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Science 4 December 1992:
Vol. 258. no. 5088, pp. 1624 - 1626
DOI: 10.1126/science.258.5088.1624
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Articles

Terrestrial Carbon and Nitrogen Isotopic Ratios from Cretaceous-Tertiary Boundary Nanodiamonds

I. Gilmour 1, S. S. Russell 1, J. W. Arden 2, M. R. Lee 3, I. A. Franchi 1, and C. T. Pillinger 1

1 Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom
2 Department of Earth Sciences, Oxford University, Oxford OX1 3PR, United Kingdom
3 Department of Physics, University of Essex, Colchester Essex CO4 3SQ, United Kingdom

One hypothesis for the origin of the nanometer-size diamonds found at the Cretaceous-Tertiary (K-T) boundary is that they are relict interstellar diamond grains carried by a postulated asteroid. The 13C/12C and 15N/14N ratios of the diamonds from two sites in North America, however, show that the diamonds are two component mixtures differing in carbon and nitrogen isotopic composition and nitrogen abundance. Samples from a site from Italy show no evidence for either diamond component. All the isotopic signatures obtained from the K-T boundary are material well distinguished from known meteoritic diamonds, particularly the fine-grain interstellar diamonds that are abundant in primitive chondrites. The K-T diamonds were most likely produced during the impact of the asteroid with Earth or in a plasma resulting from the associated fireball.

Submitted on June 8, 1992
Accepted on September 15, 1992


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Cathodoluminescence investigations on the Popigai, Ries, and Lappajarvi impact diamonds.
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Extraterrestrial impacts on earth: the evidence and the consequences.
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Geochemistry of carbon in terrestrial impact processes.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)