Toward 3D Deep Mineral Imaging: CSEM, ERT, and IP Strategies for Depths Beyond 1 Km

This study outlines a robust workflow for imaging deep-seated mineral deposits using Electrical Resistivity Tomography (ERT), Induced Polarization (IP), and Controlled-Source Electromagnetics (CSEM) at depths beyond 1 km. Deep-target surveys pose significan technical and logistical challenges, requiring careful planning of current injection parameters, array geometry, and instrumentation.

To address these challenges, we evaluated survey strategies through synthetic modeling to guide decisions on injection period, source power, and the use of nodal systems. These pre-survey assessment enabled an optimized balance between signal quality, depth sensitivity, and field efficiency.

A large-scale 3D field survey was conducted at the Koillismaa Layered Intrusion Complex in Finland, targeting mafic-ultramafic intrusion from a depth of 1.4 km. Using 25 long transmitter dipoles (∼1 km) and 114 receiver stations utilising nodal system which allows much flexible configuration at the field site across ∼200 km².

Inversion results from ERT and CSEM revealed deep conductive features, with CSEM identifying three distinct anomalies in greater detail. The IP model also captured a phase anomaly aligned with a known mafic-ultramafic intrusion. This work demonstrate the effectiveness of the proposed approach and support its broader application in deep mineral exploration.