Modeling the physical properties and composition of the mantle lithosphere using magnetotellurics combined with other information (Invited)

There are but two ways of directly sensing the physical properties of the lithosphere, rather than by inference from modeling, and these are seismological techniques and electromagnetic ones. The former primarily yield information on bulk, vibrational properties of the medium, namely compressional and shear velocities, whereas the latter primarily yield information on transport properties of the medium, often dictated by a well-interconnected minor phase, namely electrical conductivity. As such, they are highly complementary and taken together, either informally in co-operative modelling/inversion or formally in joint modelling/inversion, are far more powerful than each in isolation. Further than this, there is a wealth of additional data available virtually everywhere that can be utilized to constrain the thermal structure and composition of the lithosphere, namely gravity, geoid, surface heat flow, and elevation. Examples will be shown of studies in cratons (Southern Africa, Canada) and active regions (Atlas Mountains, Tibet) where magnetotellurics combined with seismological and other information is able to provide firm constraints on the thermal structure, physical properties and composition of the mantle lithosphere. In particular, MT can map the presence or absence of water in the lithospheric column, which is important for the debate on rheological properties and deformation.