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Title: Thickness and Clapeyron slope of the post-perovskite boundary

Abstract

The thicknesses and Clapeyron slopes of mantle phase boundaries strongly influence the seismic detectability of the boundaries and convection in the mantle. The unusually large positive Clapeyron slope found for the boundary between perovskite (Pv) and post-perovskite (pPv) (the 'pPv boundary') would destabilize high-temperature anomalies in the lowermost mantle, in disagreement with the seismic observations. Here we report the thickness of the pPv boundary in (Mg{sub 0.91}Fe{sub 0.09}{sup 2+})SiO{sub 3} and (Mg{sub 0.9}Fe{sub 0.1}{sup 3+})(Al{sub 0.1}Si{sub 0.9})O{sub 3} as determined in a laser-heated diamond-anvil cell under in situ high-pressure (up to 145 GPa), high-temperature (up to 3,000 K) conditions. The measured Clapeyron slope is consistent with the D'' discontinuity. In both systems, however, the pPv boundary thickness increases to 400-600 {+-} 100 km, which is substantially greater than the thickness of the D'' discontinuity (<30 km). Although the Fe{sup 2+} buffering effect of ferropericlase could decrease the pPv boundary thickness, the boundary may remain thick in a pyrolitic composition because of the effects of Al and the rapid temperature increase in the D'' layer. The pPv boundary would be particularly thick in regions with an elevated Al content and/or a low Mg/Si ratio, reducing the effects of the large positivemore » Clapeyron slope on the buoyancy of thermal anomalies and stabilizing compositional heterogeneities in the lowermost mantle. If the pPv transition is the source of the D'' discontinuity, regions with sharp discontinuities may require distinct compositions, such as a higher Mg/Si ratio or a lower Al content.« less

Authors:
; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1006004
Resource Type:
Journal Article
Journal Name:
Nature
Additional Journal Information:
Journal Volume: 462; Journal Issue: 12, 2009
Country of Publication:
United States
Language:
ENGLISH
Subject:
58 GEOSCIENCES; EARTH MANTLE; BOUNDARY CONDITIONS; THICKNESS; SEISMIC WAVES; MAGNESIUM SILICATES; IRON SILICATES; ALUMINIUM SILICATES; PRESSURE RANGE GIGA PA; TEMPERATURE RANGE 1000-4000 K

Citation Formats

Catalli, K, Shim, S -H, Prakapenka, V, MIT), and UC). Thickness and Clapeyron slope of the post-perovskite boundary. United States: N. p., 2009. Web. doi:10.1038/nature08598.
Catalli, K, Shim, S -H, Prakapenka, V, MIT), & UC). Thickness and Clapeyron slope of the post-perovskite boundary. United States. https://doi.org/10.1038/nature08598
Catalli, K, Shim, S -H, Prakapenka, V, MIT), and UC). Thu . "Thickness and Clapeyron slope of the post-perovskite boundary". United States. https://doi.org/10.1038/nature08598.
@article{osti_1006004,
title = {Thickness and Clapeyron slope of the post-perovskite boundary},
author = {Catalli, K and Shim, S -H and Prakapenka, V and MIT) and UC)},
abstractNote = {The thicknesses and Clapeyron slopes of mantle phase boundaries strongly influence the seismic detectability of the boundaries and convection in the mantle. The unusually large positive Clapeyron slope found for the boundary between perovskite (Pv) and post-perovskite (pPv) (the 'pPv boundary') would destabilize high-temperature anomalies in the lowermost mantle, in disagreement with the seismic observations. Here we report the thickness of the pPv boundary in (Mg{sub 0.91}Fe{sub 0.09}{sup 2+})SiO{sub 3} and (Mg{sub 0.9}Fe{sub 0.1}{sup 3+})(Al{sub 0.1}Si{sub 0.9})O{sub 3} as determined in a laser-heated diamond-anvil cell under in situ high-pressure (up to 145 GPa), high-temperature (up to 3,000 K) conditions. The measured Clapeyron slope is consistent with the D'' discontinuity. In both systems, however, the pPv boundary thickness increases to 400-600 {+-} 100 km, which is substantially greater than the thickness of the D'' discontinuity (<30 km). Although the Fe{sup 2+} buffering effect of ferropericlase could decrease the pPv boundary thickness, the boundary may remain thick in a pyrolitic composition because of the effects of Al and the rapid temperature increase in the D'' layer. The pPv boundary would be particularly thick in regions with an elevated Al content and/or a low Mg/Si ratio, reducing the effects of the large positive Clapeyron slope on the buoyancy of thermal anomalies and stabilizing compositional heterogeneities in the lowermost mantle. If the pPv transition is the source of the D'' discontinuity, regions with sharp discontinuities may require distinct compositions, such as a higher Mg/Si ratio or a lower Al content.},
doi = {10.1038/nature08598},
url = {https://www.osti.gov/biblio/1006004}, journal = {Nature},
number = 12, 2009,
volume = 462,
place = {United States},
year = {2009},
month = {12}
}