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Initial strontium for a chondrite and the determination of a metamorphism or formation interval

Wasserburg, G. J. and Papanastassiou, D. A. and Sanz, H. G. (1969) Initial strontium for a chondrite and the determination of a metamorphism or formation interval. Earth and Planetary Science Letters, 7 (1). pp. 33-43. ISSN 0012-821X. doi:10.1016/0012-821x(69)90008-9.

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A precise Rb-Sr internal isochron was determined for Guarena, an H6 chondrite, yielding an age of 4.56 ± 0.08 × 10⁹ years. Rb-poor, Sr-rich phosphate phases (whitlockite and apatite) were obtained resulting in a precise measurement of the initial Sr isotopic composition (⁸⁷Sr/⁸⁶Sr)_I = 0.69995 ∓ 0.00015. It is shown that from precise age and initial (⁸⁷Sr/⁸⁶Sr)_I measurements we can obtain information on the differential evolution of Rb-Sr systems involving either simple metamorphism of closed systems or multi-stage processes. The high initial ratio obtained for Guarena with respect to the value for the basaltic achondrites is the first clear demonstration of differential Sr evolution of a chondrite and affords the simple explanation of Guarena having been metamorphosed 74 million years after its formation. This approach may yield a “time” evolution index for the classification of meteorites.

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Wasserburg, G. J.0000-0002-7957-8029
Additional Information:© 1969 Published by Elsevier B.V. Received 5 August 1969. We thank Mr. J.Brown for his competent and meticulous work in obtaining the phosphate separates. This research was principally supported by grants from the National Science Foundation (GP-9433 and GP-9114).
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Caltech Division of Geological Sciences1655
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Official Citation:G.J. Wasserburg, D.A. Papanastassiou, H.G. Sanz, Initial strontium for a chondrite and the determination of a metamorphism or formation interval, Earth and Planetary Science Letters, Volume 7, Issue 1, 1969, Pages 33-43, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115201
Deposited By: Tony Diaz
Deposited On:17 Jun 2022 20:40
Last Modified:17 Jun 2022 20:40

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