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Transient electrical response of San Quintin Dunite as a function of oxygen fugacity changes: Information about charge carriers
Author(s) -
Roberts Jeffery J.,
Duba Alfred G.
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl03347
Subject(s) - olivine , mineral redox buffer , fugacity , seebeck coefficient , oxygen , crystallite , electrical resistivity and conductivity , mineralogy , analytical chemistry (journal) , materials science , thermoelectric effect , thermodynamics , condensed matter physics , geology , chemistry , metallurgy , physics , organic chemistry , chromatography , quantum mechanics
The electrical conductivity (σ) of San Quintin dunite (SQD) measured between 950 and 1150°C at controlled oxygen fugacity ( f O2 ) within the olivine stability field shows transients in response to changes in f O2 . Such behavior has not been reported previously for measurements made under similar conditions on either olivine single crystals or polycrystalline samples (dunites and lherzolites) in which olivine is the major phase. In general for olivine, an increase in f O2 results in an increase in σ. The transient is manifested as a change in σ from a stable equilibrium value at a specific f O2 to a quickly established subsequent value, the direction of which is opposite that of the final value that will be attained for the f O2 change. This transient may be caused by a changing population of electrons produced by oxygen vacancies, the grain boundaries, or a short‐lived defect. We postulate that the transient is observed in this particular dunite because of its large surface area to volume ratio. The transient is more pronounced at relatively high f O2 3 and temperatures between 950 and 1100°C. At relatively low f O2 s and temperatures higher than 1100°C, the effect is diminished. The Seebeck coefficient (S), at 1200°C, is slightly smaller than that reported for single‐crystal olivine, and at 1100°C is similar to that reported for single crystal olivine.