Lower Mantle composition

Wolf, G. H., and M. S. T. Bukowinski (1987). Theoretical study of the structural properties and equations of state of MgSiOj and CaSiOj perovskites implications for lower mantle composition. In High Pressure Research in Mineral Physics (M. Manghnani and Y. Syono, eds.) Tokyo Amer. Geophys. Union/Terra Pub. Co. 

Figure 5 Contours of r.m.s misfit (%) to seismological reference model akl35 of density (red) and bulk sound velocity (green) for candidate lower-mantle compositions, parametrized in terms of Mg/(Mg -f Fe) (= Xmj) and Si/(Mg -f Fe)(= Xpv), over the entirety of the lower mantle. Shaded region at Xpv > 1 indicates free silica. Triangle denotes pyrolite. Plus signs denote minima of r.m.s. misfit. Root of lower-mantle adiabat is 2,000 K at 660 km depth.

Aside from the core-mantle boundary region, a pyrolite lower-mantle composition appears to be consistent with seismological constraints. Silica enrichment of the lower mantle can be accommodated if the lower mantle is hotter than expected for a simple adiabat rooted at the 660 km y— pv + mw transition (Figure 9). Because any chemical boundary layer between the upper and lower mantle would be accompanied by a corresponding thermal boundary layer, such a model... 

Bina C. R. and Silver P. G. (1990) Constraints on lower mantle composition and temperature from density and bulk sound velocity profiles. Geophys. Res. Lett. 17, 1153—1156. 

Xe and radiogenic Xe in the upper mantle are derived from the lower mantle. This lower-mantle compositions, obtained by subtracting from MORE xenon the U-derived Xe produced in the upper mantle, corresponds to closure times that are similar to that of the atmosphere, indicating that early losses occurred from the deep mantle as well (Porcelli et al, 2001). These losses must have been prior to the assumed closed-system evolution. 

Bukowinski, M.S.T. and Wolf, G.H. (1990) Thermodynamically consistent decompression implications for lower mantle composition, J. Geophys. Res. 95, 12583-12593. 

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