Investigation of magnetization and density of a north Atlantic seamount using Poisson's theorem

Abstract

The relationship between the gravitational and magnetic potentials caused by a uniform distribution of mass and magnetization may be used to obtain independent information about these physical properties. The general relationship in the frequency domain between the Fourier transforms of the gravity and magnetic anomaly fields is established through the Poisson theorem. The discrete Fourier transforms of the sampled continuous functions are used in an analysis which leads to a system of linear equations involving terms in density, magnetization, and calculated finite Fourier-series coefficients. A least squares solution of the system yields the three components of the total magnetization vector divided by the density. From these results, the direction of total magnetization and the minimum of the Koenigsberger ratio Q can be determined uniquely. The remanent magnetization direction and certain other information can be derived for special cases in which the value of one or more of the physical property terms can be assigned. Accurate results were obtained in the analysis of data from a theoretical model. Analysis of gravity and magnetic data from the North Atlantic Gilliss seamount indicates the presence of a significant component of remanent magnetization and leads to derived physical properties which are in fairly close agreement with dredged sample data. The calculated direction of remanent magnetization indicates a paleomagnetic pole position in eastern Siberia, in general agreement with the predicted position for a Cretaceous source in the North Atlantic. The seamount example illustrates certain contingent problems to be considered in practical application of the method.