Mineralogy, Trace Element Composition, and Classification of Onello High-Ni Ataxite

Abstract

The trace element composition of the Onello meteorite is analyzed in detail using SEM and LA-ICP-MS. The following Ni contents of minerals are determined (wt %): 23.0–25.4 in taenite, 5.8–8.8 in kamacite, 22–26 in schreibersite, 44–52 in nickelphosphide, 20.6–21.8 in allabogdanite, and 75–81 in awaruite. In the trace element content, the Onello meteorite corresponds to the IAB group of iron meteorites. Inside this group, it mostly matches the sHH subgroup (with high Au and Ni contents). The presence of allabogdanite in the meteorite indicates the high PT parameters of its formation: >8 GPa and 1000–1400°C. Thus, the formation of the Onello meteorite is related to impact metamorphism of a parental body of iron meteorites of the IAB group and vinonaites, in which a P- and Ni-rich area underwent melting and further crystallization.