Electromagnetism of ultramafic rocks from the Luobusa ophiolite studied at room temperatures and pressures

It is generally accepted that a major phase of the Earth's upper mantle is represented by ultramafic rocks, including olivine pyroxenites, dunites, and peridotites. Studies on the electrical conductivity of ultramafic rocks continue to attract a great deal of interest, and much progress in the study of the electrical conductivity of rocks and minerals at high temperatures and pressures has been achieved recently. However, publications that consider the electromagnetism of ultramafic rocks at room temperatures and pressures are few and far between. In this paper, we present a study of the complex impedance properties of ultramafic samples from the Luobusa ophiolite, and their relationship to petrography. Samples were regularized and were not processed (e.g., fluid extraction, including soaking) before they were measured, and an impedance/gain-phase analyzer was used for complex impedance measurements across a frequency range, 0.005~1000 Hz. Density, susceptibility, major minerals, and trace element contents for most of samples were measured for comprehensive analysis, but just density features and weight content of serpentine are discussed in this paper. Results show that chromite exhibits complex resistivity, far lower than harzburgite, but larger than dunite. Chromite also has more complex phases than dunite at frequencies lower than 0.02 Hz, while at the same time exhibiting less phases at frequencies ranging from 0.02 to 1000 Hz. In terms of resistivity, serpentine content, and sample density, resistivity increases alongside density, and serpentine content decreases. Given that serpentine content and density have a clear relationship with petrography and the degree of metamorphism of the Ophiolite complex, our study opens up new possibilities for understanding the inner structure and phases of ultramafic complexes, as well as their relationships to geological processes, using ground-based geo-electrical methods.