ELECTRICAL CONDUCTIVITY STRUCTURES OF THE SOUTHERN CANADIAN CORDILLERA AND ITS RELATIONSHIP WITH OTHER GEOPHYSICAL AND GEOLOGICAL DATA.

Juanjo Ledo and Alan G. Jones.
Geological Survey of Canada. 1, Observatory Crescent.  Ottawa K1N 8Y3, ON. Canada.
e-mail: ledo@cg.nrcan.gc.ca, jones@cg.nrcan.gc.ca

The southern Canadian Cordillera of western Canada lies in a region of oceanic 
and island-arc lithosphere accreted to North America during subductions over 
the last 200 Ma. The crust is a complex of accreted terranes detached from 
their subducted lithosphere. The MT data hae been split into four sets showing 
different regional electrical strikes. The models obtained are similar in most 
features.  This indicates that although some data show 3D behaviour the 
responses can still be inverted in a 2D manner to obtain a broad regional 
pattern of the conductivity structure in the Canadian Cordillera. To first 
approximation the resistive upper crust of the Canadian Cordillera can be 
related to structural or seismic structures.  However the more conductive lower 
crust must be related to metamorphic episodes that occurred after the 
accretion of the terranes.

The main topic of this paper is to present a regional electrical structure of 
the Canadian Cordillera to explain the main features of the MT data and its 
relationship with other geophysical and geological data.