Cordierite under hydrostatic compression
- Autor(en)
- Ronald Miletich-Pawliczek, G. Diego Gatta, Thomas Willi, Peter W. Mirwald, Paolo Lotti, Marco Merlini, Nicola Rotiroti, Thomas Loerting
- Abstrakt
The high-pressure behavior of cordierite was investigated by means of in situ experiments using piston-cylinder press and diamond-anvil cell. Static compression in diamond-anvil cells was conducted with various penetrating and non-penetrating pressure media (H2O up to 2 GPa, argon and 4:1-methanolethanol up to 7 GPa). The measurement of lattice parameters revealed neither a significant influence on the elasticity nor any indication for effects in analogy to over-hydration within the experimental pressure ranges. Volumetric compression experiments at constant rates up to 1.2 GPa in a piston-cylinder apparatus insinuate subtle irregularities in the low-pressure range at around ~0.35 and ~0.85 GPa. The ΔV/V contribution related to the anomalous compression behavior in that pressure range is of the order of 5 × 10-4. The results obtained from single-crystal X-ray diffraction between 10-4 and 7 GPa revealed an unexpected and anomalous linear volume decrease, corresponding to KT,298 = 131±1 GPa for the bulk modulus and K′ = -0.4±0.3 for its pressure derivative for a third-order Birch-Murnaghan equation of state. The compressional behavior of the main axis directions is anisotropic with βa-1 ≈ βb-1 > βc-1 for an initial pressure regime up to ~3 GPa. At pressures above ~4 GPa, the compression of the a- and b-axis starts to differ significantly, with the b-axis showing elastic softening as indicated by negative values for ∂(βb-1)/∂P. The diversification between the a- and b-axis is also expressed by the pressure-depending increase of the distortion parameter Δ. The pronounced elastic softening in both the b-axis and c-axis directions ∂(βb-1)/∂P = -4.3±0.9, ∂(βc-1)/∂P = -1.2±0.8) are responsible for the apparent linear bulk compression, which indicates the structural instability and precedes a so far not reported ferroelastic phase transition to a triclinic polymorph, following a primitive lattice above the critical transition at ~6.9 GPa.
- Organisation(en)
- Institut für Mineralogie und Kristallographie
- Externe Organisation(en)
- Leopold-Franzens-Universität Innsbruck, Universität Heidelberg, Università degli Studi di Milano-Bicocca
- Journal
- American Mineralogist: an international journal of earth and planetary materials
- Band
- 99
- Seiten
- 479-493
- Anzahl der Seiten
- 15
- ISSN
- 0003-004X
- DOI
- https://doi.org/10.1515/am.2014.4487
- Publikationsdatum
- 02-2014
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105116 Mineralogie, 105113 Kristallographie
- Schlagwörter
- ASJC Scopus Sachgebiete
- Geochemistry and Petrology, Geophysics
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/605cf061-c8c2-499d-b508-4cdcead81b20