Compressional pathways of α-cristobalite, structure of cristobalite X-I, and towards the understanding of seifertite formation
- Author(s)
- Ana Cernok, Katharina Marquardt, Razvan Caracas, Elena Bykova, Gerlinde Habler, Hanns-Peter Liermann, Michael Hanfland, Mohamed Mezouar, Ema Bobocioiu, Leonid Dubrovinsky
- Abstract
In various shocked meteorites, low-pressure silica polymorph α-cristobalite is commonly found in close spatial relation with the densest known SiO
2 polymorph seifertite, which is stable above ∼480 GPa. We demonstrate that under hydrostatic pressure α-cristobalite remains untransformed up to at least 15 GPa. In quasi-hydrostatic experiments, above 11 GPa cristobalite X-I forms-A monoclinic polymorph built out of silicon octahedra; the phase is not quenchable and back-transforms to α-cristobalite on decompression. There are no other known silica polymorphs, which transform to an octahedra-based structure at such low pressures upon compression at room temperature. Further compression in non-hydrostatic conditions of cristobalite X-I eventually leads to the formation of quenchable seifertite-like phase. Our results demonstrate that the presence of α-cristobalite in shocked meteorites or rocks does not exclude that materials experienced high pressure, nor is the presence of seifertite necessarily indicative of extremely high peak shock pressures.
- Organisation(s)
- Department of Lithospheric Research
- External organisation(s)
- Universität Bayreuth, Université Claude-Bernard-Lyon-I, Deutsches Elektronen-Synchrotron DESY, European Synchrotron Radiation Facility ESRF
- Journal
- Nature Communications
- Volume
- 8
- No. of pages
- 10
- ISSN
- 2041-1723
- DOI
- https://doi.org/10.1038/ncomms15647
- Publication date
- 06-2017
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105116 Mineralogy, 105113 Crystallography
- Keywords
- ASJC Scopus subject areas
- General Physics and Astronomy, General Chemistry, General Biochemistry,Genetics and Molecular Biology
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/12901055-9f8d-42f5-925a-5c2a05fc820d