Other
Scientific paper
Jul 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993metic..28r.381k&link_type=abstract
Meteoritics, vol. 28, no. 3, volume 28, page 381
Other
Argon, Interstellar Dust, Isotopes, Nitrogen
Scientific paper
Introduction: Presolar grains such as diamond, SiC, and graphite have been reported to have isotopically anomalous nitrogen [1-3]. Because of their stability to chemical treatment, they are relatively easily concentrated in laboratories. There are probably other, less-durable presolar materials in primitive meteorites. We have therefore been searching for such presolar grains in UOCs, using the nitrogen isotope ratio as an indicator. In fact, isotopically heavy nitrogen in Yamato 74191 (LL3.7) and light nitrogen in ALHA 77214 (L3.4), which are not those of diamond, SiC, or graphite, have been reported [4]. Here, we report some other nitrogen isotope anomalies, especially light nitrogen found in many UOCs. Results and Discussion: Nitrogen and argon extracted by the stepped combustion method from 200 degrees C to 1200 degrees C every 100 degrees C are measured with a static QMS. ALHA 77278 (LL3.7), LEW 86018 (L3.1), and ALHA 77216 (H3.7/3.9) have isotopically heavy nitrogen. There is a possibility that these chondrites have solar nitrogen, because ALHA 77216 has a large amount of solar neon and ALHA 77278 has a small amount of solar neon. ALHA 78119 (L3.5) shows a similar degassing profile to ALHA 77214 [4]. Therefore, it may have the same carriers of anomalous nitrogen as ALHA 77214. Since Chainpur also has a similar degassing profile to ALHA 77214, although its light nitrogen abundance is smaller, it has probably the same nitrogen carrier. ALHA 78084 (H4), Grady (H3.7), and Yamato 74024 (L3.8) have very small amounts of nitrogen, probably because of metamorphic loss, and their delta ^15N values are nearly 0 per mil. ALHA 81251 (H3.2/3.4) degasses isotopically light nitrogen and primordial ^36Ar around 1100 degrees C (see Fig. 1), and delta ^15N goes down to -60 per mil at this temperature. Nearly the same degassing profiles have been found in ALH 83007 (L3.2/3.5), ALH 83010 (L3.3), EET 83399 (L3.3), LEW 86022 (L3.2), Yamato 791500, Yamato 82038, and Mezo Madaras (LL3.4/3.7), although the amounts of light nitrogen are less than that of ALHA 81251. Here, excess ^15N, which is defined as excess ^15N = [nitrogen abundance] X delta ^15N X [^15N/^14N](sub)air, is introduced. Excess ^15N (>500 degrees C) of a bulk sample of ALHA 81251 is -6.3 ppb and 80% of this light nitrogen is removed by H2O2 treatment (see Fig. 1), while almost all primordial ^36Ar remains. Most light nitrogen of ALHA 81251 is not due to SiC or diamond because of differences in rare gases components. Conclusion: Some types of isotopically anomalous nitrogen components exist in UOCs, and there is a possibility that the carrier of this light nitrogen in ALHA 81251 is a new presolar grain. References: [1] Lewis R. S. et al. (1987) Nature, 326, 160-162. [2] Bernatowicz T. et al. (1987) Nature, 330, 728-730. [3] Amari S. et al. (1990) Nature, 345, 238-240. [4] Sugiura N. and Hashizume K. (1992) EPSL, 111, 441-454. Fig. 1, which appears here in the hard copy, shows excess ^15N released by stepped combustion of ALHA 81251.
Hashizume K.
Kiyota Kaoru
Sugiura Norimasa
No associations
LandOfFree
Isotopically Anomalous Nitrogen in Unequilibrated Ordinary Chondrites does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Isotopically Anomalous Nitrogen in Unequilibrated Ordinary Chondrites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Isotopically Anomalous Nitrogen in Unequilibrated Ordinary Chondrites will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1073028