Abstract: Here we report on the petrology and mineralogy of GRV 022888 and GRV 052408 ureilites recovered from the Grove Mountains in Antarctica. Based on the petrologic and mineralogical characteristics, we provide new insight into the origin and evolution of ureilites. The mineral assemblages in GRV 022888 were mainly olivine (~98%), with a few pyroxene and carbonaceous opaque interstitial assemblages (~2%). The GRV 052408 ureilite was composed mainly of olivine (~60%), pyroxene (~35%), and carbonaceous opaque interstitial (~5%) mineral assemblages. The olivines in both meteorites had a distinctly reverse-zoned structure, and the cores had a high Fe content while the rims had a high Mg content. The petrologic characteristics classified both as type-I monomict ureilites. The formation temperature calculated using an olivine-pigeonite-liquid geothermometer was high, at about 1220°C. Our findings suggest that the magma of these ureilites is the partially melted residue of a ureilite parent body, similar to material involved in the formation of chondrites.

Key words: Antarctic meteorite, ureilite, reverse zoning, origin