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I-Xe Dating: The Time Line of Chondrule Formation and Metamorphism in LL ChondritesRefractory inclusions, considered to be the oldest solids formed in the solar nebula. (4567.2 0.6 Ma) [1], are common in many carbonaceous and in some ordinary and enstatite chondrites. High-precision Pb- Pb ages for CAI s and chondrules (from different meteorites) suggested that chondrule formation appeared to have started about 2 Ma later than that of CAIs [1]. However, recent 26Al/26Mg data suggest simultaneous formation of CAI s and chondrules in Allende [2]. The I-Xe ages of CAI s in Allende are about 2 Ma younger than the I-Xe ages of Allende chondrules [3] but, like all chronometers, the I-Xe system records closure time of its particular host phase. In the case of Allende CAI s, the major iodine-bearing phase is sodalite, a secondary phase presumably formed by aqueous alteration, so I-Xe reflects the post-formational processes in these objects. In chondrules the iodine host phases vary and can reflect formation and/or alteration but, to put chondrule ages on a quantative basis, some problems should first be addressed.
Document ID
20050173926
Acquisition Source
Headquarters
Document Type
Conference Paper
Authors
Pravdivtseva, O. V.
(Washington Univ. Saint Louis, MO, United States)
Hohenberg, C. M.
(Washington Univ. Saint Louis, MO, United States)
Meshik, A. P.
(Washington Univ. Saint Louis, MO, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 2005
Publication Information
Publication: Lunar and Planetary Science XXXVI, Part 16
Subject Category
Geophysics
Funding Number(s)
CONTRACT_GRANT: NAG5-12776
Distribution Limits
Public
Copyright
Public Use Permitted.
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