The electrical conductivity of olivine under highly reducing conditions |
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Authors: | L P Lemelle A G Duba F Guyot |
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Institution: | (1) Laboratoire de Mineralogie et Cristallographie de Paris, U.A. 09 CNRS, 4, place Jussieu case 115, F-75252 Paris cedex 05, France e-mail: Guyot@lmcp.jussieu.fr, FR;(2) Geosciences and Global Security Program, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA, US;(3) Département des Géomatériaux, Institut de Physique du Globe de Paris, 4, place Jussieu, F-75252 Paris cedex 05, France, FR |
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Abstract: | The electrical conductivity of San Carlos olivine has been measured at 1100 °C under reducing conditions at controlled oxygen
fugacity, inside and outside the olivine stability field, in order to study the kinetics of olivine destabilization. Electrical
conductivity increases along the direction 010] and decreases along 001]. as oxygen fugacity decreases. To understand these
dependences, electrical conductivity transitory regimes were studied. In response to decreases in oxygen fugacity, two transient
regimes with different time scales have been observed. A fast (≈1–2 min) increase of electrical conductivity is first observed,
followed by a slower decrease (1–10 h, depending on the crystal orientation). After a few hours of annealing, precipitation
of metallic iron and nickel and formation of amorphous silica can be observed at the crystal surface. The fast conductivity
increase in the first transient regime is ascribed to an increase in the population of electrons at the olivine surface. Two
effects: (1) equilibration of surface defects with the bulk of the crystal, and (2) iron loss from the olivine due to metal
precipitation, could explain the subsequent decrease of electrical conductivity. Anisotropic diffusion of surface defects
to the bulk of the crystal, by a process faster than atomic diffusion is the most likely.
Received: 3 September 1997 / Revised, accepted: 16 April 1998 |
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Keywords: | electrical conductivity olivine |
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