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Fractionation of ruthenium from iridium at the Cretaceous-Tertiary boundary

Evans, Noreen Joyce and Ahrens, Thomas J. and Gregoire, D. C. (1995) Fractionation of ruthenium from iridium at the Cretaceous-Tertiary boundary. Earth and Planetary Science Letters, 134 (1-2). pp. 141-153. ISSN 0012-821X. doi:10.1016/0012-821X(95)00117-U.

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New data on Ru/Ir abundance ratios are presented for nonmarine (Hell Creek, Montana; Frenchman River, Saskatchewan) and marine Cretaceous-Tertiary boundary sites (Brazos River, Texas; Beloc, Haiti; DSDP 577 and DSDP 596). The Ru/Ir ratio varies from 0.5 to 1 within 4000 km of Chicxulub and increases to 2–3 at paleodistances (65 Ma) of up to 12,000 km from the impact site. For CI chondrites, Ru/Ir= 1.5. A ballistic model of ejecta cloud cooling and expansion, which employs the available vapor-pressure versus temperature data for Ru and Ir, predicts qualitatively similar global variation in the Ru/Ir ratio but by only a factor of 1.5. We infer that several other factors, such as remobilization of PGE during diagenesis, preferential oxidation of Ru, condensation kinetics and atmospheric chemical and circulation processes, may account for the observed larger Ru/Ir variation.

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Additional Information:© 1995 Elsevier Science B.V. Received 10 November 1994; accepted 12 June 1995. We are grateful to A. Hildebrand, D. Beeson and J. Lerbekmo for providing samples. We thank the ODP for supplying samples of DSDP cores 596 and 597. We thank reviewers C. Koeberl, F. Asaro and G. Ravizza, who made numerous suggestions which we believe improved this paper. Discussions with L. Watson, M. Hirschmann, W. W. Anderson and B. McInnes also improved the paper. This research was supported in Canada by NSERC and in the USA by NASA. We are grateful for paleoreconstruction provided by the Plates Project, Institute for Geophysics, The University of Texas, Austin. This is contribution 5446 of the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California. [MK]
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Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
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Caltech Division of Geological and Planetary Sciences 5446
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Official Citation:Noreen Joyce Evans, Thomas J. Ahrens, D.C. Gregoire, Fractionation of ruthenium from iridium at the Cretaceous-Tertiary boundary, Earth and Planetary Science Letters, Volume 134, Issues 1–2, August 1995, Pages 141-153, ISSN 0012-821X, (
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ID Code:50732
Deposited By: Ruth Sustaita
Deposited On:23 Oct 2014 18:49
Last Modified:10 Nov 2021 18:59

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