The remote determination of magnetic remanence

Recovery of Resultant Magnetization Vectors from Magnetic Anomalies

“…These results are also summarised in Table 2. There is good agreement between our results and those found by Foss and McKenzie (2011) and Pratt et al (2012) for the CMP anomaly. Foss and McKenzie (2011) suggest that the remanent component direction is similar to that found in NRM measurements for the nearby BHN, but with a higher Q value.…”

“…The pattern of the anomalies in the area show an obvious negative to the north/north-east, which is opposite to the pattern observed for an induced anomaly in a local field of declination 8.3° and inclination -66.9°. This suggests a strong natural remanent magnetisation (NRM) which has been studied by many authors (e.g., Pratt et al 2012;Foss and McKenzie, 2011;Philips, 2005;Rajagopalan et al 1993), to constrain apparent polar wonder paths (APWP), for example .…”

“…Foss and McKenzie (2011) suggest that the remanent component direction is similar to that found in NRM measurements for the nearby BHN, but with a higher Q value. Pratt et al (2012) used APWP to constrain this remanent direction to the upper limit of the high temperature NRM component at 230° declination and 18° inclination, and hence inferred a Q=5. The directions of Phillips (2005) do not agree closely with others and appear to be too steep and northward.…”

New approaches to dealing with remanence: magnetic moment analysis using tensor invariants and remote determination of in situ magnetisation using a static tensor gradiometer

“…Table 3 compares magnetic moment and depth estimates for all pipes. Note that Pratt et al (2012) give depths to the tops of the modelled pipes, not depths to centroids. Twice the difference between the two depths may give an indication of the depth extent of the pipes.…”

“…Anomalies over inferred intrusions, corresponding to four prominent discrete equidimensional anomalies within a relatively subdued background field, have been studied in detail. Pratt et al (2012) modelled the sources of these anomalies, which they labelled Pipes A-D, and estimated magnetisations of the causative bodies. The northern pair of pipes are clearly reversely magnetised (Figure 1), indicating that their magnetisations are dominated by reverse polarity remanence, whereas the southern pair of anomalies (Figure 2) have magnetisations of normal polarity, making the presence of remanence less obvious.…”