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How can NMR magnetometers help locate mineral deposits or archaeological remains?

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magnetic resonance Figure 1: Precession of a magnetic dipole moment μ in the presence of a constant field H and a rotating field H′ (see text)

NMR magnetometers, such as those utilizing proton-precession technology, assist in locating mineral deposits and archaeological remains by detecting subtle magnetic anomalies in the Earth's field.12

These devices function by measuring the precession frequency of proton spins, which is directly proportional to the strength of the surrounding magnetic field. When incorporated into portable magnetometers, this technology achieves high sensitivity, allowing for the detection of field variations as small as $10^{- 8}$ gauss.1

In practical applications, these instruments identify localized disturbances in the geomagnetic field caused by materials or structures beneath the surface. For example:1

Mineral Exploration: Magnetic surveys map features in igneous and metamorphic rocks, such as dikes or faults, which are often associated with mineral concentrations.2
Archaeological Remains: The high sensitivity of these magnetometers allows researchers to identify magnetic signatures linked to buried archaeological features.1

By measuring these variations, surveyors can create contour maps or profiles to pinpoint the location of subsurface anomalies that differ from the surrounding geological environment.2