Detecting serpentinization-related electrical anisotropy using magnetotelluric phase tensor: application in geologic hydrogen exploration

Abstract The detection and characterization of serpentinization in ultramafic rocks, such as mantle-derived peridotites in ophiolite formations, is essential for geologic hydrogen (H₂) exploration. Current approaches to detecting serpentinization in source rocks primarily target changes in bulk geophysical properties, such as seismic velocity, density, magnetic susceptibility, or electrical conductivity. However, an alternative approach is to leverage directionally dependent physical properties arising from deformation and serpentinization-related processes, including mineral alignment, fracturing, interconnected porosity, and the development of conductive minerals. In this study, we examine the use of magnetotelluric (MT) phase tensor analysis to detect electrical anisotropy as a proxy for the presence of serpentinization. Through numerical simulations of MT responses over 1D anisotropic conductivity layers, we examine the characteristic phase tensor responses that are usable in detecting and differentiating anisotropic conductivity. We further demonstrate the practical utility of the method in detecting serpentinization-related electrical anisotropy through the MT data acquired above buried ophiolite in the United Arab Emirates with confirmed serpentinization and associated anisotropic conductivity. The result from this study provides an additional tool for source rock-centered geologic hydrogen exploration.