238U/235U Variations in Meteorites: Extant 247Cm and Implications for Pb-Pb Dating

被引：135

作者：

Brennecka, G. A. ^{[1
]}

Weyer, S. ^{[2
]}

Wadhwa, M. ^{[1
]}

Janney, P. E. ^{[1
]}

Zipfel, J. ^{[3
,5
]}

Anbar, A. D. ^{[1
,4
]}

机构：

[1] Arizona State Univ, Sch Earth & Space Explorat, Tempe, AZ 85287 USA

[2] Goethe Univ Frankfurt, Inst Geowissensch, Frankfurt, Germany

[3] Senckenberg Forsch Inst, Frankfurt, Germany

[4] Arizona State Univ, Dept Chem & Biochem, Tempe, AZ 85287 USA

[5] Natl Museum, Frankfurt, Germany

来源：

SCIENCE | 2010年 / 327卷 / 5964期

关键词：

EARLY SOLAR-SYSTEM; ISOTOPIC COMPOSITION; LIVE CM-247; FRACTIONATION; CONDENSATION; AGE; INCLUSIONS; URANIUM; SEARCH; NEBULA;

D O I：

10.1126/science.1180871

中图分类号：

O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];

学科分类号：

070301 [无机化学]; 070403 [天体物理学]; 070507 [自然资源与国土空间规划学]; 090105 [作物生产系统与生态工程];

摘要：

The U-238/U-235 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 (CAIs) of the Allende meteorite display variable U-238/U-235 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 CAIs, 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 U-238/U-235 in CAIs were produced by the decay of extant curium-247 to uranium-235 in the early solar system, with an initial Cm-247/U-235 ratio of approximately 1.1 x 10(-4) to 2.4 x 10(-4).

引用

页码：449 / 451

页数：3

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