Multiple nitrogen isotopic components coexisting in ureilites

• Published in: Meteoritics & Planetary Science
• Main Authors: YAMAMOTO, TOMOKO, HASHIZUME, KO, MATSUDA, JUN‐ICHI, KASE, TOMOHIKO
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1998
• Subjects: Antarc*; Antarctic
• Online Access: http://dx.doi.org/10.1111/j.1945-5100.1998.tb01692.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1945-5100.1998.tb01692.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1945-5100.1998.tb01692.x

Abstract— Nitrogen and noble gas isotopic compositions and C abundance of ureilites were analyzed using a stepwise combustion technique. Four Antarctic ureilites, ALHA77257, Asuka 881931, Yamato 791538 and Yamato 790981 were analyzed. Multiple N isotopic components were observed in these ureilites. The δ 15 N values of these N components ranged from +160 to −120%. The minimum δ 15 N values of typically −120% were observed at combustion temperatures at 700–900 °C where large amounts of C were released. A heavy N component was observed in only two ureilites, ALHA77257 and Asuka 881931. Silicate‐enriched fractions and C‐concentrated fractions were prepared for these two ureilites. We conclude that both the light N and the heavy N are trapped in the carbonaceous vein minerals. The lack of correction between the N/C ratio and the 36 Ar/C ratio suggests that the primary carrier phase of the light N does not correspond to that of the planetary noble gases. We consider that the isotopically heavy N, which was observed in this study, is related to the heavy N observed among polymict ureilites. Small amounts (<0.5 ppm) of light N with the minimum δ 15 N value of −120% were observed among the silicate fractions at the highest combustion temperature of 1200 °C, although the exact carrier phase of this light N is not known. We consider that the currently observed ureilites were produced by injection of several volatile‐rich objects into volatile‐poor ureilitic silicates.