Isotopic Composition of Noble Gases, Nitrogen, and Carbon in the Ozerki New L Chondrite

Abstract

The isotopic composition of noble gases, nitrogen, and carbon in two samples of the Ozerki L chondrite, which differ in the degree of impact metamorphism, analyzed by the methods of stepwise oxidation and crushing, is reported. The data obtained indicate that the meteorite contains gases trapped on the asteroid during the impact events. The isotopic composition of trapped argon, studied by the stepwise crushing method, is dominated by radiogenic 40Ar (the average 40Ar/36Ar values are 846 in the chondrite material and 1908 in the melt with fine chondrite fragments). Most of the trapped 36Ar is located in positions inaccessible for crushing. The isotopic composition of Ne is a mixture of the solar-wind neon, cosmogenic, and most likely planetary (Q) components. The elemental composition of the trapped noble gases is formed by mixing of the solar, planetary (Q), and cosmogenic components in different proportions. Diffusion processes caused by impact events most likely influenced the elemental abundance of noble gases, primarily helium. Almost all carbon and nitrogen are chemically bound in the rock. In general, their isotopic composition corresponds to that of ordinary chondrites; however, an atypically light carbon isotopic composition with a bulk value δ13C = –47.6 ± 4.8 (‰) was detected in a sample of the chondrite material. The nitrogen released during crushing is isotopically lighter than that released during oxidation. This may indicate that in the course of impact processes, solar nitrogen is more easily mobilized and redistributed into voids than organic nitrogen enriched in the heavy isotope.