Iodine-xenon analysis of Chainpur (LL3.4) chondrules

The I‐Xe chronometer and the early solar system

“…Huss et al (2001) reported Al-Mg measurements on 7 chondrules, 4 of which yielded ages corresponding to 4562.5-4565.5 Gyr in the scheme adopted here, the remainder having no detectable 26 Mg excesses. I-Xe data have a somewhat similar distribution: Swindle et al (1991a) reported 12 chondrules of which 3-4 had I-Xe ages consistent with those datable in the Al-Mg system, while Holland et al (2005) reported 5 I-Xe ages from a suite of 10 chondrules, of which 2 were within the Al-Mg age range. There is thus some evidence that Al-Mg and I-Xe tell a consistent story in the analyses of chondrules from these meteorites.…”

“…The I-Xe system in Allende CAIs clearly dates secondary processes since the carrier is sodalite, a product of aqueous alteration Kirschbaum 1988;Swindle 1998;Pravdivtseva et al 2003). The spread of I-Xe ages in Chainpur chondrules is suggestive of secondary processing (Swindle et al 1991a), but Holland et al (2005) sought separate evidence of such processes in the Chainpur chondrules they dated without success. Pravdivtseva et al (2005) argued that the spread of I-Xe ages among individual chondrules from LL chondrites increases with metamorphic grade, with chondrules from the low metamorphic grades clustering tightly shortly after CAI formation, and inferred that formation and alteration play complimentary roles in the I-Xe ages of chondrules.…”

Cosmogenic and trapped noble gases in individual chondrules: Clues to chondrule formation

“…In nebular setup heterogeneous precursors and/or differential melting of precursors, might explain variable iodine contents resulting in variable 129 Xe r . On the other hand, resetting of I-Xe systematics of chondrules can also occur on parent body surfaces e.g., Holland et al (2005) explained ~18 Ma range of I-Xe ages between Chainpur chondrules by impact melting on parent body.…”

Xenon isotopes in size separated nanodiamonds from Efremovka: 129Xe*, Xe-P3, and Xe-P6

“…However, I-Xe analyses of primitive meteorites such as those exhibiting significant 129 Xe* in their nanodiamond populations often have highly disturbed I-Xe systems with large amounts of uncorrelated iodine, requiring loss of 129 Xe* for much longer than 50Ma (e.g., Whitby et al, 2004). The youngest reliable chondrule I-Xe ages (high temperature correlations) are also found in the least processed meteorites, such as Chainpur (Swindle et al, 1991;Holland et al, 2004). It is quite clear that samples that are relatively unprocessed are not necessarily those that closed to xenon loss earliest, and it is the belief that low temperature components in nanodiamonds survived this late processing unscathed while 129 Xe* was lost from other low-temperature sites that would be extraordinary.…”

“…For a given 129 I/ 132 Xe ratio, different degrees of degassing occurring after a fixed period of decay define curves whose form depends on the decay interval. We assume that the initial 129 Xe/ 132 Xe ratio is 1.04 since there is no convincing evidence for a lower value of this ratio in solar system material (Holland et al, 2004). To proceed further it is necessary to introduce constraints on other relevant parameters.…”