HR: 1340h
AN: T13A-0427    [Abstracts]
TI: The Electrical Lithosphere of the Archean: Insights from the Kaapvaal craton and elsewhere.
AU: * Garcia, X
EM: xavi@cp.dias.ie
AF: Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin, 2 Ireland
AU: Jones, A G
EM: alan@cp.dias.ie
AF: Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin, 2 Ireland
AU: Evans, R L
EM: revans@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Geology and Geophysics Clark South 172 360 Woods Hole Road, Woods Hole, MA 02543 United States
AU: Evans, S
EM: shane.evans@debeersgroup.com
AF: De Beers Group Services, Private X01, Southdale, 2135 South Africa
AU: Fourie, S
EM: stoffel@geoscience.org.za
AF: Council for Geoscience, 280 Pretoria Street, Silverton, Pretoria, 12 South Africa
AU: Mountford, A
EM: Andy.Mountford@riotinto.com
AF: Rio Tinto Mineral Exploration Inc., PO Box 695 7th Floor Castlemead Lower Castle Street, Bristol, BS99 1FS United Kingdom
AB: Deep probing measurements of electrical conductivity, made with the magnetotelluric (MT) method, offer important insights into the structure of the lithosphere, as conductivity is sensitive to variations in thermal structure, composition, and grain size, and the interconnectivity of a conducting phase, such as fluid content, presence of metallic oxides, graphite, and sulphides. These variations map fossil fabrics and structural geometries of the lithosphere, from which formation and deformation processes can be inferred. The Kaapvaal craton is arguably the best studied craton in the world, featuring extensive seismic and geochemical coverage. Over the last two years, as part of a project named SAMTEX (Southern African Magnetotelluric Experiment), we have collected an extensive MT data set across the Kaapvaal craton and its immediate surroundings to complement those other geoscientific studies. The MT data set provides insights into the regional electrical structure to depths of several hundred kilometers, including the depth distribution of anisotropic fabrics. Together with other data sets, these new measurements allow us to understand better how the craton was assembled. Results from the Kaapvaal craton can also be compared to those from other cratons, such as the Slave and Superior cratons of Canada, where similarly extensive and high quality electrical data sets exist. We can also look at differences between Archean and Proterozoic terranes. We present initial results from the Kaapvaal craton and discuss these in the light of other cratons and lithospheric structure in general.
DE: 0925 Magnetic and electrical methods (5109)
DE: 8031 Rheology: crust and lithosphere (8159)
DE: 8103 Continental cratons
DE: 8125 Evolution of the Earth (0325)
DE: 9623 Archean
SC: Tectonophysics [T]
MN: Fall Meeting 2005