Modelling Of The Contribution Of Upper Mantle Magnetism To The Magnetic Anomaly Map Observed On Earth’s Surface: Analysis Of Different Tectonic Settings

Abstract:

Magnetic anomalies of the Geomagnetic Field have been increasing interest in recent years in particular with acquisition of new data from satellite missions. Traditionally, anomalies have been modelled from Earth’s surface down to the crust-upper mantle boundary, considering the Moho as the magnetic-non magnetic interface. However, long wavelength magnetic anomalies appear as residuals not modelled in most global and large regional magnetic models.

In the last years, several publications have proposed and analysed the magnetic signal from fresh upper mantle xenolith showing the presence of minor inclusions of magnetite that might be in ferrimagnetic state at those depths, depending on the particular geotherm of the geological setting.

It has been modelled the effect on Earth surface of those magnetite inclusions taking into account the variation of magnetic intensity at depth, magnetic susceptibility and concentration of magnetite reported from mantle xenolith on different setting finding the effect of the inclusions can have measurable intensities at the surface. Results show that the effect of magnetite in the upper mantle could have a relevant effect when modelling magnetic signal from satellite missions.