Area selection using magnetotellurics examples from Southern Africa.

Abstract

The electrical conductivity of the continental upper mantle is highly sensitive to ambient temperature (e.g., Jones et al., 2008; Ledo and Jones, 2005), to iron content (Mg) (Jones et al., 2008), to the presence of an interconnected conducting phase, such as a solid phase like graphite or sulphides (e.g., Duba and Shankland, 1982; Ducea and Park, 2000; Jones et al., 2003) or a fluid phase like partial melt (e.g., Park and Ducea, 2003), or to bound water through hydrogen diffusion (e.g., Hirth et al., 2000; Karato, 1990; Karato, 2006). Given these sensitivities, deep-probing magnetotellurics (MT) can aid in area selection for potential diamondiferous prospective regions by mapping regions of deep lithospheric roots and by mapping regions that possibly contain high quantities of carbon (Jones and Craven, 2004).The Southern African Magnetotelluric Experiment (SAMTEX) project is imaging the three-dimensional regional-scale geometry of the electrical conductivity of the continental lithosphere below southern Africa using the natural-source electromagnetic method magnetotellurics. Herein we present images of the electrical resistivity (inverse of conductivity) at various depths, and compare the inferred resistivities with seismic parameters at the same depths obtained from body wave and surface wave data from the Kaapvaal Seismic Experiment