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Shock metamorphism in plagioclase and selective amorphization

Plagioclase feldspar is one of the most common rock‐forming minerals on the surfaces of the Earth and other terrestrial planetary bodies, where it has been exposed to the ubiquitous process of hypervelocity impact. However, the response of plagioclase to shock metamorphism remains poorly understood....

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Autores principales: Pittarello, Lidia, Daly, Luke, PickersgilL, Annemarie E., Ferrière, Ludovic, Lee, Martin R.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7507835/
https://www.ncbi.nlm.nih.gov/pubmed/32999586
http://dx.doi.org/10.1111/maps.13494
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author Pittarello, Lidia
Daly, Luke
PickersgilL, Annemarie E.
Ferrière, Ludovic
Lee, Martin R.
author_facet Pittarello, Lidia
Daly, Luke
PickersgilL, Annemarie E.
Ferrière, Ludovic
Lee, Martin R.
author_sort Pittarello, Lidia
collection PubMed
description Plagioclase feldspar is one of the most common rock‐forming minerals on the surfaces of the Earth and other terrestrial planetary bodies, where it has been exposed to the ubiquitous process of hypervelocity impact. However, the response of plagioclase to shock metamorphism remains poorly understood. In particular, constraining the initiation and progression of shock‐induced amorphization in plagioclase (i.e., conversion to diaplectic glass) would improve our knowledge of how shock progressively deforms plagioclase. In turn, this information would enable plagioclase to be used to evaluate the shock stage of meteorites and terrestrial impactites, whenever they lack traditionally used shock indicator minerals, such as olivine and quartz. Here, we report on an electron backscatter diffraction (EBSD) study of shocked plagioclase grains in a metagranite shatter cone from the central uplift of the Manicouagan impact structure, Canada. Our study suggests that, in plagioclase, shock amorphization is initially localized either within pre‐existing twins or along lamellae, with similar characteristics to planar deformation features (PDFs) but that resemble twins in their periodicity. These lamellae likely represent specific crystallographic planes that undergo preferential structural failure under shock conditions. The orientation of preexisting twin sets that are preferentially amorphized and that of amorphous lamellae is likely favorable with respect to scattering of the local shock wave and corresponds to the “weakest” orientation for a specific shock pressure value. This observation supports a universal formation mechanism for PDFs in silicate minerals.
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spelling pubmed-75078352020-09-28 Shock metamorphism in plagioclase and selective amorphization Pittarello, Lidia Daly, Luke PickersgilL, Annemarie E. Ferrière, Ludovic Lee, Martin R. Meteorit Planet Sci Articles Plagioclase feldspar is one of the most common rock‐forming minerals on the surfaces of the Earth and other terrestrial planetary bodies, where it has been exposed to the ubiquitous process of hypervelocity impact. However, the response of plagioclase to shock metamorphism remains poorly understood. In particular, constraining the initiation and progression of shock‐induced amorphization in plagioclase (i.e., conversion to diaplectic glass) would improve our knowledge of how shock progressively deforms plagioclase. In turn, this information would enable plagioclase to be used to evaluate the shock stage of meteorites and terrestrial impactites, whenever they lack traditionally used shock indicator minerals, such as olivine and quartz. Here, we report on an electron backscatter diffraction (EBSD) study of shocked plagioclase grains in a metagranite shatter cone from the central uplift of the Manicouagan impact structure, Canada. Our study suggests that, in plagioclase, shock amorphization is initially localized either within pre‐existing twins or along lamellae, with similar characteristics to planar deformation features (PDFs) but that resemble twins in their periodicity. These lamellae likely represent specific crystallographic planes that undergo preferential structural failure under shock conditions. The orientation of preexisting twin sets that are preferentially amorphized and that of amorphous lamellae is likely favorable with respect to scattering of the local shock wave and corresponds to the “weakest” orientation for a specific shock pressure value. This observation supports a universal formation mechanism for PDFs in silicate minerals. John Wiley and Sons Inc. 2020-05-30 2020-05 /pmc/articles/PMC7507835/ /pubmed/32999586 http://dx.doi.org/10.1111/maps.13494 Text en © 2020 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals LLC on behalf of The Meteoritical Society (MET) This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Articles
Pittarello, Lidia
Daly, Luke
PickersgilL, Annemarie E.
Ferrière, Ludovic
Lee, Martin R.
Shock metamorphism in plagioclase and selective amorphization
title Shock metamorphism in plagioclase and selective amorphization
title_full Shock metamorphism in plagioclase and selective amorphization
title_fullStr Shock metamorphism in plagioclase and selective amorphization
title_full_unstemmed Shock metamorphism in plagioclase and selective amorphization
title_short Shock metamorphism in plagioclase and selective amorphization
title_sort shock metamorphism in plagioclase and selective amorphization
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7507835/
https://www.ncbi.nlm.nih.gov/pubmed/32999586
http://dx.doi.org/10.1111/maps.13494
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