Hidden secrets of deformation: impact-induced compaction within a CV chondrite

Forman, L.V. et al. (2016) Hidden secrets of deformation: impact-induced compaction within a CV chondrite. Earth and Planetary Science Letters, 452, pp. 133-145. (doi: 10.1016/j.epsl.2016.07.050)

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.

• Item Type: Articles
• Additional Information: This work was funded by the Australian Research Council via their Australian Laureate Fellowship programme (FL110100074) (PAB). This research was supported by the Curtin International Postgraduate Research Scholarship awarded to LF and LD, and GKB acknowledges support from Curtin University via their Research Fellowship scheme. GSC and TMD acknowledge funding from the UK Science and Technology Facilities Council STFC grant ST/J001260/1.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Daly, Dr Luke
• Authors: Forman, L.V., Bland, P.A., Timms, N.E., Collins, G.S., Davison, T.M., Ciesla, F.J., Benedix, G.K., Daly, L., Trimby, P.W., Yang, L., and Ringer, S.P.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences
• Journal Name: Earth and Planetary Science Letters
• Publisher: Elsevier
• ISSN: 0012-821X
• ISSN (Online): 1385-013X
• Published Online: 12 August 2016
• Copyright Holders: Copyright © 2016 The Authors
• First Published: First published in Earth and Planetary Science Letters 452: 133-145
• Publisher Policy: Reproduced under a Creative Commons License