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A petrographic, chemical, and isotopic study of calcium-aluminum-rich inclusions and aluminum-rich chondrules from the Axtell (CV3) chondrite

Srinivasan, G. and Huss, G. R. and Wasserburg, G. J. (2000) A petrographic, chemical, and isotopic study of calcium-aluminum-rich inclusions and aluminum-rich chondrules from the Axtell (CV3) chondrite. Meteoritics and Planetary Science, 35 (6). pp. 1333-1354. ISSN 1086-9379. http://resolver.caltech.edu/CaltechAUTHORS:20140415-085757526

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Abstract

Petrographic, compositional, and isotopic characteristics were studied for three calcium-aluminum-rich inclusions (CAIs) and four plagioclase-bearing chondrules (three of them Al-rich) from the Axtell (CV3) chondrite. All seven objects have analogues in Allende (CV3) and other primitive chondrites, yet Axtell, like most other chondrites, contains a distinctive suite of CAIs and chondrules. In common with Allende CAIs, CAIs in Axtell exhibit initial ^(26)Al/^(27)Al ratios ((^(26)Al/^(27)Al)0) ranging from ∼5 × 10^(−5) to <1.1 × 10^(−5), and plagioclase-bearing chondrules have (^(26)Al/^(27)Al)0 ratios of ∼3 × 10^(−6) and lower. One type-A CAI has the characteristics of a FUN inclusion. The Al-Mg data imply that the plagioclase-bearing chondrules began to form >2 Ma after the first CAIs. As in other CV3 chondrites, some objects in Axtell show evidence of isotopic disturbance. Axtell has experienced only mild thermal metamorphism (<600 °C), probably not enough to disturb the Al-Mg systematics. Its CAIs and chondrules have suffered extensive metasomatism, probably prior to final accretion. These data indicate that CAIs and chondrules in Axtell (and other meteorites) had an extended history of several million years before their incorporation into the Axtell parent body. These long time periods appear to require a mechanism in the early solar system to prevent CAIs and chondrules from falling into the Sun via gas drag for several million years before final accretion. We also examined the compositional relationships among the four plagioclase-bearing chondrules (two with large anorthite laths and two barred-olivine chondrules) and between the chondrules and CAIs. Three processes were examined: (1) igneous differentiation, (2) assimilation of a CAI by average nebular material, and (3) evaporation of volatile elements from average nebular material. We find no evidence that igneous differentiation played a role in producing the chondrule compositions, although the barred olivine compositions can be related by addition or subtraction of olivine. Methods (2) and (3) could have produced the composition of one chondrule, AXCH-1471, but neither process explains the other compositions. Our study indicates that plagioclase-bearing objects originated through a variety of processes.


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http://dx.doi.org/10.1111/j.1945-5100.2000.tb01520.xDOIArticle
http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2000.tb01520.x/abstractPublisherArticle
Additional Information:© 2000 The Meteoritical Society. Issue published online: 4 FEB 2010; Article first published online: 4 FEB 2010; Received 1999 November 17, accepted in revised form 2000 August 7). We thank J. R. Beckett for useful discussions and M. B. Baker for providing the computer program with which we performed the mixing calculations and advice on its use. We thank E. Jarosewich for permitting us to use his unpublished analysis of Axtell. We also thank T. Ireland and an anonymous reviewer for their constructive reviews. Supported by NASA grant NAG5-4083 (G. J. W.) and NAG5-8158 (G. R. H.). Caltech Division of Geological and Planetary Sciences Contribution #5830 (976).
Funders:
Funding AgencyGrant Number
NASANAG5-4083
NASANAG5-8158
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Caltech Division of Geological and Planetary Sciences5830
Lunatic Asylum Lab976
Record Number:CaltechAUTHORS:20140415-085757526
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140415-085757526
Official Citation:SRINIVASAN, G., HUSS, G. R. and WASSERBURG, G. J. (2000), A petrographic, chemical, and isotopic study of calcium-aluminum-rich inclusions and aluminum-rich chondrules from the Axtell (CV3) chondrite. Meteoritics & Planetary Science, 35: 1333–1354. doi: 10.1111/j.1945-5100.2000.tb01520.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:44947
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:16 Apr 2014 14:30
Last Modified:16 Apr 2014 14:30

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