Which geophysical technique is less likely to be used to investigate a massive sulfide ore body?

• A. Electrical resistivity
• B. Ground-penetrating radar
• C. Magnetotelluric
• D. Seismic refraction

Answer: (D)

Massive sulfide ore bodies are strongly conductive, so geophysical methods that detect electrical conductivity contrasts are particularly effective. Electrical resistivity imaging measures how easily current flows underground; sulfide-rich zones typically appear as low-resistivity bodies against surrounding rock, helping delineate the ore body at shallow to moderate depths. Magnetotellurics extends this idea to greater depths by using natural EM fields to map conductivity structure, making it suitable for detecting deep-seated sulfide-rich zones.

Ground-penetrating radar relies on dielectric properties and works best in dry, resistive near-surface materials. In ore settings, especially where sulfides are present, the ground can be conductive and radar signals attenuate quickly, limiting usefulness for mapping a substantial sulfide body, though it can help in shallow, non-conductive environments.

Seismic refraction, on the other hand, depends on velocity contrasts of seismic waves through rocks. A sulfide ore body often does not produce a clear, simple velocity contrast against the host rock, and the geometry of such ore bodies can be complex, making seismic refraction less sensitive and less practical for identifying a massive sulfide body compared with EM methods.

Therefore, seismic refraction is the least likely technique to be used for investigating a massive sulfide ore body.