Dynamic re-weighting matrix inversion of magnetic data for enhanced identification of mafic–ultramafic intrusions: A case study from the Tianfang magmatic sulfide deposit, southwestern China

ABSTRACT Identifying mafic–ultramafic intrusions is critical for exploring magmatic sulfide deposits, especially those with abrupt morphological changes that may host mineralization. A dynamic iterative reweighting matrix inversion method enhances the resolution of magnetic susceptibility anomaly reconstruction and improves the characterization of intrusion morphology. This method initially constructs a weighted matrix based on cross-correlation coefficients between observed data and theoretical responses generated by a unit source. It then optimizes a dual-objective function balancing data fitting and weight distribution, iteratively refining the weighted matrix to adapt to subsurface structures. Finally, the optimized weighting matrix is used as a constraint to solve for the magnetic susceptibility anomaly model. A synthetic model test demonstrates significant improvement in detecting a single magnetic body with varying dip angles at different depths. Applied to the Tianfang magmatic sulfide deposit in Sichuan Province, China, this method successfully maps intrusion distribution and morphology using unmanned aerial vehicle aeromagnetic data. Two potential favorable ore-prospecting areas are identified: (1) transitional zones between steep and gentle dips and (2) neck regions of bottle-shaped intrusions. The integration with polarizability and resistivity anomalies led to two high-confidence drill targets, with drilling confirming disseminated sulfide mineralization at predicted depths of 340–400 m. These results indicate the effectiveness of dynamic reweighting matrix inversion in guiding magmatic sulfide deposit exploration. The method may also be useful for exploring other mafic–ultramafic-hosted deposits and magnetite ores.