HR: 10:20h
AN: T21F-01 INVITED     [PDF]
TI: Lower Mantle Composition From Mineral Physics Data
AU: * Bass, J D
EM: jaybass@uiuc.edu
AF: University of Illinois, Geology Department 1301 W Green St., Urbana, IL 61801 United States
AU: Jackson, J M
EM: jmjackso@uiuc.edu
AF: University of Illinois, Geology Department 1301 W Green St., Urbana, IL 61801 United States
AU: Mattern, E
EM: estelle.mattern@ens-lyon.fr
AF: Ecole Normale Superieure de Lyon, LST 46 allee d'Italie, Lyon cedex 07, ced 69364 France
AU: Matas, J
EM: jan.matas@ens-lyon.fr
AF: Ecole Normale Superieure de Lyon, LST 46 allee d'Italie, Lyon cedex 07, ced 69364 France
AU: Siogeikin, S V
EM: sinogeik@uiuc.edu
AF: University of Illinois, Geology Department 1301 W Green St., Urbana, IL 61801 United States
AB: The questions of lower mantle composition and thermal structure pose a considerable challenge for mineral physics. The pressures and temperatures of this region are difficult to simulate and measure accurately in the laboratory, and the phases likely present in this region are difficult to synthesize as high quality samples for accurate physical properties measurements. Nevertheless, over the last decade there has been enormous progress on characterizing the elastic and thermal properties of lower mantle phases. We review some of the recent experimental breakthroughs. These results have been used to infer the average composition of the lower mantle by extrapolation of mineral properties to lower mantle conditions and comparing them to global 1D Earth models, and also via formal inversion of seismic velocity and density profiles for composition. Inversions of density and bulk sound velocity are able to place constraints on the Mg/Si and the Mg/Fe ratios, but are less sensitive to Al and insensitive to Ca contents. This is in part due to recent experimental results which indicate that the bulk modulus of (Mg,Fe,Al)(Si,Al)O3 perovskite does not change much with Al content (contrary to previous experiments). However, the shear properties of aluminous perovskite differ substantially from those of Al-free perovskite, making the shear properties of the lower mantle a sensitive indicator of Al content. We discuss the range of compositional models consistent with the present laboratory results, and the most critical mineral physics results needed to further refine compositional and thermal models for the lower mantle.
DE: 1025 Composition of the mantle
DE: 1212 Earth's interior--composition and state (8105)
DE: 3909 Elasticity and anelasticity
DE: 3924 High-pressure behavior
SC: Tectonophysics [T]
MN: 2003 Fall Meeting