On Poisson's ratio and composition of the Earth's lower mantle |
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| Institution: | 1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;2. National Engineering Research Center for Magnesium Alloys, Chongqing 400044, China;1. Vietnam Education Publishing House, 81 Tran Hung Dao, Hanoi, Vietnam;2. Hanoi National University of Education, 136 Xuan Thuy, Hanoi, Vietnam;3. University of Transport and Communications, Lang Thuong, Dong Da, Hanoi, Vietnam;4. Institute of Research and Development, Duy Tan University, K7/25 Quang Trung, Danang, Vietnam;1. Géosciences Environnement Toulouse, UMR 5563, UPS OMP- CNRS – IRD, Université de Toulouse III Paul Sabatier, 14 Avenue E. Belin, 31400 Toulouse, France;2. Geological Department, Lomonosov Moscow State University, Vorobievu Gory, 119899 Moscow, Russia;3. Institut de Recherche en Astrophysique et Planétologie, UMR 5277, UPS OMP – CNRS – CNES, Université de Toulouse III Paul Sabatier, 9 Avenue du Colonel Roche, 31028 Toulouse Cedex, France |
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| Abstract: | Poisson's ratio of the lower mantle, calculated from recently published values of seismic wave velocities and extrapolated to atmospheric pressure and room temperature is found to be in the range 0.23 ? ν ? 0.25. These values are compared with the values of Poisson's ratio calculated for binary mixtures of MgSiO3 perovskite and magnesiowüstite with various iron contents. Current values of the experimental error on measured elastic moduli give little hope to be able to discriminate between pyrolite and chondritic lower mantles: both are acceptable if the shear modulus of perovskite is in the upper range of Liebermann et al. estimates. A similar calculation using the seismic parameter φ confirms the results obtained by considering Poisson's ratio and further constrains the value of the shear modulus of perovskite to lie between 1600 and 1700 kilobars for current mantle models to remain plausible. Chemical stratification of the mantle is, therefore, possible but not required by seismological data. |
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