INDUCED MAGNETIZATION OF THE OCEANIC LITHOSPHERE AND OCEAN-CONTINENT MAGNETIZATION CONTRAST INFERRED FROM MAGSAT ANOMALIES

A petromagnetic forward model of induced magnetization of Iceland Plateau is presented. Magnetic susceptibilities of Icelandic rocks from the literature are placed in a vertical stratigraphic context according to a model of igneous and metamorphic layering of the Icelandic crust that is compatible with seismic and other geophysical data. Curie isotherm depths for the magnetic forward model are based on the geothermal gradients measured in drill holes and those derived from magnetotelluric surveys. The petromagnetic model is used to predict the satellite altitude (400 km) magnetic field of Iceland Plateau. Comparison of calculated and Magsat anomalies shows that the total induced magnetization (the vertically integrated induced magnetization) in the surrounding oceanic lithosphere is almost-equal-to 2300 A. This value is very similar to independent estimates based on rock magnetic models of the oceanic crust. Rockall Plateau is a Precambrian microcontinent largely surrounded by oceanic crust a few hundred kilometers south and east of Iceland. The size, age, and location of this plateau are ideally suited to characterize the ocean-continent magnetization contrast. The total induced magnetization contrast between the plateau and its surroundings estimated from the Magsat anomaly of Rockall Plateau is almost-equal-to 14,000 A.