Collaborative Research: Identification of magnetic sources in the upper mantle

The view that the upper mantle is universally non-magnetic because it lacks ferromagnetic minerals and would be too hot to carry a magnetic remanence needs to be revisited because converging evidence suggests that some magnetic sources reside at mantle depths. This situation occurs in cold geotherm settings. We propose to carefully measure the magnetic properties of mantle xenoliths using new collections of fresh mantle rocks. The magnetic measurements will be supported by thorough petrologic investigations and by experiments in piston cylinders replicating the rapid ascent of mantle rocks to the Earth surface. The results these investigations will most likely transform the interpretation of data returned by the Swarm mission, deployed in November 2013, which will provide an unprecedented resolution of the lithospheric magnetic field.

Our understanding of the internal structure of the Earth relies on geophysical approaches including for example seismology, gravimetry and magnetism. The magnetic field at the Earth's surface informs us about temperature at depth because below the Curie depth, minerals become too hot to be magnetic. Up to now, we thought that mantle rocks, at depths of about 30 kilometers, did not carry any magnetic minerals, an assumption based on measurements made in the 1980?s. The proposed research will re-evaluate this non-magnetic mantle concept and provide a far more accurate knowledge base to interpret magnetic satellite data. The information deduced from magnetic satellites provides vital information on regions of the globe where tectonic plates collide and create abundant seismicity.