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Shocked and thermally metamorphosed zircon from the Vredefort impact structure, South Africa; transmission electron microscopic study

Wolf U. Reimold, Hugues Leroux and Robert L. Gibson
Shocked and thermally metamorphosed zircon from the Vredefort impact structure, South Africa; transmission electron microscopic study
European Journal of Mineralogy (October 2002) 14 (5): 859-868

Abstract

TEM analysis of zircon crystals from a migmatitic pelitic granulite from the central part of the Vredefort Dome (250-300 km diam.) reveals a nm to mu m scale subplanar lamellar structure that is attributed to high-P (> 15 GPa) shock deformation during a 2020 m.y. mega-impact event. Two types of subplanar structure occur: 1) dislocation bands and 2) nm-scale lamellar features. The dislocation bands could represent the optically discernible planar features described in naturally deformed zircon from a number of impact structures and Cretaceous/Tertiary boundary deposits. The annealing of these bands and localized formation of subgrains is consistent with the slow decay of shock heat from rocks beneath the very large Vredefort impact crater. Following the shock event, amorphization (metamictization) has locally destroyed the zircon structure.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 14
Serial Issue: 5
Title: Shocked and thermally metamorphosed zircon from the Vredefort impact structure, South Africa; transmission electron microscopic study
Affiliation: University of the Witwatersrand, Impact Cratering Research Group, Johannesburg, South Africa
Pages: 859-868
Published: 200210
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 59
Accession Number: 2002-071648
Categories: Igneous and metamorphic petrologyMineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map
S27°00'00" - S27°00'00", E27°15'00" - E27°15'00"
Secondary Affiliation: Universite de Sciences et des Technologies de Lille, FRA, France
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200222
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