FREQUENCY DEPENDENT ELECTRICAL PROPERTIES OF MINERALS AND PARTIAL-MELTS

Abstract. The resistance to current flow of minerals and partial-melts i a frequency dependent electri-cal property. Measurements of the frequency dependent electrical impedance of single crystal olivine, polycrystalline olivine, dunites, metapelites, and partial-melts, between 10-4 and 105 Hz, when plotted in the complex impedance plane, reveal rcs that correspond to different conduction mechanisms in the material being studied. In polycrystalline materials, two impedance arcs related to material proper-ties (as opposed to electrode properties or electrode-sample interactions) are observed. Each impedance arc is activated over a distinct range of frequency, that is, the mechanisms occur in series. Based on experiments comparing single and polycrystalline impedance spectra, experiments on samples with different electrode configurations, and on samples of varying dimension, the mechanisms responsible for these impedance arcs are interpreted as grain interior conduction (~gi), grain boundary conduction (in polycrystalline materials; ~rgb) , and sample-electrode interface effects, from highest to lowest frequency, respectively. Impedance spectra of natural dunitic rocks reveal analogous behavior, that is, ~rgb and O'g i add in series. The grain boundaries do not enhance the conductivity of any of the materials studied (a direct result of the observed series electrical behavior) and, under certain conditions, limit the total conductivity of the grain interior-grain boundary system. By examining the frequenc