Laboratory measurements of electrical conductivity in a gabbro of the Oman ophiolite at high–pressures and high–temperatures: implications for interpretation of resistivity structures of lower oceanic crust

We performed laboratory measurements of the electrical conductivity of a gabbro sample of the Oman ophiolite under high-pressures (0.6 and 0.8 GPa), high-temperatures (250-908 degrees C), and dry conditions using a piston-cylinder type high-pressure apparatus. The studied gabbro can be regarded as a representative sample of the lower oceanic crustal rocks based on its previously reported elastic wave velocities. The gabbro sample was powdered and hot pressed, and then sintered prior to the electrical conductivity measurements. The measured electrical conductivity of the sample decreased with decreasing temperature, which is consistent with the Arrhenius relationship. Compared with the electrical conductivity values of lower oceanic crust derived from a recent electromagnetic survey in offshore Nicaragua, the measured electrical conductivity of the sample was considerably lower in the temperature ranges expected for lower oceanic crust. The discrepancy can be explained by the presence of conductive pore-fluids in the lower oceanic crust.