SNORCLE - NORTHERN CORDILLERA MT EXPERIMENT: 
REGIONAL STRUCTURES

Juanjo Ledo(1), Alan G. Jones(1), Ian Ferguson(2), Lisa Wolynec(2), 
Jessica Spratt(1), Grant Wennberg(2)
(1) Geological Survey of Canada
    615 Booth St., Ottawa, Ontario, K1A 0E9, Canada
(2) Department of Geological Sciences
    University of Manitoba
    Winnipeg MB R3T 2N2, Canada
ledo@cg.nrcan.gc.ca

The Slave-Northern Cordillera Lithospheric Evolution -SNORCLE- 
Transect addresses LITHOPROBE's theme of crustal evolution through an 
integrated program of geological and geophysical studies across a 
geologically diverse region and through four billion years of Earth's 
history. Previous work focused on the Archean and Proterozoic aspects 
of SNORCLE, but the new MT data acquisition in Autumn 1999 was on the 
Cordillera. The application of the magnetotelluric -MT- method to the 
study of the northern Cordillera has three principal objectives. The 
first concerns characterization of the regional conductivity 
properties of the northern Cordillera in relation to the major 
tectonic units. The second thrust involves upper mantle features: 
determination of the depth extent and internal variation within the 
lithosphere beneath the Cordillera the fate of the vast amount of 
pacific lithosphere overridden by North America during the past. The 
third specific goal is determination of the subsurface geometry and 
character of the Tintina strike-slip fault zone for comparison with 
the reflection data and a better understanding of reasons for 
conductivity enhancement at faults. The MT experiment was the largest 
ever undertaken by LITHOPROBE, and consists of more than two hundred 
MT sites -AMT, broad band and long period- covering over 2000 km of 
transect. In this paper we will present the first results 
characterizing the regional conductivity distribution.