Interpretation of MT data across the exposed internides 
of the Trans-Hudson Orogen.

Xavier Garcia, University of Barcelona, Spain
Alan G Jones,  Geological Survey of Canada, Ottawa, Canada

The THO94 MT data set was recorded in northern Saskatchewan 
during the Fall of 1994. The main goal of this transect was 
to trace the enigmatic NACP anomaly onto the exposed rocks of 
the internides of the Trans-Hudson orogen. After processing the 
time series data from the 23 MT stations to remove strong auroral 
effects, the MT responses were tensor decomposed, modelled, and 
geologically interpreted.

The GB-based tensor decomposition gave a N60W strike as most 
appropriate, which confirms the rotation of the deep conductivity 
structures to the east as suggested by Gupta et al. The regional
responses were inverted, using RRI, in this coordinate system.

The conductivity model from the profile further south correlates 
with the seismic interpretation of subduction of La Ronge metasediments 
to the Hearne craton edge. The NACP anomaly is imaged in the La Ronge 
Domain, in the contact with the Rottenstone Domain, just over the Guncoat 
thrust, suggesting the same origin for the anomaly in the north of the 
Province of Saskatchewan as the one suggested to the south. To the 
south of the profile there is a body deeping to the North interpreted 
as the Sask craton.

Session 9: Local and regional electromagnetic studies