Appendix B: Advice and Recommendations
Measurements of bulk susceptibility or conductivity using a new handheld meter can be
used in a wide range of applications in various geological fields, making the instrument
useful for both geologists and geophysicists. But there are some considerations that must
be followed in order to obtain good results and protect the instrument against damage.
These are as follows:
•
Do not take measurements with weak batteries (exchange batteries after the low battery
signal appears at your earliest convenience).
•
Do not take measurements in the rain when the surfaces of rocks are very wet.
•
The first and third steps in a measurement (measuring with coil in the air, otherwise
known as free air measurements) should not be executed near earrings, necklaces or any
other metallic objects. When taking free air measurements, maintain distance of at least
50 cm from anything metallic.
•
When taking readings on drill cores, avoid measuring near the nails of the wooden core
box. Never measure cores placed in metallic boxes. For best results, it is recommended
that cores be removed from the boxes during measurements.
•
When measuring on outcrops, care must be taken to find convenient surfaces in order to
eliminate the influence of weathering. Weathering results in a decrease of susceptibility,
which is intensified the more the sample is weathered. It is important to remember that
the coil is most strongly influenced by the rock nearest to the coil’s surface, even if one
measures using the pin. Magnetic anisotropy exists and measure parallel and
perpendicular to the foliation in metamorphic rocks. Make corrections for the unevenness
of the rock surfaces. Susceptibility distribution in any outcrop is found relatively reliably
if more than 12 measurements are made; one, two or three measurements are insufficient.
Take care not to measure near the geological hammer you may have with you.
•
When placing the meter on a rock’s surface, do so gently. Beware that shocks and
rough handling of the meter on rocks can damage the measuring coil.
•
To verify magnetic anomalies, it is recommended that users measure all kinds of rocks
available in the region of interest, even small rocks and soil debris. They may not cover
the entire surface of the coil and may be very thin; but, it is important to remember that
the value you obtain is informative only. From a collection you gathered you can take the
characteristic pieces for the lab measurement, sufficiently big and suitable for cutting the
lab specimens. Susceptibility measurements help you to take representative samples for
lab measurement of anisotropy and/or remnant magnetization measurement.
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