Noble gas retention chronologies for the St Séverin meteorite |
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Authors: | C.M Hohenberg B Hudson B.M Kennedy F.A Podosek |
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Affiliation: | McDonnell Center for the Space Sciences, Washington University, St Louis, MO 63130, U.S.A. |
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Abstract: | 40Ar-39Ar and 129Xe-128Xe analyses were performed on two lithologies (light and dark) of the St Séverin (LL6) chondrite. For the light and dark fractions, respectively, we obtained 40Ar retention ages of 4.38 and 4.42 AE and 129Xe retention ages of 8.4 and 15.2 myr after Bjurböle. The two methods give age differences of opposite sense, and by both methods the differences are significant. Both the 40Ar and the 129Xe ages are interpreted as dating relaxation of metamorphic conditions. These two chronometers are decoupled, however, and do not date the same events. 40Ar-39Ar reflect chondritic metamorphisrn on a 108 yr time scale. The 129Xe-128Xe ages reflect isotopic closure at higher temperatures and earlier times. |
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