Experimental Studies on Elasticities of Forsterite-Enstatite Composites:Towards an Understanding of the Rules of Mixture |
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| Authors: | Ji Shaocheng and Wang Zichao |
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| Institution: | Ji Shaocheng and Wang ZichaoDepartment of Geology,University of Montreal,Montreal,Quebec,H3C 3J7,Canada Institute of Geology,China Seismological Bureau,P.O. Box 634,Beijing 100029,China |
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| Abstract: | Which rule of mixture is the best for predicting the overall elastic properties of polyphase rocks based on the elastic properties and volume fractions of their constituents? In order to address this question, we sintered forsterite-enstatite polycrystalline aggregates with a varied forsterite volume fraction (0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0). Elastic properties (shear, bulk, and Young's moduli) of these synthesized composites were measured as a function of pressure up to 3.0 GPa in a liquid-medium piston-cylinder apparatus using a high-precision ultrasonic interferometric technique. The experimental data can be much better described by the shear-lag model than by the commonly used simple models such as Voigt, Ruess and Hill averages, Hashin-Shtrikman bounds, Ravichandran bounds, Halpin-Tsai equations, and Paul's calculations. We attributed this to the fact that the elastic interaction and stress transfer between phases are neglected in all the models except for the shear-lag model. In particular, the present study suggests that olivine in the mantle may be more abundant than it was previously thought to be simply based on the comparison between seismic Earth model velocities and calculated overall elastic properties of mantle mineral composites according to the Hill average or Hashin-Shtrikman bounds. |
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| Keywords: | Elasticity High pressure Forsterite Enstatite Composite Ultrasonic Interference Shear-lag model |
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