Title :

Textures Induced by the Coesite‐Stishovite Transition and Implications for the Visibility of the X‐Discontinuity

Author(s) :

Krug, Matthias [Auteur]
Westfälische Wilhelms-Universität Münster = University of Münster [WWU]
Saki, Morvarid [Auteur]
Institut für Geophysik [Münster]
Ledoux, Estelle [Auteur]
Unité Matériaux et Transformations (UMET) - UMR 8207
Gay, Jeffrey-Phillip [Auteur]
Unité Matériaux et Transformations - UMR 8207 [UMET]
Chantel, Julien [Auteur]
Unité Matériaux et Transformations (UMET) - UMR 8207
Pakhomova, Anna [Auteur]
Deutsches Elektronen-Synchrotron [Hamburg] [DESY]
Husband, Rachel [Auteur]
Deutsches Elektronen-Synchrotron [Hamburg] [DESY]
Rohrbach, Arno [Auteur]
Westfälische Wilhelms-Universität Münster = University of Münster [WWU]
Klemme, Stephan [Auteur]
Westfälische Wilhelms-Universität Münster = University of Münster [WWU]
Thomas, Christine [Auteur]
Institut für Geophysik [Münster]
Merkel, Sébastien [Auteur]
Unité Matériaux et Transformations (UMET) - UMR 8207
Sanchez‐Valle, Carmen [Auteur]
Westfälische Wilhelms-Universität Münster = University of Münster [WWU]

Journal title :

Geochemistry, Geophysics, Geosystems

Abbreviated title :

Geochem Geophys Geosyst

Volume number :

23

Pages :

e2022GC010544

Publisher :

American Geophysical Union (AGU)

Publication date :

2022-09-25

ISSN :

1525-2027

English keyword(s) :

coesite-stishovite transition
microstructures
multigrain crystallography
X-discontinuity
reflection coefficients
mantle heterogeneities

HAL domain(s) :

Chimie/Matériaux
Physique [physics]/Matière Condensée [cond-mat]/Science des matériaux [cond-mat.mtrl-sci]
Physique [physics]/Physique [physics]/Géophysique [physics.geo-ph]

English abstract : [en]

The coesite-stishovite phase transition is considered the most plausible candidate to explain the X-discontinuity observed at around 300 km depth in a variety of tectonic settings. Here, we investigate the microstructure ...
Show more >The coesite-stishovite phase transition is considered the most plausible candidate to explain the X-discontinuity observed at around 300 km depth in a variety of tectonic settings. Here, we investigate the microstructure in SiO2 across the coesite-stishovite transition in uniaxial compression experiments. We apply the multigrain crystallography technique (MGC) in a laser-heated diamond-anvil cell (LH-DAC) to identify the seismic signature of the transition and the amount of SiO2 in the mantle. While coesite displays weak lattice-preferred orientations (LPO) before the transition, stishovite develops strong LPO characterized by the alignment of [112] axes parallel to the compression direction. However, LPO has little effect on the impedance contrast across the transition, which is up to 8.8% for S-waves in a mid-ocean ridge basalt (MORB) composition at 300 km depth along a normal mantle geotherm, 10 GPa-1700 K. Therefore, 10–50 vol.% of a MORB component, corresponding to 0.6–3.2 vol.% SiO2, mechanically mixed with the pyrolytic mantle would be required to explain the range of impedance (and velocity) contrasts observed for the X-discontinuity. Based on the reflection coefficients computed for the coesite-stishovite transition, we show that the incidence angle or epicentral distance is critical for the detection of silica-containing lithologies in the upper mantle, with highest detection probabilities for small incidence angles. The intermittent visibility of the X-discontinuity may thus be explained by the seismic detectability of the coesite-stishovite transition rather than by absence of the transition or chemical heterogeneities in some specific tectonic settings.Show less >

Language :

Anglais

Peer reviewed article :

Oui

Audience :

Internationale

Popular science :

Non

ANR Project :

Transformations de phase, microstructures, et leur signatures sismiques dans le manteau terrestre

Administrative institution(s) :

Université de Lille
CNRS
INRAE
ENSCL

Collections :

• Unité Matériaux et Transformations (UMET) - UMR 8207

Research team(s) :

Matériaux Terrestres et Planétaires

Submission date :

2022-10-04T19:33:14Z
2022-10-05T09:11:55Z