Pressure and composition dependence of the electrical conductivity of iron-rich synthetic olivines to 200 kbar |
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| Authors: | André Lacam |
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| Institution: | 1. Institut de Physique du Globe, Université Paris VI, 4 place Jussieu, 75230, Paris Cedex 05, France
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| Abstract: | The objectives of this study of olivines are, to calibrate the variation of electrical conductivity with pressure, up to 200 kbar in a diamond-anvil cell, and to determine how this is influenced by chemical composition. Experimentally, we have found that the variation of the electrical conductivity of three synthetic olivines containing 50, 75 and 100 mole percent of fayalite, is an exponential function of pressure P, closely represented at room temperature by:σxP=σx·exp ·(B x·P) where x is the iron content of the olivine, σ x the extrapolated value of conductivity at normal pressure and B x the slope of the regression line in semi-logarithmic coordinates. It is thus possible to express the temperature dependence of conductivity through the Boltzmann relationship:σxPT= σαT· exp ·(-H*/RT)=σxT·exp ·-(E*+PV * x )/RT] where H* is the activation enthalpy, E* the activation energy and V x * the activation volume. At constant temperature V * x =B x·RT and is approximately equal to 0,6 cm3/mole at 295 K. On the other hand, we have found that σxT is an exponential function of x and thus, B x and of course V x * are linear functions. The experimental procedure is described and the results discussed. |
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