@article {Garcia2014a, title = {{Constraints on a shallow offshore gas environment determined by a multidisciplinary geophysical approach: The Malin Sea, NW Ireland}}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {15}, number = {4}, year = {2014}, pages = {867{\textendash}885}, issn = {15252027}, doi = {10.1002/2013GC005108}, url = {http://doi.wiley.com/10.1002/2013GC005108}, author = {Garcia, Xavier and Monteys, Xavier and Evans, Rob L. and Szpak, Michal} } @article {Evans2011, title = {{Electrical lithosphere beneath the Kaapvaal craton, southern Africa}}, journal = {Journal of Geophysical Research}, volume = {116}, number = {B4}, year = {2011}, month = {apr}, pages = {B04105}, abstract = {A regional-scale magnetotelluric (MT) experiment across the southern African Kaapvaal craton and surrounding terranes, called the Southern African Magnetotelluric Experiment (SAMTEX), has revealed complex structure in the lithospheric mantle. Large variations in maximum resistivity at depths to 200-250 km relate directly to age and tectonic provenance of surface structures. Within the central portions of the Kaapvaal craton are regions of resistive lithosphere about 230 km thick, in agreement with estimates from xenolith thermobarometry and seismic surface wave tomography, but thinner than inferred from seismic body wave tomography. The MT data are unable to discriminate between a completely dry or slightly "damp" (a few hundred parts per million of water) structure within the transitional region at the base of the lithosphere. However, the structure of the uppermost \~{}150 km of lithosphere is consistent with enhanced, but still low, conductivities reported for hydrous olivine and orthopyroxene at levels of water reported for Kaapvaal xenoliths. The electrical lithosphere around the Kimberley and Premier diamond mines is thinner than the maximum craton thickness found between Kimberley and Johannesburg/Pretoria. The mantle beneath the Bushveld Complex is highly conducting at depths around 60 km. Possible explanations for these high conductivities include graphite or sulphide and/or iron metals associated with the Bushveld magmatic event. We suggest that one of these conductive phases (most likely melt-related sulphides) could electrically connect iron-rich garnets in a garnet-rich eclogitic composition associated with a relict subduction slab. Copyright 2011 by the American Geophysical Union.}, issn = {0148-0227}, doi = {10.1029/2010JB007883}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-79955426798\&partnerID=tZOtx3y1}, author = {Evans, Rob L. and Jones, Alan G. and Garcia, Xavier and Muller, Mark and Hamilton, Mark and Evans, Shane and Fourie, C. J. S. and Spratt, Jessica and Webb, Susan and Jelsma, Hielke and Hutchins, Dave} } @article {Jones2009, title = {{Area selection for diamonds using magnetotellurics: Examples from southern Africa}}, journal = {Lithos}, volume = {112}, year = {2009}, month = {nov}, pages = {83{\textendash}92}, abstract = {Southern Africa, particularly the Kaapvaal Craton, is one of the world{\textquoteright}s best natural laboratories for studying the lithospheric mantle given the wealth of xenolith and seismic data that exist for it. The Southern African Magnetotelluric Experiment (SAMTEX) was launched to complement these databases and provide further constraints on physical parameters and conditions by obtaining information about electrical conductivity variations laterally and with depth. Initially it was planned to acquire magnetotelluric data on profiles spatially coincident with the Kaapvaal Seismic Experiment, however with the addition of seven more partners to the original four through the course of the experiment, SAMTEX was enlarged from two to four phases of acquisition, and extended to cover much of Botswana and Namibia. The complete SAMTEX dataset now comprises MT data from over 730 distinct locations in an area of over one million square kilometres, making SAMTEX the largest regional-scale MT experiment conducted to date. Preliminary images of electrical resistivity and electrical resistivity anisotropy at 100 km and 200 km, constructed through approximate one-dimensional methods, map resistive regions spatially correlated with the Kaapvaal, Zimbabwe and Angola Cratons, and more conductive regions spatially associated with the neighbouring mobile belts and the Rehoboth Terrane. Known diamondiferous kimberlites occur primarily on the boundaries between the resistive or isotropic regions and conductive or anisotropic regions. Comparisons between the resistivity image maps and seismic velocities from models constructed through surface wave and body wave tomography show spatial correlations between high velocity regions that are resistive, and low velocity regions that are conductive. In particular, the electrical resistivity of the sub-continental lithospheric mantle of the Kaapvaal Craton is determined by its bulk parameters, so is controlled by a bulk matrix property, namely temperature, and to a lesser degree by iron content and composition, and is not controlled by contributions from interconnected conducting minor phases, such as graphite, sulphides, iron oxides, hydrous minerals, etc. This makes quantitative correlations between velocity and resistivity valid, and a robust regression between the two gives an approximate relationship of Vs [m/s] = 0.045 * log(resistivity [ohm m]) + 4.5. {\textcopyright} 2009.}, keywords = {Cratonic lithosphere, Diamond exploration, Electrical conductivity, Kaapvaal Craton, Sub-continental lithospheric mantle, Zimbabwe Craton}, issn = {00244937}, doi = {10.1016/j.lithos.2009.06.011}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-72149117671\&partnerID=tZOtx3y1}, author = {Jones, Alan G. and Evans, Rob L. and Muller, Mark R. and Hamilton, Mark P. and Miensopust, Marion P. and Garcia, Xavier and Cole, Patrick and Ngwisanyi, Tiyapo and Hutchins, David and Fourie, C.J.S. and Jelsma, Hielke and Evans, Shane and Aravanis, Theo and Pettit, Wayne and Webb, Sue and Wasborg, Jan} }