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Actinide microdistributions in the enstatite meteorites

Murrell, M. T. and Burnett, D. S. (1982) Actinide microdistributions in the enstatite meteorites. Geochimica et Cosmochimica Acta, 46 (12). pp. 2453-2460. ISSN 0016-7037. http://resolver.caltech.edu/CaltechAUTHORS:20150424-142033701

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Abstract

Oldhamite is a major Th and U bearing phase in the enstatite meteorites. Oldhamite from E-6 chondrites has mean Th and U abundances of 1550 ± 80 ppb Th and 410 ± 20 ppb U, with Th/U = 3.8 ± .2. With the exception of ferroan alabandite which contains 25 ± 1 ppb U, no other Th or U enriched phases were located in the E-6 chondrites, and nearly all of the total rock Th and U can be accounted for by oldhamite. In Khairpur (E6), excess fossil fission tracks were observed in enstatite grains in contact with oldhamite which indicates the presence of ^(244)Pu in oldhamite. Oldhamite from St. Mark's (E5) and Abee (E4) also shows actinide enrichments but at levels about half the E-6 results. Niningerite in Abee contains 45 ± 5 ppb U and due to its high reported modal abundance is an important U reservoir in Abee. The U content of oldhamite from the aubrite Peña Blanca Spring is 1920 ± 100 ppb. All Th/U values measured in this study cluster tightly around a value of 4 which indicates a lack of Th-U fractionation in both oldhamite and in the enstatite meteorites, themselves. This lack of fractionation, along with the presence of ^(244)Pu in oldhamite and reported rare earth enrichments also in oldhamite, suggests that the enstatite chondrites may be well-suited for Pu-U chronology and for providing the initial Pu-U value in the early solar system.


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http://dx.doi.org/10.1016/0016-7037(82)90368-4 DOIArticle
http://www.sciencedirect.com/science/article/pii/0016703782903684PublisherArticle
Additional Information:© 1982 Pergamon Press Ltd. Received May 5, 1982; accepted in revised form August 23, 1982. This paper has benefited from the careful reviews of G. Crozaz and K. Marti. We are indebted to R. Clarke (U.S. National Museum), R. Hutchison (British Museum of Natural History), G. Kurat (Naturhistorisches Museum, Wien) and J. T. Wasson for providing the meteorite samples used in this study. We are grateful for the excellent cooperation of the LBL 88-in. cyclotron staff, in particular Ruth Mary Larimer. Also, Dorothy Woolum provided essential hardware and guidance in the cyclotron irradiation. We are pleased to acknowledge the help of R. S. Rajan in the etching of ^(244)Pu fission tracks. We thank W. R. Heuser for experimental assistance and Lou Ann Cordell and Bernice Taylor for typing this paper. This research was supported by NSF grant EAR79-20091.
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Funding AgencyGrant Number
NSFEAR79-20091
Record Number:CaltechAUTHORS:20150424-142033701
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150424-142033701
Official Citation:M.T. Murrell, D.S. Burnett, Actinide microdistributions in the enstatite meteorites, Geochimica et Cosmochimica Acta, Volume 46, Issue 12, December 1982, Pages 2453-2460, ISSN 0016-7037, http://dx.doi.org/10.1016/0016-7037(82)90368-4. (http://www.sciencedirect.com/science/article/pii/0016703782903684)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56966
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Apr 2015 22:16
Last Modified:24 Apr 2015 22:16

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