Developing an Original Geophysical Inversion Methodology for 3D Subsurface Imaging of Mineral Deposits in the Nigerian Basement Complex

Three-dimensional subsurface imaging of mineral deposits in the Nigerian basement complex using geophysical inversion methods is hampered by non-uniqueness of potential field inversion, sparse data coverage, and the absence of inversion algorithms specifically calibrated to the complex geological architecture of West African Precambrian shield terrains. This research develops an original constrained three-dimensional inversion methodology integrating gravity, magnetic, and electrical resistivity data for imaging mineral deposit geometry in the basement complex of north-central Nigeria. A novel cross-gradient structural coupling constraint derived from information-theoretic principles is formulated to enforce geological consistency between independently inverted gravity density, magnetic susceptibility, and electrical resistivity models without requiring explicit a priori geological model assumptions. The inversion algorithm is implemented in Python using a preconditioned conjugate gradient solver with adaptive regularization parameter selection based on L-curve criterion analysis. Synthetic model tests demonstrate successful recovery of a 200 m x 100 m orebody target at 50 m depth using simulated data noise levels representative of Nigerian field survey conditions. Field validation was conducted using ground gravity, proton precession magnetometry, and induced polarization surveys over a documented gold mineralization target in Zamfara State. The inverted three-dimensional models identify a steeply dipping mineralized zone consistent with published geological cross-sections, and quantitative volume estimates of the anomalous body agree within 22 percent of drilling-based resource estimates. The methodology is packaged as an open-source software tool for distribution to Nigerian mining sector practitioners. Keywords: geophysical inversion, 3D imaging, mineral deposits, basement complex, Nigeria