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An igneous-textured clast in the Peace River meteorite: insights into accretion and metamorphism of asteroids in the early solar system

Herd, Christopher D. K.; Friedrich, Jon M.; Greenwood, Richard C. and Franchi, Ian A. (2013). An igneous-textured clast in the Peace River meteorite: insights into accretion and metamorphism of asteroids in the early solar system. Canadian Journal of Earth Sciences, 50 pp. 14–25.

DOI (Digital Object Identifier) Link: https://doi.org/10.1139/e2012-078
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Abstract

The mineralogy, petrology, and geochemistry of an igneous-textured clast in the Peace River L6 chondrite meteorite was examined to determine the roles of nebular processes, accretion, and parent-body metamorphism in its origin. The centimetre-scale clast is grey and fine grained and is in sharp contact with the host chondrite. Two sub-millimetre veins cut across both the clast and host, indicating that the clast formed prior to the impact (shock) event(s) that produced the numerous veins present in the Peace River meteorite. The clast and host are indistinguishable in terms of mineral compositions. In contrast, there are differences in modal mineralogy, texture, as well as trace element and oxygen isotope composition between the clast and host. These differences strongly suggest that the clast was formed by impact melting of LL-group chondritic material involving loss of Fe–FeS and phosphate components, followed by relatively rapid cooling and incorporation into the Peace River host meteorite. Subsequent metamorphism on the Peace River parent body caused recrystallization of the clast and homogenization of mineral compositions and thermally labile element abundances between the clast and host. Shock metamorphism, including formation of shock melt veins, occurred post-metamorphism, during fragmentation of the L chondrite parent body. The results suggest that the formation of the Peace River parent asteroid included the incorporation of material from other asteroids and that the pre-metamorphic protolith was a breccia. Accordingly, we propose that the Peace River meteorite be reclassified as a polymict breccia.

Item Type: Journal Item
Copyright Holders: 2013 Canadian Science Publishing or its licensors
ISSN: 1480-3313
Project Funding Details:
Funded Project NameProject IDFunding Body
Astronomy and Planetary Sciences at the Open University (SP-12-089-MG)ST/L000776/1STFC (Science & Technology Facilities Council)
Extra Information: This article is one of a series of papers published in this CJES Special Issue on the theme of Canadian contributions to planetary geoscience.
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 44795
Depositing User: Richard Greenwood
Date Deposited: 13 Nov 2015 10:56
Last Modified: 07 Dec 2018 10:36
URI: http://oro.open.ac.uk/id/eprint/44795
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