DEEP CONDUCTIVITY STRUCTURE IN ABITIBI, CANADA, USING LONG DIPOLE MAGNETOTELLURIC MEASUREMENTS

Magnetotelluric data recorded in the period range 10(2) - 2.10(4)s usi ng 100 km telluric dipoles in western Quebec, Canada, yield impedance estimates free from galvanic distortion and static shift. Analysis of the apparent resistivity, phase and magnetic transfer function data fa vors a regional 1D anisotropic model for the subsurface resistivity st ructure in the Abitibi Subprovince; lower resistivity direction of the anisotropy is EW, parallel to the main fault system. Joint 1D inversi on of both principal impedances indicates a conductivity anisotropy in ;he upper and middle crust and in the upper mantle. It might originate for all depths from the same tectonic mechanism, mainly a NS shorteni ng followed by an EW dextral shearing in the Archean.