A granite window to the lower electrical crust and upper mantle

The structure and properties of the deep crust and upper mantle can be investigated using magnetotelluric observations. Near-surface and upper crustal complexities may distort or limit the capability of the data to adequately resolve deep structure. Granite batholiths have been regarded as windows into the lower crust in the context of seismic reflection data although the granite bodies themselves are not usually detected. Magnetotelluric data from SW England are here used to demonstrate that, in addition to imaging the internal structure and base of a granite, the batholith itself provides a suitable environment for the effective estimation of the resistivity structure to lower crustal and upper mantle depths.