Advances in Magnetic and Electromagnetic Techniques for Mineral Exploration: Enhancing Resource Discovery

1. Introduction

The rapid technological progress of the 20th century significantly advanced magnetic and electromagnetic (EM) techniques, establishing them as key tools for the discovery of mineral resources. Magnetic surveys, which detect subtle variations in the Earth’s magnetic field, are particularly effective in mapping magnetite concentration [1,2]. Initially applied in the exploration of iron formations [3], magnetic techniques have evolved into powerful tools for regional geological mapping [4], and for delineating the geological context of non-magnetic mineral deposits such as gold [5].

Electromagnetic methods, by contrast, involve the use of natural or artificial electromagnetic sources and receivers that detect subsurface conductivity variations [6]. These techniques are capable of directly detecting conductive ore bodies such as massive sulfides [7], or indirectly indicating the presence of deposits like uranium through related conductivity anomalies [8].

Recent advances in these methods span several domains. In acquisition, the deployment of magnetic and EM systems on airborne platforms has been transformative [9,10]. Concurrently, improvements in sensor design, data acquisition systems, and processing techniques have enhanced sensitivity and resolution [11]. Computational developments have also led to increasingly sophisticated data interpretation workflows that integrate geophysical signatures with geological frameworks [12]. These techniques have been successfully applied in diverse geological settings worldwide, further validating their utility and expanding their scope.

This special issue presents a curated selection of studies that reflect current directions in magnetic and electromagnetic exploration. It particularly highlights case studies demonstrating innovative or unconventional applications of these methods in mineral discovery.

2. Overview of Published Articles

Contribution 1: Cai and Ma article introduce a novel inversion method termed self-structural constraint (SSC), which enhances aeromagnetic data interpretation. Applied to a gold exploration project in western Henan, China, the SSC method aids in delineating volcanic zones with potential magmatic-hydrothermal mineralization.

Contribution 2: Liu et al. describe a multi-method approach combining magnetics, self-potential surveys, trenching, and drilling that led to the discovery of graphite deposits in northeastern China. Initial magnetic anomalies guided follow-up surveys and confirmed mineralization.

Contribution 3: Dong et al. apply the Audio-Magnetotelluric (AMT) method to the Gouli gold field, in the East Kunlun metallogenic belt, China. Two-dimensional inversions of EM data helped characterize alteration zones associated with gold mineralization, correlating well with drilling results.

Contribution 4: Vallée and Moussaoui propose a new method for calculating response moments from time-domain electromagnetic (TDEM) data. This approach is system agnostic and was tested using two distinct airborne TDEM systems over the Reid-Mahaffy test site, in Ontario, Canada. The technique enables comparative evaluation of system performance in identifying subsurface conductors.

Contribution 5: Cheng et al. report on the use of magnetic data to guide exploration for non-magnetic fluorite in the Gobi Desert, China. A low magnetic anomaly associated with structurally favorable setting was identified as a proxy for the fluorite-hosting environment.

Contribution 6: Zhang et al. combine gravity and magnetic to investigate deep geological structures related to gold mineralization in Fujian, China. The integrated interpretation highlighted prospective zones by correlating physical property anomalies with known geology.

Contribution 7: Prikhodko et al. introduce MobileMT, an innovative airborne EM system that uses natural field measurements to enhance deep penetration of the subsurface. They demonstrate its applicability across varied mineralization contexts: uranium in Canada’s Athabasca Basin, massive sulfides in Ecuador, Ni-Cu deposits in Sudbury, Canada, and porphyry systems in British Columbia, Canada.

Contribution 8: Gong et al. employ a suite of geophysical techniques–magnetics, vertical electrical sounding, and controlled source audio-magnetotellurics– to explore agate deposits in Liangshan, China. These sedimentary host deposits lie above resistive basalt and are characterized by distinct resistivity contrasts.

Contribution 9: Vallée et al. present a global review of magnetic and EM applications over the last fifteen years. The authors classify studies by deposit type, location and technique, and summarize trends in tabular and graphical forms. Although biased toward North American case studies, this comprehensive synthesis serves as a practical guide for future exploration strategy development.

3. Conclusions

Magnetic and electromagnetic techniques continue to play an essential role in the evolving landscape of mineral exploration. As exploration targets diversify and move into more complex environments across all continents, technological advances–especially those integrating artificial intelligence–are expected to further revolutionize both data acquisition and interpretation. The ongoing development of these methods will be critical in meeting the global demand for mineral resources.