Comment on “Li and Be isotopic variations in an Allende CAI: Evidence for the in situ decay of short-lived Be and for the possible presence of the short-lived nuclide Be in the early solar system,” by M. Chaussidon, F. Robert, and K.D. McKeegan |
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| Authors: | SJ Desch N Ouellette |
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| Institution: | Department of Physics and Astronomy, Arizona State University, P.O. Box 871504, Tempe, AZ 85287, USA |
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| Abstract: | Recently Chaussidon et al. reported isotopic measurements of the Allende meteorite Ca, Al-rich inclusion (CAI) 3529-41 that they claim as evidence that live 7Be was incorporated into this CAI at the time of its formation Chaussidon, M., Robert, F., McKeegan, K.D., 2006. Li and Be isotopic variations in an Allende CAI: evidence for the in situ decay of short-lived 10Be and for the possible presence of the short-lived nuclide 7Be in the early solar system. Geochim. Cosmochim. Acta70, 224-245]. They claim their data show excesses of 7Li/6Li above the chondritic value, and that the 7Li/6Li excesses correlate linearly with 9Be/6Li, implying that the excess 7Li arose from the decay of 7Be (t1/2 = 53 days). In this Comment we dispute this claim. We show that the authors did not statistically analyze their data correctly, and that a linear correlation between 7Li/6Li and 9Be/6Li can in fact be ruled out. We show that the authors over-corrected for the effects of spallogenic Li, and in fact no statistically significant excesses of 7Li above chondritic ratios exist. Finally, we show that many of the spots in Allende 3529-41 that the authors counted as isotopically undisturbed show evidence of isotopic disturbance. We demonstrate that while their data support the late addition of isotopically light Li in spots with low Be/Li, their data are otherwise consistent with constant 7Li/6Li at near-chondritic levels. The data do not provide support for live 7Be in the early Solar System. |
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