A detailed palaeomagnetic investigation has been made of the Mull (Scotland) regional dyke swarm. 165 dykes were sampled in a 7-km section across the swarm from Quinish to Ardmore in northern Mull. A major question arising from the results of the investigation is whether the cleaned NRM directions for the dykes are equivalent to the original cooling TRM directions. The question arises since evidence from several lines shows that the dykes have experienced considerable hydrothermal alteration, with reheating temperatures averaging 200C and major changes in the iron titanium oxides responsible for the NRM. Surprisingly, the answer appears to be that original cooling TRM directions are probably still well represented by cleaned NRM directions.
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Ade‐Hall et al. (1972) studied this question.
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