Interesting read from ASU - with supporting details and fascinating info regarding Allende's CAIs
http://asunews.asu.edu/20091231_brennecka http://www.sciencemag.org/cgi/content/abstract/science.1180871 Published Online December 31, 2009 Science DOI: 10.1126/science.1180871 Reports 238U/235U Variations in Meteorites: Extant 247Cm and Implications for Pb-Pb DatingG. A. Brennecka,1, S. Weyer,2, M. Wadhwa,1 P. E. Janney,1 J. Zipfel,3 A. D. Anbar1,4 The 238U/235U isotope ratio has long been considered invariantin meteoritic materials (i.e., 137.88). This assumption is acornerstone of the high-precision Pb-Pb dates that define theabsolute age of the Solar System. Calcium-aluminum-rich inclusionsof 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 previouslydetermined by Pb-Pb dating of CAIs, which may be overestimatedby several million years. The correlation of U isotope ratioswith proxies for Cm/U (i.e., Th/U and Nd/U) provides strongevidence that the observed variations of 238U/235U in CAIs wereproduced by the decay of extant 247Cm to 235U in the early SolarSystem, with an initial 247Cm/235U of ~ 1.1 to 2.4 x 10-4. 1 School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA. 2 Institut fur Geowissenschaften, Goethe-Universität, Frankfurt, Germany. 3 Senckenberg Forschungsinstitut und Naturmuseum, Frankfurt, Germany. 4 Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA. Current address: Institut für Geology und Mineralogie,Universität zu Köln, Cologne, Germany. To whom correspondence should be addressed. E-mail: brenne...@asu.edu ________________________________ Received for publication 20 August 2009. Accepted for publication 11 December 2009. ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
