Understanding the Complexity of the 660-km Seismic Discontinuity

Project: Research project

Description

Progress Summary The goal of this research project is to measure the effects of element partitioning on the depths, Clapeyron slopes, and boundary thicknesses (widths of the phase loops) of the post-spinel, post-garnet, and post-ilmenite boundaries in mantle-related multi-component, multi-phase systems, such as pyrolitic (average mantle composition), basaltic (enriched subducted oceanic crust), and harzburgitic (depleted subducted oceanic lithosphere) compositions. This dataset is expected to provide key information on the interpretation of the complex seismic structures observed near the 660-km depth. My group has conducted X-ray diffraction measurements on the mineral phases in pyrolitic and basaltic compositions in the laser-heated diamond-anvil cell at the Advanced Photon Source. So far we have completed experiments on iron-free and iron-bearing pyrolitic compositions, which enables us to reveal the effects of iron on the phase relations. We found that akimotoite, ilmenite-structured (Mg,Fe)SiO3, is stable to much higher temperatures than previously thought, which would change the seismic structures in the bottommost transition zone.
StatusFinished
Effective start/end date10/1/1211/30/14

Funding

  • National Science Foundation (NSF): $58,467.00

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discontinuity
ilmenite
iron
mantle
diamond anvil cell
oceanic lithosphere
spinel
transition zone
oceanic crust
garnet
partitioning
laser
X-ray diffraction
mineral
experiment
effect
research project