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| Titel |
Effect of phase transformations on microstructures in deep mantle materials |
| VerfasserIn |
Sébastien Merkel, Christopher Langrand, Angelika Rosa, Nadège Hilairet |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250149077
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| Publikation (Nr.) |
 EGU/EGU2017-13393.pdf |
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| Zusammenfassung |
| Phase transformations induce microstructural changes in deep Earth materials, including
changes in grain size and orientation distribution. The effect of phase transformations on
mineral microstructures is usually studied using electron microscopy on quench
products from high P/T experiments. The method allows for a precise evaluation of the
microscopic mechanisms involved. It is limited, however, to samples that can be quenched
to ambient conditions and allows for investigations at a single P/T point for each
experiment.
In recent years, we extended the use of multigrain crystallography to samples inside diamond
anvil cells under mantle P/T conditions. The method allows for monitoring the orientations of
hundreds of grains and grain size variations during various physical processes, such as plastic
deformation and successions of phase transformations (Rosa et al 2015, Langrand et al
2017).
Here, we will show results concerning hydrous Mg2SiO4 during the series of α-β-γ phase
transformations up to 40 GPa and 850 ∘C. Such results are important to understand the
descending behaviour of subducted slabs, observations of seismic anisotropy, and polarity
changes for seismic waves reflected of deep Earth interfaces. The data is used to asses the
effect of the transformation on grain orientation and grain sizes. In particular, we do not
observe orientation relationships between the parent α-phase and the daughter β-phase
phase, suggesting an incoherent growth. We also observe significant grain size
reductions and only little grain growth within the newly formed phases (Rosa et al
2016).
These new results are important for understanding the mechanical behavior of subducting
slabs, seismic anisotropy in the Earth’s mantle, and phase transformation mechanisms in
olivine. Now that it is validated, the method can also be applied to other phases that can not
be studied using electron microscopy, such as perovskite and post-perovskite.
Langrand, Hilairet, Nisr, Roskosz, Ribárik, Vaughan, Merkel, Reliability of Multigrain Indexing
for Orthorhombic Polycrystals above 1 Mbar: Application to MgSiO3-Post-Perovskite, J
Appl Cryst 50, in press (2017)
Rosa, Hilairet, Ghosh, Garbarino, Jacobs, Perrillat, Vaughan, Merkel, In situ monitoring of
phase transformation microstructures at Earth’s mantle pressure and temperature using
multi-grain XRD, J Appl Cryst 48, 1346-1354 (2015)
Rosa, Hilairet, Ghosh, Perrillat, Garbarino, Merkel, Evolution of grain sizes and orientations
during phase transitions in hydrous Mg2SiO4, J Geophys Res 121, 7161–7176
(2016) |
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