The interpretation of magnetic anomalies between Iceland and Scotland

Abstract

The collection of data, and the results of a detailed magnetic survey on the crest of the Iceland-Faeroes Rise are described, A matrix method is developed to transform gravity anomalies to magnetic anomalies, and vice versa, to determine the ratio of magnetism to density in an equivalent layer, to solve for the angle of magnetisation of a body causing a magnetic anomaly and to separate magnetic anomalies caused by different types of source body. The data from the detailed survey area are interpreted as supporting the conclusions of previous authors that the crustal structure of the Iceland-Faeroes Rise is highly anomalous for an oceanic setting, and 16 similar to that of Iceland, with at least two magnetic layers which contain central intrusive complexes; granitic rocks may also be present. The matrix methods developed in the first part of this work are used to interpret gravity and magnetic data from a previous Durham survey on the Iceland-Faeroes Rise. Results indicate that the magnetic anomalies are controlled by seismic structure on NE - SW profiles, but include a component which is independent of seismic structure which is of greater significance on NW - SE profiles. The latter component is identified as magnetisation changes as a function of time. Magnetic and gravity anomalies from the Scottish Continental Shelf region are used to demonstrate further the scope of the matrix methods for combined analysis of gravity and magnetic anomalies.