Thermal regime and state of hydration of the Antarctic upper mantle from regional-scale electrical properties

Large-scale electrical resistivity investigations of the Antarctic crust and upper mantle utilizing the magnetotelluric method (MT) are limited in number compared to temperate regions, but provide physical insights difficult to obtain with other techniques. Key to the method's success are instrumentation advances that allow micro-volt level measurements of the MT electric field in the face of mega-ohm contact resistances. Primarily in this chapter, we re-analyse existing data from three campaigns over the Antarctic interior using modern 3D non-linear inversion analysis and offer additional geophysical conclusions and context beyond the original studies. A profile of MT soundings over transitional Ellsworth–Whitmore block in central West Antarctica implies near-cratonic lithospheric geothermal conditions with interpreted graphite–sulfide horizons deformed along margins of high-grade silicate lithological blocks. Re-analysis of South Pole soundings confirms large-scale low resistivity spanning Moho depths that is consistent with limited seismic tomography and elevated crustal thermal regime inferences. Upper mantle under a presumed adiabatic thermal gradient below the Ross Ice Shelf near the central Transantarctic Mountains appears to be of a moderately hydrated state but not sufficient so as to induce melting. The degree of hydration there is comparable to that below the north-central Great Basin province of the western US.