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Sm-Nd isotopic evolution of chondrites

Jacobsen, Stein B. and Wasserburg, G. J. (1980) Sm-Nd isotopic evolution of chondrites. Earth and Planetary Science Letters, 50 (1). pp. 139-155. ISSN 0012-821X. doi:10.1016/0012-821X(80)90125-9.

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The ^(143)Nd/^(144)Nd and ^(147)Sm/^(144)Nd ratios have been measured in five chondrites and the Juvinas achondrite. The range in ^(143)Nd/^(144)Nd for the analyzed meteorite samples is 5.3 ε-units (0.511673–0.511944) normalized to ^(150)Nd/^(142)Nd= 0.2096. This is correlated with the variation of 4.2% in ^(147)Sm/^(144)Nd (0.1920–0.2000). Much of this spread is due to small-scale heterogeneities in the chondrites and does not appear to reflect the large-scale volumetric averages. It is shown that none of the samples deviate more than 0.5 ε-units from a 4.6-AE reference isochron and define an initial ^(143)Nd/^(144)Nd ratio at 4.6 AE of 0.505828 ± 9. Insofar as there is a range of values of ^(147)Sm/^(144)Nd there is no unique way of picking solar or average chondritic values. From these data we have selected a new set of self-consistent present-day reference values for CHUR (“chondritic uniform reservoir”) of (^(143)Nd/^(144)Nd)_(CHUR)^0 = 0.511836 and (^(147)Sm/^(144)Nd)_(CHUR)^0 = 0.1967. The new ^(147)Sm/^(144)Nd value is 1.6% higher than the previous value assigned to CHUR using the Juvinas data of Lugmair. This will cause a small but significant change in the CHUR evolution curve. Some terrestrial samples of Archean age show clear deviations from the new CHUR curve. If the CHUR curve is representative of undifferentiated mantle then it demonstrates that depleted sources were also tapped early in the Archean. Such a depleted layer may represent the early evolution of the source of present-day mid-ocean ridge basalts. There exists a variety of discrepancies with most earlier meteorite data which includes determination of all Nd isotopes and Sm/Nd ratios. These discrepancies require clarification in order to permit reliable interlaboratory comparisons. The new CHUR curve implies substantial changes in model ages for lunar rocks and thus also in the interpretation of early lunar chronology.

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Wasserburg, G. J.0000-0002-7957-8029
Additional Information:© 1980 Elsevier Scientific Publishing Company. Received February 19, 1980. Revised version received June 3, 1980. This work has been supported by NSF grant EAR 76-22494 and NASA grant NGL 05-002-188. We thank D.A. Papanastassiou for his comments on the manuscript and his generous aid in matters spectrometric. We appreciate the thorough and scholarly reviews of the paper by L.E. Nyquist and N .M. Evensen which presumably led us to substantially improve the manuscript. The sources of the meteorite samples are as follows: Murchison, Field Museum of Natural History, Chicago. Juvinas and St. Severin, Museum of Natural History, Paris. Peace River, University of Alberta. Guarefia, Museo Nacional de Ciencias Naturales de Madrid.
Funding AgencyGrant Number
NSFEAR 76-22494
NASANGL 05-002-188
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Caltech Division of Geological and Planetary Sciences3371
Lunatic Asylum Lab336
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Official Citation:Stein B. Jacobsen, G.J. Wasserburg, Sm-Nd isotopic evolution of chondrites, Earth and Planetary Science Letters, Volume 50, Issue 1, October 1980, Pages 139-155, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42086
Deposited By: Ruth Sustaita
Deposited On:28 Oct 2013 16:20
Last Modified:10 Nov 2021 04:38

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