HR: 1340h
AN: T13A-0428    [Abstracts]
TI: Electromagnetic Images of the Subcontinental Mantle: Shining a Light on Archean Mantle Processes.
AU: * Craven, J A
EM: craven@NRCan.gc.ca
AF: Geological Survey of Canada, 615 Booth St., Ottawa, ON K1A 0E9 Canada
AU: Ferguson, I J
EM: ferguso@ms.umanitoba.ca
AF: University of Manitoba, Dept. of Geological Sciences, Winnipeg, MB R3T 2N2 Canada
AU: Skulski, T
EM: tskulski@NRCan.gc.ca
AF: Geological Survey of Canada, 601 Booth St., Ottawa, ON K1A 0E8 Canada
AB: Electromagnetic methods such as those obtained by magnetotellurics provide an image of modern and ancient subduction zones. MT images complement those obtained from earthquake and active-source seismic studies of the crust and mantle at subduction zones due to the inherent ensitivity of EM methods to: saline fluids released from the subducting slab; electrically-conductive sedimentary rocks scraped from the subducting oceanic slab and imbricated in the overlying crust and mantle; and hydrated rocks in the mantle above the subducting slab. A dramatic north-dipping electrical structure is observed penetrating into the mantle lithosphere at a boundary between two Meso-Archean crustal blocks within the western portion of the Archean Superior craton of North America. Taken together with seismic images, and the observation of magmatic rocks similar to those observed in modern subduction settings, the resistivity image provides evidence that old subcontinental lithosphere was affected by subduction processes similar to those occurring in modern plate tectonics. Such processes provide a viable explanation for formation of buoyant continental lithosphere required to explain global preservation of Archean cratons.
DE: 0925 Magnetic and electrical methods (5109)
DE: 1515 Geomagnetic induction
DE: 8125 Evolution of the Earth (0325)
SC: Tectonophysics [T]
MN: Fall Meeting 2005