrane, and genesis from an early cumulate mantle-source region generated by extensive differentiation of the Moon.

Keywords


lunar Meteorites;Lunar mare;Lunar petrogenesis;mineralogy;bulk chemistry;Miller Range

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