The electrical conductivity of ophiolite in Southern Tibet

Recent magnetotelluric (MT) field measurements indicate the existence of high conductivity zones (HCZ) in the crust and upper mantle of Tibetan Plateau. As ocean basin lithosphere fragments in continental orogenic belts, the electrical conductivity of ophiolites may provide useful information to understand the electrical structure of the crust and the mantle. Using the samples of altered gabbro, basalt, hornblende peridotite and harzburgite collected from Yarlung Zangbo ophiolite zone in south Tibet, we detected the electrical conductivities of ophiolites by using the impedance spectrum method at 1 or 3 GPa and different temperatures respectively. The results show that the logarithm of electrical conductivity of ophiolites varies from -6 to -0. 5 S/m, the conductivity increases by 4 similar to 5. 5 orders of magnitude with the increase of experimental temperature. Before dehydration, the activation enthalpies are 0. 4 similar to 0. 6 eV for different samples at low temperature and 1. 7 similar to 2. 6 eV at high temperature. Meanwhile, we studied the effect of the water content and the iron content on the experimental conductivity, our result verified the positive correlation between the conductivity of the samples and the water content or iron content. While we normalized the water content or iron content of samples, the relationship of conductivity was consistent with the iron content or water content of the samples. The results were applied to Earth's interior and compared with the magnetotelluric observations, our model is consistent with the electrical conductivity structures derived from geophysical observations.