Hidden Secrets Of Deformation: Impact-Induced Compaction Within A CV Chondrite

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Title: Hidden Secrets Of Deformation: Impact-Induced Compaction Within A CV Chondrite
Author(s): Forman, LV
Bland, PA
Timms, NE
Collins, GS
Davison, TM
Ciesla, FJ
Benedix, GK
Daly, L
Trimby, PW
Yang, L
Ringer, SP
Item Type: Journal Article
Abstract: The CV3 Allende is one of the most extensively studied meteorites in worldwide collections. It is currently classified as S1—essentially unshocked—using the classification scheme of Stöffler et al. (1991), however recent modelling suggests the low porosity observed in Allende indicates the body should have undergone compaction-related deformation. In this study, we detail previously undetected evidence of impact through use of Electron Backscatter Diffraction mapping to identify deformation microstructures in chondrules, AOAs and matrix grains. Our results demonstrate that forsterite-rich chondrules commonly preserve crystal-plastic microstructures (particularly at their margins); that low-angle boundaries in deformed matrix grains of olivine have a preferred orientation; and that disparities in deformation occur between chondrules, surrounding and non-adjacent matrix grains. We find heterogeneous compaction effects present throughout the matrix, consistent with a highly porous initial material. Given the spatial distribution of these crystal-plastic deformation microstructures, we suggest that this is evidence that Allende has undergone impact-induced compaction from an initially heterogeneous and porous parent body. We suggest that current shock classifications (Stöffler et al., 1991) relying upon data from chondrule interiors do not constrain the complete shock history of a sample.
Publication Date: 15-Oct-2016
Date of Acceptance: 28-Jul-2016
URI: http://hdl.handle.net/10044/1/38407
DOI: https://dx.doi.org/10.1016/j.epsl.2016.07.050
ISSN: 0012-821X
Publisher: Elsevier
Start Page: 133
End Page: 145
Journal / Book Title: Earth and Planetary Science Letters
Volume: 452
Copyright Statement: © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Sponsor/Funder: Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Funder's Grant Number: ST/J001260/1
ST/M007642/1
ST/N000803/1
Keywords: Geochemistry & Geophysics
02 Physical Sciences
04 Earth Sciences
Publication Status: Published
Appears in Collections:Faculty of Engineering
Earth Science and Engineering



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