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Elasticity and rheology of Al-rich Calcium Ferrite Phase (CF) at high P-T conditions: Implications for the fate of subducted slabs

Applicant Wang Jingyun
Number 129129
Funding scheme Marie Heim-Voegtlin grants
Research institution Institut für Mineralogie und Petrographie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Mineralogy
Start/End 01.03.2010 - 28.02.2011
Approved amount 108'400.00
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Keywords (6)

Brillouin scattering; Calcium Ferrite-type Phase (CF); Elastic properties; Anisotropy; Rheology and deformation mechanism; X-ray radial diffraction

Lay Summary (English)

Lead
Lay summary
Seismic and tomographic studies have provided evidence for heterogeneities in the chemical composition of the lower mantle that strongly suggest the presence of unmixed remnant subducted slab components (enriched in aluminum and alkalis) at depth (660-2200 km). Understanding the origin of mantle heterogeneities thus requires knowledge of mineralogy, and thermal and geochemical properties of the deeply subducted slab. Seismic tomography and geodynamics studies have shown that some subducted slabs can deflect and flatten at 660 km depth while the others penetrate through the transition zone (410-660 km depth) into the lower mantle. Essentially, the ultimate fate of the slab depends on the density contrast with the surrounding mantle that is in turns controlled by the mineral and chemical composition of the slab.

Calcium Ferrite-type Phase (CF) has been identified in petrological studies as an important phase in subducted slabs, This phase may play an important role in 1) the recycling of aluminum and alkalis (Na, K) in the lower mantle and 2) in controlling the density contrast between the slab and the surrounding mantle, hence determining whether slabs deflect below the transition zone or penetrate into the mantle. In order to determine the fate of deep subducted slabs and put tighter constrains on the recycling of aluminum and alkalis in the mantle, knowledge of the thermoelastic properties of CF are necessary, but often not available. The aim of this proposal is to investigate the elastic and rheological properties of CF phases at high pressure and temperature conditions using Brillouin scattering spectroscopy and X-ray radial diffraction in conjunction with the diamond anvil cell. These results will further provide important constrains on the fate of subducted slabs and recycling of Al and alkalis (Na, K) in the mantle via subduction of the oceanic crust, contributing to better our understanding of the geodynamic and geochemical evolution of the convective mantle.
Direct link to Lay Summary Last update: 21.02.2013

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Abstract

Calcium Ferrite-type Phase (CF) has been identified in petrological studies as an important phase in subducted slabs. This phase may play an important role in 1) the recycling of aluminum and alkalis (Na, K) in the lower mantle and 2) in controlling the density contrast between the slab and the surrounding mantle, hence determining whether slabs deflect below the transition zone or penetrate into the mantle. In order to determine the fate of deep subducted slabs and put tighter constrains on the recycling of aluminum and alkalis in the mantle, knowledge of the thermoelastic properties of CF are necessary, but often not available. Here I propose to investigate the elastic and rheological properties of CF phases at high pressure and temperature conditions using Brillouin scattering spectroscopy and X-ray radial diffraction in conjuction with the diamond anvil cell.
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