Oceanic magnetic anomaly amplitudes: variation with sea-floor spreading rate and possible implications |
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| Authors: | HR Jackson I Reid |
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| Institution: | Atlantic Geoscience Centre, Geological Survey of Canada, Bedford Institute of Oceanography, Dartmouth, N.S. B2Y 4A2Canada |
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| Abstract: | A qualitative examination of oceanic magnetic anomalies suggests that their amplitudes increase with the spreading rate of the ocean floor. This suggestion has been investigated quantitatively by inversion of the anomalies. A variance matching technique has been used to calculate the average magnetisation of the crust with crustal thickness held constant or to calculate the thickness with the magnetisation fixed. In spite of variations in the computed intensities of magnetisation and thickness when compared to spreading rates the results show an over-all increase in the intensities with the rate of spreading. The mechanisms responsible for this could include greater irregularity in distribution of magnetic polarities within the crust at slow spreading ridges, greater intensity of magnetisation in crust produced at fast spreading due to initial chemical properties or enhanced hydrothermal alteration, and a dependence of crustal thickness on spreading rate. |
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