Ballen quartz and cristobalite in impactites: New investigations
- Autor(en)
- Ludovic Ferriere, Christian Köberl, Eugen Libowitzky, Wolf Uwe Reimold, Ansgar Greshake, Franz Brandstätter
- Abstrakt
The study of α-quartz and α-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 and also in suevite, and more rarely in other types of impactites. Ballen α-cristobalite by itself was observed only in samples from the youngest craters studied here (at Bosumtwi and El'gygytgyn), but it occurs in association with α-quartz ballen in impactites from structures with intermediate ages (from ca. 35 to 120 Ma); thus, our observations suggest that α-cristobalite ballen are back-transformed to α-quartz with time. Transmission electron microscope observations show that α-cristobalite and α-quartz ballen have similar microtextures and are formed of several tiny angular crystals with sizes up to ~6 μm. The observation of toasted α-quartz ballen, notably at the Popigai impact structure, further supports the notion that toasting is due to vesicle formation after pressure release, at high post-shock temperatures, and, thus, represents the beginning of quartz breakdown due to heating. Our investigation increases the number of impact structures at which ballen silica has been found to 35.
- Organisation(en)
- Department für Lithosphärenforschung, Institut für Mineralogie und Kristallographie
- Externe Organisation(en)
- Humboldt-Universität zu Berlin, Museum für Naturkunde Berlin - Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Naturhistorisches Museum Wien (NHM)
- Band
- 465
- Seiten
- 609-618
- Anzahl der Seiten
- 10
- DOI
- https://doi.org/10.1130/2010.2465(29)
- Publikationsdatum
- 09-2010
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105105 Geochemie, 1051 Geologie, Mineralogie
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/cb7af4e0-a80e-4347-9b52-d8c969d4f0fa