Broadband Total-Field Airborne Magnetotellurics for Mineral Exploration: Principles and Field Performance over the El Teniente and La Huifa Porphyry Systems

Airborne natural-source electromagnetic methods are increasingly applied in mineral exploration, yet direct comparisons between different passive systems remain limited. This study evaluates the performance of the broadband, total-field MobileMT system relative to the ZTEM tipper method using coincident survey data acquired over the El Teniente and La Huifa porphyry deposits in central Chile. MobileMT applies classical magnetotelluric principles to airborne three-component magnetic measurements and a stationary electric-field reference, producing broadband admittance tensors and rotationally invariant responses across 30 narrow frequency windows. The results show that MobileMT achieves superior geological resolution even in the presence of a strong cultural noise (El-Teniente), and in low-noise conditions (La Huifa) due to greater usable bandwidth, and improved sensitivity to both shallow and deep conductivity structures. At El Teniente, ZTEM data are strongly affected by powerline interference, limiting usable bandwidth and obscuring conductive alteration zones, whereas MobileMT retains coherent responses and resolves potassic cores, alteration shells, and subvertical feeder structures. At La Huifa, where cultural noise is minimal, ZTEM still produces comparatively weak, laterally incoherent anomalies, while MobileMT defines a continuous structural corridor and the vertical extent of the porphyry system. These findings demonstrate that broadband total-field airborne MT provides enhanced geological resolution and depth penetration in rugged terrain and culturally noisy environments, offering clear advantages for porphyry exploration.