Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4694821 | Tectonophysics | 2007 | 9 Pages |
Abstract
We conducted electrical conductivity measurements perpendicular and parallel to mineral foliation in dry gneiss at up to 1000Â K and a constant pressure of 1Â GPa. The analyzed gneisses were obtained from the Higo metamorphic belt, Kyushu, Japan. As the metamorphic conditions of these rocks have been well determined by previous studies, we were able to select samples that were representative of the middle to lower crust. Prior to the conductivity measurements, the samples were maintained at the maximum temperature for a long period, until the electrical conductivity had stabilized. Our experiment results reveal linear and reproducible conductivity data between temperatures of 600 and 1000Â K. Conductivity measured perpendicular and parallel to foliation differ by an order of magnitude over the same temperature window. A plausible explanation for this discrepancy in conductivity is the contrasting configuration of minerals in the two sample orientations, as observed by backscattered electron image (BEI) and electron probe microanalysis (EPMA). We evaluated the conductivity and computed activation energy for each of the samples and compared the results with those of previous studies; our results are consistent with the conductivity values reported for other types of rocks. We also compared the experiment results with data derived from electromagnetic (EM) soundings. Electrical conductivity measurements undertaken perpendicular to foliation can account for the subsurface conductivity structure beneath central Kyushu, Japan.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Earth-Surface Processes
Authors
Kiyoshi Fuji-ta, Tomoo Katsura, Takuya Matsuzaki, Masahiro Ichiki, Tomoyuki Kobayashi,