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^(36)Cl-^(36)S in Allende CAIs: Implication for the origins of ^(36)Cl in the early solar system

Tang, H. and Liu, M-C. and McKeegan, K. D. and Tissot, F. L. H. and Dauphas, N. (2017) ^(36)Cl-^(36)S in Allende CAIs: Implication for the origins of ^(36)Cl in the early solar system. In: 48th Lunar and Planetary Science Conference, March 20-24, 2017, The Woodlands, TX.

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Chlorine-36 (t_(1/2)=0.3 Myr) decays to either ^(36)Ar (98%, β-) or ^(36)S (1.9%, ε and β+). This radionuclide can be produced by either charged particle irradiation [1,2] or stellar nucleosynthesis [3]. Evidence for the prior existence of ^(36)Cl in the Early Solar System (ESS) comes from radiogenic excesses of ^(36)Ar [4,5] and/or ^(36)S [6-9] in secondary phases (e.g., sodalite and wadalite) of ESS materials such as Ca, Al-rich inclusions (CAIs) and chondrules. However, the inferred initial ^(36)Cl/^(35)Cl ratios vary over three orders of magnitude among different chondrite constituents (5×10^(-6)-9×10^(-3)) [6-9]. Interestingly, although the initial ^(36)Cl/^(35)Cl ratios inferred in previous studies vary widely, all secondary phases bearing evidence for live ^(36)Cl in the ESS measured so far lack resolvable ^(26)Mg excesses due to the decay of ^(26)Al (t_(1/2) = 0.7 Myr), implying that ^(36)Cl and ^(26)Al may have been produced by different processes and/or incorporated into ESS solids at different times. Given that secondary phases may have formed late, the ^(36)S anomalies in secondary phases point to either a very high ^(36)Cl/^(35)Cl initial ratio (~10^(-2)) in the ESS, or a late irradiation scenario for the local production of ^(36)Cl (> 3 Myr after CAI formation) [9]. The elevated ESS ratio of ^(36)Cl/^(35)Cl ~10^(-2) inferred from [9] far exceeds the predictions from any model of stellar nucleosynthesis; therefore, a late irradiation scenario producing ^(36)Cl is currently the favored idea. In this framework, ^(36)Cl would be be produced in the nebular gas and then incorporated into the CAIs via aqueous alteration, which formed secondary phases.

Item Type:Conference or Workshop Item (Paper)
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Tissot, F. L. H.0000-0001-6622-2907
Dauphas, N.0000-0002-1330-2038
Additional Information:© 2017 Lunar and Planetary Institute.
Record Number:CaltechAUTHORS:20180615-132505821
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87163
Deposited By: Tony Diaz
Deposited On:15 Jun 2018 21:32
Last Modified:09 Mar 2020 13:18

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