The formation of impact coesite

Abstract Coesite in impact rocks is traditionally considered a retrograde product formed during pressure release by the crystallisation of an amorphous phase (either silica melt or diaplectic glass). Recently, the detailed microscopic and crystallographic study of impact ejecta from Kamil crater and...

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Autores principales: F. Campanale, E. Mugnaioli, M. Gemmi, L. Folco
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Lenguaje:EN
Publicado: Nature Portfolio 2021
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Acceso en línea:https://doaj.org/article/cdf0e856fae14f29bc69ebf991c0722a
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spelling oai:doaj.org-article:cdf0e856fae14f29bc69ebf991c0722a2021-12-02T17:06:25ZThe formation of impact coesite10.1038/s41598-021-95432-62045-2322https://doaj.org/article/cdf0e856fae14f29bc69ebf991c0722a2021-08-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-95432-6https://doaj.org/toc/2045-2322Abstract Coesite in impact rocks is traditionally considered a retrograde product formed during pressure release by the crystallisation of an amorphous phase (either silica melt or diaplectic glass). Recently, the detailed microscopic and crystallographic study of impact ejecta from Kamil crater and the Australasian tektite strewn field pointed in turn to a different coesite formation pathway, through subsolidus quartz-to-coesite transformation. We report here further evidence documenting the formation of coesite directly from quartz. In Kamil ejecta we found sub-micrometric single-coesite-crystals that represent the first crystallization seeds of coesite. Coesite in Australasian samples show instead well-developed subeuhedral crystals, growing at the expenses of hosting quartz and postdating PDF deformation. Coesite (010) plane is most often parallel to quartz {10–11} plane family, supporting the formation of coesite through a topotactic transformation. Such reaction is facilitated by the presence of pre-existing and shock-induced discontinuities in the target. Shock wave reverberations can provide pressure and time conditions for coesite nucleation and growth. Because discontinuities occur in both porous and non-porous rocks and the coesite formation mechanism appears similar for small and large impacts, we infer that the proposed subsolidus transformation model is valid for all types of quartz-bearing target rocks.F. CampanaleE. MugnaioliM. GemmiL. FolcoNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-8 (2021)
institution DOAJ
collection DOAJ
language EN
topic Medicine
R
Science
Q
spellingShingle Medicine
R
Science
Q
F. Campanale
E. Mugnaioli
M. Gemmi
L. Folco
The formation of impact coesite
description Abstract Coesite in impact rocks is traditionally considered a retrograde product formed during pressure release by the crystallisation of an amorphous phase (either silica melt or diaplectic glass). Recently, the detailed microscopic and crystallographic study of impact ejecta from Kamil crater and the Australasian tektite strewn field pointed in turn to a different coesite formation pathway, through subsolidus quartz-to-coesite transformation. We report here further evidence documenting the formation of coesite directly from quartz. In Kamil ejecta we found sub-micrometric single-coesite-crystals that represent the first crystallization seeds of coesite. Coesite in Australasian samples show instead well-developed subeuhedral crystals, growing at the expenses of hosting quartz and postdating PDF deformation. Coesite (010) plane is most often parallel to quartz {10–11} plane family, supporting the formation of coesite through a topotactic transformation. Such reaction is facilitated by the presence of pre-existing and shock-induced discontinuities in the target. Shock wave reverberations can provide pressure and time conditions for coesite nucleation and growth. Because discontinuities occur in both porous and non-porous rocks and the coesite formation mechanism appears similar for small and large impacts, we infer that the proposed subsolidus transformation model is valid for all types of quartz-bearing target rocks.
format article
author F. Campanale
E. Mugnaioli
M. Gemmi
L. Folco
author_facet F. Campanale
E. Mugnaioli
M. Gemmi
L. Folco
author_sort F. Campanale
title The formation of impact coesite
title_short The formation of impact coesite
title_full The formation of impact coesite
title_fullStr The formation of impact coesite
title_full_unstemmed The formation of impact coesite
title_sort formation of impact coesite
publisher Nature Portfolio
publishDate 2021
url https://doaj.org/article/cdf0e856fae14f29bc69ebf991c0722a
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