238U/235U variations in meteorites: Extant 247Cm and implications for Pb-Pb dating

G. A. Brennecka; S. Weyer; Meenakshi Wadhwa; P. E. Janney; J. Zipfel; Ariel Anbar

doi:10.1126/science.1180871

²³⁸U/²³⁵U variations in meteorites: Extant ²⁴⁷Cm and implications for Pb-Pb dating

G. A. Brennecka, S. Weyer, Meenakshi Wadhwa, P. E. Janney, J. Zipfel, Ariel Anbar

Research output: Contribution to journal › Article › peer-review

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Abstract

The ²³⁸U/²³⁵U isotope ratio has long been considered invariant in meteoritic materials (equal to 137.88). This assumption is a cornerstone of the high-precision lead-lead dates that define the absolute age of the solar system. Calcium-aluminum-rich inclusions (CAls) of the Allende meteorite display variable ²³⁸U/²³⁵U ratios, ranging between 137.409 ± 0.039 and 137.885 ± 0.009. This range implies substantial uncertainties in the ages that were previously determined by lead-lead dating of CAls, which may be overestimated by several million years. The correlation of uranium isotope ratios with proxies for curium/uranium (that is, thorium/uranium and neodymium/uranium) provides strong evidence that the observed variations of ²³⁸U/²³⁵U in CAls were produced by the decay of extant curium-247 to uranium-235 in the early solar system, with an initial ²⁴⁷Cm/²³⁵U ratio of approximately 1.1 × 10^-4 to 2.4 × 10^-4.

Original language	English (US)
Pages (from-to)	449-451
Number of pages	3
Journal	Science
Volume	327
Issue number	5964
DOIs	https://doi.org/10.1126/science.1180871
State	Published - Jan 22 2010

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title = "238U/235U variations in meteorites: Extant 247Cm and implications for Pb-Pb dating",

abstract = "The 238U/235U isotope ratio has long been considered invariant in meteoritic materials (equal to 137.88). This assumption is a cornerstone of the high-precision lead-lead dates that define the absolute age of the solar system. Calcium-aluminum-rich inclusions (CAls) of the Allende meteorite display variable 238U/235U ratios, ranging between 137.409 ± 0.039 and 137.885 ± 0.009. This range implies substantial uncertainties in the ages that were previously determined by lead-lead dating of CAls, which may be overestimated by several million years. The correlation of uranium isotope ratios with proxies for curium/uranium (that is, thorium/uranium and neodymium/uranium) provides strong evidence that the observed variations of 238U/235U in CAls were produced by the decay of extant curium-247 to uranium-235 in the early solar system, with an initial 247Cm/235U ratio of approximately 1.1 × 10-4 to 2.4 × 10-4.",

author = "Brennecka, {G. A.} and S. Weyer and Meenakshi Wadhwa and Janney, {P. E.} and J. Zipfel and Ariel Anbar",

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AU - Brennecka, G. A.

AU - Weyer, S.

AU - Wadhwa, Meenakshi

AU - Janney, P. E.

AU - Zipfel, J.

AU - Anbar, Ariel

PY - 2010/1/22

Y1 - 2010/1/22

N2 - The 238U/235U isotope ratio has long been considered invariant in meteoritic materials (equal to 137.88). This assumption is a cornerstone of the high-precision lead-lead dates that define the absolute age of the solar system. Calcium-aluminum-rich inclusions (CAls) of the Allende meteorite display variable 238U/235U ratios, ranging between 137.409 ± 0.039 and 137.885 ± 0.009. This range implies substantial uncertainties in the ages that were previously determined by lead-lead dating of CAls, which may be overestimated by several million years. The correlation of uranium isotope ratios with proxies for curium/uranium (that is, thorium/uranium and neodymium/uranium) provides strong evidence that the observed variations of 238U/235U in CAls were produced by the decay of extant curium-247 to uranium-235 in the early solar system, with an initial 247Cm/235U ratio of approximately 1.1 × 10-4 to 2.4 × 10-4.

AB - The 238U/235U isotope ratio has long been considered invariant in meteoritic materials (equal to 137.88). This assumption is a cornerstone of the high-precision lead-lead dates that define the absolute age of the solar system. Calcium-aluminum-rich inclusions (CAls) of the Allende meteorite display variable 238U/235U ratios, ranging between 137.409 ± 0.039 and 137.885 ± 0.009. This range implies substantial uncertainties in the ages that were previously determined by lead-lead dating of CAls, which may be overestimated by several million years. The correlation of uranium isotope ratios with proxies for curium/uranium (that is, thorium/uranium and neodymium/uranium) provides strong evidence that the observed variations of 238U/235U in CAls were produced by the decay of extant curium-247 to uranium-235 in the early solar system, with an initial 247Cm/235U ratio of approximately 1.1 × 10-4 to 2.4 × 10-4.

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²³⁸U/²³⁵U variations in meteorites: Extant ²⁴⁷Cm and implications for Pb-Pb dating

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