Recent developments in large-scale geophysical inversions made it possible to invert the results of entire airborne geophysical surveys over large areas into 3D models of the subsurface. This paper presents the methods for and results of the interpretation of the data acquired by a multiphysics airborne geophysical survey in Saudi Arabia. The project involved the acquisition, processing, and interpretation of airborne electromagnetic, gravity, and magnetic geophysical data over an 8000 square kilometer area. All the collected data were carefully analyzed and inverted in 3D models of the corresponding physical properties of the subsurface, including 3D density, magnetization vector, and conductivity models. This paper summarizes the interpretation of all geophysical data sets collected during the field airborne survey. The goal of the paper is to demonstrate how the advanced 3D modeling and inversion methods can be effectively used for interpretation of multiphysics airborne survey data and to study and analyze the potential of the survey area for natural resource exploration in Saudi Arabia.

This paper develops a novel method of 3D inversion of induced polarization (IP) survey data, based on a generalized effective-medium model of the IP effect (GEMTIP). The electrical parameters of the effective-conductivity model are determined by the intrinsic petrophysical and geometrical characteristics of composite media, such as the mineralization and/or fluid content of rocks and the matrix composition, porosity, anisotropy, and polarizability of formations. The GEMTIP model of multiphase conductive media provides a quantitative tool for evaluation of the type of mineralization, and the volume content of different minerals using electromagnetic (EM) data. The developed method takes into account the nonlinear nature of both electromagnetic induction and IP phenomena and inverts the EM data in the parameters of the GEMTIP model. The goal of the inversion is to determine the electrical conductivity and the intrinsic chargeability distributions, as well as the other parameters of the relaxation model simultaneously. The recovered parameters of the relaxation model can be used for the discrimination of different rocks, and in this way may provide an ability to distinguish between uneconomic mineral deposits and zones of economic mineralization using geophysical remote sensing technology.