Petrology and geochemistry of nakhlite MIL 03346: A new Martian meteorite from Antarctica

MIL 03346 is a newly discovered meteorite from Miller Range in Antarctica, which belongs to the nakhlite group of Martian meteorites [1]. It is an unbrecciated, mediumgrained olivinebearing clinopyroxenite with a cumulate texture, similar to the 6 other previously known nakhlites. This is only the 2 nakhlite in Antarctic collections, the other being Yamato 000593 and its pairs. The Meteorite Working Group (MWG) allocated us two polished sections (MIL 03346,102 & MIL 03346,116), and 1 g rock chip (MIL 03346,37) for carrying out petrological and geochemical investigations. Petrography and Mineral Chemistry: The rock displays a cumulate texture (Fig. 1) consisting predominantly of zoned euhedral clinopyroxene (0.5-1 mm long) and glassy mesostasis, with rare olivine grains (up to 1 mm, Fig. 2). Accessory minerals mostly occur in the mesostasis, and include Ti-magnetite, fayalite, a sulphide phase, and free silica. Shock effects are evident in the form of extensive cracks and shock induced twinning in some pyroxenes. The mineralogy, Fe to Mn ratios in pyroxene and olivine (Fig. 3, after [2]) and bulk-rock composition (Table 1) confirm the Martian origin. In textural appearance, this rocks appears most similar to the nakhlite, NWA 817 [3]. The modal mineralogy of MIL 03346 is dominated by cumulus pyroxenes (~70%) followed by glassy mesostasis (~25%). Olivine is only present in minor amounts and no crystalline plagioclase was observed in our sample. However, the composition of the glassy mesostasis is most closely