Ballen quartz and cristobalite in impactites: New investigations
- Author(s)
- Ludovic Ferriere, Christian Köberl, Eugen Libowitzky, Wolf Uwe Reimold, Ansgar Greshake, Franz Brandstätter
- Abstract
The study of alpha-quartz and alpha-cristobalite ballen in rocks from 16 impact structures(Bosumtwi, Chesapeake Bay, Chicxulub, Dellen, El’gygytgyn, Jänisjärvi, Lappajärvi,Logoisk, Mien, Popigai, Puchezh-Katunki, Ries, Rochechouart, Sääksjärvi, Ternovka,and Wanapitei) shows that ballen silica occurs mainly in impact melt rock andalso in suevite, and more rarely in other types of impactites. Ballen - cristobalite byitself was observed only in samples from the youngest craters studied here (at Bosumtwiand El’gygytgyn), but it occurs in association with alpha-quartz ballen in impactitesfrom structures with intermediate ages (from ca. 35 to 120 Ma); thus, our observationssuggest that -cristobalite ballen are back-transformed to alpha-quartz with time.Transmission electron microscope observations show that -cristobalite and -quartzballen have similar microtextures and are formed of several tiny angular crystals withsizes up to ~6 µm. The observation of toasted -quartz ballen, notably at the Popigaiimpact structure, further supports the notion that toasting is due to vesicle formationafter pressure release, at high post-shock temperatures, and, thus, representsthe beginning of quartz breakdown due to heating. Our investigation increases thenumber of impact structures at which ballen silica has been found to 35.
- Organisation(s)
- Department of Lithospheric Research, Department of Mineralogy and Crystallography
- External organisation(s)
- Humboldt-Universität zu Berlin, Museum für Naturkunde Berlin - Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Naturhistorisches Museum Wien (NHM)
- Volume
- 465
- Pages
- 609-618
- No. of pages
- 10
- DOI
- https://doi.org/10.1130/2010.2465(29)
- Publication date
- 09-2010
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105105 Geochemistry, 1051 Geology, Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/cb7af4e0-a80e-4347-9b52-d8c969d4f0fa