International Geologiical Congress - Oslo 2008


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EIL-01 General contributions to the lithosphere


The Southern African Magnetotelluric Experiment (SAMTEX) images the underbelly of southern Africa


Alan Jones, Dublin Institute for Advanced Studies (Ireland)
Mark R. Muller, Dublin Institute for Advanced Studies (Ireland)
Mark P. Hamilton, Dublin Institute for Advanced Studies (Ireland)
Marion P. Miensopust, Dublin Institute for Advanced Studies (Ireland)
Xavier Garcia, Dublin Institute for Advanced Studies (Ireland)
Rob L. Evans, Woods Hole Oceanographic Institution (United States)
Patrick Cole, Council for Geoscience (South Africa)
Tiyapo Ngwisanyi, Geological Survey of Botswana (Botswana)
Dave Hutchins, Geological Survey of Namibia (Namibia)
Stoffel Fourie, Council for Scientific and Industrial Research (South Africa)
Shane F. Evans, DeBeers Group Services (South Africa)
Andy Mountford, Rio Tinto Mining and Exploration (United Kingdom)
Wayne Pettit, BHP Billiton (South Africa)
MT Team SAMTEX, Dublin Institute for Advanced Studies (Ireland)


The Southern African Magnetotelluric Experiment (SAMTEX) is making electromagnetic measurements on a regional basis across Botswana, Namibia and South Africa. It is the largest EM experiment conducted, and, when comleted after Phase IV in April, 2008, will comprise deep (200+ km) EM probing into the Earth at over 750 locations across an area of over one million square kilometres. SAMTEX was initiated in 2003 with four partners (DIAS, WHOI, CGS and DeBeers) as a project based entirely in South Africa to provide EM complementary data to the Southern African Seismic Experiment. It has grown over its four phases and now has eleven partners in the consortium from academia (DIAS, WHOI, Wits), government (CGS, CSIR, GSB, GSN) and industry (ABB, BHP-Billiton, DeBeers, Rio Tinto) and measurements over most of Namibia and all of Botswana in addition to the South African ones.
Strong regional variations in electrical conductivity at crustal and lithospheric mantle level are readily apparent in images and models from the data. In particular, the cratonic regions (Kaapvaal, Zimbabwe and Angola cratons) are resistive for much of their lithospheric extent, whereas the stitching mobile belts are far more conductive. There is a strong correlation between the diamondiferous kimerlites and the locations of deep (200+ km) resistive regions, and of non-diamondiferous kimberlites with less-resistive deep lithosphere.
Other aspects, including correlations between electrical and seismic velocities, will be presented.


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