In development over 70 years, magnetotelluric (MT) sounding, a high-resolution technique for subsurface electrical resistivity imaging, has been widely applied in resource exploration in the Earth. The key factors of the metallogenic system of metallic mineral deposits can be closely correlated to the electrical anomalies of the lithosphere. In this paper, we review the relationship between the electrical resistivity model of the lithosphere and the metallogenic system. At the beginning, we indicate why the electrical parameters relate to the metallogenic system in all geophysical parameters. The advantage of MT sounding in sketching an electrical resistivity model of the lithosphere is subsequently discussed, and some methods of data processing, analysis and inversion are also introduced. Furthermore, we summarize how to bridge the relationship between the electrical resistivity model of the lithosphere and metallogenic system, and analyze the influence of the rheological variation estimated from conductivity in the lithosphere on mineralization. In the end, we list some typical cases of the application of MT sounding in mineral exploration, and also give some suggestions for future work. This study is aimed at providing guidance in discussing the metallogenic system using an electrical resistivity model.

Marine controlled-source electromagnetics (MCSEM) is an effective method to map the spatial distribution of gas hydrate and calculate gas hydrate saturation. An MCSEM survey is conducted in the Lingnan low uplift (LNLU), Qiongdongnan Basin (QDNB), South China Sea (SCS), and then the measured data are processed to obtain the geoelectric structure. The estimated gas hydrate stability zone (GHSZ) ranges from 0 to 320 mbsf, and shallow high-conductive sediments serving as gas hydrate caps are at depths ranging from 0 to 100 mbsf (meters below the seafloor). The 2D resistivity model reveals multiple high-resistivity bodies at depths ranging from 100 to 320 mbsf, and BSRs are at depths of 240 mbsf to 280 mbsf, indicating a transversely uneven gas hydrate reservoir in the study area. Moreover, two high-resistivity bodies are detected beneath the GHSZ, implying the presence of potential gas transport pathways. The gas hydrate saturation with a variation of 0–68.4% is calculated using the MCSEM resistivity and Archie’s law. According to the resistivity model and geological data, the transversely uneven gas hydrate reservoir may be associated with multiple gas sources, including shallow biogenic gas and deep pyrolytic gas. The shallow biogenic gas is transported to the GHSZ via short-distance migration and free diffusion, and the deep pyrolytic gas is transported to the GHSZ via two microcracks. In addition, this case emphasizes that the dynamic accumulation of gas hydrate is an important factor causing reservoir heterogeneity.

This study presents the first application of a deep-towed transmitter–receiver marine controlled-source electromagnetic (TTR-MCSEM) system for gas hydrate exploration in the Shenhu area of the South China Sea. High-resolution electromagnetic data were acquired along a 13 km transect using dynamic source–receiver offsets and a 500 A transmitter. The results reveal the following: (1) unprecedented near-seafloor resolution (20~100 m) for the precise delineation of hydrate-bearing caprock, surpassing conventional ocean-bottom electromagnetic systems; (2) laterally continuous high-resistivity anomalies (~10 Ω·m) extending from the base of the gas hydrate stability zone to the seafloor, which correlate with seismic bottom-simulating reflector (BSR) distributions and suggest heterogeneous hydrate saturation; and (3) fault-controlled fluid migration pathways that supply hydrate reservoirs and lead to seabed methane seepage at structural highs. Through 2D inversion, we show that the inverted resistivity values (~10 Ω·m) are slightly higher than those obtained from resistivity logs (~5 Ω·m). Saturation values derived from inverted resistivity exhibit remarkable consistency with well-log-based measurements. The high efficiency of the system confirms its potential for the transformative quantitative assessment of hydrate systems, seafloor massive sulfides, and marine geohazards.

In recent years, exploration and development of marine oil and gas have been gradually turned to deep water area from shallow water area, and the exploration is becoming more and more difficult. Traditional technology can no longer meet the exploration task. However, a newly developed method, marine controlled-source electromagnetic exploration technology, plays an important role in oil and gas exploration. At present, the marine controlled-source electromagnetic exploration technology has developed into a relatively perfect technology system, which has been fully developed in the basic theory, electromagnetic instruments, data processing and interpretation. In the future, marine controlled-source electromagnetic technology will develop towards all directions, high efficiency, high precision, and wide range.

The marine controlled source electromagnetic (CSEM) method has been recognized as an effective exploration method of shallow hydrocarbons around the world. We developed our own underwater marine CSEM transmitter that consisted of many functional modules with various response times. We previously adopted a centralized software-control technology to design the transmitter circuit topological structure. That structure probably generated a control disorder or malfunction. These undesirable conditions could lead to repeated recovery and deployment of the transmitter, which not only consumed time but also affected data continuity and establishment of stable and continuous CSEM field. We developed an instrument design concept named 'control technology of hardware parallelism'. In this design, a noteworthy innovation of our new technology is to solve the above-mentioned problems at the physical and fundamental levels. We used several self-contained control-units to simultaneously accomplish the predetermined functions of the transmitter. The new solution relies on two technologies: multi-core embedded technology and multi-channel parallel optical-fiber data transmission technology. The first technology depends on many independent microcontrollers. Every microcontroller is only used to achieve a customized function. The second one relies on several multiple optical-fiber transmission channels realized by a complex programmable logic device and two optical-fiber conversion devices, which are used to establish a communication link between the shipboard monitoring and control-unit and underwater transmitter. We have conducted some marine experiments to verify the reliability and stability of the new method. In particular, the new technology used in the transmitter system could help us obtain more useful measured data in a limited time, improve real-time efficiency, and support the establishment of a stable CSEM field.

The Northeastern Hunan Province (NEH), situated within the Central Jiangnan Orogen, hosts abundant Au-polymetallic deposits. However, the coupling mechanism between the deep tectono-magmatism and Au-polymetallic mineralization remains poorly understood. In this study, a three-dimensional (3D) resistivity model derived from 59 magnetotelluric (MT) stations is presented to investigate the lithospheric architecture and its relationship to Au-polymetallic mineralization. The model reveals three prominent mid-to-lower crustal conductors (3–30 Ω·m) at 15–35 km depth beneath Au-polymetallic deposits along NE faults. These anomalies are interpreted as source zones and pathways for magmatic-hydrothermal fluids during the Late Mesozoic tectono-magmatism, likely formed by the enrichment of graphite films and sulfides along faults, which thus account for the observed conductive features. Moreover, the model reveals a thinning electrical lithosphere–asthenosphere boundary (eLAB) at ~80 km depth beneath the Southeastern NEH, attributed to lithospheric delamination triggered by the rollback of the Paleo-Pacific plate. This delamination facilitated the upwelling and lateral migration of asthenospheric materials, which promoted intense extension and crust–mantle interaction. Consequently, metallic elements were extensively extracted from the crust and concentrated into large-scale Au-polymetallic deposits in the NEH. Integrating with previous geochemical study, a deep-seated magmatic underplating and MASH model is proposed as key drivers of Au-polymetallic enrichment in the NEH, effectively linking deep tectono-magmatism with shallow mineralization. From a rheological perspective, three low-viscosity zones within the mid-to-lower crust likely acted as both vertical conduits and deep sources for metallogenic fluids, providing favorable pathways for their migration and accumulation.