Impacts on the CV parent body: a coordinated, multiscale fabric analysis of the Allende meteorite

Forman, L. V., Daly, L. , Bland, P. A., Benedix, G. K. and Corrigan, C. (2023) Impacts on the CV parent body: a coordinated, multiscale fabric analysis of the Allende meteorite. Meteoritics and Planetary Science, 58(4), pp. 529-545. (doi: 10.1111/maps.13970)

Abstract

Evidence of impact-induced compaction in the carbonaceous chondrites, specifically CMs and CVs, has been widely investigated utilizing microscopy techniques and impact experiments. Here, we use high-resolution photography and large area and high-resolution electron backscattered diffraction (EBSD) mapping analyses in tandem, to explore the effects of impact-induced compaction at both the meso- and micro-scales in the Allende CV3.6 carbonaceous chondrite. Macro-scale photography images of a ~25 cm slab of Allende captured meso-scale features including calcium-aluminum inclusions (CAIs) and chondrules. CAIs have a long-axis shape-preferred orientation (SPO). Examination of such meso-scale features in thin section revealed the same trend. Matrix grains from this section display a large amount of heterogeneity in petrofabric orientation; microscale, high-resolution, large area EBSD mapping of ~300,000 olivine matrix grains; high-resolution large area EBSD map across an elongate CAI; and a series of high-resolution EBSD maps around two chondrules and around the CAI revealed crystallographic preferred orientations (CPOs) in different directions. Finally, internal grains of the CAI were found to demonstrate a weak lineation CPO, the first crystallographic detection of possible CAI “flow.” All results are consistent with multiple, gentle impacts on the Allende parent body causing hemispheric compaction. The larger, more resistant components are likely to have been compressed and oriented by earlier impacts, and the matrix region petrofabrics and CAI “flow” likely occurred during subsequent impacts. Meteoritic components respond differently to impact events, and consequently, it is likely that different components would retain evidence of different impact events and angles.

• Item Type: Articles
• Additional Information: LD would like to acknowledge funding from the University of Glasgow Early Career Mobility Scheme 2019 and funding from the UK Science Technology Facilities Council (STFC) grant (ST/T002328/1). Open access publishing facilitated by Curtin University, as part of the Wiley - Curtin University agreement via the Council of Australian University Librarians.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Daly, Dr Luke
• Authors: Forman, L. V., Daly, L., Bland, P. A., Benedix, G. K., and Corrigan, C.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences
• Journal Name: Meteoritics and Planetary Science
• Publisher: Wiley
• ISSN: 1086-9379
• ISSN (Online): 1945-5100
• Published Online: 27 March 2023
• Copyright Holders: Copyright © 2023 The Authors
• First Published: First published in Meteoritics and Planetary Science 58(4):529-545
• Publisher Policy: Reproduced under a Creative Commons license

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
308251		UK leadership in extraterrestrial sample return	Martin Lee	Science and Technology Facilities Council (STFC)	ST/T002328/1	P&S - Physics & Astronomy